CA1199732A - Method and device for matching fingerprints with precise minutia pairs selected from coarse pairs - Google Patents

Abstract

Abstract of the Disclosure:

A pair candidate list (73) is formed by selecting minutia pairs with reference to a minutia list (71) showing original position and direction data given for minutiae by principal coordinate systems preliminarily selected on a search and a file fingerprint and those relation data of the minutiae which are substantially independent of the coordinate systems. It is very likely that the pair candidate list shows coarse pairs because the coordinate systems may not yet be optimally matched to each other. One of the coordinates systems is transformed by those optimum amounts to provide transformed position and direction data which are decided by the original position and direction data of the minutia pairs of the pair candidate list. A pair list (86) is formed by precisely selecting minutiae from the pair candidate list with reference to the transformed position and direction data and the original position and direction data given by the other principal coordinate system and to the relation data. On forming the pair list, an additional minutia list (81) is preferably formed which shows the transformed position and direction data and the last-mentioned original position and direction data together with the relation data.

Description

METHOD AND DEYICE FOR MATCHINC FINCERPRINTS WITH
PRECISE MINUTIA PAIRS SELECTED FROM COARSE PAIR~

ack~round of the Invention~
This invention relats~ to a method and a device for matching fingerprint~, The ~ord "fingerprint" iæ herein used as a repre~entatlve of a ~ingarpr~n~ or a like pattern or figure, More particularly, the fin~er~rint ~ay bo an actual finger, a palm print, a toe prlnt~ a soleprint, a squamou3 patter~, and a streaked pattern co~po~ed of str0~k~ The fingerprint ~ay al80 be a diagram dra~n by a skilled per~on to repre~ent a faint fingerprint r~main whlch 10 i8, for example, le M at a scene of crlm~, The "matching" i8 for recognition of a flngerprint ~th reference to a plurality of known fingerprints, The ~atching may also be for diseri~ination, collation, and/or identification of the f~ngerprintO
A f1n~erprint to be matched ~lth a known fingerprint, i8 usually called a Rsarch fingerprint. Ths known fingerprint is called a file fingerprint, Each fingerprint i~ featured by ridges and ~ore ~pecifically by minutlae.
It i~ con~entional o~ carrying out the fingerprint ~atching to select a coordinate system on each finge~print as Yill later be described ~ith reference to a few of ~bout forty figures of the accompanying dra~in~s, The coordinate system is u~d to repres~nt the position or locatlon Nhich each minutia has on the fingsrprint, Furthermore~ a dlrection i~ d~flned ~., 7~;~

together with the sense ln connection ~ith each minutia ~ith raference to the coordinate systa~ In addition to the position and direction data of 0ach minutia, a local feature char~cteristic to each mlnutia, is known which iB independent of the soordinate syste~. An example of quch local features i8 the differenco between types of minutiae. Other examples are "relation data"
which are repressntatiYs of relationships between e~ch ~inutia and adJacent minutiae. The relation data are substantially independent of the coordinate ~ystem as ~ill become clear as ths description proceed6 ~ith reference to the accompanying drawing. At any rate, the coordinate system will be called a principal coordinate system.
Fingerprint matchin~ has bs~n carried out by comparing the minutia position and direction data and relation data of a search fingerPrint with those of each file fingerprint. Inasmuch a~ the coordinate systems ar~ indipendently selected on the respective fin~erprint~, the position and direction data of a fin~ërprint must be transformed so as to be represented by a coordinate system which is in best ~atch with the coordinate sy~tem selected on the other fingerprint, The best match has been attained Hlth tlme ccn~uming procedures, E~en ~ikh the best match, the fingerprint matching has been unreliable ~ue to various circumstance3 under ~hich the fingerprints are prlnted, Thi~ has resulted in objectionable performsnce of a conYentional mothed of fingerprint ~atching and of a con~entional fingerprint matching device. Incidentally, the pos~tion and directiu~ data given aither by the principal coordinate syste~s or by a coordinate ~ystem into which at least 73~

one of the coordinate systems i~ transformed to provide a certain degree.of match, ~ill be called origlnal position and direction data ln contrast to transformed position and directlon data which are ~btained after ~pecific coordinat0 transformation, Summar~ of the Inventions It ~s an object of the present invention to provide a method of reliably matching a search fingerprint Hith each file fingerprint.
It is another object of this invention to provide a ~ethod of the typ~ described, which rapidly carrie~ out the matchingO
It is a further ob~ect of this invention to provide a fingerprint matching device for use ~n carrying out the method o~ the types described, A nethcd according to this invention is for deciding a degree o~ ~atch between a seaxch and a file fingerprint, A~
is ~ell known in the art, such a method lncludes the step~ of selecting principal coordinate system~ on the respective fingerprints~
selecting a search and a fils fingerprint area where minutiae are clear, forming a minutia list showi~g those original position and d~rection data of the l~inutiae and those relation data of the minutiae which are given by the respectiv0 principal coordinate syste~s and ~hich are substantially independPnt of the princip~l coordinate system3, respecti~ely, and ~electing pairs of minutiae fro~ the minutise of the respective fingerprint~ by Gomparing the originaI pasition and dlrectlon data given for the respective flngerprints and fllrthermore comparing the relat~on data given for the respecttve fingerprints.

73;2 The methcd according to thls inYention is characterlzed by the 6teps of forming a pair c~ndidate list ~h1ch shows the above-mentloned paira of minutiae as candidate p~ir~; re3pectiYely, declding those optimum amounts by referrlng to the original position ~~
and direction data of the minutiae of the pair candidates which are for matching the principal coordinate sy~tems with each other, transfor~ing the original position and direction data given by one of the principal coordinate systems for the minutiae of the pair candidates into tr3nsformed position and direction data given by ~ transfor~ed coordinate system into which the above-mentioned one principal coordinate system i8 transformed by the optimu~
amount~, forming a pair list by referring to the ~lnutia list, the pair candidate list, and the search and the file fingexprint areas, ~hich pair li~t shows pr~cise pairs of ~lnutiae selected from tho~e~inutiae of the pair candidates which are present in an area common to the ~earch:and the flle fingerprlnt areas ~herein the ~inutiae of each precise palr have a precise local ~i~ilarity bet~een the transformed pvsition and direction data and the original position and direction data given by the other principal coordinate system and between the relatlon data and which pair list furthermore shows evaluation~, each repre~entative of the local ~lmilarlty, and deciding the d~gree of match by using the minutiae of the precise palrs and by referring to the eYaluations .
A fingerprint matching devlce accordlng to this inventlo~
i5 for declding a degree of ~atch bet~een a ~earch and a file fingerprintO A convent~onal fingerpr~nt matching devlce includes minutla list meMory means for ~emorizing a minutla 11st showing ~,IEb~ g ~d those original position and direction data of minutiae which are given by principal coordinate systems prelminarily selected on the search and the file fingerprints, respectively, and those relation data of the minuti ae Nhich are substantially independent --of the principal coordinate systems, fingerprint area memory means for memorizing a search and a file fingerprint area Hhere the minutiae are clear9 and selecting means coupled to the minutia list memory means for selecting pairs of minutiae from the minutiae of the respective fingerprints by comparing the original po~ition and direction data given for the respecti~e fingerprints and furthermore comparing the relation data given for the respective fingerprints D
The fingerprint ~atching device according to this invention is characterized by pair candidate list memory means coupled to the selecting means for memoriæing a pair candidate list ~hich ~hows the a~ove-mentioned pairs of minutiae as pair candidates, respectively, optimum amount deciding mean6 coupled to the minutia list memory means and the pair candidate list memory means for deciding tho~e optimum amounts by referring to the orlginal position and direction data of the minutiae of the pair candidates which are for ~atching the principal coordinate syste~ ~ith each other~
coordinate transforming means coupled to the ~inutia 11st memory means, the pair candidate list memory means, and the optimu~

aMount decidin~ means for transforming one of the principal coordinate systems into a transformed coordinate system by the optimum amo~mts ~h~reby the original position and direction data given by that one principal coordinate system are transformed into transformed positlon and direction data, pair list momo~y ~eans coupl~d to 7~

the minutia list memory ~ans, ths pair candid~te 11st m~mory means, and the fingerprint area memory mean~ for memori~ing a pair li~t which sho~s precise pairs of ~inutiae selected from those minutias of the p~ir candidates which are present in an area common to the search and the file fingerprint areas wherein the minutiae o~ each precise pair have a precise local similar~ty between the transformed position and direction data and the original position and direction data given by ths other principal coordinate system and between the relation data, which pair list furthermore shows evaluations, each representative of the local similarity, and deciding means coupled to the pair list me~ory means for deciding the degree of ~atch by using the minutiae of the pair list and by referring to the evaluations D
Brief Lescription of the Dkawings Fig, 1 is a block diagram of a fingerprint matching system~
~ig. 2 i8 a block diagram of a fingerprint matching deYice for use in the system depicted in E'ig. 1 according to the instant inventionS
~ig~ 3 is a block diagram of another fingerprint matching device for use in the syste~ of Fig, 1, according to a ~ore prefPrred embodi~ent of this invention Fig, 4 diagrammatlcally shows a fingerprlnt5 Fig. 5 is a block diagram of a control unit used in either of ths devicas illustrated in Flgs, 2 and 3 ~ig, 6 is a block diagram of a leading matcher used in either of the deYi.css sho~n in Figs, 2 and 3l ~g73~:

Flg. 7 i~ a block diagram of a precise ~atcher used in either of the devlces depicted in Figs. 2 and 3~
Fig. 8, drawn below Fig. 5 merely for convenience of illustration, shows minutia data which are generally used in fingerprint ~atching~
Fig. 9 sho~s a flo~ chart for use ln descrlbing a fingerprint matching method accordlng to an embodiment of this invention~
~ ig. 10 shoNs an example of a minutia list which i6 usually used in a fingerprint matching method or device~
Fig, 11 sllows coordinate systems for use in describing coordl~ate transformation in general~
Fig. 12 shows a flow chart for use in describing general coordinate transformation;
Fi~. 13 1~ a block dia~ram of a coordinate transforming circuit Hhich i8 preferred for use in a fingerprint ~atchlng deYice according to an aspect of thl~ inventlon;
Fig. 14 shows another example of the minutia list;
Fig. 15 ls a block diagram of a proximate minutia recovery circuit for use in the leading matcher illustrated in ~lg. 6~
Fig. 16 (a), draw~ below Fig, 14, sho~s a leading part of a flow chart illustrative of operation of the proxi~ate minutia recovery circuit depicted in Fig. 15;
Fig. 16 (b) shows the remaining par$ of the flo~ chart Fig, 17 i~ a block diagram of a pair detection clrcuit for use in the leading matcher shown in Fig 6 Fig. 18 shows an example of the content of a minut1a list used in the pair detection circuit depicted in Fl~. 17;

973~

Fig, 19 i8 a block diagra~ of a relation linking unit for use in the pair detection circuit of Flg, 17~
Flg, 20 is a block diagram of a mlnutia list for u8e in the pair detecti~n circuit of Fig, 17~
Fig, 21 is a b}ock diagram of a pair detect~ng unit for use in the pair detection circuit of F1~7 17~
Fig, 22 is a block diagram of a part of a modification of the pair detecting unit depicted in FiB~ 21~
Fig~ 23 shows a coordlnate plane for use in describing additional xelation data;
Fig. 24 is a block dia~ram of a pair detectio~ c~rcuit in Hhich the additional relation data ara used~
Fig, 25 sho~s an example of the content of a co~posite minutia list used in the pair detection circuit illustrated in Fig. 24~
Fi~. 26 shows an example of a pair candidate list ~emory used in the leadin~ ~atcher illustrated in F~g. 6S
Fis. 27 is a block diagram of an adiustmen~ amount decidi~g circult for use in the leadinK matcher depicted in Fig.
6;
Fig. 28 shows a weight ~ap formed in the adjust~ent amount deciding circuit exemplified in Fig, 27~
~igo 29 shows a flow chart for US8 in describing operation of the ad~ustment amou~t deciding clrcuit of Fig~ 27~
Fig. 30, drawn below F~g. 28, sh~s a actor table which is auto~atically taken into consideratiG~ by the adjustment a~ount deciding circult shown in Fig, 27 ~9 373~

Fig. 31 shows another flo~ char~ f'or use in descrlbing the operation of the adjustment amount deciding circuit~
Fig, 32 show~ ~till another flo~ chart for use ln describing the oporation of the adjustment amount deciding circuitl Fig, 33 shows a set of 3eYeral minutiae of a search and a file fingerprint;
F~g. 34 is a sche~atic diagram of a pair list memory for use in the precise matcher illustraked in Fig~ 7~
Fig, 35 shows an example of the content of the pair l~st ~emory depicted in F~g~ 34~
Fig, 36 shows another set of` several ~inutiaeS
Fig. 37 show~ another example of the content of' the pair list memory;
Fig, 38 shows two ~inutiae of a ile fingerprint;
~ig. 39, dra~n belo~ Fig. 20~ sho~s exampl~s of ~inutia pairs;
Fig, 40 is a block diagram of a direction ~hecking-circuit for use in a precise matcher of the type exemplified in Fig, 7;
Fig. 41 exemplifies a search and a file fingerprint ar~a together with minutiae thareofj and Fig, 42 ls a block diagram of a destination deolding circuit for use in the control unit depicted in.~lg. 5, Description of the Preferred Embodiments~
(0~ C~neral Descriptlon Referring to Fi~. 1, a fingerprint ~atching system comprises four f`ingerprint ~atching devices 51a, 51b, 51c, and 51d which haYe a com~on struct~re according to the present inYention, '7~

The number of the devices 51's (the affixes a and others being omitted) need not necessarily be four, Only one deYice 51 may be used ln the systemO The Rystem furthar comprises a data input deYice 52, a data control and processing device 53, a data storing --deYice 54, and a matching control device 55, all of which ~ill later be described in detail.
Turning to Fig, 2, each fingerprint matching device 51 comp~es a leading matcher 56, a precise matcher 57, and a control unit 59, all of which ~ill presently be described in outline and later in greater detail.
As exemplified in Fig, 3, the fingerpri~t matching dev~ce 51 may comprise a plurality o~ leading ~atcher~ S6a, 56b, 56c, and 56d and a less number of precise matchers 57a and 5~b.
In either e~ent, the fingerprint matching device 5l is for dsclding a degree of match ~ bet~een a search and a file fingerprint by compar~ng data of the search fingerprint ~ith data of a great number of file fingerprints. One, i~ any, of the file flngerprint is selected, that gives a best match ~ith the search fingerprint as regards the degree of match ~. ~en a plurality of search fingerprints are given formatching, the device 51 repeats the comparlson. Merely for brevity of description, it ~ill be assumed that the de~ice 51 compares data o~ only one search fingerprint ~ith data of the fil2 fingerprints unuless otherwise stated~ The data of the search and the file flngerpri~t~
will be identified by affixes S and F, Referrlng to ~ig~ 4, each fingerprint is A -pattern or figure composed of r1dges exemplified by thin lines in an area depicted on an enlarged scale, Some of the ridges ha~e J~L~ ~r~

abrupt endingR, Rldges.that have or have not abrupt endings, may have bifurcation~ or branches. Furthermore, the ridges ~ay a singular polnt at Nhich the rldge i8 irregular a~, for exampla, very thick, The fingerprint may ha~e a cross point of two or --more ridges, The abrupt endings, the bifurcations, and 80 forth are called minutiae, The difference bet~een the abrupt ending~, the bifurcation~, and the like iR referred to as a difference betNeen types of ~inutiae or minutia types, The fingerprint generally includes an unclear area or region indicated by a hatched area in ~hich at least tha minutiae are not clear. It is possible to ~elect, as b~ excluding such unclear area or area~ from the fingerprint, a search and a file fingerprlnt area where the minutia~
are clear, In order to quantitatively deal with the minutiae, an X-Y co~rdinate syste~ i5 selected BO as to have an origin 0 at, for example, a lowest one of the abrupt endings of a leftmost ridge extending towards the pal~, The Y axis has the po~itive sense or direction towards the f1nBer tip, The coordinate system ~ill herein be callsd a princlpal coordinate system, Incidentally, it is po~sible in general to jud~e the direction of the finger tip from the directions ln which the ridge~ flow or trail~
~ he minutiae are con~ecutlYely numbered with reference to the coordinate system, The minutia number~ will be denoted by Mo~ ~ , M2, ~.~, Mi, a~ MJJ ,,,, and M~, ~hioh denotation ~ill be u~ed also to represant the minutiae, It i to b~ noted in thi~ connection that a natural numbar 1 n0ed not al~ays be greater than anoth0r natural nu~ber i but ~ay aither be equal to or le~s than the other natural number i~ The last number 73~

z usually differs from a fingerprint to another, For example, a search fingerprint has less than sixty-four minutiae in general, A flle fingerprint ~ay have nearly one hundred and ninty-two minutlae, --The typa of the i-th minutia Mi will be designated by Qi' Each minutia Mi has a position or location ~iven by coordinates (X~, Yi) of the principal coordinate system~ It is known in the art to define a direction with sense Di for eaeh abrupt ending or bifurcation Mi with reference to the principal coordinate system, As indicated by a short thick line, th~ directlon of an abrupt endlng is defined by the direction in ~hich the ridge extends from the abrupt ending, The dlrection of a bif~rcation is precisely defined in United States Patent No, 4,310,827 i3sued to Xoh Asai, one of the present applicants and assignor to the instant assignee.
A concentration or density Ci is defined for each minutia - M~ by the number of other minutlae ~hich are present in a prescribed area including the minutia Mi being taken into consideration.
The prescribed area is conveniently a circle having the center at the minutia Mi under consideration and a predetermined radius.
For the example aepicted on the enlarged scale, the concentration Ci is seven for the minutia Mi, An x-y local coordinate syste~ will be selected for each minutia Mi. The local coordinate system has a local orl~in ~5 at the mlnutia Mi. The ~ axis ha~ the positive sense in coincidence ~ith the minutia direction D~, The x-y coordin~te plans i8 di~ded into a predetermined number of sector~ ha~ing a common ~ertex at the minutia Mi, A proxi~ate minutia, if any, is selected a~Y~
O ~ht in each Rector For the example being illustrated, the sectors are the first through the fourth quadrants of the local coordinate system. Minutiae M1o, M~l, Mi2, and Mi3 are repreRentati~e of the proxlmate Minutlae in the first, the second, the fourth, --and the third quadrants, respectively, It should be noted that the dsuble suffixes iO through i3 are representative of pertinunt ones of 0 throueh the natural number z and that the suffix endings 0 through 3 are-:selected for the respectiYe quadrants so as to simplify the circuitry of the fingerprint matchin~ d~ice 51 ~Figs. 1 through 3) as ~ill later become clear, The proximate ~inutiae Mio through Mi3 will either singly or collectively be designated by Mir. As the case may be, the i-th minutia Mi used a~ the local origin, will be called a reference minutia in contrast to the proximate minutia or minutiae Mir.
~he numb~r of ridge~ that lie between a reference minutia Mi and each proximate minutia Mir, i~ herein named a rid~e count and denoted by Rir. The ridge count ~ir is what is called a relationship in the above-referencod Asai Patent and is different from the "rldge count" described in a reference cited ln the Asai Fatent, The illustrated minutia Mi has ridge counts Rio~
Ril~ Ri2, and Ri3 which are equal to 1, 2, 4, and 1, respectiYely, In some oases, the ridge count Rir may be zero, R0ferring now to Fig, 5~ the control unit 58 (Figs~

2 and 3) co~prise~ a buffor ~emory 61 which is loaded, as will bacome clear a5 the description proceeds, with data from the matching control unit 55 (Fig, 1) through a bus 62 and a de~ice interface circuit 63 and furthermore with ~ata from the precise ~atcher 57 or matchers 57's through a bus 64 a~d a ~atcher interfaco :~9g73~

circuit 65, The buffer memory 61 i~ controlled by a control circuit 66. A destination deciding circuit 67 i5 for deciding the destination of the data in the manner to be later described, Tbrning to Fig, 6, each leading matcher 56 (Fig, 2 or 3) comprises a sequence controller 69 connected9 a~ will later become clear, to a first minutia list memory ~1 directly and also through a coordinate transforming circuit 72, a pair candidate list memory 73, a working area 74, a control memory 75, a proximate minutia recovery circuit or relation calculating circuit 76, a pair detection circult 77, and a (coordinate) adjustment amount deciding circuit 78, As will soon become clear, the minutia list memory 71 eomprises search and file fingerprint me~ories 71S and 71F, The control memory 75 is preliminarily loaded with a microprogram (microeode) for use in controlling, among others, the adjuxt~ent amount deciding circuit 78 as ~ill later be de cribed in detail, ~urther turning to Fig, 7, each precise ~atcher 57 (Fig. ~ or 3) comprise~ a sequence controller 79 connected, like in the leading matcher 56, to a ~econd ~inutia list memory 81 directly and through a coordinate transformin~ cireu$t 82, a pair eandidate list ~e~ory 83, a Horking area 84, a control memory 85~ a pair list memory 86, a region pattern list me~ory 87, a candidate flngerprint list memory 88, and an arithmetic unit ~9 which is connected also to the working area 84, The Gontrsl me~ory 85 is for eontrolllng the arithmetic unit 890 A fingerprint ~atching de~ice 51 according to preferred embodiment3 of this invention, ~ill be de~cribed more in detail under the followlng subsection6 ,, (1) Read out of Minutia Data~
(2) Coordinate Transformation,

(3) Reco~ery of Proximate Minutiae,

(4) Pa~r Detection~ --

(5) ~odification~ of Pair Detection,

(6) Pair Candidate List,

(7) Amounts of Coordinate ~djustment,

(8) Precise Matcher,

(9) Fingerprint Matchin~, and~10) Destination Deciding Clrcult.
A closing paragraph ~ill be added to the description as an additional subsection (11).
(1) Read out of Minutia Data Referring.to Fig. 8, aata for each fingerprint are composed of identification or descripti~e data, a region pattern list, and a (first) minutia list, The identificatlon data of each file fingerprint consist of an ~dentification number ~iven to the file fingerprint, the name of the person who printed the fingerprint, male or female, the date of birth, ths name of finger9 the date and the locality of print, and the like. The identificati~n data of ~ach search fingerprint may comprise some of these, The region pattern and the m.inutia lists of a search fingerprint may be formed by the data input device 52 (Fig, 1) from the search fingerprint. The device revealed in the aboYe-cited Asai Patent is effective for this purpose. The ~dentlfication data and the region pattern and the m~nutia lists of a great number of fll~
fingerprints may preliminarily be stored in the data input device 52~ At any rate, the region pattern list gl~es the search and 732:

the file fingerprint area3 by the principal coordinate system, Th0 minutia list will shortly be described in detail.
Referring back to Flg. 1, data of the search finge~prlnt are transferred from the data input device 52 by the data control and processing device 53 to the data storing de~ice 54 and stored therein, Al~o, data of the file fingerprints..are successively stored in the data storing dev~ce 54 through the data control and processing device 53, On so transferring the data, the data control and processing deYice 53 may or may not edit the data, For e~ample, the data control and processing device 53 may keep the ~dentiflcation data excapt the identificatio~ numbers, which are sent to the data storing device 54 for storage therein, After storage of the data of the search and the file fingerprint~ in the data storing devic0 54, the data control and pro~essing de~ice 53 sends a command to the matching control device 55 through a bus to start the flngerprint matehing, Before eventually supplied from the matching control deYice 55 through the bus with a result slgnal ~hich repre~ents the success or ~ncuccas of the flngerprint matching, the data control and processing de~ice 53 is free to deal with other ~obs, such as transfer of the data of another search fingerprint from the data input device 52 to the data storing devlce 54. Incidentally, the result signal represents the degree of match g upon success of the fingerpxint matrhing and:at least the identiflcation number of the ~ile fingsrprint best matched with the search fingerprint.
Referring to Fig. 9 in addition to Figs. 1 through 6 and 8, a first step of the fingerprint matching is to read out the data of the search and the file fingerprinti from the data storing device 54 by the ~atching control device 55 in response to the command. At the outset, the data of the search fingerprint are read out and delivered to the fingerprint matching devicee 51's. In each fingerpirt matching device 51, the data of the search fingerprint are supplied to the leading matcher 56 (Fig.
2) or matchers 56's (Fig. 3) through the control unit 59 and a bus 90 (also ln Fig, 5) and stored in the search minutia list memory 71S of e~ery leading matcher 56 through the sequence controller 69.
Subsequently, the ~atching control devicc 55 deli~ers the data of one of the file fin~e:rprints to one of free l~ading matchers 56's of the fin~erprint matchlng devices 51's in the manner ~hich will later be exemplified in connection with the de~tination deciding circuit 67 (Fig~ 5)~ In the free one of the leading matchers 56's, the data are stored in the file minutia list memory 71F. I~ there are other freo leading matchers 56'5, the m3tching control device 55 feeds the data of other file flngerprints thereto, The fingerprint matching system comprising a plurality of finRerprint matchin~ devices 51's as exemplified in Fig, 1, ls therefore capable of substant~ally concurrently matching the data of a search fingerprint with the data of a plurality of file ~ingerprints. Operation will, ho~ever, bedescribed in the follo~ing as regards the data of only one file fingerprint unle~s other~se stated, Turning to Fig, 10, the first minutia list memory 71 (Fi~ 6, 71S or 71F) comprises a plurality of memory ~ections ha~ing ro~ addresses which can be specified by a row address signal indicative of a ~inutia number Mi at a time, Each memory sector has a plurality of memory fields having column addresses which can b~ indicated by a column address signal as will become clear as the descriptlon proceeds, Incidentally, the minutia memory 71 ~ay temporarily store the identification numbers and the region pattern lists o the search and the file fingerprints, According to one of the preferred embodiments of this invention, the memory fields of a memory sector accessible by the ~inutia number Mi, comprises a first field for the minutia type Qi' a second field for the positlon and the direction data Xi, Y1, and Di, a third field for the concentration Ci, and a fourth field for the ridge counts RiO.through Ri3 or Rir. In the first field an end mark is stored in the memory sector which next follows the memory sector for the last-nu~bered minutia M~, (2) Coordinate Transfor~ation Inasmuch as the search and thé file fingerprints are prlnted under different c-lrcumstances, it is necessary on matching the search fingerprint with the file finge~print to subject the minutia list of at least one of the search and the file fingerprints to a certain modification, By ~-ay of example, different first and second principal coordinate systems are used in general ~n describing the ~inutia positions and directlons of the search and the file fingerprints, respectively. The first (princlpal) coordlnate system must be subjected to for~ard (coordinate) transf`ormation to be a new principal coordinate syste~ that gives a best match w~th the second coordinate system and ~ill be referre~ to as a "centrall' 73~

coordinate system merely for convenience.of discriminationO
Incidentally, it is convenlent to subject the first coordinate system to the coordlnate transfor~ation rather than.the second coordinate system because of a generally much less number of the minutlae.
The region pattern list of the search fingerprint, however, need not be forwandly transformed as will later become clear, During comparison of the minutia lists between the search and the file fingerprints, the positlon data represented by the central coordinate ~yste~ ~ust therefore be subjected to back (coordinate) transformation for comparison ~ith the region pattern list.
As will soon become clear, such coordinate transformation is necessary in a great number of cases, Referrlng to Fig. 11, the princip~l coordinate system has a principal origin Op and principal X and Y axes Xp and Yp.
The central co~rdinate system has a central origin Oq and central X and Y axes Xq and Yq. It will be presumsd merely foor simplicity of descriptlon that each coordinate system is a right-hand orthogonal cooxdinate systam, The central origin Oq has coordinates (x, y) according to the principal coordinate systs~. The central X axis Xq i8 counterclockwise rotated by an angle of rotation 0 from the principal X axis Xp, In othex words, the forward transfor~ation i8 to translate the principal origin Op by translation components x and ~ and to rotate the princlpal coordinate pl~e by the angle of rotation 0.

3~

Central coordinates (xq, yq) of a point M are related to principal coordinates (xp, yp) of the point M by~
xq _ (xp - x)cos~ ~ (yp - y)sinP (1) and yq - (yp - y)cos~ - (xp ~ x)sin~. (2) Turning to Fig, 12, a first phase of the for~ard transforma-tion is to calculate ~alues cos~ and sin0 of the trigonometric or circular function. A second phase is to calculate first and second differences (xp - x) and (yp - y), A third phase is to calculate first and second products (xp - x)cos~ and (yp - y)sinp, A fourth phase is to calculate an ultimate su~ according to Equation (1), A fifth phase is to calculate third and fourth products (yp - y)cos~ and (xp - x)sin0. A sixth phase ls to calculate an ultimate difference in co~pliance ~ith Equation (2), It is possible to simultaneously carry out the third and the fifth phases and~also th~ fourth and the sixth phases, Incidentally, the bac~ward transformation i5 carried out in accordance with~
xp _ xqcos0 - y~sin~ ~ x (3) and yp - yqcos~ + xqsin~ ~ y, (4) The forward and the back~ard transformation has been carried out by the use of software, ~rhich is not suited to rapld processing, In particular, a complicated electronic digital computer is indispensable on carrying out the first phase and the third and the fifth phases.
Referrlng now to Fig, 13, an example of the coordinate transforming circuit 72 (Fig, 6) is for rapidly carrying out the for~ard and the backward transformation with simple circuitry, As ~ill later be described, a mode signal MOD .i8 supplled from ~973;2 the sequence controller G9. The mode signa~ MOD indicates the forward and the back~ard transformation by, for example, blnary zero and one, respectively, As will also be described in the follo~ing, X, Y, and D input terminals XI~ YI~ and DI are supplied at first ~ith initial data consisting of thc translatlon components x and ~ and the angle of rotatlon ~, When a latch pulse LAT iq supplied from the sequence controller 69, the initial data are stored in X, Y, and D registers 91, 92, and 93. me latch pulse LAT i5 500n switched off.
The angle of rotation 0 stored in the D re~ister 93 is dellvered to an ROM ~4 as an address signal and to a D adder-sub-tractor 95 ~or the purposc which ~ill shortly be described, Values of the trlgono~etric function are prelimlnarily store~
in the ROM 94 for various values o* the angle of rotation 0, Accessed by the addres~ signal, the ROM 94 produces the values cos~ and sin~ to carry o~t the first phase (~ig. 12), Incidentally, each angle 0 ~ay be gi~en a binary number having up to elght bits, Each value cos~ or sin0 may be represented by a binary number of ten bits.
On carrying out the forward transformation, the input term~nals XI, YI, and DI are supplied with the principal position data xp and yp and a princlpal direction datum dp from the minutia list memory 71 (Fig~ 6) ac ~ill soon be described, Responsive to the ~ode si~nal MOD indicative of the forward transfor~ation, first X and Y selectors 96 and 97 select the input data fed directly thereto fro~ the input terminals Xl ~d YI to deliver the principal coordinates xp and yp to fir3t ~ and Y adder-subtractors 98 and ~973Z

99, Controlled by the mode ~ign~l MOD, the adder-subtractors 98 and 99 calculate the flr~t and the second differences to carry out the ~econd phase, Controlled also by the mode signal MOD, ~econd X and Y seleetors 101 and 102 feed the differences to ---first and second multipllers 103 and 104, ~hich calculat~ th~
first and the second products to carry out the thlrd phase, The second X and Y selectors 101 and 102 furthermore deliYer the differences to thir~ and fourth multipliers 105 and 106, which calculate the thlrd and the fourth products accorhing to the fifth phase, R~spon~ive to the mole signal MOD, second X and Y adder-sub tractors 107 and 108 calculate the ulti~ate su~ and difference to carry out the fourth and the sixth phases, respectively~
Thi~d X and Y selectors 109 and 110 are controlled by the mo1e si~nal MO~ to ~eed the ultlmate su~ and difference to X and Y
output termlnals XO and YO a~ the central coordinates xq and - yq, The D adder-subtractor 95 calculates a differenc~ (dp - 0) and deliver the difference to a ~ output terminal Do as a central direction datum dp.
For the backward tran~formation, the mode si~nal MOD
i~ ~ade to lndlcate the sa~e. The input terminals XI~ Yx~ and DI are ~upplied at first with the initial data, whioh are ~tored ln the registers 91 through 93 by the latch pul~e LAT. It i~
poss~ble to make th~ regi~ters 91 throu~h 93 keep the lnitial data stored thereln before beglnning of the for~ard transformation.
At any rate, the input termi~al~ XI, YI, and DI are now supplied ~ith the central positlon and direction data xq, y , and d . Re~ponsive to the mode ~ignal ~OD lndlcative of 73~

the backward tran~formatlon, the second X and Y ~electors 101 and 102 selact the input data dcll~ered thereto directly from 'he X and Y input terminals XI and Y~ to feed the centr~l coordinates xq and yq to the fir~t and the second multipliers 103 and 104, rcspectively, and also to the third and the fourth Multipliers 105 and 106. The fi.rst and the second multipliers 103 and 104 calculate the prsduots used in Equation (3) and the thlrd and the fourth ~ultiplier~ 105 and 106, the products used in Equation ~4).
Respcnsive to the mode signal MOD, the second X and Y adder-subtractor~ 107 and 108 calculate a di~ference and a 6um of the productg according to Equations ~3) and (4), respectively, The fir6t X and Y selectors 96 and 97 now select the input data fed thereto from the second X and Y adder-subtractors 107 and 108 to deliver the differenca and the sum to the flrst X and Y add~r-subtractors 98 and 99, which calculats $he right-hand sidss of Equations (3) and (4), respectively, Controlled by the mode si~nal MOD~ the third X and Y selectors log and 110 selsct the input data supplied thereto from the first X and Y adder-subtractors 98 and 99 to deliver the principal coordinates xp and yp to the X and the Y output terminals XO and YO, The D adder-subtractor 95 ~um~ the central direction datum d~ and the angle of rotation P to fead the principal direction datum dp to the D output t~rminal Do~
?5 It may be helpful depending on the circumstances to refer to the central coordinate ~ystem again as a first principal coordinate system, As wlll become clear as the descrlption proc~eds, the coordinate transforming circuit being illustarted, is capable '73~

of carrying out forward and back~ard transformation bet~een the principal coordinate sy~tem and a local coordinate system, When used in the leadin~ matcher 56 (Fig, 6), the coordinate transforming circuit 72 need not carry out the backward transformatlon~ On --the other hand, the coordinate transformation circuit ~2 (Fig, 7) need not carry out the forward transfoxm~tion. The coordinate transforming circuits 72 and 82 therefore need not comprise the selectors 96, 97, 101, 10~, 109, and 110~ The sequence controllers 69 and 79 need not produce the mode signal ~OD, The circuitry illustrated with reference to Fig, 13 i8 useful when n single ~inutia li t memory is used in place of the fir~t and the second minutia memories 71 and 81 in storing the minutia list referred to herelnabove as the first minutia list. Use of the fir~t and the second minutia list memories 71 and 81 is preferred becausa provision of the leading and the precise matcher~ 56 and 57 is thereby enabled and because the seccnd minutia list ~emory 81 need not have a large memor~ capicity as ~ill later become clear.
(3) Recovery of Proximate Minutiae Referring to Fig. 14, a memory sector for the i-th 2Q minutia Mi ln the search and the file minutia list me~ories 71S
and 71F of the ~irst minutia list ~emory 71 (Fig, 6) may comprise fir~k through eighth fields accessible by the column address signal, The fi~th through the eighth fields are for storing the proximate minutia numbers M~r, namely, the num~ers given to the proximate minutiae Mir, Reco~ery of the proxlmate minutiae Mir is unnecessary in this e~ent. The recovery is neces~a~y as shown at a second ~tep A2 ln Fig, 9 when the minutla list memory 71 is loaded ~ith the minutia li8t in compllance with Figo 10 in order to reduce the memory cap~citie~ of variou3 memories used in the fingerprint matching ~ysta~ (Fig. 1).
5peaking more ln general, lt is nece~sary on matching two fingerprints to compare a local feature o~ a minutia M~S ---of the search fingerprint with a corresponding local feature of a minutla MjF of the file fingerprint. me local features should preferably be independent of selection of the principal coordinate systems for the respecti~e finger~rints, Example~
of such local features are the minutia types ~ S and Q~F and the concentrationR Cis and Cj~, On defining the concentration, it i~ possible to use instead of a single prescribed area a plurality o~ prescribed areas for each reference minutia, such as the sector~
described heretobefoer in connection ~ith ths ri~ge counts Rir The ridge counts RirS and RjrF are al80 useful as the local featurei Discussion ~ill, ho~e~er, later be given to the ridge count~ R1r~
It has now been confirmed that a~other local f0atura ls effective on carrying out the comparieon. Thc other local feature is a distance between the reference minutia M~ and each proxi~ate minutia Mir, More ~pecifically, the distance is conveniently calculated by the use of the local coo~dinate system de~cribed in conjunction ~ith Fig, 4~ The distance~ for correspondine proximate minutiae, such as MioS and M~oF~ are used ln avaluatlng a loc&l similarity between the minutiae MiS and MJF under considerationO ~hen a di-fference bet~een such distances is less than a predetermined threshold, the local similarity batween the minutlaa Mi~ and MjF is glYen a mark 1 If the ~ifference3 for the respectiYe 9~32 2~

proximate minutlae Mir in four quadrants are ali less than the threshold, the local similarity is given a full mark 4, As thu~ far been describsd, the rldge counts, the concentra-tlon or concentrations, the differences, and/or the llke are calculated for each minutia with reference to a local coordinate system having a local origin at the minutia under considerat~on, These data will be referred to as xelation data, which are substantial-ly independent of the principal coordinate syste~ and are helpful in foundi~g a local ~imilarity between a reference minutla of th~ search fingerprint and a reference minutia in the file fingerprint, Calculation or evaluation of the local similarity will be called relation evaluation. The relation evaluation must be carried out rapidly and yet with a high rellability because each search finger~rint must be co~pared wikh an enormous number of file fingerprint3, The relatlon evaluation is also used in recovery of the proximats minutiae.
Referring to Figs. 15 and 16, an example of the proxi~ate minutia recovery circuit 76 (Fig. 6) comprises a local controller 111 operabls according to a microprogram stored thereln. Start of the dlstance calculation is indicated by a start si~nal ST~T
from the sequence controller 69 as shown at a zercth step Bo (Fig. 16).
In compliance with the microprogram, the local controller 111 set3 an initlal value of ~ero in each o~ first and second fields A and B of a first address register 112 at a ~irst Rtep Bl~ The address register 112 i~ for producing a composite address signal AD for specifying the row and the column addresses in one of the search and the file minutia list memories 71S and 3~

71F at a time that may be selected by a read slgnal R according to the microprogram, Incidentally, a ~econd address regi3ter 113 is fox si~llarly accessing the same minutia list memory 71 (71S or 71F) by a like address signal, de~ignat~d also by AD, and has flrst and second fields which will bs denoted by E and F, The first fields A and E are for producing ths row address signals representative of the minutia numbers ~i and Mj. The second fi~lds B and F are for likewise produceng the column address signals for either the same field or different fields, When zero is set in the second fields ~ and ~ and moreover when the i-th minutia Mi is concurrently specified by the row address signals produced from the first flelds A and E, the minutla list memory ~1 produces the minutia type ~ from the first field, It will now be assumed that the address signals AD are for the search minutia list memory 71S and that the zero column address signal accesse~ also the ~e~ond fleld, As indicated at a second step B2, the controller 111 makes the first address register 112 produce the address signal AD, The minutia type ~ S thereby read out, is set i~ a Q field of a parameter register 114. The other data XOs, Yo$~ and DoS
are delivered to the X! Y, and D register~ 91 through 93 (Fig, 13), Immediately thereafter, the sequence controller 69 is made to produce the latch pulse LAT (Fig. 13~ and the mode slgnal MOD indicative of the for~ard transfoxmation, ~he positlon data XO and YO (the su~f`ix S being omitted for a short Nhile~ provlde the translation components x and ~ described in connection wlth Fig. 13, The directlon datum Do provides the angle of rotation ~.

73;2 Inasmuch as the mode signal MOD in uncecessary for the coordinate transforming circuit 72 (Fig, 6), the latch pulse LAT is produced by the local controller }11 rather than by the sequence controller 69 ln the example being illustrated, It Hill now be surmised for brevity of descrlption that the position and the direction data Xi, Yi, and Di are read from the search mlnutia list me~ory 71S, At a third step B3, the controller 111 checks whether or not the minutia type Qi stored in the Q field is the end m~rk, If not, the..controller 111 set~ the initial Yalue of zero in each of the fi~lds E and F of the second address register 113 and another initial value of one in each of address fields Mo~
Ml, M2, and M3 and distance fields Do~ Dl, D2, and D3 of a register fiie 115 as shown at a fourth step B4, The correspondingly numbered address and distance fields, such as Mo and Do~ are t~o fields of a partial re~ister of the register flle 115, As ~ill pre~ently become clear, the addres~ field~ Mr are eventually loaded with the proximate minutia nu~bers Mir which are present in the first, the second, the fourth, and the third quandrants for the 1-th minutia Mi being dealt with and used a~ the reference minutia, The initial value of one set in the address fields Mr and in the distance field6 Dr indlcate that there ~s no proximate minutiae ln the respecti~e quadrants and that the distance between the reference minutia Mi and a minutls in the correspondlng quadrant is infinitely long.
As sho~ at a fifth step B5, the controller 111 m~kes the second address register 113 produce the address sl~nal6 AD
representative of the contents of the fields E and F, The roN

addres~ thereby specified, is for the 3eroth mi~utia Mo~ It will, however, be presumed like for the address signal AD produced from the flrst address register 112 that the row address for the j-th ~inutia ~ i~ indicated by the roH address signal producqd ---by the first field E of the second addre~s register 113, The Q field of the parameter register 114 is rowritten into the minutia type Qj. The other data Xj, Yj, and Dj are ~upplled to the X, Y, and ~ adder-subtractors 98, 99, and 95 (Fig, 13) as the principal data xp, yp~ and dp~ At a sixth step B6, the for~ard transfor~atlon is automatically carried out.
The local (coordinate) data xq, yq, and dq are ~tored in X, Y, and D field~ of the parameter register 114 at a seventh step B7, ~ne local position data xq and yq retained ln the X
and Y fields of the parameter register 114 are deli~ered to X
and Y square calculators 116 and 117, respectively, Squares thereby calculated, are fed to an adder 118, The square of the distanc~
between the i-th minutia Mi under consideration and the j th mlnutia M; being selected, is supplied to one of tHo input ports of a comparator 119.
In the meantime, a permutatlon of the si~n bits of the local position data yq and xq stored in the y and X fields of the parameter register 114, is delivered towards a selector 121 to repressnt a twG-digit binary number. The binary number lndicates that the j-th minutia Mj is present ln one of the quadrant~
that is decided a3 follows, If the binary number is 00 or decimal 0, the j-th minut~a Mj is in the first quadrant, If the binary number 15 equal to 01, 11, and 10, namely, decimal 1, 3, and 3o 2, the j-th minutia Mj iB in the second through the fourth quadrants, respectively.
Unless the minutia type Q~ kept in the Q field of the parameter register 114 shows the end mark, the controller 111 ~.
sends a selection signal to the selector 121 to make the same supply the sign bit permunation to the register file 115 as an address signal for accessing the partial re~lster having the address field Mr that is allotted to the quadrant indicated by the sign bit permutation. The content of tha distance field Dr of the accessed partial register is supplied to the other input poxt o the compaxator 119.
As collecti~ely shown at an eighth step B8, the comparator 115~ compares the sum (Xq2 ~ yq2) ~ith the distance D(sign[yq], signtXq]) read out of the distance fleld Dr of the accessed partial registerO If the former i~ 1CRS than the latter, the j-th minutae Mj iB nearer to the i-th ~inutla Mi than another minutia ~h~ch is previously dealt ~ith to provide the distance being read out, The comparator 119 informs the controller 111 of the fact by, for example, a binary one signal.
MeanHhile, contents of the first fields A and E o the address register6 112 and 11~ are supplied to a coincidence detector 122. When the contents are the same, the coincidence detector 112 produces a coincidence ~ignal of lo~ic one~ That i8~ the logic one coi~cidence signal i~ produced Nhen the ~-th minutia Mj is not different from the i-th minutia Ml. The coincldence signal is fsd to an inhibit port of an inhibit gate 123 to inhibit the binary one signal delivered thexeto from the comparator 1190 In the ~eanwhile, the content of the first field E
of the second addr0s3 register 113 is delivered to the addre~s fields Mr of the register file 115, Furthermore, the Ru~ calculated by the adder 119 is supplled toward3 the distance field3 Dr~
When the coincidence signal is logic ~ero to indicate that the j-th minutia Mj i8 different from the i-th minutia Mi and consequent-ly in one of the quadrantR except the local origln Mi~ the inhibit gate 123 suppl~es the binary one signal to the register file 115 ~ a ~rite-in signal. At a ninth step B9, the content~ of the addre~s and the distance field~ Mr and Dr of one of the partisl registers that is accessed by the ~ign bit per~utation supplied thereto through the selector 121, are renewed ts the co~tent of the first field E o the second address register 113 (the m~nutia number of the j-th minutla Mj) and to the sum (square f tha di~ance betHeen the mlnutiae Mi and M~), ~ ither lf the sum i8 not la8s than the previously calculated su~ or if the j-th minutia M; is in fact the i-th minutia Mi, the eighth ~tep B8 jumps to a tenth step Blo where the controller 111 makes ~ on~-adder 124 add one to the cont~nt of the E field of tha second addres~ register 113. When the sum is less than the previously calculated su~ and ~uxthermore ~hen the j-th minutia ~ is diferant from the i-th minutia Mi, the above-described ninth step B9 ~s followed by the tenth st~p Blo, The contents of the register file 115 are thus renew~d whenever a nearer ~lnuti~
is found in a certain one of the quadrants, By so repeating elthsr thc steps B5 throu~h ~lG or the steps B5 through B8 and Blo ~ith the ninth ~tep B9 skipped, the controller 111 rene~ the content~ oE the register flle 115, 73;~

Recovery of tha proximate minutlae Mir for the i-th minutia Mi ends when the end mark is eventually detected at the seventh step B7, At thi~ instant, the proximate minutia nu~bern Mir are kept in the respectlve address fields Mr, If no proximate mlnutia is found in a certain one of the quadrant~, the lnltlal value of one is held in the address field Mr allotted to that quadrant.
The process no~ proceed~ to transfor of the prox.tmate minutiae Mir of the i-th minutia Mi, In the exa~ple being illustrated, the transfer is carried out to that ono of the search and the file minutia list memorie~ 71 (~lS and 71F) from which the l-th ~inutia Mi is read. As a re~ult of the transfer, conten~s of the memory sector for tha i-th minutia Mi are changed from those exemplified in Fig. 10 to those exempllfied in Fig, 14, 1$ It ~ill now be a~sumed merely for convenience of description that the column addres~ of the fifth field (Fig. 14) for the minutia number Mio is declmal 4 or binary 100, At an eleventh st0p Bll, the local controller 111 initiali~es the content of the second field B of the first address re~i~ter 112 to 4, Two consecutive les6 significant bit~ of the ~econd field B are 3upplied to the selector 121, ~hich are now OQ out of the b1nary 100 and correspond to the addres~ cignal u~ed in acce66ing the partial register (Mo and ~) a~signed in the register file 115 to th~

first quadrant, As a part of tho comp~ite address ~ignal AD, 23 the second ~ield B produces the column addres~ signal for th~
fifth field, ~he row addres~ signal proluced from the first field A as another part of the address signal ~D, still spacifies the xow ~ddress for the i-th minutia Mi ln the minutla list mamoxy 73~

71 ln question, Concurrently wlth the eleventh step Bll, the controller 111 ~ake3 the selector 121 select the two les~ significant blts, The register file 115 produce~ the content of the accessed . .
address field Mo a~ a data signal WD9 ~hich is delivered towards the minutia list memory 71 under consideration. The con-Lroller 111 supplies a write-in signal ~ to the minutia list me~ory ~1, Ths:minuti~ number Mio i~ therefore pertinently written in the minutia lisb memory 71 at a twelfth step B12, . At a thi~teenth step B13, the controller 111 make~
the ona-adder 124 add one to the content of the second field B~ The content ~pecifie~ the column addre~s for the proxim~
minutia Mil, The two les~ significant bit~ designates the second quadrant, At a fourteenth 6tep B14, the controllex 111 check~
the content of the second field ~ whether or not overflo~ re~ult~
from the addition of one to render the content equal to dec1mal 0. If not, the proce~s returns from the fourteenth step B14 to the t~relfth step B12, Repeating the steps B12 through B14, the controller 111 transfer~ the proximate minutia numbers Mir to the minutia list memory 71 being dealt with~ When the overflow i detected~
at the fourteenth step ~14~ the controller 111 makes the one-adder 124 add one to the content of the fir~t field A at a fifteenth step B15~ The rvw addres~ or the ~ th minuti2 is now ~pecified, The pxoceAs return~ from the M fteenth step B15 to the second step ~2' In this manner, the proximate minutlae, if any, are recovered su~cessively for the minutiae Mo~ Ml, ,,., M1, ....
and M~ and stored in the minutia li~t ~emory 71 in questlon.
After the proximate minutia number M~3 ls eventually stored in the minutia li~t memory 71, the content of the first field A
of the first address register 112 becomes equal to (z t 1) at the fifteenth step B15. The end mark is now stored in the Q
field of the parameter register 114. When the controller lll detects the end ~ark at th~ third ~tep B3, the recovery of the proximate minutiae comes to an end as shown at a sixteenth step B16 ~
(4) Pair Detection For each minutia Mi~ the minutia type ~, the position and the directlon data Xi, YI, and Di, and the like ~ill now be called minutia data of ths minutia Mi. The pr~xlmate minutia numbers Mir and the ridge count~ Rir will be named fundamental relation aata of the minutia Ml. The minutia data and the fundamental relation data will collectively be called overall minutia data of the minutia Mi. A link or combination of the position and the direction data xir, Yir- and dir of the proxlmate minutiae Mir aa regards the local coordinate system for the minutia ~i used as the reference minutla, and the ridge count~ Rir will now be referred to a~ relation link data of the reference minutla Mi, The minutia data and the relation link data ~ill collectively be called overall relation link data of the reference ~inutia Mi. For each fingerprint, a set of the overall minutia data or the overall relation link data of all minutiae will now be called fingerprlnt data of that fingerprint.

7~
~V~

On matching a search fin~erprint with each file fingerprlnt, it i~ important to find a palr of minutia of the search fingerprint and a minutia of the file fingerprint, On finding 3uch pairs, it is already known to use the overall relation link data for each combination of a minutia of the search fingerprint and a minutla of the file fingerprint, The memory for storing the fingerprint ~ata of the 6sarch and the file flngerprints, therefore must ha~e a large memory capacity. This has rendered the conventi~nal fingerprint matching devlce bulky and expensive, lQ It should be noted in this connection that a plurality of minutiae may be found at first in one of the search and the file fingerprints as pairs of a minutia of the other fingerprint at a third step A3 depicted ln Fig, 9. The pair~ are later process~d as regards the detail into a single pair, Such "pairs" will also be ca~led a "pair" for the time being, At any ratc, it is not mandatory according to this invention to care fQr Ruch a plurality of pairs, Each of the position and the direction data Xi, Yi, and Di may therefore be gi~en for the palr detection by a relati~ely coarse or wide quantization step as, for example, by only four consecutive more significant bits of each data Xi, Yi, or Di.
Referring to Fi~. 17, an example of the pair detection circuit 77 (Fig, 6) is effecti~e in rendering the fingerprint matching deYice 51 (Fig~ 1) compact and inexpensive, The illustrated pair detection circuit 77 comprises a relation linking unit 126, a minutia memory 127, and a pair detecting unit 128 as will be de~cribed in the following.

Turnlng to Flg, 18, the minutia memory 127 may store, as ~ill shortly be described in detail, the overall relation (link) data for the search fingerprint and one file fin~erprint.
In a memory section (to be later described) accesslble by a row ~--address Rienal indicative of a reference minutia M~, the minutia data Qi~ Ci, Xi, Yi, and Di are stored in successive columng..
Furthermore, the relation link da-ta Rio, xiO, Yio- dio, Ril, x~ di2' Ri3- xi3~ Yi3, and di3 are stored in successive columns, It will therefore be assumed that the minutia 11st memory 71 (Fig, 6, 71S or 71F~ is for storing, for sach minutia Mi, the minutia data and the fundamental relation data i~ the order of Qi' Ci' ~i' Yi~ Di~ Rio~ Mio~ Ril' ~1' i2 i3 and Mi3, rather than in the order exempllfied in Fig. 14, I'he local position and direction data xir, Yir~ and dir may~ Yor storage in~the minutia me~ory 127, be given by the coarse quanti~tion ~tep. ~hen no proxi~ate minutia iS fo~nd in a quadrant r, a specific code is stored in place of the ridge count ~ir for the proximate minutia Mir~
neferring to Fig. 1~, the relation linkine unit 126 (Fig. 17) comprises a central controller 1~9 put into operation by the sequence controller ~ (Fig. 6) after completion of recoYery of proximate ~inutiae for the ~earch fingerprint, The oontroller 129 sends a first addre~s signal 131 ~also in Figo 17~ to the search minutia list memory ?lS of the minutia list ~emory 71, An input data signal 132 ~also in Fig, 17) is ~ent back to the relation linkin~ unit 126, When the add~e s signal 131 indlcates the i th minutia M~S as ~ill pre~ently be de~cribed, th2 data signal 132 represents the overall minutia data, namely, the minutia 3~

QiS' iS~ Xis, YiS, and DiS and the funda~ental relation t ~iO~' MiOS' ~ilS' ~ Ri3s- and Mi3s, It is pos6ible to make the address signal 131 give the positlon and the directlon data Xis, YiS~ and DiS by the coarse quantization step, ...
The fundamental relatlon data are fed towards a shift register 134, The positlon and the direction data Xis, YiS, and DiS are supplied towards-X, Y, and D registers 135X, 135Y, and 135D, At least the minutia type Qi~ is supplied to the controller 129, The controller 129 produces a latch pul~e ~AT to store the fundamental relation data ln the shift register 134 and the position and the directlon data in the registers 135'-~, An output data signal 136 (also in Fig, 17) supplied towards the minutia memor~ 127, represents the minutia data and then other data which will later be described, ~le controller 129 check9 whether or not the minutia type Q~ (the suffix S being omltted for a short while) represents in fact a minutia type, Having confirmed, the controller 129 supplies th3 minutia memory 127 with a second address signal 137 indicative of a row address for the i-th minutia Ml and a column addreæs for the minutia data and sends a direotive signal DIR to the shi~t register 134 to make the same supply the foremost proximate minutia number M~o back to the controller 129~ which makes the ~irst address ~ignal 131 ind~cate the proximat~ minutia number Mio instead of the i-th minutia n~mber Mi, The shlft register 134 furthermore produces the ridge count Rio as the output data signal 136.
The input data ~ignal 132 now represents the ov~rall minutia data for the iO-th minutia Mio, The controller 129 makes 73~

the second address signal 137 indicate the ro~ address for the 1-th mlnutla Mi and the colu~n address for the rldge count Rio and the positlon and the directlon data xiO, Ylo~ and dio whlch the pro~imate ~inutia Mio of the flrst quadrant has relatlve to the i-th ~lnutia Mi used as the reference minutla, Among the overall minutia data of the iO-th ~inutia Mlo, the position and the directlon data X10, Yio~ and Dio are supplied dlrectly to X, Y, and D subtractors 138X, 138Y, and 138D which are also supplied with the contents of the registers 135's, The subtractors 13~'s calculate X, Y, and D differences ( iO i)~ (Yio Yi), and (Dio - Di), The content.of the D
regiRter 135D is supplled also to an ROM 139, slmllar to the RQM 94 (Fig, 13), for producing values cosD~ and sinDi, The ROM 139 may, however, be simpler than the R~M 94 because each value cosDi or sinD~ may haYe a les~ number of bits, The X ~nd the Y diferences are supplied to fir6t and second multipliers 141 and 142, respectively, to which the ~alue cosDi is supplied in common. The dlfferences are supplied also to thlrd and fourth multipliers 143 and 144, to which the value sinDl is supplied in co~on. First and second product3 are delivered to an adder 146 and a subtractor 147, respectively, Third and fourth products are fed to the adder 146 and the subtractor 147, respecti~ely, It ls now understool that the ele~ents 135 ' S, 13~B~ 139, 141 through 144, 146, and 147 are for carrying out the forward transformation of the principal coordinate system for the search fingerprint to a local coordlnate system for the i-th ~inutia Mio The adder 146, th~ su~tractor 147, and the D sllbtractor 138D are for ~æking the output data signal 136 include 73;~

the position and the direction data xiO. Yio- and dio ~hich the proximate mlnutia Mio has in the local coordlnate system, Thereafter, the controller 129 again produceR the directi~e signal DIR to make the ~hift register 134 send the next following ---proximate minutia number Mil back to the controlle~ 129 and the ridge count Ril as a part of the output data signal 136, The second address signal 13~ is now made to represent the row address for the i-th ~inutia Mi and the column address for the ridge count Rll and the position and the direction data xil, Yil~ and dll, The input data signal 132 supplies the position and the direction data Xil, Yil, and Dil of the il-th minutia Mil to the ~ubtractors 138'~, The coordinate transformation is again carried out to make the output data signal 136 include the position and the direction data xil, Yil- and dil The proce~ses described aboYe ln connection Hith the proxi~ate minutiae ~iO and M~l are repeated for the other proximate minutiae Mi2 and Mi3 to complete the relation linking operation for the i-th minutia Mi. When the processes are carried out for the last mi.nutia M~ of the search fingerprint, the controller 129 ~upplies the minutia memory 127 (Fig, 17) with a transfer signal 149 for the purpose which will shortly be described.
rrhe relation linking unit 126 subsequently repeats the relatio~
linklng operation as regards the minutiae Mo through M~ of the file fingexprint (the ~ufflx z u~ed for the flle flngerprint being generally greater than the suffix ~ for the search fingerprint as pointed out heretobe~ore), Turning to Fig, 20~ the minutia memory 127 (Fig, 17) compri~es first and second buffer memorles 151 and 152, aach ~9 ~, ~73;2 haYing me~ory sectors accessible by the second address signal 137 indicative of the reference minutia numbers, such as Ml, Each memory sector ha~ fields having column addresses acces~ed also by the second address signal 137, --Each of search and file minutia memories 153 and 154 also has memory sectors accessible by the address signal 137 to store the o~erall rslation data as exemplified in Fig, 18~
As descrlbed heretobefore, the output data signal 136 produced by the relation linking unit 12S for the i-th minutia Mi~ represents at first the minutla data of the minutla Mi~
Later, the data signal 146 repeatedly produced for each proxi~ate minutia Mir of the i-th minutia Mi, represents the ridge count ~ir bet~een the i-th and the ir-th pxoximate minutiae ~i and Mir and al50 the position and the direction data x~r, y~, and dir of the.proximate minutia Mir a regerds the local coordinate system defined for the i-th minutia Mi, The data represented by the output data signal 136 are successively ~tored b~ the second address sig~al 137 in the respecti~e fields of the ~emory sector for the i-th minutia Mi in one of the first and the second buffer memoriea 151 and.. ~52 that is rendered emptly as will presently become clear~ Merely for clarlty of description, let the fixst buffer ~emory 151 be empty for the time being, The overall relation data obtained for the minutlae Mo through M~ of the search 1ngerprint7 are thus stored in the fir~t buffer memory 151 At this lnstant, the central controller 129 (Fig 193 produce~ the tran~fer s1gnal 149 as described before, The tran~fer ~ignal 149 is for mo~ing the o~erall relatio~ data ~rom the irst buffer mamol~ 151 to ~9732 ~1 the search minutia memory 153, The first buffer me~ory 151 i~
thus rendered empty.
During transfer of the overall relatlon data for the search fingerprint by the transfer signal 149 and the second --address signal 137~ the relation linking unit 126 successively produces the overall relation data for the file fingerprint, According to the assumption described above, the 6econd buf~er memory 152 i3 rendered e~pty already before:beginninK of the relation linkin~ operation for the file fln~erprint. The overall relation data are therefore stored in the 6econd buffer memory 152, me transfer signal 149 produced subsequent to completion of the relatlon:linking operation for the file fingerprint, i8 for ~oving the overall relat~on data from the ~econd buf~er memory 152 to the file ~inutia memory 154 and for eventually rendering the::~econd~buffer ~emory 152 empty, As described before, a great number of file fingerprints must be checked for each search fingerpr~nt. While the o~erall re}ation data are moved from the second buffer me~ory 152 to the file minutia me~ory 154, the relation linking operation is carried out for a second one of the file flngerprints, The o~er~ll relation data for the second file flngerprint are stored 1n the first buffer memory 151, A~ will later be described, the overall relation data pre~iously stored in the file mlnutia Memory 154 are successlYely supplied to the pair detecting unit 128 (Fig. 27). The file ~inutia ~emory 154 i thereby rendered empty. The o~erall relation data for the second f~ le fingerprint are therefore moved fro~
the fir~t buffer me~ory 151 to the file minutia memory 154 by the transfer signal 149.
It is now understood that the transfer signal 149 is for the search i~inutia ~emioxy 153 at flrst and then repeatedly for the flle minutia ~emory 154. In thi~ manner, the first and the ~econd buffer memories 151 and 152 are alternatingly used in loading the file mii~utia memory 154 with the overall relation data of the suGcessive ones of the $ile fingerprints. Mean~hila, the search minutia memory 153 keeps the overall r~lation data for each search fingPrprint. After the o~e~all relation data of all flle flngerprints are used by the pair detecting unit 128, it i8 possible to use the search minutia memory 153 for the overall relation data of another ~earch fingerprint, Referring to Fig. 21, an example of the palr detecting unit 128 (Fig~ 17) comprLses a local controller 159. Each time ~hen the f~le ~ingerprint data (overall relation data of Oile flle fingerprint) are stored in the fils minu~ia mei~ory 153 (Fig, 20) ~ith the search fingerprint data kept in the ~earch miinutia memory 153, the central controllcr 129 (Flg. 19) prcduces a command signal 161 (also in Fig~ 17), Supplied wlth the coi~and ~nal 161, the looal contrallsr 159 deli~ers an address signal 162 (also in F~gs, 17 and 20) to the search and the fi~e miinutia memories 153 and 154, The controller 159 furthermore sends a selection signal SEL to a th~rshold ganerator 163, In ~ach of the m$nutia mei~ories 153 and 154, the address ~ignal 162 accesses at first the memory ~ector for the zeroth mlnutia Mo~ In each memory secto~, the address signal 162 specifies the column addres~ for the minu-tia data at first and then successi~ely the column addre~ses for the re~pecti~e proximate minutiae~

Thereafter, the address ~ignal 162 similarly acce~ses the memory sector~ for the succe3sive flle (fingerprint) minutiae whlle accessin~ the zeroth search minutia Mo~ Subsequently, the addres~
signal 162 likewise accesses the next search mlnutia and the --suocessive file minutiae, Let lt now be assumed that the addres signal 162 acces3es the i-th search mi~utia MiS and the j-th fil~ minutia MjF, The minutia numbers MiS and Hj~ are retained ~n the controller 159 for the purpose which ~ ter become c10aro While each colu~n address for the minutia data i~ speciied by the address signal 162, the selection signal SEL make~ the threshold generator 163 produce coar~e thresholdR T~, Tx, Ty~
and TD ~hich will presently become clear, While the column addre~
for each proxlmate minutia is specifled, the selection xignal SEL makes the threshold generator 163 produce other coar~e thresholds r' x' y' d Resp~nsive to the addresx ~ignal 162, the ~earch and the file minutla memories 153 a~d 154 supply data xienals 164 and 165 (also in Figs, 17 and 20) to R, X! Y, and D subtractor~
166~, 166X, 166Y, and 166D, each being for calculating the ab~olute value of a difference betwsen the data represented by the data signals 164 and 165, The absolute values are delivered to R, X, Y, and D comparators 167R, 167X, 167Y, and 167D for comparing the absolut~ values with the respective (coarxe~ threshold& as H111 be dexcribed in the following, At the out3et, the R subtractor 166R is for the concentrations C~S and CjF, The other subtracto~s I66's are for the posltlon and the direction data of the ~earch and the fil~ mlnutiae~

732~
aL .

The comparator~ 1671.~ supply an AND circuit 168 ~ith logic one signals if~

iS ~ CjFI ~ TG' ¦Xis ~ XjF¦ ~ Tx, .IYiS Yj~l - Ty~
and ¦DiS ~ DJF¦ ~ TD-The AND circuit 168 sends an output signal to the controller 159 only ~hen the logic one signals are sppplied thereto from a}l co~parator~ 167'~, Responsive to -the output ~ignal, the controller 159 send~ ~ directive signal DIR to rsst first and second counters 171 and 172 to zero, Furthermore, the oontroller 159 makes the addres3 signal 162 specify the column address for the fore~ost proximate minutia in each memory sector as briefly described before, ~he R subtractor 166R is no~ for the ridge counts ~ir~
and ~jrF~ As desexibed hereinabove and will shoxtly become clearer the ridge counts RirS and RjrF repre~ented by the re~pective data signals 164 and 165 are supplled also to a code detector 173 for detecting if the specific code is present instead of the rldge count R~rS or RjrFo The AND circuit 163 delivers the output ~lgnal to the controller 159 only if~

~irs RjrFI ~ Tr irS XjrFI - Tx~ (6 ¦ Ylrs - YjrF ¦ 3 y ~
and IdirS ~jrFI ~d Responsive to thi~ output ~ignal~ the controller 159 sends a count signal CT~ to the ~econd counter 172 to add one to its co~tent. If the speclfic code is detect~d instead of 73;~:

at lea~t one of the ridge counts RirS and RjrF, the code detector 173 send~ a detectlon signal DET to the first counter 171 and also to the controller 159~ The detection signal DET adds one to the content of the first counter 171 and prevents the controller 159 from producin~ the count ~I~nsl e~ irre3pective of the output signal of the AND circuit 168, The content of the first counter 171 is supplied to the threshold generator 163, which produces a threshold coxresponding to the number of specific codes. The threshold is delivered to a comparator 174 for co~pari~on with the count of the second counter 172, When the count of the second counter 172 is equal to or greater than the thre~hold, the comparator 174 supplies the controller 159 with a similarity si~nal indicative of a local similarity betHeen the minutiae MiS and MjF, ~esponsive to the similarity signal, the controller 159 ~upplies the sequ~nce controller 69 (Fig, 6) ~ith an address signal 176 (also in Fig. 17) represen~ati~e of the aearch and the file minutia numbers MiS and M~F retained therein~ The controller 159 furthermore supplies the sequence controller 69 with a data signal 177 representative of the local simllarity represented by the similarity signal, Meanwhile the controller 159 may keep the address signal 162 indicative of the row addresses for the Minutiae MiS and MjF to make the minutia memories 153 and 154 (Fig~ 20) produce the data signala 164 ~nd 165 (collectlvely denoted by 17a 1n Fie. 17), Moreover, the controller 159 delivers an instructlon signal 179 (also ln ~ig~ 17) to the sequence controller ~9, Thereafter, the controller 159 makes the addres~ signal 162 indicate a next one of th~ search minutiae and successi~ely and successlYely the zeroth through the z-th file minutiae, It will now be understood that the order of the minutiae MiS and MjF de3ignated by the address signal 162 need not be as described abo~e. The minutia memory 127 may not be an lndependent unit but may be a paxt of the relation linking unit 126 or of the pair detecting unit 128.
(5) Modifications of Palr Detection As will presently be described more in detail, a certain amount of error is unavoidable between the principal coordinate syætem selected for each file fingerprint and the central coordinate sy~tem into ~hich the principal coordinate system for each search finge~print i8 forwardly transfQrmed, This i8 al60 the case e~en when the principal coordinate system for the file ~ingerprint is forwardly tran~formed to provlde a match with the principal coo~dinate-syste~ ~or each search fingerprint, The error between the origin~ of the principal and the central coordinate syste~s equally affects the position and the dlrection data of a minutia near to each origin and the data of a minutia remote therefrom, It is therefore posslble to cover the error by the thresholds Tx, Ty~ and TD and Tx, Ty~ and Td, The error result1ng from the direction of the coordinate axis, however, grow~ greater for remoter minutlae, If the threshold~
are selected to co~er the greater error, the accuracy of the pair detection degrades for nearer minutiae, Referring to Flg. 22, a modification of the pair detecting unit 128 (Flgs. 17 and 21) i~ for rai~ing the accuracy, For use as a part of the pair detecting unit 128 illus~rated ~ith reference to Flg. 21, a th~eshold ~el0ctor 181 is ~upplied with the data signal 164 successively representative o~ combinations of th0 position data Xis and YiS and the position data xi~s and YirS (coll~ctively denoted by X and Y~, On the other hand, tha position data X and Y and the position data X' and Y' (XjF and Y~F or xjrF and YjrF) are supplied to search and file selectors 182 and 183, The local controller 159 (Fig, 21) selects one of the combinationc X and X' and the combi~atlon Y and Y' at flrst and then the other, The selected combination X and X' or Y and Y' is supplied to a subtractor 184 and thence to an abosolute ~alue clrcuit 185, which supplies a co~parator 186 ~lth ¦X - X'¦ or ~Y - Y'¦, In the threshold ~elector 181, the position data X
and Y are delivered to X and Y absolute value circuits 191 and 192, The absolute values produced by the absolute value circuits 191 and 192 are fed to a selector 193 and further~ore oompared Hith each other by a co~parator 194. Supplied with the greater absolute value, the threshold generator 163 (corresponding to that described in conjunction with Fig. 21) produces the threshold T or t and TD or Td.
A combination of the subtractor 184 and the ab~qolute value circuit 185 correspond to a com~lnation of the qubtractors 166X and 166Y, The comparator 186 corre6ponds to a combination of the comparator6 167X and 1~7Y~ The thre6hold T is for use a3 either of the thrssholds TX and Ty and the thre~hold t, as eit~er of Tx and Ty~
Referring now to Flg, ~3~ the relation data are sub6~antially independent of the principal coordinate sy~tem as pointed out herelnaboY~ The error error between the prlnc~pal cooxdinate ~L~ o ~

systems, however, results in an err~ between the local coordlnate systems ~hich are deflned for a search and a flle minutia. An i-th minutia Mi of a fils fingerpxint of a certain fln~er wlll be taken into consideration as a reference minutia. Acco~dlng --5 to an x-y local coordinate systam based on the principal coordinate system, the reference minutia Mi has proxi~ate minutiae Mir as exemplified in Fig. 4~ The proximate minutiae will no~ be called primary proximate minutiae and represented by Mie, Mif9 M~g, and Mih as depicted in ~ig, 23, m e primary proxl~ate minutiae Hill either Ringly or collecti~ely denoted by Mik, A search fingerprlnt of the finger under cons1deration is printed on differenet conditions as described heretobefore.
It is very likely that a different principal coordinate syq1,em is selected for the search fingerprint, E~en though transformed fxom the different principal coordinate syste~,~ith best cara, the central coordinate system may hava a difference from the principal coordinate 3ystem selected for the file f~neerprint, Let the minutia in questlon in the search fingerprint be numbered also as the i-th minutia Mi for breYity of description, In the illustrated example, an x'-y' local coordinate system is based on the central coordinate system, Ths proximate minutia Mig is remoter than the minutia Mie in the f~rst quadrant of the local x'-y' coordin~te system and is therefore not found as a primary proximate minutla. Instead, ahothcr minutia ~u i6 found as ~ primary proximate mlnutia in the fourth quadrant, Thi~ again re~ults in a reduction in the accuracy, Referring to Fie, 24~ a modlflcatlon of khe pair detection clrcuit 77 (Fi~, 6) is effectlve in r~lsing the acGuracyO The 73%

clrcuit 77 comprises a composlte relation linking unit 196, a composite minutia memory 197, and a composite pair det~cting unit 198, all simllar to the corresponding unlts 126 through 128 described in conjunction ~lth Figs. 1~ through 21, Incidentally, it will be assumed that the minutia list memory 71 (Fig, 6) is already lsaded with the minutia data and the fundamental relation data of both a search fingerprint and one file fingerprint in the manner exemplifled in Fi~, 14.
Turning back to Fig, 23, the x-y coordinate system having the local origin at a reference minutia Ml will now be called a pri~ary coordinate system, The relation link data Rik, Xik~ Yik. and dik calculated for the prlmary proximate minutia Mik and shown in Fi~. 18, will be referred to as primary relation data of the reference minutia Mi, ~n the manner described in connection ~ith the prlmary coordinate system, secondary coordinate systems xe-ye~ X~-yf, xg-yg~ and xh-yh or Xk-y~ are defined to ha~e the respective origins at the primary proximate minutiae Mik and the coordinate axes coincident ~ith the direction data dik of the primary prox.lmate minutiae Mik~ Proximate minutiae Mikr which are found in relation to the secondary coordinates system defined,'for each primary proximate minutia M~k, will be called secondary proximate minutiae of the reference minutia Ml, If a specific minutia proximate to one of the primary proxi~ate minutie Mik is coincident ~ith the reference minutia Mi Dr another primary proximate minutia, the specific minutia need not be included in the secondaxy proximate minutiae. If a secondary proxi~ate minutla found as re~arda a primary proxlmate minutia Mik, coincides ~ith a 3econdary proximate . ~

3~

minutia resulting from another primary proximate minutia, it is sufficient to use only one of the t~o as a secondary proximate minutia.
For the example being illustrated, the secondary proximate minutiae are minut~ae MieO~ Miel~ Mifo~ Mif2~ Mif3' Migo' Migl' ~ig3~ Mih2, and Mih3, A minutia which is proximate to tha primary proximate minutia Mie in the fourth quadrant of the ~econdary coordinate system xe-ye and whlch may be selected as a cecondary proximate minutia Mie2, is coincident with the primary proximate minutia Mig. A minutia proximate to the primary proximate minutia Mia in the third quadrant to be selected a3 a secondary proxlmate minutia Mi~3, is coincident wlth the re~erence minutia Mi~ A
mlnutia to be selected as a secondary proximate minutia Mifl in the secondary coordinate system Xf-yf, i8 already ~elected as the secondary proxi~a~e minutia Miel, The secondary proximate minutiae selected in this manner9 will either.singly or c~llectively be denoted by Mik~.
It is already described that the primary proximate minutiae Mik have the primary relation data of the minutia Mi, namely, the ridge counts Rik relative to the reference minutia Mi and the position and the direction data xik, Yik9 and di~
as regards the primary ooordinate sy~tem having ths local origin at the minutia Mi, Like~lse, each ~econdary proxi~ate minutia Mikr has position and direction data ~ikrk, Yikrk- and dlk~k as regards the secondary coordinate sy~te~ xk-yk havlng the origin at each primary proxim~te minutia Mik and a ridge count Rikr bet~een the secondary -proximate minutia Mikr and the primary proximate minutia Mik.

Each primary proximate minutla Mik, although so named, in an ik th minutia The ridge count and the position and the dlrection data whlch the ~econdary poroximate minutiae Mikr have relative to the primary proximate minutia Mik, are there~ore readily obtained by the relation llnking unit 126 lllustrated with reference to Flg, 19 with reference to the minutia list memory 71 (Fig, 6) ~oadsd ~ith the minutia and the fundamental relation data of the ik-th ~inutia Mik aq exemplified in Fig, 14, It is, however, desirable for use in the pair detection that the ridge count should bc the num~ex of ridges between the referance minutia Mi and each ~econdary proximate minutia Mikr.
Furthermore, the position and the direction data should be given in direct relation to the primary coordinate system having the local orldin at the xeference minutia Mi. The latter ridge counts and position and dir~ction data for all ~econdzry proximate minutiae of the reference minutia Ml ~ill be called secondary r~elation data of the reference ~inutia Mi, The secondary relatlon data of either one or all of the secondary proximate minutiae Mikr Nill no~ be denoted by rikr~ Xikr' Yikr' ikr Like the primary rroximate minutia Mik, each secondary proxl~ate minutia Mikr i~ an lkr-th minutia It is therefore pos~ible to readily obtain the position and the direction data xi~r~ Yikr, and dikr by usin~ the xelation llnking unit 126 exemplifi~d in F'ig1 19 and by giYing the translation components x and ~ and the angle of rotation ~ the position and the direction ~ata Xi, ~: Yi, and D1 of the reference minutia Mi rather than the position and the direction data Xik, Yik, and D1k of each primary proxl~ate minutia Mi~, A~ for the ridgé count r1kr, attention ~hould be direct0d to the fact that each secondary proximate minutia Mikr i8 remoter from the reference minutla Mi than the prl~ary proximate minutia Mik for the ~econdary proximate minutia Mikr under considerati~n in that quadrant of the primary coordinats system in which the primary proximate minutia Mik is present, The ridge count rikr is therefore readily calculat0d by using the ridge count~ Rik and Rikrk, The ridge count R~k is given ln the minutia list ~emory 71 (Fig, 6) for the reference minutia Mi, The other ridge count Rikrk is also given in the minut1a list memory 71 for the ik-th minutia Mik.
Turning to Fig. 25, the composite minutia memory 197 is for storing a ~e~uence of the mlnutia data of each minutia Ml and the primary and the secondary relation data thereof for the search fingerprint and one file finge~print at a tlme. The sequence will be called composite relation link data, Re~erring to Fig, 24 once again, the composite relation linking unit 196 is for calculating the composito relation link data of aach minutia Mi of the search or the file fingerprint for storage in the composite mlnutia memory 197 as exempl~fied ln Fig, 25, An exsmple of the composite relat10n llnking mit 196 comprl~es a ridge count re~ister 201 and a ridge count calculator 202 in addition to the circuitry illu~trated with refere~ce to Fig~ 19. The ridge count register and calculator 201 and 202 ~ill presently be described more in detail, The signal~ used for and in the pair detection circuit 77 wil be called as before and de~ignated by like reference numerals although there ~re ~9~73~

certain differencea between the s~gnal~ being used and the previously described signals as w~ll shortly become clear, Turning back to Fig. 19, the illustrated relation linklng unit 126 carries out the relatlon linking operation also in the composite relation linking unit 196 (~lg, 24) a~ described heretobefore until the fundamental relation data Rik and Mik ~' the i-th minutia M~ are suppplied as the input data signal 132 from the minutia list memory 71 (Fig, 6, 71S or 71F) accessed by the first address sl~nal 1~1 indicative of the minutia number Mi, The output data signal 136, the ~econd address signal 137, and the transfer signal 149 are delivered toward~ the composite ~inut~a memory 197 lnstead of the minutia ~emory 127 (Figs, 17 and 20), ~ efore delivery of the foremost primary proximate minutia Mie back to the central controller 129 from the shlft register 134, the ridge count Rie produced from ths shift register 134 and included in the output data signal 136, ls fed also to the ridge count register 201 ~Fig.`24) and stored therein, When the ie-th minutia Mie is indicated by the first address signal 131 instead of the i-th ~inutia Mi, the controller 129 retains the re~erence minutia number Mi, The fundamental relation data RieO' MleO' Rie~ Ri~3~ and Mie3 of the ie-th minutia Mie, namely the prlmary proximate minutia Mie, are included in the input data signal 132 and stored in the shift register 134 in the shift reglster stageE next following the stage to which the la~t datum Mih ~ the previously stored fundamental relation data of the i-th minutia M~ i3 shhfted, The controller 129 retains al~o the primary proximate minutia number Mie, 73~

Having cEtrfied dut the relation li~nking operatlon of the primary relation data as regard~ the primary proxlmate minutia Mie, the controller 129 receive~ the next followlng primary proximata minutia number Mif from the shift reglster 134 to make the flr3t 5 addre~ slgnal 131 specify the if-th minutla Mif as described hereinabove, The controller 129 retains the minutia number Mif, In thi~ manner, the controller 129 retain~ for each reference minutia Mi, the reference minutia number Mi and the primary proximate minutia numbers Mik. The ridge count register

10 201 keeps the ridge counts Rik. The registers 135's still keep the position and the direction data Xi, Y1, and D1 of the reference ~s1nutia Mi~
After the primary ~e~atioh data bf.the reference minutia Mi are stored in the composite minutia memory 19~, the controllcr 15 129 receives the foremost secondary proximade minutia number, such aæ Mieo~ from the ~hift reg1ster 134 and compare~ the same with the minutia numbers Pli and Mik retained therein. If different, the controller 129 holds the minutia number Mieo and makes the first address signal 131 speclfy the ieO-th minutia Mieo and 20 the second address signal 137 indicate the ro~ address of the reference minutia Mi and the column address for the ridge count r~eO and the posit~on and the di~ection data xleO, Yieo- and dieo, In the meantlme, the controller 129 makes the ridge 25 count register 201 supply the ridge count Rik to the ridge count calculator 202 and the shift reglster 134 deliver the ridge count Rieo also to the rid~e count calculator 202, The ridge count calculator 202 produces the rldge count r~ as a part of the 7~

output data signal 136, The posltion and the direction data ~ieO~ ~leO~ and ~leO comprised by the input data slgnal 132 are dell~ered directly to the subtractors 138'~. The adder 146, the subtractor 147, and the D s~lbtractor 138D produce the position and direction data xieO, Yieo~ and dieo as another part of the OUtpllt data signal 136.
Subsequently, the controller 129 receiYes the next follo~ing s~condary pr~ximate minu-tia number, such as the iel-th minutia number M1e~, If the minutia number Miel is different from the reference minutia number Mi, the primary proximate minutia numbers Mik1 and the already retained secondary proximate minutia number or mlmbers, such as M1eo, the above-described processes are repeated, If the secondary proximate minu-tia number being supplied, is e~ual to one of the reference, the primary proximate, and the already stored secondary proximate minutia numbers, th~
. controller 129 at once receives the next foilo~ing secondary proximate minutia number rom the shlft register 134, In this manner, the secondary relation data of the reference minutia Mi are stored in the co~posite minutia memory 197~
Thereafter, the controll~r 129 makes the first addxes signal 131 indicate the next following reference minutia number, clearing the ridge count register 201. The shift register 134 ~s~ ead~.~endered empty. After the composite relation data f the la t reference minutla Mz are stored in the (buffer memory 151 or 152 of t-he~ composite minutia memory 197, the controller 129 produces the transfor signal 149, Referring to Fig, 21 again, the 0xemplified pair dotecting unit 128 serves well as an example of the composite palr detecting unit 198 if the local controller 159 is ~lightly modlfled; More specifically, attention will be directed to the i.nstant at whlch comparison of Formulae (5) come~ to an end for the foremost primary proximate mlnutie MieS and MjeF in the search and the file fingerprints with the second counter 172 renewed to a certain ¢ount, The controller 159 does not thereafter makes the address ~ignal 162 immediately indicate the next follo~ing pri~ary proximate minutiae of the search and the file fingerprints but acces 9 while keeping acces5 to the data Rl8s~ XieS~ YieS' and'dieS' the secondary proximate minutia data rierF, xierF, Yier~, and dierF-If the specific code is detected by the code detector 173 in pla~e of any one of the ridge count5 xierF, the flr~t counter 171 is counted up, The sacond counter 172 i5 counted up by the output signal ~hich the AND circuit 168 produce~ ~hens I rieS rjgrF I - Tr ' lXieS XjerFl ~ Tx' (~) ¦Yi~S Y~erFI - Ty, and IdieS djerFI ~ Td' The controller 159 thereafter makes the address signal 162 indicate each of the pri~ary proximate minutiae M~erS and successively the foremost primary proximate minutia M~eF and the secondary proximate minutiae M~erF, After access to the last combination o~ the secondary proximate minutiae Mi~rS and MjerF, the address sl~nal 162 is made to acceqs the next prlmary proximate minutiae MifS and M~fF, ~ ~ ~ ~z (6) Pair Candidate List Referring to Fig, 26, an example of the pair candidate list memory 73 (FLg. 6) has sixty-four row addresses accessible by the address signal 176 (Figs, 17 and 21) representative of 5 the respectlve search minutiae Mo through Mz (or M63). The memory 73 has sixteen column addresses assigned to the file minutia numbers M~ (0 through 15) which are represented also by the address signal 176 and are selected from the file minutia numbers Mo through M~ ~for example, Mlgl) and rearranged as follows.
A pair candidate list is formed in the memory ~3 at a fourth step A4 shown in Fig. 9, Each entry apecified by a search minutia number Mi and one of rearrangPd file minutia number~
M~ has a pair candldate f1eld ~i~ and a weight field Wi~. The local similarltie~ represented by the data signal 1~7 (Figs, 17 and 21) bet~leen each search minutia MiS and the 3elected file minuti~e (pairs in fact) MjF indicated by the address signal 1~6 are compared wlth one another by the sequence controller 69 (Fig, 6) or elsewhere, The file minutia number~ Mj~ are thereby rearranged in the descending order of the local similarity.
The column addresses are accessed in this descending order~
Eor example, the zeroth column Mio of the row address accessible by the search min~tia number Mi, is for a file minutia having the hi~hest local similarity ~ith the search minutia Mi~, The local similarlty, noH call0d a ~elght Wij, is stored ln the ~eight field Wi~, When only one file minutla i.s found for the search minutia Mi during the pair detection as a single pair, data are stored in only the zeroth column, As a consequence, each row address may be loaded with the data only to a certain column address depending on the threshold supplied to the comparator 164 (Fig, 21), A speclfic mark is stored ln the welght field ~lj of the next following empty column address, It i~ posslble to understand that a minutia number of the ~ile fingerprint is stored in the column address in which the speci~ic mark is stored ln place of the weight and consequently that each row addre~s for a search minutia MiS is loaded ~ith a plurality o~ file minutlae which aro found ~o be in pair~ wlth the search minutia MiS, (7) Amounts of Coordinate Adjustment As describ~d above, the pair candidate list memory ?3 (Figs, 6 and 26) is formed by detecting the minutla pair~
based on the relatively coarse quantization step, Each search minutia is related in the pair candidate list me~ory 73 to at lPast one file minut~a in the descending order of the local simllarity or weight ~ The pair candidate li~t memory 73 i~ useful on more preclsely matching the pri~cipal coordinate system 6elected for the search fingerprint with the principal coordinate system of each file fingerprint by deciding a set of optimum amounts of coordinate adjustment for the principal coordinate systems.
It will be assumed that the principal coordinate system of the search fingerprlnt should be more precisely matched to the principal coordinate system of a file fingerprintO
Referring to Figo 27~ an example of the ~coord~ate) adjuatment amount deciding clrcuit ~ (Fig. 6) is for rapldly 25 and reliably deciding the optimum amounts as shown at a flfth step A5 in Fig. 9, Decision of the optlmum adjustment amounts is carried out by referring to the exemplified pair candldate list memory 73 ~Fig~ 26) and to either the minutia memory 127 ~ ~9~2 W

(F`igs. 17 and 20) or more preferably back to the minutia lls-t memory 71 Hhlch may be loaded with the precise data as exemplified in Fig, 10, Each set of ad3~stment amounts consists of ~ pair of translation components and an angle of rotation, which will now be denoted again by x and y and afresh by n~', It is to be noted that the angle ~' represents a preselected unit angle and that the letter n, an integer, At the outset~ the principal coordinate plane of the search fingerprint is rotated by an angle n0' into a coordibate system, which ~ill be called a search coordinate system, Let the position data Xi and Yi of a search minutla Mi be forward transformed by the rotation of the prlncipal coordinate plane to a temporary set of position data Xsi and YSi, Let one of the file minutiae that ls given in the pair candidate list memory ~3, be the ~-th minutia ~jF~ The position data of the minutia MJF will be designated by Xmij and Ymij, which may be read from the file minutia memory 71F of the minutia list memory 71, A
pair of differences x' and y' are caloulated by:
x' _ Xmij ~ Xsi ~ (8) and y _ Ymij Ysi' The exemplified adjustment amount deciding circuit ~8 comprlses a difference coordinate plane memory 211 representative of a difference coord1nate plane (denoted also by the reference numeral 211) which will shortly be described moxe in dstail, The clrcuit 78 forms a weight map on the difference coordinate plane 211 as will bs dsscribed in the following, Turning to Flg, 28, an example of the difference coordinate plane memory 211 has abscissa address accessible by the difference x' and ordinate address accessibly by the difference y', An address specified by a combination of the diffcrences x' and y' will be called a coordinate address, It is assumed that each difference x' or y' is from minus ô up to plus 7, both inclusive, Referring to Fig, 29 in addition to Fig~ 27, the control memory 75 (Fig, 6) specifies a search minutia Mi to read the precise positon and direction data Xi, Yi, and Di directly from the mlnutia list memory 71, As will later become clear, let the amounts of adjustment x', y', and n~' be provisionally selected and stored by .the control memory 7~ ln ~he re~isters 91 :thxough 93 (Fig. 13) of the exempli~led coordinate transforming clrcuit 72. For the time being, zero is used at a first ~tep Cl as x' and y' ~hich are provisionally selected as the translati~n components x and ~. The (precise) position and direction data r~ad out of the minut~a list memory 71 are transformed by the coordinate transforming circuit 72 into the search position and dlrection data Xsi, YSi, and Dsi. Incidentally, the ROM 94 produces the values cos(n~') and sin~n0').
Subsequently, the control memory 75 accesses the row address allotted ln the pair candidate list memory 73 to the search minutia Mi~ and a certain column address to find a file minut1a MjF ~hich provides a pair ~ith the search minutia MiS, The (precise) position and direction data of the file minutia MjF are read directly from the minutia list memory 71 as Xmij, Ymij, and Dmij, Differences x', y', and d' are calculated. according to Equations (8) and to:

73~:

ol d' = Dmi; Ds.t' The control memory 75 supplies the differences x' and y' to X and Y input terminals XI and YI and also a control s~gnal to a control input terminal CI, When the control signal takes a binary one value9 X and Y selectors 212 and 213 supply the differences x' and y' to the difference coordinate plane memory 211, The contents of a coordinate address specifled by the differences x' and y' in the memory 211, is supplied to one of t~o inp~lt ports of an adder 214, The other input port is supplied with the weight Wi~ from the pair candidate list memory 73 through a weight input terminal ~I~ The sum calculated by the adder 214 is stored in the coordinate address being accessed, In thi~ manner, the weights Wij are accumulated on the difference coordinate plane 211 according to the differsnces x' and y' to provide th~ weight map, The wei~hts ~ij accumulated on the respective coordinate addresses are dependent on the angle of rotation n0'~ Incidentally, the exemplif:led abscissa and ordlnate addresses are relatively coar~ely quantized although the position and the direction data Xsi, Xmij, and so forth are preclse, l`he access to a coordlnate address is therefore carried ~ut by using only ~our consecutive more significant bits of each - of the ro~ and the column address signals, More particularly, the control memory 7S initializes the co~tents of the respectlve coordinate addresses to zero at a second step C2, At this instant, the address signal 162 is made to indicate the zeroth search minutia Mo as shoun at a third step C3, The search position and dlrection data Xsi, Y5it and DBi are calculated at a fourth step C4, with the search minutiae 7 a~
~, ~

successively specified. At a fifth step C5, the minutia type Qi is checked, If the end mark is detected, the weight map is complete, If the end mark i~ not detected at the fifth step C5, the column address is initiallzed to zero at a sixth step C6, T~e ~à~r càn~lda~ë list memory 73 i8 accessed by the row and the column ad~resses at a seventh step C7. The accessed weight field Wij is checked at an eighth step C8 whether or not the specific mark is present~ If the specific ~ark i~ detected, the eighth step CB returns ko the fourth step C4, If the specific ~ark ls not detected at the eighth step C8, the m~nutia list memory 71 is accessed at a ninth step Cg. ~he position and the direction data Xmij~ Ymi~, and Dmij are read out and used to calculate the differences x', y', and d' according to Equations (8) and (9). The file minutia number is increased by one, At a tenth step C10, the differences x', y', and d' are checked against preselectsd thresholds tx, ty, and td~ If at ~east one of the differences exceeds the threshold, the tenth step C10 returns to the seventh step C70 If all difference~
are equal to or less than the respectiYe thresholds, the welght Wij is added to the content of the coordinate address at an eleYenth step Cll, The steps C7 through Cll or the steps C7 through C9 and Cll are repeated. In the ~eight map exemplified in Fig, 28, .

the accumulated weights are exemplified by numbers selected frcm 1 through 8.
Turning to Fi~o 3~, a factor table 216 is exempli1ed for use ln ~earching a specific csordinate address at whlch the accumulated welght is maximum, The table 216 i9 preferred ln order to exclude a coordinate address at whlch the accumulated weight shows an unduly high value, The table 216 ls u~ed as will presently be described for each coordinate address of search and gives factors to be multiplied by the weights accumulated on ni~e coordinate addresses which form a matrix of three rows and three columns with the coordinate address of search at the center.
Referring to Flg. 31 besides Fig, 27, an initial value of ~ero is set at a first step Dl in first through third registers 221, 222, and 223, a maximum register 225, and fir~t and second register fil~s 226 and 227, Another initial Yalue of minu~ 8 i8 set in X and Y registers 228 and 229 to indicSLte a start point of search (the l~ftmost and lowest coordinate address of th~
difference coordinate plane 211). A bi~a~y zero Yâ3~e.~s ~i~en to the control signal (CI), responsive to ~hich the selector~
212 and 213 make the contents of the X and Y registers 22~ and 229 access the weight map and responsi~e to which the difference coordinate plane memory 211 is adapted to read out.
The first register file 226 is fed directly from the diffarence coordinate plane memory 211. The second register file 227 is ~ed from the first register file 226, me regi.ster files 226 and 227 are accessed by the Y register 229, The adjustment amount deciding circuit 78 compriæeR
first through third selectors 231, 232, and 233, A timing signal input terminal, depicted separately at 234 and 235, 1s suppl~ed ~ith a timine signal from the control memory 75. The timlng signal ~pecifies flrst and second timings Tl and T2 bY? for example, 73~
~, logic ~ero and one ~alues, respectively, A first adder 2.~6 is for adding tHice the data selected by the second selector 232 and the data ~elected by the thlrd selector 233. A second adder 237 is for adding the data supplied from the first adder 236 and the data selected by the first ~elector 231 to supply the sum to the first register 221 and also to a comparator 238, The sum is furthermore directed towards the maxlmum register 225.
During the first timing Tl, the registers 221 through 223 are enabled, Furthermore, the selectors 231 through 233 are made to select the data supplied directly from the difference coordinate plane memoxy 211 and the data supplied from the register files 226 and 227, respectiYely. The f~llowing processes are therefore carried out concurrently at a second step D2.
. RKl ~- DIF(DX~ DY) ~ 2f~1(DY)3 ~ RF2(DY), RX2 ~- RKl, (10) RK3 ~~ RK2, . RFl(DY) ~- DIF(DX, DY), 20and R~2(DY) ~- REl(DY), where DX and DY, DIF, RKl through RK3, and RFl and RF2 represent contents of the X and Y registers Z28 and 229, of the difference coordinate plane memory 211, of the registers 221 through 223, and of the reglster flles 226 and 227, respectlYely, The data on the right-hand side~ represent the contents before rene~al and those on the left-hand sides, renewed data.
During the second timing T2, the registers 221 through 223 are disabled, The selectors 231 through 233 are m~de to 73~:

select the data fed from ths reglsters 221 through 223~ respectively.
As a result, the second adder 237 produces a sum (RKl t 2[~K2]
t RK3). The comparator 238 compares the sum ~lth the content (MDIF) of the maximum reglster 225. If the ~um i~ less than the content, the comparator 238 enables an AND clrcuit 239 for the logic one timing signal. An input port of the maximum register 225 is therefore enabled. m e following processes are simultaneously carried out at a third step D3, MDI~ ~- RKl ~ 2[~ t RK3, DX' ~- DX, (ll) and DY' ~- DY, J
where DX' and DY' represent the contents of X' an,~ Y' re~isters 241 and 242~
Thereafter, the control memory 75 sends another timing signal to an input ter~inal 243 to enable inputs to the X and Y registers 228 and 229~ At a fourth step D4, a first one-adder 246 adds one in general to the content ~Y of the 'I register 229, Qnly ~hen the content DY represents seven, the one-adder 246 supplias a carry to a second one-adder 247~ which adds one to 20 the content DX of the X register 228~ When the content DX becomes equàl to ~even, the second one-adder 247 delivers a carry to an end output terminal 2480 The latter carry is detected by the control memory 75 as an end of the search at a fifth step D5, BefDre dctection of the latter carry, the prccesses return 2S from the fifth step D5 to the second step D2, When the lattsr carry is detected, the contents DX' and DY' ~re read out of the X' and Y' registers 241 and 242 as the translatlon components x and ~ at a sixth step D6.

In order to facilitate an understandlng of the Yearch, let it be assumed that the contents DX and DY o~ the X and Y
regi8terB 228 and 229 are for the Abscissa address x' of 3 and the ordinate address y' of 5 of the dlfference coordinate plane S 211 exemplifled in Fig, 28. During the ~irst timing Tl, Formulae (10) shows that the contents RFl(5), RF2(5), and RKl throu~h RK3 are equal to DIF(2, 5), DIF(l, 3), (DIF(3, 5) ~ 2[DI~(2, 5)]
~ DIF(l, 5)), (DI~(3, 4) t 2tDIF(2, 4)~ t DIF(l, 4)) or the content RKl which the first register 221 had at the previous instant ~hen DY wa equal to 4, and (DIF~3, 5) ~ 2[DIF(2, 3)] ~ DI~(l, 3)~ or the content RKl which the first register 221 had at the next previous instant when DY Nas equal to 3, respectively, In the course of the second timing T2, prvcesses are carried out according to ~or~ulae (11). The second adder 23 15 give8 a sum Hhich is equal tot DIF(3, 5) t 2~DIF(2, 5)] ~ DIF(l, 5) t 2tDIF(3, 4) ~ 4[DIF(2, 4)] ~ 2[DIF(1~ 4)]
~ DIF(3, 3) 1 2[DIF(2, 3)] ~ DIF(l, 3), (12) which sho~s that the above-described search is carried out by multiplying nine accumulated Neight3 by the factors of the factor table 216 (Fig, 30) and by summing up the products, It i.~ to be noted in conneotlon with Equation (12) that the greate~t factor of 4 is multlplied to DIF(2, 4), namely, the weight accumulated on the coordinate address (2, 4) rather than the coordinate addres~
(~' 5) being checked, The coordinate addre~s on which the maximun ~eight is accumulated, is therefore given by (X' - 1, Y' - 1), l'he optimum amounts of coordinate adjustment are obtain~d by alt~rnatingly repeatin~ the above-described accumulation and search.
Referring afresh to F'ig, 32 and again to Fig. 27, the working area 74 (Fig, 6) iB for storing the unit angle of rota-tion 0', the integers n, the maximum value of the integer N, an angla of rotation ~ as ~ill shortly be described, (X' - 1~ and (Y' - 1) previously obtained from the contents X' and Y' of the X' and Y' register~ 241 and 242, and that content read out of the maximum register 225 which will now be called a previous maximum and denoted by MDIF', At the outsett the control memory 75 sets the unit angle 0' and the maximum integer N in the working area 74 at a first step El. The memory 75 gives an initial value oD zero to the integer _ and al~o to the previous maximum MDIF' at a second step E2, Ihe control memory ~5 makes the exemplifled ad~usting amount deciding circuit 78 (Fig. 27) form a weight ~ap at a third step E3 and then the search at a fourth step E4, Responsive to the end of search signal, the memory 75 reads the maximum r~gister 225 and compares the maximum MDIF with the previGus maximum MDIF' at a fifth step E5, When the read-out maximum MDIF is greater than the previous maximum MDIF' 7 the control memory 75 substitutes the former ~br the latter at a sixth step E6, Furthermore, the memory ~5 reads the X' and Y' registers 241 and 242 and substltutes (X' - 1) and (Y' - 1~ for the prevlously read-out values in the working area 75 and rewrites the angle of rotation ~ by the angle of rotation n~' by which the new maximum is obtained, The control memory ~5 changes the sign of the integur n at a seventh step E7 If the read-out maximum MDIF is equal to or less than the previous maximum MDIF', the 6tep E5 ju~ps to the step E7, An an eighth step E8~ the memory 75 checks whether or not the new integer is equal to or greater than zero, If not, the step E8 returns to the step E3~ If the ne~ integer is equal to or greater than zero, the memory 75 checkR whether or not the new integex is e~ual to the maximum integer N at a ni~th step E9, If not, the memory ?5 adds one to the new integer at a tenth step Elo and makes the process return to the second step E2, If ;the maximum integer N is reached, the optimum amounts are obtained, It may be that the maximum MDIF eventually obtained as a result of the abo~e-described steps, is found at a slxth step A6 of-~ig. 9 to bP less than a p~eselected threshold. In this event, the control memory 75 judges that the file fingerprint being mat.ched, is different from the search fingerprint, In other words, the match~ng is unsuccesful The memory 75 suspends the matching and inform~ the matching control deYice 55 (Fig, 1) of the fact Only when the eYentually obtalned maximum MDIF
exceeds the threshold, the memory 75 transfers the precise position and dirsction data and so forth from the minutia list memory 71 (Fig, 63 to the precise matcher 57 (Flg, 2 or 3) through a bus 249 (Fig, 2) or the buses 64 and 90 (Fig, 3) at a seventh step ~ of Fig. 9~ The t~ansfer of the position and directicn data and the li~e ls preferably carrled out w~th reference to the pair candidate list memory 73 and through the coordinate transformlng circuit 72 in which the optimum amounts of adjustment g732 are set for the forward transformation.
(8) Precisé Matcher Referrlng back to Fig. 7, the first minutia list is transferred as a second ~inutia list in the second mlnutia li~t memory 81, As will presently become clear, the minutlae used in the precise matcher 57 are those listed in the pair candidate list memory 73 and the (primary) proximate minutiae of the search and the file minutiae given in the pair candidate list, It Hill be assumed for convenisnce of description that the minutla list memory 81 is loaded ~ith the second minutia list in the form sho~n in Fig, 18 together with the identification numbers of the search and the file flngerprint~ being deal* with, The pair candid~te list memory 73 is rendered empty by transfer of the pair candidate l~st provisionally to tha pair candidate list memory 83,- The region pattern 11st i~ transferTed eithe~ from the first mlnutia 11st memory 71 or directly fro~ the data storing de~ice 54 (Fig, 13 to the region pattern li~t memory 87, At an eighth step A8 depicted in Flg, 9, the sequence controller ?9 (Flg, 7) read~ the position and the direction data of the pair candidate~ ~Dom th0 mlnutia list me~ory 81 with reference to the pair candldate list memory 83. The read out is carried out directly without the use of the coordinate transformln~ circuit 82. Thi~ i8 because the data are stored in the minutia list memory 81 ~lth the coordinates opt~mally matched at the seventh step A7, The read-out data are checked a~ainst threshclds ~hlch are stricter than thcse used 1n Formulae (5), Com~3ri~0n defined by Formulae (6) and (7) i~ no more necessa~y, 'rhe sequence controller 79 ~elects those oL` the pair candidateR together ~Jith the Hei~ht~, 7o which are within the stricter thresholds, Referring now to Fig, 33, the selected search minutiae ~ill be denoted by N~. The file minutla which is in a stricter pair (the stricter pair being poR~ibly still "pair~") with each selected search minutia NB~ will be designated by Mf where f represents a stric~ly selected one of 0 through ~ for the file fin~erprint, The weights which are provisionally moved to the pair candidate list me~ory 83, remain only for the stricter pairs after the eighth step A8 (Fig, 9)~
At a ninth step A9 of Fig, 9, the pair candidate list memory 83 (Fig. 7) is modified as regards the remainin~ weights, As described above, the proximate minutiae NSr and Mfr are stored in the minutia list memory Bl, The sequence eontroller 79 (Fig. 7) successi~ely accesses the minutia list memory 81 by the minutla nu~bers Ns and M~ to read the proximate minutia ~umbers NSr and Mfr. The controller 79 searche~ the pair candidate li t memory 83 for the pro~imate minutiae M~r in the row address assigned to each proximate minutia NSr, If one is found as depicted at Mf, (Fig, 33), the file minutia Mf, is in stricter pair ~ith the proximate search minutia NSr being dealt with. The weight for the pair Nsr and Mf, is added to the weight for the pair N~ and Mf to pro~ide a modified weight for the pair Ns and Mf.
In each row adderss of the pair candidate list memory 83, the pair~ are rearranged in the descending order of the modified weights, The modified weights ~o rearranged, will be denoted by Wst ~here t represents 0, 1, 0,, ~

w Referring to Fig, 34, the pair list memory 86 (Fig. 7) comprises search and file palr list memorie~ 86S and 86~. The search pair list memory 86S has row addresses assigned to (strictly selected) search minutiae Nl through NS as will presently be described, Each row address Ns has a pair field Mf and an e~aluation field V5, The file pair list memory 86F likewise has ro~ addresses allotted to (strictly selected) file minutiae Ml through MF, Each row address Mf has a pair field Ms and an evaluation field f' At a tenth step ~ 0 of Fig, 9, the pai~ list me~ory 86 i8 formed as follows, At the outset, the evaluation f`ieldR
V~ and Vf are initialized to a negative value, The pair candi~ate list memory 83 i8 repeatedly sca~ned from the row address Nl to the row addre 3 Ns. From the pair ~Ns, MSo) having the maximum modified weight and consequently stored in the ~eroth column, khe modlfied weight ~sO is read out. A dlfference between the maximum modified ~eight WsO and the ~ext follo~ing mo1ified weight ~sl is calculated.
Reliability of the pair is deci ~d for each pair (N8-MSo) in consideratlon of the modified ~eight WsO and the diff~rence, The pairs of each row address are rearranged in the descending order of the reliabillty. The pairs (Ns, MSo) are renumbered into pairs (Ns, Mf) or (Nl, Ml), ,,., (N~, Ms), ,.,, (Nf, ~ ), ,,, (the suffix s being not necessarily less than the other suffix Z5 f), The modified weight, now oalled evaluations Y~ ,, V~t ,,., Vf, ~,9 ar0 substituted for the negative value in the respecti~e evaluation fields Vl, ,,,, V~ ,, Vf, ,,, ~ The pairs re~aining in the pair candidate list me~ory 83 are erased, Turning to Figs, 35 and 36, one of proximate minutiae of a searCh minutia N~ (renumbered) is depicted at NSr together with a file minut~a Mf (also renumbered) ln a pair for the search minutla N8 in the manner depicted in Fig~ 33, Like the modification of the pair candidate list memory 83, the pair li-~t ~emory 86 is modified in a former half of an eleventh step All illustrative of deci~ion of the evaluation in Fig, 9, At first, the row addre~s Ms is checked in the search pair list memory 86S, If the evaluation V8 is positive ~not the initial value), the file minutia number Mf of the pair i~
read out~ The search minutia N~ is uRed to acces~ the minutia list ~emory 81 (Fig, 7) to read the proximate minutia numbers Nsr, Each proximate minutia N8r is used to check the search pair list memory 86S whether or not the evaluation field Vsr is positive. 'I~ po~itlv~; the evaluatioh'Vsr ~s`added to ths eY~lUation V3. The evaluation Vs is rewritten by the sum, Hhich will be called a .~odified evaluatîon and again denoted by V3, The other row adddress of the pair list memory ô6 are simllarly dealt with.
Further turning to Flgs, 37 and 38, a file minutla Mf, is depicted together with a proxlmate minutia Mf,r, The proximate mlnutiae Mf~r are read from the minutia li~t ~emory 81 as before, The modificat~on of the pair list me~ory 86 is followed by relaxation of the evaluation in the latter half of the eleventh step All of Fig7 9. D~ing modification of the pair list me~ory 86, the negative initial value may be read from the evalllation field Vf, of the row address for the minutia ~,. The position 3~

data of the minutia Mf, are read directly from t~e minutia list me~ory 81 and used to access the reglon pattern list memory 87, If the region pattern list ~emory 87 indicates that the minutia M~, is in the unclear area (Fig, 4), the negatlve initial value --is rewritten ln the eYaluation field Vf, to ~ero which is indicati~e of "don't care," If the minutia M~, 1s in the ile :: fingerprint area, the negative initial value is left as it stands, The relaxation of the evaluatlon is carried out also for the search minutiae N~, In this connection, attention should be dlrected to the facts that the position and the direction data of thc scarch minutiae are given by a coordinate system into which the principal coordinate ~ystem for the search fin~erprint i5 foxwardly transformed on loading the minutia list memory 81 by the use of th~ optimum amounte of coordinate adjust~ent and that the pattern region list of the search fin~erprint ls given in tho pattern region list memor~ 87 by the pxincipal coordinate ~ystem, The coordinate transforming circuit 82 should therefore be used on reading the position data from the minutia list memory 81 to access the region pattern list memory 87~ For this purpose, 20 the reglsters which correspond to the registers 91 through 93 in the circuit 82, ~hould preliminarily be ~oaded ~ith the optimum amounts ~hen the fingerprint matching is transferred from the leading matcher 56 to the precise matcher 57, A search minutla for whlch the negative initial value is left untouched in the evaluation field, will be denoted by Ns,, The relaxation of the evaluation is continuedD ~he ridge count Rf~r (Fig, 36) which the file minutia Mf, has relative to each proxlmate minutia Mf, r9 is read ~rom the m.inutia li~t `73~

memory 81. If the ridge count ~f~r ls equal to zero, the minutiae Mf, and Mf,~ are very closely posltioned on the file fln~erprint and will be called close minut~ae, The dlrection data Df, and D~r are checked as will shortly be described, whether or not the directions Df, and Df~r are oppos1te to each other. If the negative initial value is left also in the evaluation field Yf,r, the negati~e initial values are changed in the evaluatlon flelds Vf, and V~,r to zero indicative of "don't care" as before. The process is carried out also for the search minutiae Ns,, The direction data are checked i~ the exemplified precise matcher 57 by the arithmetic unit 89 under the control of the control memoxy 85 and ln cooperation Hith the working area 84, Fig, 39 exemplifies se~eral combination~ of close minutiaa having opposite directions. It is to be noted that the direction f a bifurcation is depicted opposite to that defined in the abo~e-referenced Asai Pat~nt, Referreng to Fig 409 a direction checking circuit .
is for use in place of the arithmetic unit 89 in solely checking the directions. The position and the direction data of the close minutiae Mf, and M~r or N~, and NS,r will be denoted merely by X, Y~ and D and X', Y', and D', A complement calculator 251 ls supplied ~lth the direction datum D' to produce a direction datum Do opposite to the direction D' 9 namely, a sum of D' and ~, The absolute ~ralues of differences between X and X', between Y and Y', and bet~een D and Do are calculated by absolute difference calculators 252, 253, and 254. A threshold ROM 256 is for supplying comparators 257, 258, and 259 with thresholds for comparison ~ith the re3pective absolute values of dlfferences, 373~
..~

Attentlon should be''directed to the direction data D and Do so that the angle of 7c radians ~ay be given by the most signlficant bit. This i8 in order to lnsure the difference (D - Do) as regard~ the periodicity of angle, A direction ROM 261 ls acces~ed by the differences (X - X') and (Y ~') or by the absolute values of the differences and the sign bits of the respective differences, The RO~ 261 is preliminarily loaded with angles 0 (the same symbol being again used) given by~
0 = arctan[(Y' - Y)/(X' - X)~.
The absclute values of differences between the direction datum D and the angle ~ and between the direction datum Do and the angle 0 are calculated by additional absolute differenoe~
calculators 262 and 263. The threshold ROM 256 supplies additional comparators 267 and 268 with an addi*ional threshold for comparison Hith the absolute values calculated by the calculators 262 and 263. Atten~ion should be directed to the facts that each difference is nearly equal to æero and that the most significant bit of the difference would correspond to ~z/2~
An AND gate 269 is supplied with the results of comparison from the comparators 257 through 259, 267, and 268, Only when all results show that the absolute values of the differences are not greater than the thresholds, the AND gate 269 supplies the sequence controller 79 (Fig, 7) with an output signal indicative of the fact that the close minutiae have opposite directlons.
Referring to Fig. 41, small circles show flle minutiae Mf and M~o Dots show search minutiae N~ and Ns " It may be found that close minutiae do not have opposlte directions, In ii73~

this eYent, the minut1a list memory 81 i9 accessed by the minutla numbers ~fl and Mflr to read the concentrations Cf, and Cflr, If the concentrations C~, and C~,~ ha~e a great valus as compared with a threshold, the evaluation fields Yf, and V~,r are rewritten to zero indicati~e of "don't care," Summarizi~g, the relaxation of the pair list memory 86 is carried out as regards the rninutiae which are not in an area common to the Rearch and the file fingerprint areas~ The relaxation iA furthermore carried out in connection with tho~e of the close minutiae which either have opposite directions or are densely positioned. Such close minutiae are enclosed in Fig, 41 with dashed-line curves.
(9) Fingerprint Matching The precise matcher 57 carries out precise matching between a search fingerprint and one of the file fingerprints at a time by eventually calcuiating a match score (degree of match) ~ as indicated at a t~elfth step A12 in Fig, 9, More particularly, the 6e~uence controller 79 (Fig, 7) reads the pair list me~ory 86 and makes the control memory 85 control the arithmetic unit 89, Using the working area 84, the arith~netic unit 89 calculates the match score ~ in accordance ~ith~

S F
q ~ ( ~ ~s x ~; Vf)/(S x F~, where S and F are representative of the numbers of search and file minutiae Hhlch are present in the common area describ~d in conjunction with Fig, 41~ The sequence controller 69 compares the match score ~ with a threshold at a thirteenth step A13 of Flg. 9.
If the match score ~ ls less than the threshold, the precise matching is at once suspended, The precise matcher 57 373;~
~., undor consideration is ready for preclse ~tching for another file flngerprint, If the match score ~ is not less than the threshold, the ldentification nu~ber of the f11e fingerprint is stored in 5 the candidate flngerprint list memory 88 (Fig, 7) at a fourteenth step ~ 4 of Fig, 9 together with the match score ~, In a fingerprint matching system depicted in F~g, 1 and comprising leading and precise matchers, the match scores ~ obtained for a search fingerprint are compared with one another~ The matching control device 55 is infoxmed of the identification number of the file fingerprint , that has the maximum of the match scores q, The matching control device 55 sends the identification number to the data control and processing de~ice 53, which produces a result ~ignal indicative of the identification data of the file ~ingerprint, Meanwhile, the data o~ another search fingerprint are transferred to the fingerprint matching de~ices 51'~, (10) Destination Deciding Circuit Referring to Fig, 42, an example of the destination deciding circuit 67 (Fig, 5) is specifically useful in the fingerprint matching device 51 exemplified in Fig, 3 and comprises first through third decition circults 271, 272, and 273, The fir~t decision circuit 271 is supplied with first through third primary busy signals 265, 277, and 278 which indlcate that the first through the third leadlng matchers 56a~ 56b; and 56c are busy, First and second secondary b~sy signals 281 and 282 indicati~e of the facts that the fir-~t and the second precise matchers 57a and 57b are busy, are delivered to the second and the third declsion circuits 272 and 273, The third decision circuit 273`produces ., ~73~

fir~t through third primary allowance signals 286, 28?, and 288 and first and second secondary allowance signals 291 and 292 which allow transfer of data to the first through the third leading matchers 56a, 56b, and 56c and to the first and the second precise matchers 57a and 57b, respecti~ely~ The primary busy and allowance signals 276 through 278 and 286 through 288 are transm{tted through the bus 90 (Figs. 2 and 3). The secondary busy and allo~ance signals 281, 282, 2~1, and 292 are transmitted through the bus 64, When a command indicative of transfer of data from the data storing device 54 (Flg, 1) to the leading or the precise matchers 56's or 57's, is supplied through the bus 62, the deYice interface circuit 63, and the control circuit 66, the first decision circuit 271 produces ~i~st~through third primary decision signals 296, 297, and 298. According to logic operation~ the signal~
296 through 298 are produced ~hen the first throueh the thlrd primary busy signals 276 through 288 are absent~ respectively, When supplied with flrst through third transfer request signals 301, 302, and 303 from the first through the third leadlng matchers 56's through the bus 90, the second decision circuit 272 produces an inhibit signal 309 and first through fifth secondary decision signals 311, 312~ 313, 314, and 315, The ~nhibit signal 309 is produced either (1) Hhen at least one of the transfer request signals 301 through 303 i8 present and further~ore ~hen the secondary busy signals 281 and 282 are both present or (2 when all transfer request signals 301 through 303 are absent, The first secondary decision signal 311 is produced ln the presence of the first transfer request signal 301, The second secondary 73~

decision signal 312 is produced when the second transfer request sienal 302 is present in the absence of the first transfer request signal 301, The thlrd seconda~y decision signal 313 is pr~duced ~hen the third transfer request signal 303 is present in the 5 absence of the first and the secor.d transfer request signals 301 and 302, The fourth and the fifth secondary decision signals 314 and 315 are produced when at least one of the transfer requst signals 301 through 303 is present in the absence of the first and the second secondary busy signals 281 and 282, respectively, First through third AND circuits 316, 317, and 318 are supplied ~ith the inhlbit signal 309 in common. Responslve to the first through the third primary decision signals 296 through 298, the flrst through the third AND circuits 316 through 318 produce first through third ternary declsion signals 321, 322, and 323, respectively. The third decision circuit 273 includes a flip-flQp (not shown) for selecting either of the first and the second precise matchers 57's when both are idle, It wlll be assumed that the flip-flop produces first and second qua~ernary decision signals 326 and 32~ (not shown) to select the first 20 and the second precise matchers 57's, re~pectiYely, The ~irst primary allowanc~ slgnal 281 is produced ~hen at least one of the first secondary and ternary decision signals 311 and 321 is presenta The second primary allo~ance slgnal 28~ 15 produced when at least one of the seGond secondary and ternary decision signalB 312 and 322 ls present, The third pr~mary allowance signal 288 is produced when at least one of the third secondary and ternary declsion signals 313 and 323 is present, ~9~73;~

The fir~t secondary allowance sl~nal 291 is produced when the fourth ~econdary declsion ~Ignal 314 i8 present and moreover either when the flrst secondary busy signal 281 is absent or ~hen the first quaternary decision signal 316 is present in the absence of the second secondary busy signal 282, The second secondary allowance signal 292 is produced when the fifth secondary decision signal 315 is present and furthermore either when the second secondary busy ~i~nal 282 is absent or ~hen the second quaternary decisio~ signal 327 i-~ present in the absence of the flrst secondary busy signal 281.

(11) Closing Paragraph While the preferred embollments of this in~entlon and modifications thereof have so far been described ~ith reference to the accompanying drawing, it ~ill now readily be possible for one skilled in the art to carry this invention into effect in ~arious other manners. For ex~mple, modification of the pair candidste list memory 83 and of the pair list memory 86 should preferabl~ be carried out for all combinations of the proximate minutiae, The memories, such as the minutia memorie~ 153 and 154, may be l~aded with the data in other ways~ Attention should finally be directed to the fact that it is posslble to lmplement th~ sequence controllers 69 and 79, the pair detecting unit 128 or 198, and the like by microcomputers as will readily be understood from the description of operation,

Claims

WHAT IS CLAIMED IS:
1. A method of deciding a degree of match between a search and a file fingerprint, including the steps of;

selecting principal coordinate systems on the respective fingerprints;
selecting a search and a file fingerprint area where minutiae are clear;
forming a minutia list showing those original position and direction data of the minutiae which are given by the respective principal coordinate systems, said minutia list furthermore showing those relation data of the minutiae which are substantially independent of said principal coordinate systems; and selecting pairs of minutiae from the minutiae of the respective fingerprints by comparing the original position and direction data given for the respective fingerprints and furthermore comparing the relation data given for the respective fingerprints;
wherein the improvement comprises the steps of;
forming a pair candidate list which shows said pairs of minutiae as pair candidates, respectively;
deciding optimum amounts by referring to the original position and direction data of the minutiae of said pair candidate said optimum amounts being for matching said principal coordinate systems with each other;
transforming the original position and direction data given by one of said principal coordinate systems for the minutiae of said pair candidates into transformed posittion and direction data given by a transformed coordinate system into which said (Claim 1 continued) one principal coordinate system is transformed by said optimum amounts;

forming a pair list by referring to said minutia list, said pair candidate list, and said search and said file fingerprint areas, said pair list showing precise pairs of minutiae selected from those minutiae of said pair candidates which are present in an area common to said search and said file fingerprint areas, the minutiae of each precise pair having a precise local similarity between the transformed position and direction data and the original position and direction data given by the other principal coordinate system and between -the relation data, said pair list furthermore showing evaluations, each evaluation being representative of said local similarity; and deciding said degree of match by using the minutiae of said pair list and by referring to said evaluations, 2. A method as claimed in Claim 1;
said minutia list forming step including the steps of;
selecting those primary local coordinate systems which have primary local origins at the respective minutiae;
selecting those primary proximate minutiae with reference to the respective primary local coordinate systems which are proximate to the respective local origins; and deciding primary data of said primary proximate minutiae with reference to the respective primary local coordinate systems;

wherein said minutia list forming step comprises the steps of;

(Claim 2 continued) selecting those secondary local coordinate systems which have secondary local origins at the respective primary proximate minutiae;
selecting those secondary proximate minutiae with reference to the respective secondary local coordinate systems which are proximate to the respective secondary local origins;
deciding secondary data of said secondary proximate minutiae with reference to the respective primary local coordinate systems; and listing said primary and said secondary data as said relation data.
3, A method as claimed in Claim 1, wherein said pair list forming step comprises the steps of;
forming an additional minutia list which shows said transformed position and direction data, the original position and direction data given by the other principal coordinate system for the minutia of said pair candidates, and the relation data of the minutiae of said pair candidates; and forming said pair list by referring to said additional minutia list, said pair candidate list, and said search and said file fingerprint areas, the transformed position and direction data given in said additional minutia list being used on evaluating said precise local similarity, 4. A fingerprint matching device for deciding a degree of match between a search and a file fingerprint, including;
minutia list memory means for memorizing a minutia list showing those original position and direction data of minutiae (Claim 3 continued) which are given by principal coordinate systems preliminarily selected on said search and said file fingerprints, respectively, said minutia list furthermore showing those relation data of said minutiae which are substantially independent of said principal coordinate systems;

fingerprint area memory means for memorizing a search and a file fingerprint area where the minutiae are clear; and selecting means coupled to said minutia list memory means for selecting pairs of minutiae from the minutiae of the respective fingerprints by comparing the original position and direction data given for the respective fingerprints and furthermore comparing the relation data given for the respective fingerprints;

wherein the improvement comprises;

pair candidate list memory means coupled to said selecting means for memorizing a pair candidate list which shows said pairs of minutiae as pair candidates, respectively;

optimum amount deciding means coupled to said minutia list memory means and said pair candidate list memory means for deciding optimum amounts by referring to the original position and direction data of the minutiae of said pair candidates, said optimum amounts being for matching said principal coordinate systems with each other;

coordinate transforming means coupled to said minutia list memory means, said pair candidate list memory means, and said optimum amount deciding means for transforming one of said principal coordinate systems into a transformed coordinate system by said optimum amounts, said coordinate transforming means thereby (Claim 3 twice continued) transforming the original position and direction data given by said one principal coordinate system for the minutiae of said pair candidates into transformed position and direction data;

pair list memory means coupled to said minutia list memory means, said pair candidate list memory means, and said fingerprint area memory means for memorizing a pair list showing precise pairs of minutiae selected from those minutiae of said pair candidates which are present in an area common to said search and said file fingerprint areas, the minutiae of each precise pair having a precise local similarity between the transformed position and direction data and the original position and direction data given by the other principal coordinate system and between the relation data, said pair list furthermore showing evaluations, each evaluation being representative of said local similarity and deciding means coupled to said pair list memory means for deciding said degree of match by using the minutiae of said pair list and by referring to said evaluations, ?. A fingerprint matching device as claimed in Claim 4;

said minutia list memory means including first means for memorizing a part of said minutia list, said part showing the original position and direction data given by the respective principal coordinate systems and furthermore showing that part of said relation data which gives primary data represented by primary local coordinate systems selected to have primary local origins at the respective minutiae, said primary data being given (Claim 5 continued) to those primary proximate minutiae with reference to the respective primary local coordinate systems which are selected proximate to the respective primary local origins with reference to the respective primary local coordinate systems;

wherein said minutia list memory means comprises second means for memorizing a remaining part of said minutia list, said remaining part showing that remaining part of said relation data which gives secondary data represented by the respective primary coordinate systems, said secondary data being given to secondary proximate minutiae which are selected proximate to the respective primary proximate minutiae with reference to the respective ones of secondary local coordinate systems selected to have secondary local origins at the respective primary proximate minutiae.

6. A fingerprint matching device as claimed in Claim 4, wherein;

said minutia list memory means comprises;
first minutia list memory means for memorizing a first minutia list which shows the original position and direction data given by the respective principal coordinate systems and the relation data of the respective minutiae; and second minutia list memory means coupled to said coordinate transforming means and said pair candidate list memory means for memorizing a second minutia list which shows said transformed position and direction data, the original position and direction data given by the other principal coordinate system for the minutiae of said pair candidates, and the relation data for the minutiae of said pair candidates;

(Claim 6 continued) said selecting means being coupled to said first minutia list memory means;

said selecting means being coupled to said first minutia list memory means;

said optimum amount deciding moans being coupled to said first minutia list memory means and said pair candidate list memory means;

said coordinate transforming means being coupled to said first minutia list memory means, said pair candidate list memory means, and said optimum amount deciding means;

said pair list memory means being coupled to said second minutia list memory means, said pair candidate list memory means, and said fingerprint area memory means, the transformed position and direction data used in giving said precise local similarity being those given by said second minutia list memory means,