US2884486A - Photoconductive facsimile transmitting apparatus - Google Patents

Description

April 28, 1959 R. J.-WlSE PHOTOCONDUCTIVE FACS'IMILE mmsmw'rmc APPARATUS Filed Dec. :50, 1952 4 Sheets-Sheet 1 i 'i'iiiiiimiiiifiEmmi INVENTOR R. J.WISE

ATTORN EY R. J. WISE April 28, 1959 PHOTOCONDUCTIVE 'FACSIMILE TRANSMITTING APPARATUS Filed Dec. :50, 1952 4 Sheets-Sheet 2 JMZZ IO OZBOPDO INVENTOR.

R. J. WISE ATTORNEY R: J. WISE April. 28, 1959 PHOTQCONDUCTIVE FACSIMILE TRANSMITTING APPARATUS I 4Sheehs-Sheet 3 Filed Dec] 50, 1952 INVENTOR.

R. J. WISE AT RN EY April 28, 1959 R. J. WISE 4,

, PHOTOCONDUCTIVE FACSIMILE TRANSMITTING APPARATUS Filed Dec. 30, 1952 4 Sheets-Sheet 1 OUTGOING CHANNEL CHARGE INVENTOR.

R. J. WISE v TORNEY United States Patent PHOTOCONDUCTIVE FACSIMILE TRANSMITTING APPARATUS Raleigh I. Wise, Arlington, N.J., assignor to The Western Union Telegraph Company, New York, N.Y., a corporation of New York Application December 30, 1952, Serial No. 328,612

15 Claims. (Cl. 178--7.1)

analog for storage and for transmission from such stor-,

age to a distant location.

Devices presently used for this purpose all require that the subject matterbe transmitted by dividing it into alarge number of elementary areas, according to some prearranged regular pattern, and performing successive photometric measurements or electric scanning of each such area, using the resulting brightness or electrical values to set at a corresponding level some convenient variable of the transmitted carrier, such as its voltage, frequency, phase, or the timing or other characteristic of a discontinuity therein. 7

.In order for such a process to have practical value, however, it must be adapted to being received on a device which can produce light or dark areas on the reproducing surface corresponding to the variations of the incoming carrier, and, of equal importance, it must be able to locate these successive light and dark areas on the reproducing surface in exact correspondence with the location of those being transmitted.

It is this latter problem of synchronization which has led to the wide use of rotating drum transmitters and reproducers for facsimile systems, because in them it is necessary only to arrange for the transmitting and receiving drums to operate at the same speed, in order to ensure exact synchronism between corresponding elemental areas of the transmitted and received material.

This convenience, however, necessitates that the ma terial to be transmitted be arranged on the surface of a drum so that it can be rotated at high speed. A method of doing this which is in wide current use is to wrap the paper message blank or other subject material around the drum and hold it in place with clips or a garter spring. This requires that the material be flexible enough to wrap around the drum, strong enough to withstand high speed rotation, very nearly the exact size of the drum, and have a minimum of surface irregularities. Moreover, an individual hand operation normally is required to place it in position on the machine, which must be done before each transmission can be started.

One of the objects of this invention is to provide a novel arrangement which overcomes these difliculties, by permitting the transmitted material to be of any size of contour, even a three-dimensional scene, without the necessity for physically applying it to a drum, thus avoiding the need for bending the sheet of material that carries'it, or for rotating the resulting assembly. Since the subject material can be transmitted equally well from a flat position, it is well adapted to being fed automatically, as by the continuous or intermittent advancement of a belt or by an automatic feed, such as that used on a conventional letter press. An important advantage, moreover, lies in the fact that under such an arrangement a backlog of messages or other subject material can be supplied to the transmitting machine at any convenient time, which time need bear no relation to the time at which the machine concludes its operation on 'any particular message. As a consequence of this, one machine operator can service a larger number of machines with greater ease, and with much less probability that any machine will remain idle despite the existence of a message waiting to be sent on it, as occasioned by the operator being engaged in servicing another machine at the time.

Another object of this invention is to accomplish the scanning operation on any type of subject matter without the use of a photoelectric cell.

A further object of the invention is to provide a simplified form of rotary scanner capable of transmitting information from fiat subject matter such as stiff cards and the like.

Another object of the invention is to provide a means of storing scanned facsimile subject matter for subsequent transmission.

Other objects and advantages of the invention will be apparent from the following detailed description of .an illustrative embodiment thereof, taken in conjunction with the accompanying drawings, in which:

Fig. 1 is an isometric view of a motorized storage scanner, and retransmitting assembly;

Fig. 2 is a schematic wiring diagram applicable to Fig. 1;

Fig. 3 is an isometric view of an automatic belt type easel usable with the scanning mechanism of Fig. 1;

Fig. 4 is a schematic wiring diagram applicable to the mechanism of Figs. 1 and 3;

Fig. 5 is a view of the lens and scanner mechanism of Fig. lenclosed in a lightproof housing.

Referring now to Fig. l, numeral 11 designates a drum having a conductive surface, said surface being coated with photoconductive material 12. The drum is carried on shaft 13 which is retained in upper and lower end bearings not shown in the figure. The term photoconductive material is employed to define any material which normally has a high insulating value sufficient to retain a substantial surface charge when not exposed to light, but which becomes sufliciently conductive when illuminated to selectively dissipate such charge in the illuminated areas. Materials of this class are anthracene, anthraquinone, sulphur, various mixtures thereof, and certain other substances, as disclosed by C. F. Carlson in Patent No. 2,297,691, issued October 6, 1942. By

applying a charge of high voltage direct current elec-.

tricity uniformly to the outer surface of such a layer contained on the conductive backing material of the drum, while it is in the dark or high resistance condition, and then directing thereon the real photic image of some desired subject material, for an appropriate time,

the charge is differentially dissipated through the photoconductive layer in degree having a direct relation to the intensity of the incident light. This results in the desired conformal mapping of the said image in terms of electrical potential over the surface of the substance on the drum 11. Electrode 16 constitutes an electrical charge sprayer comprising a multiplicity of relatively sharp discharge points 17 affixed thereto in proximity to but spaced from the drum 11, supported on insulator 18 and energized as required through wire 19 with a high voltage direct potential with respect to grounding wire 21 which contacts drum '11 through the action of brush 22 sliding thereon. Such a high voltage direct potential can be obtained from any convenient and suitable source of familiar kind, such as a mains driven high voltage transformer equipped with a thermionic rectifier and a filter, a medium voltage transformer with voltage multiplying rectifier and filter, a so-called .RF

power supply employing a radio frequency or ultra-- sonic frequency oscillator, air core transformer, thermionic rectifier, and simplified filter, orsimply by means of a static electricity generator of the Wirnshurst or Van de Grafi type p Clutch plate 23, having a slotted hub 24 engages a pin 26 driven into shaft 13, so that the clutch plate is rotationally afiixed thereto while being slidable longitudinally for engagement with the lowenor driving stir-e face of electromagnet 27 when the latter is energized. Said electromagnet is'energized at predetermined times through wires-28 and 29 connectedto brushes 31 and 32 bearing on the collector rings 33 and 34 and is afiixed 'atesto open switch 37 at a definite angular position thereof, and worm wheel 38, through which the quill can be rotated by energizing wires 39 and41 of low speed motor 42, this operating worm 43 which engages 2,884,486 7 i w r r With a latentimage of the subject material thus impressed on the surface 12 of drum 11 as areas of graduated electrical charge, clutches 27 and 44 are deenergized and high speed motor 68 energized to drive helical gears 69, idler gear 71, and also one way clutch member 74 which is pinned tojshaft 13, through the 'wedging action of. bearing balls 73 against driving member 72.

Gear 76, to which is afi'ixed leadtscrew 77, is also roi Q tated by idler gear'71, and at the same time half-nut 78 to quill 14, as are the cam 36 whose singleulobe opersaid worm wheel 38. Quill 14 is thusv rotatable by low speed motor 42 through the closing of a pair of contacts in one of the supply wires, here wire 39,.to said.

low speed motor and by simultaneously energizing clutch 27 as hereinafter described. By electrically connecting motor and clutch in parallelyand switch 37 in series with them, any starting-of low speed motor 42 made by H from connection therewith. During this single revolut-ion, the application of a high potential to electrode '16 results in the production of electricalcharge in the sharp pointed conductors 17 which, in the absence of ambient light, as would occur in a darkened room, or preferably by enclosing the mechanical structure including the drum 11 in a light tight case, causes an induced electrical. charge to be distributed uniformly over the surface of photoconductive layer 12 on the surface of drum 11.

, drum 11 for one revolution, and then to disengage it This highlycharged condition of the exterior surface of layer 12. persists because of the insulating condition of the layer, brought about by the absence of light,

After thus sensitizing the surface 12 of drum 11, mag

netic clutch44 is energized through wires 46 and 47 toattract and engage movable clutch plate 48, thuscrotationally connecting pulleyj49 to the shaft 13. By again causing low speed motor 42 to turn drum 11 through one revolution, belt 51 is drawn around idler pulley 52 and wound up on pulley 49 to which its end is fastened. Wheel 53, to which the other end of belt 51 is fastened, is turned thereby, as is the shaft 54'to which the Wheel is fastened. ,Shaft 541 is rotatably mounted in bearing 57 securedin fixed base 56, and is urged in the return direction by spring 58, both to .retain tension in belt 51, and also to causereturn to a fixed angular position determined by stop pin 59 upon disengagement of clutch 44.

Rotation of shaft 54 causes rotation of front surfaced mirror 61 instep with drum 11.' This causes an image of the subject matter 62 mounted on easel 63, as cast by lens 64 under control of shutter 66 operated by solenoid 67, to sweep across the vertical slit in diaphragm 68 at such a speed that each element of said image traversmitting key, 106 is depressed.

circuits through limit switch 89 for half-nut magnet ing the slit and impinging on drum llwhere'on it is focused, remains in step therewith.

By thus sweeping onto the charged surface of drum which is secured to the carriage79 whichslides freely on ways 81, is held in engagement with lead screw 77 by the energized electromagnet coils 83; Drum 11 is thus constrained to rotate,-and carriage 89 to move paral lel thereto, by the operation of high speed motor 68, Stylus 84, which is anelectricalpickofi or charge detector in the form of a metal electrode supported O 11 an insulating block 86 attached, tothe carriage, is thus carried across the faceof the rotating drum 11 at a uniform rate. Single'lob'ed cam .87, which is pinned to shaft 13, operates switch 88 to close its contacts once every revolution of the-drum 11, at'a predetermined phase position in the cycle, thus providing means to produce a synchronizing impulse for transmission to a distant receiver. At the conclusion of the travel of carriage 79 along the ways 81, the switch 89 fastened to the carriage strikes the end of leadscrew77, and is operated by it to open'the circuit leading to electromagnet coils 83. This enables spring 82 to disengage half-nut 78 from engagement with :lead screw 77, and allows spring" 91 to return the carriage to its original position.

During the advance ofcarriage 79, the electrical signals picked up from the surface 12 of drum 11 by stylus 84 are applied by a vacuum-tube coupler 92 to an amplifier 93, which is connected to further circuitry as later described.

In Fig. 2 is shown the electrical wiring arrangement of the elements set forth above, which provides for their cooperative action in an established sequence. V Operation of the equipment, is initiated by throwing the switch 101 to the charge position and momentarily depressing the starting key102. Thiscompletes the circuit to relay 105, magnetic clutch 27 andrelay 103.- Relay 105 controls low speed motor 42, startingit and causing switch 37 to close, in parallel with'the starting key, permitting the latter to be released without further immediate effect.

Magnetic clutch 27 simultaneously engages clutch plate 23 to drive drum 11, and relay 103 applies alternating mains voltage to transformer 104, w ch, through conventional converter means 110, applies a high direct potential between drum 11 and charge sprayer 16 during one revolution of the drum, as terminated by the ultimate reopeningof switch 37 when operatedbycam 36, thusapplying the uniform surface charge to the storage,

drum 11. c t a t With switch 101 thrown to the expose, position,

starting key 102 is again depressed to initiate another revolution of drum 11 as before, except thatrelay 103 controlling thehighvoltage supply is now deenergized,

shutter magnet 67 is energized to open shutter 66 admitting the desired image to be impressed onthe drum 11,, and clutch 44 is energized so that pulley 49 in winding up tapeSl causes the image to be swept across drum 11 in synchronisrn with the rotation thereof. r

311 an image composed of areas having differing intensity of light, the surface potentials of itsdiiferent regions are changed; the highly charged parts untouched by light remaining so, and those exposed to the full intensity of illumination caused by bright areas on the subject material 61 being appreciably dischargcddue to. the

temporarily increased conductivity of photoconductive layer 12 brought about by the light incident thereon.

Upon the stopping of the drum at the completion of the above-described second orstorage revolution, trans? This completes parallel and relay 107. The latter pulls up and locks in on contact A. Contact C completes the circuit to high 1 speed motor 68, which drives lead screw 77 and, through overriding clutch 74, drum 11.

Y i Contact B applies power from battery 108 through synchronizing switch 88 to the fiiefih of carriage 79 and thereby a scanning of the rotating drum 11 by stylus 84. Limit switch 89 is opened by, impingement at the conclusion of carriage travel in a: predetermined amount, causing relay 107 andhalfnutt magnet 83 to release and causing spring 91- to return the, carriage to. itsv starting position. Electrical signals picked up bystylus 84 from the charged surface of drum 11 are coupled by vacuum tube 92 to amplifier 93 and together with signals derived from oscillator 111- are converted in modulator 112 to modulated continuous wavesfor transmission over a wire line to a remote reeiver.

In Fig. 3 is illustrated another form of equipment for supplying to the sensitized drum 11 of Fig. 1 an image of thesubject matter to be transmitted, it being understood that the mechanism of thisfigure may be substituted for the copy-holder and oscillating mirror mechanism and itsrb'elt' drive of Fig. 1. In this construction a belt 116 of; textile fabric or other flexible material passes over rolls 1.1-7: and: 118 having flanged ends for the purpose of guiding. and. retaining the belt in position. Cleats 123 are secured to belt 116, separated by a distance convenientfor the retention of subject matter sheets 62 between them by means of slidable retaining clips 129. Prism 127- is: fixedly mounted in relation to lens 64 at an appropriate distance above subject matter 62, and causes an. image thereof to be projected into a plane tangent to the sensitized drum 11 of Fig. 1. Roll 117 is afiixed to? shaft. 119 which is driven through reducing gear 121 by; a. motor 122 which operates synchronously with the low speed. motor 42 previously described, to drive the belt 116. Subject matter 62, in thus traversing prism 127 at a fixed rate of travel with respect to drum 11 as predetermined by the ratio of reducing gear 121, casts an image in a plane tangent to the surface of drum 11 opposite to the slit 65, this image moving laterally across the slit at a speed equal to the surface speed of the drum. In consequence of this, the image is placed on the drum without distortion due to foreshortening. Switch 124 is actuated to open its contacts by the arrival of cleat 123 under its operating lever. As will next be described, this causes motor 122 and solenoid 125 to be deenergized, the latter causing brake 126 to be applied by spring 120 to stop shaft 119 immediately.

Fig. 4 is a schematic diagram of the electrical wiring used to operate the equipment shown and described under Fig. 3. It will be. seen that except for the deletion of clutch 87 and belt 51 of Fig. 2, it comprises only the addition of control means thereto for use in connection with the: belt 116. Charging of the drum 11 is efiected as previously described, by closing of starting key 102 with. switch 101: in the charge position. Upon throwing switch 101 to the expose position and again momentarily depressing starting key 102a, the coil of relay 131 is energized together with the shutter magnet 67. Relay 131v closes its contact A, releases brake 126 by energizing solenoid 125 and also closes its contact B to start motor 122. Cleat 123 immediately moves beyond switch 124, which then closes its contacts and holds relay 131 in the energized condition through the contacts A until arrival of the next such cleat under the operating lever of switch 124, at which time said switch isopened thereby, and relay 131 is deenergized, opening contacts A and B to deenergize motor 122 and bring belt 116 to a stop with the cleat in exact register with the switch by' applying brake 126.

Fig. illustrates a structure enclosing the scanner mechanism and especially the photosensitive drum 11 of Fig. l in a light tight housing in order to permit the use of the assembly under ordinary conditions of ambient light. It is seen that the housing 151 is terminated on the diaphragm 68 and that an additional housing 152 prevents stray light which does not pass through lens 64 from reaching the central portion, of. diaphragm 68. Housings 151 and 152 may be combined into a single unitary assembly if-v desired. The. housing structure shown, or its equivalent, has been deleted from Fig. 1 solely for the purpose of clarity of representation, and is to be considered a part thereof as if, there shown.

It will be obvious that various modifications,. alterations and elaborations of the devices shown in thedrawings and described herein can be effectedwithoutcdeparting from the spirit or the essential attributes.- of: the. in;- vention as disclosed, and it is therefore intended. that only such limitations be placed thereon as are. specifically set forth in the appended claims.

What is claimed is:

l. A facsimile transmitter for sending subject matter, comprising a photoconductive storage member, means for uniformly charging said member to a predeterminedpotential, exposure means for subjecting said member to successive narrow but full member length linear elements of a light image of the subject matter to produce thereon a corresponding electrostatic charge image, and scanning mechanism including an electrical pickup device and means for scanning said member with said do vice to produce facsimile signals corresponding to the electrostatic charge on the elemental areas of said member.

2. A facsimile transmitter for sending subject matter, comprising a photoconductive storage member, means for uniformly charging said member to a predetermined pc tential, exposure means for subjecting said member to sue.- cessive narrow but full member length linear elements of a light image of the subject matter to produce thereon a cor responding electrostatic charge image, and scanning mechanism including an electrical pickup device andmeansfor scanning said member with said device to produce facsimile signals corresponding to the electrostatic charge on the elemental areas of said member wherein said photoconductive storage member comprises a rotatable drum having means for rotating the same in one cycle to produce: said electrostatic charge image and in another cycle to impart the charge thereon to said electrical pickup device.

3. A facsimile transmitter for sending subject matter, comprising a photoconductive storage member, means for uniformly charging said member to a predetermined po tential, exposure means for subjecting said member to successive narrow but full member length linear elements of a light image of the subject matter to produce thereon a corresponding electrostatic charge image, and scanning mechanism including an electrical pickup device and means for scanning said member with said device to produce facsimile signals corresponding to the electrostatic charge on the elemental areas of said member wherein said photoconductive storage member comprises a rotatable drum having means for rotating the same in one cycle to produce said electrostatic charge image and in another cycle to impart the charge thereon to said electrical pickup de vice and wherein said exposure means produces. said. electrostatic charge image on said drum insuccessive ale-- mental line areas substantially coextensive with the linear elements of said drum.

4. A facsimile transmitter for sending subject matter;..

comprising a photoconductive storage member, means for uniformly charging said member to a predetermined po-- ing means for rotating the same in one cycle to produce said electrostatic charge image and in another cycle to impart the charge thereon to said electrical pickup device in which said exposure means includes a mask. disposed closely adjacent to the surface of said drum in tangential relation thereto and having a dissecting aper-' "of said aperture, and means i j I 7 ture extending substantially throughout said tangential portion, means for projecting alight image into the plane for moving said image past said aperture concurrently with the rotation of said drum and at a rate proportional to said rotation. v 5. A facsimile transmitter for sending subject matter, comprising a photoconductive storage member, means for uniformly charging said member to a predetermined poten- ,tial, exposure meansgfor subjedtingsaid member to succestial, exposure means for subjecting said member to successive narrow but full member length linear elements of a light image of the subject matter to produce thereon a' corresponding electrostatic charge image, and scanning mechanism including an electrical pickup device andmeans for during the said first mentioned cycle of rotation of said 8. A facsimile transmitter for sending subject matter,

comprising a photoconductive storage member, means for uniformly charging said member to a, predetermined potensive narrow but full member length linear elements of a light image of the subject matter to produce thereon a cor;

responding electrostatic chargeimage, and scanning mach-Y anism includingan electrical pickup 0 device and means 'fonscanning said member with said device to produce a i facsimile signals corresponding to the electrostatic charge to J onsth'e elemental areas of said member; wherein said scanning said member with said device to produce facsimile signals corresponding to the electrostatic charge on the elemental areas of said member wherein said photoconductive storage member comprises a rotatable drum having means for rotating the same in one cycle to produce said electrostatic charge image and in another cycle to impart the charge thereon to said electrical pickup device in a projection system, a copyholder forsupporting' copy to be transmitted and means for producing relative movement between said projection system and the copy on which said exposure means includes a dissecting aperture mask disposed adjacent to said drum,

pickup device, in which said exposure means includesfa dissecting aperture mask disposed adjacent to the said said copyholder to advance the projected image of said sending subject matter,

scanning said member with said device to produce facsimile signals corresponding to the electrostatic charge on the elemental areas of said member wherein said photoconit ductive storage member comprises a ing means for rotating the same in one cycle to produce said electrostatic charge image and in another cycle to impart the charge thereon to said rotatable drum havelectrical pickup photoconductive storage member comprises a rotatable drum having means forrotating the same in one cycle to produce said electrostatic charge image and in another cycle to impart the charge thereon to said electrical drum, a projection system, acopyholder for supporting copy to be transmitted, and means for moving said copyholder relative tosaid projcctionsystem in coordinated relation to the rotation of said drum to advance the projected= image of saidcopy across thedissecting aperture of said mask during said firstmentioned cycle of rotation of said drum.

9. A facsimile transmitter for sending subject matter,

comprising arotatable drum'havinga photoconductive surface layer, meansfor rotating said drum through first and second cycles of operation, means foruniformly electrostatically charging said drum to a predetermined potential during said firstcycle, means for exposing said drum to successive narrow but full drum length linear elements of a light image of the subject matter during 1 saidsecond cycle, means for rotating said drum through a third cyclepand means to electrically scan said drum during said third cycle to produce facsimile signals cor-j responding to said, light image.

10. A facsimile transmitterfor sending subject matter,

a photoconductive drum through first comprising a rotatable drum havin surface layer, means for rotating said and second cycles of operationat a predetermined speed,

i means for uniformly electrostatically charging said drum:

device in which said exposure means includes a dissecti ing aperture mask disposed adjacent to saiddrum, alens system, a copyholder for supporting copy to be transmitted, means for reflectingan image of the copy on said copyholder to the said lens system and meansforproto a predetermined potential during said first cycle, means for exposing said drum to successive narrow but full drum length linear elements of a lightimage of the subject matter during said second cycle, means for rotating said drum through a third cycle at a higher speed, and

ducing relative movement between said lens, system and I said reflected image to said copy across the dissecting aperture ofsaid mask advance the projected image of:

during said first mentioned cycle of rotation of-said drum.

7. A facsimile transmitter for sending subject matter, comprising a photoconductive storage member, means for uniformly charging said member to a predetermined potential, exposure means for subjecting said member to successive narrow but full responding electrostatic charge image, andscanning mechanism including an electrical pickup device and means for scanning said member with said device to produce facsimile signals corresponding to the electrostatic charge on the elemental areas of said member wherein said photoctmductive storage member'comprises a rotatable drum having means for rotating the same in one cycle to produce said electrostatic charge image and .in, another cycle to mpart the charge thereon to saidelectrical pickup de vice in which said exposure means includes a dissecting aperture mask disposed adjacent to said drum, a lens system, a copyholder for supporting copy to be transmitted, means for reflecting an image of the copy on said copyholder to saidlens system andmeans for oscillating said reflecting means in coordinated relation to the,

rotation of said drum to project the refiectedimage of said copy across the dissecting aperture of said mask member length linear elements of a light image of the subject matter to produce'thereon a cor-' potential during said first :cycle, means for exposing said means to electrically scan said drum duringsa'id third cycle to produce facsimile signals correspondingto said light image.

11. A facsimile transmitter for sending subject matter,

comprising a rotatabledrum H having aphotoconductive surface layer, means for rotating said drum, through: first and second cycles of operation, :means for uniformly electrostatically charging said drum to a predetermined drum to successive narrow but full drum length linear elements of a light image of the subject matter during said second cycle, means for rotating said drum through image deflecting means positioned to third cycle. I i i 12, A facsimile'transmitter for sending subject matter, comprising a rotatable drum havingxa photoconductive surface layer, means for rotating said drum through suc-t I cessive cycles of operation, means for electrostatically during a first said N cycle of operation, drum masking means having a staa third cycle, means to electrically scan said drum dur-' produce facsimile signals cortex ing said third cycle to sponding to said light image, and means for generating function signalsduring rotation ofsaid drum in said charging the surface of, said drum tionary linear aperturein the i plane of a drum element for dissecting a light image,tmeans to of subject matter in a plane tangentlto said drum, light sweep said apes ture ata rate proportioned to the speed of said dmni form a light image during a single revolution thereof whereby to distribute a subject matter light image on the surface of said drum and thereby to create a corresponding electrostatic charge means operatively interconnecting said light image deflecting means and said drum for causing said light image deflecting means so to sweep, and means to electrically scan said drum during a subsequent cycle of operation to produce image intelligence bearing facsimile signals.

13. A facsimile transmitter comprising a rotatable drum having a photoconductive surface capable ofsustaining a distributed charge thereon, charging means therefor, a light mask fixed in a plane tangent to the drum and having a slit adjacent to the drum and extending entirely thereacross parallel to the axis thereof, a subject matter image producing lens fixedly disposed to form an image on said mask, a mirror opposite said mask, and rotatable about an axis parallel to said drum in step therewith to sweep an image from said lens across said mask during a single revolution of said drum means so to rotate said mirror, and means to scan the said drum to produce facsimile signals representative of said subject matter.

14. A facsimile transmitter comprising a rotatable drum having a photoconductive surface adapted to retain a distributed charge of electricity thereon, electrostatic means to charge said drum surface, a light mask fixedly mounted adjacent the side of said drum and slotted therealong throughout substantially the entire length of said drum, a copyholder movable oppositely to the drum and in step therewith, means so to move said eopyholder a copy image forming lens fixedly mounted between said copyholder and said light mask to cast a copy image element on said drum, and drum scanning means to pick off from said drum facsimile signals representing acopy image.

15. A facsimile image storage system comprising a rotatable drum having a photoconductive surface for selectively retaining distributed charges thereon, a light mask fixedly mounted adjacent the side of the drum and slotted therealong, and means for sweeping an optical real image across the exposed surface of the drum in step with the rotation thereof to form a corresponding electrical charge image on the drum.

References Cited in the file of this patent UNITED STATES PATENTS Re. 21,417 Jenkins Apr. 2, 1940 1,880,289 Sukumlyn Oct, 4, 1932 1,979,722 Zworykin Nov. 6, 1934 2,143,214 Selenzi Jan. 10, 1939 2,169,840 Lewis Aug. 15, 1939 2,301,199 Bruce Nov, 10, 1942 2,330,682 Clothier et a1 Sept. 28, 1943 2,357,809 Carlson Sept. 12, 1944 2,583,546 Carlson Ian. 29, 1952 2,624,652 Carlson Jan. 6, 1953

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