US2256385A - Projection printer - Google Patents

Description

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R. M. EVANS ET'AL PROJECTION PRIQNTER Filed Aug. 7, 1940 9 Sheets-Sheet 1 RALPH M fm/vs BENJAMIN E. Lagos/n52 v INVENTORS BY I A TTORNE Y R. M. EVANS ETAL PROJECTIONv PRINTER Sept. 16, 1941.

9 Sheets-Sheet 2 IQALPH M. EVANS fif/vJAm/lvziLz/aosflfz INVENTORS BY W./

Filed Aug. 7, 1940 ATTORNEY Sept, 16, 1941. R. M. EVANS ETAL PROJECTION PRINTER Filed Aug. 7, 1940' zQALPHMfl A/YS fLz/aosflsz INVENTORS ATTORNEY Ma Q Sept. 16, 1941. ,R. EVANS ETAL PROJECTION PRINTER- 9 Sheets-Shet 5 Filgd Aug. 7, 1940 ATTORNEY R. M. EvANs- :rm. 2,256,385

PROJECTION PRINTER Filed Aug. 7, 1940 9 Sheets-Sheet 6 1 Sept. 16, 1941.

A T'IORNE Y Sept. 16, 1941.

R. M. EVANS ETAL IZROJECTION PRINTER Filed Aug. '7, 1940 9 Sheets-Sheet 7 IQILPHMfWI/YS BENJAM/NL'TA 0505/7 52 INVENTORJ BY a AT ORNE Sept. 16, 1941.

R. M. EVANS ETAL I PROJECTION PRINTER Filed Aug. 7, 1940 9 Sheets-Sheet 8 M. Em/vs RALPH EE/YJAM/N ooooooo OOOOOOO a H w w L E m w E V m.

w E N m A EIAL PROJECTION PRINTER R. EVAN? Sept. 16, 1941.

Filed Aug. 7, 1940 9 Sheets-Sheet 9 IQQPHMEWINS BEMAM/NEL O S Z I Who ATTORNEY Patented Sept. 16, 1941 PROJECTION PRINTER Ralph M. Evans and Benjamin E. Luboshez, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application August 7, 1940, Serial No. 351,762

11 Claims.

This invention relates to projection printers for photographic purposes.

It relates generally to the same subject matter as copending applications Serial Nos. 351,761 and 351,763 filed concurrently herewith by one of us (Luboshez) It is a general object of the invention to provide a projection printer for making prints, usually on paper, from transparencies.

It is a particular object of the invention to provide a projection printer for making color prints from color transparencies. The specific objects of the invention are listed below:

1. It is an object of the invention to provide a printer with means for correcting errors in color balance of the original. This is not the type of correction corresponding to masking.

2. It is an object of the invention to provide means for judging when the color balance has 7 been fully corrected.

3. It is an object of the invention to provide a simple compact optical system for providing a white border adjacent to the original to be printed or to an image thereof which border will not interfere either with this image or with the one exposing the sensitive material upon which the print is to be made.

4. It is an object of the invention to provide means for correcting for errors in color balance of the sensitivity of any particular photosensitive material being used.

5. It is an object of the invention to provide a means for satisfying object No. 4 which means can be fixed in place for any one roll of printing paper and need not be moved during the judg ing of the colorbalance of the original and which will not interfere with this judging. Further more, it is arranged so that it does not interfere with the correction made in accordance with this judging.

According to the invention, the general and specific objects listed above are accomplished by combining the following features in a printer. A projection printer is provided having a record gate preferably horizontal for holding the original color transparency and a printing gate preferably vertical for holding color sensitive paper upon which prints are to be made. A lens (preferably with a reflector) is provided for focusing an image of the record gate on the printing gate. The gates are movable to permit differences in magnification and as they are moved, correct focus is maintained by suitable coupling means therebetween. According to the invention specifically described here the following features are included to provide color correction.

Color correction in color photography as ap-- plied to the making of a duplicate or print of a colored photographic record may be divided into four types. Two of these, one depending upon subjective color responses and the other on deficiencies in the final printing colors are not involved here since they have to do with the interrelation of the separate colors. I refer to the types of color corrections such as those involving masking. The other two types are concerned with the relative amounts of the separate colors, 1. e. with color balance. To correct for error in color balance in the original record, for example the original may be too blue or too magenta, color filters are provided to be positionable in the light beam somewhere between the light source and the image which is todo the printing. Preferably these filters are placed in the light beam before the light reaches the original to correct the appearance of the original itself. Various filters are used, all of them relatively thin optically and are positionable separately or in combination in the light beam.

To aid in judging the hue as well as the density of the original, an image of the original is formed on a viewing screen for example by a re movable mirror such as a reflex mirror. The borders of this viewing screen around the image are colored white preferably by direct illumination with white light. We have found that any errors in overall hue of the record appear very pronounced and it is quite, easy to judge the correct hue when this white border is provided whereas, when looking directly at the original, the eye has a tendency to adapt itself and small deviations from true colors cannot be detected. As a control on the density of the image so that the comparison with a white border of fixed intensity is made easier and/or so that a constant printing time may be used an adjustable wedge is also provided in the light beam.

In order to illuminate the borders on the viewing screen uniformly with white light, a lamp is placed behind the removable mirroigand is surrounded by a truncated four-sided pyramidal mirror which reflects light from the lamp past the removable mirror on all sides and to the,

borders of the viewing screen as required. Various baflles including the removable mirror itself prevent light from this lamp reaching the image on the viewing screen or reaching the printing gate.

' The above described arrangement incorpoardized as to color temperature and intensity and can be used only for a minor portion of their total life because their color and intensity varies with age beyond all tolerancelimits. Similarly,

since the printing beam is quite intense, any

filters therein soon fade and must be replaced.

According to the present invention all this is avoided by referring everything having to do with color and intensity to a single easily maintained standard, the above described borders. The lamp used to illuminate the borders is considerably undervoltage which results both in a longer useful life for the lamp and practically no deterioration of any filters placed in the comparison beam.

The standard borders provide even more than a photometer for the printing lamp since when the comparison of the image and the borders, together with necessary adjustments, is completed, correction has been made for any discrepancies in color or intensity of the printing lamp, color or densityof filters used, color or density of the original transparency being printed and, as will be described below, sensitivity or color sensitivity of the printing paper. The whole unit containing the reflex mirror and comparison system is removable and interchangeable with other similar units each of which may be separately standardized to correspond to a particular roll of printing papen To correct for the other source of color error, namely the color balance of the sensitivity of the photosensitive material being used, a compensating filter must be placed in the printing beam. It is'not desirable to have this filter in the beam between the record and the printing gates, parthat of the resulting print, 1. e. the filter which when placed over a light illuminating the P p r makes the paper look gray. Of course, the fact that light travels twice through the color layer when paper is viewed by reflected light and only once through the filter must be taken into account in selecting a complementary color filter.

Other objects and advantages of the invention will be apparent from the following description when read in connection with the accompanying drawings in which:

Fig. 1 shows a front elevation of the printer. Fig. 2 shows a side elevation of the printer. Fig. 3 shows a side elevation in cross section.

Fig. 4 shows a horizontal cross section of the viewing screen. i

Fig. 5 is a geometrical diagram of the focusing system.

Fig, 6.ls a perspective view of tem.

Fig. 7 is a front elevation of the record gate masking system.

Fig. 8 is a side elevation of this record gate masking system.

Fig. 9 is a side elevation of the printing gate masking system.

the optical sys- Fig. 10 is a rear elevation of the printing gate Fig. 15 is a side view of the viewing screen system.

Fig. 16 is a perspective view of the paper advancing mechanism.

Since Figs. 1 and 2 are outside views, the cooperation of the details is not apparent therein.

' Therefore, the following description will vbe made Therefore, it is placed with the other filters near the light source. However, whilethe color balance of the original is being tested and corrected, it would not do to have this additional filter in the path since its effect would be corrected-out when the image on the viewing screen was made to look right as compared with a white border. On the other hand, it is a nuisance to have to remove this filter while the color balance of the original is being checked and to replace it for every print. Therefore, we place an identical filter in the path of the light illuminating the white borders. exactly white, but white is not an exact term anyway. The balance of the color of the original record is made with respect to the white borders with both filters in place and hence their effects cancel one another as far as the color judging is concerned, but the one in the printing beam is still there during the printing to correct for improper color balance, if any, of the particular roll of paper being used. The filters for this purpose, i. e. to correct for errors in color balance of the sensitive paper, are preselected by sensitometric tests of the paper and each roll carries That is. these borders are not with reference to the other figures, the optical system being shown best inFigs. 3 and 6. However, reference to the first two figures when reading the description will bring out one of. the main advantages of the invention, namely the absolute convenience of all controls to the operator.

Figs. 3 and 6 will now be described together. The printer housing consists mainly of two parts-a camera 20 carried by a supporting housing 20'. The camera 20 carried by wheels "8 (in grooves I35 see Fig. 14) is movable horizontally on the supporting housing 2|! and all of the features are carried directly or indirectly by these two supports 2|! and 20'. Light from a lamp 22 travels in a substantially horizontal line through suitable condensers 23 and relay lenses 24 to a reflector 25 whence it is reflected vertically upward through a field lens 26 to a record gate 2| in which the original is mounted horizontally.

' piece a to the eyes of the operator who may then observe :.:the record in the record gate 2| directly. The eye-piece 33 is thus in a most a front view of the viewing screen i its stud 44 is made exactly equal to the distance convenient position above and near the record gate 2I. Stops 35 and 35 are provided for limiting the movement of the mirror 21 to these two positions 21 and 21'. The hinge 34 about which the mirror 21 rotates is above the optic axis 45 as it travels through the lens 25. The mirror 21 is operated by a handle I25 (shown in Figs. 1 and 2) connected to the shaft of the hinge 34. Even if no other viewing means were present to cooperate with this one, the use of a hinged mirror alternatively to send light to the camera and to the observer simultaneously and in a very simple manner accomplishes an obviously desirable -feature.

A removable mirror 35 is positioned in the path of the light from the lens 25 to the printing gate 29 so that it reflects light upward to a viewing screen 3| on which an image is formed. A refiector 32 above the viewing screen 3I permits this image to be seen in the eye-piece 33.

In order to change the magnification of the print, the record gate 2I carried by a supporting member I28 is moved upward and the printing gate 29 is moved horizontally. Correct focus is maintained by means of lever 40 which rotates about a point 4I and has longitudinal slots 42 and- 43 therein in which studs 44 and 45 move. The stud 44 is carried by the supporting member I28 and is constrained to move vertically in a slot I21 in the housing I25. This housing I25 for the condenser 25 is rigidly attached to the housing The stud 45 is constrained to move horizontally while the printing gate and all of the members associated therewith (i. e. camera 20) are carried by the'wheels I35 moving in grooves I35 as best seen in Fig. 14.

The geometry of this focusing system is best shown in Fig. 5. In this figure the vertical line of motion of the stud 44 is labeled 4'! and the horizontal line of motion of the stud 45-is labeled 4 8. These lines of motion intersect at a point 49. Actually of course, if the lever 45 had an offset in it, the studs. and 45 might not have coplanar motion but in any case it would be equivalent thereto. The pivot H of the lever 40 i positioned a distance equal to the focal length of the lens from each of these lines of motion 41 and 45. Thus the points H, 49, 55, and 5| form a square whose side equals I, the focal length of the lens 23. The line 40' representing the lever 45'forms two triangles 44, 50, 4|, and 4|, 5|, 45. It will be noted that by simple geometry these two triangles are exactly similar and remain similar to one another as the line 45' rotates about the point 4|. Therefore 11:} equals f:b.. That is aXb equals f. Now going over from simple geometry to optics itis known that if distances a and b obey this rule, the distance 1+! will always be conjugate to the distan ;e b+j for a lens of focal length 1. Therefore the distance 44-49 (i. e. from 44 to 49) would always be conjugate to the distance 49-45 with respect to the lens 25. This principle is incorporated into the present printer by making the distance from the record gate 2I to the lens 25 along the optic axis 45 equal to the distance 44-49 and the disbetween the point 53 and the lens 25, where the point 53 is the intersection of the optic axis 45- and a horizontal plane through the horizontal line 45. Similarly the .distance e between the lens 25 and a plane through the vertical line 41 is made equal to the distance d between the stud 45 and the printing plane 29. The planes through the lines of motion are of course the ones perpendicular to the plane of the drawing; they are in each case orthogonal to the optic axis. Although there is only one horizontal plane through the line 49 there are an infinite number of vertical planes through the line 41 and hence the term orthogonal is used to specify the planes in each case. It will be noted that the distances (1 and e are actually negative since they are measured back from the lens and from the printing tance from the lens 20 to the printing gate as equal to the distance. -45. Actually the distances must be measured to the principal planes 52 of the lens 25 and that is what is meant by measuring the distance to the lens 25. As far as the optical principles of the system are concemed the lens 25 may be either side of the reflector 21. To get the above relation 'of distances, the distance c between the printing gate 2I and the magnification is changed, it

gate respectively. As the record gate is moved vertically and the printing gate is moved horizontally, the distance 2 I-53 changes, but the distance from 2| to the lens 28 always remains equal to the distance between the stud 44 and the point 49 and the corresponding correlation is maintained with respect to the printing gate.

The arrangement for masking the record gate is best illustrated in Figs. 6, 7, and 8. The width of the printinggate is made constant in this printer, which is, of course, the most economical method of using paper in rolls. Therefore, as is necessary to mask the record gate (as far as the width is concerned) to a degree which is inversely proportional to the magnification. This width masking is provided by masks which are moved by screws 51 carried on a shaft 55. 'Vertical motion of the printing gate to change the magnification causes a pinion 55 to movealong a rack 54 which is held rigidly by the printer housing 20'. This pinion 55 is thus rotated and rotates the shaft 55 and the screws 51 causing the mask 58 to move in and out as the printing gate is moved up and down.

The length masking of the record gate is more complicated by the fact that different shaped records are often to be printed. The length masking operation may be divided into two parts,

carried by racks 54 which move with the record gate. Thus as the record gate moves up, the stud 53 moves along the groove 52 pulling the horizontal rack 54 with it. This motion of the rack 54 cause a pinion 55 to rotate which rotates its shaft 55 and another pinion 51 thereon, which other pinion moves a rack 55 horizontally causing the length masks 59 to move in. Thus for successive prints of records of the same shape but different sizes, different magnifications are obtained by vertical motion of the record gate and both the width and length masking of this gate move in accordance with the change in magnification.

In this general connection, attention is drawn to the fact that the magnification necessary is very easily selected by the operator when viewing the record directly, 1. e. when the rotatable refiector is in the position 21. The operator merely I has to raise or lower the horizontal record gate .until the automatic masking of the width of this gate is brought to the area desired at which time camera housing 28 as far as any horizontal motion is concerned. The other ends of the levers 8| carry pivots 88 which. are fastened to the mask 81. Suitable slots 82 are provided in'lthe length masks have to be changed independently of the width masks. For this purpose a crank 18 rotates a shaft 1| and gears 12 which in turn rotate a shaft 14 having screw threads 15 thereon. These screw threads 18 cause nuts 16 to move horizontally carrying the stud 11 referred to above. This horizontal movement of the stud 11 causes the arm 88 to rotate about the pivot 8|, the stud 11 moving a short distance along the groove 82. This movement of the arm 88 causes the other stud 83 to move'carrying the rack 84.

and moving the length mask 88 in the same way as before. It will be noted that the stud 11 moves only horizontally with respect to the printer whereas the stud 88 moves vertically with changes in magnification. Thus the correlation between the horizontal movement of the stud 11 and the movement of the mask 88 is always modified by the magnification factor. When a high degree of magnification is being used, the record gate is very high and the studs 88 are high in the grooves 82 and close together. In this case a relatively large horizontal movement of the stud 11 is required to give a relatively small change in the length masking.

/ The shaft 1| which is rotated by the crank 10 has a square portion 18 extending back toward the printing gate. This square portion carries a set of bevel-gears 18 which can move along the shaft 18 as the magnification is changed, but which in any position will be rotated by rotation of this shaft 18. These gears 18 in turn rotate a shaft 18 and another set of gears 88 which operate through a shaft 8| and screw threads 82 to change the length masking of the printing gate. The length masking of the printing gate 28 as formed by the plate 84 is best shown in Figs. 9, 10, and 11. In these figures the plate 84 has an aperture therein which in part constitutes the printing gate. Actually the top and bottom edges of the printing gate and hence its width is defined by the front plate of a roll holder 85 which carries the paper and is carried by the plate 84. In the arrangement shown the roll holder 85 can be used successively in three positions so that three strips of pictures may be made. The edges of the printing gate between the three positions are defined by strips 2 extending across the aperture in the roll holder. One end of the printing gate 28 is defined by the edge 88 of the aperture in the plate 84. As the length, masking crank 18 is rotated causing rotation of the screw thread 82, the whole plate 84 carried by a nut 88 operating on the screw 82 is moved horizontally. The plate 84 is carried by a groove I28 and moved in this groove only a relatively small distance as is best seen in Fig. 13.

' The other end of the printing gate isdeflned by a movable mask 81 carried by the plate 84. As the plate 84 is moved by the screw 82 and nut 88, it carries with it a pivot 88. This pivot 88 acts as the common point for two connected levers 8| which are pivoted at the points 88. These points 88 are rigid with respect to a plate I which in turn is rigid with respect to the.

levers 8| for longitudinal motion of the pivots 88 and 88. Slots 83 are provided in the plate? to permit assembling of the pivots 88 and to per;- mit movement of the plate 84 with respect tb these pivots, especially in the case 'of the pivot which extends into this plate by reason: of the fact that one of the levers 8| is on topof the other and is immediately adjacent to the plate 84. Slots 84 are provided in the plate 84 topermit the pivots 88 to extend through from. the

' mask 81 to the levers 8| which are on the opposite side of the plate, and to permit these pivots 88 to move with respect to the plate 84. Holes 85 are provided in the plate 4| to permit assembly of the pivots 88 and 88.

As the plate 84 moves in one direction carrying the edge 88 with it, the mask 81 moves in the opposite direction with the same speedwith respect to the plate I and the printer housing 28. It-will be noted that the movement of the mask 81 with respect to the plate 84 is at twice the speed of the movement of the plate 84 with respect to the plate |4|. Thus the light to the printing gate passes through the window 58 in the camera housing 28, the top and bottom of the gate are formed by the roll holder 85 with its cross strips 2 and the ends of the gate are formed in the adjacent plate 84 by edge 88 and mask 81.

Referring back to Fig. 3 particularly with reference to Figs. 4, l4, and 15, the viewing system will now be described.

The movable mirror 88 is carried by a housing 88 in the front of which is a window to admit light from the lens 28. A lens 81 positioned in this window reduces the size and increases the brilliance of the image on the viewing screen 8| with respect to the image which. in the absence of the reflector 88 reaches the printing gate 28. Around this image on the viewing screen 3| are provided borders which are illuminated by white light by means of a lamp 88 positioned behind the mirror 38. Light from this lamp 88 is reflected by an inverted four-sided pyramid mirror 88 upward to the borders of the viewing screen 8|. It

is of course desirableto prevent any light from this lamp 88 reaching the image on the screen 8| and for this reason suitable baiiies I88 are pro-' vided. If one were to remove the viewing screen 8| and to look down from this point, one would see an arrangement such as that shown in Fig. 4 wherein the central area consists of the mirror 88 surrounded by sloping bailies I88 having a discrepancies in the color balance of the original which is in the printing gate 2|. For example, an original may be slightly too green; but viewing it separately it would not show up this defect because the eye would adapt itself, whereas the overall green appearance is exaggerated by the presence of a pure white border and hence the opera-tor is made definitely aware of even the slightest discrepancy. By means of various color filters MI in the-optical system somewhere be'- tween the lamp 22 and the removable mirror 38,

preferably between the lamp 22 and the record gate 2 I, the overall hue or the record is changed until it has the correct color as compared to the white border of the viewing screen 3|. As shown in Fig. 12, these filters are mounted on individual handles I02 pivoted on a bar I03 which is supported by an'arm I94 connected to the printer housing 28'. The movement of these filters III is controlled by individual flexible cables III! connected to buttons I08 shown in Figs. 1 and 2.

For two reasons, namely for most convenient comparison of color and in order to permit exposure of a fixed time it is also desirable to vary the density of the image striking the printing gate, and correspondingly the density oi! the image on the viewing screen 3|. For this purpose a density wedge III! as best seen in Fig. 6 is positioned in the light beam and is operated by gears I08 through a rotatable flexible shaft I89 which is connected to a dial or knob H shown in Fig. 1. Thus the filters I 0| and the density wedge I01 are used to correct for errors in color balance in the original transparency and in the light source 22 and for variations in intensity of the image striking the printing gate.

In a color printing system of this type there is another source of possible error in color balance which can be corrected for. We refer to the fact that the sensitivity of the color sensitive paper on which the print is to be made, may vary somewhat from the correct value. From a theoretical point of view there are two ways of considering this efiect. Since the white borders on the viewing screen 3| are used to define what is the correct hue of the pictures which strike the printing gate, the color of the light from the lamp 98 must be that for which the sensitivity of the printing paper is balanced: To provide for variations of sensitivity balance, a filter H3 corresponding to the sensitivity of the particular roll of paper to be used is placed in the path of the light from the lamp 98 to the borders of the viewing screen. Because of the adaptation of the human eye, the borders of the viewing screen will still be considered to be white and a. balance 0! 5 paper, it isdecidedly inconvenient to have to remove this filter between the exposures in order to prevent it interfering with the balancing out of discrepancies in the color balance of the original transparency. Therefore, the filter H4 is placed permanently in place and the filter H3 is placed in the illuminating system that gives the white borders on the viewing screen II where'- by the effect of the-filter III on the color balance of the original is balanced out. That is, either or both oi! the filters H3 and H, are necessary, but both are preferable since it i I4 only is used, it must be removed from the optical system during judging and if filter H3 only is used, the filters IIII may not have sufllcient range to compensate for the effect of the filter H3. Actually filter H3 is selected with critical accuracy and filter H4 need only be approximately the same since adjustable filters Illl will make up for any discrepancies in the color of H4 or for that matter in their own color since everything is referred to the standard borders. I

A suitable shutter III is provided in the optical system and is arranged so that it may be held open during masking and judging, held closed while the viewing system carried by the housing 96 is removed from the optical system and operated once giving a fixed exposure. As shown in Fig. 6, the shutter I I I is provided with an adjustable sector to vary the. amount of the exposure in the well-known way. The shutter I I I is operthe color of the image appearing thereon until it appears correct with respect to this white, may be made. At such a time, the image striking the viewing screen 3| (hence the image striking the printing gate 29 when the removable mirror 30 is removed) will have the correct hue to give correct color balance on the particular sensitive paper used. In order to insure that correct color balance can be easily obtained with the filters lIlI even when the filter I I3 is in place, a filter H4 roughly identical in spectral transmission to the filter H3 is positioned adjacent to the filters IOI.

Of course this is necessary only if the filters IIlI do not cover a sufllcient range to provide the correct color hue when the filter H3 is in place. That is, the filters HII are usually made to cover only the range variations in hue of transparencies and may not extend to a range including variations in color balance or the sensitive paper.

Looking at this subject from another point or view, the filter H4 which is selected to correspond to the sensitivity 01' the paper being used is placed in the illuminating system at the time prints are being made. If this filter H4 can be easily removed during the judging, and replaced while the exposure is being made on the printing gate 29, only one filter will be needed. However, since the filter I II has to stay in place and is not changed during the whole of one roll of. sensitive ated preferably electrically by a button I I 2 shown in Fig. 1.

In Fig. 13, the paper holding means is illustrated from above. As pointed out above the camera housing 20 carries a plate I which is constrained to move in-vertical grooves I43 to permit difierent strips of the roll of paper to be used. This plate I has a horizontal groove I29 on which plate -84 carrying the printing gate moves under the action of the screw 82 which forms part of the length masking system. This plate 84 carries the roll holder 85 in which are located the supply roll H1 and the take-up roll H8 carrying the sensitized paper H5. Rollers I I8 and H9 adjacent to the .printing gate plane guide the paper through this plane. As far as the printing gate is concerned roller H6 constitutes the supply roll and roller H9 constitutes-the take-up roll.

So that no paper will be wasted, the take-up mechanism is arranged so that after each exposure the area exposed plus a slight and fixed margin between prints is moved past the printing gate and onto the take-up system. Since ac.- cording to the invention one side of the printing gate acts as the mask for one end of that gate, the amount of paper on the take up roll doesnot have tobe moved even though the length masks are changed. This is', of course, the reason for having one end of the printing gate fixed and having a double speed mask operating over the other end. The so-called fixed end of the printing gate is the one next to the take-up roll. Means areprovided for assuring that the amount 01' the paper'advancedafter each exposure will be just exactly that necessary to bring the exposed area plus a suitable margin past the gate independent of the length of that exposed area.

This paper advancing'system is best explained with reference to-Fig. 16 which illustrates the driving mechanism which forms part of the paper holding system 85. At this point, attention is drawn to the fact that in the cross section shown in Fig. 3 only the rewind mechanism consisting in order to advance the paper, a

- I51 causes a gear I56 to rotate.

of motor I28, shaft I2I, and clutch system I22 for operating the supply roll II1 as a take-up roll during rewinding is shown. system shown in Fig. 16 is similarly fixed below the rollers H8 and I I9. Since the actual take-up roll II8 cannot conveniently be used for controlling the exact amount of paper taken up (the amount taken up depends on the diameter of the roll and how much paper has already been wound thereonto) the roller I19 is used as the driving roller and is accurately controlled. The roller H8 is driven by studs thereon extending into the plate I66 and the take-up roll H8 is driven by studs thereon extending into the plate I15. Normally the switch I68 is closed by a spring I68. Hence when the switch I61 is closed solenoid I52 pulls the core I53 against the force of a spring I88 causing a switch I18 to close and a lever arm I54 to rotate pawls I55 upward. The closing of the switch I18 starts the motor I68 which, through the gears I59, shaft I58, and worm gear The pawls I55 push this gear upward so that through a friction drive I6I the wheel I66 starts to rotate. On the same shaft, there is mounted a rotatable plate I62 which under the force of the friction drive,

rotates carrying an electrical contacting member I63 with it. When \this rotation proceeds far enough, the contacting member I63 engages contacts I58 mounted on a stud I48. Through wires I5I the closing of this contact I58 causes a solenoid or relay I1I to operate and open the switch I68 which turns off the solenoid I52 releasing the switch I18 and the pawls I55 stopping further operation.

Thus the friction drive I6I is released and under the action of a spring carrying the contacting member I63 is drawn rapidly back to its original position wherein the member I63 is against a back stop I65. Ob-

.viously the position of the contacting post I48 carrying the contacts I58 determines how far the wind-up operations will proceed before being cut oil. This contacting post I48 is carried by an arm I58 mounted on a gear I41 which is. free to rotate on the shaft of the driving system. This gear I41 is adjusted through a pinion I46 which moves on a rack I45 which, as shown in Fig. 13 is mounted on the plate I which is horizontally fixed with respect to the camera housing 28. The pinion I46 is carried by the printing gate plate 84 and hence as this gate 84 is adjusted for length masking, the pinion I46 moves along the rack I45- and at the same time turns the gear I41 adjusting the position of the contacting stop I48. Thus this driving system constitutes means for accurately advancing the paper by an amount equal to the exposed area plus a suitable margin between prints. The actual take-up roll H8 is driven by the same motor II6 through gears I12 and I13 and the roll engaging member I16. Since this must be a slip drive to compensate for changes in diameter of the paper roll, a spring I14 is provided and the driving is done through this spring.

For rewinding,- it is necessary to release the the driving wheels I66 and I15 respectively. This is done by a solenoid I18 whose core I18 is moved against a spring I8I causing the crank I11 to The take-up I64 the plate I62 I engagement between the rollers H8 and H8 and v turn which in turn moves pawls I16 downward releasing the engagement between the driving ance is made with the filters I8I,

are shown in Figs. 14 and 15. The viewing housing 86 carrying the mirrors 38 and 32 and the bames I8 and lens 91 is positioned to move horizontally rack I33 and pinion I32. This pinion I32 is driven by a chain drive I3I by a motor I38. As the housing 36 moves-completely out of the optical path an electric switch I34 is operated to shut ofi the motor 38 to prevent any further motion. As best shown in Figs. 1, 2, and 3-bellows 38 are provided to permit vertical motion of the record gate 2I and bellows 31 and 38 permit horizontal movement of camera 28 relative ,to lens 28 and eye-piece 33.

focusing studs 45 and the wheels I36 upon which the whole camera mechanism 28 ismounted to move ingrooves I35 in the printer housing 28. This motion of camera 28 relative to the support 28 requires that some provision be made for the wire carrying current to the motors I28 and I68, etc. The wires (not shown) are held in the housing 28' and fed out over a roller I24 mounted on the rear thereof and back to the motors in the camera 28.

The operation of the printer is as follows. The transparency is loaded into the record gate 2I. The magnification is set using the width of the transparency in auto-masking and auto-focusing as described above. The length masking is set. The mirror 21 is swung down to the position 21' in the objective beam, permitting viewingof the image on the ground glass 3i. Then color balvia buttons I86 and the exposure level is set with the wedge I81, via'dial H8. The printing cycle is started by closing a switch button I I2 shown in Fig. l which closes the shutter, preferably electrically. The viewing box 86 moves clear of the beam incidentally opening a switch I34, see Fig. 14, to prevent its being driven too far. An exposure is made by operating the shutter. The paper is advanced as described above. Incidentally, this may be repeated for multiple printing without bringing the viewing box back into the beam. Otherwise the viewing box is moved back into the beam, the shutter is opened for viewing and the objective mirror 21 is swung up to the upper position (21) for viewing the next transparency. 0bviously,- everything is done automatically as far as mechanical operations are concerned and only the minimum of skill is required on the part of the operator.

Having thus described our invention, we wish to point out that it is not limited to the specific structure shown, but is of the scope of the appended claims.

What we claim and desire to secure by Letters Patent of the United States is:

1. A projection printer for making a color print from a color transparency comprising a gate for holding the transparency, means for illuminating the transparency gate, a gate for holding color sensitive material upon which the print is to be made, a lens for focusing an image of the transparency gate on the print gate. a viewing screen substantially at right angles to the print gate, a removable mirror in front of the print gate for reflecting the image to said viewing screen,

11 suitable guides and is driven by a means for Illuminating with subilluminating means, said lens, said mirror, said viewing screen, and said filters and filter moving I means.

2. A projection printer according to claim 1 in which there is also included an adjustable density wedge in said light beam and means for adjusting it.

3. A projection printer according to claim I in which a filter whose color is that which corrects the color balance of the color sensitive material is in the light beam illuminating said borders whereby when said overall hue is altered to a natural hue compared with the borders as white, correction both of the color balance of the original and for the color balance of the sensitive material is made.

4. A projection printed according to claim 1 in which a filter whose color is that which corrects the color balance oi the color sensitive material is in the light beam illuminating said borders, and a filter of approximately the same color is in the light beam. forming the image.

5. A projection printer according to claim 1 in which the means for illuminating the borders of the screen consist of a lamp behind the removable mirror and removable therewith, a truncated four-sided pyramidal mirror surrounding said lamp for reflecting light from the lamp past the removable mirror on all sides and to said borders and means for preventing light from the lamp reaching the image area inside said borders.

6. A projection printer for making a color print from a color transparency comprising a gate for holding the transparency, means for illuminating the transparency gate, a gate for holding color sensitive material upon which the print is to be made, a lens for focusing an image of the transparency gate on the print gate and a removable viewing box positionable between the lens and the print gate and having at least two windows therein, said box consisting of a housing, a viewing screen carried in the housing and visible through one of the windows, a mirror in the housing for receiving light through the other window from the lens and for reflecting it to said screen, the screen being positioned at the plane whereat the image is formed which corresponds to the one on the print gate, a positive lens adjacent to said other window for reducing the size and increasing the brilliance of the image on the screen compared to the alternative one on the print gate, means for illuminating the borders of the screen adjacent to the image area thereof, said illuminating means consisting of a lamp in the housing behind the mirror, an inverted pyramidal mirror carried in the housing for receiving light from the lamp and reflecting it past the first mentioned mirror on all sides to the screen, bames including the first mentioned mirror for preventing light from the lamp reaching the image area of the screen and means for holding in the path of the light from the lamp to the screen borders, light filtering material whose color corresponds to that for which said color sensitive material is balanced.

7. A projection printer for making a color print from a color transparency comprising a gate for holding the transparency, means for illuminating the transparency gate, a gate for holding color sensitive material upon which the print is to be made, a lens for focusing an image of the transparency gate on the print gate, color filters positionable in the path of the light from said illuminating means for altering the overall hue of the printing beam, a density wedge adjustable in said light path for altering the intensity of the printing beam and a unit for standardization of the printing beam, Said unit consisting of a viewing screen positioned in a plane optically equivalent to said print gate whereby on the screen is formed an image corresponding in color and intensity to the one on said print gate, borders on the screen a jacent to the area in which the image is formed, means for illuminating the borders with light of predetermined color and intensity, and a housing with a window to admit light from the lens, a window through which to view theviewing screens and borders and containing said screen and border illuminating means.

8. A projection printer according to claim 7 in which the standardization unit is completely removable as a unit for separate calibration.

9. A projection printer according to claim '7 in which the standardization unit includes filters positionable in the path of the light illuminating said borders whereby the border color may be adjusted to correspond to the sensitivity of the color sensitive material being used.

10. A projection printer according to claim 7 in which the standardization unit includes a positive lens in line with the light admitting window for reducing the size and increasing the brilliance oi the image on the viewing screen whereby a correspondingly increased level of illumination is permitted for the comparison borders.

11. A projection printer according to claim 7 in which the standardization unit has the viewing screen substantially at right angles to the print gate, a mirror is positioned behind the light admitting window to reflect the light to the screen and the border illuminating means consists oi a lamp behind the mirror, a pyramidal mirror for receiving light from this lamp and reflecting it past the mirror on all sides to the screen borders and baflies for preventing light from the lamp reaching the image area of the screen.

' RALPH M. EVANS.

BENJAMIN E. LUBOSHEZ.

CERTIFICATE OF CORRECTION. v Patent No. 2,256,385: September 16, 1914.1.

' RALPH n. EVANS, 4317 AL.

Itis hereby certified that error appears ,in the printed specification of the above numbered patent requiring correction as follows: Page 6, first column, line for "am 159" read "arm 114.9; page 7, first column, 1ine 26, claim 1;, for inted" read --printer and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Petent Office:

signed and sealed this 25rd day of December, A. D. 191a.

Henry Van Arsdale,

(seal) Acting Commissioner of Patents CERTIFICATE OF CORRECTION. v Patent No. 2,256,385." September 16, 19m.

' RALPH n. EVANS, "ET AL.

Itis hereby certified that error appears ,in the printed epecifioation of the above numbered patent requiring correction as follows: Page 6, first column, line for "am 159 read --arm ll .9-; page 7, first column,l1ne 26, claim n for "printed" read --printer and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office:

Signed and sealed this 25rd day of December, A. D. 19in.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

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