US2905070A - Photoprinting apparatus - Google Patents

Description

sept. 22, 1959 H. GELB 2,905,070

PHOTOPINTING APPARATUS Filed Aug. 28. 1956 INVENTOR Herbert Gelb United States Patent() PHOTOPRINTING APPARATUS Herbert Gelb, Cranford, NJ. K Application vAugust`28, 1956, Serial No. 606,685

i A 2 Claims. (Cl. 95-75) This is a continuation-impart of my copending application for United States patent for an Illuminator, led October 30, 1951, and bearing Serial Number 253,880, now Patent No. 2,760,419.

This invention relates to photography, and, in particular, to the art of photoprinting light-sensitive material through a transparency.

The general object of the invention is to provide novel and highly eticient apparatus for the precision photoprinting, through atransparency, of light-sensitive material. whereby under'burning and blurring may be substantially eliminated.

A particular feature o-f the invention is that it may be embodied in aA simple apparatus which is adapted progressively to illuminate a transparency, and contacting light-sensitive material therebeyond, with a traveling band of light comprising rays which are perpendicular, or nearly perpendicular, to the transparency and the material to be printed.

Ideally, of course, in contact photoprinting, the rays `of the 4photographic light source should be absolutely parallel to each other and at right angles to the work so that the pattern of areas .of differing relative opacity of the transparency is precisely reproduced on the lightsensitive surface without underburning or blurring. Rays impinging on a transparency at angles other than 90 produce, on the light-sensitive surface, a pattern which is more or less staggered with respect to, as well as somewhat heavier than, the pattern of the transparency. Where the photographic rays comprise a fan thereof, with some rays normal to the work and others diverging in usual manner to the right and left of the normal rays, it is obvious that an opaque line upon the transparency produces, on the light-sensitive surface, a shadow which, in width, corresponds more or less faithfully to the line, and a penumbra on either side of the shadow, so that the ultimate print is by no means a clean reproduction of the line on the transparency.

Obviously, where photographic light comprises a scattering of rays which may impinge upon the transparency at a variety of angles, with some rays actually crossing other rays, the immediate result upon the light-sensitive material is a shadowy area roughly corresponding to the overlying area of the transparency, but having a penumbral margin with the actual periphery greater than the related area of the transparency.

The foregoing matter applies to any adjacent lightsensitive surface, as that of an emulsion-coated sheet of film, paper, glass, or metal. On development of the sensitized material the distortion of the transparency will be obvious. Of course, the foregoing, for convenience, assumes a positive transparency. However, a similar but reversed, result is had where the transparency is a negative, as, for example, in the making of a letterpress line cut, with the transparency in contact with emulsion coated metal. If the photographic rays are not parallel and normal to the work, the meatllic surface, after development, washing out, and cooking, does not present ice to the etching acid an unmasked pattern faithfully reproducing that of the transparency; and the acid-resisting mask upon the metallic surface is a pattern of more or less ragged-edged areas. The dierence between the lightness, or heaviness, and clarity, of the areas of the transparency and those of an impression in ink made `from the nished plate may be so slight as to be triiling .in most printingjobs; but the present invention is particularly intended for use in the finest type of work.

The present invention contemplates photoprinting apparatus capable of making contact prints of considerable sizefor example, several square feet in area-with all portions of the sensitized material printed with photographic rays of light which are substantially parallel to leach other and normal to the work.

Where the area of the transparency and of the related light-sensitive material is quite small, as in the printing of a motion picture lm, panel by panel, optical means have been devised for overcoming some of the `dificulties in making accurate contact prints; but such means would be prohibitively expensive, if operable at all, for making contact prints several square feet in compass.

The persent invention solves the problem of obtaining clean contact prints of relatively great area by sweeping the transparency and the light-sensitive surface by a narrow, though long, band of light moving from one side of the work to an opposite side thereof. Further the in- -vention contemplates the use of a common linear gaseous arc light. Rectification of certain of the rays is accomplished by the use of an elongated reflector of parabolic cross section, the construction of which is well known. A novelty of the invention is the maski-ng of certain other rays tending to parallel the axis of the are; and this is accomplished by a specially constructed series of bales preferably mounted in the mouth of the reflector and between the arc and the work. The result is that the available photographic light is a narrow band of rays which are predominantly parallel to each other. ln the present invention the linear arc, the reflector, and the baffles move as a unit for the purpose of sweeping the transparency.

Another feature of the invention is that the interposition of the series of baffles betWee-n the arc and the work does not result in streaking the sensitized material due to the movement of the arc, reflector, and baies. All areas of the work are uniformly illuminated by the apparatus of the invention.

A further feature of the invention is that it comprises a contact printing frame which operates successively to bring narrow transverse strips of the sensitized material into contact with the transparency in synchronism and in register with the progressive illumination of the latter. In the exemplary embodiment of the invention illustrated herein the transparency 10 lies flat upon the printing frame 11, and both the transparency and the frame are stationary. The sensitized material 12, such as a film, is wrapped around a cylinder 13 which is adapted to roll from end to end of the frame, in synchronism and in register with the light source 14, and its reflector 1S and batlies 16, so that successive transverse strips of the sensitized material 12 is maintained in contact with the transparency 10 under pressure. Herein the cylinder 13 around which the sensitized material 12 is wrapped is journaled in a carriage 17 which may travel at a predetermined constant speed from one end of the frame 11 to the other thereof, the cylinder as well as the carriage itself, being incapable of end play with respect to the frame and transparency. Further, the cylinder is so journaled in the carriage that the weight of the former (and of the sensitized material) guarantees intimate oontact between the material and the transparency without E) Y respect to the thickness of either thereof. The frame 11 is provided with a transparent cover 18, on either side of which is a groove 19, or other suitable guide, in or on which the carriage rolls--the guides, of course, being parallel. The transparency is supported by the cover of the frame, and may be prevented from shifting relative thereto by any well -known means. In the illustrated embodiment the frame is horizontally disposed, and gravity is availed upon for the intimacy of contact between the cylinder, and the sensitized material, if present, and the cover of the frame, and a transparency, if present. In the embodiment shown the frame is horizontally disposed-although this is not a limitation of the inven- 'tion-and the cylinder is supported by the carriage above the cover of the frame, while the means for illuminating the transparency are supported by the carriage beneath rthe cover. Hence the members supported by the carriage may move from end to end of the frame as a unit.

It will be immediately understood that since the invention involves relative movement between the frame, with its xed transparency, and the carriage, with the members supported thereby, it is merely a matter of convenience that the frame is preferably stationary.

The illustrated apparatus provides means for causing the carriage to roll from end to end of the frame, and may well be provided with means for predetermining the speed of movement of the carriage so that adequate exposure of the sensitized material may be had in accordance with its photographic characteristics and without varying the intensity of the light. Preferably the apparatus is arranged so that the carriage makes one round trip for each exposure, e.g., away from and back to a masked or otherwise opaque end portion ofthe cover of the fame. In the illustrated embodiment only one end portion of the cover of the frame is shown to be provided with an opaque area 20; but it will be readily understood that each end of the frame cover may be opaqued to avoid overexposure during a reversal of the carriage.

A motor 21 is provided for moving the carriage, the

'shaft 22 of the motor being journaled in the near end 4 23 of the frame in the drawing; and the carriage 17, as shown, is connected to a chain loop 24 which is in mesh with a sprocket 25 on the end of the shaft and an idler sprocket 26 at the other end of the frame.

The baffles 16 are diagonally disposed so that the light passing through any two operates to illuminate any shadow line previously cast.

In the drawing the mouth 27 of the reector is extremely wide so that the bafes may be clearly seen; in actual practice the mouth of the reector is very narrow indeed.

I claim:

l. Apparatus for contact-printing light-sensitive material through a transparency which comprises a cylinder upon which light-sensitive material may be mounted; a linear light source axially parallel with said cylinder; said cylinder and said light source being disposed in opposition within said apparatus; a transparency interposed between said cylinder and said source; a series of bales interposed between said transparencyand said source and fixed with relationship to said source; and means for effecting relative linear movement between said cylinder, source, and bales, as a unit, and said transparency, as another unit, and for rotating said cylinder about its own axis during said relative linear movement, said baffles being disposed other than in the line of said relative linear movement.

2. Apparatus according to claim `1 including a frame for holding said transparency, said frame providing a track upon which said cylinder may roll in contact with said transparency; and wherein said means include members one thereof rigidly mounted at each end of said References Cited in the tile of this patent UNITED STATES PATENTS 1,868,709 La Pointe July 26, 1932 2,170,896 Henderson Aug. 29, 1939 Reynolds Sept. 23, 1947

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