US3298297A - Continuous contact printer - Google Patents

Description

C. O. ARL$ON ETAL counuuous counc'r Pnnvrnn I'illd June 10. 1964 Jan. 17, 1967 Roller Prcssm Area. 44

'xasuref? ion p 46" f mf. ASFW/ l lnvenf Carl d Carlson Bnyhnin F. Schar United States Patent O 3,298,297 CONTINUOUS CONTACT PRINTER Carl 0. Carlson, Los Angeles, and Benjamin F. Scherf,

Hawthorne, Calif., assignors to The National Cash Register Company, Dayton, Uhio, a corporation of Maryland Filed June 10, 1964, Ser. No. 374,120

Claims. (Cl. 95--77.5)

This invention relates to a photographic contact printer and, more particularly, to an improved contact printer for printing high -resolution images by establishing a high degree of contact between the surfaces of a master negative and a film on which the images are to be printed.

Microimages having an equivalent resolution of 1,000 lines per millimeter or better are readily produced using known techniques and apparatus, for example, as disclosed in a copending United States application Ser. No. 111,759, filed on May 22, 1961, now Patent No. 3,185,026, inventors Carl O. Carlson et al., and assigned to' the same assignee as this application. -Tbe copending patent application teaches that very high resolution microimages can be formed by projection onto a photomethachromic (hereinafter called photochromic) emulsion that is coated on a glass plate. Also the copending application teaches that permanent copies of the microimages formed in the photochromic coating can be contact printed onto a high resolution, conventional photographic film by using a contact printer having a resilient or felt-like support. The resilient support provides for transmitting only a normal, evenly distributed pressure to the interface between the two coatings thereby tending to compensate for any non-flatness of the surfaces of the emulsion coatings which surface nnevenness is a property of emulsions, especially when supplied as coatings on films. While, with care, high resolution contact prints can thus be made vby using such a resilient support for the lm, when it is desired to more easily and consistently contact print arrays' of high resolution microimages onto conventional photographic film. a more convenient and reliable manner of obtaining a high degrec of intimate contact between the coatings is required. Since the degree of resolution in the contact print is related to the degree of contact between coatings, the measure of uniformity of contact can be noted by inspecting the lack of or the number of light interference fringes present at the interface of the coatings. The spacing between coatings is directly related to the number and spacing of fringes formed, and is further related to the unevenness of the tilm coating. Thus, optimum contact, i.e., perfect Contact, refers to the condition existing when no light interference fringes are formed over the interface of the contact surfaces. It is to be noted that although a contact print with acceptable resolution could be produced when afew widely spaced interference fringes are present, the contact prints are greatly degraded when many fringes are present. It has been found that the fringe regions are produced when pockets of air have been captured around clumps of emulsion at the time initial contact was made, and that the fringes or thc fringe regions can be reduced by one or more of the steps of applying more pressure to the contacting surfaces, removing air from between the surfaces before applying pressure, and/or waiting after pressure is applied for any air that might be entrapped between the surfaces to leak out or be absorbed by the material to thereby assure better contact before exposing the film. The first approach, that is the use of more pressure to acquire more intimate contact. is impracticable because there is a tendency to break the'master plates as larger pressures are applied. The second approach, that is "ice the removal of air-before applying pressure, requires a vacuum system which materially complicates the design and which is better avoided if possible. The third approach, which is waiting for the bubbles of trapped air to dissipate, while generally helpful, provides no guarantee that the time delay will improve the contact, inasmuch as it could happen that an optimum contact has been formed around the air pocket cutting ott' the means for the air to escape. lt has also been suggested that a matching refractive index liquid be placed between master and copy to eliminate the interference fringes or that a fine grit be placed therebetween to make the `fringes so numerous as to be unresolvable. However,

this approach does not prevent the images from being. undercut by diffused illumination or prevent diffraction effects with semi-specular or specular illumination from blurring the microimages at points where master and copy fail to bc in optimum contact. It should thus be clear that in order to transfer the maximum. amount of very fine-line information from the master to the copy, optimum or near optimum contact should be produced at the interface between coatings.

lt has been mentioned above that optimum contact is achieved between the two coatings when no interference fringes are noticeable at the interface. 1t shouldV be noted that interference fringes are not noticeable when the spacing between the coatings is less than one-quarter wavelength or when the spacing is relatively large so as to make the interference fringes unresolvable. However, when the spacing is between these two limits and a red light of narrow bandwidth is used to illuminate the coatings, light and dark patterns are alternately formed. ylt has thus been observed that acceptable high resolution is produced in contact prints when the spac ing between coatings is equal to no more than four wavelengths, which spacing is measured by counting the interference fringes from a region of optimum contact in the proper manner as each continuous dark area represents a fixed spacing between coatings. Acceptable high resolution in a contact print is accomplished for the p'urposes and intent of the present invention when a six point type font of characters which has been reduced about 200 diameters onto a master, is contact printed onto a photographic tilm, and the characters recorded or printed in the contact prints can be resolved with proper viewing equipment, for example.

A primary object of this invention is thus to provide an improved contact printer that can make contact prints of microimages having a high resolution by rapidly establisbing optimum or near optimum contact between a master negative and a photographic film.

Another object of this invention is to provide a continuously operating contact printer comprising a resilient roller having a generally spheroidal shape for bringing together the coatings of a photographic film and a master negative. Because of its shape, the roller initially contacts the film at the center of its line of travel, and gradually increases the contact pressure and thus widens the area of contact toward the edges of the film as the roller rolls over the film, to thereby even-out the surface of the film in the region of contact in which exposure is to take p ace.

Still another object of this invention-is to provide an improved contact printer that can make a high resolution contact print from a master negative by moving the master Generally, the present invention comprises a resilient roller that initially applies pressures at only a very small area on a photographic film so as to press it against a fmaster negative that is rigidly supported by a transparent member. Since the initial contact area is small, a very high pressure is produced, and the high points in the films coating are effectively squashed so that the valleys as well as the high points in the films coating are placed in intimate contact with the coating on the master in a narrow region under the resilient roller. A suitably shaped light source focuses a narrow rectangularly shaped light beam through the transparent member toward the bottom of the resilient roller. The narrow4 rectangularly shaped region, illuminated by the light spot, extends along the surface of the roller, parallel lto the axis thereof. It should be noted that this feature enables the film to be exposed only in the region wherein the roller forces the film and master into maximum intimate contact. In the preferred embodiment of the invention, this result is readily accomplished by forming the transparent member, for supporting the master, into a large roller or drum. Then as the resilient roller rolls over andpresses the film against the master, the film and master advance between the rotating rollers and are forced into intimate contact in the region of illumination, thereby providing the desired conditions for printing the images from the master onto the film.

It should be noted that only a portion of the images on the master, the portion in the illuminated region, is

--being exposed or printed at any given instant of time.

By making the illuminated region relatively small, only a small contact area is required. Thus, higher pressure contact can be made by the roller so as to ensure a high degree of contact between the master and the film. As the master and film are carried through the region of illumination all the images are printed on the film.

Other objects, advantages and features of the present invention will become apparent from consideration o f the following description when taken in conjunction with the appended claims and the drawings, wherein:

FIG. 1 shows a contact print as produced on a photographic film by a master negative containing over 1200 high resolution microimages;

FIG. 2 is a greatly enlarged pictorial 'view yof a frag- 4 ment of the master negative and support therefor as used to print the contact print shown in FIG. 1;

FIG. 3 is an exaggerated enlarged section of 'a fragment of an unexposed flexible photographic film showing a typical emulsion clump or high point protruding above the normal surface of the emulsion coating;

FIG. 4 is a pictorial schematic of the high resolution contact printer in accordance with this invention; and

FIG. 5 is a view taken on line 5-5 of FIG. 4 in the direction of the arrows showing the region where the film and master are in intimate contact.

Referring to the drawings, FIG. 1 shows one of the high resolution Contact prints of michoimages that is made in accordance with the teachings of this invention. -The contact print shown has an' array comprising 50 columns and 25 rows of high resolution microimages 12 formed on a flexible photographic film. Each microimage 12 represents a page (5 x 8 inches) of a book which h as been reduced over 200 diameters, for example. Such a reduction readily provides 32 microimages to the inch in each row and microimages to the inch in each column. Thus, an array of over 1200 microimages can be formed within an area smaller than 2 inches by 2 inches on the contact print, and the resolution of each microimage is sufficient so that the printing can be easily and clearly readable when the mirooimages are enlarged by a viewer specially designed to handle such small microimages, such as the viewer disclosed in the commonly assigned copending patent application Serial No. 329,743, filed December 1l, i963, now U.S. Patent No. 3,267,801.

The contact print shown in FIG. l is made from a master 16, a fragment of which is shown greatly enlarged in FIG. 2. The master 16 contains an array of microimages 17 which are of the same size as microimages 12. The resolution of the microimages 17 is sufficiently high to allow for some degrading during the contact printing process. It is well known that there are a number of factors that contribute to degrading the resolution of a contact print, among others, these factors include the degree of contact between coatings, the thickness of the coating, and the type of light exposing the coatings. The master 16 includes a transparent substrate 18 coated with a photosensitive coating 19 on which the. microimages 17 are formed. It should be understood that both the thickness of the substrate 18 and the thickness of the coating 19 are shown exaggerated in the drawings. In actual practice, to record the high resolution images thethickness of the coating 19 should be very thin, preferably in the order of one mireon. However, commercially available high resolution films have coatings, such as coating 19, which are approximately six microns thick. Therefore, the images are restricted to the surface of the coating, penetrating the coating to a depth of the order of one micron. The thickness of the substrate can be any convenient thickness, for example a few thousandths of an inch to one quarter of an inch.

Copies of microimages that are to be generally disseminated and are to receive a lot of handling should preferably 'be made on a exible photographic film, such as the contact print shown in FIG. 1. Referring to FIG. 3, there is shown an enlarged cross-section of a typical high resolution flexible photographic film 2l. The high resolution film 21 has a flexible base made of, for example, cellulose acetate 22 coated with a silver halide emulsion coating 23. However, due to limitations in the process of applying a silver halide coating on a cellulose acetate film, the surface of the resultant coating 23 is relatively uneven making it difficult to obtain a near perfect contact between coatings during the printing process. The thickness of coating 23 is shown greatly exaggerated in FIG. 3 in comparison to the thickness of the cellulose acetate base 22. The cellulose acetate 'base has a thikness of about microns, but the coating 23 thereon has been observed to have peaks, for example, peak 24 formed by an emulsion clump, which may be protruding several microns above the normal surface of the coating 23, which may have an average thickness of 6 microns. Peaks, like the peak 24, are spaced irregularly in the coating 23. It becomes apparent, therefore, that, when the surface of th ecoating 19 on the master 16 is pressed against an uneven surface -forrned on the coating 23 bf the film 2l, air pockets may be trapped in the valleys formed around the peak 24 unless precaution is taken during contact printing to prevent this from occurring. Air pockets are detrimental in printing very high resolution microimages because the emulsion coatings 19 and 23 are prevented from making optimum contact. As is well understood in the art, spacing between emulsion coatings during contact printing fon'ns diffraction patterns and interference fringes when the film is exposed to light, resulting in a blurring of the microimages being printed. Since the microimages represent greately reduced printed information, the air pockets could be large enough to blur out the words on half of a page, for example.

Referring to FIG. 4, there is shown a device that produces optimum or near optimum contact between the emulsion coatings of the master and lm as required for high resolution contact printing. The contact printer shown is of the continuous type wherein a strip of photographic film 21 and a master 16 are squeezed together into intimate contact as they advance between two rollers 26 and 27. The roller 26 has a resilient covering 28 made of, for example, hard rubber, having a larger diameter at the center than at the ends thus forming a segment of a spheroid. The roller 26 is mounted on a rigid hub 29, which, in turn, is mounted on an axle 31 that rotates within two 'bearings 32 and 33. Bearings 32 and 33 are suitably mounted (by structure not shown) so Pda-u lthat an adjustment can be made to the mountings f the bearings to urge the roller 26 to have the desired pressure against the roller 27.

When the film 21 and the master 16 are initially disposed between the rollers 26 and 27, the roller 26 initially contacts the film 21 in a small area along the center line of its travel, urging th`e film 21 against the master 16. In turn, the master is urged against the cylindrical glass wall 36. Since the area in contact is small, a large pressure is produced on the few high points or peaks which may exist in the emulsion coating on the film 21 within the area in contact to flatten the clumps and form intimate contact between the coatings on the film 21 and master 16. As the roller 26 is rotated in the direction of arrow 57 by a motor and gearing assembly 56, the film and master advance between the rotating rollers 26 and 27. The convex surface on the resilient covering 28, upon coming Y into contact with the film, yields to conform to the contour of the larger diameter cylindrical glass wall 36. In

turn, the small area in contact Ibetween the film and master increases outwardly placing more of the film 21 into intimate contact with the master 16. It should be noted that, as any given point on the film advances between the rollers 26 and 27, the pressure applied to the point increases until the point is located along the region 46 parallel to the axes of rotation of the rollers 26 and 27. When the film and master are disposed between the rollers 26 and 27 as shown in FIG. 4, the covering 28 is deformed to make contact with the film within an elongated roller pressure larea 44 (enclosed by the two dtted lines, PIG. 5) which is wider at the center than at the ends. The pressure at the center of the area 44 is greater than at the edges, because'the portion of the resilient covering 28 at the center of area 44 yielded more than at the edges. Since a pressure gradient exists Within area 44, air bubbles have a tendency to be displaced toward the outer edges of the area, thereby aiding in the prevention of the formation of air pockets.

Since the degree of contact between the film and master can be determined by inspecting the interface with a red light, axle 31 can be moved toward or away from roller 27 by suitable adjustment means until a few or no interference fringes are observed along the center portion of the elongated roller pressure area 44. When optimum or near optimum contact is obtained, the bearings 32 and 33 can be fixed in place, and a narrow, rectangularly shaped, light spot is focused by the light source 37 and directed toward the bottom of the resilient roller 26, as shown. A narrow, rectangular exposure region 4 6 is illuminated by the light spot, and the region 46 extends along the surface of the roller 26 parallel to th axis thereof. Thus, as the motor and gear assembly 56 cause the master 16 and film 21 to advance in between the rollers 26 and 27, the rollers force them into intimate contact within the region of illumination thereby providing the desired conditions for exposing (printing) the images from the master 16 onto the film 21. Only a portion of the images on the master, the portion within the exposure region 46, is being exposed or printed at any given instant of time. As the master and film are carried by the rotating rollers through the exposure 46, all the images are printed on the film.

lt should be noted that a large diameter roller 27 prevents the resilient covering 28 from wrinkling due to excessive yielding. Therefore, the exposure region 46 can 6 ciably more force to the roller 26. Also, it should be noted that by making the diameter of the resilient roller 26 relatively small, a relatively small roller pressure area 44 is formed. Thus, the large roller 27 and the small roller 26 provide a means of producing a high degree of contact within a workable region without the use of excessive force.

The light source 37 shown in FIG. 4, being held stationary by suitable means (not shown), focuses the narrow, rectangularly shaped, light spot toward the bottom of the roller 26 in the following manner: light rays from a suitabley pin-hole source 48 are collimated by a lens 49. In turn, the collimated rays are stopped down .by a mask 51 having a narrow, rectangularly shaped opening. A lens system 52 focuses the narrow opening in the mask 51 onto the exposure region 46 after the light rays are reflected and directed toward the roller 26 by a mirror 53, that is held stationary by suitable means (not shown). The light rays are directed radially by the mirror to the inside surface of the glass wall 36 so that any distortions to the light rays due to the glass wall are minimized. Optimum sizes and spacing between the optical elements can be readily determined by using known optical principles. lt should be undestood that the light source 37 could be disposed to direct the light rays through the cylindrical glass wall 36 to a mirror or `mirrors located within the roller 27 to be reflected toward the roller 26. Then, the other end of the glass wall 36 could also be enclosed by another disk, similar to disk 38, to provide greater rigidity.. The roller 26, since it has a greater diameter at its center than at the ends, provides a feature which helps to 1 further ensure that air pockets will not be formed in be tween the emulsion coatings as the film and master are carried through the exposure region 46. As mentioned before, since the roller pressure area 44 is wider at the center than at the ends, then as the rollers 26 and 2 7 ro- 1 tate, the central portion of the film 21 initially makes i contact with the master 16 before the edge portions. This be made to have a workable width without adding appremotion tends to laterally stretch the film and master preventing the formation of any minute wrinkles, thereby en- A suring better contact as the film and master advance through the rollers. Also, as the film advances between the rollers, any trapped air bubbles which -may tend to be formed can be forced toward the edges of the film as well as in front of the roller 26, reducing the probability of forming air pockets which would ruin the resolution. The embodiment of the contact printer described is useful to make contact prints from a high resolution mas.

ter negative in roll form as may be exposed in an aerial photography camera. Also, the master 16, if it has suicient flexibility, could 'be wrapped around the cylindrical glass wall 36 so that the micro-images on the master may be repeatedly printed on the film 21. Various other embodiments and variations of the present invention are contemplated and will become apparent to those skilled in the art without departing from the spirit and scope of the invention. The invention is not limited to the exemplary apparatus and procedures described, but

includes all embodiments within the scope of the claims. t

What is claimed is:

l. A photographic contact' printer for contact printing high resolution images onto a photographic film from a master negative containing high resolution images, said printer comprising: a resilient roller having a larger diameter at the center than at the ends; a transparent member disposed for supporting the master negative so that the photographic film can be exposed by light rays transmitted through the master negative; means for rotating said resilient roller and for forcing said resilient roller against said transparent member so that, when the photographic film and master negative are disposed therebetween, said roller rolls over said photographic film forcing the surface of the film directly under the roller into intimate contact with the master negative; and means for directing and focusing a light spot toward said resilient roller and through said transparent member, so as to expose only the portion of the film having intimate contact with the master negative.

2. A photographic contact printer for contactprinting high resolution images onto a photographic film from a master negative containing high resolution images, said printer comprising: a resilient roller having a larger diameter at the center than at the ends; a rigid roller hav ing a transparent wall for supporting the master negative so that the photographic film can be exposed by light rays transmitted through the master negative; said rollers being mounted to rotate about parallelly disposed axes so that-the surfaces of the rollers roll over each other; means for rotating and for forcing said rollers together so that, when the photographic film'and master negative are advanced therebetweem'the surfaces of the lm and the master negative directly between the rollers are forced into contact; and means for directing and focusing a light spot toward Athe resilient roller and through said transparent wall to the region where the film and negative are in contact for exposing only the portion of the photographic film in contact with the master negative.

3. A photographic contact printer for contact printing high resolution images onto a photographic film from a master negative containing high resolution images, said printer comprising: a resilient roller having a larger diameter at the centerthan at the ends; a rigid roller having a transparent wall of substantially greater diameter; than said resilient roller; said rollers mounted to rotate about parallelly disposed axes so that the surfaces of the rollers roll over each other; means for rotating and for forcing said rollers together so that, when the photographic film and master negative are advanced therebetween, said resilient roller yields contacting the film within a small area forming intimate contact between the film and negative within a narrow area disposed at the cen'ter of the small area and parallel to said axes; and means for directing an/d focusing a narrow light spot onto the narrow area to expose the film as the film and master negative advance between said rollers.

4. A photographic contact printer for contact printing high resolution images onto a photographic film from a master negative containing high resolution images, said printer comprising: a resilient roller having a larger diameter at the center than at the ends; a rigid roller having a transparent wall for-supporting the master ncgative so that the photographic film can be exposed by iight rays transmitted through the master negative; said rollers being mounted to rotate about parallelly disposed axes soA in Contact with the negative.

5. A photographicv contact printer for printing high resolution images comprising: a resilient roller having a larger diameter at the center than at the ends; a master containing high resolution images; a transparent member disposed for supporting the master; a 'film provided with a coating of emulsion positioned over said master; means for rotating said resilient roller over said film and for forcing said resilient roller against said film so that the portion of the film under the roller is forced into contact with the master; and means for directing and focusing a light spot toward said resilient roller and through said transparent member and for causing relative movement between the light spot and the film as said roller rolls over the film to expose only the portion of film in contact with the master.

References Cited bythe Examiner UNITEDSTATES PATENTS 2,427,443 9/ 1947 Cochran.

3,148,611 9/1964 Eisner et al. 95-7'7.5 3,150,262 9/1964 Ulseth et al. 95-77.5 X 3,168,022 2/ 1965 Limberger 95-77.5 X

JULIA E. COINER, Primary Examiner.

Claims (1)

1. A PHOTOGRAPHIC CONTACT PRINTER FOR CONTACT PRINTING HIGH RESOLUTION IMAGES ONTO A PHOTOGRAPHIC FILM FROM A MASTER NEGATIVE CONTAINING HIGH RESOLUTION IMAGES, SAID PRINTER COMPRISING: A RESILIENT ROLLER HAVING A LARGER DIAMETER AT THE CENTER THAN AT THE ENDS; A TRANSPARENT MEMBER DISPOSED FOR SUPPORTING THE MASTER NEGATIVE SO THAT THE PHOTOGRAPHIC FILM CAN BE EXPOSED BY LIGHT RAYS TRANSMITTED THROUGH THE MASTER NEGATIVE; MEANS FOR ROTATING SAID RESILIENT ROLLER AND FOR FORCING SAID RESILIENT ROLLER AGAINST SAID TRANSPARENT MEMBER SO THAT, WHEN THE PHOTOGRAPHIC FILM AND MASTER NEGATIVE ARE DISPOSED THEREBETWEEN, SAID ROLLER ROLLS OVER SAID PHOTOGRAPHIC FILM

Images