US3217625A - High resolution reproduction apparatus - Google Patents

Description

Nov. 16, 1965 F. o. TRUMP 3,217,625

HIGH RESOLUTION REPRODUCTION APPARATUS Filed July 5, 1963 3 Sheets-Sheet 1 INVENTOR. FfifOfR/C/f 0. TRUMP Nov. 16, 1965 o, TRUMP 3,217,625

HIGH RESOLUTION REPRODUCTION APPARATUS Filed July 5, 1965 5 Sheets-Sheet 2 1.. "1m 45 ii? El E- 45 INVENTOR FRfDfR/C/f 0. TRUMP BY A 40/14,!

A TORNEYS Nov. 16, 1965 F. O. TRUMP HIGH RESOLUTION REPRODUCTION APPARATUS Filed July 5, 1963 HOLE p/AME 75R INCHES RESQLUT/ON L/MM 5 Sheets-Sheet 3 EXPOfi/RE T/ME- SECONDS o \n h (a mo HOLE LENGTH-INCHES RESOLUT/D/V L/M 0 is $512 Z1 HGLE LENGTH-l/VCl-lfs INVENTOR ATTORNEYS United States Patent 3,217,625 HIGH RESOLUTIQN REPRODUCTION APPARATUS Frederick 0. Trump, West fipringfield, Mass., assignor to Tecnifax Corporation, Hoiyoke, Mass., a corporation of Massachusetts Filed July 5, 1963, Ser. No. 293,025 8 Claims. (Cl. 95-775) This invention relates to reproduction or facsimile apparatus, and more particularly to high speed, high resolution equipment used in the reproduction of film strips of the type employed in aerial reconnaissance.

The almost limitless altitude ceilings of modern aircraft and aerial photographic equipment has given rise to a need for high speed photographic reproduction systems capable of more faithful and accurate reproduction of films obtained by aerial photography for interpretive processing. In the reproduction field, resolution is the term used to indicate the ability of a film to distinguish between closely spaced objects or targets. The degree of resolution with which this invention is concerned is in the area of 200-500 lines per millimeter (l./mm.). It is essential moreover, that resolution be maintained from copy to copy in multi-generation printing.

The principal object of this invention is to provide improved film strip reproduction apparatus capable of obtaining maximum resolution and reproduction speed commensurate with the inherent capabilities of the sensitized copying material used.

It is another object of this invention to provide high resolution apparatus for film strip reproduction which is capable of being utilized with various types of sensitized materials, such as for example diazo and silver halide materials.

The above and other objects and advantages of this invention will be more readily apparent from the following description and with reference to the accompanying drawings in which:

FIG. 1 is an elevational view, in section, showing one type of reproduction apparatus embodying this invention;

FIG. 2 is a partial perspective view of the apparatus shown in FIG. 1;

FIG. 3 is a partial perspective view showing a modified form of collimating cylinder;

FIG. 4 is an elevational view, in section, of a modified type of reproduction apparatus embodying this invention;

FIG. 5 is a partial perspective view of a collimating screen particularly adapted for high speed film; and

FIGS. 6-9 are graphs showing various functional relationships involved in reproduction carried out in accordance with this invention.

Referring in detail to the drawings, in FIG. 1 is shown a photographic printing unit 4 embodying this invention. The unit 4 comprises a light source 6 preferably of tubular configuration. The tubular light source is disposed within a film supporting member 8 which, as shown, is a transparent cylinder. The cylinder 8 may be of any transparent suitable material such as a ground or polished Pyrex glass, or a transparent synthetic plastic, such as polished acrylic.

The printing unit 4 includes means for advancing original and copying film strips along or about a predetermined path spaced from the tubular light source. In the embodiment shown, a sensitized film strip, shown at 10, and the original image bearing film strip which is to be reproduced shown at 12 are carried in superposed relation about and in contact with the outer surface of the ported for rotation about its axis by means of a plurality of rolls 17 which may be located at opposite ends of the cylinder, as shown in my prior Patent No. 2,690,106. The belt 14 is continuously driven and tensioned sufficiently to advance the sensitized film strips and at the same time rotate the cylinder 8, whereby the sensitized film is exposed to the light emitted by the light source transmitted through the cylinder wall. It is essential that the original and reproduction film strips be held in intimate surface-to-surface engagement so as to obviate any parallax errors. It has been found that the required degree of contact can be achieved without sacrificing reproduction speed by carrying the film strips on the rotating cylinder.

Means for conditioning the light rays which activate the sensitized film is disposed between the light source 6 and the film carrying and supporting cylinder 8. In the embodiment shown the light conditioning means comprises a cylinder 18 having a plurality of light collimating openings 20. The openings 20 function to transmit light in essentially parallel rays, normal to the surface of film path. The collimator also serves to extract a substantial amount of heat from the light transmitted therethrough so that in effect light striking the film is cooled and collimated. As shown, the cylinder 18 is provided with a plurality of tubular ports, passages or openings 20 extending radially through the cylinder wall, the axes b of the openings being disposed generally normal to the axis a of the tubular light source 6.

In FIG. 3 is shown a portion modified form of light conditioning cylinder. The cylinder comprises a plurality of individual tubes 22 preferably metallic, joined together by any suitable means, such as adhesive, in parallel relation to form a collimating cylinder functionally the same as the cylinder 18 previously disclosed.

It is important that the walls of the tubular openings 20 and tubes 22 be essentially non-reflective in character and preferably black so that radiant heat will be absorbed. In this connection it is preferable that the collimating cylinder be entirely dark colored or black and formed of a material capable of good heat transfer, so that absorbed heat can be dissipated rapidly and carried away from the area of the transparent cylinder. In this connection it has been found that the transparent cylinder temperature should not be substantially greater than F.; above this temperature, the heat causes a noticeable deleterious effect on the film. Since only about 10-15% of the light spectrum is useable in the diazo reproduction process, it has been found that by providing a heat absorbing material between the light source and the film, a great deal of radiant heat in the form of infra-red light, is extracted from the light rays and converted into conductive heat which can be more easily extracted by means of cooling without diminishing printing effectiveness.

To provide for elficient and continuous heat transfer the cylinder 18 is preferably maintained at a relatively lower temperature than the light source. This may be accomplished in a number of ways, one of which is to provide an air conditioner or cooling unit which continuously circulates cool air by means of ducts, such as shown at 24. The air is circulated through, over and around the cylinder 18, thereby maintaining it in a relatively cool condition so that it is capable of eificient heat absorption and transfer to the cooling air. In cooling the air it is also preferable that a filter system be provided so that dust particles larger than 1 micron are removed from the air. In addition, the light tube may be water cooled further minimizing adverse thermal effect on the film.

In addition to cooling the light, the light conditioning cylinder collimates the light to produce light beams or bundles composed of parallel rays. In effect the plurality of holes or tubular openings 20 and 22 are similar to a plurality of telescope tubes with the result that omnidirectional light within the collimation cylinder is trans mitted to the film as parallel light rays normal to the film path. Collimating the light in this manner insures accurate reproduction with maximum resolution for the type of film being used. The holes or tubes 22 are oriented to prevent streaking or uneven density in the copy caused by the light pattern transmitted by the collimator. Such streaking of the film is known as banding and interferes with photographic interpretation. It has been found that the incidence of banding increases with faster sensitized materials, increased resolution, and speed of reproduction. In addition, the distance of the collimator from the film also influences the degree of banding. As the collimator is moved away from the film, toward the light source, banding increases but the collimating effect on the light is also reduced so that this is not an entirely satisfactory way of eliminating banding.

In FIG. 4 a modified form of apparatus embodying this invention is shown generally at 30. This unit is particularly adapted for use in high speed, high resolution silver halide type reproduction. The unit is generally of the same construction as shown in FIG. 1, except that in place of the perforated collimating cylinder 8, a light chamber 32 is provided. The light chamber is supported within transparent cylinder 34 by a plate 36 mounted on brackets 38 at opposite ends of the chamber. As shown, the light chamber is generally semi-cylindrical in cross section with tubular light source 6 disposed within the chamber and generally parallel to the axis of the cylinder.

The light chamber 32 is provided with an aperture 40 through its upper wall portion; the aperture extends through an arc sufficient to provide for adequate exposure of silver halide film traversing the aperture at high speed.

Disposed in the aperture 40 is a collimator 42 shown also in FIG. 5 on a greatly enlarged scale. The collimator 42 functions in generally the same manner as the collimating cylinder of the FIG. 1 embodiment. As described above, it has been found that while collimation produces good resolution it also tends to cause banding on the copying material. Since banding is thought to be the result of light patterns cast by the walls defining the collimating passages or ports, its discernible effects can be reduced by staggering the location of the collimating passage so they are not arranged in regular rows parallel and/or perpendicular to the path of the film strip movement. Banding is unacceptable in high resolution reproduction because it makes accurate photographic interpretation more difficult by obscuring targets. It is thus important to minimize or eliminate the causes of handing particularly Where reproduction work involves fast films, such as silver halide. It has been found that in reproduction using silver halide, the dimensions of the collimator passages are much more critical. Moreover, the number of collimating passages in a given area is an important factor because if the passages are spaced too far apart very pronounced banding results. It was discovered that the banding problem could be overcome by providing very finely perforated material which would collimate the light into parallel light rays, normal to the film path without too great a reduction in the quantum of effective light transmitted whereby high speed, high resolution reproduction was obtained without noticeable banding. Tests have indicated by increasing the number of collimating openings by unit area, banding can be minimized and its adverse effects eliminated. A suitable collimating material for silver halide reproduction was found to be a fine mesh screen composed of a number of individual screens laminated together. Each of the screens is finely perforated by electrochemical action providing holes 45 on the order of .005 inch in diameter with a wall thickness intermediate adjacent holes also on the order of about .005 inch. Each of the screens may also be approximately .005 inch in thickness. The finely perforated screens are laminated together with their holes 45 in axial alignment as shown in FIG. 5 in which four identical screens are laminated together.

The collimating holes 45 have a diameter of about .005 inch and a total length of about .020 inch which is a hole length to diameter ratio of 4:1. The collimator 42 is preferably black or dark in color so that it will absorb heat from the light emitted by the light source, whereby light passing through the collimator is cooled and collimated.

The glass cylinder 34 is supported in a pair of end rings, one of which is shown at 48. The glass and end rings may be joined together by any suitable means such as silicone rubber cement 50. The end rings 48 serve as light battles to minimize passage of light from the ends of the light chamber 32. The rings and glass cylinder are rotatably supported by the rollers 17 heretofore shown in the FIG. 1 embodiment. The rollers are engaged with the outer surface of the rings whereby smaller diameter glass cylinders suitable for silver halide reproduction are adapted to be used in the same apparatus as the larger diameter cylinders shown in FIG. 1. A smaller diameter cylinder is used for silver halide reproduction because the duration of light exposure is much less than for slower films, such as diazo.

Since silver halide film is so light sensitive, means is provided for protecting the film from pro-exposure before its passage across the aperture 40. As shown in FIG. 4, light sealing rolls 52 are disposed in longitudinally extending grooves or slots 54 provided in the wall of the light chamber 32. The rolls are preferably rubber cov ered to provide a good light seal against the inner surface of cylinder 34. As shown, the rolls are journaled at opposite ends in plates 56 having downwardly opening slots 58 in which roller bearings 60 are fitted with sufiicient clearance to be slidable therein, whereby gravity urges the rollers into contact with the inner surface of the glass cylinder 34 even if it is out-of-round.

As previously described, with reference to FIG. 1, the cylinder 34 is rotated by means of an endless belt 14 disposed around pulleys 16 one of which is driven. The endless belt 14 continuously tracks around the pulleys rotating the cylinder 34 together with the original and repnoduction film strips 10 and 12 (as shown in FIG. 5). The belt 14 is sufficiently tensioned to press the film strips tightly together and against the surface of the cylinder. This is, of course, essential for high resolution reproduction.

The following general relationships have been established for printing apparatus embodying this invention:

(1) Printing speed is directly proportional to collimating hole diameter and inversely proportional to the radial length or depth 0 (FIG. 2) of the collimating holes.

(2) Resolution is directly proportional to the hole length and inversely proportional to the diameter of the holes.

(3) Resolution and handing are inversely proportional to the distance of the collimator from the film.

These relationships having been established, it will be realized that there are a large number of possible combinations of hole diameter and hole length which would give desirable results. To be effective, however, it has been found that the hole length to diameter ratio should be in the range of 2-4: 1.

Experimentation in diazo reproduction shows that for maximum resolution the best relationship is either a diameter hole 7 in length, or a diameter hole in length. With these relationships resolution of around 300-400 l./ mm. were obtained. To obtain higher resolution generally requires some reduction in printing; speed. Tests with silver halide have yielded excellent: resolution results with no discernible banding with holediameters of .005 and hole length of .020. These results indicate that the printing apparatus should be provided with a plurality of different collimators. each b ing calibrated to give diiferent resolution and printing speed capabilities for various reproduction materials. The selection of any particular collimator would depend on whether the emphasis is to be placed on high printing speed or maximum resolution and the kind of sensitized material to be employed.

In carrying out these tests low contrast targets were employed. The targets were on a diazo sensitized material and silver halide materials. Each test film had a predetermined number of lines closely spaced parallel per millimeter. The greater the number of separately discernible l./mm., the greater is the resolution of the reproduction. Some of the samples used had as many as 711 l./mm. from which resolutions as high as 565 l./mm. were obtained.

In FIG. 6 is shown the relationship of printing speed, the linear speed of movement of the film over the surface of the printing cylinder, to hole diameter of the collimating cylinder. The graph shown in FIG. 6 was obtained using a cylinder wall or hole length. Point A represents a printing speed of 5 feet/minute obtained with a hole diameter, Point B 7 feet/minute speed for A2 diameter hole, Point C shows 8 feet/ minute printing speed for a A hole and Point D feet/minute speed for a A" hole. This graph is demonstrative of relationship that printing speed is directly proportional to collimating hole diameter.

In FIG. 7 the graph extending from Points E to F represents the increase in exposure time (inverse of printing speed) with increases in hole length, or depth, for a A" hole diameter.

In FIG. 8 is shown the relationship of resolution measured in lines per millimeter (l./mm.) to hole diameter. The graph extends from a low at Point G of 400 l./mm. for a Mr hole diameter to a high at Point H of 500 l./mm. for Ms" hole diameter. The data for the FIG. 8 graph was obtained using a hole depth of A".

FIG. 9 shows the very marked increase in resolution with increase in hole length from less than 300 l./mm. at Point I to 400 l./ mm. at I with a hole length increase from to A. The data for the latter graph was obtained using a A" diameter hole.

While in the embodiment shown, the light source for photographic reproduction is disposed within the glass support cylinder and the film path located on the outer surface of the cylinder, it is apparent that physical rearrangement of the components can be effected without departing from the basic concept of the invention.

Having thus described this invention, what is claimed 1. Reproduction apparatus comprising a transparent cylinder supported for rotation about its axis, a tubular light source disposed within said transparent cylinder, and a collimator interposed between said light source and said cylinder, said collimator having open tubular passage, the axes of which are disposed radially to said light source and having a length to diameter ratio in the range of 2-4:1, and an endless band engaged with the outer surface of said transparent cylinder, and means for moving said band to advance said film strips for continuous exposure to said light source and to rotate simultaneously said transparent cylinder.

2. Reproduction apparatus as set forth in claim 1 in which said collimator is made of metallic material, dark in color for absorbing infra-red from the light emitted by said tubular light source.

3. Reproduction apparatus as set forth in claim 2 and further including an air conditioning apparatus circulating cooling air through said transparent cylinder where by the cylinder is maintained at a temperature not substantially exceeding F.

4. Reproduction apparatus for a high speed, high resolution reproduction of strip film comprising a tubular light source, a transparent cylinder disposed around said light source and supported for rotation about its axis, a light chamber enclosing said light source and disposed within said transparent cylinder, said chamber having an aperture for light, a collimator disposed to collimate the light emitted through said aperture, said collimator comprising overall a finely perforated metallic material of cylindrical cont-our with its center at said light source, with the longitudinal axes of said perforations extending generally radially relative to said light source, and an endless band engageable with the cylinder outwardly of said collimator for urging film strips against said cylinder and simultaneously advancing the film strips and cylinder across said aperture.

5. Reproduction apparatus as set forth in claim 4 further including means for limiting the passage of light between the inner surface of said cylinder and said light chamber whereby pre-exposure of film is prevented.

6. Reproduction apparatus as set forth in claim 5 in which light sealing means comprises rolls engaged with the inner surface of said cylinder supported by said light chamber.

7. Reproduction apparatus for high speed, high resolution reproduction of strip film comprising a tubular light source, a transparent cylinder disposed around said source, the axis of said cylinder being generally parallel to the axis of said light source, said cylinder supported for rotation about its axis, a light chamber enclosing said light source within said cylinder and having an aperture for transmission of light through said cylinder, a collimator disposed to collimate the light emitted from said aperture and comprising an overall finely perforated metallic material with its perforations extending generally radially with respect to the light source, said perforations having a length to diameter ratio of approximately 4:1, the Wall thickness between adjacent perforations being not substantially greater than their diameter, and an endless band engageable with the portion of the cylinder located outwardly of said collimator, said band tensioned to urge said film strips against said cylinder and to simultaneously advance the film and cylinder over said aperture.

8. Reproduction apparatus as set forth in claim 7 in which said collimator comprises a laminated structure, each of the laminates being individually finely perforated.

References Cited by the Examiner UNITED STATES PATENTS 2,653,516 9/1953 Johnson 88--57 2,990,763 7/1961 Frantz 77.5 2,991,705 7/1961 Bryan et al. 95-775 FOREIGN PATENTS 285,738 2/1928 Great Britain.

EVON C. BLUNK, Primary Examiner.

Claims (1)

1. REPRODUCTION APPARATUS COMPRISING A TRANSPARENT CYLINDER SUPPORTED FOR ROTATION ABOUT ITS AXIS, A TUBULAR LIGHT SOURCE DISPOSED WITHIN SAID TRANSPARENT CYLINDER, AND A COLLIMATOR INTERPOSED BETWEEN SAID LIGHT SOURCE AND SAID CYLINDER, SAID COLLIMATOR HAVING OPEN TUBULAR PASSAGE, THE AXES OF WHICH ARE DISPOSED RADIALLY TO SAID LIGHT SOURCE AND HAVING A LENGTH OF DIAMETER RATIO IN THE RANGE OF 2-4:1, AND AN ENDLESS BAND ENGAGED WITH THE OUTER SURFACE OF SAID TRANSPARENT CYLINDER, AND MEANS FOR MOVING SAID BAND TO ADVANCE SAID FILM STRIPS FOR CONTINUOUS EXPOSURE TO SAID LIGHT SOURCE AND TO ROTATE SIMULTANEOUSLY SAID TRANSPARENT CYLINDER.

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