US 3720806 A
An apparatus for optical development of very faint or invisible latent images which provides a high level of intensity of radiation uniformly distributed over the optical development area, and having a high collection efficiency from a radiation source.
Claims available in
Description (OCR text may contain errors)
11011 llmted States tet 1191 1111 3,720,806 10110110 1March 13, 11973 1 GPTHCAL IDEVEILQ 3,099,403 7/1963 Strawick ..240 47 APPARATUS 2,225,401 12 1940 Levy ...240 103 R x 3,395,631 8/1968 Smith ..355/106 X  Inventor: Richard A. lFotland, Warrensv1lle 3,187,174 6/1965 Germ] ct alm 240/4135 R X "9131118101110 1,460,501 7 1923 Ritter ..240 41 3 3,150,262 9/1964 Ulseth et a1 ...355/l06 X  Asslgnee' 'l lncm'lmmed a 3,215,054 11/1965 Hamilton ..355/106 Horizons Research Incorporated, Cleveland, Ohio Primary Examiner--John M. Horan  Flledi June 18, 1971 Assistant ExaminerFred L. Braun  APPL NQJ 154,552 Att0rney-Lawrence I. Field 52 11.5. c1 ..219/216, 95/89 R, 219/347  ABSTRACT  int. Cl. ..1105b 111/09 An apparatus for optical development of very faint or Field 0f Search invisible latent images which provides a high level of 5/ 06; 41-35 103 intensity of radiation uniformly distributed over the optical development area, and having a high collection  References Cited efficiency from a radiation source.
UNITED STATES PATENTS 5 Claims, 4 Drawing Figures 3,033,980 5/1962 Pickering et a1 ..240/47 OPTICAL DEVELOPMENT APPARATUS This invention relates to optical development of latent dye salt images by the process described in US. Pat. No. 3,510,300 issued May 5, 1970. More particularly, it relates to an apparatus for providing radiation over an optical development area at a high level of intensity and with uniformity.
A number of non-silver free-radical photosensitive compositions have been described in patents issued to Eugene Wainer and others at Horizons Research Incorporated. Many of the compositions printout directly on exposure to a suitable dose of radiation. Others, eg those described in U.S. Pat. No. 3,042,517, require a post exposure to develop a visible image from the latent image formed as a result of a photographic exposure.
One process for making latent dye salt image visible is described in US. Pat. No. 3,510,300. As described, an intense illumination of red, or red and near-infrared, or near-infrared alone, causes the development of a latent image from a previous exposure in a number of non-silver organic photochemical formulations. The development multiplication or intensification factor varies exponentially with total development radiation. Thus; for high intensification factors,which may range up to 1,000 to 100,000, it is essential that the development radiation be highly uniform over the area of film or paper being developed. The slightest non-uniformity (for example 1%) will cause visible differences in the density of developed images.
Secondly, it is important that the intensity of radiation be as high as is practically possible in order to minimize the development time. In the examples of the aforementioned patent, 3,000 kw of lamp power is employed in optical development; the development times ranging upwards to several minutes.
The requirements for a high level of uniformity over a relatively large area, high intensity of red and near-infrared radiation at the film plane, and high collection efficiency place stringent requirements on collection optics and thermal loading of filters, particularly those high coefficient of expansion filters necessary for restricting development to the near-infrared regions.
The present invention provides means for minimizing or circumventing these problems by the utilization of spectrally-selective, diffusely-reflecting surfaces and simple geometry to provide a high collection efficiency and good uniformity.
A principal object of the invention is to provide an apparatus from which high intensity radiation is directed onto the optical development area in a highly uniform manner.
A further object of the invention is to provide such an apparatus having a high efficiency of radiation collection.
Still a further object of the invention is to provide a relatively simple apparatus which can be adapted to provide high intensity radiation of a desired wavelength and which avoids overheating of optical elements used in the apparatus.
These and other objects will become apparent or will be pointed out in the description which follows.
The invention will be better understood from the description taken in conjunction with the drawings in which:
FIG. 1 is a plan view in section showing the integrating sphere optical development apparatus;
FIG. 2 is similar view of a modification of the apparatus of FIG. 1;
FIG. 3 is a similar view ofa further modification; and
FIG. 4 is a perspective of a further modification showing the use of a cylinder instead of a sphere.
In the following examples describing the use of the apparatus shown in the figures, it should be understood that, although specific dimensions are provided in these examples, the apparatus may be scaled up or down without effectively changing the operation. In addition, although tungsten incandescent illumination is indicated as the radiation source, it will be apparent that this source may be replaced with a xenon or mercury arc containing small amounts of metal salts to improve the radiation efficiency in the red and infrared regions of the spectrum.
Example 1 A cross section view of the integrating sphere optical development apparatus is shown in FIG. 1. The integrating sphere 10 is 10 inches in diameter. A lamp 12 (General Electric 650 watt DVY) is mounted on supports 14 in the center of the sphere. An opaque mask 16 is mounted in the sphere to prevent the direct illumination rays of the lamp from reaching the end window which is 3 inches in diameter. A red Corning glass filter 18 is positioned over this opening. The film or paper 20 being optically developed is positioned immediately behind the red glass filter. Water cooling coils 22 are soldered to the metal integrating sphere and provide cooling of the sphere to dissipate the heat absorbed by the sphere from radiation from the lamp. The interior of the sphere is painted with Eastmans white reflectance paint (Cat. No. 6080). This highly reflecting white paint, containing barium sulphate pigment, has a high spectral reflectance throughout the visible and part of the near-infrared regions of the spectrum. It is a nearly perfect diffuse reflector. The mask is also painted with this paint.
The radiant flux at all points on the surface of an integrating sphere is uniform if the reflectivity is reasonably high. The intensity at any point on the surface is, to a first approximation, equal to the product of the average intensity at a distance from the lamp to the sphere (in this case 5 inches) if the sphere were not present and the reflectivity of the spheres surface divided by 1 minus the reflectivity of the sphere paint. Since the paint reflectivity is close to percent, the average intensity at any point on the sphere is 9 times greater than the average intensity at that distance if the integrating sphere were not present. The uniformity of radiation over the film plane was measured with a Gamma Instruments Corp. cosine probe, having a probe diameter of one-eighth inch. The uniformity was found to be better than 1 percent. The intensity of illumination over the region of 600 to 800 nanometers ranged from 650 to 700 microwatts/cm per nanometer; an increase of approximately 6 over that measured a distance of 5 inches from the DVY lamp with the integrating sphere not present.
Example 2 It is often desired to place a number of colored glass filters; neutral density filters, water absorption cells and the like between the light path and the film being developed in order to control the spectral distribution of development radiation. It is also desirable in many cases to move the film a sufficient distance away from the filters so that development may be carried out by visual inspection. In order to provide a means for spacing the film away from the filters, it is necessary to modify the integrating sphere design of Example 1. If, for example, the film is moved three-fourths inch away from the filter in the integrating sphere design of Example l, the radiation intensity drops off severely near the edges of the development area.
In order to overcome this limitation, the integrating sphere or geometric housing may be modified to comprise a hemisphere plus a truncated cone as shown in FIG. 2. Here, a inch diameter hemisphere 24 is joined to a truncated section 28, whose diameter at the opening is 5 A inches and whose heighth is 2 74 inches. The lamp in this example is a General Electric Quartzline Ql500T4/4Cl. The uniformity of illumination 1 inch below the exit filter is :3 percent over a 4 inch square. The radiation level at the film plane averages 1,000 .I. watts/cm per nanometer over the spectral region of 600 to 900 nanometers. The uniformity over a square 2 inches on a side and 2 inches from the exit window is :2 percent.
Example 3 The illumination output from the integrating hemisphere truncated cone apparatus of Example 2 contains a significant amount of infrared radiation. Because of the high power levels, the intense infrared radiation may heat the film or paper being developed to an undesired extent. In order to filter out this infrared or thermal radiation, the apparatus of Example 2 may be modified as shown in FIG. 3 by the addition of two Vycor windows 30 at each end of the truncated cone. This provides a sealed area through which water may be circulated. The optical absorption of water is rather high for wavelengths above 900 nm. The water filter serves quite effectively in removing unwanted radiation while providing a high transmission below 900 nm.
Example 4 For developing a film continuously, the film being in the form of a continuous web 38, the integrating cylinder arrangement shown in FIG. 4 may be employed. The integrating cylinder 31 is 4 inches in diameter and 6 inches in length. Mounted in the center of the integrating cylinder is a General Electric l500T4/CL, 1500 watt, incandescent lamp 32. A Corning red glass filter 36 is mounted in a 9k inch slit provided along the length of the cylinder. The film web 38 passes immediately under the optical filter 36. End mirrors 40 are provided and serve the function of making the lamp appear infinite in extent as viewed from the optical filter. In this case, as in the previous three examples, the interior of the integrating metal surface 31 is painted with a white reflecting paint.
Example 5 Any of the aforementioned diffusely reflecting or integrating type reflective surface apparatus may be modified by replacing the white paint with a fluorescent pigment, for example, a Dayglow Corporation red fluorescent pigment. The Dayglow red, a rhodamine pigment, fluoresces at 620 nm when excited with ultraviolet, violet, blue or green illumination. Thus, at a wavelength of 620 nm (when illuminated with white illumination) it is found that the Dayglow pigment has a reflectivity of percent. This arises, of course, from the conversion of violet, blue and green illumination to red radiation. It is found that, with the integrating sphere, an increase in output at 620 nm of approximately 30% is obtained when using this paint. Fluorescent pigments may, therefore, be usefully employed in the various types of apparatus described above if the film being developed can satisfactorily utilize illumination in the wavelength region at which the fluorescent pigment is an effective emitter.
Example 6 Certain organic photosystems may be most effectively developed by radiation lying in the near-infrared regions of the spectrum. Filters which pass illumination in this region (while totally absorbing in the visible) are limited to certain optical glasses having a high thermal coefficient of expansion. When employed at these high radiation levels, difficulty is often experienced with filters cracking because of this high thermal coefficient of expansion. One filter particularly effective for developing organic photosensitive systems having a sensitivity through the visible is a Corning No. 2600 (CS No. 7-69). The limitation due to thermal stresses in this filter, when used as a normal optical filter, may be overcome by pulverizing the filter, mixing the powdered filter with a suitable binder such as polycarbonate resin dissolved in methylene chloride, and painting the resulting pigment composition onto the inside walls of any of the apparatus described in the first four examples. It is found that the radiation outside of the narrow band, extending from 700 to 800 nm is absorbed at the wall while the normally transmitted radiation is diffusely reflected to appear at the exit window or slot of the development apparatus. Since the reflected radiation appearing at the exit window corresponds to that radiation normally transmitted by this filter, a conventional Corning 2600 glass filter may be placed at the exit window with a greatly reduced thermal loading over that which would be present if a white paint were employed.
Having described a number of preferred embodiments of the invention, it is not intended that it be limited except as may be required by the appended claims.
1. An apparatus for optical development of very faint or invisible latent images in which a high level of uniformity over a relatively large area is obtained with a high collection efficiency, which apparatus comprises:
an integrating geometric housing defining an enclosure;
a highly diffusely reflecting paint on the inner surface of said housing;
a source of radiation mounted on supports in the center of the said enclosure;
an end window at one side of said housing;
means to support a film to be optically developed adjacent to said window and in the area in which a high level of uniformity of radiation is to be obtained;
a sphere and said source of radiation is near the center of the enclosure.
3. The apparatus of claim 1 wherein said enclosure is a hemisphere joined to a truncated cone.
4. The apparatus of claim 1 wherein said enclosure is a cylinder.
5. The apparatus of claim 1 wherein the reflecting paint contains a fluorescent pigment.