1992-07-02
1994-05-24
Rutledge, D.
354319, 354320, 354324, G03D 1300, G03D 308
Patent
active
053153375
DESCRIPTION:
BRIEF SUMMARY
This invention relates to photographic film processing, and is more particularly concerned with the control of such processing.
U.S. Pat. No. 2 296 048 discloses a method of photographic development which relates to a predetermined value of contrast. The method comprises subjecting two areas of the film to be developed to two exposures of different values and observing two radiant beams through these two areas during the development process. The intensities of the two radiant beams are chosen so that the difference between the logarithms of these intensities corresponds to the difference in densities to be obtained in the two areas after correct development. Suitable infrared filters can be used to absorb all radiation to which the emulsion being developed is sensitive.
U.S. Pat. No. 3 680 463 relates to a method and apparatus for selectively processing silver halide photographic film or the like by following the steps of partially developing the latent image on the film in a standard developing solution, scanning the film with infrared radiation, sensing the density of discrete areas of the film by sensing the amount of infrared radiation reflected or transmitted through the partially exposed film, using information relating to the infrared radiation reflected or transmitted through the film to automatically control the temperature of processing of discrete areas of the film and thereafter finishing the developing process in a conventional developing bath.
U.S. Pat. No. 3 785 268 relates to apparatus for developing X-ray film and allows the film to be developed with any desired density within know limitations regardless of whether the film has been over- or under-exposed. The apparatus incorporates a control system which responds to the scanning of the exposed film in a developing solution by an infrared beam to which the film is relatively insensitive and which causes the developing process to be terminated when a desired density is achieved. Very clear and very opaque areas of the film are eliminated from the processing and the desired density is establisted by processing the film between such minima and maxima.
FR-A-1 200 243 discloses development and processing apparatus in which the density or range of densities of a photographic emulsion or other sensitive material can be rigourously controlled during development. Development of the emulsion or other sensitive material is terminated when a predetermined value is reached which corresponds to the difference in infrared energy supplied to the detector through two control zones.
In standard film processing techniques, the exposed film is developed, bleached and then fixed prior to printing. At each stage of the processing technique, the amount of developing, bleaching, or fixing tends to be determined by time. This can lead to incorrect processing of films which are either over-or under-exposed thereby producing unsatisfactory results.
It is known that during film processing, the levels of silver and/or silver halide present in the film change in each of the development, bleaching and fixing stages. It is an object of the present invention to utilise means for measuring such changes in the silver and/or silver halide levels to control the processing process.
According to one aspect of the present invention, there is provided a film processing apparatus comprising a plurality of film processing stations, each station executing a predetermined step in the processing operation and includes infrared monitoring means, characterized in that the infrared monitoring means measures the density of silver and/or silver halide present in the film.
By this arrangement, optimum processing of an exposed film can be achieved.
Advantageously, the monitoring means comprises an infrared source and an infrared detector. In a preferred embodiment, the infrared light source is an infrared light emitting diode, and the infrared detector is an infrared sensitive photodiode.
Preferably, the source and detector are spectrally matched, and operate on a wavelength of around 950 nm
REFERENCES:
patent: 2296048 (1942-09-01), Planskoy
patent: 3462221 (1969-08-01), Tajima et al.
patent: 3680463 (1972-08-01), Attridge et al.
patent: 3785268 (1974-01-01), Gregg et al.
patent: 4881095 (1989-11-01), Shidara
patent: 5179405 (1993-01-01), Osada et al.
Eastman Kodak Company
Rutledge D.
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