1993-05-03
1995-05-16
Rutledge, D.
354321, 354334, G03D 302
Patent
active
054165504
DESCRIPTION:
BRIEF SUMMARY
This invention relates to photographic processing apparatus and is more particularly concerned with infra-red densitometry for determining the position of photographic material within such apparatus.
BACKGROUND OF THE INVENTION
It is known to use infra-red densitometry to measure the variations in the optical density of a moving web. British Patent Specification GB-A-1364439 discloses such a method which comprises illuminating a spot on the moving web with a source of infra-red radiation and using a photosensitive detector positioned on the opposite side of the web from the source to measure the diffused radiation issuing from the web. A radiation-absorbing screen is used to prevent specular radiation from reaching the detector. The energy impinging on the detector is related to the distance of the web from the detector. The optical density of the web can then be determined from the level of radiation received by the detector. The arrangement is such that the optical density measurement is not affected by any vibrations produced in the moving web.
SUMMARY OF THE INVENTION
International Patent Applications WO-A91/10941 & WO-A-91/10940 (British Patent Applications 9000637.0 and 9000620.6 respectively) disclose the use of infra-red densitometry to monitor the infra-red density of photographic film. In the former case, the infra-red density of the film at any stage provides an indication of the amount of processing which the film has undergone. In the latter case, the infra-red density of the film is used to determine replenishment needs for photographic processing apparatus.
It is known to use cyclic processing apparatus for processing photographic material. In such apparatus, photographic material is made to travel around a continuous loop whilst it is totally immersed in processing solutions. The material is maintained in a particular processing solution until the requisite processing time has elapsed. The material is then transferred into the processing solution of the next stage of the processing apparatus. Material transport speed needs to be high so that the time for which the material spends in the air during such transfer is minimised. This is because air causes oxidation of many of the photographic processing materials used and rapidly reduces their effectiveness.
It is important that the transfer or switching mechanisms are operated at precisely the correct time to prevent damage to the material being transferred from one processing solution to the next.
It is therefore an object of the present invention to provide apparatus and method for controlling such transfer or switching of photographic material from one processing tank to another during processing of the material.
According to one aspect of the present invention, there is provided photographic processing apparatus for processing photosensitive material, the apparatus comprising: positioned substantially close to the entrance to the processing tank, the densitometer arrangement being operable to measure the infra-red density of the photosensitive material; and arrangement; which provides the output signal when a change of infra-red density is detected, photosensitive material from one processing tank to another.
Advantageously, an infra-red opaque label is attached to the photosensitive material to generate the change in infra-red density.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, reference will now be made, by way of example only, to the accompanying drawings in which:
FIG. 1 is a schematic block diagram of apparatus constructed in accordance with the present invention;
FIG. 2 is a circuit diagram of a threshold detector circuit as used in the apparatus of FIG. 1
FIG. 3 is a schematic diagram of a photographic processing apparatus made in accordance with the present invention.
Although the present invention will now be described with reference to the processing of photographic film, it is equally applicable to any cyclic processing apparatus in which the material being processed needs to
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 et al.
Earle Anthony
Skye David A.
Taylor Nicholas J.
Ward Paul C.
Eastman Kodak Company
Pincelli Frank
Rutledge D.
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