Patent GB-1356706-A (GB)
Title: Process and apparatus for sensitometry of a liquid photosensitive emulsion
IPC: G01J1/42
Filed: 1972-01-20
Abstract: 1356706 Sensitometry EASTMAN KODAK CO 20 Jan 1972 [21 Jan 1971] 2819/72 Heading G2X [Also in Divisions F2 and G1] The sensitivity of liquid photo-sensitive emulsion is measured by measuring the optical density of a sample of emulsion before development, to derive a reference measurement exposing the sample to a preselected radiation, developing it and measuring the optical density of the developed sample and relating this measurement to the reference measurement. General system, (Fig. 1.) The system operates under the control of a punched tape programmer 110, 111 to control the sequence of operation of valves and electronic circuitry by means of valving arrangement 17, 18, 23, 29, 30, 32, a metered sample of emulsion is removed from kettle 11, diluted with water from tank 24 and pumped to mixer 21. This and its valving arrangement is detailed in Fig. 2 (not shown). Air pressure is used to change the mixer valve and allow the sample to flow via 44, and metering pump 43, to its densitometer 50, where the first (reference) measurement is made. The sample then passes to sensitometer 65 where there is provided a controlled exposure of a continually varying intensity as the sample flows through. The sample is then mixed at 75 with developer from 25, passes through coil 91 in which processing is completed and back to a different sample cell in the densitometer for the second measurement. The reference and second  measurements are indicated as curves 95 and 96 of density versus log. exposure on a recorder 126. The densitometer, (Fig. 3), comprises two sample cells 51, 52 each provided with an infrared source 57, 58, a further reference source 59 being provided. The sources are operated in sequence, in correspondence with the delivery of samples to the respective cells. A common detector 62 detects the transmitted radiation or direct radiation from 59, via internally reflective cone 61. The sensitometer, (Fig. 4), comprises tungsten lamp 70 providing a wide spectral band, lenses 71, 72 and a tube 73 for passage of the emulsion to be exposed. Diffuse reflector 82 may be  provided. Neutral density filters may be selected by rotation of disc 77. As a sample passes through tube 73, a neutral density filter wheel 80 having a logarithmic variation in density with angular increment, is rotated by a stepping motor so as to provide an exposure such that the logarithmic intensity varies linearly with time. Spectral filters may be selectively introduced if required by slide 85. Cleaning, calibration. Cleaning of cell 52 to prevent build up of silver complexes by flushing with bleach via valving system 103, 104, 105 and subsequent washing with water before the next sample is tested. A calibration check is carried out under control of a special program tape, the intensity at 73 in the sensitometer being sensed by conducting light via fibre optic guide 108 to the densitometer detector. The trace produced is compared with a standard one. Modifications, colour process. It is also envisaged to carry out a reference measurement on a sample which has been exposed and mixed with developer (i.e. at line 92) but before processing has occurred. A modified processer is described, for addition of bleach and fixer, for use in monitoring a colour forming emulsion, Fig. 6 (not shown). In this case, the densitometer has a wide band source e.g. a tungsten lamp and selectable spectral filters. An example of application to a cyan emulsion is described.