GB1436638A - Method of and device for identifying colours - Google Patents

Abstract

1436638 Facsimile systems FRANZ MORAT GmbH 8 May 1973 [13 May 1972] 21948/73 Heading H4F [Also in Division G1] A system for identifying colours including an opto-electronic scanning device for the production of electrical analogue signals proportional to the primary colours present includes division and/or addition and/or subtraction circuits for deriving further signals from the analogue signals and a logical evaluation circuit for the two sets of signals so that separation zones are formed between colours in which no colour identification is possible. A drawn pattern of a grid type, e.g. the pattern to be used in knitting or weaving technology, is scanned by a device such as that shown in Specifications 1,170,947 and 1,196,600 and the reflected light is detected by three photo-cells 35 rendered sensitive to red, blue and green light by colour filters. The detector outputs after amplification at 37 are fed to further respective amplifiers 39 which provide analogue signals representative of the primary colours and also to difference amplifiers 41, 43, 45 which also provide the absolute values of the differences. The amplifier outputs are then fed to an analogue to digital converter which acts as an amplitude discriminator and normalizer and which includes three NAND gates 51, 53, 55 for each amplifier. The outputs from the converter are then applied to a logic evaluation device 49 which includes a NAND gate 57 assigned to each colour channel i.e. the three primary colours, three mixed colours and white. The circuitry is such as to function in accordance with the following "truth" table where r, b, g are primary colour signals lying above a threshold "S", Fig. 5, r, b, g are primary colour signals below the threshold and /r - b/, /b - g/, /g - r/ are the differences of the colour fractions of the mixed colour above a threshold and /r - b/, /b - g/, /g - r/ the differences below the threshold value. Thus for the colour quadrant for red, blue and magenta, Fig. 5 shaded areas thereon indicate zones in which a "white" signal is produced if the colour lies therein and there is no identification. Details of difference, addition and division circuits are described Figs. 12, 13, 14 (not shown) and various colour diagrams with differing zones may be formed Figs. 6-10 (not shown) using different logic circuits.