GB1227766A - - Google Patents

Abstract

1,227,766. Facsimile apparatus. DR.-ING. RUDOLF HELL. 17 May, 1968 [22 July, 1967], No. 23700/68. Heading H4F. To produce colour correction signals or colour separation signals, the primary colour signals R, G and B which are preferably initially subjected to logarithmic conversion and contrast adjustment in stages 1, Fig. 1, and produced with both polarities in stages 2, e.g., by separate rectification of the positive and negative half-cycles of the carrier-wave frequencymodulation signals or by producing signals of opposite phase. In Fig. 1, mg, ye and cy represent the basic colours magenta, yellow and cyan, or, gn and vi represent the mixed primary colours orange, green and blue-violet, and wh represents white. In adding stages 3 the positive signal of one channel and the negative signal of another channel are added, i.e., difference signals are produced, and the difference signals are separated according to their polarity to produce partial signals +mg+or, cy - gn, &c. Pairs of these partial signals which contain a common signal component of different polarity are added in stages 4, the common signal components neutralizing each other, and the remaining signal components representing two colours are separated according to their polarity. Six basic colour signals are thus available with both polarities, these signals being subjected before use to non-linear conversion (contrast adjustment). ' In a second embodiment, Fig. 2 (the details for two colours only being shown), the partial signals from stages 3 are made available with both polarities by polarity-reversing stages 5, and pairs of partial signals are selected in which a common colour signal component appears with the same polarity and in stages 6 they are compared and only the momentarily smaller (with regard to amplitude) partial signal is switched to the output, this smaller signal representing a basic colour. In the case where the primary colour signals are not derived from colour negatives they are initially inverted in amplitude, and in Fig. 2 the stages 6 are arranged to pass the momentarily larger partial signal which represents a basic colour.