GB1250555A - - Google Patents

Abstract

1,250,555. Colour facsimile systems. MATSUSHITA ELECTRIC INDUSTRIAL CO. Ltd. 19 May, 1969 [4 June, 1968], No. 26560/69. Heading H4F. In the receiver of a line sequential colour facsimile system the output of a light source is appropriately coloured by means of a rotating multi-colour filter and the resulting beam is scanned across a recording medium, the field scan being at such a speed that successive lines overlap one another. In the transmitter of the system a colour original is placed on a drum which is rotated by a motor to produce the line scan. A pick-up system incorporating a dichroic prism and three photomultipliers is moved along the length of the drum to provide the field scan and generates red, green and blue component signals which are modulated on to carriers, the resulting signals being applied to a masking circuit which corrects for the density of the original and then to gating circuits which produce a line sequential output under the control of a ring counter driven by synchronizing pulses one of which is generated for each revolution of the drum. In the receiver the signal is demodulated and used to control the light emission of a lamp in front of which is rotated a tricolour filter. A line scanning system comprising a rotating cranked light guide feeding a circular array of optical fibres which are transposed to form a linear output scan, together with the rotation of the tricolour filter, are synchronized with the rotation of the drum at the transmitter. The coloured output lines of the scanning system are recorded on a colour film which is moved past the linear part of the scanning system to provide the field scan. The speed of the field scan is selected so that each line overlaps two-thirds of the proceeding line so that every point of the film is exposed to signals from all three colour channels. For monochrome reproduction the speed of the field scan may be. tripled so that the lines do not overlap one another.