Crosfield Electronics Limited

Richard M Gascoigne

Peter C Pugsley

Michael J Perriman

In apparatus for making a half-tone reproduction of an image and having a row of light source elements which together expose a line across a component screen area of a film to be exposed, screen-representing signals are electronically generated when pulses exist in corresponding locations of a pair of shift register devices having trains of pulses moving in opposite directions. Each shift register device may comprise a pair of shift registers having trains of pulses moving in the same direction, the relative phase of the pulse trains in the two shift registers varying with the picture signal.

Apparatus for making a screen reproduction of an image

In the reproduction of a half-tone image, x and y pulse trains are generated in synchronism with the production of image-representing signals resulting from scanning the image to be reproduced; the x pulse train is multiplied in frequency by first and second factors and the y pulse train by third and fourth factors, all factors being irrational or nearly irrational and being different functions of the screen angle selected for printing; the first and third pulse trains are accumulated and combined and the second and fourth pulse trains are separately accumulated and combined, the resulting signals being applied to a function generator which produces a predetermined screen pattern signal which is a periodic two-dimensional function of the position of the scanned image element in the two mutually perpendicular directions.

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Kingston-upon-Thames, United Kingdom

Richard M Gascoigne