Dispositif pour voiler les images floues

1,096,376. Copying in colour by scanning. D. J. KYTE. Sept. 6, 1966 [Sept. 20, 1965], No. 40081/65. Heading H4F. Apparatus for improving the sharpness i.e. contract, of colour separation images produced from coloured originals comprises photo-electric sharp scanning equipment and associated colour separation equipment for producing electrical colour separation signals e.g. yellow (Y), magenta (M) and cyan (C) signals, photoelectric unsharp scanning equipment for producing electrical " white " (W) signals, means for determining a first and a second difference (if any) between the maximum individual signal amplitude occurring among the Y, M, C and W signals and the Y, M and C signals and between the minimum individual signal amplitude occurring among the Y, M, C and W signals and the Y, M and C signals respectively, and means for adding the sum of the first and second differences, referred to as a detail contrast signal, to each of the colour separation signals to form the signals to be used in the production of the colour separation images. A black printer separation signal (B) is also produced to which is added the sum of the first and second differences. The Specification discusses with reference to Figs. 3A-3P (not shown) the manner in which the detail contrast signal improves the contrast of neutral details (greys) and of boundaries between neutral and coloured areas without substantially affecting the coloured details themselves. When the detail contrast signal is used to produce the black printer separation (the visual effect on the printed result being more noticeable for this separation) (a) where a grey detail stands against a light neutral background, the grey detail is made darker whilst the background adjacent to the detail is made lighter; (b) where a grey detail stands against a dark neutral background, the grey detail is made lighter whilst the background adjacent to the detail is made darker; (c) where coloured details stand against a lighter background, the background adjacent to the details is made lighter; and (d) where coloured details stand against a dark background, the background adjacent to the details is made darker. In the embodiment described, Fig. 1, the unsharp scanning equipment which produces the W signal comprises partially reflecting surface 25, filter 26, photo-cell 27, amplifier 28 and circuit 29, Figs. 2 and 4, not shown, which includes maximum and minimum selectors, subtracters and an adder for producing the detail contr