Abstract: In a method of preparing a screened reproduction, a laser beam modulated in an on-off manner scans a film or plate comprising a substrate resistant to the laser beam and a two-layer coating which is removed by the laser beam, after which correction is carried out by subjecting the image-defining coating dots to the action of a chemical agent. The coating layer adjacent the substrate is attacked by the chemical agent but the overlying coating layer is resistant to the chemical agent and protects the top surface of the first layer, permitting a reduction of the size of the coating dots without a reduction in their thickness.

Abstract: Apparatus for reproducing a half-tone image of an original comprises a support, preferably in the form of a cylinder, for a light-sensitive record medium, an exposing head for exposing a record medium on the support, and means preferably in the form of a mechanism for rotating the cylinder and a lead screw for moving the head axially of the cylinder, to produce a relative scanning motion between the exposing head and the record medium. The exposing head includes a row of side-by-side light modulators or light sources extending in a direction such that the areas illuminated by the modulators or sources on the record medium extend in a direction across the width of a scanning line on the record medium. The area of illumination of the record medium provided by each light modulator or source varies in the said direction and is of lower intensity at its ends than at its middle and each area overlaps the areas of illumination provided by adjacent modulators or sources.

Abstract: In apparatus for excavating material from a gravure cylinder surface, for example, by means of a laser beam, the polarization of the laser beam is modulated and the modulated beam is then passed through a polarization analyzer system to a focusing lens which focuses light on to the surface to be excavated. The polarization analyzing system includes an aperture through which a central portion of the laser beam passes, regardless of its polarization the extent to which the remainder of the beam is transmitted by the analyzer depending upon its polarization modulation. The effect of the aperture is to reduce variation in excavation width with the intensity of the beam.

Abstract: 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.

Abstract: 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.

Abstract: In a method of preparing a gravure printing member by excavating materials from the surface by a scanning laser beam or other energy beam, the path of the beam to the surface is periodically intercepted during the scanning by a rotary shutter, the position and speed of the rotary shutter and the relative movement of the scanning system and the surface of the printing member being such that the shutter shadow is substantially stationary relative to the surface of the printing member during its passage across the beam, the protected portions of the surface constituting the walls of the gravure cells.

Abstract: In a laser scanning apparatus, in which a laser and a focusing lens are moved in a direction parallel to the cylinder axis during rotation of the cylinder so that the focused laser beam traces out a helical path on the cylindrical surface, the laser and focusing lens are mounted to permit relative movement in the said direction parallel to the cylinder axis and are separately driven, the driving means for the focusing lens being such as to permit a rate of movement of the focusing lens in the said direction more uniform than can be achieved with the laser driving means, the size of the lens aperture and the extent of the said relative movement during operation of the driving means being such that the laser beam always passes through the lens aperture; the uniformity of the movement of the focused laser beam along the cylindrical surface is then governed by the uniformity of the movement of the focusing lens, the lens head being lighter in weight than the laser head.

Abstract: To provide an electronically reproduced image of an original in which defects have been removed by retouching, defects in the original are marked in such a manner that the signals from an analysing scanner corresponding to the defect marking are distinguishable from those corresponding to the remainder of the original and the sensing of the defect-representing signals is used to cause a replacement signal, derived as a function of the densities of picture elements adjacent the defect in the original, to be substituted for the defect-representing signal before the train of signals from the analysing scanner is used to control the treatment of an output surface to form the image.

Abstract: In a system for producing screened images, for each set of image-representing signals derived from one rotation of an input scanner cylinder, n sets of screen-representing densities are derived corresponding to screen densities of parallel tracks each of which has a width which is a fraction of the screen pitch. The set of image-representing signals for a line of the image is modified n successive times as a function of the n respective sets of screen-representing densities and each of the n sets of screen-modified image-representing signals is applied in turn to modulate a single output element in an output scanner in which the scanning beam scans the image-reproducing area at a pitch that is n times finer than that of the input scanner.