Abstract: A digital image processing system comprises a processor at a central, first site; and digital image processing equipment such as an analyze scanner and an expose scanner at a second site remote from the first site. The processor and the digital image processing equipment are connectable and are adapted to pass signals therebetween corresponding to signals generated by the digital image processing equipment. These signals may be representative of operator commands or digital data generated at the second site which can be monitored at the first site.

Abstract: A method of detecting the position of a feature, such as a register mark, in a color separation comprises printing the color separation on a substrate with an ink containing a pigment corresponding to the color of the separation and a dye which is detectable only when exposed to radiation outside the visible range. The printed color separation is exposed to the said radiation and the position of the feature in the printed color separation is determined by detecting radiation, such as fluorescence, from the dye.

Abstract: Image display apparatus comprises, a monitor (6); a monitor control system (4,5) connected to the monitor (6); and a color modifying circuit (2) for receiving from a store (1) first signals representing the color content of pixels of an image and for generating monitor control signals for each pixel which are fed to the monitor control system. The color modifying circuit (2) generates for any first signals representing a color which falls outside the gamut of colors normally displayable by the monitor (6), monitor control signals representing a respective equivalent color which falls within the monitor gamut, by applying a predetermined algorithm to the first signals which desaturates all the image colors while leaving hue and intensity unaffected.

Abstract: A method of generating a half-tone representation of an image from digital data defining the color content of pixels arranged in a series of substantially parallel, overlapping input scan lines comprises exposing at least one record medium to an exposing beam in a series of substantially parallel, overlapping output scan lines each corresponding to a respective input scan line. The exposing beam is modulated under the control of the digital data and half-tone information. The intensity of the exposing beam, which typically includes a number of subsidiary beams, is such that an area of the record medium will only record a half-tone dot or a portion of a half-tone dot after all output scan lines passing through that area have been exposed.

Abstract: Digital signals are generated for each pixel of an image to be reproduced, corresponding to the values of color components in each pixel. The respective color component values of each pixel are applied to a set of look-up tables (30) so loaded that they recognize whether the color component values of a pixel fall within a color range(s) for which a processing operation is to be carried out. The look-up tables provide an output signal representing one of a number of possible processing operations for that pixel, in the form of an operation number. The operation number signal is applied through a processor (32) to an operation select table (36) which converts the operation number into a specific processing operation for each color component. The processing operations may be retouching, image retention (no change), replacement by a tint value, or dropout.

Abstract: Apparatus for enhancing an image represented by picture signals corresponding to respective color components of successive elements of the image comprises signal generators for generating sharp and unsharp signals from the picture signals. Fringe signal generators derive a plurality of fringe signals by combining the sharp and unsharp signals in a predetermined manner; a correction circuit applies connected in parallel with the fringe signal generators modifying functions to the sharp or unsharp signals or other premodified picture signals to derive modified picture signals; and an adding circuit sums the fringe signals with the modified picture signals to derive a plurality of output signals.

Abstract: A method and apparatus for matching the transmission characteristics of two beam modulators (4,4') comprises radiation generating means (30); and the first and second beam modulators (4,4'), the radiation generating means causing beams of radiation (16,16') to impinge on each modulator. Control means (20) generates first and second control functions for application to the first and second modulators (4,4') respectively, the first control function cyclically varying between first upper and lower values (V.sub.1,V.sub.2) and the second control function cyclically varying between second upper and lower values (V.sub.3,V.sub.4) at the same rate and at the same time as the first control function, the range of the first and second control functions being such that the transmission characteristics of the first and second beam modulators overlap.

Abstract: A method of operating a radiation sensor is described. The sensor has a plurality of radiation sensitive devices such as photodiodes, transfer buffers associated with the radiation sensitive devices, and at least one isolation buffer identical with the transfer buffers but not associated with a radiation sensitive device. The method comprises (a) exposing the radiation sensor to radiation, whereby each radiation sensitive device stores a charge related to the total radiation incident thereon, and simultaneously sequentially reading out the contents of the transfer and isolation buffers at a regular rate; (b) transferring the charge stored in the radiation sensitive devices into the corresponding transfer buffers; and, (c) while exposing the sensor under substantially the same conditions as in step (a), sequentially reading out the contents of the transfer and isolation buffers at the same regular rate.

Abstract: A method and apparatus for generating a beam of radiation in which a beam of coherent radiation (2) is fed to a pair of A/O modulators (3,4). The beam is modulated by the modulator (4) in response to a chopped control function which chops between two levels, one of the levels comprising a reference level (V.sub.low). The radiation beam is sampled at times corresponding to the application of the reference level control function to the modulator (4) and a feedback signal corresponding to the sampled power is fed to a comparator (12) where it is compared with a reference voltage (V.sub.ref). The resultant error signal is applied to the modulator (3) so as to maintain at a substantially constant level the power of the sampled radiation when the chopped control function is at the reference level.

Abstract: A method and apparatus for retouching an image represented by color printing data in the form of a number of sets of input data, one set for each of the printing colors, is described. The apparatus comprises a source (1) of color component image data; a reference data set generator (2;9,10) for generating a reference data set comprising the color components of a limited plurality of reference colors; and a color converter (2;9,10) for generating a temporary data set from the color printing data and the reference data set, the temporary set representing the original image in terms of the reference colors. A refresh store (3) receives the temporary data set and feeds the temporary data set to a monitor (8) via a conversion system. The conversion system includes one or more look-up tables (5) defining printing ink modifying functions and an operator table (6) for controlling the contents of the or each look-up table (5).

Abstract: Methods of electronically enhancing one or more color components (C, Y, M) which together represent the chromatic components of a pixel of an image are described. The methods comprise subtracting from each color component respective quantities which when combined correspond to a grey level (4) to generate reduced color components. These reduced color components are then multiplied by a factor and the modified reduced color components are then added back to the subtracted quantities or to the original color components to generate enhanced color components (13,14), whereby the factor is chosen such that the hue of the original pixel is not substantially changed after enhancement. In one method, the magnitude of the maximum reduced color component is determined and a factor is chosen which is related to the determined magnitude. In another method, the color components are ranked in order of magnitude and compared to derive two equivalent color component values.

Abstract: Scanning apparatus for generating signals representing color components of successively scanned picture elements of an original colored image comprises a light source (1); means (42,45) for causing relative movement between the original image (3) and a light beam generated by the light source (1) whereby successive picture elements of the original image are scanned. Means (13) for generating a sharp light beam for each color component of each element and an unsharp light beam for at least one color component of each element are provided. Common detection means (10) receives the sharp and unsharp light beams and provides corresponding output signals. Sequencing means such as a filter wheel (13) causes the sharp and unsharp beams sequentially to impinge on the detection means (10).

Abstract: In color printing, it is customary to analyze the color content of an original using red, blue and green filters and to make color-component printers for the complementary colors, i.e. cyan, magenta, and yellow, with or without a black printer. The present invention concerns the preparation of a special color printer for a printing ink the color of which is not complementary to one of the said filters, for example a brown separation. According to the invention, sets of values (Ybr, Mbr, Cbr) defining the characteristic elements of curves for yellow, magenta and cyan, which curves together correspond to a range of values for the required color separation, are stored. For each picture element, a combination of color-component values for yellow, magenta and cyan (Y, M, C), are derived and are compared with different sets of values (Ybr, Mbr, Cbr) derived from the stored curve elements, each set corresponding to a different value of the required special-color separation (Br).