Abstract: A method and apparatus for processing original data defining the values of pixels of an original colored image represented in a spatial domain by two or more color separations each color separation defining the respective color component content of pixels arranged in a two dimensional array extending in X and Y directions. The apparatus comprises a store 6 for storing the original data; and a frequency transform circuit 8 for performing a three dimensional transformation on the store representation to generate transformed data representing the original image in three dimensional frequency space. Two of the three dimensions represent the variation in pixel value in the X direction and the Y direction respectively and the transformed data has a single zero order frequency term.

Abstract: A method and apparatus for processing a screened separation comprises an analyze scanner for scanning the separation at a resolution higher than the screen ruling to generate a binary value for each high resolution pixel of the separation; a processor for generating signals representing single values for respective blocks of the high resolution pixels from the binary data in the blocks; and a descreening system to which the signals from the processor are fed, the descreening system generating signals representing a descreened version of the original separation.

Abstract: Apparatus for interactively modifying an image represented by digital data defining the color component content of pixels of the image, comprises an image store for storing the said digital data; a display; look-up tables defining retouch curves for each color component; and a microprocessor for applying the image in the image store to the LUTs and thereafter to the display to display the retouched image. The microprocessor also enables an operator to modify the retouch curves so that a second selected image point is retouched to the color of a first selected image point by modifying a color component retouch curve for each color component used to define the original image such that a pixel located at the second selected point will be retouched to have the color content of a pixel at the first selected point.

Abstract: A method and apparatus for reproducing a colored original image represented by first signals defining the color content of pixels of the original image in terms of a first set of color components. The colored original image is reproduced using at least two separations representing respective color components of a second set which is different from the first set. The color components of the second set are ranked in order of similarity to each pixel and a value is selected for the highest ranked color component for which each of the first set of color component values defining said selected color component does not exceed the corresponding pixel values. The pixel values are then adjusted to take account of the select value of the color component of the second set. The process is then repeated for each of the remaining color components of the second set in the order of ranking.

Abstract: Apparatus for processing a digital representation of an image in which each pixel is defined by at least one digital color component value, the value comprising one of a first set of values defining a first scale of color component values. The apparatus comprises a store for storing digital color component values for the image pixels; and a first look-up table (LUT) addressed by a color component value from the store corresponding to a selected pixel, the first LUT generating a signal representing a modified color component value chosen from a set of modified color component values defining a second scale coarser than the first scale. Three second LUTs are provided which are addressed by the color component value from the store in parallel with the first LUT, each second LUT generating an error value signal, the sum of the error values being equal to the difference between the modified color component value and the color component value from the store as measured on the first scale.

Abstract: A method and apparatus for monitoring the passage of a mark on a web. The web is caused to move through a detection station at which at least that portion of the web carrying the mark is illuminated. An image of the mark is projected onto a quadrant array of photodetector elements at the detection station. The axes defined between the elements are transverse to the direction of movement of the web. The times t.sub.1, t.sub.2 at which substantially equal areas of a mark are projected on either side of the axes are determined which provides an indication of registration of the web.

Abstract: A method and apparatus for enhancing a video image defined by luminance information and chromaticity information comprises, for a number of selected regions of the image,(a) determining using a microcomputer (22) a statistical relationship between the luminance information and the chromaticity information for the selected region; and,(b) generating modified chromaticity information for at least a portion (1) of the selected region by applying the determined statistical relationship to the luminance information for the said portion.

Abstract: Apparatus for displaying an image defined by digital data representing the color content of the pixels of the image comprises a monitor; a first store for storing digital data representing an image at low resolution and a second store for storing digital data representing a magnified portion of the image at high resolution. A microcomputer is connected to the stores and to the monitor and an indicator assembly is acutable by an operator to select an area of an image displayed by the monitor. The microcomputer is responsive to a "magnify" signal from the indicator assembly to cause the monitor to display a portion of the selected after magnification, the portion being displayed within the selected area. The microcomputer suppresses pixels of the orginally displayed image within the remaining portion of the selected area, the degree of magnification being such that the magnified portion substantially fills the selected area.

Abstract: A method and apparatus for electronically retouching an image are described. The apparatus comprises a source (1) of color component image signals representing the color component values for the picture elements of the image to enable the image to be displayed on a monitor screen (8). A source (9) of color data is provided representing the color component values of a first range of colors, adjacent colors differing from each other by more than a predetermined amount. A control device (2) such as a minicomputer causes the monitor screen (8) to display the first range of colors.

Abstract: In color printing it is customary to print images in a combination cyan, magneta, and yellow printing inks. However, it is sometimes required in the printing of the final image, to include an ink of a special color, for example a brown ink, which cannot be reproduced by combining cyan, magenta and yellow inks. The present invention is concerned with the preparation of a special color printer for a special printing ink. According to the invention sets of values (C.sub.ROP, M.sub.ROP, Y.sub.ROP, K.sub.ROP) defining the characteristic elements of curves for cyan, magenta, yellow, and black, which curves together correspond to a range of values for the overprinted colored separation, are stored. For each picture element, a combination of color component values for cyan, magenta, yellow and black (C,M,Y,K) are derived and compared with different sets of values (C.sub.ROP, M.sub.ROP, Y.sub.ROP, K.sub.

Abstract: The invention relates to a method and an apparatus for reducing the diameter tolerance of a laser beam. A lens (3) is positioned so that one of the focal planes of the lens (3) is in the region of a limit (5) of the Rayleigh range of the beam (19). The lens (3) forms a second beam waist at a position (6), where a modulator (10) is placed. The beam (21) then passes through beam expansion apparatus (11,12,13) before being collimated by a lens (14). The collimated beam (25) is then focussed to a third beam waist at the recording drum (17), via a lens (18) and mirror (15).

Abstract: A method of operating a radiation sensor, such as a charged coupled device array, having a number of radiation sensitive devices and associated transfer buffers. The method comprises (1) illuminating the radiation sensor for a predetermined duration whereby the radiation devices each store a charge relating to the total radiation incident thereon; (2) after the illumination step, transferring the stored charges to the transfer buffers; (3) reading out the charges in the transfer buffers; and, (4) repeating steps 1 to 3 until the transferred charge is substantially constant. Image scanning apparatus incorporating apparatus for performing this method is also described.

Abstract: A method of generating a recording beam control function for reproducing an original colored image in which a record medium is exposed to a recording beam of radiation under the control of the control function comprises (a) generating a proof (7) from the original image; (b) generating a first recording beam control function (4) at least partly from the original image using a different reproductive process (2,3); (c) comparing the color of one or more selected areas of the proof (7A,7B) with the color of the corresponding area or areas defined by the first control function; and, (d) modifying the first control function in response to the result of the comparison step to generate a second control function (6) adapted to minimize differences in color between the proof and the reproduced image.

Abstract: A method and apparatus for modifying an image represented by digital data defining the content of one or more pluralities of cells constituting one or more color separations is described. The digital data indicates for each cell whether the respective color is "present" or "absent". The apparatus comprises scanning means (15,16) for electronically scanning along a plurality of scan lines with a mask of preselected dimensions; the respective plurality of digital data corresponding to a region including a boundary for one or more of the color separations. Programmable logic determines at each position of the mask whether the portion of the color separation within the mask includes at least one cell the content of which indicates color "present"; and modifies the digital data at another, predetermined position within the mask to change the content of the respective cell or cells of the color separation to represent color "present" or color "absent" when color "present" is detected within the mask.

Abstract: A method of generating an electronic representation of an original image (2) comprises illuminating the image (2) with a scanning beam; causing relative movement between the scanning beam impinging on the image and the image (2) whereby the original image (2) is scanned in a series of overlapping scan lines. The scanning beam is caused to impinge on one or more arrays of radiation sensitive elements (14-16), each array having dimensions smaller than the dimensions of the image (2), and the elements being sensitive to the intensity of respective portions of the incident beam received from corresponding pixels of the original image within a scan line at least some of which extends transversely to the scanning direction. The sensed intensities are regularly monitored and data related to the intensities monitored in a predetermined number n of the monitoring steps is stored in a memory (20).

Abstract: An exposure system and method comprising a radiation generator (15'); and a modulator (4) which comprises a device for controlling the transmission of radiation passing through the modulator in accordance with an applied control function, the response characteristic of the modulator to the control function exhibiting a maximum or minimum and onto which radiation from the generator is incident. A microprocessor (19) controls the transmission condition of the modulator (4), and is responsive to predetermined control signals during an exposing stage and, during a compensation stage prior to the exposing stage, generates a test control function having a DC component and a cyclically varying component for application to the modulator.

Abstract: This relates to the modification of the whole, or a substantial part, of an image, for example to the merging of two images or to applying a tint to an image. To achieve this, using only the normal data processing capability provided for handling a single image, two images (I.sub.1, I.sub.2) are stored in first and second portions of a normal image store; for example, if the normal image store has a capacity of 1024.sup.2 pixels, each image may be stored at a resolution of 512.sup.2 pixels. In a further 1-bit store there is stored a mask consisting of alternate 1's and 0's and the mask output is used to select pixels from the two portions of the image store alternately. The mask output also selects multiplying factors A and (1-A) alternately. Then each pixel from the first image, after multiplication by A, is added to an immediately succeeding pixel from the second image after its multiplication by (1-A). The resulting sum signals are used to control an image display (34).

Abstract: A method and apparatus for controlling the spectral components of a light beam are described. The apparatus comprises means (3-7) for generating a collimated light beam; means (9) for dispersing the collimated beam; a mask (1) including an aperture (2) the size of which is such that a portion of the dispersed beam passes through the aperture in use; and movement means (not shown) for causing relative transverse movement between the light beam and the aperture. A memory (not shown) is provided for storing in use a profile of the relative transverse movement between the light beam and the aperture (2) required to obtain a desired spectral response in the transmitted light beam, the movement means being responsive to the stored profile to cause relative transverse movement in accordance with the predetermined profile.

Abstract: Apparatus for splitting a light beam into a plurality of parallel beams of equal intensity comprises at least two blocks of isotropic light-transmissive material, each block having one major face, on which the input beam is incident, coated to be partially transmissive, and an opposite parallel major face which is silvered. The blocks are arranged in series so that the input beam, on reaching the first block divides into a reflected part and a transmitted part which enters the block and, after total internal reflection, provides an output beam parallel to the reflected part of the first beam, each subsequent block receiving all parallel beams from the preceding block or blocks. Optical means may be provided in the beam path to ensure that each beam entering each block has equal S- and P- polarization components.

Abstract: A method and apparatus for generating a representation of a half-tone image including areas of different resolution. The apparatus comprises stores (2, 26) for storing digital color data representing color density information at low and high resolution respectively. A second store (25) stores spatial data indicating the type of image data to be used at each position on a record medium (7). A third store (2') is provided for storing half-tone dot information. A group of six light modulators (10) which generate six scanning beams are arranged side-by-side. A support (8) supporting the record medium (7) to be exposed to the scanning beams is provided while drive motors (6',9') cause relative movement between the support and the scanning beam.