Abstract: The invention relates to methods and apparatus for interpolating between coarse stored data to achieve a more accurate answer, and is particularly applicable to color scanning reprographic equipment. Color scanners (5) analyze an original to obtain digital signals (8) representing three primary color intensities. The values for the intensities of each of four printing colors, including black, are functions of all three primary color intensities, and a limited quantity of these sets of four values is stored in a three dimensional matrix (25), consisting of cubes with values at their corners. To obtain values from these coarse stored data corresponding to a point (P) within a cube, an interpolator (26) determines which one, of the three pyramids (e.g. W B G C V in FIG. 2) comprising the cube, contains the point, and interpolates within that pyramid between the values at its five vertices.

Abstract: To record on a single sheet (9) both a picture image and alphanumeric characters, each character to be recorded is stored (24) in the form of signals representing a multi-column pattern of dots which make up that character. Signals derived in synchronism with the scanning of successive lines on the recording sheet are applied to circuits (19, 20, 23, 25) to derive a column address signal for the character store (24), which is also addressed with a data signal representative of a selected character (32). In this way, signals corresponding to a selected column of the required character are taken from store and are applied to a selector circuit which also receives the picture signals and applies either the picture signals or the character signals to the recording head.

Abstract: Longitudinal drive mechanisms are usually provided in combination with a component (17) of a machine which is mounted on a slide way to move the component along the slide way. Such mechanisms usually include a nut (2) running along a screwthreaded shaft or leadscrew (1) and any deviations from staightness or any discrepancies in the pitch of the leadscrew (1) cause extraneous or irregular movement of the component (17) along the slideway. By including a first pair of links (4) pivotally connected to the nut (2) and to a collar (3) and a second pair of links (7 and 8) pivotally connected to the collar (3) and the component (17) inaccuracies in the leadscrew (1) are absorbed by the pivoted links and so not transferred to the component (17).

Abstract: This relates to a method of image reproduction in which detail enhancement is carried out using sharp and unsharp signals (S and U), for example in accordance with the expressionP=K (log U- log S)- log Swhere P is the derived picture signal and K is a constant. To reduce the disparity between the fringe amplitudes and steepness on the two sides of a density boundary, the above expression is modified, in accordance with the invention toP=K {log[U+L (U-S)]}-(K+1) log S.Another expression involving the same subtractions of sharp and unsharp signals as the first expression above but in a form suitable for use with signals which have been compressed to represent luminance, is modified in accordance with the invention in a similar way.

Abstract: To produce a whole page image from a number of separate images, the input images are separately scanned and reproduced at the required enlargement or reduction to produce pre-prints which are then assembled on a digitizer table in the relative positions required for the finished page; signals representing the boundaries of these positions are generated and stored; the boundary representing signals then control the derivation of output signals suitable for a scanner making the whole-page reproduction, each whole-page line signal including the line signals for each of the input images crossed by the page line, the output signals controlling the treatment of a sheet or surface for use in the preparation of a printed page.

Abstract: For presetting values of parameters in an image-reproducing process, an operator selects a spot on a transparency to be reproduced, for example by visual inspection of a projected image of an area of the transparency illuminated by a defocused light beam. The light beam is then temporarily brought to a focus on the selected spot and the light transmitted through the transparency on a photomultiplier, the signal from which is sampled within a very short period and held, after which the focused light beam is again defocused to enable the operator to select a further spot. The value of the sample signal is used in the presetting of the said parameter values. The period for which the focused light beam falls on the transparency is made small enough to avoid the bleaching of the transparency at the illuminated spot.

Abstract: In a method of image reproduction in which both pictures and test are to be combined in an image on a single sheet for use in the reproduction of a printed page, and in which the signals resulting from the scanning of the pictures are stored prior to the preparation of the sheet, a high resolution is achieved in the reproduction of the text without requiring excessive storage capacity for the picture signals by scanning the text at a resolution which is an integral multiple n of the picture resolution and, when the text and picture signals are merged to control an output scanner operating at the higher resolution, applying each line of picture signals extracted from store n successive times to the output scanner.

Abstract: A beam splitter is disclosed in which a light beam entering a block of light-transmitting material is internally reflected a plurality of times between a pair of parallel sides, one side being coated to enhance such internal reflection and the other side having in the direction of its length a succession of areas which are differently coated to control the amount of the beam which is reflected internallly and the amount of the beam which emerges; a plurality of parallel emergent beams of substantially equal intensity can be obtained in this way. The application of such a beam splitter to an image-reproducing system is described, the beams contributing to the formation of half-tone dots in the image.

Abstract: For the lateral guidance of travelling webs, three photoelectric detectors are arranged under one margin of the web in a transverse line such that the path of light from a light source, on the other side of the web plane, to a first of the detectors is blocked by the web, the light path to a second of the detectors is partially blocked by the web, and the third detector is fully exposed to the light source, when the web is in its normal lateral position. Signals from the three detectors are combined in such a manner that a signal is derived representing the extent to which the second detector is covered by the web, the value obtained being corrected for variations in light source intensity and for web translucence.

Abstract: In an image-reproducing system in which a number of parallel light beams contribute to the formation of half-tone dot areas on a record medium and scan over the record medium together, a reversing prism is included in the beam path to permit the line fit or line overlap to be closely controlled. The prism also adjusts the spacing between beams in the scanning direction which is provided when a coherent light source is used to avoid interference between adjacent beams.

Abstract: In an image-reproducing system in which a number of beams scan over a record medium together and contribute to the formation of half-tone dots, an anamorphic system is included in the beam path to match the beam cross-section to the shape of mask apertures in the light paths and to compress the length of the line of beams, transverse to their direction.

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: For the reproduction of colored originals, a set of standard color patches is scanned with an original to be reproduced and corresponding signals are applied to a display system having controls for adjusting the appearance of the displayed original and color patches. The standard color patch signals applied to the display are gated out and used to adjust a color-modifying means in the signal path between the input scanner and the output scanner, for reproducing the original, in such a manner that the standard color patches if reproduced by the output scanner would simulate the appearance of the displayed standard color patches after the adjustment of the display system.

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.