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: 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 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: 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 decoding a digital codeword of a codeword system comprising digital codewords of varying length in which no short codeword forms the prefix of a longer codeword in the same system comprises detecting with means (26) whether the codeword has a predetermined prefix, the predetermined prefix being shorter than any codeword containing it. Further means (26) are provided for decoding only the suffix of the codeword or the entire codeword respectively according to whether or not the predetermined prefix is detected.

Abstract: A method and apparatus for modifying the phase characteristics of a coherent beam of radiation (7) are described. The apparatus comprises a laser (6) for generating a coherent beam of optical radiation (7). A support (1) for a record medium (1') sensitive to the radiation is provided, the beam of radiation (7) and the record medium (1') being relatively movable whereby the beam of radiation scans the record medium. First modulation means including an E/O modulator (8) and beam computer (9) is provided for modulating the beam (7) in accordance with image information. Second modulation means including an A/O modulator (10) or phase diffraction grating is responsive to a control function generated by a control function generator (11). The control function has a frequency which is repeatedly swept through a range of frequencies at a relatively fast rate to control the transmission characteristics of the grating.

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: 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.

Abstract: To produce a plurality of parallel light beams from a single input beam, the input beam is incident on a partially transmissive face of a triangular prism, the other two faces of which are silvered. The input beam strikes the partially-transmissive face at such a position and at such an angle of incidence that it gives rise to only two parallel emitted beams, part of the emitted light arising from internal reflections at both silvered faces. A number of such prisms may be arranged in series so that the n.sup.th prism receives 2.sup.n-1 beams and emits only 2.sup.n parallel output beams.The partially-transmissive face or faces may be coated to give rise to output beams of substantially equal intensity. In one form, each beam entering each prism has equal S- and P-polarization components.

Abstract: Angle measuring apparatus, particularly for measuring doctor blade angle, comprises an elongate support (1); a horizontal level detecting device (4) pivotally connected to an upper surface of the support (1); and means (5, 8) for determining the angle between the support (1) and the horizontal level detecting device (4). An under surface of the support (1) includes a pair of projecting feet (13, 14), the arrangement being such that when the apparatus is placed on a cylinder, the upper surface of the support (1) is substantially parallel with a chord of the cylinder.

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: Method and apparatus for generating a half-tone dot representation of an original image which has been previously generated as one or more color separations each comprising a plurality of cells (12), each cell being digitally encoded in accordance with the color density at that point is described. The apparatus comprises a record medium support (8); a plurality of scanning beam generators arranged side by side, the scanning beams (B1-6) and the record medium support (8) being relatively movable. First control means controls the scanning beams during relative movement between the scanning beams and the record medium support (8) in response to the digital information and half-tone dot information to generate a plurality of half-tone dots (14) at a first rate, each dot corresponding to one or more of the plurality of cells (12).

Abstract: A method and apparatus for coding signals representing a stream of digital data groups (for example run lengths) for transmission or storage, each group representing a numerical quantity, is described. The signals are supplied via input and modify registers (4,6) and an encode latch (11) to a set of encode PROMs (12). The PROMs (12) generate for each data group a code representing the group, the code comprising a terminator codeword and, where necessary, one or more make-up codewords. The codewords are based on one or more multiplicative modifiers. The codewords are fed in parallel to output registers (13,14) and then serially shifted out of the output registers for subsequent transmission, storage, or further processing.

Abstract: In a video retouching system having an image source (40), a refresh store (42) fed from the image source, and a monitor (46) supplied from the refresh store, an image modifier (44) is interposed between the refresh store and the monitor and is controlled by a modifying store having a multi-bit location for each picture element. The stored multi-bit values may be used, for example to modify the display to obtain a vignetting effect, or to lighten or darken picture elements or modify chrominance. Preferably a mask store (48) having one bit per pixel defines those pixels which may be modified and those which must not be modified. In one form, the store with a multi-bit location for each picture element controls the merging of two images.

Abstract: A method and apparatus for detecting digital codewords or predetermined portions of digital codewords in a stream of codewords is described. The apparatus comprises a shift register (21) having a length at least one bit greater than the length of the longest codeword or predetermined codeword portion to be detected; and means including an inverter (24) for loading the shift register (21) with the logical complement of the leading bit of the stream of codewords. A clock (25) is provided to cause data in the data stream to be serially shifted into the shift register (21). The contents of the shift register after each shift are then used to address one or more PROMs (26) to determine whether the data in the shift register (21) upstream of the first change between data in the shift register of one type and data in the shift register of the complementary type comprises a codeword or a predetermined codeword portion.

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).

Abstract: This concerns retouching a set of n input image signals (1), one for each of the image printing colors, by converting these signals into a set of signals in a format (R, G, B) suitable for displaying the image on a monitor (3) to be viewed by an operator controlling the retouching. The converter (21) simulates the effect of the characteristics of the printing inks. In the present invention, for a rapid monitor response during retouching, the operator first generates, outside the main signal path from the image source to the monitor, a record (A) of n one-dimensional modifying functions corresponding respectively to the n printing colors. These printing-color modifying functions are converted into monitor-format modifying functions for storing in respective one-dimensional stores (B) in the said main signal path, where they modify the monitor-format image signals and therewith the displayed image.