Patent GB-828501-A (GB)
Title: Apparatus for producing colour separation records directly from an original subject
IPC: H04N1/48
Filed: 1957-11-22
Abstract: 828,501. Copying-by-scanning. MIEHLE-GOSS DEXTER Inc. Nov. 22, 1957 [Nov. 23, 1956], No. 36488/57. Class 40 (3). In an arrangement for producing a copy of a coloured original (pictures &c.) by scanning the latter to produce sets of electrical signals each set being representative of elemental areas thereof in a different one of a plurality of colour aspects and each set of signals being then supplied to a picture reproducing device from which a like plurality of (different) colour separation records are derived and employed to reproduce the required copy by known (printing &c.) techniques, each set of signals, initially, consists of signals representative of four or more different colour aspects which are combined in proportions determined by the particular colour separation being produced and the characteristics of the particular ink, paper and pigments to be used in making the final copy to produce the sets of signals supplied to the picture reproducing. Fig. 1 shows one embodiment in which the original 10 is scanned, point-by-point, by producing suitable relative movement between it and a light source 11 the reflected light being directed via a mirror 14 on to a dispersing prism 15 which produces, for each point on the original, a plurality of different colour bands. Selected ones (e.g. eight) of the latter are directed on to a like number of photo-electric cells 16 the output signals from which are then individually amplified in 18 by factors which may be either positive or negative determined by the parameters outlined above. The output signals of 18 are then combined in circuit 19 from which they are fed to a further adding circuit 20 if required (i.e. if the signals from 19 have opposite algebraic signs) and thence to a glow lamp 22 to produce a light beam modulated in accordance with the input signals. This light beam is then employed to scan a film 23, synchronously with the scanning of the original 10, to produce the corrected colour separation record. This process is repeated for each colour separation record required, the modifying circuit amplifier 18 being adjusted in accordance with the requirements set out above. This adjustment is fully explained in U.S. Specification 2,567,240. Instead of the analysing and recording arrangement shown, a flying-spot scanner tube and a cathode-ray picture tube, respectively, may be employed. Fig. 2 shows a second embodiment in which a television camera tube 31 and a rotating multi-colour (eight section) filter 29 are employed to scan the original 27. Each filter is positioned in the light path to the tube for the duration of one frame scan and the signals produced during the scans corresponding to all the filters are recorded on individual tracks on a magnetic tape in unit 32. When this has been done the tape is then " played-back " and the (eight) recorded signals simultaneously derived by means of separate " play-back " heads the signals produced by which are modified in the circuits of 33, 34 and 35 (as described in connection with the circuits 18, 19 and 20 in the embodiment of Fig. 1) and supplied to a further recording head which records them on another separate track. This is done for each set of colour separation signals (e.g. those concerned with yellow, cyan and magenta) and then by a further play-back the corrected signals from each track are supplied sequentially to a picture tube 38 the picture produced by which is recorded on a film 40 to form the desired corrected colour separation record. Alternatively, the corrected signals from the amplifier 35 may be fed directly to the picture tube 38 without being stored on the tape. Instead of employing the camera tube 31, an image of the original may be directed on to a mosaic of photo-electric cells via a colour filter similar to 29 and scanning effected by a commutator arrangement which connects the cells in sequence to the magnetic storage unit (Fig. 3, not shown). In a further arrangement for effecting analysis of the original 10 (Fig. 4) the latter is imaged via a series of dichroic elements 54, and a series of mirrors 55 on to separate linear arrays of photoelectric cells 56 equal in number to the number of colour aspects of the image required for the production of each set of corrected colour separation signals. Each cell in each array 56 is connected to individual contacts of separate rotary switches 57 which thus effect a line scanning action simultaneously in each of the colours appropriate to the various dichroics 54 and by arranging a suitable relative movement between the complete optical assembly and the subject 10 the whole of the latter is scanned. In another scanning arrangement (Fig. 5, not shown) arrays of the photo-electric cells similar to 56 are arranged radially in a circle each array being associated with appropriate optical devices (mirrors, lenses and a colour filter) such that an image of the original which is positioned on the centre of the circle is directed on to each array via respective colour filters. As in the arrangement of Fig. 4 scanning is effected by a series of rotary switches and relative movement between the optical assembly and the original. In a yet further arrangement the scanning of the original is effected by relative movement between the latter and a flying-spot cathoderay tube arranged to produce a single trace, the light from the original, as a result of such scanning, being directed via the required number of colour filters on to a like number of elongated photo-electric cells the signals from which are fed directly to the modification circuits. Each of the arrangements described may be modified for use with transparent instead of opaque originals and the recording of the corrected colour separations may be effected by means other than those described, e.g. by etching or burning away a plastic printing plate or by the use of other types of light modulating devices.