Patent GB-666994-A (GB)
Title: Improvements relating to colour television systems
IPC: H04N9/11
Filed: 1948-12-13
Abstract: 666,994. Television. ANGEL, Y. Dec. 13, 1948 [Dec. 27, 1947], No. 32225/48. Class 40 (iii). In a colour television system a threefold image of the object to be televised constituted by three colour-selection monochromatic images placed side-by-side, each being optically anamorphosed such that the aspect ratio of the threefold image is that of a standard television image is scanned by electron beam means to generate electrical signals for transmission. Figs. 1 to 3 show one arrangement in which a threefold image of normal aspect ratio comprising the optically anamorphosed colour-selection images B, G, R is set-up on a surface which is scanned by means (not shown) employing conventional line and frame scanning frequencies. With this arrangement the band-width required for transmission of the signals generated is equal to that necessary with a conventional black-white transmission system and a further economy of band-width may be obtained if the width of each primary image is made proportional to the resolving power of the eye for the corresponding colour of each image (Fig. 4). Signals transmitted by the present system may be received and reproduced either sequentially or simultaneously. Sequential reproduction may be obtained using a single picture reproducing tube, employing a line scanning frequency which is three times the line scanning frequency employed at the transmitter, co-operating with a three-colour filter the colours of which change at line frequency. To obtain simultaneous reproduction a single picture reproducing tube, operating with the same line scanning frequency as the transmitter, reproduced three images side - by - side (equivalent to the side-byside images of the transmitter) which, after optical transmission through appropriate colour filters, are superimposed by means of a suitable optical system which also reintroduces the correct aspect ratio. Instead of using colour filters a picture reproducing tube the screen of which is divided into three adjacent areas each of which is arranged to fluoresce in one of the desired colours may be employed. In an alternative arrangement for simultaneous reproduction in which three picture reproducing tubes are employed the control electrode of each and the deflection means of each are connected in parallel and the line deflection saw-tooth wave is given an amplitude equal to three times that required for a full line traverse on one tube so that each tube reproduces only one component image. These images are then superimposed by optical means including appropriate colour filters to give a complete coloured picture (Figs. 5 and 6) The present invention may also be employed to generate television signals by scanning kinematograph film either by employing three separate colour-selection films or by employing a film of special type such as shown in Fig. 7, in which each frame is divided into three elementary frames each corresponding to a different primary colour (B., G., R.) of the image, the aspect ratio of each of which is anamorphosed such that the complete frame has the standard aspect ratio. The Specification as open to inspection under Sect. 91 describes an arrangement employing a " flying spot " scanner for scanning a conventional three-colour film, the light passing through the film via a colour-beam-splitter to three photo-electric cells, Fig. 7 (Cancelled, not shown), or, via a rotating colour filter to a single photo-electric cell, Fig. 8 (Cancelled, not shown). This subject-matter does not appear in the Specification as accepted.