Patent GB-384463-A (GB)
Title: Improvements in and relating to television apparatus
IPC: H04N3/04
Filed: 1932-01-18
Abstract: 384,463. Television. KOEPPE, L., 49, H³hlweg, Halle, Saale, Germany. Jan. 18, 1932, No. 1509. [Classes 39 (i) and 40 (iii).] Transmitters ; scanning. In television apparatus of the kind in which the area of the image to be transmitted is divided into a number of field elements or zones which are scanned simultaneously and transmitted separately, the scanning movement is effected in a direction transverse to the boundaries between the individual zones. In the arrangement shown in Fig. 1 an image of the object 1 is formed in the plane of a rotary scanning member 5 by a lens 2, a frame 3 being. mounted adjacent thereto, while the image field is divided into three zones I, II, III, Fig. 4, by means of prisms 7, 7<1> associated with lenses 8, 9 and an intervening gap associated with a lens 10. The scanning apertures are arranged in a number of groups of 12 apertures, Fig. 4, each group consisting of sets of apertures all, a<11>1 .. , b<1>1, b<11>1 .. , c<1>1, c<11>1 .. so disposed that at any time each of the zones is being traversed by a single aperture, while the scanning of all the zones by the group of apertures occurs in non-contiguous or zigzag lines. The image is completely scanned by 10 groups, i.e. by 120 apertures, and the latter may be arranged either on a spoked annulus as shown in Fig. 2, the image being scanned completely in one-half revolution, or on a travelling band or drum, Fig. 4, in which. case the scanning is completed in one revolution. The light reflected by the prisms 7, 7<1> and passed by the intervening gap falls on three photo-electric cells 11, 12, 13, and the resultant signals, after amplification at 14, 15, 16, are transmitted on different wavelengths from a common aerial 17. In the transmission of films the frame 3 is dispensed with and the film, which is moved intermittently and scanned picture by picture, occupies the position of the frame. Photo-electric cells. In order to render the cells 11, 12, 13 sensitive to all the component colours of white light, the cathodes are composed of two or more materials of different sensitivities to different wave-lengths, the materials being arranged either as annuli or, preferably, as sectors, e.g. as shown in Fig. 6, in which the cathode comprises five materials with a free centre portion. Receivers. The signals received on the three wave-lengths, after amplification at 36, 37, 38, Fig. 7, are applied to the plates 33, 34, 35 of three Kerr's cells associated respectively with lamps 18, 19, 20, lenses 21, 22, 23, prisms 24, 25 and intervening gap, and with polarizing and analysing Nicols 27, 28, 29, 271, 281, 29<1>, and further lenses 39, 40, 41. The image field is scanned by a disc or band 42 of similar construction to the device used at the transmitter, and the image may be viewed directly by the observer, or projected by a lens 43 upon a screen positioned at 44, 44<1>, or 46 according to requirements. A grating 47 consisting of a thin metal sheet or photographic film, out of which a number of openings are cut, and placed adjacent to the scanning member 42, may be employed to reduce striation, but it also reduces the general brightness of the image. By replacing the lens 43 by a camera or film-camera a record of a stationary or moving picture may be obtained. Synchronizing. At the completion of each image-scanning operation, i.e. twice during the revolution of the disc 5, or once during the traversal of the band 5a, Fig. 4, a light 50, Fig. 1, co-operates with additional apertures 49 in the disc or band and with an aperture in the frame 3 to transmit, via cell 12 and amplifier 15, a synchronizing impulse. At the receiver the speed of the motor is adjusted. until the stripe produced by such impulses is continuously visible at the edge of the image. Reproduction in colour. For transmission and reception in colour, filters 4, 48 are arranged respectively between the lens 2 and scanning member 5, and between the lens 43 and scanning member 42. Each filter comprises an annulus composed, as shown in Fig. 9, of elements successively of a reddish-orange, yellowish-green, and blueish-violet colour, and rotated, when the member 5 is a disc, at <10>/3 times the speed of the disc, or when the member 5 is a band, at the speed thereof, with the result that the zones I, II, III, Fig. 4, are scanned in successively changing colours.