Patent GB-347251-A (GB)
Title: Method of and apparatus for universal splitting up and assembling of pictures for electrical picture transmission, television and similar purposes
IPC: H04N3/08
Filed: 1930-01-21
Abstract: 347,251. Television; copying telegraphy. FRIES, G., 28, Luxemburgerstrasse, Cologne, and SOMMER, P., 3, Siegbr³cke, Siegen, Westphalia, both in Germany. Jan. 21, 1930, No. 2135. Convention date, Jan. 21, 1929. [Class 40 (iii).] A picture is scanned in the primary direction of scanning x, Fig. 2, under the action of a primary scanning control and a secondary scanning control effects scanning in the direction y, the two controlsbeing operated and adjusted independently of each other and the size of the picture spots being adjustable so that pictures built up with different numbers of picture spots may be received, or transmitted. The secondary scanning control consists of a disc a, Fig. 2, having mirrors sp mounted to swing about axes tangential to the disc. Each mirror in passing through the beam of light modulated at p describes a line y upon the screen. The primary control consists of a cam b having a cam surface q upon which spherical parts st of the mirrors sp beat. The cam b effects the spacing of the lines y in the direction x and in one rotation completely scans the screen in the direction x. The mirrors are also supported in radial slots in a wheel e to prevent lateral movement. The mirror wheel a is fixed to a shaft m driven by a motor c whose speed is adjusted by a resistance n and the cam b is fixed to an independent shaft m<1> and is driven by the friction between the cam way q and the moving spherical parts st under pressure from springs z, a further drive if necessary being effected by an electromagnet l fixed to the shaft m. The cam b is controlled by a governor s and, in the case of television, rotates at a constant speed of not less than 10 revs. per sec. in order that at least 10 pictures may be produced each second. A glow lamp g rotates with the shaft m<1> and is lit once each revolution of the shaft m by a brush contacting with a conducting segment o of a disc f rotating with shaft m. If the mirror wheel a has 100 mirrors sp then when its speed is the same as that of cam b the picture is formed with 100 lines y or 10,000 picture spots and the lamp g illuminates a mark on an interchangeable disc i, Fig. 3a. Figs. 3b, c, d show other forms of the discs i corresponding to speeds (c) of the mirror wheel and picture spot numbers (given by the number of lines y squared). An adjustable diaphragm may be used to control the size of the picture spot so that the entire surface of the screen is illuminated. The number of mirrors sp is the minimum number of lines into which the picture may be explored or assembled. A scale o, Fig. 6, is provided at the side of the receiving screen so that if the picture is incorrectly framed the amount by which the disc i, Figs. 2 and 6, is to be adjusted may be known. The system is then again adjusted so that the glow lamp g illuminates the marks on the disc i thus virtually rotating the cam b through the necessary angle. In the application to copying telegraphy, the picture at the transmitter is optically scanned by a stationary beam of light and a rotating drum and at the receiver the speed of the cam b is adjusted to make one revolution during the complete scanning of the picture. The mirror wheel a is then adjusted to pass mirrors through the path of the recording beam equal in number to the lines into which the picture has been divided at the transmitter and the time taken to pass these mirrors through the path of the beam is made equal to the time of complete scanning of the picture. The size of the picture spots is suitably adjusted. The picture may be recorded photographically. Where it is desired to produce alternately directed lines y, Fig. 7, two mirror wheels a, a<1> are provided cooperating with two cam ways q, ql on the cam b the mirrors sp coming into operation and positioned alternately, Fig. 8. The wheels a, a<1> are connected by a differential gear r, or other means, so that they rotate in opposite directions. The gear r may be adjusted by an arm w to lock the two wheels a, a<1> together and so produce the type of scanning of Fig. 2. The relative positions of the mirrors may be adjusted by displacing the gear r. The driving motor c may be synchronized by the known means of tuning forks or through the medium of the picture spot frequency.