GB306542A - Improvements in or relating to electro-optical image producing systems - Google Patents

Abstract

306,542. Electrical Research Products, Inc., (Assignees of Manderfeld, E. C.). Feb. 24, 1928, [Convention date]. Television; synchronous movements.-In a television apparatus the current resulting from scanning the object is used to control the production of the image and to maintain the scanning apparatus in synchronism. The dimension, in the direction of the scanning lines, of the opening 11 in a screen 12, which defines the field of view, is made less than the distance between the centres of adjacent apertures 16 in a scanning-disc 14 (Fig. 2A, not shown), so that the light-beam is periodically reduced to a. low value at a rate determined bv the number of apertures multiplied by the speed of rotation of the disc. Alternatively this frequency component is introduced into the image current by making the width of the opening in the screen such that the last element of one line and the first element of the succeeding line are scanned simultaneously (Fig. 2B, not shown). At a receiver B the synchronizing component is selected from the image currents by a filter 33, 34 and impressed on the grid circuit of a thermionic valve 38. A generator 41, which is driven by the driving-motor 40 of a scanning-disc 26 and produces a current of the same frequency as the synchronizing-current, supplies current to the plate circuit of the valve. The amplitude of the plate current varies in accordance with the phasedifference between the locally generated current and the synchronizing current, and an electromotive force, which varies in accordance with the variations of the plate current, is impressed on a control winding 47 of the motor to maintain the scanning-discs 26, 14 in synchronism. According to modifications, a harmonic of the frequency determined by the number of apertures multiplied by the speed of rotation is used; the synchronizing-frequency energizes a motor at the receiver; or a mechanical damping-device 49, 50, 51, described in Specification 295,325, [Class 80 (ii), Gearing, Variable-speed &c.], between the motor and the scanning-disc is replaced by an electric damping-apparatus. Specifications 288,238, 292,597, and 317,537 also are referred to.