GB526875A - Improvements in light modulating devices - Google Patents

Abstract

526,875. Light modulating. I.M.K. SYNDICATE, Ltd., NAGY, P., and GODDARD, M. J. Jan. 4, 1939, Nos. 2465 and 2587. [Classes 39 (i) and 40 (iii)] A light modulating device intended especially for television receivers comprises a transparent medium capable of bearing mechanical oscillations therein, means for producing a plurality of independent oscillations in said medium, and an electron beam for successively exciting said oscillation producing means. As shown in Fig. 1, the transparent medium is constituted by a fluid in a container 17 in the base of which a line of piezo-electric crystals 18a is arranged having a common metal layer 19 on one side against the fluid medium and separate metal strips 20 on the other side connected to separate metal strips 21 in a cathoderay tube 10 provided with means for oscillating the electron beam along the line of strips 21 and for modulating the intensity of the beam or the deflection of the beam laterally of the line of strips 21. The electron beam charges the strips 21 directly or preferably by secondary emission, in which case a grid system of wires 22 at anode potential is provided along and adjacent the line of strips 21. The tube is arranged to provide a flat beam and to control this beam in a generally well-known manner, being provided for these purposes with a cathode 11, a control grid 12, an anode 13, a lining 14 connected to the anode, a focusing coil 15, and deflecting plates 16. To improve the efficiency of the light modulating device, the transparent medium is divided by horizontal surfaces 24 designed to produce reflection and resonance, and the electron beam may be made to apply a succession of impulses to the piezo-crystals at a frequency corresponding to the resonance frequency of the piezo-electric crystal. Various other details of the light modulating cell are also described. In use in a television receiver, the electron beam is modulated according to the received image signals, and is oscillated at line frequency ; the separate oscillations produced by the separate piezo-electric crystals correspond to the intensities of the image points of a line and are made to persist for the duration of scanning of a line. This image line is reproduced on a screen VS, Fig. 3, by light from a source X modulated by passage through the transparent material in the container 17. Successive lines of the image signals produce successive modulations of the line of light ; and the modulated lines of light are successively displaced by a mechanically rotated mirror drum SS to reproduce the image frame on the screen VS.