GB326498A - Improvements in or relating to light-sensitive devices and the utilisation of light-energy to control other forms of energy - Google Patents

Abstract

326,498. Robinson, J. Dec. 1, 1928. Telegraphic transmitters. - A modulated light-b e a m causes variations of electric energy by incidence on a piezo-electric crystal. The invention is applicable to telegraphy and to reproduction from sound films. In the arrangement shown in Fig. 1 the light from a neon lamp 10 is subjected to pulsating voltage from the source 11 and consequently exerts a fluctuating mechanical pressure on the surface 16 of the piezo-electric crystal 14 which resonates and so energizes a tuned circuit 13. The surface 16 may be black, reflecting, or photo-electric. In modifications the light may fall upon a fixed photoelectric surface, the electrons from which impinge upon a metallic surface on the face of the crystal (Fig. 2, not shown). Part of the energy from the resonant system 13 may be fed back to the lamp 10 (Fig. 3, not shown, and Fig. 5) or to a Kerr cell placed in the path of the fluctuating light beam (Fig. 4, not shown). The length of the light-path may be varied by adjustment of two mirrors 27, 28, and in this way the relative phases of the input and output oscillations of the system may be controlled. An object such as a sound film record may be interposed in the path of the light and modify the intensity of the latter by reflection or transmission.