GB822107A - Apparatus for the conversion of electromagnetic to mechanical energy - Google Patents

Abstract

822,107. Photo-electric systems. DU PONT DE NEMOURS & CO., E.I. July 23, 1957 [July 26, 1956], No. 23297/57. Class 40 (3). [Also in Group XXXVI] A device for producing mechanical movement in accordance with incident electromagnetic radiation consists of a condenser with one movable plate and one plate transparent to the said radiation, a steady potential being applied between the plates and the dielectric material between the plates being such that its permittivity varies with variation of the incident radiation. The Fig. 1 embodiment shows a fixed conductive layer 3 of tin oxide mounted on a transparent rigid place 2, and adjacent to layer 4 which contains photo-dielectric particles dispersed in a light-transparent dielectric medium. A partially movable resilient plate 5 co-operates with the layer 3 to form a condenser across which a potential is applied from a suitable D.C. source 9. Changes in the electrostatic forces between plates 3 and 5 due to changes of the dielectric constant of layer 4 cause the plate 5 to move. In Fig. 2 (not shown), the movable plate 5 is mounted on a flexible diaphragm and the voltage applied across the plates is from a generator and may be A.C. If a D.C. potential is applied and if the incident light has an audio-frequency modulation an audible sound is produced. If the frequency of the said A.C. voltage is in the audio range the output of the device will be intensity modulated sound. The photo-electric substances may be, for example, zinc sulphide or cadmium sulphide and the dielectric medium (and also the transparent plate 2) may be any of such substances as beeswax polystyrene, polymethyl methacrylate, ethylcellulose cellulose nitrate, or plasticised polyvinyl chloride.