GB124805A - Improvements in Sound Transmission by Light Rays Actuating Photoelectric Cells. - Google Patents

Abstract

124,805. Bragg, W. H., and Rankine, A. O. April 11, 1916. Selenium cell and like optically-sensitive relays; telephones. - In a non- circuit-closing relay or a microphone employing a light-sensitive cell, the light from a source is divided into a number of beams by means of a grating, and the various beams focussed upon a mirror adapted to be oscillated directly or indirectly by speech waves or other signalling impulses. The beams after reflection pass through a second grating, and the varying amounts of light passing through this grating are focussed upon a sensitive cell placed in the circuit of the receiver. In a modification a single grating provided with reflecting opaque portions is employed, and the light reflected from the grating is arranged to fall again on the grating after reflection from the oscillating mirror. When the sun is employed as the source of light, a heliostat, operated by a clock, is used to direct the light to the first grating, and a heat absorbing dell is placed in the path of the light before it reaches the mirror. In the arrangement shown in Fig. 5, the light from a source S, after passing through a lens L', and a grating G<1> is reflected by an oscillating mirror M to a second grating G<2> which is near to or upon the surface of a mirror C. The beams, after reflection from the mirror C, are rendered parallel and are focussed by a mirror C<3>, Fig. 4, upon a cell S<1> in the circuit of the receivers T. in a modification the beams are rendered parallel, after passing through the second grating, by means of a lens. In a further modification, the lens L' Fig. 5, is replaced by a concave mirror having the grating G<1> near or upon its surface. In the modification shown in Fig. 8, a single grating, provided with reflecting opaque strips, is employed in combination with a plano-convex lens L. The parallel beams P<1>, P<1>, which pass directly through the lens and grating without reflection, are invariable in intensity, but the beams P, P, which pass through the grating after reflection therefrom and from the mirror M, are variable, and separate from the beams P<1>, P<1> a distance. In the modification shown in Fig. 9, a plane mirror M is employed, with a lens X between it and the first grid G<1>. The mirror M may be operated directly by speech waves by connecting it to the diaphragm d, Fig. 2, of a sound receiver, or indirectly by mounting it in a diaphragm or reed r, Fig. 3, operated by an electro-magnet, when the apparatus operates as a relay. When the arrangement is used as a microphone, the lightsensitive cell is placed at the transmitting-station and is connected in a battery and receiver circuit. Specification 3885/80 is referred to.