GB307545A - Means for controlling the intensity of a beam of light in accordance with electrical oscillations, for use, for example, in recording sound - Google Patents

Abstract

307,545. Whitaker, A., Manifold, M. B., and Gramophone Co., Ltd. Dec. 10, 1927. Light-valves.-In the known method of controlling the intensity of a beam of polarized light in accordance with electrical variations, corresponding to acoustic frequencies, which produce a variable magnetic field through which the beam is passed, as for example in recording sound, electrical correcting means comprising resistance are included in the circuit between the coil and the source of the variations to increase the response at the higher frequencies. Fig. 1 shows as correcting means a condenser C with parallel resistance R1 in the circuit from the source of variations to the coil which embraces an insulating tube T with end windows and containing nitrobenzene, the beam being directed through a polarizing prism N, the tube T, and an analysing prism N2 to a slit D in front of a record strip B. In another arrangement a negative resistance analogous to a Boucherot network and also a positive resistance may be employed in series with the source of variations the coil being connected across either of the resistances. In another arrangement, the source of variations A, Fig. 3, is connected through a negative resistance Q with a thermionic valve V and a resistance R3 and an impedance, which may comprise a resistance R2 and inductance L2 in series, is connected across the input, the output E, F being connected to the coil which influences the beam.