GB666332A - Improvements relating to systems for the recording of intelligence on photographic film and the reproduction thereof - Google Patents

Abstract

666,332. Optical sound-recording. FERRANTI, Ltd., and TAYLOR, M. K. March 24, 1950. [Jan. 29, 1949] No. 2517/49. Class 40 (ii). [Also in Groups XX and XXXIX] A method of recording from a plurality of sources for subsequent reproduction such as' for producing a stereophonic sound effect in conjunction with a kinematograph, comprises modulating beams of different spectral colours by the different sources and recording the light variations along a track on colour-sensitive photographic material. In the embodiment described, light from sources 1, 2, 3 is modulated by devices 12 controlled by microphones 7, 8, 9. Filters 4, 5, 6 of different colours are placed prior to or following the modulating devices 12, so that modulated light beams of different colours are focussed, by means of an objective lens 17, on to a moving colour film 20. A prism or diffraction grating 16 may be employed for the purpose of projecting the separate beams simultaneously on the same part of the length of the film, in which case reproduction of the separate original signals is effected by dividing the beam from a light source 30 into its component colours by means of a prism or diffraction grating 34, and using the separate beams so . obtained to energize photo-electric cells 36 which are coupled to amplifiers 37 and loud-speakers 41, 42, 43. Variable width or variable density recording may be employed or a combination of both.