A High-Quality Optical Sound Recording System Using a Scanned Laser Beam

Abstract

A unique 16mm variable-area sound recording system using a scanned laser beam has been developed by Yokohama Cinema Labs, Inc. under the technical guidance of NHK Technical Research Labs, of the Japan Broadcasting Corporation. This system (U.S. patent approved) has no mechanically moving parts, and the limits of the exposed area depend only on the sound input signal. Its purpose is to extend the frequency bandwidth of the sound record. The frequency bandwidth of the reproduced signal is limited by the characteristics of the film and by the theoretical limits imposed by the reproducing aperture. By virtue of the high intensity of the laser beam, a low-speed photographic film having high resolution can be used as a recording medium. This makes possible the direct recording on color print film, which would be impossible with a conventional recorder. Performance data for Eastman color print film type 7381 processed with normal soundtrack development were as follows: frequency response was −3 dB at 10 kHz with a reproducer aperture of 12 μm; distortion was 2.2% at 400 Hz, with 80% modulation.