GB456998A - Improvements in or relating to photographic sound recorders - Google Patents

Abstract

456,998. Optical sound - recording apparatus. RADIO CORPORATION OF AMERICA, 30, Rockefeller Plaza, New York, U.S.A. Sept. 16, 1935, No. 25694. Convention date, Sept. 27, 1934. [Class 40 (ii)] Relates to optical sound-recording apparatus by means of which either a variable-width or a variable-density record may be produced as desired. According to the invention, the apparatus comprises a light source 10, an aperture 12<1> arranged to be imaged upon a slit 17<1>, and a galvanometer mirror 13 for shifting the image transversely of the slit, the aperture 12<1> comprising a portion of uniform width and varying illumination (the rectangular portion shown in Fig. 3), and a contiguous portion of varying width and uniform illumination (the triangular portion, Fig. 3). For variable width recording, the mirror 13, which vibrates about an axis in the plane of the paper, Fig. 1, is so adjusted that the triangular part of the aperture 12<1> is imaged upon the slit 171, as at A, Fig. 3. The modulated light passing through the slit is focused by a lens 16 upon the film 18, thus producing a variable width track. When a variable-density record is required, the adjustment of the mirror 13 is changed so that the aperture 12<1> is imaged upon the slit 17<1> at the position indicated at B, Fig. 3. A stop 19, inserted in the position shown in Fig. 1, produces a uniform gradation of intensity of light illuminating the rectangular portion of the aperture, this portion being operative when the adjustment for variable-density recording has been made. Visual means for monitoring during recording may be provided as described in Specification 301,391, [Class 40 (ii)], and may be used for monitoring both kinds of recording. Means for ground noise reduction may also be applied as described in Specification 361,907. Specifications 401,192 and 420,265 also are referred to.