GB485637A - Photographic recording of sound - Google Patents

Abstract

485,637. Optical sound-recording apparatus. RADIO CORPORATION OF AMERICA. Aug. 15, 1936, No. 22539. Void. Convention date, Aug. 23, 1935. [Class 40 (ii)] Apparatus for producing photographic sound records incorporates means which compensate or neutralize the distortion arising from the non-linear parts of the H and D curves of the negative and positive prints. Such means may comprise a wedge of graded density which is mounted in the aperture 12, Fig. 1, of a screen 13. The wedge may be made photographically or by grinding and polishing a piece of dark glass to such a graded thickness as will give the desired effect. The recorder includes a lamp 10, lenses 11, 14, 16, 19, a vibrating mirror 15, and a screen 18 with a slit 17, the light from the mirror being reflected on to the film 20. In a modified arrangement, Fig. 4, a condenser 23 is mounted between the lamp 22 and screen 24, the latter having a number of rectangular apertures through which the light passes. A lens 14 close to the mirror 15 forms an image of the screen on a second screen 25, while the condenser 23 forms an image of the lamp filament on the mirror. Lenses 26 and 27 form an image of the filament on the film 20. The apertures on the screen 25 are suitably shaped to produce the required effect. In a further construction, the light wedge of Fig. 1 is replaced by an aperture member which produces a light beam which varies both in contour and density from one edge to the other.