GB538319A - Improved method of optically copying sound tracks - Google Patents

Abstract

538,319. Photographic sound records. PHILIPS LAMPS. Ltd. Feb. 10, 1940, No. 2614. Convention date, Feb. 13, 1939. [Class 98 (ii)] In the photographic reproduction, by optical projection, of sound record tracks which are mechanically cut in a carrier comprising a recording layer and an opaque covering layer, the effect of lens action in the recording layer is avoided by illuminating the track with transmitted diffused light, and focusing the projection system on the covering layer, preferably on the surface thereof remote from the recording layer. An objective with little depth of field is preferably used, e.g. a microscope objective. As shown, the original record 13, Fig. 1, is illuminated through the support 12 by a lamp 10 with a diffusing screen 11, and an objective 16, focused on the opaque covering layer 15, projects an image on to the light-sensitive copy film 17. Stray light may be intercepted by a diaphragm 18. In a modification, the record is illuminated obliquely from the front by a lamp and condenser system, and a mirror is placed behind the support 12 to reflect the light back to the objective. In this case, diffusion of the light is effected by a diffusing layer on the rear of the support 12 or by frosting the surface of the mirror.