GB535600A - Improvements in or relating to the printing of sound record films - Google Patents

Abstract

535,600. Producing variable density from variable width sound records. KODAK, Ltd. May 8, 1940, No. 8275. Convention date, July 25, 1939. [Classes 97 (i) and 98 (i)] [Also in Group XXXVIII] Means for printing on a film a variable density sound track from a variable width track comprises means for illuminating the latter and an optical system consisting of lenses including cylindrical and spherical or slightly aspherical refracting surfaces which form on the film an astigmatic line image of each point on the variable width track, which image extends across the whole width of the variable density track but is punctual longitudinally of it, so that the density of the image is everywhere proportional to the width of the variable width track from which it is printed. As shown in Fig. 1, a 35 mm. film 1, bearing a variable-width sound track 2, and a 16 mm. film 6 on which the variable-density track is to be printed are driven by sprockets on a common shaft 4. The sound track 2 is illuminated by a lamp 5 and the variable-density image is produced by an optical system comprising collective lenses 8, 9, a cylindrical lens 10 adjacent the film 6, and totallyreflecting prisms 11, 12. Diaphragms 14, 15 define the horizontal and vertical aperture dimensions of the system. Fig. 4 shows a similar system in which the prisms are omitted. The collective lens 8 forms an image of the track on the film 1 in the second collective lens 9, this image being focused by the cylindrical lens 10 on the film 1 as an astigmatic image in which each point of the track on the film 1 is represented reproduced as a line extending over the width of the variable-density track. The film 6 is conjugate to a plane at or near the lens 8 with respect to the lens 9, and a diaphragm 14 in this plane defines the width of the track. Lenses 8 and 10 are approximately conjugate with respect to lens 9. The vertical aperture dimension of the system is defined by a diaphragm 15 and includes more than two cycles of the highest frequency recorded. The illuminating system comprises a collective lens 18 which forms an image of the elongated lamp filament in a second collective lens 19, by which the light is focused on to the film 1. Diaphragms 20, 21 define respectively the vertical and horizontal dimensions of the aperture of the illuminating system. In modifications, the projection system comprises a single collective lens and a cylindrical lens adjacent one or other of the films.