GB555670A - Improvements in and relating to the projection of sterescopic kinematograph images - Google Patents

Abstract

555,670. Stereoscopic kinematography. WRIGHT, E. H. Nov. 26, 1941, Nos. 15216/41, 3550/42 and 10951/42. [Class 97 (i)] Stereoscopic pairs of images arranged in alternation on a single-rank film are projected with the aid of a stationary polarizer in the light beam and of means for rotating the plane of polarization during picture shifts ; the plane rotator may be an endless strip, a disc, or a cylinder, &c., comprising half-wave plates which are effective during the projection of alternate images. Fig 1 shows a projection system comprising aggregated nicol prisms 4 forming the polarizer, and an endless band 7 passing through the gate 6, with the film 5, and forming the plane rotator. The band 7 may comprise an endless strip of mica forming a half-wave plate, portions corresponding to alternate picture frames being cut away or rendered optically inactive, and perforations corresponding to film perforations being provided in the margins ; alternatively it may be a flexible carrier with mica windows covering film-frame apertures. A halfwave plate 11, insertable into or rotatable in, the projection beam, may be provided to adjust the planes of polarization in accordance with the planes of the spectators' spectacles, or the polarizer 4 may be adjustable for this purpose. A modification is described in which the nicol prisms are replaced by sheet material comprising oriented crystals or molecules and rendered dichroic, and a half-wave plate is permanently located in the projection beam and rotated one eighth of a revolution during each picture shift through gearing by a flexible shaft connected to the intermittent sprocket. Further constructions of plane rotator comprising respectively an apertured disc, apertured drum, discs alternatively moved into the beam by solenoids, and halfwave plates rotatable round a fixed polarizer, are described.