GB570878A - Improvements in or relating to the projection of stereoscopic cinematograph images - Google Patents

Abstract

570,878. stereoscopic kinematography. WRIGHT, E. H. Oct. 16, 1943, No. 15220. Addition to 555,670. [Class 97 (i)] A system for projecting right and left eye stereoscopic images arranged alternately on a film comprises stationary means situated in the light beam for producing plane-polarized light and means for converting the plane-polarized light during picture shifts alternately into clockwise and anti-clockwise circularly polarized light, so that the right and left eye images are projected respectively by light of clockwise and anti-clockwise polarization, or vice versa. As shown, the light beam passing the condenser 2 is plane-polarized by passage through a plurality of Nicol prisms 4 with their polarizing axes parallel. It then passes through the film 5 and a band 7 of half-wave retardation material which is formed with sprocket holes and moved with the film, and is such that it rotates the plane of polarization through a right angle during the projection of alternate frames. Thus, it may consist of a flexible carrier with windows of mica or other half-wave retardation material with their axes alternately at 45 degrees,. and parallel, to the plane of polarization. Alternatively, it may consist of a continuous strip of half-wave retardation material with the portions corresponding to alternate film frames cut away or rendered inactive. The light beam then passes through the objective 8 and a quarter-wave retardation plate 31 which causes the beam to be circularly polarized in opposite directions during the projection of successive frames. An angularly adjustable half-wave retardation plate 11 may be provided to phase the polarized light correctly with the viewing analyzers. Quarter-wave retardation devices may be substituted in the endless band 7 for the active and inactive half-wave portions, the stationary quarter-wave plate 11 being dispensed with. Other systems are described using rotating or oscillating half- or quarterwave plates in place of the flexible band 7. Specifications 486,111 and 519,488 are referred to.