GB692321A - Improvements in or relating to stereoscopic picture projection apparatus - Google Patents

Abstract

692,321. Stereoscopic picture projectors. GRUBER, W. B. March 1, 1951 [March 2, 1950], No. 4966/51. Class 97 (i). Twin objectives are moved for focusing by a single control, their axes being maintained parallel during the movement and the separa. tion ot the lens axes being varied, to adjust the convergence of the projection axes, so that substantially identical superposition of the projected images is obtained independently of the screen distance. Fig. 2 shows one lens mount supporting arrangement in horizontal section taken at different levels in the regions of the two lenses. Each mount is carried on a lug 12 upstanding from a base 11 with downwardly projecting pins 46, engaging a slot 45 in the base 10, and a downwardly projecting stem 15 in a clearance hole 17 in the base. The slots 45 beneath the two objectives are oppositely inclined and the lens mounts are guided, by the pins 46, during axial focusing movements to produce the accompanying lateral movements. The slots may be straight but theoretically should have a slight curvature, the nature of which is derived in the Specification. The adjusting mechanism is shown in Fig. 3. Levers 22 are held by a connecting spring 41 with slots 23 engaged with pins 24, secured to the plate 10, and ends 38 abutting the end of the screw 37 carrying an operating knob 35 and being engaged in a screw-threaded lug 29. Other slots 21 are engaged with reduced end portions 20 of the stems 15 projecting from the bases 11. To check the convergence of the projection axes a test slide is provided having reference lines, or other marks, with a separation equal to that of the lens axes when focused as for a screen at infinity. When the projected images are superposed the systems are correctly focused. A similar arrangement of two objectives, with a focusing system as described and using a test slide for checking the focus, may be used even when one objective is to be used for non-stereoscopic projection. The Specification discusses which parts of projected stereoscopic pictures should be superposed for minimum eye strain when viewing.