GB548158A - Improvements in or relating to stereoscopic optical systems - Google Patents

Abstract

548,158. Stereoscopic systems. MAINARDI, P., and MAINARDI, M. N. Oct. 16, 1941, No. 13348. Convention date, May 22. [Classes 97 (i)] and 98 (ii)] A stereoscopic optical system comprises a single lens in front of two images, an inner pair of reflectors in front of the lens, and an outer pair of reflectors, the reflectors being arranged so that rays between the inner and outer ones cross the optical axis of the lens; the reflectors may be embodied in a camera or projector, or in an attachment therefor, and may be arranged to turn the images through right angles in opposite directions about the axes of the beams. As shown in Fig. 4, outer reflectors 45 reflect rays from a scene through the nearer faces of a triangular prism 20 to be internally reflected by the opposite faces so as to pass through a lens 15 on to the image plane 17. The whole lens receives rays from each reflecting face of the prism, and the images 43 become oriented so as to be head to head. The image fields should be restricted by a mask 50 so that the upper rays 48 are horizontal, overlap of the film images and keystone distortion being thus avoided ; the axis 41 of the view finder system 39, 40 should be parallel to the central rays 32 of the image beams. Additional reflectors may be embodied in the system to produce a vertical film plane, and three arrangements of such reflectors are described. Fig. 11 shows an attachment for a projector 78 wherein the additional reflector 72 is, optically, between the reflectors 45 and colour filters 81 at the front window of the casing of the attachment, the filters enabling the projected images to be selectively perceived by the eyes of the spectators in known manner; the mask 76 is hingedly carried above the window. Fig. 6 shows a modification in which the prism 20 is replaced by mirrors 52, 53 having upper edges intersected by the lens axis. The prism 20, Fig. 7, may be arranged to reflect rays from both film images 59 vertically, the reflected rays being received by mirrors 61, 62 and directed to the screen 63. The images visible on the screen may be restricted to one pair by limiting the reflecting area of the screen by a mask &c., and complementary colour or polarizing filters 67, 68 may be provided in the image beams. The prism 20 has, preferably, an equilateral triangular section so that colour fringing of the beams may be a minimum ; if the section is not equilateral, it may be isosceles with a larger or smaller vertical angle, and glass wedges 84, Fig. 12, may be provided on the reflecting surfaces to reduce colour fringing, the apices of the prisms 84 being towards or away from the apex of the prism 20.