Patent GB-649777-A (GB)
Title: Improvements in or relating to the photography, viewing and projection of pictures with stereoscopic effect
Inventor: DEWHURST HUBERT
IPC: G03B35/00
Filed: 1947-10-27
Abstract: 649,777. Stereoscopic apparatus. MINISTER OF SUPPLY. Oct. 27, 1947, No. 28619. [Classes 97 (i) and 98 (ii)] An optical system for photographing, projecting or viewing stereoscopic pairs arranged side uppermost on a carrier comprises a beam splitter giving two beams directed outwardly perpendicular to the axis of incidence, reflecting means directing each beam through 90 degrees in a plane perpendicular to the axis of incidence and further reflecting means directing the two beams forwardly parallel to the axis of incidence, the system as a whole being movable or parts thereof rotatable to vary the separation of the two erect images produced by the system. The pairs may be head to head, tail to tail, or head to tail. Fig. 1 shows a projection system with a pair of images arranged head to head on a carrier 1. Erect images are formed in superposition on the screen 6 by lens 2, beam splitting reflector 3 and reflectors 4a or 4b and 5. To effect correct registration either reflectors 4a or 4b or both are rotated about axes Xa ... Xa<SP>1</SP>, Xb .. , Xb<SP>1</SP> respectively, or both reflectors 4a, 4b are rotated about axis Y ... Y<SP>1</SP> and reflector 5 about axis 22<SP>1</SP> or the system of reflectors and lens is moved bodily parallel to the line of separation of the images on the carrier 1. For viewing the images directly the reflectors are fixed in a suitable housing in which eyepieces are provided, the necessary adjustment being effected by sliding the picture carrier, or by moving the mirror system relative to the picture carrier by a rack and pinion. To adjust the reflectors 4a, 4b simultaneously about the axes Xa, Xa<SP>1</SP> and Xb, Xb<SP>1</SP>, they are supported in carriers 12, 13 (Fig. 2), having inturned ends 19, 19a held by a spring 18 against a ball 20 on a stem 22. The stem may be moved vertically by a rotatable cam disc 28 to cause the mirrors to pivot simultaneously. The mirrors may be replaced by a suitable prism system which may comprise separate parts rotatable respectively about the axes Y, Y<SP>1</SP> and Z, Z<SP>1</SP>. Such a system may be applied to a camera 50, Fig. 5, having a focusing lens mount 51 and a bracket 52 to which are pivoted at 56 two prism-carrying cradles 54, 55, the cradle 54 carrying a prism system corresponding to the beam splitter 3 and mirrors 4a, 4b, and the cradle 55 carrying a prism system corresponding to the mirror 5. The cradles 54, 55 have respectively rollers 57, 58 spring pressed against the mount 51 to move therewith, the roller 57 being twice as far from the pivot 56 as the roller 58 so that the cradle 55 turns through half the angle of the cradle 54 as the lens moves for focusing. Two prism systems are described in which the images are located head-to-tail across the picture carrier and in which registration is effected by rotating one half of the beam splitter and its associated reflectors above a transverse axis in the opposite direction to the rotation of the other half of the system.