GB544026A - Improvements in or relating to optical projection apparatus - Google Patents

Abstract

544,026. Optical-projection apparatus. KODAK, Ltd. April 4, 1941, No. 4527. Convention date, April 13, 1940. [Class 97 (i)] To permit variation in the size of the projected image, the projection screen, a reflector directing the beam from a projector thereto, and the projection lens, are all movable, and are interconnected so that the throw of the beam may be varied while maintaining a focused image on the screen. As shown, a lamp house 20 is hinged at 21 to a bracket 19, and film spools 26 and glass plates 24, 25 are mounted on a rotatable turret 23 ; an image of the illuminated film, between the plates 24, 25, is projected by a lens 28 and mirror 44 on to a screen 33. The screen 33 is carried by a hinge 34 and is secured to side plates 37 each provided with a cam slot 71. The mirror 44 is mounted on a frame comprising end members 46, 47 each pivoted to a rod 53 and secured to a trunnion 66 slidable in one of the slots 71 in the side plates 37. The rod 53 and trunnions 66 are carried by arms 51, 59 pivoted in collars 57, 62 on the side walls of the cabinet, and the lengths of the arms the spacing of the end pivots, and the shape of the slots 71 are such that, as the screen is turned about its hinge 34, the mirror is displaced and turned so as to increase the throw of the beam and to direct the beam on the screen. A lever 78 pivoted at 79 to a cabinet wall carries an adjustable slotted plate 80 engaged by a roller 76 on one of the side plates 37, the slot is shaped so that, as the screen 33 is moved, the lever 78 is moved vertically and controls the lens focus by means of a cord 85 secured to the lever and anchored at its other end through a spring 89 to a stud 90, the cord being passed round a pulley 31 on an internally screw-threaded sleeve engaging the lens barrel. The screen 33 is movable by a handle 35, a rack 39 meshes with a pinion 40 on a shaft carrying locking means or a magnification indicator, or both, and a pair of springs 74 counterbalances the weight of the parts.