GB719463A - Improvements in or relating to optical projection apparatus - Google Patents

Abstract

719,463. Optical projection apparatus. OPTICAL MEASURING TOOLS. Ltd. March 27. 1952 [March 27, 1951], No. 7131/31. Class 97(1) [Also in Group XIX] Profile projection apparatus comprises a mounting for a plurality of objectives, movable to bring a selected one into operation, a projection screen, an object holder movable for focusing, an illuminant for the object and a system comprising one or more reflectors movable to vary the light path and the magnification of the projected image. In the form shown the top 12 of a casing 11 carries a lens turret 13, an object holder 14 and, in trunnions 29, a lamphouse 15 with condenser 34. The turret carries lenses 20, 21, 22, 23, 24 and knobs 35 by which the turret may be rotated to bring the lenses into use. The turret positions are determined by detent mechanism. The turret carries near each lens, an adjustable mirror 37 by which light from the lamphouse is directed on to the object on the holder 14. The lenses 20 &c. being of different focal lengths are arranged at different heights so that the images projected by each are in focus. The mirrors 37 are also at different heights and cams, not shown, are provided on the turret periphery connected to a link which tilts the lamphouse about the trunnions 29 to direct the light beam on to the mirror 37 in use. The object holder 14 has a central glass panel with transverse adjustments by knobs 43, 44 and a focusing adjustment by a knob 42. The light reflected from the object falls on an inclined mirror 25 and is thence reflected by mirrors 26, 27, 28, in a chamber 16, on to a screen 19. The mirrors 25. 26 are carried on a cradle 47 vertically movable on pillars 53, 54. The pillars each have, at the top, a ball 58 in a fixed socket and. at the bottom, transverse screw adjustments to render the pillars parallel. The cradle 47 is connected to a counterweight 71 by a steel tape 68 passing over a drum 69 rotatable, through worm gearing, by a knob 77 or by an electric motor, not shown, operated in opposite directions by push buttons 82, 83 on a panel 84. Limit switches stop the motor at the ends of travel of cradle 47. The drum 69 drives through gearing 88, 89 a drum 85 behind a window 87. The drum carries scales showing the magnification of the projected image. There is one scale for each objective, the scale in use being illuminated. Lamps for this purpose are controlled by switches actuated by the lens turret.