Patent GB-681058-A (GB)
Title: Optical compensator for apparatus using continuously moving motion picture film
IPC: G03B41/06
Filed: 1950-10-27
Abstract: 681,058. Kinematograph apparatus. WESTERN ELECTRIC. CO., Inc. Oct. 27, 1950 [Oct. 29, 1949], No. 26221/50. Class 97 (i). [Also in Group XL (b)] An optical compensator for continuous feed apparatus comprises plane mirrors pivotally mounted in diametrically pairs on a drum, all the pivot axes being parallel to the drum axis and equidistant therefrom, each mirror being arranged to move, during the effective part of its rotation, so that its plane always contains a fixed axis parallel to the drum axis and, during the remainder of its rotation, to maintain the diametrically-opposite mirror pairs in dynamic balance. In the illustrated embodiment the invention is applied to a television scanner for kinematograph film. An image of a raster formed on a cathode-ray tube screen 51 is formed on the film in the gate 10 by a system comprising a lens 52, a field curving lens 54 secured to an apertured member 53, a lens 55, a fixed mirror 56, a lens 57 and one of the mirrors of the drum 23. Light passed by the film is concentrated by a condenser lens 58 on a photo-electric cell 59. The system may also be used, omitting the condenser lens and photo-electric cell, for photographing television images formed on the screen 51. Again, the system may be used for kinematographic projection of film images. To take account of film shrinkage the film gate 10 is mounted on a slide 90 to be movable relatively to the mirror drum simultaneously with an axial adjustment of the lens. Both movement are produced by a bell-crank 63 actuated by a knob 60 which rotates a cam 61 engaging the crank. The drum 23 is formed with a number of bores in each of which is located a tube 73 carrying a number of pads 27. A screw through the periphery of the drum pulls the tube outwards in the bore to locate it on the pads. The tube contains bearings for a spindle having at one end a flange 71 to which is secured a bracket having lugs 91 against which the mirror 65 is located by a spring-blade behind. To the other end of the spindle is rigidly secured a forked member 77 from the arms of which an adjusting screw and a return spring bear on opposite sides of an arm 29. The arm is spring-urged to maintain a follower roller 28 in contact with an endless cam track 25 which is symmetrically shaped and disposed relatively to the drum axis to maintain the dynamic balance. The drum 23 is rotatable relatively to its driving spindle to provide a framing adjustment by means of a worm and worm-wheel 44, 45. The worm is rotatable through gearing 40, 42, 43 from a spindle 39 carrying a pinion 38 rotatable in turn by axial through gearing 40, 42, 43 from a spindle 39 carrying a pinion 38 rotatable in turn by axial movement of a rack 37. This axial movement is produced by the rotation of a knob 30 carried on a screw-thread on a fixed support. The film is fed into the apparatus by a sprocket 2 and then passes between a roller 3 and a sprocket 4 retarded by a friction pad 7 to maintain film tension at the gate. From the gate the film passes under a roller 12, over a sprocket 11, between rollers 13. and 74 and over a sprocket 14. The pressure-pad 15, cooperating with the sprocket 11, and the roller 74, as well as the pivot for the spring-urged arm 20 carrying the roller 13, are all carried on a gear-wheel 16 rotatable round the sprocket axis by a knob 18 and pinion 19. Specifications 189,282 and 293,630, [both-in Class 97 (i)], are referred to.