Patent GB-1199327-A (GB)
Title: Optical Projection and Display Apparatus
Inventor: PRATT GOODRICH BOOTH
IPC: G09B5/02
Filed: 1967-08-15
Abstract: 1,199,327. Practising and teaching appliances. BRUNSWICK CORP. 15 Aug., 1967 [22 Aug., 1966], No. 37390/67. Heading A6D. [Also in Divisions G2, G3, G4 and H4] Projection apparatus suitable for golf practice which randomly selecting any one of the picture frames on a film strip and positioning that frame for projection on to a screen comprises a servo system operative in two modes, firstly to position the selected frame within a few frames of the correct position and secondly to position the frame within a fraction of a frame, camming means to adjust the frame within a few thousandths of an inch, and optionally, a sensing means to detect optical identifying means on the frame and control further fine adjustment. The apparatus may comprise an indoor golf game and the frame selection is performed at high speed, and the servo system is provided with a velocity loop arrangement whereby the system runs at full speed independently of the error signal until the frame is nearly correctly placed when the system speed then becomes dependent on the size of the error signal. The Film 30 has each frame divided into a picture half and an alignment position which is opaque with a clear spot to provide a narrow beam of projected light which falls on a photocell quadrant. Optics. An arc lamp 40 is adjustably mounted on rails 42 to direct light through the film plane 45 via a condenser system 133 slidably carried on a shaft 132 extending from the collar 126 in which projection lens 127 is mounted. Rotatably mounted on shaft 132 is an arm carrying a de-focusing lens which is moved into the optical paths during film positioning. A blower cools the film 30. Film supply and drive. Supply and take-up .reels 46, 44 are separately driven by reversible motors whose speeds are controlled by dancer arms 48, 50 with idler rollers 56 engaging the film adjacent fixed rollers 58. From rollers 56, the film passes over capstan driven sprockets 76, 90 which draw the film through projection plans 45 by way of film tensioning idlers 80, 82, 86. These sprockets and idlers are mounted on a housing 71 which is axially or rotatably movable between ball bearings 102, 104 for the accurate fine adjustment of the selected frame in plane 45. Torque motor 110 provides the axial motion through an eccentric connection with link 114 to housing 71. A similar motor and connection to a lug beneath housing 71 provides the rotation. Sprocket drive. High-speed reversible servo motor 150, Fig. 8, has an output gear 158 which has a tachometer 160 on its shaft at which drives a single gear 162 in mesh with gears 164, one on the shaft of each sprocket 76, 90. Gear 162 also meshes with a gear 170 freely rotatable on shaft 172, Fig. 9. Followers 174 dependant from gear 170 are engaged by a wedge cam 188 when a shaft 176 is rotated by motor 184. This engagement provides a small rotation of gear 170 and, via gear 162, of film sprockets 76, 90; this is the second film frame adjustment. Film tensioning. Cams 192, 194 on shaft 176 engage followers 202 and rotate shafts 200 which rotate rollers 80, 86 in opposite directions to tension the film subject to a tension limiting device controlled by disc 232 on shaft 176. Film pressure plates in plane 45 are unnecessary. Scene selection. Shafts 166, 168 of driven sprockets 76, 90 drive through gearing the wipers of two potentiometers, one wiper having ten unique positions for any group of ten adjacent frames, and the other having as many unique positions as there are such groups. Those potentiometers provide fine and coarse feed-back signals. Each potentiometers is placed in one arm of a coarse and fine positioning bridge network, manual push-buttons controlling the magnitude of resistance in the opposite arms of the two bridges to select a certain frame. Servo motor 150 then drives sprockets 76, 90 and the potentiometer wipers until the bridges balance. The error signals are applied through relays and the motor speed is therefore independent of signal magnitude until the balance point is approached. Tachometer 160 signals and error signals are then summed, amplified and fed to one or the other of two field windings of the motor for forward or reverse drive. When the summed signals fall below a certain value, control is switched to the fine positioning mode. Final frame adjustment. After fine positioning, motor 184 so energised to rotate cam-shaft 176 until stopped by means of a micro switch. The same microswitch also energises the photocell quadrant in which form photocells have a common junction and in which pairs of photocells are balanced against a potentiometer, one for each pair, across a respective DC supply. Each potentiometer controls microrelays actuating the axial shift rotor 110 or the rotational shift motor. Housing 71 and house the film frame is therefore adjusted until all four photocells are equally illumined.