GB836245A - Optical coding system - Google Patents

Abstract

836,245. Electric selective signalling systems. ATELIERS DE CONSTRUCTION BEAUDOUIN. June 4, 1957 [June 12, 1956], No. 17704/57. Class 40 (1). [Also in Groups XX and XL (b)] An arrangement for converting variations of a magnitude as indicated by displacement of a member into a set of digital code indications comprises an optical system including an optical scanning element (e.g. a mirror) secured to the displaceable member and adapted to direct on to light-responsive receiving means a light beam in the path of which is interposed a coding screen having opaque and clear areas so arranged that different screen portions provide different patterns constituting digital code representations. As shown, light from lamp 5 is passed through lens 6 and a coding screen 7 to a mirror 4 which is deflected in accordance with variations in a magnitude and reflects the light towards a moving film 1. In front of film 1 is an opaque screen 2 with a slot 3, parallel to the rotary axis of mirror 4, and a rotary shutter 8 having a radial slot. Screen 7 has, as shown in Fig. 2, transparent and opaque areas adapted to represent numbers in a selected digital code (e.g. Gray's minimum error code) so that, each time film 1 is uncovered by shutter 8, there will be imaged thereon the digital code representation corresponding to the mirror position (and thus the magnitude) at that time. An analogue indication of each mirror position is simultaneously formed on the film 1 through reflection by mirror 4 of light from a lamp 9 on to a mirror assembly 10 which causes the light beam to move parallel to slot 3. Mirror 4 may be rotated about an axis perpendicular to slot 3, in which case the assembly 10 is omitted. In place of film 1, an array of photo-electric cells may be provided to deliver voltage pulses corresponding to the mirror position and these pulses may be fed after amplification to a digital computer or digital remote transmission system.