Pulse generating apparatus responsive to shaft rotation

Claim 1

Apparatus for generating pulses in response to shaft rotation comprising: a. an optical encoder including l. a disc coupled to said shaft, said disc including a plurality of openings formed therein and equally spaced in a circle about said disc, 2. a pair of radiant energy sources positioned on one side of said disc, 3. a pair of radiant energy detectors positioned on the opPosite side of said disc, each of said pair of radiant energy sources being in optical alignment with a respective one of said pair of radiant energy detectors, 4. and means for confining the width of the beams radiated by said radiant energy sources, said confining means having a pair of spaced apertures through which the radiant energy beams are directed towards said detectors, b. a bistable device connected to the output of said pair of radiant energy detectors, c. means for processing electrically the outputs of said bistable device to provide pulses proportional in number to shaft rotation, d. the effective spacing between the apertures being approximately one-half the spacing between adjacent openings, and e. the spacing between said openings and the sizing of said openings and apertures being selected so that the angular hysteresis of said shaft Ha/m is at least 2*, where Ha represents angular hysteresis of said disc as determined by the equation: Ha 360 (L/2 - s - d)/d, and m is the shaft-to-disc gear ratio, and where L is the spacing between the centers of adjacent openings measured along a circle of radius R, s is opening width, d is aperture width, and D 2R.