Optical angular position detection apparatus and method

An angular position detection apparatus comprising

• a first light detector disposed on a first imaginary circle centered on an axis, said first light detector including first and second photosensors spaced side-by-side, each photosensor producing an output depending upon the area thereof exposed to light;
• at least one pair of light emitters spaced in front of said first light detector on a second imaginary circle centered on said axis, said light emitters being arranged and adapted to direct separate, well-defined, overlapping light beams simultaneously to all the photosensors;
• a light blocker rotatably mounted on said axis between the detector and emitters, said light blocker being arranged and adapted to block the light to different extents of said first and second photosensors depending on its orientation about said axis;
• a processor responsive to the outputs from all the photosensors for producing a position signal that varies with the angular position of the light blocker;
• and
• a calibration circuit for adjusting, independently, an intensity of each light emitter so that the position signal is substantially linear at all operative angles of the light blocker.