Rotary encoding device with polygonal reflector and centroid detection
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorDouglas B. Leviton
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Abstract
A device for positioning encoding of a rotating shaft in which a polygonal mirror having a number of facets is mounted to the shaft and a light beam is directed towards the facets. The facets of the polygonal mirror reflect the light beam such that a light spot is created on a linear array detector. An analog-to-digital converter is connected to the linear array detector for reading the position of the spot on the spots on the linear array detector. A microprocessor with memory is connected to the analog-to-digital converter to hold and manipulate the data provided by the analog-to-digital converter on the position of the spot and to compute the position of the shaft based upon the data from the analog-to-digital converter.
Claims17
A high resolution device for encoding the angular displacement of a rotating shaft about its axis of rotation comprising:
- a polygonal mirror having a plurality of facets thereon affixed to said shaft;
- a light beam having an invariant spatial distribution directed towards said facets;
- said facets of said polygonal mirror each reflecting in turn said light beam such that a light spot having an invariant spatial distribution is projected on a plurality of pixels on a position sensitive detector means;
- an analog-to-digital converter means connected to said detector means for reading an output from said plurality of pixels upon which said light spot is projected;
- processing and memory means connected to said analog-to-digital converter means to hold and manipulate data provided by said analog-to-digital converter means on the position of said spot and to compute the angular displacement of said shaft about its axis of rotation based upon a computation of the centroid of the light spot distribution upon said plurality of pixels upon which said light spot is projected.
Dependencies are inferred from the claim text.