Infrared scanning and display system having a noncontacting angle encoder

摘要

A scanning mirror position sensor operable from the back side of a scanning mirror which utilizes the front side of the mirror for scanning a scene to be interrogated or displayed. A rectangular uniformly distributed light source is reflected from the back surface of the scanning mirror across a grating consisting of alternate transparent and opaque regions placed in the focal plane in front of a single large area photodetector. As the light from the light source sweeps across the grating, the detector is alternately energized and deenergized to form a serial pulse train which is coupled to a pulse counter which accumulates the pulse count to thereby provide a continual and accurate measure of the mirror position.