Self-aligning retroreflector target carrier

Abstract

A distance measurement system employs a monochromatic coherent light source which produces an outgoing ray which impinges upon a target reflector which reflects the beam back as a reflected beam to an interferometry detector. A portion of the outgoing ray also is delivered to the interferometry detector. As the target reflector position is changed, the interferometry detector continuously calculates changes in distance of the target reflector. The orientation angles of the target reflector are constantly and automatically adjusted so that the reflected light beam accurately strikes the interferometry detector. A misalignment detector senses the elevation offset and the azimuth offset of the target reflector and creates corresponding signals. The elevation and azimuth offset signals are then provided to an elevation actuator and an azimuth actuator, respectively, which correct the elevation and azimuth angles of the target reflector to maintain continuous reflection of the return beam to the interferometry detector. The misalignment detector either monitors a light source located near the interferometry detector, or splits off part of the monochromatic beam, which is directed to a four quadrant photodetector. Differences in the signal between opposite quadrants determine the angular pointing errors which are used to drive the azimuth and elevation actuators. This results in an interferometry measurement system which constantly measures distance and corrects for misalignment of the reflector.

Dependencies are inferred from the claim text.