Abstract: An electromagnetic (e.g., laser) beam acquisition and tracking system that is particularly useful onboard high-speed aircraft (10) to acquire and track a target (12) supporting a retroreflector (13) is disclosed. The acquisition and tracking system includes two deflection systems--a mechanical deflection system (19) and an acousto-optic deflection system (17)--for controlling the direction of the electromagnetic beam (14). The two deflection systems are serial, i.e., first one system deflects the beam and then the other system deflects the beam. The deflection systems are controlled in different manners, depending upon the mode of operation of the acquisition and tracking system, which comprise a search mode, a spiral search mode and a tracking mode. In the search mode of operation the mechanical deflection system (19), which includes one or more servo-driven scanning mirrors (54 and 56), relatively slowly sweeps the electromagnetic beam in either a line scan (18) or an area scan (16) search pattern.

Abstract: A filter and beam combiner is comprised of a small glass plate having a microscopic two sided elliptical mirror on one side thereof. The signal beam is spatially filtered on one side of the mirror and then directed to a target. On the other side of the mirror there is a compensating glass plate through which the reference beam passes, to correct for refraction relative to its passing through the first plate, before it enters the other glass plate and is directed onto said other side. The reference beam is spatially filtered by the mirror for combination with the signal beam, which returns from the target substantially enlarged by diffraction so as to pass around the mirror and through the plate to be combined with the reference beam.The signal beam is passed through acousto-optic modulator (AOM). The reference beam is passed through an 81 MHz AOM. The AOM's produce a doppler shift of the coherent light source frequency as the light is diffracted by a moving sound wave in the modulator.