An airborne laser tracker was designed around a two-level beam deflection system. An xy acoustooptic beam deflector provides high angular rate control of the l-mrad divergeBce helium-neon laser beam over a 0.8 degree square field of view. Wide angle pointing (20 azimuth and 50 elevation) is accomplished with a 2-axis mirror beam deflector. The out-going and return beams are coaxial. The angular accuracy is <.5 milliradian. The track-loop angular velocity is greater than one radian/second.
C. R. Pond,
L. L. Slack,
"Acousto-Optic Deflection Applied to A Laser Tracker", Proc. SPIE 0247, Advances in Laser Engineering and Applications, (31 October 1980); doi: 10.1117/12.959398; https://doi.org/10.1117/12.959398