Glint tracking using adaptive optical techniques

Adaptive optical techniques have been employed to track target glint returns using two-axis steering and focus correction. Measurements were made on laboratory apparatus, operating at 10.6 µm. The apparatus consists of a low power CO2 laser, a 300-Hz bandwidth wavefront manipulator, focusing optics to form a far-field beam pattern, a moving glint (a small polished sphere), and an on-axis receiver that views target return. Adaptive control is implemented by tagging each correction mode with a high-frequency low-amplitude dither which is a small fraction of the available mode range. Classical hill-climbing servos are used to maximize glint return by nulling the dither component of each correction at a zero slope point corresponding to maximum target power.