Characterization Techniques For Deformable Metal Mirrors

TLDR: In this article, the authors describe and compare several laboratory techniques currently being used to measure these and other deformable metal mirror characteristics for two mirror types: dither (high frequency, small surface excursion), and control (low frequency, large surface excursions).

Abstract: Deformable mirrors must be subjected to a series of tests in order to accurately assess their structural integrity and predict their operational performance in a closed-loop system. These tests consist of monitoring the surface under various drive conditions. Among the parameters determined from the surface measurements are actuator surface influence functions, hysteresis effects and frequency response. They are used to characterize a deformable mirror by providing information about inter-actuator coupling, drive response linearity and frequency bandwidths. When piezoelectric actua-tors are used, large drive voltages are necessary, which when coupled with high drive frequencies and small surface motion, makes acquisition of accurate data a complex task. This paper describes and compares several laboratory techniques currently being used to measure these and other deformable metal mirror characteristics for two mirror types: dither (high frequency, small surface excursion), and control (low frequency, large surface excursions).