Modeling, Calibration and Control for Extreme-Precision MEMS Deformable Mirrors

Iris AO will develop electromechanical models and actuator calibration methods to enable open-loop control of MEMS deformable mirrors (DMs) with unprecedented precision. Error budget analysis will establish feasibility of open-loop operation with nanometer-scale positioning accuracy and sub-nanometer resolution and stability. Although a number of MEMS based DMs have been demonstrated for adaptive optics applications, little work has been carried out to characterize their wavefront correction ability to precisions required by NASA space telescope missions. This proposal directly addresses this issue for a class of electrostatically actuated DMs with extremely high optical quality and low voltage-to-stroke ratios. High-precision, large actuator count DMs are critical for high-contrast astrophysical imagers, including the Terrestrial Planet Finder program. Existing non-MEMS DMs that approach NASA requirements feature high actuation voltages, low actuator densities and uncertain scalability beyond a few thousand actuators. MEMS DMs offer natural scalability, but do not yet meet the stringent precision and stability requirements for space telescopes applications. Better understanding of the electromechanical behavior, positioning error sources and calibration methods for these devices is essential to understand and improve performance, bringing MEMS DMs to mission readiness.