An optical alignment mirror mechanism (AMM) has been developed with angular positioning accuracy of ±0.2 arcsec. This requires the mirror’s linear positioning actuators to have positioning resolutions of ±112 nm to enable the mirror to meet the angular tip/tilt accuracy requirement. Demonstrated capabilities are ±0.1 arc-sec angular mirror positioning accuracy, which translates into linear positioning resolutions at the actuator of ±50 nm.
The mechanism consists of a structure with sets of cross-directional flexures that enable the mirror’s tip and tilt motion, a mirror with its kinematic mount, and two linear actuators. An actuator comprises a brushless DC motor, a linear ball screw, and a piezoelectric brake that holds the mirror’s position while the unit is unpowered. An interferometric linear position sensor senses the actuator’s position. The AMMs were developed for an Astrometric Beam Combiner (ABC) optical bench, which is part of an interferometer development. Custom electronics were also developed to accommodate the presence of multiple AMMs within the ABC and provide a compact, all-in-one solution to power and control the AMMs.