Large, high performance, fast steering mirrors with FPGA-embedded controls

摘要

The wavefront control community relies on fast and accurate subsystems for optical tilt correction. New technology enables large diameter (172 mm), optically-flat (<32 nm rms surface error), highly accurate, fast (500 Hz) steering mirrors (FSMs) with very low stabilization errors (50 nrad jitter). Applied Technology Associates (ATA) builds and tests FSMs using Silicon Carbide lightweight optics on very rigid aluminum mounts. Optical encoders provide position feedback and the mirror control algorithms are embedded in an FPGA processing architecture with fabric-based doubleprecision arithmetic capability. To characterize mirror performance, ATA integrated a performance verification system using an xPC MATLAB-based Track Loop Controller to close a 200 Hz optical loop around the FSM. This paper describes the mirror and FPGA control that enables a new level of FSM stabilization performance and presents both modeled and measured performance for the system.