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Design and performance of a small two-axis high-bandwidth steering mirror

A two-axis, high-bandwidth, small-aperture steering mirror called the High Bandwidth Steering Mirror (HBSM) has been designed, fabricated, and tested. The mirror/mechanism prototype functions within a servo loop either scanning a field of view or tracking a radiation source. The design focused on elements making up the beam-steering mechanism: mirror, restoring flexures, actuators, position sensors, and encompassing housing, and the part each component plays in making a mechanical system suitable for high-bandwidth operation. Inclusion of a novel flexural support allows one-degree peak-to-peak angular stroke (shaft space) at low frequencies and a small-signal closed-loop bandwidth of up to 10 kHz without the usual mechanical resonance-induced loop instabilities. This increased bandwidth allows substantial rejection of a disturbance spectrum in the 10-1000 Hz range and execution of fast, complex scan patterns. Pointing accuracies of 0.2 micronrad have been achieved in the laboratory. Details of the mechanical design and fabrication issues as well as the control-loop implementation are discussed. Test data are presented along with reports of the mirror's performance in use as an extended sensor.