There is a need for ever-larger apertures for use in space based optical imaging systems. Requirements on optical
instrumentation for future observations in space will place rigorous demands on wavefront quality. The design of
such mirrors involves a balance between the utilization of ultra-lightweight mirror and support structures, and the
active correction of the increased deformations due to these compromises in structural rigidity. Performing
wavefront control with a primary mirror requires precision and stability over a large structure. The wavefront
correction, therefore, can be partitioned in spatial frequency between the primary mirror and a tertiary deformable
mirror (DM). To realize the full potential of new ultra-lightweight, active primary mirror, the large-stroke
microactuator and DM technologies need to be developed. This paper presents a set of candidate components: linear
microactuator technology and a piezoelectric unimorph-based large-stroke DM technology, in the context of a
lightweight active mirror concept.
This paper describes the results of our demonstration on a proof-of-concept piezoelectric unimorph-based deformable mirror (DM) with continuous single-crystal silicon membrane. A PZT unimorph actuator of 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5 μm at 50 V. DMs consisting of 10 μm thick single-crystal silicon membranes supported by 4×4 actuator arrays were fabricated and optically characterized. An assembled DM showed a stroke of 2.5 μm at 50 V with a resonant frequency of 42 kHz and influence function of approximately 25%.
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