Deformable mirrors are at the heart of any adaptive optics system. We present the results of tests of deformable mirrors from Microscale. One of the key innovations of these deformable mirrors is that the facesheet is created from a silicon on insulator (SOI) wafer with integral posts for mechanical linkage to the actuators. This dramat- ically reduces the variability of the influence function. The facesheet is bonded to an array of piezoelectric stack actuators. The actuators are currently PZT, but single crystal PMN actuators are being developed. We present results of optical and electrical tests of the performance of the DM.
The development of compact, high performance Deformable Mirrors (DMs) is one of the most important technological challenges for high-contrast imaging on space missions. Microscale Inc. has fabricated and characterized piezoelectric stack actuator deformable mirrors (PZT-DMs) and Application-Specific Integrated Circuit (ASIC) drivers for direct integration. The DM-ASIC system is designed to eliminate almost all cables, enabling a very compact optical system with low mass and low power consumption. We report on the optical tests used to evaluate the performance of the DM and ASIC units. We also compare the results to the requirements for space-based high-contrast imaging of exoplanets.
We report on an effort of building a new form of deformable mirror (DM) driven by an array of giant piezo
microactuators and being integrated with an ASIC driver electronics. The actuator layer is obtained by bonding a thin Si
wafer with a thin PMN-PT crystal substrate, and is in attachment with a bulk-micromachined mirror hierarchy
comprising of a supporting Si layer as the spacer, a Si post layer as the motion sampler, and atop of which a Si
micromembrane layer as the deformable mirror. The ASIC employs a charge controlled approach to actuate the large
capacitance (~nF) in associating with the high-energy-density actuators, capable of charging/discharging an array from
quasi-static to 20 kHz framing rate, and with ultra-low-power dissipation that approximates the theoretical minimum of a
driver electronics. The DM to ASIC integration is currently accomplished at chip level. An integrated DM prototype has
32x32 actuator elements at 600um pitch, weighing ~50 grams, as compact as ~1 cubic inch, and uses 25 wires to access
the 1024 actuators. Fundamental characterizations of a few ASIC drivers are also presented.
After laboratory studies have demonstrated that the DM-based adaptive optics ophthalmic instruments are promising for
future clinical applications, the next step would be to further enhance the functionality of ocular adaptive optics for
research and commercialize it for clinical applications. The first essential requirement is the stroke which should cover
most wavefront errors of the eyes in clinical population, for which, we presented here design, modeling, and
experimental performance of PMN-PT unimorph actuators suitable for generating large stroke up to 50μm per 1-mm
pixel in order to cover wavefront correction for older adults and patients with diseased eyes. Clinical acceptance will
also requires DMs to be low cost, have a small form factor, running low power, have satisfactory speed, and be an easy
add-on for system integration, thus we further presented an effort of developing a high voltage amplifier (HVA) based
application specific integrated circuits (ASIC) for driving the mirror actuators with significantly reduced power and
system form factors.