Stroke saturation on a MEMS deformable mirror for woofer-tweeter adaptive optics.

摘要: High-contrast imaging of extrasolar planet candidates around a main-sequence star has recently been realized from the ground using current adaptive optics (AO) systems. Advancing such observations will be task for Gemini Planet Imager, an upcoming "extreme" AO instrument. High-order "tweeter" and low-order "woofer" deformable mirrors (DMs) supply >90%-Strehl correction, specialized coronagraph suppress stellar flux, any planets can then imaged in "dark hole" region. Residual wavefront error scatters light into DM-controlled dark hole, making difficult to image above noise. It is crucial this regard that high-density tweeter, micro-electrical mechanical systems (MEMS) DM, have sufficient stroke deform shapes required by atmospheric turbulence. Laboratory experiments were conducted determine rate circumstance saturation, i.e. insufficiency. A 1024-actuator 1.5-microm-stroke MEMS device was empirically tested with software Kolmogorov-turbulence screens r(0) =10-15 cm. The when solitary suffered saturation approximately 4% time. Simulating woofer DM 5-10 actuators across 5-m primary mitigated occurrence fraction percent. While no adjacent saturated at opposing positions, mid-to-high-spatial-frequency did saturate more frequently than expected, implying correlations through influence functions are important. Analytical models underpredict requirements, so empirical studies