Stroke saturation on a MEMS deformable mirror for woofer-tweeter adaptive optics - Astrophysics > Instrumentation and Methods for AstrophysicsReport as inadecuate




Stroke saturation on a MEMS deformable mirror for woofer-tweeter adaptive optics - Astrophysics > Instrumentation and Methods for Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: High-contrast imaging of extrasolar planet candidates around a main-sequencestar has recently been realized from the ground using current adaptive opticsAO systems. Advancing such observations will be a task for the Gemini PlanetImager, an upcoming -extreme- AO instrument. High-order -tweeter- and low-order-woofer- deformable mirrors DMs will supply a >90%-Strehl correction, aspecialized coronagraph will suppress the stellar flux, and any planets canthen be imaged in the -dark hole- region. Residual wavefront error scatterslight into the DM-controlled dark hole, making planets difficult to image abovethe noise. It is crucial in this regard that the high-density tweeter, amicro-electrical mechanical systems MEMS DM, have sufficient stroke to deformto the shapes required by atmospheric turbulence. Laboratory experiments wereconducted to determine the rate and circumstance of saturation, i.e. strokeinsufficiency. A 1024-actuator 1.5-um-stroke MEMS device was empirically testedwith software Kolmogorov-turbulence screens of r 0=10-15cm. The MEMS whensolitary suffered saturation ~4% of the time. Simulating a woofer DM with ~5-10actuators across a 5-m primary mitigated MEMS saturation occurrence to afraction of a percent. While no adjacent actuators were saturated at opposingpositions, mid-to-high-spatial-frequency stroke did saturate more frequentlythan expected, implying that correlations through the influence functions areimportant. Analytical models underpredict the stroke requirements, so empiricalstudies are important.



Author: Katie Morzinski, Bruce Macintosh, Donald Gavel, Daren Dillon

Source: https://arxiv.org/







Related documents