The extreme adaptive optics testbed at UCSC: current results and coronagraphic upgrade

Severson, Scott; Bauman, Brian; Dillon, Daren; Evans, Julia W.; Gavel, Don; Macintosh, Bruce; Morzinski, Katie M.; Palmer, Dave; Poyneer, Lisa

doi:10.1117/12.672341

Cited by 10 publications

(4 citation statements)

References 10 publications

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“…Cases that will benefit from the dOTF calibration are test benches demonstrating techniques for ultra-high contrast imaging needed in space-based exo-planet detection (e.g., HCIT [16]), experiments for ground-based extreme adaptive optics (ExAO testbed [17], HOT [18], FFREE [19]) and the pathfinder XAO instruments (GPI [20], SPHERE [21]).…”

Section: Discussionmentioning

confidence: 99%

Calibrating a high-resolution wavefront corrector with a static focal-plane camera

et al. 2013

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We present a method to calibrate a high-resolution wavefront (WF)-correcting device with a single, static camera, located in the focal-plane; no moving of any component is needed. The method is based on a localized diversity and differential optical transfer functions to compute both the phase and amplitude in the pupil plane located upstream of the last imaging optics. An experiment with a spatial light modulator shows that the calibration is sufficient to robustly operate a focal-plane WF sensing algorithm controlling a WF corrector with 40,000 degrees of freedom. We estimate that the locations of identical WF corrector elements are determined with a spatial resolution of 0.3% compared to the pupil diameter.

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Section: Discussionmentioning

confidence: 99%

Calibrating a high-resolution wavefront corrector with a static focal-plane camera

et al. 2013

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“…Measurements were made using the phase-shifting diffraction interferometer [27], a subnanometer-absolute-accuracy measuring instrument situated on the ExAO testbed [28,29] at the LAO. A spherical wave (f/220) converges from a beam size of 12 mm at the MEMS plane to the surface of a pinhole aligner, where it is combined with a reference beam.…”

Section: Methodsmentioning

confidence: 99%

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

Morzinski,

Macintosh,

Gavel

et al. 2009

Preprint

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

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“…These were to demonstrate nanometer metrology of an optical system, to demonstrate < 2 nm rms wavefront error (WFE), to demonstrate 10 −7 contrast at visible wavelengths and consistency with wavefront measurements, 4 to install a MEMS deformable mirror, to demonstrate ability to flatten the MEMS to < 1 nm rms WFE over controllable spatial frequencies, 5 to demonstrate contrast of 10 −6 (goal: 10 − 7) with a MEMS, 5 to characterize the MEMS device and identify performance limitations, 2, 6-10 to demonstrate nanometer-accuracy measurements with a Shack-Hartmann WFS, and testing of other ExAO instrument components. 11,12 Selected readings for those interested in MEMS performance in the lab are: Evans et al 5…”

Section: The Laboratory For Adaptive Opticsmentioning

confidence: 99%

MEMS practice: from the lab to the telescope

Morzinski

Norton²,

Evans³

et al. 2012

MEMS Adaptive Optics VI

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Micro-electro-mechanical systems (MEMS) technology can provide for deformable mirrors (DMs) with excellent performance within a favorable economy of scale. Large MEMS-based astronomical adaptive optics (AO) systems such as the Gemini Planet Imager are coming on-line soon. As MEMS DM end-users, we discuss our decade of practice with the micromirrors, from inspecting and characterizing devices to evaluating their performance in the lab. We also show MEMS wavefront correction on-sky with the "Villages" AO system on a 1-m telescope, including open-loop control and visible-light imaging. Our work demonstrates the maturity of MEMS technology for astronomical adaptive optics.

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The extreme adaptive optics testbed at UCSC: current results and coronagraphic upgrade

Cited by 10 publications

References 10 publications

Calibrating a high-resolution wavefront corrector with a static focal-plane camera

Calibrating a high-resolution wavefront corrector with a static focal-plane camera

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

MEMS practice: from the lab to the telescope

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