The open-loop control of MEMS: modeling and experimental results

Morzinski, Katie M.; Harpsøe, K.; Gavel, Don; Ammons, S. Mark

doi:10.1117/12.710428

Cited by 37 publications

(38 citation statements)

References 13 publications

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“…Shapes at the limit of achievable mirror spatial frequencies were achieved with less than 15nm RMS error [11]. Others have also implemented open loop AO control with BU/BMC mirrors, demonstrating comparable results [12,13]. That open loop control architecture and the BU/BMC DM was demonstrated in the first civilian use of MEMS-based astronomical AO in the Villages project led by Gavel in the past year [14,15].…”

Section: Wavefront Correction Technologymentioning

confidence: 92%

MEMS deformable mirrors for astronomical adaptive optics

et al. 2010

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Abstract. We report on the development of microelectromechanical (MEMS) deformable mirrors designed for ground and space-based astronomical instruments using adaptive optics. These light-weight, low power deformable mirrors will have an active aperture of up to 25.2mm consisting of thin silicon membrane mirror supported by an array of up to 4096 electrostatic actuators exhibiting no hysteresis and sub-nanometer repeatability. The continuous membrane deformable mirrors, coated with a highly reflective metal film, are capable of up to 4µm of stroke, have a surface finish of <10nm RMS with a fill factor of 99.8%. The segmented device has a range of motion of 1um of piston and 600 arc-seconds of tip/tilt simultaneously and a surface finish of 5nm RMS. Presented in this paper are device characteristics and performance results for these devices. Motivation for high-resolution wavefront correctionMost large ground based telescopes now employ AO as an essential and enabling tool for highresolution imaging. Though recent progress in AO for current and future large telescopes has been technologically exciting, its impact on astronomical science remains modest to date. AO technology is still inadequate to compensate for the larger wavefront errors and shorter atmospheric coherence lengths associated with visible wavelength observation. Its simplest implementation allows only a narrow field of compensation, and more ambitious instrument concepts are limited by the cost, size, and complexity of AO components, especially the DM. A critical assessment of AO technology was funded by the National Science Foundation several years ago, resulting in a 2008 report entitled A Roadmap for the Development of United States Astronomical Adaptive Optics. The roadmap identifies single major goal for wavefront correction: "Development of scalable, cost-effective DM technologies" and recommends a high-priority research investment to achieve this goal: "High stroke, high actuator count [deformable] mirrors to enable correction at high spatial frequencies over narrower fields of view."The coming generation of ELTs, will be the first to be designed with AO at the outset. Since the benefits of AO increase nonlinearly with telescope aperture, a phenomenon sometimes called D 4 scaling, AO will be essential for many ELT science goals [1,2]. Promising AO instruments that will require new DMs include multi-conjugate adaptive optics (MCAO), multi-object adaptive optics (MOAO), and extreme adaptive optics (ExAO) [3]. MCAO employs two or more guide stars to enable tomographic wavefront error sensing, and then two or more deformable mirrors in series to correct those errors. The result is a wider corrected field of view [4]. This technique was recently used to produce the sharpest whole-planet (Jupiter) picture ever taken from the ground [5]. MOAO is an instrument concept that also uses multiple guide stars and multiple deformable mirrors [6]. However in MOAO, many DMs would be used in parallel to apply independent corrections for the turbulence-induce...

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Section: Wavefront Correction Technologymentioning

confidence: 92%

MEMS deformable mirrors for astronomical adaptive optics

et al. 2010

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“…At least three different efforts have worked towards detailed modeling of the face sheet motion and how to control that surface with high precision. [15][16][17][18][19] However, our own work has shown that the non-linearity due to the face sheet is low enough that GPI does not require an advanced algorithm to determine actuator voltages. 20 Calibration of the quadratic voltage-phase relationship (see below) and the influence function are all that is necessary.…”

Section: Influence Function Superpositionmentioning

confidence: 99%

The use of a high-order MEMS deformable mirror in the Gemini Planet Imager

et al. 2011

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We briefly review the development history of the Gemini Planet Imager's 4K Boston Micromachines MEMS deformable mirror. We discuss essential calibration steps and algorithms to control the MEMS with nanometer precision, including voltage-phase calibration and influence function characterization. We discuss the integration of the MEMS into GPI's Adaptive Optics system at Lawrence Livermore and present experimental results of 1.5 kHz closed-loop control. We detail mitigation strategies in the coronagraph to reduce the impact of abnormal actuators on final image contrast.

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“…For comparison, Morzinski et al 21 report 15 nm RMS error for a 500 nm peak-to-valley Kolmogorov-like shape with a non-linear shaping algorithm. Stewart et al 22 give a result of less than 15 nm RMS open-loop error for input aberrations up to 1.5 µm peak-to-valley, but only simple modes, and not a Kolmogorov shape, were used in those tests.…”

Section: Lsi Control Strategiesmentioning

confidence: 99%

“…23 Open-loop control algorithms that account for inherent device linearity have been proposed by Vogel and Yang, 24 Morzinski et al 21 and Stewart et al 22 among others. For GPI our primary concern is whether we will need such a non-linear compensation algorithm, or if the non-linearity of the GPI MEMS will be small enough that use on closed-loop will not degrade performance.…”

Section: Non-linear Mems In Closed-loopmentioning

confidence: 99%

“…At least three different approaches exist for such a modeling and solution of the MEMS surface from input voltages: the same work of Vogel and Yang as above, 24 Baker, 25 and the work of Gavel 26 followed by Morzinski et al 21 For both its ease of implementation and reasonable computational cost, we have chosen the Vogel and Yang model. Though this model is incomplete (see Section 4.B of that paper for discussion of how), it provides a reasonable starting point for a non-linear MEMS in our simulation.…”

Section: Non-linear Mems In Closed-loopmentioning

confidence: 99%

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MEMS adaptive optics for the Gemini Planet Imager: control methods and validation

Poyneer

Dillon

2008

SPIE Proceedings

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The Gemini Planet Imager (GPI) Adaptive Optics system will use a high-order MEMS deformable mirror for phase compensation. The MEMS mirror will be used in a Woofer-Tweeter configuration, with a frequencydomain based splitting of the phase between the two mirrors. Precise wavefront control depends on the ability to command them MEMS to make the exact phase desired. Non-linearities in the MEMS may prevent this. We determine that influence-function pre-compensation can remove most, but not all, open-loop error. We use simulation and a simulation of a non-linear MEMS to address the issue of how much non-linearity can be tolerated in closed-loop by GPI.

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The open-loop control of MEMS: modeling and experimental results

Cited by 37 publications

References 13 publications

MEMS deformable mirrors for astronomical adaptive optics

MEMS deformable mirrors for astronomical adaptive optics

The use of a high-order MEMS deformable mirror in the Gemini Planet Imager

MEMS adaptive optics for the Gemini Planet Imager: control methods and validation

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