Design and development of a 331-segment tip–tilt–piston mirror array for space-based adaptive optics

Stewart, Jason B.; Bifano, Thomas G.; Cornelissen, Steven; Bierden, Paul; Levine, B. M.; Cook, Timothy A.

doi:10.1016/j.sna.2007.04.051

Cited by 46 publications

(28 citation statements)

References 7 publications

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“…That work will be advanced by a recently awarded NSF MRI grant to Gavel, which will support integration of a 1024 actuator BMC DM on the Shane telescope AO system. BU and BMC collaborated recently on a project to deliver advanced DMs for space-based astronomical imaging supported by NASA JPL [23]. That work involved development of a segmented tip-tilt-piston mirror for a visible nulling coronagraph envisioned as part of the Terrestrial Planet Finder (TPF) program.…”

Section: Astronomical Ao With Mems Dmsmentioning

confidence: 99%

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: Astronomical Ao With Mems Dmsmentioning

confidence: 99%

MEMS deformable mirrors for astronomical adaptive optics

et al. 2010

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“…4 The epipoly silicon provides the mirror segment with additional rigidity while allowing polishing to better than 1nm RMS local surface roughness. This eliminates print-through effects.…”

Section: Continued On Next Pagementioning

confidence: 99%

“…4 This DM will be used in a visible nulling coronagraph to demonstrate the feasibility of the instrument for the TPF Coronagraphic observatory. The technology is also being extended to a NASA Discovery mission for detecting extrasolar giant planets, which will require an hexagonal array of 1027 mirror segments.…”

Section: Continued On Next Pagementioning

confidence: 99%

Ultra-flat micromirror arrays with tip, tilt, and piston control

Stewart¹

2007

SPIE Newsroom

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A new mechanical design and microfabrication process can create deformable mirror segments with a surface quality that meets requirements for next-generation telescopes.The space-based observatories planned within the framework of NASA's Terrestrial Planet Finder (TPF) mission are being designed to perform high-contrast diffraction-limited imaging of extrasolar Earth-like planets. However, the required optical systems face a variety of unconventional wavefront control challenges. One example is provided by the visible nulling coronagraph under development at the Jet Propulsion Laboratory, which uses an interferometric approach to block parent starlight while enhancing planet light in the visible spectrum for detection. For successful planet imaging, parent starlight must be suppressed by a factor of 10 10 , which requires the nulling coronagraph to control both the phase and amplitude of recombined wavefronts to a very high precision. [1][2][3] This technological challenge provided the impetus for the development of a new class of segmented deformable mirrors (DM) based on microelectromechanical systems (MEMS) technology. The DM has three adjustable degrees of freedom per subaperture that control out-of-plane rotation (tip and tilt) and surface normal motion (piston) over a continuous range of ±3mrad and 1µm, respectively. To perform wavefront phase and amplitude control on the collected planet and star light, the nulling coronagraph pairs this tip-tilt-piston (TTP) DM with a coherent array of optical fibers, coupling each mirror segment or subaperture to a fiber. Phase errors between the recombined interferometer wavefronts are corrected on a subaperture-by-subaperture basis using mirror segment piston motion. Amplitude errors are controlled by introducing tilt to unbalanced wavefront subapertures, which couple more or less light into their corresponding optical fibers (see Figure 1).To produce interference nulls with the level of contrast required for planet detection, the TTP DM segments must have a deviation from flatness of less than 1nm RMS over their Figure 1. Implementation of a tip-tilt-piston (TTP) deformable mirror (DM) for the amplitude and phase control of recombined wavefronts at a beam splitter (BS). For a mirror segment, piston motion matches phase, and tip-tilt motion matches amplitude to achieve optimum interference upon exit from fiber array.complete range of motion. This requirement translates into significant design and microfabrication challenges due to the tendency of thin polysilicon components to bend during actuation and curl as a result of the residual stress gradients embedded in the deposited materials. Furthermore, the surface micromachining process used to fabricate DMs is prone to printthrough effects, meaning that successive polysilicon layers adopt the topography of prior depositions, thus reducing surface flatness. To address these issues, we have developed a new mechanical design and microfabrication process capable of producing micromirrors with the desired surface planarity....

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“…The phase and amplitude of the wavefront must be controlled precisely. A 331 segmented tilt-tip-piston (TTP) device is being used within a coronagraph and has demonstrated good performance [4,5]. In addition, a 1021 segmented device having 3063 individually addressable elements is also presented here that has the potential of significantly improving coronagraph performance.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of two high actuator count MEMS deformable mirrors

et al. 2013

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Two new MEMS deformable mirrors have been designed and fabricated, one having a continuous facesheet with an active aperture of 20mm and 2040 actuators and the other, a similarly sized segmented tip tilt piston DM containing 1021 elements and 3063 actuators. The surface figures, electro mechanical performances, and actuator yield of these devices, with statistical information, are reported here. The statistical distributions of these measurements directly illustrate the surface variance of Boston Micromachines deformable mirrors. Measurements of the surface figure were also performed with the elements at different actuation states. Also presented here are deviations of the surface figure under actuation versus at its rest state, the electromechanical distribution, and a dynamic analysis.

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Design and development of a 331-segment tip–tilt–piston mirror array for space-based adaptive optics

Cited by 46 publications

References 7 publications

MEMS deformable mirrors for astronomical adaptive optics

MEMS deformable mirrors for astronomical adaptive optics

Ultra-flat micromirror arrays with tip, tilt, and piston control

Performance analysis of two high actuator count MEMS deformable mirrors

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