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108:. For predefined statistics of aberrations a deformable mirror with M actuators can be equivalent to an ideal Zernike corrector with N (usually N < M) degrees of freedom. For correction of the atmospheric turbulence, elimination of low-order Zernike terms usually results in significant improvement of the image quality, while further correction of the higher-order terms introduces less significant improvements. For strong and rapid wavefront error fluctuations such as shocks and wake turbulence typically encountered in high-speed aerodynamic flowfields, the number of actuators, actuator pitch and stroke determine the maximum wavefront gradients that can be compensated for.
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smooth continuous wavefronts. Sharp edges of the segments and gaps between the segments contribute to light scattering, limiting the applications to those not sensitive to scattered light. Considerable improvement of the performance of the segmented mirror can be achieved by the introduction of three degrees of freedom per segment: piston, tip and tilt. These mirrors require three times as many actuators compared to piston-segmented mirrors. This concept was used for fabrication of large segmented primary mirrors for the
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over the membrane, they are transparent. It is possible to operate the mirror with only one group of electrodes positioned under the mirror. In this case, a bias voltage is applied to all electrodes, to make the membrane initially spherical. The membrane can move back and forth with respect to the reference sphere.
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equilibrium between the magnetic, gravitational and surface tension forces. Using proper magnetic field geometries, any desired shape can be produced at the surface of the ferrofluid. This new concept offers a potential alternative for low-cost, high stroke and large number of actuators deformable mirrors.
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high speed - <ms timeframe. As the membrane is a single sheet of material, very high optical quality is also achievable. This technology can exhibit good stability and keep its shape almost unchanged for weeks. The actuator count can range from several tens of actuators to several thousand actuators.
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mirrors are formed by a thin conductive and reflective membrane stretched over a solid flat frame. The membrane can be deformed electrostatically by applying control voltages to electrostatic electrode actuators that can be positioned under or over the membrane. If there are any electrodes positioned
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mirrors consist of a thin flexible continuous membrane actuated by voicecoils and magnets. This technology allows great design flexibility to achieve very different performances. Depending on the design choices made, they can achieve unrivaled stroke - up to a hundred microns of deformation - or very
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mirrors are formed by two or more layers of different materials. One or more of (active) layers are fabricated from a piezoelectric or electrostrictive material. Electrode structure is patterned on the active layer to facilitate local response. The mirror is deformed when a voltage is applied to one
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mirrors are formed by independent flat mirror segments. Each segment can move a small distance back and forth to approximate the average value of the wavefront over the patch area. Advantageously, these mirrors have little or zero cross-talk between actuators. Stepwise approximation works poorly for
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are nonlinear actuation effects that decrease the precision of the response of the deformable mirror. For different concepts, the hysteresis can vary from zero (electrostatically-actuated mirrors) to tens of percent for mirrors with piezoelectric actuators. Hysteresis is a residual positional error
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is the characteristic shape corresponding to the mirror response to the action of a single actuator. Different types of deformable mirrors have different influence functions, moreover the influence functions can be different for different actuators of the same mirror. Influence function that covers
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is the maximum possible actuator displacement, typically in positive or negative excursions from some central null position. Stroke typically ranges from ±1 to ±30 micrometres. Free actuator stroke limits the maximum amplitude of the corrected wavefront, while the inter-actuator stroke limits the
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made with a suspension of small (about 10 nm in diameter) ferromagnetic nanoparticles dispersed in a liquid carrier. In the presence of an external magnetic field, the ferromagnetic particles align with the field, the liquid becomes magnetized and its surface acquires a shape governed by the
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P. Laird; R. Bergamasco; V. Berube; E.F. Borra; A. Ritcey; M. Rioux; N. Robitaille; S. Thibault; L. Vieira da Silva Jr; H. Yockell-Lelievre (August 2002). "Ferrofluid-based deformable mirrors: A new approach to adaptive optics using liquid mirrors". In
Wizinowich, Peter L.; Bonaccini, Domenico
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mirrors with discrete actuators are formed by the front surface of a thin deformable membrane. The shape of the plate is controlled by a number of discrete actuators that are fixed to its back side. The shape of the mirror depends on the combination of forces applied to the faceplate, boundary
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The shape of a DM can be controlled with a speed that is appropriate for compensation of dynamic aberrations present in the optical system. In practice the DM shape should be changed much faster than the process to be corrected, as the correction process, even for a static aberration, may take
233:. They enable a higher actuator count at a more cost-effective price allowing for accurate wave-front correction. MEMS mirrors offer fast response times from the actuators with limited hysteresis. An additional benefit is that micromachining technologies allow for the benefit of
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shows how much the movement of one actuator will displace its neighbors. All "modal" mirrors have large cross-coupling, which in fact is good as it secures the high quality of correction of smooth low-order optical aberrations that usually have the highest statistical weight.
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conditions (the way the plate is fixed to the mirror) and the geometry and the material of the plate. These mirrors allow smooth wavefront control with very large - up to several thousands - degrees of freedom.
194:. Numerous methods exist to accurately co-phase the segments and reduce the diffraction patterns introduced by the segment shapes and gaps. Future large space-based telescopes, such as the NASA
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shows how quickly the mirror will react to the control signal. Can vary from microseconds (MEMS and magnetics mirrors) to tens of seconds for thermally controlled DM's.
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or more of its electrodes, causing them to extend laterally, which results in local mirror curvature. Bimorph mirrors are rarely made with more than 100 electrodes.
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will also possess a segmented primary mirror. The development of robust methods to increase the contrast is key for the direct imaging and characterization of
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104:) the mirror can correct. It is very common to compare an arbitrary DM to an ideal device that can perfectly reproduce wavefront modes in the form of
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mirrors are fabricated using bulk and surface micromachining technologies. They consist of a thin reflective membrane controlled by a multitude of
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is the distance between actuator centers. Deformable mirrors with large actuator pitch and large number of actuators are bulky and expensive.
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from previous actuator position commands, and limits the mirror ability to work in a feedforward mode, outside of a feedback loop.
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A DM usually has many degrees of freedom. Typically, these degrees of freedom are associated with the mechanical
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Bifano, T.; Cornelissen, S.; Bierden, P. (2010). "MEMS deformable mirrors in astronomical adaptive optics".
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550:. Proceedings of SPIE Astronomical Telescopes and Instrumentation meeting. Vol. 4839. p. 733.
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the whole mirror surface is called a "modal" function, while localized response is called "zonal".
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Ferrofluid Based
Deformable Mirrors - a New Approach to Adaptive Optics Using Liquid Mirrors
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Madec, P. (2015-06-07). "Overview of
Deformable Mirror Technologies for Adaptive Optics".
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Wallace, Brian P.; Hampton, Peter J.; Bradley, Colin H.; Conan, Rodolphe (2006-10-30).
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to create cheaper and lighter deformable mirrors with a greater number of actuators.
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Facility. The shell is 1120 millimetres across but just 2 millimetres thick.
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453:"Evaluation of a MEMS deformable mirror for an adaptive optics test bench"
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maximum amplitude and gradients of correctable higher-order aberrations.
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636:"Wavefront correction with a 37-actuator ferrofluid deformable mirror"
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1st AO4ELT conference - Adaptive Optics for
Extremely Large Telescopes
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can be used to correct wavefront errors in an astronomical telescope.
342:"OKO Introduces Linear Piezoelectraptiveoptics.org/News_0106_2.html"
229:. MEMS mirrors could break the high price threshold of conventional
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and it can be roughly taken that one actuator corresponds to one
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P. Laird; N. Caron; M. Rioux; E. F. Borra; A. Ritcey (2006).
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Denis
Brousseau; Ermanno F. Borra; Simon Thibault (2007).
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determines the number of degrees of freedom (wavefront
42:whose surface can be deformed, in order to achieve
50:. Deformable mirrors are used in combination with
514:. Optical Society of America. pp. AOTh2C.1.
412:. Paris, France: EDP Sciences. p. 06003.
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381:"Super-thin Mirror for Sharper Star Images"
356:"The VLT's new Deformable Secondary Mirror"
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16:Mirror whose surface can be deformed
196:Large UV Optical Infrared Surveyor
58:. In 2006 they found a new use in
46:control and correction of optical
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54:and real-time control systems in
289:Boston Micromachines Corporation
589:"Ferrofluidic adaptive mirrors"
511:Imaging and Applied Optics 2015
309:Microelectromechanical systems
251:A ferrofluid deformable mirror
93:’s Deformable Secondary Mirror
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206:Continuous faceplate concept
81:Deformable mirror parameters
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521:10.1364/AOMS.2015.AOTh2C.1
327:AO Tutorial: WF correctors
188:James Webb Space Telescope
155:Deformable mirror concepts
270:liquid deformable mirrors
60:femtosecond pulse shaping
427:10.1051/ao4elt/201006003
299:Electrostatic-Pneumatic
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163:Thin shell mirror for
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661:10.1364/OE.15.018190
613:10.1364/AO.45.003495
478:10.1364/OE.14.010132
169:Very Large Telescope
66:several iterations.
652:2007OExpr..1518190B
646:(26): 18190–18199.
605:2006ApOpt..45.3495L
469:2006OExpr..1410132W
463:(22): 10132–10138.
418:2010aoel.confE6003B
106:Zernike polynomials
98:Number of actuators
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235:economies of scale
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125:Influence function
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32:Deformable mirrors
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599:(15): 3495–3500.
566:10.1117/12.459065
531:978-1-943580-00-2
437:978-2-7598-0496-2
385:ESO Announcements
304:Ferrofluid mirror
190:, and the future
179:Segmented concept
132:Actuator coupling
75:degree of freedom
52:wavefront sensors
25:deformable mirror
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388:. Retrieved
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102:inflections
48:aberrations
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365:1 November
321:References
264:Ferrofluid
200:exoplanets
146:Hysteresis
574:119057652
487:1094-4087
227:actuators
148:and creep
71:actuators
44:wavefront
670:19551117
621:16708094
546:(eds.).
495:19529409
277:See also
690:Mirrors
648:Bibcode
601:Bibcode
465:Bibcode
414:Bibcode
390:5 March
266:concept
223:concept
40:mirrors
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570:S2CID
552:arXiv
294:CILAS
284:ALPAO
192:E-ELT
666:PMID
617:PMID
526:ISBN
491:PMID
483:ISSN
432:ISBN
392:2012
367:2016
221:MEMS
89:The
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165:ESO
91:VLT
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