A new deformable mirror architecture for coronagraphic instrumentation

Groff, Tyler D.; Lemmer, Aaron; Riggs, A. J. Eldorado

doi:10.1117/12.2233692

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…Additionally, focus powered DMs are desired to minimize the number of reflections in some systems, for example, in coronagraphs 62 and adaptive optics systems. 31 Mounting geometry optimization and bonding process refinement are also expected to minimize the mounting stress visible in Fig.…”

Section: Summary and Future Workmentioning

confidence: 99%

Demonstration of magnetic and light-controlled actuation of a photomagnetically actuated deformable mirror for wavefront control

et al. 2021

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Deformable mirrors (DMs) have wide applications ranging from astronomical imaging to laser communications and vision science. However, they often require bulky multichannel cables for delivering high power to their drive actuators. A low-powered DM, which is driven in a contactless fashion, could provide a possible alternative to this problem. We present a photomagnetically actuated deformable mirror (PMADM) concept, which is actuated in a contactless fashion by a permanent magnet and low-power laser heating source. We present the laboratory demonstration of prototype optical surface quality, magnetic control of focus, and COMSOL simulations of its precise photocontrol. The PMADM prototype is made of a magnetic composite (polydimethylsiloxane + ferromagnetic CrO 2 ) and an optical-quality substrate layer and is 30.48 mm × 30.48 mm × 175 μm in dimension with an optical pupil diameter of 8 mm. It deforms to 5.76 μm when subjected to a 0.12-T magnetic flux density and relaxes to 3.76 μm when illuminated by a 50-mW laser. A maximum stroke of 8.78 μm before failure is also estimated considering a 3× safety factor. Our work also includes simulation of astigmatism generation with the PMADM, a first step in demonstrating control of higher order modes. A fully developed PMADM may have potential application for wavefront corrections in vacuum and space environments.

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Section: Summary and Future Workmentioning

confidence: 99%

Demonstration of magnetic and light-controlled actuation of a photomagnetically actuated deformable mirror for wavefront control

et al. 2021

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“…Groff et al 5 used a shaped pupil coronagraph (SPC) 8 ripple3 design to do trade studies to determine the efficacy of using parabolic DMs for wavefront control. The study shows that 1) the full width half max (FWHM) of the actuator has a significant effect on the achieveable contrast and 2) the minimum number of the parabolic DM actuators required to achieve the desired high contrasts in broadband light is actually quite modest as long as there is one high actuator density DM at the pupil.…”

Section: Wavefront Control Using Parabolic Dmmentioning

confidence: 99%

“…In addition to this risk, the minimum distance required between the DMs to effectively dig the dark holes for missions such as LUVOIR are so long that it causes packaging issues with the existing rocket fairings. Groff et al 5 showed that the parabolic mirrors used in the optical train could be made deformable with fewer actuator counts than the flat DMs to reduce the risk of a space-based coronagraphic instrument by building redundancy into the DM control. This would also increase through put by reducing the number of optical surfaces.…”

Section: Introductionmentioning

confidence: 99%

Design and modeling of the off-axis parabolic deformable mirror laboratory

Subedi

Juanola-Parramon

Groff

2019

Techniques and Instrumentation for Detection of Exoplanets IX

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Coronagraph-equipped direct imaging missions need an active wavefront control system to cancel out the optical aberrations that degrade the performance of the coronagraphs. A fast steering mirror is used to control Line-of-Sight (LoS) pointing error caused by the telescope jitter. In addition to controlling other low-order aberrations such as astigmatism and coma, high stroke, high actuator density deformable mirrors (DMs) are also used to control the electric field at the required high spatial frequencies. We are designing a testbed to verify a different deformable architecture, where the powered optic in the optical train are controllable and have lower actuator count compared to the existing DMs with flat nominal surfaces. This simplifies the packaging issue for space missions and reduces both cost and risk of having the entire coronagraph instrument's performance depending on one or two high-actuator count DMs. The testbed would also be capable of testing different low-order wavefront sensing algorithms, which focuses in the near-term on a new adaptive Kalman filtering and gradient decent method to estimate the harmonic LoS errors that affect space telescopes. In the long run, we would test different machine learning techniques to estimate low-order aberrations and non-linear algorithms for digging the region of high contrast called the dark holes (DH).

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“…cannot match that of contemporary electrocapacitive or electrostrictive DMs, it possesses a means to tune its nominal optical power via pressure regulation. With the capacity to control nominal focus the DM is no longer restricted to collimated space, and as shown in Groff, et al, 14 when used in conjunction with a high-actuatorcount DM, this enables an entirely new approach to AO system design in which nearly every optical surface is accessible by the closed-loop control law and may thus contribute to the system's overall corrective precision and capability. In this new paradigm, mid-spatial frequency errors are corrected via a series of lower-actuator-count DMs that provide controllability at each conjugate plane within the coronagraph, instead of relying on one or two high-risk, controllable surfaces.…”

Section: Rethinking Ao For Space-based Coronagraphy: Ferrofluid Deformentioning

confidence: 99%

Mathematical and computational modeling of a ferrofluid deformable mirror for high-contrast imaging

et al. 2016

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Deformable mirrors (DMs) are an enabling and mission-critical technology in any coronagraphic instrument designed to directly image exoplanets. A new ferrofluid deformable mirror technology for high-contrast imaging is currently under development at Princeton, featuring a flexible optical surface manipulated by the local electromagnetic and global hydraulic actuation of a reservoir of ferrofluid. The ferrofluid DM is designed to prioritize high optical surface quality, high-precision/low-stroke actuation, and excellent low-spatial-frequency performance-capabilities that meet the unique demands of high-contrast coronagraphy in a space-based platform. To this end, the ferrofluid medium continuously supports the DM facesheet, a configuration that eliminates actuator print-through (or, quilting) by decoupling the nominal surface figure from the geometry of the actuator array. The global pressure control allows independent focus actuation. In this paper we describe an analytical model for the quasi-static deformation response of the DM facesheet to both magnetic and pressure actuation. These modeling efforts serve to identify the key design parameters and quantify their contributions to the DM response, model the relationship between actuation commands and DM surface-profile response, and predict performance metrics such as achievable spatial resolution and stroke precision for specific actuator configurations. Our theoretical approach addresses the complexity of the boundary conditions associated with mechanical mounting of the facesheet, and makes use of asymptotic approximations by leveraging the three distinct length scales in the problem-namely, the low-stroke (∼nm) actuation, facesheet thickness (∼mm), and mirror diameter (∼cm). In addition to describing the theoretical treatment, we report the progress of computational multiphysics simulations which will be useful in improving the model fidelity and in drawing conclusions to improve the design.

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A new deformable mirror architecture for coronagraphic instrumentation

Cited by 4 publications

References 5 publications

Demonstration of magnetic and light-controlled actuation of a photomagnetically actuated deformable mirror for wavefront control

Demonstration of magnetic and light-controlled actuation of a photomagnetically actuated deformable mirror for wavefront control

Design and modeling of the off-axis parabolic deformable mirror laboratory

Mathematical and computational modeling of a ferrofluid deformable mirror for high-contrast imaging

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