Why Adaptive Secondaries?

Lee, J. H.; Bigelow, Bruce C.; Walker, David D.; Doel, A. P.; Bingham, R. G.

doi:10.1086/316496

Cited by 6 publications

(6 citation statements)

References 11 publications

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“…1). Lee et al 1 present a detailed case in favor of an adaptive secondary. Besides the reduced infrared emissivity, the optical throughput is greatly increased.…”

Section: Adaptive Secondariesmentioning

confidence: 99%

Application of distributed control techniques to the adaptive secondary mirror of Cornell's Large Atacama Telescope

2003

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In this paper we apply, recently developed, distributed control techniques to the control of an adaptive secondary mirror. The control technique implemented uses the l 2 induced norm as a performance criterion. A finite difference model for the mirror is developed using shift operators. We determine the necessary constants from the physical properties of the mirror, from the typical dimensions of such a system, and from our performance requirements for operating the telescope in the near and mid-infrared region.The closed loop system is simulated by modelling the deformable mirror in Abaqus, a commercial finite element software, and by implementing the controller in Matlab.

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“…1). Lee et al 1 present a detailed case in favor of an adaptive secondary. Besides the reduced infrared emissivity, the optical throughput is greatly increased.…”

Section: Adaptive Secondariesmentioning

confidence: 99%

Application of distributed control techniques to the adaptive secondary mirror of Cornell's Large Atacama Telescope

2003

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“…The other notable advantages are (i) enhanced photon throughput that measures the proportion of light which is transmitted through an optical set-up, (ii) introduction of negligible extra IR emissivity, (iii) causes no extra polarization, and (iv) non-addition of reflective losses (Lee et al 2000). Due to the interactuator spacing, the resonant frequency of such a mirror may be lower than the AO bandwidth.…”

Section: Adaptive Secondary Mirrorsmentioning

confidence: 99%

“…On Earth, ozone is photochemically produced from O 2 and, as a component of the stratosphere, is not masked by other gases. Finding ozone would, therefore, indicate a significant quantity of O 2 that should have been produced by photosynthesis (Léger et al 1993). Moreover, for a star-like the Sun, detecting ozone can be done 1000 times faster than detecting O 2 at 0.76 µm: estimates made by Angel and Woolf (1997) show that the requirements for planet detection in the visible with an 8 m telescope are not detectable with current technology.…”

Section: Astrobiologymentioning

confidence: 99%

“…The usage of a adaptive secondary mirror (ASM) for corrections making relay optics obsolete that are required to conjugate a DM at a reimaged pupil, as well as to minimize thermal emission is a new key innovation (Bruns et al 1997). The other notable advantages are (i) enhanced photon throughput that measures the proportion of light which is transmitted through an optical set-up, (ii) introduction of negligible extra IR emissivity, (iii) causes no extra polarization, and (iv) non-addition of reflective losses (Lee et al 2000). Due to the interactuator spacing, the resonant frequency of such a mirror may be lower than the AO bandwidth.…”

Section: Adaptive Secondary Mirrorsmentioning

confidence: 99%

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Modern optical astronomy: technology and impact of interferometry

Saha

2002

Rev. Mod. Phys.

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The present 'state of the art' and the path to future progress in high spatial resolution imaging interferometry is reviewed. The review begins with a treatment of the fundamentals of stellar optical interferometry, the origin, properties, optical effects of turbulence in the Earth's atmosphere, the passive methods that are applied on a single telescope to overcome atmospheric image degradation such as speckle interferometry, and various other techniques. These topics include differential speckle interferometry, speckle spectroscopy and polarimetry, phase diversity, wavefront shearing interferometry, phase-closure methods, dark speckle imaging, as well as the limitations imposed by the detectors on the performance of speckle imaging. A brief account is given of the technological innovation of adaptive-optics (AO) to compensate such atmospheric effects on the image in real time. A major advancement involves the transition from single-aperture to the dilute-aperture interferometry using multiple telescopes. Therefore, the review deals with recent developments involving ground-based, and space-based optical arrays. Emphasis is placed on the problems specific to delay-lines, beam recombination, polarization, dispersion, fringe-tracking, bootstrapping, coherencing and cophasing, and recovery of the visibility functions. The role of AO in enhancing visibilities is also discussed. The applications of interferometry, such as imaging, astrometry, and nulling are described. The mathematical intricacies of the various 'post-detection' image-processing techniques are examined critically. The review concludes with a discussion of the astrophysical importance and the perspectives of interferometry.

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“…5,6 Finally, a group is working on development of deformable carbonfiber-reinforced mirrors using magnetostrictive actuators. [7][8][9] Related to studies of an ELT with a primary mirror diameter of 50 m ͑the Euro50͒ at Lund Observatory, 10 a conceptual design of a 4-m DM has been undertaken and an actuator test stand built. Here we report on the progress of that work.…”

Section: Introductionmentioning

confidence: 99%

Novel concept for large deformable mirrors

et al. 2006

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Large, high-bandwidth deformable mirrors ͑DMs͒ with thousands of actuators for adaptive optics are of high interest for existing large telescopes and indispensable for construction of efficient future extremely large telescopes. Different actuation and sensing principles are possible. We propose a novel concept using commercially available voice coil actuators attached to the back of the mirror with suction cups and using LVDT sensors on the actuators for local stabilization. Also, a new low-cost sensor for easy measurement of DM displacement or velocity has been developed. It has a sensitivity better than 20 nm and a bandwidth wider than 20 to 1000 Hz. Finally, studies are in progress of global, hierarchical mirror form controllers based on many parallel multiple-input, multiple-output regulators of low order.

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Why Adaptive Secondaries?

Cited by 6 publications

References 11 publications

Application of distributed control techniques to the adaptive secondary mirror of Cornell's Large Atacama Telescope

Application of distributed control techniques to the adaptive secondary mirror of Cornell's Large Atacama Telescope

Modern optical astronomy: technology and impact of interferometry

Novel concept for large deformable mirrors

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