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Journal ArticleDOI

Open-loop control of a MEMS deformable mirror for large-amplitude wavefront control

01 Dec 2007-Journal of The Optical Society of America A-optics Image Science and Vision (Optical Society of America)-Vol. 24, Iss: 12, pp 3827-3833
TL;DR: In this paper, a method for predicting control voltages that will generate a prescribed surface shape on a MEMS deformable mirror was proposed based on an analytical elastic model of the mirror membrane and an empirical electromechanical model of its actuators.
Abstract: A method is introduced for predicting control voltages that will generate a prescribed surface shape on a MEMS deformable mirror. The algorithm is based upon an analytical elastic model of the mirror membrane and an empirical electromechanical model of its actuators. It is computationally simple and inherently fast. Shapes at the limit of achievable mirror spatial frequencies with up to 1.5 μm amplitudes have been achieved with less than 15 nm rms error.
Citations
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Journal ArticleDOI
TL;DR: The AOSLO can resolve the smallest foveal cones in certain eyes, and this effect within the foveola is confounded by factors other than cone density that have high levels of intersubject variability.
Abstract: PURPOSE. Adaptive optics scanning laser ophthalmoscopy (AOSLO) under optimized wavefront correction allows for routine imaging of foveal cone photoreceptors. The intersubject variability of foveal cone density was measured and its relation to eye length evaluated. METHODS. AOSLO was used to image 18 healthy eyes with axial lengths from 22.86 to 28.31 mm. Ocular biometry and an eye model were used to estimate the retinal magnification factor. Individual cones in the AOSLO images were labeled, and the locations were used to generate topographic maps representing the spatial distribution of density. Representative retinal (cones/mm 2 ) and angular (cones/deg 2 ) cone densities at specific eccentricities were calculated from these maps. RESULTS. The entire foveal cone mosaic was resolved in four eyes, whereas the cones within 0.03 mm eccentricity remained unresolved in most eyes. The preferred retinal locus deviated significantly (P 0.001) from the point of peak cone density for all except one individual. A significant decrease in retinal density (P 0.05) with increasing axial length was observed at 0.30 mm eccentricity but not closer. Longer, more myopic eyes generally had higher angular density near the foveal center than the shorter eyes, but by 1°, this difference was nullified by retinal expansion, and so angular densities across all eyes were similar. CONCLUSIONS. The AOSLO can resolve the smallest foveal cones in certain eyes. Although myopia causes retinal stretching in the fovea, its effect within the foveola is confounded by factors other than cone density that have high levels of intersubject variability. (Invest Ophthalmol Vis Sci. 2010;51:6858‐6867)

169 citations

Journal ArticleDOI
TL;DR: In this article, an electrothermally actuated tip-tilt-piston micromirror with a large optical aperture of 1 mm was designed and tested for biomedical imaging and laser beam steering.
Abstract: This paper presents the design, optimization, fabrication, and test results of an electrothermally actuated tip-tilt-piston micromirror with a large optical aperture of 1 mm. The fabrication of the device is a combination of thin-film surface micromachining and bulk silicon micromachining based on silicon-on-insulator wafers. The device has 3-DOF of actuations, including rotations around two axes in the mirror plane, and out-of-plane piston actuation. The micromirror shows an optical scan range of plusmn30deg about both x- and y-axes and displaces 480 mum in the z-axis, all at dc voltages that are less than 8 V. Dynamic testing of the micromirror shows that the thermal response time of each actuator is about 10 ms. Resonant frequencies of the piston and rotation motion are 336 and 488 Hz, respectively. The unique structural design of the device ensures that there is no lateral shift for the piston motion and no rotation-axis shift for the rotation scanning. With the large tip-tilt-piston scan ranges and low driving voltage, this type of device is very suitable for biomedical imaging and laser beam steering applications.

134 citations

Journal ArticleDOI
TL;DR: Adaptive optics (AO) is a technology used in ground-based astronomy to correct for the wavefront aberrations and loss of image quality caused by atmospheric turbulence.
Abstract: Adaptive optics (AO) is a technology used in ground-based astronomy to correct for the wavefront aberrations and loss of image quality caused by atmospheric turbulence. Provided some difficult technical problems can be overcome, AO will enable future astronomers to achieve nearly diffraction-limited performance with the extremely large telescopes that are currently under development, thereby greatly improving spatial resolution, spectral resolution and observing efficiency which will be achieved. The goal of this topical review is to present to the inverse problems community a representative sample of these problems. In this review, we first present a tutorial overview of the mathematical models and techniques used in current AO systems. We then examine in detail the following topics: laser guidestar adaptive optics, multi-conjugate and multi-object adaptive optics, high-contrast imaging and deformable mirror modeling and parameter identification.

71 citations

Journal ArticleDOI
01 May 2011
TL;DR: A review of the emerging advances in the modeling and control of these micro- and nanoscale devices and converges on the exciting research in on-chip control, with a mechatronics and controls perspective and concludes by projecting future trends.
Abstract: In the current times, microelectromechanical systems and nanoelectromechanical systems form a major interdisciplinary area of research involving science, engineering, and technology. A lot of work has been reported in the area of modeling and control of these devices, with the aim of better understanding their behavior and improving their performance. This paper presents a review of the emerging advances in the modeling and control of these micro- and nanoscale devices and converges on the exciting research in on-chip control , with a mechatronics and controls perspective and concludes by projecting future trends.

65 citations

Journal ArticleDOI
TL;DR: This work derives alternative modal basis sets directly from the actuator influence functions, thus avoiding the approximation errors in the choice of aberration modes in a sensorless adaptive imaging system.

42 citations

References
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Book
01 Jan 1959
TL;DR: In this article, the authors describe the bending of long RECTANGULAR PLATES to a cycloidal surface, and the resulting deformation of shels without bending the plates.
Abstract: CONTENTS: BENDING OF LONG RECTANGULAR PLATES TO A CYLINDRICAL SURFACE PURE BENDING OF PLATES SYMMETRICAL BENDING OF CIRCULAR PLATES SMALL DEFLECTIONS OF LATERALLY LOADED PLATES SIMPLY SUPPORTED RECTANGULAR PLATES RECTANGULAR PLATES WITH VARIOUS EDGE CONDITIONS CONTINUOUS RECTANGULAR PLATES PLATES ON ELASTIC FOUNDATION PLATES OF VARIOUS SHAPES SPECIAL AND APPROXIMATE METHODS IN THEORY OF PLATES BENDING OF ANISTROPIC PLATES BENDING OF PLATES UNDER THE COMBINED ACTION OF LATERAL LOADS AND FORCES IN THE MIDDLE PLANE OF THE PLATE LARGE DEFLECTIONS OF PLATES DEFORMATION OF SHELLS WITHOUT BENDING GENERAL THEORY OF CYLINDRICAL SHELLS SHELLS HAVING THE FORM OF A SURFACE OF REVOLUTION AND LOADED SYMMETRICALLY WITH RESPECT TO THEIR AXIS.

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Book
01 Jan 2001
TL;DR: In this article, a minor numerical error in going from Eq. 16.39 to eq.16.40 is found, which has an obvious effect on the calculations that follow, increasing the minimum detectable temperature change to about 2 mK.
Abstract: p. 445 There is a minor numerical error in going from Eq. 16.39 to Eq. 16.40. The factor of 2 in the 1/f term was omitted, so the correct numerator for the second term in Eq. 16.40 is 1.44 x 10 -7 . This error has an obvious effect on the calculations that follow, increasing the minimum detectable temperature change to about 2 mK (Eq. 16.44) and, correspondingly, increasing the RMS noise calculated from Eq. 16.49 by sqrt(2).

1,917 citations

Book
01 Jan 1965
TL;DR: In this article, the authors propose formulas for stress and strain in the form of formulas for strain and stress, which are derived from the formula for stress-and-stress and strain.
Abstract: Formulas for stress and strain , Formulas for stress and strain , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

1,830 citations

Journal ArticleDOI
01 Nov 1941-Nature
TL;DR: Timoshenko as mentioned in this paper is one of the outstanding exponents of the mathematical theory of elasticity and of the application of this theory to a variety of practical problems, and has written on these topics for thirty years, and his books have become indispensable to every engineer who has to apply mathematical principles and methods to such problems.
Abstract: PROF. TIMOSHENKO is one of the outstanding exponents of the mathematical theory of elasticity and of the application of this theory to a variety of practical problems. He has written on these topics for thirty years, and his books have become indispensable to every engineer who has to apply mathematical principles and methods to such problems. Theory of Plates and Shells By Prof. S. Timoshenko. (Engineering Societies Monographs.) Pp. xii + 492. (New York and London: McGraw–Hill Book Co., Inc., 1940.) 42s.

1,097 citations