TOPICS IN ADAPTIVE OPTICS pot

TOPICSIN ADAPTIVEOPTICS  EditedbyRobertK.Tyson           Topics in Adaptive Optics Edited by Robert K. Tyson Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2011 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Dejan Grgur Technical Editor Teodora Smiljanic Cover Designer InTech Design Team First published January, 2012 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechweb.org Topics in Adaptive Optics, Edited by Robert K. Tyson p. cm. ISBN 978-953-307-949-3 free online editions of InTech Books and Journals can be found at www.intechopen.com   Contents  Preface IX Part 1 Atmospheric Turbulence Measurement 1 Chapter 1 Optical Turbulence Profiles in the Atmosphere 3 Remy Avila Chapter 2 Atmospheric Turbulence Characterization and Wavefront Sensing by Means of the Moiré Deflectometry 23 Saifollah Rasouli Part 2 Imaging and Laser Propagation Systems 39 Chapter 3 Direct Imaging of Extra-Solar Planets – Homogeneous Comparison of Detected Planets and Candidates 41 Ralph Neuhäuser and Tobias Schmidt Chapter 4 AO-Based High Resolution Image Post-Processing 69 Changhui Rao, Yu Tian and Hua Bao Chapter 5 Adaptive Optics for High-Peak-Power Lasers – An Optical Adaptive Closed-Loop Used for High-Energy Short-Pulse Laser Facilities: Laser Wave-Front Correction and Focal-Spot Shaping 95 Ji-Ping Zou and Benoit Wattellier Part 3 Adaptive Optics and the Human Eye 117 Chapter 6 The Human Eye and Adaptive Optics 119 Fuensanta A. Vera-Díaz and Nathan Doble Chapter 7 Adaptive Optics Confocal Scanning Laser Ophthalmoscope 151 Jing Lu, Hao Li, Guohua Shi and Yudong Zhang VI Contents Part 4 Wavefront Sensors and Deformable Mirrors 165 Chapter 8 Advanced Methods for Improving the Efficiency of a Shack Hartmann Wavefront Sensor 167 Akondi Vyas, M. B. Roopashree and B. Raghavendra Prasad Chapter 9 Measurement Error of Shack-Hartmann Wavefront Sensor 197 Chaohong Li, Hao Xian, Wenhan Jiang and Changhui Rao Chapter 10 Acceleration of Computation Speed for Wavefront Phase Recovery Using Programmable Logic 207 Eduardo Magdaleno and Manuel Rodríguez Chapter 11 Innovative Membrane Deformable Mirrors 231 S. Bonora, U. Bortolozzo, G. Naletto and S.Residori   Preface  Advances in adaptive optics technology and applications move forward at a rapid pace.Thebasicideaofwavefrontcompensationinreal‐timehasbeenaroundsincethe mid1970s.Thefirstwidelyusedapplicationofadaptiveopticswasforcompensating atmospheric turbulence effects in astronomical imaging and laser beam propagation. While some topics have been researched and reported for years, even decades, new applications and advances in the supporting technologies occur almost daily. This bookbrings together 11originalchapters ontopics relatedtoadaptiveoptics,written byaninternationalgroupofinvitedauthors. InSection1, DrAvila andDr Rasouli supportthisvolume with2 chapterson optical turbulenceaberrationprofiles, measurement,and characterization.Dr Avila’schapter concentratesonadescriptionoftheturbulentatmosphereandparametersnecessaryto characterizeit,suchasindexofrefractionfluctuations,scintillation,andwindprofiles. Dr Rasouli’s chapter describes turbulence characterization and wavefront sensing by exploitingtheTalboteffectandmoirédeflectometry. In Section 2, specific applications and solutions are addressed. Dr Schmidt and Dr Neuhäusershowhowadaptiveopticsisusedonlargetelescopes,suchasthearrayof four8.2metertelescopesknownastheVeryLargeTelescope(VLT), todirectlyimage  faint objects such as brown dwarfs and extrasolar planets orbiting nearby stars. ProfessorRao andcolleaguespresentachapterdescribinghighresolutionimagepost‐ processing needed to compensate residual aberrations not corrected by the real‐time adaptive optics. This section concludes with a chapter by Professors Zou and Wattellier, who study the adaptive opticsability to compensate wavefronts and spot shapescausedbythermaleffectsinahighpeakpowerlaser. Section 3 is devoted to adaptive optics and the human eye. Dr Doble provides a chapteroverviewofthestructureandopticalaberrationsoftheeyewithpartsdevoted to  adaptive optics retinal imaging and vision testing. Professor Lu and colleagues present a chapter showing the operation of an adaptive optics scanning laser ophthalmoscope,withresultsforretinalimagingincludingsuper‐resolutionandreal‐ timetracking. X Preface Thefinalsection,Section4,concentratesonthesubsystemsofadaptiveoptics,namely the wavefront sensors and deformable mirrors. The first chapter, by Mr. Akondi, provides various solutions for improving a Shack‐Hartman wavefront sensor. These include suchtopics as improvedcentroiding algorithms, spot shape recognition, and applyingasmalldither totheoptics.AchapterbyDrLiandcolleaguesisanextensive investigation of the measurement error associated with a Shack‐Hartmann sensor. A chapterbyDrMagdalenoandDrRodriguezprovidesadetaileddesignofawavefront reconstructorusingfield ‐programmablegatearraytechnologythatcanbridgethe gap tohigh‐speedoperationforthecalculationalburdenofadvancedlargetelescopes.The final chapter, by Dr Bonora and colleagues, describes a number of novel designs of micro‐electro‐mechanical systems (MEMS) deformable mirrors. The novel designs include resistive actuators, photo‐controlled deformations, and a solution to the “push‐pull” problemofconventionalelectrostaticMEMSdeformablemirrors.  RobertK.Tyson,PhD AssociateProfessor DepartmentofPhysicsandOpticalScience UniversityofNorthCarolinaatCharlotte Charlotte,NorthCarolina USA  [...]... Kolmogorov proposed that the kinetic energy is transferred from larger to smaller eddies at a rate that is independent from the eddy spatial scale ρ This is the so called "Kolmogorov cascade" Under this hypothesis, in the case of a completely developed turbulence and considering homogenous and isotropic three-dimensional velocity fluctuations, Kolmogorov showed that the second order structure function1 is... exceeds that of the stratification The quotient of those energies is represented by the mean Richardson number: Ri = ¯ g ∂θ/∂z θ |∂u/∂z|2 ¯ (2) ¯ ¯ where g is the acceleration of gravity, θ is the mean potential temperature, u is the mean wind velocity and z is the vertical coordinate If Ri is higher than 1/4, then the air flow is laminar If Ri is lower than 1/4 but positive, then the flow is turbulent... However, the wave reaching the ground, having gone through multiple this screens along the lowest 20 km of the atmosphere approximately, carries amplitude and phase perturbations In the weak perturbation hypothesis, which is generally valid at astronomical observatories when the zenith angle does not exceed 60◦ , the power spectrum of the fluctuations of the complex amplitude Ψ(r) (r indicating a position... simply as cross-correlation The method is based on the following principle: Let us assume that the turbulent structures are carried by the mean wind without deformation This assumption is known as Taylor hypothesis, and is valid for short enough time intervals In this case, the scintillation pattern produced by a layer at altitude h, where the mean horizontal wind velocity is V(h), moves on the analysis... scintillation produced by a layer at an altitude h 2 and unit CN It differs from the theoretical autocorrelation C only by an eventual temporal decorrelation of the scintillation (partial failure of Taylor hypothesis) and an eventual fluctuation of V(h) during the integration time The decorrelation would make Cc smaller than C , and the fluctuation of V(h) would make Cc smaller and wider than C (Caccia et al.,... the atmospheric turbulence study will be reviewed One of the mean purposes of this chapter is to describe the abilities of the moiré based techniques in the study of atmospheric turbulence with their potentials and limitations Also, in this chapter a new moiré based wavefront sensing technique that can be used for adaptive optics will be presented At the end of this chapter, a brief comparison of use... such as metrology and optical testing It is used to study numerous static physical phenomena such as refractive index gradient (Karny & Kafri, 1982; Ranjbar et al., 2006) In addition, it has a severe potential to study dynamical phenomena such as atmospheric turbulence (Rasouli & Tavassoly, 2006a;b; 2008; Rasouli, 2010), vibrations (Harding & Harris, 1983), nonlinear refractive index measurements (Jamshidi-Ghaleh . Closed-Loop Used for High-Energy Short-Pulse Laser Facilities: Laser Wave-Front Correction and Focal-Spot Shaping 95 Ji-Ping Zou and Benoit Wattellier Part 3 Adaptive Optics and the Human Eye 117. and Wattellier, who study the adaptive opticsability to compensate wavefronts and spot shapescausedbythermaleffectsinahighpeakpowerlaser. Section 3 is devoted to. Shack‐Hartman wavefront sensor. These include suchtopics as improvedcentroiding algorithms, spot shape recognition, and applyingasmalldither totheoptics.AchapterbyDrLiandcolleaguesisanextensive investigation