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Spie Press Book

Field Guide to Adaptive Optics, Second Edition
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Book Description

This Field Guide provides a summary of the methods for determining the requirements of an adaptive optics system, the performance of the system, and the requirements for the components of the system. Many of the expressions are in the form of integrals, in which case the authors show the results graphically for a variety of practical values. This second edition has a greatly expanded presentation of adaptive optics control system design and operation. Discussions of control models are accompanied by various recommendations for implementing the algorithms in hardware.

Book Details

Date Published: 13 April 2012
Pages: 142
ISBN: 9780819490179
Volume: FG24

Table of Contents
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Glossary

Introduction
Conventional Adaptive Optics System
Image Spread with Atmospheric Turbulence
The Principle of Phase Conjugation
Point Spread Function for an Astronomical Telescope

Modeling the Effect of Atmospheric Turbulence
Fried's Coherence Length
Isoplanatic Angle
Kolmogorov Model
Atmospheric Turbulence Models
Coherence Length for Various Wavelengths and Turbulence Models
Greenwood Frequency
Wind Models
Scintillation
Zernike Polynomials
Legendre Polynomials
Angle of Arrival (Tilt) Fluctuations (Image Motion)
Modulation Transfer Function

Beam Propagation
System Performance Estimation
Modal and Zonal Fitting Error

Wavefront Sensors
Partial Correction
Shack-Hartmann Wavefront Sensor and Error
Shack-Hartmann Lenslet Array Selection
Curvature Wavefront Sensor and Error
Pyramid Wavefront Sensor and Error

Deformable Mirrors
Photodiodes
Photodiode Noise
Lateral-Effect Position-Sensing Detectors
Quad Cells
Noise Equivalent Angle
The Strehl Ratio: Laser-Beam Propagation to the Far Field with Wavefront Error
Strehl Ratio
Laser "Brightness"
Laser Beam Quality
Astronomical "Brightness"
Spot Size for a Gaussian Beam
Spot Size for a Uniform Circular Aperture
Temporal Error
Focal Anisoplanatism (the "Cone Effect")
Laser Guide Stars
Subsystem Requirements: The Wavefront Sensor
Angular Isoplanatic Error
Subsystem Requirements: Tilt Mirror
Subsystem Requirements: How many actuators? Zonal or Modal Control
Subsystem Requirements: Deformable Mirror
Deformable Mirror Actuator Configurations
Ferroelectric Actuators
Electrostatic Actuators
Voice Coil Actuators
Deformable Mirror Influence Function Models
Bimorph and MEMS Mirrors
Segmented Deformable Mirrors

Control and Reconstruction
Actuator and Wavefront Sensor Layouts
Correctability and Flattening of a Deformable Mirror
Adaptive Optics System Feedback Configuration
Deformable Mirror Dynamic Model
Controller Dynamic Model
Wavefront Sensor Dynamic Model
Latency
One-Dimensional Sampling
Two-Dimensional Sampling
Temporal Sampling Rate Selection
System Stability
General Control-System Parameters
Sensitivity Functions
Bandwidth Estimation from Controller Gains
Poke Matrix
Example System Geometry
Singular-Value Decomposition of the Poke Matrix
Actuator and Subaperture Observability
Identification of Actuator Locations
Poke Matrix Smoothing
Actuator Slaving: Active Actuator Identification
Actuator Slaving: Slave Logic
Adding Slaving into the Reconstructor
Tilt Removal
Piston and Waffle Removal
Reconstructor Generation: Least Squares
Reconstructor Generation: Regularization
T-Filter
Modal Suppression
Interactuator Shear Suppression
Nullspace Suppression
Weighting Matrices
Modal Feedback
Reconstructor Generation: Procedure
Reconstructor Comparison
Slope Discrepancy
Offloads and Woofer-Tweeter Systems
Open-Loop Wavefront Estimation
Kalman Filtering
Multivariable System Performance
Disturbance Injection
Wavefront Sensor Calibration
Centroiding and Thresholding
Misregistration
Subaperture Spillover

Equation Summary

Bibliography

Index


There have been a number of books and thousands of papers published with descriptions and mathematical expressions regarding adaptive optics. The material in this Field Guide is a summary of the methods for determining the requirements of an adaptive optics system, the performance of the system, and requirements for the components of the system. This second edition has a greatly expanded presentation of adaptive optics control system design and operation. Discussions of control models are accompanied by various recommendations for implementing the algorithms in hardware.

This book is not just another book on adaptive optics. There are already many fine volumes. This volume is intended for students, researchers, and practicing engineers who want a "go to" book when the calculation was "needed yesterday" (by a customer who won't be paying for it until the next fiscal year).

Many of the expressions are in the form of integrals. When that is the case, we show the results graphically for a variety of practical values. Some of the material in this volume duplicates similar expressions found in other volumes of the Field Guide series. We have attempted to remain consistent with symbols of the other volumes. In some cases, however, we chose different symbols because they are well known within the adaptive optics literature.

Descriptions of the operation of subsystems and components and specific engineering aspects remain in the citations of the Bibliography.

This Field Guide is dedicated to the late Horace Babcock, whose pioneering ideas created the field of adaptive optics.

Robert K. Tyson
Benjamin W. Frazier
April 2012


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