Principles Of Adaptive Optics

Principles of Adaptive Optics covers the basic principles of optics, wavefront sensing, controls, and wavefront correction that encompass the specialized field called adaptive optics. This book is composed of eight chapters that summarize the fundamental technology developments and the basic understanding of the various disciplines used in adaptive optics. After briefly reviewing the history, background, and developments of adaptive optics, this book goes on discussing the many sources of phase aberrations addressed by adaptive optics systems, such as linear effects due to turbulence, optical manufacturing, and misalignments, as well as errors that result from nonlinear thermal effects and fluid properties. The subsequent chapter deals with the performance enhancing role of adaptive optics systems in various disturbances. Other chapters describe the wavefront sampling, sensing, and correction subsystems. The concluding chapters explore the fundamental principles behind the adaptive optics control system and present summary expressions to determine the basic system parameters of an adaptive optics atmospheric compensation system. Communication scientists and engineers will find this work invaluable.

Table of Contents:
Foreword Preface 1 History and Background 1.1 Introduction 1.2 History 1.3 Physical Optics 1.3.1 Propagation with aberrations 1.3.2 Imaging with aberrations 1.3.3 Engineering terms 1.3.4 Representing the wavefront 1.3.5 Interference 1.4 Adaptive Optics Terms 2 Sources of Aberrations 2.1 Atmospheric Turbulence 2.1.1 Descriptions of atmospheric turbulence 2.1.2 Refractive index structure constant 2.1.3 Propagation effects, intensity variation 2.1.4 Propagation effects, phase variation 2.1.5 Fried's coherence length 2.1.6 Time dependence of turbulence 2.2 Thermal Blooming 2.2.1 Blooming strength and critical power 2.2.2 Turbulence, jitter, and thermal blooming 2.3 Non-atmospheric Sources 2.3.1 Optical misalignments and jitter 2.3.2 Thermally induced distortions of optics 2.3.3 Manufacturing and microerrors 2.3.4 Other sources of aberrations 3 Adaptive Optics Systems 3.1 Phase Conjugation 3.2 Conventional Adaptive Optics Concepts 3.2.1 Outgoing wave concepts 3.2.2 Adaptive imaging concepts 3.2.3 Return wave approach 3.2.4 Predictive adaptive optics approach 3.2.5 Combined outgoing and return wave approaches 3.2.6 Pros and cons of the various approaches 3.3 Unconventional Adaptive Optics 3.3.1 Nonlinear optics 3.3.2 Elastic photon scattering, DFWM 3.3.3 Inelastic photon scattering 3.4 Limitations of Phase Conjugation 3.4.1 Limitation on turbulence compensation 3.4.2 Limitations for other random wavefronts 3.4.3 Limitations for deterministic wavefronts 3.4.4 Partial phase conjugation 3.5 System Engineering Methods 3.6 Practical Engineering Guidelines 4 Wavefront Sampling 4.1 Introduction 4.2 Transmissive Samplers 4.2.1 Beamsplitters 4.2.2 Hole gratings 4.3 Reflective Samplers 4.3.1 Temporal duplexing 4.3.2 Reflective wedges 4.3.3 Diffraction gratings 4.4 Hybrids 4.5 Sensitivities of Sampler Concepts5 Wavefront Sensing 5.1 Directly Measuring Phase 5.1.1 The non-uniqueness of the diffraction pattern 5.1.2 Determining phase information from intensity 5.1.3 Modal and zonal sensing 5.2 Direct Wavefront Sensing — Modal 5.2.1 Importance of wavefront tilt 5.2.2 Measurement of tilt 5.2.3 Focus sensing 5.2.4 Modal sensing of higher-order aberrations 5.3 Direct Wavefront Sensing — Zonal 5.3.1 Interferometric wavefront sensing 5.3.2 Hartmann wavefront sensors 5.4 Indirect Wavefront Sensing Methods 5.4.1 Multidither adaptive optics 5.4.2 Image sharpening 5.5 Special Considerations 5.5.1 Detectors 5.5.2 Noise 6 Wavefront Correction 6.1 Introduction 6.2 Basic Forms of Wavefront Correction 6.2.1 Modal tilt correction 6.2.2 Modal higher-order correction 6.2.3 Multichannel correction 6.3 Bimorph Corrector Mirrors 6.4 Membrane Mirrors 6.5 Discrete Actuator Deformable Mirrors 6.5.1 Actuation techniques 6.5.2 Recent developments in discrete actuator DMs 6.6 Edge Actuation 6.7 Large Correcting Optics 6.8 Special Correction Devices 6.8.1 Spatial light modulators 6.8.2 Charged-large-array mirrors 6.9 Design and Selection Principles7 Reconstruction and Controls 7.1 Introduction 7.2 Single-Channel Linear Control 7.2.1 Fundamental control tools 7.2.2 Transfer functions 7.2.3 Proportional control 7.2.4 First- and second-order lag 7.2.5 Feedback 7.2.6 Frequency response of control systems 7.2.7 Digital controls 7.3 Multivariate Adaptive Optics Controls 7.3.1 Solution of linear equations 7.4 Direct Wavefront Reconstruction 7.4.1 Phase from wavefront slopes 7.4.2 Modes from wavefront slopes 7.4.3 Phase from wavefront modes 7.4.4 Modes from wavefront modes 7.4.5 Zonal corrector from continuous phase 7.4.6 Modal corrector from continuous phase 7.4.7 Zonal corrector from modal phase 7.4.8 Modal correctors from modal phase 7.4.9 Indirect reconstructions 7.4.10 Modal corrector from wavefront modes 7.4.11 Zonal corrector from wavefront slopes 7.5 Spatiotemporal Considerations 8 Atmospheric Compensation Summary Bibliography Figure Credits Index