This Field Guide covers the various components and types of active electro-optical sensors referred to as lidars in the text from simple 2D direct-detection lidars to multiple subaperture synthetic aperture lidars. Other topics covered include receivers, apertures, atmospheric effects, and appropriate processing of different lidars. Lasers and modulation are presented in terms of their use in lidars. The lidar range equation in its many variations is discussed along with receiver noise issues that determine how much signal must be received to detect an object. This book is a handy reference to quickly look up any aspect of active electro-optical sensors. It will be useful to students, lidar scientists, or engineers needing an occasional reminder of the correct approaches or equations in certain applications, and systems engineers interested in gaining a perspective on this rapidly growing technology.
Author(s): Paul McManamon
Series: SPIE Field Guide FG36
Publisher: SPIE Press
Year: 2015
Language: English
Pages: 168
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Glossary of Symbols and Acronyms x
Introduction 1
Introduction 1
Terms for Active Electro-optic Sensing 2
Types of Lidars 3
Lidars for Surface-Scattering (Hard) Targets 4
Lidars for Volume-Scattering (Soft) Targets 5
History of Lidar 6
Lidar Detection Modes 7
Spatial Coherence 8
Temporal Coherence 9
Eye Safety Considerations 10
Laser Safety Categories 11
Monostatic versus Bistatic Lidar 12
Transmit/Receive Isolation 13
Lidar Range Equation 14
Lidar Range Equation 14
Lidar Cross Section 15
Cross Section of a Corner Cube 16
Speckle 17
Atmospheric Absorption 18
Atmospheric Scattering 19
Atmospheric Turbulence 20
Aero-optical Effects on Lidar 21
Extended (Deep) Turbulence 22
Laser Power for Lidar 23
Lidar Signal-to-Noise Ratio 24
Direct Detection Signal-to-Noise Ratio 25
Noise Probability Density Functions 26
Thermal Noise 27
Shot Noise 28
The Sun as Background Noise 29
Dark Current, 1/f, and Excess Noise 30
Avalanche Photodiodes and Direct Detection 31
Number of Photons Required for a GMAPD Lidar
Camera 32
Heterodyne Detection 33
Temporal Heterodyne Detection 34
Heterodyne Mixing Efficiency 35
Quadrature Detection 36
Carrier-to-Noise Ratio for Temporal
Heterodyne Detection 37
Spatial Heterodyne Detection/Digital Holography 38
SNR for Spatial Heterodyne Detection 39
Types of Lidars 40
1D Range-Only Lidar 40
Tomographic Imaging Lidar 41
Range-Gated Active Imaging (2D Lidar) 42
3D Scanning Lidar 43
3D Flash Imaging 44
Geiger-Mode APD Flash Lidar 45
Linear-Mode APD Flash Lidar 46
Polarization-based Flash Lidar using Framing
Cameras 47
Laser Vibration Detection 48
Synthetic Aperture Lidar 49
Inverse Synthetic Aperture Lidar 50
Range Doppler Imaging Lidar 51
Laser-Induced Breakdown Spectroscopy 52
Laser-Induced Fluorescence Lidar 53
Active Multispectral Lidar 54
Lidars Using Polarization as a Discriminant 55
Speckle Imaging Lidar 56
Phased Array of Phased-Array Imaging Lidar 57
Multiple Subapertures on Receive for Lidar 58
Multiple-Input, Multiple-Output Lidar 59
Methods of Phasing MIMO Lidars 60
Lidar Sources and Modulations 61
Lidar Sources and Modulations 61
Laser Resonators 62
Three-Level and Four-Level Lasers 63
Bulk Solid State Lasers for Lidar 64
Fiber Lasers for Lidar 65
Higher-Peak-Power Waveguide Lasers for Lidar 66
Diode Lasers for Lidar 67
Quantum Cascade Lasers for Lidar 68
Laser Pumping Considerations 69
Nonlinear Devices to Change the Lidar Wavelength 70
Q-Switched Lasers for Lidar 71
Pockels Cells 72
Mode-Locked Lasers for Lidar 73
Laser Seeding for Lidar 74
Laser Amplifiers for Lidar 75
Multiple Coherent Laser Transmitters 76
Laser Waveforms for Lidar 77
Polypulse Laser Waveforms 78
Linear Frequency Modulation for Lidar 79
Pseudo-random-Coded Lidar 80
RF Modulation of a Direct Detection Lidar 81
Lidar Receivers 82
Linear-Mode APD Arrays for Lidar 82
Geiger-Mode APD Arrays for Lidar 83
Receivers for Coherent Lidars 84
Acousto-optic Frequency Shifting 85
Long-Frame-Time Framing Detectors for Lidar 86
Gated Framing Cameras for 2D Lidar Imaging 87
Lidar Image Stabilization 88
Range Resolution of Lidar 89
Velocity Resolution of Lidar 90
Unambiguous Range 91
Point Spread Function 92
Beam Steering for Lidars 93
Gimbals for Use with Lidar 93
Fast-Steering Mirrors 94
Risley Prisms and Gratings 95
Rotating Polygonal Mirrors 96
Modulo 2p Beam Steering 97
Largest Steering Angle for an Optical Phased Array 98
Liquid Crystal Optical Phased Arrays 99
LC Fringing-Field Effect on Steering Efficiency 100
Reduction in Steering Efficiency Due to
Quantization 101
Chip-Scale Optical Phased Arrays 102
MEMS Beam Steering for Lidar 103
viii
Field Guide to Lidar
Electrowetting Beam Steering for Lidar 104
Steerable Electro-evanescent Optical Refractors 105
Electro-optical Effects 106
Polarization Birefringent Grating Beam Steering 107
Step Angle Steering with LC Polarization Gratings 108
Multiple-Stage LCPGs 109
Lenslet-based Beam Steering 110
Electronically Written Lenslets 111
Mixed-Lenslet Arrays 112
Holographic Gratings for Beam Steering 113
Geometrical Optics 114
Lidar Processing 115
Inertial Measurement Units 115
Microscanning of Lidar Images for Improved
Sampling 116
Range Measurement Processing 117
Nyquist Sampling a Range Profile 118
Threshold, Leading Edge, and Peak Detectors 119
Range Resolution, Precision, and Accuracy 120
Fourier Transforms 121
Developing 3D Maps from Lidar 122
3D Metrics for Lidar Images 123
Multiple-Subaperture Spatial Heterodyne
Processing 124
Definitions of Lidar Data Processing Stages 125
Processing Laser Vibrometry Data 126
Target Classification Using Lidar 127
Equation Summary 128
Figure Sources 138
Bibliography 141
Index 143
