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Field Guide to Lidar
Author(s): Paul McManamon
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Book Description

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.

Book Details

Date Published: 30 March 2015
Pages: 168
ISBN: 9781628416541
Volume: FG36

Table of Contents
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Glossary of Symbols and Acronyms

Terms for Active Electro-optic Sensing
Types of Lidars
Lidars for Surface-Scattering (Hard) Targets
Lidars for Volume-Scattering (Soft) Targets
History of Lidar
Lidar Detection Modes
Spatial Coherence
Temporal Coherence
Eye Safety Considerations
Laser Safety Categories
Monostatic versus Bistatic Lidar
Transmit/Receive Isolation

Lidar Range Equation
Lidar Range Equation
Lidar Cross Section
Cross Section of a Corner Cube
Atmospheric Absorption
Atmospheric Scattering
Atmospheric Turbulence
Extended (Deep) Turbulence
Laser Power for Lidar
Lidar Signal-to-Noise Ratio
Direct Detection Signal-to-Noise Ratio
Noise Probability Density Functions
Thermal Noise
The Sun as Background Noise
Dark Current, 1/f, and Excess Noise
Avalanche Photodiodes and Direct Detection
Number of Photons Required for a GMAPD Lidar Camera
Heterodyne Detection
Temporal Heterodyne Detection
Heterodyne Mixing Efficiency
Quadrature Detection
Carrier-to-Noise Ratio for Temporal Heterodyne Detection
Spatial Heterodyne Detection/Digital Holography
SNR for Spatial Heterodyne Detection

Types of Lidars
1D Range-Only Lidar
Tomographic Imaging Lidar
Range-Gated Active Imaging (2D Lidar)
3D Scanning Lidar
3D Flash Imaging
Geiger-Mode APD Flash Lidar
Linear-Mode APD Flash Lidar
Polarization-based Flash Lidar using Framing Cameras
Laser Vibration Detection
Synthetic Aperture Lidar
Inverse Synthetic Aperture Lidar
Range Doppler Imaging Lidar
Laser-Induced Breakdown Spectroscopy
Laser-Induced Fluorescence Lidar
Active Multispectral Lidar
Lidars Using Polarization as a Discriminant
Speckle Imaging Lidar
Phased Array of Phased-Array Imaging Lidar
Multiple Subapertures on Receive for Lidar
Multiple-Input, Multiple-Output Lidar
Methods of Phasing MIMO Lidars

Lidar Sources and Modulations
Lidar Sources and Modulations
Laser Resonators
Three-Level and Four-Level Lasers
Bulk Solid State Lasers for Lidar
Fiber Lasers for Lidar
Higher-Peak-Power Waveguide Lasers for Lidar
Diode Lasers for Lidar
Quantum Cascade Lasers for Lidar
Laser Pumping Considerations
Nonlinear Devices to Change the Lidar Wavelength
Q-Switched Lasers for Lidar
Pockels Cells
Mode-Locked Lasers for Lidar
Laser Seeding for Lidar
Laser Amplifiers for Lidar
Multiple Coherent Laser Transmitters
Laser Waveforms for Lidar
Polypulse Laser Waveforms
Linear Frequency Modulation for Lidar
Pseudo-random-Coded Lidar
RF Modulation of a Direct Detection Lidar

Lidar Receivers
Linear-Mode APD Arrays for Lidar
Geiger-Mode APD Arrays for Lidar
Receivers for Coherent Lidars
Acousto-optic Frequency Shifting
Long-Frame-Time Framing Detectors for Lidar
Gated Framing Cameras for 2D Lidar Imaging
Lidar Image Stabilization
Range Resolution of Lidar
Velocity Resolution of Lidar
Unambiguous Range
Point Spread Function

Beam Steering for Lidars
Gimbals for Use with Lidar
Fast-Steering Mirrors
Risley Prisms and Gratings
Rotating Polygonal Mirrors
Modulo 2π Beam Steering
Largest Steering Angle for an Optical Phased Array
Liquid Crystal Optical Phased Arrays
LC Fringing-Field Effect on Steering Efficiency
Reduction in Steering Efficiency Due to Quantization
Chip-Scale Optical Phased Arrays
MEMS Beam Steering for Lidar
Electrowetting Beam Steering for Lidar
Steerable Electro-evanescent Optical Refractors
Electro-optical Effects
Polarization Birefringent Grating Beam Steering
Step Angle Steering with LC Polarization Gratings
Multiple-Stage LCPGs
Lenslet-based Beam Steering
Electronically Written Lenslets
Mixed-Lenslet Arrays
Holographic Gratings for Beam Steering
Geometrical Optics

Lidar Processing
Inertial Measurement Units
Microscanning of Lidar Images for Improved Sampling
Range Measurement Processing
Nyquist Sampling a Range Profile
Threshold, Leading Edge, and Peak Detectors
Range Resolution, Precision, and Accuracy
Fourier Transforms
Developing 3D Maps from Lidar
3D Metrics for Lidar Images
Multiple-Subaperture Spatial Heterodyne Processing
Definitions of Lidar Data Processing Stages
Processing Laser Vibrometry Data
Target Classification Using Lidar

Equation Summary

Figure Sources



This Field Guide covers active electro-optical sensing, in which a sensor sends out a laser pulse and then measures the parameters of the return signal. Various groups refer to this type of sensor as a ladar, lidar, LIDAR, LADAR, or laser radar. For simplicity, only the term lidar is used throughout this book.

The book is presented from the perspective of a lidar engineer. It covers a wide breadth, from simple 2D directdetection lidars to multiple subaperture synthetic aperture lidars. It also covers a broad range of objects to be viewed, and distances from which to view the objects. Lasers and modulation are discussed in the context of their use in lidars. Other topics covered include receivers, apertures, and atmospheric effects in the context of lidar use and design.

All lidars will be limited by the media between the lidar and the target, but atmospheric compensation techniques can often mitigate this limitation. These limitations and compensation approaches are presented. Many types of lidars are included along with appropriate data processing techniques. 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 Field Guide is a handy reference to quickly access information on any aspect of lidars. It will be useful to students and lidar scientists or engineers who need an occasional reminder of the correct approaches or equations to use in certain applications. It will also be useful to systems engineers gaining a perspective on this rapidly growing technology.

Paul McManamon
March 2015

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