Library of Congress Cataloging-in-Publication Data

Daniels, Arnold.

Field guide to infrared systems, detectors, and FPAs / Arnold

Daniels. − 2^nd ed.

p. cm. − (The field guide series)

Rev. ed of: Field guide to infrared systems / Arnold Daniels.

© 2007.

Includes bibliographical references and index.

ISBN 978-0-8194-8080-4 (alk. paper)

1. Infrared technology–Handbooks, manuals, etc. 2. Optical detectors—Handbooks, manuals, etc. 3. Focal planes–Handbooks, manuals, etc. I. Title.

TA1570.D36 2010

621.362–dc22

2010000421

Published by

SPIE

P.O. Box 10

Bellingham, Washington 98227-0010 USA

Phone: +1.360.676.3290

Fax: +1.360.647.1445

Email: books@spie.org

Web: http://spie.org

The content of this book reflects the work and thought of the author. Every effort has been made to publish reliable and accurate information herein, but the publisher is not responsible for the validity of the information or for any outcomes resulting from reliance thereon.

Printed in the United States of America.

Introduction to the Series

Welcome to the SPIE Field Guides—a series of publications written directly for the practicing engineer or scientist. Many textbooks and professional reference books cover optical principles and techniques in depth. The aim of the SPIE Field Guides is to distill this information, providing readers with a handy desk or briefcase reference that provides basic, essential information about optical principles, techniques, or phenomena, including definitions and descriptions, key equations, illustrations, application examples, design considerations, and additional resources. A significant effort will be made to provide a consistent notation and style between volumes in the series.

Each SPIE Field Guide addresses a major field of optical science and technology. The concept of these Field Guides is a format-intensive presentation based on figures and equations supplemented by concise explanations. In most cases, this modular approach places a single topic on a page, and provides full coverage of that topic on that page. Highlights, insights, and rules of thumb are displayed in sidebars to the main text. The appendices at the end of each Field Guide provide additional information such as related material outside the main scope of the volume, key mathematical relationships, and alternative methods. While complete in their coverage, the concise presentation may not be appropriate for those new to the field.

The SPIE Field Guides are intended to be living documents. The modular page-based presentation format allows them to be updated and expanded. We are interested in your suggestions for new Field Guide topics as well as what material should be added to an individual volume to make these Field Guides more useful to you. Please contact us at fieldguides@SPIE.org.

John E. Greivenkamp, Series Editor

College of Optical Sciences

The University of Arizona

The Field Guide Series

Field Guide to Geometrical Optics, John E. Greivenkamp (FG01)

Field Guide to Atmospheric Optics, Larry C. Andrews (FG02)

Field Guide to Adaptive Optics, Robert K. Tyson & Benjamin W. Frazier (FG03)

Field Guide to Visual and Ophthalmic Optics, Jim Schwiegerling (FG04)

Field Guide to Polarization, Edward Collett (FG05)

Field Guide to Optical Lithography, Chris A. Mack (FG06)

Field Guide to Optical Thin Films, Ronald R. Willey (FG07)

Field Guide to Spectroscopy, David W. Ball (FG08)

Field Guide to Infrared Systems, Arnold Daniels (FG09)

Field Guide to Interferometric Optical Testing, Eric P. Goodwin & James C. Wyant (FG10)

Field Guide to Illumination, Angelo V. Arecchi; Tahar Messadi; R.John Koshel (FG11)

Field Guide to Lasers, Rüdiger Paschotta (FG12)

Field Guide to Microscopy, Tomasz S. Tkaczyk (FG13)

Field Guide to Laser Pulse Generation, Rüdiger Paschotta (FG14)

Field Guide to Infrared Systems, Detectors, and FPAs, Second Edition, Arnold Daniels (FG15)

Field Guide to Laser Fiber Technology, Rüdiger Paschotta (FG16)

Field Guide to Infrared Systems, Detectors, and FPAs, 2^nd Edition

Field Guide to Infrared Systems, Detectors, and FPAs, Second Edition, is written to clarify and summarize the theoretical and practical principles of modern infrared technology. It is intended as a reference for the practicing engineer and/or scientist who requires effective practical information to design, build, and/or test infrared equipment in a wide variety of applications.

This book combines numerous engineering disciplines necessary for the development of an infrared system. It describes the basic elements involving image formation and image quality, radiometry and flux transfer, and explains the figures of merit for detector performance. It considers the development of search infrared systems and specifies the main descriptors used to characterize thermal imaging systems. Furthermore, this guide clarifies, identifies, and evaluates the engineering tradeoffs in the design of an infrared system.

The 2^nd edition provides the reader with an up-to-date view of the various third-generation infrared focal plane array (IRFPA) technologies currently in use or being actively researched. It also includes an overview of a new target acquisition model known as the “Targeting Task Performance (TTP) metric.” The applicability of this range performance model extends to sample imagers, digital image enhancement, and other features of modern imaging systems.

I would like to acknowledge and express my gratitude to my professor and mentor Dr. Glenn Boreman for his guidance, experience, and friendship. The knowledge that he passed on to me during my graduate studies at CREOL ultimately contributed to the creation of this book. I also would like to thank Dr. Boreman for reviewing a draft copy of the IRFPA 2^nd edition manuscript.

I extend my sincere appreciation to Dr. Mel Friedman, NVESD, who took upon himself the onerous task of improving and clarifying the TTP metric concepts and its contents.

Above all, I voice a special note of gratitude to my kids Becky and Alex and my wife Rosa for their love and support.

Lastly, I would particularly like to thank you, the reader, for selecting this book and taking the time to explore the topics related to this motivating and exciting field. I trust that the contents of this book will prove interesting and useful to engineers and scientists working in one of the various infrared fields.

This Field Guide is dedicated to the memory of my father and brothers.

Arnold Daniels

October 2010

Table of Contents

Glossary of Symbols xi

Introduction 1

Electromagnetic Spectrum 1

Infrared Concepts 2

Optics 3

Imaging Concepts 3

Magnification Factors 4

Thick Lenses 5

Stops and Pupils 6

F-number and Numerical Aperture 7

Field of View 8

Combination of Lenses 9

Afocal Systems and Refractive Telescopes 10

Cold-Stop Efficiency and Field Stop 11

Image Quality 12

Image Anomalies in Infrared Systems 14

Infrared Materials 15

Ceramic and Amorphous Materials 19

GASIR Chalcogenide Glass Materials 20

Material Dispersion 21

Atmospheric Transmittance 23

Radiometry and Sources 24

Solid Angle 24

Radiometry 25

Radiometric Terms 26

Flux Transfer 28

Flux Transfer for Image-Forming Systems 29

Source Configurations 30

Blackbody Radiators 32

Planck’s Radiation Law 33

Stefan-Boltzmann and Wien’s Displacement Laws 35

Rayleigh-Jeans and Wien’s Radiation Laws 36

Exitance Contrast 37

Emissivity 38

Kirchhoff’s Law 39

Emissivity of Various Common Materials 40

Radiometric Measure of Temperature 41

Collimators 43

Performance Parameters for Optical Detectors 44

Infrared Detectors 44

Primary Sources of Detector Noise 45

Noise Power Spectral Density 46

White Noise 47

Noise-Equivalent Bandwidth (NEDΔf) 48

Shot Noise 50

Signal-to-Noise Ratio: Detector and BLIP Limits 51

Generation-Recombination Noise 52

Johnson Noise 53

1/f Noise and Temperature Noise 54

Detector Responsivity 55

Spectral Responsivity 57

Blackbody Responsivity 58

Noise-Equivalent Power 59

Specific or Normalized Detectivity 60

Photovoltaic Detectors or Photodiodes 61

Sources of Noise in PV Detectors 62

Expressions for D^*_PV,BLIP, D^**_PV,BLIP, and D^* _PV,JOLI 63

Photoconductive Detectors 64

Sources of Noise in PC Detectors 65

Third-Generation Infrared Imagers 66

Indium Antimonite (InSb) Photodiodes 67

Mercury Cadmium Telluride (HgCdTe) Photodetectors 68

Control of the Alloy Composition 69

HgCdTe Photodiodes and FPAs 70

DLHJ Photodiodes 71

Dual-Band HgCdTe FPAs 72

HDVIP Photodiodes 73

Uncooled HgCdTe Photodiodes 75

Quantum Well Infrared Photodetectors (QWIPs) 77

Types of QWIPs 80

Superlattices (SLs) 82

Multispectral QWIPs 83

Light Couplers 85

Pyroelectric Detectors 88

Pyroelectric Detectors—Mathematical Approach 90

Microbolometers 93

Microbolometers—Mathematical Approach 96

Infrared Dynamic Scene Simulators 99

Thermoelectric Detectors 100

Infrared Systems 101

Raster Scan Format: Single-Detector 101

Multiple-Detector Scan Formats: Serial Scene Dissection 103

Multiple-Detector Scan Formats: Parallel Scene Dissection 104

Staring Systems 105

Search Systems and Range Equation 106

Noise-Equivalent Irradiance 109

Performance Specification: Thermal-Imaging Systems 110

Modulation Transfer Function (MTF) Definitions 111

Optics MTF: Calculations 114

Electronics MTF: Calculations 116

MTF Measurement Setup and Sampling Effects 117

MTF Measurement Techniques: PSF and LSF 118

MTF Measurement Techniques: ESF and CTF 119

MTF Measurement Techniques: Noiselike Targets 121

MTF Measurement Techniques: Interferometry 123

Noise-Equivalent Temperature Difference (NETD) 124

NETD Measurement Technique 125

Minimum Resolvable Temperature Difference (MRTD) 126

MRTD: Calculation 127

MRTD Measurement Technique 128

MRTD Measurement: Automatic Test 129

Johnson Metric Methodology 130

Johnson Criteria Flaws 132

Targeting Task Performance (TTP) Metric Methodology 133

Human Vision—Distribution of Retinal Photoreceptors 134

Contrast Threshold Function (CTF) 136

Target Acquisition Performance 141

Probability of Task Performance 144

N50 to V50 Conversion (Example) 146

Acquisition Level Definitions 147

TTP Summary 148

Equation Summary 149

Bibliography 163

Index 167