Introduction to Infrared and Electro-Optical Systems (Artech House Optoelectronics Library)

425 Pages·1998·21 MB·English

by  Ronald G. Driggers

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Introduction to Infrared
and Electro-Optical Systems
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. Ronald G. Driggers
Paul Cox
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Timothy Edwards
Artech House
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Boston • London
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Library of Congress Cataloging-in-Publication Data
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Driggers, Ronald G.
.l
,Inrroduction to infrared and electro-optical systems / Ronald G. Driggers, Paul
Cox, Timothy Edwards.
p. cm.
Includes bibliographical references and index.
ISBN 0-89006-470-9 (alk. paper)
1. Infrared technology. 2. Eleccroopcical devices. I. Cox, Paul. II. Edwards,
Timothy. III. Title.
TA1570.D75 1998
621.36'72-dc21 98-53327
.j CIP , ,
11
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British Library Cataloguing in Publication Data
'J
1 Driggers, Ronald G.
I Inrroduction to infrared and electro-optical systems. - (Anech House
optoelectronics library)
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1. Electrooptics 2. Imaging systems 3. Infrared equipmenr 4. Optoelectronics ' .. ,
I
! 5. Electrooptics - Mathematics
II 1. Tide II. Cox, Paul III. Edwards, Timothy
623.7'314
ISBN 0-89006-470-9
Cover design by Lynda Fishbourne
© 1999 ARTECH HOUSE, INC.
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685 Canton Street ;', .~~
Norwood, MA 02062
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All rights reserved. Printed and bound in the Uniced States of America. No part of this ,
book m,ay be reproduced or utilized in any form or by any means, electronic or me ...... i
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chanical, including photocopying, recording, or by any information storage and re "I. .
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trieval system, without permission in writing from the publisher.
All terms mentioned in this book chat are known to be trademarks or service marks
have been appropriately capitalized. Artech House cannot attest to the accuracy of this
information. Use of a term in this book should not be regarded as affecting the validity
of any trademark or service mark.
International Standard Book Number: 0-89006-470-9
Library of Congress Catalog Card Number: 98-53327
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Contents1_ -•. _.-.---... _ ........ _._ .. _ ._. ..•. _.______ --. . ,
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Preface xiii "" .'''1 r
xvi
References
1 :'.1 '
, Chapter I Introduction I
j 1.1 r2R and EO Systems 2
3
1.2 Wavelength Issues
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4
1.3 Typical EO Scenario
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1 1.4 Typical rZR Scenario 6 7)'
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.1 1.5 Analytical Parameters 7 ~!!;.
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1.6 Sensitivity and Resolution
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1.7 Linear Systems Approach
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1.8 Summary
12
References
13
Part 1 Background
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15
Chapter 2 Mathematics :. '
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15
2.1 Complex Functions
17
2.2 One-Dimensional Functions
21
2.3 Two-Dimensional Functions
25
2.4 Convolution and Correlation
28
2.5 The Fourier Transfonn
30
2.6 Properties of the Fourier Transfonn
31
2.7 Transform Pairs
2.8 Important Examples 32 "-"--'
36
Exercises T
38 .1
References l
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Chapter 3 Linear Shift Invariant fR and EO Systems 39
41
3. I Linear Systems
42
3.2 Shift Invariance
43
3.3 Basics of LSI Systems
45
3.4 Impulse Response
50
3.5 Transfer Function
3.6 Spatial Sampling 52 l. . ~
55 ,
3.7 Spatial Sampling and Resolution
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57
Exercises l- -,
59
References
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',.' 6"
:!' viii Introduction to Infrared and Electro-Optical Systems
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,( '1 : Chapter 4 Diffraction 61
\, 4.1 TEM Waves 62
4.2 Coherence 65
4.3 Diffraction 67
, I"; 4.4 Effects of Lenses on Diffraction 70
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{ 1_ _ L..j 4.5 F-F System 73
4.6 FF-FF System 74
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: 4.7 Transfer Functions 76
r 4.8 Generalized Optical Systems 78
\ ... ,": Exercises 81
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References 82
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! ,: Part 2 Components 83
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Chapter 5 Sources of Radiation 85
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5.1 Radiometry and Photometry 86
5.2 Infrared Targets and Backgrounds 96
, . : ....
. 5.3 Electro-Optical Targets and Backgrounds 108
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':~ 5.4 Other Sensitivity Considerations 116
5.5 Target and Background Spatial Characteristics ------' 118
Exercises 124
(, References 126 •
( '--L Chapter 6 Atmospherics 127'
6.1 Atmospheric Components and Structure 128
I , , 6.2 Atmospheric Transmission 131
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6.3 Absorption 132
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6.4 Scattering 136
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6.5 Path Radiance 139
6.6 Turbulence 139
6.7 Atmospheric Modulation Transfer Function 143
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, 6.8 Models 145
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! .- Exercises 149
References 150
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[,,> ~ Chapter 7 Optics 153
: 7.1 Light Representation and the Optical Path Length 154
I L...:: 7.2 Reflection and Sne 11' s Law of Refraction 156
7.3 Gauss's Equation 157
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7.4 Vergence 161
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-~ 7.5 Multiple-Lens Systems 165
., 7.6 Field-of-View 167
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7.7 Resolution I
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7.8 Modulation Transfer Function
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5 7.9 Aberrations and Vign~tting /I 177 ... \
7 7.1 0 Optical Materials _-- III 181 .. .. J .
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7. I 1 A Typical Optical System \ . . "-'--------1I 182 -... ,'
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j Exercises 184
References
186
Chapter 8 Detectors and Scanners 189
8. I Types of Detectors 190 -'
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8.2 Photon Detectors 191
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8.3 Thermal Detectors 197
8.4 Charge-Coupled Devices 200
8.5 Detector Responsivity 201 " ·1
8.6 Detector Sensitivity 203
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8.7 Detector Angular Subtense 211
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8.8 Scanning Configurations and Implementations 212
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8.9 Detector Transfer Functions 218
8.10 Infrared Detectors 223
8. I I Electro-Optical Systems 224
8.12 Noise 225 ~l"
Exercises 226 ".:'" '
References 227
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:~ Chapter 9 Electronics 229
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9.1 Detector Circuits 229
9.2 Conversion of Spatial and Temporal Frequencies 234
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.) 9.3 Electronics Transfer Function 237
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9.4 Noise 240
9.5 MTF Boost Filter 244
9.6 EO MUX MTF 245
9.7 Digital Filter MTF 246
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9.8 CCDs 248 ,...,.,L.J
9.9 Uniformity Correction 249 ",J.
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Exercises 251
References 252
Chapter 10 Displays, Human Perception, Automatic Target Recognizers 253
10.1 Displays 254
10.2 Cathode Ray Tubes 255
10.3 Light Emitting Diodes 258
10.4 Liquid Crystal Displays 260
10.5 Sampling an~ Display Processing 261
Introduction to II1frared and Electro-Optical Systems
x
10.6 Human Perception and the I-Iuman Eye 266
10.7 The Modulatidn Transfer Function of the Eye 268
10.8 Contrast Threshold Function of the Eye 271
10.9 Automatic Target Recognition 273
Exercises. 277
References 277
. Pa rt 3 Systems 279
1;-"; Chapter 11. Infrared Systems 281
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r'~ r: 11.1 Sensitivity and Resolution 2I 84
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11.2 Noise Equivalent Temperature Difference 286
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! ;. 11.3 Three-Dimensional Noise 293
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11.4 Modulation Transfer Function 295
11.5 Minimum Resolvable Temperature Difference 298
11.6 Two-Dimensional MRT 312
11.7 Probabilities of Discriminatibn 312
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, Exercises 326
References 330
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Chapter 12 Electro-Optical Systems 333
- 12.i Resolution 336
\ 12.2 Sensitivity and EO Noise 337
l ;; 12.3 Sensitivity Parameters 342
[ -, 12.4 Rosell's Minimum Resolvable Contrast Model 345
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12.5 Vol1merhausen's MRC Model 349
12.6 General Image Quality Equation 362
Exercises 369
References 370
----
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Chapter 13 Sensor Design Considerations 373
13.1 Waveband Selection 373
13.2 Resolution, Field-of-View, and Coverage 377
13.3 Staring Versus Scanning Performance 380
13.4 Optics Considerations 382
13.5 Search (Dynamic Discrimination) 383
13.6 Example of Imaging Infrared Systems 384
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13.7 Missile Seekers 387
References 395
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Symbols List 397
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About the Authors
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Index
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L Preface
This book is intended to provide the reader with a complete introduction to
I
infrared and electro-optical imaging systems. In particular, this introduction
L...
includes a strong emphasis on the analysis and design of these systems. Imaging
1 •••
systems can be analyzed with the same tools and techniques as electrical circuits
1 L
and modem communications systems. The requisite courses for an undergraduate
f electrical engineering degree provide the majority of skills necessary to perform
l'i.1
J l' detailed system-level pyrformance evaluations. Linear-shift-invariant (LSI) system
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principles and analytical function manipulations combined with calculus and
domain transformations provide the mathematical foundations of imaging system
f i.'~. ',
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analysis. Here, the system begins with the various sources of light, continues-with
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1 its propagation through the atmosphere, the formation of an image, conversion to
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an electrical signal at the detectors, subsequent signal processing, and display toa
~ human observer. This book presents a systems analysis approach, which allows an
1--.
f understanding of this complex process and results in quantitative characterizations
;. "#; of performance metrics such as modulation transfer functions, minimum
resolvable temperature difference, and probability of object discrimination. We
f' ."
then use these metrics to analyze a number of infrared and electro-optical systems.
Goodman [1] and Gaskill [2] both provide excellent treatments of optical
[
systems using LSI principles. However, the optical elements are only a part of an
...
;: infrared or electro-optical imaging system. The performance analyses of these
systems include source characteristics, atmospherics, detectors, electronics,
displays, and human vision (or automatic processing). LSI principles can be
applied to all these components, but like Goodman's and Gaskill's treatments of
optics, the subject matter for each component can consume an entire text. We
present LSI system principles here, but limit our discllssions to the basic
descriptions of the components necessary to indoctrinate the student and to
calculate overall system performance. References have been included at the end of
each component section, which can provide additional component-level detail.
i, Lloyd [3] and Holst [4] provide excellent treatments of overall imaging
system performance. These texts are Used by many practicing analysts as
references in the performance estimation of proposed and actual imaging systems.
f They are not intended as an introduction to imaging systems and assume that the
reader has some background in optics, detectors, or other components within the
, :... . ...:
\
.. system.
xiv Introduction to Infrared and Electro-Optical Systems
:)
Therefore, we provide an introductory text that emphasizes the LSI system
apprbach. The analysis is direct, yet elegant, and provides an effective means for
evaluating the performance of infrared and electro-optical imaging systems. In
I ~J
particular. the LSI approach allows impact assessment on performance for changes
",
in components such as entrance-pupil shapes, detector shapes. and display
I
charrlcteristics. The reader is led through a number of analysis-and-design,
examples where the effects of these component changes are realized.
\Vhile there are many excellent books in the field. they can be roughly
",I .
divided into two categories: those that focus on a particular component and
system-level books where the reader is assumed to have some background in the
subject area. This book is written to complement these texts by bridging the two ~l
categories. This complementary nature of the text allows the reader to understand
the entire analysis-and-design process. 71
\Ve begin with an introduction to two-dimensional functions and . ,
mathematics used to describe image transfer characteristics and imaging system
component models. Next, LSI principles are presented to show image transfer 'j
characteristics for application to imaging systems. The final background chapter is
that of diffraction, showing the fundamental limits of imaging system
performance. In this chapter, the diffraction concepts of coherent imaging systems
are presented to show the development of the incoherent diffraction principles.
Following the review of basic background material, the component.s of an :.·r
im<!ging system are presented. An imaging system "map" is used to chart the;flow
of infomlation through the system. The map begins with the source of radiation
and traverses through the atmosphere and into the imaging system. The path
continues with the image forming optics and then onto the detector. The detector
converts the light into an electrical signal that is amplified and processed by
system electronics. This electrical signal continues to a display or, in some cases,
an automated processor (e.g., target tracker). A display converts the electrical
signal into an optical signal for human visual consumption. The human eye is
typically included as part of system performance, so it, too, is considered a
component in the imaging system. Each of the components in the map is addressed
in Chapters 5 through 10. These chapters include component descriptions,
component analysis techniques, and LSI modeling descriptions. There you have it:
~nalysis begins with the sources of light and ends with the response of the eye and
brain.
The emphasis then turns to infrared and electro-optical system
performance descriptio~s, design rules, and examples. Chapters II and 12 provide
infrared and electro-optical system performance analysis techniques, respectively.
These are the chapters where the components are brought together to provide an
overall system description. The sources of radiation and the atmosphere are
typically not included in imaging system performance estimates intended for
generic application to a variety of target, background, and atmospheric conditions.
The analysis process then continues here as system-scenario performance, which