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Front Matter
Abstract
This front matter contains an introduction, table of contents, and symbol glossary.

Library of Congress Cataloging-in-Publication Data

Daniels, Arnold.

Field guide to infrared systems / Arnold Daniels.

p. cm.-- (The Field guide series ; no. 1:9)

Includes bibliographical references and index.

ISBN 0-8194-6361-2 (alk. paper)

1. Infrared technology--Handbooks, manuals, etc. I. Title. II. Series: Field guide series (Bellingham, Wash.) ; no. 1:9.

TA1570.D36 2006 621.36'2--dc22

2006015467

Published by

SPIE—The International Society for Optical Engineering

P.O. Box 10

Bellingham, Washington 98227-0010 USA

Phone: +1 360 676 3290

Fax: +1 360 647 1445

Email: spie@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. Asig-nificant 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 easily 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

Optical Sciences Center

The University of Arizona

The Field Guide Series

Keep information at your fingertips with all of the titles in 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 and 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,EricP. Goodwin and James C. Wyant (FG10)

Field Guide to Infrared Systems

Field Guide to Infrared Systems is written to clarify and summarize the theoretical principles of infrared technology. It is intended as a reference work 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 involving 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.

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. Thanks are extended to Merry Schnell for her hard work and dedication on this project. I voice a special note of gratitude to my kids Becky and Alex for their forbearance, and to my wife Rosa for her 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 truly hope that you will find the contents of this book interesting and informative.

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

Arnold Daniels

Table of Contents

Glossary x

Introduction 1

Electromagnetic Spectrum 1

Infrared Concepts 2

Optics 3

Imaging Concepts 3

Magnification Factors 4

Thick Lenses 5

Stop 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

Material Dispersion 19

Atmospheric Transmittance 21

Radiometry and Sources 22

Solid Angle 22

Radiometry 23

Radiometric Terms 24

Flux Transfer 26

Flux Transfer for Image-Forming Systems 27

Source Configurations 28

Blackbody Radiators 30

Planck's Radiation Law 31

Stefan-Boltzmann and Wien's Displacement Laws 33

Rayleigh-Jeans and Wien's Radiation Laws 34

Exitance Contrast 35

Emissivity 36

Kirchhoff's Law 37

Emissivity of Various Common Materials 38

Radiometric Measure of Temperature 39

Collimators 41

Performance Parameters for Optical Detectors 42

Infrared Detectors 42

Primary Sources of Detector Noise 43

Noise Power Spectral Density 44

White Noise 45

Noise-Equivalent Bandwidth 46

Shot Noise 48

Signal-to-Noise Ratio: Detector and BLIP Limits 49

Generation-Recombination Noise 50

Johnson Noise 51

1/f Noise and Temperature Noise 52

Detector Responsivity 53

Spectral Responsivity 55

Blackbody Responsivity 56

Noise Equivalent Power 57

Specific or Normalized Detectivity 58

Photovoltaic Detectors or Photodiodes 59

Sources of Noise in PV Detectors 60

Expressions for DPV,BLIP*, DPV,BLIP**, and DPV,JOLI* 61

Photoconductive Detectors 62

Sources of Noise in PC Detectors 63

Pyroelectric Detectors 64

Bolometers 66

Bolometers: Immersion Optics 68

Thermoelectic Detectors 69

Infrared Systems 70

Raster Scan Format: Single-Detector 70

Multiple-Detector Scan Formats: Serial Scene Dissection 72

Multiple-Detector Scan Formats: Parallel Scene Dissection 73

Staring Systems 74

Search Systems and Range Equation 75

Noise Equivalent Irradiance 78

Performance Specification: Thermal-Imaging Systems 79

MTF Definitions 80

Optics MTF: Calculations 83

Electronics MTF: Calculations 85

MTF Measurement Setup and Sampling Effects 86

MTF Measurement Techniques: PSF and LSF 87

MTF Measurement Techniques: ESF and CTF 88

MTF Measurement Techniques: Noiselike Targets 90

MTF Measurement Techniques: Interferometry 92

Noise Equivalent Temperature Difference 93

NETD Measurement Technique 94

Minimum Resolvable Temperature Difference 95

MRTD: Calculation 96

MRTD Measurement Technique 97

MRTD Measurement: Automatic Test 98

Johnson Criteria 99

Infrared Applications 101

Appendix

Equation Summary 103

Notes 112

Bibliography 113

Index 116

Glossary

A

Area

Ad

Detector area

Aenp

Area of an entrance-pupil

Aexp

Area of an exit-pupil

Afootprint

Footprint area

Aimg

Area of an image

Alens

Lens area

Aobj

Area of an object

Aopt

Area of an optical component

As

Source area

B

3-db bandwidth

c

Speed of light in vacuum

Cd

Detector capacitance

CTF

Contrast transfer function

ddiff

Diameter of a diffraction-limited spot

D*

Normalized detectivity of a detector

DBLIP*

D-star under BLIP conditions

D**

Angle-normalized detectivity

Denp

Diameter of an entrance-pupil

Dexp

Diameter of an exit-pupil

Dimg

Image diameter

Din

Input diameter

Dlens

Lens diameter

Dout

Output diameter

Dobj

Object diameter

Dopt

Optics diameter

e

Energy-based unit subscript

Ebkg

Background irradiance

Eimg

Image irradiance

Esource

Source irradiance

ESF

Edge spread function

ε

Energy of a photon

feff

Effective focal length

f

Focal length

b.f .l

Back focal length

f .f .l

Front focal length

f (x, y)

Object function

FB

Back focal point

FF

Front focal point

F(ξ, η)

Object spectrum

fo

Center frequency of an electrical filter

FOV

Full-angle field-of-view

FOVhalf-angle

Half-angle field-of-view

F/#

F-number

g(x, y)

Image function

G(ξ, η)

Image spectrum

G

Gain of a photoconductive detector

h(x, y)

Impulse response

H(ξ, η)

Transfer function

h

Planck's constant

H

Heat capacity

HIFOV

Horizontal instantaneous field-of-view

HFOV

Horizontal field-of-view

himg

Image height

hobj

Object height

i

Electrical current

i¯

Mean current

iavg

Average electrical current

ibkg

Background rms current

idark

Dark current

ij

rms Johnson noise current

i1/f

rms 1 /f-noise current

iG/R

Generation-recombination noise rms current

inoise

Noise current

ioc

Open circuit current

ipa

Preamplifier noise rms current

irms

rms current

isc

Short circuit current

ishot

Shot noise rms current

isig

Signal current

J

Current density

k

Boltzmann's constant

κ(ξf)

Spatial-frequency dependant MRTD pro-portionality factor

K

Thermal conductance

L

Radiance

LSF

Line spread function

Lbkg

Back round radiance

Lλ

Spectral radiance

M

Exitance

Mmeas

Measured exitance

Mobj

Exitance of an object

Mλ

Spectral exitance

MRTD

Minimum resolvable temperature difference

MTF

Modulation transfer function

MTFd

Detector MTF

Magnification

ang

Angular magnification

n

Refractive index

nd

Number of detectors

ne

Number of photogenerated electrons

nlines

Number of lines

NEI

Noise-equivalent irradiance

NEP

Noise-equivalent power

NEΔf

Noise-equivalent bandwidth

OTF

Optical transfer function

Pavg

Average power

p

Object distance

PSD

Power spectral density

PSF

Point spread function

q

Image distance

R

Resistance

Rd

Detector resistance

Req

Equivalent resistance

Rin

Input resistance

RL

Load resistance

Rout

Output resistance

SNR

Signal-to-noise ratio

SR

Strehl-intensity ratio

𝓡

Responsivity

𝓡i

Current responsivity

𝓡υ

Voltage responsivity

𝓡(λ)

Spectral responsivity

𝓡(T)

Blackbody responsivity

t

Time

T

Temperature

TB

Brightness temperature

Tbkg

Background temperature

TC

Color temperature

Td

Detector temperature

Tload

Load temperature

Trad

Radiation temperature

Tsource

Source temperature

Ttarget

Target temperature

VIFOV

Vertical instantaneous field-of-view

VFOV

Vertical field-of-view

υ¯

Mean voltage

υin

Input voltage

υj

Johnson noise rms voltage

υn

rms noise voltage

υoc

Open-circuit voltage

υout

Output voltage

υsc

Short-circuit voltage

υs

Shot-noise rms voltage

υscan

Scan velocity

υsig

Signal voltage

V

Abbe number

W

W proportionality factor

α

Coefficient of absorption

β

Blur angle caused by diffraction

ε

Emissivity

Δf

Electronic frequency bandwidth

Δt

Time interval

ΔT

Temperature difference

Δλ

Wavelength interval

θ

Angle variable

θmax

Maximum angle subtense

η

Quantum efficiency

ηscan

Scan efficiency

λ

Wavelength

λcut

Cutoff wavelength

λmax

Maximum wavelength

λmax-cont

Maximum contrast wavelength

λpeak

Peak wavelength

λo

Fixed wavelength

ν

Optical frequency

σ2

Variance

σ

Standard deviation

σe

Stefan-Boltzmann constant in energy units

σP

Stefan-Boltzmann constant in photon units

ρ

Reflectance

τ

Transmittance

τatm

Atmospheric transmittance

τdwell

Dwell time

τext

External transmittance

τint

Internal transmittance

τframe

Frame time

τline

Line time

τopt

Optical transmittance

Φ

Flux

Φλ

Spectral flux

Φabs

Absorbed flux

Φbkg

Background flux

Φd

Detector flux

Φimg

Flux incident on an image

Φinc

Incident flux

Φobj

Flux radiated by an object

Φref

Reflected flux

φsig

Signal flux

Φtrans

Transmitted flux

ξ

Spatial frequency in x-direction

ξcutoff

Spatial cutoff frequency

η

Spatial frequency in y-direction

Ω

Solid angle

Ωd

Detector solid angle

Ωs

Source solid angle

Ωbkg

Background solid angle

Ωexp

Exit pupil solid angle

Ωenp

Entrance pupil solid angle

Ωimg

Image solid angle

Ωlens

Lens solid angle

Ωobj

Object solid angle

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