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
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Fax: +1 360 647 1445
Email: spie@spie.org
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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 , , and 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
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
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
ℳ
Magnification
ℳang
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
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