Spie Press Book
Photonics Rules of Thumb, Third EditionFormat | Member Price | Non-Member Price |
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Updated and expanded, the third edition of Photonics Rules of Thumb represents an evolving, idiosyncratic, and eclectic toolbox intended to allow any engineer, scientist, manager, marketeer, or technician (regardless of specialty) to make rapid and accurate guesses at solutions in a wide range of topics during system design, modeling, or fabrication. This book will help any electro-optics team to make quick assessments, generally requiring no more than a calculator, so that they can quickly find the right solution for a design problem.
This book has been assembled to introduce anyone working in the optics and photonics community to a wide range of critical topics through simple calculations, graphics, equations, and explanations. Useful design principles and rules, simple-to-implement calculations, and numerous graphs and tables of important basic information allow you to rapidly pinpoint trouble spots, ask the right questions at meetings, and are perfect for quick checks of last-minute specifications or performance feature additions. Offering a convenient arrangement according to specialty, this unique reference spans the spectrum of photonics. Eighteen chapters cover optics, atmospherics, radiometry, focal plane arrays, degraded visual environments, economics, and photogrammetry, as well as technologies related to security and surveillance systems, infrared, lasers, electro-optics, phenomenologies, self-driving vehicles, and many others.
Pages: 740
ISBN: 9781510631755
Volume: PM314
Table of Contents
- Preface
- Acknowledgements
- 1 Astronomy
- Introduction
- Blackbody Temperature of the Sun
- Number of Stars as a Function of Wavelength
- Simple Model of Stellar Populations
- Number of Infrared Sources Per Square Degree
- Number of Stars above a Given Irradiance
- Direct Lunar Radiance
- Atmospheric Seeing
- Comparison of Resonant Fluorescence and Rayleigh Guide Stars
- Number of Actuators in an Adaptive Optic
- Bandwidth Requirement for Adaptive Optics
- Photon Rate at a Focal Plane
- Reduction of Magnitude by Airmass
- Night-Sky Exposure Time with a Fixed Camera
- 2 Atmospherics
- Introduction
- Vertical Profiles of Atmospheric Parameters
- Visibility Distance for Rayleigh and Mie Scattering
- Atmospheric Effects at 10.6 Microns
- Cn2 as a Function of Weather
- Cn2 Estimates
- Impact of Weather on Visibility
- Bufton Vertical Profile of Wind Speed
- Index of Refraction of Air
- Fried Parameter
- Horizontal-Path Fried Parameter
- Phase Error Estimation
- Day vs. Night Scintillation Models for Laser Beams
- Resolution Looking Down
- Isoplanatic Angle
- Strehl Ratio of the Atmosphere
- Aperture Averaging
- Adaptive Optics Influence Function
- Shack–Hartmann Noise
- Laser Beam Wander Variance Is Approximately Proportional to About the Cube of the Pathlength
- Pulse Stretching in Scattering Environments
- Optimal Truncation of a Gaussian Beam Propagating in the Atmosphere
- Increased Requirement for Rangefinder SNR to Overcome Atmospheric Effects
- Free-Space Link Margins
- Summary of Phase Modulators for Adaptive Optics
- Telescope Seeing Created by a Dome Floor
- Telescope Seeing Due to Still or Ventilated Air
- 3 Acquisition, Tracking, and Pointing
- Introduction
- Correct Measure of Detection Performance
- Tracker vs. Detection
- Detection Criteria
- Signal-to-Noise Ratio Requirements
- Psychometric Function
- Optical Blur Should Be Oversampled by FPA Pixels (Don't Overdo It!)
- Dwell in Cell
- Probability of Detection Estimation
- Limits of Position Estimation
- Multisensor Tracking
- Johnson Criteria
- Extension of Johnson Criteria to Other than 50 Percent
- Identification and Recognition Improvement for Interpolation
- Resolution Requirement
- Resolution Required to Read a Letter
- Detection Nomograph
- Correcting for Probability of Chance
- National Image Interpretability Rating Scale
- 4 Backgrounds
- Introduction
- Clutter and Signal-to-Clutter Ratio
- Clutter Power Spectral Density
- Infrared Clutter Behavior
- Frame Differencing Gain
- Earth's Emission and Reflection
- Illuminance at Earth's Surface from Various Sources
- Illuminance Changes during Twilight
- Emissivity Approximations
- Reflectivity of a Wet Surface
- Effective Sky Temperature
- Sky Irradiance
- Zodiacal Light
- Backgrounds from Asteroids
- 5 Cost and Economics
- Introduction
- Moore's Law
- Metcalfe's Law
- Englebart's Law
- The Value of Early Investment
- Cost Reduction Techniques
- Learning Curves
- Learning Curves for Optics
- Optics Cost
- Cost Function of a Lens
- Price of a Custom vs. Off-the-Shelf Optic
- Telescope Component Costs
- Impact of Tolerances on the Cost of Optics
- Stahl Segmented Cost Rule
- Tolerancing Guidelines for Glass Spherical Optics
- Tolerancing Guidelines for Plastic Optics
- Cost of Digital Image vs. Film
- Small Pixels Reduce Cost
- System Percentage Costs
- Length of a Job Search
- Photolithography Yield
- 6 Degraded Visual Environments
- Introduction
- Basic Attenuation and Visibility: Beer's Law
- Atmospheric Attenuation Curves
- Atmospheric Visibility Curves
- Attenuation vs. Particle Size
- Visibility in Smoke
- Equations for Empirical Visibility
- Penetration vs. Resolution
- Mandatory Mitigation for Sensor Blindness
- Deep Wells Are Good
- 7 Focal Plane Arrays
- Introduction
- Infrared Detector Characterization
- Responsivity and Quantum Efficiency
- ROIC Charge Capacity
- Low Quantum Efficiency Detectors Are Useful
- Silicon Quantum Efficiency
- HgCdTe x Concentration
- Quantum Dot Fundamentals
- Avalanche Photodiode Performance
- Responsivity of Avalanche Photodiodes
- Peak vs. Cut-Off
- CMOS Depletion Scaling
- Focal Plane Array Noise Sources
- Rule 07
- Law 19
- Radiative Estimate of Dark Current
- Defining Background-Limited Performance for Detectors
- The Concepts of D and D*
- Ideal D* and View Angle
- Dependence on R0A
- Shot Noise Rule
- Infrared Detector DC Pedestal
- Digitizer Sizing
- Noise as a Function of Temperature
- Noise Bandwidth of Detectors
- Noise Equations for CMOS
- Specifying 1/f Noise
- Nonuniformity Effects on SNR
- Correlated Double Sampling
- 8 Human Vision
- Introduction
- Retinal Illumination
- Diffraction Effects in the Human Eye
- Energy Flow into the Eye
- Pupil Size
- Quantum Efficiency of Rods and Cones
- Rod and Cone Response Models
- Cone Density of the Human Eye
- Rod Density Peak
- Eye Resolution
- Optical Fields of View
- Contrast Performance
- Simplified Optical Transfer Functions for Eye Components
- Eye Motion during the Formation of an Image
- Visual Performance as a Function of Age
- Old-Age Rules
- Superposition of Colors
- Dyschromatopic Vision
- Eye Adaptation Time
- Eat Your Vegetables
- Stereograph Distance
- Assorted Eye Facts
- Head-Mounted-Display Latency
- 9 Lasers
- Introduction
- Lidar Basic Equations
- Laser Brightness
- Laser Beam Quality
- Gaussian Beam Radius
- On-Axis Intensity of a Beam
- Aperture Size for Laser Beams
- Laser Beam Divergence
- Laser Beam Spread vs. Diffraction
- Types of Lidars
- Laser Radar Range Equation
- Lidar Bidirectional Reflectance Distribution Function
- Thermal Focusing in Laser Rods
- Cross-Section of a Retroreflector
- Air Breakdown
- 10 Materials and Structures
- Introduction
- Diameter-to-Thickness (Aspect) Ratio
- The Influence of the Mounting Method on Plate Deflection
- Self-Weight Deflection of Mounted Mirrors
- Mirror Support Criteria
- Fundamental Frequency of a Vibrating Plate
- Natural Frequency of a Deformable Mirror
- Design Guidelines for Pressure Windows
- Dome Collapse Pressure
- Glass Does Not Flow
- Allowable Stress in an Optic
- Relationship between Tensile and Compressive Stress
- Estimation of Preload Torque
- Stress Birefringence Induced by an Applied Load
- Maximum Stress on an Optic Due to a Metal Retainer
- A Bonded Mirror Is Three Times More Stable in Tension or Compression than Shear
- Mechanical Stability Rules
- Mass Is Proportional to Element Size Cubed
- Deflection of a Mirror at the End of a Beam
- Scan Mirror Deflection
- Figure Change of Metal Mirrors
- Foam Core Mirrors
- Spin-Cast Mirrors
- Serrurier Truss
- Spacecraft Issues Related to Space Optics
- Damage Mechanisms Associated with Micrometeoroids
- Black Coatings
- Index of Refraction Resources
- Carbon-Silicon Carbide Coefficient of Thermal Expansion
- Properties of Aluminum as a Function of Temperature
- Permeability of Gases through Thin Films of Aluminum
- Time to Uniform Temperature
- Temperature Dependence of the Verdet Constant
- Modeling Cryo Multilayer Insulation
- 11 Miscellaneous
- Introduction
- Position of the Sun
- Distance to Horizon
- Contrast
- Digital Pixel Equivalent of Chemical Film
- Common Image and Video Compression Formats
- The Power of Dimensional Analysis
- Scissor Integration
- Number of Seconds in a Year
- Solid Angles
- Speed of Light
- Water Weighs a Ton
- Avoid Galling Metal
- Failure of Cylinders and Spheres under External Pressure
- Defining Screw Threads
- Friction-Induced Pointing Error after Rate Reversal
- Shipping Environments
- Clean Room Classifications
- Converting Transmission and Optical Density
- Safety Factors for Optics
- Use Speckle to Focus
- 90 Percent of Anything Is Plumbing
- Arrhenius Equation
- Miller's Rule of Test Failure
- Cooling with Liquid or Solid Cryogen
- Joule-Thomson Cool-Down Time
- Low-Earth-Orbit Thermal Changes
- Crickets as Thermometers
- Image Intensifier Resolution
- Photomultiplier Tube Power Supply Noise
- Quantization Error
- 12 Ocean Optics
- Introduction
- Index of Refraction of Seawater
- Absorption Coefficient
- Absorption of Ice at 532 nm
- Absorption Caused by Chlorophyll a
- Bathymetry
- f-stop under Water
- Underwater Detection
- Underwater Glow
- Ocean Reflectance
- Wave Slope
- 13 Optical Design and Analysis
- Introduction
- Small-Angle Approximation
- Effects from Light Passing Through a Plane Parallel Plate
- Beam Deviation Due to a Thin Wedge Prism
- Impacts of Optical Element Motion
- Defocus for a Telescope Focused at Infinity
- Hyperfocal Distance
- Focal Length and Field of View
- Limit on FOV for Reflective Telescopes
- Maximum Useful Pupil Diameter
- Minimum f-Number
- f-Number for Circular Obscured Apertures
- Why Light Won't Refract in a Cube
- Aberration Scaling
- Spherical Aberration and f-Number
- Blur vs. Field-Dependent Aberrations
- Reducing Optical Design Sensitivities
- Separate the Centers of Curvature
- Reduce the Ray Angles of Incidence
- Efficient Reflective Triplet Layout for Feasibility Checks
- Properties of Visible Glass
- Per Pixel Resolution of a Spectrometer
- Smith's Modern Optics Design Rules of Thumb
- Diffraction Graph
- Diffraction Is Proportional to Perimeter
- Diffraction Principles Derived from the Uncertainty Principle
- Why There Are Spikes Radiating from Only Some Objects Seen in Astronomical Images
- Estimating Surface Scatter
- Power Spectral Density of Surface Roughness
- In-Field Source Contribution to Stray Light in the Focal Plane
- Fest's Stray Light Rules of Thumb
- Performance Budgeting Using the Hopkins Ratio
- Linear Approximation for the Optical Modulation Transfer Function
- Telescope Aberrations Not Caused by the Atmosphere
- Strehl for Obscured Apertures
- Total Error Using the Root-Sum-Square Approach
- Optical Performance of a Telescope
- Visible Imaging System Resolution
- Optimal Telescope Resolution for the Human Eye
- Peak-to-Valley Approximates Four Times the Root Mean Square
- Ritchey-Chretien Telescope Aberrations
- Spectral Bandwidth and Resolution of Acousto-optical Tunable Filters
- Circular Variable Filters
- Blazed Grating Performance
- Fabry-Perot Etalons
- Pulse Broadening in a Fabry-Perot Etalon
- Hollow Waveguides
- Inflated Mirrors
- Handheld Binocular Efficiency
- Stop Down Two Stops
- Anti-reflection Coating Index
- Coating Shift with Angle of Incidence
- Coating Shift with Temperature
- Grating Blockers
- Far-Field Model of a Light Source, or the "Rule of 5"
- Lambertian Source Illumination of a Detector
- Detecting Linear Polarization
- Modeling an Optical System Using the Fast Fourier Transform
- A Collection of Optical Engineering Rules of Thumb
- Use a "Pencil Bounce" to Determine Image Orientation
- Thermal Gradients in a Primary Mirror
- Thermal Lensing
- 14 Optical Manufacture and Test
- Introduction
- Progress in Optical Fabrication of High-Quality Mirrors
- Caution while Cleaning Optics
- Thickness of a Doublet Bond
- Sag of an Optic
- Scratch-Dig Specifications
- Oversizing an Optical Element for Producibility
- Mind Your Karow Factor
- Cyanoacrylate Usage
- Surface Tilt Is Typically the Worst Error
- Diamond-Turned Mirror Substrate Design
- Diamond-Turned Mirror Figure Error
- Accuracy of Figures
- Fringe Movement
- Approximations for the Foucault Knife-Edge Test
- Effect of Surface Irregularity on the Wavefront
- Hartmann Test for Pinhole Size
- Maximum Size of the Opening for an Integrating Sphere
- Choosing an Eyepiece for Star Tests
- Collimator Design
- Temperature Control Is Critical for Accurate Inhomogeneity Testing
- Optical Table Displacement Requirements
- Detection of Flatness by the Human Eye
- Lesser-Known Lab Tools
- Yoder's Rules of Thumb
- 15 Photogrammetry
- Introduction
- Basic Optical Equations
- Triangulation vs. Model-Based Pose Estimation
- Stereo vs. Triangulation
- Basic Triangulation Equations
- Two-Camera Triangulation Accuracy
- Triangulation Error Tree
- Sensor Placement for Triangulation
- Maximum Triangulation Range
- Triangulation Equations for Cameras
- Azimuth Corrections for Euclidean Coordinate Systems
- Model-Based Pose Estimation: Number of Points and Spatial Distribution
- From What Point in an Optical System Is Range Measured?
- 16 Radiometry
- Introduction
- The Electromagnetic Spectrum
- Photons-to-Watts Conversion
- Brightness of Common Sources
- The Blackbody Equation
- Logarithmic Blackbody Functions
- Narrow-band Approximation to Planck's Law
- Peak Wavelength of Wien's Displacement Law
- Choice of Waveband
- Lambert's Law
- Etendue
- In-Band Solar Irradiance at the Top of the Atmosphere
- Rule of 4(f/#)2
- Relationship between Minimum Resolvable Temperature and Noise-Equivalent Temperature Difference
- Ideal NEΔT Simplification
- Cavity Emissivity
- Incorrectly Sizing Radiometric Areas
- No Ice Cream Cones
- Calibrate under User's Conditions for Best Results
- Radiometry of a Spherical Cow
- Dependence on R0A
- Quick Test of NEΔT
- 17 Systems
- Introduction
- Pick Any Two
- Divide by the Number of Visits
- Dawes Limit
- BLIP Limiting Rule
- Rayleigh Criterion
- Focal Length and Resolution
- Diffraction Limit in LWIR
- Procedures to Reduce Narcissus Effects
- System Off-Axis Optical Rejection
- Signal-to-Noise Ratio for Different Targets
- Simplified Range Equation
- General Image Quality Equation
- Mechanical Shock Response
- Estimating rms Acceleration Response due to Random Vibrations
- Typical Values of Electro-optical System Parameters
- Vibration Isolation
- Wind Loading
- 18 Target Phenomenology
- Introduction
- Emissivity Approximations
- Solar Reflection Always Adds to the Signature
- Lambertian vs. Specular
- Bidirectional Reflectance Distribution Function
- Hagen-Rubens Relationship for the Reflectivity of Metals
- Causes of White Pigment's Color
- Human Body Signature
- Infrared Skin Characteristics
- Jet Plume Phenomenology
- Plume Thrust Scaling
- Rocket Plume Rules
- Temperature as a Function of Aerodynamic Heating
- Laser Cross-Section
- Chlorophyll Absorptance
- Normalized Difference Vegetation Index
- Appendix
- Glossary
- Tables of Numerical, Physical, and Material Properties (or Other Information)
- Properties of Infrared Materials
- Thermal and Structural Properties of Materials
- CIE Chromaticity Diagram
- Basic Equations
- Blackbody Nomograph
- Nomoscope of Telescope Performance
- Azimuth and Elevation Conventions
- Photonic Noise Sources
- Guidelines for Writing SI Units
- Derivation of the Third Equation in the Rule "The Relation of Ideal D* to View Angle"
- Index
- * It should be easy to implement.
- * It should provide roughly the correct answer.
- * The main points should be easy to remember.
- * It should be simple to express.
- * It should highlight the important variables and diminish the role of generally unimportant variables.
- It should provide useful insight to the workings of the subject matter.
Preface
The evolution of the photonic sciences parallels, and feeds from, developments in a number of somewhat unrelated fields, including astronomy, satellite and remote sensing technology, materials science, electronics, biomedical sciences, optical communications, military developments, and many others. The common thread of all of this effort, which was defined in the 1950s, is that scientists and engineers have been able to combine highly successful electronic technologies with the more ancient concepts and methods of optics and electromagnetic wave propagation. The merging of these fields has provided an unprecedented capability for instruments to "see" targets and communicate with them in a wide range of wavelengths for the benefit of security systems, science, defense, and (more recently) consumers. In the future, we see the rise of autonomous systems as a sea change that will drive a significant increase in the need for sensing systems to allow the autonomous system to sense and understand its environment.
Major departments at universities are now devoted to producing new graduates with specialties in this field. There is no end in sight for the advancement of these technologies, especially with the continued development of electronics and computing as increasingly integral parts of photonic instrumentation. One of the disturbing trends in this technology is the constant narrowing of the role of engineers. As the technology matures, it becomes more difficult for anyone working in an area of photonics to understand all that is being done in the related sciences and engineering. This book has been assembled to make a first, small step to expose anyone working in the optics and photonics community to a wide range of critical topics through simple calculations and explanations.
There is no intent to compete with classic texts or the many journals or conferences devoted to the photonics field, all of which provide considerable detail in every area. Rather, this book is intended to allow any engineer or scientist, regardless of specialty, to make rapid and accurate guesses at solutions in a wide range of topics that might be encountered in system design, modeling, or fabrication, as well as to provide a guide for choosing which details to consider more diligently. This book will help any electro-optics (EO) team to make quick assessments, generally requiring no more than a calculator, so that they quickly find the right solution for a design problem.
The book is also useful for managers, marketeers, and other semi-technical folks who are new to the optics industry (or are on its periphery) to develop a feel for the difference between the chimerical and the real. Students may find the same type of quick-calculation approach valuable, particularly in the case of oral exams in which the professor is pressuring the student to do a complex problem quickly. Using these assembled rules, you can keep your wits about you and provide an immediate and nearly correct answer, which usually will save the day. But after the day is saved, you should go back to the question and perform a rigorous analysis. These rules are useful for quick sanity checks and basic relationships. Being familiar with the rules allows one to rapidly pinpoint trouble areas or ask probing questions in meetings. They aid in thinking on your feet and in developing a sense of what will work and what won't. Another potential application of the contents is to provide a checklist for reviewers asked to assess the completeness of a design or resolve trade studies early in the development of a system. But they are not, and never will be, the last word.
Dear reader, it is fully recognized that errors may still be present, and for that we apologize in advance to you and to those from whom the material was derived. We try to the best of our abilities to remove errors we inherit from the references we used and in new material we created. To assist us in this endeavor, we have solicited the cooperation of as many experts as would agree to help. Their input gives us a wide variety of experience from many different technical points of view. Alas, technology advances, and all of us wonder how we can possibly keep up. Hopefully, this book will not only provide some specific ideas related to photonics technology, it will also suggest some ways of thinking about things that will lead to a whole new generation of such rules and ideas.
As we discovered with the previous editions of this book, not everyone has the same thing in mind when considering "a rule of thumb." To qualify for our definition of a rule of thumb, a rule should be useful to a practitioner and possess at least most of the following attributes:
As in earlier editions of books in this series, we found it valuable to create a detailed standard form and stick to it as closely as possible. We did in this edition as well. References are provided whenever possible. In addition, reference material is mentioned that can be considered as recommended reading for the reader with a desire for more detail than could be presented in the "rule" and "discussion." The reader should note that each rule "stands on its own," so the abbreviations and terminology may not be entirely consistent throughout. This is intentional; we use the notation of the reference whenever we can so that if you read the original material you will recognize what that author defined. Some rules are derived from the laws of physics, and some represent existing technology trends. Many derive from observations made by researchers in the field, augmented by curve fitting that results in polynomial approximations.
The authors of the previous versions of this book arrived at the same place by very different paths. John (now retired, but busy consulting) spent some of his career in infrared astronomy before joining the aerospace industry to work on infrared sensors for space surveillance. He later worked on tactical sensors for search-and-rescue, self-driving cars, active imaging and enhanced vision systems. Ed (now retired, but very busy teaching) spent most of his career working on remote sensing technologies applied to Earth, its atmosphere and oceans, and, more recently, astronomical instruments and advanced pointing systems. John and Ed met in Denver in 1985, both working for a major government contractor on exotic electro-optical systems.
Those were halcyon days, with money flowing like water, and contractors winning billions of dollars for some concepts that were overly optimistic or barely possible at best. In the center of the whole fray were bureaucrats, politicians, and managers who were demanding that we design systems that would be capable of the impossible. We saw many requirements and goals being levied on our systems that were far from realistic, often resulting from confusing (and poorly understood) interpretations of the capabilities of optical and electro-optical systems and the properties of targets or backgrounds. We found a common ground when managers discovered that many co-workers, in an attempt to outdo the competition, were promising to perform sensor demonstrations that violated many rules of engineering, if not physics. On one multibillion-dollar program, after some consistent exposure to neophytes proposing all sorts of undoable things, we decided to try to educate everyone by creating a half-serious, half-humorous posting for the local bulletin board (this was before websites were ubiquitous) called "Dr. Photon’s Rules of Thumb." It was a list of basic rules that apply when optics or electro-optics are used. Figure 1 shows the first version that we found all across the company, and even among competitors.
For the current version, John and Ed invited (maybe some would say tricked) three other younger authors to modernize, enhance, and yield a new perspective. These luminaries are Jack Sanders-Reed,Brian McComas, and Katie Schwertz, whose bios appear in the back matter of this book.
Katie is a hybrid optical and optomechanical designer, drawing from her time at both the University of Rochester and University of Arizona optics programs. She primarily works on commercial and industrial optical subsystems. Her time spent under the tutelage of Jim Burge in Arizona taught her the value of a good estimation, which she didn’t fully appreciate until her time spent in industry. Her Master’s work involved optomechanics "rules of thumb." Jack has 40 years of experience ranging from medical imaging, to surface science, to pilot vision systems and atmospheric phenomenology, to target detection, tracking, and photogrammetry and covering the electromagnetic spectrum from hard x-ray through visible and infrared to millimeter-wave with both passive and active imaging. Brian has over 30 years of experience working on EO systems for military, astronomical, remote sensing, and industrial use. His Ph.D. was developed under the direction of Ed Friedman.
To summarize, this collection of rules and concepts represents an evolving, idiosyncratic, and eclectic toolbox. The rules, like tools, are neither good nor bad; they can be used to facilitate the transition of whimsical concepts to mature hardware or to immediately identify a technological path worth pursuing. Conversely, misused, they can obfuscate the truth and, if improperly applied, derive incorrect answers. Our job was to refine complex ideas to simplified concepts and present these rules to you with appropriate cautions. However, it is your responsibility to use them correctly. Remember, it is a poor worker who blames their tools and we hope you will find these tools useful.
John L. Miller
Edward Friedman
Jack Sanders-Reed
Katie Schwertz
Brian McComas
March 2020
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