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Library of Congress Cataloging-in-Publication Data Ray Williamson Field guide to Optical Fabrication / Ray Williamson p. cm. -- (The field guide series ; FG20) Includes bibliographical references and index. ISBN 978-0-8194-8676-9 1. Optical instruments--Design and construction. 2. Optical instruments--Testing. I. Title. TS513.W55 2011 681'.4--dc23 2011018206 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 SeriesWelcome 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 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 College of Optical Sciences The University of Arizona The Field Guide SeriesKeep information at your fingertips with all of the titles in the Field Guide Series: Field Guide to Adaptive Optics, Tyson & Frazier Atmospheric Optics, Andrews Binoculars and Scopes, Yoder, Jr. & Vukobratovich Diffractive Optics, Soskind Geometrical Optics, Greivenkamp Illumination, Arecchi, Messadi, & Koshel Infrared Systems, Detectors, and FPAs, Second Edition, Daniels Interferometric Optical Testing, Goodwin & Wyant Laser Fiber Technology, Paschotta Laser Pulse Generation, Paschotta Lasers, Paschotta Microscopy, Tkaczyk Optical Fabrication, Williamson Optical Lithography, Mack Optical Thin Films, Willey Polarization, Collett Special Functions for Engineers, Andrews Spectroscopy, Ball Visual and Ophthalmic Optics, Schwiegerling IntroductionMost Field Guides address a particular subset of physics and/or mathematics and, as such, can be treated in a linear exposition of theory from first principles. In contrast, optical fabrication consists of a collection of disparate crafts, technologies, and business decisions in the service of making nearly perfect physical instances of those geometric and physical theories. I have attempted to organize the subject matter in ways that make sense to me: What the designer needs to know before making final choices, how to specify the components before they are ordered, how conventional fabrication proceeds for representative components, alternative and emerging methods, how the manufacturer plans the work, product evaluation, and calculations used. This Field Guide is intended to serve several audiences, and introduce each to the other. I hope to provide designers and purchasers with some perspectives and appreciation for the craft and business, the shop manager with a concise reference, the optician with a wider overview than one is likely to get within any single company, and the optical community at large with some insight into this fascinating and dynamic enterprise. Thanks are due to Oliver Fähnle for inputs to synchrospeed and fluid jet. I want to particularly acknowledge three influences, true masters in the field: Dick Sumner, Norm Brown, and Frank Cooke. Dick personified excellence in craft, a passionate curiosity, and a focus on effectiveness. Norm brought the light of science and engineering to the hidden mysteries of this once-black art with accessible clarity. Frank was an inspiration to all through his boundless creativity and zest. We are in transition between 20th Century craft and 21st Century technology, and the field will be hardly recognizable in twenty years. This Field Guide is dedicated to my wife, Lore Eargle, in recognition of her encouragement, patience, support, editing, and so much more. Ray Williamson August 2011 Table of ContentsGlossary of Symbols and Acronyms x Introduction for Designers 1 From Functional Desires to Component Tolerances 1 Clear Aperture 2 Thickness versus Stability and Ease of Fabrication 3 Flatness versus Transmitted Wavefront 4 Scale Factors for Surface and Wavefront 5 Wedge in Nearly Concentric Optics 6 Surface Quality versus Performance 7 “Difficult” and Preferred Materials 8 Pressure-Bearing Window Thickness 9 Specifications Checklist 10 Realistic Tolerances 11 Designing Aspheres for Manufacturability 12 What Kind of Shop Is It? 13 Conventional Fabrication Methods 14 Stages of Conventional Fabrication 14 Shop Safety 15 Blocking Layout 17 Blocking Methods 18 Pitch Pickup Blocking 20 Spot Blocks 21 Wedge Tools 22 Sawing 23 Milling 24 Curve Generating 25 Free-Abrasive Grinding 26 Abrasive Types and Grades 27 Fixed-Abrasive Lapping 28 Beveling 29 Dicing 30 Coring and Drilling 31 Edging 32 Centerless Edging 33 Centering 34 Fractures, Chips, and Stoning 35 Marking: Spot Bevels, Dots, Arrows, etc. 36 Polishing 37 Polishing Compounds 38 Pitch Laps: Channels and Figure Control 39 Polishing Pads 40 Crystal Shaping and Orientation 41 Crystal Lapping 42 Overarm Spindle Machine 43 Stick Lens Fabrication 44 Planetary Lapping 45 Double-Sided Lapping 46 Cylindrical and Toric Lapping 47 Intrashop Transportation and Storage 48 In-Process Cleaning 49 Cleaning for Thin-Film Coating 50 Thin-Film Coating 51 Assembly 52 Packaging for Shipping 53 Alternative Fabrication Methods 54 CNC with Spindle-Mounted Tools 54 CNC Synchrospeed Polisher 55 CNC Belt Style Machine 56 CNC Bonnet Polisher 57 Magnetorheological Finishing (MRF®) 58 Fluid Jet Polishing (FJP) 59 Single-Point Diamond Turning (SPDT) 60 Replication 61 Plastic Injection Molding 62 Thermoset Casting and Compression Molding 63 Hot Pressing 64 Process-Planning Factors 65 Raw Material and Forms of Supply 65 Starting Material Dimensions 66 Yield from Dicing and Coring 67 Efficient Production and Optimum Quantities 68 Planning for Yield Losses 69 Block Capacity: Flat 70 Wedge Tool Capacity 71 Block Capacity: Radius 72 Scheduling for Coating 73 Directional Inhomogeneity 74 Stresses within Optical Components 75 Stresses Applied to Optical Components 76 Thermal Settling Time 77 Thermal Failure 78 In-Process Inspection Points 79 Dice After Coating? 80 Cements and Adhesives 81 Evaluation 82 Sampling Inspection and AQL 82 Cosmetic Surface Quality 83 Angle Testing with an Autocollimator 84 Sag and Spherometers 85 Radius, Irregularity, Power, and Figure 86 Interferometry 87 Interferometric Setups 88 PV, RMS, and PVr 89 Fringe Patterns 90 Fringe Scale Factors 91 Conics and Aspheres 92 Dimensional and Geometric Measurement 93 Slope Evaluation Methods 95 Slope Tolerancing 97 Material Properties 98 Material Properties of Interest in the Shop 98 Material Properties Table 99 Optical Properties Table 100 Thermal Properties Table 101 Physical Properties Table 102 Equation Summary 103 References 110 Bibliography 112 Index 116 Glossary of Symbols and AcronymsAOI Angle of incidence AQL Acceptance quality level b Bevel leg length radial to part diameter BFS Best-fit sphere BK7 Schott glass type 517642 BRDF Bidirectional reflectance distribution function C Curvature, 1/radius
Degree Celsius CA Clear aperture CGH Computer-generated hologram CMM Coordinate measuring machine CNC Computer numerical control Cp Specific heat CT Center thickness CTE Linear coefficient of thermal expansion D Diopter, reciprocal meter, unit of focal power D Thermal diffusivity deg Degree, angular dn/dT Change of index with respect to temperature DPTWF Double-pass transmitted wavefront e Natural logarithm base, ~2.718281828 E Young’s modulus EFL Effective focal length ET Edge thickness ETV Edge thickness variation Degree Fahrenheit FS Fused silica GPa Gigapascals h Height of surface form error normal to surface HF Hydrofluoric acid HIP Hot isostatic pressing HK Knoop hardness IR Infrared K Kelvin, absolute temperature units k Thermal conductivity mrad Milliradian MRF Magnetorheological finishing MSDS Material safety data sheet n Index of refraction nm Nanometer, 10−9 m OPD Optical path difference OPL Optical path length PSD Power spectral density PV Peak to valley PVr Peak to valley, robust (due to C. Evans) r Radial distance from axis R Radius of curvature RMS Root-mean-square RSS Root-sum-square RWF Reflected wavefront s Sag SCOTS Software-configurable optical test system S-D Scratch-dig (surface quality) SFE Surface form error SPDT Single-point diamond turning SQ Surface quality SSD Subsurface damage t Thickness T Temperature tc Center thickness te Edge thickness Tg Glass transition temperature TIR Total internal reflection TIS Total integrated scatter TWD Transmitted wavefront distortion TWF Transmitted wavefront UV Ultraviolet y Radial distance from axis z distance along axis α Linear coefficient of thermal expansion α Prism angle, wedge, or tilt α Angular error from reference, as from 90 deg δ Beam deviation θB Brewster’s angle θC Critical angle κ Conic constant κ Thermal diffusivity λ Wavelength μm micrometer, 10−6 m μrad Microradian, 10−6 rad ν Abbé number; reciprocal dispersion ρ Specific gravity σf Rupture strength τ Time ϕ Diameter ϕblock Block diameter ϕeff Effective diameter including spacing |
CITATIONS
Geometrical optics
Optical fabrication
Adaptive optics
Atmospheric optics
Visual optics
Coating
Fiber lasers
