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Ebook Topic:
Front Matter
Abstract
This section contains the introduction, the table of contents, and the glossary of symbols and acronyms.

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.

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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. 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 Series

Keep 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

Introduction

Most 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 Contents

Glossary 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 Acronyms

AOI

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

C

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

F

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

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