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Library of Congress Cataloging-in-Publication Data Names: Symmons, Alan, author. | Schaub, Michael P., author. Title: Field guide to molded optics / Alan Symmons and Michael Schaub. Other titles: Molded optics Description: Bellingham, Washington USA : SPIE Press, [2016] | copyright 2016 | Series: SPIE field guides | Includes bibliographical references and index. Identifiers: LCCN 2015047156| ISBN 9781510601246 (spiral ; alk. paper) | ISBN 1510601244 (spiral ; alk. paper) | ISBN 9781510601253 (PDF) | ISBN 1510601252 (PDF) | ISBN 9781510601260 (epub) | ISBN 1510601260 (epub) | ISBN 9781510601277 (Kindle) | ISBN 1510601279 (Kindle) Subjects: LCSH: Optical instruments-Design and construction-Handbooks, manuals, etc. | Optical materials-Handbooks, manuals, etc. | Plastics-Optical properties-Handbooks, manuals, etc. Classification: LCC TS513 .S96 2016 | DDC 620.1/1295-dc23 LC record available at http://lccn.loc.gov/2015047156 Published by SPIE P.O. Box 10 Bellingham, Washington 98227-0010 USA Phone: 360.676.3290 Fax: 360.647.1445 Email: Books@spie.org Web: www.spie.org Copyright © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE) All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means without written permission of the publisher. The content of this book reflects the thought of the authors. 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. First printing. For updates to this book, visit http://www.spie.org and type “FG37” in the search field.
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 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 the SPIE Field Guides: Adaptive Optics, Second Edition, Robert K. Tyson and Benjamin W. Frazier Astronomical Instrumentation, Christoph U. Keller, Ramon Navarro, and Bernhard R. Brandl Atmospheric Optics, Larry C. Andrews Binoculars and Scopes, Paul R. Yoder, Jr. and Daniel Vukobratovich Diffractive Optics, Yakov G. Soskind Digital Micro-Optics, Bernard Kress Displacement Measuring Interferometry, Jonathan D. Ellis Fiber Optic Sensors, William Spillman, Jr. and Eric Udd Geometrical Optics, John E. Greivenkamp Holography, Pierre-Alexandre Blanche Illumination, Angelo Arecchi, Tahar Messadi, and R. John Koshel Image Processing, Khan M. Iftekharuddin and Abdul Awwal Infrared Systems, Detectors, and FPAs, Second Edition, Arnold Daniels Interferometric Optical Testing, Eric P. Goodwin and James C. Wyant Laser Pulse Generation, Rüdiger Paschotta Lasers, Rüdiger Paschotta Lens Design, Julie Bentley and Craig Olson Lidar, Paul McManamon Linear Systems in Optics, J. Scott Tyo and Andrey S. Alenin Microscopy, Tomasz S. Tkaczyk Nonlinear Optics, Peter E. Powers Optical Fabrication, Ray Williamson Optical Fiber Technology, Rüdiger Paschotta Optical Lithography, Chris A. Mack Optical Thin Films, Ronald R. Willey Optomechanical Design and Analysis, Katie Schwertz and James H. Burge Physical Optics, Daniel G. Smith Polarization, Edward Collett Probability, Random Processes, and Random Data Analysis, Larry. C. Andrews and Ronald L. Phillips Radiometry, Barbara G. Grant Special Functions for Engineers, Larry C. Andrews Spectroscopy, David W. Ball Terahertz Sources, Detectors, and Optics, Créidhe M. O’Sullivan and J. Anthony Murphy Visual and Ophthalmic Optics, Jim Schwiegerling Field Guide to Molded OpticsIn the last few decades, molding has become the dominant optical manufacturing process around the world, although one could hardly tell in the United States. It is the authors’ hope that the concept of a Field Guide to provide a convenient and concise source of knowledge on optical molding technologies will be a valuable reference for any optical engineer. The most common optical molding technologies are injection molding of optical plastics and precision glass molding. This guide primarily focuses on these two technologies but also covers the full spectrum of optical molding. Molding processes continue to innovate and push the boundaries of optical systems, not only for state-of-the-art, high-volume consumer products, but also touching on almost every application where optics are used, from automotive headlights and medical endoscopes to thermal weapon sights. This work would not have been possible without the support of the team at LightPath Technologies Inc., who the author (A.S.) wholeheartedly believes are the world’s experts in precision glass molding. The authors would like to thank SPIE and specifically Tim Lamkins and Dara Burrows for the opportunity to write this guide and for their support along the way. This book is dedicated to: my family—Lauren, Carter, Cooper, and Holden—for their support; my parents for making me who I am today; and Yanggiong ‘Alvin’ Lai, a good friend and a great engineer, who was taken from us way too soon. A.S. This Field Guide is dedicated to Elsa, Shadow, Shira, and Patinhas. M.S. Alan Symmons Michael Schaub May 2016 Table of ContentsGlossary of Symbols and Acronyms xi Introduction 1 Molded Optics 1 Why Use Molded Optics? 2 Applications of Molded Optics 3 Comparison of Molded Optics 4 Conventional Manufacturing versus Molded Optics 5 Aspheric Advantage 6 Material Properties 7 Index of Refraction 7 Dispersion 8 Abbe Diagram 9 Birefringence 10 Transmission 11 Plastic Optic Transmission 12 Thermal Properties 13 Heat Expansion 14 Glass Viscosity 15 Materials 16 Moldable Glass 16 Moldable Glasses for Precision Glass Molding 17 Chalcogenide Glass 18 Glass Datasheets 19 Plastic Optic Materials 21 Plastic Optic Materials Summary 22 Plastic Optic Glass Map 23 Infrared Plastic Optics 24 Plastic Materials Data Sources 25 Thermal Characteristics 26 Glass versus Plastic 27 Molded Glass versus Molded Plastics 28 Environmental Regulations 29 Optical Plastics: Material Selection Criteria 30 Optical Plastic Material Specification 31 Manufacturing 32 Glass Replication 32 Wafer-Level Glass Replication 33 Blank Molding 34 Glass Molding 35 Plastic Optics Manufacturing Methods 36 Precision Glass Molding (PGM) 37 Precision Glass Molding (PGM) 37 PGM Configurations 38 Preforms for PGM 39 Spherical or Ball Preforms 40 Gob Preforms 41 PGM Processing 42 The PGM Zone 43 Process Simulation 44 Annealing Rates 45 Annealing Coefficient 46 Index Drop 47 Index Tolerances 48 Tooling Configurations 49 PGM Machine Diagram 50 PGM Machine Description 51 Transfer Molding 52 PGM Cavitation 53 Vacuum Molding 54 Volumetric Molding 55 Nonvolumetric Molding 56 Very Low-Tg PGM 57 Low-Tg PGM 58 High-Tg PGM 59 Array and Wafer-Level Molding 60 Insert Precision Glass Molding 61 Cost of PGM 62 Injection-Molded Plastic Optics (IMPO) 63 Injection Molding Process 63 Injection Molding Machine Diagram 64 Injection Molding Machine Description 65 Injection Mold Diagrams 66 Injection Mold Description 67 Undercuts, Slides, and Threads 69 Injection Mold Materials 70 Mold Cavitation 71 Family Molds 72 Mold Processing 73 Molding Capacity 74 Optical Molds 75 Optical Molds 75 Mold Materials 76 PGM Mold Design 77 IMPO Mold Compensation 78 Single-Point Diamond Turning 79 Ultraprecision Grinding 80 Vertical Grinding 81 Other Grinding Methods 82 Mold Coatings 83 Mold Metrology 84 Diffractive Surfaces 85 Precision Glass Molding Design Guidelines 86 PGM Glass Selection 86 PGM Lens Terminology 87 PGM Shapes 89 PGM Optomechanical 90 PGM Slope 94 PGM Tolerances 95 Insert Precision Glass Molding 96 Injection-Molded Plastic Optics Design Guidelines 97 IMPO Shape 97 IMPO Flanges 98 IMPO Draft 99 IMPO Gate Flats and Vestige 100 IMPO Center Thickness 101 IMPO Edge Thickness 102 IMPO Clear Aperture 103 IMPO Achromatization 104 IMPO Athermalization 105 IMPO Stray Light 106 IMPO Tolerances 107 IMPO Cost Considerations 108 IMPO Assembly 109 Drawings and Post-processing 110 ISO 10110 110 Geometrical Dimensioning and Tolerancing 111 PGM Drawing Sample 112 PGM Drawings 113 IMPO Drawing Sample 114 IMPO Drawings 116 Antireflection Coatings 117 IMPO Coatings 118 IMPO Secondary Operations 119 PGM Secondary Operations 120 Vendor Input and Review 121 Prototyping Injection-Molded Plastic Optics 122 Prototyping Injection-Molded Plastic Optics 122 Plastic Optics: Additive Manufacturing 123 Prototype Machining 124 Prototype Molding 125 Prototype Assembly 126 Prototype Testing 127 Applications of Molded Optics 128 Glass Mold Applications: Condenser Lenses 128 PGM Applications: Diode Collimation 129 PGM Applications: Fiber Coupling 130 PGM Applications: Camera Lenses 131 PGM Applications: Thermal Imaging 132 IMPO Applications: Cellphone Cameras 133 Appendices 134 Appendix A: Moldable Glasses 134 Appendix B: Chalcogenide Glasses 142 Appendix C: Optical Plastic Properties 144 Equation Summary 145 Bibliography 149 Index 151 Glossary of Symbols and AcronymsAp Annealing point temperature At Yield point or dilatometric softening point temperature, also Ts AOI Angle of incidence AR Antireflection AR Aspect ratio BD Beam diameter BFS Best fit sphere BRC Blend radius cracking c Surface curvature CA Clear aperture CC Center of curvature CCM Cellphone camera module CGH Computer-generated hologram ChG Chalcogenide glass CMOS Complementary metal-oxide semiconductor CNC Computerized numerical control COC Cyclic olefin copolymer COP Cyclic olefin polymer CT Center thickness CTE Coefficient of thermal expansion dn/dT Thermo-optic coefficient DOE Diffractive optical element dPa Decipascal DPW Die per wafer DSC Digital still camera ECHA European Chemicals Agency EFL Effective focal length ET Edge thickness FEA Finite element analysis Fr Fringes GMP Glass molding press iPGM Insert precision glass molding IR Infrared k Conic constant kgf Kilogram force LDT Laser damage threshold LVDT Linear variable displacement transducer LWIR Longwave infrared mnd Annealing coefficient for index of refraction mνd Annealing coefficient for Abbe number MTF Modulation transfer function MWIR Midwave infrared NA Numerical aperture NAS® A transparent styrene acrylic copolymer from INEOS Styrolution Group GmbH nC Index of refraction at 656.27 nm (red hydrogen line) nd Index of refraction at 587.56 nm (yellow helium line) ne Index of refraction at 546.07 nm (green mercury line) nF Index of refraction at 486.13 nm (blue hydrogen line) Nirreg Number of fringes, irregularity Npower Number of fringes, power NIR Near infrared O-PET Optical polyethylene terephthalate OD Outside diameter OG Optical grade P Partial dispersion Pa Pascal PA Physical aperture PC Polycarbonate PEI Polyetherimide PES Polyethersulfone PGM Precision glass molding PMMA Poly(methyl methacrylate) PS Polystyrene PSU Polysulfone P/V Peak-to-valley ratio Q Heat flux per unit area R Radius of curvature RMS Root mean square RoHS Restrictions on Hazardous Substances SA Spherical aberration SAN Styrene acrylonitrile SG Specific gravity SPDT Single point diamond turning Sp Littleton softening point temperature Stp Strain point temperature SWIR Shortwave infrared T Temperature T7.6 Temperature at which glass has a viscosity of 7.6 poise or dPa·s T10 Temperature at which glass has a viscosity of 10 poise or dPa·s T13 Temperature at which glass has a viscosity of 13 poise or dPa·s T14.5 Temperature at which glass has a viscosity of 14.5 poise or dPa·s Tg Glass transition temperature Tm Molding temperature Ts Yield point or dilatometric softening point temperature, also At TIR Total indicated runout TVG Tilted vertical grinding (or 45-deg vertical grinding) UV Ultraviolet VG Vertical grinding (or cross-axis grinding) VGA Video graphics array VIS Visible VLT Very low Tg WD Working distance WL Wafer level WLC Wafer-level camera WLGR Wafer-level glass replication WLO Wafer-level optics WLP Wafer-level packaging WLPGM Wafer-level precision glass molding WNG Wheel normal grinding α Coefficient of thermal expansion, also CTE αg CTE, glass αL CTE, liquidus αm CTE, mold αS CTE, solidus β Annealing coefficient λ Wavelength φ Power of an optical surface σPV Wavefront error, peak-to-valley σRMS Wavefront error, root mean square νd Abbe number at 587.56 nm (yellow helium line) νe Abbe number at 546.07 nm (green mercury line) |
CITATIONS
Geometrical optics
Thermography
Optics manufacturing
Precision glass molding
Glasses
Adaptive optics
Atmospheric optics
