UNIFIED OPTICAL SCANNING TECHNOLOGY

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1 UNIFIED OPTICAL SCANNING TECHNOLOGY

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5 UNIFIED OPTICAL SCANNING TECHNOLOGY LEO BElSER IEEE PRESS JOHN WILEY & SONS PUBLICATION

6 Copyright by.john Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either th e prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, , fax , or on the web at www,copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken. NJ 07030, (201) , fax (201) , permreq@wiley.com. Limit of LiabilityiDisclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services please contact our Customer Care Department within the U.S. at , outside the U.S. at or fax Wiley also publishes its books in a variety of electronic formats. Some content that appears in print, however, may not be available in electronic format. Library of Congress Cataloging-in-Publication Data: Beiser. Leo. Unified optical scanning technology / Leo Beiser p. cm. Includes bibliographical references and index. A Wiley-Interscience publication. ISBN (cloth) 1. Optical scanners. 2. Optical storage devices. I. Title TK7882.S.B dc Printed in United States of America

7 To Edith My Golden Coherent Light

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9 CONTENTS Preface xi 1 INTRODUCTION-TECHNOLOGY OVERVIEW AND UNIFYING PRINCIPLES Optical Scanning Characteristics and Disciplines / Active and Passive Scanning / Conjugate Image Representations / Retroreflection and Double-Pass Systems / Input, Output, and Remote Sensing Systems / Optical and Resolution Invariants; Optical Transfer / System Architecture / Objective Lens Relationships / 13 2 SCANNING THEORY AND PROCESSES The Point Spread Function and Its Convolution / PSF Developed from Uniform Illumination of an Aperture / PSF Developed from Aperture Illumination with a Gaussian Distribution / Scanning-Controlled Movement of the PSF; Its Convolution / 25 vii

10 viii CONTENTS 2.2 Quantized or Digitized Scan / The Sampling Criterion Gaussian Beam Propagation i Representation and Development of the Gaussian :Beam Gaussian Beam Focusing Characteristics i Scanned Quality Criteria and the Modulation Transfer Function i The Fourier Transform / fie Modulation Transfer Function i 40 3 SCANNED RESOLUTION Influence and Significance of Scanned Resolution / Basis of Scanned Resolution / liesolution Nomograph / Aperture Shape Factor / ljniformly Illuminated Apertures / Summary of Apertue Shape Factors / The Resolution Equation, the Resolution Invariant, and Beam Propagation i Propagation of Noise and Error Components / Augmented Resolution i Radial Symmetry and Scan Magnification i Augmented Resolution for Holographic Scanners / Resolution in Passive and Remote Sensing Systems / 61 4 SCANNER DEVICES AND TECHNIQUES Scanner Technology Organization / High-Inertia Scanning / Rotating Polygons i Ilistinctions Between Pyramidal and Prismatic Polygons / Duty Cycle i Over- and Underillumination (Over- and Underfilling) of the Facet / 68

11 CONTENTS ix Facet Tracking / Design Considerations I Passive Scanning for Remote Sensing I Holographic Scanners I Scanner Configurations and Characteristics / Implementation of Holographic Scanners / Oscillatory (Vibrational) Scanners / The Galvanometric Scanner / The Resonant Scanner / Suspension Systems and Position Control I The Fast-Steering Mirror / The Fiber Optic Scanner / Scanner-Lens Relationships I Scanner-Lens Architecture / Double-Pass Architecture I Aperture Relaying I kens Relationships for Control of Deflection Error I Low-Inertia Scanning / Acoustooptic Scanners / Operating Principles / Fundamental Characteristics / Alternate Acoustooptic Deflection Techniques / Electrooptic (Gradient) Scanners / Tmplementation Methods / Drive Power I Agile Beam Steering / Phased Array Technology I Decentered Microlens Arrays I Summary of Agile Beam Steering I CONTROL OF SCANNER BEAM MISPLACEMENT Cross-Scan Error and Its Correction / General Considerations and Available Methods / Passive Methods / 150

12 X CONTENTS 5.2 The Ghost Image and Its Elimination / Skew Beam Method of Ghost Elimination / Beam Offset Method of Ghost Elimination / SUMMARY-MAJOR SCANNER CHARACTERISTICS Comparison of Major Scanner Types / 164 References Index

PREFACE What is Optical scanning? Let me offer a definition. Optical scanning is a systematic articulation of light to provide information transfer. Then, what is information?

13 PREFACE What is Optical scanning? Let me offer a definition. Optical scanning is a systematic articulation of light to provide information transfer. Then, what is information? Consider that it means simply organized knowledge. What were the first optical scanning innovations? Semaphores? Or, how about, smoke signals? That is, amplitude modulation of scattered light from controlled groups of particulate aerosol, which disperse as they rise, as observed from a distance. This is a form of serial information transfer. The two principal forms of optical information transfer are identified as serial and parallel. The parallel form is represented classically by fields such as telescopy, microscopy, and photography-effectively rendering simultaneous transport of the information. The serial form is dominated currently by familiar fields such as television, , and the reproduction of the graphic arts and sounds, utilizing an arranged timed series of pixels, pels, or voxels. This temporal factor is of basic interest, for it allows (via the optical/electrical transducer-modulator and detector), efficient electronic processing. It is because of this fundamental flexibility that optical scanning has engendered such a commanding role for information transfer. As is surely recognized, many of the classic parallel systems have evolved to either hybrid serial/ parallel or fully serial utilizing various forms of spatial scanning to gain the operational advantages in data manipulation and transfer. Adept development requires, however, dedicated attention to the breadth of the disciplines that may be integrated into these typically diverse xi

14 Xii PREFACE systems. An objective of this work is to render a unified orientation to these fundamental and often secluded related factors. Optical scanning may be conducted with many shades of light, ranging spectrally from UV through the visible to IR and exhibiting incoherent to coherent order. Although the transfer of optical information that is outside that range of electromagnetic radiation is perfectly valid, as notably by CT (X-ray) scans, they are limited in the angular scan flexibility manifest in the dominant forms of optical scanning. Similarly, with the introduction of the laser in the early 1960s, exhibiting its extremely disciplined propagation characteristics, active optical scanning is typically of the laser beam, identified compactly as laser scanning. One important exception is the field of remote sensing. Here, passive incoherent radiation from a remote source is collected optically at a distance. Its spatial and spectral composition is analyzed by scanning/detection devices to form organized patterns of pixels for subsequent reconstitution. Significant for us is that the scanning devices for each field-operating from very independent viewpoints-exhibit remarkably common factors. This has been highlighted only recently in a publication by this author and R. Barry Johnson, with the objective of unification of the technology. The background and comparative disciplines are expanded in this work. Other aspects of commonality are the fundamental analogies between different disciplines, as in optical and electronic scanning theory, and in the sampling requirements for effective image, data, and acoustic reconstitution. Recurrent cross-referencing of related factors appears in different portions of this volume. Included is attention to significant arcane techniques such as the Scophony system and several other enlightening acoustooptic scanning methods. Another realization of this work is the periodic heuristic clarification of the fundamentals, with little dependence on the use of detailed mathematical affirmation-which may be accessed readily in the referenced literature. In recognizing a scanning technology with an extensive background, which has been enhanced under government support for over a decade, this volume offers the first general publication on the advancing field known as agile beam steering. Germinating over the past three decades (reported by this author in 1974), it has attained serious R&D attention for broad application. Agile beam steering is reviewed and presented comprehensively as another unifying dimension. Rendering now only the thematic highlights, it is noteworthy that the final chapter in this volume summarizes the principal thrust of each chapter. It closes with a unique and potentially controversial indepen-

15 PREFACE Xiii dent compilation of the major scanner types, avoiding the almost inevitable preferences that can appear in summaries published by wellmeaning researchers, developers, or manufacturers. Taking a moment to reflect on and recognize the people who have nurtured this work, I extend my unlimited admiration and thanks first to my loving wife, Edith, who has tolerated the diversions, machinations, interruptions, and seclusions, for the sake of whatever accomplishment this may have represented in our minds. Since I have retired officially recently, after 25 years of independent consultation practice, with many prior rewarding writing experiences behind me, and now looking forward to long-delayed relaxation, I d be out of my mind to even think of doing this again. Valued support and guidance was rendered in astute review of several chapters by R. Barry Johnson of Optical ETC. Inc., with whom I have had the pleasure of working closely in prior co-authorship and in many exhilarating discussions. Another esteemed review was conductd by Ed Watson of the Air Force Research Labs, rendering revealing and supportive comment on my coverage of a technology of his renowned specialty. The collective total of my professional relationships has surely nurtured this work. My colleague Gerald Marshall, who, after joining the consultation field, also joined me in cochairing many of our SPIE Technical Conferences and rendering valued diversity. More recently, this resource was enhanced with the cochairmanship of Steven Sagan, who adds the inspiration of youth and the breadth of lens design to our conference skills. Many more-far too many to identify-have surely formed a composite inspiration. You know who you are. Special regard is accorded to George Telecki, Associate Publisher at John Wiley & Sons, Inc., who has provided much appreciated patience and understanding in his guidance of this work. My sincere thanks to all. Leo Beiser Flushing, New York

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