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MICHAEL W. BURKE

META VISION ATLANTA

Published by Chapman & Hall,2-6 Boundary Row, London SEt SHN, UK

Chapman & Hall, 2-6 Boundary Row, London SEI 8HN, UK

Chapman & Hall GmbH, Pappelallee 3, 69469 Weinheim, Gennany

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Chapman & Hall Australia, 102 Dodds Street, South Melbourne, Victoria 3205, Australia

Chapman & Hall India, R. Seshadri, 32 Second Main Road, CIT East, Madras 600 035, India

First edition 1996

© 1996 Micheal W. Burke Softcover reprint of the hardcover 1st edition 1996

ISBN-13:978-94-01O-6S20-7 e-ISBN-13:978-94-009-0069-1 DOl: 10.1007/978-94-009-0069-1

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the tenns of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the tenns of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the tenns stated here should be sent to the publishers at the London address printed on this page.

The publisher makes no representation, express or implied, with regard to the accuracy of the infonnation contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made.

A catalogue record for this book is available from the British Library

Library of Congress Catalog Card Number: 95-68341

~ Printed on pennanent acid-free text paper, manufactured in accordance with ANSIINISO Z39.48-1992 and ANSIINISO Z39.48-1984 (pennanence of Paper).

To the memory of my mother,

Grace Adriana Christensen Burke

VOLUME

TABLE OF CONTENTS

About the Author ••••.••.•.•.•.••••.•••••.••.•.•.•• xii

Series Preface •..••.•.•......•...•••.•.•.•.•.•.•.. xiii Goals of the book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xv Citations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xviii Other MV books ............................... xviii The role of theory ............................... xix

Theory ...................................... xix Practice ..................................... xix A rapprochement .............................. xx A note on mathematics ........................ xxi

Who this book is for ............................. xxi What the reader needs to know .................... xxiii Organization and overview ....................... xxiii Colophon ..................................... xxiv Summary ..................................... xxiv

Volume Preface • . • . • • • • • • • . • • . . . • . . . . . . . . . . . . . . •. xxvi

Acknowledgements ...•..•....................... xxvii

Symbol Glossary. • . . • . • • . • . • . • . . • . • . . . • . • . • . • . • • .• xxx

1 Lighting I: Principles . . . . . . . . . . • . . .. 1 1.1 Introduction.................... • • . • . • • . • . • • • •. 1

1.2 Nature of light .•••••••••.•.•.•.•.•.•••.•.•.••••. 4 1.2.1 Interaction with matter ..................... 16 1.2.2 Model of the atom ........................ 19 1.2.3 Interference effects. . . . . . . . . . . . . . . . . . . . . . .. 22 1.2.4 Diffraction.............................. 23 1.2.5 Scattering............................... 26

1.3 Measurement oflight. . . . . . . • . . . . . . • • . • . • . • • • • .• 26 1.3.1 Radiometry.............................. 28

1.3.1.1 Radiant flux. . . . . . . . . . . . . . . . . . . . . .. 28 1.3.1.2 Radiant intensity ................... 29

Point-source intensity ................ 33 1.3.1.3 Radiant exitance / emittance. . . . . . . . .. 34 1.3.1.4 Radiant incidence /irradiance. . . . . . . .. 34 1.3.1.5 Radiance / sterance ................. 38

1.3.2 Photometry .............................. 41 1.3.2.1 Luminous flux. . . . . . . . . . . . . . . . . . . .. 43 1.3.2.2 Luminous intensity . . . . . . . . . . . . . . . .. 44 1.3.2.3 Illuminance....................... 46 1.3.2.4 Luminous exitance . . . . . . . . . . . . . . . .. 48 1.3.2.5 Luminance / sterance ....•.•......... 48

1.3.3 Measurement procedures ................... 51 1.3.3.1 Irradiance / illuminance. . . . . . . . . . . . .. 51 1.3.3.2 Exitance .......................... 51

1.3.3.3 Intensity.......................... 51 1.3.3.4 Sterance.......................... 53 1.3.3.5 Flux measurement. ................. 54

1.4 Generation of light. • • • . • • • . . . • • • • • • • • • • • . • . . • .• 61 1.4.1 Incandescence............................ 62 1.4.2 Luminescence............................ 63

1.4.2.1 Phosphorescence / fluorescence . . . . . .. 63 1.4.2.2 Electroluminescence................ 64 1.4.2.3 Cathodoluminescence............... 64

1.4.3 Electric arc . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 64

1.5 Lighting models ••••.••••••.•.••••.•••.••.•••.• 65 1.5.1 Scene radiometry ......................... 76

1.5.1.1 Generic surface and extended source ... 80 1.5.1.2 Lambertian surface / extended source ... 82 1.5.1.3 Lambertian surface / directed source ... 84 1.5.1.4 Diffuse source . . . . . . . . . . . . . . . . . . . .. 84 1.5.1.5 Specular surfaces ................... 85 1.5.1.6 Albedo ........................... 86 1.5.1.7 Empirical measurement ofRDF ....... 87

1.5.2 Source geometry .......................... 88 1.5.2.1 Point-sources ...................... 88 1.5.2.2 Finite-area patch . . . . . . . . . . . . . . . . . .. 89 1.5.2.3 Circular disk ...................... 90 1.5.2.4 Spherical source .. . . . . . . . . . . . . . . . .. 92 1.5.2.5 Linear source. . . . . . . . . . . . . . . . . . . . .. 93 1.5.2.6 Cylinder / tube ..................... 98 1.5.2.7 Rectangular strip . . . . . . . . . . . . . . . . . .. 99 1.5.2.8 Tube sources ..................... 101 1.5.2.9 Square diffuser ..... . . . . . . . . . . . . .. 101

1.5.3 Non-standard sources ..................... 103 1.5.3.1 Elliptical source ................... 105 1.5.3.2 Transparent / arc sources. . . . . . . . . . .. 106

1.6 Lighting geometry I techniques. • . • . • • • • . • . . . • • •• 107 1.6.1 Frontlighting............................ 109

1.6.1.1 Directional. ...................... 109 Darkfield . . . . . . . . . . . . . . . . . . . . . . .. 111 Brightfield. . . . . . . . . . . . . . . . . . . . . .. 112

1.6.1.2 Diffuse lighting. . . . . . . . . . . . . . . . . .. 112 1.6.1.3 Integrating sphere enclosures ........ 116

1.6.2 Backlighting............................ 117 1.6.2.1 Directional ....................... 119

Collimated. . . . . . . . . . . . . . . . . . . . . .. 119 Condensed. . . . . . . . . . . . . . . . . . . . . .. 120

1.6.2.2 Diffuse.......................... 121 1.6.3 Structured lighting. . . . . . . . . . . . . . . . . . . . . .. 123

1.7 Summary .•.•.•.•.•.•.•..•.••••••.•.•.••••••• 124

viii

2 Lighting ll: Sources • • • • • • • • • • • • .• 127 2.1 Introduction................................. 127

2.2 Ambient light ••••• • • • • • • • • • • • • • • • • • • • • • • • • ... 130 2.2.1 Daylighting ...............•.•...•...•••• 131

2.2.1.1 Solar irradiance . . . . . . . . . . . . . . . . . .. 131 2.2.1.2 Skylighting ...................... 136

2.2.2 Nightlighting ........................... 138

2.3 Incandescent lamps ................... • • • • • • •• 139 2.3.1 Filaments ..••••.•.•...•.•.............. 140 2.3.2 In-rush current .. .. .. .. .. .. .. .. .. .. .. .... 142 2.3.3 Flicker................................. 143 2.3.4 Fill-gases............................... 144 2.3.5 The bulb. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 145 2.3.6 Service life .....................••••.... 146 2.3.7 Spectral content (color) .•.••.............. 149 2.3.8 Efficacy ................................ 149

2.4 Quartz-halogen lamps • • • • • • • • • • • • • • • • • • • • • • • •• 151

2.5 Arc and gas discharge. • • • • • • • • • • • • • • • • • • • • • • •• 155 2.5.1 Short-arc lamps .•.•.•...•.•.............• 156 2.5.2 Gas-discharge lamps. . . . . . . . . . . . . . . . . . . . .. 158

2.5.2.1 Low-pressure discharges ••.•••...... 160 2.5.2.2 Filament structures. . . . . . . . . . . . . . .. 165 2.5.2.3 Fill-gases........................ 166 2.5.2.4 Arc starting. . . . . . . . . . . . . • . . . . . . .. 168

2.5.3 Fluorescent lamps ................••••.... 169 2.5.3.1 Temperature effects ................ 172 2.5.3.2 Phosphors and colors. . . . . . . . . . . • • •. 174 2.5.3.3 Service life ....••...•...•.••••.... 180 2.5.3.4 Lamp ignition ................ .... 182 2.5.3.5 Bulb types • • • • • • • • • • • • • • • • • • • • • •• 183

2.5.4 HID lamps •••.....•.•..........•.•••... 185 2.5.4.1 High-pressure discharges ..........• 187 2.5.4.2 High-pressure mercury lamps ........ 191 2.5.4.3 Blended light.. .. .. .. .. .. .. .. .. ... 195 2.5.4.4 Metal halide lamps ...... .. .. .. .... 196 2.5.4.5 Low-pressure sodium •. . . • . . . . . . • .. 201 2.5.4.6 High-pressure sodium . . . . . . . . . . . . .• 205

2.5.5 Ballasting gear . .. .. .. .. .. .. .. .. .. .. .. ... 209 2.5.5.1 HID ballasting .................... 220 2.5.5.2 Flicker ............•............. 224 2.5.5.3 EMI ............................ 225 2.5.5.4 HID usage. • • • . • . • . . . . . • . . . . • • • .• 226 2.5.5.5 Arc lamp safety •••••.•..•••.•••••• 228

2.5.6 Strobes................................ 229 2.5.6.1 Flash intensity .................... 235 2.5.6.2 Flash duration .. .. .. .. .. .. .. .. .... 236 2.5.6.3 Guide number .................... 237 2.5.6.4 Flash rate • . . . . . . . . . . . . . . . . • • . • . .. 238 2.5.6.5 Strobe synching.. .. .. .. .. .. .. .. ... 239

2.6 Lasers ••••••••••••••••••••••••••••••••••••••• 239 2.6.1 Beam modes. . . . . . . . . . . . . . . . . . . . . . . . . . .. 243 2.6.2 Coherence .............................. 245 2.6.3 Laser optics •.•..••.•.....•.•••..•.•.•.•. 246 2.6.4 Gas lasers . • . • • . • • • • • • • • . • . . . . . . . . . . • . .. 247 2.6.5 Solid lasers .. .. . .. .. .. .. . .. .. .. .. .. .. ... 248

2.6.5.1 Semiconductor diode lasers ..••.••••• 248 2.6.5.2 Thnable lasers .. .. .. .. .. .. .. .. .... 256

Table of Contents

2.6.6 LEDs .................................. 256 2.6.6.1 Pulsed operation .... .. .. .. .. .. .... 259

2.6.7 Laser safety •.............••....•.••..... 261

2.7 Electroluminescent panels. • • • • • • • • • • • • • • • • • • • •• 264

2.8 Specialized spectral sources •••••••••••••••••••• 266 2.8.1 Ultraviolet sources ••••••••••••••••••••••• 266 2.8.2 Infrared ................................ 272 2.8.3 X-ray sources ........•.•.••.......•..... 275 2.8.4 Ultrasonics............................. 279

2.9 Summary •••••••••••••••••••••••••••••••••••• 281

3 Optics I: Imaging ••••••••••••••• 284 3.1 Introduction ••••••••••••••••••••••••••••••••• 284

3.2 Optical systems ••••••••••••••••••••••••••••••• 284 3.2.1 Transmission ......•.•••.....••..•....•.. 286 3.2.2 Refraction.............................. 287 3.2.3 Reflection.............................. 294

3.2.3.1 Fresnel's equations - dielectrics. . . . .. 295 3.2.3.2 Fresnel's equations - metals. . . • • . . .. 298 3.2.3.3 TIR............................. 299 3.2.3.4 Laser speckle.. .. .. .. .. .. .. .. .. ... 300

3.3 Lenses ...................................... 300 3.3.1 Pinhole model. • . . . . . . . . . • • • . . • • • . . . . . . •. 301 3.3.2 Paraxial / Gaussian optics. . . . . . . . . . . . . . . . .. 305 3.3.3 Field-of-view........................... 306 3.3.4 Focal length • . . . . . . . • . . . . . . . . • . . . . . . • . .. 307

3.3.4.1 Magnification .................... 311 3.3.4.2 Thicklens ....................... 317 3.3.4.3 Compound lenses .••••.•.••......• 319

Two positive lenses. . . . . . . . . . . . . . .. 323 Positive + negative lenses . . . • . . . . . .. 323 Multiple lens systems .. .. .. .. .. .... 324

3.3.5 Lens aperture /lens speed ....••......•••.. 326 3.3.5.1 Aperture stops .................... 327 3.3.5.2 Field stops . . .. .. . .. .. . .. .. .. . .... 328 3.3.5.3 Relative aperture .. .. .. .. .. .. .. .... 329

Effective aperture .. .. .. .. .. .. .. ... 334 Transmission aperture. . . . . . . . . . • • .. 335 Iris ..••..........•....•.•.....•• 335

3.3.5.4 Pupils ........................... 336 Entrance pupil. . . • • • • • • • • • • . . . . • •• 337 Exit pupil. • . . . . . . . . . . . • • . . . . . . . •• 338 Pupil factor • • • • . . . . • • . . . • • • . • • • .• 338

3.3.5.5 Vignetting .. .. .. .. .. .. .. .. .. . .... 340 Optical vignetting .. .. .. .. .. .. .. ... 340 Mechanical vignetting •.....•......• 342

3.3.5.6 Numerical aperture .. .. .. .. .. .. .... 345 3.3.6 Depth-of-view ••......•••••..•.••......•• 348

3.3.6.1 Depth-of-focus ................... 352 3.3.7 Aberrations ..........•.••••...•••..•.... 353

3.3.7.1 Spherical aberrations .•.....•....... 355 3.3.7.2 Coma •.•••....••••••.•.•••.••..• 358 3.3.7.3 Astigmatism ..................... 359 3.3.7.4 Field curvature .................... 360 3.3.7.5 Distortion ...••••.••.•.•••••••.... 361 3.3.7.6 Chromatic aberration ...•.•....••••• 363

Table of Contents

3.3.7.7 Summary ........................ 365 3.3.8 Lens types .............................. 367

3.3.8.1 Positive singlets. . . . . . . . . . . . . . . . . .. 367 Plano-convex. . . . . . . . . . . . . . . . . . . .. 368 Double-convex .. . . . . . . . . . . . . . . . .. 368 Positive meniscus .. . . . . . . . . . . . . . .. 369 Positive achromats. . . . . . . . . . . . . . . .. 370

3.3.8.2 Negative singlets. . . . . . . . . . . . . . . . .. 371 3.3.8.3 Doublets......................... 372 3.3.8.4 Triplets, etc . . . . . . . . . . . . . . . . . . . . .. 373 3.3.8.5 Cylindrical lens ................... 373 3.3.8.6 GRIN lenses ..................... 377

Lens arrays ...................... 378 3.3.8.7 Fresnel zone plates ................ 379 3.3.8.8 Specialty lenses. . . . . . . . . . . . . . . . . .. 380

Zoom lenses ...................... 380 Large-fonnat lenses ................ 380 Projection lenses. . . . . . . . . . . . . . . . .. 381

3.3.9 Holographic optics ....................... 382 3.3.10 Anti-reflection coatings . . . . . . . . . . . . . . . . . .. 382

3.3.10. 1 Film thickness inspection ........... 386

3.4 Imaging mirrors .••.•.•.•.........•.•.••••.•.• 387 3.4.1 Plane mirrors ........................... 390 3.4.2 Concave spherical mirrors ................. 391 3.4.3 Convex spherical mirrors. . . . . . . . . . . . . . . . .. 392 3.4.4 Mirror coatings. . . . . . . . . . . . . . . . . . . . . . . . .. 393

3.4.4.1 Aluminum ....................... 394 3.4.4.2 Silver and gold ................... 394 3.4.4.3 Thin-film ........................ 395

3.4.5 Mirror-lens systems ...................... 396

3.5 Prisms ...................................... 398 3.5.1 Optical flats ............................ 399 3.5.2 Wedge prisms ........................... 400 3.5.3 Dispersion / equilateral prisms .............. 400 3.5.4 Isoceles-Littrow prisms ................... 402 3.5.5 Right-angle prisms ....................... 403 3.5.6 Porro prisms ............................ 404 3.5.7 Rhomboid prisms ........................ 405 3.5.8 Trihedral prisms ......................... 405 3.5.9 Dove prisms ............................ 405 3.5.10 Amici (roof) prisms ...................... 406 3.5.11 Penta prisms ............................ 407 3.5.12 Prism aberrations ........................ 407 3.5.13 Beamsplitters ........................... 408

3.6 Closing remarks ••••.••.•.•.•.•.••••••••.•.••. 412

4 Optics II: Systems ••.•........•••• 414 4.1 Introduction •••••••.•••••••••.•.•.•••.••••••• 414

4.2 Optics for lighting ............................ 414 4.2.1 Beam expanders ......................... 417 4.2.2 Condensers ............................. 418 4.2.3 Collimators ............................. 421 4.2.4 Fresnellenses........................... 422 4.2.5 Aspheric lenses. . . . . . . . . . . . . . . . . . . . . . . . .. 424 4.2.6 Lighting projection. . . . . . . . . . . . . . . . . . . . . .. 425

ix

4.3 Lighting mirrors ••••••.••.•.......••••.••••••. 426 4.3.1 Spherical reflectors. . . . . . . . . . . . . . . . . . . . . .. 426 4.3.2 Paraboloidal reflectors. . . . . . . . . . . . . . . . . . .. 427 4.3.3 Ellipsoidal reflectors. . . . . . . . . . . . . . . . . . . . .. 428 4.3.4 IR mirrors. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 430

4.4 Lens filters .......•.•.•.•.•.••••.•..•••.•••••• 431 4.4.1 Spectrally selective filters ................. 433

4.4.1.1 Colored filters . . . . . . . . . . . . . . . . . . .. 433 4.4.1.2 Interference filters. . . . . . . . . . . . . . . .. 436

Band-pass filters . . . . . . . . . . . . . . . . .. 436 Edge filters ...................... 439

4.4.2 Neutral-density filters. . . . . . . . . . . . . . . . . . . .. 440 4.4.3 Protective filters. . . . . . . . . . . . . . . . . . . . . . . .. 441

4.5 Diffusers.... • • • . • . • . • . • . • . • . • • . . • • • • • . • . • . •• 443 4.5.1 Retroreflective materials .................. 445

4.6 Polarized light. . • • • • . • . • . • • • . . • . • • • • . • • • • • • . .• 447 4.6.1 Polarizers.............................. 449

4.6.1.1 Absorption / dichroism ............. 452 4.6.1.2 Refraction / birefringence. . . . . . . . . .. 453

Polarizing prisms. . . . . . . . . . . . . . . . .. 455 4.6.1.3 Selective scattering. . . . . . . . . . . . . . .. 458 4.6.1.4 Reflective polarization .. . . . . . . . . . .. 460

Polarizing beamsplitters . . . . . . . . . . .. 462 4.6.1.5 Circular polarization. . . . . . . . . . . . . .. 463 4.6.1.6 Optical activity .. .. .. . .. .. .. . .. ... 465

Retardation plates . . . . . . . . . . . . . . . . . 466 4.6.1.7 Electro-optic polarization ........... 467

Electro-optic shutters. . . . . . . . . . . . . .. 468 4.6.2 Phase-contrast imaging .................... 471

4.7 Lens physical characteristics ••••.•.••...•••••••• 471 4.7.1 Lens fonnats ............................ 472 4.7.2 Lens mounts ............................ 473

4.7.2.1 C-mount ......................... 475 4.7.2.2 Pentax U-mount ................... 476 4.7.2.3 Nikon F-mount ................... 476 4.7.2.4 Leica L-mount. ................... 477

4.7.3 Optical materials ......................... 477 4.7.3.1 Optical glasses .................... 477 4.7.3.2 Special glasses .................... 480 4.7.3.3 Fused silica ...................... 480 4.7.3.4 Sapphire ......................... 481 4.7.3.5 Plastic .......................... 482 4.7.3.6 Lens costs ....................... 483 4.7.3.7 Lens hoods ....................... 484

4.8 Shutters I exposure timing.. .. • . • . • • . • . • .. .. .... 484

4.9 Autofocusing. • • . • • . . • . • . • • • • • • • • • • • • • • • . • • • •• 487 4.9.1 Ranging ................................ 488 4.9.2 Astigmatic focusing ...................... 489 4.9.3 Knife-edge focusing ...................... 489 4.9.4 Biprism focusing ........................ 490 4.9.5 Image contrast ........................•. 491 4.9.6 Phase-detection focusing .................. 494 4.9.7 Electronic-signal focusing ................. 494 4.9.8 Others ......................•....•.•... 495

4.10 Specialized optics. • . • . • • • • • • • • • • • • • • • . • . • • • • •• 495 4.10.1 Close-up imaging ........................ 495

4.10.1.1 Macro lenses ................... 496

x

4.10.1.2 Extension tubes ......•.......... 498 Focal length conversion . . . . . . . . .. 500

4.10.1.3 Close-up lenses ..•........•.•... 500 Afocal converters . . • • • . . . . . . . . •. 501 Telescopic converters . . . . . . . • • . .. 501 Wide-angle converters ........... 502

4.10.1.4 Teleconverters. • . . . . . • . . • . . . . . .. 502 4.10.1.5 Edge location paradigms ..•....... 503 4.10.1.6 Pinhole optics .................. 505 4.10.1.7 Confocal imaging ..............• 507 4.10.1.8 Telecentric optics ....•......•... 508 4.10.1.9 Telephoto lenses •.••••..••...... 510 4.10.1.10 Relay optics .................... 511 4.10.1.11 Segmented imaging. . . . . • . . . . • • .. 511 4.10.1.12 Schlieren imaging .....•...•..•.. 512

4.10.2 Perspective •....••....•......•..•....... 513 4.10.2.1 Orthographic perspective •.•...... 515

Panoramic perspective ........•.. 515 Fisheye imaging .........•...... 516

4.10.2.2 Image-shape control .......••.... 517

4.U Beyond the visual spectrum •••••••••••••••••••• 520 4.11.1 IRoptics .•............................. 520 4.11.2 UV optics .............................. 522

4.12 Fiber-optics •••••••••••••••••••••••••••••••••• 523 4.12.1 Fibertypes •............................ 526 4.12.2 Extrinsic fiber losses .....•.....•.••....... 528

4.12.2.1 Launching losses .•.............• 528 Numerical aperture . . . . . . . . . • • . •. 528 Output losses ................... 532 Face (Fresnel) losses. . . . . . . • • . . •• 533

4.12.2.2 Connector losses ......•••...••.. 533 4.12.2.3 Defect losses. . . . . . . . . . . . . • • • . .. 534

4.12.3 Intrinsic fiber losses . . . . . . . . . . . . . . . . . . . . .. 534 4.12.3.1 Absorption losses ..••........... 535 4.12.3.2 Scattering losses ..............•. 536

4.12.4 Optical efficiency considerations .•••..••.•.. 536

4.13 Summary.................................... 537

5 Sensors I: Basics................. 539 5.1 Introduction.. .. • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 539

5.2 Pbotodetectors.. • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 542 5.2.1 Photoemissive sensors .............•....•. 543 5.2.2 Photovoltaic cells. . . . . . . . . . . . . . • • • . . . . . .. 543 5.2.3 Photoconductors ...............•...••.... 544 5.2.4 Junction photodetectors • . . . . . . . . . . . . . • . . .. 546

5.2.4.1 Semiconductors .....•••........... 547 5.2.4.2 Quantum efficiency. . • . • . . . . . . . . . .. 553 5.2.4.3 P-Njunctions .••...•.......•.•.... 555 5.2.4.4 Photovoltaic mode. . . . . . • . • . • • • • . •• 559 5.2.4.5 Photoconductive mode ......••••... 561 5.2.4.6 Photointegrative mode ............. 562 5.2.4.7 Photodiodes ...............•.....• 563

5.2.5 Photogates.............................. 566 5.2.6 Other sensing elements. . . . . . . . . . . . . • • • . • .• 569

5.3 Readout. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 570 5.3.1 Vacuum-tube cameras ......•.............. 573

Table of Contents

5.3.1.1 Orthicon tubes ..•.•.•............. 574 5.3.1.2 Vidicon ......................... 575 5.3.1.3 Others .............•...•........ 576

5.3.2 CCD transfer ......•...••..........••.... 579 5.3.2.1 The charge-transfer process ••••••••• 580 5.3.2.2 Charge-transfer efficiency. . . . . . • • . .. 586

5.3.3 Serially-switched photodiode devices ..•..•. 589 5.3.4 Charge-coupled photodiode devices ..•••.•.. 592 5.3.5 cm readout . . . . . . . . . . . . . . . . . . . . . . . . . . .. 599 5.3.6 Storage I architectures ...........•....•... 604

5.3.6.1 Linescan sensors .............•.... 605 5.3.6.2 Matrix-array sensors •.•......••.••. 613

Full frame .•••.••••.••••••••• : ••• 614 Frame transfer .................... 615 Interline transfer . . . . . . • . . . • • . • . . .. 617 Frame-interline hybrids .•...•..••... 618

5.3.6.3 IDI sensors ...........•..•..••... 619 5.3.7 Charge conversion . . . . . . . . . • . . . . . . . . • . . .. 626 5.3.8 Solid-state cameras .•...•.........••...... 628

5.4 Performance characteristics. • • • • • • • • • • • • • • • • • •• 629 5.4.1 Sensitivity I responsivity ..••.••......•.••• 630

5.4.1.1 Spectral response .....•.......•..•. 633 5.4.1.2 Linearity ............•......•.... 636 5.4.1.3 Uniformity I PRNU .......•...•...• 636

5.4.2 Detectivity and noise ...•......•..•....... 641 5.4.2.1 Noiseparameters .•...•..•...•.•.•. 643 5.4.2.2 Detectivity measurement. . . . . . . . . . .. 645 5.4.2.3 Noise sources. . . . . . . . . . . • . . . . . . . .. 648

Quantum I shot noise. . • . • • . . . • . . . •. 649 Recombination noise. . . • . . • . . . • . . .. 651 Dark current. . . • . . • . . . • . . . . . . . . . •. 652 Johnson I thermoresistive noise . . . . .. 656 Flicker noise . . . . . . . . . . • • . . • . . • • .. 657 Charge-transfer inefficiency . • . . . . . .. 657 Crosstalk I smear I streaking. . . . . . . .. 659 Readout I clock noise •. . . . . . . . • . . •. 662 kTC I reset noise .• • . • . . . • . . . . . • • •. 662 Amplifier noise. . . . . . . . . . . . . . . . • .. 664 External noise sources. . . • . . • . . • . . .. 666

5.4.2.4 Sensor chip cooling. . . . . . . . . . . . • . .. 666 Convection I radiation. • . . • . • • . • • • .. 667 Dewars .......•.•.•.•..•...•..•.• 667 Joule-Thompson cryostat .•.••..•..• 667 Stirling cycle refrigerator • • • • . • • • . .• 667 Thermoelectric (Peltier) cooling. . . • .• 667

5.4.3 Dynamic range .............•...........• 669 5.4.3.1 Optical range •••........•......... 670 5.4.3.2 Electrical range •..••........•..••. 671 5.4.3.3 Linearity range ....•.............. 672 5.4.3.4 Blooming I streaking. • . • • • . • . . • . . .. 673 5.4.3.5 Sensitivity window . . • . . . . . . . • • . . .• 674

5.4.4 Temporal characteristics. . . • . . . . . . . . • . . . . .. 676

55 Summary •••••••••••••••••••••••••••••••••••• 679

6 Sensors D: Systems.............. 681 6.1 Introduction................. • • • • • • • • • • • • • • •• 681 6.2 Quantization and resolution. • • • • • • • • • • • • • • • • • •• 683

Table of Contents

6.3 Grayscale quantization • .. .. .. .. .. .. .. .. .. .. ... 684 6.3.1 Grayscale resolution ...................... 685 6.3.2 Quantization noise . . . . . . . . . . . . . . . . . . . . . .. 688

6.4 Spatial resolution.. .. .. .. .. .. .. .. .. .. .. .. .. ... 690 6.4.1 Resolving power ......................... 693

6.4.1.1 Resolution test charts .............. 695 6.4.1.2 Spatial frequency. . . . . . . . . . . . . . . . .. 696 6.4.1.3 Nyquist-Shannon criterion .......... 697

6.4.2 Modulation-transfer function ............... 701 6.4.2.1 Optical systems theory . . . . . . . . . . . .. 706 6.4.2.2 Contrast-transfer function ........... 708 6.4.2.3 Optical subsystem. . . . . . . . . . . . . . . .. 714 6.4.2.4 Sensor subsystem ................. 718 6.4.2.5 Video bandwidth and resolution. . . . .. 722 6.4.2.6 System resolution . . . . . . . . . . . . . . . .. 725

6.4.3 Artifacts and aliasing . . . . . . . . . . . . . . . . . . . .. 727 6.4.4 Sub-pixel interpolation. . . . . . . . . . . . . . . . . . .. 731

6.5 Temporal quantization. . . . . • • . . • . • • • • • • • • • • • • •• 732

6.6 Sensor subsystem characteristics. • • • • • • • • • • • • • •• 733 6.6.1 Video signal considerations . . . . . . . . . . . . . . .. 733

6.6.1.1 RS-170video ..................... 736 Interlacing. . . . . . . . . . . . . . . . . . . . . .. 736 Horizontal sync. . . . . . . . . . . . . . . . . .. 739 Vertical sync .. . . . . . . . . . . . . . . . . . .. 742 Amplitudes ...................... 744 Bandwidth / resolution . . . . . . . . . . . .. 746

6.6.1.2 CCIR ........................... 749 6.6.1.3 RS-330 .......................... 750 6.6.1.4 EIA RS-343A .................... 751 6.6.1.5 Other standards ................... 751 6.6.1.6 Syncing ......................... 759 6.6.1.7 Gamma ......................... 760

6.6.2 Camera optics ........................... 761 6.6.2.1 Pixel size ........................ 761 6.6.2.2 Lens selection .................... 762 6.6.2.3 Lens parameters ................... 763 6.6.2.4 Lens mounts ..................... 765 6.6.2.5 Lens format ...................... 768 6.6.2.6 IR-cut filter ...................... 771

6.6.3 Video modes of operation. . . . . . . . . . . . . . . . .. 772 6.6.3.1 Solid-state shuttering ............... 773 6.6.3.2 Frame / field modes ................ 775

Non-interlaced frame integration ..... 776 Non-interlaced field integration ...... 776 Interlaced field integration .......... 778

6.6.3.3 Fast-access modes ................. 783 6.6.3.4 Slow-scan modes .................. 784

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6.6.3.5 Asynchronous reset. ............... 784 6.6.4 Physical characteristics .................... 785

6.6.4.1 Geometric faults . . . . . . . . . . . . . . . . .. 787 6.6.4.2 Protection........................ 787 6.6.4.3 Electrical parameters. . . . . . . . . . . . . .. 788

6.6.5 Photometric correction. . . . . . . . . . . . . . . . . . .. 788

6.7 Specialized cameras •.••••.••••••••••••••••.•.• 798 6.7.1 High-speed videography .................. 798 6.7.2 High-resolution cameras ................... 801 6.7.3 Digital cameras .......................... 802

6.7.3.1 Smart cameras .................... 803 Smart photosensors . . . . . . . . . . . . . . .. 805

6.7.3.2 Frame-storage cameras ............. 810 6.7.4 Circular arrays . . . . . . . . . . . . . . . . . . . . . . . . .. 812 6.7.5 Intensified cameras.. .. .. .. .. .. .. .. .. .. ... 813

6.7.5.1 Photomultiplier tubes .............. 814 6.7.5.2 Image-intensifier tubes ............. 815 6.7.5.3 Gen I tubes ....................... 817 6.7.5.4 Gen II MCP intensifiers ............ 821 6.7.5.5 Gen III intensifiers ................. 829

6.7.6 Thermal / IR imaging ..................... 829 6.7.6.1 IR imaging theory ................. 833

Two-color (ratio) IR ............... 840 6.7.6.2 IR detectors ...................... 841

Thermoelectric detectors. . . . . . . . . . .. 843 Thermocouples . . . . . . . . . . . . . . . . . .. 843 Pyroelectric detectors . . . . . . . . . . . . .. 844 Thermoresistive detectors. . . . . . . . . .. 846

6.7.6.3 Quantum IR photodetectors ......... 847 Thermoconductive detectors. . . . . . . .. 848 Junction IR detectors ............... 851

6.7.6.4 IR arrays ........................ 854 PtSi arrays. . . . . . . . . . . . . . . . . . . . . .. 855 Extrinsic arrays. . . . . . . . . . . . . . . . . .. 857 Intrinsic arrays. . . . . . . . . . . . . . . . . . .. 857 Non-quantum arrays ............... 859

6.7.6.5 IR phosphors ..................... 859 6.7.7 UV detectors ............................ 860 6.7.8 X-ray detectors .......................... 861

6.7.8.1 Fluorescent screens. . . . . . . . . . . . . . .. 866 6.7.8.2 Converter tubes ................... 867 6.7.8.3 Fiber scintillator .. . . . . . . . . . . . . . . .. 869

6.8 Summary .................................... 869

Bibliography ......................... 873

Index . ............................... 894

ABOUT THE AUTHOR

Michael W. Burke's academic background and 'real-world' experience have made him especially well-qualified to present the subject of machine vi­sion (MV) to both students and practitioners. Be­ginning his education in electrical engineering as a Texas Instruments Scholar at MIT, he received a BSc and MA in Experimental Psychology and Com­puter Science (man-machine systems) from the Uni­versity of Texas, and an MScIE in Industrial Engi­neering from Ohio State University. His PhD work was in systems engineering at the University of Ari­zona (ABD).

From 1981 to 1990, he was on the faculty of the Department of Industrial Engineering at New Mex­ico State University where he taught industrial auto­mation systems, robotics, facilities design, and manufacturing. He was also a Principle Investigator in Robotics and Machine Vision at an interdiscipli­nary artificial intelligence lab, the Computing Re­search Laboratory.

The strong applications theme running through­out the book stems from the author's close involve­ment with the design of practical MV systems in industry. Professor Burke has consulted for Intel Corporation, Johnson & Johnson (Surgikos), Sandia National Laboratories, and the Los Alamos National Laboratory. For the U.S. Army at the White Sands

Missile Range, he developed both the hardware and software for a parallel processing computer for gen­erating 3D optical sighting vectors in CAD geo­graphic databases.

During the summers of 1987, 1988, and 1989, he was a Guest Researcher at the Swedish Depart­ment of Transportation Research Institute (VTI) where he worked on a variety of applied problems including Geographical Information Systems (GIS) and the application of high-speed MV systems to automated pavement inspection. From 1990 to 1992, he was the Senior Project Engineer in the Machine Vision Group at OPQ Systems AB in Linkoping, Sweden, where he designed special­purpose hardware and software for very-high-speed MY inspection systems.

Professor Burke was an academic representative to an international consortium on Robotics Software standards (CAM-i ROMPS). He is a Charter Member of the Machine Vision Association of the 5MB, a Senior Member of Robotics International of 5MB, and a member of lIE, IEEE, and ACM. He was also founder and president of AirSight US Inc., Las Cru­ces, NM, specializing in high-speed automated in­spection applications. Professor Burke is currently the Director of Meta Vision-Atlanta, a machine­vision conSUltancy.

S ERE S

PREFACE

In the science-fiction movie Bladerunner, the char­acter played by Harrison Ford uses voice program­ming to control an image-processing system to en­hance and analyze a small section of a photograph. While the machine vision (MY) system he uses is still far in the future, such systems are coming of age. Moreover, to quote Castleman (1977):

The inherent subjective appeal of pictorial displays attracts perhaps a disproportionate amount of at­tention from the scientist and awe from the layman. Digital image processing, like other • glamour' fields, suffers from myths, misconceptions, misun­derstandings, and misinformation.

No longer are advanced machine vision systems solely the province of a science-fiction writer's day­dreams. Their presence is increasingly felt through­out industry: MV is being used in military and space applications, banking, and advanced security sys­tems.

MY engineering is a truly multidisciplinary area and, perhaps because of this, it is plagued with im­precise jargon. This series of three volumes attempts to collect the fundamental concepts into a single self-consistent exposition that will serve as a rela­tively painless introduction to the field and help dis­pel the myths. The ultimate goal is an enlightened capable of using this powerful new technology ef­fectively.

For all its potential, the current state of MY in industry is not very good. There have been vendor shakeouts, with many MY manufacturers going out

The most original modern authors are not so because they advance what is new, but simply because they know how

to put what they have to say as if it had never been said before. -GoETHE

of business and the rest losing money. Projected us­age of MY systems has been wildly inaccurate, and the percentage of active implementations has been low. What went wrong? Is the need not there? Yes, the need does exist - in fact, there is a growing awareness of the role of quality control in industry, along with a realization that humans are less than optimal as industrial inspectors. Could the problem possibly be that the technology is not yet good enough? This is unlikely since MY is currently be­ing used (very successfully) in several quite differ­ent roles in industry.

It would seem that a readily available knowledge base about both the capabilities and shortcomings of MY is not available at the current time. In my opinion, MY has been overhyped and oversold, much like what happened with robotics earlier. Like robotics, MY is a tool and as such requires proper selection, justification, and use. The supply of trained personnel is simply insufficient to meet the demand for people resources needed to match the technology of MY to the problems in industry.

It is hoped that this book will help correct this deficiency in MV engineering design capacity. It can be used by someone now in industry to get up to speed on MY technology and also as a reference source for engineers who need more background and training in MY engineering. These people are sorely needed by an industrial sector that in tum

badly needs the benefits of MY. The project man­ager can read these books (particularly Volume ill)

xiv

and make an effective decision about MY technol­ogy as a solution to his particular problems. The manufacturing or automation engineer can gain background or new insights into MV. The electrical, industrial, computer, manufacturing, or systems en­gineer can use this series as an introduction into an increasingly important interdisciplinary area of technology.

In many ways, MY is at the apex of attempts to develop advanced automation systems. MY sys­tems use knowledge from many areas, including electrical engineering, physics, industrial engineer­ing, and computer science. Acquiring, storing, and displaying images test to the extreme our current thinking about databases, real-time data collection, efficient processing algorithms, and computational architectures. In addition, designing automated MV systems involves many other areas of expertise and a significant amount of research and development work. Among these areas are electro-optics, illumi­nation engineering, signal processing, and mechan­ics. It is this strong interconnection and cross-fer­tilization among diverse technical areas that distinguishes industrial MV from traditional com­puter vision topics. Besides incorporating concepts useful to most other automated endeavors, the effort to create a machine that can see is also one of the most challenging and philosophically interesting en­deavors in engineering.

The MY field is vast, new, and fast-growing; al­most as rapid has been the proliferation of labels: image processing, computer vision, pattern recog­nition, artificial vision, etc. Most of these terms re­fer to very specific subspecializations within MY, or to a particular theoretical emphasis or research orientation. All refer to the use of computing ma­chines to emulate some function(s) of human vision. For example, the term 'image processing' is most often applied only to a subset of the full function­ality of an MV system - the initial processing stages. Moreover, this processing is usually targeted for later human interpretation rather than machine interpretation. Computer vision places primary emphasis on computer interpretation of images,

Preface

with little or no interest in image acquisition. A simi­lar sub-area is computational vision, particularly concerned with motion analysis and 3D vision. It and artificial vision are perhaps most concerned with understanding natural scenes. In this book, the term machine vision (MY) is used almost exclu­sively to refer to a more integrated and systematic approach to image acquisition, image analysis, and image understanding. The MV engineering design approach emphasizes that the computer is only one component of the entire system (albeit an important one). Moreover, its goals are more pragmatic, cov­ering both image-processing and machine interpre­tation of images but of the relatively structured scenes found in industrial applications instead of natural scenes.

Almost every industrial, business, and service or­ganization is restructuring itself to operate more ef­fectively in an increasing competitive world. Pro­ductivity improvement (PI) is the key to any successful activity, and the key to PI is the use of innovative methods and technology.

The decline in productivity has been one of the major concerns of industry since the 1980s. The revolutionary change in factory production tech­niques and management that is predicted to take place by the end of the twentieth century will re­quire unprecedented involvement of automation systems in the production process. Many of the op­erations in this factory of the future will be per­formed by intelligent devices such as MV systems, robots, etc., all integrated by a computer network. This trend toward computerized manufacturing is leading to a demand for appropriately trained engi­neers to design, implement, and maintain these sys­tems. It is already becoming increasingly important for engineers, scientists, and managers to have an accurate knowledge of what MY can do for them.

A primary resource in the continuing education of such individuals would be a well-organized, com­prehensive, yet practical treatment of the area of industrial MV. Such a book has previously not been available; it is hoped that this book can function as this kind of resource.

Preface

For a resource like this to be successful, it has

to take an interdisciplinary approach, something seemingly at odds with the usual departmentaliza­tion of knowledge. Industrial problems seldom fall within the neat but artificial demarcations of aca­demic faculties. In fact, many do fall neatly between dermed academic areas and hence are neglected in the interstices. This is perhaps one reason for the shortage of comprehensive and practical treatments of MY engineering.

Nevertheless, we need both a multi-disciplined and a more disciplined approach to MY system en­gineering. In recent years, the 'engineering' has been re-introduced into applications engineering. In the past, designs incorporating large margins of safety were acceptable; if a designer had no idea how to calculate the flexure of the base casting of a hard disk drive, he simply made it stiffer than his initial simple analysis indicated. Now, however, un­der increasingly competitive pressures, a real de­mand has been created for methods that systemati­cally improve performance. There must be more powerful tools to delimit the performance and sys­tem requirements of a design more precisely. Design is no longer a process of specifying 'enough' to sat­isfy a performance need but rather one of rmding 'just enough' to satisfy and no more.

A quick example of this is perhaps needed here. The traditional way to 'design' lighting for an MY application is to turn on some lights, move them closer or farther from the target, turn on some more lights if that's not enough, add some more if shad­ows are a problem, etc. A more enlightened ap­proach looks at the sensitivity of the camera (how much light it needs), then the distance to the target surface and its reflectivity characteristics to deter­mine how much light must fallon the surfaces. Knowing this, the desired distance and wattage of lighting can be determined, as can the radiation pat­tern of the source. This is what is meant by engi­neering input into the design of lighting for an MV application. Its use can at worst reduce the number of 'empirical iterations' of the lighting design, but

xv

at best can result in an optimal design configuration in a single such iteration.

A properly designed MV system requires sophis­ticated hardware, software, and algorithms. Unlike most other books on MV, this handbook is con­cerned not only with the selection and construction of algorithms and their coding into programs, but also with the design and/or selection of the support­ing hardware components needed for practical real­time MV system design. It is thus very much a sys­tems approach to MY engineering. This series of books has been written for those engineers and fu­ture engineers who are more interested in using the results than in proving them. We are desperately short of MV engineers, and there is, and will con­tinue to be, a very high demand for professionals with training in MY principles. Students entering this field will be required to have a solid knowledge of both the basic theory and the state-of-the-art tech­niques used in MY systems. For this group of read­ers, these volumes book should be a good starting point.

Goals of the book

You may be asking, 'Why another MV book?' First of all, there haven't been so many MV books pub­lished that we are talking 'glut' here. Secondly, 'new'is always a good reason in a rapidly changing area of study. Thirdly, this series is different.

I know, every author claims that his or her book is different. But there are several things that are unique about this book. Some of the subjects have not been discussed in any detail in an MV textbook before, e.g., WORM and parallel-transfer hard disks for off-line storage, image-processing software de­sign considerations, advanced lighting design, the new generation of VLSI chips for image processing, and techniques unique to color MV (an important new area in MV). In some instances, methodology not previously published is presented. Also, this book tries to define clearly the new role of the MV engi­neer. Lastly, and perhaps most important of all, it attempts to achieve a balance between theory and

xvi

practice and whenever possible, to integrate the two.

Naturally, some things are not unique about this book. Very little that is original material will be found in a text designed to cover a spectrum of what are basically introductory topics. The key concepts and means for making MY a success are laid out in this book. It has not been my intention, however, to make it a complete compendium of all that has been done in MY. Each subject is covered more exten­sively in works devoted to that topic alone, and these are copiously referenced. Instead, I have tried to cover a significant number of the available MY techniques, particularly those that are generally con­sidered fundamental to an understanding of the dis­cipline. However, this material is now organized in a more coherent way, using a consistent notation system.

There are a number of things that I believe should be included in any book about MY engineering, and I have written these volumes with these things in mind.

First, it should include the enduring aspects of MV, acquainting the reader with the classic prob­lems and procedures, the basic techniques of MY engineering. The classical approaches have stood the test of time. Similarly, any problem that has been with us a long time is significant. Such problemati­cal areas are often roundly cursed as a form of 'pos­terior affliction,' but they can also serve to continu­ally prod our investigations into why they are recurring problems.

Second, the book should be imminently practi­cal, providing enough hard information to allow the design and implementation of an effective and effi­cient MY system. This is an applications-oriented series, designed for present and future practitioners. Important underlying assumptions, operating constraints, realistic expectations of perform­ance, and advantages and disadvantages of the various approaches are openly discussed. It is hoped that some readers will actually implement working systems. Hence, skills development is one of the goals of these volumes. However, this must be tem-

Preface

pered by the use of an approach general enough to allow implementation within a wide variety of prob­lem areas. The development of approaches based on a few powerful principles can often be more use­ful in a wide variety of applications. Yet, it is the narrower and more specific applications of these general principles that best serve to demonstrate their shortcomings and possible constraints in their application.

Hence, a third goal for a book on MV engineering should be that it cover the basic theory, the signal and information processing theory fundamental to MY engineering, so that the assumptions underlying the procedures presented can be understood. Only then can the limitations in the application of these processes be appreciated. The basic theory of digital image processing is always presented as a tool for solving practical problems rather than as a disci­pline unto itself.

Fourth, the book should assume a systems engi­neering viewpoint: all aspects of MY engineering are addressed, not just the algorithms. The ultimate guiding principle in the preparation of this series has been the systems engineering principle, that we adopt a holistic appreciation of the subjects and problems we face - connections among broadly di­verse components, questions about priorities and tradeoffs, etc. The number of alternative algorithms for implementing a particular function can be large and interact closely with other aspects of the system. This is in addition to task and economic constraints. For example, the particular algorithm selected will in general depend greatly on the state of the image, which in tum will depend on the system's optics, lighting, and cameras. All aspects of the MY system, from optics to project management, are discussed, and the integration of components and concepts is emphasized. This addresses a major shortcoming in nearly all the other books currently available in MY - they emphasize concepts and not systems. On the other hand, the information contained herein has a solid basis in theory, and tutorials are contained throughout the book.

Preface

Fifth, the book should present a summary of MY literature, including material not just from theoreti­cal journals but also from the less accessible ap­plied sources. Much of the favorite pedagogy of beginning textbooks is quite unnecessary and, in fact, is not used by practicing engineers, while ef­fective techniques and methods in daily use often lie hidden in application notes, case studies, data sheets, and hard-to-get technical reports. A sum­mary of the literature with an emphasis on appli­cations sources would therefore be useful. The in­terdisciplinary nature of MV engineering makes finding and synthesizing relevant literature that much more difficult. The bulk of the material is widely scattered among journals on several conti­nents in such diverse areas as artificial intelligence, signal processing, computer science, electrical en­gineering, industrial/manufacturing engineering, optical science, medicine, and even astronomy and the earth sciences. The sources consist for the most part of technical journals, conference proceedings, research monographs, and a few textbooks. The lit­erature summary in this book has been gleaned from thousands of journal articles and technical reports and represents what I consider to be the critical ma­terial for present and future practitioners.

I have also made a conscious effort to include MV work from a great many countries, including England, Italy, Holland, Japan, France, Sweden, and Finland. My extended residency in Europe has gen­erated an enthusiasm and appreciation for much of the research produced there, yet it often does not receive a proper forum in U.S. literature.

Sixth, the book should enable the reader to assess the MY literature critically and to communicate with other MV professionals in an articulate man­ner. MY engineering is a fast-developing field with a rapid influx of new ideas. The concepts presented in this handbook should help develop the reader's ability to critically appraise the value of this new work, providing the necessary background concepts and vocabulary for comprehension.

Seventh, the book should prepare an engineer to make competent purchasing suggestions regard-

xvii

ing the application of MY engineering in manufac­turing. The reader should be able to assess the de­gree of MV automation required for particular manufacturing tasks, evaluate candidate systems, integrate MV with other automation equipment, and, if necessary, modify off-the-shelf MV systems to suit specific needs.

Eighth, since the ultimate goal of MV engineer­ing is the development of hardware and software to solve problems, no book on this subject would be complete without some exposure to equipment. For this reason, the algorithms presented in this book are described in sufficient detail for readers to be able to exploit them in real MV programs. In addi­tion, the description of the hardware is detailed enough that it should be possible for an engineer to select commercial products that will satisfy the ap­plication requirements. A few commercially avail­able products are described in more detail. Although commercial hardware and software are quickly out­dated in a field that is changing as rapidly as MY, I have included this kind of information because significant advances in science and technology come with significant advances in the tools of those areas. The field of MV engineering is no different: it is intimately associated with its tools. It must be noted that the discussion of selected commercially available MY components should not be construed as an endorsement of these products.

Finally, a last goal for a book on MY engineering is that the topics should be relevant and balanced. Authors tend to write primarily about their 'special­ties,' being obviously the most qualified to do this. But the unfortunate result is that many texts tend to overemphasize more esoteric research-oriented ar­eas at the expense of topics with more practical ad­vantage. I'm reminded of the joke about the drunk and the lamppost. When asked by a policeman why he is looking for his car keys under the street light when he actually dropped them over by his car, the drunk replied 'the light is better here.' I get the same feeling sometimes about these books, that even though the subject matter and topics are not of much relevance to the reader, this is where we have done

xviii

all the research and developed all the mathematical models. A text on MV engineering should be bal­anced with respect to theory and practice, between the new and the old. A thorough grounding in the basics should never be sacrificed for advanced top­ics. A more thorough understanding of the basics is more valuable than knowledge of the latest 'buz­zwords' and 'hot topics' since these are often of only transitory importance anyway.

This handbook, then, tries to fulfill all of these goals to the greatest extent possible. This kind of book would have been useful to me when I began developing MV systems in 1984, and it represents an attempt to systematize the most essential aspects of what I have learned since then.

Citations

A text such as this one can make no claim to origi­nality of material. Only the choice, arrangement, and method of presentation of the material are the author's. This author is thus deeply indebted to all the workers in the field of MY. Part of the acknow­ledgment of this debt is the bibliography.

Spread throughout this book are a great many references to MV, CV, IP, and PR literature, al­though not as many as I could have included - it is far from an exhaustive reference work. The refer­ences included herein are important for two reasons. First, a common reason for including references in a survey text is that they make it possible for the reader to pursue individual topics in greater depth than is possible within the space restriction of this book. The second reason is that MY engineering is a relatively new discipline, and there is often not complete agreement on how things should be done; the references provide the reader with access to al­ternative approaches. For these reasons, I have de­veloped a generous bibliography.

I have provided a great many entry points into the MV literature, but no effort has been made to fmd the earliest references to some concept, solely for the sake of giving credit. Rather, I have tried to confine the citations to those that are most useful

Preface

to the reader now and published in accessible places. This is not a research monograph, hence there is the obvious potential to offend someone, for which I now apologize.

Other MV books

As Charniak and McDermott (1985) have said, 'Writing a textbook is a good way to develop hu­mility about the shortcomings of other textbooks.' There are several other textbooks currently avail­able on the subject areas of MV, IP, and Cv. It may therefore be of interest to review them briefly and to compare their treatments of MY with this book's.

When I started out, the standard textbooks were Pattern Classification and Scene Analysis (Duda & Hart, 1973), Digital Image Processing (Gonzalez & Wintz, 1977), and Picture Processing by Computer (Rosenfeld, 1969). Then in 1982, in what must be a watershed year for image-processing texts, several excellent books appeared: Vision (Marr, 1982), Ma­chine Perception (Nevatia, 1982), Digital Image Processing (Rosenfeld & Kak, 1982), Computer Vi­sion (Ballard & Brown, 1982), and Algorithms for Graphics and Image Processing (Pavlidis, 1982). As my knowledge and experience in the area grew, however, I found that no one of these or any other available books contained the collection of material that I needed either for practical work or teaching. With respect to theory, all were very idiosyncratic about their choice of topics, and with respect to practical information, all were very skimpy.

Since 1982, other books have come out. Digital Image Processing: A Practical Primer (Baxes, 1984) is well written and imminently practical but covers only a relatively circumspect set of topics. The same may be said of an excellent British entry, Pattern Recognition (James, 1988). The outstanding text by Gonzalez and Wintz was updated in 1987. The book, Automated Visual Inspection, edited by Batchelor, Hill, and Hodgson (1985) is also note­worthy source material, but like most edited collec­tions, it lacks sufficient integration. It does, how-

Preface

ever, have an excellent collection of application ex­amples.

The handbook you are reading may be considered to be complementary to other, more theoretically oriented books on MY. I would highly recommend Robot Vision (Hom, 1986) for a more advanced ap­proach to MV. Hom's book is a gold mine of infor­mation (although it takes some digging). On the mi­nus side, its coverage is spotty and eccentric (starting with the book title Robot Vision, an unusual name for a book with very little on robotics). Digital Image Processing and Computer Visipn (Schalkoff, 1989) also takes a more theoretical, mathematically oriented approach to MV but is based more narrowly on the concepts of signal processing. Neither Hom's or Schalkoff's books are applications-oriented.

Both Computer Vision (Ballard & Brown, 1982) and Digital/mage Processing and Computer Vision (Schalkoff, 1989) are heavily AI-oriented, but I feel that this is extremely premature, certainly for an in­troductory engineering text in MV systems. These issues are best covered in more specialized books.

The role of theory

Although MV engineering is still a field with more interesting ideas than polished theory, a small core of accepted theory and practice is slowly emerging. At the same time, it is generally recognized that there is a sharp division between theory and prac­tice. This book attempts a rapprochement of MV theory and practice.

Theory. I stated earlier that more powerful de­sign techniques are needed by industry. I believe that a modem MV engineer should have a broad knowledge of both theoretical and practical tech­niques. A knowledge of theory would serve to en­hance one's analytical perspective in solving complex MV problems. Moreover, developments in MV engineering are occurring so rapidly that refer­ences to current literature are essential. I hope that this also conveys a taste of the excitement in this young field of technology. Therefore, it is important

xix

to introduce the theoretical underpinnings of MY, at least at the introductory level, even when such a treatment may be less than rigorous from a theoreti­cal viewpoint.

Empirical application is necessary when basic sci­ence lacks the answers. Nevertheless, the overall out­come of applied research is often just a collection of answers to specific problems, of practical importance to someone at a particular moment but not for the steady building of scientific knowledge necessary to

address a larger scope of problems. Without a theo­retical perspective, a reader cannot generate the wealth of new ideas needed to solve practical prob­lems or bridge the existing state of knowledge with the as-yet undiscovered aspects of MV, i.e., bridge the gap between what is now known and what needs to be known in the future. To quote Boltzmann: 'Nothing is as practical as a good theory.'

Practice. And yet, many readers will be aware that there is a considerable gap between the MY practitioner and the MV theorist, with considerable debate on the relative merits of each approach. Robert M. Haralick, a long-time researcher in this area, has said:

In the theory of the science of computer vision, one would expect to find the laws and principles by which computer algorithms can be designed to solve a variety of vision tasks ... When a broad ex­amination is made of computer vision research, it becomes apparent that the science is young and im­mature. The pockets of theory are sparse. The amount of replication is nearly non-existent for overly complex algorithms .... Upon reading the lit­erature, one even gets the feeling that perhaps the algorithm itself is sufficient, without a statement of what problem is being solved or without a state­ment of the degree to which any problem is being solved (Haralick, 1985).

As Haralick correctly points out, scientific advance­ment proceeds on two frontiers: the experimental and the theoretical. He makes the very cogent argu­ment that 'better science' is needed in MV, a more disciplined experimental approach to yield better

xx

theories. Haralick makes a strong point about the poor state of theoretical models in MY. I would ven­ture to add that it is not in good enough shape to base an MV engineering handbook on.

In the absence of significant applications, there is an infatuation with theorizing, usually accompa­nied by abstract mathematics. Theory is just that -something that still has to be proven. Powerful mathematical tools are still only that - a tool. They should be used only when appropriate and when simpler tools are not (the KISS principle, an updated version of Occam's Canon). Too often, mathemati­cally-based expositions are like the mythical inn­keeper, Procrustes, who cut off or stretched the legs of his guests to fit the particular bed he had (the first example of 'one size fits all'). These math mod­els stretch or lop off reality until it fits the particular mathematical tools available or those the researcher wants to use.

The law of diminishing returns also needs to be applied to the use of theoretical models: at some point the improvement in system performance in re­turn for the increased costs (computational and complexity) from the use of complex theories makes little sense, except perhaps to individuals who don't actually have to build the system. As the saying goes, 'nothing is too difficult for the indi­vidual who doesn't have to build it.'

Perhaps because of the above reasons, theory is used less often in industry. Although some of the theoretical techniques are more powerful and can solve more complex problems than the more ad hoc methods can, this increase in performance is at a disproportionately high cost of lost efficiency and implementation expense. The use of techniques that are too powerful for either the amount or quality of data available, or for the problem-solving goals, re­sults in inefficiency and/or gross over-design, which is tantamount to an appalling misallocation of ana­lytical resources.

Since MV's incipient beginnings in the early 1960s, scientists and engineers have designed hun­dreds of different MV systems and demonstrated thousands of different applications. Nonetheless, we

Preface

cannot claim to understand MV. If fundamental principles exist, we have not yet discovered them. Our knowledge of MV is almost entirely empirical, the result of 25 years of experimentation. When gen­eral observations arise, they have the character of design heuristics rather than of scientific princi­ples. Theoretical tools can be drawn from related fields, such as signal processing, but there is very little theory that bears directly on MY. The most important product of this 25 years of empiricism is an accumulation of experience, from which we might identify key issues and formulate new re­search directions.

In its defense, an applications-oriented ap­proach is what is most needed by both the student and practitioner. For the student, the important and relevant issues become more obvious, and learning is easier when one can 'see the meaning' in the ma­terial. In industry, the single greatest technical prob­lem today is not innovation, but rather applying the technology that has already been developed. Crea­tivity in applying technology is at least as important as developing it, yet it is nearly always ignored. We must try to foster an appreciation of applications.

A rapprochement. This field has exemplified the classical 'chicken-and-egg' type of initial growth problem. MV needs a theoretical base to motivate and guide the design of experiment and development, yet the MV theorist needs dynamic empirical experience as a prerequisite to building a general theory. If empirical experience is not pro­vided in step with the growth of theory, there is always the danger that theory will be built on little more than abstractions, based on how MV systems could (or should) work rather than on how they re­ally do. A theory is useless without empirical data to reinforce its validity, but empirical techniques are no less dependent upon theory.

Successful application of MV requires a sound understanding of both the underlying theory and the practical problems that are encountered in using MV in real-life situations. It is possible to pursue MV as a branch of abstract mathematics; it is also pos-

Preface

sible to pursue it as a theory-less branch of prag­matic engineering. The best approach is a compro­mise between these two approaches. While this se­ries of volumes is basically an applied handbook, it also seeks to blend theory and applications effec­tively, avoiding the extreme of presenting theory in isolation and the equally extreme encyclopedic ap­proach of giving elements of applications without the integration and context provided by a common theoretical foundation. I have been made aware of just how hard it is to extract coherent and lasting theories from a field as new, and developing as rap­idly, as MY engineering. While I feel that to a large degree, I have succeeded in satisfying the goal of a balanced presentation, this book still has aspects of the 'grab-bag' approach to MY. However, to leave those aspects out would be wrong - they still defme much of what is MY engineering.

A note on mathematics. This book intro­duces many of the mathematical models underly­ing the concepts discussed (a glance through the text reveals an appreciable amount of mathematical discourse), but it stresses a conceptual modeling approach as most appropriate to the book's goals. Signal processing concepts such as convolutions and frequency-domain concepts are fully discussed and heavily used but primarily for their usefulness, rather than for any mathematically impressive 'face Validity' they render this text.

Mathematical formulas are used only (if you'll pardon the pun) as a form of 'summing up' the ac­companying verbal description. The ideas in this book are presented more on the level of intuition than on the level of mathematical formalisms. A strong emphasis is put on the physical meaning of the concepts introduced. To quote Isaac Newton: 'Examples are more useful than rules.' All mathe­matical formulas are analyzed and dissected to re­veal their physical meaning, a pedagogical device I most appreciated from my professors at M.I.T., who had no hidden agendas in their mathematical expo­sitions.

xxi

An intuitive approach and ample verbal discus­sions are provided rather than more precise but often cryptic theorem-proof methods of presentation. I have tried judiciously to avoid the mistake of many other writers in this field - making the simple sound esoteric. Hence, rigorous mathematical proofs have been replaced by plausibility arguments that will satisfy most applied engineers and permit an exten­sion of the reasoning to other cases. The emphasis throughout has been on understanding and on ap­plications while maintaining precision, so that all results are correctly stated and properly qualified. For more rigorous proofs, the original sources are usually cited.

In a similar spirit, I have studiously avoided the statement 'it can be easily shown that. .. ' since it is seldom so. I have included a great many interme­diate mathematical steps so that readers need not wonder how to get from one equation to the next. Of course, it could be argued that this removes the element of problem-solving. In answer to that, I would say that the book is one on MY engineering, not equation solving.

Who this handbook is for

This series is for all those who must currently make decisions about the design, selection, and use of MY systems, and for those who must learn to do so. It is for anyone - practitioner or student - whose am­bition is to solve real-world problems, or to contrib­ute to their solution, using MY.

Since MY engineering appears to be a rather spe­cialized topic, it is perhaps worthwhile to draw at­tention to the pedagogic flexibility of this subject area. Drawing as it does from several disciplines, MY engineering provides a good vehicle for the presentation of a variety of topics within a single coherent framework. Even students with no long­term interests in MY should still benefit from the material covered in this text, acquiring knowledge and developing skills that will serve them well in other settings. MY engineering is not yet a discipline unto itself; rather it is an amalgam of engineering

xxii

topics. As such, it is a superb context in which to teach some of those elusive topics known as sys­tems science. It also provides a unifying theme in which to cover those practical engineering issues that are often ignored in undergraduate curricula. A formal course in MV systems, because of its inter­disciplinary nature and generalized approach, serves to focus and emphasize these attributes.

While written primarily for the industrial prac­titioner, this handbook should also be useful for any of five groups of readers: (1) students in engi­neering, (2) students in non-engineering fields like computer science, (3) MV researchers, (4) engineers in industry (e.g., applications engineers), and (5) en­gineering managers.

These volumes should be of some use as a ref­erence text for engineering students, particularly those in electrical, industrial, and manufacturing en­gineering. These individuals, upon graduation may be asked to contribute to the design of an MY sys­tem in industry or perhaps supervise the installation of such a system. The handbook, as it now stands, may be used effectively as a textbook, although it is not optimized for this purpose.

The series should also prove useful to students in non-engineering fields, such as computer sci­ence. They may begin to recognize the relevance to many areas of the real-world and applications of the theoretical principles that they are encountering in their courses or research. Computer scientists will find that this handbook deals not only with algo­rithmic processes but also with the constraints im­posed by actually implementing the algorithms.

This handbook is also for the MV researcher. As Haralick has argued, empirical validation and verification of theoretical models is an important re­quirement for the advancement of MY as a discipline. A researcher must have the proper applied tools to conduct such experimentation. MV engineering problems are usually ill-defmed, and the theories pro­posed are often too complex to be verified by intui­tive or even formal arguments. To check for obvious inconsistencies and contradictions, one develops and programs a system to reflect that theory. If the system

Preface

works, the theory is not proved, of course, but at least some understanding of how it behaves is gained. To conduct such empirical validation studies, it is im­portant that an MY researcher have a wide variety of practical tools available; this book provides the tools to develop functional MY systems.

This series of books is also intended for appli­cation engineers: all those who know what they want to accomplish using MY, though perhaps noth­ing of how to accomplish it, or even how to think about doing it, or why it should be done one way rather than another. This book is also written for the practicing engineer who is struggling to stay abreast of the 'state-of-the-art.' Engineers in indus­try seldom have the time to dig out reference ma­terial in libraries or attend conferences and seminars to familiarize themselves with the latest advances. The book has been written with the needs in mind of those who must learn much if not all of this in­formation on their own initiative. The presentation is intended to serve not only as the basis of a formal course in MV engineering but is also designed to facilitate self-instruction. To allow self-study, the text contains introductory background material on most topics.

I feel strongly that a working knowledge of MY systems will greatly benefit any engineer entering industry. Why should an engineer (not specializing in MV) bother to learn about MY? The answer is that the area has compelling practical applications in industry that are increasing in importance. A com­mon rejoinder to this argument is that MV is a highly technical specialty that is best left in the hands of specialists. But it is also a multidisciplinary subject that serves as a good introduction to a great many subject areas while emphasizing an integra­tive systems approach to problem-solving. Much of the innovative engineering in Japanese manufactur­ing is a direct result of a more interdisciplinary sys­tems approach to applications. They even have a name (and a joumal) for it - mechatronics, the design of well-integrated mechanical, electrical, optical, and electronic components. On close examination, one can see that this could also serve as a defmition of

Preface

MY engineering, and the study of MY engineering could very well instill an appreciation of this very effective design philosophy.

Lastly, this handbook is also for engineering managers, serving as a primer for manufacturing management in the technology of MV and how it can be profitably applied. It illustrates the capacity that MV has to reshape aspects of the manufacturing environment, particularly with respect to quality control. Managers and students of graduate busi­ness schools will also find the book useful as sup­plementary material in engineering and manufactur­ing management courses for its emphasis on economic as well as technical issues.

Engineering design has changed considerably in the past decades. No longer does the engineer see the complete project, but usually only one of the modules, whether as small as the physical layout of an Ie chip or at the level of a system. This book allows the engineer to see more of the details at all levels of an MV project, all components and how they fit together.

What the reader needs to know

The shear diversity of subject matter in MV engi­neering can present serious problems since no single theory or approach embraces all of these important topics. How much one needs to know about each of these areas depends on the exact application at hand, but the general prerequisites are an intuitive understanding of how a computer works (preferably through some programming experience), an initial exposure to mathematical logic, and some familiar­ity with data structures.

This book should cause no difficulty to anyone with a basic theoretical and practical background in engineering. Because MV engineering is a very multidisciplinary field, the reader should have some familiarity with probability and statistics, engineer­ing mathematics such as transforms and differential equations, and computer science concepts such as data structures. In addition, to excel in MV engi­neering, some exposure to concepts from photogra-

xxiii

phy, photogrammetry, psychology, computer graph­ics, electronics, operations research, control theory, physiology, linguistics, and computer science would be useful.

Because of its multidisciplinary nature, MY en­gineering provides at its best the pleasure of work­ing simultaneously in several fields. At its worst, it demands competence in a wide range of areas. Since the targeted readers come from a diverse collection of engineering and scientific fields, the book in­cludes brief reviews of many topics (e.g., optics, linear systems theory, sensor electronics, filter the­ory, signal detection theory, etc.) that may not fall within the background of all the readers.

Organization and overview

This handbook is composed of three volumes. The first volume is devoted to image acquisition. It ad­dresses procedures and concepts critical to acquir­ing an image. This volume covers topics on lighting, optics, and sensors.

The second volume addresses the analysis and interpretation of the images acquired using the techniques discussed in Volume 1. Here we have chapters on image enhancement, segmentation, analysis and recognition/interpretation. In addition, there is a chapter on ranging. In a real sense, it could be argued that ranging is an image-acquisition proc­ess and therefore should be included in Volume I, but it is also a form of 3D imaging, so it is discussed in Volume II.

Volume III addresses various aspects of the inte­gration of MV components and functions, examin­ing questions of their interactions and interfacing. The first chapter discusses the overall architecture of MY systems, including parallel and optical proces­sors, and addresses hardware development concerns in developing an MY processing system. This is fol­lowed by a chapter on specific aspects of auxiliary or support hardware encountered in MY systems. In­cluded are off-line storage of images, image-display devices, and the interconnections between these de­vices (such as signal formats). The next chapter ad-

xxiv

dresses MV software considerations, and is fol­lowed by chapters on implementation and case studies. The final subject-matter chapter deals with color MV and was put in Volume III as an example of an application-specific treatment of MV.

At the beginning of each chapter, there is an in­troductory section that includes the purpose and goals of the chapter and a description in simple terms of the material to be covered. Each chapter ends with a summary. New material is introduced incrementally and logically. Its understanding de­pends only on the material introduced in the pre­vious sections of the chapter. Each chapter is self­contained as much as possible with respect to the new material being introduced.

As part of mastering any area, symbology and vocabulary must be learned. To make this as easy as possible, there is a symbol glossary, and new terms are bold-faced and extensively indexed. The SI system of units is used throughout, although the English units may be given also, in parentheses.

Colophon

Finally, a word about the production of this book may be of interest. I typed the manuscript at the same time I composed it, using Microsoft Word's incredibly powerful outlining feature. The text and all equations were typed by myself, using Word's macro capabilities to embed the codes for Corel Ventura Publisher. The manuscript was then read into Ventura, which was used to set the equations, arrange the figures and tables, layout the page de­sign, and generate the table of contents and index. Ventura did everything except a bibliography. For this task, I wrote a separate program.

Text is set in lO-pt Times Roman on 13-pt lead­ing. Figure captions are in Helvetica, while head­ings are in Etema. Script fonts used for mathemati­cal symbols are Exchequer, Linus, and Coronation.

A book on MY must of necessity have a large number of illustrations. The figures were created or edited in Corel Draw, Arts & Letters, Autocad, Pub­lishers Paintbrush, and Halo DPE. Special graphics

Preface

and numerical analyses were also generated in PCMATLAB, a wonderful numerical analysis pro­gram (thank you Cleve Moler, a fellow New Mexi­can). Most of the imaging examples were generated on one of three MY systems. The first was a Data Translation frame-grabber and accelerator in an ffiMPC machine, using Image Pro II and in-house software. The Windows-based Ad Oculos image­processing software library was also used. The sec­ond machine was an Innovision IDAS Image Proc­essing workstation, a VME-buss system using the Imaging Technology Series 150 image-processing hardware modules, the OS-9 operating system, and the Innovision Insight interpreter. The third MY sys­tem was a proprietary hardware pipeline processor, developed at OPQ Systems AB (Linkoping, Swe­den). The example images were stored to disk as TIFF files and then read into Ventura. The end result was a camera-ready copy that was sent to the pub­lisher for final editing and printing.

While a word processor 'does not a Hemingway make,' all of these extremely powerful computer authoring tools do allow for the fast and efficient production of a book. This is something especially important in such a rapidly changing field, in which with less efficient methods, the book would be out­of-date by the time it was [mally published. In ad­dition, these same tools will make updating the ma­terial for future editions relatively easy.

Summary

I have felt free to 'editorialize' at several points about the inadequacies of current theoretical approaches to MV engineering. It is premature to present an intro­ductory text based solely on theory, as others have attempted. This is quickly revealed in a totailack of ability to construct a working system based on what is presented. The ultimate test of a theory is its im­plementation. On the other hand, an encyclopedia of ad hoc techniques is equally limited. The number of different ways that the large number of MV techniques can be combined and sequentially ap­plied to an image is truly staggering. The selection

Preface

of appropriate methodology must at least be con­strained by theoretical considerations, even if it can­not be completely determined by it.

MY is both a science and an engineering disci­pline. As a science, it is still in its infancy. It is more than an art but still not a fully developed science. As an engineering discipline, human judgement, ex­perience, and basic engineering skills still play im­portant roles in the formulation of successful MY system designs.

I have some strong opinions about MV engineer­ing but have tried to confine them to this preface (although I confess they may have slipped out a few times elsewhere). I wanted this book to be usable in a variety of classroom and training situations, producing a competent MV engineer as the out­come. In my opinion, it combines the 'what to do' with the 'how to do it' and the 'why do it that way,' and even the 'what other ways will work.'

xxv

As noted previously, the initial motivation for authoring this handbook was that I had been unable to fmd another book that covered all the subject areas and topics that I needed in my work. This is a value judgment that cannot be defended in abso­lute terms. The fact that several other texts exist in this field shows that other, competent authors have reached a conclusion very different from mine. This in itself is not a criticism of their work, nor, it is hoped, of mine. The reader must ultimately choose the approach that best fits his or her needs. In the end, any book is really a set of hypotheses that, like any set of hypotheses, must be tested for their use­fulness in the engineering world.

In a sense, this book is a gift to those who have challenged and inspired me to undertake this work. In another sense, it is a challenge to you to continue and improve upon it.

Important note: This is your handbook, and you can influence future editions. If you have suggestions for other topics, revisions, important or new work I have missed, or corrections of any kind, please send me a note in care of the publisher or to my E-mail address.mwburke@metavizn.com.Finally.this has been a 'labor of love.' One does not spend many years writing a series such as this with expectations of monetary reward (the $$ROI is nil), so even the faintest of supportive remarks would be welcome.

VOLUME

PREFACE

Chapter 1 (Lighting I: Principles) begins a dis­cussion of the energy source for most MV applica­tions - light. The basic concepts of lighting and illumination are discussed. There is also an ex­tended discussion of the behavior of surfaces under illumination, which forms the basis of automated (CAD-based) lighting design. Specific sources of illumination are discussed in the next chapter.

Chapter 2 (Lighting II: Sources) reviews the usage of various sources of illumination, from tung­sten lights to high-pressure arc discharge lamps. Other energy sources can also be used for MY, such as infrared (IR), ultraviolet (UV) and x-rays. These illumination sources are also discussed in this chap­ter, their advantages, disadvantages, hazards in their use, etc. Ultrasound is covered primarily in the chapter on range sensing in Volume n.

Chapter 3, (Optics I: Principles) begins with an introduction to basic optical concepts. Optical components used for modifying the characteristics of the scene image are covered here, whereas the use of optics for modifying lighting is left to the next chapter. This initial introduction to optics re­views the basics of lenses and prisms. The special usage of mirrors for imaging purposes is also dis­cussed.

Chapter 4 (Optics II: Systems) covers the use of optical components for modifying the source and characteristics of scene illumination. There is a con­tinuing discussion of the use of mirrors, and the use

The best effort of any book is that it excites the reader to self activity. - THOMAS CARLYLE

of filters (selective and protective) is introduced. Other supporting optics such as shutters (mechanical and electrical) are also covered, as are specialized topics such as autofocusing and considerations for the use of optic materials with non-visible illumi­nation sources. Electronic shuttering is reviewed in the next chapter, on cameras.

Chapter 5 (Sensors I: Basics) introduces the es­sential concepts in sensing light energy coming off objects. There is a discussion of the different types of video sensors, including tube-type but primarily solid-state, how they differ from one another, how to select them, their theory of operation, and their advantages and disadvantages. The noise charac­teristics of video sensors are carefully considered. Topics reviewed include resolution (spatial, tempo­ral, and gray-scale), dynamic range, and sensor ar­chitecture.

Chapter 6 (Sensors II: Systems) examines the more global aspects of MY sensor systems, such as photometric correction. It then delves more deeply into specific sensor systems, including those for low light conditions, such as image intensifiers. Finally, there is a section surveying some of the commercial cameras currently available, primarily for illustrative purposes. The new generation of "smart sensors" is also discussed, as are specialized sensors for IR, UV and x-ray sources. The discussion of color cameras is left to the chapter on color MY (Volume m.

ACKNOWLEDGEMENTS

This book is not entirely my fault. Because this is a survey, and not a presentation

of original research, little of the work reported is my own. There are many people whose talents and influences are reflected in this text; I wish to ac­knowledge that intellectual debt. I have simplified complex ideas, not given credit where credit is due, and generally committed a whole range of what, to an academic, are unpardonable sins. The develop­ment of a handbook like this one is a synthesis of ideas from many sources and persons, developed over a period of several years; it is not always pos­sible to recall exactly the sources used and to quote them. I have tried to be meticulous in acknow­ledging the sources of all material covered. There are, however, limitations to this and to any author slighted I offer my apologies.

I am indebted to the many contributors to the field of MV who have developed the theory and methodology discussed in this book. I have tried to indicate my primary references in the bibliography but would now like to single out a few as being particularly helpful. Pattern Classification and Scene Analysis (Duda & Hart, 1973) and Digital Image Processing, 2nd Ed. (Rosenfeld and Kak, 1982) kindled my original interest in MV. I would like to particularly mention Digital Image Process­ing (Gonzalez & Wintz, 1977), Image Processing Handbook by Russ (1992), and Pattern Recognition by James (1988) as excellent introductions to the general area of MV. The basis for much of the ma­terial on lighting came from Illumination Engineer­ing - From Edison's Lamp to the Laser (Murdoch,

1985), Lamps and Lighting, 3rd Ed. (Cayless & Marsden, 1983), Illumination Engineering (Boast, 1953), Industrial Lasers and Their Applications (Luxon & Parker, 1985), Photometry, 3rd Ed. (Walsh, 1965), and IES Lighting Handbook, 7th Ed. (Kaufman, 1984). Likewise, a great deal of the ma­terial in the chapters on optics came from Applied Photographic Optics (Ray, 1988), and Optics (Hecht & Zajac, 1979), but also from optic manu­facturers applications notes, notably those from Newport Optics, Roylyn Optics, Oriel, and Melles­Griot. The basis for much of the material on sensor systems came from journal literature. The work on CAE design of image acquisition systems is very new work and is drawn primarily from the journal literature. The classic The Art of Electronics by Horowitz and Hill (1989) served as my standard of quality technical writing.

This section also gives me the opportunity to mention the numerous people who have worked with me and supported me over the years. It is nearly impossible to list the names of all who have con­tributed, but it is fitting to mention a few who have helped the most.

Many people have influenced my ideas over the years, through articles and books, conversations, and joint research. I thank the faculty and profes­sionals who have commented on earlier versions of this book. Many of them shared their time and pa­tience toward educating me, for which I am most grateful. Of course, a Willingness to help does not imply an endorsement of the ideas. The shortcom­ings that remain are mine, not theirs.

xxviii

My mentor and friend, Professor Don Schultz of the University of Arizona, was very important to my intellectual development. He generally caused reason to prevail whenever chaos threatened. He was a model for patience and understanding, al­though I know he would have preferred a disserta­tion instead of this book. Many colleagues have helped generously by preparing detailed criticisms. Larryl Matthews of NMSU's optics lab provided constructive criticism, inspiration and ideas. Many mistakes and ambiguities would have gone unno­ticed but for his vigilance.

Kevin G. Harding's work on lighting systems has been very helpful to the evolution of many of the ideas in this volume. He also willingly served as technical reviewer on the chapters on lighting and optics. Gordon T. Uber also reviewed the chapters on lighting and optics, graciously serving as a sounding board for ideas. Steve Mersch went over recent versions of the book and made many useful suggestions. Robert Capobianco of EG&G Electro­optics provided feedback on the chapters on light­ing, particularly the discussion of strobes.

In addition to Larryl Matthews' comments, Jeff Jalkio influenced the shape of the chapters on optics in many ways and also contributed comments on the chapters on sensors.

Hal Schroeder's work in the field of MY and sen­sors in particular provided a general source of in­tellectual and pedagogical inspiration, and he gra­ciously provided guidance in the development of the chapters on MY sensor systems. In addition, Tom Jenkins (DALSA) and Jeff Jalkio (CyberOp­tics) also contributed comments on the chapters on sensors. I am greatly indebted for their guidance.

Nello Zeuch provided early advice on the form and content of the first drafts. Herbert Freeman (Rut­gers University) and Madan Gupta (University of Saskatchewan) also provided numerous useful com­ments on earlier drafts of this book. Two British re­viewers, Professor L. Norton-Wayne of the De Mont­fort University and Professor Bruce Batchelor of the University of Wales, provided thoughtful comments

Acknowledgements

on the full handbook and fresh insights into many discussion topics.

I am pleased to acknowledge the assistance of lighting, optical, camera, and MY component manu­facturers in supplying much of the material in this book, particularly the materials on lighting sources and optics. The quality and quantity of technical information from companies such as Philips, Melles-Griot, Hewlett-Packard, General Electric, Newport Corporation, GTE, and Oriel Corporation was extremely important in a handbook that stresses practical systems. The scientists, engineers, and technical staffs of these organizations have been very helpful in supplying detailed information. A number of industry people have provided support and encouragement.

I would also like to thank my former students, who have taught me how to teach - I have learned much from those I have endeavored to teach. I am indebted for the numerous questions and pleas for clarification raised by my students in the MY courses. Their persistent, often biting and usually justified criticisms have been a key driving force in the writing process. I wish to thank my editors at Chapman & Hall (especially Mark Hammond), and several anonymous reviewers for their thoughtful feedback.

A very special thanks to the staff of the Technical Library at Linkoping University for never blinking in the face of outrageous requests for source mate­rial from all over the world.

And a fmal thanks to caffeinated beverages of every sort.

This book could not have been completed with­out the financial support of several institutions. Grants from the State of New Mexico to one of NMSU's Centers of Excellence, the Computing Re­search Laboratory, got me started in machine vision. Further support came from Sandia National Labo­ratories. Finally, support was also received from RST Sweden AB (Stockholm), OPQ Systems AB (Linkoping) and from the Swedish government, through grants and visiting researcher positions at the Swedish National Road Research Laboratory

Acknowledgements

(VTI) in Linkoping. Their support has been most generous and is appreciated.

Careful reading and editing by my wife Diana Burke of The Right Type (Atlanta, GA) was indis­pensable. In addition, she designed the overall lay­out, prepared nearly all of the figures, and produced the camera-ready copy of the manuscript for the publisher. I would also like to thank her and the rest of my family (Devin Michael Paul and Amy Adri-

xxix

ana) for not complaining too much over the many hours stolen from our family life. They watched their husband and father disappear into his lab nearly every evening and weekend for the duration of this trying and often tumultuous writing cam­paign. Yet they kept the faith, and put up with the long hours, the wild mood swings, the many pro­longed absences ... and even longer excuses.

SYMBOL GLOSSARY

Note: In general, vectors are indicated by bolded tenns and "; planar values by bolded Serif font; radiometric measures by uppercase italic Times (R, I, W, etc.); photometric values by their corresponding Scriptl let­ters (!l(, '1, '111, etc.), physics tenninology such as force

* convolution

multiplication

W two dimensional

3D three dimensional

a absorption coefficient

a planar angle; complementary angle to e a critical wedge angle; prism apex angle

a£ optical atmospheric extinction coefficient (atmospheric absorption)

Clrc coupling coefficient, transmitter to cable

aCC coupling coefficient, cable end to cable end (cable losses)

aCR coupling coefficient, cable to receiver

~ planar angle; angle to source height plane

~T,A black-body factor

a angular beam deviation

a laser speckle grain size

a solar declination

ac small patch of sensor surface C

ao small patch of receiving surface 0

aF focal point shift

and energy by Script2 (:1, G, etc.), mathematical transforms by Script3 (!Y, ~ etc.); materials charac­teristics also by Script3 (ffi. 5", etc.); finally, the electri­cal/electronic tenns are indicated by a Sans font (R,

e, V, etc.).

as small patch of source surface area S -as projected source surface area

Ox differentially small quantity

~ degree of edge blur

~')., wavelength spread of laser, bandwidth, spectral purity (nm)

I!.f incrementally small frequency band; bandwidth

I!.f noise equivalent passband

~g grayscale increment or step

~j image extension

I!.O object extension

I!.L coherence length of coherent source

I!.t coherence time

&I nonnalized step index

I!.tL time zone difference, zone time correction

I!.RO difference in scene radiance, contrast

+I!.do DOV zone, distance from dO to V+

-Mo DOV zone, distance from do to V_

+Mj DOF zone, distance from dj to C+

-Mi DOF zone, distance from d j to C_

Symbol glossary xxxi

£ emissivity of a material OlC solid angle subtended by sensor

lOA. emissivity at wavelength A Ol numerical solid aperture

£ permittivity of a medium n electrical resistivity

£0 permittivity of a vacuum cP radiant energy or flux (1) (8.85 x 1O-12A.sN·m or C2/N.m) cP electrical phase angle; spatial phase

£ charge transfer loss or inefficiency cP angle of incidence, angle of inclination of

£ .. 1 b A d A vIewmg ang e, etween v an 0 incidence vector t to object normal ~

11 quantum efficiency QE cP reflectance angle or angle of reflection, A A

'Y exitance or phase angle, the angle between between r and 0 ( P = - cP )

~ and t CPB Brewster's angle

'Y sensor gamma, sensor linearity, responsivity slope CPc critical angle for TIR

'Y zenith sun distance (y = h) CPi angle of incident light

r relative photodetector responsivity (A.cm2fW) CPt angle of refraction/transmitted light

ro absolute photodetector responsivity (A.cm2fW) receiver/viewer

rA. spectral responsivity ( r at A ) CPs azimuth angle of source

~ luminous efficiency factor, photometric Watt (lm) 'II sensor tilt angle, angle between view A A

per radiant watt ( W /W ) vector v and sensor plane normal c

t'}w radiant efficacy ( W / P ) 'II photodetector sensitivity (AfW)

t'}w luminous efficacy, lumens per Watt of P electrical conductivity, P = lin electrical power ( W / P, t'}w = t'}w x t') ) P pyroelectric coefficient

t'}o nominal LED operational efficiency P albedo (reflectivity efficiency)

t'}pk peak LED efficiency Po albedo at object point 0

1C photon interaction efficiency (J Stefan-Boltzmann constant

1C Fresnel extinction coefficient (5.67 x 10-8 W / m2.oK4)

A wavelength of light (nm) (J2 x spatial variance; spatial noise

Ac critical wavelength for photoelectric effect (J2 t temporal variance; temporal noise

AG sensor cutoff A, bandgap wavelength (nm) t transmittance; transmissivity of a material

Aq photoconductance ta atmospheric transmissivity

Il permeability of a medium to unit transmissivity of a material

Ilo permeability of vacuum tx closed polarizer transmittance ( tmin ) (1.26 x 10-6 V.s/A.m or N.s/C2) to closed polarizer transmittance ( t max )

v frequency of light (Hz) t circuit time constant

Vo laser diode slope efficiency t, response rise time

vF Fresnel loss efficiency factor tc sensor/photodetector time constant

Ol solid angle (steradian, sr); angular velocity a planar angle Ol spatial frequency aD beam angle, beam spread, angle of

OlN Nyquist frequency divergence

xxxii Symbol glossary

a emittance angle, between f and Ad photodiode dark current 1\

source normal s (as) Ac current through shunt capacitance aj angle of incidence, between f and ~ ( cp ) Ac sensor output current ap phase/exitance angle, the angle between the AD laser diode current

view vector ~ and the incidence direction A AF diode forward current , ( 'Y)

ar angle of reflection, angle from reflection AL lamp current

direction ~ to object normal ~ AN noise current

(cp = ar = - cp ) Apk peak LED current

av . I b 1\ 1\ VIew ang e, etween v and 0 (£) AR diode current through shunt resistance

ar altitude angle of receiver/viewer Ar diode reverse-bias leakage current

as altitude angle of source A, recombinant shot noise current

Uc charge-carrier mobility coefficient/drift rate am angular acceleration

u+ hole mobility coefficient/drift rate A area

u_ electron mobility coefficient/drift rate A<p foreshortened area

~ charge transfer efficiency Ap area of surface patch or point

~ sensor tilt angle, between ~ and ~ Ar aspect ratio

~ elevation angle (angular height) Ac area of sensor patch

~T temperature coefficient Aa area of receiving surface patch

AR area of receiving surface, interior of sphere

A Aj area of sphere port i

AT total area of sphere ports

Cl absorbence Aw flashtube wall surface area

~ aperture area AS area of source surface patch, spherical area

~F field stop aperture As projected area of a source

fitN numerical aperture AOV angular field-of-view (angular FOV)

fita optical aperture

fits aperture stop B A electrical current (Amperes)

A average current; average LED current f}J beam candlepower (BCP)

over pulse cycle f}J<p beam candlepower seconds (BCPS)

Ai.. sensor output current at A. b number of binary bits

Ao nominal diode current B magnetic field

Ao lasing current threshold b proportion of t H used for blanking

Ao average current at nominal LED operation B bandwidth; blur ratio

point, nominal LED current Bj black-body radiant exitance, temperature Tj

Aq photodiode photocurrent BL strobe bulb aspect ratio (LB / DB)

Symbol glossary xxxiii

BCP beam candlepower Cz zonal constant

BCPS beam candlepower seconds CF sensor fonnat (diagonal extent)

BFD back focal distance, from rear lens vertex Co GRIN lens constant

to focal point CFj photometric correction factor for pixel i BFL back focal length, from rear lens vertex to C mean spherical candlepower (MSCP)

focal point at infinite focus Cq> mean spherical candlepower seconds

(CPS)

C Cw mean spherical candlepower per Watt (MSCPIW or CPW)

Cg charge-carrier generation rate CPS spherical candlepower seconds c, charge-carrier recombination rate CRI Color Rendering Index ct charge-carrier lifetime CTF contrast-transfer function C electrical capacitance (Farads)

Cf flash capacitance D Cj diode junction capacitance

Cp power factor correction capacitance 9) optical density

Cx RFI suppression capacitance D detectivity (cm2/W)

CL parasitic capacitance of video buss D diode

CD photodiode shunt capacitance Dq photodiode

Cs floating diffusion capacitance DSNU dark-signal non-unifonnity

CTE charge transfer efficiency (~ = 1-£ ) [)* nonnalized detectivity (cm • ..,fHZ/W)

CTF charge-transfer function d distance; distance from source point S to 1\

unit vector nonnal of sensor/viewer point 0 on object

c surface C dh hyperfocal distance

C the camera/viewer/sensor surface plane dg dispersive power of a glass (lIV d)

C(x,y) continuous (gray tone ) image dz depletion zone depth or width

CF flat-field image dj image conjugate distance, distance from

CB bias image PP2 to image plane; distance to image

CI1 difference image do object conjugate distance, distance from PP1 to object plane; distance to object

Co gain image dOQ perpendicular distance from plane 0 to

C+ the far limit of the sensor focus field point Q (view surface plane), defining the DOF

dB distance from receiving patch to point H C_ the near limit of the sensor focus field

dN internodal distance (separation between c speed of light PP nodes)

C1 Planck coefficient (3.74 x 10-16 W/m2) dR Rayleigh range C2 Planck coefficient (1.44 x 10-2 m2.oK) dT lens (total) conjugate distance, distance Cp covering power of lens/sensor combination from object plane to image plane

xxxiv Symbol glossary

dv principal distance, viewpoint distance eS/2 number of e_ at half-well capacity

dv distance from object to viewing surface C 'E luminous exitance or emittance (lm/m2)

D diameter E radiant exitance or emittance (W/m2)

Djt aperture diameter EA ambient radiant exitance (IR imaging)

Dp diameter of pinhole aperture E').. radiant exitance at wavelength A.

DA diameter of Airy disk Eo black-body emittance from an object

DB lamp bulb diameter; bore diameter Es exitance of a source patch

DB blur circle diameter eV electron-volt unit (1.602 x 10-19 J)

DL lens diameter EFL effective focal length, F

Dv projection of DB onto viewplane V EV exposure value

DOF depth-of-focus

DOV depth-of-view (depth of field) F

E ~ force

~r centrifugal (rotational) force

C energy ~8 centripetal (electronuclear) force

Cc conduction band energy level :f Fourier transform

Cqx energy of an x-ray photon f frequency; spatial frequency

Cq total energy in flux stream fc sensor sampling frequency

Cf flash energy fN Nyquist spatial frequency

Cx flashlamp explosion energy fc cutoff spatial frequency

CF Fermi level/energy fc equivalent cutoff spatial frequency

CG bandgap energy IIf flicker noise

CK kinetic energy fns lamp driving frequency at resonance

Cp potential energy ~ flash rate (pulse repetition frequency)

GT total energy FPN fixed-pattern noise

E electric field 1# relative aperture

Ell parallel polarized E-field; 1# effective relative aperture

ordinary ray (o-ray) Ij integrating sphere port factor

EJ.. perpendicular polarized E-field; fr T-stop number, transmissive aperture

extraordinary ray (e-ray) Fj focal length, image space (or just F ) e_ electron charge unit F focal length (nominal)

-ek kinetic energy of an electron F effective focal length (EFL)

em mass of an electron Fo front focal length (object space)

eN number of noise electrons Fo object factor

eS number of e_ at saturation (well capacity) fli parallel plane aspect factor

Symbol glossary xxxv

Fe sensor factor Hf flash circuit inductance

FF focal factor h Planck's constant (6.63 x 10-34 J.s)

FG scene factor ~ direction/orientation of linear source

FL lens factor h sun height

Fs source factor h source standoff/height, perpendicular

FD back flange distance, distance from distance from S to 0 -

camera mounting flange to focal length h effective source standoff/height

FFD front focal distance, distance from front H hour angle lens vertex to object plane H source height point on linear source axis

FFL front focal length, distance from vertex H unit exposure (J/cm2, H = I . t ) to front focal distance with 00 d j

HT total surface exposure (J, HT = H . A ) FOF field-of-focus (sensor format)

Hx x-ray exposure FOI field-of-image

source height plane (perpendicular to S H FOL field-of-lighting and through a ) FOV field-of-view

FTF flux transfer function I FWL front working length

~ incidence unit vector, direction of a with I

G respect to S, unit vector along SO

date number, day within month (1 to 31)

G electrical conductance (mhos), '1 illuminance (lUX, Im/m2)

G=lIR '1", solar illuminance outside atmosphere Ge photoconductive gain '1E solar illuminance at Earth's surface G] photointensifier gain I irradiance (W /m2)

g total number of grayscale steps I", solar irradiance outside atmosphere Gj transfer efficiency of port i (solar constant)

GN flash guide number IE solar irradiance at Earth's surface -

Go optical extent I", solar constant (average irradiance from sun)

H 10 irradiance at an incidence angle cp of 0° ~ 1\

(I = 0)

:Jl optical transfer function (OTF) IB laser beam on-axis irradiance

h aperture response function Ie irradiance at center of illumination field

H Fourier transform of aperture response Ie irradiance at edge of illumination field function

IIf' irradiance falling onto point a from an H one horizontal line time ( = tH ) incidence angle cp

H electrical inductance (Henries); choke coil Ie irradiance onto sensor surface

xxxvi Symbol glossary

10 irradiance falling onto point 0 M

IH irradiance onto horizontal surface M mortality, service life of a lamp

Iv irradiance onto vertical surface -M 'hot' AC mains voltage terminal

IR image resolvability MRT minimum resolvable temperature

MRTD minimum resolvable temperature

J difference

m interference order J perspective projection plane m£ relative optical air mass

M optical magnification

K Mj diffraction pattern minima, order i

Mo zero-order minimum (central maximum) K Kell factor

ML longitudinal magnification k Boltzmann constant (1.38 x 10-23 J / OK) Mp pupil magnification factor

K£ dielectric constant (relative permittivity) Me angular magnification

KJ.1 relative permeability of a material MFD mounting flange distance

K human observer scotopic eye response MFL mounting flange length

(rod vision) MTBF mean time before failure

K human observer photopic eye response MTF modulation transfer function (cone vision) MTF equivalent modulation transfer function

Kc sensor diagonal, sensor format factor

N L

nr number of pixels over response rise-time

2 Laplace transform np number of pixels

2 optical path length nH number of cycles output in video signal

L t total number of scanlines -N 'neutral' AC mains voltage terminal

N noise power L j number of scanlines in vertical retrace

interval (VBLANK) Nq quantization noise

length NT thermal shot noise

NJ Johnson noise L length of linear source

Ns Schottky noise L local latitude

Ne number of noise electrons Lo unit absorption length of FO NC total sensor noise

Lc sensor length NEDT noise-equivalent differential temperature

L8 bulb length; arc length NEP noise-equivalent power

LSF line-spread function NET noise-equivalent temperature

Symbol glossary xxxvii

n day number within year (1 to 365) Ns radiant intensity in the direction of

n index of refraction of a material source point S

n average index of refraction NEE noise-equivalent exposure (J/cm2)

no index of refraction of the media NU sensor array non-uniformity

ng index of refraction of glass g

no central axis index of refraction 0

no index of refraction of the media

index of refraction of coating (ARC) or 0 optical opacity

nc A

cladding (OF) 0 unit normal vector of receiving surface 0

nr index of refraction at radius r 0 object plane (containing 0); plane of illumination

nR minimum index of GRIN lens

Abbe number, the index of refraction at 0 point or patch on an object surface

nF A. = 486 nm, the F-line in hydrogen OA object accuracy

nd Abbe number, the index of refraction at OCF optical coupling function

A. = 588 nm, the d-line in helium OR object resolution

nC Abbe number, the index of refraction at OTF optical-transfer function

A. = 656 nm, the C-line in hydrogen

nH number of horizontal line-pairs in image p A

surface normal unit vector n

'X.. luminous intensity (lm/st, cd) 9' Poisson distribution

% nominal LED luminous intensity (lm/st, cd) P duty cycle, pulse proportion

% luminous intensity at emittance angle 9 P;,j discrete image (array of pixel values)

'X.. average luminous intensity (lm/st, cd) Pi value of pixel i

'X.. time-averaged LED luminous intensity P average pixel output over array

N radiant intensity (W/sr) Pi trailing packet charge size - P N average radiant intensity electrical power (Watts), P= A * V -N effective nodal point of complex lens P one pixel time (l/pixel clock)

No radiant intensity along ~ (9 = 0°) PI flashtube power (instantaneous)

No intensity at center of beam PI average flashtube power

Nr reflected intensity PL lamp power

Na radiant intensity at emittance angle e PRNU spatial photoresponse non-uniformity

Na relative radiant intensity at emittance P momentum

angle e to source axis; radiation pattern P+ number of holes (population density)

Ni nodal point of thick lens nearest image P- number of electrons (population density)

No nodal points of thick lens nearest object Pc number of charge carriers (charge carrier

Ns nominal radiant intensity of a source population density)

(Ns=No) Pq number of photons

xxxviii

P lens power (11M)

P point or patch of a surface

P packing fraction of a FO bundle

PN entrance pupil diameter

Px exit pupil diameter

PG pitch of a GRIN lens

PP principal plane of a lens

PP j image-side principal plane of thick lens

PPo object-side principal plane of a thick lens

PSD power spectral density

PSF point-spread function

PTF phase-transfer function

Q

qs signal charge

q photocharge packet

qj photocharge signal packet i

Q electrical charge (Coulombs)

q average flash power density (W/cm2)

QL lamp loading

Qp priming/bias charge, fat zero

q quantum energy, energy of a photon

q').. energy of quantumlphoton of wavelength A

q aperture shape factor

q source offset

qr photon arrival rate

qL Coddington lens shape factor

Q Callier (filter) factor

Q radiant energy (1)

Q luminous energy (lm.s) -Q radiant density (J/m3)

Q luminous density (lm.s/m3)

QB background flux density

QE quantum efficiency 11

Qy quantum yield

Symbol glossary

R

I<j image resolvability; image space resolving power

1<0 object resolution; resolving power (object space)

1<0 diffraction limit resolution

1<9 angular resolving power

I< a object accuracy

I<c sensor resolution

I< L lens resolution

I< H horizontal resolution (video)

I<v vertical resolution (video)

9t reflectance function

~I Fresnel reflectance, parallel polarization

9t.l Fresnel reflectance, perpendicular polarization

9to reflectance function at point 0 (Ro / 10 )

9tN internal reflectance

9tx external reflectance

R electrical resistance (Ohms)

RL lamp resistance; load resistor

RO laser diode current limiting resistance

RO photodiode shunt resistance

~ unit vector in direction of specular reflection

r radius of Airy disk

r radial distance; radius of cylindrical source - effective (projected) radius of source r

rm radius of curvature of mirror

rB beam radius

rw Gaussian beam waist

rR radius of rod (GRIN) lens

!It luminancelluminous sterance (lrn/m2.st or cdim2)

R radiance or radiant sterance (W/m2.sr)

Rs radiance of a source patch

Symbol glossary xxxix

Rz radiance of sky at zenith ta active video time interval

R~ radiance of sky at angular height ~ tb horizontal blanking time

Ra lamp color index (eRI) tH video horizontal line time

RDF reflectance distribution function tv vertical frame time

tz time zone

S T absolute temperature eK, Kelvin)

Tkin kinetic temperature (0C) Se photosensor array pitch

Trod radiant temperature (0C) S signal power

Te electron temperature Se floating diffusion sensitivity

Tg gas/plasma temperature SNR signal-to-noise ratio ( SIN)

Te color temperature eK, Kelvin) A s unit normal vector of source surface S

Tee correlated color temperature eK, Kelvin) s arc length; advancement

TVH TV lines per picture height S source plane (containing source point S)

TVL television lines S point or patch of source surface; spectrum

Sj a point on source plane S U

Sa resolution test chart group number

SE resolution test chart element number U uniformity of illumination field

SA spherical aberration (U=~/lc)

SEE saturation equivalent exposure (J/cm2) Uq QE uniformity

sr steradian Ue sensor uniformity

T V

5" transmittance ¥).. CIE photopic luminosity function

5i1 Fresnel transmittance, parallel polarization V electrical voltage (Volts)

5".1 Fresnel transmittance, perpendicular Vb bias voltage polarization component

Vcorr CDS correlated voltage

5"N internal transmittance V;np uncorrected (input) image voltage values

5"x external (media) transmittance Vjnp average pixel voltage value in input image

t flash duration, pulse duration Vdark voltages measured using a dark thickness input image

t exposure time; shutter time duration Vjlat voltages measured using uniform

tv corrected solar time input image

te charge carrier transit time V mean output of sensor array

te time equation correction factor Vmax largest value of pixel output voltage

tL thickness of lens (intervertex distance) Ve voltage across capacitor

xl Symbol glossary

Ve voltage/signal output from sensor C We incident flux at sensor

VD photodiode voltage WR reflected flux (W)

VF cathode and anode fall voltage Ws source flux (W)

VF LED forward voltage drop Wr power within beam at radius r VH voltage across inductor/coil

Wo power along central axis of beam VL lamp voltage W", spectral radiant flux (W /nm) VM mains voltage WD working distance VR voltage across resistor

Vs arc discharge starting voltage, strike, X breakover, ignition voltage

1\ unit vector in direction of sensor/viewer v

x distance, displacement, x -coordinate C from object point 0; viewing vector

v velocity XE polarizer extinction ratio

V viewpoint, center of perspective

V view plane (object space focal plane) y

V+ far limit of DOV height of corresponding image point Yj V_ near limit of DOV (vertical distance about optical axis at

V+ distance from do to V+ image plane)

V_ distance from do to V_ Yo height of an object (vertical distance

Vj image side vertex of a lens system about optical axis at object plane)

Vo object side vertex of a lens system

Vcp mechanical vignetting factor Z Vd constringence factor of a glass

Vp principal dispersion index Z impedance

~ impedance of a vacuum (377 n)

W ZL lamp impedance

Z thickness; depth

Wm work function of a material z", absorption length

w diffraction slit width, grating spacing ze sensor thickness

w width of source lens thickness (intervertex distance) zL

we sensor width lens edge thickness ze

we scanline width lens center thickness Zc w projected width of source

'HI luminous flux (lumens, 1m) Zc thickness of ARC film

W radiant flux (W, J/s) zd depletion zone depth

Wi incident flux (W) Z observer's zenith

Symbol glossary xli

Abbreviations EOF end-of-field

EOL end-of-line ADC analog-digital converter ES energy saving AGe automatic gain control

FC field clock ALU Arithmetic Logic Unit

FCC Federal Communications Commission ANSI American National Standards Institute

FET field-effect transistor ARC anti-reflective coating

FF full-frame ASA American Standards Association (film speed)

FIT frame-interline transfer BLIP background-limited imager performance

BLM blended-light mercury FLC ferro-electric liquid crystal

CAT computer-aided tomography FO fiber-optics

CCD charge-coupled device fps frames per second

CCPD charge-coupled priming device FT frame-transfer

CCPR Consultive Committee of Photometry and GLU Global Logic Unit

Radiometry GRIN gradient index

CDRH Center for Devices and Radiological Health HAD hole-accumulated diode

CDS correlated double sampling HCCD horizontal charge-coupled device

CGH computer-generated hologram HCT mercury-cadmium-telluride

CI conducted interference HD horizontal drive

CID compact iodide daylight HDTV high-definition TV

CIE Commission Internationale de I 'Eclairage HID high-intensity discharge

CIM computer-integrated manufacturing HMI hydragyrum metal iodine

CIPM International Commission on Weights and HO high output

Measures HOE holographic optical element

CMOS complementary metal-oxide semiconductor HPM high-pressure mercury

CMT cadmium-mercury-telluride HPS high-pressure sodium

CMY cyan-magenta-yellow I/O input/output

CPT charge-primed transfer IC integrated circuit

CPU central processing unit IEC International Electrotechnical Commission

CRT cathode ray tube IEEE Institute of Electrical and Electronic

CSI compact source lamp Engineers

DAC digital-to-analog converter lIT image intensifier tube

DLIP detector-limited imager performance ILT interline transfer

dpi dots per inch IR infra-red

DTGS deuterated triglycerine sulfate IRE Institute of Radio Engineers

EIA Electronics Industries Association ISO International Standards Organization

EL electroluminescence JFET junction field-effect transistor

ELED edge-emitting light-emitting diode KDP potassium dihydrogen phosphate

EM electromagnetic KTN potassium tantalate niobate

EMF electromotive force (voltage) LC line clock

EMI electromagnetic interference LC liquid crystal

EMR electromagnetic radiation LCD liquid crystal display

xlii Symbol glossary

LED light-emitting diode RFI radio frequency interference

LIF Lighting Industry Federation RGB red, green, blue

LPF low-pass spatial filter RLA random-line addressable

LPM low-pressure mercury RMS root-mean-square

LPS low-pressure sodium ROI region-of-interest

LSB least significant bit RPA random-pixel addressable

LIT lead-tin-telluride RPM revolutions per minute

MAX the maximum function RTR real-time radiography

MCP microchannel plate SB Schottky barrier

MCT mercury-cadmium-telluride SCR Stirling cycle refrigerator

MDAC multiplying digital-to-analog converter S/H sample/hold

MHI metal iodide SI International System of Units

Mm... metal halide SIT silicon-intensified target

MNT mercury-manganese-telluride SLR single-lens reflex

MOS metal-oxide semiconductor SLS strained-layer superlattice

MOSFET MOS field-effect transistor SMD surface-mounted device

MPP multi-pinned phase SSPD serially-switched photodiode device

MPPS million pixels per second TAB tape-automated bonding

MUX multiplex TASO Television Allocation Study Organization

MV machine vision TC time code

MWIR medium-wave infra-red TCG time-code generator

MZT mercury-zinc-telluride TDI time-delay integration

NEMA National Equipment Manufacturers Association TE thermoelectric

NIST National Institute of Standards and Testing TEM transverse electric and magnetic

NMOS N-type MOS TGS triglycerine sulfate

NTSC National Television Standards Committee TIR total internal reflection

OF optical fiber TSM Tandem Scanning Microscope

PAL phase-alternating-line (TV standard) TIL transistor-transistor logic

PAR parabolic arc reflector UHF ultra-high frequency

PC pixel clock UPAP International Union of Pure and

PCB printed circuit board Applied Physics

PE processing element UV ultraviolet

PIN P-Intrinsic-N diode VCCD vertical charge-coupled device

PLL phase-locked loop YO vertical drive

PMT photomultiple tube VHO very high output

PWM pulse width modulation VITC vertical interval time codes

PZT lead zirconate titanate VPCCD virtual-phase charge-coupled device

RAM random access memory XCAT x-ray CAT

RF radio frequency