Polarization Engineering for LCD Projection Michael G. Robinson, Jianmin Chen, and Gary D. Sharp Colorlink Inc., USA John Wiley & Sons, Ltd
Contents Series Editor's Foreword Preface XIII XV 1 Introduction 1 1.1 The Case for Projection 1 1.2 History and Projection Technology Overview 2 1.2.1 Cinema Film 2 1.2.2 CRT-based Projection Systems 3 1.2.3 Schlieren Optics-based Projector 5 1.2.4 Microdisplay-based Projection Systems 7 1.2.5 Other Projection Technologies 16 1.3 Scope of the Book 17 2 Liquid Crystal Projection System Basics 21 2.1 Introduction 21 2.2 Brightness and Color Sensitivity of the Human Eye 22 2.2.1 Brightness 22 2.2.2 Brightness Uniformity 24 2.2.3 Color 24 2.2.4 White 26 2.2.5 Color Distinction and Just Noticeable Differences (JNDs) 28 2.2.6 Contrast 28 2.2.7 Size, Resolution, Registration, and Distortion 29 2.2.8 Electronic and Panel-related Metrics 30 2.3 Photometrie Measurement 30 2.4 Summary of What Constitutes a "Good" RPTV Display in the Current Marketplace 30 2.5 System Engineering 30 2.5.1 Rear-projection Screens 31 2.5.2 Folding Mirrors 34
VIII CONTENTS 2.5.3 Projection Optics 35 2.5.4 Color Management and Modulation Subsystem 37 2.5.5 Illumination System 37 2.5.6 Light Source 40 2.6 Etendue Considerations 41 3 Polarizarion Basics 47 3.1 Introduction 47 3.2 Electromagnetic Wave Propagation 47 3.2.1 Polarization of Monochromatic Waves 48 3.2.2 Complex Number Representation 50 3.2.3 Jones'Vector Representation 51 3.2.4 Stokes' Parameters 53 3.2.5 Poincare Sphere 54 3.3 Interaction with Media 57 3.3.1 Reflection and Refraction of Plane Waves 57 3.3.2 Matrix Formulation for Isotropie Layered Media 60 3.3.3 Matrix Formulation for Anisotropie Layered Media 61 3.4 Index Ellipsoid Visualization 70 3.5 Modeling Techniques 72 4 System Components 77 4.1 Introduction 77 4.2 Retarders 77 4.3 Polarizers 83 4.3.1 Absorptive Polarizer 83 4.3.2 Reflective Polarizers 85 4.4 Interference Filters 88 4.4.1 Anti-reflection Coatings 88 4.4.2 Quarter-wave Stack 89 4.4.3 Normal Incidence Dichroic Filters 90 4.4.4 Dichroic Beam Splitters 92 4.5 Polarizing Beam Splitters (PBSs) 94 4.5.1 Dichroic Cube PBS 94 4.5.2 Multilayer Birefringent Cube PBS (MBC PBS) 97 4.5.3 Wire Grid Plate PBS 98 4.6 Other Components 100 4.6.1 Mirrors 100 4.6.2 Light-pipe 100 4.6.3 Substrates 101 5 Liquid Crystal Displays (LCDs) 105 5.1 Description and Brief History 105 5.2 Anisotropie Properties of Liquid Crystals 109 5.3 Frank Free Energy and Electromagnetic Field Contribution to Free Energy 110 5.4 Alignment Layer and LC Pretilt Angle 111 5.5 Rotational Viscosity 113 5.6 Electro-optical Effect of LCs 113 5.7 LC Modes for Projection 114 5.7.1 Electrically ControUed Birefringence (ECB) Mode 114 5.7.2 90 TN and VA 90 TN Mode 117
CONTENTS IX 5.7.3 45 Reflective TN Mode 120 5.7.4 63.6 Mixed TN (MTN) Mode 121 5.7.5 90 MTN Mode 123 5.8 FOV of LCDs 124 6 Retarder Stack Filters 129 6.1 Introduction 129 6.2 Principle and Background of RSFs 130 6.2.1 Single Stage Polarization Interference 130 6.2.2 Multilayer Polarization Interference 132 6.3 RSFs in LC Projection Systems 134 6.3.1 Optical Filters 134 6.3.2 Color Splitters/Combiners 136 6.4 Design of RSFs 137 6.4.1 Impulse Response of a Birefringent Network 137 6.4.2 Design Methodology 140 6.4.3 Impulse Response to RSF Angular Profile Mapping 140 6.5 Properties of Retarder Stacks 143 6.5.1 Unitary Jones'Matrix Representation 143 6.5.2 Properties of Symmetrie RSF Designs 143 6.5.3 General Properties of Symmetrie RSF Designs 145 7 System Contrast 153 7.1 Introduction 153 7.2 On-axis Contrast 154 7.2.1 Head-on Contrast of LC Mode 154 7.2.2 Normal Incidence Pre- and Post-polarizers 157 7.3 Off-axis Effects 159 7.3.1 Homeotropic Liquid Crystals 159 7.3.2 Off-axis Property of Sheet Polarizers 160 7.3.3 Geometrical PBS Compensation 166 7.4 PBS/LCOS Compensation 175 7.4.1 VALCOSMode 176 7.4.2 General LCOS Mode 178 7.4.3 Influence of the Reflections from Interfaces on System Contrast 182 7.5 ANSI Contrast Enhancement 186 7.6 Skew Ray Compensated Retarder Stack Filters 187 7.7 Alternative Projection Systems 191 7.7.1 Off-telecentric Wire Grid PBS System 191 7.7.2 Off-axis System 192 7.8 Overall System Contrast 194 8 Color Management 197 8.1 Introduction 197 8.2 System Color Band Determination 197 8.3 Color Management in Projection Systems 201 8.3.1 Spatial Color Separation and Recombination 202 8.3.2 Temporal Color Separation 209
X CONTENTS Transmissive Three-panel Projection System 217 9.1 Introduction 217 9.2 Brief System Description 217 9.3 System Throughput 219 9.3.1 Lamp Flux Output, <5 219 9.3.2 Illumination Efficiency, r) m 219 9.3.3 Color Management System Efficiency, r\ cm 220 9.3.4 Color Correction Efficiency, r\ cc 222 9.3.5 Modulation System Efficiency, v\ m 223 9.3.6 Imaging System Efficiency, TJ^, 224 9.3.7 Total System Lumen Output, <t> out 224 9.4 Contrast 225 9.4.1 Negative c-plate Compensation 227 9.4.2 Splayed Negative Birefnngent Film Compensation Scheme 227 9.4.3 Negative o-plate Compensation 230 9.4.4 Positive o-plate Compensation Scheme 230 9.4.5 Liquid Crystal Polymer (LCP) Compensation Scheme 233 10 Three-panel Reflective Systems 237 10.1 Introduction 237 10.2 3 x PBS/X-cube System 238 10.2.1 Description of Basic Operation 238 10.2.2 Comparison to Transmissive System 239 10.2.3 Brightness 240 10.2.4 Contrast 240 10.2.5 Systems Upgrades v 242 10.2.6 Alternative PBS Solutions 242 10.3 Polarization Color Filter Systems 247 10.3.1 The CQ3 Three-PBS Architecture 248 10.3.2 System Analysis 250 10.4 Three-panel LCOS System Comparison 255 11 Single and Dual Panel LC Projection Systems 257 11.1 Introduction 257 11.2 Generic Color Sequential Single Panel Reflective LC System 257 11.2.1 System Description 257 11.2.2 Single Panel LCOS System Throughput 258 11.2.3 System Contrast 261 11.2.4 Temporal System Issues 262 11.3 Example Single Panel Color Sequential Systems 267 11.3.1 Scrolling Color System 267 11.3.2 Field Sequential Single Panel System 267 11.4 Two-panel Systems 268 11.4.1 White Color Balance 269 11.4.2 Color Break-up 269 11.4.3 Two-panel Architectures 270
CONTENTS XI 11.5 Commercialized Single Panel Projection Systems Based on Spatial Color Separation 273 11.5.1 Angular Color Beam Separation with Panel-based Microlens Arrays 273 11.5.2 Holographie Micro-optic Color Separation 273 11.5.3 Flat-panel LCD Projection 274 Appendix A 277 Index 281 /