Introduction to Flat Panel Displays E-Book

Jiun-Haw Lee

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley Series in Display Technology
• Sprache: Englisch

Seitenzahl: 863

Veröffentlichungsjahr: 2020

Beschreibung

THE PERFECT GUIDE TO FLAT PANEL DISPLAYS FOR RESEARCHERS AND INDUSTRY PERSONNEL ALIKE

Introduction to Flat Panel Displays, 2nd Edition is the leading introductory reference to state-of-the-art flat panel display technologies. The 2nd edition has been newly updated to include the latest developments for high pixel resolution support, high brightness, improved contrast settings, and low power consumption. The 2nd edition has also been updated to include the latest developments of head-mounted displays for virtual and augmented reality applications.

Introduction to Flat Panel Displays introduces and updates both the fundamental physics and materials concepts underlying flat panel display technology and their application to smart phones, ultra-high definitions TVs, computers, and virtual and augmented reality systems.

The book includes new information on quantum-dot enhanced LCDs, device configurations and performance, and nitrate-based LEDs. The authors also provide updates on technologies like:

• OLED materials, including phosphorescent, TTA, and TADF OLEDs
• White light OLED and light extraction
• OLED for mobile and TV
• Light and flexible OLED
• Reflective displays, including e-paper technology
• Low power consumption displays

The perfect reference for graduate students and new entrants to the display industry, Introduction to Flat Panel Displays offers problem and homework sets at the end of each chapter to measure retention and learning.

Leseprobe

Table of Contents

Cover

Series Editor's Foreword

1 Flat Panel Displays

1.1 INTRODUCTION

1.2 EMISSIVE AND NON-EMISSIVE DISPLAYS

1.3 DISPLAY SPECIFICATIONS

1.4 APPLICATIONS OF FLAT PANEL DISPLAYS

References

2 Color Science and Engineering

2.1 INTRODUCTION

2.2 PHOTOMETRY

2.3 THE EYE

2.4 COLORIMETRY

2.5 PRODUCTION AND REPRODUCTION OF COLORS

2.6 DISPLAY MEASUREMENTS

References

3 Thin Film Transistors

3.1 INTRODUCTION

3.2 BASIC CONCEPTS OF CRYSTALLINE SEMICONDUCTOR MATERIALS

3.3 CLASSIFICATION OF SILICON MATERIALS

3.4 HYDROGENATED AMORPHOUS SILICON (A-SI:H)

3.5 POLYCRYSTALLINE SILICON

3.6 THIN-FILM TRANSISTORS

3.7 PM AND AM DRIVING SCHEMES

References

4 Liquid Crystal Displays

4.1 INTRODUCTION

4.2 TRANSMISSIVE LCDS

4.3 LIQUID CRYSTAL MATERIALS

4.4 LIQUID CRYSTAL ALIGNMENT

4.5 HOMOGENEOUS CELL

4.6 TWISTED NEMATIC (TN)

4.7 IN-PLANE SWITCHING (IPS)

4.8 FRINGE FIELD SWITCHING (FFS)

4.9 VERTICAL ALIGNMENT (VA)

4.10 AMBIENT CONTRAST RATIO

4.11 MOTION PICTURE RESPONSE TIME (MPRT)

4.12 WIDE COLOR GAMUT

4.13 HIGH DYNAMIC RANGE

4.14 FUTURE DIRECTIONS

References

5 Light-Emitting Diodes

5.1 INTRODUCTION

5.2 MATERIAL SYSTEMS

5.3 DIODE CHARACTERISTICS

5.4 LIGHT-EMITTING CHARACTERISTICS

5.5 DEVICE FABRICATION

5.6 APPLICATIONS

References

6 Organic Light-Emitting Devices

6.1 INTRODUCTION

6.2 ENERGY STATES IN ORGANIC MATERIALS

6.3 PHOTOPHYSICAL PROCESSES

6.4 CARRIER INJECTION, TRANSPORT, AND RECOMBINATION

6.5 STRUCTURE, FABRICATION AND CHARACTERIZATION

6.6 TRIPLET EXCITON UTILIZATION

6.7 TANDEM STRUCTURE

6.8 IMPROVEMENT OF EXTRACTION EFFICIENCY

6.9 WHITE OLEDS

6.10 QUANTUM-DOT LIGHT-EMITTING DIODE

6.11 APPLICATIONS

References

7 Reflective Displays

7.1 INTRODUCTION

7.2 ELECTROPHORETIC DISPLAYS

7.3 REFLECTIVE LIQUID CRYSTAL DISPLAYS

7.4 REFLECTIVE DISPLAY BASED ON OPTICAL INTERFERENCE (MIRASOL DISPLAY)

7.5 ELECTROWETTING DISPLAY

7.6 COMPARISON OF DIFFERENT REFLECTIVE DISPLAY TECHNOLOGIES

References

8 Fundamentals of Head-Mounted Displays for Virtual and Augmented Reality

8.1 INTRODUCTION

8.2 HUMAN VISUAL SYSTEM

8.3 FUNDAMENTALS OF HEAD-MOUNTED DISPLAYS

8.4 HMD OPTICAL DESIGNS AND PERFORMANCE SPECIFICATIONS

8.5 ADVANCED HMD TECHNOLOGIES

References

9 Touch Panel Technology

9.1 INTRODUCTION

9.2 RESISTIVE TOUCH PANEL

9.3 CAPACITIVE TOUCH PANEL

9.4 ON-CELL AND IN-CELL TOUCH PANEL

9.5 OPTICAL SENSING FOR LARGE PANELS

References

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 Resolution of FPDs.

Chapter 2

Table 2.1 Definitions of photometric units.

Table 2.2 The dimensions and quantities of the cone and rod cells.

Chapter 3

Table 3.1 A comparison of various types of flexible substrates.

Chapter 4

Table 4.1 Composition of E7.

Chapter 5

Table 5.1 White light generation techniques.

Table 5.2 Sources used for different VPE systems.

Chapter 6

Table 6.1 Luminance data of DMQA/Alq devices.

Table 6.2 Layer structures of the two-layer OLEDs.

Chapter 7

Table 7.1 Comparison of various monochromic reflective display technologies.

Chapter 8

Table 8.1 Gullstrand–LeGrand schematic eye.

Table 8.2 Arizona eye model.

Table 8.3 A survey of array-type microdisplay technologies.

Table 8.4 A survey of optical combiner technologies and design examples.

Table 8.5 Optical design examples of immersive HMDs.

Table 8.6 Optical design examples of optical see-through HMDs.

List of Illustrations

Chapter 1

Figure 1.1 Subpixel layout of a FPD: (a) stripe, (b) mosaic, and (c) delta c...

Figure 1.2 (a) White (red + green + blue) pixels lit-on at the edge of the s...

Figure 1.3 (a) stripe, (b) PenTile™ RGRB, and (c) PenTile RGBW configuration...

Chapter 2

Figure 2.1 Formation of colors.

Figure 2.2 Illustrations of photometric units.

Figure 2.3 (a) Cross section of the eye; (b) and (c): formation of image in ...

Figure 2.4 Spatial distributions of (a) cone and (b) rod cells.

Figure 2.5 Illustration of a moving object in a display.

Figure 2.6 Spectral responses of (a) photopic and scotopic regions, and (b) ...

Figure 2.7 (a) Two test patterns for vision acuity, and (b) schematic diagra...

Figure 2.8 Experimental setup of color-matching experiments.

Figure 2.9 Tristimulus space of (R, G, B) primary colors (redraw from Ref. [...

Figure 2.10 (a) Tristimulus value for different wavelengths and (b) CIE 1931...

Figure 2.11 CIE 1931 (X, Y, Z) chromaticity diagram.

Figure 2.12 MacAdam ellipses of just-visible color differences in the CIE 19...

Figure 2.13 CIE 1976

(u

′

, v

′

)

chromaticity diagram and MacAdam ellipses.

Figure 2.14 Luminance versus gray-level with (a) linear and (b) log scales....

Figure 2.15 Illusion of checkerboard with the shadow.

Figure 2.16 Schematic diagram of the observing model.

Figure 2.17 Color gamut of NTSC and BT 2020 standards.

Figure 2.18 Power intensity spectrum of a blackbody radiator at different te...

Figure 2.19 Spectra of a basketball from (a) the real object and (b) the dis...

Chapter 3

Figure 3.1 3D crystalline structures of (a) Si and (b) GaAs [4].

Figure 3.2 Energy levels in (a) an isolated atom, (b) two atoms, and (c) a c...

Figure 3.3 Energy band structure.

Figure 3.4 Calculated

E

–

k

band structures of (a)Si and (b)GaAs [7]. Solid an...

Figure 3.5 Schematic diagram of bonding of Si with (a) As and (b) B impuriti...

Figure 3.6

F

(

E

) curves at different temperatures.

Figure 3.7 Classification of Si by grain size together with their mobility v...

Figure 3.8 (a) 3-D structures, and (b) density of states of a-Si:H [9], [10]...

Figure 3.9 Schematic diagram of PECVD system.

Figure 3.10 Potential barrier height at the grain boundary as a function of ...

Figure 3.11 Grain size, TFT mobility and photographs of thin-film under diff...

Figure 3.12 Grain size with different shot numbers. NCM and PM: near-complet...

Figure 3.13 Schematic diagram and notation of a TFT.

Figure 3.14 Band diagram of an ideal MOS structures at (a)

V

G

 = 0, and (b)

V

Figure 3.15 (a) Output characteristic, and (b) transfer characteristic, and ...

Figure 3.16 TFTs with different configurations [14].

Figure 3.17 Cross section of an a-Si:H TFT.

Figure 3.18 Typical fabrication steps for coplanar top-gate poly-Si TFTs [15...

Figure 3.19 Molecule structure of (a) pentacene, and (b) rubrene.

Figure 3.20 Device configurations of OTFT: (a) top and (b) bottom contact.

Figure 3.21 (a) Device structure and (b) transmission spectra of TTFT [23]....

Figure 3.22 Schematic orbital drawing of electron pathway in conventional co...

Figure 3.23 (a) Field-effect mobility and (b) threshold voltage obtained for...

Figure 3.24 (a) image displayed on PM-LCD, and the voltage during the (b) fi...

Figure 3.25 (a) image displayed on PM-OLED, and their voltage at (b) first, ...

Figure 3.26 Four gray levels achieved by PWM.

Figure 3.27 Equivalent circuit of AM LCD.

Figure 3.28 Timing diagram of

V

G

and

V

D

of Example 3.2.

Figure 3.29 Equivalent circuit for (a)

V

G

 = 0, and (b)

V

G

 = 20 V.

Figure 3.30 Equivalent circuit of AM OLED with two-transistor one-capacitor ...

Chapter 4

Figure 4.1 Device structure of (a) edge-lit and (b) direct-lit transmissive ...

Figure 4.2 Transmission spectra of RGB color filters (dotted lines), and emi...

Figure 4.3 Diagram showing eutectic formulation of a binary mixture.

Figure 4.4 The measured polarized absorption spectra of 5CB. The middle trac...

Figure 4.5 Wavelength-dependent refractive indices of E7 at

T

 = 25 °C. Open ...

Figure 4.6 Temperature-dependent refractive indices of 5CB at

λ

 = 546, ...

Figure 4.7 (a) Rubbing and (b) ion beam etching induced pretilt angle on a P...

Figure 4.8 LC director profile in a homogeneous cell. (a) V = 0, and (b) V ≫...

Figure 4.9 LC director distribution profile of a homogeneous cell under diff...

Figure 4.10 (a) VT curve of a homogeneous cell with dΔn = 275 nm, and (b) a ...

Figure 4.11 LC and polarizer configurations of a 90° TN cell. Left: V = 0, a...

Figure 4.12 Voltage-dependent transmittance of a normally white 90° TN cell....

Figure 4.13 (a) LC tilt angles of a TN cell in a voltage-on state, and (b) v...

Figure 4.14 Viewing angle of a TN LCD. The middle image is a normal view. Ri...

Figure 4.15 Structure of the WV film and the employed discotic compound. PDM...

Figure 4.16 (a) IPS electrodes, electric fields, and LC director orientation...

Figure 4.17 The LC director distribution, electric field profile (dashed lin...

Figure 4.18 Voltage-dependent light transmittance of the IPS LCD. The device...

Figure 4.19 Simulated isocontrast contours of the IPS LCD without any compen...

Figure 4.20 Different types of compensation films used for wide view LCDs.

Figure 4.21 Device configuration, electric field distributions, and LC direc...

Figure 4.22 Simulated VT curves of n-FFS with Δε = −4.4 and p-FFS with Δε = ...

Figure 4.23 Rotational viscosity versus |Δ

ε

| of some LC mixtures with Δ

Figure 4.24 Voltage-dependent normalized transmittance of a VA cell. LC: MLC...

Figure 4.25 Schematic drawing of a VA LC cell with a pretilt angle and bound...

Figure 4.26 The overdrive and undershoot voltage method for speeding up LC r...

Figure 4.27 LC orientation in a four-domain structure. P: polarizer, and A: ...

Figure 4.28 (a) LC directors of PVA at V = 0, and (b) LC directors of PVA in...

Figure 4.29 Comparison of normalized contrast ratio of MVA and IPS.

Figure 4.30 Schematic diagram for analyzing the ACR of an LCD.

Figure 4.31 Schematic diagram for analyzing the ACR of an OLED display.

Figure 4.32 Calculated ACR as a function of different ambient lighting condi...

Figure 4.33 Calculated ACR as a function of different ambient lighting condi...

Figure 4.34 (a) Schematic diagram of optical configuration of broadband circ...

Figure 4.35 (a) Calculated luminous reflectance of BK-7 cover glass at diffe...

Figure 4.36 Simulated ambient isocontrast contour for (a) LCD smartphone at ...

Figure 4.37 (a) Calculated luminous reflectance of AR-coated BK-7 cover glas...

Figure 4.38 Simulated ambient isocontrast contour for (a) LCD TV (peak brigh...

Figure 4.39 Simulated ambient isocontrast contour for (a) conventional LCD T...

Figure 4.40 (a) Schematic diagram of a broadband and wide-view circular pola...

Figure 4.41 Simulated ambient isocontrast contour for (a) an OLED TV at 50 l...

Figure 4.42 (a) LC response time versus MPRT at four specified frame rates. ...

Figure 4.43 Definition of backlight duty ratio:

A

is the duration of backlig...

Figure 4.44 LC response time versus MPRT with different duty ratios at

f

 = 1...

Figure 4.45 (a) Potential emission spectral range of CdSe and InP QDs; (b) T...

Figure 4.46 Schematic diagram for three device geometries implementing QD ma...

Figure 4.47 Schematic diagram of mini-LED backlit LCD.

Figure 4.48 Light modulation process of mini-LED backlit LCD: (a) mini-LED b...

Figure 4.49 Simulated LabPSNR for HDR display systems with various local dim...

Figure 4.50 Schematic diagram of the dual LCD panels.

Figure 4.51 Performance comparison of LCD (solid line) versus RGB OLED (dash...

Chapter 5

Figure 5.1 Power efficiencies of LEDs with time for “long wavelength (GaAsP,...

Figure 5.2 Bandgap and emission wavelength versus lattice constant for the I...

Figure 5.3 Energy versus momentum curves for semiconductors with (a) direct,...

Figure 5.4 Growth of III-nitrides (a) with and (b) without LT buffer layers....

Figure 5.5 (a) Left: wurtzite structure, middle and right: Ga- and N-polar, ...

Figure 5.6 Emission spectra of UV (λ

p

∼400 nm) pumping (a) red (λp∼600 nm), (...

Figure 5.7 White LED structure consisting yellow phosphor pumped by a blue L...

Figure 5.8 Emission spectra of the YAG phosphors with different compositions...

Figure 5.9 Band diagram of a p–n junction under thermal equilibrium.

Figure 5.10 Schematic diagram of bonding of GaAs with (a) Se and (b) Zn impu...

Figure 5.11 Charge density, electric field and voltage distribution of an LE...

Figure 5.12 Band diagram of a LED under (a) thermal equilibrium and (b) forw...

Figure 5.13 Carrier distribution under forward bias.

Figure 5.14 Band structures of (a) single-, and (b) double-heterojunction LE...

Figure 5.15 Band structures of LED with EBL.

Figure 5.16 Band diagram of a QW structure.

Figure 5.17 Structures of (a) QW, (b) quantum wire, and (c) QD.

Figure 5.18 Recombination (typically non-radiative) via deep-level traps.

Figure 5.19 Light escape cone of LED due to the total internal reflection.

Figure 5.20 Emission spectrum from a LED.

Figure 5.21 DOS of bulk, QW and QD structures.

Figure 5.22 Temperature dependence of RGB LEDs.

Figure 5.23 (a) EQE versus electrical current for the LED at different tempe...

Figure 5.24 Schematic diagram of LPE system.

Figure 5.25 Schematic diagram of (a) chloride and (b) hydride VPE systems.

Figure 5.26 Schematic diagram of MOCVD systems.

Figure 5.27 (a) Schematic diagram of two-flow MOCVD systems, and (b) gas flo...

Figure 5.28 Device structures of (a) III-P and (b) III-N LEDs (www.epistar.c...

Figure 5.29 (a) Absorbing substrate with a thin cladding layer which has one...

Figure 5.30 (a) Mesh electrode providing a metallic current spreading layer,...

Figure 5.31 Pictures of LED under operation with different geometries: (a) a...

Figure 5.32 Illustration of a packaged LED.

Figure 5.33 Emission spectra of CCFL and RGB-LEDs, and transmission spectra ...

Figure 5.34 Illustrations of (a) conventional driving, and (b) color sequent...

Figure 5.35 Simulation results of luminance distributions of (a) CCFL, and (...

Figure 5.36 (a) Integration of micro-LEDs with a driving circuit on a Si waf...

Figure 5.37 Stamping process to selectively transfer micro-LEDs from the nat...

Chapter 6

Figure 6.1 Two-layer OLED.

Figure 6.2 Interaction of AOs forming MOs [6].

Figure 6.3 HOMO and LUMO levels.

Figure 6.4 Potential curves of electronic states with vibrational energy lev...

Figure 6.5 (a) Spectra of absorption and emission, (b) energy levels of Stok...

Figure 6.6 Singlet ground, singlet excited and triplet states.

Figure 6.7 (a) Spin angular moment, and (b) coupling of spin angular momenta...

Figure 6.8 Jablonski diagram. Abs., absorption; IC, internal conversion; ISC...

Figure 6.9 Donor emission and acceptor absorption spectra and their spectral...

Figure 6.10 (a) Excimer and (b) exciplex formation.

Figure 6.11 Absorption and fluorescence spectra of Films 1 to 4. Film1: neat...

Figure 6.12 Typical J-V characteristics of an OLED.

Figure 6.13 (a) Image charge and the electric field lines at the interface [...

Figure 6.14 Escape cone from an OLED.

Figure 6.15 A typical OLED structure.

Figure 6.16 Schematic diagram of (a) antinode and (b) multiple-beam interfer...

Figure 6.17 Power coupled to different modes of an OLED with different ETL t...

Figure 6.18 Device structure of a single-layer OLED.

Figure 6.19 Layer structure and organic materials of the first two-layer OLE...

Figure 6.20 (a) J-L-V curves, and (b) EL spectrum of the two-layer OLED [4]....

Figure 6.21 (a) Device structure and (b) molecular structures of a guest-hos...

Figure 6.22 (a) Molecular structures, (b) energy level diagram, (c) device s...

Figure 6.23 (a) Acid, and (b) base treatment at the ITO surface [38].

Figure 6.24 log J-V curves of OLEDs with different cathode materials [41].

Figure 6.25 (a) Schmatic diagram of a top-emission OLED with dielectric laye...

Figure 6.26 Molecular structures of some polymer EL materials.

Figure 6.27 Illustration thermal evaporation.

Figure 6.28 Fabrication methods for full color OLED: (a) lateral subpixelate...

Figure 6.29 Fine-pitch shadow mask for full color OLED [13].

Figure 6.30 Illustrative diagram of the LITI process [61].

Figure 6.31 Illustration of an encapsulated OLED.

Figure 6.32 Cross section of an AM-OLED with (a) bottom-emission, and (b) to...

Figure 6.33 (a) NPB and (b) energy diagram of the two-layer OLED.

Figure 6.34 (a) Experimental and (b) simulated J-V characteristics of device...

Figure 6.35 Simulated results of (a)–(c) carrier density and (d)–(f) recombi...

Figure 6.36 Measured (a) luminance versus current density and (b) EL spectra...

Figure 6.37 Pictures of EL from an OLED showing dark spots (a) when the devi...

Figure 6.38 ITO spike in an OLED which results in catastrophic failure.

Figure 6.39 Photoluminescence as a function of time from the hole and electr...

Figure 6.40 Dependency of OLED lifetimes on power efficiencies. Dashed line ...

Figure 6.41 Voltage increase rate versus the term (luminance decay rate time...

Figure 6.42 Half life versus the initial luminance on a double log scale [90...

Figure 6.43 Luminance versus time with different environment temperatures on...

Figure 6.44 Energy transfer mechanisms in a guest-host system of an OLED. (a...

Figure 6.45 Device structure and chemical structures [97].

Figure 6.46 (a) TREL response, and (b) delayed fluorescence intensity with d...

Figure 6.47 Schematic diagram of TADF emission.

Figure 6.48 Structures of (a) a conventional OLED and (b) a tandem device [1...

Figure 6.49 Schematic cross-section of a tandem OLED with conductive connect...

Figure 6.50 Energy band diagram of a tandem semiconductor LEDs with magnifie...

Figure 6.51 Horizontal and vertical dipoles in the organic thin film.

Figure 6.52 External, substrate, and waveguiding modes in a bottom-emission ...

Figure 6.53 Methods for extracting substrate mode in an OLED.

Figure 6.54 Methods for extracting waveguiding mode in an OLED.

Figure 6.55 Methods for extracting plasmonic mode in an OLED.

Figure 6.56 Device architectures of white OLED.

Figure 6.57 Energy transfer for exciton harvesting WOLED, which utilizes bot...

Figure 6.58 (a) Structure of QD for QLED. (b) normal and (c) inverted QLED s...

Chapter 7

Figure 7.1 Schematic of a vertical electrophoretic display film containing n...

Figure 7.2 (a) Surface profiles of some typical Microcup arrays. (b) Schemat...

Figure 7.3 Schematic cross-section of a color Microcup EPD. Each Microcup is...

Figure 7.4 Schematic illustration of microcapsule electrophoretic image disp...

Figure 7.5 Schematic diagram of a full-color microencapsulated electrophoret...

Figure 7.6 Cross section of an electrophoretic display based on “independent...

Figure 7.7 Changes in electrical voltage move different combinations of pigm...

Figure 7.8 Schematic diagrams of in-plane electrophoretic pixels with (a) tw...

Figure 7.9 Schematic diagram of Cole–Kashnow reflective display [10].

Figure 7.10 Schematic diagram of the White–Taylor reflective display [10].

Figure 7.11 Schematic diagram of a polymer-dispersed liquid crystal display ...

Figure 7.12 Schematic diagram of a bistable cholesteric liquid crystal displ...

Figure 7.13 Interferometric modulator display structure showing light reflec...

Figure 7.14 Electrowetting display principle. (a) A continuous film of dyed ...

Figure 7.15 Droplet-driven electrowetting principle with common electrode CE...

Chapter 8

Figure 8.1 Conceptual illustration of a monocular HMD system.

Figure 8.2 Schematic layout of the eye optics.

Figure 8.3 Schematic optical layouts of (a) an immersive and (b) optical see...

Figure 8.4 Illustration of cardinal points and paraxial properties of an eye...

Figure 8.5 Illustration of partial overlap schemes in an HMD.

Figure 8.6 Illustration of angular resolution of the virtual display in an H...

Figure 8.7 Resolution and FOV tradeoff in an HMD system.

Figure 8.8 Illustration of eyebox in the (a) lateral plane of the exit pupil...

Figure 8.9 Effects of Lagrange invariant on the tradeoffs of system FOV and ...

Figure 8.10 Examples of (a) non-pupil forming and (b) pupil-forming optical ...

Figure 8.11 Examples of (a) magnifier, (b) objective-eyepiece compound, (c) ...

Figure 8.12 (a) Optical design and (b) prototype of an HMPD system; (c) SCAP...

Figure 8.13 Beamsplitter dimension as a function of the full field angle.

Figure 8.14 Dimensions of a flat beamsplitter increase rapidly with FOV.

Figure 8.15 Dimensions of a freeform prism combiner as a function of FOV.

Figure 8.16 Schematic layout of (a) three-layer waveguide design and (b) two...

Figure 8.17 Schematic layout of (a) partially reflective mirror-array lightg...

Figure 8.18 Schematic illustration of spherical aberration on image sharpnes...

Figure 8.19 Illustration of (a) pincushion (b) barrel and (c) keystone types...

Figure 8.20 Effects of lateral chromatic aberration on different wavelengths...

Figure 8.21 Example of spot diagram of an eyepiece design.

Figure 8.22 Examples of polychromatic MTF plots simulated (a) in microdispla...

Figure 8.23 Illustration of (a) interocular vertical misalignment, (b) inter...

Figure 8.24 Illustration of crossed and uncrossed binocular disparities and ...

Figure 8.25 An ET-HMD system based on rotationally symmetric optical technol...

Figure 8.26 Example of compact ET-HMD design (a) Optical layout (b) prototyp...

Figure 8.27 Schematic layout of multi-layer modulating scheme of 2D HDR disp...

Figure 8.28 (a) Schematic layout and (b) bench prototype of a monocular HDR-...

Figure 8.29 Illustration of (a) naturally coupled actions of eye accommodati...

Figure 8.30 Optical methods for EDOF displays: (a) Maxwellian view pinhole d...

Figure 8.31 Examples of EDOF displays based on the pinhole optics method: (a...

Figure 8.32 Schematic illustration of a vari-focal plane HMD.

Figure 8.33 Example of a vari-focal OST-HMD prototype using a liquid lens: (...

Figure 8.34 Schematic illustration of a multi-focal plane HMD.

Figure 8.35 Photos captured through a dual-focal plane OST-HMD prototype wit...

Figure 8.36 Schematic model of a DFD-MFP display: the luminance ratio betwee...

Figure 8.37 (a) Optical layout of the right-eye module of a DFD-MFP system, ...

Figure 8.38 Schematic illustration of a light field based 3D display which r...

Figure 8.39 Schematic illustration of LF-3D display methods: (a) super multi...

Figure 8.40 Schematic illustration of a magnified-view configuration.

Figure 8.41 Demonstration of a 3D integral imaging optical see-through HMD u...

Figure 8.42 Example of a high-performance InI-based LF-3D OST-HMD: (a) the o...

Figure 8.43 A computational multi-layer light field stereoscope: (a) schemat...

Figure 8.44 Superimposing a virtual airplane in a well-lit real world enviro...

Figure 8.45 Schematic illustration of direct-ray blocking method for occlusi...

Figure 8.46 Schematic illustration of per-pixel method for occlusion in OST-...

Figure 8.47 ELMO-4 occlusion-capable OST-HMD: (a) schematic layout; (b) prot...

Figure 8.48 Example of a two-layer folded occlusion-capable OST-HMD design: ...

Figure 8.49 Example of a two-layer folded occlusion-capable OST-HMD using st...

Figure 8.50 Demonstration of occlusion capability in our OCOST-HMD prototype...

Chapter 9

Figure 9.1 (a) Structure of resistive touch panel, and (b) the resistive tou...

Figure 9.2 Electrode structure and operation principle of 4-wire resistive t...

Figure 9.3 Structure of 5-wire resistive touch panel.

Figure 9.4 Structure of multi-touch resistive touch panel upon (a) single, a...

Figure 9.5 Light transmission from display through touch panel to the human ...

Figure 9.6 (a) Structure of a capacitive touch panel, (b) operation principl...

Figure 9.7 (a) Layout and (b) side view of a projected capacitive touch pane...

Figure 9.8 The same responses from self-capacitance measurement by touching ...

Figure 9.9 Side views of (a) DITO, (b) SITO configurations.

Figure 9.10 Projected capacitive touch panel with different configurations: ...

Figure 9.11 On-cell touch panel integrated with (a) LCD, and (b) OLED.

Figure 9.12 Configuration of in-cell touch panel with (a) self- and (b) mutu...

Figure 9.13 (a) and (b) Layout of in-cell touch panel with optical sensor, a...

Figure 9.14 (a) Idea of the 3D optical sensing, (b) photo-sensor structure, ...

Figure 9.15 A configuration for sensing the pressure.

Figure 9.16 Optical touch panel for large display.

Guide

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Wiley – SID Series in Display Technology

Series Editor: Dr. Ian Sage

Advisory Board: Michael Becker, Paul Drzaic, Ioannis (John) Kymissis, Takatoshi Tsujimura, Michael Wittek, Qun (Frank) Yan

Display Systems: Design and Applications

Lindsay W. MacDonald and Anthony C. Lowe (Eds.)

Reflective Liquid Crystal Displays

Shin-Tson Wu and Deng-Ke Yang

Colour Engineering: Achieving Device Independent Colour

Phil Green and Lindsay MacDonald (Eds.)

Display Interfaces: Fundamentals and Standards

Robert L. Myers

Digital Image Display: Algorithms and Implementation

Gheorghe Berbecel

Flexible Flat Panel Displays

Gregory Crawford (Ed.)

Polarization Engineering for LCD Projection

Michael G. Robinson, Jianmin Chen, and Gary D. Sharp

Fundamentals of Liquid Crystal Devices

Deng-Ke Yang and Shin-Tson Wu

Introduction to Microdisplays

David Armitage, Ian Underwood, and Shin-Tson Wu

Mobile Displays: Technology and Applications

Achintya K. Bhowmik, Zili Li, and Philip Bos (Eds.)

Photoalignment of Liquid Crystalline Materials: Physics and Applications

Vladimir G. Chigrinov, Vladimir M. Kozenkov, and Hoi-Sing Kwok

Projection Displays, Second Edition

Mathew S. Brennesholtz and Edward H. Stupp

Introduction to Flat Panel Displays

Jiun-Haw Lee, David N. Liu, and Shin-Tson Wu

LCD Backlights

Shunsuke Kobayashi, Shigeo Mikoshiba, and Sungkyoo Lim (Eds.)

Liquid Crystal Displays: Addressing Schemes and Electro - Optical Effects, Second Edition

Ernst Lueder

Transflective Liquid Crystal Displays

Zhibing Ge and Shin-Tson Wu

Liquid Crystal Displays: Fundamental Physics and Technology

Robert H. Chen

OLED Displays: Fundamentals and Applications

Takatoshi Tsujimura

Interactive Displays

Achintya K. Bhowmik

Illumination, Color and Imaging: Evaluation and Optimization of Visual Displays

P. Bodrogi, T. Q. Khan

3D Displays

Ernst Lueder

Addressing Techniques of Liquid Crystal Displays

Temkar N. Ruckmongathan

Flat Panel Display Manufacturing

Jun Souk, Shinji Morozumi, Fang-Chen Luo, and Ion Bita

Modeling and Optimization of LCD Optical Performance

Dmitry A. Yakovlev, Vladimir G. Chigrinov, and Hoi-Sing Kwok

Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Fundamentals

Noboru Kimizuka, Shunpei Yamazaki

Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Application to LSI

Shunpei Yamazaki, Masahiro Fujita

Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Application to Displays

Shunpei Yamazaki, Tetsuo Tsutsui

Introduction to Flat Panel Displays

Jiun-Haw Lee

National Taiwan University

Taipei City, Taiwan

I-Chun Cheng

National Taiwan University

Taipei City, Taiwan

Hong Hua

University of Arizona

Arizona, USA

Shin-Tson Wu

University of Central Florida

Florida, USA

Second Edition

This edition first published 2020

© 2020 John Wiley & Sons Ltd

Edition History:

1e Wiley, 2008

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The right of Jiun-Haw Lee, I-Chun Cheng, Hong Hua and Shin-Tson Wu to be identified as the authors of this work have been asserted in accordance with law.

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Library of Congress Cataloging-in-Publication Data

Names: Lee, Jiun-Haw, author. | Cheng, I-Chun, 1974- author. | Hua, Hong, 1973- author. | Wu, Shin-Tson, author.

Title: Introduction to flat panel displays / Jiun-Haw Lee, National Taiwan University, Taipei City, Taiwan, I-Chun Cheng, National Taiwan University, Taipei City, Taiwan, Hong Hua, University of Arizona, Arizona, USA, Shin-Tson Wu, University of Central Florida, Florida, USA.

Description: Second edition. | Hoboken, NJ : John Wiley & Sons, Inc., [2020] | Series: Wiley-SID series in display technology | Includes bibliographical references and index.

Identifiers: LCCN 2020004365 (print) | LCCN 2020004366 (ebook) | ISBN 9781119282273 (cloth) | ISBN 9781119282198 (adobe pdf) | ISBN 9781119282228 (epub)

Subjects: LCSH: Flat panel displays.

Classification: LCC TK7882.I6 L436 2020 (print) | LCC TK7882.I6 (ebook) | DDC 621.3815/422—dc23

LC record available at https://lccn.loc.gov/2020004365

LC ebook record available at https://lccn.loc.gov/2020004366

Cover Design: Wiley

Cover Image: Yuichiro Chino/Getty Images

Series Editor's Foreword

The first edition of Introduction to Flat Panel Displays has proved to be a popular and valued resource, which has been widely used both as a textbook and for reference. However, it was published over a decade ago in 2008, and established readers of the SID book series will not need reminding how fundamentally the subject matter has changed in that time. It is worth recalling that 2008 is also reported to be the first year in which worldwide sales of LCD televisions exceeded those of CRT sets.

Continuing demand for the first edition demonstrates that there is still a need for a broad-based introductory but authoritative account of flat panel displays, and it followed that the editors of the present book should consider writing a new and revised edition. It soon became clear though, that a simple revision would not be sufficient, and the volume you are holding represents a comprehensively updated and rewritten book which reflects the present state and latest developments in flat panel display technologies and applications. In order to provide the reader with a book which is a reasonable size and properly focused on contemporary topics, chapters in the first edition which described display technologies of lesser current importance – plasma and field emission devices – have been dropped. Important new chapters have been added on topics which are now central to flat panel applications: near-eye displays, reflective/e-paper displays and touch panel devices. The chapters describing the well-established, dominant display technologies such as LCDs, OLEDs, and LEDs have been comprehensively revised and updated to reflect the full range of technologies used in commercial displays and to describe the most recent important advances in these devices. Chapters describing AM backplane devices and structures, and the key principles of vision and color science have likewise been thoroughly updated to reflect their evolution and importance. Each chapter has been authored by an expert in display science, and the enthusiasm of the writers for their subjects is evident in their work. The authors' work in preparing this new edition has been virtually the same as writing a new book from the beginning, and I am grateful to all of them for their persistence and dedication to the task.

Flat panel display technology has revolutionized the ways in which we interact with electronic systems and through that, shapes the way we lead our lives. The pace of innovation shows no signs of slowing and the new cohorts of scientists and engineers who take the subject forward will need a range of training and reference works. Providing these resources is a key objective of the SID book series, and I believe that the present volume will make an important contribution to this aim.

Ian Sage

Great Malvern

1Flat Panel Displays

1.1 INTRODUCTION

Displays provide a man–machine interface through which information can be passed to the human visual system. The information may include pictures, animations, and movies, as well as text. One can say that the most basic functions of a display are to produce, or re-produce, colors and images. The use of ink to write, draw, or print on a paper as in a painting or a book might be regarded as the longest established display medium. However, the content of such a traditional medium is static and is typically difficult or impossible to modify or update. Also, a natural or artificial source of light, is needed for reading a book or viewing a picture. In contrast, there are now many electronic display technologies, which use an electronic signal to create images on a panel and stimulate the eyes. In this chapter, we first introduce flat panel display (FPD) classifications in terms of emissive and non-emissive displays, where non-emissive displays include both transmissive and reflective displays. Then, specifications of FPDs will be outlined. Finally, the FPD technologies described in the later chapters of this book will be briefly introduced.

Displays can be subdivided into emissive and non-emissive technologies. Emissive displays emit light from each pixel which forms a part of the image on the panel. On the other hand, non-emissive displays modulate light by means of absorption, reflection, refraction, and scattering, to display colors and images. For a non-emissive display, a light source is needed. Such non-emissive displays can then be further classified into transmissive and reflective types. In historical terms, one of the most successful technologies for home entertainment has been the cathode ray tube (CRT), which enabled the widespread adoption of television (TV). It exhibits the advantages of being self-emissive and offering wide viewing angle, fast response, good color saturation, long lifetime, and good image quality. However, one of its major disadvantages is its size and bulk. The depth of a CRT is roughly equal to the length or width of the panel. For example, for a 19 in. (38.6 cm × 30.0 cm) CRT with aspect ratio of 4 : 3 the depth of a monitor is about 40 cm. Hence, it is hardly portable; its bulky size and heavy weight limit its applications.

In this book, we introduce various types of FPDs. As the name implies, these displays have a relatively thin profile, several centimeters or less, which is largely independent of the screen diagonal. Specifying a display or the design and optimization of a display-based product require selection of an appropriate technology, and are strongly dependent on the application and intended conditions of use. These issues, together with the intense pace of FPD development, which has made available many options and variations of the different display types, have made a thorough understanding of displays essential for product engineers. The options can be illustrated by some typical examples. For instance, the liquid crystal display (LCD) is presently the dominant FPD technology and is available with diagonal sizes ranging from less than 1 in. (microdisplay) to over 100 in. Such a display is usually driven by thin-film-transistors (TFTs). The liquid crystal cell acts as a light modulator which does not itself emit light. Hence, a backlight module is usually used behind a transmissive LCD panel to form a complete display module. In most LCDs, two crossed polarizers are employed which can provide a high contrast ratio. However, the use of polarizers limits the maximum optical transmittance to about 35–40%, unless a polarization conversion scheme is implemented. Moreover, at oblique angles the optical performance of the assembly is degraded by two important effects. Firstly the projections of optic axes of two crossed polarizers onto the E vector of the light are no longer perpendicular to each other when light is incident at an oblique angle, so it is difficult to maintain a good dark state in the display over a wide viewing cone. Secondly, the liquid crystal (LC) is a birefringent medium, which means that electro-optic effects based on switching an LC are dependent on the relative directions of the incident light and the LC alignment in the cell. Hence, achieving a wide viewing angle and uniform color rendering in an LCD requires special care. To achieve wide-view, multi-domain architectures and phase compensation films (either uniaxial or biaxial) are commonly used; one for compensating the light leakage of crossed polarizer at large angles and another for compensating the birefringent LC layer. Using this phase compensation technique, transmissive multi-domain LCDs exhibit a high contrast ratio, high resolution, crisp image, vivid colors (when using quantum dots or narrow-band light emitting diodes), and a wide viewing angle. It is still possible for the displayed images to be washed out under direct sunlight. For example, if we use a smartphone or notebook computer in the high ambient light conditions found outdoors in clear weather, the images may not be readable. This is because the reflected sunlight from the LCD surface is much brighter than that transmitted from the backlight, so the ambient contrast ratio is greatly reduced. A broadband anti-reflection coating and adaptive brightness control help improve the sunlight readability.

Another approach to improve sunlight readability is to use reflective LCDs [1]. A reflective LCD uses ambient light to illuminate the displayed images. It does not need a backlight, so its weight, thickness, and power consumption are reduced. A wrist watch is such an example. Most reflective LCDs have inferior performance compared to transmissive ones in terms of contrast ratio, color saturation, and viewing angle. Moreover, in fully dark conditions a reflective LCD is not readable at all. As a result, its application is rather limited.

To overcome the sunlight readability issue while maintaining high image quality, a hybrid display termed a transflective liquid crystal display (TR-LCD) has been developed [2]. In a TR-LCD, each pixel is subdivided into two sub-pixels which provide, respectively, transmissive (T) and reflective (R) functions. The area ratio between T and R can be adjusted depending on the applications. For example, if the display is mostly used out of doors, then a design which has 80% reflective area and 20% transmissive area might be used. In contrast, if the display is mostly used indoors, then we can use 80% transmissive area and 20% reflective area. Within this TR-LCD family, there are various designs: double cell gap versus single cell gap, and double TFTs versus single TFT. These approaches attempt to solve the optical path-length disparity between the T and R sub-pixels. In the transmissive mode, the light from the backlight unit passes through the LC layer once, but in the reflective mode the ambient light traverses the LC medium twice. To balance the optical path-length, we can make the cell gap of the T sub-pixels twice as thick as that of the R sub-pixels. This is the dual cell gap approach. The single cell gap approach, however, has a uniform cell gap throughout the T and R regions. To balance the different optical path-lengths, several approaches have been developed, e.g. dual TFTs, dual fields (providing a stronger field for the T region and a weaker field in the R region), and dual alignments. Although TR-LCDs can improve sunlight readability, the fabrication process is much more complicated and the performance inferior to transmissive devices. Therefore, TR-LCD has not been widely adopted in products.

Light-emitting diodes (LEDs) consist of a semiconductor p–n junction, fabricated on a crystalline substrate. Under a forward bias, electrons and holes are injected into the device where they recombine and emit light. The emission wavelength of the LED is determined by the bandgap of the semiconductor. For longer wavelength (such as red and yellow) emission, an AlGaInP-based semiconductor is needed. Three group III (Al, Ga, and In) and one group IV (P) atoms are needed to allow tuning of the emission wavelength and lattice-matching to the substrate (e.g. GaAs). However, for shorter wavelength (green and blue) emission, it was not easy to find a lattice-matched substrate. Besides, there were other technological difficulties in fabricating nitride-based LEDs such as p-type doping and InGaN growth. In recognition of their successful demonstration of the InGaN-based blue LED, Professor Isamu Akasaki, Professor Hiroshi Amano, and Professor Shuji Nakamura were awarded the Nobel Prize in Physics in 2014. By combining the blue LED with phosphors, white emission is possible from a single chip. LEDs have been used for many display and lighting applications, such as traffic lights, very large diagonal (over 100 in.) signage, backlights of LCD, and general lighting, due to their long lifetime and high efficiency. A detailed description of LEDs from the viewpoints of materials, devices, fabrication, and applications will be presented in Chapter 5.

In Chapter 6, organic light-emitting devices (OLEDs) will be introduced. The operating principle of OLEDs is quite similar to that of the LED. It is also an electroluminescence (EL) device, but fabricated from organic materials rather than a semiconductor. In contrast to LEDs, it is not necessary to fabricate OLEDs on a crystalline substrate. From the manufacturing viewpoint, the OLED is similar to an LCD because it can be fabricated on a very large glass substrate. Apart from the usual glass substrate, OLEDs can be also fabricated on a flexible substrate if suitable processes are used. The device structure of the OLED is quite simple, comprising a stack of thin organic layers (∼200 nm) sandwiched by anode and cathode electrodes. When transparent conductors are used for both the anode and cathode, a transparent display can be fabricated, while a metallic cathode layer can provide a mirror-like appearance. When the OLED is not activated the panel appears highly reflective, while information displayed on the OLED is superimposed on the mirror-like background. In addition to displays, OLEDs can provide a flat, large-area, and diffuse light source for general illumination. This is quite different from LED lighting which provides a point source and highly directional emission of light.

In Chapter 7, the basic working principles of several reflective display technologies, including electrophoretic displays, reflective liquid crystal displays, interferometric modulator displays and electrowetting displays, will be reviewed. These reflective displays do not require an internal light source. They possess some attractive features, providing low eye strain, low power consumption, and excellent optical contrast under high ambient light levels, and are favored for portable reading applications and for outdoor use. Some reflective displays require the image being displayed to be constantly refreshed, while some are bistable and retain the image without power. In bistable displays, energy is only consumed during switching operations. In addition, some have a video-rate switching capability, while others are more suitable for displaying still images. Today most monochrome reflective display technologies match the typical contrast ratio standard of 10 : 1 for printed images on paper, but the reflectance of their bright states are still less than the typical value of 80% for white paper. Many color reflective displays rely on color filters or side-by-side pixel subdivision. However, to achieve color images with good brightness and saturation, multiple colors within the same pixel area is desirable.

By fabricating a display on a flexible substrate rather than rigid glass, flexible displays (using technologies including LCD, OLED, and electrophoretic effects) can be fabricated with the advantages of being thin, robust, and lightweight.

Most FPDs have been developed to provide a format for direct-view applications, such as TVs, computer monitors, laptop screens, tablets, and smart phones. However, several FPD technologies including LCDs and OLEDs, can readily be made into microdisplays with panel sizes less than 1 in. and pixel sizes of tens of microns or less. Such microdisplays are not suitable for direct-viewing, but they have found applications in an emerging class of head-mounted displays (HMDs) which are key enablers for virtual reality and augmented reality systems. In Chapter 8, the working principles and recent development of head-mounted displays will be reviewed. Unlike a direct-view display, an HMD system requires an optical system to collect light from a microdisplay source and couple it into the viewer's eye. The system may use a single microdisplay and optical system to display a two-dimensional image to one eye, yielding a monocular information display. Alternatively, it may be configured with a microdisplay and viewing optics for each eye, yielding a binocular system with the capability of rendering stereoscopic views. In some of the most advanced HMD systems, each set of optics may be capable of rendering light fields which replicate the configuration of light rays originating from a real scene, enabling a true 3D viewing experience. The proximity of an HMD system to the eye allows it to be configured into one of two different types – either an immersive or a see-through display. An immersive HMD blocks a user's view of the real world and places the user in a purely computer-rendered virtual environment, creating the immersive visual experience known as virtual reality. A see-through HMD, on the other hand, blends views of the real world and a computer-rendered digital environment, creating an experience variously known as augmented reality, mixed reality or increasingly as spatial computing. Chapter 8 will start with a brief introduction to the optical principles of HMD systems and an overview of historical developments, then follow with a brief review of the human visual system parameters critical to the design of an HMD system. It will then review paraxial optical specifications, common miniature display sources, optical principles and architectures, summarize optical design methods and optical performance specifications critical to HMD system design, and the chapter concludes with a review of several emerging HMD technologies with advanced capabilities, such as eyetracking, addressable focus cues, occlusion capability, high dynamic range, and light field rendering.

A touch panel (TP) is not a “flat panel display.” However, it provides an intuitive interface which provides input to the machine, and provides an enhancement to many displays which is critical to their application. In some cases, a single touch sensing function is enough, such as in an automatic teller machine (ATM). On the other hand, a multi-touch function is needed for controlling many mobile devices (such as mobile phones and tablet computers). Usually, electrical parameters (such as resistance or capacitance values) of the TP are changed by touch and the x–y positions at which these changes occur provide the input function. So, a TP must be transparent to allow mounting on top of the display, and a separate TP increases the thickness of the display module. Integration of the TP and the display can reduce the module thickness. TP technologies will be introduced in Chapter 9.

1.2 EMISSIVE AND NON-EMISSIVE DISPLAYS

Both emissive and non-emissive FPDs have been developed. In emissive displays, each pixel emits light with a different intensity and color which stimulate the human eyes directly. CRTs, LED panels, and OLEDs are emissive displays. When the luminance of the panel viewed from different directions is constant, the device is called a Lambertian emitter and this represents an ideal performance for an emissive display because it results in a wide viewing angle performance. Due to the self-emissive characteristics, it can be used in conditions of very low ambient light. When such displays are turned off, they are completely dark (ignoring any ambient reflections). Hence, the display contrast ratio (see also Section 1.3.3) under low ambient light can be very high. On the other hand, displays which do not emit light themselves are called non-emissive displays. An LCD is a non-emissive display in which the liquid crystal molecules in each pixel work as a light switch, independently of the other pixels. An external voltage reorients the LC director which controls an optical phase retardation. As a result, light incident from the backlight unit or from the ambient is modulated. Most high-contrast LCDs use two crossed polarizers. The applied voltage controls the transmittance of the light through the polarizers. If the light source is behind the display panel, the display is termed a transmissive display. On the other hand, it is also possible to use the ambient light as the illumination source, imitating the principle of traditional media, such as reading a book, and the device is then called a reflective display. Different technologies for reflective displays such as electrophoretic, interferometric modulators, and electrowetting displays as well as LCDs will be introduced in Chapter 7. Since no extra light source is needed in a reflective display, its power consumption is relatively low. Under high ambient light conditions, images on emissive displays and transmissive LCDs can be washed out. In contrast, reflective displays exhibit a higher luminance as the ambient light increases. However, they cannot be used in dark conditions. Hence, transflective LCDs have been developed, which will be described in Chapter 4.

1.3 DISPLAY SPECIFICATIONS

In this section, we introduce some specifications which are generally used to describe and evaluate FPDs in terms of their mechanical, electrical, and optical characteristics. FPDs can be smaller than 1 in. for projection displays, 2–6 in. for cell phones, 7–9 in. for car navigation, ∼8–20 in. for tablets and notebooks, ∼10–25 in. for desktop computers, and ∼30–110 in. for direct-view TVs. For different FPDs, their requirements for pixel resolution also differ. Luminance and color are two important characteristics which directly affect the display performances. Dependencies of these two parameters on viewing angle as well as image uniformity, device lifetime, and response time should be addressed when describing the performances of a FPD. Contrast ratio is another important parameter, which strongly depends on the ambient environment.

1.3.1 Physical Parameters

The basic physical parameters of a FPD include the display size, aspect ratio, resolution, and pixel format. The size of a display is typically specified by the diagonal length, in units of inches. For example, a 15 in. display indicates that the diagonal of the viewable area is 38.1 cm. Display formats, include landscape, square, and portrait types, corresponding to display widths larger than, equal to, and smaller than the height, respectively. Most monitors and TVs use a landscape format with the width-to-height ratio, also called the “aspect ratio,” of 4 : 3, 16 : 9, or 16 : 10, typically.

FPDs typically provide a rectangular “dot matrix” of addressable pixels which can display images and characters. To increase image quality, one may use more pixels in a display. Table 1.1 lists some standard resolutions of FPDs. For example, video graphics array (VGA) indicates a display 640 pixels in width and 480 in height. The aspect ratio is 4 : 3. Higher resolution typically (but not necessarily) provides better image quality. The HD series includes several wide screen standards with an aspect ratio of 16 : 9. FHD has a resolution of 1920 × 1080, which may be abbreviated as 2K1K. Doubling the pixels count in columns and rows results in 4× the resolution, which is termed UHD, 4K2K, or 4K. Similarly, an 8K standard is proposed with still higher resolution. Once the resolution, display size, and aspect ratio are known, one may obtain the pitch of pixels. For example, a 5.5 in. display with aspect ratio of 16 : 9 and FHD resolution has a pitch of ∼63 μm. Or, we can use pixel per inch (ppi) to describe the pixel density of the display. The above example corresponds to ∼401 ppi.

In the case of an HMD system for VR or AR applications, a microdisplay source is used. Although the pixel resolution of the microdisplay is a critical contributor to the system performance, the image resolution perceived by the viewer also depends on the optical magnification of the viewing optics. For instance in an HMD system, a VGA resolution microdisplay can produce an image with an apparent angular resolution equivalent to or better than an image provided via a FHD microdisplay if the optical magnification to the VGA panel is substantially lower than that to the FHD panel, this angular resolution being traded off against the field of view of the image. More detailed discussion on the resolution metrics of HMD systems can be found in Chapter 8.

Note that not all of the panel area contributes to the displayed image; the active area of each pixel is normally surrounded by a small inactive area occupied by inter-electrode gaps and possibly other structures such as stray light barriers. One can define the “fill factor” or “aperture ratio” as the ratio of the active display area in a pixel over the whole pixel size, with its maximum value of 100%. Also, for a full-color display, at least three primary colors are needed to compose a color pixel. Hence, each color pixel is divided into three subpixels, red, green, and blue (RGB) which share the total pixel area. For example, if we assume that a color pixel has a size of 63 μm × 63 μm, then the dimension of each subpixel will be 21 μm × 63 μm. If the area of each active, switchable sub-pixel which contributes to light emission or transmission is 18 μm × 60 μm, then the fill factor will be ∼82%.

Table 1.1 Resolution of FPDs.

Abbreviation

Full name

Resolution

VGA

Video graphics array

640 × 480

SVGA

Super video graphics array

800 × 600

XGA

Extended graphics array

1024 × 768

HD

High definition

1280 × 720

FHD

Full high definition

1920 × 1080

UHD (4K)

Ultra-high definition

3840 × 2160

8K

7680 × 4320

Figure 1.1 Subpixel layout of a FPD: (a) stripe, (b) mosaic, and (c) delta configurations.

Figure 1.2 (a) White (red + green + blue) pixels lit-on at the edge of the slope, and (b) with subpixel rendering in a stripe configuration. (c) “m” in italic (2) without and (3) with subpixel rendering on a display [3].

Different layouts of RGB subpixels are possible, as shown in Figure 1.1. A stripe configuration, is straightforward and makes fabrication and driving circuit design relatively easy. However, for a given display area and resolution it provides a poor color mixing performance. Both mosaic and delta configurations make the fabrication process and/or the driving circuits more complicated, but the resulting image quality is higher because of their better color mixing capabilities.

When displaying an oblique black-on-white pattern on a display with a stripe subpixel configuration as shown in Figure 1.2, a clear sawtooth can be seen at the edge. However, because each pixel is formed of three subpixels, these can be switched on in a controlled sequence from the top to the bottom such that edge of the pattern appears smoother – a technique called “subpixel rendering.” [3] Obviously, the colors at the edges of some rows are no longer white. For the first and the fourth rows, the red subpixel is switched on at the edge while for the second and the fifth rows, red and green emission results in a yellow color at the edge. This is called a “color fringing artifact.” Figure 1.3 shows the letter “m” in italic, without and with subpixel rendering. A smoother edge can be clearly seen when subpixel rendering is used. Advanced sub-pixel rendering algorithms not only switch different sub-pixels on or off at an oblique edge, but also adjust their luminance values to optimize the visual quality of the image.

Figure 1.3 (a) stripe, (b) PenTile™ RGRB, and (c) PenTile RGBW configurations [3].

There are three kinds of photoreceptor cells in human eyes, which respond to long, medium, and short wavelength regions of the visible spectrum. That is the major reason we use red, green, and blue as three primaries for the display and will be discussed further in Chapter 2. The arrangement of the photoreceptor cells does not correspond to a stripe configuration. Besides this, the numbers for different types of cell are not the same. The PenTile™ configuration has been proposed to mimic the layout of different photoreceptors in the eye to achieve better color mixing [4