A High-Resolution Projection Display Based on Silicon Light Valves

HKUST

A High-Resolution Projection Display Based on Silicon Light

Valves

P W Cheng, H C Huang and H S Kwok

Centre for Display Research

Department of Electrical and Electronic Engineering

The Hong Kong University of Science & Technology

HKUST

Outline

• Silicon Light Valve

• XGA Display Features

• Optical Engine

• Conclusion

HKUST

Characteristics and Topography

• Fine pixels on the top as reflective mirrors• All the electronics are beneath the mirrors• Light shield and surface planarization

HKUST

Silicon Advantages

• Full driver Integration and fine pixels

• High fill factor

• Mature silicon VLSI technology

HKUST

SEM Pictures of Fine Pixels

• 9.6 m pixels• 86% fill factor• Virtual Reality

• 13.8 m pixels• 91% fill factor• Projection

HKUST

Effect of Pixel Size on Optical Performance(Comparison between theory and experiment)

HKUST

Fabrication Flow

• Front-end for electrical functions– Full integration of display drivers– Pixels of high breakdown voltage– Standard 0.5 m CMOS process

• Back-end for optical performance– Surface planarization and light shield– Pixels of high fill factor– Modified 0.35 m process

HKUST

HKUST-XGA Panel Specifications

• Resolution: 1024 x 768,13.8mpixels• Fill factor: 91%• Reflectivity:90% (dielectric mirror)• Process: 0.5m FE/0.35m BE• Data driver: 6-bit, 2 channels• LC Mode: MTB NW or NB• Others: Built-in gamma corrections

HKUST

Functional Block Diagram

ODD-COLUMN DATA DRIVERS

D/A CONVERTERS

SC

AN

DR

IVE

RS

1024 x 768PIXEL ARRAY

QA1BIT1SHR

SCLKFLM

SCAN_DN

CLK1DISP1ODD_DATA (0:5)

V1, V2, V3, V4

VG1, VG2, VG3,VG4

VB1, VB2

FRAME

D/A CONVERTERS

EVEN-COLUMN DATA DRIVERSR

EF

ER

EN

CE

V

OL

TA

GE

G

EN

ER

AT

OR

CLK2DISP2EVEN_DATA (0:5)

VCC, VDD, VDD2GNDSHIELD

BIT2

SOUT

• Almost identical to TFT panel with full driver integration

HKUST

Fine and Resolvable Pixels

• Advantage of digital driving scheme

HKUST

Reflectance-vs-Voltage Curves

Contrast Ratios:Red 169:1Green 101:1Blue 68:1 White 108:1

• Wide-band MTB NW mode for three primary colors

HKUST

Gamma Correction

VG1 VG2

VG3 VG4

• Fine tune of linear gray scale for three primary colors

HKUST

Optical Engine

• Trichroic prism assembly (TPA)• 16o incident angle (patent pending)

MH Lamp

BD

AC

B-LCD

G-LCD

R-LCD

PBS

• H. S. Kwok etal, to be published on Applied Optics, 1999

HKUST

Good Color Fidelity for TPA - Experimental Results

• Negligible S-P Polarization Split

HKUST

Measured color coordinates

Includes the effects of the halogen light source and the TPA

HKUST

Good Color Saturation by the Optical Engine

HKUST

Linear Gray Scale by correction

HKUST

Projected Image on the Screen

HKUST

Projector Prototype Specifications

Parameter ValueResolution 1024 H x 768 VPixel Size 13.8mAperture Ratio 91%Array Area 14.1mm H x 10.6mm VLC mode Reflective NW MTB modeContrast Ratio 100:1, typicallyLight Source 50W MH LampLuminous Flux 100 lumensColor 262,144CIE Coordinates Red: x = 0.66, y = 0.34

Green: x = 0.30, y = 0.65Blue: x = 0.17, y = 0.12

Driving Scheme Frame InversionFrame Rate 30 Hz

HKUST

Conclusions

• Highly Integrated Silicon Light Valve– Front-end for electrical functions– Back-end for optical optimization

• XGA Projection Display Features– Fine and resolvable pixels– Linear gray scale– Good color saturation

HKUST

Acknowledgements

• Dr. Steve Yeung and Mr. George Lee of Varitronix (HK) for making LC cells

• Sponsored by Industry Department of Hong Kong Government

HKUST

END (of IDRC99)

Screen