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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
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Outline
• Silicon Light Valve
• XGA Display Features
• Optical Engine
• Conclusion
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Characteristics and Topography
• Fine pixels on the top as reflective mirrors• All the electronics are beneath the mirrors• Light shield and surface planarization
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Silicon Advantages
• Full driver Integration and fine pixels
• High fill factor
• Mature silicon VLSI technology
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SEM Pictures of Fine Pixels
• 9.6 m pixels• 86% fill factor• Virtual Reality
• 13.8 m pixels• 91% fill factor• Projection
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Effect of Pixel Size on Optical Performance(Comparison between theory and experiment)
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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
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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
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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
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Fine and Resolvable Pixels
• Advantage of digital driving scheme
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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
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Gamma Correction
VG1 VG2
VG3 VG4
• Fine tune of linear gray scale for three primary colors
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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
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Good Color Fidelity for TPA - Experimental Results
• Negligible S-P Polarization Split
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Measured color coordinates
Includes the effects of the halogen light source and the TPA
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Good Color Saturation by the Optical Engine
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Linear Gray Scale by correction
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Projected Image on the Screen
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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
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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
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Acknowledgements
• Dr. Steve Yeung and Mr. George Lee of Varitronix (HK) for making LC cells
• Sponsored by Industry Department of Hong Kong Government
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END (of IDRC99)
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