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Hiroshi Toshiyoshi [email protected]
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III. MEMS Projection Displays
Micro Mirror Projection
- Texas Instruments DMD
- Daewoo Elec. AMA
Grating Light Valve
- Silicon Light Machines
Image Projection
Color Synthesis
Pixel Addressing
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Hiroshi Toshiyoshi [email protected]
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History of Micromechanical Projection Display (1)
Westinghouse Mirror-Matrix Device
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Surface micromachined
Built on SOS (Sapphire)
Addressed by electron beam
Deflect up to 4°Contrast ratio: 10 to 1
Difficulty in HNA release etch
Limited resolution in electronbeam
R. N. Thomas, "The mirror matrix tube: A novel light valve for projection display," IEEE T-ED, 22, 765 (1975)
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Hiroshi Toshiyoshi [email protected]
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History of Micromechanical Projection Display (2)IBM Cantilever Light Modulator Array
K. E. Petersen, "Micromechanical Light Modulator Array Fabricated on Silicon," Appl. Phys. Lett. vol. 31, 521 (1977).
~ +/- 1 deg.
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History of Micromechanical Projection Display (3)
Texas Instruments, Deformable Mirror Device (DMD)
L. J. Hornbeck, "128 x 128 Deformable Mirror Device," IEEE Trans. ED (1983).
128 x 128 Deformable Mirrors
Mirror Size 51 m x 51 m
DRAM like operation (hold & refresh)
response 25 s
hold 200 ms
Addressed by embedded MOS
Transistors
Air gap 620 nm
Mirror fill factor 32 %
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L. J. Hornbeck,"Deformable Mirror Spatial Light Modulator, " Proc. SPIE vol. 1150 (1989)
Prototypes of TI DMD
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MEMS Projection Display (1)
Digital Micromirror Device
Texas Instruments
[1] Graphic Images --> http://www.ti.com/dlp/resources/library/[2] Up-to-date --> P. F. Van Kessel, L.J. Hornbeck, R. E. Meier,M. R. Douglass, "A MEMS-based projection display," Proc. IEEE, vol.86, 1687-704 (1998)http://ielimg.ihs.com/iel4/5/15216/00704274.pdf [3] Up-to-date --> L. J. Hornbeck, "Digital Light Processing for High Brightness, High Resolution Applications," Proc. SPIE vol. 3013 (Electronic Imaging EI'97, Feb. 10-12, 1997, San Jose, CA).[4] MEMS & DMD ---> Gregory A. Magel, "Micromachining in Optics," http://www.ti.com/dlp/resources/whitepapers/pdf/micro.pdf[5] History overview ---> L. J. Hornbeck,"From cathode rays to digital micromirrors: A history of electronic projection display technology ,"http://www.ti.com/dlp/resources/whitepapers/pdf/titj03.pdf
References
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Good Example of "Quantity Changes Quality"Texas Instruments
Digital Mirror Device (DMD) for Digital Light Processing (DLP)
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Principle of Image ProjectionElectrostatic On-Off Control of Mirror Array
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Advantage of MEMS Projection Display
LCD Image DLP Image
Compared with Liquid Crystal Display
+ High Contrast and High Brightness due to Fill Factor ~ 1
+ Controlled both in digital mode (PWM) and analog mode (SLM)
+ Small size
+ New market for Portable Projector and Large Screen TV Monitors
PWM: Pulse Width Modulation
SLM: Spatial Light Modulation
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Structure of DMDAluminum Mirror on Addressing CMOS SRAM
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Fabrication Process of DMDAl mirror ---- CMOS Process compatible
Photoresist sacrificial layer --- removed by plasma etching
DMD on CMOS SRAM by 6 mask process
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Electrostatic Operation
GNDDriving Electrodes
Landing Electrode
Angle Angle Angle
Angle Angle
Electrostatic Torque
Mechanical Restoring Torque
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Resonant Frequency ~ 50 kHz
Step Response ~ 12 s
Temporal Response to Step Voltage
Mechanical Characteristics of DMD
CMOS 5 V Drive
450 Billion Contacts
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SVGA XGA SXGA
848 x 600 1024 x 768 1280 x 1024
Typical Notebook PC LCD
508,800 786,432 1,310,720
Number of Pixels
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Addressing ArchitectureCMOS SRAM for Electrostatic Operation
CMOS 5 V Drive
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Brightness Control
Pulse Width Modulation for Gray Scale Image
Similar to the principle of LCD display
ON
OFF
Bright
Dark
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Color Synthesis by One DMD Chip
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Color Synthesis by Two DMD Chips
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Color Synthesis by Three DMD Chips
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Schematic of Three-DMD Projector
Can you figure out how it works ? ...
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