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Innovators in image processing

Innovators in image processing. Projection Technologies. CRT Light Valve DMD LCD D-ILA (LCOS). Projections : The basics. CRT. LCD and DMD. optical path. Screen. Screen. Lens. Lamp. Light source = Lamp Image source = LCD 2000 - 12000 lumens 1280 x 1024.

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Innovators in image processing

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  1. Innovators in image processing

  2. Projection Technologies • CRT • Light Valve • DMD • LCD • D-ILA (LCOS)

  3. Projections : The basics CRT LCD and DMD optical path Screen Screen Lens Lamp Light source = LampImage source = LCD 2000 - 12000 lumens 1280 x 1024 Light source = CRTImage source = CRT 250 - 500 lumens 3200 x 2500 • high resolution • geometry • mature technology • flexible positioning • photo-realistic • brighter • maintenance • alignment • easy setup • pixelization

  4. CRT technology

  5. CRT technology Lenses CRTs Screen Electronics

  6. CRT technology Different tube size 7 inch 8 inch 9 inch 12 inch

  7. Scheimpflug correction NOK Projection can’t be done on tilted surface -> focus problem!

  8. Scheimpflug correction after correction OK Required for projection on tilted screens

  9. Picture build-up • A picture can be built up with the following three scanning methods: • Raster scan (standard CRT projector) • Vector scan (e.g. radar screen) • Raster-calligraphic (combination of two) • Geometry can easily be modified in raster scan through influencing of deflection fields

  10. Raster <->Calligraphic Raster image 1280*1024 60Hz Day mode 1280*1024 60Hz 16 ms Pixel remains onscreen for 10 ns Point remains onscreen for 1.5 µs 150 times longer !

  11. Calligraphy Calligraphic Light points Raster Image

  12. CRT technology Strengths: Resolution (up to 2500x2000) Good contrast Easy geometrical correction / flexibility Color matching and uniformity Digital soft-edge Unbeatable video and data image quality Life time picture tubes Proven technology Weaknesses: Limited brightness up to 500 ANSI Lumen Needs low ambient lighting conditions Setup time Maintenance Not portable

  13. Light valve projection • Polarization • LCD • LCOS • DMD • 3-chip • single-chip

  14. Polarization Typical polarizer “eats” 50% of the unpolarized light power

  15. LCD pixel By applying voltage over LCD pixel, transmission of light can be modulated.

  16. LCD panel: implementation • Response speed limited by thickness and characteristicsof LC material • transmission limited byinterconnects and transistors • Increase in resolutionnecessitates higher miniaturization(can be compensated by microlenses)

  17. Panel technologies Amorphous Si HT Poly Si • normal glass, low cost • larger transistors=> suitable for displays > 3” • external drivers • Quartz glass, expensive • smaller transistors=> suitable for displays < 2” • integrated drivers

  18. LCD Panels Panel sizes 1.1-1.8 inch (p-Si) 3 inch (a-Si) 6 inch (a-Si) 10 inch (single panel)

  19. LCD pros and cons • Well-established technology, stable • Compact, rugged, portable • “zero delay” • UXGA resolution available • Efficient in passive stereo projection (see further) • Response speed limited by LC material some smearing in fast moving images • non-perfect black (contrast ratio 200-300:1, but improving) • pixellization

  20. LCOS: Liquid Crystal on Silicon • Essentially: LCD in front of a reflector • Available for microdisplays, projection • D-ILA is JVC’s trade name for LCOS

  21. LCOS implementation • LCD on top of CMOS chip that includes transistors and has reflective surface • Aperture ratio is higher than that of LCD (so less pixel visibility) • Efficiency comparable to LCD due to non-perfect reflection • Easy to cool the chip!

  22. LCOS addressing • Requires complex optics:side at which chip is illuminated is the same as where the light needs to be extracted from!

  23. LCOS integration Complex structure required!

  24. LCOS pros and cons • Higher resolutions possible (up to QXGA) • small chip size (1.3” and smaller) • good response speed • good pixellization (smooth image) • higher contrast possible: up to and over 1000:1 reported • chips can be cooled to take high power illumination • alignment hard due to small chip size & high res • difficult to integrate • uniformity? (although seems to be countered now)

  25. DMD: another reflective tech Does not require polarized light! Ant leg on DMD chip

  26. DMD microstructure Only allows on/off modulation!

  27. DMD: grayscale synthesis • Frame delay! • 1 frame for de-interlacing • 1 for sending data through CMOS chip • 0-1 frame (depending on gray scale) for gray synthesis

  28. 3-chip DMD integration Each chip runs at 10 bits depth, 60 Hz NOTE: 10 bit Linear Gamma equals 8 bit LCD Gamma

  29. 3-chip DMD pros & cons • Excellent picture quality (pixels almost invisible) • can take high power illumination • long life (?) • no smearing (but • good intensity uniformity, good color matching • good contrast (400:1) • Expen$ive! • BIG! • PWM artifacts • TI monopoly • Frame delay • Resolution limited to SXGA • Bright edge around chip makes optical blending difficult

  30. Single-chip DMD • Sequential illumination of single DMD chip • 3 or 4 segment color wheel • chip runs at 8 bit, 240 Hz less bit depth! • Compact • Moving part inside, requires synchronization • Motion artifacts (color breakup) due to color wheel

  31. Thank you for your attention...

  32. Innovators in image processing

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