1. Display Technology INFO410 & INFO350 S2 2015 Jack Pinches INFORMATION
SCIENCE

2. Outline CRT Plasma Display LCD Projectors DLP

3. Electrons (-) attracted to anode (+)
Cathode Ray Tube (CRT)
Electrons (-) attracted to anode (+)
Electron beam flies through vacuum, hits the flat screen.
Screen phosphor coated.
Anode: positive
Cathode: negative
Phosphor: substance that phenomenon of luminescence.
Luminescence: emission of light not from heating. In this case its electrical energy.

4. Phosphor inner close up
Cathode Ray Tube (CRT)
Electron guns
Electron beams
Focusing coils
Deflection coils
Anode connection
Mask
Phosphor layer
Phosphor inner close up

5. Holes aligned with phosphor Fire beam as needed.
Cathode Ray Tube (CRT)
Shadow mask
Holes aligned with phosphor
Fire beam as needed.
Mask: thin metal screen, perforated with small holes.
White: All beams.
Black: No beams.

6. Cathode Ray Tube (CRT) Advantages: Good black level Reliable
Viewing angle
Disadvantages:
Bulky
Power consumption
Burn in
Screen size limited
Health Concerns:
Ionizing radiation
Toxicity
Flicker
High frequency noise
Radiation: xray radiation a result of electron beams bombardment of the mask.
Toxicity: Toxic substances used, likely older CRTs.
Flicker: some low end monitors have a low refresh rate, and so can cause discomfort.
Noise: Operation of some monitors can cause a high pitched tone.

7. Burn in example Uneven usage of pixels.
Phosphor compounds lose luminance over time.
Burn in example

8. Plasma Display Panel (PDP)
Tiny cells containing gas
Voltage causes plasma
Releases UV photons
Photons interact with phosphor
Mg0 = Magnesium Oxide
Plasma = ionized gas with positive ions and free electrons, resulting in roughly no electric charge

9. Plasma Display Panel (PDP)
Advantages:
Produce deeper blacks
High refresh rate and response time
Cheaper?
Disadvantages:
Screen burn in
Bulkier
High power consumption
Altitude requirements

10. Liquid Crystal Display (LCD)
Backlight
Millions of pixels
Polarizing filters
Liquid crystal

11. Liquid Crystal Display (LCD)
Backlight
Horizontal filter
Horizontal light waves
Electricity off
Vertical light waves
Vertical filter
Pixel lit

12. Liquid Crystal Display (LCD)
Advantages:
Thinner, lighter
Lower power consumption
Lower radiation emission
Size variability
Disadvantages:
Image persistence
Black levels can be poor
Dead pixels
Viewing angle
Fixed colour depth
Image persistence: similar to burn in. Seems to be also from non uniform usage of pixels. Exact reasons unclear. Reversible, leave display off.
Colour depth: number of bits used to indicate colour in a single pixel

13. Light Emitting Diode Projector (LED)
Projectors
Light Emitting Diode Projector (LED)
Liquid Crystal Display Projector (LCD)
Digital Light Processing Projector (DLP)
Two general types:
Transmissive
Reflective
Transmissive: passing light through panels
Reflective: using a mirror to direct the images

14. Digital Micromirror Device (DMD) Array of mirrors (reflective)
DLP Projector
DLP chip:
Digital Micromirror Device (DMD)
Array of mirrors (reflective)
Up to 8.8 million
Hinges, independent movement
DLP chip, rectangular array of mirrors on hinges
Hinges to tilt towards the light source, or away from it.
This gives a grayscale image.

15. DLP Projector
Beam of light
Spinning Wheel
DMD chip
Lens
Projection Screen

16. Convergence (single chip) Image persistence Projector size
DLP Projector
Advantages:
Fully sealed chip
Convergence (single chip)
Image persistence
Projector size
Colour degradation
Disadvantages:
Colour wheel not sealed
Rainbows
Restricted zoom capabilities
Representation of greys
Rainbows: issue with single chip projectors, displaying sequential colour. Meaning there is actually only 1 colour on the screen. Bright objects appear to have trails of multi-coloured light, often on a dark background. Some people notice these.

17. LCD Projector LCD panel Tiny cells Mirrors divide light Three panels
Combiner/Prism
Dichroic mirrors: reflect only certain colours (specific wavelengths)
Panels: all have same image, but different hues.

18. Generally less expensive than DLP Support use with zoom lenses
LCD Projector
Advantages:
No moving parts
Generally less expensive than DLP
Support use with zoom lenses
Sharper image
Disadvantages:
Pixels can burn out
Dust can interfere
Limited lifetime
Black levels
Size and weight
Image persistence
Limited lifetime: panel degradation causing colour degradation

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