Transcript Display Technology

A Primer on LCD, DLP, LCoS, and
Plasma Technologies
Prepared by- Patel uday
Mishra pooja
Guided by-Proff.Ritisha bhatt
The CRT is Getting Old
– Technology is over 100 years old
– Monochrome CRTs used from 1910s
– Color CRTs developed in early 1950s (RCA)
– Monochrome tubes were used in front
projectors in 1980s – 90s (7”, 8”, 9”)
– Manufacturing has largely moved to China
• High-volume, low-margin product
• Thomson TTE, TCL, and others make them
CRT Imaging Process
– Low-voltage emission of electrons
– High-voltage anode attracts electrons
– Electrons strike phosphors, causing them
to glow brightly
– Color CRTs use three electron guns
– Projection CRTs use single-color phosphors
– Response of CRT is linear for wide
grayscales
CRT Imaging Process
CRT Performance
• Advantages:
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CRTs can scan multiple resolutions
Wide, linear grayscales are possible
Precise color shading is achieved
CRTs have no native pixel structure
• Drawbacks:
– Brightness limited by tube size
– Resolution (spot size) linked to brightness
– Heavy, bulky displays for small screen sizes
What Will Replace The CRT?
• Contenders for direct-view applications:
– Liquid-crystal displays (LCDs)
– Plasma display panels (PDPs)
• Contenders for front/rear projection applications:
– Liquid-crystal on silicon (LCoS)
• Silicon Xtal Reflective Device (SXRD)
• Digital Image Light Amplifier (D-ILA)
– Digital Light Processing (DLP)
Transmissive Liquid-Crystal
(LCD) Displays
LCD Display Technology
• Liquid-crystal displays are transmissive
• LC pixels act as light shutters
• Current LCD benchmarks:
– Sizes to 82” (prototypes)
– Resolution to 1920x1080 pixels
– Brightness > 500 nits
• Power draw < plasma in same size
• Weight < plasma in same size
LCD Imaging Process
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Randomly arranged LCs pass light (“off” )
Aligned LCs block light (“on”)
This effect is called “birefringence”
Principle is the same for low-temperature
and high-temperature polysilicon LCDs, and
liquid crystal on silicon (LCoS) panels
LCD Imaging Process
LCD Imaging Process
Building a Better Mousetrap
The Sharp Approach
The Samsung Approach
The LG Philips Approach
Real-World LCD Benchmarks
• A review sample 45-inch LCD monitor
delivered 304 nits (89 foot-Lamberts) with
ANSI (average) contrast measured at 217:1
and peak contrast at 234:1
• Typical black level was 1.6 nits (8x CRT)
• Native resolution – 1920x1080
• Power consumption – 284.2 watts over a 6hour interval (total of 1.726 kWh)
Real-World LCD Benchmarks
• Color Rendering
– Test panel uses CCFLs
– Gamut is smaller than
REC 709 coordinates
– Green way
undersaturated
– Red, blue are closer to
ideal coordinates
LCD Display Technology
• Technology Enhancements:
– Better color through corrected CCFLs, LEDs
– Improved black levels (compensating films)
– Higher contrast (pulsed backlights)
– Wider viewing angles (compensating films)
– Higher resolution (1920x1080 @ 37”)
– Improved LC twist times (various)
Emissive Imaging:
Plasma Display Panels (PDPs)
PDP Technology
• Plasma displays are emissive
• Current PDP benchmarks:
– Sizes to 103”
– Resolution to 1920x1080
– Brightness >100 nits (FW), 1000 nits peak
• Power draw 15%-20% > same size LCD
• Weight 20%-25% > same size LCD
Plasma Imaging Process
• Three-step charge/discharge cycle
– Uses neon – xenon gas mixture
– 160 - 250V AC discharge in cell stimulates
ultraviolet (UV) radiation
– UV stimulation causes color phosphors to glow
and form picture elements
– Considerable heat and EMI are released
Plasma Imaging Process
PDP Rib Structure (Simple)
Deep Cell Structure (Advanced)
• Waffle-like structure
• Higher light output
• Less light leakage
between rib barriers
• Developed by Pioneer
Plasma Tube Structure (Future?)
• Phosphors, electrodes,
and Ne/Xe gas combined
into long tubes
• Reduces cost of larger
screens
• Flexible displays?
• Developed by Fujitsu
Real-World Plasma Benchmarks
• A review sample 50-inch plasma monitor
measured from 93 nits (full white) to 233 nits
(small area), with ANSI (average) contrast
measured at 572:1 and peak contrast at 668:1
• Typical black level .21 nits (closer to CRT)
• Native Resolution - 1366x768
• Power consumption – 411.3 watts over a 6hour interval (total of 2.089 kWh)
Real-World Plasma Benchmarks
• Color Rendering
– Gamut is smaller than
REC 709 coordinates
– Green somewhat
undersaturated
– Red, blue are very
close to ideal
coordinates
Plasma Display Technology
• Technology Enhancements:
– Wider color gamuts (films, phosphors)
– Improved lifetime (gas mixtures)
– Higher resolution (1920x1080 @ 50”)
– Resistance to burn-in (change in gas mixture)
Reflective Imaging:
Digital Light Processing (DLP)
Displays
DLP Imaging
• Digital micromirror device (DMD) used
• Rapid on-off cycling of mirrors (pulse-width
modulation) builds grayscale image
• Color added and blended:
– With color wheel (single chip)
– With polarizing beam splitter (3-chip)
• Lens projects image to screen
Pulse-Width Modulation
• Technique to re-create
grayscale intensities digitally
with DMD
• DMD mirror positions are ON
(1) and OFF (0)
• Rapid cycling between ON
and OFF mirror positions
produces grayscale values
• Total mirror tilt is 12o
Pulse-Width Modulation
• PWM grayscale values
related to on/off ratios
• In a given interval:
– If more ON DMD tilt
positions than OFF,
lighter value results
– If more OFF DMD tilt
positions than ON,
darker value results
ON > OFF
OFF > ON
DLP Imaging – Single Chip
DLP Imaging – Three-Chip
Three-Chip Imaging
• Uses Polarizing Beam
Splitter (PBS) for highpower three-chip DLP
projectors
• Light travels in both
directions through it
• Red, green, and blue
colors added in PBS
Digital Micromirror Devices
• DMDs can be made in
many sizes
• 4:3 - 16:9 aspect
ratios are supported
• Simple light path with
single chip
• Pure digital light
modulator
SXGA (left) and XGA (right) DMDs
Reflective Imaging:
Liquid-Crystal on Silicon (LCoS)
Displays
LCoS Imaging
• LCoS is a reflective imaging system
• Switching transistors are on backplane
• Greater imaging surface available – higher
fill factor than HTPS LCD
• Easier to achieve high pixel density in small
panels than with HTPS LCD
LCoS Panel Cutaway
LCoS Optical Engine
LCoS Panels
• JVC Direct Drive Digital
Light Amplifier (D-ILA) is
LCoS technology
• Resolutions to 4K
• High ‘fill factor’ (>90%)
• Used in front and rear
projection systems
JVC 4096x2160 D-ILA Panel
LCoS Panels
• Sony Silicon Xtal
Reflective Device (SXRD)
also LCoS technology
• Panels made with both
2K and 4K resolution
• Used in front/rear
projection systems
Sony 4096x2160 SXRD panel
Image Quality Parameters
Brightness/Contrast/Grayscale
• Pixel-based imaging breaks the link between
brightness and resolution
• Peak brightness levels to 1000 nits in LCD
and plasma achieved, > 10,000 lumens in
LCoS and DLP projectors
• Average contrast to 500:1 (LCD, LCoS)
• Average contrast > 1000:1 (DLP, plasma)
Color and White Balance
• CRT offers ‘pure’ RGB color blending and clean
white balance
• Plasma color balance affected by gas mixture
and UV emissions
• LCD, LCoS, DLP projectors dependent on light
source (short-arc lamps)
– UHP/UHE less expensive, color is tricky
– Xenon more costly, color quality is superior
Illuminants:
Projection Lamps
• Short-arc mercury vapor
lamps
• UHP, UHE, SHE are
common designations
• Uneven spectral output
• Life 1000–3000 hours
150W UHP Lamp
Illuminants:
Projection Lamps
• Short-arc xenon lamps
• Higher wattage than
comparable UHP lamps
• Evenly-distributed
spectral output
• Life 500-2000 hours
325W Xenon Lamp
Illuminants:
Cold-Cathode Backlights
• Compact design
• Uneven spectral energy –
high in green/blue
• Bright sources of diffuse
lighting
• Life 50,000 – 60,000 hrs
• Not “green!” (contains Hg)
Two CCFL Lamps
Illuminants:
LED Backlights
• Compact design
• Evenly-distributed spectral
energy
• LED matrix is weighted
• LED life estimated at 50,000
– 100,000 hours
• LEDs are “current hogs”
GRB LED Array
Illuminants:
Plasma Phosphors
• Rare earth formulations
similar to CRT
• Red, blue easy to
saturate; green is tougher
• Ne/Xe mixture affects
color balance and life
(estimated 40,000 –
60,000 hrs)
Close-up of RGB Phosphors
See It Now:
A Primer on LCD, DLP, LCoS, and
Plasma Technologies
Pete Putman, CTS, ISF
Publisher, HDTVexpert.com
Contributing Editor, Pro AV