See It Now:A Primer on LCD, DLP, LCoS, and

Plasma Technologies

See It Now:A Primer on LCD, DLP, LCoS, and

Plasma Technologies

Pete Putman, CTS, ISF

Publisher, HDTVexpert.comContributing Editor, Pro AV

The CRT is Getting OldThe 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 ProcessCRT 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 ProcessCRT Imaging Process

CRT PerformanceCRT Performance

• Advantages: – 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?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

Transmissive Liquid-Crystal (LCD) Displays

LCD Display TechnologyLCD 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 ProcessLCD Imaging Process• 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 ProcessLCD Imaging Process

LCD Imaging ProcessBuilding a Better Mousetrap

LCD Imaging ProcessBuilding a Better Mousetrap

The Sharp Approach

The LG Philips Approach

The Samsung Approach

Real-World LCD BenchmarksReal-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 6-hour interval (total of 1.726 kWh)

Real-World LCD BenchmarksReal-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 TechnologyLCD 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)

Emissive Imaging:Plasma Display Panels (PDPs)

PDP TechnologyPDP 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 ProcessPlasma 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 Plasma Imaging Process

PDP Rib Structure (Simple)PDP Rib Structure (Simple)

Deep Cell Structure (Advanced)Deep Cell Structure (Advanced)

• Waffle-like structure • Higher light output• Less light leakage

between rib barriers• Developed by Pioneer

Plasma Tube Structure (Future?)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 BenchmarksReal-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 6-hour

interval (total of 2.089 kWh)

Real-World Plasma BenchmarksReal-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 TechnologyPlasma 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

Reflective Imaging:Digital Light Processing (DLP)

Displays

DLP ImagingDLP 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 ModulationPulse-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 ModulationPulse-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 ChipDLP Imaging – Single Chip

DLP Imaging – Three-ChipDLP Imaging – Three-Chip

Three-Chip ImagingThree-Chip Imaging

• Uses Polarizing Beam Splitter (PBS) for high-power three-chip DLP projectors

• Light travels in both directions through it

• Red, green, and blue colors added in PBS

Digital Micromirror DevicesDigital 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

Reflective Imaging:Liquid-Crystal on Silicon (LCoS)

Displays

LCoS ImagingLCoS 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 CutawayLCoS Panel Cutaway

LCoS Optical EngineLCoS Optical Engine

LCoS PanelsLCoS 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 systemsJVC 4096x2160 D-ILA Panel

LCoS PanelsLCoS 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 ParametersImage Quality Parameters

Brightness/Contrast/GrayscaleBrightness/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 BalanceColor 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

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

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

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 BacklightsIlluminants:

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

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

See It Now:A Primer on LCD, DLP, LCoS, and

Plasma Technologies

Pete Putman, CTS, ISF

Publisher, HDTVexpert.comContributing Editor, Pro AV