LIQUID CRYSTAL DISPLAY (LCD)

What Is LCD???A liquid crystal display (LCD) is a thin, flat panel

used for electronically displaying information such as text, images, and moving pictures.

Its uses include computer monitors ,televisions , instrument panels, and devices ranging from aircraft cockpit displays, to every-day consumer devices such as clocks , calculators, and telephones.

It is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source(backlight) or reflector to produce images in color or monochrome.

What is a liquid crystal????

The term “liquid”

crystal refers to the fact that

these compounds

have a crystalline

arrangement of molecules yet they flow like a

liquid.

VARIOUS APPLICATIONS OF LCD

TYPES OF LCD TECHNOLOGYAs LCD technology evolves, different techniques

for producing color emerge.

Passive-matrix technologies(flat

panels).

Active-matrix or TFT (thin film transistor) technology

produces color and images as sharp as any CRT.

COMPONENTS & THEIR FUNCTIONSAn LCD monitor consists of five layers:1. Backlight, 2. Sheet of polarized glass3. “Mask" of colored pixels,4. Layer of liquid crystal solution responsive to a wired grid of

x, y coordinates5. second polarized sheet of glass.

By manipulating the orientations of crystals through precise electrical charges of varying degrees and voltages, the crystals act like tiny shutters, opening or closing in response to the stimulus, thereby allowing degrees of light that have passed through specific colored pixels to illuminate the screen, creating a picture.

ON STATE

OFF STATE

COLOR DISPLAYIn color LCDs each

individual pixel is divided into three cells, or subpixels, which are colored red, green, and blue, respectively, by additional filters.

Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel.

A Subpixel Of A Color LCD

ADVANTAGESBrightness

Produces very bright images due to high peak intensity. Very suitable for environments that are brightly lit .

EmissionsProduce considerably lower electric, magnetic and electromagnetic fields than CRTs.

Geometric Distortion

No geometric distortion at the native resolution. Minor distortion can occur for other resolutions.

Power Consumption

Energy efficient. Consume less than 1/3 the power of a comparable CRT. Consume less electricity than a CRT and produce little heat.

Physical Aspects

Take up about 40% less desk space. LCDs are thin and compact.

Screen Shape Completely flat screen.

Sharpness

At the native resolution, the image is perfectly sharp. Adjustments are required at all other resolutions which can result in measurable degradation to the image.

DISADVANTAGESAspect Ratio The aspect ratio and resolution are fixed.

Black-LevelNot proficient at producing black and very dark grays. In a "standard" configuration, not appropriate for use in dimly lit and dark conditions.

Contrast Lower contrast than CRTs due to a poor black-level.

CostConsiderably more expensive purchase price than comparable CRTs . (Cheaper lifetime cost: lasts about 13,000 - 15,000 more hours than a typical CRT.)

Motion Artifacts

Slow response times and scan rate conversion result in severe motion artifacts and image degradation for moving or rapidly changing images.

Resolution

Works best at the native resolution. The native resolution can not be changed. All other resolutions require adjusting procedures which can cause considerable deterioration of the image.

Viewing Angle

Restricted viewing angles. Viewing angles affect the brightness, contrast and colors shown. Wide angles can lead to contrast and color reversal.

Thanking You,

ANINYA SAHA

ANNESHA PAUL