LCD TVs vs Plasma TVs

LCD Television

LCD stands for Liquid Crystal Display. Light in an LCD panel isn’t created by the liquid crystals themselves; instead, a light source behind the panel shines light through the display, while a white diffusion panel behind the LCD redirects and scatters the light evenly to ensure a uniform image.

The display consists of two polarising transparent panels and a liquid crystal solution sandwiched in between. The screen’s front layer of glass is etched on the inside surface in a grid pattern to form a template for the layer of liquid crystals. Liquid crystals are rod-shaped molecules that bend light in response to an electric current – the crystals align so that light cannot pass through them. Each crystal acts like a shutter, either allowing light to pass through or blocking the light. This pattern of transparent and dark crystals is what forms the image.

One of the biggest challenges for LCD TV manufacturers has been speeding up the pixel response time (how fast an individual pixel switches from fully off to fully on) to ensure that fast-moving objects don’t exhibit "motion lag" of ghosting. It’s especially critical for larger screen LCD TVs where much of the viewing will be DVD movies and/or HDTV.

LED Television - How LED technology is used in LCD TVs

The are currently two main forms of LED lighting:

Edge Lighting
LED backlights are placed along the outside edges of the screen. The light is then dispersed across the screen. The advantage of this method is that the LED/LCD TV can be made very thin. The disadvantage of Edge lighting is that black levels are not as deep and the edge area of the screen has a tendency to be brighter than the centre area of the screen.

Full-Array
(Also referred to sometimes as Full LED). Several rows of LEDs are placed behind the entire surface of the screen. The advantage is that these sets can employ "local dimming". (Local dimming -  each LED or a group of LEDs can be turned on and off independently within certain areas of the screen. Providing more control of the brightness and darkness for each those areas. LCD TVs that employ full array or full LED backlighting are thicker than LCD TVs that employ an Edge-lit LED light source.



Plasma Television

A plasma display consists of two transparent glass panels with a thin layer of pixels sandwiched in between. Each pixel is composed of three gas-filled cells of sub-pixels (one each for red, green and blue). A grid of tiny electrodes applies an electric current to the individual cells, causing the neon and xenon gas in the cells to ionize. This ionized gas (plasma) emits high-frequency UV rays, which stimulate the cells’ phosphors, to glow the desired colour. Because a plasma panel is illuminated at the sub-pixel level, images are extremely accurate, and the panel's light output is both high and consistent across the entire screen area.