Re: lcd...plasma

wow! ders a whole new look ta dis whole site now. anyway. whats da difference between plasma and lcd flatscreens. i''''m thinking more of da computer screens now.

[apcarandang]

Here''s a summary of both technologies...<p>Enjoy....<p>LCDs rely on the properties of polarised light for their operation. Polarised light can be described as consisting of light waves that are vibrating in only one plane. These can be produced by passing light through a polarising filter. A single polarising filter passes only light waves that are in the same plane as the filter structure. If a second filter is placed in line with the first, then rotating either filter so that the polarising structure of one is at 90 degrees to the other will block almost all light. <p> An LCD consists of two sheets of glass with a narrow gap between them. The gap is filled with a special fluid--the liquid crystal. This glass/liquid sandwich is backlit with a polarising filter interposed between the light source and the panel, so the light illuminating the liquid is polarised in one direction. <p> Liquid crystals are liquids composed of long molecules. The molecules in liquid crystals are encouraged to line up in the same direction by grooves brushed into a coating on the inside surface of the containing glass panels. When an electric field is applied between the two sandwiching glass panels, the molecules in the liquid change orientation or twist. As light passes through the liquid the orientation of these molecules can be used to rotate the plane of polarisation so it''s either blocked by, or passes through, a second polarising filter at the top of the assembly. <p>To make an LCD that can display an image, many parallel conductors are fashioned on the inside of the top and bottom plates using photochemical techniques. The conductors on the bottom plate running at 90 degrees to those on the top plate. A display cell is formed at each cross over point between the two sets of conductors. Any portion of the display can then be accessed by applying signals to one of the top and one of the bottom conductors. In colour displays, three cells are used for each picture element, with each cell having either a red, green or a blue filter.<p><br />Plasma <p>Plasma displays work on the principle that passing a high voltage through a low-pressure gas generates light. Displays based on this have been around since the earliest days of electronics--the picture on John Logie Baird''s first televisor was created by mechanically scanning a neon bulb. More recently, neon-based monochrome displays have been used on a few mains-powered portable PCs from Compaq, Grid and IBM. These had a grid of wires in asea of gas; when a high voltage existed between a column and a row wire, the gas became incandescent and the pixel lit up. <p>The major advantages were that it was thin and bright and had a fast response time. Against<br />that, it was very power hungry and the control electronics needed to switch high voltages quickly; as soon as LCDs stopped being dim, smudgy and expensive, the plasma display was pensioned off. <p>Now a new breed of plasma displays is catching the eye. By having a mix of gases that emit ultraviolet light and coating the inside of the display with different coloured phosphors, full-colour images can be created. Because a plasma pixel is simple it''s easy to make large displays. Currently, 40in. displays are available for around $6000. However, the resolution on these is low--typically 640 by 480--and the power consumption in the hundreds of watts.<p>They''re most suitable for video and television applications.<br /> biggrin.gif border=0 biggrin.gif border=0 biggrin.gif border=0<p>< December 19, 2001: Message edited by: apcarandang ></p>