LCD Projectors

An LCD projector is a device utilized for displaying video images or data. It is the modern equivalent to the slide projector and overhead projector used in the past. more...

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Overview

LCD (liquid crystal display) projectors usually contain three separate LCD panels, one each for the red, green, and blue components of the video signal. However single panel LCD projectors have been produced in the past. Light from a halogen lamp, which outputs an ideal color temperature and a broad spectrum of color is split by a prism into the three component colors. These lamps also have the ability to produce an extremely large amount of light within a small area, on average for current projectors of 2,000-4,000 ANSI lumens. As light passes through the LCD panels, individual pixels can be opened to allow light to pass, or closed to block the light, as if each little pixel were fitted with a Venetian blind. This activity modulates the light and produces the image that is projected onto the screen by allowing many different shades from each color LCD panel.

With a lens that "projects" the image on any flat surface and does not require large "furniture" (like a big TV would), LCD projectors tend to be smaller and much more portable than older systems. The best image quality can be accomplished with a blank white or grey surface to project on, and for this reason dedicated projection screens are often used. However since white is more of a neutral color it is best suited for people wanting "natural color tones". However it is also true that the darkest your darkest black will get is the equivalent of how dark your screen on which you're projecting on is. This is why some prefer to use grey screens which make the user perceive higher contrast levels due to the image being projected on a darker background. But the trade-off that is made with this "perceived higher contrast" levels is that the color tones will be off (like purple lips...etc), this can be adjusted through the use of the color and hue settings of the projector but can never be completely and correctly adjusted.

History

Early LCD systems were often intended to be used with existing overhead projectors, built as a large "plate" that was put on the projector in place of the transparencies. This provided the market with a stop-gap solution in the era when the computer was not yet the universal display medium so that there was a market for LCD projectors before their current main use became popular.

This technology is employed in some sizes of rear projection television consoles, as there are cost advantages when employed in mid size sets (40 to 50 inch diagonal). This is not expected to have much longevity in the "home theater" marketplace due to expected improvements cost/performance of competing technologies, particularly in direct-view LCD panels at the lower range of sizes and DLP projection in the larger sizes. Another advantage of using this LCD projection system in large television sets is to allow better image quality as opposed to a single 60 inch television, although currently an equal of an LCD projector is the LG 100 inch LCD TV, still in prototype stages this TV is a huge advancement towards projector sized televisions. A common rule of thumb is that an LCD's image quality will decrease with its size. A workaround is to use a small lcd panel (or panels) and project them through a lens onto a rear projection screen to give a larger screensize (with a decreased contrast ratio) but without the quality loss.

Read more at Wikipedia.org