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LCD projector

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.Perceived color in a projected image is a factor of both projection surface and projector quality. Since white is more of a neutral color, white surfaces are best suited for people wanting "natural color tones"; as such, white projection surfaces are more common in most business and school presentation environments. 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. Because of this, some presenters and presentation space planners prefer to use grey screens, which make the user perceive higher contrast levels due to the image being projected on a darker background. The trade-off that is made with this "perceived higher contrast" levels is that the color tones will be off (like purple lips...etc), something can be adjusted through the use of the color and hue settings of the projector but can never be completely and correctly adjusted.
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.
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 a size increase. 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.In 2004 and 2005, LCD front projection has been enjoying a come-back because of the addition of the dynamic iris which has improved perceived contrast up to the levels of DLP.The basic design of an LCD projector is frequently used by hobbyists who build their own DIY projection systems. The basic technique is to combine a high CRI HID lamp and ballast with a condenser and collector fresnel, an LCD removed from a common computer display and a triplet.