digital projector (digital projection display system)

1) A digital projector, also called a digital projection display system, is a specialized computer display that projects an enlarged image on a movie screen. Such devices are commonly used in presentations.

There are two main types of digital projection display systems. The older, less expensive type employs three transparent liquid-crystal-display (LCD) panels, one for each of the primary colors (red, green, and blue). The light transmittivity of each pixel varies depending on the image data received from the computer. The light from a lamp is directed through the LCD panels, collimated using a lens, and projected onto a screen. The overall construction of the device is similar to that of a slide projector, where the "slide" consists of the three LCD panels placed close together near the focal point of the projection lens. Advantages of LCD technology include efficiency, ease of brightness and contrast adjustment, and high image resolution .

A newer, more expensive scheme is known as Digital Light Processing (DLP), a proprietary technology developed by Texas Instruments. In a DLP display, tiny mirrors are used instead of transparent panels. Each mirror represents one pixel. The light, rather than passing through the panel, is reflected from it. The mirrors move back and forth, varying the amount of light that reaches the projection lens from each pixel. Color is obtained by passing the light from the lamp through a rotating wheel with red, green, and blue filters. This subjects the mirrors to light at each of the primary colors in a rapid rotating sequence. The result is a color-modulated image that the human eye sees as natural color. Advantages of DLP technology include light weight, high contrast, and lack of pixelation.

2) The term digital projector is sometimes used for a program that facilitates the viewing of three-dimensional (3D), interactive, full-motion audio-visual files on a personal computer. Versions are available for both IBM-compatible and Macintosh computers, and can be downloaded from the Internet. They can be used as plug-ins for popular browsers for viewing animated Web-page content. For optimum performance on the Internet, a broadband connection should be used because of the high-speed, interactive nature of the content, and because the transmitted files are often large.