Digital Projectors: The Big Picture

Digital projectors are those appliances used in conference rooms for making video presentations. They receive video signals usually from desktop or laptop computers and project the resulting video on large screens so it is visible to all in the gathering.

Two Types of Digital Projectors

There are two categories of digital projectors, the older ones being those manufactured using LCD (liquid crystal display) technology. These have transparent, independent LCD panels for each primary color (red, green and blue.) The light signals received from the computer are redirected through these LCD panels and a lens and onto the screen. The LCD-based projectors look similar to the older slide projectors. They are simple to construct and are cheaper than their successors, the DLP projectors. The LCD can be thought of as slides placed at the focal length of the lens. The clarity of the picture in a LCD projector depends on its pixel resolution. (A pixel is the smallest area of picture holders)

DLP Projectors: The Latest

DLP (Digital Light Processing) technology was developed in 1987 by Texas Instruments. DLP projectors represent a new and different technology in image projection in meeting rooms. DLP projectors utilize tiny micro mirrors to reflect light images allowing them to pass through a projector lens and onto the screen. Each mirror can be said to represent a pixel. These micro mirrors reflect primary colors in a rapidly rotating sequence just like a fast rotating color wheel. The resulting image with rapidly changing colors constructs the video for human eye perception. The micro mirrors are called DMD or 'digital micromirror device.'

In DMD projectors, a rotating wheel is provided with a plain patch that allows plain white light. These types of DMD projectors are called single chip projectors. The three chip projectors offer better clarity but are a bit more complicated. A prism splits the light from a lamp into its constituent colors which are then redirected to the DMD which recombines the colors before projecting the image through the lens.

DLP projectors are less heavy and give far better picture quality. A Single chip version resolves 16.7 million colors while the three chip model can do 35 trillion different colors.

Commercial Models

Texas Instruments of America is the pioneer that owns the patent for the DLP technology. However, Fraunhofer Institute of Dresden in Germany had also developed the same technology simultaneously and markets it as 'Spatial Light Modulators'. Samsung, HP and Epson are the other market leaders in both LCD and DLP projectors.