Today’s projectors come in two basic technologies: DLP (which replaces the three LCD’s with a silicon chip) and LCD (containing three tiny liquid crystal display devices with a series of mirrors and lenses). The best selling type of video projector in use today is the DLP (Digital Light Processing) projector. :
DLP projectors are just like their rear-projecting brothers. DLP projectors use scads of tiny mirrors to reflect an image onto the screen. Like LCD, the actual image is displayed on a chip, however, the chip used in a DLP projector is different. A digital projector based on DLP Cinema™ technology transfers the digitized image file onto three optical semiconductors known as Digital Micromirror Devices, or DMDs. Each of these chips is dedicated to one primary color-red, green, or blue. A DMD chip contains a rectangular array of over one million microscopic mirrors.
Photo courtesy Newstream
A digital projector from Sharp
- They have good black level.
- Their price is falling (relative to the cost of other FPTV systems).
- They have poor viewing range.
Light from the projector’s lamp is reflected off the mirrors and is combined in different proportions of red, green and blue, as controlled by the image file, to create an array of different colored pixels that make up the projected image. Think of the DMD mirrors as the colored cards held up by an audience in a sports arena to create a giant image. Each person holds up a single colored card, yet when combined, these thousands of cards create a picture. If the card colors are changed, the picture changes too.
The DMD mirrors tilt either toward or away from the light source thousands of times per second to reflect the movie onto the screen. These images are sequentially projected onto the screen, recreating the movie in front of you with perfect clarity. All DLP projectors have 16.7 million colors and all DLP projectors are PC and Mac compatible
The advantages of this system make the DLP projector suitable for home theater application, but DLP technology is also in use in some movie theaters for feature film projection. Basically the films are digitally converted and stored to either hard drive or optical disc (similar to DVD – only in High Definition), then fed into the DLP projector and projected onto the movie screen. The high resolution DLP chips made for this application render an image that is almost as good as 35 or 70mm film, without all those film scratches!
Other advantages of the DLP projector include excellent color accuracy, no “screen door” effect (as with LCD), due to its micro-mirror construction, compactnesss, low power consumption, and high contrast and brightness (although typcially not as bright as LCD types but much “smoother” looking).
However, as previously mentioned DLP projectors do have drawbacks.
First: Just as with LCD, each DLP chip has a finite number of pixels.
Second: Although a DLP projector doesn’t exhibit the “screen door” effect of many LCD units, a DLP projector can exhibit what is referred to as “the rainbow effect”. Fortunately, this does not occur frequently and many people do not have sensitivity to this effect at all.
Third: Just as in LCD projectors, the light source must be changed every 1,000 to 2,000 hours.
Although DLP isn’t perfect, the DLP projector is the favorite amongst home theater enthusiasts.