A video projector is an electronic device that projects the image from a
video signal on a screen. Video projectors are used for presentation
and training purposes as well as for home entertainment. Some
manufacturers are making projectors that handle PowerPoint presentations
as well as DVD movies, but most video projector models are designed
for either business or home theater use.
Three video projector technologies in use today include CRT, LCD,
and DLP. A CRT (Cathode Ray Tube) projector is based on proven
television technology; there are three small cathode ray tubes (one each
for primary colors red, green, and blue) coupled with a light magnifying
lens. A CRT projector's image is not limited to a fixed pixel field
so it can effectively display a variety of resolutions. It can
produce very dark blacks and a full range of colors, and the projection
tubes have a long life expectancy (potentially 20,000 hours).
However, its large size makes it inconvenient for travel, it must be used
in a very dark room, and all three projection tubes must be replaced if
one fails. Furthermore, CRT projectors are fairly expensive.
An LCD (Liquid Crystal Display) projector passes a powerful light source
through a transparent LCD chip consisting of individual pixels, and it
projects the image on a large screen through a lens. It works well
for business presentations because it is compact and portable, has high
contrast, and consumes little power. However, LCD projectors can
exhibit what it known as the "screen door" effect. This is when the
individual pixels are visible on-screen, appearing as if the viewer is
looking through a screen door. When used in a home setting, the
image presented by an LCD projector may appear too bright and harsh.
Additionally, if one or more pixels burns out, the entire chip must be
replaced. The light source in an LCD projector costs several hundred
dollars, and it must be replaced about every 1,500 hours.
A DLP (Digital Light Processing) projector employs a chip known as a DMD
(Digital Micromirror Device) that displays the video image. The
tiny mirrors tilt rapidly as the image changes; color is added as light
passes through a high speed color wheel and is reflected off the
micromirrors. This technology is also used in some movie theaters
for feature film presentation. The advantages of a DLP projector
include color accuracy, no "screen door" effect, and lower power
consumption. Like an LCD, the light source in a DLP projector
must be changed every 1,000 to 2,000 hours, but DLP projectors are
quickly becoming a favorite of users everywhere.
Find technology solutions for audiovisual, video, and
professional audio needs, including display systems, media conferencing,
and videoconferencing products. www.HBCommunications.com