Projection Televisions 101
Projection televisions have been around for quite some time now.
When first introduced, the images created by these sets were
fuzzy and only viewable at a distance. As great strides in TV
technology have been made, projection TV images have become
sharper and more comparable to those of their competitors.
For people in the market for a large screen TV, either for a
home theatre system or a classroom/boardroom presentation
setting, a Projection TV is the most efficient choice. CRT or
cathode ray tube set's size maxes out around 40", and at that
size they are extremely heavy and bulky. Plasma displays are
manageable with larger screen sizes but can be very expensive.
Projection TV technology can create very large screen TVs which
are not only manageable but affordable.
Projection televisions have four main components: a projector,
screen, control panel, and a sound system. There are two main
types of projectors used for these TVs: a transmissive
projector, where light shines through the image forming element
(CRT tube, LCD panel), and a reflective projector in which light
is bounced off of the image forming element. In both projectors,
a lens gets the image from the image forming element, magnifies
the image and focuses it onto a screen. Top of the line
projection TVs use primarily reflective projectors because the
advances in reflective projector technology of late have been
more progressive than those pertaining to transmissive projector
technology.
The image forming elements used in transmissive projectors are
CRTs and LCDs. TVs using a CRT for projection actually have a
small (around 9" diagonal) television built in. A lens in front
of this small, extremely bright CRT TV magnifies the image and
projects it onto the screen. Three basic configurations are used
in these sets. Transmissive projectors using an LCD for
projection are substantially lighter with a higher resolution
capacity than their CRT counterparts. The LCD panel used in
projection TVs is very similar to that of a full sized LCD only
smaller and brighter. This panel is backlit by a halogen lamp,
the image on the panel is transmitted through a magnifying lens
and projected onto a screen.
Reflective projectors use a small reflective chip to form the
image. When light shines on this chip, it is reflected off of
it, through a projection lens and onto the screen. The most
exciting developments in projection TV technology have been made
with reflective projectors using micro-electromechanical systems
and liquid crystal on silicon.
With advances in LCD and MEM technologies, projectors will
become smaller and form closer competition between projection
TVs and the new plasma displays, in areas such as resolution and
crispness of image detail. A relatively new application of
projection TV technology is, "virtual reality", in which the
viewer feels surrounded by, or as though he/she is a part of,
the image being viewed. Projection TVs may not be the next big
thing to hit the shelves, but we can be sure they will continue
to be a viable, low priced option when shopping for your new TV.
----------------------------------------- Alan Rhinehart is an
avid media and technology critic. He contributes to various
online publications including "New Technology TV", a popular
blog covering TV technology and home theater systems. Visit for
more information on LCD
TVs and exclusive Dish Network
deals.