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 plasma TVs.
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