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| Other Elements of Rear-projection TV | Projection Lenses
The second key element in rear-projection television, are the type of lenses used to enlarge the projected image. Normally, several lens elements are used. It is usual for a rear-projection television to use four or five lens elements; some sets use more. The motive for this is that several successive lenses are needed to keep up shape and brightness integrity of the image. A single lens can make things look good in the center of the image. But additional lens elements are needed as the light and image content is dispersed across the area needed for the size of screen used. Additional lens maintain the general image shape so that objects in the image look the same on the sides and corners as they do in the center of the screen.
All-glass assemblies are the best, especially in terms of withstanding high temperature variations from both internal and external factors. However, many manufacturers employ a combination of glass and acrylic-based lens construction. This may not be bad, but there may be differences, which can be noticed not only in the final image, but general image performance in the long term. Before buying a rear-projection television, you should check the information on the type of lenses used in their projection assemblies.
Mirrors
The other element necessary in the design of a rear-projection television is the mirror. A mirror is put in the path of the projection element, magnifying lenses, and the screen, since the projected image has to be projected on a large surface within a relatively small space (in comparison to a traditional video projector and screen). This helps the projection elements and magnifying lenses to be arranged at the bottom of the projection television cabinet. This provides the projected image with a longer path to the screen itself so that a bigger image can be demonstrated as well redirecting the path of the projected image so that it will be presented to the viewer in a proper way.
The Screen
The fourth element of a rear-projection television is the actual screen upon which the image is presented for viewer. The types of screen used in projection televisions and those used for front video projection or film are different. A rear-projection television screen is consists of two primary elements. First element is the inner Fresnel surface, which further enlarges and disperses the brightness of the image across the screen. Second element is an external Lenticular surface, which provides the final shape integrity of the image, as well as contrast and the wideness of the televisions viewing angle. If you touch a rear-projection television screen (which you should never do under normal circumstances) you will feel that its surface is not smooth, as is a conventional film or video projection screen. This is because you are actually touching the Lenticular surface etched into the screen itself.
The Box
The fifth important element of the rear-projection television itself is the box in which all the elements are contained in. The size of the box depends directly on the size of the screen surface itself. Rear projection televisions can have any size, but normally the sizes of screen is 41-inch to 76-inch. The size of the box that is right for you is influenced by your room size and/or your actual viewing distance from the television screen. Before buying the rear-projection television you should know optimum television screen viewing distance.
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