Feature: ColorTuned™ Diamond Shield™

Benefit: Protects the projection TV screen and enhances picture contrast without reducing brightness.

Explanation: The screen in a rear projection video display is a high-quality optical system that is carefully designed to deliver sharp, bright images with even illumination. Among the many improvements Mitsubishi has made to screen technology is their ColorTuned™ Diamond Shield™. It not only protects the screen from damage. It also provides a unique filter system that delivers higher contrast without dimming the picture.

It is particularly difficult to reproduce black with a projection TV system. You may recall that the textbook definition of black is the complete absence of light. However, TVs are rarely viewed in a truly dark environment. Any light that contacts the projection TV screen partially washes out the screen. By that, we mean that ambient light changes what would be a black screen to a shade of gray. Depending on the amount of light, that shade of gray may be rather bright. Projection TVs by their very nature create light and direct it onto a screen. From this, one can see that a projection TV cannot restore the black color of a screen that is washed out by the light in the room. So projection TV engineers try to work around the limitation of a washed out screen and create the illusion of black as best they can.

One way is to make the TV picture as bright as possible. While this doesn't make the blacks any blacker, it makes the whites whiter, and thereby creates illusion of blacker blacks. There is a limitation to how bright a TV picture can be, however. If the CRTs that create the light are driven too hard, their whites appear to lose focus due to the intense beam current that saturates the phosphors. This is called "blooming". This high drive level also shortens the life of the CRTs.

Another way to try to deal with the light in the room is to add a layer of tinted material in front of the screen. This tinted material absorbs some of the light in the room so that it doesn't wash out the screen. This effectively darkens the screen. However, it also dims the picture because the tinted material also absorbs the desired light from the TV screen.

Until recently, all projection TV manufactures have been using a mix of these 2 techniques to achieve the best possible picture in a partially illuminated room. Then Mitsubishi's optical engineers developed a solution that provides the best of both techniques. They named it the ColorTuned™ Diamond Shield™. It works as follows:

All CRT-based projection TVs create red, green and blue light. When all 3 of these colors at their full brightness are combined, the TV screen appears to be white. This is actually an optical illusion. Our eyes tell us the screen is white but it is not. In this same way, using only the red and green CRTs creates the illusion of the color yellow, and the illusion of the color violet is created by using only the red and blue CRTs.

Knowing this, Mitsubishi's engineers developed a filter that only allows red, blue and green light to pass through it, and blocks yellow, orange, violet and all other colors. They applied this filter to an acrylic shield, along with a special hardened surface layer, and placed it on the outside of a projection TV. This filter allowed the red, blue and green light from the CRTs to pass through to the TV viewing area, but did not allow the yellow and orange light from sunlight and lamps to wash out the projection screen. So the bright whites were not dimmed and the blacks remained black.