Join Date: Sep 2000
Location: Stewart Filmscreen Corporation. USA
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Rear Projection screens are rarely discussed in this forum. I am going to take this opportunity to to make a few comments.
Most rear screen technology come from two different manufacturing process. One is called "Optical Lens" type screens" and the other is "Diffusion" Type screens. Their are some other types too: Light Pipe, Embeded Glass Bead but have yet to make much of an impact on the market. The optical lens screen are manufactured by a casting process. Each side of the screen has a separate lens pattern. The projector side of the screen has a Fresnel lens. Each circular ring on this lens has a different calculated pitch which collimates the projected light through the screen. (A side note here: When purchasing a optical screen, one should match the focal length of the projector lens with the focal length of the screen's fresnel lens). On the optical screens viewing side there is a Lenticuar lens. The primary job of this lens is to distribute the collimated light in the horizontal viewing axis. With this highly light efficient type screen design, rear lens type screens can be made over 5 gain. These high gain screens are employed within systems requiring large images with CRT projectors. Also, with extreme ambient light, like behind a news caster on TV set, lens type screens are used with a high lumen output digital projectors. The cost of these giant lens screens are between 6 and 9 K for a 100 inch four by three AR. The maximum size available Lens Screens are 200 inches diagonal.
The most commonly used Diffusion rear screens run from about 1 to 2 gain. At the risk of over simplifying how a diffusion rear screen works, take a translucent substrate, lets say tracing paper and place it in front of your projector. You will see somewhat of a diffused image. Professionally manufactured diffusion screens use different types of tiny particles suspended in a film to diffuse the projected image. The screen's gain, vertical and horizontal viewing axis, color temp, contrast, etc, will vary depending upon the films formulation. Diffusion screens come in flexible models along with rigid acrylic and glass substrates models. The MSRP price for a 100 inch RP diffusion screen will range from $400.00 to about $2,200.00 The flexible type screen can be manufactured in sizes over 100 feet for large venues. The rigid types rarely exceed 25 feet in width.
[This message has been edited by Don Stewart (edited 03-24-2001).]