The introduction of high-definition rear-projection TVs and the coming rear-projection computer monitors has placed new demands on screen technology. Plus, many new systems will use flat-panel display technology instead of CRTs as the image-generating source. Such microdisplay-based systems feature compact image engines, small, high-resolution panels, and bright arc-lamps to drive the system. All of this means new designs are needed for the screens. Often neglected in rear-projection systems, the screen is finally getting the attention it needs to improve image quality.
Jenmar Visual Systems, Fremont, Calif., has developed several types of BlackScreen technology. The screens feature an optical beaded film with a proprietary conformal backcoat bonded to a clear substrate. They work with a Fresnel lens that collimates light to enter the screen. The thin vertical beads then focus the light to pass it through tiny openings in the black layer and out through the plastic or glass substrate. An anti-reflection or anti-glare coating can be used on the front surface to improve visual performance.
Recently, Jenmar publicly introduced Hi-Gain BlackScreen technology, featuring a gain of 1.7. This is 70% brighter than the company's Unity-Gain BlackScreens. The half-gain angle is reduced from ±45° to ±35° with the Hi-Gain version, though. The screen is now in use by Clarity Visual Systems, Wilsonville, Ore.
Jenmar has developed a Fine-Grain BlackScreen technology too, featuring resolution of 400 line pairs per inch. Overall transmission is 49%, ambient reflectance is 3.6%, and specular reflectance is 1.1%. A Unity-Gain version of this screen is currently shipping, and the company has begun shipping a Hi-Gain (1.7 gain) version to several customers prototyping rear-projection monitor and consumer TV products. The Fine-Grain screens are best for products under 60 in. in diagonal. Jenmar's vice president, John DiLoreto, says work is being done on a speckle mitigation solution, too. This is part of the lamination stack, and it will involve a nondiffusive phase-randomization layer. Alternative solutions have tended to use diffusive layers that compromise on-screen resolution.
3M's Projection Display Components Group, St. Paul, Minn., developed a new beaded screen technology that uses optical microspheres. It's similar to Jenmar's BlackScreen technology, but it has no conformal backcoat layer. The screen is available with an anti-reflection or a nonglare coating, and the beads supposedly are less than 100 microns in diameter. The gain is 1.15, viewing angles are ±35° vertically and horizontally, and diffuse transmission is about 55%.
Debuting with its first product is a new company called Lumin-oZ, Culver City, Calif. The revolutionary product is a flexible screen that can be bent, molded into 3D forms, or cut to any size and shape while retaining sharp picture quality in high ambient light. The technology consists of an optical polymer film that can be vacuum-formed into any shape. It doesn't utilize surface manipulation of light like the Fresnel/lenticular design, but embeds the optical properties of the screen in the film itself. As a result, there's no loss of brightness or viewing angle, or restrictions on the resolution of the image. These recent screen advances should all help make the presentation of high-resolution images much crisper and attractive on next-generation projection systems.
