Hyper-diffusion Screens for Professional Applications
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High-resolution non-sensitive rear-projection screens
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Cost effective alternatives to optical screens
Wednesday, October 24, 2007
Darmstadt, Germany – Rear-projection panels made from PLEXIGLAS® from the High Performance Polymers Business Unit of Essen, Germany-based Evonik Industries allow high-resolution large-screen projection for professional purposes.
An old technology rediscovered
Although the technology of rear projection - where the image is projected by a projector from the rear on to a translucent, light-scattering screen - has long been known due to its use in the early years of cinema, it has experienced a renaissance only over the last few years. Special screens known as optical screens have been developed for, for example, rear-projection TVs or animated backgrounds in TV studios, or as components for large-screen projection in control centers. Their combination of Fresnel lenses and high-contrast light-scattering layers has proven to be superior to conventional diffuser screens, providing a high-contrast image with uniform brightness control and without formation of hotspots. But optical screens are easily scratched and prone to dirt deposits; additionally, the microstructures that are needed make them difficult to produce and therefore enormously expensive.
New development with PLEXIGLAS®
The new development of a rear-projection panel made from PMMA (polymethyl methacrylate) required that high quality be maintained while avoiding the disadvantages. A new production process combines the functional scattering layer directly with the highly transparent PLEXIGLAS® support panel. Through the concentration of different microlens systems in the hyper-diffusion layer, this combination achieves - entirely without the use of Fresnel lenses - a high-contrast projection with highly uniform brightness control. As the viewing angle increases, image brightnesses are significantly higher and more uniform than for optical screens.
Advantages of the new series of screens
There are other significant advantages over Fresnel lenses. Because resolution is not limited by dot pitch, Evonik's hyper-diffusion screen achieves significantly higher resolution than any optical screen. The microstructures of Fresnel lenses are easily clogged by dirt; cleaning is difficult and can damage the microstructures. In the PLEXIGLAS® screens, the optically functional structures are situated within the volume of the material; the surface is therefore non-sensitive and can be cleaned easily. It therefore has a more attractive appearance in the long term, and brightness and illumination are more uniform. Additionally, the projection distance can be chosen freely for all projectors, even with powerful wide-angle lenses. This is in contrast to the fixed focal lengths of Fresnel lenses, which result in loss of optical resolution.
Adapted for the application
Two screens are available, STUDIO and CONTROL, which have been developed in conjunction with customers in professional fields of application.
STUDIO is specially designed to meet high demands in TV studios, which are increasingly being equipped with digital TV cameras. Because these achieve higher image and contrast resolution, demands on rear projection panels used in the studio have risen significantly. Additionally, with the increasing number of pan shots in TV studios, the STUDIO has been shown to be superior to optical RP screens because there is no fluctuation of image brightness with changes in camera position (or viewing angle).
CONTROL, on the other hand, is specially optimized for use in control centers: even images produced with wide-angle projectors possess high uniformity of brightness and color reproduction. In particular, no differences in brightness arise at the transition between individual cubes, allowing a genuinely seamless technology.
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