Presentation system with overhead projector
First Claim
1. A presentation system comprisingan illumination system which provides a polarized projection beam having an intensity and a direction of polarization, said illumination system comprising a cholesteric filter, a light source, and a reflector surrounding said light source at a side away from the cholesteric filter,an image record carrier which modulates the intensity of the polarized projection beam with image information, thereby producing a modulated and polarized beam having said direction of polarization,an optical head for projecting the modulated and polarized beam onto a screen, said illumination system, said image record carrier, and said optical head forming an overhead projector, anda polarizing screen which receives said modulated and polarized beam from said overhead projector and transmits radiation having said direction of polarization.
2 Assignments
0 Petitions
Accused Products
Abstract
A presentation system comprising an image projection screen and an overhead projector is described. The overhead projector comprises an illumination system, a support for supporting an image record carrier and a projection head for projecting the image present in the image record carrier on the image projection screen. The image projection screen is a polarizing screen which transmits radiation having a well-defined direction of transmission polarization, and the overhead projector is adapted to supply light having this direction of polarization. In this way, the quantity of radiation used for forming the image is considerably increased and substantially half the quantity of ambient light incident on the screen is suppressed, so that images having a considerably enhanced contrast and brightness are obtained.
31 Citations
12 Claims
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1. A presentation system comprising
an illumination system which provides a polarized projection beam having an intensity and a direction of polarization, said illumination system comprising a cholesteric filter, a light source, and a reflector surrounding said light source at a side away from the cholesteric filter, an image record carrier which modulates the intensity of the polarized projection beam with image information, thereby producing a modulated and polarized beam having said direction of polarization, an optical head for projecting the modulated and polarized beam onto a screen, said illumination system, said image record carrier, and said optical head forming an overhead projector, and a polarizing screen which receives said modulated and polarized beam from said overhead projector and transmits radiation having said direction of polarization.
Specification