| 摘要 |
A projection screen (30) for the representation of images that are projected by means of overhead projection, comprising several holographic-optical elements (10) arranged on the same plane. The holographic-optical elements are illuminated by a projector (14) consisting of three projection devices (22,24,264). Each projection device (22,24,26) produces a light beam (16,18,20) that contains the chromatic components of an image that is to be projected. Each holographic-optical element (10) has at least one lens and a diffraction grid enabling the different beams (16,18,20) to be diffracted in such a way that the holographic-optical element (10) emits an exiting light beam (28) with the same exit angle ( beta ) in the direction of a viewer (12). The amount of light scattered when using the inventive projection screen is very small indeed. As a result, the inventive projection screen can be used during daylight and in the projection of large surface images.
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