Projection screen

Details Projection screen Projection screen

G - Physics

02

B

G02B 5/32 (2006.01) G03B 21/62 (2006.01)

Patent

CA 2333969

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, 26). 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.

Un écran de projection (30) pour la visualisation d'images par rétroprojection comporte plusieurs éléments opto-holographiques (10) disposés dans un plan. Ces éléments opto-holographiques sont éclairés par un projecteur (14) possédant trois systèmes de projection (22, 24, 26). Chaque système de projection (22, 24, 26) produit un faisceau lumineux (16, 18, 20) contenant respectivement les extraits de couleur d'une image à projeter. Chaque élément opto-holographique (10) comporte au moins une lentille et un réseau de diffraction permettant de diffracter les différents faisceaux lumineux (16, 18, 20) de telle manière que l'élément opto-holographique (10) délivre un faisceau de sortie lumineux (28) présentant le même angle de sortie (.beta.) en direction d'un observateur (12). Avec un tel écran de projection, la lumière dispersée est très faible, de sorte que l'écran de projection peut s'utiliser également avec la lumière du jour et pour des projections d'image sur grande surface.

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