Abstract: A projection screen (30) for representation of images by back-projection comprises a plurality of holographic-optical elements (10) arranged in one plane. The holographic-optical elements are illuminated by a projector (14) comprising three projection devices (22,24,26). Each projection device (22,24,26) generates a light bundle (16,18,20) respectively including the chromatic components of an image to be projected. Each holographic-optical element (10) comprises at least one lens and one diffraction grating which are diffracted in such a manner by the different light bundles (16,18,20) that the holographic-optical element (10) will emit an exiting light bundle (28) with an identical exit angle (&bgr;) in the direction of the viewer (12). Such a projection screen will scatter the light only to a small extent so that the projection screen can be used also at daylight and for large-surface image projection.

Abstract: The external wall element has an outer pane with lens-like holographic elements. On the inner pane, radiation receiving elements for generating energy are arranged in the focal plane of the holographic elements. The incident light may either by focused on the radiation receiving elements or on translucent portions of the inner pane. The external wall element optionally permits the generation of energy or reflection, transmission of diffuse light being effected in both cases.