Screen for free observation mode and limited observation mode

摘要

The present invention relates to a screen (1) which can operate in at least two modes of operation, namely B1 for free observation mode and B2 for limited observation mode. The screen (1) includes an image display unit (2), a plate-shaped transparent light guide (3) disposed in front of the image display unit (2) when viewed in the observation direction, and a light guide ( And 3) a light source (4) arranged in the lateral direction at the edge. In such a screen, the image display unit (2) is placed behind the light guide (3) when viewed in the viewing direction, and the light guide is 20% measured according to ASTM-D1003. Having a haze value of less than In operation mode B1, the light source (4) is such that the light originating from the image display unit (2) passes through the light guide (3) essentially unaffected in a state modulated by the image information. ) Is switched off. In the operation mode B2, the light source (4) is switched on. In the first alternative limb, due to scattered particles (5) dispersed in the light guide (3) in space and / or in relation to its concentration, or on a large surface of the light guide (3) Measured at an angle α in relation to the surface normal of at least one large surface of the light guide (3), where 0 ° ≦ α ≦ θ, due to the output coupling element arranged or formed in at least one upper part The light guide emitted at an angle θ in relation to the surface normal, with an average luminance of X ≧ 1.2, at least by a factor X, 10 ° ≦ θ ≦ 60 ° (3) A light emission characteristic is generated that is less than the maximum measurable brightness on the same large face F1. In the second alternative limb, the image display unit (2) is realized at an angle of α ≧ θ with respect to the brightness realized in the direction of the surface normal of the image display unit (2). It has light emission characteristics that exceed those of Thereby, in the operation mode B2, the light derived from the image display unit (2) is superimposed on the light emitted by the surface of the light guide (3) over a wide angle range in a state modulated by the image information, Thereby, at the observation angle α θ, the visibility of the image information presented on the image display unit (2) is reduced or hindered in some cases.