DK513484A - light curtain - Google Patents

Abstract

A light grid for shielding passing beams to only passing out from the front side 7 of the light grid within a certain angular interval, comprises parallel, light absorbing slats 3. Adjoining the front side of said slats, a plate-shaped device is placed, consisting of parallel, integral, substantially triangular prisms 6, one side of which, lying opposite to the slats 3, is flush with each other and forms a substantially smooth surface on the front side of the light grid, while one 12 of the two other sides of the prisms is covered by the slats 3, and the third side 13 of the slats extends freely between adjacent pairs of slats. The slats have an extension L in the direction away from and substantially orthogonal to the front side of the light grid, and said extension is matched with the angles α and β of the prisms such that any beam passing through the sloping, uncovered prism sides 13 from the rear side or the slat side of the light grid, will either pass directly forward to the front side 7 of the light grid and be refracted in the direction of the desired angular interval, or pass forward until the neighbouring, covered prism side 12 and be reflected from there in such a direction that it at the front side of the light grid is being refracted in the direction of the desired angular interval. This light grid is relatively inexpensive to manufacture, and the light occurring within the angular interval concerned has a relatively high intensity. Outside the angular interval concerned, no unwanted light beams occur whatsoever. <IMAGE>