Grating comprising sub-gratings with light-diffusing patterns

Abstract

A transparent substrate including at its surface a grating of parallel lines of patterns separated by zones with a refractive index different from that of the patterns, the grating diffusing light and including at least 4 sub-gratings, each sub-grating including plural blocks of identical patterns with a width L, each block including 2 to 10 of the patterns. Centers of gravity of neighboring patterns inside a block are separated by a constant period p, the distance Db between neighboring blocks vary in a non-monotonic manner when passing from one edge of the sub-grating to the other edge of the sub-grating, while being greater than 0 times L and less than 20 times L, and so that it is at least once greater than 1.2 Dbm and at least once less than 0.7 Dbm, Dbm being the arithmetic mean of distances between blocks of the sub-grating, and the period p varying from one sub-grating to another in a non-monotonic manner between 0.5 pm and 1.5 pm when passing from one edge of the grating to the other, pm being the arithmetic mean of periods p characteristic of the sub-gratings, and so that at least one sub-grating has a period greater than 1.2 pm and that at least one sub-grating has a period less than 0.8 pm. The substrate may be fitted to a window of a building and serve to redirect sunlight toward a ceiling.

Dependencies are inferred from the claim text.