The invention relates to a transparent substrate comprising at its surface a grating of lines of at least 200 light-diffusing elements, said elements being separated by domains with a different refractive index from that of the elements, the distance d between centers of gravity of neighboring elements varying in a non-monotonic manner from one edge of the grating to the other, so that for any group of 50 successive elements, the distance d between the centers of gravity of neighboring elements of said group is at least once greater than and at least once less than the mean distance dm of distances d between centers of gravity of neighboring elements of said group, dm lying between 75 nm and 200 μm. This substrate is transparent in direct vision and redirects the light while diffusing it without iridescence in a daylighting application.