Patent ID: 8657479

Claim:
An illumination device comprising: at least one light source; a light redirecting slab made of optically transmissive material and comprising an optical output surface and an array of optical redirecting elements, each of the optical redirecting elements having an optical coupling surface situated distally from the optical output surface and at least one light redirecting surface for receiving light from the optical coupling surface and redirecting the light received therefrom toward the optical output surface for emission therefrom; a substantially planar light guide slab made of an optically transmissive material and having a first surface, a second surface opposite the first surface and at least one input surface, the at least one input surface for receiving light from the at least one light source; wherein the first surface comprises a planar light guide layer and a plurality of light steepening elements extending from the planar light guide layer, each of the light steepening elements comprising at least one reflective surface for moderating the steepness of angles of the light being transmitted through the light guide slab to provide output light of generally uniform intensity across the light output surface; and an array of optical apertures optically interconnecting the light guide slab and the light redirecting slab, wherein the first surface, the second surface and the array of optical apertures are arranged one with respect to the other such that light entering the light guide slab is guided through the light guide slab via one or more reflections for insertion into the light redirecting slab.