US Patent 8155489 Method for coupling light into a thin planar waveguide

A light distributing device (100) comprises a thin planar waveguide (10) and a waveguiding ridge (20). An incoming light beam (B1) coupled into the ridge (20) forms a second light beam (B2) waveguided in the ridge (20). The ridge (20) and the planar waveguide (10) have a common portion (23) such that light is further coupled from the side of the ridge (20) into the planar waveguide (10) through said common portion (23). Thus, optical power of a broad incoming beam (B1) may be effectively coupled to a relatively thin planar waveguide (10). The planar waveguide (10) may further comprise diffractive out-coupling elements (30) to direct light towards a display (400).