US Patent 10222615 Optical waveguide with coherent light source

A waveguide increases the optical path of a portion of light received from a coherent light source. The waveguide includes a first element that allows light from an exit pupil of a coherent light source to enter the waveguide, and a second element that directs some of the entered light to exit the waveguide through a first set of pupils. The waveguide includes additional elements that cause the remaining light to make an additional path through the waveguide and the second element before exiting through a second set of pupils to increase the path of the exiting light. The pupils of the first set and the second set are staggered so that light exiting a pupil does not interfere with the light exiting via the neighboring pupils.