Patent ID: 8422840

Claim:
A light guide comprising: an input slab having an input slab input face and a second input slab face; and an output waveguide to receive rays from the input slab, and to emit the rays through an output face, the output waveguide having the output face and a second output waveguide face, wherein a thickness of the input slab tapers at a constant first angle in a direction of ray travel and a thickness of the output waveguide between the output face and the second output waveguide face tapers at a second angle that is different from the first angle, in which the second angle at which the output waveguide taper increases in the direction of wave travel, the input slab being configured so a steepest possible propagating ray entering the input slab through the input slab input face and propagating to the output waveguide reflects off the second input slab face, the output waveguide being configured so a second propagating ray entering the input slab through the input slab input face and propagating to the output waveguide reflects off the second output waveguide face.