Patent ID: 8152315

Claim:
A light guide comprising: an input slab for expanding a projected image injected into an input end as the projected image travels toward an output end; and an output waveguide arranged to receive rays from the output end of the input slab, and to emit the rays at a point on an output face that corresponds to an angle at which the ray is received, in which all rays injected into the input end undergo a same number of reflections in total before leaving the output face, and a thickness of the input slab is varied in a transverse direction perpendicular to a centre-line corresponding to a central axis of ray travel so that light travelling at an out-of-plane angle of incidence from the input end of the input slab toward the output waveguide leaves the input slab at close to a critical angle and bounces a same number of times in the input slab, regardless of a fan-out angle away from the central axis in the transverse direction.