Abstract: 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.

Abstract: A resonating optical waveguide that increases image intensity and uniformity is provided. The waveguide includes a first diffractive optical element that allows light from an exit pupil of a projector to enter the waveguide and travel in a first direction, and a second diffractive optical element that directs some of the entered light to exit the waveguide to form an expanded pupil. Rather than allow the remaining, non-directed, light to exit at an edge of the waveguide, the optical waveguide further includes a third diffractive optical element that redirects some the remaining light back through the second diffractive optical element in a second direction where it may exit the waveguide as part of the expanded pupil. An additional fourth diffractive optical element may be included to further redirect the light through the second diffractive optical element again.