Patent ID: 7798699

Claim:
An apparatus, comprising: a layered light guide structure; and a light source arranged for providing light to the layered light guide structure, the light source comprising a first color light beam of a first wavelength range, and a second color light beam of a different second wavelength range, wherein the layered light guide structure comprises: a first light guide and a second light guide in a stacked arrangement, wherein the first light guide comprises a first surface, an opposing second surface and an edge surface joining the first surface and the second surface, the edge surface arranged to receive the first color light beam into the first light guide for forming a first guided beam, the first light guide comprising a first diffractive structure located on the first surface, the first diffractive structure configured to diffract part of the first guided beam out of the first light guide away from the first surface for forming a first diffracted beam along an illumination direction; and the second light guide comprises a first surface, an opposing second surface and an edge surface joining the first surface and the second surface, the first surface of the second light guide facing the second surface of the first light guide, the edge surface of the second light guide arranged to receive the second color light beam into the second light guide for forming a second guided beam, the second light guide comprising a second diffractive structure located on the first surface of the second light guide, the second diffractive structure configured to diffract part of the second guided beam out of the second light guide for forming a second diffracted beam through the first light guide along the illumination direction, the first diffracted beam and the second diffracted beam forming a combined diffracted beam, wherein the first color light beam and the second color light beam are independently adjustable for changing color of the combined diffracted beam.