Patent ID: 7430076

Claim:
A diffraction element comprising: a substrate with an incoming-side surface opposite to an outgoing-side surface, the incoming-side surface configured to receive light from a light source external to the substrate; an incoming-side diffraction grating having a concave/convex shape in cross-section disposed in a central region of the incoming-side surface; a first outgoing-side diffraction grating having a concave/convex shape in cross-section disposed in the outgoing-side surface and configured to receive light not diffracted by the incoming-side diffraction grating; and a second outgoing-side diffraction grating covered by a reflective layer and having a concave/convex shape in cross-section, the second outgoing-side diffraction grating positioned on a light path of a light diffracted by said incoming-side diffraction grating, a grating pitch of the incoming-side diffraction grating being substantially equal to a grating pitch of the second outgoing-side diffraction grating, wherein the incoming-side diffraction grating is configured relative to the light source such that only a center portion of the external light, having a stronger intensity than a peripheral portion of the external light, is not diffracted by the incoming side diffraction grating.