Patent ID: 8508848
Filing Date: 2013-08-13
Classification: G02B

Abstract:
1. An apparatus, comprising: a first substrate of optical material having a first surface and a second surface which is opposite to the first surface, wherein the first surface defines a first plane; an in-coupling diffractive element disposed on the first or the second surface of said first substrate; one or more out-coupling diffractive elements disposed on the first or the second surface, wherein said in-coupling diffractive element is configured to diffract optical rays of the input optical beam, which are incident from one half space relative to a second plane perpendicular to said first plane and parallel to periodic lines of the in-coupling diffractive element, so as to provide one diffracted optical beam substantially within said first and second surfaces such that at least a portion of said one diffracted optical beam is coupled only to one of said one or more out-coupling diffractive elements; a second substrate of optical material having a further first surface and a further second surface and being positioned substantially parallel to the first substrate and in juxtaposed spaced relationship hereto, wherein the further second surface is opposite to the further first surface; a further in-coupling diffractive element disposed on the further first or the further second surface substantially in alignment with said in-coupling diffractive element and having further periodic lines parallel to said periodic lines of the in-coupling diffractive element, and configured to receive a portion of said input optical beam which propagates through said first substrate into the further substrate; and one or more further out-coupling diffractive elements disposed on the further first or the further second surface and each being substantially opposite to a corresponding diffractive element of said one or more out-coupling diffractive elements, wherein said further in-coupling diffractive element is configured to diffract optical rays of the portion of the input optical beam, which are incident from the other half space relative to said second plane, to provide a further one diffracted optical beam substantially within said further first and further second surfaces such that at least a portion of said further diffracted optical beam is coupled only to one of said one or more further out-coupling diffractive elements which is opposite to said only one of the one or more out-coupling diffractive elements to which the one diffracted optical beam is coupled, and wherein said one of the one or more out-coupling diffractive elements is configured to couple by diffraction parts of said one diffracted optical beam from the first substrate for providing an output optical beam out of said first substrate with an expanded exit pupil in one or two dimensions, said output optical beam being propagated through said second substrate, and said one of the one or more further out-coupling diffractive elements is configured to couple by diffraction parts of said further one diffracted optical beams from the second substrate for providing a further output optical beam out of said second substrate with said expanded exit pupil in said one or two dimensions.