Patent ID: 8830584

Claim:
An apparatus, comprising: a non-flat substrate of optical material having a first surface and a second surface which is opposite to the first surface, wherein said first and second surfaces have a spherical or aspheric shape; an in-coupling diffractive element disposed on the first or the second surface of the non-flat substrate for receiving an input optical beam; one or more out-coupling diffractive elements disposed on the first or the second surface of the non-flat substrate; wherein said in-coupling diffractive element is configured to diffract the input optical beam, so as to provide one or more diffracted optical beams substantially within said first and second surfaces such that a portion of each of said one or more diffracted optical beam is coupled to a corresponding out-coupling diffractive element of said one or more out-coupling diffractive elements; wherein each of said one or more out-coupling diffractive elements is configured to couple by diffraction parts of said one or more diffracted optical beams from the non-flat substrate for providing one or more output optical beams out of said non-flat substrate; wherein grooves of the in-coupling diffractive element and of said one or more out-coupling diffractive elements are along parallels of a spherical coordinate system; and wherein a spacing projected on a reference plane between adjacent grooves of the in-coupling diffractive element or of the one or more out-coupling diffraction elements is inversely proportional to sine of an angle between a line crossing a middle point of one of the adjacent grooves of the in-coupling diffractive element or of the one or more out-coupling diffraction elements and an origin of the spherical coordinate system and a line crossing said middle point and a pole of said spherical coordinate system, wherein said reference plane is a focal plane of a spherical or an aspheric inner surface comprising the first or the second surface of the non-flat substrate, whichever is closer to said focal plane.