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US 8,830,584 B2Granted
Exit pupil expanders with spherical and aspheric substrates
AssigneeNokia Corporation
InventorsPasi Saarikko, Tapani Levola
Life of this patent
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Abstract
The specification and drawings present a new apparatus and method for using exit pupil expanders (EPE) with spherical or aspheric non-flat substrates and a plurality of diffractive elements for expanding the exit pupil of a display for viewing in order to reduce image spreading. This can also enable improved image resolution and utilization of shorter focus distances.
Claims21
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.
5 more elements
A method, comprising:
- receiving an input optical beam by an in-coupling diffractive element disposed on a first or a second surface of a non-flat substrate, wherein said first and second surfaces have a spherical or aspheric shape and are opposite to each other;
- diffracting the input optical beam 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 one or more out-coupling diffractive elements disposed on the first or the second surface of the non-flat substrate;
- coupling by diffraction parts of said one or more diffracted optical beams from the non-flat substrate using said one or more out-coupling diffractive elements 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.
3 more elements
Dependencies are inferred from the claim text.