IMAGE QUALITY OF PANCHARATNAM BERRY PHASE COMPONENTS USING POLARIZERS
Various embodiments set forth a near eye display (NED) that includes an electronic display configured to output image light. Further, the NED includes multiple Pancharatnam Berry Phase (PBP) optical elements that are combined with one or more circular polarizers to improve optical performance. A PBP element produces an output of three diffraction orders. Typically in an optical system that includes such a PBP element, one of the three diffraction orders is used while the other two are undesirable and preferably maintained at a relatively low intensity. A circular polarizer may reduce the intensities of the two undesired diffraction orders.
1 . An optical system, comprising:
a geometric phase element configured to produce a first light beam associated with a first diffraction order and a second light beam associated with a second diffraction order in response to receiving input light; and
an elliptical polarizer configured to reduce an intensity of the first light beam and substantially preserve an intensity of the second light beam.
2 . The optical system of claim 1 , further comprising a second elliptical polarizer.
3 . The optical system of claim 2 , wherein the elliptical polarizer comprises a circular polarizer having a first handedness and the second elliptical polarizer comprises a circular polarizer having a second handedness that is opposite to the first handedness.
4 . The optical system of claim 2 , further comprising a depolarizer configured to provide unpolarized light to the second elliptical polarizer.
5 . The optical system of claim 1 , wherein the geometric phase element is further configured to produce a third light beam associated with a third diffraction order, and the elliptical polarizer is further configured to reduce an intensity of the third light beam.
6 . The optical system of claim 1 , wherein the geometric phase element comprises a switchable Pancharatnam Berry Phase (PBP) lens.
7 . The optical system of claim 1 , wherein the geometric phase element comprises a stack of two or more Pancharatnam Berry Phase (PBP) lenses.
8 . The optical system of claim 1 , further comprising a traditional lens to provide the input light to the geometric phase element.
9 . The optical system of claim 1 , wherein the geometric phase element comprises a first stack that includes a first PBP lens having a first optical power and a second PBP lens having a second optical power, the optical system further comprising:
a lightguide configured to provide image light to the elliptical polarizer; and
a second stack of PBP lenses comprising a third PBP lens having an optical power that is a conjugate of the first optical power and a fourth PBP lens having an optical power that is a conjugate of the second optical power.
10 . The optical system of claim 9 , wherein at least one of the first, second, third, and fourth PBP lenses comprises a switchable PBP lens to provide a switchable image plane.
11 . The optical system of claim 9 , further comprising a plurality of electrically switchable PBP liquid crystal half-wave plates, each of the plurality of electrically switchable PBP liquid crystal half-wave plates adjacent to a different one of the first, second, third, and fourth PBP lenses, the plurality of electrically switchable PBP liquid crystal half-wave plates and the first, second, third, and fourth PBP lenses configured to provide a switchable image plane.
12 . The optical system of claim 9 , further comprising a liquid crystal display device to provide the image light to the lightguide.
13 . The optical system of claim 1 , wherein the optical system is included in an augmented reality head mounted device.
14 . The optical system of claim 1 , further comprising:
a first quarter-wave plate and a second quarter-wave plate adjacent to the geometric phase element; and
a linear polarizer between the first and the second quarter-wave plate.
15 . The optical system of claim 1 , wherein the geometric phase element comprises a Pancharatnam Berry Phase (PBP) grating.
16 . A head-mounted display (HMD), comprising:
an electronic display configured to emit image light;
a first stack of Pancharatnam Berry Phase (PBP) geometric phase elements configured to produce a first light beam associated with a first diffraction order and a second light beam associated with a second diffraction order in response to the image light; and
an elliptical polarizer configured to reduce an intensity of the first light beam and substantially preserve an intensity of the second light beam.
17 . The HMD of claim 16 , further comprising:
a second stack of PBP geometric phase element configured to produce output light; and
a lightguide between the first and the second stack of PBP geometric phase elements, the lightguide configured to provide the image light to the first stack of PBP geometric phase elements and to transmit the output light produced by the second stack of PBP geometric phase elements.
18 . The HMD of claim 16 , wherein the first stack of PBP geometric phase elements includes a first PBP lens having a first optical power and a second PBP lens having a second optical power, and wherein the second stack of PBP geometric phase elements includes a third PBP lens having an optical power that is opposite to the first optical power and a fourth PBP lens having an optical power that is opposite to the second optical power.
19 . The HMD of claim 18 , further comprising electrically switchable PBP liquid crystal half-wave plates respectively adjacent to the first, second, third, and fourth PBP lenses, the electrically switchable PBP liquid crystal half-wave plates and the first, second, third, and fourth PBP lenses to provide a switchable image plane.
20 . A head-mounted display (HMD), comprising:
an electronic display configured to emit image light;
a first elliptical polarizer configured to produce elliptically polarized light based on the image light;
a geometric phase element configured to produce a first light beam associated with a first diffraction order and a second light beam associated with a second diffraction order in response to receiving elliptically polarized light; and
a second elliptical polarizer configured to reduce an intensity of the first light beam and substantially preserve an intensity of the second light beam.