Optical devices and head-mounted displays employing tunable cylindrical lenses
This disclosure describes in-plane switching mode liquid crystal geometric phase tunable lenses that can be integrated into an eyepiece of an optical device for the correction of non-emmetropic vision, such as in an augmented reality display system. The eyepiece can include an integrated, field-configurable optic arranged with respect to a waveguide used to project digital imagery to the user, the optic being capable of providing a tunable Rx for the user including variable spherical refractive power (SPH), cylinder refractive power, and cylinder axis values. In certain configuration, each tunable eyepiece includes two variable compound lenses: one on the user-side of the waveguide with variable SPH, cylinder power, and axis values; and a second on the world side of the waveguide with variable SPH.
1. An optical system, comprising:
a first in-plane switching (IPS) mode liquid crystal (LC) element arranged along an optical axis;
a second IPS mode LC element arranged along the optical axis;
a third IPS mode LC element arranged along the optical axis; and
an electronic controller in communication with the first, second, and third IPS mode LC elements, the electronic controller being configured, during operation, to provide drive signals to the first, second, and third IPS mode LC elements, respectively, so that the first, second, and third IPS mode LC elements collectively form an optical element having an overall non-zero spherical refractive power (SPH), non-zero cylinder refractive power (CYL), and cylinder axis (Axis) according to a prescription (Rx),
wherein each of the IPS mode LC elements comprises a respective layer of a LC material between two substrates,
each of the IPS mode LC elements comprises a respective electrode layer supported by one of the two substrates, and
each electrode layer comprises a respective two-dimensional array of pixel electrodes, wherein each two-dimensional array of pixel electrodes comprises a plurality of rows of pixel electrodes and a plurality of columns of pixel electrodes,
wherein each pixel electrode comprises a respective plurality of conducting lines, and the pluralities of conducting lines across the two-dimensional array of pixel electrodes are oriented in a same direction.
2. The system of claim 1 , wherein each of the IPS mode LC elements is a respective geometric phase (GP) cylindrical lens during operation of the system.
3. The system of claim 2 , wherein each respective GP cylindrical lens has a cylinder axis aligned in a different direction.
4. The system of claim 1 , wherein the LC material is a nematic phase LC material.
5. The system of claim 1 , wherein the electronic controller is programmed to drive each array of pixel electrodes to uniformly align the LC material along a first direction in a plane of the respective IPS mode LC element and to vary an alignment of the LC material along a second direction in the plane orthogonal to the first direction.
6. The system of claim 5 , wherein the alignment of the LC material along the second direction comprises a plurality of 2π rotations of a nematic director of the LC material.
7. The system of claim 6 , wherein a spatial wavelength of the 2π rotations varies across the IPS mode LC element in the second direction.
8. The system of claim 7 , wherein the spatial wavelength of the 2π rotations in the second direction increases from a center of the IPS mode LC element towards edges of the IPS mode LC element.
9. The system of claim 5 , wherein the electronic controller is programmed to drive different subsets of the pixel electrodes at different times and to switch back and forth between the different subsets with a cycle shorter than a relaxation time of the LC material.
10. The system of claim 1 , wherein the first IPS mode LC element is configured with a first cylinder axis arranged at a first radial direction, the second IPS mode LC element is configured with a second cylinder axis arranged at a second radial direction, and the third IPS mode LC element is configured with a third cylinder axis arranged at a third radial direction, and wherein an angular separation between the first and second radial directions is equal to an angular separation between the second and third radial directions.
11. The system of claim 10 , wherein, for a Cartesian coordinate system orthogonal to the optical axis, the first radial direction is at 30°, the second radial direction is at 90°, and the third radial direction is at 150°.
12. The system of claim 11 , wherein a first cylindrical corrective refractive power, C 30 , of the first IPS mode LC element, a second cylindrical corrective refractive power, G 90 , of the second IPS mode LC element, and a third cylindrical corrective refractive power, C 150 , of the third IPS mode LC element, and values for spherical lens refractive power(S), cylindrical lens refractive power (C), and cylindrical lens angular orientation (A) are related according to the formulae:
C
30
=
2
3
S
+
(
2
3
cos
2
A
+
2
3
3
cos
A
sin
A
)
C
C
90
=
2
3
S
+
(
sin
2
A
-
1
3
cos
2
A
)
C
C
150
=
2
3
S
+
(
2
3
cos
2
A
-
2
3
3
cos
A
sin
A
)
C
.
13. The system of claim 1 , wherein a cylindrical refractive power of each of the first, second, and third IPS mode LC elements is variable through a range from −5 D to +5 D.
14. The system of claim 1 , wherein the optical element has an aperture having an area of at least 1 cm 2 , 5 cm 2 , 10 cm 2 , or 16 cm 2 .
15. The system of claim 1 , wherein each of the first, second, and third IPS mode LC elements exhibits a thickness along the optical axis of at most 10 mm, 6 mm, 4 mm, 3 mm, 2 mm, or 1 mm.
16. A head-mountable display, comprising:
a first optical element having a variable spherical refractive power (SPH);
a second optical element having
a variable SPH, a variable cylinder refractive power (CYL), and
a variable cylinder axis (Axis), the second optical element comprising at least one in-plane switching (IPS) mode liquid crystal (LC) element,
wherein each IPS mode LC element comprises a respective layer of a LC material between two substrates,
each IPS mode LC element comprises a respective electrode layer supported by one of the two substrates,
each electrode layer comprises a respective two-dimensional array of pixel electrodes, wherein each two-dimensional array of pixel electrodes comprises a plurality of rows of pixel electrodes and a plurality of columns of pixel electrodes,
wherein the first optical element comprises two variable cylindrical lenses having their respective cylinder axes orthogonal to each other;
a see-through display arranged between the first optical element and the second optical element; and
an electronic controller in communication with the first optical element, the second optical element, and the see-through display, the electronic controller being programmed to adjust the SPH of the first optical element and the SPH, CYL, and Axis of the second optical element according to a prescription (Rx) of an individual user of the head-mounted display,
wherein each pixel electrode comprises a respective plurality of conducting lines, and the pluralities of conducting lines across the two-dimensional array of pixel electrodes are oriented in a same direction.
17. The head-mountable display of claim 16 , further comprising a frame to which the first optical element, the second optical element, and the see-through display are mounted.
18. The head-mountable display of claim 17 , wherein the second optical element is arranged between the see-through display and the user during use of the head-mountable display.
19. The head-mountable display of claim 16 , wherein the second optical element comprises three IPS mode LC elements arranged such that their respective cylinder axes are in different radial directions.
20. The head-mountable display of claim 16 , further comprising an eye-tracking module, the electronic controller being programmed to vary the prescription of the second optical element based on information, received from the eye-tracking module, describing where the user of the head-mountable display is looking.
21. The head-mountable display of claim 20 , wherein the electronic controller is programmed to vary the SPH, CYL, and Axis of the second optical element from a near-vision prescription to a distance-vision prescription depending on where the user is looking.
22. The head-mountable display of claim 16 , further comprising a biometric identification module, the electronic controller being programmed to identify the user based on information from the biometric identification module and adjust a prescription of the second optical element based at least partly on the identity of the user.
23. The head-mountable display of claim 22 , wherein the biometric identification module is an iris identification module.