Augmented reality systems and methods with variable focus lens elements
An augmented reality display system includes a pair of variable focus lens elements that sandwich a waveguide stack. One of the lens elements is positioned between the waveguide stack and a user's eye to correct for refractive errors in the focusing of light projected from the waveguide stack to that eye. The lens elements may also be configured to provide appropriate optical power to place displayed virtual content on a desired depth plane. The other lens element is between the ambient environment and the waveguide stack, and is configured to provide optical power to compensate for aberrations in the transmission of ambient light through the waveguide stack and the lens element closest to the eye. In addition, an eye-tracking system monitors the vergence of the user's eyes and automatically and continuously adjusts the optical powers of the pair of lens elements based on the determined vergence of those eyes.
1. A display system comprising:
a head-mountable display configured to display a virtual object on one or more depth planes, the display comprising:
a first variable focus lens element;
a second variable focus lens element;
one or more waveguides between the first variable focus lens element and the second variable focus lens element, wherein the one or more waveguides are configured to:
output light for forming the virtual object, and
transmit light from a surrounding environment through the one or more waveguides; and
an eye tracking system,
wherein the display system is configured to:
determine eye parameters indicative of a vergence of a viewer's eyes; and
cause the second variable focus lens element to modify a wavefront divergence of the light outputted from the one or more waveguides to display the virtual object on a depth plane, wherein an amount of the modification of the wavefront divergence is based on the eye parameters indicative of the vergence and on an amount to correct a refractive error of a first eye of the viewer.
2. The display system of claim 1 , wherein the system is further configured to project another virtual object to the viewer via the one or more waveguides,
wherein the another virtual object is disposed on a different depth plane than the virtual object, and
wherein the amount of modification of wavefront divergence is based on the depth plane of the virtual object when a determined depth of the vergence of the viewer's eyes corresponds to the depth plane of the virtual object and the amount of modification of the wavefront divergence is based on the depth plane of the another virtual object when the determined depth of the vergence of the viewer's eyes corresponds to the depth plane of the another virtual object, wherein the amounts of modification for the virtual object and for the other virtual object are different.
3. The display system of claim 1 , wherein the display system is configured to cause the first variable focus lens element to modify a wavefront divergence of incoming light from the surrounding environment,
wherein an amount of the modification of the wavefront divergence modified by the first variable focus lens element is based on the determined eye parameters indicative of the vergence of the viewer's eyes and on an amount to correct the refractive error of the viewer's first eye.
4. The display system of claim 1 wherein the display system is configured to adjust the amount of corrected refractive error of the first variable focus lens element in response to the amount of corrected refractive error of the second variable focus lens element.
5. The display system of claim 1 , wherein the one or more waveguides are configured to output light with a divergent wavefront to the viewer to display the virtual object.
6. The display system of claim 1 , wherein the one or more waveguides comprises a plurality of waveguides each having a fixed optical power.
7. The display system of claim 6 , wherein at least some of the waveguides have different optical powers than others of the waveguides.
8. The display system of claim 1 , further comprising: a third variable focus lens element;
a fourth variable focus lens element; and
one or more second waveguides between the third variable focus lens element and the fourth variable focus lens element, wherein the one or more second waveguides are configured to:
output light for forming the virtual object in a second eye of the viewer, and
transmit light from the surrounding environment through the one or more second waveguides.
9. The display system of claim 8 , wherein the display system is configured to cause the fourth variable focus lens element to modify a wavefront divergence of the outputted light for forming the virtual object on a depth plane,
wherein an amount of the modification of the wavefront divergence is based on the eye parameters and on an amount to correct a refractive error of the second eye of the viewer.
10. The display system of claim 9 , wherein the display system is configured to cause the third variable focus lens element to modify a wavefront divergence of incoming light from the surrounding environment,
wherein an amount of the modification of the wavefront divergence of incoming light is based on the determined eye parameters indicative of the vergence of the viewer's eyes and on an amount to correct the refractive error of the viewer's second eye.
11. The display system of claim 1 , wherein the amount to correct refractive error is adjusted in accordance with a prescription for correcting the vision of the viewer's first eye at two or more distances.
12. The display system of claim 1 , wherein the display system has three or more preset prescriptions for refractive errors for each of the first and second variable focus lens elements.
13. The display system of claim 1 , wherein a number of available refractive error prescriptions is equal to at least a total number of depth planes for the display.
14. The display system of claim 1 , wherein one or both of the first and second variable focus lens elements comprises a layer of liquid crystal sandwiched between two substrates.
15. The display system of claim 14 , further comprising an electronic hardware control system configured to vary the refractive index of the first and/or second variable focus lens element by application of an electrical current or voltage.
16. A method for displaying images on a head-mountable display, the method comprising:
providing the display mounted on a head of a viewer, the display configured to display a virtual object on one or more depth planes and comprising:
a first variable focus lens element facing a surrounding environment;
a second variable focus lens element facing the viewer; and
one or more waveguides between the first variable focus lens element and the second variable focus lens element, wherein the one or more waveguides are configured to:
output light for forming the virtual object, and
transmit light from a surrounding environment to the viewer;
determining eye parameters indicative of a vergence of the viewer's eyes; and
correcting a refractive error of a first eye of the viewer by:
varying optical power of the second variable focus lens element, wherein the second variable focus lens element modifies a wavefront divergence of the outputted light for forming the virtual object on a depth plane, wherein an amount of the modification of the wavefront divergence is based on the eye parameters indicative of the vergence of the viewer's eyes and on an amount to correct the refractive error of the first eye; and
varying optical power of the first variable focus lens element, wherein the optical power of the first variable focus lens element modifies a wavefront divergence of incoming light from the surrounding environment, wherein an amount of the modification of the wavefront divergence of the incoming light is based on the eye parameters indicative of the vergence of the viewer's eyes and on an amount to correct the refractive error of the first eye.
17. The method of claim 16 , further comprising: providing:
a third variable focus lens element;
a fourth variable focus lens element; and
one or more second waveguides between the third variable focus lens element and the fourth variable focus lens element; and
correcting a refractive error of a second eye of the viewer by:
varying an optical power of the fourth variable focus lens element, wherein the fourth variable focus lens element modifies a wavefront divergence of the outputted light for forming the virtual object on the depth plane, wherein an amount of the modification of the wavefront divergence is based on the eye parameters indicative of the vergence of the viewer's eyes and on an amount to correct the refractive error of the viewer's second eye; and
varying an optical power of the third variable focus lens element, wherein the third variable focus lens element modifies a wavefront divergence of the incoming light from the surrounding environment, wherein an amount of the modification of the wavefront divergence is based on the eye parameters indicative of the vergence of the viewer's eyes and on an amount to correct the refractive error of the viewer's second eye.
18. The method of claim 17 , wherein determining eye parameters indicative of a vergence of the viewer's eyes comprises tracking the first and second eyes of the viewer using one or more cameras.
19. The method of claim 16 , wherein the optical power of the first variable focus lens element is varied simultaneously with the optical power of the second variable focus lens element.
20. The method of claim 16 , wherein the one or more waveguides each comprises diffractive optical elements configured to output divergent light from the waveguides.