Systems and methods for astigmatism correction in a head-mounted display

1. A system comprising:

a lens assembly that provides an electronically controllable cylindrical power, oriented along an electronically controllable axis, on an optical path between a display device and an eye of a viewer, wherein the lens assembly comprises:

a first liquid crystal lens providing a first electronically controllable cylindrical power, oriented along a first constant axis, in response to a first control signal; and

a second liquid crystal lens providing a second electronically controllable cylindrical power, oriented along a second constant axis that is rotationally offset from the first constant axis, in response to a second control signal; and

a controller that:

receives information indicating a cylindrical power component and a cylindrical axis component of an eyeglass prescription for the viewer;

determines, based on the information, the first and second electronically controllable cylindrical powers that result in providing the cylindrical power component, oriented along the cylindrical axis component, for the viewer; and

generates, based on the first and second electronically controllable cylindrical powers, the first and second control signals to cause the lens assembly to provide the cylindrical power component, oriented along the cylindrical axis component, for the viewer without physical rotation of either the first liquid crystal lens or the second liquid crystal lens.

2. The system of claim 1 , wherein a rotational offset between the first constant axis and the second constant axis ranges from greater than zero degrees to less than 180 degrees.

3. The system of claim 2 , wherein the rotational offset between the first constant axis and the second constant axis is approximately 45 degrees.

4. The system of claim 1 , wherein:

the system further comprises an actuator that alters a distance between the display device and the eye of the viewer based on at least one additional control signal; and

the controller:

receives further information indicating a spherical power component of the eyeglass prescription for the viewer; and

generates, based on the further information, the at least one additional control signal to compensate for the spherical power component for the viewer.

5. The system of claim 1 , wherein:

the system further comprises:

a viewing lens on the optical path between the display device and the eye of the viewer; and

an actuator that alters a distance between the viewing lens and the display device based on at least one additional control signal; and

the controller:

receives further information indicating a spherical power component of the eyeglass prescription for the viewer; and

generates, based on the further information, the at least one additional control signal to compensate for the spherical power component for the viewer.

6. The system of claim 1 , further comprising:

an input interface that receives the information indicating the cylindrical power component and the cylindrical axis component of the eyeglass prescription for the viewer.

7. The system of claim 6 , further comprising:

a memory that stores the information received via the input interface; and

a biometric device that detects a biological characteristic of the viewer;

wherein the controller:

determines an identity of the viewer based on the biological characteristic; and

retrieves the information from the memory based on the identity of the viewer.

8. The system of claim 7 , wherein the biological characteristic comprises a characteristic of at least one of a fingerprint, an iris, or a retina of the viewer.

9. The system of claim 1 , wherein:

the system further comprises a biometric device that detects a biological characteristic of the viewer; and

the controller generates, based on the biological characteristic, the information indicating the cylindrical power component and the cylindrical axis component of the eyeglass prescription for the viewer.

10. The system of claim 9 , wherein the biometric device comprises an optical wavefront sensor.

11. A system comprising:

a display device that provides an image to be viewed by a viewer;

a lens assembly that provides an electronically controllable cylindrical power, oriented along an electronically controllable axis, on an optical path between the display device and an eye of the viewer, wherein the lens assembly comprises:

a first liquid crystal lens providing a first electronically controllable cylindrical power, oriented along a first constant axis, in response to a first control signal; and

a second liquid crystal lens providing a second electronically controllable cylindrical power, oriented along a second constant axis that is rotationally offset from the first constant axis, in response to a second control signal;

an actuator that alters an effective focal length between the eye of the viewer and the display device based on at least one additional control signal; and

a controller that:

receives information indicating a spherical power component, a cylindrical power component, and a cylindrical axis component of an eyeglass prescription for the viewer;

determines, based on the information, the first and second electronically controllable cylindrical powers that result in providing the cylindrical power component, oriented along the cylindrical axis component, for the viewer;

generates, based on the first and second electronically controllable cylindrical powers, the first and second control signals to cause the lens assembly to provide the cylindrical power component, oriented along the cylindrical axis component, for the viewer without physical rotation of either the first liquid crystal lens or the second liquid crystal lens; and

generates, based on the information, the at least one additional control signal to compensate for the spherical power component for the viewer.

12. The system of claim 11 , wherein the actuator moves the display device relative to the eye of the viewer to alter the effective focal length between the eye of the viewer and the display device based on the at least one additional control signal.

13. The system of claim 11 , wherein:

the system further comprises a viewing lens on the optical path between the display device and the eye of the viewer; and

the actuator moves the viewing lens relative to the display device to alter the effective focal length between the eye of the viewer and the display device based on the at least one additional control signal.