Varifocal apparatuses, systems, and methods employing a deformable stepped lens

1. An apparatus comprising:

a deformable stepped lens that:

provides a first optical power when a shape of the deformable stepped lens comprises a first state; and

provides a second optical power different from the first optical power when the shape of the deformable stepped lens comprises a second state different from the first state; and

an actuator coupled to the deformable stepped lens that is configured to apply an amount of force identified with the second optical power to the deformable stepped lens to alter the shape of the deformable stepped lens from the first state to the second state.

2. The apparatus of claim 1 , wherein the actuator applies the force about a perimeter of the deformable stepped lens toward a center of the deformable stepped lens.

3. The apparatus of claim 2 , wherein the force applied by the actuator moves the center of the deformable stepped lens either:

toward an eye of a viewer so that the second optical power is greater than the first optical power; or

away from the eye of the viewer so that the second optical power is less than the first optical power.

4. The apparatus of claim 2 , wherein:

the actuator comprises:

a ring;

a plurality of pads contacting the perimeter of the deformable stepped lens;

a plurality of flexures connecting the plurality of pads to the ring; and

a first shape-memory alloy (SMA) wire routed about the actuator via at least one of:

one or more of the plurality of pads; or

one or more of the plurality of flexures; and

the first SMA wire applies the force in response to carrying electrical current.

5. The apparatus of claim 4 , wherein:

the actuator further comprises a second SMA wire routed about the actuator at the plurality of pads;

the second SMA wire applies a second force about the perimeter of the deformable stepped lens toward the center of the deformable stepped lens in response to carrying electrical current; and

the second SMA wire is located relative to the first SMA wire such that the second force causes the center of the deformable stepped lens to move in an opposite direction to that caused by the force applied by the first SMA wire.

6. The apparatus of claim 5 , wherein the first SMA wire and the second SMA wire are located on opposing sides of a plane defined by the perimeter of the deformable stepped lens.

7. The apparatus of claim 4 , wherein:

the perimeter of the deformable stepped lens is circular; and

the plurality of flexures are of a same thickness such that:

the same force is applied at each of the plurality of pads onto the perimeter of the deformable stepped lens; and

the shape of the deformable stepped lens is symmetrical about the center of the deformable stepped lens when the deformable stepped lens is in a deformed state as a result of the force being applied at each of the plurality of pads.

8. The apparatus of claim 4 , wherein:

the perimeter of the deformable stepped lens is not circular; and

the plurality of flexures vary in thickness to apply differing forces at the plurality of pads onto the perimeter of the deformable stepped lens so that the shape of the deformable stepped lens is symmetrical about the center of the deformable stepped lens when the deformable stepped lens is in a deformed state as a result of the force applied at each of the plurality of pads.

9. The apparatus of claim 1 , wherein:

the actuator applies the force in a manner that results in:

a first force vector being applied at a first portion of the deformable stepped lens; and

a second force vector being applied at a second portion of the deformable stepped lens.

10. The apparatus of claim 9 , wherein the first force vector comprises a direction component that is different than a direction component of the second force vector.

11. The apparatus of claim 9 , wherein the actuator comprises a plurality of actuators that has:

a first actuator that applies the first force vector to the first portion of the deformable stepped lens; and

a second actuator that applies the second force vector to the second portion of the deformable stepped lens.

12. The apparatus of claim 9 , further comprising an aperture mechanism that:

is coupled to the deformable stepped lens at a plurality of different locations, wherein the plurality of different locations comprises the first and second portions of the deformable stepped lens; and

when actuated by the actuator, applies the force to the deformable stepped lens at each of the plurality of different locations.

13. The apparatus of claim 1 , further comprising a rigid lens that is located between the deformable stepped lens and an eye of a viewer and that provides an additional optical power, wherein the rigid lens is dimensioned to compensate for a thickness of the deformable stepped lens that differs as a function of a radius of the deformable stepped lens.

14. The apparatus of claim 1 , wherein:

the deformable stepped lens comprises at least one substantially flat side; and

a side of the deformable stepped lens opposite the substantially flat side comprises a plurality of concentric ridges.

15. The apparatus of claim 1 , further comprising:

a display subsystem that generates an image for viewing by a viewer, wherein the actuator holds the deformable stepped lens between a display and an eye of the viewer;

a control subsystem that directs the actuator to apply the force to the deformable stepped lens; and

a deflectometry subsystem that measures a current state of the shape of the deformable stepped lens, wherein the control subsystem selects the force applied to the deformable stepped lens based, at least in part, on the current state of the shape of the deformable stepped lens.

16. A method comprising:

identifying an amount of force to be applied to a deformable stepped lens; and

directing an actuator to apply the identified amount of force to the deformable stepped lens to alter a shape of the deformable stepped lens from a first state to a second state, wherein:

the deformable stepped lens comprises a first optical power in the first state;

the deformable stepped lens comprises a second optical power in the second state; and

the first optical power is different than the second optical power.

17. The method of claim 16 , wherein identifying the amount of force comprises:

detecting a level of focus of an image being projected through the deformable stepped lens onto an eye of a viewer; and

determining, based on the level of focus, the amount of force to be applied to the deformable stepped lens.

18. The method of claim 16 , wherein identifying the amount of force comprises:

receiving, at an input subsystem, information about an optical correction prescription of a viewer; and

determining, based at least in part on the optical correction prescription, the amount of force to be applied to the deformable stepped lens.

19. The method of claim 18 , wherein:

receiving the information about the optical correction prescription comprises receiving information about a cylindrical component of the optical correction prescription;

determining the amount of force to be applied is based on the cylindrical component;

the first optical power comprises a first cylindrical power; and

the second optical power comprises a second cylindrical power that is different than the first cylindrical power and that at least partially corrects for an astigmatism of the viewer.

20. A method comprising:

mechanically coupling an actuation subsystem to a deformable stepped lens that, when held in a first state by the actuation subsystem, has a shape that provides a first optical power; and

communicatively coupling, to the actuation subsystem, a control subsystem that:

identifies an amount of force to be applied to the deformable stepped lens; and

directs the actuation subsystem to apply the amount of force to the deformable stepped lens, wherein:

the amount of force alters the shape of the deformable stepped lens from the first state to a second state; and

the deformable stepped lens, when held in the second state by the actuation subsystem, provides a second optical power that is different than the first optical power.