Compact variable focus configurations

1. A head-wearable viewing component for presenting virtual image information to a user, comprising:

a. a head wearable frame;

b. a left optical element for a left eye of the user, the left optical element coupled to the head wearable frame and comprising two left perimetric frame members, a left electromechanical device connected between the two left perimetric frame members and a left fluid/membrane lens between the two left perimetric frame members and having an electromechanically adjustable focal length for the left eye of the user while maintaining image stability when the two left perimetric frame members are moved relative to one another by the left electromechanical device;

c. a right optical element for a right eye of the user, the right optical element coupled to the head wearable frame and comprising two right perimetric frame members, a right electromechanical device connected between the two right perimetric frame members and a right fluid/membrane lens between the two right perimetric frame members and having an electromechanically adjustable focal length for the right eye of the user while maintaining image stability when the two right perimetric frame members are moved relative to one another by the right electromechanical device; and

d. a controller operatively coupled to the left electromechanical device and the right electromechanical device and configured to provide one or more commands thereto to modify the focal lengths of the left fluid/membrane lens and the right fluid/membrane lens.

2. The head-wearable viewing component of claim 1 , wherein at least one of the left and right electromechanical devices comprises an actuation motor intercoupled between the two perimetric frame members of the respective optical element.

3. The head-wearable viewing component of claim 2 , wherein the actuation motor is configured to provide linear actuation.

4. The head-wearable viewing component of claim 2 , wherein the actuation motor is configured to provide rotational actuation.

5. The head-wearable viewing component of claim 2 , wherein the perimetric frame members of the respective optical element are coupled to the fluid/membrane lens perimetric frame members of the respective optical element and configured to change the focal length for the user by linearly moving relative to each other.

6. The head-wearable viewing component of claim 2 , wherein the two perimetric frame members of the respective optical element are rotatable relative to each other to modify the focal length for the user.

7. The head-wearable viewing component of claim 2 , wherein the two perimetric frame members of the respective optical element are displaceable relative to each other in a non-rotational manner.

8. The head-wearable viewing component of claim 2 , wherein the actuation motor comprises a stepper motor.

9. The head-wearable viewing component of claim 2 , wherein the actuation motor comprises a servo motor.

10. The head-wearable viewing component of claim 2 , wherein the actuation motor comprises a piezoelectric actuator.

11. The head-wearable viewing component of claim 2 , wherein the actuation motor comprises an ultrasonic motor.

12. The head-wearable viewing component of claim 2 , wherein the actuation motor comprises an electromagnetic actuator.

13. The head-wearable viewing component of claim 2 , wherein the actuation motor comprises a shape memory metal alloy actuator.

14. The head-wearable viewing component of claim 1 , wherein the controller is configured to command the left and right optical elements to adjust to one of two selectable predetermined focal lengths.

15. The head-wearable viewing component of claim 1 , wherein the controller is configured to command the left and right optical elements to adjust to one of three or more selectable predetermined focal lengths.