Control of variable-focus lenses in a mixed-reality device for presbyopes

A head-mounted display (HMD) device wearable by a presbyopic user and configured for supporting a mixed-reality experience including viewing, by the presbyopic user, of holographic images from a virtual world that are combined with views of real-world objects in a physical world, comprising:

• a see-through display system through which the presbyopic user can view the real-world objects and on which the holographic images are displayed within a field of view (FOV) of the see-through display system;
• a negative lens disposed between the see-through display system and an eye of the presbyopic user, the negative lens acting over the FOV and configured to render the holographic images at a focal plane having a predetermined distance from the presbyopic user;
• a variable-focus positive lens disposed on an opposite side of the see-through display system from the negative lens, the variable-focus positive lens being controllably configured to cancel effects of the negative lens on the views of the real-world objects responsive to the presbyopic user being engaged in viewing beyond the predetermined distance, and the variable-focus positive lens being controllably configured with increased optical power to optically push real-world objects into sharp focus responsive to a determination that the presbyopic user is accommodating within the predetermined distance;
• an optical power controller operatively coupled to the variable-focus positive lens;
• and
• an eye tracker operatively coupled to the optical power controller, the eye tracker tracking vergence of the presbyopic user’s eyes or tracking a gaze direction of at least one eye of the presbyopic user to determine whether the presbyopic user is accommodating within the predetermined distance, in which the optical power controller controls the variable-focus positive lens responsively to operations of the eye tracker.