US Patent 10429647 Focus adjusting virtual reality headset

A virtual scene presented on a display of a virtual reality headset can be adjusted using a varifocal element by changing the shape of one or more optical elements of a pancake lens block, by varying the distance between the two optical elements, or both, based on where in a virtual scene a user is looking. The headset tracks a user's eyes to determine a vergence depth from gaze lines in order to accommodate the user's eye for the determined vergence depth. Accordingly, the shape of one or more optical elements is adjusted, the distance between the two optical elements, or both, is changed to focus light from the display of the virtual reality headset at the vergence depth to keep the user's eye in a zone of comfort as vergence and accommodation change.