BACKGROUND

1. Technical Field

This disclosure relates generally to tracking methods for eye-mounted displays.

2. Description of Related Art

In one type of eye-mounted display, a tiny projector (referred to as a femtoprojector for convenience) is mounted inside a contact lens. A typical femtoprojector is no larger than about one or two millimeters in any dimension in order to fit inside the contact lens. The femtoprojector produces images and projects those images onto the user's retina. If the external environment is also visible, the projected images will be overlaid on the user's view of the external environment.

As the user's eye moves, the contact lens and femtoprojector also move—and the user's eye is always moving. For example, an eye may make involuntary saccadic motions, or voluntarily track a moving target using smooth pursuit motion. Whatever the circumstances, voluntary, or involuntary, eye motion occurs continuously as part of the human visual process. Because the femtoprojector also moves with the user's continuous eye motion, the location of where a projected image appears relative to the external environment constantly changes. However, eye-mounted displays capable of estimating the eye's orientation, position, or pose may use that estimate to give a projected image the appearance of remaining fixed with respect to the external environment.

