A display system aligns the location of its exit pupil with the location of a viewer's pupil by changing the location of the portion of a light source that outputs light. The light source may include an array of pixels that output light, thereby allowing an image to be displayed on the light source. The display system includes a camera that captures images of the eye and negatives of the images are displayed by the light source. In the negative image, the dark pupil of the eye is a bright spot which, when displayed by the light source, defines the exit pupil of the display system. The location of the pupil of the eye may be tracked by capturing the images of the eye, and the location of the exit pupil of the display system may be adjusted by displaying negatives of the captured images using the light source.