In order to capture what the eye is seeing as accurately as possible, an EyeTap uses a beam splitter to send the same scene (with reduced intensity) to both the eye and a camera. The camera then digitizes the reflected image of the scene and sends it to a computer. The computer processes the image and then sends it to a projector. The projector sends the image to the other side of the beam splitter so that this computer-generated image is reflected into the eye to be superimposed on the original scene. Stereo EyeTaps modify light passing through both eyes, but many research prototypes (mainly for reasons of ease of construction) only tap one eye.