Explicit raytracing for gimbal-based gazepoint trackers

A system for computing a first gaze axis of an eye in a first coordinate system, comprising:

• a camera, wherein the camera focuses on the eye and moves to maintain the focus on the eye as the eye moves in the first coordinate system;
• a gimbal, wherein the gimbal is connected to the camera and wherein the gimbal is used to move the camera, and
• a processor,
• wherein the processor is connected to the camera and the gimbal such that the processor controls the focus, controls movement of the gimbal, and measures a first location of the camera in the first coordinate system;
• wherein the processor measures a second location of the eye and a gaze direction of the eye within a second coordinate system;
• wherein the processor computes a second gaze axis within the second coordinate system from the second location and the gaze direction;
• and
• wherein the processor computes the first gaze axis from the second gaze axis and the first location using a first coordinate transformation that comprises one or more rotational parameters.