Point of Gaze Estimation through Corneal Surface Reflection in an Active Illumination Environment

Eye gaze tracking (EGT) is a common problem with many applications in various fields. While recent methods have achieved improvements in accuracy and usability, current techniques still share several limitations. A major issue is the need for external calibration between the gaze camera system and the scene, which commonly restricts to static planar surfaces and leads to parallax errors. To overcome these issues, the paper proposes a novel scheme that uses the corneal imaging technique to directly analyze reflections from a scene illuminated with structured light. This comprises two major contributions: First, an analytic solution is developed for the forward projection problem to obtain the gaze reflection point (GRP), where light from the point of gaze (PoG) in the scene reflects at the corneal surface into an eye image. We also develop a method to compensate for the individual offset between the optical axis and true visual axis. Second, introducing active coded illumination enables robust and accurate matching at the GRP to obtain the PoG in a scene image, which is the first use of this technique in EGT and corneal reflection analysis. For this purpose, we designed a special high-power IR LED-array projector. Experimental evaluation with a prototype system shows that the proposed scheme achieves considerable accuracy and successfully supports depth-varying environments.