UBC Theses and Dissertations
Improving eye-gaze tracking accuracy through personalized calibration of a user's aspherical corneal model Taba, Isabella Bahareh
The eyes present us with a window through which we view the world and gather information. Eye-gaze tracking systems are the means by which a user's point of gaze (POG) can be measured and recorded. Despite the active research in gaze tracking systems and major advances in this field, calibration remains one of the primary challenges in the development of eye tracking systems. In order to facilitate gaze measurement and tracking, eye-gaze trackers utilize simplifications in modeling the human eye. These simplifications include using a spherical corneal model and using population averages for eye parameters in place of individual measurements, but use of these simplifications in modeling contribute to system errors and impose inaccuracies on the process of point of gaze estimation. This research introduces a new one-time per-user calibration method for gaze estimation systems. The purpose of the calibration method developed in this thesis is to calculate and estimate different individual eye parameters based on an aspherical corneal model. Replacing average measurements with individual measurements promises to improve the accuracy and reliability of the system. The approach presented in this thesis involves estimating eye parameters by statistical modeling through least squares curve fitting. Compared to a current approach referred to here as the Hennessey's calibration method, this approach offers significant advantages, including improved, individual calibration. Through analysis and comparison of this new calibration method with the Hennessey calibration method, the research data presented in this thesis shows an improvement in gaze estimation accuracy of approximately 27%. Research has shown that the average accuracy for the Hennessey calibration method is about 1:5 cm on an LCD screen at a distance of 60 cm, while the new system, as tested on eight different subjects, achieved an average accuracy of 1:1 cm. A statistical analysis (T-test) of the comparative accuracy of the new calibration method versus the Hennessey calibration method has demonstrated that the new system represents a statistically significant improvement.
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