A fast approach to refraction-aware 3D eye-model fitting and gaze prediction

Kai Dierkes, Moritz Kassner, Andreas Bulling

Proc. ACM International Symposium on Eye Tracking Research and Applications (ETRA), pp. 1–9, 2019.

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Estimating eyeball position by a least-squares intersection of lines. (A) Ignoring refraction effects occuring at corneal surfaces, the 3D circular pupil is mapped to a 2D ellipse in the image plane via perspective projection (shown in side view). After disambiguation, circular unprojections of the 2D pupil ellipse have a normal parallel to the gaze direction and their centers form a line passing through the center of the 3D pupil (dashed red line). Since the distance between eyeball and pupil center, R, is fixed, the eyeball center is constrained to lie on a parallel line (red solid line). (B) A change in gaze gives rise to an independent constraint for eyeball position. (C) Eyeball position is estimated by a least- squares intersection of constraining lines derived from a set of pupil contours.

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Abstract

By temporally integrating information about pupil contours extracted from eye images, model-based methods for glint-free gaze estimation can mitigate pupil detection noise. However, current approaches require time-consuming iterative solving of a nonlinear minimization problem to estimate key parameters, such as eyeball position. Based on the method presented by [Swirski and Dodgson 2013], we propose a novel approach to glint-free 3D eye-model fitting and gaze prediction using a single near-eye camera. By recasting model optimization as a least-squares intersection of lines, we make it amenable to a fast non-iterative solution. We further present a method for estimating deterministic refraction-correction functions from synthetic eye images and validate them on both synthetic and real eye images. We demonstrate the robustness of our method in the presence of pupil detection noise and show the benefit of temporal integration of pupil contour information on eyeball position and gaze estimation accuracy.

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