Horizontal Wide-Range Gaze Detection System by Combination of Pupil Ellipticity and Pupil-Corneal Reflection Methods

Abstract

We have developed gaze detection systems based on the pupil-corneal reflection method for driver monitoring, digital signage, and so on. However, when a user looks at angularly remote positions (>±30° – ±40°) on a monitor screen from the optical systems for the gaze detection, the gaze detection becomes impossible because the corneal reflection does not appear. In the present paper, to expand the measurable horizontal range of the gaze, we proposed a method combing the pupil-corneal reflection method and the pupil ellipticity method. These two types of the gaze detection methods functioned on the same platform. In this combined method, a line of sight was always calculated using the ellipticity of the pupil ellipse and the inclination of the minor axis of the pupil ellipse. When the angle of the line of sight exceeded 30°, the gaze detection was determined using the pupil ellipticity method. When it was 30° or less, the pupil-corneal reflection method was used. When the pupil ellipticity method is used, it is unclear which direction a subject looks on the minor axis of the ellipse, e.g., right or left. To solve this problem, we proposed a method utilizing the difference in the pupil ellipticity between the right and left camera images. In the experiment, subjects were asked to look at 27 visual targets evenly arranged on horizontally arranged three monitors’ screens. The experimental result showed that the measurable range of the gaze detection was expanded into approximately ±45° horizontally by the combination of the two types of the gaze detection methods. In the total range, the average angular gaze error for all subjects was 2.02 ± 1.38°.