Recording gaze trajectory of wheelchair users by a spherical camera

Wheelchairs are widely used in the facilities of rehabilitation. In this paper, we propose a method of recording the gaze trajectory of wheelchair users by using a spherical camera mounted on the wheelchairs. A spherical camera has a full field of view and can observe the entire surrounding scenes. First, the gaze point of a user sitting on a wheelchair is estimated from the corneal reflection image observed by a wearable eye camera. Then, the gaze point is mapped onto the full-view image captured by the spherical camera via feature matching. Since it is not guaranteed that the gaze point in an eye image is a distinctive feature point, the matching of a gaze point between these two images cannot be carried out directly. To cope with this problem, we use a coarse-to-fine approach, in which, first, distinctive feature points are used to estimate the relative orientation between the eye camera and the spherical camera, and then, the estimated relative orientation matrix is used to determine the location of gaze points. The effectiveness of the proposed method is shown by real-world experimental results.