Development of head-mounted display with eye-gaze detection function for the severely disabled

The physically handicapped people such as the amyotrophic lateral sclerosis (ALS) patients who can move only eyes have difficulty in communicating with others. As a communication device which a user could operate by eye movement, we made a prototype of a head-mounted display (HMD) with the eye-gaze detection function. In the conventional HMD with eye-gaze detection system, the size was large and the eye-gaze calibration procedure must be repeated if the user moves relative to the HMD. To reduce the size of the HMD, first, in the developed prototype, a part of the optical path for displaying and that of the path for eye-gaze detection were used together. In addition, the HMD was used for one eye. Second, to improve the eye-gaze detection function, the eye-gaze point was determined from the relative position between the pupil center and the corneal reflection of the light source which were detected by the camera. In addition, the light source for irradiating the eye and the camera for capturing the eye image were arranged in infinite virtually. Furthermore, the display screen was set in infinite ideally. However, actually, the optical system for displaying was adjusted to myopia. As a result, the eye-gaze error due to the eye displacements relative to the finder of the HMD was yielded. So we proposed an eye-gaze compensation method to compensate the eye-gaze points. Finally, the Japanese character input experiment was conducted for three healthy students. The input speed was 3.45, 2.70, and 2.15 sec per one character, respectively.