Dependence on the display methods of change in accommodation and convergence when a target moves along the depth direction

We have studied human behavior while using a small tablet or a digital book in terms of eye movement. These display media are widely used in conditions that cause hand movement, like on a moving bus or train. Therefore, we focused on the tracking accuracy of accommodation and convergence while subjects viewed a display that was moving in the depth direction. We developed an experimental device that measures the lens accommodation and convergence eye movement simultaneously and can be combined with equipment that moves a small tablet or a digital book linearly in the depth direction. We then evaluated changes in accommodation and convergence angle during depth-direction movement with different kinds of display media, fonts and font sizes. The amount of change in accommodation showed a tendency to depend on the display medium and the size of the font, and the type of font to the motion of a depth direction. The change in the angle of convergence was not dependent on the type of display medium, and the size of the font and the type of font depended only on the depth movement of the target. The tendency overshot in the direction approaching a subject was seen.