Size perception in stereoscopic displays based on binocular disparity considering interpupillary distance

Several studies have shown that when observing objects through binocular parallax virtual reality devices such as head-mounted displays (HMDs) and CAVE systems, observers perceive the size of virtual objects to be smaller than the size of real objects. The purpose of this study is to clarify this visual mechanism while taking into account the influence of individual differences in interpupillary distance. The three parameters that influence size perception are the interpupillary distance of the observer, the distance between the cameras that render the stereoscopic virtual space, and the distance between the lenses of the HMD. In this experiment, all of these values were adjusted to those of the participants. The results showed that regardless of the shape of the object, it was perceived to be approximately 7.7 to 11.1% smaller than its actual size. Furthermore, it was suggested that participants did not perceive the objects as smaller due to perceiving them at different distances. Instead, it was proposed that they might have perceived the objects as smaller, even though they perceived the distances to the objects somewhat accurately.