To investigate properties of surface reconstruction modules in the human visual system, an experimental system using a virtual reality technique was developed. The system produces visual cues for surface reconstruction, such as binocular disparity, motion parallax, shading, textures etc. and presents them on a stereo graphics display. Also, observer\u27s head motion is fed back to evaluate the mechanisms of active vision. In this report, moving random dot patterns are used to investigate the human visual system\u27s sensitivity to sinusoidal depth modulations specified by motion parallax. Modulation transfer functions (MTF) are affected both by dot average velocity and dot density. Three dots per period are necessary to perceive the sinusoidal surfaces. The value of (threshold of perception) / (average dot interval) is constant in every dot density and frequency condition. This implies that the surface reconstruction from motion parallax utilizes the gradient of the velocity field. These experimental results are similar to those in surface reconstruction from binocular disparity.本研究は文部省科研費（課題番号07551003および09044189）の助成を受けたことを付記する
