A natural 3D display is required for the next-generation display techniques. We have already demonstrated that the accommodation responses are evoked when a large number of directional images, which are orthographic projections of 3D scenes, are projected into the corresponding directions with a very small angle pitch. We have also constructed a three-dimensional display which displayed 64 directional images into different horizontal directions with the horizontal angle pitch of 0.34°. With high-density directional images, not parallax images (perspective projection of 3D scenes), very smooth motion parallax is obtained in addition to the accommodation evocation. In this study we develop a new 3D display which is used to investigate the natural 3D displaying conditions on commission of the Japanese ministry of internal affairs and communications. It can display 128 directional images simultaneously by using 128 small LCD panels. The horizontal viewing angle is 29.6° and the horizontal display angle pitch is 0.23°. The screen size is 13.2 inches. The 3D display is controlled by a PC cluster consisted of 16 PC"s. We are also developing equipment which can measure the dynamic responses of the accommodation, the vergence, and the pupil diameters of both eyes. This equipment will be used to investigate the optimum 3D display conditions.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.