We introduce three experiments on depth perception from monocular motion parallax for more realistic depth representation in 3D applications. Motion parallax is a physiological factor for depth perception. When moving the head position, depth can be perceived from motion parallax even when using one eye because motion parallax provides enough information for depth estimation. In our first experiment, we evaluated the perceived depth from monocular motion parallax with passive head movements. The results show that perceived depth with passive head movement is comparable to that with active head movement. For more realistic 3D scenes, we should clarify the critical factor of visual information in motion parallax. Therefore, in our second experiment, we evaluated the perceived depth from motion parallax with and without direction change of the stimulus movement. The results suggest that visual information at the time of direction change plays an important role in stable and unambiguous depth perception. In our third experiment, we evaluated the minimum duration of motion parallax stimulus with direction change for stable and unambiguous depth perception. The results indicate that a stimulus duration of only 15% of the total trial time provides stable and unambiguous depth perception if direction changes of the visual stimulus are presented. These findings can be applied to 3D applications using motion parallax.
This paper proposes a new way of forming an aerial three-dimensional (3D) image that gives viewers smooth motion parallax. The proposed aerial 3D display is composed of an arc 3D display and aerial imaging by retro-reflection (AIRR), which features a wide viewing angle, a large-size scalability, and a low cost with mass-productive process. The arc 3D display consists of arc-shaped scratches on a transparent plastic plate. The principle of the arc 3D display is based on directional scattering. When a light impinges an arc-shaped scratch, the light is scattered mainly to the radial direction. The position of the bright spot on an arc scratch depends on the pupil position. The distance between the bright spots for both eyes on an arc scratches is proportional to the radius of curvature and is equivalent to the binocular parallax. Thus, by changing the radius of curvature, we can show a 3D image by use of a single LED illumination. This paper proposes an optical system to form an aerial 3D image with AIRR. AIRR consists of a light source, a beam splitter, and a retro-reflector. Arc scratches are illuminated by a quasi-parallel light that is generated by a Fresnel lens and a lightemitting diode (LED). In order to extract the directional scattered lights, we place the retro-reflector parallel to the beam splitter. The transmitted light does not impinge the beam splitter. Only the scattered lights reflect on the beam splitter and form the aerial image of the arc 3D display.
Security is one of the big issues in automated teller machine (ATM). In ATM, two types of security have to be maintained. One is to secure displayed information. The other is to secure screen contamination. This paper gives a solution for these two security issues. In order to secure information against peeping at the screen, we utilize visual cryptography for displayed information and limit the viewing zone. Furthermore, an aerial information screen with aerial imaging by retro-reflection, named AIRR enables users to avoid direct touch on the information screen. The purpose of this paper is to propose an aerial secure display technique that ensures security of displayed information as well as security against contamination problem on screen touch. We have developed a polarization-processing display that is composed of a backlight, a polarizer, a background LCD panel, a gap, a half-wave retarder, and a foreground LCD panel. Polarization angle is rotated with the LCD panels. We have constructed a polarization encryption code set. Size of displayed images are designed to limit the viewing position. Furthermore, this polarization-processing display has been introduced into our aerial imaging optics, which employs a reflective polarizer and a retro-reflector covered with a quarter-wave retarder. Polarization-modulated light forms the real image over the reflective polarizer. We have successfully formed aerial information screen that shows the secret image with a limited viewing position. This is the first realization of aerial secure display by use of polarization-processing display with retarder-film and retro-reflector.