Haruki Mizushina

The cyclopean illusion unleashed.

The cyclopean illusion is the apparent lateral shift of stationary stimuli on a visual axis that occurs when vergence changes. This illusion is predictable from the rules of visual direction. There are three stimulus situations reported in the literature, however, in which the illusion does not occur. In the three experiments reported here we examine those stimulus situations. Experiment 1 showed that an afterimage seen on a stimulus moving on the visual axis does not produce the illusion as reported in the literature but an afterimage seen on a screen does. Experiment 2 showed that the illusion occurs for an intermittently presented stimulus in contrast to what has been reported previously. Experiment 3 showed that a monocular stimulus presented against a random-dot background produced the illusion, also in contrast to what has been reported. The results were consistent with the rules of visual direction.

Measurements of vergence and accommodation while viewing a real 3D scene and its 2D image on a display

It is widely thought that conflict between vergence and accommodation may be a major factor of visual fatigue and discomfort caused by viewing stereoscopic images on 3D displays. However, few studies measured vergence and accommodation simultaneously while viewing a real 3D scene and its 2D image on a traditional display. In this study we measured vergence and accommodation responses simultaneously while viewing a 3D real object located at various distances from the participant and its 2D image (photograph) including background scene presented on a display located at fixed distance. The result shows that vergence and accommodation varied with changing target distance while viewing the 3D real object, as expected. On the other hand changing target distance depicted in the photographic image while viewing the 2D display evoked no systematic change of vergence and accommodation. Some participants showed that noticeable accommodation lag and fixation disparity. In addition to that we observed considerable conflicts between vergence and accommodation in both 3D and 2D conditions, but no one reported perceived defocus and/or double vision. There were varieties of individual differences in the pattern of the conflicts.

Relationship between Emotional State and Pupil Diameter Variability under Various Types of Workload Stress

We carried out two experiments to explore the relationship between the frequency characteristic of pupil diameter variability and emotional state under various types of workload. The workload required the subjects to listen to spoken words and categorize them. The difficulty of the task was adjusted by changing the time interval of the stimulus presentation in Experiment 1 (time-based task) and the number of categories in Experiment 2 (cognitive-based task). Pupil diameter was monitored and recorded using an infrared video camera while observers were performing the tasks. In both experiments, a significant correlation was observed between the frequency characteristic of pupil diameter variability and emotional state. Our results indicated the frequency characteristic of pupil diameter variability to be a potentially useful index for evaluating mental stress.

Forming aerial 3D images with smooth motion parallax in combination of arc 3D display with AIRR

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.

Aerial secure display by use of polarization-processing display with retarder film and retro-reflector

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.