Takehito Kojima

A Temporal Analysis of Body Sway Caused by Self-Motion During Stereoscopic Viewing

While continuously viewing objects in motion, humans may develop an illusionary sense of moving in the opposite direction as the objects, despite being quiescent. This phenomenon is termed as vection. In this study, we investigated the effect of long-duration viewing through binocular stereopsis on vection by measuring the body sway. Subjects watched a static movie for a minute, sinusoidal-motion movie at 0.3 Hz for 3 min, and the initial static movie for a minute, in sequence. We had three observations from the results of this study. First, the longer the viewing time, the higher the synchrony with direction of motion in the movie. Stoppage of the motion-movie and returning to viewing a static movie decreases the synchrony gradually. Second, synchrony is higher while viewing a 3D- than a 2D-movie. Third, the body sways in the anteroposterior direction in a cyclical manner by sensing self-motion in the horizontal direction.

Effects of Two-Minute Stereoscopic Viewing on Human Balance Function

Recently, with the rapid progress in image processing and three-dimensional (3D) technologies, stereoscopic images are not only available on television but also in theaters, on game machines, and elsewhere. In contrast to two-dimensional (2D) films that project flat images, stereoscopic films elicit the feeling of being at a live performance. However, asthenopia and visually-induced motion sickness (VIMS) can result from the exposure to these films. Even though various hypotheses exist, the pathogenesis of VIMS is still unclear. There is not enough knowledge on the effects of stereoscopic images on the living body, and the accumulation of basic research is thus important. The aim of this paper is to accumulate information relevant to VIMS and to examine whether the exposure to 3D video clips affects the human equilibrium functions. We evaluated body sway by conducting stabilometry studies. As a result, we verified that 3D viewing effects on our equilibrium function depends on exposure time.

Verification of the minimum illuminance for comfortable reading of an e-paper

Various e-paper devices also have been released (e.g. Amazons Kindle DXTM), and their features include paper-like display and low power consumption. In our previous studies, in high light conditions, readability of the backlight LCD dropped significantly, because of the glare of the surrounding background. On the other hand, the readability of the electronic paper is increased, it was easy to read than backlit LCD. The e-paper that have low contrast ratio, evaluation of readability was low. In low light, the evaluation of the readability of the backlit LCD was high. The aim of this experiment was to verify the minimum illumination for comfortable reading with e-paper in low illumination (300 or less lx).

Measurement of Lens Focus Adjustment While Wearing a See-Through Head-Mounted Display

In recent years, many visual devices have been produced for consumers. The development of see-through smart glasses has attracted much attention. These glasses overlap virtually images by using Augmented Reality (AR) technology. Epson released the BT-2000 see-through smart glasses, which change distance of display by changing convergence. It is not confirmed that changing distance of display allow to change distance of lends accommodation. In this experiment, we measured lens accommodation of subjects viewing images displayed on see-through smart glasses. The results found that lens accommodation moved with the image position for over one hundred people. Therefore, our study verified that correct reaction occurred visual physiologically.

Comparison by Simultaneous Measurement of Lens Accommodation and Convergence in 3D Vision and Their Distributions

—In general, disagreement between accommodation and convergence is considered to be a main reason for the visual fatigue and the visually induced motion sickness (VIMS). In this study, we devised a method to simultaneously measure lens accommodation and convergence, and used it to characterize 3D vision. Time courses of these fixation distances and their distributions are compared while they viewed 2D and 3D video clips. As a result, the convergence almost agreed with the distance between a subject and a 3D image. Therefore, we succeeded in measuring convergence while the distance of the accommodation focal length shifted.

A Study on Within-Subject Factors for Visually Induced Motion Sickness by Using 8K Display

Visually induced self-motion perception (vection) is one of the phenomena related to human vision. It often emerges as a precursory symptom of motion sickness while viewing moving images. Employing a large number of subjects in a wide range of age groups and using a large-scale 8 K display, we investigated within-subject factors which can influence a sense of vection. We report some results of statistical analyses of vection-induced body sway which occurred when the subjects viewed rotating images on the display. Then we find that our fundamental study may provide useful information in order to set safety guidelines for large-scale ultra-high-definition displays such as 4K and 8K which are becoming popular in public use.

Effects of long-time 3d viewing on the eye function of accommodation and convergence

Recently we developed a device by combining a binocular autorefractometer and an eye mark recorder. Then, using the device together with images of very natural and high quality, we have carried out a sequence of experiments on simultaneous measurements of both accommodation and convergence while viewing virtual 3D objects. The results show that there is essentially no discrepancy in the dynamical behaviors of accommodation and convergence especially for young subjects and that they are hence very close to the case of natural viewing of real 3D objects. Following our previous experiments, we now investigate effects of long-time viewing of virtual 3D objects on the eye function of accommodation and convergence. We show that the synchronous dynamical behaviors of accommodation and convergence are definitely not a temporal effect but last for a long time.

Multilingual medical dialog system developed as smartphone/tablet application

Along with the concomitant rise in foreign residents in Japan has come the need to improve understanding at several social levels. The need for clear communication is most immediate in the area of the emergency or health care fields. Several types of apps exist that can be used to assist with communication between Japanese medical staff and foreign patients. However, there are problems with ease of use. This study asked 34 subjects to evaluate three types of touch designs with the “ExLanguage Nurse” to improve the usability of such multilingual apps. Results indicate that touch designs on the apps are related to ease of usability.

Accommodation response for visually equivalent light field 3D display

Visually Equivalent Light Field 3D (VELF3D) is an autostereoscopic flat-panel 3D display. Though it has a very simple structure, it can reproduce not only binocular parallax and convergence but also smooth motion parallax. It displays multiple viewing zones and uses oblong pixels and a parallax barrier to enable adjacent zones to be linearly blended well and provide continuous reproduction of motion parallax. However, the potential for accommodation reproducibility has yet to be clarified. In this paper, we demonstrate accommodation responses of monocular vision induced by changes in displayed depth as determined by an autorefractor / keratometer. We calculate point spread functions and retinal images when an observer is watching a linear blending display, and analyze mechanisms to induce accommodation.

Change in the Fusion Limit by Insertion of a Middle Image Equally Dividing the Parallactic Angle of 3D Stereoscopic Images

OBJECTIVES The purpose of this study was to identify and clarify the requirements for 3D stereoscopic images that do not cause viewing discomfort to the human eye even when the protrusion distance is large. METHODS A total of 140 healthy men and women aged 14 to 79 years participated in this study. We first measured the fusion limits in these participants using two 3D stereoscopic images. We then measured the expansion of the fusion limit by inserting a middle image in a region located equally parallax from the two images. RESULTS The results showed that the fusion limits were significantly expanded (p<0.01) after inserting the middle image. CONCLUSIONS Insertion of middle images with parallax can extend the fusion limit. This method was shown to be an effective for viewing 3D stereoscopic images without causing discomfort.