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Recent advances in 3D technology have been accompanied by increasing complaints of visual fatigue. The usual explanation for such fatigue is that accommodation and convergence are mismatched during stereoscopic vision. The aim of this study was to measure fixation distances between lens accommodation and convergence in young subjects while they viewed real objects and 3D video clips. Measurements were made using an original instrument. The 3D video clips were presented to subjects using a liquid crystal shutter glass system. The results showed that when viewing real objects, the diopter values of subjects' accommodation and convergence were similar and changed periodically. This measurement method was thus considered to be appropriate for the measurement of stereoscopic vision. We also investigated lens accommodation and convergence when subjects viewed 3D video clips. Both accommodation and convergence were found to move along with the virtual position of 3D video clips. Therefore, there was little discrepancy between accommodation and convergence during the viewing of 3D images.

In this study, we invented a method to simultaneously measure lens accommodation and convergence used for natural and 3D vision. We found that there is almost never a difference between natural vision and 3D vision in terms of accommodation and convergence.

1Department of Information Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan 2Department of Information and Media Studies, Nagoya Bunri University, 365 Maeda, Inazawa-cho, Inazawa, Aichi 492-8520, Japan 3Graduate School of Engineering Human and Artificial Intelligent Systems, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan 4Facility of Home Ergonomics, Kobe Women’s University, 2-1 Aoyama, Higashisuma, Suma-ku, Kobe 654-8585, Japan ∗E-mail address: miyao@nagoya-u.jp

A few studies have evaluated swaying motion of the body in the seated posture; however, these studies did not evaluate motion sickness caused by watching movies, traveling, etc. This study aimed to analyze stabilograms recorded while the individuals were seated. Stabilometry was performed on 7 healthy male subjects (age, 21–22 years) in the seated position 5 min before, and at 5-min intervals from 5 to 60 min after alcohol load. Alcohol caused a decrease in the cerebellar equilibrium function that controls the vestibulospinal reflex. We adjusted the degree of simulative effect on the human equilibrium function. The stabilograms of the test subjects were analyzed according to the area of sway, total locus length, and total locus length per unit area. We found that significant alcohol-induced changes in the sway values in the seated posture were similar to those in the upright posture.

Accommodation and convergence were measured simultaneously while subjects viewed 2D and 3D images. The aim was to compare fixation distances between accommodation and convergence in young subjects while they viewed 2D and 3D images. Measurements were made using an original machine that combined WAM-5500 and EMR-9, and 2D and 3D images were presented using a liquid crystal shutter system. Results suggested that subjects' accommodation and convergence were found to change the diopter value periodically when viewing 3D images. The mean values of accommodation and convergence among the 6 subjects were almost equal when viewing 2D and 3D images respectively. These findings suggest that the ocular functions when viewing 3D images are very similar to those during natural viewing. When subjects are young, accommodative power while viewing 3D images is similar to the distance of convergence, and the two values of focusing distance are synchronized with each other.

Convergence, accommodation and pupil diameter were measured simultaneously while subjects were watching 3D images. The subjects were middle-aged and had weak hyperopia. WAM-5500 and EMR-9 were combined to make an original apparatus for the measurements. It was confirmed that accommodation and pupil diameter changed synchronously with convergence. These findings suggest that with naked vision the pupil is constricted and the depth of field deepened, acting like a compensation system for weak accommodation power. This suggests that people in middle age can view 3D images more easily if positive (convex lens) correction is made.

In the experimental study, we measured visibility and readability of text characters presented on a small 3D liquid crystal display (LCD) and evaluated features of the 3D character representation for application to mobile devices. For the visibility evaluation, we focused on time lag for first recognition, time required for full reading, and maximum distance of 3D objects popping out from the fixed display. We also report the dependency of the results on the age of subjects in comparison with 2D and 3D representations.

Human beings can perceive that objects are three-dimensional (3D). as a result of simultaneous lens accommodation and convergence on objects, which is possible because humans can see so that parallax occurs with the right and left eye. Virtual images are perceived via the same mechanism, but the influence of binocular vision on human visual function is insufficiently understood. In this study, we developed a method to simultaneously measure accommodation and convergence in order to provide further support for our previous research findings. We also measured accommodation and convergence in natural vision to confirm that these measurements are correct. As a result, we found that both accommodation and convergence were consistent with the distance from the subject to the object. Therefore, it can be said that the present measurement method is an effective technique for the measurement of visual function, and that even during stereoscopic vision correct values can be obtained.