Tomoki Shiomi

Simultaneous measurement of lens accommodation and convergence to real objects

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.

Visibility Experiment and Evaluation of 3D Character Representation on Mobile Displays

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.

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.

Effect of weak hyperopia on stereoscopic vision

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.

Non-linear analysis of stabilograms with alcoholic intake

Equilibrium function in the cerebellum (vestibulo-cerebellar system) can deteriorate under the influence of alcohol. In the Romberg posture, the center of gravity, which was measured every 50 ms by stabilometry, appeared to shift with alcohol ingestion. In the previous study, a locus in the center of gravity (stabilogram) was converted to values of statistical indices such as area of sway, total locus length, and locus length per unit area, although these indices could not always distinguish between the statokinesigrams sampled from seven healthy young males in sober and intoxicated states. This measurement was made with an AMTI force plate. In this study, “translation error” was estimated in a d-dimensional embedding space in order to compare statokinesigrams recorded before and after the ingestion of doubly diluted brandy in 30 s (1 ≤ d ≤ 10). We succeeded in validating a stochastic differential equation as a mathematical model of the body sway. The randomness in the model was preserved after alcohol intake and significantly increased in the medial/lateral direction. Visual information referred by the postural control system when standing might be interfered by the effects of intoxication, which was regarded as disturbance. This method is considered to be useful to diagnose the disorders of the vestibulocerebellar system.

Evaluation of Body Sway in a Seated Posture after Alcohol Ingestion with an Aim to Evaluate Motion Sickness Caused by Three-Dimensional Images

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.