Kazuhiro Fujikake

Lens Accommodation to the Stereoscopic Vision on HMD

The purpose of this study was to clarify the effect on visual function of gazing at stereoscopic images on a head mounted display (HMD). We measured visual accommodation during stereoscopic viewing while using a HMD by using our original instrument of measurement. The presented image was shown 3-dimensionally on an HMD set up at a visual distance of 3 cm. A spherical object moved back and forth toward and away from the observer in a 10 sec cycle. While the subjects were gazing at the 3D image with both eyes, the lens accommodation in the right eye was measured and recorded. Accommodation to the virtual objects was shown during the viewing of stereoscopic images of 3D computer graphics, but was not shown when the images were displayed without appropriate binocular parallax. It is suggested that stereoscopic moving images on HMD induced the visual accommodation by the expansion and contraction of the ciliary muscle, which is synchronizing with convergence.

Readability of Characters on Mobile Phone Liquid Crystal Displays

Subject performance in reading characters on mobile phone liquid crystal displays was researched by using (a) English sentences with 3 or 4 different sizes of characters on 2 types of displays with different resolutions(n = 23; age = 31.0 ± 6.0 years), (b) Japanese characters in 3 different sizes and 2 types of font (n = 98; age = 44.5 ± 18.5 years), and (c) Japanese characters vertically enlarged 1—4 times (n = 120; age = 46.9 ± 18.6 years). Subjective evaluation, reading speed, number of reading errors, and viewing distance were recorded. Readability was higher with higher resolution displays, and with Gothic than with Mincho font in Japanese. Young subjects shortened the viewing distance as characters became smaller, whereas elderly subjects increased the viewing distance irrespective of the size of characters. Characters of 3–5 mm are appropriate for the young but inadequate for the elderly. Readability of Japanese characters improved when they were vertically enlarged to approximately twice the width.

Evaluation of Body Sway and the Relevant Dynamics While Viewing a Three-Dimensional Movie on a Head-Mounted Display by Using Stabilograms

The viewers of three-dimensional (3D) movies often complain of blurring and bleeding. They sometimes experience visually induced motion sickness (VIMS). In this study, the effect of VIMS on body sway was examined using stabilograms. We measured the sway in the center of gravity before and during the exposure to images projected on a head-mounted display (HMD). While viewing, the subjects were instructed to remain in the Romberg posture for the first 60 seconds and maintain a wide stance (midline of the heels, 20 cm apart) for the next 60 seconds. Employing Double-Wayland algorithm, we measured the degree of determinism in the dynamics of the sway in the center of gravity with respect to viewing 3D movies on HMD. As a result, the dynamics of the sway during and before the exposure was considered to be stochastic. Thus, exposure to 3D movies would not change the dynamics to a deterministic one.

Readability of character size for car navigation systems

An experiment was conducted on the ease with which a car navigation system could be read by elderly, middle-aged and young people. 127 subjects (19-76 years of age) evaluated ease of reading of the displayed characters. The experiment evaluated characters displayed on a liquid crystal display (LCD) similar to those used in car navigation systems, and evaluated readability in 9 stages. Five character sizes for traffic terms and two languages (Japanese and English) were used in the experiment. The experiment was conducted with the LCD in 2 positions: directly in front of the subject and diagonal to the left (about 30 degrees). The results showed that the directly frontward position was significantly more readable than the position of diagonal to the left.

Comparison of Measurement of Accommodation between LCD and CRT at the Stereoscopic Vision Gaze

In the present study, we examined the visual accommodation of subjects who were gazing fixedly at 3D images from two different displays: a cathode ray tube (CRT) while wearing special glasses and a liquid crystal display (LCD) while not wearing special glasses. The subjects in this experiment were two healthy people aged 22 and 39 years, all with normal vision. The instrument objectively measured visual accommodative changes of the right eye in both binocular and natural viewing conditions. The results suggested that it was easy and comfortable to focus on both the LCD and CRT. When the subjects viewed the progressively receding target, their accommodation was about 0.8 D at the presumed furthest points, a level at which the ciliary muscle is relaxed. The accommodative power differed by about 1.5 D from the near to far point. Thus, the ciliary muscle is repeatedly strained and relaxed while the subject views the moving target.

On a Qualitative Method to Evaluate Motion Sickness Induced by Stereoscopic Images on Liquid Crystal Displays

Visually induced motion sickness (VIMS) is known to be caused by sensory conflict, which is the disagreement between vergence and visual accommodation while observing stereoscopic images. The simulator sickness questionnaire (SSQ) is a well-known method that is used herein for verifying the occurrence of VIMS. We quantitatively measure the sway of the centre of gravity of the human body before and during exposure to several images. During the measurement, subjects are instructed to maintain the Romberg posture for the first 60 s and a wide stance (midlines of the heels 20 cm apart) for the next 60 s. The stereoscopic images decrease the gradient of the potential function involved in the stochastic differential equations as a mathematical model of the body sway. We have succeeded in estimating the decrease in the gradient by using an index called sparse density.

Effect of LCDs displaying blurred images on the postural control system

In order to evaluate display devices, a geostationary image and the character were generally used in previous studies. We have proposed a new method for comparing the standing posture when a subject views a liquid crystal display (LCD) displaying a movie scrolling from the left to the right. In this study, we mathematically measured the degree of determinism in the dynamics of the sway of center-of-gravity. The Double-Wayland algorithm was used as a novel method. As a result, the dynamics of the sway when subjects viewed the movie as well that of the sway in the resting state was considered to be stochastic. The moving map task would not change it into a deterministic one.

Readability of characters on liquid crystal displays in mobile phones

Subject performance in reading characters on mobile phone liquid crystal displays was researched with the use of: (1) sentences without meaning, made from randomly ordered alphanumeric characters having 3 different sizes of characters and 4 different contrasts (n=78; age=39.9±17.6), (2) Japanese characters of 5 different sizes and 2 types of font (n=98; age=44.5±18.5), and (3) Japanese characters vertically enlarged 1-4 times (n=120; age=46.9±18.6). Readability was higher with higher contrast displays, and with Gothic than with Mincho font in Japanese. Readability of Japanese characters improved when they were vertically enlarged to approximately twice the width.

Multi-evaluation method of visual fatigue and motion sickness while viewing 2d/3d video clips on a liquid crystal display

It is physiologically known that the vestibular system and the autonomic nervous system interact with each other. The motion sickness can affect both these systems, and severity of the motion sickness is expected to be measured by dysfunction of the equilibrium system. We have proposed a new index, sparse density (SPD), of stationary stabilograms for detecting the metamorphism in the (temporally averaged) potential function of stochastic differential equations, which occurs when a human attempts to maintain an upright posture. It is known that a mathematical model of the body sway can be developed by a stochastic process. The authors have succeeded in finding the nonlinearity in the potential function. Subjects in a standing position were stimulated by a movie scrolling from left to right on a liquid crystal display (LCD) in measurement 1 and a stereoscopic video clip on an LCD in measurement 2. As a result, the dynamics of the body sway in the presence of the stimulus as well as in its absence were considered to be stochastic. The metamorphism in the potential function during exposure to blurred images and a stereoscopic video clip could be detected by using the SPD.

Comparison of form in potential functions while maintaining upright posture during exposure to stereoscopic video clips

Visually induced motion sickness (VIMS) is caused by sensory conflict, the disagreement between vergence and visual accommodation while observing stereoscopic images. VIMS can be measured by psychological and physiological methods. We propose a mathematical methodology to measure the effect of three-dimensional (3D) images on the equilibrium function. In this study, body sway in the resting state is compared with that during exposure to 3D video clips on a liquid crystal display (LCD) and on a head mounted display (HMD). In addition, the Simulator Sickness Questionnaire (SSQ) was completed immediately afterward. Based on the statistical analysis of the SSQ subscores and each index for stabilograms, we succeeded in determining the quantity of the VIMS during exposure to the stereoscopic images. Moreover, we discuss the metamorphism in the potential functions to control the standing posture during the exposure to stereoscopic video clips.