Tetsuo Mitsuhashi

A study of visual fatigue and visual comfort for 3D HDTV/HDTV images

We compared visual fatigue caused by HDTV and stereoscopic HDTV at the viewing distance of 4.5 m. We measured the degree of visual fatigue using a subjective test method and compared it to an objective measure, namely the change in accommodation before and after viewing images. We also detected visual discomfort image scenes from the best program using the single stimulus continuous quality method. As a result, the mechanism between convergence eye movement and the accommodation function in the depth of focus in addition to conflict of convergence eye movement and accommodation function appears to affect visual fatigue. From the examination between the results of single stimulus quality evaluation and the feature characteristics of test stereoscopic images, we found that a local low subjective evaluation appeared for both high degree of parallax and amount of motion in the test stereoscopic images. But motion components were very small, the subjective evaluation value was rarely very low.

Perception of edge sharpness in three-dimensional images

The quality of 3D images is usually perceived as being better than that of 2D images. In 2D images, edge sharpness is responsible for the quality. Accordingly, we examined the effects of the stereoscopic perception of edge sharpness on image quality by employing the categorized pair comparison method. We compared the sharpness of two types of natural 3D images with 2D images and found that the sharpness of 3D was not always perceived as being sharper than 2D. Next experiments were carried out to examine the role of rivalry on edge sharpness using a geometric image to which a local rivalry was artificially added. Results showed that the artificial local rivalry reduced the edge sharpness. Further experiments compared the sharpness of the vertical or horizontal edges in 3D images, which consisted of two planes (near and far), with that in 2D images. Consequently, the 3D vertical edge was as sharp as the 2D one, while the horizontal edge was perceived as being sharper than the 2D. As a result, the improvement in edge sharpness raises overall 3D image quality. Moreover, the perception of an occluded region in 3D images affected the edge sharpness. We also refer to the relationship between the perception and rivalry that might have caused interocular suppression.

Objective evaluation of 3-D wide-field effect by human postural control analysis

A new evaluation method of visual wide-field effects using human postural control analysis is proposed. In designing a television system for future, it is very important to understand the dynamic response of human beings in order to evaluate the visual effects of displayed images objectively. Visual effects produced by 3-D wide-field images are studied. An observers body sway produced by postural control is discussed using rotating 2-D and 3-D images. Comparisons between stationary and rotating images are also performed. A local peak appears in power spectra of the body sway for the rotating images (3-D and 2-D). On the other hand, no distinctive component appears in the power spectra for the stationary images. By extending the visual field, the cyclic component can be proved from the audio-correlation function of the body sway for the rotating images. These results suggest that displayed images induce the postural control. The total length of the body sway locus is also analyzed to evaluate the postural control. The total length for the rotating images increases in proportion to viewing angles, and is nearly saturated after 50 (deg). Moreover, it is shown that the total length for the rotating 3-D image is greater than for the rotating 2-D image.

A 50-inch diagonal rear-projection display for HDTV with automatic convergence correction

Abstract A 50-inch diagonal rear-projection display for HDTV has been developed. The resolution on the screen is more than 1000 TV lines, and the contrast ratio is improved by the optical coupling between the CRTs and the projection lenses. The display contains two mirrors in order to make the depth of the display smaller. One of the mirrors contains three photodiodes in order to allow the detection of the convergence error that occurs on the screen. Examining the outputs of the photodiodes, a CPU, located within the display, can detect and correct the convergence error.

Sharpness of Edge in 3-D Images.

平面画像と立体画像のエッジの鮮鋭度を主観評価により比較した.平面画像に比べて立体画像の横エッジの鮮鋭度は向上するが, 縦エッジでは片目にしか見えない領域の影響で鮮鋭度は向上しないことがわかった.