Tetsuri Inoue

Surmised state of accommodation to stereoscopic three-dimensional images with binocular disparity

Three-dimensional image (3-D image) was experimentally generated by the binocular disparity principle, and psychological tests were performed in relation to the state of accommodation. An image of a square formed by the time-sharing system using liquid crystal (LC) shutter glasses was displayed before the CRT screen (forward image) by the crossed visual-line method and behind the monitor screen (backward image) by the non-crossed visual-line method. The subjects were requested to subjectively compare each image with the original image on the CRT screen in relation to the size. The forward image displayed by the crossed visual lines looked smaller than the original image, while the backward image displayed by the non-crossed visual lines looked larger. In consideration of the developmental mechanism of micropsia occurring in patients with accommodative palsy or paresis of accommodation and macropsia occurring in patients with accomodative spasm, it was surmised that, in the generation of 3-D image due to binocular disparity, accommodation works so that the original image position is maintained.

Measurement of the human factors of 3-D images on a large screen

Three dimensional displays using binocular disparity techniques are widely used. Binocular stereoscopic images can produce a mismatch of distance between plane of focus (accommodation) and plane of fixation (convergence) of the observe?s eyes. The viewing distance, i.e. plane of required focus, is generally greater when looking at a large screen than when look at a small display. In this study the fusional ranges of the binocular three dimensional image are compared when viewing a large screen (75inch,projection type TV display) at a distance of 350cm and when observing a small display (2linch CRT) at a distance of 100cm. We found that the fusional range was more extended on the larger screen than the smaller display. Accommodative responses were measured when looking at the 3D image. Accommodation does not remain in the plane of the display but changes to the stereoscopic distance of the 3D image fixated by the observer. The changes required when using a longer viewing distance were smaller than those measured with an a short viewing distance. These results suggest the longer viewing distance reduces an unnatural feeling of viewing 3D images due to the mismatch of distance between the planes of accommodation and convergence. Accommodation response time was measured after looking at stereoscopic 3D images. Far-to-near response time was longer than before viewing these images. The results showed that the viewing stereoscopic 3D images provided the observers visual system with different type of stimuli from these experienced in normal viewing.