Influence of image-quality degradation on accommodation mechanism in human vision: Conditions necessary for objective image-quality evaluation metrics

• Published in: Journal of the Society for Information Display 2012-07, Vol.20 (7), p.367-379
• Main Author: Matsui, Toshikazu
• Format: Article
• Language: English
• Subjects: accommodation; accommodation lag; human factor; Image quality; missing fundamental square wave; noise; objective image-quality evaluation metric; pseudo-contour; sharpness
• ISSN: 1071-0922; 1938-3657
• DOI: 10.1002/jsid.96

This paper clarifies the relationship between image quality and accommodation in human vision through two types of experiments. One examines how image‐quality degradation influences the accommodation mechanism, and the other examines which type of information of quality‐degraded images activates the accommodation mechanism. Actually, accommodative responses are measured using an infrared optometer while subjects are subjectively evaluating sharpness, noise, and pseudo‐contours and while they are observing sine, square, and missing fundamental (MF) square waves. The following results were derived: (1) the accommodation lag increases as the degree of sharpness is degraded regardless of the tone‐reproducing methods; (2) the accommodation lag decreases considerably in the existence of noise or pseudo‐contours, whereas it increases for uniform or gently curved planes; (3) the spatial features of presented images activate the accommodation mechanism. These results suggest that accommodative responses influence human subjective judgments as well as being a human factor related closely to image quality and that the spatial features of quality‐degraded images underlie human subjective judgments. In other words, they imply that objective image‐quality evaluation metrics should satisfy the following two conditions: the incorporation of the accommodation characteristics into such metrics and the formulation of such metrics in the spatial region.