Abstract
It has been computationally clarified how the image observation characteristics influence the sharpness evaluation function in human vision. This is accomplished by using a sharpness evaluation method based on the cooperative human vision model with image observation characteristics similar to those in human vision and examining the effect of the model's image observing mechanism on the model's sharpness metric performance. Evaluated images were continuous-tone generalized knife-edge images and their digital halftone images. Consequently, the following results were obtained: (1) The vision model reproduced accommodation characteristics during subjective sharpness evaluation; (2) the sharpness evaluation metric with the image observing mechanism was superior in evaluation performance to the metric without it. These results suggest that the adaptive change in the image observation characteristic for evaluated images prevents the evaluation performance from deteriorating according to evaluation conditions and furthermore a similar phenomenon can occur in the sharpness evaluation process in human vision.
