Evaluation of Human Contrast Sensitivity Functions Used in the Nonprewhitening Model Observer with Eye Filter

Model observers which can serve as surrogates for human observers could be valuable for the assessment of image quality. For this purpose, a good correlation between human and model observer is a prerequisite. The nonprewhitening model observer with eye filter (NPWE) is an example of such a model observer. The eye filter is a mathematical approximation of the human contrast sensitivity function (CSF) and is included to correct for the response of the human eye. In the literature several approximations of the human CSF were found. In this study the relation between human and NPWE observer performance using seven eye filters is evaluated in two-alternative-forced-choice (2-AFC) detection experiments involving disks of varying diameter and signal energy and two background types. The results show that the shape of the CSF has an impact on the correlation between human and model observer. The inclusion of a CSF may indeed improve the relation between human and model observer. However, we did not find an eye filter which is optimal in both backgrounds.