Image enhancement with lightness correction and image sharpening based on characteristics of vision for elderly persons

In general, as people age the functions of their sensory organs deteriorate. For example, in the eye of an elderly person, the visual field becomes dark owing to a decrease in the amount of light reaching the retina. Moreover, objects appear blurred due to a decrease in contrast sensitivity. In particular, the contrast sensitivity decreases remarkably as the spatial frequency increases. In this study, we propose an image enhancement method that considers the visual characteristics of elderly persons. The proposed method combines lightness correction and amplification of high spatial frequency components to obtain images with optimized visibility for elderly persons. In particular, lightness enhancement that guarantees color gamut via tone mapping is conducted. In addition, image sharpening is applied based on the inverse characteristic function of the contrast sensitivity curve. The experiments were performed using several digital color images to confirm the effectiveness of the proposed method.