ABSTRACT

This chapter summarizes the visual processing of human eyes, because they are an ideal imaging system and a model for complementary metal-oxide-semiconductor (CMOS) imaging systems. It discusses the human visual system with CMOS image sensors. The human eye has the focal plane processing function of spatio-temporal image preprocessing. The photoresponse curve adaptively shifts according to the environmental illumination and eventually converts over seven orders of magnitude. The human eye has a wide dynamic range under moonlight to sunlight due to this mechanism. Rods are mainly distributed in the periphery of the retina and have a higher photosensitivity without color sensitivity, while cones are mainly concentrated in the center of the retina or fovea and have color sensitivity with less photosensitivity than rods. Rod photoreceptors have higher photosensitivity than cones and have adaptivity for light intensity. Under uniform light illumination, the rod works in a range of two orders of magnitude with saturation characteristics.