Selective Visual Attention: Computational Models and Applications

2.1 Human Visual System (HVS)

Research on the HVS can be traced back to more than 100 years ago [1], and the basic physiological aspects of the HVS have been investigated and published in literature, such as [2–7]. The front end of the HVS, the human eye, is illustrated in Figure 2.1. The crystalline lens transfers the light from the visual field onto the back of the eye. The light entering the retina traverses several layers of neurons before reaching the light-sensitive layer of photoreceptors and being finally absorbed in the pigment layer. There are two kinds of photoreceptors in the retina, cones and rods, and at the centre of the retina is the fovea that has a concentration of cones, so the fovea has higher visual acuity than its periphery. Table 2.1 lists and explains the relevant major parts in the human eye as an easy reference for Figure 2.1. Note that we cannot show the neural layers and photoreceptors of the retina in Figure 2.1 due to the size limitation.

Table 2.1 A list and explanations of human eye and their abbreviations.

Part	Description
cornea	the white outer part of the eye, to cause most of bending (refraction) of the light from objects
iris	the coloured part of the eye, to regulate the amount of light entering the eye by controlling the pupil
lens	the crystal clear part of the eye behind the iris, to focus the light onto the back of the eye
pupil	the opening through which light enters the eye
ciliary muscle	to hold the lens in place and help ...