What is glare? When there are extremely bright objects or strong luminance contrast in the field of view, it will cause eye discomfort or visual weakening. This is called glare. In other words, when the brightness exceeds the degree to which the eyes can adapt, people feel irritated. Actually, glare phenomena are often encountered in our life, such as the eye-blinding car headlights at night on a dark road, or sun glare on a sunny day on the mountain.

Glare can be categorized into direct glare and reflected glare. Direct glare is the glare produced by a high luminance light source that is not adequately shaded in the field of view, while reflected glare is produced by a shiny surface illuminated in the field of view.

Glare is one of the causes that lead to visual fatigue. Inappropriate location and height of lamp installation may cause a home lighting design that is prone to cause glare to human eyes, as in, human eyes will unavoidably look directly at the light source (see Fig. 1.6.1), while scientific optical scheme and professional lighting design can effectively avoid this problem. Especially when there are children or elderly people at home who are more sensitive to glare, we should try to reduce the possibility of glare.