It refers to a type of visible light with a wavelength between 380nm and 500nm, among which blue light between 380nm and 445nm is called harmful blue light. It has extremely high energy and penetrability, and can penetrate the human lens directly to the retina, causing pigment cell decay or death, leading to macular degeneration. Moreover, during the penetration process, the absorption of some blue light by the crystalline body can also increase the occurrence of cataracts. The blue light between 445nm and 500nm is called beneficial blue light, and appropriate irradiation can regulate the secretion of hormones in the human body, which has a positive effect on assisting sleep and regulating metabolism.