Mainly rely on its own absorption of light to achieve the purpose of reducing the intensity of sunlight. Different coloring compounds are added to the glass to make sunglasses of different colors, and the wavelengths of light waves they absorb are also different.
It is a metal film coated on the glass lens, which relies on the reflection of the lens to protect the eyes.
It is usually colorless and transparent indoors, and when exposed to sunlight, it quickly turns gray or other colors. The color of this type of glasses can automatically become darker or lighter depending on the strength of the sun. This is because a small amount of silver halide is added to the color-changing lens as a sensitizer, and a trace amount of copper is used as a sensitizer. This automatic adjustment of the light and dark lens can be ground into a lens with a degree of corrective vision, suitable for use in myopia and hyperopia patients. Unfortunately, its degree can't exceed ±3 diopter (commonly known as 300 degrees), because the degree is larger, the thickness of the center and the edge are very different, and the difference in color and shade of the glasses is greatly different.