Photochromic lens is a lens which color changes with the change of external light. It can turn dark quickly under sunlight, and its transmittance goes down dramatically. The stronger the light, the darker the color of the lens, and vice versa. When the lens is put back indoors, the color of the lens can quickly fade back to the original transparent state.
The color change is mainly oriented by the discoloration factor inside the lens. It is a chemical reversible reaction.
Generally speaking, there are three types of photochromic lens production technology: in-mass, spin coating, and dip coating.
Lens made by the way of in-mass production has long and stable prod...