Fotokromic

Fotokromic is a term derived from photography and relates to light-sensitive materials and processes. In a broad sense, it refers to the phenomenon where certain substances change color or appearance when exposed to light, particularly ultraviolet (UV) radiation. This change is usually reversible, meaning the material returns to its original state when the light source is removed.

The most common application of fotokromic technology is in eyeglass lenses, often referred to as photochromic lenses. These lenses contain special compounds that react to UV light. When exposed to sunlight, the compounds darken, reducing the amount of light that reaches the wearer's eyes and providing a sunglasses-like effect. Indoors, or when the UV light source is absent, the lenses gradually become clear again. This offers convenience by eliminating the need to switch between regular glasses and sunglasses.

Beyond eyewear, fotokromic principles are explored in various fields, including security features on documents and currency, specialty inks and dyes, and even in some types of sensors. The specific compounds used and the mechanism of color change can vary, but the underlying concept of light-induced reversible transformation remains central to the fotokromic effect. Research continues to develop new materials with enhanced sensitivity, faster response times, and a wider range of color transitions for diverse applications.