Invisible Ink

Invisible ink (UV/IR ink) is undetectable under normal lighting but fluoresces or reflects under ultraviolet or infrared light. For QR codes, it enables dual-layer authentication: consumers scan the visible QR code with smartphones while manufacturers verify authenticity using UV readers on the hidden code.

It also preserves aesthetics on luxury products and artwork by embedding information without altering appearance. The same principle underlies banknote anti-counterfeiting technology.