US Patent 10157338 Graphene-based micro-scale identification system

A system for labeling an object uses at least one object label made from a material that absorbs and reflects incident energy uniformly across all wavelengths of incident energy at a ratio proportional to a thickness of the material and that includes a pattern having variations in the thickness of the material along at least one of two orthogonal directions across the label. An interrogator directs a predetermined wavelength of radiation to the at least one label, and a reader to receives reflected radiation from the label at the predetermined wavelength and interprets the reflected radiation to recognize the pattern.