A method and apparatus for labeling an item using
diffraction grating-based encoded
optical identification elements 8 includes an optical substrate 10 having at least one
diffraction grating 12 disposed therein. The
grating 12 has one or more colocated pitches Λ which represent a unique identification digital code that is detected when illuminated by incident light 24. The incident light 24 may be directed transversely from the side of the substrate 10 (or from an end) with a
narrow band (single
wavelength) or multiple
wavelength source, and the code is represented by a
spatial distribution of light or a
wavelength spectrum, respectively, or a combination thereof. The element 8 can provide a large number of unique codes, e.g., greater than 67 million codes, and can withstand harsh environments. The encoded element 8 may be used to
label any desired item, such as large or small objects, products, solids, powders, liquids, gases, plants, minerals, cells and / or animals, or any combination of or portion of one or more thereof. The
label may be used for many different purposes, such as for sorting, tracking, identification,
verification,
authentication, anti-theft / anti-counterfeit, security / anti-terrorism, or for other purposes. In a manufacturing environment, the elements 8 may be used to track inventory for production information or sales of goods / products.