Patent ID: 7874495

Claim:
A substantially visibly transparent optically readable tag formed on a substrate, the tag comprising: an array of machine-readable data bits, each data bit having one of two or more optically contrasting appearances, wherein one of the two or more optically contrasting appearances is defined by a first bit value structure comprising a higher reflectance than transmittance at one or more infrared wavelengths greater than 750 nm and a higher transmittance than reflectance at visible wavelengths less than 750 nm, the first bit value structure having a transmittance of at least 60% for visible wavelengths less than 750 nm; and wherein another of the two or more optically contrasting appearances is defined by a second bit value structure comprising a higher absorbance than transmittance at one or more infrared wavelengths greater than 750 nm and a higher transmittance than absorbance at visible wavelengths less than 750 nm such that all data bits have a higher transmittance at visible wavelengths less than 750 nm than at the one or more infrared wavelengths greater than 750 nm.