An optically detectable marker including luminescent dopants and system and method for reading such markers

An optically detectable marker comprising a matrix material, which is doped with a plurality of individual luminescent dopants and comprising at least a first luminescent dopant, a second luminescent dopant, and a third luminescent dopant, wherein

• the first luminescent dopant comprises a first unique absorption band such that the first luminescent dopant may be excited by illumination of a first wavelength, and wherein the first luminescent dopant is distributed in the matrix material so as to form a first spatial pattern in the matrix material, which first spatial pattern may be optically detected by illuminating the optically detectable marker by a light source illuminating light of the first wavelength,
• the second luminescent dopant comprises a second unique absorption band such that the second luminescent dopant may be excited by illumination of a second wavelength, different from the first wavelength, and wherein the second luminescent dopant is distributed in the matrix material so as to form a second spatial pattern in the matrix material, which second spatial pattern may be optically detected by illuminating the optically detectable marker by a light source illuminating light of the second wavelength, and
• the third luminescent dopant comprises a third unique absorption band such that the third luminescent dopant may be excited by illumination of a third wavelength, different from the first and second wavelength, and wherein the third luminescent dopant is distributed in the matrix material so as to form a third spatial pattern in the matrix material, which third spatial pattern may be optically detected by illuminating the security tag by a light source illuminating light of the third wavelength, wherein
• the first wavelength, the second wavelength, and the third wavelength are located within 50 nm of each other, advantageously between 445 nm and 495 nm.

A method of reading out an optically detectable marker, wherein

• the optically detectable marker comprises a matrix material, which is doped with a plurality of individual luminescent dopants comprising at least:
• a first luminescent dopants comprising a first unique absorption band such that the first luminescent dopants may be excited by illumination of a first wavelength, wherein the first luminescent dopants are arranged in a first spatial pattern in the optically detectable marker;
• and
• a second luminescent dopants comprising a second unique absorption band such that the second luminescent dopants may be excited by illumination of a second wavelength, wherein the second luminescent dopants are arranged in a second spatial pattern in the optically detectable marker, wherein the method comprises the steps of:
• a) optically exciting the first luminescent dopants by illuminating the optically detectable marker with light of the first wavelength,
• b) reading out the first spatial pattern,
• c) optically exciting the second luminescent dopants by illuminating the optically detectable marker with light of the second wavelength, and
• d) reading out the second spatial pattern.

A method of reading out an optically detectable marker, wherein

• the optically detectable marker comprises a matrix material, which is doped with a plurality of individual luminescent dopants comprising at least:
• a first luminescent dopants comprising a first unique absorption band such that the first luminescent dopants may be excited by illumination of a first wavelength, wherein the first luminescent dopants are arranged in a first spatial pattern in the optically detectable marker;
• a second luminescent dopants comprising a second unique absorption band such that the second luminescent dopants may be excited by illumination of a second wavelength, wherein the second luminescent dopants are arranged in a second spatial pattern in the optically detectable marker;
• and
• a third luminescent dopants comprising a third unique absorption band such that the third luminescent dopants may be excited by illumination of a third wavelength, wherein the third luminescent dopants are arranged in a third spatial pattern in the optically detectable marker
• wherein the method comprises the steps of:
• a) optically exciting the first luminescent dopants by illuminating the optically detectable marker with light of the first wavelength,
• b) reading out the first spatial pattern,
• c) optically exciting the second luminescent dopants by illuminating the optically detectable marker with light of the second wavelength,
• d) reading out the second spatial pattern,
• e) optically exciting the third luminescent dopants by illuminating the optically detectable marker with light of the third wavelength, and
• f) reading out the third spatial pattern,
• wherein the first wavelength, the second wavelength, and the third wavelength are located within 50 nm of each other, advantageously between 445 nm and 495 nm.