Valuable document e.g. credit card, safety marking testing method, involves producing diffraction structure with multi-photon absorption under application of ultra short pulses of femto-second laser inside transparent polymer

摘要

The method involves producing a diffraction structure with a multi-photon absorption under application of ultra short pulses of a femto-second laser (1) inside a transparent polymer and reading the structure with the laser. The structure is produced by refractive index change of the laser. The read structure is compared with a reference image.