METHOD FOR FORMING AN IDENTIFICATION MARK FOR MARKING VALUABLE ITEMS AND A VALUABLE ITEM

摘要

A surface to be marked is polished and a processing layer is applied thereto, via which layer an image of a mark which can be rendered optically visible in reflected light at a diffraction angle is made on the aforesaid surface in the form of a diffraction structure. The structure is arranged in the manner of a reflective phase diffraction grating and is formed by ion etching the surface in conjunction with the structure of the processing layer. Before the mark is formed on the surface, a diffraction structure in the form of a regular microrelief with a sinusoidal profile is formed in the processing layer by ablation of the material thereof with a pulse of interfering beams of coherent laser radiation. As a result, the diffraction structure is formed in the processing layer with holographic precision. The structure is formed by the partial removal of the thickness of the processing layer material. Images of the mark in the form of a diffraction structure on the surface to be marked are also formed with holographic precision by interfering coherent laser beams. The diffraction structure formed in the processing layer is exposed to an ion beam.