Abstract: The inventions relate to means for protecting precious and semiprecious stones. In order to provide for an increase in the contrast of an image for a wide range of sizes, an article 3 is mounted and fixed on a positioning means 4 so as to ensure that the center of a surface being examined coincides with the optical axis of a means of an optical system with the possibility of visualizing and observing a mark in reflected rays of light by means of adjusting the visualization means of the optical system. The distance between the center of the surface 2 being examined of the article 3 and the focus F of the eyepiece 12 of the optical system is provided with a constant value for the set range of sizes of the articles 3 being detected.

Abstract: The invention relates to read/write methods for information hidden from visual perception and can be used to visualize hidden images of identification of an object, which provide protection against unauthorized reproduction. The surface of the object is first polished. An optically invisible marking image is formed on the polished surface by modifying at least one area of the surface, which changes the surface energy of modified sites. Said marking image is visualized by establishing a meta-stable environment in the vicinity of the aforementioned surface of the object. The marking image is produced in the form of distinguished structures formed by stable phase particles of the meta-stable environment at the sites of the object surface having different surface energy. Prior to performing a visualization process of the optically invisible marking image, the surface containing the modified areas is electrically-charged and cleaned by friction.

Abstract: The disclosure relates to methods of marking valuable items, mainly precious stones and in particular, cut diamonds, and can be used for their identification. To implement the marking procedure, the identification surface of the product is first polished. A marking image, optically visible in reflected light is formed on the polished surface by modifying the identification area of said surface by means of a guided ion beam with a given ion energy. In the modification process, the composition of the surface layer is modified with the possibility of changing the optical properties of modified sites in relation to the optical properties of untreated sites of the identification surface.

Abstract: The utility model can be used to visualize hidden images (marks) that are used to identify the object, thereby providing protection against forgery. The device includes means for cooling of the viewed object (VO), the mirror-like surface (MS) of which includes an optically invisible marking image formed by modifying an area of MS by chaining the surface energy of the modified area. Said optically invisible marking image is characterized by the possibility of visualization through the establishment of a meta-stable environment of water vapor in the area of the MS of the object in the process of cooling VO. A visually perceptible image of the optically invisible mark is obtained in the form of distinguished structures formed by stable phase particles of the meta-stable environment at the sites of the MS of VO having different surface energy. The cooling device contains a designated placement location for VO is embodied in the form of Peltier element realizing the Peltier effect.