A method for marking a product (1) with a photoluminescent mark, said mark comprising a photoluminescent portion (10) which is transparent under normal light conditions and revealed by photoluminescence under UV illumination, said mark further comprising a non photoluminescent portion (9) which is transparent under normal light conditions as well as under UV illumination, said method comprising: deposing on said product a stack, said stack comprising alternatively layers (2, 4), such as AlN, with a thickness of less than 1 micron and layers (3) of a second material, such as GaN, with a thickness of less than 10 nm; raising the transparency of said non photoluminescent portion (10) with a deposition of transparent material (6) or incorporation of ions into said non photoluminescent portions.

A method for marking a product (1) with a photoluminescent mark, said mark comprising a photoluminescent portion (10) which is transparent under normal light conditions and revealed by photoluminescence under UV illumination, said mark further comprising a non photoluminescent portion (9) which is transparent under normal light conditions as well as under UV illumination, said method comprising: deposing on said product a stack, said stack comprising alternatively layers (2, 4), such as AlN, with a thickness of less than 1 micron and layers (3) of a second material, such as GaN, with a thickness of less than 10 nm; raising the transparency of said non photoluminescent portion (10) with a deposition of transparent material (6) or incorporation of ions into said non photoluminescent portions.

In order to perform high-accuracy authentication of a forgery prevention medium having a forgery prevention structure, the forgery prevention structure provided in or on the medium for performing authentication of the medium is formed so as to include a mixed area with a plurality of kinds of resonator structures each of which resonates with a terahertz electromagnetic wave having a different polarization direction.

In order to perform high-accuracy authentication of a forgery prevention medium having a forgery prevention structure, a forgery prevention structure provided in or on a medium for performing authentication of the medium includes: an anisotropic resonator that resonates in response to being irradiated with a first terahertz electromagnetic wave at a first frequency, a transmissivity of the first terahertz electromagnetic wave changes with a polarization direction of the first terahertz electromagnetic wave, and an isotropic resonator that resonates in response to be irradiated with a second terahertz electromagnetic wave at a second frequency, a transmissivity of the second terahertz electromagnetic wave does not change with a polarization direction of the second terahertz electromagnetic wave.

The present disclosure relates to a security structure including a non-opaque, preferably transparent, substrate. The substrate supports metal elements forming a revealing pattern. The metal is thin enough for the metal to be non-opaque. A lacquer is placed at least partially, preferably exactly, on top of the metal elements. The lacquer may be in contact with the metal elements.

A security device is provided including a first pattern of elements and a second, overlapping, pattern of elements spaced by a transparent layer, the first and second patterns in combination obstructing the passage of light transmitted to a viewer through the device to a varying degree depending on the viewing position. The first and second patterns of elements are configured such that a first region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a first tilt axis, and a second region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a second tilt axis which is not parallel to the first tilt axis.

A security device is provided including a first pattern of elements and a second, overlapping, pattern of elements spaced by a transparent layer, the first and second patterns in combination obstructing the passage of light transmitted to a viewer through the device to a varying degree depending on the viewing position. The first and second patterns of elements are configured such that a first region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a first tilt axis, and a second region of the device exhibits a maximum change in the degree of obstruction when the device is tilted relative to the viewer about a second tilt axis which is not parallel to the first tilt axis.

A security foil including at least a carrier layer, a protection layer and a functional layer. The functional layer has at least one clearance. The security foil includes a printed layer arranged within and partially filling the clearance and adjacent to and non-overlapping with the functional layer. The printed layer represents a marking. Also disclosed is a method for producing such a security foil from an original foil by selectively removing parts of the functional layer of the original foil to produce the clearance in the functional layer and by printing a marking within the clearance to produce the printed layer adjacent to and non-overlapping with the functional layer.

A security foil including at least a carrier layer, a protection layer and a functional layer. The functional layer has at least one clearance. The security foil includes a printed layer arranged within and partially filling the clearance and adjacent to and non-overlapping with the functional layer. The printed layer represents a marking. Also disclosed is a method for producing such a security foil from an original foil by selectively removing parts of the functional layer of the original foil to produce the clearance in the functional layer and by printing a marking within the clearance to produce the printed layer adjacent to and non-overlapping with the functional layer.

An authentication system includes an object including an authentication hologram disposed over an area of a surface of the object. The authentication hologram is defined by a pattern of reflective material and includes latent authentication information. The system includes a computer-readable medium including program instructions for execution by one or more processors. The program instructions are executable by the one or more processors to: (i) receive, from an image capture device, a digital image of the authentication hologram, wherein light reflected by the reflective material is captured in the digital image of the authentication hologram, and (ii) detect the latent authentication information in the digital image of the authentication hologram, wherein an effect of the reflected light is reduced to detect the latent authentication information.