A method of obtaining a plurality of infrared images of a banknote that involves simultaneously illuminating the banknote with infrared light at a first wavelength and infrared light at a second wavelength, capturing an image of the banknote with an RGB camera, obtaining from both a first output channel signal and a second output channel signal of the RGB camera sensor where the intensity distribution of the infrared light at the first wavelength and the intensity distribution of the infrared light at the second wavelength uses a first calibration coefficient and a second calibration coefficient of the RGB camera sensor, producing separate infrared images of the banknote at the first wavelength and the second wavelength from the respective intensity distributions.

Device for detecting reactive luminescent particles embedded in a substrate or surface having an infrared or ultraviolet illuminator; a near-infrared photodiode sensor; a dark chamber, inside which the illuminator and photodiode sensor are mounted; a logarithm amplifier; an electronic data processor configured to detect the reactive luminescent particles by carrying out the steps of: illuminating the substrate or surface with the illuminator; acquiring the amplified linearized signal captured by the photodiode sensor; detecting the presence of luminescent particles in the substrate or surface from the linearized decay of the acquired signal. A further near-infrared photodiode sensor, a further logarithm amplifier, and a differentiator for obtaining a difference between amplified signals received by each photodiode sensor can be utilized.

A security system, such as a banknote, comprises: i) a substrate, ii) a first ink, which is applied on at least a part of at least one surface of the substrate, wherein the first ink includes at least one IR luminescent dye and/or at least one IR luminescent pigment, and iii) a second non-luminescent ink, which is applied on at least a part of at least one surface of the substrate onto which the first ink is/are applied, wherein the second ink includes at least one non-luminescent IR absorbing pigment and/or a least one non-luminescent IR absorbing dye, wherein the first ink and the second ink at least partially overlap on the at least one surface of the substrate, wherein the second ink is applied in the overlapping area onto the first ink, and wherein the emission spectrum of the first ink and the absorption spectrum of the second ink at least partially overlap.

A security system, such as a banknote, comprises: i) a substrate, ii) a first ink, which is applied on at least a part of at least one surface of the substrate, wherein the first ink includes at least one IR luminescent dye and/or at least one IR luminescent pigment, and iii) a second non-luminescent ink, which is applied on at least a part of at least one surface of the substrate onto which the first ink is/are applied, wherein the second ink includes at least one non-luminescent IR absorbing pigment and/or a least one non-luminescent IR absorbing dye, wherein the first ink and the second ink at least partially overlap on the at least one surface of the substrate, wherein the second ink is applied in the overlapping area onto the first ink, and wherein the emission spectrum of the first ink and the absorption spectrum of the second ink at least partially overlap.

An optical sensor of the present disclosure detects light reflected by a transported sheet and/or light transmitted through the sheet as well as light emitted from the sheet. The optical sensor includes: a light source configured to irradiate a sheet with excitation light and detection light; a controller configured to keep the light source turned off during each of light-off periods after the emission of the excitation light; and a light receiver configured to receive light resulting from reflection of the detection light by a sheet and/or light resulting from transmission of the detection light through the sheet in each of the light-on periods and receive phosphorescence emitted from the sheet in each of the light-off periods. The controller is configured to generate data of one pixel by summing up output values based on respective phosphorescence components received by the light receiver in each of the light-off periods.

A subwavelength grating displaying a colored image exhibiting a color corresponding to a grating period of a subwavelength grating in reflection directions including a specular reflection direction. A relief surface displaying a reflection image in monochromatic reflected light in reflection directions including a direction different from the specular reflection direction. An optical element has a first state in which neither a colored image nor a reflection image is displayed, a second state in which the colored image is mainly displayed, and a third state in which the reflection image is mainly displayed. A plane in which the optical element is disposed and a plane including a line of sight of an observer form an observation angle therebetween. The optical element is observed in any of the first, second and third states according to the observation angle.

A security or identification device comprises a membrane laser structure configured to be optically pumped. The membrane laser structure comprises a flexible emission layer comprising a gain material; and one or more structures formed in or associated with the flexible emission layer and configured to provide optical feedback in the emission layer to produce a laser light output having at least one property representing an identifier.

A security article includes an optical component that includes a plurality of optical channels with a Fano resonance characteristic. An optical channel, of the plurality of optical channels, is configured to pass a first portion of a first set of light beams (that are associated with a first wavelength range) when the first set of light beams falls incident on at least one of a first surface or a second surface of the optical channel, reflect a second portion of the first set of light beams when the first set of light beams falls incident on the first surface of the optical channel, and reflect at least a portion of a second set of light beams (that are associated with a second wavelength range) when the second set of light beams falls incident on the second surface of the optical channel.

A method and associated system for authentication, including irradiating an item including a polymer security thread including a polymer material and a doping material within the polymer material and configured to produce a radiation spectrum in response to the irradiating, the doping material capable of absorbing, scattering, or emitting radiation, and detecting the produced radiation spectrum to confirm the presence of the polymer security thread.

A method and associated system for authentication, including irradiating an item including a polymer security thread including a polymer material and a doping material within the polymer material and configured to produce a radiation spectrum in response to the irradiating, the doping material capable of absorbing, scattering, or emitting radiation, and detecting the produced radiation spectrum to confirm the presence of the polymer security thread.