Glossary

The complete group of waves that range in frequency from radio waves to gamma rays, but all travel at the speed of light.

The technique of scanning a focused beam of electrons to draw custom shapes on a surface covered with an electron-sensitive film called a resist. The whole origination process is undertaken in a vacuum chamber where the e-beam writes onto the resist plate. This is sometimes referred to as a direct write process. It is used to create holographic images.

The transfer of a raised pattern from a hard plate to a softer material. This mechanical transfer (which can be made through a seal, stamp or die) is usually facilitated by means of heat and always with pressure.

A framework used to assess an organisation’s business practices and performance on various sustainability and ethical issues.

Part of the qualification process to receive a tender document. The buyer (eg. a government organisation) is requesting a provider to express an interest in providing goods and services for a project.

A black rectangle printed on the edge of labels and other printed materials, which is read by a machine to locate where one label starts and the next ends. 

An optically variable element visually perceived as an image hovering or floating in space above or below a document’s surface.

A material comprising a polyester carrier with one or more coatings, a release layer and an adhesive layer. The foil is transferred – generally by heat – onto paper, and the carrier is stripped away, leaving the coating bonded to the substrate by the adhesive. This coating can be plain or imaged, monochrome or coloured, colour-shifting, iridescent, metallised, holographic, etc. Also known as hot stamping or transfer foil. Foils are generally applied to banknotes as a continuous stripe (typically measuring 6-10mm wide) or a patch (typically square, circular or elliptical).

Security feature reserved for special departments or officials. Special tools or laboratories are required to reveal their presence and characteristics. The presence and nature of these features are generally kept a closely guarded secret and they are typically used after an enforcement raid to provide definitive proof of the authenticity of a product or document. Such proof can be used, if necessary, as evidence in a court of law.

Capable of being broken. Refers to security labels or tax stamps which break up when removed or tampered with.

A subset of artificial intelligence that focuses on creating new content, such as text, images, audio, or video, by learning patterns from existing data. Common examples include language models like GPT (which powers ChatGPT) or image generation models like DALL-E. Unlike agentic AI, generative AI operates under user prompts and can’t perform tasks on its own initiative.

An array of parallel lines with spacing comparable to wavelengths of light. The array has the ability to split white light into a rainbow because the different wavelengths are bent, or diffracted, by different amounts. Such gratings were originally produced by using a diamond to rule closely spaced lines onto glass, but they are now more often produced by optical interference.

The refractive index of a material is a dimensionless number that describes how fast light travels through the material. In situations where a transparent hologram is required, for instance as a laminate to cover the variable data of a passport or other ID document, instead of coating the holographic image with a metallic film, a transparent coating is made using a material with a high refractive index. The HRI materials used in this process are typically oxides (eg. titanium dioxide) or sulphides (eg. zinc sulphide). In this way, the light diffracted by the hologram can be seen, as can the variable data underneath.

The term ‘hologram’ is derived from two Greek words: ‘holos’ meaning whole or complete and ‘graphos’ meaning an image. The term therefore describes a recorded image which is complete, in that it shows, through the diffraction of light, the whole volumetric space of the image – with depth, colour and movement. This is in contrast to a conventional picture, painting or photograph which displays an object from a single viewpoint only.

A pre-recorded image that is played back as a projection under controlled lighting and audience conditions.

An optical device that uses diffraction to shape a wavefront, as opposed to a refractive optical element (using materials with differing refractive indexes) that depends on refraction.

A constructed box or theatre rigging used to create a holopresence effect.

Real-time transmitted realistic images that appear solid to the viewer and that the viewer can interact with.

A method of transferring a foil from a polyester carrier to paper or other substrate through the combination of heat and pressure. Hot foil stamping can be used to support holographic anda other optically variable images which can be transferred, using heat and pressure, onto another substrate such as paper or plastic. The layers containing the image are extremely thin, typically 5-6 microns. Therefore, they need to be supported on a thicker material such as 19-micron thick polyester. The action of stamping the foil with a heated die causes a ‘release’ layer between the image and polyester support to melt, while simultaneously softening an adhesive ‘size’ coating. These combined effects allow the image to leave the polyester support and adhere to its new location.

An adhesive that is solid at room temperature and becomes liquid when heated. Used to bond two surfaces when cool.

The production, distribution or sale of counterfeit, adulterated or diverted goods via illegal and unregulated channels. Also includes the evasion of taxes on legally produced goods.

The light that emanates from a defined light source, such as the sun or a lightbulb, and illuminates an object.

The part of the electromagnetic spectrum between 700nm and 1.0mm wavelength. IR light lies immediately beyond red visible light and is therefore invisible to the naked eye. IR light is used in detectors and special equipment to detect security features of banknotes and other documents.

The result of the interaction between two superposing waves. Interference pigment flakes are used in colour-shifting inks, and interference foils with colour-shifting properties also exist.

An independent, non-governmental international organisation with a membership of 165 national standards bodies. Through its members, ISO brings together experts to share knowledge and develop voluntary, consensus-based, market-relevant international standards that support innovation and provide solutions to global challenges.

The ability of some materials to create rainbow effects when they reflect white light. Pearls, oil films on water and bubbles all show iridescence. The effect can be created with foils, ink, and laminates to create optically variable devices.

An ISO guidance standard for performance criteria for authentication solutions used to combat counterfeiting of material goods. This standard was revised under a new number: ISO 22383:2020.

An ISO compliance standard specifying requirements for a security printing management system for security printers. The certifying organisation behind 14298 is Intergraf.

An ISO guidance standard for the selection and performance evaluation of authentication solutions for material goods.

An ISO guidance standard for securing physical documents.

An adjective whose roots in the Greek word ‘kinesis’ indicate motion. A holographic image which displays movement of form or colour is said to be kinetic. Often, such images are patterns rather than objects. The patterns can be made up of fine lines or graphic elements and appear to scintillate when moved.

A tamper-resistant feature employing a die-cutting process whereby adhesive-backed foils or papers are cut through, but the laminated backing paper is not.

An acronym of ‘light amplification by stimulated emission of radiation’, a device that produces coherent light by stimulated emission of radiation.

Pictures and text are engraved in plastic laminates or cards by means of a laser. In the laser engraving process the data are written by blackening (carbonising) laser-sensitive foils. Using different photo-sensitive materials, colours can also be obtained.

An image formed by parallel straight relief strokes perpendicular to background strokes. The image is almost invisible in incidental white light at a right angle. It is visualised as an achromatic image in sliding white light at an acute angle of observation due to the shadow cast by the relief strokes. The background and image are applied by means of intaglio and have the same colour and stroke density.

A latent image formed by multicolour relief strokes. A latent multicolour image is slightly visible in white light. It is visualised as a chromatic image under oblique light. Every chromatic element of the image changes colour when rotating the document around the vertical axe without changing the angle of observation. Background strokes are applied by offset and relief lines by intaglio.

A latent image that has been fragmented and encoded according to a special algorithm. The image is visualised via a lenticular decoding device.

An array of lenses, designed so that when viewed from slightly different angles reveal different parts of an image. The most common example are the lenses used in lenticular printing to give an illusion of depth, or to make images that appear to change or move according to the viewing angle.

A multistep process consisting of creating a lenticular image from at least two existing images, and combining it with a lenticular lens. This process can be used to create various frames of animation (for a motion effect), offsetting the various layers at different increments (for a 3D effect), or simply to show a set of alternate images which may appear to transform into each other.

A commonly used means of grading security features created by the European Central Bank and adopted for use across the banknote industry. Level 1 refers to features that can be verified by the public, untrained examiners or specialist examiners with the naked eye. Level 2 refers to semicovert features that require some form of reading device or tool to be authenticated. They are typically deployed for use by retailers, cashiers and inspectors but are also detected by sensors in machines (the ECB defines Level 2a, 2b and 2c). Level 3 refers to covert features, generally rare chemicals or compounds that can only be identified by sensors in high speed processing machine verification used in cash centres. Level 4 authentication uses forensic examination to verify banknotes and is used solely by central banks/police.

A collective term for the effects of colour change or other visible characteristics under different sources of illumination.

An umbrella term for solving problems for which development of algorithms by human programmers would be cost-prohibitive, and instead the problems are solved by helping machines ‘discover’ their ‘own’ algorithms, without needing to be explicitly told what to do by any human-developed algorithms. While artificial intelligence encompasses the idea of a machine that can mimic human intelligence, machine learning does not. Machine learning aims to teach a machine how to perform a specific task and provide accurate results by identifying patterns.

A security feature requiring an instrument to verify its presence or data content.

The ability of a computer to see. The technology and methods used to provide imaging-based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry.

An analytical technique to quantify known materials and identify unknown compounds within a sample and elucidate the structure and chemical properties of different molecules.

The coating of films or surfaces with a very thin layer of metal using a metal deposition technique. Metallisation is what gives holograms their silver or similar metallic appearance.

Thin 2D metamaterial layers that allow or inhibit the propagation of electromagnetic waves in desired directions.

Small lenses, typically only a few microns in size.

Tiny microscopic mirrors created using origination techniques similar to those used for diffractive OVDs (optically variable devices). Micromirrors reflect light in a specific manner defined by the size and orientation of the mirrors.

A unit of measurement commonly used in authentication when referring to the thickness or gauge of physical substrates and features. One micron is equal to one millionth (10-6) of a metre.