Glossary

A printing press that requires sheets (as opposed to continuous rolls or webs) to be fed into the press prior to printing.

The first step in mass hologram production is to create embossing plates called shims. A shim is made from a thin plate of metal, usually nickel, which is attached to the embossing cylinder. A ‘master’ or ‘mother’ shim is produced by an electro-deposition process whereby the plate with recombined images is immersed into a galvanic tank and metallic nickel is caused to accumulate on its surface. The mother shim is then usually used to prepare ‘daughter’ shims for the mechanical embossing process.

At some point in the hologram replication process, one or more metal shims need to be mounted around the circumference of the embossing cylinder. The point at which the shims join often produces a visible line in the resulting embossed film. This line is most problematic where the finished result is intended to be a continuous pattern. Those skilled in the art have developed procedures which successfully minimise or even eliminate such optical discontinuities in the final product.

A cellular (or mobile) telephone with an integrated computer, camera, and other features not originally associated with a mobile phone.

The illegal transportation of objects, substances, information or people across an international border, in violation of applicable laws or other regulations, often to avoid taxation.

An advanced Raman spectroscopy technique used to analyse chemical compositions beneath the surface of a sample without needing to physically cut or otherwise disturb it. In traditional Raman spectroscopy, the laser light and detector are aligned directly on the sample surface, which only provides surface-level information. SORS, however, works by offsetting the detector to capture Raman signals from deeper within the sample.

Produced by the mutual interference of a set of coherent wavefronts. Speckle patterns have been used in a variety of applications in microscopy, imaging, optical manipulation and document biometrics (or fingerprinting). They typically occur in diffuse reflections of monochromatic light such as laser light.

The study of the absorption and emission of light and other radiation by matter. Involves the splitting of light (or more precisely electromagnetic radiation) into its constituent wavelengths (a spectrum), which is done in much the same way as a prism splitting light into a rainbow of colours. More recently, the definition has been expanded to include the study of interactions between particles such as electrons, protons, and ions, as well as their interaction with other particles as a function of their collision energy.

A type of hologram created from sequential images of a piece of movie footage. Each frame of the movie is converted into a vertical slit image and stacked against another slit image of the adjacent frame. The result is a hologram which, when the viewing angle changes from side to side, produces the same image motion as the movie footage, given that the frames are seen one after another.

The material or base – eg. paper or film – on which an image is printed or a feature applied.

Security features that are applied to the surface of a banknote or secure document (eg. foil stripes, foil or optically variable ink patches, iridescent coatings) as opposed to features that are created through combinations of printing techniques or features integrated into the substrate, such as threads, fibres and watermarks.

The most ubiquitous and popular type of hologram, mainly exhibiting a characteristic rainbow-coloured pattern. The details of the hologram image are recorded as an interference pattern on the surface (rather than through the volume) of the material. The value of surface relief holograms is that they can be mass-produced mechanically by embossing or casting a relief pattern or image into an inexpensive thermoplastic film or viscous coating on a film or paper.

Molecular or microscopic particle that can be organic or inorganic in composition and exhibit specific and unique physical, biological, chemical or spectroscopic properties. Added in very low concentration to substrates or ink as a covert authentication feature.

A device such as a seal or closure that demonstrates that a product or packaging has been (fraudulently) opened or otherwise accessed prior to its proper use.

The superposition of two or more lightwaves, causing their mutual amplification or reduction depending on how the phases of these waves are related to each other.

The amount by which a measurement or calculation might change and still be acceptable.

A hologram that can be seen by light passing through the material containing the holographic recording. Ironically, all metallised, embossed holograms are transmission holograms but are conveniently seen by reflected light because the incident light passes through the diffractive grating and is reflected back by the mirror coated on the reverse side.

The passing of light through an object (as opposed to light reflecting off or absorbed by an object). Watermarks in security paper are usually viewed in transmitted light by holding the paper up to the light source.

A photochemical process in which high-intensity ultraviolet light is used to instantly cure or ‘dry’ inks, coatings or adhesives.

Electromagnetic waves located beyond the blue end of the visible light spectrum, commonly defined within the wavelength range of 100nm-400nm. UV light is often used to analyse secure documents and banknotes, and security features such as paper brightness, fluorescent inks and fluorescent fibres. UV lamps used in shops and banks to verify banknotes operate at a wavelength of 365nm.

A process for creating a layer of metal on a substrate. Involves heating the metal target material until it vapourises inside a vacuum chamber. This allows the metal vapour to condensate and form a thin layer over the top of the substrate. Vacuum deposition is a common method of producing security threads.

The use of digital print processes to apply personalised and serialised information, such as unique identifiers and barcodes, to products and documents.

The process of verifying specific identity, document or product attributes, or determining the authenticity of credentials in order to give authorisation for a particular service.

A technology that immerses the viewer in a computer-generated simulation of a 3D scene and allows them to interact with it using a digital interface. VR devices often use the term ‘hologram’ to describe the heightened sense of realism they provide.

Wavelengths within the visible spectrum of 380nm-740nm.

Refers to holograms where the thickness of the recording material is much larger than the wavelength of light used for recording. One of the most common types of hologram (together with surface relief holograms), volume holograms are mass-produced through optical copying of a master hologram onto photopolymer materials, so they retain more of the optical properties of the master than the mechanical, surface relief process. This allows them to be used for classical holograms which are fully 3D images, displaying depth and both vertical and horizontal parallax. Volume holograms are either monochromatic or two-colour, with a distinctly different appearance to rainbow holograms, which are based on diffraction.

A property of electromagnetic radiation that denotes the distance between waves of light.

A mathematical means for performing a signal analysis when signal frequency varies over time.

A continous roll of flexible material, usually paper, foil, film or laminate in a roll form.

A paper-embedded security thread surfacing at regular intervals in a document and full visible when viewed in transmission.

A device comprising gratings of less than the wavelength of visible light (ie. below 400nm). Can be produced by embossing and displays unique colour effects depending on the device’s plane of rotation.