A hologram is a physical structure that uses light diffraction to create images, including three-dimensional ones.
The main difference between a hologram and a photograph is that holography is a recording of a light field, not an image formed by a lens. A holographic medium, i.e. an object formed by a holographic process (which in itself can be called a hologram), is usually not perceived visually, unlike a photographic image, when viewed in diffused ambient light. This is the coding of the light field as an interference pattern of changes in opacity, density, or surface profile of the photographic environment. Under proper lighting, the interference pattern “diffuses” the light to reproduce accurately the original light field, and the objects in it show visual three-dimensional components, such as parallax and perspective, that actually change relative to the observer’s position.
In its pure form, holography requires the use of laser light to illuminate an object and to view the finished hologram. The microscopic level of detail throughout the recorded scene can be reproduced. However, in common practice, significant compromises in image quality are made to eliminate the need for laser lighting to view the hologram and in some cases for its manufacture. Holograms can now also be completely generated on a computer to display objects or scenes that never existed.
Holography differs from lenticular and other previous technologies of the autostereoscopic 3D display, which can give superficially similar results but are based on conventional images of optical elements.
In recent decades, holograms have become widely used to protect securities, documents, and goods in the form of holographic security elements (HSE). Holographic security features are used as one of the degrees of protection against counterfeiting in combination with printing and other types of protection. HSEs are also used on their own to protect against counterfeiting or as means of access control (various holographic seals, etc.).
The subject of hologram examination is established in the manner prescribed by procedural law factual data related to the manufacture and use of holograms, which are obtained based on special knowledge in the field of forensic holograms and intermediate products of holographic production.
The objects of hologram examination are:
- holographic security elements;
- holograms which are used as means of control;
- image, visual holograms;
- intermediate products of holographic production, such as software, photo templates, and models, primary holograms, relief-phase holograms-originals, master hologram matrices, metal matrices for hologram duplication, etc.
Tasks to be solved during hologram examination
The main tasks of hologram examination are:
- hologram type setting;
- setting levels of hologram protection;
- establishing the identity of the hologram or the correspondence of the hologram to its description (terms of reference, passport to the hologram);
- determination of the holograms provided for the examination from the provided or other matrices;
- establishing the correspondence of the provided photo templates and layouts with the image of the logo elements, which are reproduced by the hologram;
- establishing the correspondence of the original of the primary hologram to the rainbow hologram;
- compliance with the provided software and graphic file of the hologram with the synthesized hologram.
Issues to be solved during the hologram examination
- How are the holograms provided for the examination made?
- Do the holograms provided for examination correspond to the samples and technical descriptions of holograms entered in the Unified Register of Holographic Security Elements? If not, how is it made?
- With the help of the provided or other matrices, were the holograms provided for the examination reproduced?
- Has the hologram been made using holographic intermediate products provided for examination?
- Have the holograms provided for the examination undergone any chemical, mechanical or other changes, if so, which ones?
- Which of the holograms submitted for research have the highest level of protection against counterfeiting?
- How is the individual marking applied to the hologram?