Dichromated Gelatin (DCG)

a chemical-gelatin mix that produces very bright images in a golden-yellow colour. The images have limited depth but can be viewed in extended light sources of poor quality. See Volume Hologram.


the general process of using a die (a specialised tool to cut or shape material) to shear webs of low-strength materials into the final product, such as holographic labels.


the phenomenon whereby light waves spread out as a result of passing through small apertures whose dimensions are comparable to the wavelength of light. Of particular interest are gratings with line spacings close to the wavelength of light because these have the...

Diffractive Optically Variable Image Device (DOVID)

a generic term which comprises all security devices that are based on the diffraction of light by fine gratings. The different DOVIDs differ in their image resolution, brightness, and their animation capabilities. Examples of DOVIDS include holograms which by...

Dot matrix

a surface relief hologram built up from an array of tiny diffractive gratings arranged at certain angles. The ‘dots’ are a point at which two microscopic beams of laser light meet at an angle and produce an interference pattern. In a dot matrix machine, a...