What is a hologram
8 12 2007WHAT IS HOLOGRAPHY? The physical basics of holography are optics of waves, especially interference and diffraction.
“Definition of Holography” - A method of recording (usually photographically) a three-dimensional image of an object. Normally laser light is used, but other radiations (including sound) can give holograms. The object is illuminated with laser light and the reflected light from the object is combined with direct light from the source, to give an interference pattern on a photographic plate. A three-dimensional image of the object is reconstructed by illuminating the interference pattern with the original light. The pattern includes information about phase and direction as well as intensity and color.
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The hologram is a true, three-dimensional record of the original object. It contains depth and parallax, which is the ability to see around the object to objects placed behind. The word hologram is composed of the Greek terms, “holos” for “whole view”; and gram, meaning “written”. A hologram is a three-dimensional record of the positive interference of laser light waves. A technical term for holography is wave front reconstruction. In holography, we record the positive interference of matching wave fronts of laser light. This three-dimensional record is formed as a diffraction pattern; a series of very fine lines, or concentric circles. This diffraction grating bends the viewing light back onto the path of the original recording wave fronts of laser light. The three-dimensional version of the object - the hologram – is reconstructed as light. |
Since their introduction on payment cards in the early 1980’s, holograms have become one of the most common overt or public security features on value documents and branded goods, their presence both indicating the authenticity of these items and providing a powerful deterrent to counterfeiting. Today, Holograms are used by more than 90 issuing authorities on nearly 250 bank notes denominations worldwide. They are used in many currencies such as EURO, Canadian Dollar, Brazilian Real, British Pound, Japanese Yen, South Korean Won etc. In
