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Holography was invented in 1947 by the Hungarian-British physicist Dennis Gabor, work for which he received the Nobel Prize in Physics in 1971. Pioneering work in the field of physics by other scientists including Mieczyslaw resolved technical issues that previously had prevented advancement. Holography is a technique which enables a light field to be recorded, and reconstructed later when the original light field is no longer present. Rainbow holograms are commonly seen today on credit cards as a security feature and on product packaging. These versions of the rainbow transmission Hologram are commonly formed as surface relief patterns in a plastic film, and they incorporate a reflective aluminum coating that provides the light from "behind" to reconstruct their imagery. Specular holography is a related technique for making three-dimensional imagery by controlling the motion of specularities on a two-dimensional surface. It works by reflectively or refractively manipulating bundles of light rays, whereas Gabor-style holography works by diffractively reconstructing wavefronts. One of the most promising recent advances in the short history of holography has been the mass production of low-cost solid-state lasers, such as those found in millions of DVD recorders and used in other common applications, which are sometimes also useful for holography. These cheap, compact, solid-state lasers can, under some circumstances, compete well with the large, expensive gas lasers previously required to make holograms and are already helping to make holography much more accessible to low-budget researchers, artists and dedicated hobbyists. Though holography is often referred to as 3D photography, this is a misconception. A photograph represents a single fixed image of a scene, whereas a hologram, when illuminated appropriately, re-creates the light which came from the original scene; this can be viewed from different distances and at different orientations just as if the original scene were present. The hologram itself consists of a very fine random pattern, which appears to bear no relationship to the scene which it has recorded. When the object is removed, an observer who looks into the hologram "sees" the same image on his retina as he would have seen when looking at the original scene. This image is often called a virtual image, as it can be seen even though the object is no longer present. The figure shown at the top of this article is an image produced by a camera which is located in front of the developed hologram which is being illuminated with the original reference beam. The camera is focused on the original scene, not on the hologram itself. Making a hologram He object and the reference beams must be able to produce an interference pattern that is stable during the time in which the holographic recording is made. To do this, they must have the same frequency and the same relative phase during this time, that is, they must be mutually coherent. Many laser beams satisfy this condition, and lasers have been used to make holograms since their invention, though the first holograms by Gabor used "quasi-chromatic" light sources. In principle, two separate light sources could be used if the coherence condition could be satisfied, but in practice, a single laser is always used. The medium used to record the fringe pattern must be able to resolve it, and some of the more common media used are listed below. The spacing of the fringes depends on the angle between the object and reference beams. For example, if this angle is 45° and the wavelength of the light is 0.5 µm, the fringe spacing is about 0.7 µm or 1400 lines/mm. A working hologram can be obtained even if not all the fringes are resolved, but the resolution of the image is reduced as the resolution of the recording medium decreases. Mechanical stability is also very important when making a hologram. If the phase of one beam changes with respect to the other due to vibration or air movement, the fringe pattern moves across the field of view. If the fringe pattern moves by one or more fringe spacings, the light intensity is averaged out, and no holographic recording is obtained. A relative path change of half a wavelength shifts the interference pattern by one fringe. Thus, the stability requirement is very stringent. Pavan, for information on Hologram, Hologram Sticker, Security Hologram, Hologram Exporter, Scratched Hologram,Hologram and Paper Label,Hot Stamped Hologram Labels and Hologram and Hologram Manufacturer in Delhi.Please visit our site : http://www.3rdeyeholographicsolutions.com/
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