Holograms: Images Of The Future

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Holograms: Images of the Future

Faced with a growing number of fake credit cards, Visa and Mastercard in the early eighties decided to print holograms of their individual seals on the credit cards. When there was an alarming increase in fake driver's licences, the California Department of Motor Vehicles incorporated a hologram of the seal of the State on all driver's licences. Scientists at several laboratories are using holograms to improve imaging of cells and tissues of plants and other biological systems. Rock videos are now routinely produced with amazingly real graphics, thanks to advances in holography and computer generated graphics. These are but some of the examples of how holograms, or "3-D pictures" are revolutionizing several areas of technology.

In 1947, a Hungarian born physicist, Dennis Gabor, working at the Imperial College of Science and Technology in London, discovered a technique for photography, which had the potential for 3- dimensional effects. In the next few years not only did he develop the technique systematically, (including its use in his field of interest namely electron microscopy) but also coined the word hologram from the Greek holos (whole) and gramma (a letter). Though a lot of work on holography went on in the West and in the erstwhile Soviet Union, the technology needed for the production of quality holograms was not available and so the interest in holography was restricted to scientific laboratories.

All this changed in the sixties with the invention of the other landmark technology of the late twentieth century: Lasers. Laser light has certain remarkable properties which make it indispensable for producing holograms. It is exceptionally monochromatic i.e a red laser beam has only red light as opposed to ordinary red light which is a mixture of several colors with red dominating. It is very coherent and can be transmitted over great distances without the beam spreading. In fact, in a now classic experiment, lasers were used to find out the distance to the moon because a laser beam from earth can travel all the way to the moon without any appreciable spreading, and then be reflected back!

Holography, photography by wave front reconstruction, lens less photography; all these synonyms capture only a part of the "depth" of this fascinating technology. It is similar to ordinary photography and yet fundamentally different from it. In photographing an object, light from the object is captured by the camera lens and focussed onto a recording media, usually a film of some kind.

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