How are holographic images made?
The word "hologram" comes from the Greek roots "holos" and "gramma," meaning literally, "whole message." Holograms, unlike conventional pictures, convey complete information about depth, shape and texture from many angles.
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History
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Laser technology is the key to holography. Dennis Gabor developed the theory of holography in 1947, but the need for intense, focused light kept any holograms from being immediately produced. In 1962, four years after the invention of the laser, Emmett Leith and Juris Upatnieks produced the first holographic image.
Method
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A lens splits a laser into two beams. One beam (the "object beam") illuminates the object being holographed, and the other (the "reference beam") points directly at holographic film. The object beam converges with the reference beam at the film, creating interference patterns that result in the holographic effect.
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In the Movies
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The 3D image of Princess Leia from "Star Wars" was not a real hologram; it was a film effect. Holograms today cannot show moving images, and cannot project an image into open space.
Pulsed Holography
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The least movement during hologram capture will ruin the image. Pulsed holography, where the laser is activated for only a few nanoseconds, allows the capture of living people and other moving subjects.
On Money
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Embossed holograms are used on money and other documents to prevent counterfeiting. The holographic interference patterns are printed onto plastic and then backed with a light-reflecting foil. Embossed holograms can be mass produced very cheaply.
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References
- Photo Credit Image by Flickr.com, courtesy of Evan Image by Flickr.com, courtesy of Kevin Dooley
