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Name: kolin
Status: N/a
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993


Question:
How do holograms work?



Replies:
Most of the time we can ignore the wave nature of light, since it basically travels in straight lines and obeys simple laws when passing through lenses or with mirrors. However, when light is specially prepared (as in a laser) the wave nature can be readily seen - for example, laser light passed through a pair of slits will produce an "interference" pattern of alternating dark and light areas as long as the slits are close enough together, and this is very different from the straight line images you might expect. A hologram is made by "interfering" in this sort of fashion, laser light that has been reflected from a 3-dimensional object with light directly from the laser, or reflected from a flat mirror. Because of the different distances traveled by the light striking different parts of the object, the light waves arrive at different parts of their cycle and combine or cancel out. This produces a very complicated image, which can be recorded on film as a hologram, and played back to produce something resembling the original 3-dimensional image (played back by shining laser light through it in the other direction). The details are pretty complicated, and I have always been amazed that it actually works. People can now produce these interference patterns on the computer, and generate a hologram that can be used to produce three-- dimensional images that were designed on the computer.

Arthur Smith



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