Hologram is a pattern, usually made on photographic film,
which can produce a three dimensional image of a scene.
This holographic image is so lifelike that it appears to be
a real scene viewed through a window. The viewer can see
around objects in the foreground by moving his/her head,
just as he/she looks around real objects. If part of the
hologram is covered, the complete scene can still be seen
in the remaining part as if part of the window were covered.
Holograms are produced by illuminating the scene with light
from a device called a laser. The holographic image is then
created by shining a similar beam of light on the hologram.
The hologram changes this light to reconstruct the light
patterns which came from the original scene.
Holograms were invented in 1947 by Hungarian scientist
Dennis Gabor, but they were ignored for years. Gabor's
theory about light waves was ahead of its time. The lasers
needed to produce clean waves and thus clean 3-D images
weren't invented until 1960. Gabor coined the name for his
photographic technique from holos and gramma, Greek for
"the whole message. " But for more than a decade, Gabor had
only half the words. Gabor's contribution to science was
recognized at last in 1971 with a Nobel Prize.. A perfect
holographic portrait of the late scientist looking up from
his desk with a smile could go on fooling viewers into
saying hello forever. 

When it comes to looking at the future uses of holography,
pictures are anything but the whole picture.
Here are just a couple of the more unusual possibilities.
Consider this: you're in a windowless room in the middle of
an office tower, but you're reading by the light of the
noonday sun! How can this be? A new invention that
incorporates holograms into widow glazings makes it
possible. Holograms can bend light to create complex 3 D
images, but they can also simply redirect light rays.
The window glaze holograms could focus sunlight coming
through a window into a narrow beam, funnel it into an air
duct with reflective walls above the ceiling and send it
down the hall to your windowless cubbyhole. That could cut
lighting costs and conserve energy. The holograms could
even guide sunlight into the gloomy gaps between city
skyscrapers and since they can bend light of different
colors in different directions, they could be used to
filter out the hot infrared light rays that stream through
your car windows to bake you on summer days.
Or, how about holding an entire library in the palm of your
hand? Holography makes it theoretically possible. Words or
pictures could be translated into a code of alternating
light and dark spots and stored in an unbelievably tiny
That's because light waves are very, very skinny. About
1000 lightwaves can be placed side by side across the width
of the period at the end of this sentence. One calculation
holds that by using holograms, the U. S. Library of
Congress could be stored in the space of a sugar cube. For
now, holographic data storage remains little more than a
fascinating idea because the materials needed to do the job
haven't been invented yet. But it's clear that holograms,
which author Isaac Asimov called "the greatest advance in
imaging since the eye" will continue to make waves in the
world of science. 


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