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| DEFINITION |
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hologram
- (HOL-o-gram)
definition:
usually a three-dimensional image, produced by capturing
a laser light interference pattern on film.
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The
word "hologram" is formed from two Greek words,
holos (whole) and gramma (message).
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TECHNICAL
EXPLANATION |
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Holograms
are the perfect practical example of the "wave" nature
of light. |
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While
we often think of light in terms of "photons," light
is also a "wave." The different colors of light
that we see are actually different wavelengths of the light:
red is a longer, blue is shorter, and green is in the middle.
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Laser
light is used for holograms because it is a very pure source
of light (only one color, or wavelength) with very
orderly waves. When two beams of laser light come
together, they form an interference
pattern. This is the most basic form of a hologram. |
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Imagine
throwing a rock into a quiet lake. The ripple pattern is like
the waves that come from a laser. If you throw two rocks into
the water, the two wave patterns will collide in the middle,
creating some areas that have waves twice as big and some
areas where the waves cancel each other out. This is interference.
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To
make a hologram, laser light is split into two different
beams. One is reflected off of an object and then scatters to
the film, while the other beam goes directly to the film. The
two beams meet at the film causing an interference pattern of
microscopic bright and dark lines. The film captures this pattern,
which is the hologram. |
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A
regular photograph is only two-dimensional (2D) because it
only records the INTENSITY of the light hitting the film,
recording shades of brightness and darkness. A hologram is
three-dimensional (3D) because it records both the INTENSITY
and the DIRECTION of the light that hits the film. This additional
information is recorded in the interference pattern, and allows
you to "look around" the recorded object as if it
were really there.
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To
view
the hologram after it is developed (if you are using
the Litiholo "Instant Hologram" Film, there is no
developing necessary), it is placed back in its original position
and illuminated with only one beam coming directly from the
laser. The recorded holographic interference pattern will now
diffract the laser light passing through it, creating a 3D image
of the original object as if it was still there. |
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Diffraction
is the bending of light due to a pattern of closely spaced
lines. If you look at the bottom of a CD or DVD disk, you
will see a rainbow of colors. This is because the tracks on
the CD create microscopic lines that bend (or diffract) the
light into separate colors, much like a prism.
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HISTORY |
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Holography
was first invented and discovered by Hungarian physicist
Dennis
Gabor in 1947. He later won the Nobel Prize
for his discovery. |
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