Hologram is a two or three dimensional photographic image
produced by laser light. It was discovered by Gabor. The term hologram
was coined from the Greek words holos, meaning "whole," and
gramma, meaning "message." The process by which the image is
recorded is called holography.
A hologram contains information about the size, shape, brightness and
contrast of the object being recorded. This information is stored in a
very microscopic and complex pattern of interference. The interference
pattern is made possible by the properties of light generated by a
laser.
Laser light is used more often because the light from a laser is of one
color and leaves the laser with one wave in perfect step with all
others. Such a light that is highly directional and of one colors is
called coherent.
The hologram presents a true three dimensional recreation of the
original object when re-illuminated and viewed under normal light. For
the observer, the perception of depth is virtually indistinguishable
from reality.
Holograms are available in assorted styles and types. Each hologram
requires it's own individual technique for production. Some holograms
require a laser to view them, others rely only on regular light. Some
holograms show motion, and some change images as you move by them.
Holograms can be in full-color, change color and even project their
image out in space toward you when you view them.
Properties of Holograms
- Sensitivity to vibration - Holograms record
specific information about light at the level of individual light
waves. Thus, the holographic plates are sensitive enough to record a
single wavelength of light, 650 nm for red laser light.
- Divisibility - A hologram can be divided into
small pieces that still retain the entire image of the object. The
object's wavefront is preserved throughout the hologram, and can be
viewed from a tiny piece of the whole.
Applications of Holograms
- Art, science and technology
- Used on certain product packaging
- Used for labelling
- Embellishment on printed media
- On credit cards and driving license to help stop counterfeiting
- Used in airplanes to provide the pilot with critical information
- Also used for artistic expression
- Security applications
