HOLOGRAPHY
Holography is a technique which enables three-dimensional images to be made. It involves the use of a laser, interference, diffraction, light intensity,recording and suitable illumination of the recording. The images changes as the position and orientation of the viewing system changes in exactly the same way as if the object were still present, thus making the image appear three-dimensional.
WORKING
1.LASER
Holograms is recorded using a flash of light that illuminates a scene and then imprints on a recording medium, much in the way a photograph is recorded. In addition, however, part of the light beam must be shone directly onto the recording medium-this second light beam is known as the reference beam.
2.APPARATUS
A hologram can be made by shining part of the light beam directly onto the recording medium, and the ohter part onto the object in such a way that some of the scattered light fails onto the recording medium.A more flexible arrangement for recording a hologram requires the laser beam to be aimed through a series of elements that change it in different ways. The first element is a beam splitter that divides the beam into two identical beams, each aimd in different directions.
3.PROCESS
When the two laser beams reach the recording medium, their light waves intersect and interfere with random, each other. It is this interference pattern that is imprinted on the recording medium. The pattern itself is seemingly random, as it represents the way in which the scene's light interefered with the original light source but not the original light source itself. The intereference pattern can be considered an encoded version of the scene, requiring a particualr key the original light source in order to view it contents.
4.HOLOGRAPHY VS. PHOTOGRAPHY
A hologram represents a recording of information regarding the light that came from the original scene as scattone direction,range of directions rather than from only as if it were still present.
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