9. HOW HOLOGRAM IS MADE?
Holography is the science of recording interference pattern of light in space specific to an object.
Hologram is the result of recording interference patterns of light for a specific object on a photo – sensitive plate. A laser light beam generated by a single laser is used to make the hologram; the beam is split into two – one half of the beam, is called the reference beam and this is shone directly onto the photo – sensitive recording plate.
The second half, known as the object beam is shone onto the object to be recorded. The light reflected from the object strikes the recording plate, causing an interference pattern with the reference beam and the interference pattern created is specific to the object being recorded.
The exposed plate is developed in a similar manner to that employed for photographic process. The hologram is replayed by illuminating the developed plate with a beam at the same angle as the reference beam. When viewing the hologram, one sees a three dimensional image of the recorded object.
Moving holograms can also be made with specially filmed motion pictures of 3 to 10 second lengths that can be used to create animated holographic images. This process is known as stereogram and the resultant image can ideally be viewed under point source light.