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 be viewed under tungsten (point source) light.
The hologram records an infinite number of views of the object, whereas a photograph records only one view. Thus, when viewing a hologram, the left eye sees a different set of information than the right eye so that the image appears three dimensional.
Unlike photograph, hologram cannot be reduced or enlarged. Hologram made from 3 dimensional models are recorded in identical size as the original object and the image size cannot be changed. Whereas computer generated holograms can be reduced or enlarged; stereogram holography which is created on computer from movie footage, can be varied in size
A hologram can be made from flat art designs but it will not add any depth which was not originally there, similarly photographs reproduced in a hologram will only show what is in the photograph. The holographic process cannot add depth to a photograph being made into a hologram
True-colour holograms can be made, but the true colours are viewable only at one specific angle and once you shift your view point the image will cycle through the rainbow spectrum.