Holography comes from the greek word HOLOS and GRAPHOS which means ‘complete’ and ‘writing’ respectively.
It is a technique of photography that allows an image to be recorded in 3 dimensions
it is a common to confuse volumetric displays with holograms, Particularly in science fictions such as Star Trek/Star Wars/red dwarf & Quantum Leap.
HOW TO CREATE A HOLOGRAM:-
1. To Create a hologram the technique is to use a reference beam which is then combined with the light from the scene or the object
2. If these 2 beams are coherent, optical interference between the reference beam and object beam due to the superposition of light waves producing series of intensity fringes that can be recorded on standard on standard photographic film
3. These fringes form a type of diffraction grating on the film which is called the hologram.
The cental goal of holography is that when the recorded grating is later illuminated by a substitute reference beam, the original object beam is reconstructed , producing a 3-d image.
=> A diffraction grating is a transparent sheet with thin slits, the distance between them and their diameter being of the order of the wavelength of light.