Holography is a photographic process that renders the image of objects by using the interferences of two laser beams. The principle makes it possible to encode the information of an object on a support. To make a hologram, a laser light is needed. This one is divided in two beams : one for the object and the other for the reference. The reference beam is enlarged through a lens and arrives directly on the holographic plate: support of our hologram. The object beam meanwhile, will reflect on the object before reaching the photographic plate. Both beams will interfere and create dark areas -destructive interferences- and clear areas -constructive interferences-.

The interferences created will make it possible to create a relief image on the holographic plate. In principle to visualize the hologram then, it is necessary to reuse the same source which made it possible to create it: same wavelength of the laser. However, now it is possible to observe holograms in the light of day for example. The principle is the same as the one for the photography, but this method does not only recover the information concerning the luminous intensity data. Indeed, it also makes it possible to recover information on the phase, or a degree of harmony – or coherence – between the wavefronts of the light reflected by the object. This is what differentiates the methods of photography and holography.