The principle of holography is based on the diffraction and interference of light. Here are the crucial steps of this process:

• Recording of the hologram: to create a hologram, a laser beam needs to be divided into two parts. One of those, the “object beam” is directed towards the object that will be photographed. The light reflected by this object is then captured on a photosensitive surface such as a film or CCD sensor. The other part of the beam, the “reference beam” is directed towards the same photosensitive surface.
• Interference: when the two beams meet, they interfere with each other. This phenomenon produces an interference pattern which encodes the light intensity as well as the phase of light reflected by the object. This pattern corresponds to the content of the hologram.
• Image reconstruction: in order to visualise the recorded object, a light beam similar to the one used for the recording is projected onto the hologram. This allows for the reconstruction of a three-dimensional image, which appears to be floating in space. When moving the eye, you can see different perspectives of the object, as if you were looking at it directly.

Holography is utilised in many applications, from document security (holograms on credit cards for instance) to medicine, where it can be used to create tissues or organ images. In the artistic field, holography is used to create interactive and immersive artworks.

In conclusion, holography is a spectacular demonstration of the ability science possesses to capture and reproduce reality. Using basic light and interference principles, holography adds a new dimension  to the visualisation and representation of objects.