Hologram and Holography

Holography is defined as a method of producing a three-dimensional (3-D) impression of an object. The recording and the image it brings to life are each referred to as holograms.

This impression is taken by splitting a beam of coherent (that is, uniform over distance as well as over time) radiation along two paths. One is known and stays undisturbed, to act as a reference. Another strikes the object and is diffracted in an unpredictable fashion along the object's contours. This can be compared to throwing one rock into a pool of water, which creates a regular pattern of rings, and then scattering smaller stones afterwards, to see what kind of design appears where the expanding rings intersect with each other. Likewise, intersections of radiation waves hold crucial information. The aim is to track and record the pattern of interference of the split rays.

The surface of the hologram acts as a diffraction grating by alternating clear and opaque strips. When you view a common optical hologram, this grating replicates the action of ordinary illumination, capturing the phase and amplitude of the light beam and its interference pattern, in an additive fashion. You can not only see how bright a jewel is, you can see how the light sparkles on each facet if you shift your own position.