Home > Encyclopedia of Science > Hologram and Holography

• Birth of the hologram
• Uses for holograms

Holography is a method of producing a three-dimensional (3-D) image of an object. (The three dimensions are height, width, and depth.) The image it brings to life is referred to as a hologram, from the Greek word meaning "whole picture." Unlike a two-dimensional picture, a hologram allows a person to look "around" and "behind" its subject.

The hologram is actually a recording of the difference between two beams of coherent light. Light is composed of waves that are all the same length and that travel in all directions. Coherent light is in phase, meaning its waves are vibrating and traveling together in the same direction. To create a hologram, a laser beam (coherent light) is split in two: one beam that stays undisturbed, called the reference beam, strikes a photographic plate. The second beam, called the...