What is a Hologram?
A hologram is often described as a three-dimensional picture. While this is a good way to get a general idea of what you would experience looking at one, holography has very little in common with traditional photography.
While a photograph has an actual physical image, a holgram contains info about the size, shape, brightness and contrast of the object being recorded. This info is stored in a very microscophic and complex pattern of interfeerence. The interference pattern is made possible by the properties of light generated by a LASER.
The light reflected by a three dimensional object forms a very complicated pattern that is also three dimensional. In order to record the whole pattern, the used must be highly directional and must be of one color. Such light is call coherent. Because the light from a laser is one color, and leaves the laser with one wave in perfect step with all others, it is perfect for making holograms.
When you shine a light on the hologram, the info that is stored as an interference pattern takes the incoming light and re- creates the original optical wavefront that was reflected off the object. YOUR EYES AND BRAIN NOW PERCEIVES THE OBJECT AS BEING IN FRONT OF YOU ONCE AGAIN...
