Principles of Holography: Wavefront Reconstruction and Holographic Theory

The Perception Of Depth

A binocular stereoscopic image, either in a viewer or projected on a screen, can reconstruct only a single viewpoint. Moving one's viewing position does not change the perspective: it merely foreshortens the image. A photographic image is necessarily two-dimensional. Even a stereoscopic pair of photographs records only a pair of 2-D views as seen from the position of the viewer's right and left eyes. Because of the way our perceptive mechanism works the two slightly different images combine to form a three-dimensional impression. The effect is severely restricted compared with that of a holographic image, because traditional photography can record only the time-averaged light intensity The relation between the phases of the combined reflected light waves incident on the sensitive material, which are the part that contains information about the depth of the subject matter, are not recorded. But a hologram does record this information.