Stereogram

A stereogram is any image that, through one of several techniques, is able to convey the experience of depth perception to the viewer by means of stereopsis for binocular vision. Originally, stereogram referred to a pair of stereo images which could be viewed using a stereoscope. Nowadays, there are many other methods to display stereoscopic images.

The stereogram was discovered by Charles Wheatstone in 1838. He found an explanation of binocular vision which led him to construct a stereoscope based on a combination of prisms and mirrors to allow a person to see 3D images from two 2D pictures. Between 1849 and 1850, David Brewster, a Scottish scientist, improved the Wheatstone stereoscope by using lenses instead of mirrors, thus reducing the size of the device. Oliver Wendell Holmes, Sr. invented an improved form of stereoscope in 1861, which had no mirrors and was inexpensive to produce. These stereoscopes were immensely popular for decades. Salvador Dalí created some impressive stereograms in his exploration in a variety of optical illusions. In the early 1900s, devices like the View-Master were developed, gaining moderate popularity.

Stereograms were re-popularized by the creation of autostereograms on computers, wherein a 3D image is hidden in a single 2D image, until the viewer focuses the eyes correctly. The Magic Eye series is a popular example of this. Magic Eye books refer to autostereograms as stereograms, leading most people to believe that the word stereogram is synonymous with autostereogram.