Unlike normal stereograms, autostereograms do not require the use of a stereoscope. A hidden 3D scene emerges when the image is viewed with the correct vergence. In this type of autostereogram, every pixel in the image is computed from a pattern strip and a depth map. The well-known Magic Eye books feature another type of autostereogram called a random dot autostereogram, similar to the first example, above. When viewed with proper vergence, the repeating patterns appear to float above or below the background. The simplest type of autostereogram consists of a horizontally repeating pattern with small changes throughout that looks like wallpaper.

Individuals with disordered binocular vision and who cannot perceive depth may require a wiggle stereogram to achieve a similar effect. The optical illusion of an autostereogram is one of depth perception and involves stereopsis: depth perception arising from the different perspective each eye has of a three-dimensional scene, called binocular parallax. Viewing any kind of stereogram properly may cause the viewer to experience vergence-accommodation conflict.

The 3D scene in an autostereogram is often unrecognizable until it is viewed properly, unlike typical stereograms.

Autostereograms use only one image to accomplish the effect while normal stereograms require two. The top and bottom images produce a dent or projection depending on whether viewed with cross- ( ) or wall- ( ) eyed vergence.Īn autostereogram is a two-dimensional (2D) image that can create the optical illusion of a three-dimensional (3D) scene.

Stereogram shark