This proved that depth perception is a neurological process. Julesz used a computer to create a stereo pair of random-dot images which, when viewed under a stereoscope, caused the brain to see 3D shapes.
![stereogram definition stereogram definition](https://cdn.wallpapersafari.com/12/65/QWdOIC.jpg)
At the time, many vision scientists still thought that depth perception occurred in the eye itself, whereas now it is known to be a complex neurological process. In 1959, Bela Julesz, a vision scientist, psychologist and MacArthur Fellow, invented the random dot stereogram while working at Bell Laboratories on recognizing camouflaged objects from aerial pictures taken by spy planes. This is the basis of wallpaper-style "autostereograms" (also known as single-image stereograms). He noticed that staring at repeated patterns in wallpapers could trick the brain into matching pairs of them as coming from the same virtual object on a virtual plane behind the walls. īetween 18, David Brewster, a Scottish scientist, improved the Wheatstone stereoscope by using lenses instead of mirrors, thus reducing the size of the contraption.īrewster also discovered the "wallpaper effect". When people looked at these flat, two-dimensional pictures, they experienced the illusion of three-dimensional depth. He supported his explanation by showing pictures with such horizontal differences, stereograms, separately to the left and right eyes through a stereoscope he invented based on mirrors. In 1838, the British scientist Charles Wheatstone published an explanation of stereopsis (binocular depth perception) arising from differences in the horizontal positions of images in the two eyes. Wall-eyed viewing requires that the two eyes adopt a relatively parallel angle, while cross-eyed viewing requires a relatively convergent angle. Most autostereograms (including those in this article) are designed to be viewed in only one way, which is usually wall-eyed. There are two ways an autostereogram can be viewed: wall-eyed and cross-eyed. It pairs two adjacent patterns into a virtual object based on wrong parallax angles, thus placing the virtual object at a depth different from that of the autostereogram image. With an autostereogram, the brain receives repeating 2D patterns from both eyes, but fails to correctly match them. A stereoscope presents 2D images of the same object from slightly different angles to the left eye and the right eye, allowing the brain to reconstruct the original object via binocular disparity. Usually, a hidden 3D scene emerges when the image is viewed with the correct vergence.Īutostereograms are similar to normal stereograms except they are viewed without a stereoscope. In this type of autostereogram, every pixel in the image is computed from a pattern strip and a depth map.
![stereogram definition stereogram definition](https://cdn.wallpapersafari.com/86/83/9SsVo3.jpg)
One such autostereogram is illustrated above right. The Magic Eye books feature another type of autostereogram called a random dot autostereogram. When viewed with proper vergence, the repeating patterns appear to float above or below the background. The simplest type of autostereogram consists of horizontally repeating patterns and is known as a wallpaper autostereogram.
![stereogram definition stereogram definition](http://geniusbrainteasers.com/archive/2016/09/13/stereogram-2745.png)
In order to perceive 3D shapes in these autostereograms, the brain must overcome the normally automatic coordination between focusing and vergence. Click on thumbnail to see full-size image.Īn autostereogram is a single-image stereogram (SIS), designed to create the visual illusion of a three- dimensional (3D) scene from a two-dimensional image in the human brain. A random dot autostereogram encodes a 3D scene which can be "seen" with proper viewing technique.