Stereogram - Types

Types

Stereoscopic imaging relies on the principle of stereoscopy to present a slightly different image to each eye. The stereo pair can be viewed with the naked eye, if the images are placed side by side. The stereo pair is then viewed using a parallel view or cross-eyed view method. The stereo pair can also be viewed with devices such as the Stereoscope or the View-Master. More advanced methods include Head-mounted displays, Polarized 3D images, Active shutter 3D images and other 3D display methods. The following are some examples of techniques that are mainly used for still images.

• Anaglyph images, also recognized as "red/green" or "magenta/cyan" images, combine two stereo images from slightly different viewpoints into a single image. These images may then be viewed with "anaglyph glasses", which use color filters to moderate the light reaching each eye to create the illusion of a three dimensional image.

• Random dot stereograms employ either two stereoscopic images or one anaglyph. The input image (or images) contain random dots with no discernible shapes. When the proper viewing device is used, a hidden 3D scene emerges from these random dots.

• Autostereograms produce an illusion of depth using only a single image. The image is usually generated by computer by repeating a narrow pattern from left to right. By decoupling eye convergence from focusing operations, a viewer is able to trick the brain into seeing a 3D scene. An autostereogram can be observed by allowing the eyes to focus behind the image (diverge), or, less often, in front of it (converge). These two methods are also known as wall-eyed and cross-eyed, respectively. The slight differences in vertical repetitions of figures or random dots create the illusion of depth in the 2D image, just as the slight difference in perspective between one's eyes creates the perception of depth on 3D objects and scenes.

According to Magic Eye, a maker of autostereograms, "most people prefer the diverging method". However, with normal stereograms, this imposes a limit on the size of the image, since there is a limit to how much the eyes diverge; images created for the cross-eyed method can be larger. If a stereogram is viewed with the wrong method, the depth information is seen 'reversed'; points intended to be in the background appear in the foreground and vice versa.

• Wiggle-gram is an animated computer image which gives 3D percept without using glasses using only a single image. It usually contains a few frames.

• Lenticular prints are images that create an illusion of depth by using lenticular lenses.

• A Bubblegram or Laser Crystal is a 3D image composed of points suspended in a medium, typically a plastic block.

• Vectographs are a type of stereoscopic print or transparency viewed using the polarized 3D glasses.