Stereoscopy refers to a technique for re-creating the 3D depth perception when humans view real objects.
Stereoscopic vision is done by by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are combined by the brain to give the perception of 3-D depth.
Throughout the ages, different strategies have been used to achieve this effect. Some have the viewer wear eyeglasses to combine separate images from two offset sources, or the viewer wear eyeglasses to filter offset images from a single source separated to each eye, or have the lightsource split the images directionally into the viewer's eyes (no glasses required; known as Autostereoscopy).Lenticular Prints
Lenticular printing is a technique by which one places an array of lenses, with a texture much like corduroy, over a specially made and carefully aligned print such that different viewing angles will reveal different image slices to each eye, producing the illusion of three dimensions, over a certain limited viewing angle. This can be done cheaply enough that it is sometimes used on stickers, album covers, etc. It is the classic technique for 3D postcards.
A variant of this for portable electronic devices, the parallax barrier, has begun deployment. Similar technology is also used in 3D cameras and video cameras to offer a convenient way to immediate review of recorded 3D effect captured using the same device.Wiggle Stereoscopy
Wiggle stereoscopy is possibly the simplest stereogram viewing technique, is to simply alternate between the left and right images of a stereogram.
It does give a rudimentary effect of depth as the human brain can usually interpolate the transition between the left and right images.Most wiggle images use only two images, leading to an annoyingly jerky image. A smoother image, more akin to a motion picture image where the camera is moved back and forth, can be composed by using several intermediate images (perhaps with synthetic motion blur) and longer image residency at the end images to allow inspection of details. Another option is a shorter time between the frames of a wiggle image.
However more recent software interpolation of good quality Left-Right images from 3D cameras with 2 image sensors is able to improve this effect.
Advantages of the wiggle viewing method include:
No glasses or special hardware required
Most people can "get" the effect much quicker than cross-eyed and parallel viewing techniques
It is the only method of stereoscopic visualization for people with limited or no vision in one eye.Source :