Stereoscopy, stereoscopic imaging or 3-D (three-dimensional) imaging is any technique capable of recording three-dimensional visual information or creating the illusion of depth in an image. The illusion of depth in a photograph, movie, or other two-dimensional image is created by presenting a slightly different image to each eye. Many 3D displays use this method to convey images. It was first invented by Sir Charles Wheatstone in 1838 . Stereoscopy is used in photogrammetry and also for entertainment through the production of stereograms. ⁵

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Many 3D displays use this method to convey images. It was first invented by Sir Charles Wheatstone in 1840. The recent advent of wider HD and computer flat screens has made wider 3D digital images practical in this side by side mode, which hitherto has been used mainly with paired photos or in print form. There are examples of the ultra wide aspect cross glasses images, as well as narrower “portrait” format, which fills a 4�3 computer screen efficiently.¹

It has been said that photography is the daughter of perspective because photography, the camera obscura, and perspective produce images that obey the same laws. One of the key applications of the rivalry cue is as an optical comparator of similar objects or images. Any minute differences are noted in a perception of flicker or oscillating relief. The creation of monocular images began with the European cave paintings of 20,000 years ago. In contrast, the first binocular images were Wheatstone’s revolutionary 3-D drawings published in 1838.²

The IRIS-3D is the first workstation to incorporate a concave mirror system that re-directs 3D images back to the viewer and eliminates image crosstalk - the bane of more conventional autostereo display systems. For the viewer this means exceptional image clarity and viewing comfort with UXGA resolution and no glasses in sight. The Center’s collection of stereocards are available for viewing and the reference library is open to visitors. There are daily 3D slide projections. Soon he was developing photographic prints and noting down his thoughts and impressions on pieces of paper, which were to become the beginnings of his lifelong diary. An unfailingly curious amateur, he experimented with all the available photographic techniques, from stereoscopic images and autochromes to multiple exposures, meticulously arranging his several thousands of images in large albums.⁴

In the late 19th and early 20th century stereo cards were popularly sold. The cards had a pair of photographs, usually taken with a special camera that took the pair of images from slightly separated views simultaneously. The viewer wears low-cost eyeglasses which also contain a pair of orthogonal polarizing filters. As each filter only passes light which is similarly polarized and blocks the orthogonally polarized light, each eye only sees one of the images, and the effect is achieved. In the 1940s, a modified and miniaturized variation of this technology was introduced as “The View-Master®”. Pairs of stereo views were printed on translucent film attached to a round card.¹⁰

A random pattern, which (for the most part) has a horizontal periodicity of about the same as an average person’s interocular distance (distance between one’s eyes), has specific flaws in the periodicity to give the impression of depth. Only one angle on the scene is viewable. To use one: find a brightly-lit place with no shadows nearby, put a stereograph in the holder (centred over the rod), look through the visor, and slide the holder until the pictures are in focus. The pictures will be magnified by the lenses to cover a larger field of view, so the experience is more immersive. One can view the same scene from different angles horizontally over a somewhat narrow range (looking up or down at the picture has no effect), and simple animation can be done in 3D by having the viewer move side to side. In the more sophisticated integral photography, instead of lines of hemicylinders there’s a honeycomb of hemispheres.⁶

The depth information is coded into the images using colours. When such images are viewed with double prism refraction ChromaDepthTM 3D glasses, a pronounced 3D effect is achieved.¹²

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This image corresponds to a research on birth pain made by Prof. You may copy the whole animation scene (2 Mb) representing the transition of pain regions on the mother’s body before and after birth altogether with some files to make the computer viewer program (Aaplay). Although it is apparently simple, it must be carefully made, selecting inks and filters and positioning elements on the image (registering tecnhique) with skill. The appearence of any parasitic image spoils the effect and bothers the observer, who may not return to stereoscopy anymore. This technique is employed in magazines and journals, in may 1999 appeared in the newspapers “O Estado de S�o Paulo” and “Folha de S�o Paulo”, two of the three more important of Brazil. It was employed in cinematography, but can not be employed in television because the compusite color system mixes colors.²⁰

Many of the landscape photographers also took stereographs. These double pictures, taken after 1856 with twin-lens cameras, produce a remarkable effect of three dimensions when viewed through a stereoscope. Wheatstone’s mirror stereoscope, however, was not practical for use with photographs, and the invention languished until the Scottish scientist Sir David Brewster designed a simplified viewing instrument, which was exhibited at the 1851 Great Exhibition in the Crystal Palace, London. Queen Victoria was entranced by the stereo daguerreotypes she saw there, and with the introduction of the collodion process, which simplified exposure and printing techniques, three-dimensional photography became a popular craze. The instantaneous street scenes, which showed pedestrians and vehicles stopped in their tracks, were made possible because the small size of the stereo-camera reduced exposure times to less than half a second. To minimize movement street views were usually taken from a first-floor window with the camera focused directly down the street.³

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If the stereogram is not too large, it is possible with a little practice to learn the art of “free-viewing,” that is, viewing in three dimensions without the use of a stereoscope. You may try this on the example below. Do not cross your eyes, but let them drift apart so that their directions of gaze are virtually parallel. It helps to concentrate your attention on the same object in both images, until you are able to make them merge into one.¹⁴

There are clues to the depth of field of objects which can be perceived/appreciated monocularily. Monocular or one eye depth perception deals with in-born cues that humans instinctively employ when viewing objects. There are limits, however, to monocular depth perception. Put a coin on end on a table and view it with only one eye. It is very difficult to tell if they are really in a line or staggered. Basically what your eye brain mechanism will do in this case is employ other clues to help determine the depth of the trees (again, these are essentially the monocular cues described above).¹⁷