Stereopsis (from stereo meaning solidity, and opsis meaning vision or sight) is the process in visual perception leading to the sensation of depth from the two slightly different projections of the world onto the retinas of the two eyes. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain The differences in the two retinal images are called horizontal disparity, retinal disparity, or binocular disparity. Stereopsis (from stereo meaning solidity and opsis meaning vision or Sight) is the process in Visual perception leading to the sensation Stereopsis (from stereo meaning solidity and opsis meaning vision or Sight) is the process in Visual perception leading to the sensation Binocular disparity refers to the difference in image location of an object seen by the left and right Eyes resulting from the eyes' horizontal separation The differences arise from the eyes' different positions in the head. Stereopsis is most commonly referred to as depth perception.

History of stereopsis

Stereopsis was first described by Charles Wheatstone in 1838. Sir Charles Wheatstone FRS (6 February 1802 - 19 October 1875 was a British Scientist and Inventor of many scientific breakthroughs Year 1838 ( MDCCCXXXVIII) was a Common year starting on Monday (link will display the full calendar of the Gregorian Calendar (or a Common ”… the mind perceives an object of three-dimensions by means of the two dissimilar pictures projected by it on the two retinæ…”. ^[1] He recognized that because each eye views the visual world from slightly different horizontal positions, each eye's image differs from the other. Objects at different distances from the eyes project images in the two eyes that differ in their horizontal positions, giving the depth cue of horizontal disparity, also known as retinal disparity and as binocular disparity. Stereopsis (from stereo meaning solidity and opsis meaning vision or Sight) is the process in Visual perception leading to the sensation Stereopsis (from stereo meaning solidity and opsis meaning vision or Sight) is the process in Visual perception leading to the sensation Binocular disparity refers to the difference in image location of an object seen by the left and right Eyes resulting from the eyes' horizontal separation Wheatstone showed that this was an effective depth cue by creating the illusion of depth from flat pictures that differed only in horizontal disparity. An illusion is a distortion of the senses revealing how the Brain normally organizes and interprets sensory stimulation To display his pictures separately to the two eyes, Wheatstone invented the stereoscope. Stereoscopy, stereoscopic imaging or 3-D (three-dimensional imaging is any technique capable of recording three-dimensional visual

Leonardo da Vinci had also realized that objects at different distances from the eyes project images in the two eyes that differ in their horizontal positions, but had concluded only that this made it impossible for a painter to portray a realistic depiction of the depth in a scene from a single canvas. Leonardo di ser Piero da Vinci ( April 15 1452 – May 2 1519 was an Italian Polymath, having been a scientist Mathematician, Engineer ^[2] Leonardo chose for his near object a column with a circular cross section and for his far object a flat wall. Had he chosen any other near object, he may have discovered horizontal disparity of its features. ^[3] His column was one of the few objects that projects identical images of itself in the two eyes.

Stereopsis became popular during Victorian times with the invention of the prism stereoscope by David Brewster. Culture The Victorian fascination with novelty resulted in a deep interest in the relationship between modernity and cultural continuities Sir David Brewster, FRS ( 11 December 1781 &ndash 10 February 1868) was a Scottish scientist inventor and writer This, combined with photography, meant that tens of thousands of stereograms were produced. Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing

Until about the 1960s, research into stereosis was dedicated to exploring its limits and its relationship to singleness of vision. Researchers included Peter Ludvig Panum, Ewald Hering, Adelbert Ames Jr., and Kenneth N. Ogle. Peter Ludvig Panum ( December 19, 1820 - May 2, 1885) was a Danish Physiologist and Pathologist. Karl Ewald Konstantin Hering ( August 5, 1834 &ndash January 26, 1918) was a German Physiologist who did much research Adelbert Ames Jr ( August 19, 1880 -1955 was an American scientist who made contributions to Physics, Physiology, Ophthalmology Kenneth N Ogle (1902-1968 was a scientist of human vision Born in Colorado, he earned a bachelor's degree from Colorado College in 1925 and a Ph

In the 1960s, Bela Julesz invented random-dot stereograms. Béla Julesz ( February 19, 1928 &ndash December 31, 2003) was a visual neuroscientist and experimental psychologist in the fields of visual A Random Dot Stereogram (RDS is a technique created by Dr Bela Julesz, described in the book Foundations of Cyclopean Perception. ^[4] Unlike previous stereograms, in which each half image showed recognizable objects, each half image of the first random-dot stereograms showed a square matrix of about 10,000 small dots, with each dot having a 50% probability of being black or white. No recognizable objects could be seen in either half image. The two half images of a random-dot stereogram were essentially identical, except that one had a square area of dots shifted horizontally by one or two dot diameters, giving horizontal disparity. The gap left by the shifting was filled in with new random dots, hiding the shifted square. Nevertheless, when the two half images were viewed one to each eye, the square area was almost immediately visible by being closer or farther than the background. Julesz whimsically called the square a Cyclopean image after the mythical Cyclops who had only one eye. Cyclopean image is a single mental Image of a scene created by the Brain by combining two images received from the two Eyes The mental process behind construction In Greek mythology and later Roman mythology, a cyclops (ˈsaɪklɒps or kyklops ( Greek) is a member of a primordial race of This was because it was as though we have a cyclopean eye inside our brains that can see cyclopean stimuli hidden to each of our actual eyes. Random-dot stereograms highlighted a problem for stereopsis, the correspondence problem. Given two or more images of the same 3D scene taken from different points of view the correspondence problem is to find a set of points in one image which can be identified as the same This is that any dot in one half image can realistically be paired with many same-coloured dots in the other half image. Our visual systems clearly solve the correspondence problem, in that we see the intended depth instead of a fog of false matches. Research began to understand how.

Also in the 1960s, Horace Barlow, Colin Blakemore, and Jack Pettigrew found neurons in the cat visual cortex that had their receptive fields in different horizontal positions in the two eyes. Professor Horace Basil Barlow FRS (born December 8, 1921) is a British visual neuroscientist Colin Blakemore is a British Neurobiologist specializing in vision. John Douglas ("Jack" Pettigrew (born 1943 is Emeritus Professor of Physiology and Director of the Vision Touch and Hearing Research Centre at the Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information WikipediaManual of Style (spelling, articles should conform to one overall spelling style of English typically the one most linked to the article topic (if it is geographic The term visual cortex refers to the primary visual cortex (also known as striate cortex or The receptive field of a sensory Neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron ^[5] This established the neural basis for stereopsis. Their findings were disputed by David Hubel and Torsten Wiesel, although they eventually conceded when they found similar neurons in the monkey visual cortex. David Hunter Hubel (born February 27, 1926) was co-recipient with Torsten Wiesel of the 1981 Nobel Prize in Physiology or Medicine, for their Torsten Nils Wiesel (b June 3, 1924) was a Swedish co-recipient with David H A monkey is any member of either the New World monkeys or Old World monkeys two of the three groupings of Simian Primates the third group being ^[6] In the 1980s, Gian Poggio and others found neurons in V2 of the monkey brain that responded to the depth of random-dot stereograms. The term visual cortex refers to the primary visual cortex (also known as striate cortex or ^[7]

In the 1990s, Christopher Tyler invented autostereograms, random-dot stereograms that can be viewed without a stereoscope. Christopher W Tyler is a visual psychophysicist and is the Head of the Smith-Kettlewell Brain Imaging Center. An autostereogram is a single-image Stereogram (SIS designed to create the visual illusion of a three- Dimensional (3D scene from a two-dimensional ^[8] This led to the popular Magic Eye pictures. Magic Eye is a series of books published by NE Thing Enterprises (Renamed in 1996 to Magic Eye Inc

Popular culture

A stereoscope is a device by which each eye can be presented with different images, allowing stereopsis to be stimulated with two pictures, one for each eye. Stereoscopy, stereoscopic imaging or 3-D (three-dimensional imaging is any technique capable of recording three-dimensional visual This has led to various crazes for stereopsis, usually prompted by new sorts of stereoscopes. In Victorian times it was the prism stereoscope (allowing stereo photographs to be viewed), in the 1950s it was red-green glasses (allowing stereo movies to be viewed), in the 1970s it was polarizing glasses (allowing coloured movies to be viewed), and in the 1990s it was Magic Eye pictures (autostereograms). Culture The Victorian fascination with novelty resulted in a deep interest in the relationship between modernity and cultural continuities A photograph (often shortened to photo) is an Image created by Light falling on a light-sensitive surface usually Photographic film or an electronic Anaglyph images are used to provide a stereoscopic 3D effect when viewed with 2 color glasses (each lens a chromatically opposite color usually red and cyan Polarized 3D glasses create the illusion of three-dimensional images by restricting the light that reaches each Eye, an example of Stereoscopy. Magic Eye is a series of books published by NE Thing Enterprises (Renamed in 1996 to Magic Eye Inc An autostereogram is a single-image Stereogram (SIS designed to create the visual illusion of a three- Dimensional (3D scene from a two-dimensional Magic Eye pictures did not require a stereoscope, but relied on viewers using a form of free fusion so that each eye views different images.

Geometrical basis for stereopsis

Stereopsis appears to be processed in the visual cortex in binocular cells having receptive fields in different horizontal positions in the two eyes. The receptive field of a sensory Neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron Such a cell is active only when its preferred stimulus is in the correct position in the left eye and in the correct position in the right eye, making it a disparity detector.

When a person stares at an object, the two eyes converge so that the object appears at the center of the retina in both eyes. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Other objects around the main object appear shifted in relation to the main object. In the following example, whereas the main object (dolphin) remains in the center of the two images in the two eyes, the cube is shifted to the right in the left eye's image and is shifted to the left when in the right eye's image.

The two eyes converge on the object of attention.	The cube is shifted to the right in left eye's image.	The cube is shifted to the left in the right eye's image.
We see a single, Cyclopean, image from the two eyes' images.	The brain gives each point in the Cyclopean image a depth value, represented here by a grayscale depth map.

Because each eye is in a different horizontal position, each has a slightly different perspective on a scene yielding different retinal images. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Normally two images are not observed, but rather a single view of the scene, a phenomenon known as singleness of vision. Nevertheless, stereopsis is possible with double vision. This form of stereopsis was called qualitative stereopsis by Kenneth Ogle. ^[9]

If the images are very different (such as by going cross-eyed, or by presenting different images in a stereoscope) then one image at a time may be seen, a phenomenon known as binocular rivalry. Stereoscopy, stereoscopic imaging or 3-D (three-dimensional imaging is any technique capable of recording three-dimensional visual Binocular rivalry is a phenomenon of Visual perception in which perception alternates between different images presented to each Eye.

Computer stereo vision

Computer stereo vision, is a part of the field of computer vision. Computer vision is the science and technology of machines that see It is sometimes used in mobile robotics to detect obstacles. A Mobile Robot is an automatic machine that is capable of movement in a given environment See also Robot Robotics is the science and technology of Robots and their design manufacture and application

Two cameras take pictures of the same scene, but they are separated by a distance - exactly like our eyes. A computer compares the images while shifting the two images together over top of each other to find the parts that match. The shifted amount is called the disparity. The disparity at which objects in the image best match is used by the computer to calculate their distance.

For a human, the eyes change their angle according to the distance to the observed object. To a computer this represents significant extra complexity in the geometrical calculations (Epipolar geometry). Epipolar geometry refers to the geometry of stereo vision. When two cameras view a 3D scene from two distinct positions there are a number of geometric relations between the In fact the simplest geometrical case is when the camera image planes are on the same plane. The images may alternatively be converted by reprojection through a linear transformation to be on the same image plane. In Mathematics, a linear map (also called a linear transformation, or linear operator) is a function between two Vector spaces that This is called Image rectification. Image rectification is a transformation process used to project multiple images onto a common image surface

Computer stereo vision with many cameras under fixed lighting is called structure from motion. In Computer vision, structure from motion refers to the process of finding the three-dimensional structure by analyzing the motion of an object over time Techniques using a fixed camera and known lighting are called photometric stereo techniques, or "shape from shading".

Computer stereo display

Many attempts have been made to reproduce human stereo vision on rapidly changing computer displays, and toward this end numerous patents relating to 3D television and cinema have been filed in the USPTO. See also [[stereoscopy]] In film the term 3-D (or 3D) is used to describe any visual presentation system that attempts to maintain or recreate moving images Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic The United States Patent and Trademark Office ( PTO or USPTO) is an agency in the United States Department of Commerce that issues Patents to At least in the US, commercial activity involving those patents has been confined exclusively to the grantees and licensees of the patent holders, whose interests tend to last for twenty years from the time of filing.

Discounting 3D television and cinema (which generally require a plurality of digital projectors whose moving images must be synchronized by computer), several stereoscopic LCDs are going to be offered by Sharp, which has already started shipping a notebook with a built in stereoscopic LCD. WOWvx is a type of monitor screen and software tools manufactured by Philips which offers 3D images without glasses for several viewers at a time () is a Japanese Electronics manufacturer founded in 1912 It takes its name from one of its founder's first inventions the Ever-Sharp Mechanical pencil, which Although older technology required the user to don goggles or visors for viewing computer-generated images, or CGI, newer technology tends to employ fresnel lenses or plates over the liquid crystal displays, freeing the user from the need to put on special glasses or goggles. A Fresnel lens (pronounced or) is a type of lens invented by French physicist Augustin-Jean Fresnel.

References

Bibliography

• Julesz, B. (1971). Foundations of cyclopean perception. Chicago: University of Chicago Press

• Scott B. Steinman, Barbara A. Steinman and Ralph Philip Garzia. (2000). Foundations of Binocular Vision: A Clinical perspective. McGraw-Hill Medical. ISBN 0-8385-2670-5.

See also

• Horopter
• Orthoptics
• Vectograph
• Correspondence problem
• Epipolar geometry
• Stereoblindness

External links

• Middlebury Stereo Vision Page
• What is Stereo Vision?