Stereoscopy (also called stereoscopics , or stereo imaging ) is a technique for creating or enhancing the illusion of depth in images through stereopsis for binocular vision. The word stereoscopy comes from the Greek ??????? (stereo) , which means 'solid, solid', and ?????? (skope?) , which means 'see, see'. Each stereoscopic image is called stereogram . Initially, the stereogram refers to a pair of stereo images that can be viewed using a stereoscope.
Most stereoscopic methods present two offset images separately to the left and right eye of the observer. This two-dimensional image is then combined in the brain to provide 3D depth perception. This technique is distinguished from a 3D view that displays images in three full dimensions, enabling observers to enhance information about 3-dimensional objects displayed by head and eye movements.
Video Stereoscopy
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Stereoscopy creates the illusion of three-dimensional depth from a given two-dimensional image. The human vision, including the perception of depth, is a complex process, which only begins with the acquisition of visual information taken through the eye; many processes occur within the brain, as they seek to understand the raw information. One of the functions that occur in the brain because it interprets what the eye sees is to assess the relative distance of the object from the viewer, and the dimensions of the depth of the objects. The cues that the brain uses to measure relative distance and depth in the perceived scene are included
- Stereopsis
- Accommodation of the eye
- Overlap one object with another
- Unlimited viewing angle of objects with known size
- Linear perspectives (parallel edge convergence)
- Vertical position (objects closer to the horizon at the scene are likely to be perceived further)
- Fog or contrast, saturation, and color, larger distances are generally associated with larger haze, desaturation, and a shift toward the blue
- Text size pattern text size changes
(All but two of the first of the above instructions are in traditional two-dimensional drawings, such as paintings, photographs, and television.)
Stereoscopy is the production of depth illusion in photographs, films, or other two-dimensional images with a slightly different image presentation on each eye, which adds the first gesture (stereopsis). Both images are then combined in the brain to provide depth perception. Since all the points in the image generated by the stereoscopy focus on the same plane irrespective of its depth in the original scene, the second gesture, focus, is not duplicated and therefore the illusion of depth is incomplete. There are also mainly two unnatural stereoscopy effects for human vision: (1) incompatibility between convergence and accommodation, caused by the difference between the perceived position of the object in front of or behind the scenes or screen and the real origin of that light. ; and (2) the possibility of crosstalk between the eyes, caused by improper image separation in some stereoscopy methods.
Although the term "3D" is used everywhere, the presentation of a double 2D image is clearly different from displaying images in three full dimensions. The most striking difference is that, in the case of the "3D" view, the observer's head and the observer's eye movements do not alter the received information about the 3-dimensional object being viewed. Showing holographic and volumetric views do not have these restrictions. Just as it is not possible to re-create a full 3-dimensional sound field with just two stereophonic speakers, it is a redundant statement to call a 2D double "3D" image. The accurate term "stereoscopic" is more complicated than the erroneous "3D", which has been ingrained for years without accident. Although most stereoscopic views do not qualify as real 3D views, all real 3D views are also stereoscopic views because they meet the lower criteria as well.
Most 3D displays use this stereoscopic method to deliver images. It was first discovered by Sir Charles Wheatstone in 1838, and repaired by Sir David Brewster who made the first portable 3D viewing device.
Wheatstone initially used a stereoscope (a rather large tool) with images because photography was not yet available, but the original paper seemed to predict the development of a realistic imaging method:
For illustrative purposes, I only use outline numbers, since shadows or colorations have been introduced, it may be suspected that the effect is wholly or partially due to these circumstances, whereas by letting them not be considered, no dubious spaces remain. that the whole effect of relief is due to the simultaneous perception of two monocular projections, one on each retina. But if it takes to get the most loyal resemblance of a real object, shadowing and coloring can appropriately be used to enhance the effect. Careful attention will allow an artist to draw and paint two component images, thus presenting to the observer's mind, in the resulting perception, of the perfect identity with the object being represented. Flowers, crystals, sculptures, vases, instruments of various kinds, & amp; c, so it may be represented so as not to be distinguished by the visions of the real object itself.
Stereoscopy is used in photogrammetry and also for entertainment through the production of stereograms. Stereoscopy is useful in viewing images provided from large multi-dimensional data sets such as those produced by experimental data. Modern three-dimensional photography can use 3D scanners to detect and record three-dimensional information. Three-dimensional depth information can be reconstructed from two images using a computer by connecting pixels in the left and right images. Troubleshooting Correspondence in Computer Vision aims to create meaningful in-depth information from two images.
Visual requirements
Anatomically, there are 3 levels of binocular vision necessary to view the stereo image:
- Concurrent perception
- Fusion (single vision binocular)
- Stereopsis
These functions develop in early childhood. Some people with strabismus interfere with the development of stereopsis, but orthoptic treatment can be used to improve binocular vision. Stereoacuity of a person determines the minimum image disparity they can feel as depth. It is believed that about 12% of people can not see 3D images well, due to various medical conditions. According to another experiment up to 30% of people have very weak stereoscopic vision that prevents them from depth perception based on stereo disparity. This cancels or greatly reduces the effect of stereo immersion to them.
Stereoscopic vision can be made artificially by the viewer's brain, as demonstrated by the Van Hare Effect, in which the brain sees stereo images even when the paired image is identical. This "wrong dimension" results from the stereoacuity developed in the brain, allowing the viewer to fill in depth information even when some 3D cues are actually available in the paired image.
Maps Stereoscopy
Side by Side
Traditional stereoscopic photography consists of creating a 3D illusion starting from a pair of 2D images, a stereogram. The easiest way to increase the perception of depth in the brain is to give the eyes of viewers with two distinct images, representing two perspectives of the same object, with small deviations similar to or similar to the perspective that both eyes naturally receive in binocular vision.
To avoid eye fatigue and distortion, each of the two 2D images must be presented to the viewer so that each object at an infinite distance is perceived by the eye as straight forward, the observer's eyes are not crossed or divergent. When images do not contain objects at infinite distance, such as horizons or clouds, the images should be placed close together.
The advantage of side-by-side viewers is the lack of brightness reduction, allowing the presentation of images at very high resolution and in full-spectrum colors, simplicity in creation, and little or no additional image processing is required. In certain circumstances, such as when a pair of images are presented for free viewing, no additional optical device or equipment is required.
The main disadvantage of side-by-side viewers is that displaying large images is impractical and the resolution is limited by the lower display media or the human eye. This is because when the dimensions of an image are raised, either the viewer or the viewer itself must move proportionately further away from it in order to view it comfortably. Moving closer to the image to see more details will only be possible by looking at equipment that is adjusted for the difference.
Freeviewing
Freeviewing is looking at the pair of side-by-side images without using the viewing device.
Two methods are available for freeview:
- The parallel viewing method uses pairs of images with left-eye images on the left and right eye images on the right. The fused three-dimensional images appear larger and farther from the actual two images, making it possible to simulate life-size scenes. The viewer seeks to see through images with eyes that are substantially parallel, as if seeing the actual scene. This can be difficult with normal vision because the eye focus and binocular convergence are usually coordinated. One approach to separating the two functions is to see the pair of images very close to the eye that is completely relaxed, not trying to focus clearly but only achieving a comfortable stereoscopic blend of two blurry images with a "see-through" approach, and only then exerting efforts to focus them more clearly, increasing the required visibility. Regardless of the approach used or the image medium, to see the stereoscopic comfort and accuracy the size and distance of the image should be such that the corresponding points of the very distant objects in the scene are separated by the same distance as the eyes of the viewers, but not more; the average interocular distance is about 63 mm. Looking at far more separate images is possible, but because the eye never deviates from normal use it usually requires some prior training and tends to cause eye strain.
- The cross-eyed viewing method of exchanging left and right eye pictures so that they will be seen correctly with squint eyes, left eye viewing images on the right and vice versa. The fused three-dimensional image looks smaller and closer than the actual image, so that large objects and scenes look miniature. This method is usually easier for beginner freeviewing. As an aid to fusion, the fingertips can be placed just below the division between the two images, then slowly brought directly toward the eyes of the viewer, keeping the eyes directed at the fingertips; at some distance, the fused three-dimensional image seems to be hovering just above the finger. Alternatively, a piece of paper with small opening pieces into it can be used in a similar way; when positioned correctly between the image pairs and the viewer's eyes, it seems to be framing a small three-dimensional image.
Prism glasses and self-masking are now used by multiple cross-eyed supporters. This reduces the required convergence level and allows large images to be displayed. However, seeing help that uses prisms, mirrors or lenses to help fusion or focus is just the type of stereoscope, excluded by the general definition of freeviewing.
Stereoscopically combining two separate images without the aid of a mirror or prism while keeping them in sharp focus without the aid of a suitable vision lens definitely requires an unnatural combination of eye vergence and accommodation. Therefore, a simple free view can not accurately reproduce the physiological depth guidance of the real-world viewing experience. Different individuals may experience different levels of ease and comfort in achieving good fusion and focus, as well as different tendencies for fatigue or eye strain.
Autostereogram
An autostereogram is a single image stereogram (SIS), designed to create the visual illusion of a three-dimensional (3D) scene in the human brain from an external two-dimensional image. To see the 3D shape in this autostereogram, one must overcome the automatic coordination between focusing and vergency.
Stereoscope and stereographic card
A stereoscope is essentially an instrument in which two photographs of the same object, taken from a slightly different angle, are presented simultaneously, one for each eye. A simple stereoscope is limited in the size of a usable image. A more complex stereoscope uses a pair of horizontally similar periscope devices, enabling the use of larger images that can present more detailed information in a wider field of view.
Transparency viewers
Some stereoscopes are designed to view transparent photos on film or glass, known as transparency or diapositive and commonly called slides . Some of the earliest stereoscope views, published in the 1850s, were in glass. At the beginning of the 20th century, glass slides 45x107 mm and 6x13 cm are common formats for amateur stereo photography, especially in Europe. Several years later, several movie-based formats were used. The most famous formats for commercially-released stereo views on movies are Tru-Vue, introduced in 1931, and View-Master, introduced in 1939 and still in production. For amateur stereo slides, the Stereo Realist format, introduced in 1947, is by far the most common.
Displays head-mount
Users usually wear helmets or sunglasses with two small LCD or OLED screens with magnifying lenses, one for each eye. This technology can be used to display stereo movies, images or games, but can also be used to create a virtual view . Head-mounted displays can also be combined with a head-tracking device, which allows users to "browse" the virtual world by moving their heads, eliminating the need for separate controllers. Performing this update quickly enough to avoid nausea in the user requires a lot of computer image processing. If a six-axis position (direction and position) sensing is used then the user can move within the limits of the equipment used. Due to the rapid advances in computer graphics and the continued miniaturization of videos and other equipment, these devices are available for a more reasonable cost.
Useable or worn glasses can be used to view translucent images worn in real-world views, creating what is called augmented reality. This is done by reflecting the video image through a partial reflective mirror. A real-world view is seen through the reflective surface of a mirror. Experimental systems have been used to play games, where virtual opponents can peer from real windows when a player moves. This type of system is expected to have extensive applications in complex system maintenance, as it can give an technician what is the effective "x-ray vision" by combining the rendering of hidden element computer graphics with the technician's natural vision. In addition, technical data and schematic diagrams may be sent to this same equipment, eliminating the need to obtain and carry large paper documents.
Augmented stereoscopic vision is also expected to have applications in operation, as it allows a combination of radiographic data (CAT scan and MRI imaging) with the vision of the surgeon.
Displays the virtual retina
The virtual retina display (VRD), also known as retinal scan (RSD) or retinal projector (RP), should not be equated with "Retina Display", is a display technology that draws raster images (like television images) directly into the retina of the eye. Users see what appears to be a conventional display floating in space in front of them. For real stereoscopy, each eye must be equipped with its own discrete display. To produce a virtual display that occupies a very useful visual angle but does not involve the use of a relatively large lens or mirror, the light source must be very close to the eye. Contact lenses that combine one or more semiconductor light sources are the most common form of submission. In 2013, the inclusion of suitable light-beam scanners in contact lenses is still very problematic, as is the alternative of planting a fairly transparent arrangement of hundreds of thousands (or millions, for HD resolution) from collimated light sources.
3D Viewers
There are two categories of 3D viewer technology, active and passive. Active viewers have electronics that interact with the screen. Passive viewers filter the constant flow of binocular input to the appropriate eye.
Active
System Shutter
The shutter system works by openly displaying images aimed at the left eye while blocking the right eye view, then displaying the right eye image while blocking the left eye, and repeating this so quickly that the interruptions do not interfere with the fusion that the two images are feeling into a 3D image. It generally uses a liquid crystal shutter glass. Each glass eye contains a liquid crystal layer that has properties darkened when applied voltage, becomes transparent. The glass is controlled by a time signal that allows the glasses to alternate dark over one eye, and then the other, in sync with the screen refresh rate. The main disadvantage of active windows is that most videos and 3D movies are taken with the left and right view simultaneously, thus introducing "time parallax" for anything moving on the sides: for example, a person walking at 3.4 mph looks 20% too close or 25% too far in the latest case of 2x60 Hz projection.
Passive
System polarization
To present a stereoscopic image, two projected images are superimposed onto the same screen through a polarizing filter or presented on a screen with polarized filters. For projection, the silver screen is used so that polarization is maintained. In most passive displays, each pixel row is polarized for one eye or the other. This method is also known as interlaced. Spectators wear cheap glasses that also contain a pair of opposite polarization filters. Since each filter just passes the same light polarized and blocks opposing polarized light, each eye only sees one of the images, and the effect is reached.
Interference filter system
This technique uses certain wavelengths of red, green, and blue for the right eye, and different red, green, and blue wavelengths for the left eye. Glasses that filter very specific wavelengths allow the user to see full-color 3D images. It is also known as spectral comb filtering or the wavelength of multiplex visualization or super-anaglyph . Dolby 3D uses this principle. The Omega/Panavision 3D 3D system has also used a better version of this technology. In June 2012, the Omega/Panavision 3D 3D system was discontinued by DPVO Theatrical, who marketed it on behalf of Panavision, citing "challenging global economic and global 3D markets"?.
Anaglyph color system
Anaglyph 3D is the name given to the 3D stereoscopic effect achieved by encoding the image of each eye using a different (usually colored) color filter, usually red and cyan. The Red-cyan filter can be used because our vision processing system uses red and cyan comparisons, as well as blue and yellow, to determine the color and contour of the object. Anaglyph 3D images contain two color images that are filtered differently, one for each eye. When viewed through the "color-code" "anaglyph" glasses, each of the two images reaches one eye, showing an integrated stereoscopic image. The brain's visual cortex brings this into a scene perception or three-dimensional composition.
Chromadepth System
The ChromaDepth Procedure of American Paper Optics is based on the fact that with prisms, colors are separated by varying degrees. ChromaDepth glasses contain a special look, which consists of a small microscopic prism. This causes the image to be translated by a certain amount depending on the color. If one uses a prism foil now with one eye but not the other, the two images viewed - depending on the color - are more or less widely separated. The brain produces a spatial impression of this difference. The advantage of this technology consists of all the fact that one can assume the ChromaDepth image also without glasses (thus two dimensions) is problem-free (unlike with two anaglyph colors). However the color can only be selected in a limited way, as it contains the depth of image information. If someone changes the color of an object, the observed distance will also be changed.
Pulfrich Method
The Pulfrich effect is based on a slower human eye-processing image phenomenon when there is less light, such as when looking through a dark lens. Since the Pulfrich effect depends on movement in a particular direction to instill the illusion of depth, it is useless as a common stereoscopic technique. For example, it can not be used to indicate stationary objects that seem to widen in or out of the screen; equally, the object moving vertically will not be visibly moving in depth. The unintentional movement of objects will create fake artifacts, and these incidental effects will be seen as artificial depths unrelated to the actual depth in the scene.
Over/under Format
Stereoscopic observations are achieved by placing the pairs of images one on top of each other. Custom audiences are created for over/under formats that tilt the right vision slightly upward and the vision to the left slightly down. The most common with mirrors is Magic View. Another with prismatic glasses is the KMQ viewer. The use of this technique recently is the openKMQ project.
Other viewing methods without audiences
Autostereoscopy
The autostereoscopic display technology uses an optical component on the screen, not used by the user, to allow each eye to view different images. Because headgear is not required, it is also called "free 3D glasses". Optics divide the image directly into the viewer's eye, so the view geometry display requires a limited head position that will achieve a stereoscopic effect. The autoresiskopi screens provide many of the same scenes, not just two. Each view is visible from different positions in front of the screen. This allows the viewer to move left and right in front of the screen and see the correct view of any position. This technology includes two broad display classes: one that uses head tracing to ensure that each of the two eyes of vision sees different images on the screen, and those that display multiple views so that the screen does not need to know where viewers' eyes are directed. Examples of autostereoscopic display technologies include lenticular lenses, parallax barrier, volumetric display, holography, and light field display.
Holography
Laser holography, in its original "pure" form of photographic transmission holograms, is the only technology created that can reproduce objects or scenes with such complete realism that visual reproduction can not be distinguished from the original, remembering original lighting conditions. This creates a field of light identical to what emanates from the original scene, with parallax about all the very wide axes and angles. The eyes differentially focus the object at different distances and subject detail is maintained to the microscopic level. The effect is exactly like looking through windows. Unfortunately, this "pure" form requires a laser-lit subject and absolutely immobile - into a small part of the wavelength of light - during photographic exposure, and a laser beam must be used to see the results correctly. Most people have never seen a transmission hologram with a laser beam. The types of holograms commonly encountered have highly compromised image quality so that ordinary white light can be used for viewing, and imaging processes between non-holographic are almost always used, as an alternative to using powerful and harmful pulsed lasers, when live subjects are photographed.
Although the original photographic process has proven to be impractical for general use, the combination of computer-generated holograms (CGH) and optoelectronic holographic displays, both in development over the years, has the potential to transform the dream of a half-century long-pipe 3D holographic television into reality; so far, however, a large number of calculations are required to produce only one detailed hologram, and the large bandwidth required to transmit its flow, has limited this technology to the research lab.
In 2013, Silicon Valley Company LEIA Inc. began producing holographic displays suitable for mobile devices (watches, smartphones or tablets) using multi-directional backlight and allowing wide-angle full-parallax views to view 3D content without the need for glasses.
Showing volumetric
Volumetric displays use several physical mechanisms to display the point of light in the volume. Such a display uses voxels instead of pixels. Volumetric displays include multiplanar displays, which have multiple stacked display planes, and rotate the panel display, where rotating panels sweep the volume.
Other technologies have been developed to project the point of light in the air above the device. Infrared lasers are focused on purpose in space, producing tiny plasma bubbles that emit visible light.
Integral imagery
Integral imagery is a technique for producing autostereoscopic and multiscopic 3D display, which means that 3D images are viewed without the use of special glasses and different aspects are seen when viewed from different positions horizontally or vertically. This is achieved by using array microlenses (similar to lenticular lenses, but XY or "fly's eye" arrays where each lenslet usually forms its own image of a scene without the aid of a larger objective lens) or a small hole to capture and display the scene as a field 4D light, produces stereoscopic images that show real parallax changes and perspectives when viewers move left, right, up, down, closer, or farther.
Wiggle stereoscopy
Wiggle stereoscopy is an image viewing technique achieved with a fast alternating view from the left and right sides of a stereogram. Found in animated GIF format on the web. An online example is seen in the New York Public Library stereogram collection. This technique is also known as "Piku-Piku".
stereo photography techniques
For general purpose stereo photography, where the aim is to duplicate the natural human vision and give the visual impression as close as possible to actually be there, the correct baseline (the distance between where the right and left images are taken) will equal the distance between the eyes. When images taken with such baselines are viewed using a display method that duplicates the conditions in which the image is taken then the result will be an image that is almost identical to what will be seen on the site the photo was taken. This can be described as "stereo ortho."
However, there are situations that may be desirable to use a longer or shorter baseline. Factors to consider include the viewing method to be used and the purpose of taking the picture. The baseline concept also applies to other branches of stereography, such as stereo images and computer-generated stereo images, but involves the selected viewpoint rather than physical separation of the camera or the actual lens.
Stereo window
The concept of stereo windows is always important, since windows is a stereoscopic image of the external boundaries of the left and right views that are stereoscopic imagery. If there is an object, which is cut off by the lateral side of the window, placed in front of it, the result of unnatural and undesirable effects, this is called "window transgression". This can be understood by returning to the actual physical window analogy. Therefore, there is a contradiction between two different depth gestures: some image elements are hidden by the window, so the window appears closer than these elements, and the same element of the image appears closer than the window. So the stereo window should always be adjusted to avoid window violations.
Some objects can be seen in front of windows, as long as they do not reach the lateral side of the window. But these objects can not be seen as too close, because there is always a limit of parallax coverage to look comfortable.
If the scene is seen through a window, the whole scene is usually behind the window, if the view is far away, the distance will be far behind the window, if it is nearby, it will appear outside the window. The smaller object of the window itself can even penetrate the window and appear partially or completely in front of it. The same applies to parts of larger objects that are smaller than windows. The purpose of setting the stereo window is to duplicate this effect.
Therefore, the window location versus the entire image should be adjusted so that most of the images are visible outside the window. In terms of viewing on a 3D TV, it is easier to place a window in front of the image, and leave the window in the display area.
In contrast, in case of projection on a much larger screen, it is much better to set the window in front of the screen (it's called "floating window"), for example so that it is seen about two meters by the viewer sitting in the first row. Therefore, these people will usually see the background image on the infinite. Of course the viewer sitting outside will see the window farther, but if the image is made in normal condition, so the first row viewers see this background in infinity, other viewers, sitting in the back, will also see this background in infinity, because this background parallax is the same as the average human interocular.
The entire scene, including the window, can be moved back or forwards in depth, by moving the left eye and right eye view relative to each other horizontally. Moving one or both images away from the center will bring the whole scene away from the viewer, while moving one or both images to the center will move the entire scene towards the viewer. This may be, for example, if two projectors are used for this projection.
In the adjustment of stereo photography window is done by shifting/cropping the image, in other forms of stereoscopy such as drawings and computer generated picture windows are built into the image design when generated.
Images can be trimmed creatively to create stereo windows that do not have to be rectangular or lie flat on a plane perpendicular to the sight line of vision. The edge of the stereo frame can be straight or curved and, when viewed in 3D, can flow in or away from the viewer and through the scene. This designed stereo frame can help emphasize certain elements of the stereo image or can be an artistic component of the stereo image.
Usage
While stereoscopic images are commonly used for entertainment, including stereographic cards, 3D movies, stereoscopic video games, prints using anaglyph and images, posters and autostereograms books, there are also other uses of this technology.
Art
Salvador DalÃÆ' created some impressive stereograms in his explorations in various optical illusions. The red-and-cyan anaglif stereoscopic images have also been hand-painted.
Education
In the 19th century, it was realized that stereoscopic images provide an opportunity for people to experience places and things far away, and many series of tours are produced, and published books allow people to learn about geography, science, history, and eyes other lessons. The usage continued into the mid-20th century, with Keystone View Company producing cards into the 1960s.
Space exploration
The Mars Exploration Rovers, launched by NASA in 2003 to explore the surface of Mars, is equipped with a unique camera that allows researchers to view stereoscopic images of the Martian surface.
Two cameras that make up Povers every rover are located 1.5 m above ground level, and separated by 30 cm, with 1 degree toe-in. This allows the image pair to be made into a scientifically useful stereoscopic image, which can be viewed as a stereogram, anaglif, or processed into a 3D computer image.
The ability to create realistic 3D images from a pair of cameras at a human height would give researchers an increased insight into the nature of the landscape seen. In environments without known blurred atmospheres or landmarks, humans rely on stereoscopic directions to assess distances. Therefore, a single camera point of view is more difficult to interpret. Some stereoscopic camera systems such as Watch overcome this problem with unmanned space exploration.
Clinical use
Stereogram cards and vectographs are used by optometrists, ophthalmologists, orthopedists and vision therapists in the diagnosis and treatment of binocular vision and accommodative disorders.
Use of math, scientific and engineering
Source of the article : Wikipedia
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