Stereoscopic and Polerized imaging


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Stereoscopic and Polerized imaging

  3. 3. INTRODUCTION Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth. Three strategies have been used to accomplish this 1. have the viewer wear eyeglasses to combine separate images from two offset sources 2. have the viewer wear eyeglasses to filter offset images from a single source separated to each eye 3. have the light source split the images directionally into the viewers eyes (no glasses), Autostereoscopy SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 3
  5. 5. HISTORYStereoscopy creates the illusion of three-dimensional depth from images on a two-dimensional plane. Human vision needs some aid to see those illusion:Like,1. Stereopsis2. Accommodation of the eyeball (eyeball focus)3. Occlusion of one object by another4. Subtended visual angle of an object of known size5. Linear perspective (Parallel edges)6. Vertical position7. Haze, desaturation, and a shift to bluishness8. Change in size of textured pattern detail SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 5
  6. 6. All of above, Leaving first two, Are available in the form of paintings, pictures and television.Stereoscopy is the enhancement of the illusion of depth in a photograph, movie, or other two-dimensional image by presenting a slightly different image to each eye, and thereby adding the first of these cues (stereopsis) as well.Stereoscopy is also used in stereograms for entertainment purpose. Stereoscopy is useful in viewing images rendered from large multi-dimensional data sets such as are produced by experimental data. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 6
  8. 8. VISUAL REQUIREMENTAnatomically, there are 3 levels of binocular vision required to view stereo images:1. Simultaneous perception2. Fusion (binocular single vision)3. StereopsisThese functions develop in early childhood. Some people who have strabismus disrupt the development of stereopsis, however orthoptics treatment can be used to improve binocular vision. A persons stereoacuity determines the minimum image disparity they can perceive as depth. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 8
  10. 10. SIDE BY SIDETraditional stereoscopic photography consists of creating a 3-D illusion starting from a pair of 2-D images, a stereogram. The easiest way to enhance depth perception in the brain is to provide the eyes of the viewer with two different images, representing two perspectives of the same object, with a minor changes to the both parallel view eye balls.Each of the two 2-D images preferably should be presented to each eye of the viewer so that any object at infinite distance seen by the viewer should be perceived by that eye while it is oriented straight ahead, the viewers eyes being neither crossed nor diverging. When the picture contains no object at infinite distance, such as a horizon or a cloud, the pictures should be spaced correspondingly closer together. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 10
  11. 11. CHARACTERISTICSLittle or no additional image processing is required. Under some circumstances, such as when a pair of images is presented for crossed or diverged eye viewing, no device or additional optical equipment is needed.The principal advantages of side-by-side viewers is that there is no loss of brightness so images may be presented at very high resolution and in full spectrum color. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 11
  13. 13. FREEVIEWINGFreeviewing is viewing a side-by-side image without using a viewer.The parallel view method uses two images not more than 65mm between corresponding image points; this is the average distance between the two eyes. The viewer looks through the image while keeping the vision parallel.The cross-eyed view method uses the right and left images exchanged and views the images cross-eyed with the right eye viewing the left image and vice-versa. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 13
  15. 15. TRANSPARENCY VIEWERSPairs of stereo views are printed on film which is then mounted around the edge of a cardboard disk, images of each pair being diametrically opposite. A lever is used to move the disk so as to present the next image pair. A series of seven views can thus be seen on each card when it was inserted into the View-Master viewer. These viewers were available in many forms both non-lighted and self-lighted and may still be found today.Low-cost folding cardboard viewers with plastic lenses have been used to view images from a sliding card and have been used by computer technical groups as part of annual convention proceedings. These have been supplanted by the DVD recording and display on a television set. By exhibiting moving images of rotating objects a three dimensional effect is obtained through other than stereoscopic means. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 15
  17. 17. HEAD MOUNTED DISPLAYThe user typically wears a helmet or glasses with two small LCD or OLED displays with magnifying lenses, one for each eye. The technology can be used to show stereo films, images or games, but it can also be used to create a virtual display. Head- mounted displays may also be coupled with head-tracking devices, allowing the user to "look around" the virtual world by moving their head, eliminating the need for a separate controller.Augmented stereoscopic vision is also expected to have applications in surgery, as it allows the combination of radiographic data (CAT scans and MRI imaging) with the surgeons vision SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 17
  19. 19. 3D VIEWERSActiveLiquid crystal shutter glassesGlasses containing liquid crystal that block or pass light through in synchronization with the images on the computer display, using the concept of alternate-frame sequencing. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 19
  20. 20. PassiveLinearly polarized glassesTo present a stereoscopic motion picture, two images are projected superimposed onto the same screen through orthogonal polarizing filters. The projectors can receive their outputs from a computer with a dual-head graphics card. 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. Linearly polarized glasses require the viewer to keep his head level. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 20
  21. 21. Circularly polarized glassesTo present a stereoscopic motion picture, two images are projected superimposed onto the same screen through circular polarizing filters of opposite handedness. The viewer wears low-cost eyeglasses which contain a pair of analyzing filters of opposite handedness. The result is similar to that of stereoscopic viewing using linearly polarized glasses, except the viewer can tilt his or her head and still maintain left/right separation (though the tilt will still affect the brains ability to fuse the two images and correctly perceive depth).Other Technologies:1. Infitec glasses2. Inficolor 3D SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 21
  23. 23. COMPLEMENTARY COLOUR ANAGLYPHComplementary color anaglyphs employ one of a pair of complementary color filters for each eye. The most common color filters used are red and cyan. The eye is sensitive to three primary colors, red, green, and blue. The red filter admits only red, while the cyan filter blocks red, passing blue and green (the combination of blue and green is perceived as cyan). If a paper viewer containing red and cyan filters is folded so that light passes through both, the image will appear black.Other Technologies1. Colour code 3d SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 23
  25. 25. CHROMADEPTH METHOD AND GLASSESThe ChromaDepth procedure of American Paper Optics is based on the fact that with a prism, colors are separated by varying degrees. The ChromaDepth eyeglasses contain special view foils, which consist of microscopically small prisms. This causes the image to be translated a certain amount that depends on its color. If one uses a prism foil now with one eye but not on the other eye, then the two seen pictures – depending upon color – are more or less widely separated. The brain produces the spatial impression from this difference. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 25
  27. 27. AUTOSTEREOSCOPYAutostereoscopy is any method of displaying stereoscopic (3D) images without the use of special equipment or glasses on the part of the viewer. Because headgear is not required, it is also called "glasses-free 3D".The technology includes two broad classes of displays:1. those that use head-tracking to ensure that each of the viewers two eyes sees a different image on the screen,2. those that display multiple views so that the display does not need to know where the viewers eyes are directed. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 27
  28. 28. OTHER DISPLAY METHODS1. Autostereograms: More recently, random-dot Autostereograms have been created using computers to hide depth information in a field of apparently random noise, so that until viewed by diverging or converging the eyes in a manner similar to naked eye viewing of stereo pairs, the subject of the image remains a mystery.2. Pulfrich effects: In the classic Pulfrich effect paradigm a subject views, binocularly, a pendulum swinging perpendicular to his line of sight. When a neutral density filter (e.g., a darkened lens -like from a pair of sunglasses) is placed in front of, say, the right eye the pendulum appears to take on an elliptical orbit, being closer as it swings toward the right and farther as it swings toward the left.3. 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. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 28
  30. 30. TAKING PICTURESIt is necessary to take two photographs for a stereoscopic image. This can be done with two cameras, with one camera moved quickly to two positions, or with a stereo camera incorporating two or more side-by-side lenses.Many of the conventional cameras used the film for 35 mm transparency slides, and the new stereoscopic cameras utilized the film to make stereoscopic slides. The Stereo Realist camera was the most popular, and its 5P picture format became a standard.The beginning of the 21st century marked the coming of the age of digital photography. Stereo lenses were introduced which could turn an ordinary film camera into a stereo camera by using a special double lens to take two images and direct them through a single lens to capture them side-by-side on the film. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 30
  31. 31. Longer base line for distant objects "Hyper Stereo"If a stereo picture is taken of a large, distant object such as a mountain or a large building using a normal base it will appear to be flat. This is in keeping with normal human vision, it would look flat if you were actually there, but if the object looks flat, there doesnt seem to be any point in taking a stereo picture, as it will simply seem to be behind a stereo window, with no depth in the scene itself, much like looking at a flat photograph from a distance.For making stereo images featuring only a distant object the camera positions can be separated by a larger distance than the adult human norm of 62-65mm. This will effectively render the captured image as though it was seen by a giant, and thus will enhance the depth perception of these distant objects, and reduce the apparent scale of the scene proportionately. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 31
  32. 32. Shorter baseline for ultra close-ups "Macro stereo"When objects are taken from closer than about 6 1/2 feet a normal base will produce excessive parallax and thus exaggerated depth when using ortho viewing methods. At some point the parallax becomes so great that the image is difficult or even impossible to view. For such situations, it becomes necessary to reduce the baseline in keeping with the 1:30 rule. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 32
  33. 33. Stereoscopic Motion Measurement (6D-Vision)6D-Vision tracks points with known depth from stereo over two or more consecutive images and fuses the data. The result is an improved accuracy of the 3D-position and an estimation of the 3D-motion (velocity and direction) of the considered points at the same time. SIDDHARTH AYER DHARMENDRABHAI (08DCE025) 33