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94-442: Magic Eye is a series of books that feature autostereograms . After creating its first images in 1991, creator Tom Baccei worked with Tenyo, a Japanese company that sells magic supplies. Tenyo published its first book in late 1991 titled Miru Miru Mega Yokunaru Magic Eye ("Your Eyesight Gets Better & Better in a Very Short Rate of Time: Magic Eye"), sending sales representatives out to street corners to demonstrate how to see

188-558: A "dangerous and degrading speculation". He accepted adaptive changes, but he strongly opposed Darwin's statement about the primordial form , which he considered an offensive idea to "both the naturalist and the Christian." Brewster married twice. His first wife, Juliet Macpherson (c. 1776–1850), was a daughter of James Macpherson (1736–1796), a probable translator of Ossian poems. They married on 31 July 1810 in Edinburgh and had four sons and

282-478: A clergyman. He received his MA in 1800, was licensed as a minister of the Church of Scotland , and then preached around Edinburgh on several occasions. By then, Brewster had already shown a strong inclination for the natural sciences and had established a close association with James Veitch of Inchbonny . Veitch, who enjoyed a local reputation as a man of science and was particularly skilled in making telescopes ,

376-415: A complex, repeated background. Yet, despite the apparent chaotic arrangement of patterns, the brain is able to place every tiger icon at its proper depth. Autostereograms where patterns in a particular row are repeated horizontally with the same spacing can be read either cross-eyed or wall-eyed. In such autostereograms, both types of reading will produce similar depth interpretation, with the exception that

470-536: A daughter: Brewster married a second time in Nice, on 26 (or 27) March 1857, to Jane Kirk Purnell (b. 1827), the second daughter of Thomas Purnell of Scarborough. Lady Brewster famously fainted at the Oxford evolution debate of 30 June 1860. Brewster died in 1868, and was buried at Melrose Abbey , next to his first wife and second son. The physics building at Heriot-Watt University is named in his honour. A bust of Brewster

564-592: A later period he was one of the leading contributors to the Encyclopædia Britannica (seventh and eighth editions) writing, among others, the articles on electricity, hydrodynamics , magnetism , microscope , optics , stereoscope , and voltaic electricity . He was elected a member of the American Antiquarian Society in 1816. In 1819 Brewster undertook further editorial work by establishing, in conjunction with Robert Jameson (1774–1854),

658-440: A person to see 3D shapes from a single 2D image without the aid of optical equipment. In 1991 computer programmer Tom Baccei and artist Cheri Smith created the first color random-dot autostereograms, later marketed as Magic Eye . A computer procedure that extracts back the hidden geometry out of an autostereogram image was described by Ron Kimmel . In addition to classical stereo it adds smoothness as an important assumption in

752-460: A regular contributor to the Edinburgh Magazine , of which he acted as editor 1802–1803 at the age of twenty. In 1807, he undertook the editorship of the newly projected Edinburgh Encyclopædia , of which the first part appeared in 1808, and the last not until 1830. The work was strongest in the scientific department, and many of its most valuable articles were from the pen of the editor. At

846-496: A result, the number of depth planes must be smaller than the pattern width. The fine-tuned gradient requires a pattern image more complex than standard repeating-pattern wallpaper, so typically a pattern consisting of repeated random dots is used. When the autostereogram is viewed with proper viewing technique, a hidden 3D scene emerges. Autostereograms of this form are known as Random Dot Autostereograms. Smooth gradients can also be achieved with an intelligible pattern, assuming that

940-435: A single image stereogram in 1970 and Swiss painter Alfons Schilling created a handmade single-image stereogram in 1974, after creating more than one viewer and meeting with Julesz. Having experience with stereo imaging in holography , lenticular photography , and vectography , he developed a random-dot method based on closely spaced vertical lines in parallax. In 1979, Christopher Tyler of Smith-Kettlewell Institute ,

1034-477: A student of Julesz and a visual psychophysicist , combined the theories behind single-image wallpaper stereograms and random-dot stereograms (the work of Julesz and Schilling) to create the first black-and-white random-dot autostereogram with the assistance of computer programmer Maureen Clarke using Apple II and BASIC . Stork and Rocca published the first scholarly paper and provided software for generating random-dot stereograms. This type of autostereogram allows

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1128-599: A work which embodied the results of more than 20 years' investigation of original manuscripts and other available sources. Brewster's position as editor brought him into frequent contact with the most eminent scientific men, and he was naturally among the first to recognise the benefit that would accrue from regular communication among those in the field of science. In a review of Charles Babbage 's book Decline of Science in England in John Murray's Quarterly Review , he suggested

1222-485: Is an early example of dissociating vergence from accommodation—a necessary ability for seeing autostereograms. However, Porta saw competition between images viewed by the two eyes, binocular rivalry . It was not until 1838 that the Charles Wheatstone published an example of cooperation between the images in the two eyes: stereopsis (binocular depth perception). He explained that the depth arose from differences in

1316-404: Is capable of learning to see the images within autostereograms. "Like learning to ride a bicycle or to swim, some pick it up immediately, while others have a harder time." As with a photographic camera , it is easier to make the eye focus on an object when there is intense ambient light. With intense lighting, the eye can constrict the pupil , yet allow enough light to reach the retina. The more

1410-441: Is especially apparent at the left hand edge of the screen where the scan speed is still settling after the flyback phase. On a TFT LCD , which functions differently, this does not occur and the effect is not present. Higher quality CRT displays also have better linearity and exhibit less or none of this effect. Much advice exists about seeing the intended three-dimensional image in an autostereogram. While some people may quickly see

1504-399: Is important in being able to see 3D images. Thus it may help to concentrate on converging/diverging the two eyes to shift images that reach the two eyes, instead of trying to see a clear, focused image. Although the lens adjusts reflexively in order to produce clear, focused images, voluntary control over this process is possible. The viewer alternates instead between converging and diverging

1598-569: Is in the Hall of Heroes of the National Wallace Monument in Stirling . Brewster's views on the possibility of evolution of intelligence on other planets, contrasted with the opinion of William Whewell , are cited in the novel Barchester Towers . He appears as a minor antagonist in the 2015 video game Assassin's Creed Syndicate as a scientist working for the game's opposing faction. He

1692-501: Is one of depth perception and involves stereopsis : depth perception arising from the different perspective each eye has of a three-dimensional scene, called binocular parallax . Individuals with disordered binocular vision and who cannot perceive depth may require a wiggle stereogram to achieve a similar effect. The simplest type of autostereogram consists of a horizontally repeating pattern, with small changes throughout, that looks like wallpaper . When viewed with proper vergence ,

1786-416: Is possible because the grayscale depth map allows individual pixels to be placed on one of 2 depth planes, where n is the number of bits used by each pixel in the depth map. In practice, the total number of depth planes is determined by the number of pixels used for the width of the pattern image. Each grayscale value must be translated into pixel space in order to shift pixels in the final autostereogram. As

1880-415: Is referred to as the depth or z -axis value of a particular pattern in the autostereogram. The depth value is also known as Z-buffer value. The brain is capable of almost instantly matching hundreds of patterns repeated at different intervals in order to recreate correct depth information for each pattern. An autostereogram may contain some 50 tigers of varying size, repeated at different intervals against

1974-434: Is repeated at a different interval to place it on a different depth plane. The two non-repeating lines can be used to verify correct wall-eyed viewing. When the autostereogram is correctly interpreted by the brain using wall-eyed viewing, and one stares at the dolphin in the middle of the visual field, the brain should see two sets of flickering lines, as a result of binocular rivalry . While there are six dolphin patterns in

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2068-401: Is the visual blending of two similar but not identical images into one, with resulting visual perception of solidity and depth . In the human brain, stereopsis results from complex mechanisms that form a three-dimensional impression by matching each point (or set of points) in one eye's view with the equivalent point (or set of points) in the other eye's view. Using binocular disparity ,

2162-449: Is viewed with the correct vergence. Unlike normal stereograms, autostereograms do not require the use of a stereoscope . A stereoscope presents 2D images of the same object from slightly different angles to the left eye and the right eye, allowing the viewer to reconstruct the original object via binocular disparity . When viewed with the proper vergence, an autostereogram does the same, the binocular disparity existing in adjacent parts of

2256-607: The Edinburgh Philosophical Journal , which took the place of the Edinburgh Magazine . The first ten volumes (1819–1824) were published under the joint editorship of Brewster and Jameson, the remaining four volumes (1825–1826) being edited by Jameson alone. After parting company with Jameson, Brewster started the Edinburgh Journal of Science in 1824, 16 volumes of which appeared under his editorship during

2350-741: The Royal Swedish Academy of Sciences , and in 1822 a Foreign Honorary Member of the American Academy of Arts and Sciences . Among the non-scientific public, his fame spread more effectually by his invention in about 1815 of the kaleidoscope , for which there was a great demand in both the United Kingdom, France, and the United States. As a reflection of this fame, Brewster's portrait was later printed in some cigar boxes. Brewster chose renowned achromatic lens developer Philip Carpenter as

2444-510: The absorption spectra and he described for the first time the red fluorescence of chlorophyll . As well as his many scientific works and biographies of notable scientists, Brewster also wrote The History of Free Masonry, Drawn from Authentic Sources of Information; with an Account of the Grand Lodge of Scotland, from Its Institution in 1736, to the Present Time , published in 1804, when he

2538-601: The diffraction of light. The results of his investigations were communicated from time to time in papers to the Philosophical Transactions of London and other scientific journals. The fact that other scientists – notably Étienne-Louis Malus and Augustin Fresnel – were pursuing the same investigations contemporaneously in France does not invalidate Brewster's claim to independent discovery, even though in one or two cases

2632-473: The rector of Jedburgh Grammar School and a teacher of high reputation. David was the third of six children, two daughters and four sons: James (1777–1847), minister at Craig, Ferryden; David; George (1784–1855), minister at Scoonie, Fife; and Patrick (1788–1859), minister at the abbey church, Paisley. At the age of 12, David Brewster matriculated at the University of Edinburgh with the intention of becoming

2726-465: The stereoscope , which – though of much later date (1849) – along with the kaleidoscope did more than anything else to popularise his name, was not as has often been asserted the invention of Brewster. Sir Charles Wheatstone discovered its principle and applied it as early as 1838 to the construction of a cumbersome but effective instrument, in which the binocular pictures were made to combine by means of mirrors . A dogged rival of Wheatstone's, Brewster

2820-477: The "father of modern experimental optics" and "the Johannes Kepler of optics." Brewster was a pioneer in photography. He invented an improved stereoscope , which he called "lenticular stereoscope" and which became the first portable 3D-viewing device. He also invented the stereoscopic camera , two types of polarimeters , the polyzonal lens, the lighthouse illuminator, and the kaleidoscope . Brewster

2914-468: The 3D image in an autostereogram with little effort, others must learn to train their eyes to decouple eye convergence from lens focusing. Not every person can see the 3D illusion in autostereograms. Because autostereograms are constructed based on stereo vision , persons with a variety of visual impairments, even those affecting only one eye, are unable to see the three-dimensional images. People with amblyopia (also known as lazy eye) are unable to see

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3008-627: The Natural History of Creation , in the North British Review . which he considered to be an insult to Christian revelation and a dangerous example of materialism. In 1862, he responded to Darwin's On the Origin of Species and published the article The Facts and Fancies of Mr Darwin in Good Words . He stated that Darwin's book combined both "interesting facts and idle fancies" which made up

3102-418: The air above the background image. The 3D effects in the example autostereogram are created by repeating the tiger rider icons every 140 pixels on the background plane, the shark rider icons every 130 pixels on the second plane, and the tiger icons every 120 pixels on the highest plane. The closer a set of icons are packed horizontally, the higher they are lifted from the background plane. This repeat distance

3196-421: The autostereogram, the brain should see seven "apparent" dolphins on the plane of the autostereogram. This is a side effect of the pairing of similar patterns by the brain. There are five pairs of dolphin patterns in this image. This allows the brain to create five apparent dolphins. The leftmost pattern and the rightmost pattern by themselves have no partner, but the brain tries to assimilate these two patterns onto

3290-402: The background, after you stare at the picture long enough", or "the 3D objects will just emerge from the background". It helps to illustrate how 3D images "emerge" from the background from a second viewer's perspective. If the virtual 3D objects reconstructed by the autostereogram viewer's brain were real objects, a second viewer observing the scene from the side would see these objects floating in

3384-424: The background, whereas if viewed cross-eyed it will instead appear as a cut-out behind the background and may be difficult to bring entirely into focus. In 1593, Giambattista della Porta viewed one page of a book with one eye and another page with the other eye. He was able to read one of the pages, the other being invisible, and switch "the visual virtue" to read the other page, the first becoming invisible. This

3478-414: The brain derives the points' positions in the otherwise inscrutable z -axis (depth). When the brain is presented with a repeating pattern like wallpaper , it has difficulty matching the two eyes' views accurately. By looking at a horizontally repeating pattern, but converging the two eyes at a point behind the pattern, it is possible to trick the brain into matching one element of the pattern, as seen by

3572-402: The brain is able to recognize these small gaps and fill in the blanks ( illusory contours ). While intelligible, repeated patterns are used instead of random dots, this type of autostereogram is still known by many as a Random Dot Autostereogram, because it is created using the same process. When a series of autostereograms are shown one after another, in the same way moving pictures are shown,

3666-411: The brain matches additional patterns using roughly the same degree of convergence. When one moves one's attention from one depth plane to another (for instance, from the top row of the chessboard to the bottom row), the two eyes need to adjust their convergence to match the new repeating interval of patterns. If the level of change in convergence is too high during this shift, sometimes the brain can lose

3760-493: The brain perceives an animated autostereogram. If all autostereograms in the animation are produced using the same background pattern, it is often possible to see faint outlines of parts of the moving 3D object in the 2D autostereogram image without wall-eyed viewing; the constantly shifting pixels of the moving object can be clearly distinguished from the static background plane. To eliminate this side effect, animated autostereograms often use shifting background in order to disguise

3854-429: The brain to attribute different sizes to patterns with identical 2D sizes. In the autostereogram of three rows of cubes, while all cubes have the same physical 2D dimensions, the ones on the top row appear bigger, because they are perceived as farther away than the cubes on the second and third rows. If one has two eyes, fairly healthy eyesight, and no neurological conditions which prevent the perception of depth, then one

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3948-464: The combined image can be represented by a grayscale pixel on a 2D image, for the benefit of the reader. The closer a point appears to the brain, the brighter it is painted. Thus, the way the brain perceives depth using binocular vision can be captured by a depth map (Cyclopean image) painted based on coordinate shift. The eye operates like a photographic camera. It has an adjustable iris which can open (or close) to allow more (or less) light to enter

4042-641: The creation of "an association of our nobility, clergy, gentry and philosophers". This was taken up by various Declinarians and found speedy realisation in the British Association for the Advancement of Science . Its first meeting was held at York in 1831; and Brewster, along with Babbage and Sir John Herschel , had the chief part in shaping its constitution. In the same year in which the British Association held its first meeting, Brewster received

4136-777: The cross-eyed reading reverses the depth (images that once popped out are now pushed in). However, icons in a row do not need to be arranged at identical intervals. An autostereogram with varying intervals between icons across a row presents these icons at different depth planes to the viewer. The depth for each icon is computed from the distance between it and its neighbor at the left. These types of autostereograms are designed to be read in only one way, either cross-eyed or wall-eyed. All autostereograms in this article are encoded for wall-eyed viewing, unless specifically marked otherwise. An autostereogram encoded for wall-eyed viewing will produce inverse patterns when viewed cross-eyed, and vice versa. The wall-eyed depth map example autostereogram to

4230-587: The development of early photography in Scotland and eventually allowing for the formation of the first photographic society in the world, the Edinburgh Calotype Club , in 1843. Brewster was a prominent member of the club until its dissolution sometime in the mid-1850s; however, his interest in photography continued, and he was elected the first President of the Photographic Society of Scotland when it

4324-402: The eighth edition of the Encyclopædia Britannica : "His scientific glory is different in kind from that of Young and Fresnel; but the discoverer of the law of polarization of biaxial crystals, of optical mineralogy, and of double refraction by compression, will always occupy a foremost rank in the intellectual history of the age." In addition to the various works of Brewster already mentioned,

4418-512: The equivalent pattern to the left can be expressed in a depth map . A depth map is simply a grayscale image which represents the distance between a pixel and its left counterpart using a grayscale value between black and white. By convention, the closer the distance is, the brighter the color becomes. Using this convention, a grayscale depth map for the example autostereogram can be created with black, gray and white representing shifts of 0 pixels, 10 pixels and 20 pixels, respectively as shown in

4512-445: The equivalent pixel in the depth map image, and uses this value to determine the amount of horizontal shift required for the pixel. One way to accomplish this is to make the program scan every line in the output image pixel-by-pixel from left to right. It seeds the first series of pixels in a row from the pattern image. Then it consults the depth map to retrieve appropriate shift values for subsequent pixels. For every pixel, it subtracts

4606-420: The established depth plane of adjacent dolphins despite binocular rivalry. As a result, there are seven apparent dolphins, with the leftmost and the rightmost ones appearing with a slight flicker, not dissimilar to the two sets of flickering lines observed when one stares at the 4th apparent dolphin. Because of foreshortening, the difference in convergence needed to see repeated patterns on different planes causes

4700-420: The eye resembles a pinhole camera , the less it depends on focusing through the lens . In other words, the degree of decoupling between focusing and convergence needed to visualize an autostereogram is reduced. This places less strain on the brain. Therefore, it may be easier for first-time autostereogram viewers to "see" their first 3D images if they attempt this feat with bright lighting. Vergence control

4794-410: The eye. As with any camera except pinhole cameras , it needs to focus light rays entering through the iris (aperture in a camera) so that they focus on a single point on the retina in order to produce a sharp image. The eye achieves this goal by adjusting a lens behind the cornea to refract light appropriately. Stereo-vision based on parallax allows the brain to calculate depths of objects relative to

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4888-461: The eyeballs adopt a wall-eyed convergence on a distant plane, even though the autostereogram image is actually closer to the eyes. Because the two eyeballs converge on a plane farther away, the perceived location of the imaginary object is behind the autostereogram. The imaginary object also appears bigger than the patterns on the autostereogram because of foreshortening . The following autostereogram shows three rows of repeated patterns. Each pattern

4982-454: The following may be added: Notes and Introduction to Carlyle's translation of Legendre's Elements of Geometry (1824); Treatise on Optics (1831); Letters on Natural Magic , addressed to Sir Walter Scott (1832) The Martyrs of Science, or the Lives of Galileo, Tycho Brahe, and Kepler (1841); More Worlds than One (1854). In his Treatise he demonstrated that vegetal colors were related with

5076-411: The greyscale example autostereogram. A depth map is the key to creation of random-dot autostereograms. A computer program can take a depth map and an accompanying pattern image to produce an autostereogram. The program tiles the pattern image horizontally to cover an area whose size is identical to the depth map. Conceptually, at every pixel in the output image, the program looks up the grayscale value of

5170-419: The hard-earned decoupling between focusing and convergence. For a first-time viewer, therefore, it may be easier to see the autostereogram, if the two eyes rehearse the convergence exercise on an autostereogram where the depth of patterns across a particular row remains constant. In a random dot autostereogram, the 3D image is usually shown in the middle of the autostereogram against a background depth plane (see

5264-497: The hidden image. Within a few weeks the first Japanese book became a best seller, as did the second, rushed out shortly after. The first North American Magic Eye book was Magic Eye: A New Way of Looking at the World . Magic Eye stereograms have been used by orthoptists and vision therapists in the treatment of some binocular vision and accommodative disorders. Autostereogram The optical illusion of an autostereogram

5358-513: The honour of knighthood and the decoration of the Royal Guelphic Order . In 1838, he was appointed Principal of the united colleges of St Salvator and St Leonard, University of St Andrews . In 1849, he acted as president of the British Association and was elected one of the eight foreign associates of the Institute of France in succession to J. J. Berzelius ; and ten years later, he accepted

5452-535: The horizontal positions of the images in the two eyes. He supported his explanation by showing flat, two-dimensional pictures with such horizontal differences, stereograms , separately to the left and right eyes through a stereoscope he invented based on mirrors . From such pairs of flat images, people experienced the illusion of depth. In 1844, David Brewster discovered the "wallpaper effect". He noticed that when he stared at repeated patterns in wallpapers while varying his vergence, he could see them either behind

5546-456: The left eye, with another (similar looking) element, beside the first, as seen by the right eye. With the typical wall-eyed viewing , this gives the illusion of a plane bearing the same pattern but located behind the real wall. The distance at which this plane lies behind the wall depends only on the spacing between identical elements. Autostereograms use this dependence of depth on spacing to create three-dimensional images. If, over some area of

5640-432: The lenses on a nearby autostereogram where patterns are repeated and by converging the eyeballs at a distant point behind the autostereogram image, one can trick the brain into seeing 3D images. If the patterns received by the two eyes are similar enough, the brain will consider these two patterns a match and treat them as coming from the same imaginary object. This type of visualization is known as wall-eyed viewing , because

5734-452: The middle plane is created by shifting an icon 10 pixels to the left, effectively creating a spacing consisting of 130 pixels. The brain does not rely on intelligible icons which represent objects or concepts. In this autostereogram, patterns become smaller and smaller down the y -axis, until they look like random dots. The brain is still able to match these random dot patterns. The distance relationship between any pixel and its counterpart in

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5828-597: The most important of them all: his biography of Sir Isaac Newton . In 1831 he published the Life of Sir Isaac Newton , a short popular account of the philosopher's life, in Murray's Family Library , followed by an 1832 American edition in Harper's Family Library; but it was not until 1855 that he was able to issue the much fuller Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton ,

5922-434: The moving parts. When a regular repeating pattern is viewed on a CRT monitor as if it were a wallpaper autostereogram, it is usually possible to see depth ripples. This can also be seen in the background to a static, random-dot autostereogram. These are caused by the sideways shifts in the image due to small changes in the deflection sensitivity (linearity) of the line scan, which then become interpreted as depth. This effect

6016-485: The office of principal of the University of Edinburgh, the duties of which he discharged until within a few months of his death. In 1855, the government of France made him an Officier de la Légion d'honneur . He was a close friend of William Henry Fox Talbot , inventor of the calotype process, who sent Brewster early examples of his work. It was Brewster who suggested Talbot only patent his process in England, initiating

6110-439: The pattern is complex enough and does not have big, horizontal, monotonic patches. A big area painted with monotonic color without change in hue and brightness does not lend itself to pixel shifting, as the result of the horizontal shift is identical to the original patch. The following depth map of a shark with smooth gradient produces a perfectly readable autostereogram, even though the 2D image contains small monotonic areas;

6204-402: The picture, the pattern is repeated at smaller distances, that area will appear closer than the background plane. If the distance of repeats is longer over some area, then that area will appear more distant (like a hole in the plane). People who have never been able to perceive 3D shapes hidden within an autostereogram find it hard to understand remarks such as, "the 3D image will just pop out of

6298-413: The point of convergence. It is the convergence angle that gives the brain the absolute reference depth value for the point of convergence from which absolute depths of all other objects can be inferred. The eyes normally focus and converge at the same distance in a process known as accommodative convergence . That is, when looking at a faraway object, the brain automatically flattens the lenses and rotates

6392-493: The population is affected by amblyopia. Depth perception results from many monocular and binocular visual clues. For objects relatively close to the eyes, binocular vision plays an important role in depth perception. Binocular vision allows the brain to create a single Cyclopean image and to attach a depth level to each point in it. The brain uses coordinate shift (also known as parallax) of matched objects to identify depth of these objects. The depth level of each point in

6486-409: The priority must be assigned to others. A lesser-known classmate of his, Thomas Dick , also went on to become a popular astronomical writer. The most important subjects of his inquiries can be enumerated under the following five headings: In this line of investigation, the prime importance belongs to the discovery of These discoveries were promptly recognised. As early as 1807 the degree of LL.D.

6580-472: The repeating 2D patterns. There are two ways an autostereogram can be viewed: wall-eyed and cross-eyed . Most autostereograms (including those in this article) are designed to be viewed in only one way, which is usually wall-eyed. Wall-eyed viewing requires that the two eyes adopt a relatively parallel angle, while cross-eyed viewing requires a relatively convergent angle. An image designed for wall-eyed viewing if viewed correctly will appear to pop out of

6674-407: The repeating patterns appear to float above or below the background. The well-known Magic Eye books feature another type of autostereogram called a random-dot autostereogram ( see § Random-dot , below ), similar to the first example, above. In this type of autostereogram, every pixel in the image is computed from a pattern strip and a depth map . A hidden 3D scene emerges when the image

6768-399: The right encodes 3 planes across the x -axis. The background plane is on the left side of the picture. The highest plane is shown on the right side of the picture. There is a narrow middle plane in the middle of the x -axis. Starting with a background plane where icons are spaced at 140 pixels, one can raise a particular icon by shifting it a certain number of pixels to the left. For instance,

6862-536: The shark autostereogram). It may help to establish proper convergence first by staring at either the top or the bottom of the autostereogram, where patterns are usually repeated at a constant interval. Once the brain locks onto the background depth plane, it has a reference convergence degree from which it can then match patterns at different depth levels in the middle of the image. David Brewster Sir David Brewster KH PRSE FRS FSA Scot FSSA MICE (11 December 1781 – 10 February 1868)

6956-409: The shift from the width of the pattern image to arrive at a repeat interval. It uses this repeat interval to look up the color of the counterpart pixel to the left and uses its color as the new pixel's own color. Unlike the simple depth planes created by simple wallpaper autostereograms, subtle changes in spacing specified by the depth map can create the illusion of smooth gradients in distance. This

7050-546: The sole manufacturer of the kaleidoscope in 1817. Although Brewster patented the kaleidoscope in 1817 (GB 4136), a copy of the prototype was shown to London opticians and copied before the patent was granted. As a consequence, the kaleidoscope became produced in large numbers, but yielded no direct financial benefits to Brewster. It proved to be a massive success with two hundred thousand kaleidoscopes sold in London and Paris in just three months. An instrument of more significance,

7144-401: The surface reconstruction. In the late '90s many children's magazines featured autostereograms. Even gaming magazines like Nintendo Power had a section specifically made for these illusions. Since then several books were published with Magic Eye Beyond 3D: Improve Your Vision being one key publication that placed this intriguing illusion into the mainstream. Stereopsis , or stereo vision,

7238-421: The three-dimensional images. Children with poor or dysfunctional eyesight during a critical period in childhood may grow up stereoblind , as their brains are not stimulated by stereo images during the critical period. If such a vision problem is not corrected in early childhood, the damage becomes permanent and the adult will never be able to see autostereograms. It is estimated that some 1 percent to 5 percent of

7332-437: The time, many vision scientists assumed that stereopsis required prior analysis of visible contours of images in each eye, but Julesz showed it occurs with images with no such visible contours in each of the eyes. The contours of the depth object become visible only after stereopsis had processed the differences in the horizontal positions of dots in the two eyes' images. Japanese designer Masayuki Ito, following Julesz, created

7426-413: The two eyeballs for wall-eyed viewing. It is possible to train the brain to decouple these two operations. This decoupling has no useful purpose in everyday life, because it prevents the brain from interpreting objects in a coherent manner. To see a human-made picture such as an autostereogram where patterns are repeated horizontally, however, decoupling of focusing from convergence is crucial. By focusing

7520-416: The two eyes, in the process seeing "double images" typically seen when one is drunk or otherwise intoxicated. Eventually the brain will successfully match a pair of patterns reported by the two eyes and lock onto this particular degree of convergence. The brain will also adjust eye lenses to get a clear image of the matched pair. Once this is done, the images around the matched patterns quickly become clear as

7614-536: The wall (with wall-eyed vergence) or in front of the wall (with cross-eyed vergence). This is the basis of wallpaper-style autostereograms. In 1939 Boris Kompaneysky published the first random-dot stereogram containing a hand-drawn image of the face of Venus, intended to be viewed with a device. In 1959, Bela Julesz , vision scientist, psychologist, and MacArthur Fellow , invented random dot stereograms while working at Bell Laboratories on recognizing camouflaged objects from aerial pictures taken by spy planes. At

7708-404: The years 1824–1832, with very many articles from his own pen. He contributed around three hundred papers to the transactions of various learned societies, and few of his contemporaries wrote as much for the various reviews. In the North British Review alone, seventy-five articles of his appeared. A list of his larger separate works will be found below. Special mention, however, must be made of

7802-420: Was a Freemason at the time he wrote the book, nor any that he became one later. Brewster's Christian beliefs stirred him to respond against the idea of the transmutation of species and the theory of evolution. His opinion was that "science and religion must be one since each dealt with Truth, which had only one and the same Author." In 1845 he wrote a highly critical review of the evolutionist work Vestiges of

7896-466: Was a Scottish scientist, inventor, author, and academic administrator. In science he is principally remembered for his experimental work in physical optics , mostly concerned with the study of the polarization of light and including the discovery of Brewster's angle . He studied the birefringence of crystals under compression and discovered photoelasticity , thereby creating the field of optical mineralogy . For this work, William Whewell dubbed him

7990-650: Was a devout Presbyterian and marched arm-in-arm with his brother during the events of the Disruption of 1843 , which led to the formation of the Free Church of Scotland . As a historian of science, Brewster focused on the life and work of his hero, Isaac Newton . Brewster published a detailed biography of Newton in 1831 and later became the first scientific historian to examine many of the papers in Newton's Nachlass . Brewster also wrote numerous works of popular science , and

8084-425: Was active earlier in the field than Fresnel, describing the dioptric apparatus in 1812. Brewster pressed its adoption on those in authority at least as early as 1820, two years before Fresnel suggested it, and it was finally introduced into lighthouses mainly through Brewster's persistent efforts. Although Brewster's own discoveries were important, they were not his only service to science. He began writing in 1799 as

8178-458: Was characterized by Sir Walter Scott as a " self-taught philosopher, astronomer and mathematician ". Brewster is buried in the grounds of Melrose Abbey , in Roxburghshire . Though Brewster duly finished his theological studies and was licensed to preach, his other interests distracted him from the duties of his profession. In 1799 fellow-student Henry Brougham persuaded him to study

8272-620: Was conferred upon Brewster by Marischal College , Aberdeen ; in 1815 he was elected a Fellow of the Royal Society of London , and received the Copley Medal ; and in 1816 the French Institute awarded him one-half of the prize of three thousand francs for the two most important discoveries in physical science made in Europe during the two preceding years. In 1821, he was made a foreign member of

8366-404: Was empirical, and the laws that he established were generally the result of repeated experiment. To the ultimate explanation of the phenomena with which he dealt he contributed nothing, and it is noteworthy although he did not maintain to the end of his life the corpuscular theory he never explicitly adopted the wave theory of light. Few would dispute the verdict of James David Forbes , an editor of

8460-410: Was founded in 1856. Of a high-strung and nervous temperament, Brewster was somewhat irritable in matters of controversy; but he was repeatedly subjected to serious provocation. He was a man of highly honourable and fervently religious character. In estimating his place among scientific discoverers, the chief thing to be borne in mind is that his genius was not characteristically mathematical. His method

8554-663: Was one of the founders of the British Science Association , of which he was elected president in 1849. He became the public face of higher education in Scotland, serving as Principal of the University of St Andrews (1837–1859) and later of the University of Edinburgh (1859–1868). Brewster also edited the 18-volume Edinburgh Encyclopædia . David Brewster was born in the Canongate in Jedburgh , Roxburghshire , to Margaret Key (1753–1790) and James Brewster (c. 1735–1815),

8648-457: Was only 23. The work was commissioned by Alexander Lawrie, publisher to the Grand Lodge of Scotland , to whom the work has been, frequently, mis-attributed. Given that the book bears Lawrie's name and not Brewster's this is understandable. The book became one of the standard works on early Scottish freemasonry although it has been largely superseded by later works. There is no evidence that Brewster

8742-489: Was the suggestion to use prisms for uniting the dissimilar pictures; and accordingly the lenticular stereoscope may fairly be said to be his invention. A much more valuable and practical result of Brewster's optical researches was the improvement of the British lighthouse system. Although Fresnel, who had also the satisfaction of being the first to put it into operation, perfected the dioptric apparatus independently, Brewster

8836-449: Was unwilling to credit him with the invention, however, and proposed that the true author of the stereoscope was a Mr. Elliot, a "Teacher of Mathematics" from Edinburgh, who, according to Brewster, had conceived of the principles as early as 1823 and had constructed a lensless and mirrorless prototype in 1839, through which one could view drawn landscape transparencies, since photography had yet to be invented. Brewster's personal contribution

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