Stereogram
Encyclopedia
A stereogram
is pair of two-dimensional panels depicting the view of a scene or an object from the vantage points of the right and left eyes. Observing the panels superimposed in a stereoscope results in the experience of three-dimensionality by virtue of the fact that object depth is encoded as right/left position difference in the panels. Because in a stereoscope one views a representation rather than a real scene, the word illusion is sometimes associated with a stereogram.
Originally, stereogram referred to a pair of stereo images which could be viewed using a stereoscope. Other types of stereograms include anaglyph
s and autostereogram
s. The stereogram was discovered by Charles Wheatstone
in 1838. He found an explanation of binocular vision
which led him to construct a stereoscope based on a combination of prism
s and mirror
s to allow a person to see 3D images from two 2D pictures. Oliver Wendell Holmes, Sr.
invented an improved form of stereoscope in 1861, which had no mirrors and was inexpensive to produce. These stereoscopes were immensely popular for decades.
Stereograms were re-popularized by the creation of autostereogram
s on computers, wherein a 3D image is hidden in a single 2D image, until the viewer focuses the eyes correctly. The Magic Eye
series is a popular example of this. Magic Eye books refer to autostereograms as stereograms, leading most people to believe that the word stereogram is synonymous with autostereogram. Salvador Dalí
created some impressive stereograms in his exploration in a variety of optical illusions.
An autostereogram
is an optical illusion
of depth usually observed by allowing the eye
s to focus behind the image (diverge), or, less often, in front of it (converge). These two methods are also known as wall-eyed and cross-eyed, respectively. The slight differences in vertical repetitions of figures or random dots create the illusion of depth in the 2D image, just as the slight difference in perspective between one's eyes creates the perception of depth on 3D
objects and scenes.
According to Magic Eye
, a maker of autostereogram
s, "most people prefer the diverging method". However, with normal stereograms, this imposes a limit on the size of the image, since there is a limit to how much the eyes diverge; images created for the cross-eyed method can be larger. If a stereogram is viewed with the wrong method, the depth information is seen 'reversed'; points intended to be in the background appear in the foreground and vice versa.
motion pictures, posters and books of autostereogram
s, and historical replicas of early stereograms, there are also practical uses of the technologies.
producing cards into the 1960s.
s, launched by NASA
in 2003 to explore the surface of Mars
, are equipped with unique cameras that allow researchers to view stereoscopic images of the surface of Mars.
The two cameras that make up each rover's Pancam are situated 1.5m above the ground surface, and are separated by 30 cm, with 1 degree of toe-in. This allows the image pairs to be made into scientifically useful stereoscopic images, which can be viewed as stereograms, anaglyphs, or processed into 3D computer images.
The ability to create realistic 3D images from a pair of cameras at roughly human-height gives researchers increased insight as to the nature of the landscapes being viewed. In environments without hazy atmospheres or familiar landmarks, humans rely on stereoscopic clues to judge distance. Single camera viewpoints are therefore more difficult to interpret. Multiple camera stereoscopic systems like the Pancam address this problem with unmanned space exploration.
and accommodative
disorders.
Cartographers may also generate stereopairs using computer programs in order to visualise topography in three dimensions.
In biology and chemistry, complex molecular structures are often rendered in stereopairs. The same technique can also be applied to any mathematical (or scientific, or engineering) parameter that is a function of two variables, although in these cases it is more common for a three-dimensional effect to be created using a 'distorted' mesh or shading (as if from a distant light source).
Stereogram
A stereogram is pair of two-dimensional panels depicting the view of a scene or an object from the vantage points of the right and left eyes. Observing the panels superimposed in a stereoscope results in the experience of three-dimensionality by virtue of the fact that object depth is encoded as...
is pair of two-dimensional panels depicting the view of a scene or an object from the vantage points of the right and left eyes. Observing the panels superimposed in a stereoscope results in the experience of three-dimensionality by virtue of the fact that object depth is encoded as right/left position difference in the panels. Because in a stereoscope one views a representation rather than a real scene, the word illusion is sometimes associated with a stereogram.
Originally, stereogram referred to a pair of stereo images which could be viewed using a stereoscope. Other types of stereograms include anaglyph
Anaglyph image
Anaglyph images are used to provide a stereoscopic 3D effect, when viewed with glasses where the two lenses are different colors, such as red and cyan. Images are made up of two color layers, superimposed, but offset with respect to each other to produce a depth effect...
s and autostereogram
Autostereogram
An autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
s. The stereogram was discovered by Charles Wheatstone
Charles Wheatstone
Sir Charles Wheatstone FRS , was an English scientist and inventor of many scientific breakthroughs of the Victorian era, including the English concertina, the stereoscope , and the Playfair cipher...
in 1838. He found an explanation of binocular vision
Binocular vision
Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
which led him to construct a stereoscope based on a combination of prism
Prism (optics)
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
s and mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
s to allow a person to see 3D images from two 2D pictures. Oliver Wendell Holmes, Sr.
Oliver Wendell Holmes, Sr.
Oliver Wendell Holmes, Sr. was an American physician, professor, lecturer, and author. Regarded by his peers as one of the best writers of the 19th century, he is considered a member of the Fireside Poets. His most famous prose works are the "Breakfast-Table" series, which began with The Autocrat...
invented an improved form of stereoscope in 1861, which had no mirrors and was inexpensive to produce. These stereoscopes were immensely popular for decades.
Stereograms were re-popularized by the creation of autostereogram
Autostereogram
An autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
s on computers, wherein a 3D image is hidden in a single 2D image, until the viewer focuses the eyes correctly. The Magic Eye
Magic Eye
Magic Eye is a series of books published by N.E. Thing Enterprises . The books feature autostereograms , which allow people to see 3D images by focusing on 2D patterns. The viewer must diverge his or her eyes in order to see a hidden three-dimensional image within the pattern...
series is a popular example of this. Magic Eye books refer to autostereograms as stereograms, leading most people to believe that the word stereogram is synonymous with autostereogram. Salvador Dalí
Salvador Dalí
Salvador Domènec Felip Jacint Dalí i Domènech, Marquis de Púbol , commonly known as Salvador Dalí , was a prominent Spanish Catalan surrealist painter born in Figueres,Spain....
created some impressive stereograms in his exploration in a variety of optical illusions.
Types
- Stereoscopic imagingStereoscopyStereoscopy 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...
relies on the use of a stereoscope to present a slightly different image to each eye. The stereo pair can be viewed with the naked eye, if the images are placed side by side. The stereo pair is then viewed using the same viewing technique used to see autostereogramAutostereogramAn autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
s. - Anaglyph imageAnaglyph imageAnaglyph images are used to provide a stereoscopic 3D effect, when viewed with glasses where the two lenses are different colors, such as red and cyan. Images are made up of two color layers, superimposed, but offset with respect to each other to produce a depth effect...
s, also recognized as "red/green" or "magenta/cyan" images, combine two stereo images from slightly different viewpoints into a single image. These images may then be viewed with "anaglyph glasses", which use color filters to moderate the light reaching each eye to create the illusion of a three dimensional image. - Random dot stereogramRandom dot stereogramRandom Dot Stereograms are pairs of images of random dots which when viewed with the aid of a stereoscope, or with the eyes focused on a point behind the images, produce a sensation of depth, with objects appearing to be in front of or behind the actual images....
s employ either two stereoscopic images or one anaglyph. The input image (or images) contain random dots with no discernible shapes. When the proper viewing device is used, a hidden 3D scene emerges from these random dots. - AutostereogramAutostereogramAn autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
s produce an illusion of depth using only a single image. The image is usually generated by computer by repeating a narrow pattern from left to right. By decoupling eye convergenceVergenceA vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision..When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both...
from focusingAccommodation (eye)Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
operations, a viewer is able to trick the brain into seeing a 3D scene. - SIRDS (Single Image Random Dot Stereogram) is a form of autostereogram where each repeated pattern is altered slightly, creating a hidden image which is not discernible unless the right viewing technique is used.
- Wiggle-gram is an animated computer image which gives 3D percept without using glasses using only a single image. It usually contains a few frames.
Autostereograms
Autostereogram
An autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
is an optical illusion
Optical illusion
An optical illusion is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source...
of depth usually observed by allowing the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
s to focus behind the image (diverge), or, less often, in front of it (converge). These two methods are also known as wall-eyed and cross-eyed, respectively. The slight differences in vertical repetitions of figures or random dots create the illusion of depth in the 2D image, just as the slight difference in perspective between one's eyes creates the perception of depth on 3D
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...
objects and scenes.
According to Magic Eye
Magic Eye
Magic Eye is a series of books published by N.E. Thing Enterprises . The books feature autostereograms , which allow people to see 3D images by focusing on 2D patterns. The viewer must diverge his or her eyes in order to see a hidden three-dimensional image within the pattern...
, a maker of autostereogram
Autostereogram
An autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
s, "most people prefer the diverging method". However, with normal stereograms, this imposes a limit on the size of the image, since there is a limit to how much the eyes diverge; images created for the cross-eyed method can be larger. If a stereogram is viewed with the wrong method, the depth information is seen 'reversed'; points intended to be in the background appear in the foreground and vice versa.
Practical uses
While stereograms have typically been used for amusement, including "3D" movies using anaglyphAnaglyph
Anaglyph may refer to:* Anaglyph image, a method of encoding a three-dimensional image in a single picture by superimposing a pair of pictures* Ornament carved in low relief...
motion pictures, posters and books of autostereogram
Autostereogram
An autostereogram is a single-image stereogram , designed to create the visual illusion of a three-dimensional scene from a two-dimensional image in the human brain...
s, and historical replicas of early stereograms, there are also practical uses of the technologies.
Education
In the 19th Century, it was realized that stereoscopic images provided an opportunity for people to experience places and things far away, and many tour sets were produced, and books were published allowing people to learn about geography, science, history, and other subjects. Such uses continued till the mid 20th Century, with the Keystone View CompanyKeystone View Company
The Keystone View Company was a major distributor of stereographic images, and was located in Meadville, Pennsylvania. From 1892 through 1963 Keystone produced and distributed both educational and comic/sentimental stereoviews, and stereoscopes. By 1905 it was the world's largest stereographic...
producing cards into the 1960s.
Space exploration
The Mars Exploration RoverMars Exploration Rover
NASA's Mars Exploration Rover Mission is an ongoing robotic space mission involving two rovers, Spirit and Opportunity, exploring the planet Mars...
s, launched by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
in 2003 to explore the surface of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
, are equipped with unique cameras that allow researchers to view stereoscopic images of the surface of Mars.
The two cameras that make up each rover's Pancam are situated 1.5m above the ground surface, and are separated by 30 cm, with 1 degree of toe-in. This allows the image pairs to be made into scientifically useful stereoscopic images, which can be viewed as stereograms, anaglyphs, or processed into 3D computer images.
Clinical uses
Stereograms cards are frequently used by orthoptists and vision therapists in the treatment of many binocular visionBinocular vision
Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
and accommodative
Accommodation reflex
The accommodation reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object , comprising coordinated changes in vergence, lens shape and pupil size...
disorders.
Mathematical, scientific and engineering uses
As in the stereopair image of the lake, stereopair photographs are sometimes used to help visualise aerial photographs.Cartographers may also generate stereopairs using computer programs in order to visualise topography in three dimensions.
In biology and chemistry, complex molecular structures are often rendered in stereopairs. The same technique can also be applied to any mathematical (or scientific, or engineering) parameter that is a function of two variables, although in these cases it is more common for a three-dimensional effect to be created using a 'distorted' mesh or shading (as if from a distant light source).
Further reading
- 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