Computer stereo vision
Encyclopedia
Computer stereo vision is the extraction of 3D information from digital images, such as obtained by a CCD camera. By comparing information about a scene from two vantage points, 3D information can be extracted by examination of the relative positions of objects in the two panels. This is similar to the biological process Stereopsis
.
. By comparing these two images, the relative depth information can be obtained, in the form of disparities, which are inversely proportional to the differences in distance to the objects.
To compare the images, the two views must be superimposed in a stereoscopic device, the image from the right camera being shown to the observer's right eye and from the left one to the left eye.
In real camera systems however, several pre-processing steps required.
systems. Stereo vision is highly important in fields such as robotics
, to extract information about the relative position of 3D objects in the vicinity of autonomous systems. Other applications for robotics include object recognition, where depth information allows for the system to separate occluding image components, such as one chair in front of another, which the robot may otherwise not be able to distinguish as a separate object by any other criteria.
Scientific applications for digital stereo vision include the extraction of information from aerial survey
s, for calculation of contour maps or even geometry extraction for 3D building mapping, or calculation of 3D heliographical
information such as obtained by the NASA STEREO
project.
Stereopsis
Stereopsis refers to impression of depth that is perceived when a scene is viewed with both eyes by someone with normal binocular vision. Binocular viewing of a scene creates two slightly different images of the scene in the two eyes due the the eyes' different positions on the head...
.
Outline
In traditional stereo vision, two cameras, displaced horizontally from one another are used to obtain two differing views on a scene, in a manner similar to human 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...
. By comparing these two images, the relative depth information can be obtained, in the form of disparities, which are inversely proportional to the differences in distance to the objects.
To compare the images, the two views must be superimposed in a stereoscopic device, the image from the right camera being shown to the observer's right eye and from the left one to the left eye.
In real camera systems however, several pre-processing steps required.
- The image must first be removed of distortions, such as barrel distortionBarrel distortionIn geometric optics and cathode ray tube displays, distortion is a deviation from rectilinear projection, a projection in which straight lines in a scene remain straight in an image...
to ensure that the observed image is purely projectional. - The image must be projected back to a common plane to allow comparison of the image pairs, known as image rectificationImage rectificationImage rectification is a transformation process used to project two-or-more images onto a common image plane. It corrects image distortion by transforming the image into a standard coordinate system....
. - The displacement of relative features is measured to calculate a disparity mapBinocular disparityBinocular disparity refers to the difference in image location of an object seen by the left and right eyes, resulting from the eyes' horizontal separation. The brain uses binocular disparity to extract depth information from the two-dimensional retinal images in stereopsis...
- Optionally, the disparity as observed by the common projection, is converted back to the height map by inversion. Utilising the correct proportionality constant, the height map can be calibrated to provide exact distances.
Applications
3D stereo displays finds many applications in entertainment, information transfer and automatedAutomation
Automation is the use of control systems and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization...
systems. Stereo vision is highly important in fields such as robotics
Robotics
Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...
, to extract information about the relative position of 3D objects in the vicinity of autonomous systems. Other applications for robotics include object recognition, where depth information allows for the system to separate occluding image components, such as one chair in front of another, which the robot may otherwise not be able to distinguish as a separate object by any other criteria.
Scientific applications for digital stereo vision include the extraction of information from aerial survey
Aerial survey
Aerial survey is a geomatics method of collecting information by using aerial photography, LiDAR or from remote sensing imagery using other bands of the electromagnetic spectrum, such as infrared, gamma, or ultraviolet. It can also refer to the chart or map made by analysing a region from the air...
s, for calculation of contour maps or even geometry extraction for 3D building mapping, or calculation of 3D heliographical
Heliography
Heliography is the photographic process invented by Joseph Nicéphore Niépce around 1822, which he used to make the earliest known permanent photograph from nature, View from the Window at Le Gras . The process used bitumen , as a coating on glass or metal, which hardened in relation to exposure to...
information such as obtained by the NASA STEREO
STEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
project.
See also
- AutostereoscopyAutostereoscopyAutostereoscopy is any method of displaying stereoscopic images without the use of special headgear or glasses on the part of the viewer. Because headgear is not required, it is also called "glasses-free 3D" or "glassesless 3D"...
- Epipolar geometryEpipolar geometryEpipolar geometry is the geometry of stereo vision. When two cameras view a 3D scene from two distinct positions, there are a number of geometric relations between the 3D points and their projections onto the 2D images that lead to constraints between the image points...
- Computer visionComputer visionComputer vision is a field that includes methods for acquiring, processing, analysing, and understanding images and, in general, high-dimensional data from the real world in order to produce numerical or symbolic information, e.g., in the forms of decisions...
- Stereo cameraStereo cameraA stereo camera is a type of camera with two or more lenses with a separate image sensor or film frame for each lens. This allows the camera to simulate human binocular vision, and therefore gives it the ability to capture three-dimensional images, a process known as stereo photography. Stereo...
- Stereoscopic Depth RenditionStereoscopic Depth RenditionStereoscospic depth rendition specifies how the depth of a three-dimensional object is encoded in a stereoscopic reconstruction. It needs attention to ensure a realistic depiction of the three-dimensionality of viewed scenes and is a specific instance of the more general task of 3D rendering of...