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Humphrey field analyser ( HFA) is a tool for measuring the human visual field that is commonly used by optometrists, orthoptists and ophthalmologists, particularly for detecting monocular visual field. [1] The results of the analyser identify the type of vision defect. Therefore, it provides information regarding the location of any disease ...
Cardinal point (optics) In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the focal points, the principal points, and the nodal points; there are two of each. [1] For ideal systems, the basic imaging properties such as image size ...
Machine vision is the technology and methods used to provide imaging -based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry. Machine vision refers to many technologies, software and hardware products, integrated systems, actions, methods and expertise.
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or half-angle of inclination between those two lines. [1] [2] Due to foreshortening, nearby objects show a larger parallax than farther objects, so parallax can be used to determine distances.
In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres. At this distance, the symbols on the line representing "normal" acuity subtend an angle of five minutes of arc, and the thickness of the lines and of the spaces between the lines subtends one minute of arc. This line, designated 6/6 (or 20/20), is the ...
Optical flow. The optic flow experienced by a rotating observer (in this case a fly). The direction and magnitude of optic flow at each location is represented by the direction and length of each arrow. Optical flow or optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion ...
A Luneburg lens (original German Lüneburg lens) is a spherically symmetric gradient-index lens. A typical Luneburg lens's refractive index n decreases radially from the center to the outer surface. They can be made for use with electromagnetic radiation from visible light to radio waves . For certain index profiles, the lens will form perfect ...
Image rectification. A camera (red) rotates about the blue axis by 5° to 90° (green), as the images are rectified by projection to the virtual image plane (blue). The virtual plane must be parallel to the stereo baseline (orange) and for visualization is located in the center of rotation. In this case, rectification is achieved by a virtual ...