| aberration |
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noun
- The act of wandering; deviation, especially from truth or moral rectitude, from the natural state, or from a type.
- Aberrations from theory - Burke
- A partial alienation of reason.
- Occasional aberrations of intellect - Lingard
- Whims, which at first are the aberrations of a single brain, pass with heat into epidemic form - I. Taylor
- (astronomy) A small periodical change of position in the stars and other heavenly bodies, due to the combined effect of the motion of light and the motion of the observer.
- (context, optics) The convergence to different focus, foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus.
- (physiology) The passage of blood or other fluid into parts not appropriate for it.
- The producing of an unintended effect by the glancing of an instrument, as when a shot intended for A glances and strikes B.
- (context, zoology, botany) atypical development or structure
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| achromaticity |
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noun
- The state or quality of being achromatic.
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| achromatic lens |
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noun
- (optics) A lens generally composed of two separate lenses, one convex and one concave and generally of different materials, in such a way that the chromatic aberration produced by one is corrected by the other.
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| achromatism |
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noun - the state or quality of being achromatic; as, the of a lens; achromaticity - w:John Pringle Nichol, John Pringle Nichol
- Free of colors, not emitting or separating into colors.
- achromatopia
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| anaclastic |
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adjective - Produced by the refraction of light, as seen through water.
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| anaglyph |
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noun
- A decorative ornament worked in low relief.
- The three-dimensional effect created by spectacles that have usually one red and one bluish-green lens and a stereoscopically modified film.
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| analyzer |
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noun
- One who, or that which, analyzes.
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| anamorphic |
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adjective
- producing various optically distorted images
- of or relating to the gradual evolution of different types of organism
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| aperture |
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noun
- An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall.
- An aperture between the mountains. --Gilpin.
- The back aperture of the nostrils. --Owen.
- (optics) Something which restricts the diameter of the light path through one plane in an optical system.
- (context, astronomy, photography) The diameter of the aperture (in the sense above) which restricts the width of the light path through the whole system. For a telescope, this is the diameter of the objective lens. e.g. a telescope may have a 100 cm aperture.
Note: The aperture of microscopes is often expressed in degrees, called also the angular aperture, which signifies the angular breadth of the pencil of light which the instrument transmits from the object or point viewed; as, a microscope of 100° aperture.
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| apochromatic |
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adjective - (optics) corrected for both chromatic aberration and spherical aberration
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| apostilb |
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noun - (physics) a unit of luminance, being the luminance of a perfectly diffusing surface emitting light at the rate of one lumen per square metre.
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| astigmatism |
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noun
- (optics) A defect of a lens such that light rays coming from a point do not meet at a focal point so that the image is blurred.
- (pathology) A disorder of the vision, usually due to a misshapen cornea, such that light does not focus correctly on the retina causing a blurred image.
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