| 单词 | aberration | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 释义 | aberrationab·er·ra·tionA0013800 (ăb′ə-rā′shən)aberration(ˌæbəˈreɪʃən)ab•er•ra•tion(ˌæb əˈreɪ ʃən)n. ab·er·ra·tion(ăb′ə-rā′shən)aberration
aberrationaberrationnounaberrationaberration,in optics, condition that causes a blurring and loss of clearness in the images produced by lenses or mirrors. Of the many types of aberration, the two most significant to the lens maker are spherical and chromatic. Spherical aberration is caused by the failure of a lenslens,device for forming an image of an object by the refraction of light. In its simplest form it is a disk of transparent substance, commonly glass, with its two surfaces curved or with one surface plane and the other curved. ..... Click the link for more information. or mirrormirror, in optics, a reflecting surface that forms an image of an object when light rays coming from that object fall upon it (see reflection). Usually mirrors are made of plate glass, one side of which is coated with metal or some special preparation to serve as a reflecting ..... Click the link for more information. of spherical section to bring parallel rays of light to a single focus. The effect results from the operation of the laws of optics, not from defects in construction. Spherical aberration can be prevented by using a parabolic rather than a spherical section, but this involves much greater complexity and expense in lens or mirror construction. Chromatic aberration results in the blurred coloring of the edge of an image when white light is sent through a lens. This is caused by the fact that some colors of light are bent, or refracted, more than others after passing through a lens. For example, violet light is bent more than red and thus is brought to a focus nearer the lens than red. No single lens can ever be free of chromatic aberration, but by combining lenses of different types, the effects of the component lenses can be made to cancel one another. Such an arrangement is called an achromatic lens. See reflectionreflection, return of a wave from a surface that it strikes into the medium through which it has traveled. The general principles governing the reflection of light and sound are similar, for both normally travel in straight lines and both are wave phenomena. ..... Click the link for more information. ; refractionrefraction, in physics, deflection of a wave on passing obliquely from one transparent medium into a second medium in which its speed is different, as the passage of a light ray from air into glass. ..... Click the link for more information. . Aberration (optics)A departure of an optical image-forming system from ideal behavior. Ideally, such a system will produce a unique image point corresponding to each object point. In addition, every straight line in the object space will have as its corresponding image a unique straight line. A similar one-to-one correspondence will exist between planes in the two spaces. This type of mapping of object space into image space is called a collinear transformation. When the conditions for a collinear transformation are not met, the departures from that ideal behavior are termed aberrations. They are classified into two general types, monochromatic aberrations and chromatic aberrations. The monochromatic aberrations apply to a single color, or wavelength, of light. The chromatic aberrations are simply the chromatic variation, or variation with wavelength, of the monochromatic aberrations. See Chromatic aberration, Geometrical optics, Optical image The monochromatic aberrations can be described in several ways. Wave aberrations are departures of the geometrical wavefront from a reference sphere with its vertex at the center of the exit pupil and its center of curvature located at the ideal image point. The wave aberration is measured along the ray and is a function of the field height and the pupil coordinates of the reference sphere (see illustration).   ii. Geometrical inaccuracy(ies) introduced by optical, IR (infrared), or similar electromagnetic systems in which radiation is processed by mirrors. In optics, a specific deviation from perfect imagery (e.g., spherical aberration, coma, astigmatism, curvature of field, or distortion). iii. The displacement of the apparent directions of the stars resulting from the motion of the observer. Also called an atmospheric aberration. aberrationaberrationaberration[ab″er-a´shun]ab·er·ra·tion(ab'er-ā'shŭn),See also: chromosome. See also: chromosome. aberration(ăb′ə-rā′shən)AberrationA defect, deviation, or irregularityGenetics Chromosomal aberration Ophthalmology Any error that results in image degradation. Such errors may be chromatic, spherical, or astigmatic chromatic, and may include distortion or curvature of field; these can result from design or execution, or both. Physics (1) Failure of an optical or electronic lens to produce an exact geometric—and chromatic—correlation between an object and its image (2) In a video capture device or cathode-ray tube, a deviation in which the electrostatic or electromagnetic lens does not bring the electron beam to sharply focused points on the target or screen, or to correct geometric positions, as the beam is deflected. Psychiatry Mental aberration Zoology A term which, if used to denote a number of individuals within a species, unequivocally signifies infra-subspecies rank aberrationMedtalk A defect, deviation, or irregularity Psychiatry See Mental disorder.ab·er·ra·tion(ab'ĕr-ā'shŭn)See also: chromosome aberration aberrationA deviation from normal. The term derives from the Latin aberrare , to wander off. See also ABNORMAL.aberrationaxial chromatic aberration See aberration, longitudinal chromatic. lateral chromatic aberration Defect of an optical system (eye, lens, prism, etc.) in which the size of the image of a point object is extended by a coloured fringe, due to the unequal refraction of different wavelengths (dispersion). Syn. chromatic difference of magnification; transverse chromatic aberration (TCA). See dispersion; doublet. longitudinal chromatic aberration (LCA) Defect of an optical system (eye, lens, prism, etc.) due to the unequal refraction of different wavelengths (dispersion) which results in an extended image along the optical axis. In the eye, blue rays are focused in front of the retina (by about 1 D) and red rays slightly behind the retina (0.25-0.5 D) when relaxed. When the eye is accommodated for a near target, blue rays tend to be focused near the retina and red rays are focused behind the retina (1 D), because of a lag of accommodation usually occurring when viewing near targets (Fig. A1). Syn. axial chromatic aberration. See chromoretinoscopy; chromostereopsis; constringence; dispersion; doublet; achromatizing lens; macular pigment; duochrome test. monochromatic aberration Defect of an optical system (eye, lens, prism, etc.) occurring for a single wavelength of light. There are five such aberrations: spherical aberration, coma, curvature of field, oblique astigmatism and distortion. Syn. Seidel aberration. negative aberration See spherical aberration. oblique aberration Aberration induced by a point object off the optical axis of the system. These comprise coma, curvature of field, distortion and oblique astigmatism. positive aberration See spherical aberration. prism aberration Additional effects of a prism on light, in addition to the expected change in direction of light. These effects include different magnifications, curvature of field and chromatic aberration. Seidel aberration See monochromatic aberration. spherical aberration Defect of an optical system due to a variation in the focusing between peripheral and paraxial rays. The larger the pupil size, the greater the difference in focusing between the two rays. In the gaussian theory, the focus of the optical system is attributed to the paraxial rays. The distance, in dioptres, between the focus of the paraxial rays and the peripheral rays represents the amount of longitudinal spherical aberration of the system. When the peripheral rays are refracted more than the paraxial rays, the aberration is said to be positive or undercorrected. When the peripheral rays are refracted less than the paraxial rays the aberration is said to be negative or overcorrected. The relaxed human eye has a small amount of positive spherical aberration (up to 1 D for a pupil of 8 mm diameter) (Fig. A2). See caustic; aplanatic lens; gaussian theory. transverse chromatic aberration See lateral chromatic aberration. wavefront aberration The amount of deviation between an output wavefront emanating from an optical system and a conceptualized ideal (reference) wavefront. The specification of the deviation (or error) is usually fitted with a normalized Zernike expansion. The measurement of this aberration can be done subjectively or objectively (e.g. with an aberrometer based on the Hartmann-Shack principle). The method (called aberrometry) has been applied clinically to measure the aberrations displayed by optical systems, such as the eye, the eye with a correction, contact lenses (in vitro or in situ), intraocular lenses (in vitro or in situ), in corneal refractive surgery, cataract, etc. (Fig. A3). Syn. wave-front error.  " > " > " >
ab·er·ra·tion(ab'ĕr-ā'shŭn)See also: chromosome aberration
Synonyms for aberration
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英语词典包含2567994条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。
aberration - a state or condition markedly different from the norm
aberration - a disorder in one's mental state 
aberration - an optical phenomenon resulting from the failure of a lens or mirror to produce a good image