chromatic aberration

chromatic aberrationA. redB. violet

chromatic aberration

n. Deficiency in clarity of an image produced by a lens, caused by the inability of the lens to bring all colors of light to a focus at the same point. Also called false color.

chromatic aberration

n (Astronomy) a defect in a lens system in which different wavelengths of light are focused at different distances because they are refracted through different angles. It produces a blurred image with coloured fringes

chromat′ic aberra′tion

n. the variation of either the focal length or the magnification of a lens system with different wavelengths of light. [1825–35]

Thesaurus

Noun

chromatic aberration - an optical aberration in which the image has colored fringesoptical aberration, aberration, distortion - an optical phenomenon resulting from the failure of a lens or mirror to produce a good image

Translations

aberración cromáticaaberrazione cromatica

chromatic aberration

chromatic aberration:

see aberrationaberration,
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.
..... Click the link for more information. , in optics.

Chromatic aberration

The type of error in an optical system in which the formation of a series of colored images occurs, even though only white light enters the system. Chromatic aberrations are caused by the fact that the refraction law determining the path of light through an optical system contains the refractive index, which is a function of wavelength. Thus the image position and the magnification of an optical system are not necessarily the same for all wavelengths, nor are the aberrations the same for all wavelengths. See Aberration (optics), Refraction of waves

Chromatic aberration of convex lens

chromatic aberration

(krŏ-mat -ik) An aberration of a lens – but not a mirror – whereby the component wavelengths of light, i.e. ordinary white light, are brought to a focus at different distances from the lens (see illustration). It arises from the variation with wavelength of the refractive index of the lens material: red light is refracted (bent) less than blue light (see dispersion). False colors therefore arise in the image. Chromatic aberration can be reduced by using an achromatic lens. Before the introduction of achromats, objective lenses of very long focal length were used in telescopes to reduce the aberration; this led to the production of very cumbersome instruments.

Chromatic Aberration

a major aberration of optical systems, caused by the dependence of the refractive index of a transparent medium on the wavelength of light (seeDISPERSION OF LIGHT). Chromatic aberration may occur only in systems that incorporate components made of refracting materials, for example, lenses. Chromatic aberration is not characteristic of mirrors; in other words, mirrors are achromatic.

Two mutually independent types of chromatic aberration are distinguished: longitudinal aberration and lateral aberration. Longitudinal aberration is an image error whereby the images of a point that are formed by rays with different wavelengths lie at different distances from the optical system. In other words, the locations of the focal points on the optical axis do not coincide for different colors (Figure 1, the line segment O₁O₂). As a result of longitudinal aberration, a series of colored circles—rather than a single bright point—is observed perpendicular to the optical axis on a screen placed where the image is formed. Lateral aberration is an image error whereby the lateral magnifications of the images of an object that are formed by rays with different wavelengths may turn out to be different. The differences in lateral magnification result from the difference in the locations of the principal planes of the optical system (seeCARDINAL POINTS OF AN OPTICAL SYSTEM) for different wavelengths, even if the foci for the wavelengths coincide (however, in this case, the focal lengths will differ). As a result of lateral aberration, objects of finite size yield images with a colored fringe.

Figure 1. Longitudinal aberration

The larger the number of different wavelengths for which the focal points are made to coincide, the more difficult it is to correct the longitudinal aberration in an optical system. The simplest case is that in which the focal points are made to coincide for only two wavelengths (and the distance between focal points is reduced for other wavelengths). Optical systems, usually objectives, that are corrected for two wavelengths are said to be achromatic. More advanced optical systems in which the foci are made to coincide for three wavelengths are referred to as apochromatic. In an apochromatic system, the longitudinal aberration is corrected by increasing the number of components with different refractive indexes and by incorporating mirrors into the system. Apochromatic systems are widely used as, for example, photographic and astronomical objectives.

A more thorough correction of longitudinal aberration requires a more complicated system design. In this case, the number of lenses and mirrors is increased, the shapes of the lenses and mirrors are modified, or both. The larger the relative aperture and the wider the field of view of an optical system, the more complicated the corrected system. To correct lateral aberration, the principle planes also must be made to coincide for the largest possible number of wavelengths. Such correction entails major difficulties.

REFERENCES

Landsberg, G. S. Optika, 5th ed. Moscow, 1976. (Obshchii kurs fiziki.)
Herzberger, M. Sovremennaia geometricheskaia optika. Moscow, 1962. (Translated from English.)
Born, M., and E. Wolf. Osnovy optiki. Moscow, 1973. (Translated from English.)

chromatic aberration

[krō′mad·ik ab·ə′rā·shən] (electronics) An electron-gun defect causing enlargement and blurring of the spot on the screen of a cathode-ray tube, because electrons leave the cathode with different initial velocities and are deflected differently by the electron lenses and deflection coils. (optics) An optical lens defect causing color fringes, because the lens material brings different colors of light to focus at different points. Also known as color aberration.

chromatic aberration

Fringes of color at the edges of objects in a photograph due to the inability of the camera lens to deal with all wavelengths of light equally. High-quality lenses that use multiple elements generally diminish chromatic aberration. See purple fringing and lens flare.

chromatic aberration

aberration

[ab″er-a´shun] 1. deviation from the normal or usual.2. imperfect refraction or focalization of a lens.chromatic aberration unequal refraction by a lens of light rays of different lengths passing through it, producing a blurred image and a display of colors.dioptric aberration (spherical aberration) inability of a spherical lens to bring all rays of light to a single focus.ventricular aberration aberrant ventricular conduction.

chro·mat·ic ab·er·ra·tion

the difference in focus or magnification of an image arising because of a difference in the refraction of different wavelengths composing white light. Synonym(s): chromatism (2) , color aberration, newtonian aberration

chromatic aberration

Optics The differences in the focal points when multiple wave lengths–colors of light–eg, those of white light, pass through a lens system

chro·mat·ic ab·er·ra·tion

(krō-mat'ik ab-ĕr-ā'shŭn) The difference in focus or magnification of an image arising because of a difference in the refraction of different wavelengths composing white light.
Synonym(s): chromatism (2) .

chromatic aberration

Colour fringes around the edge of the image cast by a lens.

Newton,

Sir Isaac, English physicist, 1642-1727. newton - derived unit of force in the SI system.Newton disk - a disk on which there are seven colored sectors, which, when rapidly rotated, appear white.Newton law - the attractive force between any two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Synonym(s): law of gravitationNewton rings - colored rings on thin surfaces.newtonian aberration - the difference in focus or magnification of an image arising because of a difference in the refraction of different wavelengths composing white light. Synonym(s): chromatic aberrationnewtonian constant of gravitation - a universal constant relating the gravitational force, attracting two masses toward each other when they are separated by a distance.newtonian flow - the type of flow characteristic of a newtonian fluid.newtonian fluid - a fluid in which flow and rate of shear are always proportional to the applied stress.newtonian viscosity - the viscosity characteristics of a newtonian fluid.

adaptation

1. Process by which a sensory organ (e.g. the eye) adjusts to its environment (e.g. to luminance, colour or contact lens wear). 2. The reduction in sensitivity to continuous sensory stimulation. The neurophysiological correlate corresponds to a decrease in the frequency of action potentials fired by a neuron, despite a stimulus of constant magnitude. Visual adaptation is prevented from occurring by the continuous involuntary movements of the eyes. See fixation movements; action potential; stabilized retinal image.
chromatic adaptation Apparent changes in hue and saturation after prolonged exposure to a field of a specific colour.
dark adaptation Adjustment of the eye (particularly regeneration of visual pigments and dilatation of the pupil), such that, after observation in the dark, the sensitivity to light is greatly increased, i.e. the threshold response to light is decreased. This is a much slower process than light adaptation. Older people usually take longer to adapt to darkness and only reach a higher threshold than young people. See adaptometer; hemeralopia; visual pigment; duplicity theory.
light adaptation Adjustment of the eye (particularly bleaching of visual pigments and constriction of the pupil), such that, after observation of a bright field, the sensitivity to light is diminished, i.e. the threshold of luminance is increased. See duplicity theory.
prism adaptation See vergence adaptation.
sensory adaptation Mechanism by which the visual system adjusts to avoid confusion and diplopia of the perceptual impression due to an abnormal motor condition (e.g. strabismus).
vergence adaptation A process by which the eyes return to their condition of habitual heterophoria or orthophoria after a heterophoria has been induced by prisms (prism adaptation) in front of one or both eyes (as, for example, when lens centration does not coincide with the interpupillary distance), or by spherical lenses, or due to changes in the orbital contents with increasing age. This adaptation process may be related to the phenomenon of orthophorization. People who have symptomatic binocular vision anomalies do not, or only partially, show vergence adaptation to prisms. Vergence adaptation decreases with increasing age.

dispersion

Phenomenon of the change in velocity of propagation of radiation in a medium, as a function of its frequency, which causes a separation of the monochromatic components of a complex radiation. All optical media cause dispersion by virtue of their variation of refractive index with wavelengths. Dispersion is specified by the difference in the refractive index of the medium for two wavelengths. The difference between the blue F (486.1 nm) and the red C (656.3 nm) spectral lines is called the mean dispersion, i.e. n_F − n_C. Dispersion is usually represented by its dispersive power ω or relative dispersion which is equal to the mean dispersion divided by the excess refractive index of the helium d (587.6 nm) spectral line (n_d − 1), often called the refractivity of the material,ω = n_F − n_C/n_d − 1The reciprocal of the dispersive power is called the Abbé's number or constringence (Fig. D8). See aberration longitudinal chromatic; achromatic axis; Fraunhoffer's lines; achromatic prism.

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Fig. D8 Dispersion of a white beam of light by a prism

parallax

Apparent displacement of an object viewed from two different points not on a straight line with the object.
binocular parallax The difference in angle subtended at each eye by an object that is viewed first with one eye and then with the other.
chromatic parallax Apparent lateral displacement of two monochromatic sources (e.g. a blue object and a red object) when observed through a disc with a pinhole placed near the edge of the pupil. When the pupil is centred on the achromatic axis (in some people the pinhole may have to be placed away from the centre of the pupil), the two images appear superimposed. The relative displacement of the two images becomes reversed when the pinhole is on the other side of that axis. This phenomenon is attributed to the chromatic aberration of the eye. See chromostereopsis; longitudinal chromatic aberration.
monocular parallax The apparent change in the relative position of an object when the eye is moved from one position to another.
motion parallax Apparent difference in the direction of movement or speed produced when the subject moves relative to his environment (Fig. P2). Example: when viewing the landscape through the window of a moving train near objects appear to move much more quickly than distant objects. See depth perception; stereopsis.
relative binocular parallax See stereoscopic visual acuity.

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Fig. P2 An example of motion parallax

chromatic aberration

chromatic aberration

chromatic aberration

chromat′ic aberra′tion

chromatic aberration

chromatic aberration:

Chromatic aberration

chromatic aberration

Chromatic Aberration

REFERENCES

chromatic aberration

chromatic aberration

chromatic aberration

aberration

chro·mat·ic ab·er·ra·tion

chromatic aberration

chro·mat·ic ab·er·ra·tion

chromatic aberration

Newton,

adaptation

dispersion

parallax

chromatic aberration

Words related to chromatic aberration

noun an optical aberration in which the image has colored fringes

Related Words