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Topic: Coma aberration

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	Olympus Microscopy Resource Center: Physics of Light and Color - Common Optical Defects in Lens Systems (Aberrations)
		Spherical aberrations are very important in terms of the resolution of a lens because they affect the coincident imaging of points along the optical axis and degrade the performance of the lens, which will seriously affect specimen sharpness and clarity.
		The aberration is named for its strong resemblance to the shape of a comet tail, and is manifested by a streak of light that appears to emanate from a focused spot at the periphery of the viewfield.
		In the extreme, coma results in meridional rays passing through the periphery of the lens to arrive at the image plane closer to the axis than do light rays passing through the central portion of the lens (and closer to the principal ray, as illustrated in Figure 3).
	www.olympusmicro.com /primer/lightandcolor/opticalaberrations.html (2144 words)

	Coma aberration
		Coma aberration coefficient c for either refractive or reflective surface, for object at infinity, and aperture stop at the surface is given by:
		As mentioned, the above relations for coma aberration are for a concave mirror with the aperture stop at the surface.
		Considering that the magnification m is negative, coma diminishes with object distance, dropping to zero for m=-1 (for object at the mirror center of curvature) and stop at the surface, regardless of the conic.
	www.telescope-optics.net /coma.htm (1447 words)

	Molecular Expressions Microscopy Primer: Physics of Light and Color - Comatic Aberrations - Interactive Java Tutorial
		When these aberrations occur, the image of a point is focused at sequentially differing heights producing a series of asymmetrical spot shapes of increasing size that result in a comet-like (hence, the term coma; Figure 1) shape to the Airy pattern.
		The distinct shape displayed by images with comatic aberration is a result of refraction differences by light rays passing through the various lens zones as the incident angle increases.
		The severity of comatic aberration is a function of thin lens shape, which in the extreme, causes meridional rays passing through the periphery of the lens to arrive at the image plane closer to the axis than do rays passing nearer the axis and closer to the principal ray (see Figure 1).
	micro.magnet.fsu.edu /primer/java/aberrations/coma/index.html (917 words)

	The XMM Newton Satellite Schoolpage
		So, in astronomical telescopes (and car headlights) the spherical mirror is often replaced by a parabola, in which all the rays from a point source on the axis of the parabola pass exactly through the image.
		This error in the imaging is called coma, and it is greater the further the source is from the axis of the parabola.
		In the Cassegrain telescope, which is a common design for optical astronomy, a second mirror is used and various combinations of shapes for the primary and secondary mirrors allow the aberrations to be adjusted.
	www.sr.bham.ac.uk /xmm/optics.html (842 words)

	Telescope aberrations
		For relatively small aberration levels, drop in the peak intensity of diffraction pattern caused by wavefront errors is accompanied by a transfer of the "lost" energy to the area of rings.
		As already mentioned, ray aberrations are not reliable indicator of energy re-distribution within diffraction pattern, which is the key information needed to access the effect of aberration on image quality.
		The significance of the classical aberration form is that it offers a common reference sphere, which makes possible a direct calculation of the combined effect of two or more aberrations with respect to it, as given with Eq.6.
	www.telescope-optics.net /aberrations.htm (2035 words)

	Glossary
		Coma, or comatic aberration, is a phenomenon visible in the periphery of an image produced by a lens which has been corrected for spherical aberration, and causes light rays entering the edge of the lens at an angle to converge in the form of a comet instead of the desired point, hence the name.
		Coma, which can occur even in lenses which correctly reproduce a point as a point on the optical axis, is caused by a difference in refraction between light rays from an off-axis point passing through the edge of the lens and the principal light ray from the same point passing through the lens center.
		Coma increases as the angle of the principal ray increases, and causes a decrease in contrast near the edges of the image.
	www.usa.canon.com /html/eflenses/lens101/glossary/index_a.html (2578 words)

	Method of detecting aberrations of an optical imaging system - Patent 6368763
		Aberrations of an imaging system (PL) can be detected in an accurate and reliable way by imaging, by means of the imaging system, a circular phase structure (22) on a photoresist (PR), developing the resist and scanning it with a scanning detection device (SEM) which is coupled to an image processor (IP).
		The direction of the coma at a measured position is indicated by the direction of the arrow shown at that position and the size of the coma is indicated by the underlined number near this arrow.
		Coma is related to r.sub.1, astigmatism to r.sub.2 and three-point aberration to r.sub.3.
	www.freepatentsonline.com /6368763.html (12164 words)

	aberrations
		Spherical aberrations are the consequence of the failure of meridional rays to obey the paraxial approximation.
		Coma is the failure of skew rays to match the behavior of meridional rays.
		Spherical aberration is the failure of meridional rays to obey the paraxial approximation, and coma is the failure of skew rays to behave like meridional rays.
	electron9.phys.utk.edu /optics421/modules/m2/aberration.htm (1585 words)

	Higher-Order Aberrations in the Eye - AllAboutVision.com
		A higher-order aberration is a distortion acquired by a wavefront of light when it passes through an eye with irregularities of its refractive components (tear film, cornea, aqueous humor, crystalline lens, and vitreous humor).
		Aberrations also may result when dry eye diminishes your eye's tear film, which helps bend or refract light rays to achieve focus.
		Higher-order aberrations are identified by the types of distortions acquired by a wavefront of light as it passes through your eye.
	www.allaboutvision.com /conditions/aberrations.htm (1067 words)

	coma
		A state of profound unconsciousness from which one cannot be roused; may be due to the action of an ingested toxic substance or of one formed in the body, to trauma, or to disease.
		An aberration of spherical lenses; occurring in cases of oblique incidence (e.g., the image of a point becomes comet-shaped).
		coma resulting from diffuse failure of neuronal metabolism, caused by such abnormalities as intrinsic disorders of neuron or glial cell metabolism, or extracerebral disorders that produce intoxication or electrolyte imbalances.
	www.painhealth.com /word.asp?q=9150 (263 words)

	Optics: all you need to know about optical aberrations
		All you need to know about optical aberrations (I) Generally speaking, aberrations are errors occuring in the resulting image which is not conform compared to the subject, the real image.
		If polychromatic aberrations are related to colors, monochromatic aberrations or Seidel aberrations degrade (spherical aberration, coma and astigmatism) or deform (field curvature and distortion) the imaging ability of lenses or mirrors.
		Coma aberration is a variante of this effect.
	www.astrosurf.com /luxorion/report-aberrations.htm (1454 words)

	Aberration and Distortion
		Spherical aberration is defined as any deviation from the light source (" P " in the figure) along the optical axis at the focal point of paraxial rays (" P' " in the figure).
		Coma aberration is manifested by an image with a comet-like extension.
		As coma increases toward the exterior of the lens, it affects the periphery of the viewfield.
	nikon.topica.ne.jp /bi_e/encyclo/ad.htm (433 words)

	Performance of optical traps with geometric aberrations
		We assess the influence of geometric aberrations on optical traps' in-plane performance by studying the dynamics of trapped colloidal spheres in deliberately distorted holographic optical tweezers.
		Coma is typically introduced by failure to center lenses along the optical axis.
		Although aberrations are known to substantially degrade axial trapping performance, we have demonstrated that their effect on lateral trapping is less pronounced, with astigmatism and coma apparently requiring the most attention.
	www.physics.nyu.edu /grierlab/aberration5b/aberration5b.html (1894 words)

	Optics: all you need to know about optical aberrations
		All you need to know about optical aberrations (I) Generally speaking, aberrations are errors occuring in the resulting image which is not conform compared to the subject, the real image.
		If polychromatic aberrations are related to colors, monochromatic aberrations or Seidel aberrations degrade (spherical aberration, coma and astigmatism) or deform (field curvature and distortion) the imaging ability of lenses or mirrors.
		Coma aberration is a variante of this effect.
	www.astrosurf.org /lombry/report-aberrations.htm (1454 words)

	Houghton corrector with plano- lenses
		Residual system coma is about 1/6 of the mirror coma and the astigmatism is, as already mentioned, mainly that of the primary mirror (generally low in Newtonian-style arrangements).
		The cone converging from the primary is reflected by a flat - or aluminized spot - at the rear corrector surface.
		Aberration coefficients of the sub-aperture corrector are different than those given for the full-aperture, due to it being placed in a converging cone of light.
	www.telescope-optics.net /Houghton2.htm (1234 words)

	About Coma
		The dominant optical aberration in the Newtonian telescope is off-axis coma.
		The amount of coma apparent in a Newtonian telescope is a function of the focal ratio of the telescope.
		Usually, these eyepiece aberrations are larger than the telescope’s comatic aberration and they are the aberrations most prominent in the image.
	www.opticalmechanics.com /about_coma.htm (1931 words)

	Optical Design Primer
		Spherical aberration, given the symbol LA' for "longitudinal aberration,'' is present in an optical system when monochromatic rays from an object point on the axis of the system cross the axis in image space at more than a single point.
		Coma, when present in an optical system, manifests itself in flared images of object points which are off the axis of the system.
		Chromatic aberration, which is present only in systems which contain refractive elements, is a result of the fact that a refractive medium has a slightly different refractive index for different wavelengths of light.
	www.skyscientific.com /opticalprimer.htm (3480 words)

	Optics: all you need to know about optical aberrations
		This chromatic aberration can be removed by using appropriate combination of glasses of different indexes of refraction, so that all colors focus at the same focal point.
		Coma aberration which means "comet" in latin, is similar to spherical aberration; it applies to rays entering the lens at an angle.
		As coma is proportional to the distance to the central axis, more the rays are away from the center, more the focal point changes of position and get blurry images, mainly off-axis.
	www.astrosurf.org /lombry/report-aberrations2.htm (852 words)

	Essential Optics Review for the Boards: 20
		Chromatic aberration occurs strongly in the human eye; with almost 3.00D difference in the focus of the far ends the visible spectrum.
		Spherical aberration normally increases as you move towards the peripheral portion of the lens.
		Curvature of field is an advantageous aberration in the human eye because it produces a curved image on the retina, as opposed to a flat image.
	www.medrounds.org /optics-review/2006/05/20.html (566 words)

	Optics: all you need to know about optical aberrations
		This chromatic aberration can be removed by using appropriate combination of glasses of different indexes of refraction, so that all colors focus at the same focal point.
		Coma aberration which means "comet" in latin, is similar to spherical aberration; it applies to rays entering the lens at an angle.
		As coma is proportional to the distance to the central axis, more the rays are away from the center, more the focal point changes of position and get blurry images, mainly off-axis.
	www.astrosurf.com /luxorion/report-aberrations2.htm (852 words)

	Important Clinical News On LASIK
		The study authors said the corneal and ocular comas were similar in magnitude, suggesting that the increase of ocular coma with aging is mainly a result of the increase of corneal coma.
		Corneal spherical aberration did not change with age; however, there was a significant correlation between ocular spherical aberration and aging.
		The corneal spherical aberrations were approximately 0.2 µm to 0.3 µm throughout the age range; the mean ocular spherical aberration was almost zero at 20 years of age, and it gradually increased with age.
	www.talkaboutsupport.com /group/alt.lasik-eyes/messages/36265.html (449 words)

	Section 2: Monochromators & Spectrographs
		2) Coma is the result of the off-axis geometry of a PGS and is seen as a skewing of rays in the dispersion plane enlarging the base on one side of a spectral line as shown in Fig.
		Coma may be responsible for both degraded bandpass and optical signal-to-noise ratio.
		The OPD due to spherical aberration varies with the fourth power of the numerical aperture and cannot be corrected without the use of aspheric optics.
	www.jyhoriba.co.uk /jy/oos/oos_ch2.htm (4322 words)

	EyeWorld Magazine: November 2005
		Source: Brian Boxer Wachler, M.D. hile researchers often discuss higher-order aberrations (HOAs) and whether they lead to visual symptoms, it is also worthwhile to understand which visual symptoms are related to which aberrations.
		Coma aberration also was divided into vertical and horizontal components.
		“Double vision was associated with horizontal coma at all pupil sizes analyzed, and total coma was associated with double vision for a 5-mm and 7-mm pupil size,” Dr. Chalita wrote in her study.
	www.eyeworld.org /article.php?sid=2824 (790 words)

	Astronomical Glossary
		Spherical aberration results when different rays of light are brought to more than one focus, producing a blurred image or coma; chromatic aberration when different wavelengths within a ray of light are brought to more than one focus, producing an image distorted by colored fringes.
		Aberration in lenses can be overcome by the use of an achromatic lens or a combination of lenses made of glasses of different refractive indices.
		Spherical Aberration always occurs with rays that are distant from the axis and incident on a spherical mirror or lens.
	www.angelfire.com /stars5/astroinfo/gloss/a.html (13060 words)

	Nikon \| Corporate Information \| About Nikon \| History \| Nikkor -- The Thousand and One Nights \| Tale Twenty Eight : Ai ...
		It meant that the aberration of the sagittal coma flare, with which you may not be familiar, would become more difficult to correct.
		Here, in the case of a wide-angle lens in which a many concave elements are arranged in the front group, it is difficult to correct the sagittal coma flare which is believed to occur at a concave surface with a large curvature.
		A pale blaze of light due to sagittal coma flare is slightly seen in the surrounding bright stars, though you may notice it is not very conspicuous.
	www.nikon.co.jp /main/eng/portfolio/about/history/nikkor/n28_e.htm (1568 words)

	Indina Eye Seidel Aberration Values
		longitudinal spherical aberration should be proportional to the square of ray height and the constant of proportionality is called the Seidel value for primary spherical aberration.
		the odd-symmetric aberration of coma is relatively common in human eyes.
		Notice that this aberration function, like many of those in the classical literature, is asymmetric about the origin (the intersection of the foveal achromatic axis with the pupil plane).
	research.opt.indiana.edu /Library/INEye/INeyeSidel.html (1444 words)

	Glossaire des termes utilisés avec les objectifs sur le site Nikon Japon
		SEIDEL's five aberrations, which occur even with monochromatic (single-wave length) light, and two types of chromatic aberrations, which are caused by more than one frequency.
		aberration causes color smearing and a loss of sharpness in the center of the image.
		Coma spreading radially from the optical axis forms a teardrop-shaped flare, usually called a meridional coma flare.
	www.nikon-euro.com /nikoneuro_fr/faq/lens/FAQ_lens_fr_03.htm (1848 words)

	Nikon binoculars technical informations
		Spherical aberration is defined as any deviation from the light source along the optical axis at the focal point of paraxial rays.
		Coma aberration is manifested by an image with a comet-like extension.
		As coma increases toward the exterior of the lens, it affects the periphery of the viewfield.
	www.the-eye-shop.com /feat/gb/nikon_glossary.htm (2511 words)

	Journal of Vision - Compensation of corneal horizontal/vertical astigmatism, lateral coma, and spherical aberration by ...
		Artal, Guirao, Berrio, and Williams (2001) reported that the wavefront aberrations produced by the internal optics offset, or compensate for, the aberrations produced by the cornea to reduce ocular wavefront aberrations.
		We have investigated the wavefront aberrations of the cornea, internal optics, and complete eye on both the population and individual level to determine which aberrations are compensated and probable paths leading to that compensation.
		The corneal and ocular aberrations of 30 young subjects at relaxed accommodation were measured with the Topcon Wavefront Analyzer, which simultaneously measures refraction, corneal topography (videokeratoscope), and wavefront aberrations (Hartmann-Shack sensor).
	journalofvision.org /4/4/2 (304 words)

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