コマ収差

WordNet

an optical phenomenon resulting from the failure of a lens or mirror to produce a good image (同)distortion, optical aberration
a disorder in ones mental state
(botany) a usually terminal tuft of bracts (as in the pineapple) or tuft of hairs (especially on certain seeds)
a state of deep and often prolonged unconsciousness; usually the result of disease or injury (同)comatoseness
(astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed

PrepTutorEJDIC

正道からはずれること,非行,異常 / (軽い)精神異常
こん睡状態
コマ(彗星(すいせい)の核の周囲の星雲状物質) / (レンズの)非対称収差 / (種子の)種綿(たねわた)
『来たるべき』,『次の』 / 《話》前途有望な,今売り出し中の;新進の / (…の)『到来』,接近,致着(arrival)《+『of』+『名』》

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/07/17 19:55:23」(JST)

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Coma of a single lens

In optics (especially telescopes), the coma (aka comatic aberration) in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components which results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration.

Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the mirror at an angle, individual rays are not reflected to the same point. When looking at a point that is not perfectly aligned with the optical axis, some of the incoming light from that point will strike the mirror at an angle. This results in an image that is not in the center of the field looking wedge-shaped. The further off-axis (or the greater the angle subtented by the point with the optical axis), the worse this effect is. This causes stars to appear to have a cometary coma, hence the name.[1]

Schemes to reduce spherical aberration without introducing coma include Schmidt, Maksutov, ACF and Ritchey-Chrétien optical systems. Correction lenses for Newtonian reflectors have been designed which reduce coma in telescopes below f/6. These work by means of a dual lens system of a plano-convex and a plano-concave lens fitted into an eyepiece adaptor which superficially resembles a Barlow lens. ^[1]^[2]

Coma of a single lens or a system of lenses can be minimized (and in some cases eliminated) by choosing the curvature of the lens surfaces to match the application. Lenses in which both spherical aberration and coma are minimized at a single wavelength are called bestform or aplanatic lenses.

Vertical coma is the most common higher-order aberration in the eyes of patients with keratoconus.^[3] Coma is also a common temporary symptom of corneal injuries or abrasions, in which case the visual defect gradually resolves as the cornea heals.

This is a comparison of the coma in an uncorrected f/3.9 Newtonian telescope vs the affects of coma with the Baader Rowe Coma Corrector.

References[edit]

^ US a coma-correcting meniscus lens 4571036, Gebelein, Rolin J. & David Shafer, "Reflecting telescope with correcting lens", published 02/18/1986
^ Knisely, David (2004). "Tele Vue Paracor Coma Corrector for Newtonians" (pdf). Cloudy Nights Telescope Review. Retrieved 29 November, 2010.
^ Pantanelli S, MacRae S, Jeong TM, Yoon G (November 2007). "Characterizing the wave aberration in eyes with keratoconus or penetrating keratoplasty using a high-dynamic range wavefront sensor". Ophthalmology 114 (11): 2013–21. doi:10.1016/j.ophtha.2007.01.008. PMID 17553566.

External links[edit]

About coma in a Newtonian telescope
Coma Aberration in Youtube

UpToDate Contents

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English Journal

Clinical features of subepithelial layer irregularities of cornea.

Lee YW1, Gye HJ, Choi CY.
Current eye research.Curr Eye Res.2015 Jul;40(7):668-75. doi: 10.3109/02713683.2014.957323. Epub 2014 Sep 8.
PURPOSE: To illustrate surgical outcomes of subepithelial irregularities that were identified incidentally during laser refractive surgery.MATERIALS AND METHODS: The study group consisted of 406 patients who underwent 787 surface ablation refractive surgeries. Ophthalmologic evaluations were perform
PMID 25198157

Aberration compensation between anterior and posterior corneal surfaces after Small incision lenticule extraction and Femtosecond laser-assisted laser in-situ keratomileusis.

Li X1, Wang Y1, Dou R1.
Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists).Ophthalmic Physiol Opt.2015 Jun 18. doi: 10.1111/opo.12226. [Epub ahead of print]
PURPOSE: To investigate the aberration compensation between anterior and posterior corneal surfaces after SMILE and FS-LASIK.METHODS: Fifty-five subjects (55 eyes) undergoing SMILE and 51 subjects (51 eyes) undergoing FS-LASIK were enrolled in this study. Wavefront aberrations of anterior and poster
PMID 26087672

Effects of non-rotationally symmetric aberrations on the quantitative measurement of lattice positions in a graphene monolayer using high-resolution transmission electron microscopy.

Lin F1, Jian J2, Ye L2, Jin C3.
Microscopy (Oxford, England).Microscopy (Oxf).2015 Jun 12. pii: dfv025. [Epub ahead of print]
It is crucial to determine the position of lattice atoms in a monolayer specimen with high precision using high-resolution transmission electron microscopy (HRTEM). Image simulations indicate that the intensity centers of periodic lattice atoms in graphene may deviate from their intrinsic positions
PMID 26070475

Japanese Journal

Design for Underwater Aplanatic Straubel Acoustic Mirror

Sato Yuji,Mizutani Koichi,Wakatsuki Naoto [他],Nakamura Toshiaki
Jpn J Appl Phys 50(7), 07HG08-07HG08-6, 2011-07-25
… The mirror could correct spherical and coma aberrations in accordance with ray theory. … In a comparison of the aplanatic Straubel mirror with an aplanatic Fresnel lens, the mirror had less coma aberration and field curvature than the lens. …
NAID 150000057696

露光装置の収差データ活用技術の研究--線幅変動低減のための収差解析

吉武康裕,松本俊一,山本康治 [他],古居英樹
精密工学会誌 76(1), 69-73, 2010
… It is confirmed that multiple regression of the 3rd and 5th coma aberration coefficients permits the differences in the widths at the left and right edges of seven pairs of 250nm line and spatial patterns to be predicted to an accuracy of 9.4 nm(2σ). …
NAID 130000302340