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Topic: Spherical aberration

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	Lens (optics) - Wikipedia, the free encyclopedia
		Spherical aberration is caused because spherical surfaces are not the ideal shape with which to make a lens, but they are by far the simplest shape to which glass can be ground and polished and so are often used.
		Spherical aberration can be minimised by careful choice of the curvature of the surfaces for a particular application: for instance, a plano-convex lens which is used to focus a collimated beam produces a sharper focal spot when used with the convex side towards the beam.
		Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light.
	en.wikipedia.org /wiki/Lens_(optics) (2334 words)

	Nikon MicroscopyU: Water Immersion Objectives
		Spherical aberration caused by the mismatch of refractive indices in the optical path is the primary cause of the image deterioration, and this aberration increases proportionally with imaging depth.
		Spherical aberration limits these capabilities, and increases proportionally with depth in the specimen when the refractive index of the specimen differs from that of the immersion fluid.
		The focus shift induced by the spherical aberration is accompanied by a loss of intensity in the acquired image, and the decrease continues geometrically with distance into the specimen.
	www.microscopyu.com /articles/optics/waterimmersionobjectives.html (4773 words)

	LaserMyEye :: Encyclopedia :: Spherical aberration
		Specific type of wavefront aberration associated with reduced vision quality, especially night vision disturbances (starbursts and haloes) and reduced contrast sensitivity.
		Laser eye surgery for myopes is generally thought to cause spherical aberration in some amount.
		Spherical aberration is most commonly associated with reduced vision quality in dim light, including reduction in contrast sensitivity and the appearance of point light source vision disturbances (starbursts, haloes).
	www.lasermyeye.org /encyclopedia/sphericalab.html (137 words)

	Spherical aberration
		Spherical aberration (SA) is an image imperfection that is due to the spherical lens shape.
		Spherical aberration is uniform over the field, in the sense that the longitudinal focus difference between the lens margins and center does not depend on the obliquity of the incident light.
		Spherical aberration is responsible for the rugged blur character at negative distances, and the transition to a smoother appearance at positive distances.
	www.vanwalree.com /optics/spherical.html (1391 words)

	Melles Griot Optics Guide - Spherical Aberration (Site not responding. Last check: 2007-11-02)
		Spherical aberration, shown below in a computer-generated mesh, is a deviation of the laser wavefront from an ideal spherical shape.
		Spherical aberration is dependent on lens shape, orientation, and conjugate ratio, as well as on the index of refraction of the materials present.
		Theoretically, the simplest way to eliminate or reduce spherical aberration is to make the lens surface(s) with a varying radius of curvature (i.e., an aspheric surface) designed to exactly compensate for the fact that sinq is not equal to q at larger angles.
	www.mellesgriot.com /products/optics/fo_3_2_1.htm (424 words)

	Olympus Microscopy Resource Center: Anatomy of the Microscope - Optical Aberrations
		Spherical Aberration from Coverslip Thickness Variations - For microscope objectives having high numerical apertures, the optical properties and thickness of the medium lying between the front lens element and the specimen critically affect the calculations necessary to satisfy the aplanatic and sine conditions and otherwise to correct for image aberrations.
		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) shape to the Airy pattern.
		When the aperture function of an objective is non-uniform, or in the case of spherical aberration, the wavefront leaving the lens is no longer spherical with a center positioned at the point of focus in the image plane.
	www.olympusmicro.com /primer/anatomy/aberrationhome.html (1287 words)

	ipedia.com: Aberration in optical systems Article (Site not responding. Last check: 2007-11-02)
		The preceding review of the several errors of reproduction belongs to the Abbe theory of aberrations, in which definite aberrations are discussed separately; it is well suited to practical needs, for in the construction of an optical instrument certain errors are sought to be eliminated, the selection of which is justified by experience.
		The aberrations can also be expressed by means of the characteristic function of the system and its differential coefficients, instead of by the radii, &c., of the lenses; these formulae are not immediately applicable, but give, however, the relation between the number of aberrations and the order.
		The aberrations of the third order are: (1) aberration of the axis point; (2) aberration of points whose distance from the axis is very small, less than of the third order -- the deviation from the sine condition and coma here fall together in one class; (3) astigmatism; (4) curvature of the field; (5) distortion.
	www.ipedia.com /aberration_in_optical_systems.html (5545 words)

	LSA of indiana eye
		Spherical aberration of the model eye is well described by third-order optical theory for shape parameters in the range 0 ² p ² 0.7 but requires fifth-order theory for an accurate description over the parametric range 0.7 < p ² 1.0.
		Transverse spherical aberration (TSA) is defined as the angular error between the refracted ray (marked with arrow head) and the un-aberrated reference ray.
		Longitudinal spherical aberration (LSA) is defined by the vergence error of the refracted ray.
	research.opt.indiana.edu /Library/INEye/IndianaEye.html (1574 words)

	Olympus Microscopy Resource Center: Anatomy of the Microscope - Focus Depth and Spherical Aberration - Interactive Java ...
		In the presence of spherical aberration and/or astigmatism, maximum contrast may not be an indication of desirable focus, an error that can be compounded with periodic specimens.
		Furthermore, distortion introduced by spherical aberration may not only affect image quality and fidelity, which affect interpretation and measurement of the specimen, but also the efficiency of confocal and other imaging modes in which the microscope optics are used to reduce the image to obtain a diffraction-limited illuminating point.
		The effect of this induced spherical aberration on the image point should be considered, because the optical assumptions used to calculate objective lenses for aberration correction by microscope manufacturers no longer hold.
	www.olympusmicro.com /primer/java/aberrations/pointspreadaberration (1297 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		Spherical aberration is the term used to describe the fact that light rays entering a refracting (focusing) surface such as the cornea are less strongly focused at the center of the refracting surface and progressively more strongly focused off center.
		Fortunately, the spherical aberration for the eye in total is less than that introduced by the cornea because the crystalline lens corrects a portion of the aberration leaving less to degrade vision by the time light reaches the retina.
		The spherical aberration induced by any convex surface is not only a function of the surface curvature but also the convergence of the light as it enters the surface.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/28368.000518&ELEMENT_SET=DECL (7693 words)

	Spherical Aberration
		Spherical aberration is one of the most important problems that can occur after laser eye surgery, in particular with high myopic corrections.
		For lenses made with spherical surfaces, rays which are parallel to the optic axis but at different distances from the optic axis fail to converge to the same point.
		Spherical aberration is not really a problem with low myopic corrections but can be a problem with some patients having higher corrections e.g.
	www.birkacre.freeserve.co.uk /spherical_aberration.htm (448 words)

	AllRefer.com - aberration (Physics) - Encyclopedia
		Spherical aberration is caused by the failure of a lens or mirror of spherical section to bring parallel rays of light to a single focus.
		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.
	reference.allrefer.com /encyclopedia/A/aberrati.html (301 words)

	Glossary
		Spherical aberration causes parallel light rays passing through the edge of a lens to converge at a focal point closer to the lens than light rays passing through the center of the lens.
		A point image affected by spherical aberration is sharply formed by light rays near the optical axis but is affected by flare from the peripheral light rays (this flare is also called halo, and its radius is called lateral spherical aberration).
		As a result, spherical aberration affects the entire image area from the center to the edges, and produces a soft, low-contrast image which looks as if covered with a thin veil.
	www.usa.canon.com /html/eflenses/lens101/glossary/index_s.html (1655 words)

	Aberrations
		Aberrations are due to inherent shortcomings of a lens, even a lens made of the best glass, and free from manufacturing and other defects.
		Spherical aberration is the dependence of the focal length on the aperture for nonparaxial rays.
		In the absence of any spherical aberration, all of the focal lengths are the same and all of the rays arrive at a single focus.
	physics.tamuk.edu /~suson/html/4323/aberatn.html (1512 words)

	Cataract & Refractive Surgery Today
		Spherical aberration is a fourth-order aberration that varies with the radial distance from the center of the pupil.
		Surgeons have attempted to correct spherical aberrations by increasing both the blend zone and the ablation in the midperiphery and periphery of the cornea.
		Spherical aberration is an optical complication of laser vision correction that results in the visual symptoms of glare, starburst, and halos.
	www.crstodayarchive.com /03_archive/0503/17.html (1619 words)

	Melles Griot Optics Guide - Aberration Balancing (Site not responding. Last check: 2007-11-02)
		The contribution to longitudinal spherical aberration (LSA) for a lens is the -factor multiplied by the focal length and divided by the square of the f-number.
		Since the sign of the aberration is the same as focal length, to null out the effects of spherical aberrations the system requires both positive and negative focal length elements.
		Thus, it should be possible to correct the spherical aberration of this Galilean-type beam expander, which consists of a positive focal length objective and a negative diverging lens.
	www.mellesgriot.com /products/optics/fo_4_2.htm (441 words)

	Aberration
		Chromatic aberrations are caused by dispersion (the variation in the index of refraction of a medium with wavelength).
		Monochromatic aberrations are caused by geometry (the shape of the lens or mirror).
		Spherical aberration occurs because the focal length of a lens varies with distance from the principal axis.
	hypertextbook.com /physics/waves/aberration/index.shtml (328 words)

	aberration -- Encyclopædia Britannica
		Spherical aberration is present when the outer parts of a lens do not bring light rays into the same focus as...
		The change of image distance with wavelength is known as chromatic aberration, and the variation of magnification with wavelength is known as...
		Spherical aberration arises near the edge of the lens, where light meets the lens at sharper angles.
	www.britannica.com /eb/article-9003333 (729 words)

	IHB Chapter 2.3 HST's Spherical Aberration
		Though the Koesters prisms are not sensitive to symmetric aberrations (e.g., spherical aberration), small misalignments in the internal FGS optical train shift the location of the beam's axis of tilt ("b" in Figure 2.2 and in Figure 2.3) effectively breaking the symmetry of the OTA's spherical aberration.
		If the telescope were not spherically aberrated (i.e., if the wavefront were planar) misalignments up to five times this size would hardly be noticeable.
		The impact of HST spherical aberration and the improved performance of FGS1r are discussed in the next sections.
	www.stsci.edu:8082 /hst/fgs/documents/ihb_cycle11/c02_instdesign4.html (285 words)

	Journal of Vision - A population study on changes in wave aberrations with accommodation, by Cheng, Barnett, Vilupuru, ... (Site not responding. Last check: 2007-11-02)
		The population mean for the RMS of all aberration terms (Z3, Z5-Z27) for 74 subjects as a function of accommodation under three different conditions: all aberrations present (blue bars), all aberrations corrected for the relaxed state (red bars), and all aberrations except spherical aberration corrected for the relaxed state (green bars).
		The coefficient for spherical aberration as a function of the change in accommodative response for all subjects under three different stimulus conditions: triangles for 0 D, empty circles, and filled circles for 3 D and 6 D, respectively.
		Figure 6 compares the mean RMS of total aberrations (excluding defocus) as a function of accommodation under three different conditions: all aberrations present (blue bars), all aberrations corrected for the relaxed state (red bars), and all aberrations except spherical aberration corrected for the relaxed state (green bars).
	www.journalofvision.org /4/4/3/article.aspx (5082 words)

	II-VI INFRARED: TUTORIAL: SPHERICAL ABBERATION (Site not responding. Last check: 2007-11-02)
		Spherical aberration has the effect of increasing spot size as well as causing best focus to occur at a different location than the calculated Effective Focal Length.
		Spherical aberration is a function of lens shape, lens orientation and lens index of refraction.
		The most important point to note from the preceding formula is that the spot size due to spherical aberration is proportional to the cube of the beam diameter and inversely proportional to the square of the focal length.
	www.iiviinfrared.com /ttr_sphericabb.html (368 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.
		Variation of polynomial coefficients for 5th-order theoretical analysis of spherical aberration of the Indiana Eye in image space (upper diagram) and in object space (lower diagram).
		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)

	Laser Beam Measurement - Melles Griot (Site not responding. Last check: 2007-11-02)
		The aberrations of the wavefront of a laser are the only unambiguous figures of merit of laser quality.
		Another way to understand spherical aberration is that the focus for paraxial rays is at a different distance along the optical axis than the focus for marginal rays.
		Spherical aberration is sometimes described as variation of focus with aperture.
	beammeasurement.mellesgriot.com /tut_beam_analysis_para.asp (1677 words)

	ScopeCity.com
		Aberrations, if they occur, are physical optical errors caused by faulty optical design or manufacturing.
		Spherical Aberration causes monochromatic light rays to focus at different points along the optical axis.
		Chromatic Aberration is the failure of a lens to bring light of all colors to a common focus.
	www.scopecity.com /OpticalAberrations.cfm (459 words)

	ASTR 511, O'CONNELL. [Fall 2003] Lecture Notes
		The modern solution to chromatic aberration in refractive optics is to use mirrors rather than lenses, and most large telescopes employ mirrors as their primary optics.
		The modern solution to spherical aberration (the fact that parallel light rays striking the surface of a sphere do not come to a single focus) is to use non-spherical optics, especially paraboloids.
		Another famous alternative for control of spherical aberration over a wide field with a spherical primary is to use a special full-aperture refractive correcting plate called a Schmidt corrector.
	www.astro.virginia.edu /class/oconnell/astr511/lec16-teloptics-f03.html (526 words)

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