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| {{Redirect|Ray of light|other uses|Ray of light (disambiguation)}}
| | The name of the writer is Figures. My working day job is a meter reader. Puerto Rico is exactly where he's always been living but she needs to move because of her family. His wife doesn't like it the way he does but what he really likes performing is to do aerobics and he's been doing it for quite a whilst.<br><br>Here is my page [http://www.zs-imports.com/blogs/post/70017 zs-imports.com] |
| In [[optics]] a '''ray''' is an idealized model of [[light]], obtained by choosing a line that is perpendicular to the [[wavefront]]s of the actual light, and that points in the direction of energy flow.<ref>{{cite web |url=http://kb-en.radiantzemax.com/Knowledgebase/What-is-a-ray |title=What is a ray? |first=Ken |last=Moore |date=25 July 2005 |work=ZEMAX Users' Knowledge Base |accessdate=30 May 2008}}</ref><ref name=Greivenkamp2>{{cite book|last=Greivenkamp|first=John E.|title=Field Guide to Geometric Optics|year=2004|publisher=SPIE Field Guides|isbn=0819452947|pages=2}}</ref> Rays are used to model the propagation of light through an optical system, by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of [[Ray tracing (physics)|ray tracing]]. This allows even very complex optical systems to be analyzed mathematically or simulated by computer. Ray tracing uses approximate solutions to [[Maxwell's equations]] that are valid as long as the [[light wave]]s propagate through and around objects whose dimensions are much greater than the light's [[wavelength]]. Ray theory does not describe phenomena such as [[Interference (wave propagation)|interference]] and [[diffraction]], which require [[wave optics|wave theory]] (involving the relative [[Phase (waves)|phase]] of the rays).
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| ==Definition==
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| A light ray is a [[Line (geometry)|line]] or [[curve]] that is [[perpendicular]] to the light's [[wavefront]]s (and is therefore [[wiktionary:collinear|collinear]] with the [[wave vector]]). Light rays bend at the [[wiktionary:interface|interface]] between two dissimilar [[optical medium|media]] and may be curved in a medium in which the [[refractive index]] changes. [[Geometric optics]] describes how rays propagate through an optical system. Objects to be imaged are treated as collections of independent point sources, each producing spherical wavefronts and corresponding outward rays. Rays from each object point can be mathematically propagated to locate the corresponding point on the image.
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| A slightly more rigorous definition of a light ray follows from [[Fermat's principle]], which states that the path taken between two points by a ray of light is the path that can be traversed in the least time.<ref>Arthur Schuster, ''An Introduction to the Theory of Optics'', London: Edward Arnold, 1904 [http://books.google.com/books?vid=OCLC03146755&id=X0AcBd-bcCwC&pg=PA41&lpg=PA41&dq=fermat%27s-principle online].</ref>
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| ==Special rays==
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| There are many special rays that are used in optical modelling to analyze an optical system. These are defined and described below, grouped by the type of system they are used to model.
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| ===Interaction with surfaces===
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| [[File:Ray optics diagram incidence reflection and refraction.svg|thumb|350px|Diagram of rays at a surface, where <math>\theta_\mathrm i</math> is the [[angle of incidence]], <math>\theta_\mathrm r</math> is the [[angle of reflection]], and <math>\theta_\mathrm R</math> is the [[angle of refraction]].]]
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| *An '''incident ray''' is a ray of light that strikes a surface. The angle between this ray and the perpendicular or [[surface normal|normal]] to the surface is the [[angle of incidence]].
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| *The '''reflected ray''' corresponding to a given incident ray, is the ray that represents the light reflected by the surface. The angle between the surface normal and the reflected ray is known as the [[angle of reflection]]. The Law of Reflection says that for a [[Specular reflection|specular]] (non-scattering) surface, the angle of reflection always equals the angle of incidence.
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| *The '''refracted ray''' or '''transmitted ray''' corresponding to a given incident ray represents the light that is transmitted through the surface. The angle between this ray and the normal is known as the [[angle of refraction]], and it is given by [[Snell's Law]]. [[Conservation of energy]] requires that the power in the incident ray must equal the sum of the power in the refracted ray, the power in the reflected ray, and any power absorbed at the surface.
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| * If the material is [[birefringence|birefringent]], the refracted ray may split into '''ordinary''' and '''extraordinary rays''', which experience different [[index of refraction|indexes of refraction]] when passing through the birefringent material.
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| {{see also|Reflection (physics)|Refraction|Absorption (optics)|Birefringence|Specular reflection}}
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| ===Optical systems===
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| *A '''meridional ray''' or '''tangential ray''' is a ray that is confined to the plane containing the system's [[optical axis]] and the object point from which the ray originated.<ref name=Stewart>{{cite book |title=Optical Principles and Technology for Engineers |first=James E. |last=Stewart |publisher=CRC |year=1996 |isbn=978-0-8247-9705-8 |page=57}}</ref>
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| *A '''skew ray''' is a ray that does not propagate in a plane that contains both the object point and the optical axis. Such rays do not cross the optical axis anywhere, and are not parallel to it.<ref name=Stewart/>
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| *The '''marginal ray''' (sometimes known as an ''a ray'' or a ''marginal axial ray'') in an optical system is the meridional ray that starts at the point where the object crosses the optical axis, and touches the edge of the [[aperture stop]] of the system.<ref name=Greivenkamp25>{{cite book | first=John E. | last=Greivenkamp | year=2004 | title=Field Guide to Geometrical Optics | publisher=SPIE | others=SPIE Field Guides vol. '''FG01''' | isbn=0-8194-5294-7 }}, p. 25 [http://books.google.co.uk/books?id=1YfZNWZAwCAC&lpg=PP1&dq=Greivenkamp%20optics&lr=&as_brr=3&client=firefox-a&pg=PA25#v=onepage&q=&f=false].</ref><ref name=Riedl>{{cite book |title=Optical Design Fundamentals for Infrared Systems |first=Max J. |last=Riedl |publisher=SPIE |year=2001 |isbn=978-0-8194-4051-8 |series=Tutorial texts in optical engineering |volume=48 |page=1}}</ref> This ray is useful, because it crosses the optical axis again at the locations where an image will be formed. The distance of the marginal ray from the optical axis at the locations of the [[entrance pupil]] and [[exit pupil]] defines the sizes of each pupil (since the pupils are [[image]]s of the aperture stop).
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| *The '''principal ray''' or '''chief ray''' (sometimes known as the ''b ray'') in an optical system is the meridional ray that starts at the edge of the object, and passes through the center of the aperture stop.<ref name=Greivenkamp25>Greivenkamp (2004), p. 25.</ref><ref>{{cite book |first=Daniel and Zacarias |last=Malacara |title=Handbook of Optical Design |edition=2nd |year=2003 |page=25 |url=http://books.google.co.uk/books?id=7aa2nDZoAHEC&lpg=PP1&dq=%22Handbook%20of%20Optical%20Design%22&pg=PA25#v=onepage&q=&f=true |publisher=CRC |isbn=978-0-8247-4613-1}}</ref> This ray crosses the optical axis at the locations of the pupils. As such chief rays are equivalent to the rays in a pinhole camera. The distance between the chief ray and the optical axis at an image location defines the size of the image. The marginal and chief rays together define the [[Lagrange invariant]], which characterizes the throughput or [[etendue]] of the optical system.<ref name=Greivenkamp28>Greivenkamp (2004), p. 28 [http://books.google.co.uk/books?id=1YfZNWZAwCAC&lpg=PP1&dq=Greivenkamp%20optics&lr=&as_brr=3&client=firefox-a&pg=PA28#v=onepage&q=&f=false].</ref> Some authors define a "principal ray" for ''each'' object point. The principal ray starting at a point on the edge of the object may then be called the ''marginal principal ray''.<ref name=Riedl/>
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| *A '''sagittal ray''' or '''transverse ray''' from an off-axis object point is a ray that propagates in the plane that is perpendicular to the meridional plane and contains the principal ray.<ref name=Stewart/> Saggital rays intersect the pupil along a line that is perpendicular to the meridional plane for the ray's object point and passes through the optical axis. If the axis direction is defined to be the ''z'' axis, and the meridional plane is the ''y''-''z'' plane, saggital rays intersect the pupil at ''y<sub>p</sub>''=0. The principal ray is both sagittal and meridional.<ref name=Stewart/> All other sagittal rays are skew rays.
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| *A '''paraxial ray''' is a ray that makes a small angle to the optical axis of the system, and lies close to the axis throughout the system.<ref>Greivenkamp (2004), pp. 19–20 [http://books.google.co.uk/books?id=1YfZNWZAwCAC&lpg=PP1&dq=Greivenkamp%20optics&lr=&as_brr=3&client=firefox-a&pg=PA19#v=onepage&q=&f=false].</ref> Such rays can be modeled reasonably well by using the [[paraxial approximation]]. When discussing ray tracing this definition is often reversed: a "paraxial ray" is then a ray that is modeled using the paraxial approximation, not necessarily a ray that remains close to the axis.<ref>{{cite web |last=Nicholson |first=Mark |title=Understanding Paraxial Ray-Tracing |date=21 July 2005 |url=http://www.zemax.com/kb/articles/18/1/Understanding-Paraxial-Ray-Tracing/Page1.html |work=ZEMAX Users' Knowledge Base |accessdate=17 August 2009}}</ref><ref name=Atchison>{{cite book |title=Optics of the Human Eye |first1=David A. |last1=Atchison |first2=George |last2=Smith |publisher=Elsevier Health Sciences |year=2000 |isbn=978-0-7506-3775-6 |page=237 |chapter=A1: Paraxial optics}}</ref>
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| *A '''finite ray''' or '''real ray''' is a ray that is traced without making the paraxial approximation.<ref name=Atchison/><ref>{{cite book |title=Aberrations of Optical Systems |series=Adam Hilger series on optics and optoelectronics |first=W. T. |last=Welford |publisher=CRC Press |year=1986 |isbn=978-0-85274-564-9 |page=50 |chapter=4: Finite Raytracing}}</ref>
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| * A '''parabasal ray''' is a ray that propagates close to some defined "base ray" rather than the optical axis.<ref>{{cite book |title=An Introduction to Hamiltonian Optics |first=H. A. |last=Buchdahl |publisher=Dover |year=1993 |isbn=978-0-486-67597-8 |page=26}}</ref> This is more appropriate than the paraxial model in systems that lack symmetry about the optical axis. In computer modeling, parabasal rays are "real rays", that is rays that are treated without making the paraxial approximation. Parabasal rays about the optical axis are sometimes used to calculate first-order properties of optical systems.<ref>{{cite web |last=Nicholson |first=Mark |title=Understanding Paraxial Ray-Tracing |date=21 July 2005 |page=2 |url=http://www.zemax.com/kb/articles/18/2/Understanding-Paraxial-Ray-Tracing/Page2.html |work=ZEMAX Users' Knowledge Base |accessdate=17 August 2009}}</ref>
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| ===Fiber optics===
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| * A '''meridional ray''' is a ray that passes through the [[optical axis|axis]] of an [[optical fiber]].
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| * A '''skew ray''' is a ray that travels in a non-planar zig-zag path and never crosses the [[optical axis|axis]] of an [[optical fiber]].
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| * A '''[[guided ray]]''', '''bound ray''', or '''trapped ray''' is a ray in a [[multi-mode optical fiber]], which is confined by the [[Fiber_optics#Principle_of_operation|core]]. For [[Step-index profile|step index fiber]], light entering the fiber will be guided if it makes an angle with the fiber axis that is less than the fiber's [[Guided ray|acceptance angle]].
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| * A '''leaky ray''' or '''tunneling ray''' is a ray in an optical fiber that geometric optics predicts would [[total internal reflection|totally reflect]] at the boundary between the [[Fiber_optics#Principle_of_operation|core]] and the [[Cladding (fiber optics)|cladding]], but which suffers loss due to the curved core boundary.
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| {{see also|Numerical aperture}}
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| ==See also==
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| *[[Paraxial approximation]]
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| *[[Pencil beam]]
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| *[[Ray transfer matrix analysis]]
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| ==References==
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| {{reflist}}
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| [[Category:Geometrical optics]]
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| [[Category:Fiber optics]]
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The name of the writer is Figures. My working day job is a meter reader. Puerto Rico is exactly where he's always been living but she needs to move because of her family. His wife doesn't like it the way he does but what he really likes performing is to do aerobics and he's been doing it for quite a whilst.
Here is my page zs-imports.com