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Topic: Optical path length

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Optical path length - Wikipedia, the free encyclopedia Note: Optical path length is proportional to the phase shift that a lightwave undergoes along a path. Fermat's principle states that the path light takes between two points is the path that has the minimum optical path length. In a medium of varying refractive index, the integral of n δs, where δs is an element of length along the path, and n is the local refractive index. en.wikipedia.org /wiki/Optical_path_length   (140 words)

World Intellectual Property Organization The optical measurement surface is typically scanned by moving optics in the reference leg of the interferometer to vary the optical path length of the reference light at the detector. The optical measurement surface refers to a theoretical test surface in the path of test light in the interferometer that would reflect the test light to produce an optical path length difference (OPD) between the test and reference light that is equal to a constant across a detector. The difference in phase of the interference signal as a function of wavelength or reference surface position relates directly to the total optical path difference in the interferometer. www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=03/106921.031224&ELEMENT_SET=DECL   (6605 words)

Clinical Applications of the Shack-Hartmann Aberrometer Specification of optical aberrations as a difference in optical path length for an axial ray compared to a marginal ray traveling from the entrance pupil to a point of regard P in the image. Furthermore, our measurements of relative change in optical path length cannot distinguish between thinning of the tears in one location and thickening of the tears at another. Optical quality of this eye is poor as indicated by the distortion of the matrix of dots in the central region and by the poor quality of individual dots in the SH data image (A). research.opt.indiana.edu /Library/SHclinical/SHclinical.html   (6201 words)

World Intellectual Property Organization Different path lengths (s) for light interacting with the sample may be probed by the interferometric sensor through adjustment of the physical length, optical length, or optical delay of the reference arm of the interferometer. The path length or optical delay of the reference light may be changed in a known manner in order to provide a known reference to the distance inside of the material sample or tissue from which backscattered light is being received. Signals from a detector proportional to the path length resolved backscattering intensities may be used as input for a processor for calculating an absorbance, calculating the scattering, or calculating the absorbance and scattering coefficients of the sample. www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=05/17495.050224&ELEMENT_SET=DECL   (11417 words)

Olympus Microscopy Resource Center: Specialized Microscopy Techniques - Polarized Light Microscopy - Introduction to Compensators and Retardation Plates Optical anisotropy is studied in the polarized light microscope with accessory plates that are divided into two primary categories: retardation plates that have a fixed optical path difference and compensators, which have variable optical path lengths. The angle of rotation required by the compensator to cancel specimen birefringence (producing extinction) is used to calculate the relative retardation or optical path length of the specimen. Retardation plates are composed of optically anisotropic quartz, mica, and gypsum minerals ground to a precise thickness and mounted between two optical windows having flat (plane) faces, which are designed to introduce a fixed amount of retardation between the orthogonal wavefronts passing through the crystal. www.olympusmicro.com /primer/techniques/polarized/compensators.html   (2127 words)

Nikon MicroscopyU: Phase Contrast Microscopy - Introduction In optical terminology, phase plates that alter the phase of surround light relative to diffracted light by 90 degrees (either positive or negative) are termed quarter wavelength plates because of their effect on the optical path difference. For arguments in phase contrast microscopy, the role of the specimen in altering the optical path length (in effect, the relative phase shift) of waves passing through is of paramount importance. In terms of optical path variations between the specimen and its surrounding medium, the portion of the incident light wavefront that traverses the specimen (D-wave), but does not pass through the surrounding medium (S-wave), is slightly retarded. www.microscopyu.com /articles/phasecontrast/phasemicroscopy.html   (7881 words)

P216x13michelsonInterfer.doc The optical path length is the effective path determined by both the physical path length and the wavelength of the light. This is obviously the parameter of importance in describing the "path length" of A or B, since changing either the beam's wavelength, or the physical length of one of the paths, will change the relative phase between the two beams. First note that the interference depends on the relative number of oscillations or cycles between paths A and B. Hence it not only depends on the physical path length but also the wavelength of the wave or light in the respective path. www.phys-astro.sonoma.edu /people/faculty/delcorral/P216/P216x13michelsonInterfer.doc   (1598 words)

Design Principles and Limitations of Wavefront-guided Contact Lenses Using this language of optical path lengths, the problem of refractive error is that the optical path from a distant point source to the retina is not the same length for every ray entering the eye. This difference in optical path lengths between the central ray and any other ray from a distant object varies across the pupil and is greatest at the pupil margin. Each map shows the optical path length errors (relative to the pupil center) across a 6mm diameter pupil, displayed as a contour map (0.1 µm intervals). research.opt.indiana.edu /library/waveGuidedLens/waveGuidedLens.html   (2892 words)

Optical path length -- Facts, Info, and Encyclopedia article Note: Optical path length is proportional to the (Click link for more info and facts about phase shift) phase shift that a lightwave undergoes along a path. In a medium of varying refractive index, the integral of n δs, where δs is an element of length along the (An established line of travel or access) path, and n is the local refractive index. In a (A means or instrumentality for storing or communicating information) medium of constant (The ratio of the velocity of light in a vacuum to that in a medium) refractive index, n, the product of the geometric distance and the refractive index. www.absoluteastronomy.com /encyclopedia/o/op/optical_path_length.htm   (208 words)

CE-Zell In contrast to on-column detection, with its very short path length - determined by the I.D. of the fused silica capillary - the bending of a small part of the capillary column into a "Z" configuration (longitudinal alignment) generates a column with a built-in flow cell with an optical path length of 3 millimeters. This significant increase in path length in combination with an optimized angle of the UV light entering the flow cell boosts the sensitivity by a factor of approximately 10-20. The CE-ZELL capillary column has a total length of 100 centimeters, with 75 centimeters to the detector. www.lcpackings.com /products/LCMSTools/CEZell01.html   (286 words)

Phase-Shifted Laser Feedback Interferometry Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. Optical path length through a silicone oil drop on a coated silicon substrate. www.lerc.nasa.gov /WWW/RT1998/6000/6712ovryn.html   (639 words)

Abstract Title Page Coherence length is a measure of the maximum optical path difference that can exist between two waves that will still interfere with each other. The fact that the mirror is optically flat and perpendicular to the optical axis means that any ray entering the reference arm will exit from the reference arm at the same position and with the same angle. Optical coherence tomography is a method used to reconstruct the optical properties of semitransparent objects. www.liteachers.org /wankel/optics.html   (2247 words)

Early optical interferometry Instead, the appropriate difference in optical path length from the detectors to each of the slits could be produced by careful adjustment of the mirror positions. The optical path length from Q to point P on the screen is the same for rays travelling through either slit. With the optical arrangement of Figure 2 a large objective lens or mirror is required for measurements with large slit separations and much of the light that passes through the slits in the aperture mask is wasted. www.geocities.com /CapeCanaveral/2309/page2.html   (1231 words)

EPA - TTN NAAQS - Ozone Implementation - Technical Resources - Ambient Air Quality Surveillance Siting Criteria for Open Path Analyzers Closely associated with the term ``monitoring path'' are new definitions for ``monitoring path length,'' to describe the scalar length of the monitoring path, and ``optical measurement path length,'' to describe the actual length of the optical beam of an open path instrument. The length of the optical beam may be two or more times the length of the monitoring path when one or more mirrors are used to cause the optical beam to pass through the monitoring path more than once. The path-integrated pollutant concentration measured by the analyzer is divided by the optical measurement path length to determine the path- averaged concentration. www.epa.gov /ttn/naaqs/ozone/ozonetech/fr951006.htm   (12421 words)

Thin Film Applet optical path length = (index of refraction)*(physical path length) If light is in a material of higher index, and reflects from a boundary with a material of lower index, phase change of 0, "Hi off lo change of zero", and conversely, "Lo off hi, change of pi" and we can focus on the phase angle or call it a change of 1/2 wavelength. What is the path difference in this case? www.rit.edu /~agysps/courses/312.023team/cl_wkshts/th_film_applet.htm   (575 words)

AO-Baker Interference Microscope Page Two While the common polarised light microscope is capable of measuring the OPD due to the optical activity of a birefringent specimen, it is not usually considered to be an interference microscope since it cannot measure the OPD between two spatially separated paths through an optically isotropic specimen. Measuring the optical path enables either one of these quantities to be determined if the other is known. In the interferometric microscope, small differences between the object and reference optical paths can be measured often with exquisite accuracy and some modern, computer- assisted, reflected-light instruments routinely measure OPDs with an error of less than 1nm. members.aol.com /hbronstein/index/aobaker/aobakerb.htm   (523 words)

Untitled Since the optical path length is related to the time, we can restate Fermat's principle again as a light ray in going from point A to point B must traverse an optical path length that is stationary with respect to variations of that path. When a light ray traverses an optical system consisting of several homogeneous media in sequence, the optical path is a sequence of straight-line segments. If the path is resolved into components, it is clear that the direction of the incident ray is altered only by reflection along the z direction, and then in such a way that its z component is simply reversed. physics.tamuk.edu /~suson/html/4323/geometry.html   (1800 words)

ENME 489F This experiment is implemented by adjusting the optical path length difference of the interferometer using the adjusting screw shown in Figure 1. where the As are scalar amplitudes, l is the wavelength of the source and Dz is the change in the optical path of the interferometer (don’t forget that the refractive index of air is 1). is the coherence length of the source, and BW is the bandwidth of the intensity field at one half of its original intensity (as shown in Figure 2). www.enme.umd.edu /class/ENME489F_Laboratory1.htm   (548 words)

Chirped-Pulse Amplification Lasers The index of refraction determines the phase velocity of light and the optical path length experienced -- the effective phase-distance that light travels in propagating through matter -- and so intense light begins to suffer phase delays, relative to weaker light. Nonlinear optical damage: Aside from the subtler nonlinear effects caused by propagation of high-intensity light, the maximum power or fluence of a laser system may be limited by the small absorption of laser energy by components of the laser system. In travelling between two such gratings, different frequencies take different paths, and the total distances of the different paths through this diffraction-grating system are not the same. www.physics.utoronto.ca /~marj/CPAgen.html   (852 words)

Modern optical interferometry Changes in the optical path length through the atmosphere due to atmospheric turbulence are significant on time scales of five to ten milliseconds, limiting integration times (analogous to camera shutter speed) to millisecond time scales. The geometric arrangement of the COAST array allows the optical path differences on the longest baselines at COAST to be calculated from measurements made on short baselines (baseline bootstrapping). A fringe tracking capability is currently being installed at COAST allowing optical path differences to be actively corrected during observations. www.geocities.com /CapeCanaveral/2309/page4.html   (1585 words)

Experiment 4: Interferometers The phase curvatures (wavefronts) of the two interfering waves may depend on the optical path length of the interferometer arms. This is accomplished by using a vacuum cell in one arm to change the optical path length. The phase difference between these waves depends on the optical path length difference between the two arms of the interferometer. www.ee.bilkent.edu.tr /~ee428/manual/html/node8.html   (1010 words)

Pathlength spectroscopy We use optical path-length spectroscopy to obtain experimentally the path-length distribution of optical waves scattered from dynamic colloids, which are multiply scattering but not in the diffusion limit. By using a backscattering technique based on low-coherence interferometry, we are able to determine the optical path-length distribution for light reflected from a random medium and to infer the value of the transport mean free path. Systematic measurements show a nontrivial behavior of the extrapolation length ratio on the scattering anisotropy of individual particles. random.creol.ucf.edu /home/research/pathlength_spectroscopy.html   (353 words)

P216RC.InterferometerP2.doc Because the physical path length is constant in this part of the experiment, the optical path length change must be due to the change of the index of refraction of the medium in the gas cell. Here we will be modifying the optical path length of Path B by changing the index of refraction over a portion of that path. Here the idea is to evacuate the gas cell and record the number of fringe shifts (change in optical path length) versus pressure. www.phys-astro.sonoma.edu /people/faculty/chavez/P216/P216RC.InterferometerP2.doc   (970 words)

224 Physics Lab: Interference and Diffraction of Microwaves For constructive interference to occur, the optical path lengths for the reflected wave and the un-reflected wave must be some multiple of the wavelength, The optical path length of the un-reflected wave is Lloyd's Mirror with two optical path lengths displayed for the reflected wave. phoenix.phys.clemson.edu /labs/224/diffraction   (680 words)

optical path length is: the product of the actual (geometrical) length of a light path in a transparent material and the refractive index of that material. www.rdg.ac.uk /physicsnet/units/flap/glossary/OO/OPTPATHL.HTM   (23 words)

\bf University of Leicester \\ Department of Physics and Astronomy \\ Lecture Notes \\ \doctitle The optical path length along the actual path of a ray of light is the same as that for closely adjacent paths. In Fermat's Principle the optical path length can be calculated in either direction, A to B or B to A, the result is the same. A light ray takes a path which is stationary with respect to the optical path length. www.star.le.ac.uk /~rw/courses/lect220.html   (5990 words)

Newport Scientific - Optical Absorption Cells Contact SUPERPRESSURE with the working pressure and temperature, type of liquid or gas to be used, and optical path length desired. Optical Path Length (Between Inside Faces of Clear Windows): One Centimeter. Cells with path length other than those listed below can be supplied. www.newport-scientific.com /OpticalAbsorpCells.htm   (234 words)

APOL Optics Study The optical path length between two points in some media or set of media is the distance in a vacuum that would produce the same phase change. Mathematically, the optical path length is index of refraction times the propagation distance. For a set of dielectric layers perpendicular to the propagation direction, the total optical path length is www.ece.umr.edu /~optics/waves.htm   (300 words)

(WO 2005/017495) INTERFEROMETRIC SENSOR FOR CHARACTERIZING MATERIALS The light backscattered from the sample is combined with reference arm light at the same optical path length for each light collector. (57) An integrated optical sensor, using low coherence interferometry, is capable of determining analyte concentration in a material sample based on absorption, scattering and polarization. The intensity of interference may be correlated with the concentration of an analyte in the material, for example the glucose concentration in a turbid medium like skin. wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=05/17495.050224&...   (236 words)

Optical Fiber Stretcher Module    Optical delay, phase and path-length control in photonics instruments Long path length changes are achieved with less total fiber. Multiple PFM modules can be configured so that path length changes add together. www.photonics.com /fiber/XQ/ASP/url.readprod/prodid.520/QX/readprod.htm   (426 words)

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