The Basics of Polarimetric Elements in .NET framework

Make Code 3 of 9 in .NET framework The Basics of Polarimetric Elements
6 The Basics of Polarimetric Elements
Read Code 39 Full ASCII In VS .NET
Using Barcode Control SDK for .NET Control to generate, create, read, scan barcode image in .NET framework applications.
61 Introduction
Creating Code39 In .NET Framework
Using Barcode drawer for VS .NET Control to generate, create Code 3/9 image in Visual Studio .NET applications.
The optical elements used in instruments for the measurement of the state of polarization are normally polarizers and retarders, although other elements, such as polarization rotating or depolarizing devices, may sometimes be employed Most elements operate by a controlled application of birefringence, a property of some materials having alternative refractive indices according to the orientation of the electric vector of the incoming radiation Most of the devices used in astronomical polarimetry have been described by Serkowski (1974) Many of the elements within a polarimeter are constructed from natural or manmade birefringent crystals When a beam of light enters such a crystal, it splits into two and, on rotation of the crystal, the behaviour of one beam (the ordinary ray or o-ray) is unaffected while the other (extraordinary ray or e-ray) alters its direction of travel Common materials are calcite, quartz and magnesium uoride (MgF2 ) Some older systems employed wave plates made of mica, which are now used infrequently When different devices are compared for usefulness, several criteria have to be considered before the best choice can be made These may include: the ef ciency of ful lling the desired purpose, the transmittance, the angular acceptance, the wavelength range of use, the purity in terms of producing detrimental internal scattering within the instrument, ghost images by re ections within the optical interfaces, and interference effects Re ections from materials are also sensitive to polarization and this property is sometimes employed to provide polarimetric elements In other circumstances, re ections can be deleterious to a polarimetric exercise All current stellar measurements are performed using re ector telescopes with metallic coated mirrors, usually vacuum deposited aluminium As a result of imperfections in the coatings, polarizing patches may occur over the mirror surfaces Also the fact that the mirror surfaces are curved implies that the various beam re ections are not exactly normal to their directions of travel; the state of polarization of the collected light must therefore be altered to some degree by the time it arrives at the telescope focus
Decoding Code 39 Full ASCII In Visual Studio .NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
Stellar Polarimetry David Clarke Copyright 2010 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim ISBN: 978-3-527-40895-5
Bar Code Printer In Visual Studio .NET
Using Barcode creator for Visual Studio .NET Control to generate, create barcode image in .NET framework applications.
Stellar P larimetry
Read Barcode In Visual Studio .NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET applications.
In order to be able to describe the various devices used in stellar polarimetry, and to discuss other important effects, recall of some optical principles will be made where necessary For reference, the behaviour of re ection and refraction at optical surfaces, in particular, a fuller description of the Fresnel laws, can be found in Appendix A The discourse there is particularly important for checking out the behaviour of the re ection and transmission coef cients and on handedness changes that may occur within optical elements
Print USS Code 39 In Visual C#.NET
Using Barcode generator for Visual Studio .NET Control to generate, create Code 39 Full ASCII image in .NET applications.
62 Polarizers
Code 3 Of 9 Creator In .NET Framework
Using Barcode generator for ASP.NET Control to generate, create Code 3 of 9 image in ASP.NET applications.
A perfect polarizer is a device which the emergent beam is linearly polarized, regardless of the state of polarization of the incident beam It may operate either in transmission or by re ection The direction of vibration of the emergent linearly polarized light is a property of the polarizer and it relates to the polarizer s principal axis Since most elements operate in transmission, another frequently met term describing a polarizer is its transmission axis For a single-beam polarizer, any component of the incident beam whose direction of vibration is at right angles to the polarizer s axis is rejected A perfect polarizer, as de ned above, is not realizable in practice, as the rejection of the component orthogonal to the polarizer s axis is never complete Thus, if unpolarized light is incident on an actual polarizer, the emergent light will only be partially linearly polarized The degree of polarization of this light is a measure of the ef ciency of the polarizer and is known as its polarizance, p K (see (441)) All devices with polarizances less than unity (i e all real polarizers) should strictly be referred to as partial polarizers Clearly, knowledge of the polarizance is all that is necessary to assess the effect of the device on any type of polarized light, say by the application of the Mueller algebra Many polarizers rely on birefringence and sometimes two refracted beams emerge These are orthogonally linearly polarized, and their directions of vibration are referred to as the polarizer s axes Such a double-beam device may be thought of as two independent perfect polarizers simultaneously present in the same device with their axes at right angles, and each operating as if the other were not there A polarizance and transmittance can be de ned for each of the outcoming beams; the beams may behave differently in these regards Several independent principles have been used in the construction of polarizers, and their polarizances are usually almost independent of wavelength throughout the visible spectrum The list of polarizers discussed below does not pretend to be comprehensive, but most of the principles which have been employed are mentioned Throughout the discussion, it will be assumed that the polarizers, though partial, are pure , i e they do not introduce any differential retardation between the components which they pass
Create Code 3 Of 9 In Visual Basic .NET
Using Barcode creation for .NET framework Control to generate, create Code 3/9 image in VS .NET applications.
Painting Code-39 In Visual Studio .NET
Using Barcode maker for .NET framework Control to generate, create Code 39 Full ASCII image in .NET applications.
Creating DataMatrix In VS .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create ECC200 image in .NET framework applications.
Draw Code 128 Code Set C In Visual Basic .NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Code 128B image in Visual Studio .NET applications.
Decoding Code-128 In .NET
Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
Recognizing Code-39 In VS .NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
Generate Bar Code In Visual Basic .NET
Using Barcode printer for .NET framework Control to generate, create barcode image in Visual Studio .NET applications.