Monochromatic Retreat Polarizer And Liquid Crystal Depolarization

The depolarizer is relative to the polarizer and is applied to astronomy at the first time. Because most detectors have sensitivity to polarization, so it is necessary to add a depolarizer in the front of the detector in order to erase the dependence of sensitivity of detector on incident polarization, so we can increase the accuracy .Now the depolarizers are used extensively in many photoelectric measuring instrument, such as astronomical instrument, laser processing, laser medicine, optical fibre communication. So the research of depolarizer is of actual significance.Quite depolarization is more difficult than polarization. Let polarized light pass through the scattering medium or birefringent material of gradient phasic difference are the two basic methods of depolarization. Because the transmissivity of light intensity is low when polarized light pass through the scattering depolarizer, so the depolarizers are usually made with birefringent material (such as calcite, quartz and optical fibre) in fact. When linearly polarized light beam pass through the birefringent material of gradient phasic difference, the light beam will interfere each other in a small area and the ordered state will change, so the degree of polarization of emergent light drop, this is the fundamental principle to depolarize.According to the sorts of polarized light that will be depolarized,depolarizer can be divided into three types: monochromatic depolarizer, polychromatic depolarizer and circular depolarizer.This paper includes two parts, in the first part the momochromatic depolarizer was analyzed in detail, in the other part the depolarization effect of nematic liquid crystal was studied chiefly; we also discussed the possibility of using material of liquid crystal to make depolarizer.This thesis includes six chapters. The history of the depolarizer and present studying state was introduced in the first chapter.In chapter two, the basic description methods of polarized light and device: Stoke vector and Mueller matrix were introduced .The stokes vector of different polarized light and the Mueller matrix of different polarization device are given. Next, the two definitions of degree of polarization are also given; these are the foundation of experiment and analysis of theory. The coherent matrix was also introduced at last.The basic principle of depolarizer and some common depolarizer are introduced in the third chapter. Firstly the principle of the common polychromatic depolarizer (such as a flat uniaxial birefringent crystal ) and monochromatic depolarizer are analyzed in brief, then we generalized the two methods ofstudying the depolarizer--the one is Jones matrix and coherent matrix, theother is Mueller matrix--as the example of the Loyt fibre depolarizer.The optical wedge depolarizer and binary quartz depolarizer are discussed in detail in the fourth chapter. This is the main part of this thesis. The two forms of a wedge monochromatic depolarizer: calcite wedge depolarizer and quartz rotatory depolarizer are analyzed. Some conclusions were got from the calcite wedge depolarizer l)when the included angle between the direction of incident linearly polarized light with the optic axis of wedge depolarizer is 45?,the result of depolarization is the best ; 2)short wavelength is easier to be depolarized than long wavelength; 3)in the permissible range of emergent light deviation, the more structure angle B is big, the more the radius of pupil is big ,the effect of depolarization is better.We also get some conclusions from the wedge quartz rotatory depolarizer : 1) the depolarization of emergent light is independent of the direction of incident polarized light; 2) short wavelength is easier to be depolarized than long wavelength. When the radius of pupil is small, increasing the radius of pupil can improve the depolarization of visible light and infrared light just little, but can well depolarized ultraviolet light, 3)the effect of depolarization is better when structure angle increase, 4)it can not depolarize the circula...