Analysis And Optimization Of Polarization Effect Of Telescope Group Of Channel Polarization Spectrometer

In recent years,polarization spectral imaging technology has attracted extensive attention of researchers from all over the world due to its advantages of simultaneously obtaining the light intensity information,spectral characteristics and polarization information of the target object.By analyzing the above information,it is possible to obtain physical properties such as the refractive index,dielectric constant,and surface roughness of the target object that cannot be obtained by traditional spectral imaging technology,and it is not possible to analyze the target object more comprehensively.Polarization Spectral Intensity Modulation(PSIM)is a technology based on the theory of spectral intensity modulation and has a leading position in the field of polarization spectral imaging.Compared with other polarization spectroscopy imaging techniques,this technology has the advantages of good reliability,no moving parts,and easy combination with different types of spectrometers.The channel-type polarization spectral imaging technology based on this technology has broad application prospects.At present,the research work on the channel-type polarization spectrometer is in its infancy,and more work is focused on the principle exploration and experimental verification.At the same time,since various fields put forward higher requirements on the imaging quality of instruments and the accuracy of polarization measurement,it is necessary to study the polarization effect of telescope groups and the influence of the polarization detection accuracy of instruments in more depth.In this context,this paper analyzes the following aspects:(1)First,the basic theory of polarization effect is introduced,the Mueller matrix of common polarized optical elements and the representation method of polarization effect at optical interface are described,and the theory of optical thin films is introduced in detail.The modulation process of the channel polarized spectrometer,the Mueller matrix transfer method and the Fourier transform restoration method of the Stokes spectrum are studied.Through the introduction and research of the above aspects,the corresponding theoretical foundation is laid for this paper,and the theoretical support is provided for the subsequent specific analysis and optimization work.(2)Secondly,in view of the design trend of large field of view and wide spectral band of the instrument,the polarization effect of the mirror group is gradually increasing.Through the method of Mueller matrix transfer and coordinate system transformation,the mirror group Mueller matrix with second-order small quantity that retains the polarization effect is established,and its applicable conditions are analyzed.According to the principle of polarization spectral intensity modulation,the models of the polarization detection accuracy of the instrument for the front telescope group and the rear telescope group are respectively established.The analytical expression of the Stokes parameter demodulation results of the target light by the front and rear telescope groups respectively is obtained,and the influence of the polarization effect of the mirror group on the polarization effect of the instrument is theoretically analyzed.The conclusion is that both the bidirectional attenuation value and the phase delay value of the front telescope group will affect the recovery of the Stokes parameters of the target light,only the attenuation value of the rear mirror group will affect the restoration of the Stokes parameter of the target light.The above conclusions are simulated and analyzed,and the influence of the second-order small amount of the polarization effect on the polarization effect of the instrument is verified.Based on this model,the influence of the polarization effect of the mirror group on the polarization effect of the instrument is quantitatively analyzed.In the follow-up,an example analysis is carried out for the instruments used in this paper.The analysis results show that the secondorder small amount of the polarization effect of the mirror group will affect the polarization accuracy of the instrument,so it is necessary to consider the second-order small amount of the polarization effect of the mirror group to achieve the purpose of obtaining accurate polarization detection accuracy.Finally,the polarization detection accuracy of the instrument is analyzed,and it is obtained that when the light wavelength of the edge field of view is 425nm,the polarization detection accuracy of the instrument is only 94%,which seriously affects the normal use of the instrument and needs to be optimized.(3)Finally,according to the basic theory of polarization effect and the influence model of the polarization effect of the telescope group on the polarization measurement accuracy,a method for optimizing the polarization effect of the telescope group is proposed in view of the development trend of the polarization spectrometer in terms of wide band and large field of view.Under the premise of ensuring the optical performance of the instrument,this method further reduces the polarization effect of the telescope group by optimizing the optical structure of the mirror group and designing an optical film with low polarization effect,and adopting a combined film system.After optimization,the polarization effect of the optical system is significantly reduced,thereby improving the polarization detection accuracy of the instrument.The optimized structure is simulated and analyzed,and the analysis results show that the optimized polarization detection accuracy of the instrument is improved at various field angles and light wavelengths.At the wavelength of 425nm,the polarization detection accuracy of the instrument is 99.1%,which is 5.1%higher than that of the structure before optimization.This method provides an effective way to improve the polarization detection accuracy of the instrument in the design stage.