Intergrated System Design Of Spectropolarimeter Based On PSIM

Polarization spectral intensity modulation(PSIM)is a new technique which can be used to build a spectropolarimeter based on a grating spectrometer to measure synchronously the four spectral resolved Stoke vectors of target under testing.The principle of the PSIM system is that a modulator composed of two retarders and one polarizer is added in the incident light path of a spectrometer,when the light to be measured passes through the modulator,its four spectral resolved Stokes vector are modulated by the carriers of different frequencies formed by the modulator,and the intensity spectrum of the light from the modulator is the linear superposition of the modulated Stokes vector element spectrum to be measured.So,the detectors in the spectrometer needs only one exposure to record the intensity spectrum data of the measured light after passing through the modulator,and then the four spectral resolved Stokes vector of the measured light can be restored through the signal processing process of Fourier inversion,filtering,Fourier transform and demodulation.Compared with the traditional polarization spectrum measurement instrument,the spectropolarimeter based on PSIM has the advantages of high time resolution,simple system structure,no rotating parts,and high reliability,and is especially suitable for the measurement of polarization spectrum of moving objects.It has obvious application advantages in the fields of earth environment monitoring,agricultural remote sensing and camouflage identification.However,the research on this technology is still in the laboratory stage in China,and no engineering application has been reported.Supported by the national natural science foundation of China,this paper focuses on the engineering application of this technology and carries out the following research work:(1)the principle of the PSIM spectropolarimeter to achieve the polarization spectrum information modulating and demodulating of the light to be measured is analyzed systematically,and the mathematical derivation of the principle is given;(2)based on clarifying the principle of PSIM spectropolarimeter,the matching design method of key device parameters of PSIM spectropolarimeter and the algorithm of measurement data processing are established;(3)combined with the design requirements of PSIM spectropolarimeter and the matching design method of key device parameters,the integrated modulator was designed and adjusted,and the integrated hardware design of PSIM spectropolarimeter was realized;(4)integrated design and debugging of data processing software of PSIM spectropolarimeter was completed by using IDL programming language,the correctness of integrated design process of software and hardware of PSIM spectropolarimeter was verified through measurement experiments and experimental data processing of typical light source to be measured;and(5)the polarization calibration experiment of PSIM spectropolarimeter was carried,and the measurement precision of the polarization degree of the whole spectrum is better than 0.5%after calibration.The research of this paper verifies that the integrated PSIM spectropolarimeter can synchronously acquire the four spectral resolved Stokes vector of the light to be measured,and has a high measurement accuracy of degree of polarization.It lays a foundation for the engineering application of PSIM technology.