基于PSIM原理的太阳光谱偏振仪关键技术研究

It is a common problem need to be solved urgently that the time resolution of the existing solar spectr-polarimeters is not enough. All Stokes vectors spectrum from incident light can be modulated and superimposed to power spectrum in its output by Polarization Spectral Intensity Modulation (PSIM) module, made up of two piece of retarders and one polarizer, the raw data(the power spectrum) needed to analyze the stokes vectors spectrum can be recorded on the CCD in the spectrometer, and the CCD of specrometer exposures only one time. There is no any rotating part in the new solar spectro-polarimeter, and measure only one time. So, the time resolution and polarization measurement precision of the new solar spectro-polarimeter can be better theoretically that be made by adding the PSIM module to spectrometer. Based on the earlier research of PSIM, combined with the requirements of solar spectro-polarization observation, this project aims at:.●determine parameters of the key parts , analyze source of the main errors by theoretical analysis and numerical simulation;.●develop principled machine , and carry out simulative measurement experiment; and.●improve the procedure of data procedure based on the FFT, filtering and demodulating for the data of intensity spectrum , and develop a new demodulation algorithm which can self-calibrate ,and can analysis the solar spectro-polarization information accurately. The achievements of the project will promote the advanced specro-polarization information acquisition method applied in the field of astronomy, such as solar physics, in our country.

时间分辨率不高是现有光谱型太阳偏振仪需要解决的共性问题。由两块高阶延迟器和一块检偏器构成的偏振光谱强度调制（PSIM）模块，可同步调制入射光四个Stokes矢量元素谱并叠加成强度谱输出，而光谱仪中的CCD只需一次曝光即可记录该强度谱，得到解析入射光四个Stokes矢量元素谱所需原始数据。系统中无转动件，不需要分时测量。因此，在光谱仪入射光路中加装PSIM模块，理论上可构建具有更高时间分辨率和偏振测量精度的太阳光谱偏振仪。项目组拟在PSIM原理前期研究基础上，结合太阳偏振观测需求，通过理论分析、数值模拟确定系统关键件匹配设计参数，分析系统主要误差源；研制太阳光谱偏振仪原理样机，开展模拟观测实验；改进基于傅里叶变换、滤波和解调制处理的强度谱数据分析流程，发展一套含自校准功能、可精确解调太阳光谱偏振信息的数据处理算法。项目研究有利于推动先进光谱偏振信息获取技术在我国太阳物理等天文观测领域的应用。

太阳磁场定量反演依赖于高时间分辨率、高精度的偏振测量。为此，项目组提出了利用偏振光谱强度调制（PSIM）原理实现太阳大气辐射偏振光谱信息同步获取新方法，并对PSIM偏振光谱仪相关的关键技术进行了深入研究。项目组主要开展了以下几方面研究工作：（1）对PSIM偏振光谱仪系统数据处理算法进行了优化；（2）完成了PSIM偏振光谱仪集成实验样机研制，建立了调制器参数与光栅光谱仪参数间的匹配设计流程；（3）确立了PSIM偏振光谱仪偏振定标方法并对实验样机进行了偏振定标测量实验；（4）完成了一项太阳日面超长暗通道的观测研究工作，加深了对太阳磁场测量重要性及测量装置设计要求的理解。通过本项目研究，项目组全面掌握了PSIM原理实现偏振光谱信息获取过程所涉及的关键技术，在测量数据处理算法优化、系统硬件参数的匹配设计及偏振定标方法等方面积累了稳定、可靠且可重复的研究成果。项目研究结果表明：PSIM偏振光谱仪具有一次曝光即可同步解析待测光四个Stokes矢量谱的能力；定标校正后，PSIM偏振光谱仪实验样机的偏振测量精度在580nm-640nm谱段范围内约为10-4。项目研究成果将为PSIM技术在偏振遥感及天文观测领域的推广应用奠定坚实基础。