偏振型侧面遮拦日球成像仪杂散光抑制的前期研究

The polarized side-baffled heliospheric imager is the future trend of the technique of the next generation heliospheric observation. The advantage is that it can get 3-D image of the structure of solar wind in solar-terrestrial space by one position observation. Then it can improve the accuracy of space weather forecast and effectively estimate the geoeffectiveness. This project mainly focus on the technique of polarization and stray light suppression. The research on the stray light suppression of heliospheric imager is based on STEREO-HI, and some improvement are made. The purpose of this research is in order to reduce the stray light in the inner field of view of HI, add polarization, and to move forward, increase the aperture to improve the time resolution. It will be beneficial to the polarization observations of the heliosphere. This project is divided into four parts. Firstly, design the front baffle assembly which are the key components of the stray light suppression. Secondly, the influence of the defocus of the front baffle is optimized to reduce the diffraction dispersion. Thirdly, the design of the vignetting is presented. Vignetting is used to suppress the stray light in the inner field, improve the ratio of signal to noise and reduce the dynamic range of the camera. In the end, the polarization technique is added in the heliospheric imager. The method of polarization measurement and stray light brought by the polarization is researched. The implementation of this project is beneficial to our grasp on the technology of side-baffled heliospheric imager.

偏振型侧面遮拦式日球成像仪为下一代日球成像的发展方向，其优势为通过单个位置观测即可获得日地空间太阳风动态结构的三维图像，从而提高空间天气预报的准确性并有效估计其对地影响。本项目主要研究日球成像仪的偏振及杂散光抑制技术，在目前STEREO-HI日球成像仪杂散光抑制基础上进行改进，旨在降低HI内视场的杂散光，增加偏振观测，进一步增大口径，提高时间分辨率，为日球层的偏振观测提供便利。研究内容包含四个方面，首先，对日球成像仪的关键元件——前挡板组进行设计、加工并检测。其次，对成像系统造成的前挡板离焦的影响进行优化，减小由此造成的衍射弥散现象。第三，对渐晕进行设计，通过渐晕抑制内视场的杂散光，进而提高内视场的信噪比，并降低对相机动态范围的要求。最后，对日球成像仪的偏振技术进行研究，包括偏振测量方法及偏振带来的杂散光的影响。本项目的有效实施将为偏振型侧面遮拦日球成像仪的发展提供技术储备。

日球成像仪是对内日球层进行成像观测的最主要手段。偏振型侧面遮拦式日球成像仪为下一代日球成像的发展方向，其优势为通过单个位置观测即可获得日地空间太阳风动态结构的三维图像，从而提高空间天气预报的准确性并有效估计其对地影响。本项目按计划完成了偏振型侧面遮拦日球成像仪杂散光抑制的前期研究，包括：（1）完成前挡板的设计，采用等衍射法进行设计及模拟计算，并完成结构加工及实验装置搭建及实验室衍射检测；（2）完成了日球成像仪衍射强度和前挡板离焦的关系计算。获得了前挡板离焦的影响范围与最后一片挡板和物镜之间的距离之间的定量关系；（3）完成了渐晕的设计及分析，并实验发现了日球成像仪中渐晕带来的分辨率反转现象。为以后的大视场日冕仪及日球成像仪中渐晕设计提供依据；（4）完成了日球成像仪的白光偏振测量技术，获得两次测量实现IQU测量，且具有较高调制效率的偏振测量结构。