四分束风成像偏振干涉仪信噪比的研究

The signal-to-noise ratio of the quarter beam of wind imaging polarization interferometer

新型静态偏振风成像干涉仪采用四面角锥棱镜与偏振阵列的组合结构,在CCD的四个分区上一次得到四个不同相位的干涉图,可以实现对目标的实时探测,克服了动镜扫描探测模式不能对快速变化目标进行精确探测的缺陷.由于光束被四等分,强度大幅度下降,微弱的气辉信号能否被探测到成为研究的关键.本文从目标气辉光谱的特性出发,分析了静态偏振风成像干涉仪系统的光学传输特性和响应特性,CCD的噪声水平及系统信噪比,得出弱信号夜气辉在常规的探测模式下探测不到的结论.采用延长光积分时间,像素合并技术和选用探测灵敏度高的电子倍增CCD等措施,均可以有效改善信噪比,并计算出几种措施综合运用后系统的信噪比和响应度.考虑到成本和目标的快速变化,仅采用像素合并技术,模拟了信噪比和数字化输出随辐射强度的变化曲线,结果表明可实现对夜气辉等微弱信号的探测.

The novel static polarization wind imaging interferometer adopts four-face pyramid prism and polarization array to obtain four different phase interferograms on four sections of CCD once. It can detect the target in real time and overcome the moving mirror scan detection mode defect that leads to be unable to accurately detect the rapily changing target. For the signal beam that is split into four equal parts, their intensities drop significantly, so whether the signal can be detected is a key problem. In this paper, the target spectral characteristic of the airglow is taken as the starting point of analysis, then the optical transmission properties and response of the NSPWII system and CCD signal-to-noise ratio are analyzed. Finally the conclusion is obtained that weak signal （such as night airglow） cannot be detected in the conventional detecting mode. Some improving measure is presented which extends light integration time, adopts pixel merger technology and select high sensitivity CCD （as electron multiplication CCD）, they all can improve the signal-to-noise ratio effectively. After integrated using the these measures, the signal-to-noise ratio and responsiveness of NSPWII system are calculated. In view of the rapid changes of cost and objectives, only pixel binning is adopted, and the simulated curve of signal-to-noise ratio versus digital output is obtained. The result shows that the weak signal as night airglow can be detected.