高光谱全偏振成像快捷测量技术研究

Highly Efficient Measurement Technology Based on Hyper-Spectropolarimetric Imaging

为了实现声光可调滤波器(AOTF)和液晶可调相位延迟器(LCVR)相结合的新型高光谱偏振成像系统全Stokes参量的快捷准确获取,提出了一种新的测量方法。该方法采用一个驱动信号源同时控制系统中两个LCVR,当LCVR在不同波长下进行相位调制时,依次取4个固定的驱动电压,求得不同波长下LCVR1和LCVR2的4组相位延迟,通过相应的数学计算即可快速精确求得目标光全部Stokes参量。波长为632nm时,以偏振方向分别为0°、90°、45°的偏振片和1/4波片为目标物,毛玻璃为背景,通过系统成像后获取了全部Stokes参量的图像。结果表明,该测量方法不仅可以快速准确地获取目标物全部Stokes参量,而且系统成像质量良好。对532nm波长下的真假树叶进行高光谱偏振成像,进一步验证了该测量方法的快捷准确和系统的可靠性。理论分析了影响Stokes参量测量精度的因素,为提高系统测量精度提供了理论基础。

In order to acquire the full Stokes parameters in the new hyper-spectropolarimetric imaging system quickly and accurately, which is filtered by the acousto-optic tunable filter （AOTF） and modulated by the liquid crystal variable retarder （LCVR）, we propose a new measurement method that two LCVRs are controlled by one driving signal source, and we take four fixed driving voltages in turn when the LCVR phase modulation is carried out under different wavelengths. The full Stokes parameters about incident light via the corresponding mathematical calculation are obtained. In order to verify the accuracy of this method, we take three polaroids with the polarization directions of 0°, 90°, and 45° respectively and a quarter-wave plate as the target, with a sheet of frosted glass as the background. Images of all the Stokes parameters are obtained by the imaging system. The results show that the proposed method can obtain all Stokes parameters with high imaging quality. In addition, we further verify the feasibility of the system and the accuracy of the method with the aid of hyper-spectropolarimetric imaging of true leaves and false leaves with different colors. The factors that influence the measurement accuracy of Stokes parameters are analyzed theoretically, providing a theoretical basis for further improving measurement accuracy.