基于全光调制的静态高光谱全偏振Stokes成像技术研究

Spectral imaging and polarimetric imaging are both advanced optical detection techniques. Since their wide potential in military and civil communities, these techniques have rapidly developed within the past two decades and become well-recognized tools in remote sensing. In recent years, these two techniques appear new trend to merge into the imaging spectropolarimetry, and make the optical remote sensing tend to multi-dimensional and multi-information fusion. However, in conventional imaging spectropolarimeters, rotating polarization elements, electrically controllable components, and microretarder or micropolarizer arrays are typically required. These apparatuses generally suffer from vibration, electrical noise, heat generation, and alignment difficulty. Consequently, the incorporation of mechanical components typically increases the complexity and decreases the reliability of the measurement system. To overcome these drawbacks, we proposed a novel method based on all optical modulation for real time measurement of the spectrum, polarization and imaging of scenes. With specially aligned static birefringent retarders, different phase factors are modulated onto the Stokes vector of incidence light. After passing through a static birefringent interferometer, the spectrally dependent Stokes parameters are distributed into several separated interferogram channels. With corresponding Fourier-transform demodulation, all of the wavelength-dependent polarization, spectral and 1-D spatial imaging of objects can be completely obtained with a single snapshot. Key points of this project are focused on the mechanism of the all optical phase modulation and interferogram's separating, light propagation in birefringent crystal elements, the relation between the elements' parameters and interferogram's properties, the spectral and polarimetric response of the system and errors reduction method. This research gives a new way for spectropolarimetric imaging measurement, and provides theoretical and pratical supports for the development of new space remote sensors.

光谱偏振成像技术是成像光谱和偏振成像技术的有机融合，是当前空间光学遥感技术发展的最前沿。本项目针对目前光谱偏振成像三合一探测受基础原理限制，须有运动/电控调制部件、结构复杂、抗振能力差、环境适应性差、不能实时探测等问题，发展我们提出并受到国际同行认可的静态光谱偏振图像三位一体探测方案，通过特定方式排列的静态双折射晶体位相延迟器将不同位相因子分别同时调制到入射光4个Stokes参量上，再利用双折射干涉的傅立叶变换性质直接将其在光程差域上分为若干独立通道，最后对相应通道进行解调便可实现干涉光谱、全偏振信息实时探测；构建其工作机理的系统理论体系，深入研究位相因子全光调制与干涉分离机理，双折射晶体内部光传输规律、结构性能参数对干涉成像质量的影响，系统偏振光谱响应及探测精度控制，扩展光谱探测范围，提高光谱分辨率及探测精度，为光谱偏振成像探测开拓新的途径，为新型遥感器开发提供基础理论与技术支持。

本项目对基于全光调制的高光谱全偏振成像技术基本原理、实现结构、系统误差等进行了研究。主要工作和结果如下：（1）从基本双折射晶体元件构型出发，建立了全光调制模块及干涉分光模块的数学物理模型。通过模型首次揭示了全光调制实现光谱、偏振、图像信息同时获取的关键物理机制——各Stokes参量不同位相因子的分别同时调制。探明了Stokes参量干涉通道各参数的控制因素；（2）通过光线追迹法研究了双折射晶体棱镜内部光传输规律，给出了Savart偏光器的光程差完整表达式，发现其表达式中含有的入射角相关非线性二次项是影响系统干涉条纹质量的决定因素，首次提出了正、负双折射晶体补偿结构消除光程差非线性二次项，大大改善了干涉条纹质量，同时也扩展了系统工作视场角范围；（3）对基于全光调制的高光谱全偏振成像技术实现结构进行了分析，发现位相延迟器R1、R2、起偏器P、检偏器A间的光轴、偏振透过方向方位角误差是影响系统偏振、光谱测量精度的关键，提出了误差修正方法。