基于渥拉斯顿棱镜的单路实时偏振成像系统设计

针对非实时成像中动态场景偏振探测产生的虚假偏振信息问题,充分利用渥拉斯顿棱镜的分光特性,设计了一种新型实时偏振成像系统.采用像方远心望远透镜系统、准直透镜系统并设计匹配的成像镜系统,在单探测器阵列上同时获取偏振态相互垂直的两幅偏振图像.通过全系统联动设计与优化,系统的调制传递函数在截止频率处不小于0.55,全系统弥散斑均方根半径小于5.3μm,即小于探测器像元尺寸,满足成像设计要求.仿真结果证明该成像系统可有效解决传统分振幅偏振成像系统的实时性差的不足,分孔径偏振成像系统的能量利用率和分辨率低的问题以及偏振焦平面方法中光路串扰的缺陷,应用前景广阔.

A design of real-time unipath polarization imaging system based on Wollaston prism

A real-time polarization imaging system employing the Wollaston prism and a single charge-coupled device(CCD) chip covering a wavelength range of 400 nm-650 nm is proposed to avoid the false polarization information from dynamic scenes in non-real-time polarization detection imaging method. An architecture consisting of telescope lens, collimation lens, Wollaston prism, the imaging lens and a single CCD chip is employed in the system. The telescope lens is used to focus the incoming light on an intermediate image. And after collimation, the beam is angularly separated by the Wollaston prism. Two beams corresponding to ordinary light and extraordinary light are subsequently focused on the CCD plane via the imaging lens. The telescope lens is designed to have a telecentric structure in the imaging space, and the invert of which is used as the collimation lens, the completely symmetrical structure design is used to reduce the influence of aberrations. More abundant details from this system can be obtained by using matched image post-processing strategy, which is beneficial to high-quality target detection with enhanced working distance and improved environment adaptability. After joint-designing and optimization, the system modulation transfer function (MTF) value at cut-off frequency is higher than 0.55, and the root-mean-square (RMS) radius of the system is less than 5.3 μm, which is smaller than the pixel size of the CCD detector. Additionally, the lateral chromatic aberration of the system is much smaller than the diameter of airy disk, and the absolute values of all kinds of aberrations are kept smaller than 0.02 at the same time. The calculation results show that all the aberrations are mostly corrected. The system imaging is numerically modeled and analyzed, and it is demonstrated that two intensity images with perpendicular polarization states appear adjacently on the CCD plane simultaneously in the imaging simulation. One image is formed with the fraction of the backscattered light polarized parallelly to the incident light, and the other with light polarized orthogonally to the incidence, indicating that the expected design is accomplished. Compared with the traditional amplitude-split polarization imaging system, the proposed real-time polarization imaging system shows that the improved performance for real-time detection with promoted power efficiency, spatial resolution, and the light crosstalk in focal plane is well handled. Moreover, the joint design of the whole system can compensate for the distortion aberration in the vertical direction of the CCD detector, which means that a further improvement of image quality can be expected. The proposed system has a promising perspective in the fields of underwater imaging detection, astronomical observation, remote sensing, biological tissues inspection, and environmental monitoring.