基于双折射晶体的快拍穆勒矩阵成像测偏原理分析

针对传统穆勒矩阵成像测偏仪包含活动部件,需进行多次测量,容易产生测量误差,不能对运动目标或动态场景进行同时、实时测量等问题,提出了一种以改进型萨瓦偏光镜为核心分光器件的快拍Mueller矩阵成像测偏技术(MSP-SMMIP).它不含任何活动部件,能通过单次快拍测量获取目标强度图像和全部16个穆勒矩阵阵元图像.它主要由偏振态产生和偏振态分析两部分组成,偏振干涉条纹通过偏振态产生光路后定位于测试样品上,随后这些条纹通过空间载频将样品的Mueller矩阵分量编码,经偏振态分析光路成像于焦平面上.采用斯托克斯矢量-穆勒矩阵形式阐明了光场偏振态被MSP-SMMIP调制的过程,给出了其像面干涉图表达式,讨论了Mueller矩阵反演和系统定标的方法.基于CCD相机参数分析了系统的光学指标.通过数值模拟实验给出模拟测量结果,通过定性和定量评价测量结果表明该系统的可行性.MSP-SMMIP技术具有稳态、快拍、结构简洁、易定标、可同时实时获取目标强度图像和全部Mueller矩阵阵元图像的显著特点.

Principle analysis of snapshot Mueller matrix imaging polarimeter using birefringent crystal

Conventional Muller matrix imaging polarimeter (MMIP) with several rotating elements suffers mechanical complexity, vibration noise, heat generation, and other unwanted problems. To overcome those shortcomings, we present a snapshot Muller matrix imaging polarimeter (SMMIP) using a birefringent crystal with high extinction ratio. The snapshot imaging polarimeter allows a single image to be used to measure the polarization of a scene without electronic control units or moving mechanical components. This new polarimeter combines the technique of Muller matrix spectropolarimetry with a snapshot imaging polarimeter through using modified Savart polariscope (MSP-SMMIP). It contains both a generator and an analyzer module. Spatial polarization fringes are localized on a sample by incorporating modified Savart polariscope into a polarization generator module. These fringes modulate the Mueller matrix components of the sample, which are subsequently isolated with modified Savart polariscope in an analyzer module, and the analyzer and the imaging lens combine with 16 beams to create interference, resulting in spatial modulation on the two-dimensional CCD camera. Expressions for interference intensities, optical system analysis, theory of calibration and method of reconstruction are presented. Finally, the numerical simulation is used to demonstrate theoretical analysis and the feasibility of MSP-SMMIP. The layout is very easy to calibrate and the reference target is only a linear polarizer at 22.5°. Moreover, the remarkable advantages of the proposed instrument, compared with conventional Muller matrix imaging polarimeter, are that it is also simple, compact, snapshotted, and static (no moving parts). Therefore we believe that the proposed snapshot imaging polarimeter will be very useful in many applications, such as biomedical imaging and remote sensing.