Thilak Vimal, Voelz David G, Creusere Charles D
Klipsch School of Electrical and Computer Engineering, New Mexico State University, Las Cruces 88003, USA.
Appl Opt. 2007 Oct 20;46(30):7527-36. doi: 10.1364/ao.46.007527.
A passive-polarization-based imaging system records the polarization state of light reflected by objects that are illuminated with an unpolarized and generally uncontrolled source. Such systems can be useful in many remote sensing applications including target detection, object segmentation, and material classification. We present a method to jointly estimate the complex index of refraction and the reflection angle (reflected zenith angle) of a target from multiple measurements collected by a passive polarimeter. An expression for the degree of polarization is derived from the microfacet polarimetric bidirectional reflectance model for the case of scattering in the plane of incidence. Using this expression, we develop a nonlinear least-squares estimation algorithm for extracting an apparent index of refraction and the reflection angle from a set of polarization measurements collected from multiple source positions. Computer simulation results show that the estimation accuracy generally improves with an increasing number of source position measurements. Laboratory results indicate that the proposed method is effective for recovering the reflection angle and that the estimated index of refraction provides a feature vector that is robust to the reflection angle.
基于被动偏振的成像系统记录由非偏振且通常不受控制的光源照亮的物体所反射光的偏振状态。此类系统在许多遥感应用中可能很有用，包括目标检测、物体分割和材料分类。我们提出了一种方法，可根据被动偏振计收集的多次测量结果联合估计目标的复折射率和反射角（反射天顶角）。对于入射面内散射的情况，从微面元偏振双向反射模型推导出偏振度的表达式。利用该表达式，我们开发了一种非线性最小二乘估计算法，用于从从多个光源位置收集的一组偏振测量值中提取表观折射率和反射角。计算机模拟结果表明，估计精度通常随着光源位置测量次数的增加而提高。实验室结果表明，所提出的方法对于恢复反射角是有效的，并且估计的折射率提供了一个对反射角具有鲁棒性的特征向量。
