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Speckle in polarization structured light
Journal of Modern Optics ( IF 1.3 ) Pub Date : 2021-11-05 , DOI: 10.1080/09500340.2021.1996646
Basant Kumar 1, 2 , Priyanka Lochab 3 , Esha Baidya Kayal 4 , Devinder P. Ghai 2 , P. Senthilkumaran 3 , Kedar Khare 3
Affiliation  

We show that the far-field speckle patterns observed on the transmission of polarization structured light beams through a random diffuser screen have distinct spatial textures, which significantly differ from the texture of the fully developed scalar speckle. In particular, we report on speckle observed using the V-point and C-point polarization singular beams for illumination in this work. The V-point and C-point polarization singularities are generated by a combination of different orbital angular momentum (OAM) states in orthogonal polarizations. When passed through a random diffuser screen, the on-axis far-field diffraction intensity is an incoherent summation of speckle intensities due to the individual OAM states. Unlike the typical grainy structure in the scalar speckle, the speckle patterns observed with V-point and C-point illuminating beams are seen to have a noodle-like and sponge-like textures respectively. The speckle from V-point and C-point illuminations is difficult to distinguish using the usual intensity statistics which does not account for the distinct spatial structure of the speckle patterns. The Gray Level Co-occurrence Matrix (GLCM) methodology was therefore used to extract a number of spatial textural features from the speckle patterns observed using scalar and polarization structured illuminations. The principal component analysis (PCA) technique when applied to the texture parameters shows that it is possible to identify the nature of the illuminating beam by simply observing the texture properties of the resultant speckle pattern. When coherent light beams pass through a random medium resulting in a fully developed speckle pattern, the information regarding the profile of the input beam is generally considered to be lost. Our new observations on distinct textural features in speckle from structured light therefore suggest the possibility of information transmission through random media by means of switching the polarization structure of the incident beam.



中文翻译:

偏振结构光中的散斑

我们表明,在偏振结构光束通过随机漫射屏幕的传输上观察到的远场散斑图案具有明显的空间纹理,这与完全发展的标量散斑的纹理有显着差异。特别是,我们报告了在这项工作中使用 V 点和 C 点偏振奇异光束进行照明观察到的散斑。V 点和 C 点极化奇点是由正交极化中不同轨道角动量 (OAM) 状态的组合产生的。当通过随机漫射屏时,轴上远场衍射强度是散斑强度的非相干总和,这是由于各个 OAM 状态造成的。与标量散斑中典型的粒状结构不同,用 V 点和 C 点照明光束观察到的散斑图案分别具有面条状和海绵状纹理。使用通常的强度统计数据难以区分来自 V 点和 C 点照明的散斑,这不考虑散斑图案的独特空间结构。因此,灰度共生矩阵 (GLCM) 方法用于从使用标量和偏振结构照明观察到的散斑图案中提取许多空间纹理特征。应用于纹理参数的主成分分析 (PCA) 技术表明,可以通过简单地观察合成散斑图案的纹理特性来识别照明光束的性质。当相干光束通过随机介质导致完全发展的散斑图案时,通常认为有关输入光束轮廓的信息会丢失。因此,我们对结构光散斑中不同纹理特征的新观察表明,通过切换入射光束的偏振结构,可以通过随机介质传输信息。

更新日期:2022-01-06
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