通过偏振光增强激光散斑血流成像对比度  

Enhancing Contrast of Laser Speckle Blood Flow Imaging through Polarization

作　　者：曹瑞曦 桑旭 李东[1] 陈斌[1] CAO Ruixi;SANG Xu;LI Dong;CHEN Bin(State Key Laboratory of Multiphase Flow in Power Engineering,Xi'an Jiaotong University,Xi'an 710049)

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,西安710049

出　　处：《工程热物理学报》2023年第10期2736-2740,共5页Journal of Engineering Thermophysics

基　　金：国家自然科学基金重点项目(No.52036007)。

摘　　要：相干光照射生物组织会由于光程差的不同导致光线强度改变,形成明暗相间的颗粒状随机强度图像,也即激光散斑。利用激光的偏振特性能够消除光线的表面反射、增加穿透深度,达到提高散斑对比度、提升探测深度的目的。本文基于鼠脊视窗模型开展基于偏振效应增强激光散斑成像对比度的实验研究,在激光散斑成系统中加入两个可调节角度的线偏振片,利用时间散斑对比度分析算法处理原始散斑图像。在激光波长632.8 nm和曝光时间20 ms的条件下,S及P偏振下成像细节相较45?偏振更为丰富。比较加入偏振片前后各个图像的对比度数值,发现三种偏振方式均能提高散斑图像对比度,其中检偏仪夹角为120?时的S偏振,及夹角为30?时的P偏振提升幅度最大。When coherent light is used to irradiate biological tissue,the differential optical path length leads to a variegated intensity image,which is characterized by fluctuations in brightness.This phenomenon is known as laser speckle.Laser light has polarization characteristics,and linear polarizers can be leveraged to eliminate surface reflections,increase penetration depth,and enhance the contrast value of speckle,which can be used to improve the contrast value and detection depth of speckle imaging.In this study,an experimental investigation was carried out to enhance the contrast of laser speckle imaging using polarization effects,which is based on a mouse spinal window model.Two adjustable linear polarizers are added to the laser speckle imaging system,and the original speckle images are processed and compared by using the temporal laser speckle contrast analysis(tLASCA).Under the conditions of a laser wavelength of 632.8 nm and an exposure time of 20 ms,imaging details were more abundant under S and P polarization than under polarization at a 45o angle.Through comparison of the contrast value of each image before and after the addition of polarizer,it is found that all three polarization methods have improved speckle contrast.Notably,the S-polarization at a polarization angle of 120°and the P-polarization at an angle of 30°exhibited the most significant enhancements.

关 键 词：激光散斑成像 偏振效应 吸收 

分 类 号：TK3[动力工程及工程热物理—热能工程]