Imaging in turbid media using quasi-ballistic photons
Imaging in turbid media using quasi-ballistic photons
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DOI：
10.1016/s0030-4018(99)00468-x
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发表时间：
1999-11-01
影响因子：
2.4
通讯作者：
Sood, AK
中科院分区：
文献类型：
--
作者：
Gopal, V;Mujumdar, S;Sood, AK
我们通过实验和蒙特卡罗模拟研究随机介质中的光散射，以确定光子在散射介质中沿着几乎不偏离的路径传播的距离，因此能够投射嵌入介质中的不透明夹杂物的阴影。这种光子通过偏振鉴别被分离，其中输入光的线性偏振平面被连续旋转，并且出射光的偏振保持分量通过傅立叶变换被提取。该技术是锁定检测的软件实现。我们发现，图像可以恢复到远远超过光子传播的扩散理论所预测的深度。为了理解我们的实验结果，我们进行蒙特卡罗模拟模拟的随机行走行为的多重散射光子。我们提出了一个。新的定义的扩散光子在其初始传播方向的记忆方面，我们然后量化的角度相关函数。这种重新定义产生了保偏光子的穿透深度。基于这些结果，我们已经制定了一个模型来理解阴影的形成在混浊介质中，其中的预测与我们的实验结果吻合得很好。(C)1999年由Elsevier Science B.V.出版，版权所有。
We study by means of experiments and Monte Carlo simulations, the scattering of light in random media, to determine the distance up to which photons travel along almost undeviated paths within a scattering medium, and are therefore capable of casting a shadow of an opaque inclusion embedded within the medium. Such photons are isolated by polarisation discrimination wherein the plane of linear polarisation of the input light is continuously rotated and the polarisation preserving component of the emerging light is extracted by means of a Fourier transform. This technique is a software implementation of lock-in detection. We find that images may be recovered to a depth far in excess of that predicted by the diffusion theory of photon propagation. To understand our experimental results, we perform Monte Carlo simulations to model the random walk behaviour of the multiply scattered photons. We present a. new definition of a diffusing photon in terms of the memory of its initial direction of propagation, which we then quantify in terms of an angular correlation function. This redefinition yields the penetration depth of the polarisation preserving photons. Based on these results, we have formulated a model to understand shadow formation in a turbid medium, the predictions of which are in good agreement with our experimental results. (C) 1999 Published by Elsevier Science B.V. All rights reserved.