發(fā)布時間：2018-12-08 09:33

【摘要】：激光散斑是相干光傳輸?shù)闹匾F(xiàn)象之一,其在工業(yè)、生命科學領域均有著廣泛的應用,如位移測量、激光散斑血流成像等。由于生物組織和懸浮粒子溶液渾濁介質中的散射多為體散射,其中往往包含多次散射,這樣的散斑現(xiàn)象較為復雜,難以用波動方程求解,一般只能采用數(shù)值方法來進行模擬。然而傳統(tǒng)的蒙特卡洛數(shù)值模擬往往忽略了介質的運動性質,不能用以模擬研究體散射介質的布朗運動、定向流動等過程中的散斑現(xiàn)象,而這恰恰對研究動態(tài)體散射散斑的性質以及實現(xiàn)流速的定量測量十分重要。針對上述問題,本文首先從連續(xù)時間序列動態(tài)散斑模擬出發(fā),提出了動態(tài)散斑模擬的新方法,利用該方法對平移散斑、沸騰散斑的電場自相關函數(shù)進行了分析研究,給出在平移、沸騰散斑共同作用下流速與電場自相關函數(shù)的關系式(傳統(tǒng)的研究方法認為流速與散斑場的去相關時間成反比),并建立了運動渾濁體散射介質模型,利用改進的蒙特卡洛模擬方法對同時包含定向流動、布朗運動散射介質的散斑場進行了模擬與分析,為分析體散射散斑性質以及分析流速測量中的影響因素等提供了工具。本文的具體內(nèi)容包括： (1)以散斑強度伽馬分布模型研究分析散斑現(xiàn)象,提出新的連續(xù)時間序列動態(tài)散斑模擬方法,對平移散斑、洛倫茲光譜線型動態(tài)散斑等進行了模擬,給出像面上電場自相關函數(shù)的關系式,并分析了流速與襯比之間的關系。 (2)將電場蒙特卡洛模擬由無限窄光束擴展到有限尺寸大小的光束。針對由此帶來的計算量增加問題,我們實現(xiàn)了基于GPU的CUDAEMC,通過并行計算來大幅提升計算速度。使用GTX480顯卡運行CUDAEMC時,與i3-2120運行EMC(Electric field Monte Carlo)相比能取得370倍的加速比。 (3)提出了電場蒙特卡洛模擬DMEMC,能對懸浮粒子溶液模型布朗運動以及定向流動進行模擬,然后在此基礎上模擬分析運動介質的體散射散斑場。實現(xiàn)了相干光照明下,運動介質體散射散斑場的蒙特卡洛模擬。
[Abstract]:Laser speckle is one of the most important phenomena of coherent light transmission. It has been widely used in industry and life sciences, such as displacement measurement, laser speckle blood flow imaging and so on. Because the scattering in biological tissue and suspended particle solution in turbid medium is mostly bulk scattering, which often contains multiple scattering, such speckle phenomenon is more complicated and difficult to be solved by wave equation. Generally, numerical method can only be used to simulate it. However, the traditional Monte Carlo numerical simulation often ignores the motion properties of the medium and can not be used to simulate the phenomena of speckle in the process of Brownian motion and directional flow. This is very important for the study of the properties of dynamic volume scattering speckle and the quantitative measurement of velocity. In order to solve the above problems, a new method of dynamic speckle simulation based on continuous time series dynamic speckle simulation is proposed in this paper. The electric field autocorrelation function of translational speckle and boiling speckle is studied by using this method. The relationship between velocity and electric field autocorrelation function under the action of translation and boiling speckle is given (the traditional research method holds that the velocity is inversely proportional to the time of speckle field decorrelation), and the scattering medium model of moving turbid body is established. The improved Monte Carlo simulation method is used to simulate and analyze the speckle field in the medium with directional flow and Brownian motion, which provides a tool for analyzing the properties of volume scattering speckle and analyzing the influencing factors in velocity measurement. The main contents of this paper are as follows: (1) A new continuous time series dynamic speckle simulation method is proposed to analyze the speckle phenomena by using the speckle intensity gamma distribution model. The Lorentz spectral linear dynamic speckle was simulated and the relation between the electric field autocorrelation function on the image surface and the contrast ratio was analyzed. (2) the field Monte Carlo simulation is extended from an infinite narrow beam to a finite size beam. In order to solve the problem of increasing computational complexity, we realize that CUDAEMC, based on GPU can greatly improve the computing speed by parallel computing. When using GTX480 graphics card to run CUDAEMC, the speedup is 370 times higher than that of i3-2120 running EMC (Electric field Monte Carlo). (3) it is proposed that the electric field Monte Carlo simulation DMEMC, can simulate the Brownian motion and directional flow of suspended particle solution model, and then simulate and analyze the volume scattering speckle field of moving medium. Monte Carlo simulation of scattering speckle field of moving medium under coherent light illumination is realized.
【學位授予單位】：華中科技大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：R310

【參考文獻】

中國期刊全文數(shù)據(jù)庫 前1條

1 段元鋒;姜平安;葉貴如;周青松;;應用數(shù)字散斑相關法測量結構振動位移和頻率[J];公路交通科技;2011年06期

，

本文編號：2368119