共查询到20条相似文献,搜索用时 140 毫秒
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飞秒互相关时间选通技术用于光学层析成像的实验研究 总被引:1,自引:0,他引:1
利用飞秒互相关二次谐波信号时间选通技术。实现了对埋藏在高度散射介质中物体的透射成像和反射以析成像。互相关选通门有效地选出携带物体信息的弹道光子和蛇行光子,排除了给成像带来背景噪声的温射光子,分别获得了散射介质中物体的二次谐波一维和二维图像。 相似文献
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阐述了基于光子散射模型下的功能成像技术.运用蒙特卡罗方法对光子在介质中的散射路径进行了模拟和分析,从而引入光子散射的概念.通过对光子散射方程的解释引入了散射光子密度波的概念.通过无限大模型下光子密度波的波方程,引出光子密度波的异质模型.建立了基于消元的奇异值弱化重建算法,完成了对病态方程的求解,实现了对内嵌于均匀介质中异质的吸收系数分布图像的重建.在基于光散射成像技术所开发的成像系统平台下实现了异质小球的成像实验,对多个不同浓度的物体完成了成像,探测到介质中由于微小浓度改变而引起的吸收系数变化. 相似文献
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基于多维漫反射光谱技术的复杂混合溶液成分检测 总被引:1,自引:0,他引:1
为了进行复杂混合溶液的成分检测,该文提出了一种基于多维漫反射光谱技术的浓度检测方式,通过信号中携带的不同成分的多种光学性质来进行分析。实验设计了基于超连续谱激光光源、精密电控平移台和光谱仪的检测装置,选用Intralipid-20%溶液作为研究对象,用蒸馏水配制体积百分数1%~20%的溶液,分别测量距其入射点1.5~13mm(间隔0.5mm)范围内的24点漫反射光谱信号,以偏最小二乘回归算法对单点和多点漫反射光谱信号进行建模与预测。得到建模精度最高的为距离入射位置最近的1点~13点对应的光谱信号所建立的模型,预测精度最高的为距离入射位置最近的1点~7点对应的光谱信号所建立的模型。结果表明,增加不同位置信息的光谱信号,能够提高光谱的信噪比,与传统光谱技术仅利用吸光度或反射率等单一光学性质的方法相比,增加了被测物质散射特性的影响,利用被测物质多种光学性质的变化提高了建模及预测的精度,为基于多维光谱的复杂混合溶液检测提供了基础。 相似文献
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本文采用蒙特卡洛法建立了二维参与性介质中超短脉冲激光的瞬态辐射传输概率模型,通过与相关文献计算数据的对比,验证了上述物理模型及数值算法的正确性。同时,讨论了介质侧面交界处反射特性、激光入射半径及脉冲宽度对不同探测位置处透射反射信号强度及时域分布的影响,探讨入射脉冲宽度和激光传输特征时间对透射反射信号时间展宽特性的关联性,为激光主动探测过程中摄像机选通门开启时刻及持续时间的选取提供参考借鉴。 相似文献
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云雾后向散射会产生引发激光引信虚警的回波信号.基于蒙特卡罗法,对云雾散射回波进行了模拟仿真,并定量给出了云雾散射回波的波形、波峰位置、脉宽和峰值功率随发射脉冲宽度的变化规律.研究结果表明,回波峰值功率随着发射脉宽的增大而增大,且当发射脉宽增大到50ns后趋于饱和,峰值功率将不随脉冲宽度的变化而变化;脉冲展宽的程度随发射脉宽的增大而减弱;发射脉宽对云雾散射回波波峰位置的影响较小.给出的回波信号模拟仿真结果可以为窄脉冲激光引信的目标识别以及探测阈值和脉冲宽度等参量的优化设计提供依据. 相似文献
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根据光波在介质内的散射、折射特点,分析了脉冲链在参与性介质内经界面反射和介质散射后的叠加机理.导出了脉冲链入射非散射性半透明平板时透射比和反射率的解析解.利用间断有限元法和时间平移叠加法计算了脉冲链在一维散射性介质平板内传输的透射比和反射率.结果表明由于介质内部入射光与介质的相瓦影响,脉冲链受界面的反射和内部介质的散射,分裂成一系列时滞不同的子光波.经过不同的光学行程后,子光波叠加成离开平板的反射光波和透射光波.叠加效果随介质散射系数、脉冲宽度和脉冲时间间距发生变化.通过调节脉冲链的脉冲宽度和脉冲时间间距可得到不同波形的反射波和透射波. 相似文献
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The influences of the absorption μa, the scattering μs, and the anisotropy coefficient g on the optical properties of ultrashort pulse in turbid media has been simulated based on the diffusive approximation theory. The laser pulse intensity will be attenuated and the diffusive scattering pulse shape will be widened in the turbid media. Various medium parameters have different influences on the reflection of the laser pulse. The intensity loss of the diffusive reflection light is obtained when μa and μs are increased in turbid media. The pulse width of the diffusive reflection pulse is rapidly increased far away from the incident point and at the same time the pulse times that are delayed have been numerical simulated in the boundary conditions of semi-infinite homogenous media. 相似文献
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Al. S. Kiselev An. S. Kiselev N. N. Rozanov G. B. Sochilin 《Optics and Spectroscopy》2006,101(1):118-130
Analysis of the scattering of a plane monochromatic electromagnetic wave by an inhomogeneity of the velocity of motion of the medium is carried out. The inhomogeneity corresponds to the rotation of a finite portion of the medium with a constant angular velocity under the conditions of spatial homogeneity of the permittivity and the permeability. The case of oblique incidence of the wave is studied. The scattering cross sections for an inhomogeneity having the shape of a cylinder or a sphere of different dimensions are found for different angles of incidence of radiation. 相似文献
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《Physics Reports》1998,304(3):89-144
We review research on time-resolved optical imaging of objects hidden in strongly scattering media, with emphasis on the application to breast cancer detection. A method is presented to simulate the propagation of light in turbid media. Based on a numerical algorithm to solve the time-dependent diffusion equation, the method takes into account spatial variations of the reduced scattering and absorption factors of the medium due to the presence of objects as well as random fluctuations of these factors. It is shown that the simulation method reproduces, without fitting, experimental results on tissue-like phantoms. Using experimental and simulation results, an assessment is made of the reliability for extracting the reduced scattering and absorption coefficients of the medium from time-resolved reflection and transillumination data. The simulation technique is employed to study the conditions for locating mm-sized objects immersed in a turbid medium, by direct, time-resolved imaging. We discuss a simple method to enhance the imaging power of the time-resolved technique. The mathematical justification of the method, as well as some applications to simple problems, is given. The simulation technique is employed to demonstrate the effectiveness of the data processing technique. Results of time-resolved reflection experiments and simulations are presented, showing that the use of the latter allow us to locate 1 mm diameter objects under conditions which would prevent detection otherwise. Our results demonstrate that the combination of simulation and the appropriate processing of the diffusive part of the time-resolved reflected or transmitted light intensity may substantially increase the potential of the time-resolved near-infrared diffusive light imaging technique as a diagnostic tool for breast cancer detection. 相似文献
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Scattering from a Born inhomogeneity in a homogeneous, acoustical waveguide is considered and results compared to the corresponding scattering in a homogeneous, unbounded medium. It is found that the Ewald sphere in the unbounded medium case is replaced by a Ewald "strip" in a waveguide, the strip consisting of many individual Ewald spheres embedded in a ball the radius of which is twice that of an individual sphere. The physics behind the Ewald strip is discussed along with the implications of waveguide Born data. 相似文献
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V. L. Weber 《Radiophysics and Quantum Electronics》1998,41(5):417-427
The model of detection of local inhomogeneities of scattering and absorbing types in biological tissues by the methods of
reflection and transmission confocal microscopy has been developed on the basis of the theory of vision in scattering media.
General equations for calculation of the image contrast of an inhomogeneity against the background of a scattering medium
are derived. The influence of the object characteristics and observation-system parameters on the maximum detection depth
of inhomogeneities is analyzed.
Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh
Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 5, pp. 625–639, May, 1998. 相似文献
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V. L. Veber 《Radiophysics and Quantum Electronics》1996,39(7):613-623
Using the theory of vision in scattering media, we develop a model for the observation of inhomogeneity in biological tissues by the method of reflected confocal microscopy. General formulas for the calculation of image contrast of a local inhomogeneity with sinusoidal distribution of reflection factor located in an anisotropic scattering medium are derived. The influence of observation-system parameters on the maximum vision depth of inhomogeneities is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 7, pp. 925–940, July, 1996.The author thanks L. S. Dolina, A. G. Luchinin, and I. A. Sergievskaya for useful discussion of paper results.This paper was supported by the Russian Foundation for Fundamental Research (projects: 95-02-5797, 94-02-03913). 相似文献
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We describe a new method to measure the decorrelation rate of the optical coherence tomography (OCT) magnitude simultaneously in space and time. We measure the decorrelation rate of the OCT magnitude in a Fourier-domain OCT system for a large range of translational diffusion coefficients by varying the sphere diameter. The described method uses the sensitivity advantage of Fourier-domain OCT over time-domain OCT to increase the particle diffusion imaging speed by a factor of 200. By coherent gating, we reduce the contribution of multiple scattering to the detected signal, allowing a quantitative study of diffusive particle dynamics in high concentration samples. We demonstrate that this technique is well suited to image diffusive particle dynamics in samples with a complex geometry as we measure the morphology and diffusive particle dynamics simultaneously with both high spatial and high temporal resolution. 相似文献
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Comparing measurements of high-frequency phonon reflection at the uncovered and optically polished (100)-silicon surface, with calculations considering phonon focusing, reveal complete diffusive scattering with at most 4% specular reflection contribution. Two possible mechanisms causing diffusive scattering are discussed. 相似文献