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本文采用有限体积法模拟超短脉冲激光在一维参与性介质内的传输,得到瞬态辐射信号,即时域反射信号与透信号随时间变化关系,利用透射和反射信号的极值并结合微粒群算法(PSO)反演估算介质内部物性。本文研究了均匀介质时信号极值计算的目标函数随吸收、散射系数变化关系,结果表明采用极值法能够准确地反演均匀介质物性。此外,研究了两层非均匀介质时目标函数随散射系数变化关系。在吸收系数已知时,采用单面照射激光所得信号极值能够反演出两层介质各自的散射系数。最后,本文研究了同时反演两层介质的吸收和散射系数,采用综合反演的方法能够准确地反演出各层介质的吸收和散射系数。
In this paper, the finite volume method is used to simulate the transmission of ultrashort pulsed laser in one-dimensional medium, and the transient radiation signal is obtained, that is, the relationship between the time-domain reflected signal and the transmitted signal varies with time. By using the extreme values of transmitted and reflected signals combined with the particle swarm Algorithms (PSO) inversions to estimate the internal properties of the medium. In this paper, the objective function of signal extremum in homogeneous medium is studied with the change of absorption and scattering coefficients. The results show that the extreme value method can accurately reflect the properties of homogeneous medium. In addition, the relationship between the objective function and the scattering coefficient is studied when two layers of inhomogeneous media are used. When the absorption coefficient is known, the signal extremum of one-sided laser can be used to invert the scattering coefficients of two layers of media. Finally, the absorption and scattering coefficients of two layers of media are simultaneously inversed. The comprehensive inversion method can accurately reflect the absorption and scattering coefficients of each layer.