一维非均匀介质中的瞬态辐射反问题

Inversed transient radiative transfer in one-dimensional nonhomogeneous media

针对短脉冲激光入射一维非均匀参与性介质问题,计算了非均匀体的大小、位置以及吸收和散射系数对边界出射信号的影响。依据各参量敏感系数的变化,确定了信号采样的时间范围。利用共轭梯度法对非均匀体进行多参数同时反演。数值模拟结果表明,对同一非均匀介质,不同的入射位置会得到不同的敏感系数,且各参数敏感系数明显变化的时间段不尽相同,但多数变化信息包含在两倍脉冲穿越时间内。在反问题计算中,推荐选用两倍脉冲穿越时间内的信号作为采样数据。共轭梯度法能较为准确地实现介质多参数同时反演。随着测量数据误差的增加,反演结果与真值之间的偏差增大。敏感系数值较小的参量,其反演计算结果误差较大。

One-dimensional non-homogeneous media irradiated with short pulse laser was treated in this paper. The influences of size, location, absorption coefficient and scattering coefficient on boundary signals were analyzed. According to the changes of parameter sensitivity, the sampling time range of time-resolved signals can be determined. Under such conditions, multi-parameters in one dimension non- homogeneous participating media were reconstructed simultaneously with conjugate gradient （CG） method. The simulation results have shown that different sensitivities were obtained for different irradiated locations, when the other conditions remain unchanged. The peak value of sensitivity appeared in different moment for different parameters. However, most variable information was contained in the twice transmission time. Therefore, the twice transmission time was proposed as the best sampling time range in inverse problems. Accurate results were obtained in multi-parameters inversion. The differences between the inversed results and true values increases with the increase of measure errors. Lager errors were obtained in the inversed results for the parameters with small sensitivities.