Reconstruction Of The Optical Paramters In The Non-homogeneous Disperse Media Based On The Time And Frequency Domain Light Information

Disperse media are widely found in the fields of engine plume,biological tissue,furnace flame,infrared coating,aerosol particles and ceramic thermal protection materials.The internal optical parameters of the media are the basis for studying the radiative transfer process.However,in most cases,the optical parameters in the disperse media are unknown and need to be reconstructed using the optimization algorithm.In current researches of the optical parameters reconstruction,the solving of inverse problem has low efficiency and large errors.Furthermore,the cross-talk exits in the simultaneous reconstruction of multi-optical parameters field still be a trouble.So an efficient,accurate and robust algorithm is urgent to be built for the optical parameters reconstruction.This thesis focuses on the optical parameter reconstruction algorithm,and carries out the researches based on the diffusion approximation(DA)model,the frequency radiative transfer equation(FD-RTE),and the time-domain radiative transfer equation(TD-RTE)gradually.Finally,an accurate and efficient algorithm which can overcome the cross-talk is built.The main work of this thesis include the following aspects:Firstly,the optical parameters reconstruction in the disperse media and the numerical optimization algorithm based on the gradient are introduced systematically.The conjugate gradient method(CGM)is elaborated,and the core problems of the optical parameters reconstruction are analyzed.The regularization technique based on the generalized Gaussian Markov random field(CGMRF)model is used to overcome the ill-posed problem.The direct model adopts the DA equation,and the inverse problem is solved by the CGM.The absorption coefficients,the diffusion coefficients and the reduced scattering coefficients are reconstructed.The reconstructed images can show the inner structure of the media clearly.The regularization technique can improve the results efficiently.Secondly,the FD-RTE which can overcome the limit of the DA model is considered to research the optical parameters reconstruction.The adjoint differentiation(AD)and the adjoint equation(AE)are adopted to compute the gradient of the objective function,respectively.The absorption and scattering coefficients in different media are reconstructed using the CGM.It is indicated that the AD can compute the gradient of the objective function accurately,an the AE is suitable for the media with simple incident light source.In order to improve the accuracy of the reconstruction results,the TD-RTE is adopted to be direct model.The restarted CGM which can accelerate the convergence is introduced to reconstruct the optical parameters.T he reconstructed results using TD-RTE are more accurate than the results using FD-RTE.Considering that the computation of gradient and the exact linear search need large computation time,the sequential quadratic programming(SQP)and the AE method are employed to built an accurate and efficient reconstruction algorithm.The absorption and coefficients can be reconstructed accurately and efficiently.The cross-talk is eliminated effectively.Furthermore,the time-domain reconstruction algorithm is introduced to research the fluorescence tomography.Multiple fluorescent images with different contrast can be reconstructed.Finally,a multi-dimensional time-domain infrared radiation measurement platform is built based on the time-correlated single photon counting(TCSPC)and optical switch.The stability of the measurement system and the main parameters of the TCSPC are tested.The optical phantoms are made by the epoxy resin.The exitance of the laser-irradiated phantoms are measured.The simulated signal are consistent with the measured signal.Using the measured signal,the absorption and scattering coefficients of the phantoms are reconstructed simultaneously.