此程序为地震层析成像的LSQR算法，此算法用来解反问题。-This procedure for seismic tomography LSQR algorithm, the algorithm used to solve inverse problems.

对国际上通用的标准Shepp-logan人头模体进行投影和反投影、滤波反投影、ART和SART重建。-include anisotropic filter, bilateral filter and functions for tomographic reconstruction using BP, FBP, ART, SART, LSQR algorithm