[Analyzing the effect of field frequencies on reconstructive accuracy of rebuilt field with spectroscopy].

The field to be reconstructed was simulated with numerical simulation technique. The effect of a three-dimensional field's characteristics, especially, its frequency components, on the reconstructive accuracy was discussed with spectroscopy. A double-peaked field model was built with Gaussian function, and its frequency components were analyzed by Fourier transform. With algebraic reconstruction technique, the model field was reconstructed. The reconstructed field was analyzed with many error indexes. As a result, the reconstructed field was similar to the model one in respect of the position, pointing and shape of the peaks, but the heights of the peaks were shorter than those of corresponding ones in the model. The border of the reconstructive field showed obvious fluctuation. It was considered that the main causation of the reconstructive result was the filtering inserted in iterating process. To confirm this idea, the convergence factor, represented with A, of Gaussian function was changed from six to thirty in order to change the frequency components of the model field, and the same numerical simulation as the one for the first model field with A=18 was carried out for these new model ones consisting of different frequency. As a result, the idea proved to be right. At the same time, it was found that the characteristics of the field at the edge of the reconstructed zone had a deeper effect on the reconstructive accuracy. When the precondition that the field edge approximated to zero could no longer existed, the reconstructive accuracy declined, and furthermore, it would make iterating process divergent. From all the above, the characteristics of the field at the edge should draw much attention when we reconstruct a field with Algebraic reconstruction technique.