Some approaches, which include iterative reconstruction-reprojection (IRR), projection space iteration reconstruction-reprojection (PSIRR) and other interpolation methods, have already been proposed for the reconstruction of fields including opaque objects. In the IRR, the interpolation operation is performed in the object space during backprojection-reprojection. The errors associated with the interpolation degrade the reconstructed image and may cause divergence unless a large number of rays and views are adopted. In the research of optical test, the testing views are often limited; therefore, the results are usually poor when using the IRR to reconstruct the fields including opaque objects. To improve the reconstruction precision in this case, a new approach is proposed, which is based on the discrete IRR algorithm and the finite impulse response (FIR) lowpass filer (DIRRLF). This filer is used to process the reprojection data between the iterative reconstruction and the reprojection stages. Different window functions and bandwidths are adopted for the lowpass filter. The compared reconstruction results of discrete IRR algorithm and DIRRLF algorithm for an asymmetrical single-peak simulation field including a circle round opaque object are studied with the numerical simulation of computer. The results show that this algorithm has higher reconstruction precision than the discrete IRR algorithm and has a potential application of reconstructing real three-dimensional fields including opaque objects.