记录着不同深度位置的粒子全息图在数值重构过程中由于直透光、孪生像的影响以及离焦粒子像的存在，导致了聚焦粒子再现像质量的下降。针对这一问题，本文提出一种数值处理方法来减小上述三因素对聚焦粒子再现像的影响。该方法通过对数值重构出的两个聚焦与非聚焦面上粒子复振幅相减，将直透光、孪生像和离焦粒子像对聚焦粒子的影响同时减小，因此提高和改善了聚焦粒子再现像的对比度。在同轴数字全息层析再现粒子场过程中，该方法适用于在某一聚焦面仅显示聚焦粒子。此外，该过程仅需要一张全息图，而且不需要对全息图做预前和后期处理。给出了简要理论以及仿真、实验结果。

In-line digital holography is presented for the particles analysis in 3-D. Since the effects of zero order waves, conjugate image and defocused particle images degrade the reconstructed image quality of the focused particles during the reconstruction of in-line digital holography containing small particles at different depths, a numerical method for reducing these effects was proposed. A new subtraction method of reconstructed wave fields was presented for particles analysis. The effects of zero order term, conjugate image and the defocused particle images were simultaneously minimized. Therefore, the contrast of reconstructed amplitude images was improved. This method is useful to slice in-line digital holograms to display only in-focus particles at any particular plane. Furthermore, this process is accomplished from a single hologram without additionally required pre or post processing. The theory, simulation results and experimental examples were also given.