为了提高数字全息成像系统的成像分辨力，对以球面波作为参考光波的预放大数字全息成像系统的记录和再现过程进行了理论推导，得出了该系统的脉冲响应表达式，并由此分析了决定该系统成像分辨力的因素。在CCD成像分辨力高于显微物镜分辨力的情况下,通过对分辨力测试板进行实验，讨论了系统分辨力与记录距离的关系。结果表明：再现像的分辨力对记录距离不敏感；但在记录距离为零，即像面数字全息系统下，再现像具有更高的分辨力。实验结果与理论分析一致。

In order to improve the resolution of digital holographic imaging system, the recording and reconstruction processes of a premagnification digital holographic system with a spherical reference wave are theoretically deduced. Then the point spread function is obtained and the factors to determine the imaging resolution of this system are analyzed. In the case of the CCD imaging resolution higher than that of the microscope objective, the relationship between the resolution and the recording distance of the system is discussed through the experiment of resolution target USAF. The result show that the resolution of reconstructed images is not sensitive to the recording distance. But as the recording distance is zero, which is named digital imageplane holography, the resolution of reconstructed images is highest. The experimental results are consistent with the theoretical analysis.