太赫兹数字全息是太赫兹成像技术的重要研究方向。由于太赫兹波长相对较长，使得太赫兹同轴数字全息的记录距离一般都比较近，因此系统记录距离的准确测量意义重大。对真实2.52 THz伽栢同轴数字全息图应用5种自动聚焦判别函数，通过截取再现像目标提高了判别精度。实验结果表明归一化方差判据函数最好，证明了5种自动聚焦判别函数应用于太赫兹同轴数字全息的可行性。

Terahertz (THz) digital holography is an important research aspect of terahertz imaging technology. The recording distance of terahertz digital holography is generally short because of the long wavelength and restriction of the detector. The exact measurement of the real recording distance is of great significance. Autofocusing researches have been made on real 2.52 THz Gabor inline digital holograms based on five kinds of autofocusing criterion functions. The criterion precision is improved by cropping object in the reconstructed images. The experimental results show that the performance of normalized variance criterion function is the best. The results verify the feasibility of applying five kinds of autofocusing criterion functions to terahertz inline digital holography.