太赫兹被动成像技术具有很多独特的优势，已经成为安全检查领域的重要研究方向。为了进一步提高太赫兹被动成像系统的成像性能和实用性，研究了实验室自研的一套基于光机扫描的太赫兹被动成像系统的性能。通过探索不同系统参数和实验条件，包括成像距离、成像速度以及探测器状态，对背景噪声以及分辨率等图像性能的影响，获得了系统优化的性能参数，同时探究了该系统探测人体隐藏物品的能力，说明该系统可以有效地对人体进行安全检查。实验结果表明：该太赫兹被动成像系统的成像距离在机器前面1.5~2.5 m的范围内，即在大约1 m的景深内，能够显示清晰的太赫兹图像；该系统的成像速度为每帧1~2 s；探测器工作电平和增益对图像清晰度和系统噪声有较大的影响，存在一个优化的探测器工作状态，在该条件下可以获得清晰的太赫兹图像。在各项参数优化的条件下，该太赫兹成像系统可以达到的目标分辨率为1.5~2 cm，能够清晰地探测隐藏在人体衣服之下的金属物品和对太赫兹波有较强吸收的物质。

Terahertz passive imaging technology has many unique advantages and has become an important research direction in the field of security inspection. In order to further improve the imaging performance and practicability of the terahertz passive imaging system, the performance of a terahertz passive imaging system based on opto-mechanical scanning developed by our laboratory was studied. By exploring the influence of different system parameters and experimental conditions including its imaging speed, distance and the status of detector on the performance of imaging system such as the image resolution and background noise, the optimized system parameters were obtained. At the same time, the performance of imaging system to detect the human body hiding the metal objects was explored. It was shown that the system was suitable for the security inspection of human body. The experimental results show that the imaging distance of the terahertz passive imaging system is within the range of 1.5–2.5 m in front of imager, that is, its depth of field is about 1 m. The imaging speed of system is 2–4 seconds per frame. Moreover, the operating level and gain of detector have a great impact on image sharpness and system noise. There exists an optimized operating state of detector. Under the optimized condition, the clear terahertz images can be achieved and the resolution of target was 1.5–2 cm. Our imaging system can clearly detect metal objects hidden under human body’s clothes and substances with strong absorption on terahertz waves.