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图像空间分辨率是太赫兹(THz)成像系统的重要技术参数。为了测量系统的分辨率特性,仿照ISO12233标准制作了星形分辨率测试卡。通过对测试卡进行成像,将成像结果进行简单的处理即可获得系统在不同方向上对不同空间频率方波的响应曲线,从而测得系统的调制传递函数。利用自制的分辨率测试卡在已建立的THz点扫描反射成像系统上进行了实验研究,对系统的分辨率特性进行了测量及分析。最终测得该系统的分辨率为1.273 lp/mm,对应的线宽为0.393 mm,测量结果与刀口法所得结果较为一致。分析表明,利用星形分辨率测试卡能够方便地对系统的分辨率特性进行测量分析,直观、准确地得出系统的分辨率上限。
Image Spatial Resolution is an important technical parameter for THz imaging systems. In order to measure the resolution characteristics of the system, a star resolution test card was produced following the ISO12233 standard. By imaging the test card, the imaging results can be simply processed to obtain the response curve of the system in different directions to square wave with different spatial frequencies, so as to measure the modulation transfer function of the system. The self-made resolution test card was used to conduct an experimental study on the established THz point-scan reflective imaging system. The resolution characteristics of the system were measured and analyzed. The final resolution of the system was 1.273 lp / mm, corresponding to the line width of 0.393 mm, the measured results and blade results are more consistent. Analysis shows that the use of star resolution test card can easily measure the resolution of the system characteristics of the system, intuitive and accurate system resolution ceiling.