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利用CO2激光抽运太赫兹(THz)激光器,搭建了THz连续波透射式快速扫描成像系统。将样品置于平移台上,利用透镜将THz光束聚焦于样品表面,通过计算机控制平台连续移动与信号实时采集,大大缩短了成像时间,通过计算机重构获得扫描图像。从扫描速度,成像分辨率的角度出发,对连续THz扫描成像系统进行优化研究。实验对1cm×1cm的样品,用0.25mm步长进行扫描成像,得到最短成像时间仅需3 min,在输出频率为4.3THz时,图像最高分辨率达到0.1mm。对刀片与树叶进行扫描成像,分析并比较了衍射极限对成像质量的影响。结果表明,在选用高频率输出光源和扫描平台小步长移动情况下可以获得更好的成像质量。
The THz continuous wave transmission type fast scanning imaging system was constructed by CO2 laser pumping THz laser. The sample is placed on a translation stage, the lens is used to focus the THz beam on the surface of the sample, and continuous movement of the THz beam through the computer control platform and real-time acquisition of the signal greatly shorten the imaging time and obtain a scanned image by computer reconstruction. From the perspective of scanning speed and imaging resolution, the continuous THz scanning imaging system is optimized. Experiment 1cm × 1cm samples with 0.25mm step scan imaging, the shortest imaging time is only 3 min, the output frequency of 4.3THz, the maximum resolution of the image reaches 0.1mm. The blade and the leaves were scanned and analyzed, and the influence of the diffraction limit on the imaging quality was analyzed and compared. The results show that better imaging quality can be obtained when using high-frequency output light source and small step-by-step moving of the scanning platform.