THz共焦扫描成像中，由于太赫兹激光器不可能恒定输出和采集信号微弱等原因，导致成像质量有待提高；数字图像复原方法是一种节约系统成本和空间的有效手段。文中提出了一种用于太赫兹共焦扫描图像复原的基于两步背景抑制、中值非局部均值(MNLM)滤波和灰度变换的复合方法，并将此方法用于真实太赫兹图像，与中值滤波、开运算和非局部均值滤波相比较。真实图像处理结果表明，此方法具有较好的复原效果，尤其是图像对比度有明显提高。

Among the experiments of terahertz confocal scanning imaging, the image quality of the system remains to be improved for the reason that the terahertz laser used in the system can not constantly output and the signal acquisited by the detector is weak, etc. Digital image restoration is an effective method to save the cost and the space of confocal scanning imaging system. Based on the consideration above, a composite method was put forward for the use of the terahertz confocal scanning image restoration. This composite method is based on two-step background suppression, median non-local means(MNLM) filtering and gray level transformation. A comparison with median filtering, open operation and non-local means filtering was made after using this composite method on the real terahertz images. The results of real terahertz imaging processing show that this composite method has a good effect of image restoration and the image contrast is obviously enhanced in particular.