Fig. 1. Convolution imaging of a point and the PSF（airy disk）（a）schematic of airy disk formation，（b）convolution imaging diagram of a point and the PSF.

Fig. 2. Schematic of the THz imaging setup

Fig. 3. Simulation and test of 0.3-mm point imaging（All data are normalized and displayed in false color for ease of understanding）（a）the point imaging 3D map obtained using Eq. 8，（b）the point imaging 2D map obtained using Eq. 8，（c）the point imaging 3D map，（d）the point imaging 2D map

Fig. 4. Image restoration by using the PSF（a）schematic of a simple resolution plate size，where R denotes the radius of the largest circle，w₁ is the width of the light transmittance gap，w₂ is the width of the narrowest part of the mask，and dimension error is ±0.01 mm，（b）the original image outputted by the camera，（c）the image restored using the PSF