Fig. 1. Schematic diagram of optical path of terahertz passive imaging system

Fig. 2. Comparison of THz imaging results for the human body under the different levels of detector

Fig. 3. Information entropy of the images on human body under different levels of detector

Fig. 4. Comparison of THz imaging results for the human body under different gains of detector

Fig. 5. Information entropy of the image on the human body at different gains

Fig. 6. Imaging result after the optimization of level and gain

Fig. 7. Comparison of THz images for the human body under different imaging distances

Fig. 8. Comparison of information entropy and height ratio of the human body's images at different imaging distances

Fig. 9. Comparison of images on the human body at different imaging speeds

Fig. 10. Information entropy of the human body images under different rotational speeds

Fig. 11. Imaging results of metal resolution plates with different landscape stripe spacing

Fig. 12. Imaging results of a metal resolution plate with different portrait stripe spacing

Fig. 13. Imaging results for concealed cell phones and wrenches

Fig. 14. Imaging results of the knives unhidden and hidden