Fig. 1. Light path design of transmission(a) and reflection(b) and mathematical description (c) of terahertz single-pixel imaging based on modulator

Fig. 2. Schematic of the experimental setup for terahertz time-domain spectroscopy system^[46]. (a) The different colors correspond to different delay-line positions, these positions correspond to different time points in Fig.(b); (b) Measured THz time-domain signal; (c) The amplitude and phase of a signal in the frequency domain

Fig. 3. Terahertz single-pixel computational imaging based on metal pattern modulator. (a) PCB modulator^[50]; (b) Spinning metal disk modulator^[51]

Fig. 4. Schematic diagram of terahertz single-pixel imaging structure based on metasurface modulator^[56]. (a) Spatial distributon of maximum differential absorption for Hadamard pattern; (b) Image reconstruction using 64 masks with each mask displayed for 22.4 ms, giving a total image acquisition time of 1.43 s; (c) Photograph of the object studied. (d) Consecutive tiles show reconstruction using 45 Hadamard masks

Fig. 5. (a) Schematic of terahertz single-pixel imaging system based on the passivated silicon wafer^[63]; (b) Comparison of reconstruction results between conventional high-resistive silicon and passivated silicon

Fig. 6. (a) Terahertz single-pixel imaging system and its imaging results based on nonlinear electro-optic crystals^[70]; (b) Terahertz single-pixel imaging system and its imaging results based on spintronic materials^[72]

Fig. 7. Fourier single-pixel computational imaging for the terahertz regime ^[81]. (a)-(d) Fourier spectrums at different sampling rates; (e)-(h) Inverse Fourier transform terahertz image

Fig. 8. (a) Network architecture of deep convolutional auto-encoder^[86]; (b) Design of part of optimized patterns; (c) Experimental structure and video of single-pixel imaging

Fig. 9. (a) DCAN architecture ^[87]; (b) Qualitative and quantitative evaluation of conventional FSI and based on deep learning FSI

Fig. 10. Principle schematic of terahertz single-pixel computational imaging system at standoff distances and far-field imaging results^[92]

Fig. 11. Schematic of terahertz single-pixel computational imaging construction and image reconstructed results ^[94-95]. The imaging resolution is 154 μm, 100 μm and 9 μm when the intrinsic silicon thickness is (a) 400 μm, (b) 110 μm and (c) 6 μm, respectively

Fig. 12. Structural schematic of time-resolved nonlinear ghost imaging and hyperspectral reconstructed results^[97]

Fig. 13. (a) Terahertz recognition experimental setup of target; (b) Perfor- mance evaluation (confusion matrices) of the object recognition method^[100]

Table 1. Summary of terahertz wave mask technology

Table 2. Comparison of technical indexes of single-pixel imaging algorithms