Fig. 1. Classification of spectral imaging by acquisition methods^[11]. (a) Scanning spectral imaging; (b) snapshot spectral imaging

Fig. 2. Principle of metasurface based spectral imaging. (a) Structure diagram of metasurface spectral imaging chip, including two parts of metasurface layer and CMOS image sensor; (b) principle of spectral reconstruction for a single metasurface microspectrometer; (c) principle of space division multiplexing of metasurface

Fig. 3. Design objective of metasurface units. (a) Projection of spectral lines at λk、λk+1 onto transmission spectra of metasurface units; (b) corresponding measurement vectors Ik、Ik+1 for spectral lines at λk、λk+1 are two columns of measurement matrix T without considering measurement noise

Fig. 4. World's first real-time ultraspectral imaging chip and its performance^[17]. (a) Schematic diagram of chip structure; (b) reconstruction results of narrowband spectra using microspectrometer of chip; (c) center-wavelength error and linewidth error for results in (b); (d) reconstruction results of double-peak signal

Fig. 5. Ultraspectral imaging chip based on metasurfaces with freeform shaped meta-atoms^[19]. (a) Schematic diagram of structure; (b) reconstruction results of double-peak signal

Fig. 6. Spectral imaging results for a standard colorboard and a plate of fruit using ultraspectral imaging chip based on metasurfaces with freeform shaped meta-atoms^[19]. (a) Object picture of ultraspectral camera; (b) red, green, and blue (RGB) pseudo-color image of standard colorboard captured by a commercial spectral camera; (c) RGB pseudo-color image of standard colorboard reconstructed by ultraspectral camera; (d) reconstructed spectra (red lines) for 24 types of colors with spectra captured by commercial spectral camera as a reference (blue lines), in which fidelities for recovered spectra are marked in top right-hand corner; (e) spectral imaging results for a plate of fruit and spectral reconstruction results for sampling points

Fig. 7. Basic architecture of ADMM-net and reconstruction results of a standard colorboard using ADMM-net^[26]. (a) Network structure of ADMM-net; (b) spectral image reconstruction results of a standard colorboard using ADMM-net

Fig. 8. Real-time brain spectral imaging results for a rat using world's first real-time superspectral imaging chip^[17]. (a) Spectral imaging results; (b) object picture of spectral camera; (c) spectral signals of different regions; (d) changes of spectral signals of HbO and HbR over time in vascular areas; (e) changes of spectral signals of HbO and HbR over time in non-vascular areas

Fig. 9. Snapshot spectral measurement results of living faces and common camouflage materials ^[10]. (a) Live face; (b) paper mask; (c) silicone mask; (d) raw silicone material

Fig. 10. Real-time spectral imaging results of an outdoor driving scene^[26]

Table 1. Running time of different spectral imaging methods