Fig. 1. Flow chart of compressed sensing

Fig. 2. Computational spectrometer based on liquid crystal electro-optic effect. (a) Schematic diagram of liquid crystal variable phase retarder spectral measurement system and reconstructed spectra^[80]; (b) Schematic diagram of liquid crystal tunable filter structure and reconstructed spectrum^[81]

Fig. 3. Computational spectrometer based on FP cavity. (a) Schematic diagram of piezoelectric FP cavity spectral measurement system and reconstructed spectra^[52]; (b) Schematic diagram of FP microarray filter and two different spectral responses of FP cavity and reconstructed spectra^[57]

Fig. 4. Computational spectrometer based on optical thin film. (a) Schematic diagram of thin-film filter array spectrometer and its random transmittance^[58]; (b) Schematic diagram of multilayer dielectric filter structure and two different transmission spectra and reconstructed spectra^[60]

Fig. 5. Computational spectrometer based on photonic crystal. (a) Schematic diagram of photonic crystal spectrometer and reconstructed spectra of LED^[64]; (b) Schematic diagram of Si-hole photonic crystal plate structure and its transmission spectrum and multiple Lorentz line reconstructed signals^[65]; (c) Spectral signal recovery rate and relative error of different observation matrices and reconstructed spectra with sparsity of 10 and 20^[66]

Fig. 6. Computational spectrometer based on quantum dots. (a) Structure and transmission spectra of colloidal quantum dot filter and reconstructed spectra of random and monochromatic light^[67]; (b) Schematic diagram of NIR quantum dot computational spectrometer and reconstructed spectra^[68]; (c) Schematic diagram of perovskite quantum dot spectrometer and reconstructed spectra^[69]

Fig. 7. Computational spectrometer based on nanowire. (a) Schematic diagram of composition gradient nanowire spectrometer and reconstructed spectra^[78]; (b) Schematic diagram of silicon nanowire array structure and reconstructed spectra^[79]

Fig. 8. Computational spectrometer based on plasmon. (a) Schematic diagram of plasmon filter array spectral sensor and reconstructed spectra ^[72]; (b) Schematic diagram of aluminum nano-grating array structure and its spectral response curve and reconstructed spectrum^[73]; (c) Schematic diagram of on-chip mid-infrared gas sensor array and reconstructed spectrum of CO₂ molecular absorption^[74]; (d) Schematic diagram of gold nano-square array and reconstructed spectrum of polyethylene^[75]; (e) Schematic diagram of gold nano-disk array structure and reconstructed spectra