Fig. 1. Two basic mechanisms for improving resolution^[10]. (a) Frequency compression; (b) frequency shift^[11]

Fig. 2. Imaging principle of SAM. (a) Schematic of SAM system^[12]; (b) synthetic spectrum^[18]

Fig. 3. Flow chart of FPM^[20]

Fig. 4. Imaging principle of SIM. (a) Moire fringe effect of illuminating the sample with the sinusoidal structured pattern; (b) expansion of passband in one direction; (c) expansion of passband in two-dimensional orientation

Fig. 5. Comparison between SPIN and SPADE system^[34]. (a) Schematic of SPIN system; (b) schematic of SPADE system

Fig. 6. Principle of SSIM^[36]. (a) Nonlinear relationship between fluorescent emission rate and illumination intensity; (b) intensity distribution of effective emission pattern; (c) spectrum distribution of effective emission pattern

Fig. 7. Working principle of NFOMM^[39]. (a) System schematic; (b) phase coding and corresponding system effective PSFs and OTFs; (c) normalized intensity profiles of modulated foci; (d) simulated imaging results

Fig. 8. Principle of multi-focus saturated virtual modulation^[40]. (a) Scanning process; (b) multi-spot complex detection system; (c) procedure for virtual modulation

Fig. 9. Schematic of parallel detection system^[45]. (a) Scheme comparison between confocal (top) and parallel detection (bottom) detection paths; (b) position distribution of each detector in parallel detection module; (c) representative images obtained by parallel detection system

Fig. 10. Schematic of VIKMOM and its decoding procedure for super-resolution image recovery^[52]. (a) Principle of imaging system; (b) decoding procedure for super-resolution image recovery

Fig. 11. Scheme of microfibre based super-resolution imaging system^[53]. (a) 3D structure of experimental system; (b) relative positions of microfibre, sample, and focal plane of objective lens; (c)--(e) far-field imaging obtained when the microscope objective lens is focused on different positions

Fig. 12. Schematic of evanescent wave induced frequency shift for super-resolution microscopy^[54]

Fig. 13. Principle of NWRIM^[56]. (a) Schematic illustration of NWRIM; (b) super-resolution imaging results of various two-dimensional sub-diffractive structures using NWRIM

Fig. 14. Absence of spectral components caused by excessive SPP frequency shift step