Fig. 1. (a) Schematic diagram of a 4f optical system for edge detection; Amplitude response (b) and phase response (c) for the transmitted RCP light with LCP light normal incidence

Fig. 2. (a) The quasi-continuous metasurface device for edge detection; (b) Higher magnified image of the designed sample; (c)~(f) Schematic diagram of the design process for one quasi-continuous nanostrip

Fig. 3. (a) The star image to be detected; (b)~(h) The images for the target edge at the incident wavelengths of 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm and 1000 nm

Fig. 4. Energy efficiency of the quasi-continuous (blue pentagrams) and discrete (red diamonds) metasurface edge detection devices with different incidence wavelengths; The gray area represents the cross-polarization energy efficiency with changing the equivalent grating’s period