Fig. 7

CWT results of different spatial frequency feature: (a) Low- frequency surface with a wavelength of 100 μm, (b) Mid- frequency surface with a wavelength of 100 μm, (c) High- frequency surface with a wavelength of 100 μm. (d) Low- frequency surface with a wavelength of 74 μm, (e) Mid- frequency surface with a wavelength of 74 μm, (f) High- frequency surface with a wavelength of 74 μm. (g) Low- frequency surface with a wavelength of 53 μm, (h) Mid- frequency surface with a wavelength of 53 μm, (i) High- frequency surface with a wavelength of 53 μm.