Figure 8: Resolution calibration of SSUM.

(a) Insets are two sets of SEM images and SSUM results of the structures in the CPU, in which the dashed line (SSUM-1) and dotted line (SSUM-2) are used to estimate the resolution. The solid curve represents the calibrated convolution result. (b) Definition of NID. (c,d) The influence of Δz on the resolution under different illumination conditions, that is, (c) coaxial illumination and (d) partial and inclined illumination. Δz is defined in Fig. 7a, and the distance between microsphere and microscope objective does not change. The constants (Con) are the values applied to calculate the resolution (λ/Con). The data used to calculate NID (scatter data) are extracted from the experimentally measured cross-sections of the structures on the CPU chip (see the SEM image in the inset of c) using a 60 μm-diameter microsphere similar to that in Fig. 7d,e. In c and d, the solid curves, representing super-resolution, and dashed curves, representing the diffraction confinement, are achieved from the calibrated convolution results, for example, the solid curve in a. The incline angle, as defined in Fig. 7c, was set to ∼70° for the experiments under partial and inclined illumination. Scale bars, 1 μm (a).