Fig. 1. Principle and scheme of the side-assisting microscope. (a) Principal optical setup including three parts: (1) LED collimation stage; (2) ultrahigh vacuum chamber; (3) microscopic imaging. (b) Photo of the experimental setup in a clean laboratory air environment.

Fig. 2. System spatial resolution testing. (a) Image of a USAF target (groups 6 and 7); (b) region for experimenting; (c) and (d) assessed resolution of the side-assisting microscope system along the solid line (X and Y) of (b), respectively.

Fig. 3. System field curvature testing. (a) Two-dimensional image of a 20 µm-period grating with a vertical orientation. The inset in (a) shows a microscopic image of the grating. (b) The intensity profile (blue line) extracted along the white solid line in (a) and the first derivative of the line cut (red line); (c) FWHM corresponding to the peaks (black line) and troughs (red line) of the first derivatives of the intensity in (b).

Fig. 4. System distortion testing. (a) Standard grid pattern of 100 µm; (b) experimental result of standard grid pattern; (c) intensity profiles of standard grid (black lines) and experimental result (red lines) plotted via the horizontal yellow solid lines in (a) and (b); (d) intensity profiles of standard grid and experimental result plotted via the vertical yellow solid lines in (a) and (b); insets in (c) and (d) show the distortion of X direction and Y direction, respectively.

Fig. 5. Experimental results and quantitative analysis. (a) Sample morphology and region for experimenting; (b) result of square-shaped area; (c) and (d) resolution measured along the two line cuts in (b), respectively; (e) result of central stripe area with our setup; (f) result of conventional high-resolution optical microscope at 40×.

Fig. 6. Microscope images of graphene flake. (a) Conventional optical microscope image of the sample at 25×; (b) microscope image with the proposed setup.