Fig. 1. Principle of laser scanning lateral differential confocal microscope. (a) Confocal posotion; (b) front-focal position; (c) back-focal position

Fig. 2. Simulation results of laser scanning lateral differential confocal microscope. (a) Three-dimensional intensity response; (b) axial response curve

Fig. 3. Schematic diagram of spot amplification measurement. (a) Before amplification; (b) after amplification

Fig. 4. Schematic diagram of D-shaped aperture eccentricity

Fig. 5. Control signal waveform after optimized design

Fig. 6. Simulation analysis results of lighting spot scanning position. (a) Triangular wave drive signal; (b) arc tangent drive signal

Fig. 7. Structural diagram of laser scanning lateral differential confocal microscope

Fig. 8. Laser scanning lateral differential confocal microscope (LSLDCM)

Fig. 9. Experimental results of polynomial fitting coefficient calibration. (a) Measurement result; (b) fitting result

Fig. 10. Axial resolution measurement result. (a) Normalized light intensity response; (b) height of tested sample

Fig. 11. Lateral resolution test results. (a) 500 nm; (b) 400 nm; (c) 360 nm

Fig. 12. Measurement results of standard etching grating. (a) AFM; (b) LSLDCM

Fig. 13. Measurement results of semiconductor wafer. (a) 9.569 μm (LSLDCM); (b) 10.031 μm (LSLDCM); (c) 9.618 μm (OLS4000); (d) 10.044 μm (OLS4000)