Profilometry With Enhanced Accuracy Using Differential Structured Illumination Microscopy

The conventional structured illumination microscopy (SIM) reconstructs the surface through determining the focal position from the modulation depth response (MDR) using the Gaussian fitting. In this letter, an innovative differential structured illumination microscopy (DSIM) is developed. This technique exploits the position at the linear portion of the MDR to achieve the measurements. To extract this position, two detectors are used to generate the differential modulation depth response (DMDR). After that, the zero point of the DMDR for each pixel is extracted by the linear fitting technique. The experiments and theoretical analysis are elaborated to verify that the DSIM can greatly enhance the axial accuracy, providing that the potential to be applied in high-precision measurement.