Parallel multi-slit modulation and decoding technique for high-resolution surface measurement in structured illumination microscopy

•Novel parallel multi-slit modulation and decoding technique for brightfield reflection optically-sectioned structured illumination microscopy.•Specially-designed decoding algorithm based on out-of-focus background estimation ensures high-quality optical sectioning independent of illumination pattern frequency.•Incoherent structured illumination microscopy provides consistent high-resolution measurements for a wide range of engineering surface topographies. Optically-sectioned structured illumination microscopy (OS-SIM) is an important tool for biological imaging and engineering surface measurements. However, in the current OS-SIM systems, the dependence of the sectioning strength on illumination pattern frequency hinders the achievement of consistent high axial resolution for various surface topography measurements. In this paper, we develop a parallel multi-slit modulation and decoding technique for OS-SIM, called PMMD-OS-SIM, to solve the existing dependence problem. Specifically, a set of high-contrast parallel multi-slit illumination patterns are projected onto the sample to modulate the surface height information. And then, a specially-designed decoding algorithm is applied to the modulated patterns for high-quality optical sectioning. By effectively combining the above modulation and decoding techniques, the optical-sectioning strength of PMMD-OS-SIM is decoupled from the illumination pattern frequency, thereby facilitating consistent high-resolution measurements for a wide range of surface topographies. The validity of the proposed method is demonstrated by measurement experiments performed on various test samples.