Single-exposure modulation-based structured illumination microscopy using spatial area phase-shift

In structured illumination microscopy (SIM) for three-dimensional (3D) measurement, the vertical scanning position with the maximum modulation is implemented to reshape the surface topography. Generally, to obtain the modulation distribution for each scanning position, the modulation decoding algorithms mainly include temporal phase-shifting (TP) method and frequency analysis technique. In TP method, at least three images with a fixed phase-shift are required, which results in low efficiency and complex phase-shifting mechanism. Frequency analysis technique can realize modulation distribution from single image, but the high frequency information of the sample will be inevitably lost. In this paper, we propose a spatial area phase-shifting reconstruction method which requires only one exposure to decode the modulation distribution. In this technique, n pixels from one period of illuminated pattern are used to replace the corresponding n images in the temporal phase shift. Through combining the phase information of each pixel with the least square algorithm, the modulation distribution is achieved. The proposed method can achieve an accurate 3D reconstruction. Also, the high frequency information of the sample can be effectively retained compared with frequency analysis method. The simulations and experiments are conducted to verify the feasibility of this method, demonstrating the potential to be applied in high precision, complex surface and real-time measurement.