Fast structured illumination microscopy with reflectance disturbance resistibility and improved accuracy

The conventional fast structured illumination microscopy (FSIM) without vertical scanning has been proposed by Lee for fast surface profiling. Nevertheless, this method is vulnerable to nonuniform surface reflectivity which is generally caused by the different reflection characteristic of hybrid materials and the environmental fluctuations. Consequently, traditional IFSIM cannot be used in the profile measurement for the samples with surface heterogeneity. In this paper, an improved FSIM configuration (IFSIM) is explored for improving the axial accuracy and suppressing the disturbance of the reflectivity. With this technique, a sinusoidal pattern produced by the digital micro-mirror device (DMD) is illuminated onto the sample. The reflected patterns are captured by two charge-coupled devices (CCDs) that are separately placed in and behind or before the focal plane. The subtraction and sum values of the two axial modulation response curves (AMRs) are divided as the new response function, which effectively suppresses the influence of the inhomogeneous reflectivity. Both wide dynamic range and enhanced axial accuracy can be selectively obtained by controlling the defocusing amount of the two differential detectors. The theoretical analysis and experiments are conducted to verify the feasibility of this method.