Wide-field profiling of smooth steep surfaces by structured illumination

• We propose a structured illumination wide-field sectioning method for smooth steep surfaces profiling.
• The axial response curve shifts half thickness from ideal axial position without affecting reconstruction results.
• The proposed method extends the application scope of conventional structured illumination wide-field microscopy.

We propose sectioning structured illumination wide-field microscopy (SSIWM) combined with the coating of a readily removable thin fluorescent film (RTFF) for smooth steep surfaces. The profiling of smooth steep surfaces is difficult to achieve using conventional optical systems because these surfaces reflect lights away from the collective lens. In particular, when the angle between optical axis and the normal line of the surface is larger than sin−1(NA), no light reflected from the area can be collected by the collective lens. The proposed method employing an RTFF to the SSIWM can overcome the poor collection barrier and be used to measure the shape of the surface owing to the isotropic incoherent scattering property. Additionally, conventional SSIWM is a promising wide-field imaging technique with high axial sectioning ability and low cost; however, it cannot be introduced to measure a reflective surface because of the non-sectioning characteristic in using a laser (coherent). However, the proposed method can extend the application scope of SSIWM owing to the incoherent property of the coating surface. Simulations and experimental results are presented to show the validity of the proposed method.