Microsphere-assisted phase-shifting profilometry

Abstract

In the present work, we have investigated the combination of a superresolution microsphere-assisted 2D imaging technique with low-coherence phase-shifting interference microscopy. The imaging performance of this technique is studied by numerical simulation in terms of the magnification and the lateral resolution as a function of the geometrical and optical parameters. The results of simulations are compared with the experimental measurements of reference gratings using a Linnik interference configuration. Additional measurements are also shown on nanostructures. An improvement by a factor of 4.7 in the lateral resolution is demonstrated in air, thus giving a more isotropic nanometric resolution for full-field surface profilometry in the far field.

High Resolution Surface Metrology Using Microsphere‐Assisted Interference Microscopy

“…Nonetheless, it has been frustrating that while the axial resolution is so high, the lateral resolution has remained limited by diffraction to values that are several orders of magnitude worse as in classical microscopy, even by working in the near UV . Recently, several teams have succeeded in reducing this difference in scale by combining microsphere‐assisted microscopy with interferometry to greatly improve the lateral resolution in surface roughness measurement . Performing interferometry through the glass microsphere allows surface profiling with improved lateral resolution.…”

“…FWHM of the point spread function of the microsphere as a function of λ from similar results to those in Figure to show the lateral resolution theoretically attainable for a given wavelength for a glass microsphere of 24 μm diameter. Reproduced with permission . Copyright 2017, Optical Society of America.…”

“…Numerical simulation of the optical phenomena involved in microsphere imaging showing the normalized real part of the electric fields from 2 point sources separated by 800 nm propagated through a 25 μm diameter soda lime silica glass microsphere in air for λ = 400 nm. Reproduced with permission . Copyright 2017, Optical Society of America.…”

“…The white arrows indicate the propagation direction of the EM field and the previous positon of the microsphere is indicated by the dotted circles. Reproduced with permission . Copyright 2017, Optical Society of America.…”

Illumination conditions in microsphere‐assisted microscopy

“…A possible explanation may be the generation of optical aberrations (e.g. defocus or spherical aberrations) due to the perfectly spherical shape of the microsphere (Guo et al ., ; Perrin et al ., ). Moreover, the numerical analysis of the frequency response of the microsphere alone, represented by the blue dotted line in Fig.…”