Applicability of deconvolution and nonlinear optimization for reconstructing optical images from near-field optical microscope images

We have made a computer reconstruction of a nanometric optical image of a sample from an observed near-field optical image. The near-field microscope image used for investigation was obtained numerically in three dimensions with the finite-difference time-domain (FDTD) method. The sample is dielectric substrate containing nanometric two strips made of dielectric or metal. Deconvolution with non-negativity constraint is used to reconstruct the nanometric structure of dielectric strips, while nonlinear optimization is used to reconstruct the metallic strips. The difference in choice of reconstruction method between two samples comes from the difference in degree of interaction or multiple scattering of the sample structure and the probe. It is shown in the results, the resolution limit attainable in deconvolution is as fine as the size of aperture of probe.