Resolution improvement of dark-field microscopy via microparticle near-field illumination

In this Letter, a novel, to the best of our knowledge, approach to improve the imaging resolution of dark-field microscopy is proposed and demonstrated. Inspired by an existing super-resolution imaging method based on near-filed illumination using a prism or microfiber, a microparticle-generated full-direction evanescent field for sample illumination was demonstrated to achieve a multi-orientation near-field illumination in one snapshot and to obtain a super-resolution image by spatial frequency shifting. The ultimate resolution and the additional magnification factor of this method were analyzed theoretically. Imaging experiments were carried on a standard microscope calibration target MetroChip and a Blu-ray disc characterized by subwavelength microstructures. High-imaging resolution was demonstrated experimentally, and two novel illumination modes were proposed to overcome imaging direction selectivity. Our work opened up a new perspective of super-resolution imaging with near-field illumination.