Measurement of nano-particles size by evanescent interference field with conventional optical microscope

摘要

The size of a particle smaller than the diffraction limit is measured using a conventional optical microscope by adopting a standing wave evanescent field illumination. The scattering intensity from a nanoparticle is periodically modulated by shifting the intensity fringes of standing evanescent field. By measuring the intensity variation of scattered light during one cycle of modulation, particle sizes can be easily estimated. Furthermore, this technique has weak dependence on the material of particles. From the experimental result, the particle size ranging from 20 to 250 nm is successfully determined. This technique offers a low-cost size measurement for nanoparticles.