Disclosed is an optical imaging system having improved resolution. The disclosed optical imaging system may include a substrate on which a specimen dyed with a fluorescent material is placed; a multiple number of dimer nanopillars formed on the substrate; and a light source unit configured to provide a light source to the substrate, where the light source unit provides an incident ray to the substrate from a first light source to excite the fluorescent material, and afterwards turns off the first light source and activates a second light source and a third light source simultaneously to provide incident rays to the substrate. The disclosed optical imaging system can provide a resolution that is higher than the diffraction limit.