Super-resolution imaging by microsphere-assisted optical microscopy

Microsphere-assisted optical microscopy achieved the nano-scale resolution for the imaging. Some parts of evanescent waves produced by nano-structures can be transformed into propagating waves with the help of microsphere. In this paper, we develop the equations of the resolution and field of view in microsphere imaging system related to the radius and refractive index of microsphere. Through analysis the highest spatial frequency, the resolution reduces quickly with the increase of the radius when the radius is less than 10 mu m. The resolution reduces slowly with the increase of the radius when the radius is more than 10 mu m. The resolution improves with the increase of refractive index. The size of the focus spot of microsphere is simulated numerically. The simulations are in good agreement with the theoretical prediction about the microsphere-assisted microscopy. Finally, the super-resolution capability of the microsphere has been verified by the experimental results. The results are useful for the practical design of the microsphere-assisted optical microscopy.