Axial super-resolution imaging by interference in point scanning microscope

Due to the diffraction features, the illumination light will form a Gaussian profile point spread function around the microscope objective lens focus position. The size of the PSF limits the resolution of the microscope. In order to compress the PSF and improve the resolution of the point scanning microscope, the compression characteristics of point scanning microscopy point spread function (PSF) with mirror reflection interference enhancement will be discussed. Based on vector diffractive integral method, the electric field at the objective lens focal point with a mirror reflection interference has been simulated. A special sample with a mirror as the slide glass is imaged on a confocal microscope. Simulation and experimental results show that the axial full width at half maximum(FWHM) of the illumination PSF is reduced to 22% via mirror reflection interference enhancement, and the signal intensity increased by 3.4 times. With no additional complexity, the mirror-assisted excitation confinement enhanced the axial resolution 4.5-fold.It is also found that the effective range of mirror reflection interference enhancement is proportional to the wavelength and inversely proportional to the square of the numerical aperture. In point scanning microscopy, mirror reflection interference enhancement can effectively achieve the super-resolution in the axial direction and improve the signal background ratio of images.