Research On Lateral Super-resolution Methods With Radially Polarized Illumination For Confocal Microscopy

Confocal microscopy is a kind of three-dimensional optical microscopy technology which is used for measurement of micrometre and nanometre scale with its distinctive axial optical sectioning property. It has features such as high precision, non-contact, no damage to the measurement surface. Therefore, it has been widely used for measurement in optics, microelectronics, biotechnology and other fields. With the development of science and technology, the three-dimensional micro-structure measurements gradually transits from submicron to nanometer scale. It is urgent to improve the lateral resolution of a confocal system.The purpose of the study is to improve lateral resolution of confocal microscopy by using radially polarized illumination. The mathematical model of confocal microscopy with radially polarized beam is established, based on the vector diffraction theory. The system performance is analysed by means of mathematical simulation. This paper also uses polarization modulation and pupil filter modulation to improve transverse resolution of confocal microscopy. The following are the major issues addressesed in this study:Firstly, the diffraction light field of radially polarized illumination is analyzed by basing on Richards-Wolf’s vector diffraction theory. It discussed how do numerical aperture of lens and amplitude distribution of the incident beam affect the diffraction light field. As well the tight focusing property of radially polarized beam is analyzed by composing with linearly polarized light.Secondly, the theoretical mathematical model of confocal microscope with radially polarized beam is established, according to the vector diffraction theory. It considered the image formation of dielectric point scatterers in confocal polarization microscopes. Numerical results are given by simulation, which we can use to analyze the light field distribution of detection space and system image properties.Finally, it can solve the problem of a doughnut-shaped spot in detection space to use a polarization mode converter into the detection optical of confocal microscopy with radially polarized illumination. This paper analyzes theoretically this method by adding the matrix description of polarization mode converter into theoretical model of confocal microscopy with radially polarized illumination. It also analyzes the influence of objective lens numerical aperture and pinhole size on polarization modulation. A design method of annular binary phase filter is proposed to modulate phase of radially polarized illumination, which can improve the transverse resolution of a system.The methods of lateral super-resolution of confocal microscopy with using radially polarized illumination was studied in the thesis. The theoretical mathematical model of confocal microscope with radially polarized beam is established. It erases the problems of a doughnut-shaped spot in detection space through polarization modulation. The signal strength of pinhole has been enhanced, and a 7.3% improvement in transverse resolution have been achieved compared with linearly polarized light. The FWHM of lateral response curve reduces to 0.465 l from 0.51 l by pupil phase modulation. Through this method, the lateral resolution have raised by 15.5% compared with confocal microscopy with linearly polarized light. This paper shows that lateral super-resolution of confocal microscopy can be achieved by using radially polarized illumination. The research of this article provided theoretical basis for application of radially polarized beam in confocal microscopy.