Research On Polarization Modulation To Further Improve Imaging Resolution

In the technology of fluorescence polarization modulation,when rotating the linear polarized light,differently oriented fluorescent dyes emit periodic signals peaking at different times.Fluorescence intensity changes in response to the square of the cosine function,which increases the sparsity of the acquired image.Taking advantage of the sparsity of the image,the polarization modulation and demodulation algorithm reconstructs the image to obtain a further improvement in resolution.In this thesis,using the fluorescence polarization modulation to further improve the resolution in the microscopic imaging system is studied.The study of theoretical simulation analysis of the method of fluorescence polarization modulation was carried out.On the basis of the above,the experimental research on the application of fluorescence polarization modulation to wide-field fluorescence imaging was carried out.At the same time,it is proposed that the polarization modulation phenomenon is applied to the super-resolution imaging system of stimulated emission depletion microscopy to further improve the resolution of the super-resolution system.The main work of the paper includes:(1)The theoretical research of fluorescence polarization modulation to further improve the resolution was carried out.With the response of the fluorescence intensity to the polarization of the laser and the enhancement of the sparsity of fluorescence image by the modulation of the polarization,the super-resolution imaging of polarization modulation is explored.In this thesis,fluorescent dipole pairs with different distances and different directions are simulated to be excited by laser with different polarization,a series of fluorescence images with different polarization angles is obtained.The demodulation algorithm is used to perform the image reconstruction.The results show that fluorescence polarization modulation can increase image sparsity and achieve resolution beyond the diffraction limit.(2)In this thesis,the experiment of the resolution enhancement by the fluorescence polarization modulation is completed.A wide-field microscopy imaging system based on fluorescence polarization modulation was constructed.In the system,Atto590 fluorescent dye was used as the sample,and the image sequence under different polarization angles was obtained in the experiment.The reconstruction algorithm was used to reconstruct the image,which further enhanced the resolution ability.(3)Theoretical research on the application of fluorescence polarization modulation to the super-resolution system of stimulated emission depletion microscopy is carried out.Resolution enhancement of polarization modulation depends on the orientation difference between the aimed fluorescent molecules and the surrounding molecules.In this thesis,the technique of polarization modulation is applied in stimulated emission depletion super-resolution microscopy.The extremely small excitation focal spot created by the high resolution of the super-resolution system,less fluorophores contribute to the polarization response.In this way,the sparsity of the fluorescence can be enhanced,which makes it easier to achieve enhanced resolution of polarization modulation.In this thesis,the effects of the number of polarization angles,relative angle distribution of fluorescent dipoles and image noise of different test samples on the reconstructed images of Stimulated Emission Depletion microscope via polarization modulation are analyzed.