Research On Super-resolution Microscopic Imaging Method Based On Optical Superoscillation

Recently the developments of optical super-resolution technology have played an important role in fabrication,microscopic imaging,information storage in nano-scale,especially in super-resolution microscopy imaging.A variety of super resolution imaging techniques were proposed.As one of the far-field superresolution imaging methods,superoscillatory super-resolution imaging technology does not require no evanescent wave or fluorescent labelling.However,the processing precision as high as sub-wavelength in fabricating the key component and the limited working distance as short as several ten microns had significantly limited the applications of optical superoscillation.Moreover,up till now,the applications of optical superoscillation are all based on constructing superoscillatory point spread function(PSF)with a local spot which is smaller than the diffraction limited PSF.It is necessary to develop novel applications for optical superoscillation.To address these issues,we combined the superoscillatory optical field and traditional microscopy imaging system,modulated frequency spectrum at fourier plane,by Schelkunoff approach,with a spatial light modulator DMD.This method efficiently avoided nano-precision fabrication of optical elements and improved the work distance of superoscillatory optical field.Furthermore,a superresolution imaging method named superoscillatory sub-diffraction structured illumination was proposed.This method not only breakthrough the limited resolution of traditional SIM without nonlinear saturated absorption,but also resolved the problem in imaging transparent samples and in targeting studying of sub-cellular structure.This thesis mainly investigated superresolution imaging method based on superoscillatory PSF method and superreolution imaging method by superoscillatory sub-diffraction structured illumination.What have done in this thesis listed as follows.(1)Fundamental theory of superoscillation was studied.The frequency domain transmitted property of optical wave and the low-pass filtering characteristics of optical imaging system were analyzed by transmitted wave theory,and the band-limited frequency domains in optical imaging process was explained.After investigation on the theory of superscillication,a calculation method and its scope of superoscillatory optical field by vector angular spectrum theory was provided.Finally,local superresolution superoscillatory optical field was achieved by an amplitude-modulated DMD in a 4f spatial filter system.It demonstrated that there is no higher frequency component than diffraction limited frequency in superoscillatory optical field.(2)In the studies of super-resolution imaging method based superoscillatory PSF,there are two ways in achieving super-resolution imaging by superoscillatory PSF method,i.e.spot scanning or wide field imaging.Firstly,study on the super-resolution focused method by superoscillation was investigated,the optimized design of superoscillatory optical field under different numerical aperture were completed.The energy distribution of superoscillatory optical field was analyzed by Schelkunoff approach.Furthermore,the modulation of real-valued transmission was accomplished by the modified dual-pixels coding method on DMD.On this basis,super-resolution focusing based on superoscillation with small numerical aperture had been generated experimentally.At last,in order to give an unprecedented insight into the essence of the superoscillatory super-resolution imaging,the artifacts problemin superoscillatory wide imaging under certain conditions was raised and analyzed according to the simulations of the wide field in super-resolution superoscillatory imaging.(3)In order to overcome the limited resolution of linear SIM imaging without nonlinear saturated absorption,a method named superoscillatory sub-diffraction structured illumination imaging was put forward,in which SIM and superoscillation were combined.The design of superoscillatory optical field was used in SIM imaging.The super-resolution images of samples with different spatial frequency under superoscillatory SIM illuminated were simulated,and the results demonstrated that superoscillatory SIM illumination was capable to break the resolution limit of traditional linear SIM illuminated imaging.The influence of the homogeneity of ROI area to the quality of SIM reconstruction super-resolution images was further analyzed.Then,a parameter R was defined to evaluate the homogeneity and acceptable range.Finally,the frequency extension property of this method was analyzed.The problem of the missing cone in the optical transfer function was discussed.This missing cone will occur when the superoscillatory SIM frequency was above two times the diffraction limited frequency.A solution for this problem was then put forward,and the simulations demonstrated that the missing part can filled completely.