Optical Super-resolution Microscopy Based On Sub-diffraction Quasi-non-diffracting Illumination Beam

Optical microscope has been widely used in scientific research and industrial areas since its invention,such as biomedicine,pharmacy,microbiology,metallurgy and so on.However,a traditional optical microscope is restricted by diffraction effects,and it cannot achieve image resolution beyond the diffraction limit.Therefore,breaking the diffraction limit and achieving super-resolution optical microscopy has been a research hotspot in recent years.The existing super-resolution optical microscopy technique can be divided into near-field and far-field according to the working distance.The ultra-short working distance restricts the application of near field super-resolution optical microscopy,while,the commonly used far-field super-resolution optical microscopy is fluorescence label based.It requires pre-processing and suffers from photo-toxicity.In this work,we proposed a super-resolution microscope based on sub-diffraction quasi-non-diffracting(QND)illumination beam,and it can achieve label-free far-field imaging,which has a good application perspective.Now list the main work of this article as following:(1)The research background,application prospective and overseas and domestic research status of super-resolution microscopy were introduced.The features of these super-resolution microscopy were analyzed,and then we proposed the research objective and research content of our work.(2)The theory of point spread function was introduced and the diffraction limit of the point spread function of traditional optical system was explained.Then we briefly introduced the confocal microscope system and the theory of normalized angular spectrum compression.(3)The transmission function of binary phase focusing lens was introduced.The method of normalized angular spectrum compression(NASC)was applied to design a Fresnel lens to generate QND beams at wavelengths of 632.8nm and 405 nm,respectively.According to the numerical calculation,for the lens at the wavelength of 632.8nm,the working distance is 234?,the depth of focus is 100?,the smallest full-width-at-half-maximum(FWHM)is 0.4?;for the lens at the wavelength of 405 nm,the working distance is 314?,the depth of focus is 144?,the smallest ful-width-at-half-maximum(FWHM)is 0.39?.Both of lens achieve super-oscillation.(4)The module of optical device,working process and mechanical framework were designed based on the working principle of the super-resolution microscope based on QND illuminationbeam.Moreover,the main modules of upper computer system and the image construction procedure were introduced.(5)The microscope system based on super-resolution lenses were built up for super-resolution testing.The two super-resolution lens were tested in the microscope system and experimental results showed the lens for the working wavelength of 632.8nm achieved an optical needle with a length of 92? and a working distance of 224,and a minimum FWHM of 0.41?;the lens for the working wavelength of 405 nm achieve a super-resolution optical-needle of 59? and a minimum FWHM of 0.43?.In the super-resolution microscopy experiments,label-free far-field super-resolution of 0.28?(180nm)and 0.32?(130nm)were realized at wavelengths of 632.8nm and 405 nm,respectively.