Xinzhu Xu
BME PhD Proposal Presentation
Date: 2022-11-28
Time: 11.29 8:00 AM-10:00 AM (Beijing Time) / 11.28 7:00 PM-9:00 PM (EST)
Location / Meeting Link: https://emory.zoom.us/j/91692336261?pwd=ZkZFMlhjQXE4c2loNXJ3a2VEeCtidz09
Committee Members:
Peng Xi, PhD (Advisor) Shu Jia, PhD (Co-Advisor) Yujie Sun, PhD Xunbin Wei, PhD Changhui Li, PhD
Title: PSF engineering and ultrahigh framerate parallel detection super-resolution fluorescence microscopy
Abstract:
It has been 150 years since Abbe established the concept of the diffraction limit in 1873 to the breakthrough of the diffraction limit by super-resolution fluorescence microscopy. The point spread function (PSF) is the most crucial concept in diffractive imaging systems. By modulating the amplitude or phase of the incident and diffracting it through the objective lens, the desired fine imaging target is achieved. Lateral PSF modulation starts with stimulated emission depletion fluorescence microscopy (STED) enabling further reduction of PSFs beyond the diffraction limit; while structured illumination microscopy (SIM) uses sine/cosine distributed high-contrast interference fringes to act on the sample to generate High-frequency information, and then spectrum extracting and splicing in the Fourier domain to expand the optical transfer function (OTF) in the imaging system, achieving super/high resolution. The emergence of the microscopy imaging system modulated by the axial PSF is due to the demand for large depth imaging. Because light scatters and refractive index mismatches in the depth of the sample, the PSF is severely distorted at such a depth and cannot maintain required basic configuration in the imaging area. Therefore, modulating the non-diffraction PSF along the propagation direction in an appropriate way is the basis for solving depth imaging. The existing axial PSF modulation has two purposes. One is to compress its size along propagation to perform super-resolution imaging: after combining with adaptive optics to correct the distortion in the deep sample, it can work in the whole objective working distance. Super-resolution imaging can be achieved at any depth within this distance, however, due to the high phototoxicity and high photobleaching characteristics, this usefulness is very limited; the other is to extend the PSF along the axial, which is convenient to obtain a deeper excitation range while ensuring that the quality of PSF remains unchanged or better, making the excited detection volume large and deep enough to achieve giant depth imaging. In this work, three fluorescence microscopy systems are constructed from the lateral and axial PSF modulation aspects with the support of high-speed optics scanning modulators. The first system is a parallelized exposure-readout ultrahigh framerate SIM system. The hardware frame rate of the existing SIM system is determined by the camera frame rate and the response frequency of the light field modulation device. Due to the intrinsic characteristics of the camera, the existing system wastes readout time to ensure that the picture frames do not crosstalk. We innovatively take advantage of this time to boost the SIM system from a hardware perspective in an ultrahigh frame rate through precise signal synchronization of cameras and these modulation scanning devices. Combined with advanced algorithms, it can provide more possibilities for dynamic life process observation. Meanwhile, starting from the second point of axial modulation, in the latter two systems, the Bessel non-diffraction modulation and Gaussian axial-tiling modulation are performed on axial PSF, which resolves the problem of high average power distribution along both the lateral and the axial in STED, and the problems of limited frame rate and all-optical confocal detection mode in ISM-LSM, respectively.
