The Application Of Several Special Beams In Dark Field Digital Holographic Microscopy Imaging

Dark-field digital holographic microscopy is a novel microscopic imaging technique that combines the traditional digital holography microscopy with dark-field imaging. In recent years, since it has the properties such as non-contact, non-destructive, fast processing, high resolution and high contrast, which is widely used in metal nanoparticle measurement, observation of biological cells, medical diagnosis and other fields.Firstly, the paper elaborates the basic principles of dark-field imaging and digital holographic microscopy, and discusses three algorithms for diffraction propagation, named Fresnel diffraction integral method, Huygens Convolution method, and angular spectrum method. By comparing the three algorithms, the advantages and disadvantages of the three reconstruction algorithms and applications are explained.Secondly, both the adjustability of the size of the halo of Laguerre-Gaussian vortex beam and the quasi-nondiffracting property of the beam are theoretically analyzed and numerically simulated. The impacts of the diffraction property of Gaussian beam and Laguerre-Gaussian vortex beam on the imaging are illustrated. We propose a dark-field microscopy by using Laguerre-Gaussian vortex beam illumination, of which the basic principle and the corresponding setup are given in this paper. The polystyrene spheres with the size of 960 nm and 800 nm are utilized as objects in the experiment, respectively. By comparing the results of images under bright-field illumination with those under dark-field illumination, it is proved that the resolution of dark-field microscopy imaging under Laguerre-Gaussian vortex beam illumination is improved and the contrast of its images is enhanced accordingly.Finally, we discuss a dark-field digital holographic microscopy (DHM) by using several special beams illumination. The impacts of the diffraction property of Laguerre-Gaussian vortex beam and Airy vortex beam on the imaging are theoretically analyzed and numerically simulated, and the self-convergence property of Airy vortex beam is also discussed. The dark-field DHM imaging under annular illumination of several special beams are theoretically analyzed and corresponding systems are established. The polystyrene spheres with the size of 500 nm and 390nm are utilized as objects in the experiment, respectively. By comparing the results of reconstructed images under Airy vortex beam illumination with those under the other illumination, it is proved that the resolution of dark-field DHM under Airy vortex beam illumination is higher than 390nm and the contrast of its reconstructed images is enhanced accordingly.