Digital Holographic Microscopy And Experimental Study Of Obtaining Axial Displacement

The system of digital holographic microscopy is set up and it can be used to observe and measure the information of particles in solution. The laser illuminates particles in the sample cell and the transmitted light forms the object wave which is magnified and collimated by an oil-immersion objective lens and a convex lens respectively. The object wave superimposes on the reference wave which has a certain angle to the object wave to generate the interference pattern and form the off-axis hologram. The distribution of complex amplitude is obtained by a digital holographic reconstruction program, from which the intensity and phase information can be got. Then two-dimensional phase unwrapping is done to obtain the distribution of the real phase.The digital holograms of microspheres in solution are recorded, and a series of images of different intensity distribution are obtained by changing the reconstruction distance, which are corresponding to different cross sections of the microsphere. By the analysis of the intensity distribution, the3D information of the microsphere can be obtained.In order to obtain axial information of a microscopic object, the off-axis holograms of the microsphere in solution are photographed. By reconstruction of off-axis holograms of the microspheres, the complex amplitudes of images at different diffraction distances are reconstructed. The axial displacement of the microsphere is obtained by the change of different diffraction distances.