Research Of SLM-based Digital Holographic Microscopy System Under Incoherent Illumination

SLM-based digital holographic microscopy system under Incoherent illumination can record three-dimensional spatial information of the sample without any moving parts and scanning device, and it does not require coherent light source, which can get rid of the stringent requirements of the experimental conditions. The system has a simple structure, flexible reconstruction way and high research value and practical value. On the basis of the analysis of this digital holographic imaging system, we focus on its application in the field of microscopic imaging. First the point spread function, recording and reconstruction principles and the resolution impact of this SLM-based digital holographic system under Incoherent illumination is analyzed. Then we optimize the structure and parameters of the system through the experimental simulation and experiment, and a higher image quality results is obtained. An incoherent light illuminated digital holographic microscopy system is built on the basis of the basic imaging system and its feasibility in the field of microsurgery is verified and biological sample holographic recording and reproducing is given. Finally, a spiral phase modulation mode is proposed and by loading the spiral phase mask on a spatial light modulator, the edges enhancement in the microscopic imaging of the sample is obtained. Mentioned above can be summarized in four specific areas:(1) The basic imaging principle of incoherent digital holographic system is analyzed on the basis of the Fresnel diffraction integral formula in the scalar diffraction theory, the point spread function of incoherent light illuminated digital holographic recording system is derived, the specific expression of system lateral magnification and reconstruction distance is obtained, the various factors which affect the imaging resolution is qualitative analyzed too. Then the angular spectrum method and the three-step phase shift method is introduced in the reconstruction process, the conditions of use and scope of the algorithm is discussed.(2) The basic imaging properties of the SLM-based digital holographic microscopy system under Incoherent illumination is researched through simulation and experiment. The holographic recording and reconstruction of four colored objects on different planes is simulated. Experiment from experimental lateral magnification, resolution, three-dimensional imaging and color imaging, etc. are carried on to verify the ability which can obtain multi-dimensional object light field information quickly without scanning.(3) An incoherent light illumination digital holographic microscope is built and the experiment is done to verify the feasibility of this system in the microscopic field. The structure parameters of the system are optimized to improve the signal to noise ratio and resolution in this microscopy system. Then experiments of real three-dimensional biological samples is completed, the holographic recording and reconstruction of three-dimensional biological samples are demonstrated.(4) A spiral phase load mode is introduced, the differences of dual-lens model and spiral phase mode is discussed. The edge enhancement of reconstructed image is achieved using the spiral phase pattern, and experiments demonstrated that when the topological charge is 1, it is an optimal loading phase spiral pattern.