Theoretical And Experimental Study Of Underwater Parallel Phase Shift Digital Holographic Imaging System

The oceans are where life began,and there is far more biodiversity in them than on land.Marine microorganism is an important part of marine biological system and has an important impact on the development of marine ecosystem and human society,People are paying more and more attention to the development of marine microorganism resources.Marine microorganisms have been living in special physical,chemical and geological environments underwater for a long time,resulting in their diversity in species,genetic composition and morphological,which has great potential research value.Marine microorganisms have great potential for environmental detection,microbial restoration,microbial pharmacy,and the exploration of the origin and evolution of species.In this paper,the theoretical and experimental research of underwater parallel phase shift digital holographic imaging system is carried out for the in-situ detection of Marine microorganisms.The polarization camera used in the system is embedded with a micro-polarizer phase-shift array chip,and four holograms with phase shift difference of π/2 can be obtained simultaneously based on circularly polarized light interference.The distribution of holographic light field is demodulated by the four-step phase shift algorithm,then the image processing algorithm is used for filtering and denoising,finally the near-field image reproduction is completed by the Angle spectrum method.The system eliminates the interference of zero-order image and twin image by using the method of parallel phase shift,and can detect the dynamic change of target in real time.Moreover,the transmission coaxial optical path can improve the utilization ratio of CCD spatial bandwidth product,which has the advantages of small volume,strong robustness,fast reproduction speed and high resolution.Focusing on the underwater parallel phase shift digital holographic imaging system,this paper mainly completed the following research work:(1)By referring to papers and periodicals at home and abroad,the research background and significance of the subject are deeply understood,common underwater detection methods are expounded,and the development,history and application of phase shift digital holographic imaging technology are introduced.(2)This paper studies the theoretical knowledge related to parallel phase shift digital holography,including the principle of parallel phase shift digital holography technology,the realization method of parallel phase shift,the reconstruction algorithm and the image processing method.(3)The design idea and scheme of underwater parallel phase shift digital holographic imaging system are introduced.According to the design scheme to select the experimental device,and then build the debugging desktop experimental device.(4)The experiments of optical resolution inspection board,female drosophila and female mosquito in air and simulated water environment were completed,and the results and errors were analyzed and summarized.