Multiple Underwater Microbial Identification Based On Off-Axis Digital Holography

The detection of underwater microorganisms is an important means of detecting water quality.By detecting the information such as the type,quantity and density of microorganisms in water,the determination of water quality can be completed.The use of digital holography to detect microorganisms has enormous advantages over traditional methods of manually detecting microorganisms.It obtains clear microbial images through digital reproduction technology,and then uses computer digital image processing technology to extract features,and obtains microbial characteristic information to realize microbial detection and recognition.This paper presents an off-axis microscopic digital holographic detection method.The main work is as follows:Starting from the traditional digital holography,the theory of off-axis digital holography is introduced in detail,and its recording conditions,recording distance and two classical hologram reconstruction reconstruction algorithms are analyzed.Based on the Jamin interferometer,combined with digital holography,the microscope head was introduced into the optical path,and the off-axis micro-digital holography system was improved,and the optical path was analyzed,constructed and debugged.From the noise in the process of hologram recording and reproduction,research is made to improve the quality of the image reproduced by the hologram.On the basis of analyzing the commonly used denoising algorithm,the background subtraction method is used to remove the background noise and the frequency domain filtering method is used to obtain the positive first-order object image.Three autofocus algorithms are proposed to obtain a clear reproduction image.This paper uses edge detection extracts the target microbial contour,and uses roundness,squareness and Euclidean distance discrimination to identify Cyanobacteria,Scenedesmus and Paramecium,and realize the detection of various underwater microorganisms.