Off-axis Digital Holographic Particle Detection System With Cage Structure

Particulate matter pollution can damage human health,leading to a variety of diseases,such as asthma,chronic bronchitis,and even heart disease,stroke and arrhythmias.The detection of particle characteristics,mainly particle size,surface area and concentration,is of great significance for the prevention and control of particle pollution.Monitoring harmful atmospheric particulate matter in the environment is the fundamental means to solve the current regional haze pollution situation in China,and also an important guarantee to improve human health and living standards.Digital holography is a potentially disruptive new technology in imaging science,especially in microscopy and measurement.Since the 21 st century,the holographic microscopic resolution has been constantly improved and started to be applied to the detection of tiny particles.In this paper,a kind of digital holographic particle detection system with cage structure is proposed.The device is structurally stable and is not easily affected by environmental factors.Firstly,the feasibility of using holography to measure the particulate matter pollution in the air was explored.This paper analyzes the basic theory of holography and phase unwrapping technology,and analyzes several digital hologram reproduction methods and the methods of removing interference.Then based on the theory of holographic imaging,an off-axis digital holographic measuring device with cage structure was built.After the construction,the experiment was conducted and the solution was proposed based on the analysis of the sample ghosting phenomenon and the sample edge blurring phenomenon in the debugging process.Then,a one-dimensional partition board is used to calibrate the system magnification,the hologram of the partition board is reconstructed by angular spectrum method,and the edge extraction technology is used to extract a clear partition board image for calibration.Finally,after verifying the feasibility of the device with standard suspended particles,the alumina powder was used to simulate the aerosol environment for measurement to obtain a hologram of particulate matter.Detection and extraction of clear particles images,through calculation,you can get the particle size and shape parameters of particles more accurately.The cage-structured digital holographic device in this paper can accurately detect the particle size of the particles,and the device structure is stable and easy to adjust.