Contrastive Study Of Morphology Of Polyurethane And Dust Particles Based On Digital Micro-holography

Fire smoke particles are one of the earliest fire features,so the detection of fire smoke particles has always been the heated research topic in fire detection.At present,the most widely used fire detectors for fire detection are photoelectric smoke-type fire detector.The principle is to use the scattering properties of light to detect fire smoke particles.Photoelectric smoke-type fire detectors often cause false alarms in fire detection due to the influence of interference particles(dust particles)during fire detection,which poses a great problem for fire detection.Therefore,to distinguish interference particles for fire smoke particle detection has become a key factor in accurate fire detection.According to the current situation of fire detection and the need to realize early fire detection,in order to achieve more accurate fire detection,a new method is tried to detect fire smoke particles,that is,digital microscopy technology is applied to the field of fire smoke particle detection.The specific research is as follows:In order to accurately distinguish between polyurethane smoke particles and dust particles,this paper first analyzes the basic theory of off-axis digital micro-holography and confirms the feasibility of digital display micro-holography technology for the detection of fire smoke particles.Then,according to the principle of Mach-Zehnder interferometer,a fire smoke particle detection experiment system based on digital micro-holography technology is designed and built.The experimental system includes digital microscope holographic subsystem,smoke particles and interference particle generation subsystem,and hologram three-dimensional reconstruction subsystem.The particles generated by smoke particles and interference particle generation subsystem are imaged by the digital micro-hologram subsystem to obtain particle hologram,and then the particle hologram is three-dimensionally reconstructed by the hologram three-dimensional reconstruction subsystem to obtain three-dimensional morphology of smoke particles and interference particles.In the three-dimensional reconstruction subsystem of hologram,the advantages and disadvantages of the three holographic reconstruction algorithms of Fresnel transform,convolution and angle spectrum are compared and analyzed,and a MATLAB program is written.Through the comparison of simulation experiment results,the spectral reconstruction algorithm has advantages over other algorithms in terms of calculation speed and reconstruction accuracy,and the diffraction distance does not affect the amplitude.In order to realize the three-dimensional reconstruction,the phaseunwrapping algorithm was studied and analyzed,and the simulation program was compared and analyzed.It is found that the least square method phase unwrapping algorithm can effectively reduce the effects of phase errors caused by noise and residual points.The fire smoke particle detection experiment system based on digital micro-holography technology was used to conduct verification experiments.The fire smoke particles and dust were subjected to 20 repeated tests.Through the comparison and analysis of the longitudinal and horizontal experimental data,the diameter of fire polyurethane smoke particles was generally a non-spherical object less than 1um,and the diameter of interference particles and dust particles is a non-spherical object distributed around 10 um.By judging the diameter of polyurethane and dust particles,the interference of dust particles on fire detection can be effectively eliminated,thereby effectively reducing the false alarm rate of fire detection..