Detection Of Aerosol Particles By Off-axis Digital Holography

Particulate matter pollution will cause damage to human health.The detection of particulate matter is an important guarantee to improve human health and living standards.Digital holography has great application potential in particulate matter detection.In this paper,the resolution of off-axis holographic system is improved by adding grating in the system,and an off-axis digital holographic particle detection system is built.Compared with the traditional off-axis device,the resolution of the system is greatly improved.Firstly,from the traditional optical holography,the basic theory of digital holography is expounded.The advantages and disadvantages of both coaxial holography and off-axis holography are compared,and the problem of low resolution of off-axis holography is put forward.Then three kinds of common reconstruction algorithms of digital holography are introduced,and then angle spectrum method is selected as the reconstruction algorithm in this paper.Secondly,Because of the low resolution of off-axis digital holography,the method to improve the resolution of off-axis holographic system is analyzed,and grating is selected as the method to improve the resolution of the system.Based on Sagnac interferometer,an off-axis digital holography system is designed,and its optical path is analyzed,built and debugged.Finally,the resolution of the system before and after the grating is calculated by using usaf151 resolution board,and the amplification ratio of the system is calibrated.Then the feasibility of the system is verified by pre experiment on the section of Paramecium.In order to meet the needs of holographic detection of particles,an aerosol generator was designed and built to provide a stable aerosol source for the off-axis digital holography system.The alumina aerosol generated by the aerosol was holographic recorded and the particle size was calculated.The zero order image and negative order conjugate image were removed in the reconstruction process.In this paper,the resolution of off-axis digital holography device is improved by grating,and a complete off-axis digital holography particle detection system is composed of aerosol generator and off-axis digital holography device.