Based On Ultrasonic Chromatography Design Of Smoke Imaging System

In fog weather,fire scene and other environments,due to the large amount of sulfur dioxide,nitrogen oxide,dust and other particles in the air,people’s visibility is greatly reduced,causing great safety hazards for people to travel.Based on this,this paper introduces "smoke" as an interfering factor into the field of ultrasonic tomography,and USES the idea of optical tomography to design a smoke detection system based on ultrasonic tomography.The system controls the stepping motor and ultrasonic transmitting/receiving unit by the upper computer,and realizes the automatic device calibration,data acquisition,signal conditioning and image reconstruction process.According to the noise source of the system,the method to improve the SNR of the system is put forward.The Fourier slicing theorem is theoretically verified by simulation.The filter back projection algorithm is analyzed theoretically.Filter back projection algorithm is selected for image reconstruction and the influence of filter and interpolation algorithm on image quality is analyzed.Based on the problems such as curved ray propagation path,severe data loss and large noise,SIRT algorithm was selected for image reconstruction.Based on the SIRT algorithm with fixed step size,the SIRT algorithm was optimized according to the principle of maximum descent.Through the comparison of reconstructed images,it was found that the optimized SIRT algorithm had better image quality and faster reconstruction speed.At the same time,gaussian noise,salt and pepper noise and Poisson noise were added to the original image.By comparing the added noise with the reconstructed image,it was concluded that the tomography had an obvious effect on noise suppression.Based on the calibration method,flue gas concentration measurement unit is designed in the system.The specific value of flue gas concentration can be obtained by compensated temperature measurement and propagation velocity measurement.