The Research On Imaging Technology Of Ultrasonic Phased Array Detecting System

By controlling delay time of each element when transmitting and receiving pulse, the ultrasonicphased array imaging detection technology can control the deflexion and focus of ultrasonic beam.The technology can effectively improve the SNR, resolution and defect detection rate of the detectionresults, and achieve high-speed, all-sided, multi-angle test. The technology has an increasingly wideapplication in the field of industrial non-destructive testing. The main research contents of this paperare as followed:(1) This paper studied the method for calculating the delay time when the beam deflection orfocus, and analyzed the effects of delay control precision on system performance. The beam controltechniques of ultrasonic phased array are researched, including dynamic focusing, amplitudeweighting and dynamic aperture, and their imaging effects are simulated. This paper also researchedthe3D reconstruction from serial two-dimensional ultrasound images. The effects of variousparameters of two-dimensional phased array on the characteristics of sound field are studied, and therules to design probe was concluded.(2) Echo signal requires a series of signal processing to form the ultrasound image, whoseconcrete realization algorithms are given in this paper. Filters are designed to filter the echo signal bythe FDAfool toolbox of Matlab. Then, the signal is disposed by gradual semi-soft threshold method toachieve denoising. Delay compensation of echo signals was realized through two-level high precisiondigital time delay control technology. At this time16-way signals can be summed into one, thenwhose envelope is obtained by means of Hilbert transform. Finally through coordinate transformationand interpolation to form ultrasound image.(3) Upper computer software is designed and developed, which is the core of the uppermanagement of the whole system, and it performs several tasks, listed below：It is in charge of thehuman-computer interaction interface, so parameters of probe and detection can be configured easilyand conveniently.Secondly delay time of each channel can be obtained according to these parametersand focal law. Thirdly a series of processing of echo signal is completed to image.Finally the relatedfunctions of the software system were tested, which shows that the software can work normally, andthe defect can be detected.