Nonlinear Ultrasonic Transmissive Tomography for Low-Contrast Biphasic Medium Imaging Using Continuous-Wave Excitation

Industrial process tomography possesses unique advantages in biphasic medium measurement and has received broad attention in the past decades. Aiming at the widely existing low-contrast biphasic medium, this article proposes a nonlinear ultrasonic transmissive tomography (UTT) approach using continuous-wave excitation. Considering the refraction effect at the biphasic interface, the reconstruction method with nonlinear forward problem and the prototype-based resolution enhancement algorithm is proposed with higher accuracy, resolution, and speed. The UTT system is improved with a high-voltage excitation module and fan-beam transducer array to evaluate the proposed method, where the performance is qualitatively and quantitatively compared with the state-of-the-art reconstruction algorithms and measurement techniques from different perspectives. The results show that the reconstruction performance is significantly improved where the size, shape, and position of the dispersed medium can be accurately discriminated. Accordingly, the ultrasonic tomography with continuous-wave excitation is proved to be feasible and efficient in the visualized measurement of low-contrast biphasic medium.