Sampling phased array: a new technique for signal processing and ultrasonic imaging

ABSTRACT Different signal processing and image reconstruction techniques are applied in ultrasonic non-destructive material evaluation. In recent years, rapid development in the fields of microelectronics and computer engineering lead to wide application of phased array systems. A new phased array technique, called “Sampling Phased Array” has been developed in Fraunhofer Institute for non-destructive testing. It realizes unique approach of measurement and processing of ultrasonic signals. The sampling phased array principle make use of the measurement of elementary waves generated by individual elements of sensor array to reconstruct the composite phased array signal for any arbitrary angle or focus depth. The use of special signal processing and image reconstruction algorithms, allows generating A-Scans of several angles and / or Sector-Scan, which can be implemented in real time. With parallel computing structures, this principle is used for automatic testing systems at very high inspection speed. A comparative study was done with Conventional Phased Array system and Sampling Phased Array technique. The study shows that the signal characteristics in both techniques are equal. In addition, the Sampling Phased Array technique is significantly beneficial in the many aspects like quality of information in specific cases, inspection speeds and adaptability to specific inspection tasks in comparison to conventional Phased Array. The electronics was developed as a development platform for high speed automated ultrasonic inspection systems for process integrated testing and also for testing of critical components. The development results, including relevant test methodology and electro-technical/electronic aspects are presented in the current work. Key words: Sampling Phased Array, Fast Ultrasonic Imaging, Reverse Phase Matching, Automated Ultrasonic Inspection