Development of pulse-echo ultrasonic imager capable of automatic scan area detection of any customizable shape (Conference Presentation)

This paper proposes a pulse-echo ultrasonic propagation imaging (PE UPI) system for non-destructive evaluation of structures. The system can perform scans of any shape and can autonomously suggest the optimal scan area best suited for a given specimen. The system uses the bulk waves, which travel through the thickness of a specimen, for subsurface feature detection. This is achieved by joining the laser beams for the ultrasonic wave generation and sensing. Since bulk waves are less susceptible to dispersion during short travel time through the thickness, precise and clear damage assessment and defect localization is possible with minimum signal processing. The system uses a Q-switched laser for generating the ultrasonic waves, a laser Doppler vibrometer (LDV) for sensing, optical elements to combine the generating and sensing laser beams, a dual-axis automated translation stage for raster scanning and a digitizer to acquire the measurements. The system also employs a camera in its scan head to aid in customizable and automatic scan boundary delimitation. A graphical user interface (GUI) has been developed in C++ using QT framework. The software is used for autonomous scan area delimitation, signal acquisition, signal processing, result display and post-processing algorithms. The GUI is designed with a minimalist approach to promote usability and adaptability. Through the use of multi-threading, the software is able to show the results in parallel with an ongoing inspection. This is achieved by real-time and concurrent acquisition, processing, and display of ultrasonic signal of the latest scan point in a scan area.