Non-uniform manual scanning for microwave nondestructive evaluation imaging

Wide-band synthetic aperture radar (SAR) technique, capable of producing three-dimensional (3D) volumetric images, is a robust imaging tool for microwave and millimeter wave imaging involving nondestructive evaluation (NDE) applications. Conventionally, a relatively large number of measurement samples are required to image even a small area. Thus, it may take a relatively long time to perform the required scan and obtain an image. There is a significant push in the nondestructive testing community towards real-time imaging, particularly when dealing with large and critical structures (i.e., aircraft, bridges, space vehicles, etc.). Here, a method involving non-uniformly sampled wide-band reflection measurements data is described that enables the production of complete SAR images using only a fraction of the required measured data. The imaging method is based on a fast 3D wide-band SAR algorithm that produces 3D SAR images in real-time. Finally, a reconstruction algorithm is used to post-process the data resulting in high quality images with considerably lower background noise/clutter. This paper presents the measurement methodology along with a few experimentally obtained images.