METHOD AND SYSTEM FOR HIGH RESOLUTION ULTRASONIC IMAGING OF SMALL DEFECTS OR ANOMALIES

摘要

A method and system is provided for enhanced ultrasonic detection andimaging of small defects inside or at the surface of an object. The SyntheticAperture Focusing Technique (SAFT) has been used to improve thedetectability and to enhance images in conventional ultrasonics and thismethod has recently been adapted to laser-ultrasonics. In the presentinvention, an improved version of the frequency-domain SAFT (F-SAFT)based on the angular spectrum approach is described. The method proposedincludes temporal deconvolution of the waveform data to enhance both axialand lateral resolutions, control of the aperture and of the frequencybandwidthto improve signal-to-noise ratio, as well as spatial interpolation of thesubsurface images. All the above operations are well adapted to thefrequency domain calculations and embedded in the F-SAFT dataprocessing. The aperture control and the spatial interpolation allow also areduction of sampling requirements to further decrease both inspection andprocessing times. This method is of particular interest when ultrasound isgenerated by a laser and detected by either a contact ultrasonic transducer ora laser interferometer.