Synthetic aperture focusing techniques (SAFT) have been applied to B-scan images of artificial defects produced by a scanning photoacoustic probe operating under water. The probe consisted of a fibre-optic laser beam delivery system combined with a polymer (PVDF) transducer mounted at the tip of the probe for ultrasonic reception. This system had a broadband frequency response in the 1-10 MHz range. Such an integral probe was designed to optically transmit and receive near on-axis ultrasonic transients. A frequency domain synthetic aperture method was successfully applied using phantom samples to produce refined 2D images from initial B-scans. In this paper, the phantom consisted of a black nylon rectangular sample with a 1.0 mm circular defect at a depth of 5.9 mm from the surface. A comparison was made of conventional B-scan images with SAFT images. Results showed that synthetic focusing apertures, in time or frequency domains, offer better signal-to-noise ratios with improved capabilities in lateral resolution.
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