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Dynamic focusing requires computing the individual delays for every element and every focus in the image. This is an easy and relatively fast task if the inspected medium is homogeneous. Nevertheless, some difficulties arise in presence of interfaces (i.e, wedges, immersion, etc.): refraction effects require computing the Snell's law for every focus and element to find the fastest ray entry point in the interface. The process is easy but takes a long time. This work presents a new technique to compute the focusing delays for an equivalent virtual array that operates in the second medium only, thus avoiding any interface. It is nearly as fast as computing the focal laws in the homogeneous case and an order of magnitude faster than Snell's or Fermat's principle based methods. Furthermore, the technique is completely general and can be applied to any equipment having dynamic focusing capabilities. In fact, the technique is especially well suited for real-time focal law computing hardware. [ABSTRACT FROM AUTHOR]

Reception beamforming requires a high-resolution time base to keep low delay quantization lobes. Usually signals acquired at the Nyquist sampling rate are up-sampled by a factor of 4 to 16 to achieve the required time-resolution. Although this has been carried out for decades using fractional delay interpolating filters, the interpolation and coherent addition processes use a large silicon area and consume power, mainly when implemented in FPGAs. These drawbacks are reduced if the beamformer is implemented in ASICs, but this precludes any retro-fitting operation. This work presents a beamfoming architecture to overcome these shortcomings, based on the DSP cells incorporated into state-of-the art FPGAs. Since the manufacturing process is similar to that of ASIC, these cells consume low power and processing speed is high. The proposed beamformer interleaves the interpolation and the coherent sum. Besides reducing hardware resources, the design is modular and scalable, which allows to trade off among the number of channels per device, time resolution and resource requirements. It can be easily tailored to very different applications, from the low-channel count systems to the more demanding ones with multi-beamforming capabilities. [ABSTRACT FROM AUTHOR]

Most common defects in textile manufacturing processes include weaving errors (such as missing threads), oil spots and material inhomogeneities. In this work, we demonstrate the feasibility of using ferroelectret-based transducers for the inspection of woven material. A linear array of 32 elements was built for this purpose following an easy fabrication procedure recently proposed. Electronic focusing at the textile sample position allowed us to detect weaving errors and oil spots of up to ∼1 mm of width in through transmission mode, at normal incidence and with a good signal-to-noise ratio. [ABSTRACT FROM AUTHOR]