Ultrasonic array imaging algorithms have been widely developed and used for non-destructive evaluation (NDE) in the last two decades. In this paper two widely used time domain algorithms are compared with two emerging frequency domain algorithms in terms of imaging performance and computational speed. The time domain algorithms explored here are the total focusing method (TFM) and plane wave imaging (PWI) and the frequency domain algorithms are the wavenumber algorithm and Lu’s frequency-wavenumber domain implementation of PWI. In order to make a fair comparison, each algorithm was first investigated to choose imaging parameters leading to overall good imaging resolution and signal-to-noise-ratio. To reflect the diversity of samples encountered in NDE, the comparison is made using both a low noise material (aluminium) and a high noise material (copper). It is shown that whilst wavenumber and frequency domain PWI imaging algorithms can lead to fast imaging, they require careful selection of imaging parameters.

Total focusing method (TFM) has improved resolution and accuracy over traditional ultrasonic phased array technology. In this paper, an advanced parallel architecture in field programmable gate arrays is suggested to significantly accelerate the imaging efficiency of TFM. Several techniques are investigated, including the real-time concurrent calculation for time of flight, parallel generation of multiple pixels, and the Hilbert transform to the pixels array. This architecture achieves the real-time computation of the flight times for each pixel and the concurrent generation of double pixels for TFM imaging. Compared to conventional methods, the efficiency of TFM imaging is greatly accelerated and the impact from the increase of element and pixel number is also effectively reduced. Simulation data was used to verify the architecture, and experiment results confirmed that the efficiency was only related to the pulse repeated frequency and element number, which reaches to the physical limitation of TFM inspection. This approach also shows that high efficiency is maintained when pixel number increases, and a strict real-time imaging can be achieved in this architecture. As a result, an effective way for the fast inspection with TFM is provided.