Ultrasonic sparse-TFM imaging for a two-layer medium using genetic algorithm optimization and effective aperture correction

This paper introduces a sparse total focus method (TFM) as a viable solution to the trade-off between the imaging precision and computational efficiency. A corrected two-layer TFM algorithm is first established; then the element layout in the sparse arrays is optimized by the genetic algorithm to improve the spatial resolution and contrast resolution. Using the effective aperture theory, the weighting functions of the optimized sparse array elements are investigated, and the corrected sparse-TFM algorithm is developed. Experiments are conducted on the side-drilled holes in a wedged specimen. Results indicate that the proposed sparse-TFM can greatly increase the computational efficiency while maintaining a relatively low error.