Effects of directivity function on total focusing method imaging performance

The Total Focus Method (TFM) is a post-processing algorithm which uses all elements in the array to focus in both transmission and reception at every image point. The time-domain signals is captured in a process termed Full Matrix Capture (FMC). In this paper, the main objective is to research the effects of directivity function on the TFM. The TFM algorithm is based on the FMC data with weights calculated for each point in the image and for all possible combinations of the transmitter-receiver pairs. The weights are calculated using the directivity functions of the transmitter-receiver elements, which are approximated by a far field radiation pattern of a single element of the array transducer. The imaging performance of the approach is tested using FIELD II simulated FMC data of the point reflector, which allowed the penetration depth and lateral resolution to be estimated. The experimental data on the phased array block were obtained using 64 elements, 5 MHz, linear transducer array of the Multi2000 research platform. Overall, the directivity function improved the quality of the near field image and increased detection depth.