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Full matrix capture (FMC) and total focusing method (TFM)

Full matrix capture (FMC) is a specific data-acquisition process using ultrasonic phased-array probes. For an array of N elements, each element is successively used as the transmitter, while all other elements are used a receivers. The animation illustrates the sequencing of the shots fired by a phased-array probe used for FMC (orange = transmitting element, blue = receiving elements). The data are organized in a matrix S that contains all the acquired signals. Sij contains the signal transmitted by element i and received by element j.

FMC_data

Once the matrix is full, all the data are available for data processing. This signal processing is called the total focusing method (TFM). A computation zone is defined for the data reconstruction. This zone is meshed, and for each point on this grid, the focal-laws are calculated for the entire set of elements of the phased-array probe. All signals are time-shifted accordingly before summation at every point of the grid. This loop ends when the reconstruction is done for every point of the mesh.

TFM

Example demonstrating resolution: a block of Rexolite (see picture) is inspected using a 64-element linear array at 5MHz (IMASONIC probe). The probe is driven by an M2M MultiX64 phased-array system (with predefined FMC mode).

Rexolite block

After data acquisition and post-processing in CIVA, the resulting image is shown below. All the side-drilled holes located under the probe are clearly identified, as well as the bottom surface.

TFM_results