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Transducers

eSDIva models every transducer geometry as a collection of small flat rectangular patches. The Spatial Impulse Response (SIR) is computed for each patch independently, then summed with per-element delays and apodization weights to produce the total field.
Linear array Matrix array
Concave circular Custom helmet

  • Mono-elements

    Flat, concave, convex, and focused circular single-element transducers. Focusing achieved through physical curvature, not electronic delays.

  • Multi-elements

    Linear, convex, and matrix arrays with independently controlled elements. Electronic beam steering and focusing via delays and apodization.

  • Transducer Objects

    How eSDIva represents transducers as Python objects: geometry properties, patch frames, delays, apodization, and 3-D visualization.

The patch model

Every surface — no matter the shape — is approximated by a mosaic of small flat rectangles. The no_sub_x and no_sub_y parameters control subdivision density:

Parameter Effect
Higher values Better SIR accuracy, longer computation
Lower values Faster, sufficient for low-frequency or simple geometries

Good starting points: no_sub_x=2, no_sub_y=4 for arrays; no_sub_diameter=20–30 for circular transducers.

Coordinate system

Axis Direction
X Lateral — across array elements
Y Elevation — perpendicular to imaging plane
Z Axial — beam propagation direction, depth

For curved transducers the rim is always at z = 0. The medium and geometric focus lie at z > 0.

Delays and apodization

Both are applied at the element level for multi-element arrays and can be recomputed for any focal point without recreating the transducer:

tx.compute_delays(focus_mm=[0, 0, 30])
tx.compute_apodization(focus_mm=[0, 0, 30], FoverD=2.0)

For mono-element transducers, compute_delays() is ignored — focusing is purely geometric. Patch-wise apodization via set_apodization() is still physically meaningful (e.g., apodizing aperture edges).

Transducer types at a glance

Type Category Focusing
LinearArrayTransducer Multi-element Electronic
ConvexArrayTransducer Multi-element Electronic + geometry
MatrixArrayTransducer Multi-element Electronic (2-D steering)
FlatCircularTransducer Mono-element None (diverging)
ConcaveCircularTransducer Mono-element Geometric (bowl)
ConvexCircularTransducer Mono-element Geometric (dome, diverging)
FocusedCircularTransducer Mono-element Geometric (line-focus)
CustomTransducer Multi mono-element Per-element positions