Passive Focusing

Passive Focusing

The focal point along the passive axis is fix and usually different from the one on the active axis.

1. The width of the beam is along the active axis and the length along the passive axis
2. In the first part, the length and width of the beam are getting smaller
3. In the second part, the passive focal zone, the length remain the same but the width continues to get smaller
4. In the third part, the length grows and the width continues to get smaller
5. In the fourth part, the active focal zone, the length continues to grow and the width remains the same
6. Finally in the fifth part, both length and width grow

When using a 2-D probe, the distance of the focal point can be changed along both axis.