Fig. 15
for each focus depths for all the group of pulses to arrive on time at the summation block.
Commercial ultrasound machines have two, three or more delay circuit, one for each focal
zone. wave front is the biggest of three examples, and the time between the arrival of the
wave fronts at the crystals is the smallest of the three examples, so there must be a different
delay for each focus depths for all the group of pulses to arrive on time at the summation
block. Commercial ultrasound machines have two, three or more delay circuit, one for each
focal zone.
Fig. 16
Even there are machines that have a dynamic focalization system, this technology does
not have focal zones, instead the focal zone is reduced to a pixel zone and as the pixels are
so close one another the focalization is considered a continuous focalization along the reception echo line with many pixels generating many echoes, so there are focus at each pixel
as shown in figure 17, then every time each echo arrive at the probe, a different delay is
done, and a summation is also done for each delay, this offer a better image quality because the synchronization needed for the summation is continuous, this process was implemented in 1976 by von Ramm and Thurstones.
Curvilinear probes, or convex probes, (Sectorial ultrasound image)
This type of probe works the same way the linear probes do, but as the surface shape