• Universitat de València
• Universidad de Cádiz

• Lorenzo Sanchis Martínez
• Pablo Aitor Postigo Resa
• Pedro Luis Galindo Riaño
• Andrés Yáñez Escolano
• Joaquín Pizarro Junquera
• Elisa Guerrero Vázquez

An acoustic lens placed in front of a transducer allows the ultrasound beam to be focused in a controlled plane, which is very useful for example in ultrasound imaging devices to obtain good resolution. Conventional acoustic lenses focus the sound for certain frequencies and for other frequencies they behave like an insulating material. However, these lenses are based on the phenomenon of refraction, which causes several problems: they are not capable of obtaining highly focused acoustic signals, they work in pulsed mode and they do not allow working in a high frequency range. They have the limitation that their focus is on a straight line and what is important is that they focus on a selective point.

Researchers from the Universitat de València, in collaboration with the CSIC and the University of Cadiz, have developed a novel methodology that allows the design of three-dimensional acoustic lenses capable of focusing sound at a point, allowing them to work in continuous mode and in a high frequency range, overcoming the disadvantages of two-dimensional acoustic lenses. The new method is based on the dispersion of sound by rings, which, suitably distributed, allow the focus to be located at a single point in space on the axis of symmetry. The methodology for lens design uses optimisation tools based on inverse design, in particular genetic algorithms and computational techniques. The method allows control over the number and size of the concentric rings used for its design, and their spatial distribution.

The technique can be applied in the following areas:

• In medicine: For the design of new ultrasound medical devices: lithotripsy, ultrasound scans, non-incisive surgery where acoustic energy must be released in specific areas of the body at different depths, etc.
• In environmental acoustics: For the reduction of environmental noise, for example in industrial environments with machines that have a narrow spectrum of sound emission.
• In structural flaw detection: For non-destructive testing and analysis of the interior of non-transparent objects such as bridges, ship hulls and aircraft wings for cracks or other defects.

The main advantages provided by the invention are:

• Precise control of the specific area where the sound beam is focused (it allows the sound to be focused on one point), and greater beam width.
• Ease of adaptation of the lens to the necessary working frequency according to the specific use.
• Shorter exposure time for the subject due to the operation of the lens in continuous mode.
• Improved image clarity (sound) and safety in medical ultrasound imaging, especially in ultrasound imaging.
• Lower power consumption due to lower power requirements.

• Patent granted