A Novel Small F-number Ultrasound Transducer with a Dual-Focus Structure

An ultrasound transducer with a F-number around 1.0 can be applied in many fields such as medical treating, imaging, acoustic tweezers and so on. However, the existing small-F-number designs have some shortcomings as difficulty in fabrication and complexity in design. Moreover, almost all existing designs have a fixed focal length. This paper presents a new small F-number ultrasound transducer design using a combination of acoustic lens and phased array, which can also achieve an adjustable focal length. Simulations and preliminary tests are carried out to verify the performance of the compound focus design. The results show that this dual-focus transducer can reach a F-number as low as 1, and focal length is changeable when applying different time delays. Furthermore, the focal line can deviate up to 5 degrees from the acoustic axis in simulation.