Multiple Ultrasound Image Generation based on Tuned Alignment of Amplitude Hologram over Spatially non-Uniform Ultrasound Source
In this study, a method for readily and inexpensively generating real-time reconfigurable intense midair ultrasound field is proposed. Recent investigations and applications of midair convergent high-power ultrasound have been increasingly growing. For generating such ultrasound fields, specifically designed ultrasound sources or phased arrays of ultrasound transducers are conventionally used. The former can be more readily fabricated but cannot drastically reconfigure the generated ultrasound field, and the latter can create electronically controllable ultrasound fields but is much more difficult to implement and expensive. The proposed method utilizes a planar ultrasound source with a fixed surface vibration pattern and a newly designed amplitude mask inspired by the Fresnel-zone-plate (FZP). The mask is designed so that when it is placed on a specific position on the source, the partially covered source emission results in forming pre-determined ultrasound fields with corresponding specific spatial pattern. With these new masks, the generated fields can be switched among several presets by changing the mask position on the source. The proposed technique only requires slight mechanical translation of the mask over the source to instantaneously reconfigure the resulting midair ultrasound field. The proposed method enables one to create a reconfigurable ultrasound field with a large source aperture in a practically feasible setup, which will potentially broaden the workspace of current midair-ultrasound applications to the whole-room scale.