Waveguide for shortening the minimum detectable distance of a proximal ultrasonic sensor

This research deals with a method shortening the minimum detectable distance of a proximal ultrasonic sensor by coupling a waveguide. It is necessary to investigate and improve the performance of the waveguide invented to overcome the limit of minimum detectable distance, which is induced by the residual vibration of an elastic disc in an ultrasonic sensor. The purpose of this study is to evaluate the performance of shortening the minimum detectable distance by designing various waveguides. We simulated the ultrasound propagation in the designed waveguide by finite element analysis, and carried out experiments with fabricated prototypes. The shape of the waveguide was designed as linear and curved types. The inner surface of the linear waveguide is either smooth or wedged. The mouth of the curved waveguide has a horn to reduce wave reflection. It appeared that the sound pressure of received waves in the case of a circular waveguide is larger than that of a linear waveguide, which should include a reflection plane. We achieved shortening the minimum detectable distance with a circular waveguide of constant curvature.