2013 Volume 133 Issue 11 Pages 2014-2020
Estimating distances and directions of targets in short range is important for achieving hands-free speech interfaces and nursing-care robots. Conventionally, acoustic imaging methods based on time-of-flight (TOF) with ultrasound have been proposed to estimate the distances and directions of targets. However, these methods have difficulty estimating the distances and directions in the short range which has overlaps of the transmitted and reflected waves. Meanwhile, we have proposed the acoustic distance measurement method which can estimate the distances in the short range. Previously proposed method can be estimated the distance and direction of a single target, but cannot estimate that of multiple targets. Therefore, in the present paper, we propose a new acoustic imaging method based on phase interference between transmitted and reflected waves for estimating distances and directions of multiple targets in the short range. More specifically, we calculate range spectrogram by beamforming range spectra calculated from each microphone of the microphone-array. Also, the proposed method performs the distance attenuation normalization and the sidelobe suppression in range spectrogram. Finally, we confirm the validity and the effectiveness of the proposed method through computer simulations and evaluation experiments in a real environment.