An accurate and compact 3D tracking system using a single camera and ultrasound

Abstract

We propose a novel technique for 3D tracking that integrates a single camera and ultrasound. We use ultrasound with the Extended Phase Accordance Method to measure the distance accurately to a moving target and the camera for identifying the 2D position of the target on the image plane. A prototype system consists of a target unit mounting one ultrasound transmitter and three infrared LEDs surrounding it, and a receiver unit with one inexpensive camera and one ultrasound receiver. We implemented these units in a lightweight and compact way (receiver unit size: 55 mm × 44 mm) to make the system robust to non-line-of-sight problems that frequently occur in trilateration or multicamera-based systems. To improve the ranging performance, we applied phase characteristic compensation of the ultrasound transducers by interpolating with a B-spline function and creating a compensated curved surface. Experimental results show that root-mean-square errors of the proposed system are 1.20 mm and 1.66 mm for static and mobile (target velocity: 1.0 m/s) settings, respectively. Thus, the performance of the system is comparable with that of high-end systems. Limitations of the proposed system and its possible applications are also discussed.