Underwater imaging system using acoustic holography

Abstract

We have been developing the underwater ultrasonic imaging system to view some objects in turbid water. A purpose of the development of the system is to get images in order to operate remote-controlled underwater construction machines. In turbid water, optical visibility is limited because light is both attenuated and scattered. But acoustic waves have the ability to penetrate turbid water in which optics do not work. This system consists of transducer unit and control unit. The ultrasonic frequency is 600 kHz. This system using acoustic holography will be able to get real-time 3D image. The 3D image can be reconstructed by means of a single transmitting and receiving process. The operating range for distance is 1-10 m and field of view is 80/spl times/80 cm at 10 m. We carried out experiment with this imaging system in the water tank. We obtained 2D acoustic image of objects (balls) which were 9 m away.