Abstract
Ultrasound has been proven to be a valid tool for ranging, especially in water. In this paper, we design a high-resolution ultrasonic ranging system that uses a thin laser beam as an ultrasonic sensor. The laser sensing provides a noncontact method for ultrasound detection based on acousto-optic diffraction. Unlike conventional methods, the ultrasound transmitted from the transducer is recorded as the reference signal when it first passes through the laser. It can be used to improve the accuracy and resolution of the time-of-flight (TOF) by a cross-correlation method. Transducers with a central frequency of 1 MHz and diameters of 20 mm and 28 mm are used in the experiment. Five targets and a test piece are used to evaluate the ranging performance. The sound velocity is measured by the sound velocity profiler (SVP). The repeatability error of TOF is less than 4 ns, and the theoretical resolution of TOF is 0.4 ns. The results show a measurement resolution within one-tenth of the wavelength of ultrasound and an accuracy better than 0.3 mm for targets at a distance up to 0.8 m. The proposed system has potential applications in underwater ranging and thickness detection.
Highlights
Ultrasonic pulse-echo detection dates from 1912, where it was used for iceberg detection
The aim of this work is to show that the optical detection for ultrasound based on acousto-optic diffraction is helpful for improving the ultrasonic ranging resolution
The ultrasound signal was detected by the ultrasonic transducer and laser sensing system
Summary
Ultrasonic pulse-echo detection dates from 1912, where it was used for iceberg detection. The distance between the transducer and the object depends on the TOF of the ultrasonic pulses [1]. Compared to other detection methods (radar or laser), ultrasound is more suitable in water [4,5]. The objects to be measured are usually placed in water to allow sufficient energy transfer from and into the transducer, which is called immersion ultrasound detection [6]. Sound is a valid method for underwater detection, especially in the deep ocean because of the high attenuation of electromagnetic waves in water. Ultrasonic pulse-echo detection has been widely used in thickness detection, ranging, single/multi beam echo sounding, and sonar [7,8,9,10]
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