High-accuracy seawater acoustic velocity measurement method based on acousto-optic effect

Abstract

A high-accuracy seawater acoustic velocity measurement method based on an acousto-optic effect includes the steps of, when adjusting a measuring light path and a reference light path, placing a reflector with adjustable pitching and deflection as far as possible from front ends of two beams of light, adjusting the reflector to make the reference light path perpendicular to the reflector, placing asmall aperture in a forward end of the reference light path, and ensuring that the light reflected by the reflector passes through the same aperture; adjusting the position of an ultrasonic probe sothat the ultrasound perpendicularly flies over the reference light path, solving for the sound pressure at the reference light path with the ratio of obtained diffraction light intensity to the original base light intensity, solving for the sound pressure at the measuring light path based on an attenuation coefficient of the ultrasound in the water, back-calculating the light intensity ratio at the measuring light path, and adjusting the position of the ultrasonic probe; and combining the two beams of parallel light that are emitted from a water tank and produce an acousto-optic effect, receiving light signals respectively by a first photodetector and a second photodetector on the two sides of a second polarization beam splitting cube, converting the light signals into electrical signals,and then obtaining flight distance information and time information by a frequency counter and an oscilloscope.

Description

technical field [0001] The invention relates to the field of seawater sound velocity measurement, in particular to a high-precision seawater sound velocity measurement method based on the acousto-optic effect. Background technique [0002] Specifically, for the measurement of sound velocity in seawater, there are generally two types of methods, one is by measuring the flight time of ultrasonic waves within a fixed distance or the direct measurement of ultrasonic wavelength and frequency; the other is by means of seawater temperature, salinity, Indirect measurement method for depth parameter measurement. Indirect measurement methods are mainly calculated based on existing model formulas, but there are often large errors. In comparison, the direct measurement method involves fewer parameters in principle (only time and distance, or frequency and wavelength), and has higher measurement accuracy. [0003] At present, the conventional sound velocity profiler on the market is ma...

AI Technical Summary

Problems solved by technology

However, in the measurement of time parameters, the ultrasonic transmission and reception of the conventional sound velocity profiler will have a certain time delay due to the piezoelectric effect. In order to obtain a higher measurement accuracy of the sound velocity, usually the measurement of the sound wave needs to fly back and forth within a known distance for many times. That is, use the received reflected callback to trigger the circuit, and then transmit the next pulse, so that the cycle continues, which leads to an error accumulation effect, which cannot guarantee the high precision of time measurement

[0004] In the measurement of the distance parameter, because the ultrasonic probe is embedded in the distance parameter, it is difficult to ensure that the ultrasonic travel distance is strictly consistent with the calibration distance, and it is also difficult to ensure the accuracy of the measurement; there are sound velocity profilers with calibrated ultrasonic flight distances on the market. However, due to the complex environment in which the instrument is used, it is difficult to ensure the accuracy of the calibration distance

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