JPH0533731B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a water temperature measuring device, and more particularly to an indirect water temperature measuring device using laser light. [Prior Art] In ocean observation, fishing resource exploration, etc., underwater temperature measurement has important significance. Conventionally, as a means of measuring underwater water temperature in the above case, for example, a bellows equipped with a temperature sensor is dropped into the water, and the water pressure, which increases with depth, is detected by the amount of deformation of the bellows, and this is used as depth information, and at that time. A method is to capture the detected temperature on board the ship as temperature information, or by dropping a weight with a temperature sensor attached into the water and calculating depth information by integrating the relationship between the sinking speed of the weight and time. There is a known method for capturing the detected temperature on board the ship as temperature information. [Problems with the prior art] However, the former method has drawbacks such as the need for a water-resistant and water-pressure resistant structure, which makes the device large and difficult to handle, and the device itself is expensive. There is. In addition, although the latter method does not have the above-mentioned drawbacks, it is difficult to accurately determine the sinking speed of the weight.
As a result, there is a drawback that accuracy deteriorates. Furthermore, in any of the above methods, since depth information and temperature information are measured by separate means, there is no specification for detection even if there is a time or distance error between them. Therefore, even if depth information is obtained accurately, the temperature information does not necessarily correspond to the depth information, and together with the difficulty of error detection mentioned above, it is difficult to obtain accurate measurements. The drawback is that temperature information cannot be obtained. [Problems to be Solved by the Invention] In view of the above-mentioned problems, the present invention has been made for the purpose of providing a water temperature measuring device that can quickly and accurately measure temperature or temperature distribution in water. be. [Technology for Solving Problems] The water temperature measuring device of the present invention includes a laser beam emitting device that irradiates water with a laser beam having a constant beam width, and receives the return light of the Brillouin scattered light of the laser beam in the water. A light receiving device, a frequency measuring device that measures the frequency of the received Brillouin scattered light and the amount of frequency displacement of the Brillouin scattered light that depends on the underwater sound speed, and stores in advance correlation data between the frequency displacement of the Brillouin scattered light and the sound speed. an information retrieval circuit that has a memory circuit that searches for the frequency displacement obtained by the frequency measuring device and outputs the speed of sound based on the frequency displacement; and a calculation result that calculates the water temperature from the correlation between the temperature and the speed of sound in water from the obtained sound speed. and an arithmetic circuit for displaying and recording. [Function] When laser light is irradiated into water, ultrasonic waves are generated by the laser light, and the laser light is scattered accordingly. This scattering of laser light is generally known as Brillouin scattering, and it is also known that this Brillouin scattering of laser light undergoes frequency displacement depending on the propagation speed of the ultrasonic wave. Therefore, it is possible to find out the amount of displacement by irradiating a laser beam with a certain frequency into the water, measuring the frequency of the Brillouin scattered light returning from the water, and comparing the obtained displacement frequency with the above-mentioned certain frequency. Ba,
From this amount of displacement, it is possible to calculate the underwater sound speed at the depth where Brillouin scattering occurs, and from this underwater sound speed, it is also possible to calculate the water temperature from the correlation between temperature and sound speed. However, even if it is possible to measure the displacement frequency of the Brillouin scattered light, it is not easy to calculate the propagation velocity of the ultrasound based on this and then calculate the temperature of the water from the calculated value. It takes too much time to process the calculations, and it cannot be put to practical use, for example, when searching for fish in the swimming layer using the water temperature as information while placing nets. Therefore, we focused on the absoluteness of the amount of frequency displacement that depends on the ultrasound of Brillouin scattered light, calculated the correlation value between the amount of frequency displacement and the speed of sound in advance, stored this as data, and used it in the calculation to obtain the speed of sound. Regardless,
By finding this value through a search and using it as the basic value for calculating the water temperature, it is possible to quickly display the water temperature. [Example] Next, an example of the present invention will be described. FIG. 1 is a block diagram of an apparatus for carrying out the method of the present invention. The apparatus shown in FIG. 1 is composed of a laser beam emitting section 1, a laser beam receiving section 2, and a storage/arithmetic circuit 3. The laser beam emitting unit 1 includes a laser trigger signal generation circuit 13 to which an oscillation pulse from a reference oscillator 11 is input via a frequency divider 12, and a laser beam generation circuit that generates a laser beam of a constant oscillation wavelength by the trigger signal. 14. High-voltage pulser 15 that converts the laser beam into high-voltage pulses, and optical fiber 1 that converts the pulsed laser beam into
6. Consists of a laser beam emitting lens 18 that emits into the water via an optical connector 17. Further, the laser beam receiving section 2 includes a high-speed shutter tube 22 capable of receiving the incident light (Brillouin scattered light) from the imaging lens 21 with a certain time difference with respect to the laser beam emission timing, and this high-speed shutter tube. 22 is inputted via a polarizer splitter 23, a Fabry-Perot optical interferometer 24 measures the frequency of this light, and a frequency divider is used as a circuit for controlling the operation timing of the high-speed shutter tube 22. Trigger delay circuit 29A and trigger delay variable circuit 29
B, thereby controlling the shutter 22B of the high-speed shutter tube 22. The storage calculation circuit 3 includes a detection circuit 31 that detects a Brillouin frequency shift from the frequency obtained by the Fabry-Perot optical interferometer 24, and a detection circuit 31 that stores in advance the correlation between the amount of Brillouin frequency shift and the underwater sound velocity as a table, and stores the correlation between the amount of Brillouin frequency shift and the underwater sound velocity, and calculates the measured Brillouin frequency shift. It is comprised of a search circuit 32 that searches for the underwater sound speed corresponding to the amount and outputs the underwater sound speed, an arithmetic circuit 33 that calculates and stores the water temperature from this underwater sound speed, and a display device 34 that displays the calculation results. . In the above, the delay timing of the reference oscillation pulse that controls the high-speed shutter tube 22 of the laser beam receiver 2 is for specifying the measurement position where Brillouin scattering occurs after the laser beam is emitted, and is based on the target depth and distance. As an example, the delay timing has a relationship as shown in the table below.

【table】

〔effect〕

As explained above, when measuring the water temperature in water, this invention uses laser light as a medium, so the measurement can be completed within an instant, and water temperature data can be collected quickly even when observing from multiple points. . Moreover, in the process of calculating water temperature from the amount of Brillouin frequency shift, search processing is used instead of calculation processing, so measurement results can be displayed quickly.
It has various effects, such as being able to be used to measure water temperature distribution during ocean current observation, and as an information source for adjusting netting depth during fishing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention.
FIG. 2 is a graph showing the correlation between the amount of Brillouin frequency shift and the speed and frequency of underwater ultrasound.

Claims (1)

[Claims] 1. A laser beam emitting device that irradiates a laser beam with a constant beam width into water, a light receiving device that receives the return light of the Brillouin scattered light in the water of the laser beam, and measures the frequency of the received Brillouin scattered light, It has a frequency measuring device for measuring the amount of frequency displacement of Brillouin scattered light depending on the underwater sound speed, and a storage circuit in which correlation data between the frequency displacement of Brillouin scattered light and the sound speed is stored in advance, and the frequency displacement amount obtained by the frequency measuring device An information retrieval circuit that searches for frequency displacement and outputs the speed of sound based on this, calculates water temperature from the obtained sound speed by correlating it with the underwater sound speed, and displays the calculation results.
A water temperature measuring device comprising: a recording arithmetic circuit;