Doppler device, depression angle estimation method, and program

Abstract

[Problem] To provide a Doppler device, a depression angle estimation method, and a program, whereby a temperature or the speed of sound in water can be obtained at low cost in real time. [Solution] A Doppler device generates a first echo signal in a first direction d1 having a depression angle θ with respect to a reception surface 11a of a transducer 11 from a reflected wave of an ultrasonic wave, generates a second echo signal in a second direction d2 that has a depression angle θ with respect to the reception surface 11a and is different from the first direction d1, from the reflected wave, and furthermore generates a third echo signal in a third direction d3 perpendicular to the reception surface 11a from the reflected wave. The Doppler device calculates a first Doppler frequency of the first echo signal, calculates a second Doppler frequency of the second echo signal, and calculates a third Doppler frequency of the third echo signal. The Doppler device calculates the depression angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency.

Description

Technical Field

[0001] The present invention relates to a Doppler device that performs predetermined measurements using the Doppler effect, an elevation angle estimation method, and a program.

Background Art

[0002] In the field of marine fisheries, there has long been a need to remotely measure the temperature of the middle layer of seawater, which directly affects the ecology of fish living in the middle layer, rather than the surface temperature that can be easily measured by a thermometer (such as a thermistor) installed on the bottom of a ship.

[0003] As a method to meet such a need, a method of measuring the water temperature at various depths using a temperature probe is known. For example, the following Patent Document 1 describes this type of method. However, this method has a problem that the water temperature profile in water cannot be obtained in real time.

[0004] Also, as another method to meet the above need, a method of calculating the water temperature on the surface of a reflector based on the temperature of the water surface, the relative speed between the device itself and the reflector (floating object), and the Doppler frequency composed of the frequency difference between a sound wave transmitted at a predetermined elevation angle and its reflected wave is known. For example, the following Patent Document 2 describes this type of method. However, this method has a problem that various detection units are required for calculating the water temperature, resulting in a high cost of the device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, the conventional two methods have problems such as the inability to obtain a water temperature profile in real time and the increase in the cost of the device. On the other hand, the speed of sound of ultrasonic waves propagating in water changes with the change in water temperature. Therefore, if a sound speed profile in water can be obtained simply and in real time, it is possible to calculate the water temperature profile in water from the obtained sound speed profile.

[0007] In view of the above problems, an object of the present invention is to provide a Doppler device, an elevation angle estimation method, and a program capable of obtaining the speed of sound or temperature in water at low cost and in real time.

[0008] Note that the "Doppler device" means a device that performs a predetermined measurement using the Doppler effect, and includes not only a Doppler sonar but also a current meter, an ADCP (Acoustic Doppler Current profiler), and the like can be widely included.

Means for Solving the Problems

[0009] The first aspect of the present invention relates to a Doppler device. The Doppler device according to this aspect includes a transducer that transmits ultrasonic waves into water and receives a reflected wave of the ultrasonic waves, an echo signal generation module, a Doppler frequency calculation module, and an elevation angle calculation module. The echo signal generation module generates a first echo signal in a first direction having an elevation angle θ with respect to the receiving surface of the transducer from the reflected wave. Also, the echo signal The signal generation module generates a second echo signal having the depression angle θ with respect to the wave receiving surface of the transducer and in a second direction different from the first direction from the reflected wave. Further, the echo signal generation module generates a third echo signal in a third direction perpendicular to the wave receiving surface of the transducer from the reflected wave. The Doppler frequency calculation module calculates a first Doppler frequency of the first echo signal, calculates a second Doppler frequency of the second echo signal, and calculates a third Doppler frequency of the third echo signal. The depression angle calculation module calculates the depression angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency.

[0010] According to the Doppler device according to this aspect, with a simple configuration using a transducer, the depression angle θ can be calculated in real time. By applying the calculated depression angle θ to a predetermined mathematical formula, the speed of sound of ultrasonic waves in water and the temperature in water can be calculated. Therefore, according to the Doppler device according to this aspect, the water temperature or the speed of sound in water can be obtained at low cost and in real time.

[0011] In the Doppler device according to this aspect, the Doppler frequency calculation module calculates the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency from the first echo signal, the second echo signal, and the third echo signal at a plurality of water depths, and the depression angle calculation module may be configured to calculate the depression angle θ for each of the plurality of water depths.

[0012] According to this configuration, for a plurality of water depths, the depression angle θ can be calculated for each water depth. Therefore, by applying the depression angle θ calculated for each water depth to a predetermined calculation formula, the water temperature or the speed of sound at each water depth can be obtained.

[0013] In the Doppler device according to this aspect, the first direction, the second direction, and the third direction may be set in the same plane perpendicular to the wave receiving surface of the transducer.

[0014] The closer the plane in which the first direction, the second direction, and the third direction are set approaches being parallel to the traveling direction of the ship, the greater the difference between the first Doppler frequency and the third Doppler frequency becomes. The greater the difference between the first Doppler frequency and the third Doppler frequency, the less susceptible the calculation of the depression angle θ is to the influence of noise or the like, and the higher the calculation accuracy of the depression angle θ becomes. For this reason, the closer the plane in which the first direction, the second direction, and the third direction are set approaches being parallel to the traveling direction of the ship, the higher the calculation accuracy of the depression angle θ, and as a result, the higher the calculation accuracy of the sound speed or the water temperature.

[0015] Therefore, it is most preferable that the plane in which the first beam, the second beam, and the third beam are formed is parallel to the traveling direction of the ship. Thereby, the difference between the first Doppler frequency and the second Doppler frequency can be maximized, and the calculation accuracy of the depression angle θ can be maximized. As a result, the accuracy of the sound speed or the water temperature calculated from the depression angle θ can be maximized.

[0016] In the Doppler device according to the present aspect, it is preferable that the receiving surface of the transducer forms an angle β other than 0 degrees with respect to the water surface.

[0017] By tilting the receiving surface with respect to the water surface in this way, the depression angle θ can be calculated even in a situation where there is no upwelling current, and the sound speed or the water temperature can be calculated from the calculated depression angle θ.

[0018] In the Doppler device according to the present aspect, the depression angle calculation module may be configured to calculate the depression angle θ based on the ratio of the first Doppler frequency to the third Doppler frequency and the ratio of the second Doppler frequency to the third Doppler frequency.

[0019] Alternatively, the depression angle calculation module may be configured to calculate the depression angle θ based on the sum of the first Doppler frequency and the second Doppler frequency and the reciprocal of the third Doppler frequency.

[0020] According to these calculation methods, the depression angle θ can be appropriately calculated using the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency.

[0021] The Doppler device according to this aspect may further include a sound speed profile calculation module that calculates the sound speed of ultrasonic waves in water from the depression angle θ calculated by the depression angle calculation module.

[0022] According to this configuration, the sound speed of ultrasonic waves in water can be calculated in real time from the depression angle θ calculated by the depression angle calculation module.

[0023] In this case, the Doppler device may further include a temperature profile calculation module that calculates the water temperature from the sound speed.

[0024] According to this configuration, the water temperature in water can be calculated in real time from the sound speed calculated by the sound speed profile calculation module.

[0025] Alternatively, the Doppler device according to this aspect may further include a temperature profile calculation module that calculates the water temperature from the depression angle θ calculated by the depression angle calculation module.

[0026] According to this configuration, the water temperature in water can be directly calculated from the depression angle θ calculated by the depression angle calculation module without calculating the sound speed of ultrasonic waves in water.

[0027] In the Doppler device according to this aspect, the transducer includes a plurality of vibrators arranged in an array, and the echo signal generation module may be configured to form a first beam, a second beam, and a third beam in the first direction, the second direction, and the third direction, respectively, and generate the first echo signal, the second echo signal, and the third echo signal.

[0028] Alternatively, in the Doppler device according to the present aspect, the transducer includes a first vibrator, a second vibrator, and a third vibrator that transmit and receive waves in the first direction, the second direction, and the third direction, respectively, and the echo signal generation module may be configured to generate the first echo signal, the second echo signal, and the third echo signal from the reflected waves received by the first vibrator, the second vibrator, and the third vibrator.

[0029] A second aspect of the present invention relates to an elevation angle estimation method. The elevation angle estimation method according to this aspect transmits ultrasonic waves into water from a transducer, receives the reflected waves of the ultrasonic waves with the transducer, generates a first echo signal in a first direction having an elevation angle θ with respect to the wave receiving surface of the transducer from the reflected waves, generates a second echo signal in a second direction having the elevation angle θ with respect to the wave receiving surface and different from the first direction from the reflected waves, generates a third echo signal in a third direction perpendicular to the wave receiving surface from the reflected waves, calculates a first Doppler frequency of the first echo signal, calculates a second Doppler frequency of the second echo signal, calculates a third Doppler frequency of the third echo signal, and calculates the elevation angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency.

[0030] According to the elevation angle estimation method according to the present aspect, the same effect as the first aspect can be achieved.

[0031] A third aspect of the present invention relates to a program that causes a control processing circuit of a Doppler device that transmits ultrasonic waves into water by a transducer and receives reflected waves of the ultrasonic waves to generate a first echo signal in a first direction having a depression angle θ with respect to a wave receiving surface of the transducer, a second echo signal in a second direction having the depression angle θ with respect to the wave receiving surface and different from the first direction, and a third echo signal in a third direction perpendicular to the wave receiving surface, to execute a predetermined function. The program according to this aspect causes the control processing circuit to calculate a first Doppler frequency of the first echo signal, calculate a second Doppler frequency of the second echo signal, calculate a third Doppler frequency of the third echo signal, and calculate the depression angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency.

[0032] According to the program according to this aspect, the same effects as those in the first aspect can be achieved.

Effects of the Invention

[0033] As described above, according to the present invention, it is possible to provide a Doppler device, a depression angle estimation method, and a program capable of obtaining a water temperature profile or a sound velocity profile in water at low cost and in real time.

[0034] The effects or significance of the present invention will become clearer from the description of the embodiments shown below. However, the embodiments shown below are merely examples for implementing the present invention, and the present invention is not limited to those described in the following embodiments at all.

Brief Description of the Drawings

[0035]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, as an example of the Doppler device, the present invention is applied to a Doppler sonar installed on a hull such as a fishing boat. Examples are shown. However, the following embodiments are one embodiment of the present invention, and the present invention is not limited to the following embodiments at all.

[0037] <Method for estimating the depression angle θ> FIG. 1 is a diagram showing a configuration used for the method for estimating the depression angle θ according to the embodiment.

[0038] As shown in FIG. 1, in this estimation method, a transducer 11 is installed on the bottom of the ship S1. The transducer 11 transmits ultrasonic waves into the water and receives the reflected waves of the ultrasonic waves. The transducer 11 is installed on the bottom of the ship so that the receiving surface 11a forms an angle β (rad) other than 0 degrees with respect to the water surface WS. The direction in which the receiving surface 11a inclines is a direction parallel to the plane including the traveling direction of the ship S1 and the vertical direction.

[0039] The transducer 11 can generate an echo signal based on the reflected wave in a first direction d1 and a second direction d2 that respectively incline forward and backward by a depression angle θ (rad) with respect to the receiving surface 11a, and in a third direction d3 perpendicular to the receiving surface 11a. The first direction d1, the second direction d2, and the third direction d3 are included in the same plane perpendicular to the receiving surface 11a. This plane is parallel to the traveling direction of the ship S1. The depression angle θ is, for example, 60° (π / 3 rad), and the angle β is, for example, 10° (π / 18 rad).

[0040] With the depression angle θ set in this way, the ultrasonic waves transmitted in the first direction d1 and the second direction d2 then change their traveling direction in a direction parallel to the plane including the first direction d1, the second direction d2, and the third direction d3 as the speed of sound and temperature change in the water depth direction. As a result, the depression angle θ between the traveling direction of the ultrasonic waves transmitted in the first direction d1 and the second direction d2 and the receiving surface 11a changes with the water depth. Therefore, if the depression angle θ at each water depth can be estimated, the state of the speed of sound and temperature at that water depth can be estimated. In the present embodiment, the depression angle at each water depth is estimated by the following method.

[0041] In the configuration of FIG. 1, if the ground speed of the ship S1 is V G (m / s) and the speed relative to the water is V W (m / s), the relative speed in the sound axis direction between the transducer 11 and the seabed B1 in the first direction d1 is V G cos(θ + β). Therefore, when the transmission frequency of the transducer 11 is f0 and the speed of sound near the seabed is c, the first Doppler frequency fd1 observed in the first direction d1 is calculated by the following equation.

[0042] [Number]

[0043] Similarly, the second Doppler frequency fd2 observed in the second direction d2 and the third Doppler frequency fd3 observed in the third direction d3 are calculated by the following equations, respectively.

[0044] [Number]

[0045] Therefore, the following equation is obtained from the above equations (1) to (3).

[0046] [Number]

[0047] From the above equation (4), for the reflected wave reflected from the seabed B1, by extracting the first Doppler frequency fd1 in the first direction d1, the second Doppler frequency fd2 in the second direction d2, and the third Doppler frequency fd3 in the third direction d3 from the first echo signal in the first direction d1, the second echo signal in the second direction d2, and the third echo signal in the third direction d3, an estimated value of the depression angle θ at the seabed B1 can be calculated.

[0048] Also, when the flow velocity at each water depth is constant, the relative water velocity V between the ship S1 and the water in the sea W is constant for each water depth. In this case, the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 at each water depth are obtained by replacing V in equations (1) to (3) with G V W . Therefore, the estimated value of the depression angle θ at each water depth can also be calculated by the calculation of the above equation (4).

[0049] In this case, for the reflected waves reflected by the floating matter (reflector) at each water depth, the first Doppler frequency fd1 in the first direction d1, the second Doppler frequency fd2 in the second direction d2, and the third Doppler frequency fd3 in the third direction d3 are extracted from the first echo signal in the first direction d1, the second echo signal in the second direction d2, and the third echo signal in the third direction d3, so that the depression angle θ at each water depth can be calculated. For example, from the first echo signal in the first direction d1, the second echo signal in the second direction d2, and the third echo signal in the third direction d3, the frequencies at the position (time position) corresponding to the water depth D11 in FIG. 1 are taken as the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 and applied to the above formula (4), whereby the estimated value of the depression angle θ at the water depth D11 can be calculated.

[0050] <Embodiment 1> A configuration example of a Doppler sonar to which the above-described method for estimating the depression angle θ is applied will be described below. In the following Doppler sonar, the depression angle θ is estimated based on the above-described estimation method, and further, a sound speed profile and a temperature profile at each water depth are generated from the estimated depression angle θ.

[0051] FIG. 2 is a block diagram showing the configuration of a Doppler sonar 10 according to Embodiment 1.

[0052] As shown in FIG. 2, the Doppler sonar 10 includes a transducer 11, a transmission drive signal generation circuit 12, a transmission amplifier 13, a transmit-receive switching circuit 14, a receive amplifier 15, a control processing circuit 16, and a display device 17.

[0053] FIG. 3 is a diagram schematically showing the configuration of the transducer 11.

[0054] The transducer 11 is configured such that a number of vibrators 111 are arranged on the same plane at a predetermined pitch d. Each vibrator 111 transmits ultrasonic waves when a transmission drive signal is applied, and receives the reflected waves of the ultrasonic waves to generate a reception signal. The transmission and reception surfaces of these vibrators 111 are on the same plane. This plane becomes the reception surface 11a of the transducer 11. When the wavelength of the transmission drive signal (the reference wavelength of the ultrasonic waves) is λ, the pitch d of the vibrator 111 is set to, for example, (2 / 3)λ. As described above, the transducer 11 is arranged so as to be inclined by an angle β (rad) with respect to the water surface WS (the horizontal plane when the ship S1 is in a horizontal posture).

[0055] Returning to FIG. 2, the transmission drive signal generation circuit 12 outputs a transmission drive signal of a transmission frequency f0 to the transmission amplifier 13 under the control from the control processing circuit 16. The transmission amplifier 13 amplifies the transmission drive signal input from the transmission drive signal generation circuit 12 and outputs it to the transmission / reception switching circuit 14. The transmission / reception switching circuit 14 outputs the transmission drive signal input from the transmission drive signal generation circuit 12 to each vibrator 111 of the transducer 11 under the control from the control processing circuit 16. As a result, ultrasonic waves of the transmission frequency f0 are transmitted from each vibrator 111. Also, the transmission / reception switching circuit 14 outputs the reception signal output by each vibrator 111 receiving the reflected waves of the ultrasonic waves to the reception amplifier 15 under the control from the control processing circuit 16.

[0056] The reception amplifier 15 amplifies and removes noise from the reception signals from each vibrator 111 input from the transmission / reception switching circuit 14 and outputs them to the control processing circuit 16. The control processing circuit 16 includes an arithmetic processing circuit such as a CPU (Central Processing Unit), and a storage medium such as a ROM (ReadOnly Memory), a RAM (Random Access Memory), and a hard disk. The control processing circuit 16 controls each part according to a program held in advance in the storage medium 16a, thereby executing the estimation process of the depression angle θ and the generation process of the sound speed profile and the temperature profile based on the depression angle θ. The control processing circuit 16 is an integrated circuit such as an FPGA (Field-Programmable Gate Array). It may be composed of integrated circuits.

[0057] The display device 17 is composed of a liquid crystal display or the like, and displays an image showing the sound velocity profile or the temperature profile generated by the control processing circuit 16. The display device 17 does not necessarily have to be integrated with the processing unit including the transmission drive signal generation circuit 12, the transmission amplifier 13, the transmission / reception switching circuit 14, the reception amplifier 15, and the control processing circuit 16. When the display device 17 is a general-purpose display, the display device 17 is installed on the ship S1 as a device separate from the Doppler sonar 10 and is connected to the processing unit of the Doppler sonar 10 via a signal line.

[0058] Fig. 4(a) is a block diagram showing the configuration of the control processing circuit 16.

[0059] The control processing circuit 16 includes an echo signal generation module 101, a Doppler frequency calculation module 102, an elevation angle calculation module 103, a sound velocity profile calculation module 104, and a temperature profile calculation module 105. These modules may be realized as software functions by a program stored in the storage medium 16a of the control processing circuit 16, or may be composed of hardware implementing a logic circuit.

[0060] The echo signal generation module 101 applies phase control (beamforming) to the reception signals from each vibrator 111 input from the reception amplifier 15, and forms a first reception beam RB1 in the first direction d1, a second reception beam RB2 in the second direction d2, and a third reception beam RB3 in the third direction d3 as shown in Fig. 5, and generates a first echo signal, a second echo signal, and a third echo signal by these reception beams.

[0061] ​As shown in FIG. 5, the first reception beam RB1, the second reception beam RB2, and the third reception beam RB3 are formed with a predetermined spread angle. Therefore, even if the traveling directions of the ultrasonic wave and the reflected wave change within the range of the spread angle due to the temperature change in water, the first echo signal, the second echo signal, and the third echo signal based on the reflected wave can be appropriately generated.

[0062] Returning to FIG. 4(a), the Doppler frequency calculation module 102 calculates the first Doppler frequency fd1 of the first echo signal, the second Doppler frequency fd2 of the second echo signal, and the third Doppler frequency fd3 of the third echo signal for each water depth. Specifically, the Doppler frequency calculation module 102 identifies the time positions of each water depth in the first echo signal, the second echo signal, and the third echo signal from the elapsed time after transmitting the ultrasonic wave, and determines the frequencies of the first echo signal, the second echo signal, and the third echo signal at the identified time positions as the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 at each water depth, respectively, and extracts them.

[0063] The depression angle calculation module 103 applies the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 at each water depth to the above formula (4) to calculate the depression angle θ at each water depth. Thereby, a depression angle profile in which the water depth and the depression angle θ are associated is generated. The depression angle calculation module 103 outputs the generated depression angle profile to the sound speed profile calculation module 104.

[0064] The sound speed profile calculation module 104 calculates the sound speed at each water depth from the depression angle θ at each water depth. A predetermined relational expression holds between the depression angle θ and the sound speed. For example, when the depression angles θ in the first direction d1 and the second direction d2 with respect to the wave receiving surface 11a are set to 60° (π / 3 rad) and the pitch d of the vibrator 111 is 2 / 3 of the wavelength λ of the transmission drive signal, the following relational expression holds between the depression angle θ and the sound speed c.

[0065]

Equation

[0066] The sound speed profile calculation module 104 applies the depression angle θ at each water depth, the transmission frequency f0 of the transmission drive signal, and the pitch d between the vibrators 111 to the above formula (5) to calculate the sound speed c at each water depth. Thereby, a sound speed profile in which the water depth and the sound speed c are associated is generated. The sound speed profile calculation module 104 outputs the generated sound speed profile to the temperature profile calculation module 105.

[0067] The temperature profile calculation module 105 calculates the temperature at each water depth from the sound speed c at each water depth. A predetermined relational expression such as Machenzie's formula holds between the sound speed and the temperature. The temperature profile calculation module 105 applies the sound speed c at each water depth to this relational expression to calculate the temperature at each water depth. Thereby, a temperature profile in which the water depth and the temperature are associated is generated. The temperature profile calculation module 105 outputs the generated temperature profile to the display device 17. Thereby, a temperature profile indicating the temperature at each water depth is displayed on the display device 17.

[0068] Here, the sound speed c is once calculated from the depression angle θ, and then the temperature is calculated from the sound speed c. However, the temperature may be directly calculated from the depression angle θ. In this case, the configuration of the control processing circuit 16 is changed as shown in FIG. 4(b). In this configuration, the sound speed profile calculation module 104 is omitted, and the temperature profile calculation module 105 is changed to a temperature profile calculation module 106. The temperature profile calculation module 106 directly calculates the temperature at each water depth from the depression angle θ at each water depth by an arithmetic expression that integrates an arithmetic expression defining the relationship between the depression angle θ and the sound speed c and an arithmetic expression defining the relationship between the sound speed c and the temperature. Thereby, a temperature profile in which the water depth and the temperature are associated is generated.

[0069] FIG. 6 is a flowchart showing the temperature profile generation process performed by the control processing circuit 16.

[0070] First, the control processing circuit 16 transmits ultrasonic waves with a transmission frequency f0 from the transducer 11 and receives the reflected waves with the transducer 11 (S11). Next, in the echo signal generation module 101, the control processing circuit 16 generates a first echo signal in the first direction d1 from the reflected waves received by the transducer 11 (the reception signals output from each vibrator 111) (S12), and also generates a second echo signal in the second direction d2 and a third echo signal in the third direction d3 (S13, S14). The generation of these echo signals is performed by forming a first reception beam RB1, a second reception beam RB2, and a third reception beam RB3 by beamforming, as described with reference to FIG. 5.

[0071] Furthermore, in the Doppler frequency calculation module 102, the control processing circuit 16 calculates a first Doppler frequency fd1, a second Doppler frequency fd2, and a third Doppler frequency fd3 for each water depth from the first echo signal, the second echo signal, and the third echo signal (S15, S16, S17). The calculation of these Doppler frequencies is performed by extracting the frequencies of the respective echo signals at the time positions corresponding to each water depth, as described above.

[0072] Then, in the depression angle calculation module 103, the control processing circuit 16 applies the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 at each water depth to the above formula (4) to calculate the depression angle θ at each water depth (S18).

[0073] Thus, after calculating the depression angle θ at each water depth, in the sound speed profile calculation module 104, the control processing circuit 16 applies the depression angle θ at each water depth to the above formula (5) to calculate the sound speed c (sound speed profile) at each water depth. Further, in the temperature profile calculation module 105, the control processing circuit 16 applies the sound speed c at each water depth to a predetermined relational expression such as Machenzie's formula to calculate the temperature (temperature profile) at each water depth (S19).

[0074] The control processing circuit 16 outputs the temperature profile calculated in step S19 to the display device 17. As a result, the display device 17 performs processing to display the temperature profile (S20).

[0075] In this way, when the processing of one ping is completed, the control processing circuit 16 executes the processing after step S11 at the start timing of the next ping. As a result, the display of the temperature profile is updated. The control processing circuit 16 repeatedly executes the processing of steps S11 to S20 for each ping. As a result, the temperature profile directly below the ship S1 at each point in time is sequentially displayed on the display device 17. The user can confirm the temperature profile at each water depth in real time by referring to the image displayed on the display device 17.

[0076] Note that in step S20, not only the temperature profile but also the sound speed profile and the depression angle profile may be further displayed. Also, when the control processing circuit 16 has the configuration shown in Fig. 4(b), in step S19, the temperature profile is directly calculated from the depression angle θ at each water depth. Also in this case, in step S20, the temperature profile directly below the ship S1 is sequentially displayed on the display device 17 in real time.

[0077] <Effect of Embodiment 1> According to the above Embodiment 1, the following effects can be achieved.

[0078] With a simple configuration using the transducer 11, the depression angle θ can be calculated in real time. Also, by applying the calculated depression angle θ to Equation (4), the sound speed of ultrasonic waves in water can be calculated, and further, by applying the calculated sound speed to a relational expression such as Machenzie's equation, the temperature in water can be calculated. Therefore, according to the Doppler sonar 10 according to this aspect, the sound speed and temperature in water can be obtained at low cost and in real time.

[0079] As shown in FIG. 6, the Doppler frequency calculation module 102 calculates a first Doppler frequency fd1, a second Doppler frequency fd2, and a third Doppler frequency fd3 from a first echo signal, a second echo signal, and a third echo signal at a plurality of water depths (S15 to S17), and the depression angle calculation module 103 calculates a depression angle θ for each of the plurality of water depths (S18). By applying the depression angle θ calculated for each water depth to the above formula (4), a sound speed profile for each water depth can be obtained. Further, by applying the calculated sound speed profile to a relational expression such as Machenzie's formula, a temperature profile for each water depth can be obtained.

[0080] As shown in FIG. 1, the first direction d1, the second direction d2, and the third direction d3 are set in the same plane perpendicular to the wave receiving surface 11a of the transducer 11 and parallel to the traveling direction of the ship S1. Thereby, the difference between the first Doppler frequency fd1 and the second Doppler frequency fd2 can be maximized, and the calculation accuracy of the depression angle θ can be maximized. As a result, the accuracy of the sound speed or water temperature calculated from the depression angle θ can be maximized.

[0081] As shown in FIG. 1, the wave receiving surface 11a of the transducer 11 forms an angle β other than 0 degrees with respect to the water surface WS. By tilting the wave receiving surface 11a with respect to the water surface WS in this way, the depression angle θ can be calculated even in a situation where there is no upwelling current, and the sound speed or water temperature can be calculated from the calculated depression angle θ.

[0082] As shown in the above formula (4), the depression angle calculation module 103 calculates the depression angle θ based on the ratio (fd1 / fd3) of the first Doppler frequency fd1 to the third Doppler frequency fd3 and the ratio (fd2 / fd3) of the second Doppler frequency fd2 to the third Doppler frequency fd3. Alternatively, the depression angle calculation module 103 calculates the depression angle θ based on the sum (fd1 + fd2) of the first Doppler frequency fd1 and the second Doppler frequency fd2 and the reciprocal (1 / fd3) of the third Doppler frequency fd3. As described above, according to this calculation method, the depression angle θ can be appropriately calculated using the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3.

[0083] As shown in FIG. 4(a), the Doppler sonar 10 further includes a sound speed profile calculation module 104 that calculates the sound speed c of ultrasonic waves in water from the depression angle θ calculated by the depression angle calculation module 103. Thereby, in the Doppler sonar 10, the sound speed of ultrasonic waves at a predetermined water depth in water can be calculated.

[0084] Also, as shown in FIG. 4(a), the Doppler sonar 10 further includes a temperature profile calculation module 105 that calculates the water temperature from the sound speed c. Thereby, in the Doppler sonar 10, the temperature at a predetermined water depth in water can be calculated.

[0085] Also, as shown in FIG. 4(b), the Doppler sonar 10 may be configured to include a temperature profile calculation module 106 that calculates the water temperature from the depression angle θ calculated by the depression angle calculation module 103. According to this configuration, the water temperature in water can be directly calculated from the depression angle θ calculated by the depression angle calculation module 103 without calculating the sound speed of ultrasonic waves in water.

[0086] As shown in FIG. 3, in the Doppler sonar 10, the transducer 11 includes a plurality of vibrators 111 arranged in an array. As shown in FIG. 5, the echo signal generation module 101 forms a first reception beam RB1, a second reception beam RB2, and a third reception beam RB3 in a first direction d1, a second direction d2, and a third direction d3, respectively, to generate a first echo signal, a second echo signal, and a third echo signal. Thereby, the first echo signal, the second echo signal, and the third echo signal based on the reflected waves from the first direction d1, the second direction d2, and the third direction d3 can be smoothly generated.

[0087] <Embodiment 2> In the above Embodiment 1, as shown in FIG. 3, the transducer 11 in which a large number of vibrators 111 are arranged on the same plane at a predetermined pitch d was used. In contrast, in this embodiment, a transducer including a first vibrator, a second vibrator, and a third vibrator that transmit and receive waves in the first direction d1, the second direction d2, and the third direction d3, respectively, is used.

[0088] FIG. 7 is a side view schematically showing the configuration of a transducer 20 used in the Doppler sonar 10 according to Embodiment 2.

[0089] As shown in FIG. 7, the transducer 20 includes a first vibrator 211, a second vibrator 212, and a third vibrator 213. The first vibrator 211 and the second vibrator 212 are each inclined by the same angle θ' in the left-right direction with respect to the wave receiving surface 20a of the transducer 20. The third vibrator 213 is arranged parallel to the wave receiving surface 20a. The first vibrator 211, the second vibrator 212, and the third vibrator 213 are molded in a support 220 made of a material such as urethane.

[0090] Furthermore, a temperature sensor 214 for detecting the temperature near the wave receiving surface 20a in the support 220 is molded inside the support 220 together with the first vibrator 211, the second vibrator 212, and the third vibrator 213. The lower surface of the support 220 is flat, and this flat surface serves as the wave receiving surface 20a.

[0091] The ultrasonic waves and reflected waves transmitted and received with respect to the first vibrator 211 and the second vibrator 212 are refracted at the wave receiving surface 20a. The angle formed by the refracted ultrasonic wave and the wave receiving surface 20a is the depression angle θ. Since the third vibrator 213 is arranged parallel to the wave receiving surface 20a, the ultrasonic waves and reflected waves transmitted and received with respect to the third vibrator 213 are not refracted at the wave receiving surface 20a. The ultrasonic waves transmitted from the first vibrator 211, the second vibrator 212, and the third vibrator 213 pass through the wave receiving surface 20a and then travel into the water at a predetermined divergence angle.

[0092] FIG. 8 is a side view schematically showing the arrangement state of the transducer 20.

[0093] Also in the second embodiment, as in the first embodiment, the transducer 20 is arranged such that the wave receiving surface 20a is inclined by an angle β with respect to the water surface WS. Thereby, as in the case of FIG. 1, the ground speed is V G The first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 due to are respectively obtained by the above formulas (1) to (3), and the depression angle θ at each water depth in the water is calculated by the above formula (4).

[0094] However, in the configuration of the second embodiment, refraction occurs at the wave receiving surface 20a, and the speed of sound changes inside and outside the support 220. For this reason, in the second embodiment, the calculation formula for estimating the speed of sound at each water depth is changed from the above formula (5) to the following formula.

[0095]

Equation

[0096] In the above formula (6), c' is the speed at which the ultrasonic waves transmitted from the first oscillator 211, the second oscillator 212, and the third oscillator 213 propagate through the substance in the support 220, and can be defined by the material of the substance and the temperature of the substance near the receiving surface 20a, that is, the temperature detected by the temperature sensor 214. Also, θ' is the mounting angle of the first oscillator 211 and the second oscillator 212 shown in FIG. 8, and is defined in advance. Therefore, by substituting the depression angle θ of each water depth calculated by the above formula (4), the speed of sound c' of the substance in the support 220, and the mounting angle θ' of the first oscillator 211 and the second oscillator 212 into the above formula (6), the speed of sound c of each water depth can be calculated.

[0097] The Doppler sonar 10 has the same configuration as that in FIG. 2 except for the configuration of the transducer 20, and the control processing circuit 16 also has the same configuration as that in FIG. 4(a). Also, the control processing circuit 16 performs the same processing as that in FIG. 6 according to the configuration in FIG. 4(a).

[0098] However, in step S11 of FIG. 6, the control processing circuit 16 transmits ultrasonic waves and receives reflected waves in the first direction d1, the second direction d2, and the third direction d3 by the first oscillator 211, the second oscillator 212, and the third oscillator 213. Also, in the configuration of FIG. 4(a), the echo signal generation module 101 generates the first echo signal, the second echo signal, and the third echo signal by directly using the received signals (the received signals amplified and noise-removed by the receiving amplifier 15) output from the first oscillator 211, the second oscillator 212, and the third oscillator 213 by receiving the reflected waves without generating a received beam by beamforming as in the above Embodiment 1 (steps S12 to S14 in FIG. 6).

[0099] Similar to Embodiment 1, the Doppler frequency calculation module 102 identifies the time positions corresponding to each water depth from the input first echo signal, second echo signal, and third echo signal, and calculates the first Doppler frequency fd1, second Doppler frequency fd2, and third Doppler frequency fd3 from the identified time positions (Steps S15 to S17 in FIG. 6). Similar to Embodiment 1, the depression angle calculation module 103 substitutes the first Doppler frequency fd1, second Doppler frequency fd2, and third Doppler frequency fd3 calculated for each water depth into the above formula (4) to calculate the depression angle θ for each water depth (S18).

[0100] In step S19 of FIG. 6, different from Embodiment 1, the sound speed profile calculation module 104 substitutes the calculated depression angle θ for each water depth into the above formula (6) to calculate the sound speed c for each water depth. At this time, based on the temperature detected by the temperature sensor 214, the sound speed profile calculation module 104 determines the sound speed c' at which the ultrasonic waves transmitted from the first oscillator 211, second oscillator 212, and third oscillator 213 propagate through the substance near the receiving surface 20a in the support 220, and substitutes the obtained sound speed c' and the known mounting angle θ' into the above formula (6). Note that the sound speed c' may be obtained from a conversion table associating the temperature detected by the temperature sensor 214 with the sound speed c'. In this case, the sound speed profile calculation module 104 holds the conversion table in advance and obtains the sound speed c' corresponding to the temperature detected by the temperature sensor 214 from the conversion table. Alternatively, the sound speed profile calculation module 104 may calculate it from a relational expression defining the relationship between the temperature detected by the temperature sensor 214 and the sound speed c'.

[0101]

[0102] ​The processing of the temperature profile calculation module 105 in step S19 is the same as that in the above-described Embodiment 1. The temperature profile calculation module 105 applies the sound speed c calculated for each water depth by the above formula (6) to a predetermined relational expression such as Machenzie's formula to calculate the temperature at each water depth. The processing in step S20 is the same as that in the above-described Embodiment 1. Thus, the temperature profile directly below the ship S1 is displayed on the display device 17.

[0103] <Effect of Embodiment 2> Also in Embodiment 2, the same effects as those in Embodiment 1 can be achieved.

[0104] Furthermore, in Embodiment 2, as shown in FIG. 7, since the configuration of the transducer 20 is simpler than that of the transducer 11 in the above-described Embodiment 1, a temperature profile can be displayed in real time with a simpler configuration.

[0105] Note that also in Embodiment 2, in step S20 of FIG. 6, not only the temperature profile but also a sound speed profile or a depression angle profile may be displayed. Also in Embodiment 2, the control processing circuit 16 may have the configuration shown in FIG. 4(b). In this case, the temperature profile calculation module 106 directly calculates a temperature profile from the depression angle θ at each water depth calculated by the depression angle calculation module 103, the sound speed c' in the support 20, and the attachment angle θ' of the first vibrator 211 and the second vibrator 212, using an integrated formula of formula (6) and a relational expression such as Machenzie's formula. Also in this case, in step S20 of FIG. 6, the temperature profile directly below the ship S1 is displayed on the display device 17 in real time.

[0106] <Modification Example 1> In the above-described Embodiments 1 and 2, the plane including the first direction d1, the second direction d2, and the third direction d3 was parallel to the traveling direction of the ship S1, but this plane may be inclined by an angle α in the horizontal direction with respect to the traveling direction of the ship S1.

[0107] FIG. 9(a) is a plan view when viewing the states of the first direction d1, the second direction d2, and the third direction d3 in this case from above the ship S1.

[0108] As shown in FIG. 9(a), in Modification 1, a plane P0 (a plane parallel to the vertical direction) including the first direction d1, the second direction d2, and the third direction d3 is inclined by an angle α in the horizontal direction with respect to the traveling direction d0 of the ship S1. That is, in this Modification 1, the formation directions of the first reception beam RB1, the second reception beam RB2, and the third reception beam RB3 shown in the above Embodiment 1 are inclined by an angle α with respect to the traveling direction d0 of the ship S1 in a plan view. Similar to Embodiment 1, the first direction d1 and the second direction d2 have a depression angle θ with respect to the wave reception surface 11a. Further, the wave reception surface 11a is inclined by an angle β with respect to the water surface WS.

[0109] In this case, the Doppler frequencies at each water depth obtained by the first reception beam RB1, the second reception beam RB2, and the third reception beam RB3 are calculated by the following equations.

[0110]

Equation

[0111] When performing the calculation of the left side of the above Equation (4) according to the above Equations (7) to (9), the cos α in the denominator and numerator is canceled out, and the same relational expression as the above Equation (4) holds. Therefore, also in this case, similar to the above Embodiment 1, by calculating the first Doppler frequency fd1, the second Doppler frequency fd2, and the third Doppler frequency fd3 at each water depth by the first reception beam RB1, the second reception beam RB2, and the third reception beam RB3, the depression angle θ at each water depth can be calculated by the above Equation (4), and similar to the above Embodiment 1, the sound speed profile and the temperature profile can be calculated.

[0112] In the method of Fig. 9(a), compared with the case where the plane P0 is parallel to the traveling direction of the ship S1 as in the first embodiment, the first Doppler frequency fd1 and the second Doppler frequency fd2 are smaller by the amount multiplied by cosα. For this reason, the difference between the first Doppler frequency fd1 and the second Doppler frequency fd2 calculated on the left side of the above formula (4) becomes smaller than that in the first embodiment. Therefore, in the case of Fig. 9(a), compared with the first embodiment, this difference is more likely to be affected by noise or the like, and the calculation accuracy of the depression angle θ decreases.

[0113] Therefore, in order to improve the calculation accuracy of the depression angle θ, it is preferable to make the plane P0 approach parallel to the traveling direction d0 of the ship S1 as in the first embodiment, and it is most preferable to set the plane P0 parallel to the traveling direction d0 of the ship S1. Thereby, the calculation accuracy of the sound speed profile and the temperature profile can also be maximally improved.

[0114] Note that when the angle α between the traveling direction d0 of the ship S1 and the plane P0 is 90°, that is, when the plane P0 is set parallel to the left-right direction of the ship S1, no Doppler shift occurs in the first direction d1 and the second direction d2, so the depression angle θ at each water depth cannot be calculated. Therefore, when the plane P0 is inclined with respect to the traveling direction d0 of the ship S1 as in Fig. 9(a), it is necessary to set the angle α to less than 90°.

[0115] Also, the method of Fig. 9(a) is also applicable to the second embodiment. However, also in this case, for the same reason as above, the calculation accuracy of the depression angle θ decreases compared to the case where the plane P0 is set parallel to the traveling direction d0 of the ship S1. Therefore, also in the configuration of the second embodiment, it is most preferable that the plane P0 including the first direction d1, the second direction d2, and the third direction d3 is set parallel to the traveling direction d0 of the ship S1.

[0116] <Modification Example 2> In the first and second embodiments above, there was one set of the first direction d1, the second direction d2, and the third direction d3 However, a plurality of such sets may be set.

[0117] Figure 9(b) is a plan view when viewed from above the ship S1 of the states of the first direction, the second direction, and the third direction when three sets of the first direction, the second direction, and the third direction are set.

[0118] Here, three planes P1, P2, and P3 parallel to the vertical direction are set. The plane P1 is parallel to the traveling direction d0 of the ship S1, and the planes P2 and P3 are inclined in horizontal directions different from each other by an angle α with respect to the traveling direction d0 of the ship S1. The first direction d11, the second direction d12, and the third direction d13 are set on the plane P1, the first direction d21, the second direction d22, and the third direction d23 are set on the plane P2, and the first direction d31, the second direction d32, and the third direction d33 are set on the plane P3.

[0119] When the configuration of FIG. 9(b) is applied to the configuration of the first embodiment, reception beams are respectively formed in the first direction d11, the second direction d12, and the third direction, and the depression angle θ of each water depth is calculated by the above formula (4). Further, reception beams are respectively formed in the first direction d21, the second direction d22, and the third direction to calculate the depression angle θ of each water depth, and further, reception beams are respectively formed in the first direction d31, the second direction d32, and the third direction to calculate the depression angle θ of each water depth. In this way, the depression angle θ of each water depth is calculated for each set of the first direction, the second direction, and the third direction (for each of the planes P1, P2, and P3).

[0120] In this case, the depression angle calculation module 103 in FIG. 4(a) sets a representative value of the depression angle θ of each water depth using the depression angle θ of each water depth calculated for each set. For example, the depression angle calculation module 103 sets the average value of the depression angle θ of each water depth calculated for each set as the representative value of the depression angle θ of each water depth. The sound speed profile calculation module 104 in FIG. 4(a) calculates the sound speed profile using the representative value of the depression angle θ of each water depth.

[0121] However, as described in the above Modification Example 1, the depression angle θ calculated for the plane P1 parallel to the traveling direction d0 of the ship S1 has higher accuracy than the depression angles θ calculated for the planes P2 and P3 inclined with respect to the traveling direction d0 of the ship S1. Therefore, as described above, when using the average value of the depression angle θ as a representative value, the weight of the depression angle θ calculated for the plane P1 may be set larger than the depression angles θ calculated for the planes P2 and P3, and a weighted average may be performed, and this average value may be set as the representative value of the depression angle θ.

[0122] In this case, the magnitude of the weighting may be set, for example, so that it becomes smaller as the angle formed by the traveling direction d0 of the ship S1 and each plane increases. When the angles α formed by the planes P2 and P3 and the traveling direction d0 are different, the weights of the depression angles θ calculated for the planes P2 and P3 may be made different according to the magnitudes of the angles α.

[0123] Alternatively, the depression angles θ calculated for each plane may be selectively used to set the representative value of the depression angle θ at each water depth. For example, usually, the depression angle θ with the highest accuracy obtained for the plane P1 is set as the representative value, and when the depression angle θ calculated for the plane P1 is significantly different from the depression angles θ calculated for the other two planes P2 and P3, the average value of the depression angles θ calculated for the other two planes P2 and P3, or any one of the depression angles θ may be set as the representative value.

[0124] In this way, although the arithmetic processing increases by setting a plurality of sets of the first direction, the second direction, and the third direction, the depression angle θ at each water depth can be calculated more accurately and stably. Thereby, the accuracy of the sound speed profile and the temperature profile can be improved.

[0125] Note that the method of FIG. 9(b) is also applicable to the above Embodiment 2. In this case, it is necessary to individually arrange the transducers 20 for each plane.

[0126] <Other Modification Examples> In the above-described Embodiments 1 and 2 and Modification Examples 1 and 2, the depression angle θ, the sound speed c, and the temperature are calculated for a plurality of water depths. However, the depression angle θ, the sound speed c, and the temperature may be calculated for one target water depth. In this case, the user may appropriately change the target water depth to a desired water depth. Alternatively, the user may arbitrarily set a plurality of target water depths.

[0127] Further, in the above-described Embodiments 1 and 2 and Modification Examples 1 and 2, each oscillator performs both transmission and reception. However, as long as the Doppler frequency based on the reflected waves from the first direction, the second direction, and the third direction can be calculated, the transmission oscillator and the reception oscillator may be individually arranged.

[0128] Also, the configurations of the transducers 11 and 20 are not limited to the configurations shown in the above-described Embodiments 1 and 2, and may be other configurations as long as the Doppler frequency based on the reflected waves from the first direction, the second direction, and the third direction can be calculated. For example, in the transducer 11 of Embodiment 1, the number and layout of the oscillators 111 may be changed, and the pitch d between the oscillators 111 may also be changed from 2 / 3 of the wavelength λ of the transmission drive signal.

[0129] When the pitch d between the oscillators 111 is changed, the above formula (5) is also changed. For example, when the depression angles θ in the first direction d1 and the second direction d2 with respect to the receiving surface 11a are set to 60° (π / 3 rad) and the pitch d between the oscillators 111 is changed to 1 / 3 of the wavelength λ of the transmission drive signal, the denominator on the right side of formula (5) is corrected to 6f0·d. Also, when the depression angles θ in the first direction d1 and the second direction d2 with respect to the receiving surface 11a are changed from 60° (π / 3 rad), formula (5) is changed accordingly.

[0130] In addition, the embodiments of the present invention can be appropriately variously changed within the scope described in the claims.

Explanation of Reference Numerals

[0131] 10 Doppler sonar 11 Transducer 11a Wave receiving surface 16 Control processing circuit 20 Transducer 20a Wave receiving surface 101 Echo signal generation module 102 Doppler frequency calculation module 103 Elevation angle calculation module 104 Sound speed profile calculation module 105, 106 Temperature profile calculation module 111 Vibrator 211 First vibrator 212 Second vibrator 213 Third vibrator d1 First direction d2 Second direction d3 Third direction RB1 First received beam RB2 Second received beam RB3 Third received beam

Claims

1. A transducer that transmits ultrasonic waves into water and receives the reflected waves of the ultrasonic waves, an echo signal generation module, a Doppler frequency calculation module, and an elevation angle calculation module, wherein the echo signal generation module generates a first echo signal in a first direction having an elevation angle θ with respect to the wave receiving surface of the transducer from the reflected wave, generates a second echo signal in a second direction having the elevation angle θ with respect to the wave receiving surface of the transducer and different from the first direction from the reflected wave, generates a third echo signal in a third direction perpendicular to the wave receiving surface of the transducer from the reflected wave, wherein the Doppler frequency calculation module calculates a first Doppler frequency of the first echo signal, calculates a second Doppler frequency of the second echo signal, calculates a third Doppler frequency of the third echo signal, wherein the elevation angle calculation module calculates the elevation angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency, A Doppler device characterized by the above.

2. In the Doppler device according to Claim 1, the Doppler frequency calculation module calculates the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency from the first echo signal, the second echo signal, and the third echo signal at a plurality of water depths, and the elevation angle calculation module calculates the elevation angle θ for each of the plurality of water depths, A Doppler device characterized by the above.

3. In the Doppler device according to Claim 1 or 2, the first direction, the second direction, and the third direction are set in the same plane perpendicular to the wave receiving surface of the transducer, A Doppler device characterized by the above.

4. In the Doppler device according to any one of Claims 1 to 3, the wave receiving surface of the transducer forms an angle β other than 0 degrees with respect to the water surface, A Doppler device characterized by the above.

5. In the Doppler device according to any one of Claims 1 to 4, the elevation angle calculation module calculates the elevation angle θ based on the ratio of the first Doppler frequency to the third Doppler frequency and the ratio of the second Doppler frequency to the third Doppler frequency, A Doppler device characterized by the above.

6. In the Doppler device according to any one of Claims 1 to 5, The depression angle calculation module calculates the depression angle θ based on the sum of the first Doppler frequency and the second Doppler frequency and the reciprocal of the third Doppler frequency. A Doppler device characterized by the above. **Claim 7** In the Doppler device according to any one of Claims 1 to 6, further comprising a sound speed profile calculation module that calculates the speed of sound of ultrasonic waves in water from the depression angle θ. A Doppler device characterized by the above. **Claim 8** In the Doppler device according to Claim 7, further comprising a temperature profile calculation module that calculates the water temperature from the speed of sound. A Doppler device characterized by the above. **Claim 9** In the Doppler device according to any one of Claims 1 to 8, further comprising a temperature profile calculation module that calculates the water temperature from the depression angle θ. A Doppler device characterized by the above. **Claim 10** In the Doppler device according to any one of Claims 1 to 9, the transducer includes a plurality of vibrators arranged in an array, the echo signal generation module forms a first beam, a second beam, and a third beam in the first direction, the second direction, and the third direction, respectively, and generates the first echo signal, the second echo signal, and the third echo signal. A Doppler device characterized by the above. **Claim 11** In the Doppler device according to any one of Claims 1 to 9, the transducer includes a first vibrator, a second vibrator, and a third vibrator that transmit and receive waves in the first direction, the second direction, and the third direction, respectively, the echo signal generation module generates the first echo signal, the second echo signal, and the third echo signal from the reflected waves received by the first vibrator, the second vibrator, and the third vibrator. A Doppler device characterized by the above. **Claim 12** Transmit ultrasonic waves into water from a transducer, receive the reflected waves of the ultrasonic waves with the transducer, generate a first echo signal in a first direction having a depression angle θ with respect to the wave receiving surface of the transducer from the reflected waves, generate a second echo signal in a second direction having the depression angle θ with respect to the wave receiving surface and different from the first direction from the reflected waves, generate a third echo signal in a third direction perpendicular to the wave receiving surface from the reflected waves, calculate the first Doppler frequency of the first echo signal, Calculate the second Doppler frequency of the second echo signal, calculate the third Doppler frequency of the third echo signal, calculate the depression angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency, A depression angle estimation method characterized by the above.

13. While transmitting ultrasonic waves into water by a transducer and receiving the reflected waves of the ultrasonic waves, a control processing circuit of a Doppler device that generates a first echo signal in a first direction having a depression angle θ with respect to the wave receiving surface of the transducer, a second echo signal in a second direction having the depression angle θ with respect to the wave receiving surface and different from the first direction, and a third echo signal in a third direction perpendicular to the wave receiving surface, A function of calculating the first Doppler frequency of the first echo signal, A function of calculating the second Doppler frequency of the second echo signal, A function of calculating the third Doppler frequency of the third echo signal, A program for executing a function of calculating the depression angle θ from the first Doppler frequency, the second Doppler frequency, and the third Doppler frequency.

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