Underwater sensor, and control method and program of underwater sensor

Abstract

To provide an underwater sensor, and a control method and program of the underwater sensor capable of operating an ultrasonic vibrator by a target transmission power even if the transmission power of the ultrasonic vibrator is set to a small value.SOLUTION: A fish finder 100 (underwater sensor) includes: a control circuit 101 for outputting control pulses S01; an FET driver 201 for outputting a first voltage signal S11 corresponding to the control pulses S01; and an FET 202 (power transistor) for outputting a second voltage signal S21 for operating an ultrasonic vibrator 21 by conduction by input of the first voltage signal S11. The control circuit 101 suppresses a decrease in transmission power by correcting an actual pulse width from a target pulse width and outputting the control pulses S01 when the target pulse width of the control pulses S01 set according to the transmission power of the ultrasonic vibrator 21 is equal to or less than a predetermined threshold, and outputs the control pulses S01 with a target pulse width when the target pulse width exceeds a threshold.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an underwater detection device that detects underwater conditions, a control method for the underwater detection device, and a program that causes a control circuit of the underwater detection device to execute a predetermined function. [Background technology]

[0002] Conventionally, underwater detection devices that detect underwater conditions are known. In the underwater detection device, ultrasonic waves are transmitted from an ultrasonic transducer into the water, and the reflected waves are received by the ultrasonic transducer. Echo data is generated according to the intensity of the received reflected waves, and an echo image is displayed based on the generated echo data.

[0003] A user may change the transmission power applied to the ultrasonic transducer under a predetermined condition. For example, when another ship is nearby, the user may reduce the transmission power to prevent ultrasonic interference with the other ship. In addition, when the water depth is shallow, the user may reduce the transmission power to suppress saturation of the received echo.

[0004] Such control of the transmission power can be performed by adjusting the pulse width of a control pulse input from a control circuit to the transmission circuit.

[0005] For example, a power supply voltage (DC) is applied to the drain of a power transistor (e.g., a field effect transistor: FET), and a voltage signal corresponding to a control pulse is input to the gate of the power transistor via a driver. A pulsed power supply voltage generated at the source of the power transistor by the conduction of the power transistor is boosted by a transformer or the like and applied to the ultrasonic transducer.

[0006] In this configuration, when the pulse width of the control pulse is changed, the conduction period of the power transistor changes. This changes the power of the transmission signal supplied to the ultrasonic transducer, and the transmission power of the ultrasonic transducer changes. Thus, the transmission power of the ultrasonic transducer is controlled by the pulse width of the control pulse.

[0007] Such a configuration is described in the following Patent Document 1. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Publication No. 6-787 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the power transistor and the driver, a certain period (rise period) is required from the start of application of the input voltage until the output voltage stabilizes. Therefore, in the above configuration, if the transmission power of the ultrasonic transducer is low and the pulse width of the control pulse is small, for example, the control pulse may fall before the output voltage completely rises, and the actual transmission power may fall significantly from the target transmission power.

[0010] In view of such problems, the present invention aims to provide an underwater detection device, a control method for an underwater detection device, and a program that can operate an ultrasonic transducer at a target transmission power even when the transmission power of the ultrasonic transducer is set low. [Means for solving the problem]

[0011] A first aspect of the present invention relates to an underwater detection device. The underwater detection device according to this aspect includes a control circuit that outputs a control pulse, a driver that outputs a first voltage signal corresponding to the control pulse, and a power transistor that is turned on by input of the first voltage signal and outputs a second voltage signal for operating an ultrasonic transducer. When a target pulse width of the control pulse set according to the transmission power of the ultrasonic transducer is equal to or smaller than a predetermined threshold, the control circuit corrects an actual pulse width from the target pulse width and outputs the control pulse, thereby suppressing a decrease in the transmission power, and when the target pulse width exceeds the threshold, outputs the control pulse with the target pulse width.

[0012] According to the underwater detection device of this aspect, in a range where the target pulse width of the control pulse is equal to or less than the threshold, i.e., in a range where the actual transmission power may be significantly lower than the target transmission power due to the influence of the above-mentioned rise period if the target pulse width is used as is, the actual pulse width of the control pulse is corrected from the target pulse width so as to suppress this drop and obtain the desired transmission power. This makes it possible to operate the ultrasonic transducer at the target transmission power even in a range where the transmission power of the ultrasonic transducer is small, i.e., in a range where the target pulse width is equal to or less than the threshold.

[0013] In addition, in the range where the target pulse width of the control pulse exceeds the threshold, that is, in the range where the actual transmission power does not decrease significantly from the target transmission power even if the target pulse width is used as is, the control pulse is output with the target pulse width. Therefore, in this case as well, the ultrasonic transducer can be operated with the target transmission power.

[0014] In the underwater detection device of this embodiment, the control circuit can be configured to perform the correction when the target pulse width is equal to or less than the threshold value, to bring closer together the integral value of the ideal second voltage signal that should be output from the power transistor when the control pulse is output at the target pulse width and the integral value of the actual second voltage signal that is output from the power transistor when the control pulse is output at the actual pulse width.

[0015] According to this configuration, since the actual integral value of the second voltage signal approaches the ideal integral value, the transmission power of the ultrasonic transducer can be brought closer to the target transmission power, and therefore the ultrasonic transducer can be operated at the target transmission power.

[0016] The underwater detection device according to this aspect may include a memory that stores reference information that associates a first parameter value related to the pulse width of the target with a second parameter value used for the correction within a range equal to or less than the threshold value. In this case, the control circuit may be configured to obtain the second parameter value corresponding to the current pulse width of the target from the reference information and perform the correction.

[0017] According to this configuration, the pulse width of the control pulse can be corrected by a simple process of acquiring the second parameter value from the reference information.

[0018] In the underwater detection device of this aspect, the threshold value may be set based on the operating characteristics of at least one of the driver and the power transistor.

[0019] According to this configuration, the threshold value is set based on the operating characteristics of the driver or power transistor, which is a factor that causes the transmission power to decrease from the ideal value, so that the threshold value can be set appropriately.

[0020] In this case, the operating characteristic may be, for example, a rise time of an output voltage relative to a DC input voltage, and the threshold may be set based on the rise time, e.g., the threshold may be set to be substantially equal to the rise time.

[0021] This rising period substantially corresponds to the pulse width of the control pulse when the control pulse falls at the timing when the second voltage signal output from the power transistor completely rises. Therefore, if the pulse width of the control pulse is smaller than this rising period, the second voltage signal becomes a triangular wave waveform that transitions to the falling period before completely rising, and the transmission power of the ultrasonic transducer drops significantly from the target transmission power. Therefore, by setting the above threshold, i.e., the threshold that specifies the range for correcting the pulse width of the control pulse, based on this rising period, the pulse width of the control pulse can be appropriately corrected.

[0022] In the underwater detection device according to this aspect, the control circuit may be configured to output the control pulses so that the transmission wave output from the ultrasonic transducer has an envelope waveform based on a predetermined window function. In this case, by setting the threshold value, of two control pulses adjacent to each other with the threshold value as a boundary, the corrected pulse width of the preceding control pulse becomes equal to or smaller than the target pulse width of the succeeding control pulse.

[0023] This configuration makes it possible to prevent the occurrence of a reversal in the pulse width between two control pulses adjacent to each other across the threshold value, which occurs when correction is applied and not applied, thereby making it possible to suppress distortion of the envelope waveform of the transmission wave.

[0024] A second aspect of the present invention relates to a control method for an underwater detection device including a driver that outputs a first voltage signal according to a control pulse, and a power transistor that is turned on by input of the first voltage signal and outputs a second voltage signal for operating an ultrasonic transducer. In the control method according to this aspect, when a target pulse width of the control pulse set according to a transmission power of the ultrasonic transducer is equal to or smaller than a predetermined threshold, an actual pulse width is corrected from the target pulse width and the control pulse is output, thereby suppressing a decrease in the transmission power, and when the target pulse width exceeds the threshold, the control pulse is output with the target pulse width.

[0025] According to the control method of this aspect, the same effects as those of the first aspect can be achieved.

[0026] A third aspect of the present invention relates to a program for causing a control circuit of an underwater detection device, the control circuit including a control circuit for outputting a control pulse, a driver for outputting a first voltage signal corresponding to the control pulse, and a power transistor for outputting a second voltage signal for operating an ultrasonic transducer by being turned on in response to the input of the first voltage signal, to execute a predetermined function. The program according to this aspect causes the control circuit to execute a function of correcting an actual pulse width from the target pulse width and outputting the control pulse to suppress a decrease in the transmission power when a target pulse width of the control pulse set in accordance with the transmission power of the ultrasonic transducer is equal to or smaller than a predetermined threshold, and a function of outputting the control pulse with the target pulse width when the target pulse width exceeds the threshold.

[0027] According to the program of this aspect, the same effects as those of the first aspect can be achieved. Effect of the Invention

[0028] As described above, according to the present invention, it is possible to provide an underwater detection device, a control method for an underwater detection device, and a program that are capable of operating an ultrasonic transducer at a target transmission power even when the transmission power of the ultrasonic transducer is set low.

[0029] The effects and significance of the present invention will become clearer from the following description of the embodiment. However, the embodiment described below is merely an example of how the present invention can be put into practice, and the present invention is not limited to the embodiment described below. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram showing a usage pattern of a fish detector according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a fish detector according to an embodiment. [Diagram 3] FIG. 3 is a diagram showing a configuration of a transmission circuit according to an embodiment. [Figure 4] Fig. 4(a) is a time chart showing a control pulse when the pulse width is small according to an embodiment. Fig. 4(b) is a time chart showing a second voltage signal when the control pulse of Fig. 4(a) is output according to an embodiment. Fig. 4(c) is a time chart showing a method for correcting the pulse width of the control pulse according to an embodiment. [Diagram 5] 5(a) to 5(c) are diagrams illustrating a method for setting a threshold value according to an embodiment. [Figure 6] Fig. 6(a) is a diagram showing an example of the configuration of reference information according to the embodiment, Fig. 6(b) is a diagram showing another example of the configuration of reference information according to the embodiment. [Figure 7] FIG. 7 is a flowchart showing a process when the pulse width of a control pulse is set according to the transmission power of an ultrasonic transducer according to the embodiment. [Figure 8] FIG. 8 is a diagram showing a configuration of a transmission circuit according to a modified example. [Figure 9] FIG. 9 is a graph showing a schematic relationship between the waveform (ideal waveform) of a window function and the pulse width of a control pulse according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, a fish detector is shown as an example of an underwater detector.

[0032] FIG. 1 is a diagram showing a usage pattern of a fish finder.

[0033] In this embodiment, a transducer 2 is installed on the bottom of a ship 1, and a transmission beam 3 (ultrasonic waves) is transmitted from the transducer 2 underwater. The transmission beam 3 is shaped like a cone with a small apex angle and is transmitted in pulses in the vertically downward direction. The transmission beam 3 is reflected by the water bottom 4 and a school of fish 5, and the reflected waves (echoes) are received by the transducer 2. The received signal of the reflected wave based on a single transmission of the transmission beam 3 generates echo data in which the signal strength (echo intensity) of the received signal is distributed over the detection range in the water depth direction.

[0034] By accumulating echo data for a predetermined time, an echo image is generated that shows the distribution of signal intensity (echo intensity) in the water depth direction. The echo image includes the intensity distribution of the echoes from each target. The generated underwater echo image is displayed on a display unit installed in the wheelhouse of the ship 1 or the like. This allows the user to confirm targets (such as the bottom 4 and schools of fish 5) that exist underwater.

[0035] FIG. 2 is a block diagram showing the configuration of the fish detector 100. As shown in FIG.

[0036] The fish finder 100 includes a control circuit 101, a memory 102, a transmission circuit 103, a reception circuit 104, a switching circuit 105, an input unit 106, and a display unit 107, in addition to the transducer 2 shown in FIG.

[0037] The control circuit 101, memory 102, transmission circuit 103, reception circuit 104, switching circuit 105, input unit 106 and display unit 107 are installed in the wheelhouse or the like of the ship 1. The configuration except for the transducer 2 may be unitized in a single housing, or some of the components such as the display unit 107 may be separate. The switching circuit 105 is communicatively connected to the transducer 2 by a signal cable.

[0038] The transducer 2 includes a transmitting element used for transmitting ultrasonic waves and a receiving element used for receiving ultrasonic waves. In this embodiment, the transmitting element and the receiving element of the transducer 2 are configured by one ultrasonic transducer 21.

[0039] The transmission circuit 103 generates a transmission signal for driving the ultrasonic transducer 21 from a control signal (control pulse) of a predetermined frequency input from the control circuit 101, and outputs the generated transmission signal to the ultrasonic transducer 21 of the transmitter / receiver 2 via the switching circuit 105.

[0040] The ultrasonic transducer 21 transmits ultrasonic waves (transmission beam 3) into water based on the input transmission signal. The ultrasonic transducer 21 also receives the reflected waves of the transmitted ultrasonic waves, and outputs a reception signal having a magnitude according to the intensity of the reflected waves to the reception circuit 104 via the switching circuit 105. The switching circuit 105 switches between transmitting and receiving signals to the ultrasonic transducer 21.

[0041] The receiving circuit 104 includes a filter that extracts the frequency components of the transmitted waves from the received signal from the ultrasonic transducer 21, and an amplifier circuit that amplifies the received signal. The receiving circuit 104 generates echo data indicating the echo intensity for each depth based on the received signal of the frequency components extracted by the filter.

[0042] Specifically, the receiving circuit 104 generates echo data that associates the elapsed time from the timing of transmitting the ultrasonic wave (transmission beam 3) with the intensity of the reflected wave, and outputs the generated echo data to the control circuit 101.

[0043] Here, the time elapsed from the timing of transmitting the ultrasonic wave corresponds to the depth. Note that the strength of the reflected wave attenuates as the depth increases. Therefore, the receiving circuit 104 corrects the strength of the reflected wave that attenuates according to the elapsed time, and outputs the echo data with the corrected strength to the control circuit 101.

[0044] The control circuit 101 is composed of an arithmetic processing circuit such as a CPU, and an integrated circuit such as an FPGA. The memory 102 is composed of a ROM, a RAM, a hard disk, etc. Various programs and information are stored in the memory 102. These programs include a program that causes the control circuit 101 (computer) to execute a function of processing echo data to generate an image, and a function of correcting and setting the pulse width of a control signal (control pulse). The memory 102 is also used as a work area during processing by the control circuit 101. The control circuit 101 controls each part according to the programs stored in the memory 102.

[0045] The input unit 106 is composed of input means such as a mouse and a keyboard, and accepts input from a user. The input unit 106 may be a touch panel integrated with the display unit 107. The display unit 107 is composed of a display device such as a CRT monitor or a liquid crystal panel, and displays an image generated by the control circuit 101. As described above, the display unit 107 displays an echo image generated based on the echo data.

[0046] The control circuit 101 acquires echo data in which depth and echo intensity are associated with each other for each transmission timing of the ultrasonic wave (transmission beam 3). The control circuit 101 generates an echo image based on one frame of continuously acquired echo data, and displays the image on the display unit 107. The echo image is sometimes called an echogram.

[0047] An echo image is an image in which echo intensity is distributed in a coordinate region with two axes of depth and time. In an echo image, each pixel is colored or shaded in a gradation according to the signal intensity of the reflected wave. A user such as a fisherman can grasp the position and range of a school of fish in the water by referring to the echo image displayed on the display unit 107.

[0048] FIG. 3 is a diagram showing a configuration of the transmission circuit 103. As shown in FIG.

[0049] The transmission circuit 103 includes a FET driver 201, FETs 202 and 203 (field effect transistors), and an amplifier circuit 204. The two FETs 202 and 203 are connected in series between a power supply voltage Vdd and ground. The amplifier circuit 204 is connected between the two FETs 202 and 203.

[0050] The control circuit 101 outputs control pulses S01 and S02 for driving the FETs 202 and 203 to the FET driver 201. The control pulses S01 and S02 are voltage pulse signals with the same period and are out of phase with each other by a half period. The FET driver 201 outputs first voltage signals S11 and S12, which are respectively amplified from the input control pulses S01 and S02, to the gates of the FETs 202 and 203. This causes the FETs 202 and 203 to be alternately turned on at a predetermined period. The frequency of the first voltage signals S11 and S12 is the same as the frequency of the control pulses S01 and S02. Therefore, the operating frequency of the FETs 202 and 203 is also the same as the frequency of the control pulses S01 and S02.

[0051] When the upper FET 202 is turned on, a second voltage signal S21 having the power supply voltage Vdd at a high level is supplied to the amplifier circuit 204. The frequency of the second voltage signal S21 is the same as the frequency of the control pulse S01.

[0052] The amplifier circuit 204 includes a voltage conversion circuit such as a transformer. The amplifier circuit 204 boosts or lowers the second voltage signal S21 to generate a transmission signal of a predetermined frequency, and supplies the generated transmission signal to the ultrasonic transducer 21. This causes the ultrasonic transducer 21 to transmit ultrasonic waves.

[0053] When the lower FET 203 is turned on, a second voltage signal S22 is guided to ground from the amplifier circuit 204. The second voltage signal S22 is a voltage signal that remains in a transformer or the like in the amplifier circuit 204 when a transmission signal is generated. In this way, when the FETs 202 and 203 are turned on alternately by the first voltage signals S11 and S12, a transmission signal of a predetermined frequency is supplied to the ultrasonic transducer 21, and ultrasonic waves are transmitted from the ultrasonic transducer 21.

[0054] Incidentally, in the fish finder 100, the transmission power applied to the ultrasonic transducer 21 can be changed under certain conditions. For example, when another ship is nearby, the user reduces the transmission power via the input unit 106 in Fig. 2 so as to prevent ultrasonic interference with the other ship. Alternatively, when the water depth is shallow, the user reduces the transmission power to suppress saturation of the received echo.

[0055] Such control of transmission power is performed by adjusting the pulse width of the control pulse S01 input from the control circuit 101 to the transmission circuit 103 in the configuration shown in Fig. 3. When the pulse width of the control pulse S01 changes, the pulse width of the first voltage signal S11 changes, and the conduction period of the FET 202 changes. This changes the pulse width of the second voltage signal S21, and the power of the transmission signal supplied to the ultrasonic transducer 21 changes. The power of the transmission signal is determined by the voltage value and pulse width (integral value of the second voltage signal) of the second voltage signal S21. In this way, the transmission power of the ultrasonic transducer 21 can be controlled by the pulse width of the control pulse S01.

[0056] However, in the FET driver 201 and FET 202 in Fig. 3, a certain period (rise period) is required from the start of application of the input voltage until the output voltage stabilizes. For this reason, when the transmission power of the ultrasonic transducer 21 is set low and the pulse width of the control pulse S01 is small, for example, the control pulse may fall before these output voltages completely rise, and the actual transmission power may be significantly reduced from the target transmission power.

[0057] FIG. 4(a) is a time chart that typically shows the control pulse S01 when the pulse width is small, and FIG. 4(b) is a time chart that typically shows the second voltage signal S21 in this case.

[0058] In the example of Fig. 4(a), the target pulse width of the control pulse S01 according to the transmission power is a pulse width W0. The target pulse width is an ideal pulse width that is set to obtain the target transmission power.

[0059] In this case, ideally, as shown by the dashed line in Fig. 4(b), a rectangular second voltage signal S20 having the same pulse width as the pulse width W0 is output from the FET 202. However, in reality, due to the rise and fall periods in the FET driver 201 and the FET 202, a second voltage signal S21 having a waveform shown by the solid line in Fig. 4(b) is output from the FET 202. In this second voltage signal S21, the periods of inclination on the left and right sides correspond to the rise and fall periods based on the operating characteristics of the FET driver 201 and the FET 202, respectively.

[0060] In this case, the integral value of the actual second voltage signal S21, i.e., the area A21 surrounded by this second voltage signal S21 and the time axis, is much smaller than the integral value of the ideal second voltage signal S20, i.e., the area A20 surrounded by this second voltage signal S20 and the time axis. Therefore, with this second voltage signal S21, the target transmission power cannot be supplied to the ultrasonic transducer 21.

[0061] Therefore, in this embodiment, as shown in FIG. 4(c), the actual pulse width of the control pulse S01 is corrected from the target pulse width W0 to a pulse width W0' so that the integral value (area A21') of the second voltage signal S21' approaches the integral value (area A20) of the ideal second voltage signal S20 in FIG. 4(b). More specifically, the corrected pulse width W0' is set so that the area A21' is substantially equal to the area A20. As a result, the second voltage signal S21' is output from the FET 202 to the amplifier circuit 204. In this way, the ultrasonic transducer 21 can be operated at the target transmission power.

[0062] In this embodiment, such a correction is performed when the target pulse width W0 of the control pulse S01 is within a range equal to or less than a predetermined threshold value. Here, the threshold value is set based on the operating characteristics of at least one of the FET driver 201 and the FET 202.

[0063] 5(a) to (c) are diagrams showing a schematic diagram of a method for setting a threshold value.

[0064] 5(a) to 5(c) show control pulses S01 having different target pulse widths W0, respectively. The lower parts of Fig. 5(a) to 5(c) show an ideal second voltage signal S20 and an actual second voltage signal S21 output from the FET 202 when the control pulse S01 shown in the upper part is output from the control circuit 101.

[0065] The target pulse width W0 in the upper part is smallest in the case of Fig. 5(a) and largest in the case of Fig. 5(c). In Fig. 5(b), the actual rising period ΔT1 of the second voltage signal S21 and the pulse width W0 match. The rising period ΔT1 is based on the operating characteristics of the FET driver 201 and the FET 202.

[0066] 5(b) is input to FET driver 201, the output of FET driver 201 does not rise to a high level instantaneously, but gradually rises to a high level according to the operating characteristics (rise characteristics) of FET driver 201. When the output of FET driver 201 is input to the gate of FET 202, the output of FET 202 rises to a high level even more gently due to the operating characteristics (rise characteristics) of FET driver 201.

[0067] Thus, the rise period ΔT1, which is the period from the time when the output of the control pulse S01 starts (the time when the control pulse S01 changes from a low level to a high level) until the actual second voltage signal S21 reaches a high level, is determined by the operating characteristics (rise characteristics) of the FET driver 201 and the FET 202. Similarly, the fall period ΔT2, which is the period from the time when the output of the control pulse S01 ends (the time when the control pulse S01 changes from a high level to a low level) until the actual second voltage signal S21 reaches a low level, is also determined by the operating characteristics (fall characteristics) of the FET driver 201 and the FET 202. Usually, the rise period ΔT1 is shorter than the fall period ΔT2.

[0068] Here, the rise period ΔT1 is dominated by the rise characteristic of the FET driver 201 and the FET 202, whichever has the longer rise period (the one with the gentler rise gradient). Similarly, the fall period ΔT2 is dominated by the fall characteristic of the FET driver 201 and the FET 202, whichever has the longer fall period (the one with the gentler fall gradient).

[0069] In the example of Fig. 5(a), the target pulse width W0 of the control pulse S01 is smaller than the rising period ΔT1, so the output of the control pulse S01 ends before the actual second voltage signal S21 completely rises. Therefore, the actual second voltage signal S21 immediately falls to a low level thereafter. Therefore, in this case, the actual second voltage signal S21 becomes a triangular wave whose peak is smaller than the high level of the ideal second voltage signal S20.

[0070] In the example of Fig. 5(b), the target pulse width W0 of the control pulse S01 coincides with the rising period ΔT1, so the output of the control pulse S01 ends at the timing when the actual second voltage signal S21 completely rises. Therefore, after the actual second voltage signal S21 completely rises to a high level, it immediately falls to a low level. Therefore, in this case, the actual second voltage signal S21 becomes a triangular wave whose peak coincides with the high level of the ideal second voltage signal S20.

[0071] In the example of Fig. 5(c), the target pulse width W0 of the control pulse S01 is greater than the rising period ΔT1, so the output of the control pulse S01 ends a predetermined time after the actual second voltage signal S21 has completely risen. Therefore, the actual second voltage signal S21 falls to a low level after this predetermined time. Therefore, in this case, the actual second voltage signal S21 becomes a trapezoidal wave whose upper base coincides with the high level of the ideal second voltage signal S20.

[0072] Here, considering whether the correction shown in Fig. 4(c) is necessary, in the case of Fig. 5(a), the area A21 which is the integral value of the actual second voltage signal S21 is considerably smaller than the area A20 which is the integral value of the ideal second voltage signal S20, so this second voltage signal S21 cannot supply the target transmission power to the ultrasonic transducer 21. Therefore, in this case, the correction shown in Fig. 4(c) is necessary.

[0073] In contrast, in the case of Fig. 5(c), since the actual second voltage signal S21 is a trapezoidal wave, there is no significant difference between the area A21 and the area A20. Therefore, in this case, the target transmission power can be substantially supplied to the ultrasonic transducer 21, and the correction shown in Fig. 4(c) is not necessary.

[0074] In the case of Fig. 5(b), since the actual second voltage signal S21 rises to the high level of the ideal second voltage signal S20, the difference between the area A21 and the area A20 is not as large as in the case of Fig. 5(a). However, due to this difference, the transmission power supplied to the ultrasonic transducer 21 is slightly lower than the target transmission power. Therefore, in this case, it is preferable to perform the correction shown in Fig. 4(c).

[0075] From the above considerations, the threshold Th0 for determining whether or not to perform the correction in Fig. 4(c) can be set to the time width of the rising period ΔT1, for example, as shown in the lower part of Fig. 5(b). That is, when the target pulse width W0 of the control pulse S01 is equal to or less than the time width of the rising period ΔT1, which is the threshold Th0, the correction in Fig. 4(c) is performed, and the control pulse S01 having the corrected pulse width W0' is output from the control circuit 101. On the other hand, when the target pulse width W0 is larger than this threshold Th0, the correction is not performed, and the control pulse S01 having the target pulse width W0 is output from the control circuit 101.

[0076] Here, the rise time period ΔT1 can be obtained, for example, from data sheets provided by the manufacturers of the FET driver 201 and the FET 202.

[0077] In this case, if the rise period of FET driver 201 on the data sheet is shown as the period during which the output signal changes from 10% to 90% of the high level, that is, 80% of the entire rise period, the rise period of the FET driver may be obtained as the value obtained by dividing the rise period shown on the data sheet by 80% (in other words, the value obtained by multiplying the rise period on the data sheet by 1.25). The same applies to the rise period of FET 202.

[0078] As described above, the rise period ΔT1 is dominated by the longer of the rise periods of the FET driver 201 and the FET 202. For this reason, the rise period ΔT1 may be set as the longer of the rise periods of the FET driver 201 and the FET 202 obtained from the data sheet as described above.

[0079] The threshold value Th0 does not necessarily have to be set to the same time width as the rising period ΔT1, and may be set to be slightly longer than the time width of the rising period ΔT1. The threshold value Th0 may be set near the lower limit of the range of the target pulse width W0 that is assumed to be capable of substantially supplying the target transmission power to the ultrasonic transducer 21.

[0080] Furthermore, the target pulse width W0 may be set so that the target transmission power can be supplied to the ultrasonic transducer 21, taking into consideration that the actual second voltage signal S21 becomes a trapezoidal wave.

[0081] In this embodiment, in order to perform the correction in FIG. 4(c), reference information is stored in the memory 102 in FIG.

[0082] The reference information is information that associates a first parameter value related to a target pulse width W0 with a second parameter value used for the above-mentioned correction. The reference information is information that associates the first parameter value with the second parameter value in a range in which the target pulse width W0 of the control pulse S01 is equal to or smaller than the above-mentioned threshold value Th0.

[0083] FIG. 6(a) is a diagram showing the configuration of the reference information.

[0084] In FIG. 6(a), the target pulse width W0 is set as the first parameter value, and the corrected pulse width W0' is set as the second parameter value. Target pulse widths W01-W0n included in the range equal to or less than the above-mentioned threshold value Th0 are registered in the reference information as the first parameter value. These target pulse widths W01-W0n are target pulse widths that can be selectively used in the fish finder 100. The corrected pulse widths W01'-W0n' are respectively associated with the target pulse widths W01-W0n.

[0085] Here, as described with reference to FIG. 4(c), the corrected pulse widths W01' to W0n' are set in advance so that the integral value (area A21') of the second voltage signal S21' obtained from the corrected pulse widths W01' to W0n' matches the integral value (area A20) of the ideal second voltage signal S20.

[0086] That is, taking into consideration the operating characteristics (rise period ΔT1 and fall period ΔT2) of the FET driver 201 and the FET 202, for each of the target pulse widths W01 to W0n, a corrected pulse width W01' to W0n' when the area A21' matches the area A21 is calculated, and each of the calculated corrected pulse widths W01' to W0n' is linked to the corresponding target pulse width W01 to W0n.

[0087] It should be noted that the first parameter value and the second parameter value are not limited to the target pulse width W0 and the corrected pulse width W0'.

[0088] For example, as shown in FIG. 6(b), the second parameter may be a correction amount for the target pulse width W0. The correction amounts A01-A0n are the differences between the target pulse widths W01-W0n in FIG. 6(a) and the corrected pulse widths W01'-W0n'. In this case, the corrected pulse widths W01'-W0n' for the target pulse widths W01-W0n are obtained by adding the correction amounts A01-A0n to the target pulse widths W01-W0n, respectively. The second parameter value may be any value that allows the corrected pulse width W0' to be obtained.

[0089] The first parameter value may also be another value related to the target pulse width W0. For example, the first parameter value may be the magnitude of the transmission power.

[0090] FIG. 7 is a flowchart showing a process when the pulse width W0 of the control pulse S01 corresponding to the transmission power of the ultrasonic transducer 21 is set.

[0091] The control circuit 101 determines whether the transmission power of the ultrasonic transducer 21 has been changed (S101). If an input for changing the transmission power is made via the input unit 106 while the fish finder 100 is in operation, the determination in step S101 will be YES. In addition, the determination in step S101 will also be YES when the fish finder 100 is started up, that is, when the ultrasonic transducer 21 starts operating at the initial transmission power. If the determination in step S101 is YES, the control circuit 101 determines whether the target pulse width W0 corresponding to the current transmission power is equal to or less than the above-mentioned threshold value Th0 (S103).

[0092] If the target pulse width W0 is equal to or smaller than the threshold value Th0 (S102: YES), the control circuit 101 acquires a corrected pulse width W0' corresponding to the current target pulse width W0 from the reference information in Fig. 6(a) (S103). Then, the control circuit 101 sets the pulse width of the control pulse S01 to the acquired corrected pulse width W0', and performs an output operation of the control pulse S01 (S104).

[0093] On the other hand, if the target pulse width W0 is greater than the threshold value Th0 (S102: NO), the control circuit 101 sets the pulse width of the control pulse S01 to the target pulse width W0 and performs the output operation of the control pulse S01 (S105). After setting the pulse width of the control pulse S01 in step S104 or S105, the control circuit 101 ends the process. Thereafter, the control circuit 101 returns the process to step S101 and executes the same process.

[0094] <Effects of the embodiment> According to this embodiment, the following effects are achieved.

[0095] As shown in Fig. 4(a)-(c) and Fig. 7, in the range where the target pulse width W0 of the control pulse S01 is equal to or less than the threshold value Th0, that is, in the range where the actual transmission power may be significantly lower than the target transmission power due to the influence of the rising period ΔT1 in the lower part of Fig. 5(b) if the target pulse width W0 is used as is (S102: YES), the actual pulse width W0' of the control pulse S01 is corrected from the target pulse width W0 so as to suppress this drop and obtain the desired transmission power (S103, S104). As a result, even in the range where the transmission power of the ultrasonic transducer 21 is small, that is, in the range where the target pulse width W0 is equal to or less than the threshold value Th0, the ultrasonic transducer 21 can be operated at the target transmission power.

[0096] Furthermore, in a range where the target pulse width W0 of the control pulse S01 exceeds the threshold value Th0, that is, in a range where the actual transmission power does not decrease significantly from the target transmission power even if the target pulse width W0 is used as is (S102: NO), the control pulse S01 is output with the target pulse width W0 unchanged. Therefore, in this case as well, the ultrasonic transducer 21 can be operated with the target transmission power.

[0097] As described with reference to Figures 4(a) to (c), when the target pulse width W0 is equal to or smaller than the threshold value Th0, the control circuit 101 performs the above-mentioned correction so that the integral value (area A20) of the ideal second voltage signal S20 that should be output from the FET 202 (power transistor) when the control pulse S01 is output with the target pulse width W0 approaches the integral value (area A21') of the actual second voltage signal S21' output from the FET 202 (power transistor) when the control pulse S01 is output with the actual pulse width W0'.

[0098] According to this configuration, the actual integral value (area A21') of the second voltage signal S21' approaches the ideal integral value (area A21), so that the transmission power of the ultrasonic transducer 21 can approach the target transmission power. Therefore, the ultrasonic transducer 21 can be operated at the target transmission power.

[0099] 2 and 6(a) and (b), the fish finder 100 includes a memory 102 that stores reference information that associates a first parameter value related to a target pulse width W0 with a second parameter value used for correction within a range equal to or less than a threshold value Th0. Then, in the process of FIG. 7, the control circuit 101 obtains the second parameter value for the current target pulse width W0 (here, the corrected pulse width W0') from the reference information and performs the above-mentioned correction.

[0100] According to this configuration, the pulse width of the control pulse S01 can be corrected by a simple process of acquiring the second parameter value from the reference information.

[0101] As described with reference to FIGS. 5(a) to 5(c), the threshold value Th0 is set based on the operating characteristics of at least one of the FET driver 201 and the FET 202 (power transistor).

[0102] According to this configuration, the threshold value Th0 is set based on the operating characteristics of the FET driver 201 or the FET 202 (power transistor), which are factors that cause the transmission power to decrease from the ideal value, so that the threshold value Th0 can be set appropriately.

[0103] 5(a) to 5(c), the operating characteristic for setting the threshold value Th0 is, for example, the rise time period ΔT1 of the output voltage relative to the DC input voltage, and the threshold value Th0 is set based on the rise time period ΔT1. Specifically, the threshold value Th0 is set to be substantially equal to the rise time period ΔT1.

[0104] 5(a) to (c) substantially corresponds to the pulse width W0 of the control pulse S01 when the control pulse S01 falls at the timing when the second voltage signal S21 output from the FET 202 (power transistor) completely rises. Therefore, when the pulse width W0 of the control pulse S01 is smaller than this rising period ΔT1, the second voltage signal S21 becomes a triangular wave waveform that transitions to the falling period ΔT2 before completely rising, and the transmission power of the ultrasonic transducer 21 drops significantly from the target transmission power. Therefore, by setting the threshold value Th0, that is, the threshold value that specifies the range for correcting the pulse width of the control pulse S01, based on this rising period ΔT1, the pulse width of the control pulse S01 can be appropriately corrected.

[0105] <Example of change> The present invention is not limited to the above-described embodiment, and various modifications of the embodiment of the present invention are possible in addition to the above-described configuration.

[0106] For example, in the above embodiment, the corrected pulse width W0' is obtained using the reference information in Figures 6(a) and (b), but the method of correcting the pulse width W0 of the control pulse S01 is not limited to this. For example, as shown in Figure 8, the second voltage signal S21 may be fed back to the control circuit 101, and the pulse width W0 of the control pulse S01 may be feedback-controlled so that the integrated value (area A21) of the second voltage signal S21 approaches the integrated value (area A20) of the ideal second voltage signal S20.

[0107] In this case, the memory 102 stores an integrated value (area A20) of the ideal second voltage signal S20 for each pulse width W0 within a range equal to or less than the threshold value Th0. The control circuit 101 obtains the integrated value (area A20) corresponding to the current target pulse width W0 from the memory 102. Then, the control circuit 101 controls the pulse width W0 of the control pulse S01 so that the integrated value (area A21) of the actual second voltage signal S21 approaches the integrated value (area A20) during the actual ultrasonic wave transmission operation. The actual integrated value (area A21) may be an average value of the integrated values ​​(areas A21) from the current time to several previous times.

[0108] 5(a)-(c) and may be changed as appropriate. For example, in the above embodiment, the threshold Th0 is set using the larger of the rising periods of the FET driver 201 and the FET 202, that is, the one that predominantly affects the rising period ΔT1 of the second voltage signal S21, but the threshold Th0 may be set by taking into account both the rising periods of the FET driver 201 and the FET 202. Alternatively, the rising period ΔT1 of the second voltage signal S21 may be actually measured and the threshold Th0 may be set.

[0109] Furthermore, in the above embodiment, the pulse width W0 of the control pulse S01 output from the control circuit 101 is constant, but as shown in FIG. 9, for example, the pulse width W0 may vary during one wave transmission period (ping).

[0110] In the example of Fig. 9, the pulse width W0 of the control pulse S01 is adjusted so that the envelope waveform of the transmission wave (transmission power) transmitted in one transmission period becomes a waveform according to a predetermined window function. This makes it possible to suppress the influence of frequency components other than the fundamental wave, for example. As the window function, for example, a Hamming window or a Gaussian window can be used. However, the window function is not limited to these windows. The window function can be changed as appropriate depending on the purpose.

[0111] For convenience, 24 control pulses S01 are shown in Fig. 9, but the actual number of control pulses S01 is several steps more. The pulse width W0 of the control pulse S01 becomes larger toward the center of the window function period. In this way, by adjusting the pulse width W0 of the control pulse S01 according to the window function, the transmission wave is transmitted with a transmission power according to the window function.

[0112] In this case, for the control pulse S01 whose pulse width W0 is equal to or smaller than the threshold value Th0, the pulse width is corrected in step S103 of FIG. 7, whereas for the control pulse S01 whose pulse width W0 is larger than the threshold value Th0, this correction is not performed and the control pulse S01 is output with a pulse width based on the window function.

[0113] However, in this case, if the threshold value Th0 is set from the same perspective as in the above embodiment, a magnitude reversal phenomenon may occur between the corrected pulse width W0' and the uncorrected pulse width W0 at the boundary between application and non-application of correction.

[0114] That is, when the pulse width W0 in FIG. 5(b) is set to the threshold value Th0, the corrected pulse width W0'(n) is set so that the target area A20 is obtained at the pulse width W0(n) equal to the threshold value Th0. This pulse width W0'(n) is larger than the pulse width W0(n) before correction. On the other hand, the next pulse width W0(n+1) expanded from this pulse width W0(n) according to the above resolution is not corrected, so the pulse width remains W0(n+1). Therefore, when the difference between the pulse width W0(n) and the pulse width W0'(n) exceeds the difference between the pulse width W0(n) and the pulse width W0(n+1), the corrected pulse width W0'(n) becomes larger than the uncorrected pulse width W0(n+1). This causes a reversal phenomenon in the size of the pulse width around the boundary of the threshold value Th0.

[0115] In this way, when an inversion phenomenon occurs in the magnitude of the pulse width of adjacent control pulses S01 with the threshold value Th0 as a boundary, distortion occurs in the envelope waveform of the transmission power at the positions of these two control pulses S01. Therefore, when changing the pulse width of the control pulse S01 in one transmission period as shown in Fig. 9, it is preferable to set the threshold value Th0 so that the above-mentioned inversion phenomenon does not occur.

[0116] Specifically, the threshold value Th0 is set so that the difference between the pulse width W0(n) and the pulse width W0'(n) does not exceed the difference between the pulse width W0(n) and the pulse width W0(n+1) (i.e., the difference between the pulse width W0(n) and the pulse width W0'(n) is equal to or smaller than the difference between the pulse width W0(n) and the pulse width W0(n+1)). That is, the threshold value Th0 is set so that the corrected pulse width W0'(n) of the preceding control pulse S01 of these two control pulses S01 does not exceed the target pulse width W0(n) of the succeeding control pulse S01. More specifically, the threshold value Th0 is set to a value as small as possible within the range of the threshold value Th0 that can satisfy this condition, and more preferably, the threshold value Th0 is set near the lower limit of this range. This makes it possible to avoid the above-mentioned inversion phenomenon and suppress distortion of the envelope waveform of the transmission wave.

[0117] In the example of Fig. 9, the period of the control pulse S01 is constant, but the period of the control pulse S01 may be modulated. That is, a frequency-modulated transmission wave may be output from the ultrasonic transducer 21. In this case, the threshold value Th0 may be set by the method described with reference to Fig. 9.

[0118] 2, only one ultrasonic transducer 21 is arranged in the transducer 2, but multiple ultrasonic transducers may be arranged in the transducer 2. In this case, the above-mentioned correction process may be performed for each ultrasonic transducer. Alternatively, when the same type of FET driver 201 and FET 202 are used for all ultrasonic transducers, the corrected pulse width W0' may be set uniformly to the pulse width of the control pulse for all ultrasonic transducers.

[0119] In the above embodiment, the reference information is stored in the memory 102, but the reference information may be stored in an internal memory of the control circuit 101.

[0120] In the above embodiment, an example is shown in which the present invention is applied to the fish detector 100 mounted on the ship 1, but the application of the present invention is not limited to this. For example, the present invention may be applied to a fish detector installed in a fixed net, or to an underwater detection device other than a fish detector, such as a scanning sonar.

[0121] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the claims. [Explanation of symbols]

[0122] 100 Fish finder 101 Control circuit 102 Memory 201 FET driver (driver) 202 FET (power transistor) A20 Area (integral value of ideal second voltage signal) A21, A21' Area (integral value of actual second voltage signal) S01 Control pulse S11 First voltage signal S12 Second voltage signal Th0 threshold W0 Target pulse width W0' Pulse width after correction ΔT1 Rise period

Claims

1. A control circuit that outputs a control pulse; a driver that outputs a first voltage signal in response to the control pulse; a power transistor that is turned on in response to the input of the first voltage signal and outputs a second voltage signal for operating an ultrasonic transducer; The control circuit includes: When a target pulse width of the control pulse, which is set according to a transmission power of the ultrasonic transducer, is equal to or less than a predetermined threshold value, an actual pulse width is corrected from the target pulse width to output the control pulse, thereby suppressing a decrease in the transmission power; When the target pulse width exceeds the threshold value, the control pulse is output with the target pulse width. An underwater detection device characterized by:

2. 2. The underwater detection device according to claim 1, When the target pulse width is equal to or less than the threshold value, the control circuit performs the correction to bring an ideal integral value of the second voltage signal to be output from the power transistor when the control pulse is output at the target pulse width closer to an actual integral value of the second voltage signal output from the power transistor when the control pulse is output at the actual pulse width. An underwater detection device characterized by:

3. 2. The underwater detection device according to claim 1, a memory configured to store reference information that associates a first parameter value related to the target pulse width with a second parameter value used for the correction within a range equal to or less than the threshold value; the control circuit acquires the second parameter value corresponding to the current target pulse width from the reference information and performs the correction. An underwater detection device characterized by:

4. 2. The underwater detection device according to claim 1, the threshold is set based on an operating characteristic of at least one of the driver and the power transistor; An underwater detection device characterized by:

5. 5. The underwater detection device according to claim 4, the operating characteristic is a rise time of an output voltage relative to a DC input voltage, The threshold is set based on the rise period. An underwater detection device characterized by:

6. 5. The underwater detection device according to claim 4, the control circuit outputs the control pulse so that a transmission wave output from the ultrasonic transducer has an envelope waveform based on a predetermined window function; By setting the threshold value, of two control pulses adjacent to each other with the threshold value as a boundary, the corrected pulse width of the preceding control pulse is equal to or smaller than the target pulse width of the succeeding control pulse. An underwater detection device characterized by:

7. A method for controlling an underwater detection device comprising: a driver that outputs a first voltage signal in response to a control pulse; and a power transistor that is turned on by input of the first voltage signal and outputs a second voltage signal for operating an ultrasonic transducer, the method comprising the steps of: When a target pulse width of the control pulse, which is set according to a transmission power of the ultrasonic transducer, is equal to or less than a predetermined threshold value, an actual pulse width is corrected from the target pulse width to output the control pulse, thereby suppressing a decrease in the transmission power; When the target pulse width exceeds the threshold value, the control pulse is output with the target pulse width. A method for controlling an underwater detection device.

8. A control circuit for an underwater detection device, comprising: a control circuit for outputting a control pulse; a driver for outputting a first voltage signal in response to the control pulse; and a power transistor for outputting a second voltage signal for operating an ultrasonic transducer by being turned on in response to the input of the first voltage signal. a function of correcting an actual pulse width from the target pulse width of the control pulse, which is set according to the transmission power of the ultrasonic transducer, to output the control pulse when the target pulse width of the control pulse is equal to or smaller than a predetermined threshold value, thereby suppressing a decrease in the transmission power; and a program for executing a function of outputting the control pulse with the target pulse width when the target pulse width exceeds the threshold value.

Images