JP6587564B2 - Acoustic measurement device, acoustic measurement method, multi-beam acoustic measurement device, and aperture synthesis sonar - Google Patents

Description

The present invention, depth using ultrasound, acoustic measurement device for measuring the distance or the like to an object, acoustic measuring method, a multi-beam acoustic measurement device and aperture synthesis sonar.

  An acoustic sounding device is known as one of acoustic measuring devices. Acoustic sounding technology in the ocean has been practiced for a long time, and as shown in Fig. 1, an ultrasonic pulse is emitted from an ultrasonic transducer and the sound wave is reflected from the target (sea floor), and the underwater sound is detected. The depth is measured using the propagation speed of the sound wave (approximately 1500 m / s). An acoustic sounding device using this principle has been commercialized for more than 50 years, and even today, depth measurement of the sea floor is performed using this principle. This technique called echo location has been used without change, in other words, without development.

  The principle is that if an ultrasonic pulse (for example, 1 ms pulse width) is emitted and the seabed is 500 m and the round-trip distance is 1000 m and the underwater velocity Vu is 1500 m / s, 1000 / Vu = 1000/1500 = 0.667 seconds. Since it returns, after receiving the echo, it emits an ultrasonic pulse again, and at the same time, the depth of the seabed in a different place is measured as the ship advances. In this way, it is called an acoustic sounding device that measures the depth of the seabed sequentially as a ship navigates and displays it on a liquid crystal screen as recording paper or an image (see, for example, Patent Document 1).

  Conventional acoustic sounding devices have taken sounding by controlling the transmission interval so that the next transmission is not performed before the received echo in consideration of the sound speed of ultrasonic waves in water. As shown in FIG. 2, a depth measuring device having only one beam is called a single beam depth measuring device, and a device that spreads a plurality of beams in a fan shape that has recently appeared is called a multi-beam depth measuring device (see, for example, Patent Document 2). Multi-beam sounding device can measure a wide range of depth at once.

  When the depth is D, the transmission interval of transmission pulses is T, and (2D / 1500) <T, the time difference between the transmission pulse and the reception echo corresponds to (2D / 1500), as shown in FIG. The depth can be measured from this time difference. However, in the case of (2D / 1500) ≧ T, as shown in FIG. 3B, since the reception echo arrives after the transmission of the next transmission pulse, it is not known which transmission pulse the reception echo corresponds to. An incorrect depth is measured based on the time difference FD. Therefore, conventionally, the condition of (2D / 1500) <T was necessary.

If the transmission cycle cannot be shortened, the horizontal resolution of depth measurement cannot be reduced. The resolution of measurement in the traveling direction (horizontal direction) of the ship will be described with reference to FIG. The horizontal resolution ΔH (m) when the depth D (m) is measured at the ship speed V (m / s) is expressed by the following equation.
ΔH = VT> 2DV / 1500

  For example, if a ship navigates at 10 kt (10 × 1.852 km / h) and the transmission cycle is 1 second, depth measurement data can be obtained only about every 5 m. To measure the seabed at a depth of 1,000m, the transmission cycle T must be (1,000 × 2) /1,500=1.33 seconds or more, but if the ship sails at 10 kt, it is 1.33. Since it has advanced 6.7 m after 2 seconds, the measurement resolution ΔH is 6.67 m. The multi-beam sounding device can measure a wide range of depth at a time, but the resolution of the ship's direction of travel is the same as that of a single beam.

JP 2001-083247 A JP 2006-220436 A

  In the conventional acoustic sounding device, there was no method other than reducing the speed of the ship in order to increase the measurement resolution. Therefore, the conventional acoustic sounding device has a problem that the time required for sounding is long when the sounding resolution is increased.

Accordingly, an object of the present invention can eliminate the constraints of the transmission cycle, short realize the transmission period by acoustic measurement device which can increase the resolution, acoustic measurement method, the multi-beam acoustic measurement device and synthetic aperture sonar Is to provide.

This onset Ming is installed in a mobile object such as a ship, in the acoustic measurement device to detect the water to be measured,
A transmission signal forming unit having a modulation circuit for forming a transmission signal by modulating a carrier wave signal by a pseudo noise sequence signal of the pseudo-noise sequence generator and a transmission timing in synchronism with the transmit trigger pulse generating a pseudo-noise sequence signal,
A transmitter that sequentially transmits the transmission signal as an ultrasonic wave toward the bottom of the moving body; and
A receiver for receiving echoes reflected from the measurement object with ultrasonic waves transmitted from the transmitter;
By correlating the echo with the pseudo-noise sequence signal, the echo corresponding to the transmission signal is determined, and a correlator that measures the distance to the measurement object based on the time difference between the transmission signal and the echo;
A display device that displays echoes in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as the upper transmission line on the screen, displays the signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse in color, and displays the adjacent transmission trigger pulse respectively. Display corresponding detection signals in order,
The period of the transmission signal is an acoustic measurement apparatus in which the velocity of the sound wave in water is Vu and the distance to the measurement target is D, which is (2D / Vu) or less.
The present onset Ming, the acoustic measurement method for detecting the water measured by the installed sound measurement device to the moving body such as a ship,
A pseudo noise sequence signal is generated by a pseudo noise sequence generation circuit in synchronization with a transmission trigger pulse , a carrier signal is modulated by a pseudo noise sequence signal at a transmission timing, and a transmission signal is formed.
The transmission unit sequentially sends the transmission signal as an ultrasonic wave toward the bottom of the moving body,
The ultrasonic echo sent from the transmitter is received by the receiver,
By correlating the echo with the correlator, the echo corresponding to the transmission signal is discriminated, the distance to the measurement object is measured based on the time difference between the transmission signal and the echo,
Echo is displayed on the display device in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as the upper transmission line on the screen, displays the signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse in color, and displays the adjacent transmission trigger pulse respectively. Display corresponding detection signals in order,
The period of the transmission signal is an acoustic measurement method in which the velocity of the sound wave in water is Vu and the distance to the measurement target is D, which is (2D / Vu) or less.

The present onset Ming is installed in a mobile object such as a ship, in the multibeam acoustic measurement device to detect the water to be measured,
A pseudo-noise sequence generation circuit that generates a pseudo-noise sequence signal in synchronization with a transmission trigger pulse, and a transmission signal forming unit that has a modulation circuit that modulates a carrier wave signal with a pseudo-noise sequence signal at a transmission timing to form a transmission signal;
A transmitter that sequentially transmits the transmission signal as an ultrasonic wave toward the bottom of the moving body; and
A receiver for receiving echoes reflected from the measurement object with ultrasonic waves transmitted from the transmitter;
By correlating the echo with the pseudo-noise sequence signal, the echo corresponding to the transmission signal is determined, and a correlator that measures the distance to the measurement object based on the time difference between the transmission signal and the echo;
A display device that displays echoes in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as the upper transmission line on the screen, displays the signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse in color, and displays the adjacent transmission trigger pulse respectively. Display corresponding detection signals in order,
The period of the transmission signal is (2D / Vu) or less, where Vu is the velocity of the sound wave in water and D is the distance to the measurement target ,
It is a multi-beam acoustic measurement device that sends out a large number of ultrasonic beams in a fan shape by a transmitter.
Furthermore, the onset Ming is installed in a mobile object such as a ship, in synthetic aperture sonar to detect the water to be measured,
A pseudo-noise sequence generation circuit that generates a pseudo-noise sequence signal in synchronization with a transmission trigger pulse, and a transmission signal forming unit that has a modulation circuit that modulates a carrier wave signal with a pseudo-noise sequence signal at a transmission timing to form a transmission signal;
A transmitter that sequentially transmits the transmission signal as an ultrasonic wave toward the bottom of the moving body; and
A receiver for receiving echoes reflected from the measurement object with ultrasonic waves transmitted from the transmitter;
By correlating the echo with the pseudo-noise sequence signal, the echo corresponding to the transmission signal is determined, and a correlator that measures the distance to the measurement object based on the time difference between the transmission signal and the echo;
A display device that displays echoes in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as the upper transmission line on the screen, displays the signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse in color, and displays the adjacent transmission trigger pulse respectively. Display corresponding detection signals in order,
Cycle of the transmission signal, the speed of the water waves and Vu, the depth to the measurement target when is D, is less (2D / Vu),
It is an aperture synthesis sonar that creates a directivity equivalent to a long aperture transmitter / receiver by moving a pair of transmitter / receiver.

  According to the present invention, since the transmission cycle can be shortened, the resolution in the horizontal direction can be increased. In the present invention, since the transmission cycle is short, there is a correlation between the received echo signals before and after. Therefore, since the S / N ratio can be improved by adding the received echo signals before and after, the received echo signal can be added even at a low transmission output, and the apparatus can be downsized and designed to save power. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present specification.

It is a basic diagram which shows the principle of acoustic sounding. It is a basic diagram for demonstrating single beam depth measurement and multi-beam depth measurement. It is a wave form diagram used for description of the conventional acoustic sounding device. It is a basic diagram used for description of the horizontal direction resolution of the conventional acoustic sounding device. It is a block diagram which shows the structure of one embodiment of this invention. It is a block diagram used for description of the correlator in one embodiment of the present invention. It is a wave form diagram used for description of the output of a correlator. It is a basic diagram explaining the case where a received signal is displayed. It is a wave form diagram which shows an example of the modulation method of a transmission signal. It is a wave form diagram used for description of one embodiment of this invention. It is a basic diagram used for description of the horizontal direction resolution of one embodiment of this invention. It is a wave form diagram used for description of one embodiment of this invention. It is a basic diagram used for description of the horizontal direction resolution of one embodiment of this invention. It is an approximate line figure using the result of the simulation of the conventional acoustic sounding device for explanation. It is a basic diagram which uses the result of the simulation of the acoustic sounding device by this invention for description. It is a basic diagram which compares and shows the display image by the conventional acoustic sounding device and the display image by the acoustic sounding device of this invention. It is a wave form diagram of an example of the transmission signal of the acoustic sounding device by this invention. It is a wave form diagram used for description when two Gold code signals overlap in the sound sounding device by the present invention. It is a basic diagram for demonstrating the principle of an aperture synthetic | combination side scan sonar. It is a basic diagram for demonstrating the directivity characteristic of aperture synthesis. It is a basic diagram for demonstrating the principle of aperture synthesis. It is a basic diagram which shows an example of a point target. It is a basic diagram which shows the image of an example of a point target. It is a basic diagram which shows the image before aperture synthesis | combination of an example of the point target in this invention, and the image after aperture synthesis | combination. It is a basic diagram which shows the image before aperture synthesis of an example of the conventional point target, and the image after aperture synthesis. It is a basic diagram which shows the image before aperture synthesis | combination of an example of the 2-point target in this invention, and the image after aperture synthesis | combination. It is a basic diagram used for description of a multi-beam acoustic sounding instrument. It is a block diagram which shows the structure of other embodiment which applied this invention to the multi-beam acoustic sounding instrument.

Embodiments of the present invention will be described below. The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is not limited to the following description. Unless otherwise specified, the present invention is not limited to these embodiments.
The description of the present invention will be made in the following order.
<1. Embodiment>
<2. Other embodiments>
<3. Modification>

<1. Embodiment>
FIG. 5 shows an electrical configuration of an embodiment of an acoustic sounding device according to the present invention. A transmission trigger generator 1 for generating a transmission trigger pulse of a pulse signal having a constant period is provided, and the transmission trigger pulse is supplied to a gold code generator 2 as a PN sequence generator and a display or recording device 10. The display and / or recording device 10 includes a display device such as a liquid crystal and / or a recording device such as a semiconductor memory and an arithmetic device for display or recording.

The gold code generator 2 generates a gold code in synchronization with the transmission trigger pulse. A PN (Pseudorandom Noise) sequence such as an M sequence other than the gold code may be used. A gold code is supplied to the pulse modulator 3, and the gold code is digitally modulated by, for example, BPSK (Binary Phase Shift Keying). The frequency of the carrier wave is several tens kHz to several hundreds kH
z.

  The output signal of the pulse modulator 3 is supplied to the transmission amplifier 4, and processing such as amplification is performed in the transmission amplifier 4. The output signal of the transmission amplifier 4 is supplied to the transmitter 5. Underwater ultrasonic waves are sent out from the transmitter 5. The echoes of the emitted underwater ultrasonic waves are received by the receiver 6. An integrated configuration may be used as the transmitter 5 and the receiver 6.

  The received data from the receiver 6 is supplied to the receiving amplifier 7, subjected to processing such as amplification, and then supplied to the correlator 8. The output of the correlator 8 is supplied to the detection circuit 9. A correlator 8 extracts a reception echo corresponding to the transmission pulse. The detection circuit 9 performs calculation for display (for example, A / D conversion). The output of the detection circuit 9 is supplied to the display and / or recording device 8, and the time until the echo is received for the transmission pulse is displayed and / or recorded, respectively.

  FIG. 6 shows the correlation detection process. The received echo signal is input in series to the 4064-step shift register SR. It is preferable to improve the S / N ratio by adding a plurality of reception echo signals before and after the shift register SR. Noise can be reduced by the addition processing, and a low transmission output can be achieved, which enables downsizing of the apparatus and power saving design. The shift clock for operating the shift register SR is (20 × 8 = 1, 600 kHz = 1.6 MHz). This frequency is an example, and a shift clock having a frequency twice or more the carrier frequency (20 kHz) can be used. The received echo signal is sampled at a frequency eight times that of the carrier signal by being supplied to the shift register SR.

  Arithmetic circuits EXA1 to EX127 are provided in parallel to the shift register SR. Each of the arithmetic circuits EXA1 to EX127 includes an exclusive OR circuit and an adder circuit (4064 circuit). The 4064 bits of the shift register SR are commonly supplied to the exclusive OR circuits of the arithmetic circuits EXA1 to EX127.

On the other hand, a replica of the gold code G1 (replica is 4064 bits), a replica of the code G2,..., And a replica of the code G127 are supplied to the exclusive OR circuits of the arithmetic circuits EXA1 to EX127, respectively. . The exclusive OR circuit outputs “0” if the two input bits have the same value, and outputs “1” if the two input bits have different values. The 4064-bit output of each exclusive OR circuit is added. In the addition, if the number of “1” is N, a signal having an amplitude of N is output. By taking negative logic, an output with a larger value can be obtained as the two inputs coincide. The addition outputs of the arithmetic circuits EXA1 to EX127 are as shown in FIG. A large amplitude output indicates a received echo signal that matches the gold code of the transmitted pulse.

  FIG. 8 illustrates a case where display is performed on the display and / or recording apparatus 10. A transmission trigger pulse is supplied to the display and / or recording device 10, and the timing of the transmission trigger pulse is displayed as a transmission line (0 m) on the upper side of the screen. The detection signal from the detection circuit 9 for the transmission trigger pulse is displayed with a color, for example. Since the transmission trigger pulse is a fast repetitive signal of several Hz to several tens of Hz, the detection signals corresponding to each of the transmission trigger pulses from the correlator 8 are displayed so as to be sequentially arranged, thereby comparing with the conventional acoustic sounding device. As a result, the depth measurement image appears several times to several tens of times faster.

  FIG. 9 illustrates an example of pulse modulation. For example, the phase is switched between 0 and π in correspondence with the gold code bits “0” and “1” every four periods (four waves) of a 200 kHz carrier wave. The frequency of the carrier wave is an example, and other frequencies may be used, and a modulation scheme such as QPSK other than BPSK may be used. Further, not only phase modulation but also amplitude modulation may be used.

  Correlator 8 detects correlation by digital signal processing. One bit is composed of 4 periods, and each period is digitized with 8 samples. Therefore, when the code of the Gold code is 127 bits, one received echo signal is (127 × 4 × 8 = 4064 bits).

  In the above-described embodiment of the present invention, the transmission signal and the reception echo signal (sea bottom echo) can be identified. As shown in FIG. 10, the transmission signal A and the transmission signal B are different gold codes. A reception echo signal corresponding to the transmission signal A is received after the transmission signal B, and it can be identified that the reception echo signal corresponds to the transmission A. Therefore, the restriction ((2D / 1500) <T) related to the transmission cycle T as in the prior art can be eliminated.

In one embodiment of the present invention, the horizontal resolution is expressed by the following equation.
ΔH = VT

  For example, if a ship navigates at 10 kt (10 × 1.852 km / h) and the transmission cycle is 0.1 second, ΔH = 0.5 m, and the horizontal resolution (measurement interval) is determined regardless of the depth of measurement. be able to. As shown in FIG. 11, the horizontal resolution ΔH is determined only from the transmission cycle T and the ship speed V regardless of the depth. Furthermore, the case where six types of transmission signals can be identified is schematically shown in FIGS. Thus, the transmission cycle T can be shortened, depth measurement can be performed regardless of the depth, and high horizontal measurement resolution can be obtained.

  Although the transmission signal can be identified by frequency or the like, in the frequency discrimination method, if the frequency range to be used is widened, propagation loss in water varies depending on the frequency, which is not preferable because a frequency difference appears in the detection distance. In the present invention, since the transmission signal is identified by one frequency, such a problem does not occur. In other words, since the transmission signal can be identified, there is no restriction that the next transmission signal is emitted after the echo of the seabed returns as in the conventional transmission cycle, depth measurement is possible with a short transmission cycle, and the horizontal resolution is reduced. It can be improved dramatically.

  A simulation result and an example of actual measurement will be described with reference to FIGS. 14, 15, and 16. FIG. 14 shows a transmission signal and a reception echo signal (sea bottom echo) obtained by a conventional acoustic sounding device. The transmission cycle is 0.1 sec, and echoes on the sea floor appear around 0.07 sec. The transmission signal can be transmitted for the next time after the echo is received, and the depth can be known by measuring the time from transmission to reception. In this case, if the underwater sound speed is 1500 / sec, a depth of (0.07 × 1,500 / 2 = 52.5 m) can be obtained.

  On the other hand, in the acoustic sounding device according to the present invention, the transmission cycle can be determined regardless of the depth, and in the example of FIG. 15, the transmission cycle is 0.05 sec. A submarine reception echo signal is obtained between the transmission signals, but the identification numbers A, B, C,... That can be identified are added to the transmission signals, so that the reception signals can be identified after passing through the correlator. . Identification can be made even with a transmission cycle shorter than this example. Moreover, even if a transmission signal and a reception signal overlap, it can identify.

  A comparison is made between an image of a conventional sound sounding device and an image of the sound sounding device according to the present invention for an actual received echo signal. 16A and 16B are images of a conventional acoustic sounding device. FIG. 16 shows a comparison between an image of a conventional acoustic sounder and an image of an acoustic sounder according to the present invention. FIG. 16A is a conventional image with an abscissa of 30 seconds, and FIG. 16B is an image with an ordinate of 3 seconds. In this example, the image is transmitted four times per second, and the horizontal axis is a considerably coarse image.

  On the other hand, FIG. 16C is an image when the method of the present invention is applied, the transmission cycle is 0.05 sec, and transmission is performed 20 times per second. FIG. 16D is an enlarged view of a part of FIG. 16C. It can be seen that there is a considerably finer resolution in the horizontal axis direction compared to FIG. 16B. The actual transmission signal when the transmission cycle is 50 times per second is as shown in FIG. A 200 kHz signal is phase-modulated with a 5th-order 127-bit gold code and 4 waves as 1 bit, and a pulse signal modulated with a different gold code every 20 ms is arranged and transmitted.

One pulse width Pd is expressed by the following equation, where the carrier frequency is fc, the number of waves used for one bit is N cycles, and the length of the gold code is M bits.
Pd = (1 / fc) × N × M

When the carrier frequency fc = 200 kHz, the number N of waves used for 1 bit, and the gold code length M = 127, the pulse width Pd is as follows.
Pd = 1/200000 × 4 × 127 = 0.00254 = 2.54 msec

  Furthermore, even if the transmission cycle is shortened so that the two transmission pulses are transmitted, they can be separated after the correlation processing. FIG. 18 shows that even if two gold code signals (GC1 and GC2) are transmitted or received in an overlapping manner, the two gold code signals can be detected separately.

  Next, aperture synthesis will be described. Aperture synthesis is a technique for increasing the resolution by forming a directivity equivalent to a transducer with a long aperture by moving one transducer. As shown in FIG. 19, a method of obtaining horizontal resolution equivalent to that of a length L transmitter / receiver by repeating transmission / reception while moving a length d transmitter / receiver is used as an aperture synthesis sonar. Yes. Briefly, as shown in FIG. 20, the directivity angle of the length L of the transducer after aperture synthesis is sharpened by the ratio d / L as compared to the directivity angle due to the length d of the transducer. The resolution is improved.

  In the coordinate system shown in FIG. 21, the combined signal S (x, y) of the reflected signal from the position of P (x, y) can be expressed by the following equation.

  Here, An is a directivity function, tn is the time required for reciprocation to the target P, and can be expressed by the following equation, where c is the underwater sound velocity.

  It will be explained using computer simulation that the resolution is improved by aperture synthesis. If there is a point target at a position as shown in FIG. 22, the echo of the target is an arc-shaped image as shown in FIG. 23 in the conventional acoustic sounding device or sonar. FIG. 24A is an enlarged image for easy understanding, but this image has already adopted the method according to the present invention, and 20 transmissions per second, that is, 100 echoes on this image. It is a simulation image.

  If this image is processed using the aperture synthesis method, an image as shown in FIG. 24B is obtained. FIG. 24C shows an enlarged part of FIG. 24B. As can be seen from FIGS. 24B and 24C, the point target can be detected with a resolution of about 0.1 m. As conditions for aperture synthesis, the transmission cycle was 0.05 sec (20 times / sec), the transducer moving speed was 2 m / sec, and the aperture length was 10 m.

  Similarly, when the aperture synthesis method is employed in the conventional method, as shown in FIG. 25A, when the transmission cycle is once per second, the moving speed is 2 m / sec, and the aperture length is 10 m. Since only transmission is possible, there are only 5 reception echoes. Therefore, even if aperture synthesis is performed, only a low resolution image as shown in FIG. 25B can be obtained.

  FIG. 26 shows an image in which two point targets are arranged at a distance of 0.2 m. Although two point targets cannot be separated before aperture synthesis (FIG. 26A), two point targets are obtained after aperture synthesis (FIG. 26B). Can be separated. FIG. 26C shows an enlarged part of FIG. 26B.

  The aperture synthesis technique is an existing technique, but the aperture synthesis technique can be effectively used by advancing the transmission cycle using the technique of the present invention. That is, in the conventional aperture synthesis method, the next transmission is performed after the received echo returns, as in the conventional acoustic depth measurement. Therefore, the transmission cycle T when the maximum detection distance is R is (2R) as described above. / 1500 <T). Therefore, when the maximum detection distance is set to R = 500 m, (T> 2 × 500/1500 = 0.67 sec) must be set, so that the transmission cycle is normally 1 time / second. On the other hand, if the method of the present invention is used, the transmission cycle can be set without being restricted by the maximum detection distance, so 20 times / second is possible, and aperture synthesis can be used effectively.

The advantages of the present invention described above are as follows.
Conventional acoustic sounding devices and the like are restricted by the speed of sound waves in water, but this restriction is eliminated in the present invention. The restriction of the speed of sound waves in water means that a conventional acoustic sounding device or the like sends a transmission signal and then sends an echo signal from the seabed or the like and then sends the next transmission signal.
When aperture synthesis processing is performed by a conventional acoustic sounding device or the like, the transmission cycle cannot be shortened due to such a restriction, so the only way to increase the received data in the aperture is to reduce the ship speed. If the technique of the present invention is adopted, a transmission signal can be transmitted with a transmission cycle several to several tens of times that of a conventional acoustic sounding device or the like. It is.

  Since the transmission cycle cannot be shortened due to the restriction of the speed of the sound wave, the received signal often has no correlation with the previous received signal, so it is difficult to improve the SN ratio by adding a plurality of received signals. On the other hand, in the present invention, since the transmission cycle can be drastically shortened, there is a correlation between the preceding and following signals. Therefore, since the signal-to-noise ratio can be improved by adding the received signals before and after, the received signal can be added even at a low transmission output, and the apparatus can be reduced in size and designed to save power.

  Radar is known as a technology very similar to fish finder. Radar uses radio waves because it is a device used in the air. The speed of radio waves is 300,000 km / sec, which is 200,000 times faster than the speed of sound waves in water of 1.5 km / sec. For this reason, even if the radar detection range is 100 km, for example, the round-trip time of a 100 km radio wave is 0.00067 sec = 0.67 ms, and the transmission cycle can be 1 ms. That is, even if transmission is performed 1,000 times per second, it does not overlap with the received echo. On the other hand, if an attempt is made to detect the seabed of 1,000 m in water, the received echo signal returns after 1,000 × 2/1500 = 1.33 seconds, so the transmission cycle is about 1.5 seconds. The radar and acoustic sounding device have a ratio of 1.5 seconds / 1 ms = 1,500 times the actual detection distance of 100 km and 1,000 m. You can see if there is a restriction on the transmission cycle. If the present invention is used, this restriction is eliminated and the transmission cycle can be drastically shortened, so that it is possible to design an epoch-making acoustic sounding device or the like.

<2. Other embodiments>
A multi-beam acoustic sounding device will be described as another embodiment of the present invention. As shown in FIG. 27, the multi-beam acoustic sounding instrument has a directivity called a fan beam that is narrow in the traveling direction of the ship and wide in the left-right direction, and a transmission signal is transmitted from one transmitter. Since it has a plurality of beams that are wide in the longitudinal direction of the ship and narrow in the left-right direction so as to cross the transmission beam, it is called a multi-beam acoustic sounding device. FIG. 28 shows the configuration of a multi-beam acoustic sounding instrument according to another embodiment of the present invention.

  Similar to the above-described embodiment, a transmission trigger generator 1, a gold code generator 2, a pulse modulator 3, a transmission amplifier 4, and a transmitter 5 are provided as a configuration on the transmission side. Underwater ultrasonic waves are sent out from the transmitter 5. The transmission signal is a signal having a transmission cycle of several Hz to several tens of Hz.

Unlike the receiving unit of the single beam acoustic sounding device, the receiving unit of the multi-beam acoustic sounding device has a plurality of receivers 6 _{1 to} 6 _N. Receiving amplifiers 7 _{1 to} 7 _N are connected to the receivers 6 _{1 to} 6 _N , and correlators 8 ₁ to 8 _N are connected to the receiving amplifiers 7 _{1 to} 7 _N. The output signals from the correlators 8 ₁ to 8 _N are input to the beam forming circuit 11 for the output for each gold code, and are subjected to beam forming to form a plurality of received beams.

For example, as described in US Pat. No. 4,159,462, the beam forming circuit 11 includes analog delay circuits to which outputs of the correlators 8 ₁ to 8 _N are supplied, and delays of the analog delay circuits. This is a circuit including a delay selection matrix that gives a predetermined delay by selecting an element and an adder circuit that adds the outputs of the analog delay circuit. The output of the beam forming circuit 11 is supplied to the display and / or recording device 8, and the time until the echo is received for the transmission pulse is displayed and / or recorded, respectively. Even when the present invention is applied to such a multi-beam acoustic sounding instrument, the same operational effects as those of the above-described embodiment can be obtained.

<3. Modification>
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the configuration, method, process, shape, material, numerical value, and the like given in the above-described embodiment are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, and the like are used as necessary. Also good. For example, when performing correlation detection, it is possible to detect the correlation after demodulating the received echo signal into a code. Further, in the above description, the acoustic sounding device has been described. However, the present invention can be applied to devices that use sound sounding technology such as a multi-beam sound sounding device, a side scan sonar, a fish finder, and a scanning sonar. .

  The functions of the processing device in the above-described embodiment can be recorded as a program on a recording medium such as a magnetic disk, a magneto-optical disk, or a ROM. Therefore, the function of the acoustic measurement device can be realized by reading this recording medium with a computer and executing it with an MPU (Micro Processing Unit), DSP (Digital Signal Processor) or the like.

DESCRIPTION OF SYMBOLS 1 Transmission trigger pulse generator 2 Gold code generator 3 Pulse modulator 5 Transmitter 6 Receiver 6 Correlator 10 Display and / or recording device SR Shift register EXA1-EX127 Arithmetic circuit

Claims (4)

In an acoustic measurement device that is installed on a moving body such as a ship and detects an underwater measurement target,
A transmission signal forming unit having a modulation circuit for forming a transmission signal by modulating a carrier wave signal by said pseudo noise sequence signal of the pseudo-noise sequence generator and the transmission timing that produces a pseudo noise sequence signal in synchronism with the transmit trigger pulse,
A transmission unit for sequentially sent toward the previous SL transmission signal under the bottom of the moving body as an ultrasonic,
A receiving unit for receiving echoes reflected from the measurement object with ultrasonic waves transmitted from the transmitting unit;
A correlator for determining the echo corresponding to the transmission signal by performing correlation processing on the echo with the pseudo noise sequence signal and measuring a distance to the measurement object based on a time difference between the transmission signal and the echo When,
A display device that displays the echo in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as an upper transmission line on the screen, displays a signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse, and displays the adjacent signal. The detection signals corresponding to the transmission trigger pulses are displayed so as to be sequentially arranged,
The period of the transmission signal is an acoustic measurement device in which the velocity of the sound wave in water is Vu and the distance to the measurement target is D, which is (2D / Vu) or less. In an acoustic measurement method for detecting a measurement target in water by an acoustic measurement device installed in a moving body such as a ship ,
A pseudo noise sequence signal is generated by a pseudo noise sequence generation circuit in synchronization with a transmission trigger pulse, and a carrier signal is modulated by the pseudo noise sequence signal at a transmission timing to form a transmission signal,
The transmission unit sequentially transmits the transmission signal as an ultrasonic wave toward the bottom of the moving body,
An ultrasonic echo sent from the transmitter is received by the receiver,
Correlating the echo by a correlator, determining the echo corresponding to the transmission signal, measuring the distance to the measurement object based on the time difference between the transmission signal and the echo,
The echo is displayed by a display device in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as an upper transmission line on the screen, displays a signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse, and displays the adjacent signal. The detection signals corresponding to the transmission trigger pulses are displayed so as to be sequentially arranged,
The period of the transmission signal is set to be (2D / Vu) or less, where Vu is the velocity of sound waves in water and D is the distance to the measurement target. In a multi-beam acoustic measurement device that is installed on a moving body such as a ship and detects an underwater measurement target,
A pseudo-noise sequence generating circuit that generates a pseudo-noise sequence signal in synchronization with a transmission trigger pulse, and a transmission signal forming unit having a modulation circuit that modulates a carrier wave signal by the pseudo-noise sequence signal at the transmission timing to form a transmission signal;
A transmitter for sequentially transmitting the transmission signal as an ultrasonic wave toward the bottom of the moving body;
A receiving unit for receiving echoes reflected from the measurement object with ultrasonic waves transmitted from the transmitting unit;
A correlator for determining the echo corresponding to the transmission signal by performing correlation processing on the echo with the pseudo noise sequence signal and measuring a distance to the measurement object based on a time difference between the transmission signal and the echo When,
A display device that displays the echo in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as an upper transmission line on the screen, displays a signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse, and displays the adjacent signal. The detection signals corresponding to the transmission trigger pulses are displayed so as to be sequentially arranged,
The period of the transmission signal is set to (2D / Vu) or less, where Vu is the velocity of sound waves in water and D is the distance to the measurement target ,
A multi-beam acoustic measurement device that sends out a large number of ultrasonic beams in a fan shape by the transmission unit. In an aperture synthetic sonar that is installed on a moving body such as a ship and detects underwater measurement objects,
A pseudo-noise sequence generating circuit that generates a pseudo-noise sequence signal in synchronization with a transmission trigger pulse, and a transmission signal forming unit having a modulation circuit that modulates a carrier wave signal by the pseudo-noise sequence signal at the transmission timing to form a transmission signal;
A transmitter for sequentially transmitting the transmission signal as an ultrasonic wave toward the bottom of the moving body;
A receiving unit for receiving echoes reflected from the measurement object with ultrasonic waves transmitted from the transmitting unit;
A correlator for determining the echo corresponding to the transmission signal by performing correlation processing on the echo with the pseudo noise sequence signal and measuring a distance to the measurement object based on a time difference between the transmission signal and the echo When,
A display device that displays the echo in synchronization with the transmission signal,
The display device displays the timing of the transmission trigger pulse as an upper transmission line on the screen, displays a signal obtained by detecting the output signal of the correlator with respect to the transmission trigger pulse, and displays the adjacent signal. The detection signals corresponding to the transmission trigger pulses are displayed so as to be sequentially arranged,
The period of the transmission signal is (2D / Vu) or less, where Vu is the velocity of sound waves in water and D is the depth to the measurement target ,
A synthetic aperture sonar that is equivalent to a long-aperture transmitter / receiver by moving a pair of transmitters / receivers.

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