Wave generation device, object detection system, and wave generation method

Abstract

To generate a wave that provides the same effect as radiating both a carrier wave having amplitude modulated and ultrasonic wave by a signal due to one-time radiation .SOLUTION: A wave generation device comprises: an information signal generation unit; an information signal coding unit; a carrier wave generation unit; a carrier wave coding unit; and an amplitude modulation unit that performs an amplitude modulation of a carrier wave longer in a wavelength than an information signal coded by a second code by the information signal coded by a first code in which a value changes in a prescribed cycle.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wave generation device, an object detection system, and a wave generation method.

Background Art

[0002] There is a technique for emitting sound waves into the air and measuring the distance to an object based on the reflected wave from the object. In this technique, by emitting sound waves with a long wavelength, the sound waves are diffracted, and an invisible region that cannot be detected by visible light can also be detected. Emitting sound waves with a long wavelength to detect an invisible region is described in, for example, Patent Document 1.

[0003] In the technique of Patent Document 1, by radiating a carrier wave amplitude-modulated by a signal into space using a parametric speaker, the directivity of the signal is improved. Further, by encoding the signal and pulse-compressing the received reflected wave, the range resolution and the SN ratio are increased.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method described in Patent Document 1, in order to distinguish an object in the visible region from an object in the invisible region, it is necessary to radiate a carrier wave amplitude-modulated by a signal and ultrasonic waves separately. An object of the present invention is to provide a wave generation device, an object detection system, and a wave generation method that generate a wave having the same effect as radiating both a signal amplitude-modulated by a carrier wave and ultrasonic waves by radiating once.

Means for Solving the Problems

[0006] One aspect of the present invention is a wave generation device comprising: an amplitude modulation unit that amplitude modulates a carrier wave having a longer wavelength than the information signal encoded by a second code using an information signal encoded by a first code whose value changes at a predetermined period.

[0007] One aspect of the present invention is a wave generation method comprising: an amplitude modulation step of amplitude modulating a carrier wave having a longer wavelength than the information signal encoded by a second code, using an information signal encoded by a first code whose value changes at a predetermined period. [Effects of the Invention]

[0008] According to the present invention, it is possible to generate a wave that produces the same effect as emitting both a carrier wave amplitude-modulated by a signal and ultrasound by emitting them only once. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing the configuration of an object detection system. [Figure 2] This is a diagram showing the configuration of a wave generator. [Figure 3] This is an example of an encoded information signal. [Figure 4] This is an example of a multiplexed modulation signal. [Figure 5] This is a diagram showing the configuration of a wave analysis device. [Figure 6] This figure shows the relationship between the received signal f(t), the transmitted signal g(t), and the correlated signal (f*g)(t). [Figure 7] This figure shows an example of an object detection system in operation. [Figure 8] This is an example of a graph showing the correlation signal calculated by the information signal pulse compression unit. [Figure 9] This is an example of a graph showing the correlation signal calculated by the carrier pulse compression unit. [Figure 10] This graph shows the calculation results from the information signal pulse compression unit and the carrier pulse compression unit. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. <Object detection system> Figure 1 shows the configuration of the object detection system 1. The object detection system 1 includes a wave generator 11, a transmitter 12, a receiver 21, and a wave analyzer 22.

[0011] The wave generator 11 generates waves. The transmitter 12 radiates the waves generated by the wave generator 11. The transmitter 12 is, for example, a speaker. The receiver 21 receives the waves. The wave analysis device 22 analyzes the waves received by the receiver 21. In the object detection system 1, the waves generated by the wave generator 11 are radiated by the transmitter 12. The reflected waves generated when the radiated waves strike an object are received by the receiver 21. The waves received by the receiver 21 are analyzed by the wave analysis device 22 to identify information about the object.

[0012] <Wave generation device> Figure 2 shows the configuration of the wave generator 11. The wave generator 11 comprises an information signal generation unit 111, an information signal encoding unit 112, a carrier wave generation unit 113, a carrier wave encoding unit 114, and an amplitude modulation unit 115.

[0013] The information signal generation unit 111 generates an information signal. The information signal is, for example, a low-frequency sound wave. The frequency of the information signal is, for example, a frequency that falls within the range of 1 kHz to 10 kHz. Because the frequency is low, the wave diffracts and bends around the back of an object. If the frequency is below 1 kHz, the resolution of object recognition becomes coarse, and if the frequency is above 10 kHz, the wave has high straightness of propagation and no bending occurs. On the other hand, since multiple modulation can be achieved regardless of frequency, depending on the purpose, waves below 1 kHz or waves above 10 kHz may be used.

[0014] The information signal encoding unit 112 encodes the information signal to generate an encoded information signal. The first code used for encoding the information signal is a code that takes on two values at a predetermined period. The first code is, for example, a Golay code or an M-sequence code. FIG. 3 is an example of an encoded information signal. In FIG. 3, the information signal is encoded by a Golay code. The Golay code is a code that becomes 1 or -1 at a predetermined period. The encoded information signal is the product of the information signal and the Golay signal, and is a signal in which the positive and negative of the information signal during the period when the Golay signal is -1 are reversed. Reversing the positive and negative of the information signal is equivalent to inverting the phase of the signal or advancing it by 180 degrees.

[0015] The carrier wave generation unit 113 generates a carrier wave. The carrier wave is, for example, an ultrasonic wave with a frequency higher than that of the information signal. When generating a sound wave by a parametric speaker, the frequency of the carrier wave is preferably a frequency included in the range of, for example, 40 kHz to 50 kHz (for example, 44.1 kHz). Note that when using a transmitter other than a parametric speaker, the frequency of the carrier wave does not have to be limited to the above range.

[0016] The carrier wave encoding unit 114 encodes the carrier wave to generate an encoded carrier wave. The second code used for encoding the carrier wave by the carrier wave encoding unit 114 is a code that takes on two values at a predetermined period. It is desirable that the ratio of the period of the first code to the period of the second code is an integer ratio. That is, it is desirable that the timing at which the values of the first code and the second code change coincides. The fact that the ratio of the period of the first code to the period of the second code is an integer ratio includes the case where the periods of the first code and the second code are the same. The carrier wave encoding unit 114 encodes the carrier wave with, for example, a Golay code.

[0017] The amplitude modulation unit 115 amplitude-modulates the encoded carrier wave with the encoded information signal to generate a multiplexed modulation signal. FIG. 4 is an example of a multiplexed modulation signal.

[0018] The first communication unit 116 communicates with the wave analysis device 22. The first communication unit 116 transmits, for example, encoded information signals and encoded carrier waves to the wave analysis device 22.

[0019] <Transmitter> The transmitter 12 radiates the multiplexed modulation signal generated by the wave generator 11. The transmitter 12 is, for example, a parametric speaker that radiates highly directional waves.

[0020] When a multiplexed modulated signal propagates through the air, the encoded information signal is self-demodulated and propagated due to the nonlinear interaction between the encoded information signal and the encoded carrier wave. In other words, radiating a multiplexed modulated signal can achieve the same effect as radiating both the encoded information signal and the encoded carrier wave.

[0021] <Receiver> The receiver 21 receives both a signal with the same frequency as the information signal and a signal with the same frequency as the carrier wave. The receiver 21 is, for example, a microphone when receiving a signal propagating through air, and a hydrophone when receiving a signal propagating through water. The receiver 21 is installed in close proximity to the transmitter 12. For example, the receiver 21 is installed almost directly above or almost directly below the transmitter 12.

[0022] <Wave analysis device> Figure 5 shows the configuration of the wave analysis device 22. The wave analysis device 22 comprises a second communication unit 220, an information signal detection unit 221, a carrier wave detection unit 222, and an output unit 223.

[0023] The second communication unit 220 communicates with the wave generator 11. The second communication unit 220 receives, for example, encoded information signals and encoded carrier waves from the wave generator 11.

[0024] The information signal detection unit 221 detects waveforms similar to the encoded information signal from the frequency components of the information signal of the signal received by the receiver 21. For example, the information signal detection unit 221 detects similar waveforms by pulse-compressing the frequency components of the information signal of the signal received by the receiver 21 based on the encoded information signal. More specifically, the information signal detection unit 221 calculates the correlation between the encoded information signal (transmitted signal) generated by the information signal encoding unit 112 and received by the second communication unit 220 and the frequency components of the information signal (received signal) of the signal received by the receiver 21.

[0025] The correlation between the transmitted signal and the received signal is calculated using equation (1).

[0026]

number

[0027] In equation (1), f(t) represents the magnitude of the received signal with respect to time, and g(t) represents the magnitude of the transmitted signal with respect to time. In the correlation (f*g)(t), the time when the value is large is the time from when the transmitted signal is reflected by an object until the reflected signal is received. Figure 6 shows the relationship between the received signal f(t), the transmitted signal g(t), and the correlation signal (f*g)(t).

[0028] The carrier detection unit 222 detects waveforms similar to the encoded carrier wave from the frequency components of the carrier wave of the signal received by the receiver 21. The carrier detection unit 222 detects similar waveforms, for example, by pulse-compressing the frequency components of the carrier wave of the signal received by the receiver 21 based on the encoded carrier wave. More specifically, the carrier detection unit 222 calculates the correlation between the encoded carrier wave generated by the carrier encoding unit 114 and the frequency components of the carrier wave of the signal received by the receiver 21. The method for calculating the correlation is the same as for the information signal detection unit 221, using equation (1).

[0029] The output unit 223 outputs the detection results from the information signal detection unit 221 and the carrier wave detection unit 222, respectively. The output unit 223 outputs the correlation calculated by the information signal detection unit 221 and the carrier wave detection unit 222, for example. The output correlation is displayed on the display as a graph with the correlation value on the vertical axis and time on the horizontal axis. By considering the speed at which the signal is transmitted, a graph with the correlation value on the vertical axis and distance on the horizontal axis can also be created. The correlations calculated by the information signal detection unit 221 and the carrier wave detection unit 222, respectively, may be displayed superimposed on a graph for easy comparison.

[0030] <Examples> Figure 7 shows an example of the implementation of the object detection system 1. A first target 31 and a second target 32 ​​are installed opposite the transmitter 12. The first target 31 and the second target 32 ​​are objects that reflect sound waves from 1 kHz to 50 kHz, such as wooden boards or people. However, the first target 31 and the second target 32 ​​may be objects that reflect sound waves in the range of several hundred Hz to several tens of kHz. The first target 31 is installed at a distance of r1 [m] from the transmitter 12, and the second target 32 ​​is installed at a distance of r2 [m] from the transmitter 12. In this embodiment, the first code and the second code used to encode the information signal and the carrier wave are Golay codes having the same period.

[0031] In the embodiment shown in Figure 7, when the first target 31 is viewed from the transmitter 12, the second target 32 ​​is hidden behind the first target 31 and cannot be seen. In other words, the first target 31 is an object in the visible region, and the second target 32 ​​is an object in the invisible region. In the embodiment shown in Figure 7, waves with the same frequency as the information signal are diffracted, reach behind the first target 31, and are reflected by the second target 32, but waves with the same frequency as the carrier wave are not diffracted, do not reach behind the first target 31, and are not reflected by the second target 32.

[0032] Figure 8 is an example of a graph showing the correlation calculated by the information signal detection unit 221. In the graph shown in Figure 8, the vertical axis represents the signal intensity, and the horizontal axis represents the distance between the point where the signal was emitted and the point where it was reflected. In other words, the graph shown in Figure 8 shows that the information signal was reflected at points r1 [m] and r2 [m] away from the receiver 21, and that the first target 31 and the second target 32 ​​are located at those points.

[0033] Figure 9 is an example of a graph showing the correlation calculated by the carrier wave detection unit 222. In the graph shown in Figure 9, the vertical axis represents the signal intensity, and the horizontal axis represents the distance between the point where the signal was emitted and the point where it was reflected. In other words, the graph shown in Figure 9 shows that the carrier wave was reflected at a point r1 [m] away from the receiver 21, and that the first target 31 is at that point.

[0034] By comparing the graphs shown in Figures 8 and 9, the position of the first target 31 in the visible region and the position of the second target 32 ​​in the invisible region can be estimated.

[0035] The object detection system 1 encodes the carrier path, amplitude modulates the encoded information signal and the encoded carrier path, and emits the modulated signal. This allows it to acquire both the information obtained from the information signal and the information obtained from the carrier wave with a single signal emission. This enables more efficient object detection.

[0036] <Experimental Results> The details of the experiment conducted are described below. The first target 31 was placed 5 m away from the transmitter 12, and the second target 32 ​​was placed 7 m away from the transmitter 12. The first target 31 was a wooden board 90 cm high and 50 cm wide, and the second target 32 ​​was a wooden board 90 cm high and 30 cm wide. The frequency of the information signal was 1470 Hz, and the frequency of the carrier wave was 44.1 kHz.

[0037] Figure 10 is a graph showing the calculation results by the information signal detection unit 221 and the carrier wave detection unit 222. The vertical axis represents signal strength, and the horizontal axis represents distance. The solid line shows the relationship between the signal strength of the information signal and distance, while the dashed line shows the relationship between the signal strength of the carrier wave and distance. The information signal shows peaks in intensity at approximately 5m and approximately 7m. However, the carrier wave shows a peak in intensity only at approximately 5m. This indicates that there is an object in the visible region at a distance of 5m from the transmitter 12, and an object in the invisible region at a distance of 7m.

[0038] <Other Embodiments> Although one embodiment of this invention has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the spirit of this invention.

[0039] The object detection system 1 is not limited to detecting objects in the invisible region. For example, the object detection system 1 may estimate a pattern by irradiating a multiplexed modulation signal onto a pattern of uneven surfaces with different spacings, thereby acquiring two different pieces of information about the pattern.

[0040] The codes used to encode the information signal and carrier wave are not limited to codes that take binary values ​​at a predetermined period. For example, the information signal and carrier wave may be encoded using pseudo-noise or pseudo-random noise.

[0041] The method for encoding the information signal and carrier wave is not limited to phase modulation. For example, the information signal and carrier wave may be encoded by frequency modulation or amplitude modulation.

[0042] The wave generator 11 and the wave analyzer 22 may be implemented using the same device. In this case, the wave generator 11 does not need to have a first communication unit 116, and the wave analyzer 22 does not need to have a second communication unit 220.

[0043] In the embodiment described above, the wave generator 11 generates and radiates one multiplexed modulation signal, but it may radiate multiple multiplexed modulation signals with different encoding schemes. That is, the information signal encoding unit 112 may encode an information signal using a first code to generate a first encoded information signal, and encode an information signal using a second code whose period of value change is different from that of the first code to generate a second encoded information signal. The carrier encoding unit 114 may encode a carrier wave using a first code to generate a first encoded carrier wave, and encode a carrier wave using a second code to generate a second encoded carrier wave. The amplitude modulation unit 115 may modulate the first encoded carrier wave using the first encoded information signal to generate a first multiplexed modulation signal, and modulate the second encoded carrier wave using the second encoded information signal to generate a second multiplexed modulation signal. The transmitter 12 may radiate the first multiplexed modulation signal and the second multiplexed modulation signal.

[0044] The wave analysis device 22 may sum up the results of pulse compression obtained from different multiplexed modulation signals. More specifically, the wave analysis device 22 may sum up different correlations calculated by the information signal detection unit 221 based on different multiplexed modulation signals. The sum of the different correlations is the sum of the signal strengths for any given distance. This increases the peak signal strength value and reduces the peak width, making it easier to detect or confirm the peak.

[0045] Some or all of the wave generator 11 and wave analyzer 22 in the above-described embodiment may be implemented using a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. Here, "computer system" includes the OS and peripheral hardware. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and recording devices such as hard disks built into a computer system. Moreover, "computer-readable recording medium" may include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such a case. Furthermore, the above-mentioned program may be for implementing some of the functions described above, or it may be a program that can implement the above-mentioned functions in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array). [Explanation of Symbols]

[0046] 1 Object detection system, 11 Wave generation device, 12 Transmitter, 21 Receiver, 22 Wave analysis device, 111 Information signal generation unit, 112 Information signal coding unit, 113 Carrier wave generation unit, 114 Carrier wave coding unit, 115 Amplitude modulation unit, 116 First communication unit, 220 Second communication unit, 221 Information signal detection unit, 222 Carrier wave detection unit, 223 Output unit

Claims

1. An amplitude modulation unit that amplitude modulates an encoded carrier wave using an encoded information signal, Equipped with, The encoded information signal is generated by encoding the information signal with a first code whose value changes at a predetermined period. The encoded carrier wave is generated by encoding the carrier wave with a second code whose value changes at a predetermined period. The aforementioned information signal is a sound wave, The carrier wave is a sound wave with a higher frequency than the information signal. Wave generator.

2. The first and second signs are signs that take two values ​​with a predetermined period. The wave generating apparatus according to claim 1.

3. The ratio of the period of the first sign to the period of the second sign is an integer ratio. The wave generating apparatus according to claim 1 or 2.

4. A wave generating apparatus according to any one of claims 1 to 3, A speaker that emits a signal amplitude-modulated by the amplitude modulation unit, A microphone that receives a signal with the same frequency as the information signal and a signal with the same frequency as the carrier wave, An object detection system equipped with a wave analysis device, The wave analysis device is An information signal detection unit detects a waveform similar to the encoded information signal from the frequency components of the information signal of the signal received by the microphone, A carrier wave detection unit detects a waveform similar to the encoded carrier wave from the frequency components of the carrier wave of the signal received by the microphone, An object detection system equipped with the following features.

5. The system further comprises an output unit that outputs the detection results from the information signal detection unit and the carrier wave detection unit. The object detection system according to claim 4.

6. The information signal detection unit calculates the correlation between the frequency component of the information signal of the signal received by the microphone and the information signal, The carrier detection unit calculates the correlation between the frequency component of the carrier wave of the signal received by the microphone and the carrier wave. The object detection system according to claim 4 or 5.

7. An amplitude modulation step of amplitude modulating an encoded carrier wave with an encoded information signal, It has, The encoded information signal is generated by encoding the information signal with a first code whose value changes at a predetermined period. The encoded carrier wave is generated by encoding the carrier wave with a second code whose value changes at a predetermined period. The aforementioned information signal is a sound wave, The carrier wave is a sound wave with a higher frequency than the information signal. A wave generation method having the following characteristics.

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