JP2018059827A - Range finder, ranging method, and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a range finder and a ranging method that can increase calculation accuracy of distance from a plurality of measurement objects.SOLUTION: A range finder generates a transmission signal with a frequency modulated, projects a measurement wave based on the transmission signal, obtains a reception signal based on a reflection wave, detects a first frequency on the basis of a first differential frequency signal obtained from the transmission signal and the reception signal, removes a signal component related to the first frequency from the first differential frequency signal to generate a second differential frequency signal, detects a second frequency on the basis of the second differential frequency signal, and calculates distance from a measurement object on the basis of the first frequency and the second frequency.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a distance measuring device, a distance measuring method, and a vehicle.

  Conventionally, in a distance measuring apparatus, an ultrasonic device, a millimeter wave device, an infrared light device, or the like is known as a device that transmits a signal to a measurement target. As a distance measuring method, a pulse method, a phase difference method, or the like is known (for example, see Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 06-059038 JP 2000-137076 A JP 2007-256095 A JP 2002-90447 A

  In the FMCW method, a peak frequency is detected from a beat signal including information related to a frequency difference between a transmitted signal and a signal reflected from a measurement target. The distance to the measurement object is calculated based on the peak frequency. When there are a plurality of measurement objects, it may be difficult to detect the peak frequency from the beat signal. In this case, the calculation accuracy of the distance to each measurement object may be lowered.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a distance measuring device, a distance measuring method, and a vehicle that can improve the calculation accuracy of the distances of a plurality of measurement objects.

  A distance measuring device according to an embodiment of the present disclosure includes a transmitter that emits a measurement wave, a receiver that receives a reflected wave obtained by reflecting the measurement wave on a measurement target, and a control device. . The control device generates a transmission signal whose frequency is modulated. The control device controls the wave emitter to emit the measurement wave based on the transmission signal. The control device acquires a reception signal based on the reflected wave from the receiver. The control device detects a first frequency based on a first difference frequency signal obtained from the transmission signal and the reception signal. The control device generates a second difference frequency signal by removing a signal component related to the first frequency from the first difference frequency signal. The control device detects a second frequency based on the second difference frequency signal. The control device calculates a distance to the measurement object based on the first frequency and the second frequency.

  A distance measurement method according to an embodiment of the present disclosure generates a transmission signal whose frequency is modulated. The distance measuring method emits a measurement wave based on the transmission signal. The ranging method acquires a reception signal based on a reflected wave obtained by reflecting the measurement wave on a measurement target. The distance measuring method detects a first frequency based on a first difference frequency signal obtained from the transmission signal and the reception signal. In the distance measuring method, a signal component related to the first frequency is removed from the first difference frequency signal to generate a second difference frequency signal. The distance measuring method detects a second frequency based on the second difference frequency signal. The distance measuring method calculates a distance to the measurement object based on the first frequency and the second frequency.

  A vehicle according to an embodiment of the present disclosure includes a distance measuring device. The distance measuring device includes a wave emitter for emitting a measurement wave, a wave receiver for receiving a reflected wave obtained by reflecting the measurement wave on a measurement object, and a control device. The control device generates a transmission signal whose frequency is modulated. The control device controls the wave emitter to emit the measurement wave based on the transmission signal. The control device acquires a reception signal based on the reflected wave from the receiver. The control device detects a first frequency based on a first difference frequency signal obtained from the transmission signal and the reception signal. The control device generates a second difference frequency signal by removing a signal component related to the first frequency from the first difference frequency signal. The control device detects a second frequency based on the second difference frequency signal. The control device calculates a distance to the measurement object based on the first frequency and the second frequency.

  According to the distance measuring device, the distance measuring method, and the vehicle according to the embodiment of the present disclosure, it is possible to improve the calculation accuracy of the distances of a plurality of measurement objects.

It is a figure showing an example of vehicles provided with a distance measuring device concerning one embodiment. It is a functional block diagram which shows the schematic structural example of the ranging apparatus which concerns on one Embodiment. It is a functional block diagram which shows the structural example which performs distance measurement by a phase difference system. It is a figure which shows an example of a signal transmission pattern. It is a figure which shows an example of a chirp signal. It is a figure which shows an example of a beat signal. It is a figure which shows an example of a frequency spectrum. It is a flowchart which shows the example of the ranging procedure by a FMCW system. It is a flowchart which shows an example of the ranging procedure in case there exists a some measuring object. It is a flowchart which shows an example of a notch filter process. It is a figure which shows an example of the frequency spectrum of a 1st difference frequency signal. It is a figure which shows an example of the frequency spectrum of a temporary signal. It is a figure explaining the example which interference of a measurement wave arises when ranging devices based on a prior art are used. It is a timing chart which shows an example of the timing of the transmission frame of an oncoming vehicle and the transmission frame of the own vehicle concerning one embodiment. It is a timing chart explaining the production | generation of the signal transmission pattern of a measuring device. It is a flowchart which shows an example of a signal transmission pattern production | generation procedure. It is a timing chart which shows an example of a signal transmission pattern when there are a plurality of projectors. It is a schematic diagram in the top view of a 1st vehicle, a 2nd vehicle, and a 3rd vehicle. FIG. 19A is a schematic diagram of the transmitter and the receiver shown in FIG. 18, FIG. 19A is a view of the transmitter as viewed from above, and FIG. 19B is a view of the receiver as viewed from above. FIG. 19C is a view of the transmitter as viewed from the side, and FIG. 19D is a view of the receiver as viewed from the side. It is a timing chart which shows the timing of the injection | emission of the measurement wave by each wave projector group. It is a timing chart which shows the timing of the injection | emission of the measurement wave by each wave projector. It is a flowchart which shows the example of the ranging procedure in case there exist a some projector. It is a functional block diagram which shows the structural example which performs distance measurement by a pulse system. It is a flowchart which shows the example of the ranging procedure by a pulse compression system.

  As shown in FIG. 1, the distance measuring device 1 according to an embodiment can be mounted on a vehicle 2. The distance measuring device 1 includes a control device 10, a wave transmitter 40, a wave receiver 50, and a storage device 60.

  As shown in FIG. 2, the distance measuring device 1 includes a control device 10, wave projectors 40-1 to 40 -N, wave receivers 50-1 to 50 -M, and a storage device 60. The wave projectors 40-1 to 40 -N are also referred to as wave projectors 40. The receivers 50-1 to 50 -M are also referred to as receivers 50. The control device 10 may include one wave projector 40 or two or more wave generators. The control device 10 may include one receiver 50 or two or more. The number of wave emitters 40 and the number of wave receivers 50 may be the same or different.

  The control device 10 is electrically connected to each of the transmitter 40, the receiver 50, and the storage device 60. The control device 10 outputs a transmission signal to the wave projector 40. The projector 40 transmits a measurement wave based on the transmission signal to the target space. When a measurement target exists in the target space, the measurement wave is reflected by the measurement target. The control device 10 acquires a reception signal based on the reflected wave reflected by the measurement target from the wave receiver 50. The control device 10 calculates the distance to the measurement target based on the transmission signal and the reception signal. In the present disclosure, the measurement target refers to an object existing in the target space. The measurement target may not exist in the target space. The description including the measurement target is a description when an object exists in the target space.

  The control device 10 is configured as a processor, for example. The control device 10 may include one or more processors. The processor may include a general-purpose processor that reads a specific program and executes a specific function, and a dedicated processor specialized for a specific process. The dedicated processor may include an application specific integrated circuit (ASIC). The processor may include a programmable logic device (PLD). The PLD may include an FPGA (Field-Programmable Gate Array). The control device 10 may be one of SoC (System-on-a-Chip) and SiP (System In a Package) in which one or more processors cooperate. The control device 10 may store various types of information or a program for operating each component of the distance measuring device 1 in the storage device 60.

  The storage device 60 may be composed of, for example, a semiconductor memory. The storage device 60 may function as a work memory for the control device 10.

  The wave projector 40 emits a measurement wave whose intensity is controlled based on the input signal. The measurement wave can include light, electromagnetic waves, ultrasonic waves, or the like. The measurement wave emitted from the projector 40 is obtained by amplitude-modulating a carrier wave having a predetermined wavelength based on the transmission signal. The measurement wave is transmitted toward the target space and reflected by the measurement target. The measurement wave reflected by the measurement object is also referred to as a reflected wave. The reflected wave can include light, electromagnetic waves, ultrasonic waves, or the like.

  The wave projector 40 may include a light emitting element such as an LED (Light Emitting Diode) or an LD (Laser Diode). The light emitting element may emit light having a predetermined wavelength. The wave projector 40 may include a plurality of light emitting elements. The plurality of light emitting elements may emit light having different wavelengths. The light emitting element may emit infrared light including near infrared light, for example. The light emitting element is not limited to infrared light, and may emit light of other wavelengths. The projector 40 is also referred to as a projector when it includes a light emitting element. The wave projector 40 may include a generating element that emits an electromagnetic wave including an antenna or the like, for example. The electromagnetic wave generating element may emit an electromagnetic wave having a predetermined wavelength. The wave projector 40 may include a generation element that emits ultrasonic waves. The ultrasonic wave generating element may emit ultrasonic waves having a predetermined wavelength.

  The wave receiver 50 outputs a voltage or current corresponding to the intensity of the incident reflected wave. The signal generated by the voltage or current output from the receiver 50 is also referred to as a received signal. When the reflected wave enters the receiver 50, the received signal includes information related to the distance to the measurement target.

  The wave receiver 50 may include a light receiving element such as a PD (Photo Diode) or a PT (Photo Transister). When the light receiving element receives light having a predetermined wavelength, the light receiving element may output a voltage or current corresponding to the intensity of the light. The light receiving element may include a plurality of light receiving elements. The plurality of light receiving elements may output a voltage or current corresponding to the intensity of light when receiving light of different wavelengths. The wave receiver 50 is also called a light receiver when it includes a light receiving element. The wave receiver 50 may include a receiving element that receives an electromagnetic wave including, for example, an antenna. The wave receiver 50 may include a receiving element that receives ultrasonic waves including, for example, a microphone.

  The distance measuring device 1 can measure the distance to the measurement object by various methods such as a phase difference method or a pulse method.

[1. Phase difference method]
The phase difference method is a method based on a frequency difference between a signal transmitted to a target space and a signal received from a measurement target. When the distance measuring device 1 performs distance measurement using the phase difference method, the distance measuring device 1 transmits, for example, a frequency-modulated signal to the target space. The distance measuring device 1 receives a signal reflected by a measurement target. The distance measuring device 1 can calculate the distance to the measurement object based on the frequency modulation pattern of the transmitted signal and the frequency difference between the transmitted signal and the received signal.

  The phase difference method includes, for example, a two-frequency CW (Continuous Wave) method or an FMCW (Frequency Modulated Continuous Wave) method. Hereinafter, a case where the distance measuring device 1 performs distance measurement by the FMCW method will be described.

<1.1 Function block>
As illustrated in FIG. 3, the control device 10 includes a pattern generation unit 11, a clock generation unit 12, a signal generation unit 13, and a timing signal generation unit 14. The control device 10 includes an information acquisition unit 15, a distance calculation unit 16, an R signal multiplier 17R, and an I signal multiplier 17I. The control device 10 includes a complex transform unit 21, an LPF (Low Pass Filter) unit 22, a notch filter unit 23, an FFT (Fast Fourier Transform) unit 24, and a peak detection unit 25. The control device 10 includes a DA converter 26, an AD converter 27, a wave emitter driver 41, and a gain adjuster 52. The function of each component of the control device 10 may be executed by one processor. The functions of the components of the control device 10 may be executed by being appropriately distributed by a plurality of processors. The control device 10 is connected to the wave projector 40. The control device 10 is connected to the wave projector 40 via, for example, the wave wave driver 41. The control device 10 is connected to the receiver 50. The control apparatus 10 is connected to the receiver 50 via the gain adjuster 52, for example. The control device 10 is connected to the storage device 60. Each component of the control device 10 is connected to the storage device 60 as appropriate.

  The pattern generation unit 11 generates a pattern for transmitting a transmission signal from the wave projector 40. A pattern for transmitting a transmission signal is also referred to as a signal transmission pattern. The pattern generation unit 11 stores the generated signal transmission pattern in the storage device 60. The signal transmission pattern indicates in which section a signal is transmitted among a plurality of sections provided within a predetermined period. Each of the plurality of sections is also referred to as a frame. The signal transmission pattern includes a sequence of frames associated with a frame number, for example, as shown in FIG. A rectangle indicated by a solid line indicates a frame for transmitting a signal. A rectangle indicated by a broken line indicates a frame in which no signal is transmitted. A frame for transmitting a signal is also referred to as a transmission frame. A frame that does not transmit a signal is also referred to as a non-transmission frame. In the example shown in FIG. 4, signals are transmitted in the frames associated with frame numbers 1, 4 and M. The frame may be associated with a time set at a predetermined interval. The length of the frame may be a predetermined time. Each frame may be provided continuously within a predetermined period. Each frame may be provided discretely within a predetermined period. Each frame may be provided at a predetermined interval.

  The pattern generation unit 11 may generate a signal transmission pattern based on a sequence obtained from a random function. The random function may be a pseudo noise pattern, for example. The pseudo noise pattern is also called a PN (Pseude Noise) pattern. The random function is not limited to the PN pattern. The random function may be a variety of functions, arrays or patterns that generate a sequence of random numbers.

  The pattern generation unit 11 is not limited to a random function, and may generate a signal transmission pattern based on other information. The pattern generation unit 11 may generate a signal transmission pattern based on a predetermined pattern sequence. The pattern generation unit 11 may generate a signal transmission pattern based on a predetermined function.

  The clock generation unit 12 generates a clock signal that is a reference for the operation of each component of the control device 10. The clock signal is, for example, a square wave having a constant period. The clock generation unit 12 is connected to the signal generation unit 13 and the timing signal generation unit 14. The clock generation unit 12 may be connected to other components of the control device 10.

  The timing signal generation unit 14 generates a timing signal. The timing signal is a signal indicating the timing corresponding to the signal transmission pattern stored in the storage device 60. The timing signal generation unit 14 generates a signal at a time corresponding to frames whose frame numbers are 1, 4 and M, for example, based on the signal transmission pattern shown in FIG. The timing signal may be a pulse, for example.

  The information acquisition unit 15 acquires information from the outside. The information acquisition unit 15 stores the acquired information in the storage device 60. The information acquisition unit 15 may acquire a clock from a GPS (Global Positioning System) receiver. The information acquisition unit 15 may acquire a 1 PPS (Pulse Per Second) signal from the GPS receiver. The information acquisition unit 15 may acquire position information or direction information from a GPS receiver. The information acquisition unit 15 may acquire position information or direction information from the car navigation system. The information acquisition unit 15 may acquire azimuth information from the gyro sensor. The information acquisition unit 15 may acquire various information such as information related to the surrounding state from an external server.

  The signal generator 13 generates a transmission signal. The transmission signal may be a chirp signal as shown in FIG. 5, for example. A chirp signal is a signal whose frequency continuously changes over time. A signal whose frequency changes continuously is also called a frequency-modulated continuous wave. The change in frequency of the chirp signal may be increased or decreased. The change in frequency of the chirp signal may be monotonically increasing or monotonically decreasing. The change in frequency of the chirp signal may be a combination of increase and decrease. The frequency of the chirp signal may change periodically. The transmission signal may be a signal whose frequency is modulated. The transmission signal may be a complex signal including a real part and an imaginary part. The transmission signal may be a chirp signal and a complex chirp signal, which is a complex signal.

  The signal generator 13 may generate a chirp signal with a frequency change based on a preset pattern. The signal generation unit 13 may generate a chirp signal with a frequency change based on a sequence obtained from a random function.

  The signal generation unit 13 may generate a transmission signal at a timing based on the signal transmission pattern stored in the storage device 60 and the timing signal. In the present embodiment, it is assumed that the signal generation unit 13 generates a complex chirp signal having a real part and an imaginary part as a transmission signal. The signal generation unit 13 is not limited to a complex chirp signal, and may generate a chirp signal that is not a complex signal or another type of signal.

  The real part of the complex chirp signal is also called an R (Real Part) signal. The imaginary part of the complex chirp signal is also called an I (Imaginary Part) signal. The R signal is output as a transmission signal from the signal generation unit 13 to the DA converter 26 and the R signal multiplier 17R. The I signal is output from the signal generator 13 to the I signal multiplier 17I.

  The DA converter 26 converts the digital signal into an analog signal and outputs the converted analog signal. The DA converter 26 converts the transmission signal input as a digital signal into an analog signal and outputs the analog signal to the wave projector 40.

  The projector driver 41 amplifies the transmission signal input from the DA converter 26 and outputs the amplified signal to the projector 40. The projector driver 41 may offset the transmission signal so that the instantaneous value of the transmission signal becomes 0 or more.

  The wave projector 40 emits a measurement wave based on the transmission signal acquired from the wave wave driver 41. When the wave projector emits light including near infrared rays, the light of the light emitting element may be emitted after amplitude modulation with a transmission signal. In other words, the measurement wave is light that is amplitude-modulated with a signal having a chirped frequency. When the wave projector 40 emits an electromagnetic wave such as a millimeter wave band, an ultrasonic wave, or the like, the measurement wave can have the same waveform as the transmission signal generated by the signal generation unit 13. That is, the wave projector 40 can chirp the frequency of the measurement wave itself. The wave receiver 50 receives the reflected wave reflected by the measurement target. The wave receiver 50 outputs a received signal based on the reflected wave to the gain adjuster 52.

  The gain adjuster 52 acquires the received signal from the wave receiver 50. The gain adjuster 52 multiplies the reception signal based on the amplitude of the transmission signal and outputs the gain to the A-D converter 27. The gain adjuster 52 may bring the amplitude of the reception signal close to the amplitude of the transmission signal. The gain adjuster 52 may set the amplitude of the reception signal to the same level or substantially the same level as the amplitude of the transmission signal. The gain adjuster 52 may store the gain value applied to the received signal in the storage device 60.

  The AD converter 27 converts the input analog signal into a digital signal and outputs the digital signal. The A-D converter 27 converts the received signal input as an analog signal into a digital signal and outputs the digital signal to the complex converter 21. The AD converter 27 may be connected to the timing signal generator 14. The AD converter 27 may operate at a timing according to the timing signal. By doing in this way, the power consumption in the AD converter 27 can be reduced. The A-D converter 27 may store information on the received signal converted into a digital signal in the storage device 60.

  The complex conversion unit 21 performs complex conversion on the received signal. The received signal is converted into a complex signal including an R signal and an I signal. The complex conversion unit 21 outputs the R signal and the I signal to the R signal multiplier 17R and the I signal multiplier 17I, respectively. The complex signal may be generated by, for example, a Hilbert transform. The Hilbert transform performs an operation of delaying the phase of the positive frequency component by π / 2 and the phase of the negative frequency component by π / 2 with respect to the signal. The complex signal may be generated by other methods such as orthogonal transformation.

  The complex signal may be generated by a 90-degree phase difference wave from the received signal as an analog signal before being converted into a digital signal by the A / D converter 27. In this case, the R signal and the I signal are generated as analog signals and converted into digital signals by the AD converter 27, respectively.

  The R signal multiplier 17R multiplies the R signal input from the signal generation unit 13 and the R signal input from the complex conversion unit 21. The I signal multiplier 17I multiplies the I signal input from the signal generation unit 13 and the I signal input from the complex conversion unit 21. The R signal multiplier 17R and the I signal multiplier 17I are also simply referred to as a multiplier 17. The multiplier 17 outputs a signal obtained by signal multiplication to the LPF unit 22. The multiplier 17 is also called a mixer.

  When two signals having different frequencies are multiplied, a signal whose frequency is the sum of the frequencies of each signal and a signal whose frequency is the difference between the frequencies of the signals based on the product-sum formula of the trigonometric function Is generated. In the present embodiment, it is assumed that a signal having a frequency (fa) is multiplied by a signal having a frequency (fb). In this case, a signal having a frequency (fa + fb) and a signal having a frequency (fa−fb) are generated. The signal of frequency (fa + fb) is also called a sum frequency signal. The signal of the frequency (fa−fb) is also called a difference frequency signal. A signal obtained by multiplying two signals is also called a beat signal. The beat signal includes a difference frequency signal having a relatively low frequency and a sum frequency signal having a relatively high frequency. The beat signal is shown by a waveform as shown in FIG. 6, for example.

  The LPF unit 22 includes a low-pass filter. The low-pass filter passes, for example, a signal having a frequency lower than a predetermined frequency and cuts a signal having a frequency higher than the predetermined frequency. In the present embodiment, it is assumed that the LPF unit 22 cuts the sum frequency signal and passes the difference frequency signal. The LPF unit 22 cuts the sum frequency signal from the beat signal and outputs the difference frequency signal to the notch filter unit 23. When a complex signal is input, the LPF unit 22 performs filter processing on each of the real part and the imaginary part of the input signal.

  The notch filter unit 23 includes a notch filter. The notch filter is also called a band stop filter. The notch filter cuts a narrowband frequency component from the signal. The beat signal is input from the LPF unit 22 to the notch filter unit 23. The notch filter unit 23 may store the beat signal in the storage device 60 before performing the filtering process. The notch filter unit 23 may acquire a beat signal from the storage device 60.

  The notch filter unit 23 cuts a predetermined frequency component from the signal based on the information related to the frequency band to be cut. The notch filter unit 23 may acquire information on the frequency band to be cut from the storage device 60. The notch filter unit 23 outputs a signal obtained by cutting a predetermined frequency component from the beat signal to the FFT unit 24. When a complex signal is input, the notch filter unit 23 performs filter processing on each of the real part and the imaginary part of the input signal.

  The FFT unit 24 analyzes the frequency of the input signal by Fourier transform. The FFT unit 24 may analyze the frequency of a signal input as a digital signal by discrete Fourier transform or fast Fourier transform.

  When a complex signal is input, the FFT unit 24 calculates a complex Fourier coefficient by Fourier transform. In this case, the absolute value of the Fourier coefficient corresponding to each frequency represents the amplitude spectrum of the signal. The declination of the Fourier coefficient corresponding to each frequency represents the phase spectrum of the signal. When a real signal is input, the FFT unit 24 calculates a real Fourier coefficient by Fourier transform. In this case, the Fourier coefficient corresponding to each frequency represents the amplitude spectrum of the signal.

  The FFT unit 24 outputs the amplitude spectrum of the signal calculated by Fourier transform to the peak detection unit 25. The FFT unit 24 may store the amplitude spectrum of the signal in the storage device 60. If a plurality of transmission frames are set in the signal transmission pattern, the FFT unit 24 may acquire the amplitude spectrum of the signal obtained in another transmission frame from the storage device 60. The FFT unit 24 may integrate the amplitude spectrum of the signal obtained in each transmission frame and store the result in the storage device 60. A spectrum obtained by integrating the amplitude spectrum is also referred to as an integrated amplitude spectrum.

  The peak detector 25 detects the peak frequency of the signal based on the amplitude spectrum of the signal. The peak detection unit 25 may acquire the amplitude spectrum of the signal from the FFT unit 24. The peak detection unit 25 may acquire the amplitude spectrum of the signal from the storage device 60. For example, fp can be detected as the peak frequency from the signal represented by the amplitude spectrum shown in FIG. In FIG. 7, the horizontal axis and the vertical axis indicate frequency and amplitude, respectively. The peak detection unit 25 may store the detected peak frequency in the storage device 60. The peak detector 25 may detect the frequency having the maximum amplitude as the peak frequency. The peak detecting unit 25 may detect the lowest frequency among the frequencies having the maximum amplitude as the peak frequency.

  The peak detection unit 25 may acquire the integrated amplitude spectrum from the storage device 60. The peak detector 25 may detect the peak frequency of the signal based on the integrated amplitude spectrum.

  The distance calculation unit 16 calculates the distance to the measurement target based on the peak frequency detected by the peak detection unit 25. The distance calculation unit 16 may calculate the distance to the measurement target in consideration of the signal delay inside the control device 10. The distance calculation unit 16 may calculate the distance from the measurement target based on the amplitude at the peak frequency. The amplitude at the peak frequency is also referred to as peak amplitude. The distance calculation unit 16 may calculate the distance from the measurement target according to the peak amplitude when the peak amplitude is equal to or greater than a predetermined amplitude. The distance calculation unit 16 may not calculate the distance from the measurement target when the peak amplitude is less than the predetermined amplitude. By doing in this way, it becomes difficult to detect a measuring object accidentally. The distance calculation unit 16 may calculate the distance to the measurement target based on the peak frequency detected from the integrated amplitude spectrum. By doing so, the distance measurement result is less affected by noise components that may be suddenly included in the received signal.

<1.2 Examples of distance measurement methods>
The distance measuring device 1 measures the distance to the measurement target by causing each component unit to execute the processing of the flowchart shown in FIG. 8, for example. FIG. 8 illustrates the case where the measurement wave is light.

  In the control device 10, the pattern generation unit 11 generates a transmission pattern (step S1). The pattern generation unit 11 stores the transmission pattern in the storage device 60. More specific processing of step S1 is illustrated in FIGS. 16 and 22 described later. However, the process of step S1 is not limited to these.

  In the control device 10, the signal generator 13 generates a transmission signal (step S2). In the present embodiment, it is assumed that the transmission signal is a complex chirp signal having an R signal and an I signal. The signal generator 13 outputs a transmission signal at the timing indicated by the timing signal input from the timing signal generator 14. The R signal is output to the DA converter 26 and the multiplier 17. The R signal is converted into an analog signal by the DA converter 26. The I signal is output to the multiplier 17.

  The projector 40 emits light, which has been amplitude-modulated according to the transmission signal input via the projector driver 41, to the target space (step S3).

  The wave receiver 50 receives the light reflected by the measurement target (step S4). The wave receiver 50 outputs a voltage or current signal corresponding to the intensity of the received light as a received signal. The gain adjuster 52 applies a gain to the received signal. The A-D converter 27 may convert the received signal from an analog signal to a digital signal at a timing indicated by the timing signal input from the timing signal generation unit 14. The complex conversion unit 21 converts the received signal as a real signal into a complex signal.

  The control device 10 multiplies the R signal and the I signal input from the signal generation unit 13 by the multiplier 17 and the R signal and the I signal input from the complex conversion unit 21, respectively, to generate a beat signal. . The control device 10 causes the LPF unit 22 to pass a signal component having a frequency equal to or lower than a predetermined frequency in the beat signal to generate a difference frequency signal (step S5).

  In the FFT unit 24, the control device 10 performs Fourier transform on the difference frequency signal to perform frequency analysis (step S6). The peak detector 25 detects the peak frequency of the difference frequency signal based on the frequency spectrum of the difference frequency signal. The peak detector 25 stores the peak frequency of the difference frequency signal in the storage device 60.

  In the control device 10, the distance calculation unit 16 calculates the distance from the measurement target based on the peak frequency of the difference frequency signal (step S7). The control device 10 ends the process of the flowchart of FIG.

<1.3 When there are multiple measurement objects>
When the transmission signal is reflected by a plurality of measurement objects, the difference frequency signal includes information related to the distance from each measurement object. In this case, the frequency spectrum of the difference frequency signal can include a plurality of peak frequencies. The distance measuring apparatus 1 according to the present embodiment can calculate the distance to each measurement target by causing each component unit to execute the processing of the flowchart illustrated in FIG. 9.

  The control device 10 stores the difference frequency signal output from the LPF unit 22 in the storage device 60 (step S11). The difference frequency signal output from the LPF unit 22 is also referred to as a first difference frequency signal.

  The control device 10 performs Fourier transform on the first difference frequency signal by the FFT unit 24 (step S12). A frequency spectrum of the first difference frequency signal is calculated by Fourier transform.

  The control device 10 detects the peak frequency of the first difference frequency signal by using the peak detection unit 25 (step S13). The peak frequency of the first difference frequency signal is also referred to as a first frequency. In the frequency spectrum illustrated in FIG. 11, f1 can be detected as the first frequency.

  The control device 10 determines whether or not the peak amplitude is greater than or equal to a predetermined amplitude (step S14). When the peak amplitude is not greater than or equal to the predetermined amplitude (step S14: NO), the control device 10 ends the process of the flowchart of FIG. When the peak amplitude is greater than or equal to the predetermined amplitude (step S14: YES), the control device 10 performs notch filter processing (step S15).

  The notch filter processing is executed by the procedure shown in FIG. The control device 10 determines a cut band to be subjected to notch filter processing based on the peak frequency (step S101). The control device 10 may determine a cut band including the peak frequency. The control device 10 may determine a cut band having a predetermined frequency width around the peak frequency.

  The control apparatus 10 performs the filter process which cuts the frequency component of a cut band with respect to the 1st difference frequency signal by the notch filter part 23 (step S102). A signal obtained by cutting the frequency component of the cut band from the first difference frequency signal is also referred to as a temporary signal.

  The control device 10 performs Fourier transform on the temporary signal by the FFT unit 24 (step S103). The frequency spectrum of the temporary signal is calculated by Fourier transform.

  The control device 10 detects the peak frequency of the temporary signal by using the peak detection unit 25 (step S104). The control device 10 detects the peak frequency of the temporary signal under the same conditions as when the peak frequency of the first difference frequency signal is detected. When the frequency spectrum of the temporary signal is a frequency spectrum as illustrated in FIG. 12, f2 may be the peak frequency of the temporary signal.

  The control device 10 determines whether the peak frequency of the temporary signal has changed by a predetermined value or more from the peak frequency of the first difference frequency signal (step S105).

  When the peak frequency of the temporary signal has not changed by a predetermined value or more from the peak frequency of the first difference frequency signal (step S105: NO), the control device 10 changes the cut band (step S106). The predetermined value can be determined as appropriate. The control device 10 may shift the cut band to the low frequency side or the high frequency side. The control device 10 may widen or narrow the cut band. The control device 10 returns to step S102.

  When the peak frequency of the temporary signal changes by a predetermined value or more from the peak frequency of the first difference frequency signal (step S105: YES), the control device 10 stores the temporary signal as the second difference frequency signal in the storage device 60. (Step S107).

  The control device 10 stores the first frequency in the storage device 60 (step S108). When the cut band is not changed, the control device 10 stores the first frequency obtained as the peak frequency of the first difference frequency signal in the storage device 60 as it is. When changing the cut band, the control device 10 changes the first frequency according to the changed cut band and stores the first frequency in the storage device 60. The control device 10 may set the frequency at the center of the changed cut band as the first frequency. The control device 10 ends the process of the flowchart of FIG.

  Returning to the flowchart of FIG. 9, the control device 10 performs a Fourier transform on the second difference frequency signal (step S12). The control apparatus 10 performs the process of step S12-step S15 with respect to a 2nd difference frequency signal. In this case, in step S15, a notch filter process is performed on the second difference frequency signal. A third difference frequency signal can be generated by processing the second difference frequency signal. By the processing on the second difference frequency signal, the peak frequency of the second difference frequency signal can be determined as the second frequency.

  The process of the flowchart of FIG. 9 is continued until the peak amplitude detected from the frequency spectrum of the difference frequency signal becomes less than a predetermined amplitude. By doing in this way, when a plurality of measurement objects can exist, the distance to each measurement object can be measured with high accuracy. The predetermined amplitude may be set as a peak amplitude that increases the possibility of erroneously detecting the measurement target.

<1.4 When a signal transmission pattern is generated by a random function>
In one of the embodiments, the pattern generation unit 11 generates a signal transmission pattern so that a measurement wave is emitted at a timing determined based on a random function for each period of a predetermined length. The determined timing corresponds to the time when the signal of the frame in FIG. 4 is generated. Therefore, it can be said that the pattern generation unit 11 selects the frame number of the frame to be used using a random function. The pattern generation unit 11 stores the generated signal transmission pattern in the storage device 60. The timing signal generation unit 14 generates a timing signal based on this signal transmission pattern. Further, the signal generation unit 13 generates a transmission signal based on this timing signal. Therefore, a transmission signal is generated so as to emit a measurement wave at a timing determined based on a random function.

  The pattern generation unit 11 can generate a random function seed based on a value unique to the distance measuring device 1. The seed of the random function is a starting point for reading a random number in a series of pseudo random numbers of the random function. The device specific value may include the device serial number. The pattern generation unit 11 can also generate a random function seed from a value specific to the vehicle 2 on which the distance measuring device 1 is mounted. As a value unique to the vehicle 2, a vehicle body number, a vehicle registration number, or the like can be used. Further, the pattern generation unit 11 receives the travel information of the vehicle 2 and / or the position of the vehicle 2 from an ECU (Electronic Control Unit) of the vehicle 2, a GPS receiver mounted on the vehicle 2, and the like via the information acquisition unit 15. Information etc. may be acquired. The pattern generation unit 11 may generate a seed of a random function based on at least one of these values. The travel information of the vehicle 2 includes the vehicle speed, reverse (reverse signal), shift position, and engine speed. The position information of the vehicle 2 includes the GPS signal itself, latitude, longitude, altitude, direction, and the like. The above values may be used as they are for the seed of the random function. Alternatively, the seed of the random function may be calculated from the above values.

  As shown in FIG. 13, in the distance measuring apparatus according to the conventional method, distance measurement is performed at a fixed frame interval t0. If a distance measuring device that uses the same distance measuring method is installed in the oncoming vehicle, the measurement wave from the oncoming vehicle at least partially overlaps the transmission frame of the own vehicle, and the receiver of the own vehicle. 50 can be received. In that case, the reflected wave to be received by the own vehicle and the measurement wave from the oncoming vehicle may interfere with each other. In the present application, interference means that in a receiver, a measurement wave from a different measurement device overlaps with a reflected wave to be measured by the own device in time, and normal measurement is disturbed. When the distance between the host vehicle and the oncoming vehicle is measured at the same frame interval t0, there is a possibility that a plurality of measurement waves from the oncoming vehicle continuously cause interference. In that case, the distance measuring device 1 may not be able to perform normal distance measurement.

  In the distance measuring apparatus 1 according to one of a plurality of embodiments, measurement waves are randomly emitted as shown in FIG. That is, the wave emitter 40 emits measurement waves in a plurality of frames n1, n2, n3, and n4 determined based on a random function during one period (T). Here, n1, n2, n3, and n4 represent frame numbers. Frames n1, n2, n3, and n4 are transmission frames for transmitting signals. The distance measuring device 1 repeats emission of measurement waves in this pattern. As an example, in the FMCW system, the length (Δt) of one frame is 100 μs (microseconds), one period (T) is 100 ms (milliseconds), and one period (T) is one frame length (Δt). When divided, there are 1000 measurement wave transmission opportunities. The pattern generation unit 11 randomly selects a plurality of timings in order to emit measurement waves from the 1000 transmission opportunities. The transmission opportunity of one cycle is not limited to 1000 times, and the frame length (Δt) and the length of one cycle (T) can be changed to various times such as 5000 times and 10,000 times. In the following description, it is assumed that four frames are used for measurement in one period (T). Note that the number of frames used for measurement in one period (T) is not limited to four.

  When both the distance measuring devices 1 mounted on the host vehicle and the oncoming vehicle perform measurement at random timing, as shown in FIG. 14, the measurement waves do not easily interfere with each other. Even if the measurement wave of one frame causes interference during one period (T), there is a high possibility that the other frames will not cause interference. As shown in FIG. 14, when there are four measurement frames in one period (T), even if one frame causes interference, measurement in the other three frames is possible. As a result, it is possible to prevent continuous ranging from being disabled.

  Further, the pattern generator 11 generates a wave projector based on the magnitude of noise received from the wave receiver 50 at a timing determined by a random function when the wave transmitter 40 is not emitting a measurement wave. The manner in which the measurement wave is emitted to 40 can be changed. The time when the wave projection device 40 does not emit the measurement wave includes a period during which the distance measurement device 1 is not started and a distance measurement period which is periodically provided during the operation of the distance measurement device 1 is not performed. The case where the wave projector 40 is not emitting the measurement wave can be said to be the time when the distance measuring device 1 is not measuring the distance. The timing determined by the random function is a timing at which distance measurement is scheduled during distance measurement in one cycle. A combination of timings at which distance measurement is scheduled is called a transmission schedule pattern. The timing determined by the random function corresponds to each transmission frame scheduled to be measured during distance measurement. This frame is called a transmission scheduled frame.

  When distance measurement is not performed, the noise received by the receiver 50 is converted into a digital signal by the A / D converter 27 via the gain adjuster 52 and temporarily stored in the storage device 60 together with time information. The When the distance measuring device 1 is not performing distance measurement, the gain adjuster 52 may not amplify the noise, and may amplify only at a predetermined magnification. The gain adjuster 52 may adjust noise gain. In this case, the pattern generation unit 11 compares the gain value output from the gain adjuster 52 to the storage device 60 and compares it with a threshold value described below. The pattern generation unit 11 can acquire the intensity of noise and the generation time thereof stored in the storage device 60. Therefore, the pattern generation unit 11 can identify the magnitude of noise for each transmission scheduled frame.

  Changing the manner in which the measurement wave is emitted includes adding another timing to a plurality of timings at which the distance measurement is to be performed. That is, when the noise received in each frame corresponding to the timing determined by the random function exceeds a predetermined threshold, the pattern generation unit 11 transmits the transmission schedule in addition to the plurality of transmission scheduled frames set by the random function. Add another frame as a frame. The predetermined threshold is, for example, a value determined based on whether or not the reflected wave of the measurement wave at the time of distance measurement can be detected.

  A specific example is shown in FIG. Assume that there are four scheduled transmission frames n1, n2, n3, n4 during one period. Here, n1 to n4 are the frame numbers described with reference to FIG. The pattern generation unit 11 increases the number of scheduled transmission frames when there is a received noise that interferes with the scheduled transmission frame. In the example of FIG. 15, frames n2 and n3 interfere with reception noise. Therefore, the pattern generation unit 11 selects and adds two frames n5 and n6 using a random function different from the above-described random function or using another seed for the same random function. . Other means may be used for selecting the frames n5 and n6. As a result, distance measurement is performed in the frames n1 to n6, and correct distance measurement is possible in the four frames n1, n4, n5, and n6 even if distance measurement cannot be performed in the frames n2 and n3.

  Aligning a predetermined number of frames that can be measured is useful for accurate ranging. For example, in step S6 of FIG. 8, the peak detector 25 can detect the peak frequency of the signal from the integrated amplitude spectrum obtained by integrating the amplitude spectrum of the signal obtained in a predetermined number of transmission frames in one cycle. In this case, in order to perform distance measurement continuously and stably, a predetermined number of measurable transmission frames are required. Alternatively, in step S6 of FIG. 8, the peak detector 25 can be a target for calculating the distance when the peak of the difference frequency signal exceeds a predetermined threshold. The peak detection unit 25 may calculate the distance by performing a measure such as taking an average value of the measured distances when distance measurement is possible over a predetermined number of frames in one cycle. Even in such a case, it is expected that accurate ranging can be continuously performed by maintaining a predetermined number of frames capable of ranging.

  Further, changing the mode of emitting the measurement wave includes adding or switching the frequency of the measurement wave emitted by the wave projector 40. In this case, the wave projector 40 may be a light projector and may include a plurality of light emitting elements that can emit light having different wavelengths. Further, the wave receiver 50 can decompose the reflected wave into a plurality of wavelengths corresponding to the wavelength of the light emitting element of the wave projector 40 and can detect each wavelength. Further, the signal transmission pattern generated by the pattern generation unit 11 includes light emitting element information to be used. When the distance measuring device 1 does not perform distance measurement, the wave receiver 50 decomposes the noise acquired from the wave receiver 50 for each wavelength of the light emitting element of the wave projector 40 and stores the magnitude in the storage device 60. Remember. When the noise received in each transmission scheduled frame determined by the random function exceeds a predetermined threshold, the pattern generation unit 11 switches the light emitting element that emits the measurement wave to one having a different wavelength that the wave projector 40 has. It's okay. Alternatively, the pattern generation unit 11 may emit light by adding light emitting elements having different wavelengths.

  Next, a transmission pattern generation process using a random function by the pattern generation unit 11 according to an embodiment will be described with reference to FIG. The flowchart in FIG. 16 corresponds to the processing in step S1 in the flowchart in FIG. The transmission pattern generation process may be applied to a pulse-type distance measuring device. In this case, the flowchart of FIG. 16 corresponds to the processing in step S11 of the flowchart of FIG.

  In step S201, the pattern generation unit 11 generates a plurality of timings for distance measurement using a random function as a transmission schedule pattern. In other words, the pattern generation unit 11 generates a pattern of a transmission scheduled frame so as to have a random time interval (step S201).

  Next, when the distance measurement is not performed, the receiver 50 receives noise and stores the magnitude of the noise in the storage device 60 with time. The pattern generation unit 11 determines whether or not interference occurs with another device in a transmission-scheduled frame from the magnitude and time of noise stored in the storage device 60 (step S202).

  If the noise detected in the transmission-scheduled frame is higher than the predetermined threshold, the pattern generation unit 11 proceeds to the process of step S204. If the noise is not higher than the predetermined threshold value, the process proceeds to step S205 (step S203).

  When the magnitude of the noise is higher than the predetermined threshold, the pattern generation unit 11 adds a frame at another timing as a transmission scheduled frame in addition to the plurality of transmission scheduled frames selected in step S201 (step S204). Other timings may be generated by random functions. Alternatively or additionally, the pattern generation unit 11 may switch the wavelength of the measurement wave or add a measurement wave having a different wavelength.

  The pattern generation unit 11 generates a signal transmission pattern according to the transmission planned pattern when No in step S203. Moreover, when it is Yes in step S203, the pattern generation part 11 adds the change based on step S204, and produces | generates a signal transmission pattern (step S205).

  In one of a plurality of embodiments, when a plurality of wave projectors 40 are provided, measurement waves are sequentially emitted from each wave projector 40 at each of a plurality of timings selected by a random function. Can do. For example, as shown in FIG. 17, when four wave projectors 40-1 to 40-4 are provided, measurement waves are sequentially emitted from the wave projectors 40-1 to 40-4 in successive frames. Can be made. A broken line in the figure indicates a period during which a series of measurements are performed on the time axis. For example, assume that the wave projector 40-1 emits a measurement wave at the frame n1. Next, the wave projectors 40-2, 40-3, and 40-4 emit measurement waves in the frames n1 + 1, n1 + 2, and n1 + 3, respectively. A period surrounded by a broken line corresponds to a period for performing a series of measurements, and is randomly arranged on the time axis. The period during which this series of measurements is performed may be referred to as a frame group. In this case, the pattern generation unit 11 may generate the frame transmission signal so that one cycle (T) is divided by the length of the frame group, and the frame group for transmitting the signal is randomly arranged on the time axis. . In this way, the sequential measurement by a plurality of projectors is randomly arranged in one cycle (T), thereby suppressing the influence of interference with other devices as in the case of a single projector. Thus, accurate ranging can be continuously performed.

<1.5 When there are multiple projectors>
In one of the embodiments, the distance measuring device 1 includes a plurality of wave projector groups 40-1G to 40-NG as shown in FIG. Each wave group 40-kG (k = 1 to N) is configured to include wave elements 40-ka, 40-kb, 40-kc. In the example illustrated in FIG. 18, the wave projector group 40-kG includes three wave projectors, but is not limited thereto, and may include any number of wave projectors. In the following description, it is assumed that any of the projectors 40-ka, 40-kb, and 40-kc constituting each projector group 40-kG is 40-kx.

Each wave projector 40-kx includes a light emitting element that emits light having high directivity as a measurement wave, such as a light emitting diode. The transmitter 40-kx has horizontal angles θ _{1 to} θ ₃ (see FIG. 19A) in a range in which the measurement wave is emitted from the transmitter 40-kx, and the receiver 50-k It is narrower than the angle θ ₄ (see FIG. 19B) at which the reflected wave can be received. The horizontal angles θ _{1 to} θ ₃ in the range in which the measurement wave is emitted from each wave projector 40-kx are appropriately designed according to the size of the measurement target, and the measurement target to be measured is small. The higher the azimuth resolution is required, the smaller it is set. The angle θ _{5 in} the vertical direction (see FIG. 19C) in the range in which the measurement wave is emitted from each wave projector 40-kx is approximately the same as the angles θ _{1 to} θ _{3 in the} horizontal direction. “Same degree” includes not only that the angle θ ₅ is completely the same as the angles θ ₁ to θ ₃ but also that the angle θ ₅ is smaller than the angle θ ₄ . Since the angle θ ₅ is not larger than the angle θ ₄ determined according to the size of the measurement target, noise due to sunlight can be reduced.

  In the projector 40-kx, it is preferable that the direction in which the maximum output of the measurement wave of the projector 40-kx is given is higher than the horizontal direction. Specifically, the wave projector 40-kx may be disposed so as to have an angle range in which the measurement wave is not emitted to the ground within the distance range in which the measurement target is assumed to exist. When the projector 40-kx is a projector, the optical axis may be directed upward from the horizontal direction.

  Each wave generator group 40-kG is arranged at a different position of the vehicles 2-1 to 2-3 (hereinafter referred to as the vehicle 2 as appropriate), and measures waves in different ranges in the horizontal direction toward the outside of the vehicle 2. Inject. Each wave group 40-kG is arrange | positioned so that a measurement wave may be inject | emitted in a different range, respectively in a different position of this vehicle 2, respectively. For example, as shown in FIG. 18, a wave transmitter group 40-1G that emits a measurement wave in the forward direction is disposed on the left side of the front side surface of the vehicle 2, and the measurement wave in the forward direction is disposed on the right side of the front side surface of the vehicle 2. Is disposed. A wave group 40-3G that emits a measurement wave in the rear direction is arranged on the right side of the rear side surface of the vehicle 2, and a wave group 40 that emits the measurement wave in the rear direction on the left side of the rear side of the vehicle 2. -4G may be arranged.

  In the example shown in FIG. 18, an example in which the wave projector groups 40-1G to 40-4G are arranged at four locations of the vehicle 2 is shown, but is not limited thereto. For example, the wave transmitter group 40-kG may be arranged at the center of the front side surface and the rear side surface of the vehicle 2, and the measurement waves in the right direction and the left direction of the vehicle 2 are respectively measured on the right side surface and the left side surface of the vehicle 2. May be arranged.

  Here, the angle range of the measurement wave emitted by the wave projector 40-kx will be described. The plurality of wave projectors 40-ka, 40-kb, 40kc constituting the wave group 40-kG are arranged substantially adjacent to each other, and emit measurement waves in different angular ranges in the horizontal direction.

Specifically, the wave projector 40-1b emits a measurement wave in a predetermined angle range (first angle range) around the traveling direction. The wave projector 40-1a emits a measurement wave in a second angle range that spreads leftward from the horizontal left end of the first angle range. The wave projector 40-1c emits a measurement wave in a third angle range that extends in the right direction from the horizontal right end of the first angle range. The size of the first angle range (angle θ ₁ ), the size of the second angle range (angle θ ₂ ), and the size of the third angle range (angle θ ₃ ) may be the same or different. Also good. Further, any two of the angle θ ₁ , the angle θ ₂ , and the angle θ ₃ may be the same. The same applies to the projector groups 40-2G, 40-3G, and 40-4G. In the example shown in FIG. 18, the angles θ ₁ of the wave projectors 40-1a, 40-2a, 40-3a, and 40-4a may be the same or at least partially different. . The same applies to the projectors 40-kb and 40-kc.

  In the above description, the wave projector 40-1a emits the measurement wave in the second angle range that spreads leftward from the horizontal left end of the first angle range, but this is not restrictive. For example, there may be a range in which no measurement wave is emitted between the first angle range and the second angle range, or the first angle range and the second angle range may partially overlap. The same applies to the first angle range and the third angle range.

  When the distance measuring device 1 includes a plurality of projector groups 40-1G to 40-NG, the pattern generation unit 11 transmits a transmission signal that causes each of the projector groups 40-kG to emit a measurement wave. A signal transmission pattern including a frame group is generated.

  Specifically, the pattern generation unit 11 generates a signal transmission pattern so that measurement waves are sequentially emitted from the wave transmitter group 40-kG starting from the reference timing. This transmission signal pattern is generated so that the measurement wave is emitted after a predetermined elapsed time that is determined differently for each of the transmitter groups 40-kG. Therefore, the signal transmission pattern related to each wave group 40-kG is measured by the other wave groups 40-2G to 40-NG at the timing when the wave group 40-1G emits the measurement wave. It is generated not to emit waves. At this time, the pattern generation unit 11 may generate a signal transmission pattern including a frame group using the clock acquired by the information acquisition unit 15 as a reference timing.

  In one example, the pattern generation unit 11 corresponds to each wave group 40-kG so that the wave groups 40-1G to 40-NG arranged on the outer surface sequentially emit at a predetermined elapsed time. Generate a signal transmission pattern. At this time, the pattern generation unit 11 may generate a signal transmission pattern so that the measurement wave is emitted clockwise from the reference direction when viewed from the center of the vehicle 2 with the reference timing as a starting point. The order in which each wave group 40-1G-40-NG emits a measurement wave is not restricted to this. For example, the wave groups 40-NG to 40-1G arranged in order counterclockwise from the outer surface located in the reference direction may emit measurement waves in order. Further, for example, the wave transmitter group 40-kG closest to the outer surface located in the reference direction emits the measurement wave, and then the wave transmitter 40-kG furthest from the outer surface located in the reference direction is the measurement wave. May be injected.

  A method of generating a signal transmission pattern by the pattern generation unit 11 will be specifically described using an example of a timing chart illustrated in FIG. In this example, the reference direction acquired by the pattern generation unit 11 is a direction facing the front of the vehicle 2. In this case, as illustrated in FIG. 20A, the timing signal generation unit 14 and the information acquisition unit 15 receive the 1PPS signal from the GPS receiver of the vehicle 2 at t = 0. The timing signal generator 14 generates a timing signal based on the 1PPS signal. The pattern generation unit 11 generates a signal transmission pattern using the signal timing of the 1PPS signal as a reference timing. As illustrated in FIG. 20B, the pattern generation unit 11 generates a signal transmission pattern related to the wave transmitter group 40-2G. That is, the pattern generation unit 11 starts the measurement wave from the reference wave in the clockwise direction after the time t1 has elapsed, and then the measurement wave is emitted at intervals of the period T. Inject waves. Moreover, the pattern generation part 11 produces | generates the signal transmission pattern which concerns on the wave transmitter group 40-3G so that a measurement wave may be inject | emitted at the timing as shown in FIG.20 (c). That is, in the pattern generation unit 11, after time t2 (t1 <t2 <T) has elapsed from the reference timing, the next group of projectors 40-3G positioned clockwise from the reference direction emits measurement waves, and then The measurement wave is emitted at intervals of the period T. Further, the pattern generation unit 11 generates a signal transmission pattern related to the wave transmitter group 40-4G so that the measurement wave is emitted at the timing as illustrated in FIG. That is, in the pattern generation unit 11, after time t3 (t2 <t3 <T) has elapsed from the reference timing, the next group of projectors 40-4G positioned clockwise from the reference direction emits measurement waves, and thereafter The measurement wave is emitted at intervals of the period T. Similarly, the pattern generation unit 11 generates a signal transmission pattern related to the wave transmitter group 40-1G so that the measurement wave is emitted at the timing shown in FIG. That is, in the pattern generation unit 11, after time t4 (t3 <t4 <T) has elapsed from the reference timing, the last wave generator group 40-1G positioned clockwise from the reference direction emits a measurement wave, and then The measurement wave is emitted at intervals of the period T.

  As described above, when each wave group 40-kG includes a plurality of wave elements 40-ka, 40-kb, 40-kc, the pattern generation unit 11 generates a signal transmission pattern including the frame group. . In the frame group of the signal transmission pattern, there are a plurality of frames in which the plurality of projectors 40-ka, 40-kb, and 40-kc included in each of the transmitter groups 40-kG sequentially emit measurement waves. included. That is, the pattern generation unit 11 generates a signal transmission pattern including a plurality of frames so that the measurements by the plurality of projectors 40-ka, 40-kb, and 40-kc do not overlap in time.

  Specifically, as illustrated in FIG. 21A, the information acquisition unit 15 and the timing signal generation unit 14 receive a 1PPS signal from GPS at t = 0. The pattern generation unit 11 generates a signal transmission pattern including a frame group as shown in FIG. This frame group has a frame in which the wave projector 40-2a emits a measurement wave at the elapsed time from time t1 to t11 with the reference timing as a starting point. The frame group has a frame in which the wave projector 40-2b emits a measurement wave at the elapsed time from time t12 to t13. The frame group includes frames in which the wave projector 40-2c emits a measurement wave at an elapsed time from time t14 to t15.

  Further, the pattern generation unit 11 generates a signal transmission pattern including a frame group as shown in FIG. This frame group has a frame in which the wave projector 40-3a emits a measurement wave at an elapsed time from time t2 to t21 with the reference timing as a starting point. Further, the frame group has a frame in which the wave projector 40-3b emits the measurement wave at the elapsed time from time t22 to t23. The frame group includes frames in which the wave projector 40-3c emits a measurement wave at an elapsed time from time t24 to t25. As shown in FIGS. 4D and 4E, the pattern generation unit 11 generates signal transmission patterns in the same manner for the wave transmitter groups 40-4 and 40-1.

  Each wave receiver 50-k is configured to be able to receive a reflected wave obtained by reflecting a measurement wave emitted from the corresponding wave transmitter group 40-kG to the measurement object. Specifically, in the receiver 50-k, the measurement waves emitted from the transmitters 40-ka, 40-kb, and 40-kc constituting the transmitter group 40-kG are reflected on the measurement target. The obtained reflected wave is configured to be receivable.

Wave receiver 50-k is the horizontal angle of the receivable reflected wave theta ₄ (see FIG. 19 (b)), the projector-receiver 40-ka included in the corresponding projection-receiver unit 40-kG, 40- kb and 40-kc are larger than the horizontal angles θ _{1 to} θ ₃ of the measurement wave emitted. Thereby, the receiver 50-k can also receive the reflected wave of the measurement wave transmitted from any of the projectors 40-ka, 40-kb, 40-kc. Further, the vertical angle theta _{6 (see} FIG. 19 (d)) of the receivers 50-k is receivable reflected wave vertical angle of the measurement wave projector-receiver 40-k is emitted theta ₅ ( It may be approximately the same as that shown in FIG. “Same degree” not only includes being completely the same, but also includes a range smaller than the horizontal angular range of the receiver 50-k. Thereby, the receiver 50-k can reduce noise due to sunlight.

  Further, the receiver 50-k is preferably installed such that the direction giving the maximum sensitivity of the receiver 50-k is directed downward from the horizontal direction. Alternatively, the angle range in the vertical direction that can be received by the receiver 50-k receives a reflected wave from a measurement target that is approximately the same height as the vehicle body of the vehicle 2 within a distance range in which the measurement target is assumed to exist. This is an angle that can be set, and is appropriately set based on the position where the receiver 50-k is attached.

  The second vehicle 2-2 of the vehicles 2 is mounted with the distance measuring device 1 similar to the distance measuring device 1 mounted on the first vehicle 2-1, and travels in front of the first vehicle 2-1. doing. The wave transmitter groups 40-1G to 40-NG arranged in the second vehicle 2-2 sequentially emit measurement waves based on the reference direction with the GPS 1PPS signal as the reference timing. In other words, the wave generator groups 40-1G to 40-NG of the second vehicle 2-2 are the wave generator groups 40-1G to 40-NG respectively disposed at the same position of the first vehicle 2-1. At the same timing, a measurement wave is emitted in the same direction as seen from each vehicle body. In the example shown in FIG. 18, the measurement wave is emitted from the wave group 40-1G of the second vehicle 2-2 at the timing when the wave is emitted from the wave group 40-1G of the first vehicle 2-1. Is done. Similarly, the measurement wave is emitted from the wave group 40-2G of the second vehicle 2-2 at the timing when the measurement wave is emitted from the wave group 40-2G of the first vehicle 2-1. The same applies to the wave projector groups 40-3G and 40-4G.

  Therefore, at the timing when the distance measuring device 1 of the first vehicle 2-1 emits a measurement wave in the direction of the second vehicle 2-2, the distance measuring device of the second vehicle 2-2 is the first vehicle 2-1. Does not emit measurement waves in the direction. Further, at a timing when the distance measuring device 1 of the first vehicle 2-1 does not emit a measurement wave in the direction of the preceding vehicle, the distance measuring device of the second vehicle 2-2 measures the measurement wave in the direction of the first vehicle 2-1. Inject. Thereby, the measurement wave emitted from the first vehicle 2-1 is reflected in the measurement object, and the measurement wave of the second vehicle 2-2 is emitted in the direction of the first vehicle 2-1. The receiver 50 does not receive the measured waves simultaneously. Thereby, it is possible to prevent the distance measuring device 1 from misidentifying the measurement wave emitted from the second vehicle 2-2 as a reflected wave. Therefore, the distance measuring device 1 can accurately measure the distance based on the measurement wave and the reflected wave of the measurement wave.

  The third vehicle 2-3 is mounted with a distance measuring device 1 similar to the above-described distance measuring device 1 mounted on the first vehicle 2-1, and travels facing the first vehicle 2-1. The wave transmitter groups 40-1 to 40-N arranged in the third vehicle 2-3 are the wave emitter groups 40-1G to 40-NG arranged in the same position of the first vehicle 2-1. The measurement wave is emitted in the same direction at the same timing using the GPS 1PPS signal as a reference clock. In the example shown in FIG. 18, the measurement wave is emitted from the wave group 40-3G of the third vehicle 2-3 at the timing when the wave is emitted from the wave group 40-1G of the first vehicle 2-1. Is done. Further, at the timing when the measurement wave is emitted from the wave group 40-2G of the first vehicle 2-1, the measurement wave is emitted from the wave group 40-4G of the third vehicle 2-3.

  Therefore, at the timing when the distance measuring device 1 of the first vehicle 2-1 emits a measurement wave in the direction of the third vehicle 2-3, the distance measuring device of the third vehicle 2-3 is the same as that of the first vehicle 2-1. Does not emit measurement waves in the direction. Further, the distance measuring device 1 of the third vehicle 2-3 is the timing at which the distance measuring device 1 of the first vehicle 2-1 does not emit a measurement wave in the direction of the third vehicle 2-3. A measurement wave is emitted in the direction of. As a result, the reflected wave obtained by reflecting the measurement wave emitted by the distance measuring device 1 of the first vehicle 2-1 to the object to be measured and emitted from the third vehicle 2-3 toward the first vehicle 2-1. It is possible to prevent misrecognition due to the receiver 50 receiving the measured wave. That is, the distance measuring device 1 can be prevented from misidentifying the measured wave emitted from the distance measuring device of the third vehicle 2-3 as a reflected wave related to its own measured wave. Therefore, the distance measuring device 1 can accurately measure the distance based on the measurement wave and the reflected wave of the measurement wave.

  When the distance measuring device 1 includes a plurality of wave projector groups 40-1 to 40-N, the distance measuring device 1 measures the distance to the measurement target by causing each component unit to execute the processing of the flowchart illustrated in FIG. .

  The pattern generation unit 11 generates a signal transmission pattern (step S1). The pattern generation unit 11 stores the signal transmission pattern in the storage device 60.

  The signal transmission pattern generation in step S1 when the distance measuring device 1 includes a plurality of wave projector groups 40-1 to 40-N will be described in detail with reference to FIG.

  The information acquisition unit 15 acquires azimuth information indicating a predetermined reference direction from the azimuth sensor included in the vehicle 2 (step S301). Various sensors such as a geomagnetic direction sensor, a gyro sensor, and a GPS compass can be used as the direction sensor.

  When the direction information is acquired in step S301, the information acquisition unit 15 acquires a 1PPS signal from the GPS (step S302).

  When the azimuth information is acquired in step S301 and the 1PPS signal is acquired in step S302, the pattern generation unit 11 determines the order in which the measurement waves of the projector group 40-k are emitted based on the reference direction ( Step S303). For example, the pattern generation unit 11 determines that the wave projector group 40-kG emits measurement waves in the order in which they are arranged clockwise from the outer surface located in the reference direction from the center of the vehicle 2.

  When the order in which the wave group 40-kG emits the measurement wave is determined in step S303, the pattern generation unit 11 causes each wave group 40 to emit light in order after a lapse of a predetermined time from the reference timing. A signal transmission pattern corresponding to -kG is generated (step S304). At this time, the pattern generation unit 11 generates a signal transmission pattern so that transmission frames by the wave projectors 40-ka, 40-kb, and 40-kc constituting each wave group 40-kG do not overlap in time. To do.

  When the signal transmission pattern is generated in step S304, the process returns to FIG. 7, and the signal generation unit 13 generates a transmission signal for causing each wave group 40-kG to emit the measurement wave based on the signal transmission pattern. (Step S2).

  When the transmission signal is generated in step S2, the wave transmitter group 40-kG emits a measurement wave that is amplitude-modulated according to the transmission signal input via the wave wave driver 41 to the target space. (Step S3).

  After the measurement wave is emitted in step S3, the receiver 50-k receives the reflected wave reflected by the measurement target (step S4). Specifically, the receiver 50-k is emitted from each of the transmitters 40-ka, 40-kb, and 40-kc included in the corresponding transmitter group 40-k, and reflected by the measurement target. Receive reflected waves.

  Subsequent steps S5 to S7 are the same as the above <Example of distance measurement operation>.

  Similarly, the configuration of the distance measuring device 1 having a plurality of wave emitter groups 40-1G to 40-NG can be applied to a pulse-type distance measuring device to be described later. In this case, the transmission pattern generation process shown in step S21 of FIG. 24 is the same as the transmission pattern generation process described above with reference to FIG.

  The distance measuring device 1 sequentially starts a group of wave emitters based on a reference direction synchronized with another distance measuring device after a predetermined elapsed time which is determined differently for each wave wave group 40-kG from the reference timing. A measurement wave is emitted from 40-kG. Thereby, in each frame group set to the wave transmitter group 40-kG, the direction in which the wave transmitter group 40-kG emitting the measurement wave is arranged is the same between the distance measuring devices. That is, at the timing when the distance measuring device 1 emits the measurement wave in the direction of the other distance measuring device, the other distance measuring device does not emit the measurement wave in the direction of the distance measuring device 1. Thus, by receiving the reflected wave related to the measurement wave emitted by itself and the measurement wave emitted from the other distance measuring device in the same transmission frame, the measurement wave emitted from the other distance measuring device can be obtained. It can prevent misidentifying that it is a reflected wave of its own. Therefore, the distance measuring device 1 can accurately measure the distance based on the emitted measurement wave and the reflected wave of the measurement wave.

  In the above-described embodiment, measurements by the plurality of projectors 40-ka, 40-kb, and 40-kc arranged adjacent to each other in the transmitter group 40-kG do not overlap in time. Therefore, in the distance measuring device 1, the reflected wave received by the wave receiver 50 is a reflection of the measurement wave emitted from any of the wave transmitters 40-kx arranged adjacent to each other. It can be identified. Thereby, the distance measuring device 1 can accurately measure the distance using the emitted measurement wave and the reflected wave of the measurement wave. In other words, the distance measuring device 1 can prevent the interference of the measurement wave received by the receiver 50-k.

  In the above-described embodiment, the plurality of wave emitters 40-ka, 40-kb, and 40-kc emit measurement waves in different angular ranges, and the wave receiver 50-k is a plurality of wave emitters 40-ka. , 40-kb, 40-kc, the reflected wave obtained by reflecting the measurement wave on the measurement object can be received. Therefore, even when using a device that emits light with high directivity for the purpose of ranging to a minute measurement target, it is possible to measure a measurement target that may exist over a wide range. The minute measurement object means a measurement object that occupies a relatively narrow angle range as viewed from the distance measuring device. The relatively narrow angle range is, for example, a range of less than 45 degrees in the horizontal direction.

  In the above-described embodiment, the transmission frames by the plurality of projectors 40-ka, 40-kb, and 40-kc are different, and the measurements do not overlap in time. Therefore, the distance measuring device 1 can prevent interference between measurement waves and reflected waves emitted from the plurality of wave projectors 40-ka, 40-kb, and 40-kc, respectively.

  In the above-described embodiment, the pattern generation unit 11 uses the signal timing of the 1PPS signal received from the GPS by the information acquisition unit 15 as the reference timing. And the pattern production | generation part 11 makes measurement wave from each of several projector group 40-1G-40NG after the predetermined elapsed time defined differently for every projector group 40-kG from this reference | standard timing as a starting point. A signal transmission pattern was generated so that However, the embodiment of the present invention is not limited to this. For example, the pattern generation unit 11 transmits a signal so that a measurement wave is emitted from each of the plurality of wave emitter groups 40-1G to 40-NG with the clock unique to the vehicle 2 as a reference timing, starting from the reference timing. A pattern may be generated. The clock unique to the first vehicle 2-1 is determined in advance at the time of manufacture for each identification number that uniquely identifies the first vehicle 2-1. Therefore, the clock of the first vehicle 2-1 is different from the clocks of the second vehicle 2-1 and the third vehicle 2-3.

[2. Pulse method]
The pulse method is a method based on a time difference between a signal transmitted to a target space and a signal received from a measurement target. When the distance measuring device 1 performs distance measurement by the pulse method, the distance measuring device 1 transmits a pulse signal to the target space. The distance measuring device 1 receives the pulse signal reflected by the measurement object. The distance measuring device 1 can calculate the distance to the measurement object based on the time from when the pulse signal is transmitted until the pulse signal is received.

  The pulse system includes, for example, a system that transmits a single pulse or a pulse compression system that transmits a signal including a plurality of pulses. Hereinafter, a case where the distance measuring device 1 performs distance measurement by the pulse compression method will be described.

  The resolution of the distance measured in a pulsed manner can be proportional to the pulse width. On the other hand, when the pulse width is shortened, the measurable distance can be shortened. In the pulse compression method, a measurable distance can be increased by modulating and transmitting a pulse having a long pulse width. By compressing the received pulses, the distance resolution can be reduced.

<2.1 Function block>
As illustrated in FIG. 23, the control device 10 includes a pattern generation unit 11, a clock generation unit 12, a signal generation unit 13, and a timing signal generation unit 14. The control device 10 includes an information acquisition unit 15 and a distance calculation unit 16. The control device 10 includes an FIR (Finite Impulse Response) filter unit 31 and an orthogonal modulation unit 32. The control device 10 includes a transmission side FFT unit 33, a reception side FFT unit 34, a correlation calculation unit 54, a noise filter unit 35, a sampling frequency conversion unit 36, and an inverse FFT unit 37. The control device 10 includes a transmission side comparator 38, a reception side comparator 39, a wave emitter driver 41, and a sensing amplifier 53. The control device 10 is connected to the wave projector 40 via the wave emitter driver 41. The control device 10 is connected to the wave receiver 50 via the sensing amplifier 53. Each component of the control device 10 is connected to the storage device 60.

  The pattern generation unit 11, the clock generation unit 12, the timing signal generation unit 14, and the information acquisition unit 15 may have the same configuration as the above-described FMCW method. These descriptions are omitted.

  The signal generation unit 13 generates a transmission signal at a timing based on the signal transmission pattern stored in the storage device 60 and the timing signal. The transmission signal may be a pulse signal. The transmission signal may be a pulse signal subjected to frequency modulation. The transmission signal may be a chirp pulse signal whose frequency increases with time.

  The FIR filter unit 31 performs FIR filter processing on the input signal. The FIR filter process may be a process of generating a new data string based on data in a finite section in the time series data string. When FIR filtering is performed on a chirped pulse signal, the frequency band of the chirped pulse signal can be widened.

  The quadrature modulation unit 32 performs quadrature modulation on the input signal. Quadrature modulation is also called IQ modulation or complex modulation. Quadrature modulation is a method of generating two orthogonal signals from an original signal by multiplying the original signal by two signals whose phases are shifted by π / 2, such as a sine wave and a cosine wave, for example. It is. A signal generated by multiplication with a sine wave can be an R signal. The signal generated by multiplication with the cosine wave can be an I signal. In other words, the quadrature modulation unit 32 can convert the input signal into a complex signal. The R signal is output to the transmission side comparator 38 as a transmission signal. The R signal is output to the transmission side FFT unit 33. The I signal is output to the transmission side FFT unit 33.

  The transmission side FFT unit 33 calculates a frequency spectrum by Fourier transform of the input signal. The transmission-side FFT unit 33 may have the same configuration as the FMCW FFT unit 24 described above. The frequency spectrum calculated from the signal input from the quadrature modulation unit 32 has a real part and an imaginary part. The transmission side FFT unit 33 outputs the real part and the imaginary part of the frequency spectrum to the correlation calculation unit 54.

  The transmission side comparator 38 includes a comparator. The comparator performs binarization processing on the input signal. For example, when a signal having a value equal to or greater than a predetermined threshold is input, the comparator may output a first predetermined value that is greater than the predetermined threshold. For example, when a signal having a value less than a predetermined threshold is input, the comparator may output a second predetermined value smaller than the predetermined threshold. The predetermined threshold value, the first predetermined value, and the second predetermined value can be set as appropriate. The first predetermined value and the second predetermined value may be set according to, for example, a voltage or current range in which the projector driver 41 receives an input. The predetermined threshold value may be set to a value close to an intermediate value between the first predetermined value and the second predetermined value, for example. The transmission side comparator 38 binarizes the transmission signal input from the quadrature modulation unit 32 to generate a pulse signal. The transmission side comparator 38 outputs the pulse signal as a transmission signal to the projector driver 41.

  The projector driver 41 amplifies the transmission signal input from the transmission side comparator 38 and outputs the amplified signal to the projector 40.

  The wave projector 40 emits a measurement wave based on the transmission signal acquired from the wave wave driver 41. The wave receiver 50 receives the reflected wave reflected by the measurement target. The wave receiver 50 outputs a reception signal based on the reflected wave to the sensing amplifier 53.

  The sensing amplifier 53 acquires a current signal as a reception signal from the wave receiver 50. The sensing amplifier 53 converts the current signal into a voltage signal. The sensing amplifier 53 applies a gain to the voltage signal based on the threshold value of the binarization process in the reception side comparator 39. The sensing amplifier 53 may store the gain value applied to the voltage signal in the storage device 60. The sensing amplifier 53 outputs the gain-adjusted voltage signal to the reception-side comparator 39. The sensing amplifier 53 may be connected to the timing signal generator 14. The sensing amplifier 53 may operate at a timing according to the timing signal. By doing in this way, the power consumption in the sensing amplifier 53 can be reduced.

  The reception side comparator 39 includes a comparator. Description of the comparator is omitted. The reception-side comparator 39 binarizes the voltage signal input from the sensing amplifier 53 and generates a pulse signal. The reception side comparator 39 outputs the pulse signal as a reception signal to the reception side FFT unit 34. The reception-side comparator 39 may store information related to the reception signal in the storage device 60.

  The reception-side FFT unit 34 calculates a frequency spectrum by Fourier transform of the input signal. The reception-side FFT unit 34 may have the same configuration as the FMCW-type FFT unit 24 or the transmission-side FFT unit 33 described above. The frequency spectrum calculated from the signal input from the reception-side comparator 39 has a real part and an imaginary part. The reception-side FFT unit 34 outputs the real part and the imaginary part of the frequency spectrum to the correlation calculation unit 54.

The correlation calculation unit 54 calculates the correlation result of the frequency spectrum. The correlation result of the frequency spectrum is calculated based on the two input frequency spectra. For example, when the first frequency spectrum and the second frequency spectrum are input to the correlation calculation unit 54, the correlation calculation unit 54 calculates the product of the first frequency spectrum and the complex conjugate of the second frequency spectrum. To do. The first frequency spectrum and the second frequency spectrum are expressed by the following equations (1) and (2), respectively. j is a symbol representing an imaginary unit.
(First frequency spectrum) = (first real part) + j × (first imaginary part) (1)
(Second frequency spectrum) = (second real part) + j × (second imaginary part) (2)
The complex conjugate of the second frequency spectrum is expressed as the following equation (3).
(Complex conjugate of second frequency spectrum) = (second real part) −j × (second imaginary part) (3)
The product of the first spectrum and the complex conjugate of the second spectrum corresponds to the correlation result of the two spectra.

  The correlation calculation unit 54 calculates the product of the frequency spectrum input from the transmission side FFT unit 33 and the complex conjugate of the frequency spectrum input from the reception side FFT unit 34 as the correlation result of the frequency spectrum. The correlation result of the frequency spectrum is also called a correlation spectrum. The correlation calculation unit 54 outputs the correlation spectrum to the noise filter unit 35.

  The noise filter unit 35 includes, for example, a low-pass filter. The noise filter unit 35 removes a noise component from the correlation spectrum and outputs the noise component to the sampling frequency conversion unit 36. The noise filter unit 35 performs filter processing on each of the real part and the imaginary part of the correlation spectrum.

  The sampling frequency conversion unit 36 converts the sampling frequency of the frequency spectrum. The sampling frequency conversion unit 36 performs decimation and interpolation.

  Decimation is a process of deleting a predetermined number of data from data included in a frequency spectrum, for example. Decimation may be a process of deleting data included in a frequency spectrum in a predetermined cycle in order of frequency.

  Interpolation is a process of adding data so as to interpolate data included in the frequency spectrum, for example. Interpolation may be a process of interpolating data with respect to a frequency spectrum from which a predetermined number of data has been deleted.

  The sampling frequency conversion unit 36 outputs the correlation spectrum obtained by converting the sampling frequency to the inverse FFT unit 37. The sampling frequency converter 36 converts the sampling frequency for each of the real part and the imaginary part of the correlation spectrum.

  The inverse FFT unit 37 converts the correlation spectrum into a signal represented in the time domain by inverse Fourier transform. The inverse Fourier transform may be an inverse discrete Fourier transform or an inverse fast Fourier transform. The inverse FFT unit 37 may store the correlation spectrum in the storage device 60. When a plurality of transmission frames are set in the signal transmission pattern, the inverse FFT unit 37 may acquire a correlation spectrum obtained from another transmission frame from the storage device 60. The inverse FFT unit 37 may integrate the correlation spectrum obtained in each transmission frame and store the result in the storage device 60. A spectrum obtained by integrating the correlation spectrum is also referred to as an integrated correlation spectrum. The inverse FFT unit 37 may perform inverse Fourier transform on the integrated correlation spectrum.

  A signal obtained by performing inverse Fourier transform on the correlation spectrum is also referred to as a correlation signal. The correlation signal indicates the correlation between the transmission signal and the reception signal. The inverse FFT unit 37 may store the correlation signal in the storage device 60. The inverse FFT unit 37 may output the correlation signal to the distance calculation unit 16. The inverse FFT unit 37 may output a signal obtained by converting the frequency spectrum as a complex signal. A signal obtained by performing inverse Fourier transform on the integrated correlation spectrum is also referred to as an integrated correlation signal. The inverse FFT unit 37 may store the accumulated correlation signal in the storage device 60. The inverse FFT unit 37 may output the integrated correlation signal to the distance calculation unit 16.

  The distance calculation unit 16 calculates the distance to the measurement target based on the correlation signal. The distance calculation unit 16 may acquire the correlation signal from the storage device 60. The distance calculation unit 16 may acquire the correlation signal from the inverse FFT unit 37. The distance calculation unit 16 may calculate a time difference between the transmission signal and the reception signal based on the correlation signal. The distance calculation unit 16 may calculate the distance to the measurement target based on the time difference between the transmission signal and the reception signal. The distance calculation unit 16 may calculate the distance to the measurement target in consideration of the signal delay inside the control device 10. The distance calculation unit 16 may calculate the distance to the measurement target based on the integrated correlation signal. By doing so, the distance measurement result is less affected by noise components that may be suddenly included in the received signal.

<2.2 Examples of distance measurement methods>
The distance measuring device 1 measures the distance to the measurement target by causing each component unit to execute the processing of the flowchart shown in FIG. 24, for example.

  In the control device 10, the pattern generation unit 11 generates a transmission pattern (step S21). The pattern generation unit 11 stores the transmission pattern in the storage device 60. More specific processing of step S21 is illustrated in FIGS. The process of step S21 is not limited to these.

  In the control device 10, the signal generation unit 13 generates a transmission signal (step S22). In the present embodiment, it is assumed that the transmission signal is a pulse signal subjected to frequency modulation. The signal generator 13 outputs a transmission signal at the timing indicated by the timing signal input from the timing signal generator 14. The transmission signal is converted into a complex signal having a real part and an imaginary part by the quadrature modulation unit 32. The real part of the transmission signal is output to the transmission side comparator 38 and the transmission side FFT unit 33. The imaginary part of the transmission signal is output to the transmission side FFT unit 33. The real part of the transmission signal is binarized by the transmission side comparator 38 and output to the wave projector driver 41.

  The projector 40 emits light, which has been amplitude-modulated in accordance with the transmission signal input via the projector driver 41, to the target space (step S23).

  The wave receiver 50 receives the light reflected by the measurement target (step S24). The receiver 50 outputs a current signal corresponding to the intensity of the received light as a received signal. The sensing amplifier 53 converts the current signal into a voltage signal. The sensing amplifier 53 applies a gain to the voltage signal and outputs the gain to the reception-side comparator 39. The sensing amplifier 53 may convert the received signal at a timing indicated by the timing signal input from the timing signal generation unit 14.

  The control device 10 performs a frequency correlation calculation between the transmission signal and the reception signal (step S25). Each of the transmission side FFT unit 33 and the reception side FFT unit 34 performs a Fourier transform on the input signal and outputs it to the correlation calculation unit 54. The correlation calculation unit 54 multiplies the frequency spectrum input from the transmission-side FFT unit 33 and the complex conjugate of the frequency spectrum input from the reception-side FFT unit 34 to calculate a correlation spectrum. The correlation calculation unit 54 outputs the correlation spectrum to the noise filter unit 35.

  The control device 10 calculates a ranging waveform from the correlation spectrum (step S26). The noise filter unit 35 removes a noise component from the correlation spectrum and outputs the noise component to the sampling frequency conversion unit 36. The sampling frequency conversion unit 36 converts the sampling frequency of the correlation spectrum and outputs it to the inverse FFT unit 37. The inverse FFT unit 37 performs inverse Fourier transform on the correlation spectrum to calculate a ranging waveform.

  In the control device 10, the distance calculation unit 16 calculates the distance from the measurement target based on the distance measurement waveform (step S27). The control device 10 ends the process of the flowchart of FIG.

  The configuration according to the present disclosure is not limited to the embodiments described above, and many variations or modifications are possible. For example, the functions included in each component, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of components, etc. can be combined into one or divided. .

  The figure explaining the structure which concerns on this indication is typical. The dimensional ratios and the like on the drawings do not necessarily match the actual ones.

  In the present disclosure, descriptions such as “first” and “second” are identifiers for distinguishing the configuration. The configurations distinguished by the description of “first” and “second” in the present disclosure can exchange numbers in the configurations. For example, the first frequency can exchange the identifiers “first” and “second” with the second frequency. The identifier exchange is performed at the same time. The configuration is distinguished even after the identifier is exchanged. The identifier may be deleted. The configuration from which the identifier is deleted is distinguished by a code. Based on only the description of identifiers such as “first” and “second” in the present disclosure, it should not be used as an interpretation of the order of the configuration, or as a basis for the existence of identifiers with smaller numbers.

DESCRIPTION OF SYMBOLS 1 Distance measuring device 2 Vehicle 2-1 1st vehicle 2-2 2nd vehicle 2-3 3rd vehicle 10 Control device 11 Pattern generation part 12 Clock generation part 13 Signal generation part 14 Timing signal generation part 15 Information acquisition part 16 Distance Calculation unit 17 (17R, 17I) Multiplier 21 Complex conversion unit 22 LPF unit 23 Notch filter unit 24 FFT unit 25 Peak detection unit 26 D-A converter 27 A-D converter 31 FIR filter unit 32 Orthogonal modulation unit 33 Transmission Side FFT unit 34 Reception side FFT unit 35 Noise filter unit 36 Sampling frequency modulation unit 37 Inverse FFT unit 38 Transmitting side comparator 39 Reception side comparator 40 Emitter 40-1G to 40-NG Emitter group 41 Emitter driver 50 Receiver 52 Gain adjuster 53 Sensing amplifier 54 Correlation calculator 60 Storage device

Claims (4)

A projector that emits measurement waves;
A receiver for receiving a reflected wave obtained by reflecting the measurement wave on a measurement object;
Generate a transmit signal with a modulated frequency,
Controlling the wave emitter to emit the measurement wave based on the transmission signal;
Obtaining a received signal based on the reflected wave from the receiver;
Detecting a first frequency based on a first difference frequency signal obtained from the transmission signal and the reception signal;
Removing a signal component related to the first frequency from the first difference frequency signal to generate a second difference frequency signal;
Detecting a second frequency based on the second difference frequency signal;
A distance measuring device comprising: a control device that calculates a distance to the measurement object based on the first frequency and the second frequency.   The distance measuring device according to claim 1, wherein the control device generates the second difference frequency signal when a signal component related to the first frequency is equal to or greater than a predetermined threshold. Generate a transmit signal with a modulated frequency,
Injecting a measurement wave based on the transmission signal,
Obtaining a reception signal based on a reflected wave obtained by reflecting the measurement wave on the measurement object;
Detecting a first frequency based on a first difference frequency signal obtained from the transmission signal and the reception signal;
Removing a signal component related to the first frequency from the first difference frequency signal to generate a second difference frequency signal;
Detecting a second frequency based on the second difference frequency signal;
A distance measuring method for calculating a distance to the measurement object based on the first frequency and the second frequency. A projector that emits measurement waves;
A receiver for receiving a reflected wave obtained by reflecting the measurement wave on a measurement object;
Generate a transmit signal with a modulated frequency,
Controlling the wave emitter to emit the measurement wave based on the transmission signal;
Obtaining a received signal based on the reflected wave from the receiver;
Detecting a first frequency based on a first difference frequency signal obtained from the transmission signal and the reception signal;
Removing a signal component related to the first frequency from the first difference frequency signal to generate a second difference frequency signal;
Detecting a second frequency based on the second difference frequency signal;
A vehicle comprising a distance measuring device having a control device that calculates a distance to the measurement object based on the first frequency and the second frequency.

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