Distance measuring device and distance measuring method

Abstract

To measure a distance to an object with high accuracy even when the distance is short.SOLUTION: A ranging device includes a transmitter, a frequency control unit, a receiver, and a measurement unit. The transmitter outputs high-frequency signals with variable frequencies to an object in multiple output periods, and stops or suppresses outputting the frequency-signals in multiple break periods. The frequency control unit monotonously increases the frequencies of the high-frequency signals in each of the output periods. The receiver receives high-frequency signals reflected by the object, as reflected waves. The measurement unit measures a distance to the object on the basis of a difference in frequency between the high-frequency signals and the reflected waves. Each of the break periods is interposed between adjacent two output periods out of the multiple output periods. A length of time of a first break period of the multiple break periods is different from that of a second break period adjacent to the first break period.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distance measuring device and a distance measuring method. [Background technology]

[0002] Research is being conducted into technologies that measure the distance to an object by transmitting a high-frequency signal, such as a radio wave, to the object and receiving the reflected wave. For example, the FMCW (Frequency Modulation Continuous Wave) method, which outputs a frequency-modulated high-frequency signal, detects the object and measures the distance to it. A distance measuring device using this technology is attached to an aircraft, for example, to measure the aircraft's altitude.

[0003] Patent Document 1 discloses a technique for measuring distance when the rising phase of a beat signal, which is a mixture of a high-frequency signal and a reflected wave, is 0 phase or π phase, in order to reduce periodic errors.

[0004] Patent Document 2 discloses a technique for improving distance resolution by linearly increasing the frequency of a high-frequency signal with high precision.

[0005] Patent Document 3 discloses a technique for easily measuring distance by providing a high-pass filter through which a beat signal, which is a mixture of a high-frequency signal and a reflected wave, passes.

[0006] Patent Document 4 discloses a technology for performing highly accurate distance measurement within a limited frequency bandwidth by modulating the period in which the frequency of a high-frequency signal is monotonically increased so that it ends when the amplitude of the high-frequency signal becomes zero. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-175681 [Patent Document 2] Japanese Patent Application Publication No. 7-055924 [Patent Document 3] Japanese Patent Application Publication No. 7-055925 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-053390 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the inventors discovered that even with the techniques described in the aforementioned Patent Documents 1 to 4, it is difficult to measure distances with high accuracy over a wide range from long distances to short distances. For example, when using the FMCW method to measure the distance to an object by adjusting the frequency difference between a high-frequency signal and a reflected wave to be constant, harmonics spread across the frequency spectrum may be detected as the frequency difference, resulting in an erroneous distance measurement. This is because as the distance to the object becomes shorter, the time required to obtain a beat signal, which is a mixture of the high-frequency signal and the reflected wave, becomes shorter, and the beat signal contains harmonic components.

[0009] In view of the above circumstances, one of the objects of the present invention is to measure the distance to an object with high accuracy even when the distance to the object is short. Other objects can be understood from the following description and explanation of the embodiments. [Means for solving the problem]

[0010] The following describes the means for solving the problems using the numbers and symbols used in the description of the invention. These numbers and symbols are added in parentheses for reference purposes to show an example of the correspondence between the claims and the description of the invention. Therefore, the claims should not be interpreted as being limited by the parenthetical descriptions.

[0011] To achieve the above object, a distance measuring device (100) according to one embodiment includes a transmitter (130), a frequency control unit (110), a receiver (140), and a measurement unit (170). The transmitter (130) outputs a high-frequency signal (2) whose frequency can be changed to an object (3) during a plurality of output periods (210), and stops or suppresses the output of the high-frequency signal (2) during a plurality of pause periods (220). The frequency control unit (110) monotonically increases the frequency of the high-frequency signal (2) during each of the plurality of output periods (210). The receiver (140) receives the high-frequency signal (2) reflected by the object (3) as a reflected wave (4). The measurement unit (170) measures the distance to the object (3) based on the frequency difference between the high-frequency signal (2) and the reflected wave (4). Each of the plurality of idle periods (220) is sandwiched between two adjacent output periods (210) among the plurality of output periods (210). Of the plurality of idle periods (220), the length of time of a first idle period (220-1) is different from the length of time of a second idle period (220-2) adjacent to the first idle period (220-1). The frequency control unit (110) determines the length of the output period (210) so that the frequency difference between the high frequency signal (2) and the reflected wave (4) becomes a specific frequency, and the measurement unit (170) measures the distance to the target (3) based on the length of the output period (210). .

[0012] To achieve the above object, a distance measurement method according to one embodiment includes outputting a frequency-variable high-frequency signal (2) to an object (3) during a plurality of output periods (210), and stopping or suppressing the output of the high-frequency signal (2) during a plurality of pause periods (220). The distance measurement method also includes monotonically increasing the frequency of the high-frequency signal (2) during each of the plurality of output periods (210). The distance measurement method also includes receiving the high-frequency signal (2) reflected by the object (3) as a reflected wave (4). The distance measurement method also includes measuring the distance to the object (3) based on the frequency difference between the high-frequency signal (2) and the reflected wave (4). Each of the plurality of pause periods (220) is sandwiched between two adjacent output periods (210) among the plurality of output periods (210). Among the plurality of pause periods (220), the length of a first pause period (220-1) is different from the length of a second pause period (220-2) adjacent to the first pause period (220-1). The length of the output period (210) is determined so that the frequency difference between the high frequency signal (2) and the reflected wave (4) becomes a specific frequency, and the distance to the object (3) is measured based on the length of the output period (210). . [Effects of the Invention]

[0013] According to the above-described embodiment, even if the distance to the object is short, the distance can be measured with high accuracy. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a configuration diagram of a distance measuring device according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a modulation frequency of a high-frequency signal according to an embodiment. [Figure 3] 3A and 3B are diagrams for explaining a high-frequency signal and a reflected wave in one embodiment. [Figure 4] FIG. 10 is a diagram illustrating the frequency spectrum of a beat signal when the pause period is constant. [Figure 5] FIG. 4 is a diagram illustrating a frequency spectrum of a beat signal according to an embodiment. [Figure 6] FIG. 2 is a configuration diagram of a pause setting unit according to an embodiment. [Figure 7] 10 is a flowchart showing a process for outputting a high-frequency signal in one embodiment. [Figure 8] 10 is a flowchart showing a process performed when a reflected wave is received in one embodiment. [Figure 9] 10 is a flowchart showing a process for outputting a high-frequency signal in one embodiment. [Figure 10] FIG. 2 is a diagram illustrating a bandpass filter according to an embodiment. [Figure 11] FIG. 2 is a configuration diagram of a bandpass filter according to an embodiment. [Figure 12] 10 is a flowchart showing a process performed when a reflected wave is received in one embodiment. [Figure 13] FIG. 2 is a configuration diagram of a pause setting unit according to an embodiment. [Figure 14] FIG. 2 is a diagram illustrating a modulation frequency of a high-frequency signal according to an embodiment. [Figure 15] FIG. 2 is a diagram illustrating a high-frequency signal according to an embodiment. [Figure 16] FIG. 1 is a configuration diagram of a distance measuring device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Embodiment 1) As shown in FIG. 1, a distance measuring device 100 according to one embodiment measures the distance to an object 3 and outputs information representing the measured distance to a control device 1. Specifically, the distance measuring device 100 outputs a high-frequency signal 2 to the object 3 and receives the high-frequency signal 2 reflected by the object 3 as a reflected wave 4. The distance measuring device 100 measures the distance to the object 3 based on the high-frequency signal 2 and the reflected wave 4. The control device 1 is provided in a mobile object such as an automobile or an aircraft, and controls the mobile object based on the measured distance. The distance measuring device 100 may also output information representing the measured distance to a display device that displays the measured distance. For example, the distance measuring device 100 includes a radio altimeter provided in an aircraft.

[0016] 2, the high-frequency signal 2 is output during a plurality of output periods 210, and is not output during pause periods 220 sandwiched between adjacent output periods 210. The high-frequency signal 2 is modulated during the output periods 210 so that the frequency increases monotonically, for example, so that the frequency increases linearly. After the output period 210 has elapsed, the ranging device 100 stops or suppresses the output of the high-frequency signal 2 until the pause period 220 has elapsed. After the pause period 220 has elapsed, the ranging device 100 again outputs the high-frequency signal 2 until the output period 210 has elapsed. In this way, the ranging device 100 outputs the high-frequency signal 2 by alternately switching between the output periods 210 and the pause periods 220.

[0017] The distance measuring device 100 measures the distance to the object 3 based on the difference between the frequency of the output high-frequency signal 2 and the frequency of the received reflected wave 4. Since the reflected wave 4 represents the high-frequency signal 2 reflected by the object 3, the distance L to the object 3 is expressed by equation (1).

number

number

number

[0018] The frequency difference f between the frequency of the high frequency signal 2 and the frequency of the reflected wave 4 b is calculated from the frequency of the beat signal output from the frequency mixer 150 shown in FIG. 1. Here, as the distance L to the target 3 becomes shorter, the time τ from when the high frequency signal 2 is output until the reflected wave 4 is received becomes shorter. Here, the frequency difference f b In order to adjust the output period 210 so that b The period τ of the beat signal at a specific frequency b As shown in Figure 4, the frequency spectrum of the beat signal is b It changes depending on time τ b When it gets shorter, it widens.

[0019] Also, the pause period 220 is a fixed time T s When expressing the frequency difference f b and 1 / (T+T s ) and the frequency difference f bFurthermore, since the range of the frequency spectrum is widened, the distance measuring device 100 can detect the frequency difference f that has the highest energy in the beat signal. b may not be able to detect.

[0020] Therefore, the distance measuring device 100 outputs a high frequency signal 2 having adjacent idle periods 220 of different duration, as shown in FIG. 2. By varying the idle periods 220, 1 / (T+T s ) also fluctuates. As a result, the frequency difference f b The difference between the energy of the frequency f and the energy of the other frequencies becomes large, and the distance measuring device 100 detects the frequency difference f b can be detected.

[0021] (Configuration of distance measuring device) The ranging device 100 shown in FIG. 1 includes a frequency control unit 110, a pause setting unit 120, a transmitter 130, a receiver 140, a frequency mixing unit 150, a bandpass filter 160, and a measurement unit 170. Each unit may be realized by an electronic circuit. For example, the frequency control unit 110 may be realized as a frequency control circuit unit, and the pause setting unit 120 may be realized as a pause setting circuit unit. Furthermore, the transmitter 130 may be realized as a transmission circuit unit, and the receiver 140 may be realized as a reception circuit unit. Furthermore, the frequency mixing unit 150 may be realized as a frequency mixing circuit unit, the bandpass filter 160 may be realized as a bandpass filter circuit unit, and the measurement unit 170 may be realized as a measurement circuit unit.

[0022] 3, the frequency control unit 110 controls the transmitter 130 so that the frequency of the high-frequency signal 2 varies. For example, the frequency control unit 110 controls the slope θ that represents the time change of the frequency. When the distance measuring device 100 receives the reflected wave 4, the frequency control unit 110 controls the frequency difference f between the frequency of the high-frequency signal 2 and the frequency of the reflected wave 4. bThe frequency control unit 110 controls the slope θ so that the frequency ΔF increases during the output period 210 to a predetermined specific frequency. For example, the frequency control unit 110 controls the slope θ by changing the output period 210 while keeping the frequency ΔF that increases during the output period 210 constant. For example, when the distance L to the object 3 is short, the frequency control unit 110 shortens the output period 210. When the distance L to the object 3 is long, the frequency control unit 110 lengthens the output period 210. In this way, the frequency control unit 110 controls the frequency difference f between the frequency of the high-frequency signal 2 and the frequency of the reflected wave 4 regardless of the distance L to the object 3. b The gradient θ is controlled so that the frequency becomes a specific frequency.

[0023] For example, the frequency control unit 110 may calculate the frequency difference f between the frequency of the high frequency signal 2 and the frequency of the reflected wave 4. b When the frequency difference f is not detected, the transmitter 130 is controlled to sweep the length of time of the plurality of output periods 210. b When detecting the frequency of the object 3 and measuring the distance L to the object 3, the frequency control section 110 controls the transmitter 130 so that the length of the output period 210 is constant.

[0024] 2, the frequency control unit 110 controls the transmitter 130 to output the high-frequency signal 2 during a plurality of output periods 210 and to stop outputting the high-frequency signal 2 during a plurality of pause periods 220. Each of the plurality of pause periods 220 is sandwiched between two adjacent output periods 210. The length of the pause period 220 is obtained from the pause setting unit 120 shown in FIG.

[0025] The pause setting unit 120 determines the length of the pause period 220. The length of the pause period 220 is determined so as to suppress harmonic components of the high-frequency signal 2. The pause setting unit 120 determines the pause periods 220, for example, so that adjacent pause periods 220 have different lengths. For example, the length of the first pause period 220-1 is different from the length of the second pause period 220-2. The length of the second pause period 220-2 is different from the length of the third pause period 220-3. The length of the third pause period 220-3 is different from the length of the fourth pause period 220-4. For example, among multiple pause periods 220 sandwiched between two output periods 210 of equal length, adjacent pause periods 220 have different lengths. Furthermore, among any number of consecutive three or more pause periods 220, for example, 20 pause periods 220, the length of each pause period 220 may be different from the length of the other pause periods 220. Thus, among the plurality of pause periods 220, in a pause period group including a plurality of consecutive pause periods 220, the time length of the pause periods 220 differs from the time length of the other pause periods 220. The less regular the changes in the time lengths of the pause periods 220, the more the harmonic spectrum is reduced.

[0026] 6, the pause setting unit 120 includes a random number generation unit 121 and a pause period determination unit 122. The random number generation unit 121 is configured to output values ​​within a predetermined range, for example, a range greater than 0 and less than 1, with equal probability. The random number generation unit 121 may output, for example, a pseudo-random number sequence.

[0027] The pause period determination unit 122 determines the length of the pause period 220 based on the pseudo-random number sequence output by the random number generation unit 121. For example, when the random number generation unit 121 outputs a value between 0 and 1, the pause period determination unit 122 multiplies the output value by the maximum value of the pause period 220 to calculate the length of the pause period 220. Here, the maximum value of the pause period 220 may be any value. The length of the pause period 220 determined by the pause period determination unit 122 is output to the frequency control unit 110, and is set by the frequency control unit 110 as the pause period 220 of the high-frequency signal 2.

[0028] The transmitter 130 shown in FIG. 1 outputs a high-frequency signal 2 having a frequency set by the frequency control unit 110 to the object 3. The transmitter 130 outputs any wave, such as an electric wave, a light wave, or a sound wave, that propagates to and is reflected by the object 3 as the high-frequency signal 2. The high-frequency signal 2 has a frequency obtained by adding the modulation frequency shown in FIG. 3 to a high frequency, such as 2 GHz. The transmitter 130 also outputs the high-frequency signal 2 to the frequency mixing unit 150. For example, the transmitter 130 divides the high-frequency signal 2 to be output to the object 3 using a divider, and outputs the divided signal to the frequency mixing unit 150 as a voltage signal.

[0029] 1 receives a reflected wave 4 from an object 3 and outputs the received reflected wave 4 to a frequency mixing unit 150. For example, the receiver 140 converts the reflected wave 4 into a voltage signal and outputs the reflected wave 4 to the frequency mixing unit 150.

[0030] The frequency mixer 150 mixes the high frequency signal 2 received from the transmitter 130 with the reflected wave 4 received from the receiver 140, and the frequency difference f between the frequency of the high frequency signal 2 and the frequency of the reflected wave 4 is b Specifically, when the frequency mixer 150 receives the reflected wave 4, it mixes the high-frequency signal 2 output from the transmitter 130 with the reflected wave 4 to generate a beat signal. The generated beat signal is output to the band-pass filter 160.

[0031] 5, the bandpass filter 160 passes signals in a detection frequency band 300 that represents a frequency band centered on a specific frequency, and blocks or suppresses signals of other frequencies. The specific frequency is determined by the frequency difference f that is controlled to be constant by the frequency control unit 110. b The frequency difference f b represents the difference between the frequency of the high frequency signal 2 and the frequency of the reflected wave 4 when the distance measuring device 100 calculates the distance L to the object 3.

[0032] The measuring unit 170 calculates the distance L from the distance measuring device 100 to the object 3 based on the beat signal that has passed through the band-pass filter 160. The measuring unit 170 calculates the distance L from the distance measuring device 100 to the object 3 using equation (3). Here, when calculating the distance L from the distance measuring device 100 to the object 3, the frequency difference f b represents a specific frequency. The frequency ΔF that increases during the output period 210 is also a fixed value. Therefore, the measurement unit 170 calculates the frequency difference f b is a specific frequency, the time length T of the output period 210 is obtained from the frequency control section 110, and the distance L is calculated.

[0033] The measuring unit 170 also measures the frequency difference f between the frequency of the high frequency signal 2 and the frequency of the reflected wave 4. b is not a specific frequency, the frequency control unit 110 outputs a signal to change the time length of the output period 210. For example, when the frequency difference f b is greater than the specific frequency, the measurement section 170 outputs a signal to increase the length of the output period 210. b is smaller than the specific frequency, the measuring section 170 outputs a signal to shorten the length of the output period 210. In addition, the frequency difference f b When the frequency difference f b The output signal is used to sweep the length of the output period 210 over a certain range so that the length of the output period 210 that matches the specified frequency can be identified.

[0034] (High frequency signal output processing) The distance measuring device 100 outputs the high frequency signal 2 by the process shown in Fig. 7, which is included in the distance measuring method. In step S110, the frequency control unit 110 determines the length of the output period 210 during which the high frequency signal 2 is output based on the signal from the measurement unit 170. For example, when the measurement unit 170 determines that the frequency difference f bWhen the frequency control unit 110 cannot detect the time difference, the frequency control unit 110 changes the time length of the output period 210 at predetermined time intervals. For example, as shown in FIG. 2, the frequency control unit 110 determines the time length of the first output period 210-1. The frequency control unit 110 also fixes the time length of the output period 210 for a predetermined time. For example, the time length of the second output period 210-2 is equal to the time length of the first output period 210-1. The time lengths of the third output period 210-3, the fourth output period 210-4, and the fifth output period 210-5 are also equal to the time length of the first output period 210-1.

[0035] 7, the pause setting unit 120 determines the length of time of the pause period 220. For example, the pause setting unit 120 determines the length of time of a first pause period 220-1 as shown in Fig. 2. The first pause period 220-1 represents, for example, the time obtained by multiplying the value output by the random number generation unit 121 by the maximum value of the pause period 220.

[0036] 7, the frequency control unit 110 determines the frequency of the high-frequency signal 2. The frequency control unit 110 determines the frequency of the high-frequency signal 2 by adding the modulation frequency shown in FIG. 2 to the high-frequency signal. Specifically, the frequency control unit 110 determines the frequency of the high-frequency signal 2 so that the frequency increases linearly during the first output period 210-1. The frequency control unit 110 also determines to stop or suppress the output of the high-frequency signal 2 during the pause period 220.

[0037] 7, the transmitter 130 outputs the high-frequency signal 2 at the frequency determined by the frequency control unit 110. For example, as shown in FIG. 2, the transmitter 130 outputs the high-frequency signal 2 in a first output period 210-1, and stops outputting the high-frequency signal 2 in a first pause period 220-1 following the first output period 210-1.

[0038] 7, the frequency control unit 110 determines whether to change the time length of the output period 210. For example, the frequency difference f bWhen the frequency control unit 110 is unable to detect the frequency difference f and a predetermined period has not elapsed since the determination of the length of the time of the output period 210, the frequency control unit 110 determines not to change the length of the time of the output period 210. When the frequency control unit 110 determines not to change the length of the time of the output period 210, the process returns to step S120 and is repeated. Furthermore, when the frequency control unit 110 has not received a signal to change the length of the time of the output period 210 from the measurement unit 170, the frequency control unit 110 determines not to change the length of the time of the output period 210. For example, when the frequency difference f b is a specific frequency, the frequency control unit 110 determines not to change the length of the time of the output period 210. In addition, the frequency control unit 110 determines that the frequency difference f b is detected and no signal for changing the length of the output period 210 has been received from the measurement unit 170, it is determined not to change the length of the output period 210. When the process returns to step S120, the pause setting unit 120 determines the length of the second pause period 220-2, and the transmitter 130 outputs the high-frequency signal 2 during the second output period 210-2 and stops outputting the high-frequency signal 2 during the second pause period 220-2, as shown in FIG.

[0039] For example, the frequency difference f b When the frequency control unit 110 cannot detect the time difference and a predetermined period of time has elapsed since determining the length of the output period 210, the frequency control unit 110 determines to change the time length of the output period 210. When the frequency control unit 110 determines to change the time length of the output period 210, the process returns to step S110 and is repeated. In this case, for example, the frequency control unit 110 increases the time length of the output period 210 by a predetermined period of time. Furthermore, when the length of the output period 210 plus the predetermined period of time exceeds the maximum value, the frequency control unit 110 changes the time length of the output period 210 to the minimum value. Furthermore, the frequency control unit 110 may change the time length of the output period 210 to be shorter by a predetermined period of time, and when the length of the output period 210 becomes smaller than the minimum value, change the time length of the output period 210 to the maximum value.

[0040] Furthermore, the frequency control unit 110 changes the length of time of the output period 210 based on a signal from the measurement unit 170. For example, when the frequency control unit 110 receives a signal from the measurement unit 170 to change the length of time of the output period 210, it determines to change the length of time of the output period 210. For example, when the frequency control unit 110 receives a signal to increase the length of time of the output period 210, it determines in step S110 to increase the length of time of the output period 210. When the frequency control unit 110 receives a signal to decrease the length of time of the output period 210, it determines in step S110 to decrease the length of time of the output period 210.

[0041] In this way, the transmitter 130 transmits the frequency difference f b The high frequency signal 2 is output for a time period 210 corresponding to the detection of the high frequency signal 2 .

[0042] (Receiving and processing reflected waves) When the receiver 140 receives the reflected wave 4, the distance measuring device 100 calculates the distance L to the object 3 by the process shown in FIG. 8, which is included in the distance measuring method. In step S210, the frequency mixer 150 shown in FIG. 1 mixes the high-frequency signal 2 output by the transmitter 130 with the reflected wave 4 received by the receiver 140 to generate a beat signal. The beat signal is a frequency difference f b It contains frequency components of

[0043] 8, the bandpass filter 160 extracts a signal in a detection frequency band 300 from the beat signal. The detection frequency band 300 is a specific frequency, specifically, the frequency difference f between the frequency of the high-frequency signal 2 and the frequency of the reflected wave 4 when the distance measuring device 100 calculates the distance L to the target object 3, as shown in FIG. b represents a band centered on

[0044] In step S230 shown in FIG. 8, the measurement unit 170 acquires the beat signal that has passed through the band-pass filter 160 for a predetermined period of time. The predetermined period represents any predetermined period of time. For example, when the distance L to the object 3 does not fluctuate for a long period of time or when the fluctuating speed is slow, the predetermined period may be set to a long time. When the predetermined period is long, the measurement unit 170 can calculate the distance L with high accuracy due to the temporal averaging effect. When the distance L to the object 3 fluctuates in a short period of time, the predetermined period is set to a short time. When the predetermined period is short, the measurement unit 170 shortens the distance calculation cycle, and the frequency of output to the control device 1 can be increased.

[0045] In step S240, the measurement unit 170 calculates the frequency difference f at which the energy of the acquired beat signal is maximized. b is a specific frequency. For example, the measuring unit 170 detects a frequency included in the beat signal and calculates the energy of the detected frequency. As shown in FIG. 5, the measuring unit 170 calculates the frequency difference f b The measuring unit 170 detects the frequency difference f b Determine whether the frequency is the same as a specific frequency. b If it is determined that the detected frequency difference f is different from the specific frequency, the process proceeds to step S250. b If the frequency difference f is equal to the specific frequency, the process proceeds to step S260. b When the frequency difference f b is different from the predetermined specific frequency. When the difference between the largest energy and the energy of another frequency is smaller than the threshold, the measuring unit 170 determines that the frequency difference f b may be determined not to be detected.

[0046] In step S250 shown in FIG. 8, the measurement unit 170 measures the detected frequency difference f b and the specific frequency to the frequency control unit 110. For example, b When the frequency difference f is not detected, the measurement unit 170b is not detected to the frequency control section 110. b is greater than the specific frequency, the measurement section 170 outputs a signal to the frequency control section 110 to increase the length of the output period 210. b When is smaller than the specific frequency, the measuring section 170 outputs a signal to shorten the length of the output period 210.

[0047] In step S260, the measurement section 170 acquires the length of time of the output period 210 from the frequency control section 110, and calculates the distance L from the distance measuring device 100 to the object 3 based on the acquired length of time.

[0048] In this way, the distance measuring device 100 calculates the distance L from the distance measuring device 100 to the object 3 by using the high-frequency signal 2 having the pause period 220 that suppresses the harmonic components. As a result, even if the distance L from the distance measuring device 100 to the object 3 is short, the distance measuring device 100 can calculate the distance L from the distance measuring device 100 to the object 3 without erroneously detecting the harmonic components. Furthermore, the distance measuring device 100 can calculate not only short distances but also long distances. Therefore, the distance measuring device 100 can calculate the distance L over a wide range.

[0049] (Embodiment 2) As the distance L from the distance measuring device 100 to the object 3 increases, the output period 210 increases, and the time for obtaining the beat signal increases. Therefore, the spread of the frequency spectrum of the high frequency signal 2 is suppressed, and even if the pause period 220 is a fixed value of a short time, the distance measuring device 100 can obtain the frequency difference f bcan be detected. In this way, the distance measuring device 100 may set the pause period 220 to a fixed value when the distance L from the distance measuring device 100 to the object 3 is longer than a predetermined distance. When the distance L from the distance measuring device 100 to the object 3 becomes longer than the predetermined distance, the duration of the output period 210 in the high-frequency signal 2 output by the transmitter 130 becomes longer. Therefore, the distance measuring device 100 may set the pause period 220 to a fixed value when the duration of the output period 210 is greater than a threshold. For example, the pause periods 220 sandwiched between two adjacent output periods 210 among the multiple output periods 210 whose durations are greater than the threshold may have the same duration.

[0050] (Configuration of distance measuring device) The distance measuring device 100 has the same configuration as in the first embodiment except for the frequency control unit 110. When the length of the output period 210 is greater than a threshold, the frequency control unit 110 sets the length of the pause period 220 to a preset fixed value. Furthermore, the frequency control unit 110 functions in the same way as in the first embodiment.

[0051] (High frequency signal output processing) 9, which is included in the ranging method, the ranging device 100 outputs the high frequency signal 2. In step S110, the frequency control unit 110 determines the length of the output period 210 during which the high frequency signal 2 is output, based on the signal from the measurement unit 170. Step S110 is the same as in the first embodiment, and therefore a detailed description thereof will be omitted.

[0052] In step S112, the frequency control unit 110 determines whether the length of the determined time period of the output period 210 is greater than a threshold. If the length of the time period of the output period 210 is greater than the threshold, the process proceeds to step S114. If the length of the time period of the output period 210 is equal to or less than the threshold, the process proceeds to step S120. Here, the threshold is determined in accordance with the distance L from the distance measuring device 100 to the object 3, and the measurement unit 170 determines the frequency difference f b is determined based on the distance L at which it can be detected.

[0053] In step S114, the frequency control unit 110 determines a fixed value as the length of time of the idle period 220. The fixed value is a value set in advance, and can be set to any value.

[0054] If the length of time of the output period 210 is equal to or less than the threshold, in step S120, the pause setting unit 120 determines the length of time of the pause period 220. Step S120 is the same as in the first embodiment, and therefore a detailed description thereof will be omitted.

[0055] The processes from step S130 to step S150 are the same as those in the first embodiment, and therefore detailed description thereof will be omitted.

[0056] (Receiving and processing reflected waves) The process in which the distance measuring device 100 receives the reflected wave 4 and calculates the distance L to the object 3 is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0057] By changing the idle period 220 to a fixed value depending on the distance L to the object 3, the distance measuring device 100 can shorten the idle period 220 when the distance L to the object 3 is relatively long. By shortening the idle period 220, the proportion of the time during which a beat signal is obtained becomes relatively long. As a result, a shorter idle period 220 is advantageous at long distances where the received power decreases due to distance attenuation of the high frequency signal 2 and the reflected wave 4.

[0058] (Embodiment 3) The bandpass filter 160 of the distance measuring device 100 is configured to accurately measure the frequency difference f b10, in order to detect the frequency band 300, the frequency band 302 may have three filters that pass different frequency bands. For example, the band-pass filter 160 has a filter that passes signals in a low-frequency band 310 that is lower in frequency than the detection frequency band 300 and adjacent to the detection frequency band 300, and blocks or suppresses signals of other frequencies. The band-pass filter 160 also has a filter that passes signals in a high-frequency band 320 that is higher in frequency than the detection frequency band 300 and adjacent to the detection frequency band 300, and blocks or suppresses signals of other frequencies. The low-frequency band 310 may include a portion of the detection frequency band 300. The high-frequency band 320 may also include a portion of the detection frequency band 300.

[0059] The measuring unit 170 compares the energy of the beat signal that has passed through the filter of the detection frequency band 300, the energy of the beat signal that has passed through the filter of the low frequency band 310, and the energy of the beat signal that has passed through the filter of the high frequency band 320. The measuring unit 170 calculates the frequency difference f b This determines that the frequency difference f b This increases the accuracy of detecting

[0060] (Configuration of distance measuring device) As shown in FIG. 11, the bandpass filter 160 shown in FIG. 1 has a central filter 161 that passes signals in the detection frequency band 300, a first adjacent filter 162 that passes signals in the low frequency band 310, and a second adjacent filter 163 that passes signals in the high frequency band 320.

[0061] The measuring section 170 compares the energy of the beat signal that has passed through the central filter 161, the energy of the beat signal that has passed through the first adjacent filter 162, and the energy of the beat signal that has passed through the second adjacent filter 163 to determine the frequency difference f b Furthermore, the measurement unit 170 has the same functions as in the first embodiment.

[0062] The other configurations are the same as those in the first embodiment, and therefore detailed explanations will be omitted.

[0063] (High frequency signal output processing) The process by which the distance measuring device 100 outputs the high frequency signal 2 is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0064] (Receiving and processing reflected waves) When the receiver 140 receives the reflected wave 4, the distance measuring device 100 calculates the distance L to the object 3 by the process shown in Fig. 12, which is included in the distance measuring method. In step S210, the frequency mixer 150 shown in Fig. 1 mixes the high-frequency signal 2 output by the transmitter 130 with the reflected wave 4 received by the receiver 140 to generate a beat signal. The process of step S210 is the same as in the first embodiment, so a detailed description thereof will be omitted.

[0065] 12, the band-pass filter 160 extracts signals in multiple frequency bands from the beat signal, for example, signals in the detection frequency band 300, the low frequency band 310, and the high frequency band 320 shown in FIG. 10. For example, the band-pass filter 160 divides the beat signal into multiple parts and includes a center filter 161, a first adjacent filter 162, and a second adjacent filter 163 through which the divided beat signals pass. As a result, the band-pass filter 160 outputs a beat signal in the detection frequency band 300 that has passed through the center filter 161, a beat signal in the low frequency band 310 that has passed through the first adjacent filter 162, and a beat signal in the high frequency band 320 that has passed through the second adjacent filter 163.

[0066] 12, the measuring unit 170 acquires multiple beat signals that have passed through the band-pass filter 160 for a predetermined period of time and compares the energies of the multiple beat signals. For example, the measuring unit 170 calculates the energy of the beat signal that has passed through the central filter 161, the energy of the beat signal that has passed through the first adjacent filter 162, and the energy of the beat signal that has passed through the second adjacent filter 163. The measuring unit 170 compares the calculated energies of the three beat signals.

[0067] In step S224, the measuring section 170 determines whether the energy of the detection frequency band 300, which is the energy of the beat signal that has passed through the center filter 161, is the largest. For example, when the energy of the detection frequency band 300 shown in FIG. 10 is larger than the energy of the first adjacent filter 162 and larger than the energy of the second adjacent filter 163, the measuring section 170 determines whether the frequency difference f b is included in the detection frequency band 300, and process step S240. For example, when the value obtained by subtracting the energy of the low frequency band 310, which is the energy of the beat signal that passed through the first adjacent filter 162, from the energy of the detection frequency band 300 is greater than the threshold, the measurement unit 170 determines that the energy of the detection frequency band 300 is greater than the energy of the low frequency band 310. Furthermore, when the value obtained by subtracting the energy of the high frequency band 320, which is the energy of the beat signal that passed through the second adjacent filter 163, from the energy of the detection frequency band 300 is greater than the threshold, the measurement unit 170 determines that the energy of the detection frequency band 300 is greater than the energy of the low frequency band 310. Note that the threshold may be any predetermined value.

[0068] The measuring unit 170 executes the process of step S250 when the energy of the detection frequency band 300 is not the highest. For example, the measuring unit 170 determines that the energy of the detection frequency band 300 is not the highest when the energy of the low frequency band 310 is greater than the energy of the detection frequency band 300, or when the energy of the high frequency band 320 is greater than the energy of the detection frequency band 300. Alternatively, the measuring unit 170 may determine that the energy of the detection frequency band 300 is not the highest when the value obtained by subtracting the energy of the low frequency band 310 from the energy of the detection frequency band 300 is equal to or less than a threshold, or when the value obtained by subtracting the energy of the high frequency band 320 from the energy of the detection frequency band 300 is equal to or less than a threshold.

[0069] frequency difference f bis determined to be included in the detection frequency band 300, in step S240, the measurement unit 170 measures the frequency difference f b The process of step S240 is the same as that of the first embodiment, and therefore detailed description thereof will be omitted.

[0070] frequency difference f b is determined not to be included in the detection frequency band 300, or the frequency difference f b is not a specific frequency, in step S250 shown in FIG. 12, the measurement unit 170 calculates the detected frequency difference f b and the specific frequency to the frequency control section 110. For example, when the energy of the low frequency band 310 shown in FIG. 10 is greater than the energy of the detection frequency band 300, the measurement section 170 outputs the frequency difference f b is included in the low frequency band 310, and outputs a signal to shorten the length of the output period 210. For example, when the value obtained by subtracting the energy of the detection frequency band 300 from the energy of the low frequency band 310 is greater than the threshold, the measurement section 170 determines that the frequency difference f b may be determined to fall within the low frequency band 310.

[0071] Furthermore, when the energy of the high frequency band 320 is greater than the energy of the detection frequency band 300, the measurement unit 170 measures the frequency difference f b is included in the high frequency band 320, and outputs a signal to increase the length of the output period 210. For example, when the value obtained by subtracting the energy of the detection frequency band 300 from the energy of the high frequency band 320 is greater than the threshold, the measurement section 170 determines that the frequency difference f b may be determined to fall within the high frequency band 320.

[0072] Furthermore, when the energy of the detection frequency band 300, the energy of the low frequency band 310, and the energy of the high frequency band 320 are approximately equal, the measurement unit 170 calculates a frequency difference f bFor example, when the difference between the energy of the detection frequency band 300 and the energy of the low frequency band 310 is smaller than the threshold value, and the difference between the energy of the detection frequency band 300 and the energy of the high frequency band 320 is smaller than the threshold value, the measuring unit 170 determines that the frequency difference f b The measurement unit 170 determines that the frequency difference f b If the frequency difference f b The frequency control unit 110 outputs information indicating that the frequency is not detected.

[0073] The measurement unit 170 measures the frequency difference f b is included in the detection frequency band 300, and the frequency difference f b is not a specific frequency, a signal for changing the length of time of output period 210 is output to frequency control section 110, as in the first embodiment.

[0074] In step S260 shown in FIG. 12, the measurement unit 170 acquires the length of time of the output period 210 from the frequency control unit 110, and calculates the distance L from the distance measuring device 100 to the object 3 based on the acquired length of time.

[0075] In this way, the distance measuring device 100 compares the energy of the detection frequency band 300, the energy of the low frequency band 310, and the energy of the high frequency band 320, thereby determining the frequency difference f with high accuracy. b Therefore, the distance measuring device 100 can calculate the distance L to the object 3 with high accuracy.

[0076] (Variation) The above-described embodiment and modified examples are merely examples, and may be changed as long as the function is not impaired. For example, the pause setting unit 120 may determine the length of the pause period 220 by any method so as to suppress the harmonic components of the high-frequency signal 2. For example, the pause setting unit 120 may store the lengths of a plurality of pause periods 220 that are set so as to suppress the harmonic components of the high-frequency signal 2, and output the stored lengths of the pause periods 220 to the frequency control unit 110.

[0077] For example, as shown in FIG. 13 , the pause setting unit 120 may include a pause period storage unit 125 and a pause period determination unit 122. The pause period storage unit 125 stores, in order, the durations of a plurality of pause periods 220 that are set so as to suppress harmonic components of the high-frequency signal 2. For example, the pause period storage unit 125 stores, in order, the durations of the plurality of pause periods 220 shown in FIG. 2. In the example shown in FIG. 2 , the pause period storage unit 125 stores the duration of the first pause period 220-1 as the first item, and the duration of the second pause period 220-2 as the second item. Similarly, the duration of the third pause period 220-3 is stored as the third item, and the duration of the fourth pause period 220-4 is stored as the fourth item. The pause period storage unit 125 outputs the durations of the pause periods 220 to the pause period determination unit 122 in order, starting from the first item.

[0078] The pause period determination unit 122 outputs the pause periods 220 obtained from the pause period storage unit 125 to the frequency control unit 110 in the order of their time lengths.

[0079] 14, the high-frequency signal 2 may include a modulation period 215 in which the frequency monotonically decreases after the output period 210. In this case, the length T of the output period 210 used when calculating the distance L to the object 3 represents the period in which the frequency monotonically increases, and does not include the modulation period 215.

[0080] 15, the transmitter 130 may stop outputting the high-frequency signal 2 when the energy of the high-frequency signal 2 becomes zero. This can suppress the generation of high-frequency components in the high-frequency signal 2 that occur when the output of the waveform 201 of the high-frequency signal 2 is suddenly stopped. In this case, the period 212 during which the high-frequency signal 2 is output is shorter than the output period 210 determined by the frequency control unit 110. Furthermore, the maximum frequency ΔF1 of the modulation frequency of the high-frequency signal 2 is smaller than the preset frequency ΔF. However, when calculating the distance L to the object 3, the length T of the output period 210 determined by the frequency control unit 110 and the preset frequency ΔF are used.

[0081] The predetermined period when the measurement unit 170 acquires the beat signal, for example, the predetermined period in step S230 shown in FIG. 8, may be determined to be relatively short when the fluctuations in the distance L are large, and may be determined to be relatively long when the fluctuations in the distance L are small. For example, the measurement unit 170 may change the predetermined period depending on the distance L to the object 3, for example, the length of the output period 210. When the distance measuring device 100 measures the altitude of an aircraft, the aircraft may maintain a constant altitude at low altitudes to avoid collision with the ground. In this case, the measurement unit 170 determines the predetermined period to be relatively long when the distance L is greater than a threshold, for example, when the length of the output period 210 is greater than a threshold. Furthermore, the measurement unit 170 determines the predetermined period to be relatively short when the distance L is small, for example, when the length of the output period 210 is equal to or less than a threshold.

[0082] 16, the distance measuring device 100 may include an arithmetic unit 180 and a storage device 190. The arithmetic unit 180 may implement the frequency control unit 110, the pause setting unit 120, the frequency mixing unit 150, the band-pass filter 160, and the measurement unit 170 shown in FIG. 1 by executing a program 191 stored in the storage device 190.

[0083] In this case, the storage device 190 is used as a non-transitory storage medium for storing the program 191. The program 191 may be provided as a computer program product recorded on the computer-readable storage medium 10, or may be provided as a computer program product downloadable from a server.

[0084] The configurations described in each embodiment and modification may be arbitrarily modified and / or combined as long as the functions are not impaired.

[0085] The distance measuring device and distance measuring method described in each embodiment can be understood, for example, as follows.

[0086] The distance measuring device according to the first aspect includes a transmitter 130, a frequency control unit 110, a receiver 140, and a measurement unit 170. The transmitter 130 outputs a high-frequency signal 2, the frequency of which can be changed, to an object 3 during a plurality of output periods 210, and stops or suppresses the output of the high-frequency signal 2 during a plurality of idle periods 220. Of the plurality of idle periods 220, the length of a first idle period 220-1 is different from the length of a second idle period 220-2 adjacent to the first idle period 220-1.

[0087] The distance measuring device according to the second aspect is the distance measuring device according to the first aspect, and further includes a pause setting unit 120.

[0088] Since the harmonic components due to the pause period 220 are suppressed, the frequency difference between the high frequency signal 2 and the reflected wave 4 can be detected even if the distance to the object 3 is short.

[0089] The distance measuring device according to the third aspect is the distance measuring device according to the first aspect, and is configured such that the pause setting unit 120 includes a random number generation unit 121 and a pause period determination unit 122. Since the pause period 220 is determined by a random number, the frequency difference between the high frequency signal 2 and the reflected wave 4 can be detected even if the distance to the target object 3 is short.

[0090] The distance measuring device according to the fourth aspect is the distance measuring device according to the first aspect, and is configured such that the pause setting unit 120 includes a pause period storage unit 125 and a pause period determination unit 122. By storing the durations of multiple pause periods 220 that suppress the generation of harmonic components in the harmonic signal in the pause period storage unit 125, it is possible to detect the frequency difference between the high frequency signal 2 and the reflected wave 4 even if the distance to the target object 3 is short.

[0091] The distance measuring device according to the fifth aspect is the distance measuring device according to the first aspect, and is configured so that the pause periods 220 sandwiched between two adjacent output periods 210 whose duration is greater than the threshold are equal and have short durations. This relatively increases the proportion of time during which a beat signal is obtained, making it possible to calculate the distance even from a long-distance reflected wave 4 whose attenuation with distance is large.

[0092] The distance measuring device according to the sixth aspect is the distance measuring device according to the first aspect, and is configured such that the frequency control unit 110 determines the length of the output period 210 so that the frequency difference between the high frequency signal 2 and the reflected wave 4 becomes a specific frequency. The distance measuring device according to the sixth aspect is also configured such that the measurement unit 170 measures the distance to the object 3 based on the length of the output period 210.

[0093] The distance measuring device according to the seventh aspect is the distance measuring device according to the sixth aspect, and is configured to detect a band containing a frequency difference by comparing the energy of a detection frequency band 300, the energy of a low frequency band 310, and the energy of a high frequency band 320 in a beat signal obtained by mixing a high frequency signal 2 and a reflected wave 4. This makes it possible to detect the frequency difference even if the difference between the energy in the frequency difference between the high frequency signal 2 and the reflected wave 4 and the energy in other frequencies in the beat signal is small.

[0094] The ranging device of the eighth aspect is the ranging device of the seventh aspect, and is configured so that the detection frequency band 300 is sandwiched between the low frequency band 310 and the high frequency band 320 and is adjacent to the low frequency band 310 and the high frequency band 320.

[0095] The distance measuring device according to the ninth aspect is the distance measuring device according to the first aspect, wherein the measuring unit 170 calculates the frequency difference f based on a beat signal obtained by mixing the high frequency signal 2 and the reflected wave 4 in a predetermined period. b The predetermined period is configured to change according to the length of the output period 210. As a result, when the magnitude of the fluctuation in the distance L to the object 3 changes according to the distance L, the distance measuring device can obtain a temporal averaging effect according to the fluctuation in the distance L.

[0096] A distance measuring method according to a tenth aspect includes outputting a high-frequency signal 2 with a variable frequency to an object 3 during a plurality of output periods 210, and stopping or suppressing the output of the high-frequency signal 2 during a plurality of idle periods 220. The distance measuring method according to the ninth aspect is configured such that, among the idle periods 220, the length of a first idle period 220-1 is different from the length of a second idle period 220-2 adjacent to the first idle period 220-1. This suppresses harmonic components due to the idle periods 220, making it possible to detect the frequency difference between the high-frequency signal 2 and the reflected wave 4 even if the distance to the object 3 is short. [Explanation of symbols]

[0097] 1: Control device 2: High frequency signal 3: Object 4:Reflected wave 10:Storage medium 100: Distance measuring device 110: Frequency control section 120: Pause setting section 121: Random number generator 122: Rest period determination unit 125: Rest period memory section 130: Transmitter 140: Receiver 150: Frequency mixing section 160: Bandpass filter 161: Center filter 162: First adjacent filter 163: Second adjacent filter 170: Measurement section 180: Arithmetic device 190: Storage device 191: Program 201: Waveform 210: Output period 212 :Period 215: Modulation period 220: Hiatus 230: Interval 300: Detection frequency band 310: Low frequency band 320: High frequency band

Claims

1. a transmitter that outputs a high-frequency signal, the frequency of which can be changed, to an object during a plurality of output periods and stops or suppresses output of the high-frequency signal during a plurality of pause periods; a frequency control unit that monotonically increases the frequency of the high-frequency signal during each of the plurality of output periods; a receiver that receives the high-frequency signal reflected by the object as a reflected wave; a measuring unit that measures the distance to the object based on a frequency difference between the high-frequency signal and the reflected wave; Equipped with each of the plurality of idle periods is sandwiched between two adjacent output periods among the plurality of output periods; a length of a first pause period among the plurality of pause periods is different from a length of a second pause period adjacent to the first pause period; the frequency control unit determines the length of the output period so that the frequency difference between the high-frequency signal and the reflected wave becomes a specific frequency; The measurement unit measures the distance to the object based on the length of the output period. Ranging device.

2. a pause setting unit that determines the duration of the plurality of pause periods so as to suppress generation of harmonic components in the high frequency signal output from the transmitter; 2. The distance measuring device according to claim 1.

3. a pause setting unit that determines the duration of the plurality of pause periods; The pause setting unit a random number generator that outputs random numbers; a pause period determination unit that determines the length of the pause period based on the random number; The distance measuring device according to claim 1 , comprising:

4. a pause setting unit that determines the duration of the plurality of pause periods; The pause setting unit a pause period storage unit configured to store the durations of the plurality of pause periods for suppressing generation of harmonic components in the high frequency signal output from the transmitter; a pause period determination unit that determines the length of the pause period based on the lengths of the plurality of pause periods stored in the pause period storage unit; The distance measuring device according to claim 1 , comprising:

5. When a plurality of first output periods among the plurality of output periods are greater than a threshold value, a plurality of third idle periods among the plurality of idle periods sandwiched between two adjacent first output periods among the plurality of first output periods have equal time lengths.

5. A distance measuring device according to claim 1.

6. a frequency mixer that mixes the high-frequency signal with the reflected wave to generate a beat signal, The measurement unit comparing the energy of the beat signal in the detection frequency band with the energy of the low frequency band and the energy of the high frequency band; detecting whether the frequency difference between the high frequency signal and the reflected wave is included in the detection frequency band, the low frequency band, or the high frequency band; the frequency control unit determines the length of the output period in accordance with a band that includes the frequency difference; The detection frequency band includes the specific frequency.

6. A distance measuring device according to claim 1.

7. The detection frequency band is: sandwiched between the low frequency band and the high frequency band, adjacent to the low frequency band and the high frequency band 7. The distance measuring device according to claim 6.

8. the measuring unit detects the frequency difference between the high-frequency signal and the reflected wave based on a beat signal obtained by mixing the high-frequency signal and the reflected wave over a predetermined period of time; The predetermined period varies depending on the length of the output period. The distance measuring device according to any one of claims 1 to 7.

9. outputting a high-frequency signal, the frequency of which can be changed, to an object during a plurality of output periods, and stopping or suppressing the output of the high-frequency signal during a plurality of pause periods; monotonically increasing the frequency of the high frequency signal in each of the plurality of output periods; receiving the high frequency signal reflected by the object as a reflected wave; measuring a distance to the object based on a frequency difference between the high frequency signal and the reflected wave; Including, each of the plurality of idle periods is sandwiched between two adjacent output periods among the plurality of output periods; a length of a first pause period among the plurality of pause periods is different from a length of a second pause period adjacent to the first pause period; determining a time length of the output period so that the frequency difference between the high-frequency signal and the reflected wave becomes a specific frequency; measuring a distance to the object based on the length of the output period; Distance measurement method.

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