WO2023106133A1

WO2023106133A1 - Optical ranging device

Info

Publication number: WO2023106133A1
Application number: PCT/JP2022/043589
Authority: WO
Inventors: 貴祥藤澤; 善英立野
Original assignee: 株式会社デンソー
Priority date: 2021-12-08
Filing date: 2022-11-25
Publication date: 2023-06-15
Also published as: JP2023084978A

Abstract

An optical ranging device (10) for measuring the distance to an object by projection and reception of laser light, the optical ranging device (10) comprising: a projection unit (20) for projecting laser light while causing the laser light to scan; a light-receiving unit (30) for receiving laser light; and an interference determination unit (43) for determining whether or not interference is occurring, on the basis of a waveform characteristic obtained from a plurality of received light waves when there are a plurality of received light waves as the laser light received by the light-receiving unit (30) in a light reception period for receiving reflected laser light occurring from reflection of the laser light projected by the projection unit (20).

Description

optical rangefinder

Cross-reference to related applications

This application is based on Patent Application No. 2021-199403 filed in Japan on December 8, 2021, and the content of the underlying application is incorporated by reference in its entirety.

　Regarding optical rangefinders, especially technologies for detecting interference.

An optical rangefinder that measures the distance to an object by projecting and receiving laser light is known. There is another device that projects a laser beam around the optical distance measuring device, and the device itself may receive the laser light projected by the other device. In order to accurately measure the distance to an object, it is necessary to calculate the distance by removing the laser light projected by another device (hereinafter referred to as interference light). In Patent Document 1, an interference monitoring time is provided in a period immediately before projecting a laser beam. If light is received during the interference monitoring time, it is determined that interference has occurred.

JP 2018-72078 A

The technology disclosed in Patent Document 1 requires an interference monitoring time. Therefore, the total distance measurement time including the period for projecting and receiving laser light for distance measurement becomes long.

The present disclosure has been made based on this situation, and its object is to provide an optical distance measuring device capable of determining whether or not interference occurs while shortening the total distance measuring time. That's what it is.

The above object is achieved by the combination of features described in the independent claims, and the subclaims define further advantageous embodiments. The symbols in parentheses described in the claims indicate the corresponding relationship with the specific aspects described in the embodiments described later as one aspect, and do not limit the disclosed technical scope.

One disclosure for achieving the above objectives is
An optical distance measuring device that measures the distance to an object by projecting and receiving laser light,
a light projecting unit that scans and projects a laser beam;
a light receiving unit that receives laser light;
The received light signal received by the light receiving unit during one light receiving period for receiving the reflected laser light generated by the reflection of the laser light projected by the light projecting unit, or multiple times corresponding to multiple light projections If there are multiple received light waves that are laser light received by the light receiving unit in the light receiving signal to be judged, which is one of the signals obtained by integrating the light receiving signals received by the light receiving unit during the light receiving period, waveform characteristics obtained from the plurality of light receiving waves An optical distance measuring device comprising an interference determination unit that determines whether or not interference occurs based on the above.

This optical distance measuring device determines whether or not interference occurs, based on the received light signal received by the light receiving unit during the light receiving period for receiving the reflected laser beam. Make judgments based on characteristics. Therefore, since it is not necessary to provide an immediately preceding period for determining whether or not interference is occurring, the total distance measurement time can be shortened.

1 is a diagram showing the configuration of an optical distance measuring device 10 according to an embodiment; FIG. FIG. 4 is a diagram showing an example of a situation in which interference occurs; 4 is a diagram showing the relationship between time and intensity of laser light projected and received by the optical distance measuring device 10. FIG. 4 is a diagram showing the relationship between time and intensity of laser light projected and received by the optical distance measuring device 50. FIG. FIG. 4 is a diagram showing the intensity of light projected and received by the optical distance measuring device 10 in a state where interference occurs; FIG. 4 is a diagram showing the intensity of light projected and received by the optical distance measuring device 10 in a state where interference occurs; The figure which shows the process which the interference judgment part 43 performs in 1st Embodiment. FIG. 8 is a diagram showing processing subsequent to FIG. 7; The figure explaining the reason why the process of S31 to S33 is performed. FIG. 8 is a diagram showing processing executed in place of FIG. 7 in the second embodiment; FIG. 11 is a diagram showing a process executed subsequent to FIG. 10; FIG. 8 is a diagram showing processing executed in place of FIG. 7 in the third embodiment; FIG. 13 is a diagram showing processing executed subsequent to FIG. 12; FIG. 4 is a diagram for explaining the pulse width W and energy J of a received wave E; FIG. 4 is a diagram for explaining the pulse width W and energy J of a received wave E; FIG. 8 is a diagram showing processing executed in place of FIG. 7 in the fourth embodiment; FIG. 17 is a diagram showing processing executed subsequent to FIG. 16; The figure which shows the process replaced with FIG. 7 and performed in 5th Embodiment. FIG. 19 is a diagram showing a process executed subsequent to FIG. 18; The figure which shows the process replaced with FIG. 7 and performed in 6th Embodiment. FIG. 21 is a diagram showing processing executed subsequent to FIG. 20; The figure which shows the process replaced with FIG. 7 and performed in 7th Embodiment. FIG. 23 is a diagram showing processing executed subsequent to FIG. 22; The figure which shows the process replaced with FIG. 7 and performed in 8th Embodiment. FIG. 25 is a diagram showing processing executed subsequent to FIG. 24; FIG. 11 is a diagram for explaining a determination target received light signal according to Modification 3;

<First embodiment>
Hereinafter, embodiments will be described based on the drawings. FIG. 1 is a diagram showing the configuration of an optical distance measuring device 10 according to an embodiment. The optical distance measuring device 10 includes a light projecting section 20 , a light receiving section 30 and a control section 40 .

The light projecting unit 20 scans the laser light and projects it outside the device. The light projecting section 20 that realizes such an operation has, for example, a configuration including a light source and a scan mirror.

The light receiving unit 30 receives reflected laser light generated by reflecting the laser light projected by the light projecting unit 20 . The light receiving section 30 has, for example, a configuration including a light receiving element and an amplifier.

The control unit 40 can be realized by a configuration including at least one processor. For example, the control unit 40 can be implemented by a computer including a processor, nonvolatile memory, RAM, I/O, bus lines connecting these components, and the like. A program for operating a general-purpose computer as the control unit 40 is stored in the nonvolatile memory. The processor executes the program stored in the nonvolatile memory while using the temporary storage function of the RAM, so that the control unit 40 operates as a light projection/reception control unit 41, a distance calculation unit 42, and an interference judgment unit 43. . Execution of these operations means that the method corresponding to the program is executed.

The light projecting/receiving control unit 41 controls the light projecting unit 20 so that the light projecting unit 20 scans the laser light within a predetermined scanning range. Further, the light projecting/receiving control unit 41 controls the light receiving unit 30 to cause the light receiving unit 30 to detect the reflected laser light, and sequentially acquires light receiving signals indicating the received light intensity of the reflected laser light from the light receiving unit 30 .

The distance calculation unit 42 determines whether the reflected laser beam is generated based on the time from when the light projecting unit 20 projects the laser beam to when the light receiving unit 30 receives the reflected laser beam (hereinafter referred to as time of flight TOF). Calculate the distance to an object. Since the distance to the object is calculated in this manner, the optical rangefinder 10 is a dTOF type optical rangefinder.

The interference judgment unit 43 judges whether or not interference occurs based on the light reception signal acquired by the light projection/reception control unit 41 . The interference determined by the interference determination unit 43 includes at least interference caused by laser light projected by the iTOF type optical rangefinder 50 (see FIG. 2). The interference determination unit 43 determines whether the received light wave E is interference light or signal light, in addition to whether interference has occurred. The process by which the interference determination unit 43 determines interference will be described later.

The distance calculation unit 42 does not use the received wave E, which the interference judgment unit 43 has judged to be interference light, to calculate the distance. In other words, the distance calculator 42 calculates the distance based on the received light wave E that is determined not to be interference light. In the first embodiment, the interference determination unit 43 determines whether or not the light is interference light based on the periodicity of the received light wave E, as will be described later. Therefore, the distance calculation unit 42 excludes the received light wave E with periodicity and calculates the distance using the received light wave E without periodicity.

[Example of situations where interference occurs]
FIG. 2 shows an example situation in which interference occurs. An optical rangefinder 10 is mounted on a vehicle. A vehicle in which the optical distance measuring device 10 is mounted is assumed to be the host vehicle 1 . A narrow sector extending from the optical rangefinder 10 indicates laser light projected in one scanning direction.

FIG. 2 also shows another vehicle 2 running opposite the own vehicle 1. The other vehicle 2 is equipped with an iTOF type optical distance measuring device 50 . A sector centered on the optical distance measuring device 50 conceptually indicates the laser beam projected by the optical distance measuring device 50 . The laser light projected by the optical distance measuring device 50 is diffused light. As shown in FIG. 2 , the laser light projected by the optical distance measuring device 50 may be received by the optical distance measuring device 10 .

FIG. 3 is a diagram showing the relationship between the time and the intensity of laser light projected and received by the optical distance measuring device 10 for each measurement direction. In the graph shown in FIG. 3, the horizontal axis is the time t, and the vertical axis is the signal intensity I. The optical distance measuring device 10 projects a laser beam at time t0. Reflected laser light is generated when the laser light is reflected by an external object. In FIG. 3, the optical distance measuring device 10 receives the reflected laser beam at time t1. Since the time of flight TOF from time t0 to time t1 is proportional to the distance to the object, the distance to the object can be calculated based on the time of flight TOF.

FIG. 4 is a diagram showing the relationship between the time and the intensity of laser light projected and received by the optical rangefinder 50. FIG. In FIG. 4 as well, the horizontal axis is the time t, and the vertical axis is the signal intensity I. As shown in FIG. 4, the iTOF-type optical rangefinder 50 periodically projects laser light. The duty ratio between the period during which light is projected and the period during which light is not projected is 50%. In FIG. 4, projection of the first laser light is started at time t10. Then, the reflected laser light generated by the laser light starts to be received from time t11. The iTOF type calculates the distance to an object based on the phase difference between the projected laser beam and the received reflected laser beam.

　Figures 3 and 4 both showed the signal intensity I of light projection and light reception in a state where no interference occurred. 5 and 6 show the intensity of light projected and received by the optical distance measuring device 10 in a state where interference occurs, as in the state shown in FIG. In the following description, in order to distinguish between the laser light projected and received by the optical distance measuring device 10 and the laser light projected and received by the optical distance measuring device 50, the laser light projected and received by the optical distance measuring device 10 will be referred to as signal light, The laser light projected by the optical distance measuring device 50 may be referred to as interference light.

　In Figures 5 and 6, the signal light is indicated by a solid line, and the interference light is indicated by a broken line. In FIG. 5, the signal light and the interference light are separated. In FIG. 6, the signal light and the interference light are fused. These figures are conceptual diagrams, and in reality, it is not possible to clearly distinguish whether the received wave E is signal light or interference light. In both FIGS. 5 and 6, in order to correctly determine the time-of-flight TOF, the light-receiving signal indicating the signal light is determined from the light-receiving signals containing the signal indicating the interference light and the signal indicating the signal light. There is a need.

Therefore, the optical distance measuring device 10 includes an interference determination section 43 that determines whether or not interference has occurred. When the interference determination unit 43 determines that interference has occurred, the distance calculation unit 42 calculates the distance after excluding the interference light from the received light signal.

[Processing Executed by Interference Determination Unit 43]
7 and 8 show processing executed by the interference determination unit 43 in the first embodiment. The processing shown in FIGS. 7 and 8 is executed after the light receiving signal is obtained during the light receiving period for each object detection orientation. Therefore, in the first embodiment, the light receiving signal detected in one light receiving period is the determination target light receiving signal. The light receiving period is a period determined based on the time when the light projecting section 20 projects the laser light. The start time of the light receiving period can be the time when the light projecting unit 20 projects the laser light. Alternatively, the start time of the light-receiving period may be after the time at which the laser beam reflected from the device housing or the like is excluded after the time when the light projecting section 20 projects the laser beam. The length of the light receiving period is determined by the maximum distance of the object to be detected by the optical distance measuring device 10 . The length of the light receiving period should be longer than the maximum detectable distance/speed of light and shorter than the period of light projection.

In S1, set N=1, i=0, and periodic interference flag=False. In subsequent S2, the content of the periodic interference flag is determined. When S2 is executed for the first time, the periodic interference flag is False. If the periodic interference flag is False, the process proceeds to S3.

In S3, it is determined whether or not all received wavenumbers FULL are 2 or less. FULL=5 in the examples of FIGS. In addition, the received wave E may be called an echo. If the determination result of S3 is YES, the process proceeds to S4.

In S4, the N-th light receiving wave E(N) is assumed to be the true value, that is, the waveform of the signal light. When proceeding to S4, there are not enough received wavenumbers to determine that there is periodic interference. Therefore, the received wave E(N) is taken as the true value.

After executing S4, proceed to S5. In S5, N is incremented by one. In subsequent S6, it is determined whether or not N is greater than FULL. If FULL is 1, the determination result of S6 becomes YES in the first execution of S6. If FULL is 2 or more, the first determination result of S6 is NO. If the determination result of S6 is NO, the process returns to S2.

If FULL is 3 or more, the judgment result of S3 becomes NO. When the judgment result of S3 is NO, it progresses to S7. In S7, it is determined whether N is 1, that is, whether it is the first execution. If the determination result of S7 is YES, the process proceeds to S8. In S8, i is incremented by one. After executing S8, the process proceeds to S5.

If the judgment result of S7 is NO, proceed to S9. If N is 2 or more and FULL is 3 or more, the process proceeds to S9. In S9, it is determined whether or not the time difference T(N) and the time difference T(N+1) are approximate.

The time difference T is shown in FIGS. 5 and 6. The time difference T(N) is the time from the detection time of the previous waveform to the detection time of the N-th light receiving wave E. FIG. In the case of the first received wave E1, the previous waveform is the projected laser beam. The detection time of the projected laser beam is the time when the light projection unit 20 projected the laser beam. In FIGS. 5 and 6, the waveform detection time is set to the time center of the received light waveform. However, the waveform detection time can also be set to the rise time of the received light wave E. FIG. Whether or not there is approximation is determined by whether one is within ±α% of the other. α% is, for example, 10%.

If the judgment result of S9 is NO, proceed to S10. At S10, N is stored in U(i), and the time difference T(N) is stored in UT(i). Although the periodic interference flag is False when the process of S10 is executed, there is a possibility that the N-th waveform is interference light. Therefore, the time difference T(N) is stored in UT(i) in order to determine whether the N-th waveform is interference light in later processing. After executing S10, the process proceeds to S11. In S11, i is incremented by one. After executing S11, the process proceeds to S5.

If the judgment result of S9 is YES, proceed to S12. When proceeding to S12, the plurality of received waves E have periodicity. Therefore, in S12, the periodic interference flag is set to True, and the interference period is determined to be T(N). As described above, in the first embodiment, the cycle of the received light wave E is used as a waveform feature, and interference is determined to occur when the received light wave has periodicity. Since the period of the received light wave E is the time from the detection of the waveform of one received wave E to the detection of the next waveform of the received received wave E, it indicates one of the characteristics of the waveform of the received received wave E. ing. In S13, it is assumed that the N-th received wave E(N) is interference light. After executing S13, the process proceeds to S5.

When the periodic interference flag becomes True by the processing of S12, the process proceeds to S14 after the determination of S2. In S14, it is determined whether or not the time difference T(N) approximates the interference cycle. For example, if the time difference T(N) is within ±β% of the interference period, it is determined that the time difference T(N) approximates the interference period. β% is, for example, 10%. If the judgment result of S14 is NO, the process proceeds to S15, and the N-th received light wave E(N) is assumed to be a true value. If the determination result of S14 is YES, the process proceeds to S16, and it is assumed that the received wave E(N) is interference light. After executing S15 or S16, the process proceeds to S5 and S6.

If the determination result in S6 is YES due to the increase in N in S5, proceed to FIG. At the time of proceeding to the processing shown in FIG. 8, the determination of whether or not interference has occurred has been completed. In FIG. 8, it is determined whether the i-th received wave E stored in S10 is a true value.

In FIG. 8, in S21, it is determined whether i is greater than 0. If the judgment result of S21 is NO, the process of FIG. 8 is terminated. If the judgment result of S21 is YES, it will progress to S22.

In S22, the content of the periodic interference flag is determined. If the periodic interference flag is False, the process proceeds to S23. In S23, the U(i)-th light receiving wave E(U(i)) is set as a true value. At S24, i is decremented by one. In S25, it is determined whether or not i has become 0. If the determination result in S25 is NO, that is, if i is not 0, the process returns to S23. By repeating S23 to S25, all the received waves E whose numbers are stored in U(i) in S10 are set to true values. Since the periodic interference flag is False, that is, there is no periodic interference, all the received waves E are set to true values. If the determination result of S25 is YES, the process of FIG. 8 is terminated.

In the determination of S22, if the periodic interference flag is True, proceed to S26. In S26, it is determined whether or not UT(i) approximates the interference period. Whether or not the two are approximate is determined in the same manner as in S14.

If the determination result of S26 is NO, the process proceeds to S27, and the U(i)-th light receiving wave E(U(i)) is assumed to be a true value. If the determination result of S26 is YES, the process proceeds to S28, and it is assumed that the received wave E(U(i)) is interference light. After executing S27 or S28, the process proceeds to S29.

In S29, i is decremented by 1. In S30, it is determined whether or not i is greater than one. If the determination result of S30 is YES, the process returns to S26. By repeating S26 to S30, it is determined whether or not the received waves E, whose true values have not been determined, are true values up to i=2 in descending order of numbers.

When i decreases to 1, the judgment result of S30 becomes NO. If the judgment result of S30 becomes NO, it will progress to S31. In S31, it is determined whether or not the sum of the time difference T2 and the time difference T3 approximates D times the interference period. D is a user-defined integer greater than or equal to 1 (that is, a natural number). D is preferably of a plurality of types such as 1 and 2.

The method of determining whether or not T2+T3 approximates D times the interference period is the same as in S14. If the determination result in S31 is YES, that is, if the sum of the time difference T2 and the time difference T3 approximates D times the interference period, the process proceeds to S32. In S32, it is assumed that the first received wave E1 is interference light. On the other hand, if the determination result of S31 is NO, the process proceeds to S33, and the first received light wave E1 is assumed to be a true value.

The reason for performing the processing from S31 to S33 will be explained using FIG. As shown in FIG. 9, the time difference T1 is the time from the detection time of the projected laser beam to the detection time of the received wave E1. As shown in FIG. 9, although the received wave E1 is interference light, the time difference T1 and the time difference T2 are different. Therefore, it is not possible to judge whether or not the received light wave E1 is interference light based on the same criteria as the second and subsequent received light waves E. Therefore, it is determined whether or not the received wave E1 is interference light through steps S31 to S33. In the state shown in FIG. 9, T2+T3 is substantially equal to T4 and T5, which are interference periods. Therefore, the received wave E1 can be determined to be the interference light by steps S31 to S33.

If D is 2, as shown in FIG. 6, even if the second received wave E2 has a waveform in which the signal light and the interference light overlap, the received wave E1 can be determined to be the interference light. . This is because T2+T3 approximates 2×interference period.

[Summary of the first embodiment]
In the first embodiment described above, the interference judgment unit 43 judges whether or not interference has occurred, based on whether or not the received light wave E received during the light receiving period has periodicity (S9). . Therefore, since it is not necessary to provide an immediately preceding period for determining whether or not interference is occurring, the total distance measurement time can be shortened.

If the interference determination unit 43 can determine that the time differences T(N) and T(N+1) between the received light waves E that are continuous in the order of detection, that is, the time differences T(N) and T(N+1) that are adjacent to each other in the order of detection are approximate (S9: YES ), it is determined that the received wave E has periodicity (S12). By determining the periodicity in this way, the periodicity can be easily determined.

The interference determination unit 43 regards the periodic received wave E as interference light (S13, S16). The distance calculator 42 does not use the interference light to calculate the distance. In the example of FIG. 5, the received wave E2 can be determined as the interference light in S13, and the received waves E3 and E4 can be determined as the interference light in S16. In the example of FIG. 6, the received wave E4 can be determined as the interference light in S13, and the received wave E5 can be determined as the interference light in S16.

Further, when the sum of the time difference T2 between the second received wave E2 and the time difference T3 between the third received wave E3 approximates D times the interference period, the interference determination unit 43 determines that the first received wave E1 is interference light. Suppose there is (S32). In other words, if T2+T3 does not approximate D times the interference period, the interference determination unit 43 determines that the first received wave E1 is the true value, that is, the received wave E without periodicity (S33). By doing so, it is possible to determine the periodicity of the first received wave E1 as well.

<Second embodiment>
Next, a second embodiment will be described. In the following description of the second embodiment, the elements having the same reference numerals as those used so far are the same as the elements having the same reference numerals in the previous embodiments unless otherwise specified. Moreover, when only part of the configuration is described, the previously described embodiments can be applied to the other portions of the configuration.

10 and 11 are processes executed by the interference determination unit 43 instead of FIGS. In S41 of FIG. 10, the periodic interference flag is set to False.

In S42, frequency analysis is performed on the light receiving signal during the light receiving period. In S43, it is determined whether or not there is a peak in the frequency analysis spectrum at the frequency corresponding to the period of the laser light transmitted by the iTOF type optical distance measuring device 50 (hereinafter referred to as the iTOF frequency). The period of the laser light transmitted by the optical distance measuring device 50 should be a frequency completely different from the frequency of the waveform of the signal light, and should have a large peak intensity. Therefore, it can be easily determined whether or not there is a peak at the iTOF frequency in the frequency analysis spectrum.

If the determination result of S43 is NO, the process proceeds to S50 of FIG. 11 without executing S44 and S45. If the determination result of S43 is YES, the process proceeds to S44. In S44, the periodic interference flag is set to True. In S45, the reciprocal of the iTOF frequency is set as the interference period. After that, the process proceeds to S50 in FIG.

In S50 of FIG. 11, N=1. In subsequent S51, the content of the periodic interference flag is determined. If the periodic interference flag is False, the process proceeds to S52. In S52, the received wave E(N) is taken as a true value. After executing S52, the process proceeds to S60. N is incremented by 1 in S60. In the following S61, it is determined whether or not N has exceeded the total received wave number FULL. If the judgment result of S61 is NO, the process returns to S51.

　In the judgment of S51, if the periodic interference flag is True, the process proceeds to S53. In S53, it is determined whether or not N=1. At the time of execution of FIG. 11 for the first time, the determination result of S53 is YES. If the determination result of S53 is YES, the process proceeds to S54. S54, S55 and S56 are the same as S31, S32 and S33 in FIG. 8, respectively. Through S54, S55, and S56, it is determined whether the first received light wave E1 is a true value or an interference light. After executing S55 or S56, the process proceeds to S60 and S61.

When S53 is executed for the second time or later, the determination result of S53 becomes NO and the process proceeds to S57. S57, S58 and S59 are the same as S14, S15 and S16 in FIG. 7, respectively. Through S57, S58, and S59, it is determined whether the Nth received wave E(N) is a true value or an interference light. When all the received waves E(N) have been determined whether they are true values or interference light, the determination result of S61 becomes YES, and the process of FIG. 11 ends.

[Summary of the second embodiment]
In this second embodiment, the interference determination unit 43 determines whether or not the received light wave E has periodicity based on the intensity of the spectrum obtained by frequency-analyzing the received light signal during the light receiving period (S43, S44). ). Even in this way, it is possible to determine whether or not interference is occurring without providing an immediately preceding period.

<Third Embodiment>
12 and 13 are processes executed by the interference determination unit 43 instead of FIGS. In S71 of FIG. 12, the light-receiving waves E received during the light-receiving period are rearranged in descending order of peak signal intensity I. In FIG. In FIGS. 14 and 15, the received waves E are shown with numbers indicating the order of the signal intensity I of the peak. The peak signal intensity I of the received light wave E is one of the shape feature values that specify the shape of the received light waveform.

In S72, the periodic interference flag is set to False. In S73, the variable Cnt is set to 0 and N is set to 1.

In S74, the content of the periodic interference flag is determined. If the periodic interference flag is True, the process proceeds to S81 in FIG. However, initially the periodic interference flag is False. If the periodic interference flag is False, the process proceeds to S75.

In S75, it is determined whether the peak signal intensity I(N) of the Nth received wave E and the peak signal intensity I(N+1) of the N+1th received wave E are similar. Whether or not they are approximate is determined by, for example, whether one is within ±α% of the other. If the determination result of S75 is NO, the process proceeds to S79, and if YES, the process proceeds to S76.

At S76, Cnt is incremented by 1. At S77, it is determined whether or not Cnt is greater than or equal to γ. γ is a user-defined number.

If the determination result of S77 is YES, proceed to S78. At S78, the periodic interference flag is set to True, and the interference peak intensity is set to I(N). The interference peak intensity is an interference reference value to be compared with the peak signal intensity I of each received wave E in FIG.

At S79, N is increased by 1. In S80, it is determined whether or not N is greater than the received wave number FULL. If the determination result of S80 is NO, S74 and subsequent steps are executed again. If the determination result of S80 is YES, the process proceeds to S81 of FIG.

"Cnt" means the number for which the judgment result of S75 is YES. If the determination in S77 is YES, the periodic interference flag is set to True. Therefore, γ is a number set by the user to determine how many times the judgment in S77 becomes YES before it is judged as periodic interference. γ is an integer of 1 or more. As γ increases, there is an advantage that the possibility of determining that there is periodic interference when there is no periodic interference is reduced. On the other hand, the larger γ is, the more likely it is that periodic interference cannot be determined even though periodic interference is occurring. The user considers this advantage and disadvantage to determine γ. γ is preferably 2 or more.

In FIG. 14, the peak signal intensities I of the received waves E2, E3, E4, and E5 are approximate. Therefore, when N=2, 3, or 4, the determination result of S75 is YES. That is, the determination result of S75 becomes YES three times. Therefore, if γ=1, 2, or 3, the periodic interference flag becomes True. When γ=1, 2 and 3, the signal intensities I2, I3 and I4 at the peaks of the received waves E2, E3 and E4 are the interference peak intensities, respectively.

In FIG. 15, the peak signal intensities I of the received waves E2, E3, and E4 are approximate. Therefore, when N=2 or 3, the determination result of S75 is YES. Therefore, if γ=1 or 2, the periodic interference flag becomes True.

Next, FIG. 13 will be explained. N is set to 1 in S81. In S82, the content of the periodic interference flag is determined. If the periodic interference flag is False, the process proceeds to S83. In S83, the received wave E(N) is taken as a true value.

　In the judgment of S82, if the periodic interference flag is True, the process proceeds to S84. In S84, it is determined whether the peak signal intensity I(N) approximates the interference peak intensity. The method for judging whether or not there is an approximation is the same as before. If the determination result of S84 is NO, the process proceeds to S85. This received wave E(N) is a received wave E(N) whose peak signal intensity I does not approximate the interference peak intensity. In S85, it is assumed that this received wave E(N) is a true value. If the determination result of S84 is YES, the process proceeds to S86, and it is assumed that the received wave E(N) is interference light.

In S87, N is increased by 1. In S88, it is determined whether or not N is greater than the received wave number FULL. If the judgment result of S88 is NO, S82 and subsequent steps are executed again. If the determination result of S88 is YES, the process of FIG. 13 is terminated.

By the processing of FIG. 13, in the example of FIG. 14, the received wave E1 can be determined as the true value, and the received waves E2, E3, E4, and E5 can be determined as the interference light. In the example of FIG. 15, the received wave E1 can be determined as the true value, and the received waves E2, E3, and E4 can be determined as the interference light. The distance calculator 42 excludes the received light wave E determined to be the interference light, and calculates the distance using the received light wave E determined to be the true value.

As described above, by arranging the signal intensities I of the peaks of the received wave E in order of magnitude (S71) and determining whether or not the signal intensities I of the peaks adjacent to each other in this order are similar, interference can be reduced. It can be determined whether or not it has occurred (S75-S80).

Further, the signal intensity I of the peak to which the signal intensities I of adjacent peaks are similar is set as the interference peak intensity (S78), and the received wave E(N) that is not similar to this interference peak intensity is set as the true value (S85). ). The distance calculation unit 42 calculates the distance using only the received light wave E(N) that has been taken as a true value. By doing so, the distance can be calculated by excluding interference light.

<Fourth Embodiment>
The fourth embodiment is similar to the third embodiment. In the fourth embodiment, instead of FIGS. 12 and 13, FIGS. 16 and 17 are executed. In FIG. 16, S71-1, S75-1 and S78-1 are executed instead of S71, S75 and S78 of FIG.

In S71-1, the light-receiving waves E received during the light-receiving period are rearranged in the order of the pulse width W, which is the width of the light-receiving waves E. In the fourth embodiment, the pulse width W is the shape characteristic value. The pulse width W is shown in the received wave E2 in FIGS. 14 and 15. FIG. As the pulse width W, the half width of the received wave E can be used. However, the pulse width W may be determined based on other criteria as long as the shapes of the received waves E can be relatively compared. For example, the pulse width W may be the waveform width at a predetermined signal intensity I.

When the received waves E are arranged in ascending order of the pulse width W, they are arranged in numerical order of the received waves E shown in FIG. 14, similar to the peak signal intensity I. Note that the pulse widths W may be arranged in descending order.

In S75-1, it is determined whether the pulse width W(N) of the Nth received wave E and the pulse width W(N+1) of the N+1th received wave E are similar.

At S78-1, the periodic interference flag is set to True, and the interference pulse width is set to W(N). The interference pulse width is an interference reference value to be compared with the pulse width W of each received light wave E in FIG. In the examples of FIGS. 14 and 15, the pulse width W2 of the received light wave E2 is the interference pulse width.

Next, FIG. 17 will be explained. In FIG. 17, S84-1 is executed instead of S84 in FIG. In S84-1, it is determined whether the pulse width W(N) approximates the interference pulse width. If the determination result of S84-1 is NO, the process proceeds to S85, and the received light wave E(N) is assumed to be a true value. If the determination result of S84-1 is YES, the process advances to S86, and it is assumed that the received wave E(N) is interference light. 17, the received waves E2, E3, E4, and E5 become interference lights in the example of FIG. 14, and the received waves E2, E3, and E4 become interference lights in the example of FIG. On the other hand, the received wave E1 has a true value.

Interference can also be determined by determining whether the pulse widths W are similar as in the fourth embodiment, and interference light and the true value (that is, signal light) can be distinguished.

<Fifth Embodiment>
In the fifth embodiment, the presence or absence of interference is determined using the pulse width W(N) as a waveform feature. The fifth embodiment is similar to the fourth embodiment. In the fifth embodiment, instead of FIGS. 16 and 17, FIGS. 18 and 19 are executed. In FIG. 18, S75-2 and S78-2 are executed instead of S75-1 and S78-1 in FIG.

At S75-2, it is determined whether or not the pulse width W(N) is greater than a predetermined width threshold value C. The width threshold value C is set to a value that is larger than the width of the laser light projected by the light projecting section 20 and smaller than the pulse width of the laser light transmitted by the iTOF type optical distance measuring device 50 . The pulse width of the laser light transmitted by the dTOF type device and the pulse width of the laser light transmitted by the iTOF type device are significantly different. Therefore, it is easy to set the width threshold value C between these two types of pulse widths.

At S78-2, the periodic interference flag is set to True. Unlike S78-1, there is no need to set the interference pulse width. This is because the width threshold value C is used instead of the interference pulse width in S84-2 of FIG. 19, which will be described next.

In FIG. 19, S84-2 is executed instead of S84-1 in FIG. In S84-2, it is determined whether or not the pulse width W(N) is greater than the width threshold C. If the determination result of S84-2 is YES, the process advances to S86, and it is assumed that the received wave E(N) is interference light. If the judgment result of S84-2 is NO, the process advances to S85, and it is assumed that the received light wave E(N) is a true value. Interfering light and signal light can be distinguished from each other also in this fifth embodiment.

<Sixth Embodiment>
The FIG. 6 embodiment is similar to the fourth embodiment. In the sixth embodiment, instead of FIGS. 16 and 17, FIGS. 20 and 21 are executed. In FIG. 20, S71-3, S75-3 and S78-3 are executed instead of S71-1, S75-1 and S78-1 of FIG.

In S71-3, the light-receiving waves E received during the light-receiving period are rearranged in the order of the energy J of the light-receiving waves E. The energy J of the received light wave E can be calculated from the integrated value of the received light waveform. In the sixth embodiment, the energy J is the shape feature value. The energy J is shown in the received wave E2 in FIGS. 14 and 15. FIG.

In S75-3, it is determined whether the energy J(N) of the Nth received wave E and the energy J(N+1) of the N+1th received wave E are similar.

At S78-3, the periodic interference flag is set to True, and the interference energy is set to J(N). The interference energy is an interference reference value to be compared with the energy J of each received wave E in FIG. In the examples of FIGS. 14 and 15, the energy J2 of the received wave E2 becomes the interference energy.

Next, FIG. 21 will be explained. In FIG. 21, S84-3 is executed instead of S84-1 in FIG. In S84-3, it is determined whether the energy J(N) approximates the interference energy. If the determination result of S84-3 is NO, the process advances to S85, and it is assumed that the received light wave E(N) is a true value. If the determination result of S84-3 is YES, the process advances to S86, and it is assumed that the received wave E(N) is interference light. 21, the received waves E2, E3, E4, and E5 become interference lights in the example of FIG. 14, and the received waves E2, E3, and E4 become interference lights in the example of FIG. On the other hand, the received wave E1 has a true value.

Interference can also be determined by determining whether the energies J are similar as in the sixth embodiment, and interference light and the true value (that is, signal light) can be distinguished.

<Seventh embodiment>
The seventh embodiment is similar to the third and fourth embodiments. The seventh embodiment uses the peak signal intensity I used in the third embodiment and the pulse width W used in the fourth embodiment as shape feature values.

In the seventh embodiment, instead of FIGS. 12 and 13, FIGS. 22 and 23 are executed. In FIG. 22, S75-4 and S78-4 are executed instead of S75 and S78 in FIG.

In S75-4, the peak signal intensity I(N) of the Nth received wave E and the peak signal intensity I(N+1) of the N+1th received wave E approximate each other, and the Nth received wave E It is determined whether the pulse width W(N) and the pulse width W(N+1) of the (N+1)th received wave E are similar.

At S78-4, the periodic interference flag is set to True, the interference peak intensity is set to I(N), and the interference pulse width is set to W(N). In the sixth embodiment, the interference peak intensity and the interference pulse width are interference reference values.

Next, FIG. 23 will be explained. In FIG. 23, S84-4 is executed instead of S84 in FIG. In S84-4, it is determined whether the peak signal intensity I(N) approximates the interference peak intensity and the pulse width W(N) approximates the interference pulse width. If the determination result of S84-4 is NO, the process advances to S85, and it is assumed that the received light wave E(N) is a true value. If the determination result of S84-4 is YES, the process advances to S86, and it is assumed that the received wave E(N) is interference light.

By determining whether or not there is interference using two types of shape feature values as in the seventh embodiment, it is possible to determine whether or not there is interference more accurately. Moreover, by using two types of interference reference values, it is possible to distinguish between the true value and the interference light with higher accuracy.

<Eighth embodiment>
24 and 25 show processing executed by the interference determination unit 43 in the eighth embodiment. In the eighth embodiment, the numbers of the received waves E are in chronological order as in the first embodiment.

Description will be made from FIG. In S91, N=1, i=0, and periodic interference flag=False are set. The following S92 is the same processing as S3 in FIG. 7, and determines whether or not the received wave number FULL is 2 or less. If the determination result of S92 is YES, the process proceeds to FIG. If the judgment result of S92 is NO, it will progress to S93.

In S93, the content of the periodic interference flag is determined. If the periodic interference flag is False, proceed to FIG. If the periodic interference flag is True, the process proceeds to S94.

In S94, it is determined whether the three peak signal intensities I(N), I(N+1), and I(N+2) are similar, and whether the time differences T(N) and T(N+1) are similar. If both the peak signal intensity I and the time difference T are close to each other, the determination result of S94 becomes YES. If the judgment result of S94 is YES, it will progress to S95.

At S95, the periodic interference flag is set to True. Also, let the interference period be T(N) and the interference period peak intensity be I(N). After executing S95, the process proceeds to S96. Also when the determination result of S94 is NO, it progresses to S96.

In S96, N is increased by 1. In S97, it is determined whether or not N is greater than the received wave number FULL. If the judgment result of S97 is NO, S92 and subsequent steps are executed again. If the determination result of S97 is YES, the process proceeds to FIG.

Next, FIG. 25 will be explained. FIG. 25 is similar to FIG. In FIG. 25, instead of S54 and S57 in FIG. 11, S54-1 and S57-1 are executed. S54-1 is executed when N=1. In S54-1, it is determined whether T2+T3 approximates the interference period and I(N) approximates the interference peak intensity. Whether or not T2+T3 approximates the interference period is determined in S54 of FIG. Whether or not I(N) approximates the interference peak intensity is determined in S84 of FIG.

If the determination result of S54-1 is YES, the process proceeds to S55, and the received wave E1 is assumed to be interference light. If the determination result of S54-1 is NO, the process proceeds to S56, and the received light wave E1 is set as a true value.

At S57-1, it is determined whether T(N) approximates the interference period and I(N) is the interference peak intensity. Whether or not T(N) approximates the interference period is determined in S57 of FIG. Whether or not I(N) approximates the interference peak intensity is determined in S84 of FIG. If the determination result of S57-1 is NO, the process proceeds to S58, and E(N) is assumed to be true. If the determination result of S57-1 is YES, the process proceeds to S59, and E(N) is assumed to be interference light.

[Summary of the eighth embodiment]
As in the eighth embodiment, by determining whether or not interference occurs using the presence or absence of periodicity and the shape feature value, it is possible to determine whether or not interference has occurred with higher accuracy. In addition, by using the presence or absence of periodicity and the interference reference value, the true value and the interference light can be distinguished more accurately.

Although the embodiments have been described above, the disclosed technology is not limited to the above-described embodiments, and the following modifications are also included in the disclosed scope. Various modifications can be made.

<Modification 1>
In the first embodiment, the interference cycle is set only once. However, the interference cycle may be updated as needed. Also in other embodiments, the interference period may be updated as needed. Also, the interference reference value such as the peak signal intensity I of the received wave E may be updated as needed.

<Modification 2>
In the seventh embodiment, two shape feature values of peak signal intensity I and pulse width W are used. However, the energy J of the received wave E may be used instead of these two shape feature values. Alternatively, three types of shape feature values may be used. Further, in the eighth embodiment, instead of the peak signal intensity I, other shape feature values may be used.

<Modification 3>
In the embodiment, light is projected only once per direction, and the light receiving signal received by the light receiving unit 30 during one light receiving period determined by the light projection is used as the light receiving signal to be judged. However, as shown in FIG. 26, the laser beam is projected a plurality of times (three times in FIG. 26) in one direction, and the light receiving section 30 receives the light during a plurality of light receiving periods corresponding to the plurality of light projections. A signal obtained by integrating the signal intensity I of the received light signal may be used as the light receiving signal to be judged.

In the example shown in FIG. 26, the second row from the top shows the signal intensity I of the received light signal. When light is projected three times, there are three light receiving periods. When the light receiving signal received by the light receiving section 30 in each light receiving period is integrated, the light receiving signal received by the light receiving section 30 in each light receiving period is stored in a predetermined memory. Then, the timing of each light projection is matched, and the signal intensity I of the received light signal with respect to time is integrated for each time. The graph obtained in this way is the lower graph in FIG. By doing so, even if the signal intensity I of the light receiving signal received in one light receiving period is small, the light receiving signal to be judged can be increased. Therefore, the measurable range can be expanded.

(Disclosure of technical ideas)
This specification discloses a plurality of technical ideas described in a plurality of sections listed below. Some paragraphs may be presented in a multiple dependent form in which subsequent paragraphs refer to the preceding paragraphs alternatively. Moreover, some terms may be written in a multiple dependent form referring to another multiple dependent form. These clauses written in multiple dependent form define multiple technical ideas.

(Technical idea 1)
An optical distance measuring device that measures the distance to an object by projecting and receiving laser light,
a light projecting unit (20) that scans and projects the laser light;
a light receiving section (30) for receiving the laser light;
A received light signal received by the light receiving unit during one light receiving period for receiving the reflected laser light generated by reflection of the laser light projected by the light projecting unit, or corresponding to a plurality of times of light projection When there are a plurality of received light waves, which are the laser beams received by the light receiving unit, in the determination target light receiving signal, which is one of the signals obtained by integrating the light receiving signals received by the light receiving unit during a plurality of light receiving periods, an interference determination unit (43) that determines whether or not interference has occurred based on waveform characteristics obtained from the received light wave of (1).

(Technical idea 2)
The optical distance measuring device according to Technical Thought 1,
wherein the waveform feature is the period of the received wave;
The optical distance measuring device, wherein the interference determination unit determines that interference occurs when the received wave has periodicity.

(Technical idea 3)
The optical distance measuring device according to technical idea 2,
The interference determination unit calculates a time difference (T) from the detection time of the previous waveform to the detection time of the received light wave for each of the plurality of received waves, and the time differences between the adjacent received waves are approximated. an optical distance measuring device that determines that the received wave has periodicity when it can be determined that the received wave has periodicity.

(Technical idea 4)
The optical distance measuring device according to technical idea 2,
The interference determination unit determines whether or not the received light wave has periodicity based on the intensity of the spectrum obtained by frequency-analyzing the received light signal to be determined.

(Technical idea 5)
The optical distance measuring device according to any one of technical ideas 2 to 4,
An optical distance measuring device, comprising: a distance calculator (42) for calculating a distance based on, among the plurality of received light waves, a non-periodic received light wave when the determination target received light signal includes a plurality of the received light waves. .

(Technical idea 6)
The optical distance measuring device according to technical concept 3,
The interference determining unit determines the time difference as an interference period when it can be determined that the time difference between the adjacent received waves is approximate,
a distance calculation unit (42) for calculating a distance based on the non-periodic received light wave among the plurality of received light waves when the determination target received light signal includes a plurality of the received light waves,
When the sum of the time difference between the second received light wave and the time difference between the third received wave does not approximate a natural number multiple of the interference period, the interference determination unit determines that the first received wave has periodicity. an optical rangefinder, wherein the received wave is not the received wave.

(Technical idea 7)
The optical distance measuring device according to Technical Thought 1,
wherein the waveform feature is one or more shape feature values that specify the shape of each of the received light waves;
When there are a plurality of received light waves in the received light signal to be determined, the interference determination unit arranges the shape feature values of the plurality of light received waves in order of magnitude, and when adjacent shape feature values are approximate to each other. , an optical ranging device that determines that interference is occurring.

(Technical idea 8)
The optical distance measuring device according to technical idea 7,
An optical distance measuring device, wherein the shape feature value includes a peak intensity of the received wave.

(Technical idea 9)
The optical distance measuring device according to technical idea 7 or 8,
An optical distance measuring device, wherein the shape characteristic value includes the width of the received wave.

(Technical idea 10)
The optical distance measuring device according to any one of technical ideas 7 to 9,
The optical distance measuring device, wherein the energy of the received wave is included in the shape characteristic value.

(Technical idea 11)
The optical distance measuring device according to any one of technical ideas 7 to 10,
The shape feature value that is similar to the adjacent shape feature value is set as an interference reference value,
When there are a plurality of received light waves in the received light signal to be determined, a distance calculation unit for calculating a distance based on the received light wave among the plurality of received light waves whose shape characteristic value is not similar to the interference reference value. (42), an optical ranging device.

(Technical idea 12)
The optical distance measuring device according to Technical Thought 1,
wherein the waveform feature is the width of the received wave;
The interference determination unit has a width threshold value set to a value larger than the width of the laser light projected by the light projection unit and smaller than the pulse width of the laser light transmitted by the iTOF type rangefinder. and an optical distance measuring device that determines that interference occurs when the received light wave having a large width of the received light wave is included in the light receiving signal to be determined.

Claims

An optical distance measuring device that measures the distance to an object by projecting and receiving laser light,
a light projecting unit (20) that scans and projects the laser light;
a light receiving section (30) for receiving the laser light;
A received light signal received by the light receiving unit during one light receiving period for receiving the reflected laser light generated by reflection of the laser light projected by the light projecting unit, or corresponding to a plurality of times of light projection When there are a plurality of received light waves, which are the laser beams received by the light receiving unit, in the determination target light receiving signal, which is one of the signals obtained by integrating the light receiving signals received by the light receiving unit during a plurality of light receiving periods, an interference determination unit (43) that determines whether or not interference has occurred based on waveform characteristics obtained from the received light wave of (1).
The optical distance measuring device according to claim 1,
wherein the waveform feature is the period of the received wave;
The optical distance measuring device, wherein the interference determination unit determines that interference occurs when the received wave has periodicity.
The optical distance measuring device according to claim 2,
The interference determination unit calculates a time difference (T) from the detection time of the previous waveform to the detection time of the received light wave for each of the plurality of received waves, and the time differences between the adjacent received waves are approximated. an optical distance measuring device that determines that the received wave has periodicity when it can be determined that the received wave has periodicity.
The optical distance measuring device according to claim 2,
The interference determination unit determines whether or not the received light wave has periodicity based on the intensity of the spectrum obtained by frequency-analyzing the received light signal to be determined.
The optical distance measuring device according to any one of claims 2 to 4,
An optical distance measuring device, comprising: a distance calculator (42) for calculating a distance based on, among the plurality of received light waves, a non-periodic received light wave when the determination target received light signal includes a plurality of the received light waves. .
The optical distance measuring device according to claim 3,
The interference determining unit determines the time difference as an interference period when it can be determined that the time difference between the adjacent received waves is approximate,
a distance calculation unit (42) for calculating a distance based on the non-periodic received light wave among the plurality of received light waves when the determination target received light signal includes a plurality of the received light waves,
When the sum of the time difference between the second received light wave and the time difference between the third received wave does not approximate a natural number multiple of the interference period, the interference determination unit determines that the first received wave has periodicity. an optical rangefinder, wherein the received wave is not the received wave.
The optical distance measuring device according to claim 1,
wherein the waveform feature is one or more shape feature values that specify the shape of each of the received light waves;
When there are a plurality of received light waves in the received light signal to be determined, the interference determination unit arranges the shape feature values of the plurality of light received waves in order of magnitude, and when adjacent shape feature values are approximate to each other. , an optical ranging device that determines that interference is occurring.
The optical distance measuring device according to claim 7,
An optical distance measuring device, wherein the shape feature value includes a peak intensity of the received wave.
The optical distance measuring device according to claim 7 or 8,
An optical distance measuring device, wherein the shape characteristic value includes the width of the received wave.
The optical distance measuring device according to claim 7 or 8,
An optical distance measuring device, wherein the energy of the received wave is included in the shape characteristic value.
The optical distance measuring device according to claim 7 or 8,
The shape feature value that is similar to the adjacent shape feature value is set as an interference reference value,
When there are a plurality of received light waves in the received light signal to be determined, a distance calculation unit for calculating a distance based on the received light wave among the plurality of received light waves whose shape characteristic value is not similar to the interference reference value. (42), an optical ranging device.
The optical distance measuring device according to claim 1,
wherein the waveform feature is the width of the received wave;
The interference determination unit has a width threshold value set to a value larger than the width of the laser light projected by the light projection unit and smaller than the pulse width of the laser light transmitted by the iTOF type rangefinder. and an optical distance measuring device that determines that interference occurs when the received light wave having a large width of the received light wave is included in the light receiving signal to be determined.