Optical ranging device

Abstract

To provide an optical distance measuring device capable of determining whether interference occurs while shortening a total distance measuring time.SOLUTION: An optical distance measuring device 10 that measures a distance to an object by projecting and receiving laser light, comprises: a light projection unit 20 that projects laser light while scanning; a light receiving unit 30 that receives the laser light; and an interference determination unit 43 that when there is a plurality of light receiving waves that are laser light received by the light receiving unit 30 during a light receiving period for receiving reflected laser light generated by the reflection of the laser light projected by the light projection unit 20, determines whether interference occurs based on waveform features obtained from the plurality of light receiving waves.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical distance measuring device, and more particularly to a technique for detecting interference. [Background technology]

[0002] Optical distance measuring devices are known that measure the distance to an object by projecting and receiving laser light. There may be another device projecting laser light around the optical distance measuring device, and the device itself may receive the laser light projected by that other device. To accurately measure the distance to an object, it is necessary to calculate the distance by removing the laser light projected by the other device (hereinafter, "interfering light"). Patent Document 1 sets up an interference monitoring period immediately before projecting laser light. If light is received during the interference monitoring period, it is determined that interference has occurred. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-72078 Summary of the Invention [Problem to be solved by the invention]

[0004] The technique disclosed in Patent Document 1 requires an interference monitoring time, which lengthens the total distance measurement time, including the time required to project and receive laser light for distance measurement.

[0005] The present disclosure has been made based on this situation, and its purpose is to provide an optical distance measuring device that can determine whether interference is occurring while shortening the total distance measuring time. [Means for solving the problem]

[0006] The above object is achieved by the combination of features recited in the independent claims, and the subclaims define further advantageous specific examples. The reference numerals in parentheses in the claims correspond to specific aspects described in the following embodiments as one aspect, and do not limit the technical scope of the disclosure.

[0007] One disclosure to achieve the above objective is: An optical distance measuring device that measures the distance to an object by projecting and receiving laser light, a light projecting unit (20) that projects a laser beam while scanning; a light receiving unit (30) that receives laser light; an interference determination unit (43) for determining whether or not interference has occurred based on waveform features obtained from the plurality of received light waves, when a determination target received light signal is either a received light signal received by the light receiving unit in one light receiving period for receiving reflected laser light generated by reflection of laser light emitted by the light emitting unit, or a signal obtained by accumulating received light signals received by the light receiving unit in a plurality of light receiving periods corresponding to a plurality of light projections, and The waveform features are the period of the received light wave and the Peak Intensity Yes the law of nature , the interference determination unit, based on the fact that the peak intensities of three consecutive received light waves are similar to one another and that the time difference from the detection time of the first received light wave to the detection time of the second received light wave and the time difference from the detection time of the second received light wave to the detection time of the third received light wave are similar, determines the time difference from the detection time of the first received light wave to the detection time of the second received light wave as an interference period and determines the peak intensity of the first received light wave as an interference reference value to be compared with the peak intensity of the received light waves; The received light wave is judged to be interfering based on the fact that the time difference (T) from the detection time of the previous waveform to the detection time of the received light wave is close to the interference period and the peak intensity of the received light wave is close to the interference reference value. It is an optical distance measuring device.

[0008] This optical distance measuring device determines whether interference is occurring based on the waveform characteristics of the received light wave contained in the determination target received light signal, which is determined from the received light signal received by the light receiving unit during the light receiving period for receiving reflected laser light. Therefore, there is no need to set a period just before the period for determining whether interference is occurring, and the total distance measuring time can be shortened. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of an optical distance measuring device according to an embodiment. [Figure 2] FIG. 10 is a diagram showing an example of a situation in which interference occurs. [Figure 3] 4 is a diagram showing the relationship between time and intensity of laser light emitted and received by the optical distance measuring device. [Figure 4] 4 is a diagram showing the relationship between time and intensity of laser light emitted and received by the optical distance measuring device. [Figure 5] 10A and 10B are diagrams showing the intensity of light emitted and received by the optical distance measuring device when interference occurs. [Figure 6] 10A and 10B are diagrams showing the intensity of light emitted and received by the optical distance measuring device when interference occurs. [Figure 7] FIG. 4 is a diagram showing a process executed by an interference determination unit in the first embodiment. [Figure 8] FIG. 8 is a diagram showing processing following FIG. 7; [Figure 9] FIG. 10 is a diagram for explaining the reason why the processes from S31 to S33 are performed. [Figure 10] FIG. 8 is a diagram showing a process executed in place of that shown in FIG. 7 in the second embodiment. [Figure 11] FIG. 11 is a diagram showing the processing executed following FIG. 10 . [Figure 12] FIG. 8 is a diagram showing a process executed in place of FIG. 7 in the third embodiment. [Figure 13] FIG. 13 is a diagram showing the processing executed following FIG. 12. [Figure 14] 1 is a diagram explaining the pulse width W and energy J of a received light wave E. [Figure 15] 1 is a diagram explaining the pulse width W and energy J of a received light wave E. [Figure 16] FIG. 8 is a diagram showing a process executed in place of that shown in FIG. 7 in the fourth embodiment. [Figure 17] FIG. 17 is a diagram showing the processing executed following FIG. 16. [Figure 18] FIG. 8 is a diagram showing a process executed in place of that shown in FIG. 7 in the fifth embodiment. [Figure 19] FIG. 19 is a diagram showing the processing executed following FIG. 18. [Figure 20] FIG. 10 is a diagram showing a process executed in place of that shown in FIG. 7 in the sixth embodiment. [Figure 21] FIG. 21 is a diagram showing the processing executed following FIG. 20 . [Figure 22] FIG. 13 is a diagram showing a process executed in place of that shown in FIG. 7 in the seventh embodiment. [Figure 23] FIG. 23 is a diagram showing the processing executed following FIG. 22. [Figure 24] FIG. 13 is a diagram showing a process executed in place of that in FIG. 7 in the eighth embodiment. [Figure 25] FIG. 25 is a diagram showing the processing executed following FIG. 24. [Figure 26] 10A and 10B are diagrams illustrating a determination target light receiving signal according to Modification 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment 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 unit 20, a light receiving unit 30, and a control unit 40.

[0011] The light projecting unit 20 projects the laser light outside the device while scanning it. The light projecting unit 20 that realizes such an operation is configured to include, for example, a light source and a scanning mirror.

[0012] The light receiving section 30 receives reflected laser light generated by reflection of the laser light emitted by the light projecting section 20. The light receiving section 30 includes, for example, a light receiving element and an amplifier.

[0013] The control unit 40 can be realized by a configuration including at least one processor. For example, the control unit 40 can be realized by a computer including a processor, nonvolatile memory, RAM, I / O, and a bus line connecting these components. The nonvolatile memory stores a program for operating a general-purpose computer as the control unit 40. The processor executes the program stored in the nonvolatile memory while utilizing the temporary storage function of the RAM, causing the control unit 40 to operate as a light emission / reception control unit 41, a distance calculation unit 42, and an interference determination unit 43. Execution of these operations means that a method corresponding to the program is being executed.

[0014] 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. The light projecting / receiving control unit 41 also controls the light receiving unit 30 to cause the light receiving unit 30 to detect the reflected laser light, and sequentially acquires from the light receiving unit 30 a light receiving signal indicating the received light intensity of the reflected laser light.

[0015] The distance calculation unit 42 calculates the distance to the object from which the reflected laser light is emitted based on the time (hereinafter referred to as time of flight TOF) from when the light projecting unit 20 projects the laser light to when the reflected laser light is received by the light receiving unit 30. Since the distance to the object is calculated in this manner, the optical distance measuring device 10 is a dTOF type optical distance measuring device.

[0016] The interference determination unit 43 determines whether interference is occurring based on the light reception signal acquired by the light emission and reception control unit 41. The interference determined by the interference determination unit 43 includes at least interference caused by the laser light emitted by the iTOF type optical distance measuring device 50 (see FIG. 2). In addition to determining whether interference is occurring, the interference determination unit 43 also determines whether the received light wave E is interference light or signal light. The process by which the interference determination unit 43 determines interference will be described later.

[0017] The distance calculation unit 42 does not use received light waves E that the interference determination unit 43 has determined to be interference light in calculating the distance. In other words, the distance calculation unit 42 calculates the distance based on received light waves E that have not been determined to be interference light. In the first embodiment, as will be described later, the interference determination unit 43 determines whether a received light wave E is interference light based on the periodicity of the received light waves E. Therefore, the distance calculation unit 42 excludes periodic received light waves E and calculates the distance using non-periodic received light waves E.

[0018] [Examples of situations where interference occurs] Figure 2 shows an example of a situation in which interference occurs. The optical distance measuring device 10 is mounted on a vehicle. The vehicle on which the optical distance measuring device 10 is mounted is referred to as the host vehicle 1. The narrow sector extending from the optical distance measuring device 10 represents the laser light projected in one scanning direction.

[0019] FIG. 2 also shows another vehicle 2 traveling in the opposite direction to the host vehicle 1. The other vehicle 2 is equipped with an iTOF type optical distance measuring device 50. The sector shape centered on the optical distance measuring device 50 conceptually shows the laser light emitted by the optical distance measuring device 50. The laser light emitted by the optical distance measuring device 50 is diffused light. As shown in FIG. 2, the laser light emitted by the optical distance measuring device 50 may be received by the optical distance measuring device 10.

[0020] FIG. 3 is a diagram showing the relationship between time and intensity of laser light emitted and received by the optical distance measuring device 10 for each measurement direction. In the graph shown in FIG. 3, the horizontal axis represents time t and the vertical axis represents signal intensity I. The optical distance measuring device 10 emits laser light at time t0. When the laser light is reflected by an external object, reflected laser light is generated. In FIG. 3, the optical distance measuring device 10 receives the reflected laser light 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.

[0021] FIG. 4 is a diagram showing the relationship between time and intensity of laser light emitted and received by optical distance measuring device 50. In FIG. 4, the horizontal axis is time t and the vertical axis is signal intensity I. As shown in FIG. 4, optical distance measuring device 50, which is an iTOF type, periodically emits laser light. The duty ratio between the period when light is emitted and the period when light is not emitted is 50%. In FIG. 4, the first laser light is emitted from time t10. Then, the reflected laser light generated by that laser light is received from time t11. In iTOF types, the distance to an object is calculated based on the phase difference between the emitted laser light and the received reflected laser light.

[0022] Figures 3 and 4 both show the signal intensity I of the light projected and received when no interference occurs. Figures 5 and 6 show the intensity of light projected and received by optical distance measuring device 10 when interference occurs, as in the state shown in Figure 2. In the following description, to distinguish between the laser light projected and received by optical distance measuring device 10 and the laser light projected by optical distance measuring device 50, the laser light projected and received by optical distance measuring device 10 may be referred to as signal light, and the laser light projected by optical distance measuring device 50 may be referred to as interference light.

[0023] In Figures 5 and 6, the signal light is shown by a solid line, and the interference light is shown by a dashed line. In Figure 5, the signal light and the interference light are separated. In Figure 6, the signal light and the interference light are merged. These figures are conceptual diagrams, and in reality, it is not possible to clearly distinguish whether the received light wave E is signal light or interference light. In both Figures 5 and 6, to correctly determine the time of flight TOF, it is necessary to determine the received light signal indicating the signal light from the received light signal that contains a signal indicating the interference light and a signal indicating the signal light.

[0024] Therefore, the optical distance measuring device 10 includes an interference determination unit 43 that determines whether interference is occurring. If the interference determination unit 43 determines that interference is occurring, the distance calculation unit 42 calculates the distance after excluding the interfering light from the received light signal.

[0025] [Processing Executed by the Interference Determination Unit 43] 7 and 8 show the processing executed by the interference determination unit 43 in the first embodiment. The processing shown in FIGS. 7 and 8 is executed after a light reception signal is acquired during a light reception period for each object detection direction. Therefore, in the first embodiment, the light reception signal detected during one light reception period is the light reception signal to be determined. The light reception period is a period determined based on the time when the light projector 20 projects a laser beam. The start time of the light reception period can be the time when the light projector 20 projects a laser beam. Alternatively, the start time of the light reception period may be after a period of time has elapsed after the light projector 20 projects a laser beam, allowing for the laser beam reflected from the device housing or the like to be removed. The length of the light reception period is determined by the maximum distance of an object to be detected by the optical distance measuring device 10. The length of the light reception period should be longer than the maximum detection distance / speed of light and shorter than the light projection period.

[0026] In S1, N=1, i=0, and the periodic interference flag are set to False. In the following 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.

[0027] In S3, it is determined whether the total number of received light waves, FULL, is 2 or less. In the examples of Figs. 5 and 6, FULL=5. The received light wave E is sometimes called an echo. If the determination result in S3 is YES, the process proceeds to S4.

[0028] In S4, the Nth received light wave E(N) is taken as the true value, i.e., the waveform of the signal light. When proceeding to S4, there are not enough received light waves to be able to determine that there is periodic interference. Therefore, the received light wave E(N) is taken as the true value.

[0029] After S4 is executed, the process proceeds to S5. In S5, N is incremented by 1. In the following S6, it is determined whether N is greater than FULL. If FULL is 1, the first time S6 is executed, the result of the determination in S6 will be YES. If FULL is 2 or greater, the first time S6 is executed, the result of the determination in S6 will be NO. If the result of the determination in S6 is NO, the process returns to S2.

[0030] If FULL is 3 or more, the determination result of S3 is NO. If the determination result of S3 is NO, proceed to S7. In S7, it is determined whether N is 1, that is, whether this is the first execution. If the determination result of S7 is YES, proceed to S8. In S8, i is incremented by 1. After executing S8, proceed to S5.

[0031] If the determination result in S7 is NO, proceed to S9. Proceed to S9 if N is 2 or more and FULL is 3 or more. In S9, it is determined whether the time difference T(N) and the time difference T(N+1) are close to each other.

[0032] The time difference T is shown in Figures 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 Nth received light wave E. In the case of the first received light wave E1, the previous waveform is the projected laser light. The detection time of the projected laser light is the time when the light projecting unit 20 projects the laser light. In Figures 5 and 6, the detection time of the waveform is the time that is the center of the time of the received light waveform. However, the detection time of the waveform can also be the rising time of the received light wave E. Whether or not they are similar is determined by whether one is within ±α% of the other. α% is, for example, 10%.

[0033] If the determination result in S9 is NO, proceed to S10. In S10, N is stored in U(i), and the time difference T(N) is stored in UT(i). When the processing of S10 is being executed, the periodic interference flag is False, but there is a possibility that the Nth waveform is interference light. Therefore, in order to determine in later processing whether the Nth waveform is interference light, the time difference T(N) is stored in UT(i). After executing S10, proceed to S11. In S11, i is incremented by 1. After executing S11, proceed to S5.

[0034] If the determination result in S9 is YES, the process proceeds to S12. Proceeding to S12 means that the multiple received light waves E are periodic. Therefore, in S12, the periodic interference flag is set to True, and the interference period is determined to be T(N). In this way, in the first embodiment, the period of the received light wave E is used as a waveform feature, and it is determined that interference is occurring when the received light waveform is periodic. The period of the received light wave E is the time from when the waveform of one received light wave E is detected to when the waveform of the next received light wave E is detected, and therefore indicates one of the features of the waveform of the received light wave E. In S13, it is determined that the Nth received light wave E(N) is interference light. After executing S13, the process proceeds to S5.

[0035] If the periodic interference flag becomes True as a result of the processing in S12, the process proceeds to S14 after the judgment in S2. In S14, it is judged whether the time difference T(N) is approximate to the interference period. For example, if the time difference T(N) is within ±β% of the interference period, it is judged that the time difference T(N) is approximate to the interference period. β% is, for example, 10%. If the judgment result in S14 is NO, the process proceeds to S15, and the Nth received light wave E(N) is determined to be a true value. If the judgment result in S14 is YES, the process proceeds to S16, and the received light wave E(N) is determined to be interference light. After executing S15 or S16, the process proceeds to S5 and S6.

[0036] If the determination result in S6 becomes YES due to an increase in N in S5, the process proceeds to Fig. 8. At the time of proceeding to the process shown in Fig. 8, the determination of whether or not interference is occurring has been completed. In Fig. 8, it is determined whether or not the i-th received light wave E stored in S10 is a true value.

[0037] In Fig. 8, in S21, it is determined whether i is greater than 0. If the determination result in S21 is NO, the processing in Fig. 8 is terminated. If the determination result in S21 is YES, the processing proceeds to S22.

[0038] In S22, the content of the periodic interference flag is judged. If the periodic interference flag is False, the process proceeds to S23. In S23, the U(i)th received light wave E(U(i)) is set to a true value. In S24, i is decremented by 1. In S25, it is judged whether i has become 0. If the judgment result in S25 is NO, that is, if i has not become 0, the process returns to S23. By repeating S23 to S25, all of the received light waves E whose numbers were 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 of the received light waves E are set to true values. If the judgment result in S25 is YES, the process of FIG. 8 ends.

[0039] If the determination in S22 is that the periodic interference flag is True, the process proceeds to S26. In S26, it is determined whether UT(i) is close to the interference period. Whether the two are close to each other is determined in the same manner as in S14.

[0040] If the determination result in S26 is NO, proceed to S27, where the U(i)th received light wave E(U(i)) is determined to be a true value. If the determination result in S26 is YES, proceed to S28, where the received light wave E(U(i)) is determined to be interference light. After executing S27 or S28, proceed to S29.

[0041] In S29, i is decremented by 1. In S30, it is determined whether i is greater than 1. If the determination result in S30 is YES, the process returns to S26. By repeating S26 to S30, it is determined whether the received light waves E, for which it has not been determined whether they are true values, are true values ​​in order from the largest number up to i=2.

[0042] When i decreases to 1, the judgment result in S30 becomes NO. When the judgment result in S30 becomes NO, the process proceeds to S31. In S31, it is judged whether the sum of the time difference T2 and the time difference T3 is approximately D times the interference period. D is an integer (i.e., a natural number) that is defined by the user and is equal to or greater than 1. It is preferable that D be of multiple types, such as 1 and 2.

[0043] The method for determining whether T2+T3 is approximately equal to 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 is approximately equal to D times the interference period, proceed to S32. In S32, it is determined that the first received light wave E1 is interference light. On the other hand, if the determination result in S31 is NO, proceed to S33, where it is determined that the first received light wave E1 is a true value.

[0044] The reason for performing the processes from S31 to S33 will be explained using FIG. 9. As shown in FIG. 9, the time difference T1 is the time from the detection time of the projected laser light to the detection time of the received light wave E1. As shown in FIG. 9, even though the received light wave E1 is interference light, the time difference T1 and the time difference T2 are different. Therefore, it is not possible to determine whether the received light wave E1 is interference light using the same criteria as the second and subsequent received light waves E. Therefore, S31 to S33 are used to determine whether the received light wave E1 is interference light. In the state shown in FIG. 9, T2 + T3 is approximately equal to the interference period T4 or T5. Therefore, it is possible to determine that the received light wave E1 is interference light using S31 to S33.

[0045] If D is set to 2, the received light wave E1 can be determined to be interference light even when the second received light wave E2 is a waveform in which the signal light and interference light overlap, as shown in Figure 6. This is because T2 + T3 approximates 2 × the interference period.

[0046] Summary of the first embodiment In the first embodiment described above, the interference determination unit 43 determines whether interference is occurring based on whether the received light waves E received during the light receiving period have periodicity (S9). Therefore, there is no need to provide a period immediately before the occurrence of interference in order to determine whether interference is occurring, and the total distance measurement time can be shortened.

[0047] If it can be determined that the time differences T(N), T(N+1) for consecutive received light waves E in the detection order, i.e., for received light waves E adjacent to each other in the detection order, are similar (S9: YES), the interference determination unit 43 determines that the received light waves E are periodic (S12). By determining the periodicity in this manner, the periodicity can be easily determined.

[0048] The interference determination unit 43 determines that the periodic received light wave E is interference light (S13, S16). The distance calculation unit 42 does not use interference light to calculate the distance. In the example of FIG. 5, the received light wave E2 is determined to be interference light in S13, and the received light waves E3 and E4 are determined to be interference light in S16. In the example of FIG. 6, the received light wave E4 is determined to be interference light in S13, and the received light wave E5 is determined to be interference light in S16.

[0049] Furthermore, if the sum of the time difference T2 of the second received light wave E2 and the time difference T3 of the third received light wave E3 approximates D times the interference period, the interference determination unit 43 determines that the first received light wave E1 is interference light (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 light wave E1 is a true value, that is, a non-periodic received light wave E (S33). In this way, periodicity can also be determined for the first received light wave E1.

[0050] Second Embodiment Next, a second embodiment will be described. In the following description of the second embodiment, elements having the same reference numerals as those used previously are the same as those in the previous embodiments unless otherwise specified. Furthermore, when only a portion of the configuration is described, the previously described embodiment can be applied to the other portions of the configuration.

[0051] 10 and 11 show processing executed by the interference determination unit 43 in place of that shown in Fig. 7 and 8. In S41 of Fig. 10, the periodic interference flag is set to False.

[0052] In S42, the received light signal during the light receiving period is subjected to frequency analysis. In S43, it is determined whether or not a peak exists in the frequency analysis spectrum at a frequency corresponding to the period of the laser light transmitted by the iTOF 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 is a frequency that is completely different from the frequency of the waveform of the signal light, and the peak intensity should also be large. Therefore, it is easy to determine whether or not a peak exists in the iTOF frequency in the frequency analysis spectrum.

[0053] If the determination result in S43 is NO, proceed to S50 in FIG. 11 without executing S44 and S45. If the determination result in S43 is YES, proceed 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. Thereafter, proceed to S50 in FIG. 11.

[0054] In S50 of FIG. 11, N is set to 1. In the following 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 light wave E(N) is set to a true value. After S52 is executed, the process proceeds to S60. In S60, N is incremented by 1. In the following S61, it is determined whether N exceeds the total number of received light waves FULL. If the determination result in S61 is NO, the process returns to S51.

[0055] If the periodic interference flag is determined to be True in S51, the process proceeds to S53. In S53, it is determined whether N=1. The first time Figure 11 is executed, the determination result in S53 will be YES. If the determination result in S53 is YES, the process proceeds to S54. S54, S55, and S56 are the same as S31, S32, and S33 in Figure 8, respectively. S54, S55, and S56 determine whether the first received light wave E1 is a true value or an interference light. After S55 or S56 is executed, the process proceeds to S60 and S61.

[0056] When S53 is executed for the second or subsequent times, 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. S57, S58, and S59 determine whether the Nth received light wave E(N) is a true value or interference light. When it has been determined whether all received light waves E(N) are true values ​​or interference light, the determination result of S61 becomes YES, and the process of Fig. 11 ends.

[0057] Summary of the second embodiment In the second embodiment, the interference determination unit 43 determines whether or not the received light wave E is periodic based on the intensity of the spectrum obtained by frequency analysis of 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 a previous period.

[0058] <Third embodiment> 12 and 13 show processing executed by the interference determination unit 43 instead of that shown in FIGS. 7 and 8. In S71 of FIG. 12, the received light waves E received during the light reception period are sorted in descending order of peak signal strength I. In FIGS. 14 and 15, the received light waves E are shown with numbers indicating the order of peak signal strength I. The peak signal strength I of the received light wave E is one of the shape feature values ​​that specify the shape of the received light waveform.

[0059] In S72, the periodic interference flag is set to False. In S73, the variables Cnt and N are set to 0 and 1, respectively.

[0060] 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. 13. However, initially the periodic interference flag is False. If the periodic interference flag is False, the process proceeds to S75.

[0061] In S75, it is determined whether the signal intensity I(N) of the peak of the Nth received light wave E and the signal intensity I(N+1) of the peak of the N+1th received light wave E are similar. Whether they are similar is determined, for example, by whether one is within ±α% of the other. If the determination result in S75 is NO, proceed to S79, and if YES, proceed to S76.

[0062] In S76, Cnt is incremented by 1. In S77, it is determined whether Cnt is equal to or greater than γ, where γ is a number defined by the user.

[0063] If the determination result in S77 is YES, proceed to S78. In 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 that is compared with the peak signal intensity I of each received light wave E in FIG.

[0064] In S79, N is incremented by 1. In S80, it is determined whether N is greater than the number of received light waves FULL. If the determination result in S80 is NO, S74 and subsequent steps are executed again. If the determination result in S80 is YES, the process proceeds to S81 in FIG. 13.

[0065] Cnt means the number of times the determination result in S75 is YES. When the determination in S77 is YES, the periodic interference flag is set to True. Therefore, γ is a number determined and set by the user to determine how many times the determination in S77 must be YES before it is determined to be periodic interference. γ is an integer greater than or equal to 1. The larger γ is, the less likely it is that periodic interference is determined to be occurring even when it is not. On the other hand, the larger γ is, the more likely it is that periodic interference is not determined to be occurring even when it is. The user determines γ taking these advantages and disadvantages into consideration. It is preferable that γ is 2 or greater.

[0066] In FIG. 14, the peak signal intensities I of the received light waves E2, E3, E4, and E5 are similar. Therefore, the determination result in S75 is YES when N=2, 3, and 4. In other words, the determination result in S75 is YES three times. Therefore, when γ=1, 2, or 3, the periodic interference flag is True. Furthermore, when γ=1, 2, and 3, the peak signal intensities I2, I3, and I4 of the received light waves E2, E3, and E4, respectively, become the interference peak intensities.

[0067] 15, the peak signal intensities I of the received light waves E2, E3, and E4 are close to each other. Therefore, the determination result in S75 is YES when N=2 or 3. Therefore, when γ=1 or 2, the periodic interference flag is TRUE.

[0068] Next, Fig. 13 will be described. In S81, N is set to 1. 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 light wave E(N) is set to a true value.

[0069] If the periodic interference flag is determined to be True in S82, the process proceeds to S84. In S84, it is determined whether the peak signal intensity I(N) is similar to the interference peak intensity. The method for determining whether they are similar is the same as before. If the determination result in S84 is NO, the process proceeds to S85. This received light wave E(N) is a received light wave E(N) whose peak signal intensity I is not similar to the interference peak intensity. In S85, the received light wave E(N) is considered to be a true value. If the determination result in S84 is YES, the process proceeds to S86, and the received light wave E(N) is considered to be interference light.

[0070] In S87, N is incremented by 1. In S88, it is determined whether N is greater than the number of received light waves FULL. If the determination result in S88 is NO, S82 and subsequent steps are executed again. If the determination result in S88 is YES, the processing in FIG. 13 is terminated.

[0071] By the processing of Fig. 13, in the example of Fig. 14, the received light wave E1 can be determined as a true value, and the received light waves E2, E3, E4, and E5 can be determined as interference light. In the example of Fig. 15, the received light wave E1 can be determined as a true value, and the received light waves E2, E3, and E4 can be determined as interference light. The distance calculation unit 42 excludes the received light wave E determined as interference light, and calculates the distance using the received light wave E determined as a true value.

[0072] As explained above, by arranging the signal intensities I of the peaks of the received light wave E in order of magnitude (S71) and determining whether the signal intensities I of adjacent peaks in this order are similar, it is possible to determine whether interference is occurring (S75 to S80).

[0073] Furthermore, the signal intensity I of a peak whose signal intensity I of adjacent peaks is similar is set as the interference peak intensity (S78), and the received light 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 set as the true value. In this way, the distance can be calculated while excluding the interference light.

[0074] <Fourth embodiment> The fourth embodiment is similar to the third embodiment. In the fourth embodiment, the processes shown in Figures 16 and 17 are executed instead of those shown in Figures 12 and 13. In Figure 16, steps S71-1, S75-1, and S78-1 are executed instead of steps S71, S75, and S78 in Figure 12.

[0075] In S71-1, the received light waves E received during the light reception period are sorted in order of pulse width W, which is the width of the received light waves E. In the fourth embodiment, the pulse width W is the shape characteristic value. The pulse width W is shown for the received light wave E2 in FIGS. 14 and 15. The half-width of the received light wave E can be used as the pulse width W. However, since it is only necessary to be able to compare the shapes of the received light waves E relatively, the pulse width W may also be determined based on other criteria. For example, the waveform width at a predetermined signal intensity I may be used as the pulse width W.

[0076] When the received light waves E are arranged in ascending order of pulse width W, they are arranged in the order of the numbers of the received light waves E shown in Fig. 14, similar to the peak signal strength I. It is also possible to arrange them in ascending order of pulse width W.

[0077] In S75-1, it is determined whether the pulse width W(N) of the Nth received light wave E and the pulse width W(N+1) of the N+1th received light wave E are similar to each other.

[0078] In 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 that is compared with the pulse width W of each received light wave E in Fig. 17. In the examples of Figs. 14 and 15, the pulse width W2 of the received light wave E2 becomes the interference pulse width.

[0079] Next, Fig. 17 will be described. In Fig. 17, S84-1 is executed instead of S84 in Fig. 13. In S84-1, it is determined whether the pulse width W(N) is similar to the interference pulse width. If the determination result in S84-1 is NO, the process proceeds to S85, where the received light wave E(N) is determined to be a true value. If the determination result in S84-1 is YES, the process proceeds to S86, where the received light wave E(N) is determined to be interference light. As a result of the processing in Fig. 17, in the example of Fig. 14, the received light waves E2, E3, E4, and E5 become interference light, and in the example of Fig. 15, the received light waves E2, E3, and E4 become interference light. On the other hand, the received light wave E1 becomes a true value.

[0080] As in the fourth embodiment, by determining whether the pulse widths W are similar, it is possible to determine interference and distinguish between interference light and the true value (that is, signal light).

[0081] 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, the processes shown in FIGS. 18 and 19 are executed instead of those shown in FIGS. 16 and 17. In FIG. 18, steps S75-2 and S78-2 are executed instead of steps S75-1 and S78-1 in FIG. 15.

[0082] In S75-2, it is determined whether the pulse width W(N) is greater than a predetermined width threshold C. The width threshold C is set to a value greater than the width of the laser light projected by the light projector 20 and smaller than the pulse width of the laser light transmitted by the iTOF optical distance measuring device 50. The pulse width of the laser light transmitted by the dTOF device and the pulse width of the laser light transmitted by the iTOF device are significantly different. Therefore, it is easy to set the width threshold C so that it is between these two types of pulse width.

[0083] In 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 S84-2 in Fig. 19, which will be described next, also uses the width threshold C instead of the interference pulse width.

[0084] 19 executes S84-2 instead of S84-1 in FIG. 17. In S84-2, it is determined whether the pulse width W(N) is greater than the width threshold C. If the determination result in S84-2 is YES, the process proceeds to S86, where the received light wave E(N) is determined to be interference light. If the determination result in S84-2 is NO, the process proceeds to S85, where the received light wave E(N) is determined to be a true value. Even in this fifth embodiment, it is possible to distinguish between interference light and signal light.

[0085] Sixth Embodiment The embodiment shown in Fig. 6 is similar to the fourth embodiment. In the sixth embodiment, the processes shown in Fig. 20 and Fig. 21 are executed instead of the processes shown in Fig. 16 and Fig. 17. In Fig. 20, steps S71-3, S75-3, and S78-3 are executed instead of steps S71-1, S75-1, and S78-1 in Fig. 16.

[0086] In S71-3, the received light waves E received during the light receiving period are sorted in order of the energy J of the received light waves E. The energy J of the received light waves E can be calculated from the integral 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 light wave E2 in FIGS. 14 and 15.

[0087] In S75-3, it is determined whether the energy J(N) of the Nth received light wave E and the energy J(N+1) of the N+1th received light wave E are similar to each other.

[0088] In 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 that is compared with the energy J of each received light wave E in Fig. 21. In the examples of Figs. 14 and 15, the energy J2 of the received light wave E2 is the interference energy.

[0089] Next, Fig. 21 will be described. In Fig. 21, S84-3 is executed instead of S84-1 in Fig. 17. In S84-3, it is determined whether the energy J(N) is similar to the interference energy. If the determination result in S84-3 is NO, the process proceeds to S85, where the received light wave E(N) is determined to be a true value. If the determination result in S84-3 is YES, the process proceeds to S86, where the received light wave E(N) is determined to be interference light. As a result of the processing in Fig. 21, in the example of Fig. 14, the received light waves E2, E3, E4, and E5 become interference light, and in the example of Fig. 15, the received light waves E2, E3, and E4 become interference light. On the other hand, the received light wave E1 becomes a true value.

[0090] As in the sixth embodiment, by determining whether the energy J is similar, it is possible to determine interference and distinguish between interference light and the true value (that is, signal light).

[0091] Seventh Embodiment The seventh embodiment is similar to the third and fourth embodiments, but 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.

[0092] In the seventh embodiment, the processes shown in Figures 22 and 23 are executed instead of those shown in Figures 12 and 13. In Figure 22, steps S75-4 and S78-4 are executed instead of steps S75 and S78 in Figure 12.

[0093] In S75-4, it is determined whether the signal intensity I(N) of the peak of the Nth received light wave E is similar to the signal intensity I(N+1) of the peak of the N+1th received light wave E, and whether the pulse width W(N) of the Nth received light wave E is similar to the pulse width W(N+1) of the N+1th received light wave E.

[0094] In 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.

[0095] Next, Fig. 23 will be described. In Fig. 23, S84-4 is executed instead of S84 in Fig. 13. In S84-4, it is determined whether the peak signal intensity I(N) is approximate to the interference peak intensity and whether the pulse width W(N) is approximate to the interference pulse width. If the determination result in S84-4 is NO, the process proceeds to S85, where the received light wave E(N) is determined to be a true value. If the determination result in S84-4 is YES, the process proceeds to S86, where the received light wave E(N) is determined to be interference light.

[0096] By determining whether interference occurs using two types of shape feature values ​​as in the seventh embodiment, it is possible to determine with greater accuracy whether interference occurs. In addition, by using two types of interference reference values, it is possible to distinguish between true values ​​and interference light with greater accuracy.

[0097] Eighth Embodiment 24 and 25 show the processing executed by the interference determination unit 43 in the eighth embodiment. In the eighth embodiment, the numbers of the received light waves E are in chronological order, as in the first embodiment.

[0098] The description will begin with Figure 24. In S91, N is set to 1, i to 0, and the periodic interference flag is set to False. The following S92 is the same process as S3 in Figure 7, and it is determined whether the number of received light waves FULL is 2 or less. If the determination result in S92 is YES, the process proceeds to Figure 25. If the determination result in S92 is NO, the process proceeds to S93.

[0099] In S93, the content of the periodic interference flag is judged. If the periodic interference flag is False, the process proceeds to Fig. 25. If the periodic interference flag is True, the process proceeds to S94.

[0100] 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 the peak signal intensity I and the time difference T are similar, the result of the determination in S94 is YES. If the result of the determination in S94 is YES, the process proceeds to S95.

[0101] In S95, the periodic interference flag is set to True. Also, the interference period is set to T(N) and the interference period peak intensity is set to I(N). After S95 is executed, the process proceeds to S96. If the determination result in S94 is NO, the process also proceeds to S96.

[0102] In S96, N is incremented by 1. In S97, it is determined whether N is greater than the number of received light waves FULL. If the determination result in S97 is NO, S92 and subsequent steps are executed again. If the determination result in S97 is YES, the process proceeds to FIG.

[0103] Next, Fig. 25 will be described. Fig. 25 is similar to Fig. 11. In Fig. 25, S54-1 and S57-1 are executed instead of S54 and S57 in Fig. 11. S54-1 is executed when N=1. In S54-1, T2+T3 is the interference period D times and determine whether I(N) is close to the interference peak intensity. T2 + T3 is the interference period. D times Whether I(N) is approximate to the interference peak intensity is determined in S54 of Fig. 11. Whether I(N) is approximate to the interference peak intensity is determined in S84 of Fig. 13.

[0104] If the result of the determination in S54-1 is YES, the process proceeds to S55, where the received light wave E1 is determined to be interference light, whereas if the result of the determination in S54-1 is NO, the process proceeds to S56, where the received light wave E1 is determined to be a true value.

[0105] In S57-1, it is determined whether T(N) approximates the interference period and whether I(N) is the interference peak intensity. Whether T(N) approximates the interference period is determined in S57 of FIG. 11. Whether I(N) approximates the interference peak intensity is determined in S84 of FIG. 13. If the determination result in S57-1 is NO, the process proceeds to S58, where E(N) is determined to be a true value. If the determination result in S57-1 is YES, the process proceeds to S59, where E(N) is determined to be interference light.

[0106] Summary of the Eighth Embodiment As in the eighth embodiment, by determining whether interference occurs using the presence or absence of periodicity and the shape feature value, it is possible to determine with greater accuracy whether interference occurs. Furthermore, by using the presence or absence of periodicity and the interference reference value, it is possible to distinguish between the true value and the interference light with greater accuracy.

[0107] 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 scope of the disclosure. Furthermore, various modifications other than those described below can be made without departing from the spirit of the invention.

[0108] <Variation 1> In the first embodiment, the interference period is set only once. However, the interference period may be updated as needed. In other embodiments, the interference period may also be updated as needed. Furthermore, interference reference values ​​such as the peak signal intensity I of the received light wave E may also be updated as needed.

[0109] <Variation 2> In the seventh embodiment, two shape feature values, the peak signal intensity I and the pulse width W, are used. However, instead of these two shape feature values, the energy J of the received light wave E may be used. Alternatively, three types of shape feature values ​​may be used. Furthermore, in the eighth embodiment, instead of the peak signal intensity I, another shape feature value may be used.

[0110] <Variation 3> In the embodiment, light is projected only once per azimuth 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 determined. However, as shown in Fig. 26, laser light may be projected multiple times (three times in Fig. 26) per azimuth direction, and the light-receiving signal to be determined may be a signal obtained by accumulating the signal intensities I of the light-receiving signals received by the light-receiving unit 30 during multiple light-receiving periods corresponding to the multiple light projections.

[0111] In the example shown in Figure 26, the second row from the top shows the signal intensity I of the received light signal. If light is projected three times, there will be three light-receiving periods. When accumulating the received light signals received by the light-receiving unit 30 during each light-receiving period, the received light signals received by the light-receiving unit 30 during each light-receiving period are stored in a specified memory. Then, the timing of each light projection is synchronized to accumulate the signal intensity I of the received light signal over time. The graph obtained in this way is the graph in the bottom row of Figure 26. By doing this, even if the signal intensity I of the received light signal received during one light-receiving period is small, the received light signal to be judged can be made larger. This makes it possible to expand the range of distance measurement. [Explanation of symbols]

[0112] 1: Vehicle 2: Other vehicle 10: Optical distance measuring device 20: Light projecting unit 30: Light receiving unit 40: Control unit 41: Light projecting and receiving control unit 42: Distance calculation unit 43: Interference determination unit 50: Optical distance measuring device C: Width threshold E: Received light wave I: Signal strength J: Energy T: Time difference TOF: Time of flight W: Pulse width

Claims

1. An optical distance measuring device that measures the distance to an object by projecting and receiving laser light, a light projection unit (20) that projects the laser light while scanning; a light receiving unit (30) that receives the laser light; an interference determination unit (43) for determining whether or not interference has occurred based on waveform features obtained from the plurality of received light waves, when a determination target received light signal is either a received light signal received by the light receiving unit in one light receiving period for receiving reflected laser light generated by reflection of the laser light projected by the light projecting unit, or a signal obtained by accumulating the received light signals received by the light receiving unit in a plurality of light receiving periods corresponding to a plurality of light projections, and the waveform characteristics are a period of the received light wave and a peak intensity of each of the received light waves; the interference determination unit determines the time difference from the detection time of the first received light wave to the detection time of the second received light wave as an interference period, and determines the peak intensity of the first received light wave as an interference reference value to be compared with the peak intensity of the received light waves, based on the fact that the peak intensities of three consecutive received light waves are similar to each other and that the time difference from the detection time of the first received light wave to the detection time of the second received light wave and the time difference from the detection time of the second received light wave to the detection time of the third received light wave are similar to each other; The received light wave is judged to be interfering based on the fact that the time difference (T) from the detection time of the immediately preceding waveform to the detection time of the received light wave is close to the interference period and the peak intensity of the received light wave is close to the interference reference value. Optical ranging device.

2. the interference determination unit determines that the first received light wave is interference light based on the fact that the sum of the time difference from the detection time of the first received light wave to the detection time of the second received light wave and the time difference from the detection time of the second received light wave to the detection time of the third received light wave is approximate to a natural number multiple of the interference period, and the peak intensity of the first received light wave is approximate to the interference reference value.

2. The optical distance measuring device according to claim 1.

Images