Obstacle sensing device

Abstract

To provide an obstacle sensing device that can suppress an obstacle, in which reflectance of a laser beam is low, from being forgotten to be sensed.SOLUTION: An obstacle sensing device 10, which includes a lase distance measurement sensor 11, a reflector 13 that retroreflects an incident beam, and first to fifth mirrors 15a-15e that reflect the incident beam in a direction symmetric with a surface normal direction, is configured so that a laser beam emitted from the laser distance measurement sensor 11 passes through a monitoring area MA and is guided through the first to fifth mirrors 15a-15e to the reflector 13, which outputs an obstacle sensing signal unless the laser distance measurement sensor 11 cannot receive a reflected beam of the laser beam by the reflector 13.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an obstacle detection device. [Background technology]

[0002] One known example of an obstacle detection device is the obstacle detection device described in Patent Document 1. The obstacle detection device described in Patent Document 1 includes a detection device that is configured to detect whether or not there are obstacles such as people or vehicles within a set area within the railroad crossing, i.e., within a monitoring area, by receiving reflected light from a laser beam that scans within a predetermined angle range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-227608 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the obstacle detection device described in Patent Document 1, even if an object with low reflectivity of laser light, such as a dark or black vehicle, is present in the installation area (monitoring area), it may happen that the reflected light from the object is hardly received. As a result, with the obstacle detection device described in Patent Document 1, there is a risk that the device may miss detecting an obstacle with low reflectivity of laser light.

[0005] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an obstacle detection device that can prevent failure to detect obstacles with low reflectivity of laser light. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a novel obstacle detection device that includes a laser distance measuring sensor, one or more mirrors that reflect incident light in directions symmetrical with respect to a surface normal, and a reflector that retroreflects the incident light, wherein a laser beam emitted from the laser distance measuring sensor passes through a monitoring area and is guided to the reflector via the one or more mirrors, and outputs an obstacle detection signal when the laser beam reflected by the reflector is not received by the laser distance measuring sensor. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an obstacle detection device that can reduce the risk of missing detection of obstacles with low reflectivity of laser light. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic plan view of an obstacle detection device according to an embodiment; [Figure 2] 10 is a diagram showing a propagation path of a laser beam emitted from a laser distance measuring sensor in the direction of a first mirror. FIG. [Figure 3] 4 is a flowchart showing an example of an obstacle determination process performed by (a processing unit of) an obstacle detection device. [Figure 4] 4 is a flowchart showing an example of an obstacle determination process performed by (a processing unit of) an obstacle detection device. [Figure 5] FIG. 10 is a diagram illustrating a modified example of an obstacle detection device. [Figure 6] FIG. 10 is a diagram illustrating a modified example of an obstacle detection device. [Figure 7] FIG. 10 is a diagram illustrating a modified example of an obstacle detection device. [Figure 8] FIG. 10 is a diagram illustrating a modified example of an obstacle detection device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] FIG. 1 is a schematic plan view of an obstacle detection device 10 according to an embodiment of the present invention. The obstacle detection device 10 according to the embodiment is configured to determine whether or not an obstacle is present within a monitoring area MA set for a railroad crossing RC, and to output an obstacle detection signal when it is determined that an obstacle is present or that there is a possibility that an obstacle is present. Although not particularly limited, in this embodiment, the monitoring area MA is set as a substantially rectangular area in a plan view that includes all or most of the railroad crossing RC, and the four corners C1 to C4 of the monitoring area MA are located outside the railroad crossing RC. Note that T1 and T2 in FIG. 1 indicate tracks on which trains travel.

[0011] Referring to FIG. 1, the obstacle detection device 10 includes a laser distance measuring sensor 11, a reflector 13, first to fifth mirrors 15a to 15e, a processing unit 17, and a wireless communication unit 19.

[0012] The laser ranging sensor 11 is a so-called ToF sensor, and is placed outside the monitoring area MA and near a first corner C1 of the monitoring area MA. The laser ranging sensor 11 is configured to scan (two-dimensionally scan) a laser beam within a predetermined range including the monitoring area MA in a plane parallel to the road surface of the railroad crossing RC (i.e., a horizontal plane), and to receive the laser beam reflected by an object.

[0013] Specifically, the laser ranging sensor 11 is capable of (a) emitting laser light by changing the emission direction at predetermined angles within an angular range that covers the monitoring area MA along a plane (horizontal plane) parallel to the road surface of the railroad crossing RC, (b) receiving the reflected light of the emitted laser light by an object, and (c) calculating the distance to the reflection position of the laser light based on the time difference between the emission timing of the laser light and the reception timing of the reflected light of the laser light.

[0014] The reflector 13 is a device that reflects laser light, and is disposed outside the monitoring area MA and near a fourth corner C4 of the monitoring area MA. The reflector 13 is configured to reflect incident light in the direction of the incident light, i.e., to retroreflect the incident light.

[0015] In this embodiment, the laser ranging sensor 11 and the reflector 13 are arranged on the same side of the monitoring area MA, i.e., on one side (the right side in FIG. 1) of the monitoring area MA. The laser ranging sensor 11 and the reflector 13 are spaced apart in a direction intersecting the tracks T1 and T2, in other words, in the direction in which people, vehicles, etc. move across the railroad crossing RC.

[0016] The first to fifth mirrors 15a to 15e are reflective mirror devices that reflect laser light and are arranged outside the monitoring area MA. The first to fifth mirrors 15a to 15e are configured to reflect incident light in directions symmetrical with respect to the normal to the mirror surface (surface normal).

[0017] The first mirror 15a, the third mirror 15c, and the fifth mirror 15e are arranged on the opposite side of the monitoring area MA from the laser distance measuring sensor 11 and the reflector 13, i.e., on the other side (the left side in FIG. 1) of the monitoring area MA. The first mirror 15a, the third mirror 15c, and the fifth mirror 15e are spaced apart from each other in a direction intersecting the lines T1 and T2.

[0018] The second mirror 15b and the fourth mirror 15d are arranged on the same side of the monitoring area MA as the laser distance measuring sensor 11 and the reflector 13, i.e., on the one side of the monitoring area MA. The second mirror 15b and the fourth mirror 15d are arranged between the laser distance measuring sensor 11 and the reflector 13, and are spaced apart from each other in a direction intersecting the lines T1 and T2.

[0019] The first mirror 15a is installed so as to reflect, toward the second mirror 15b, the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a and incident on it. The second mirror 15b is installed so as to reflect, toward the third mirror 15c, the laser light reflected by the first mirror 15a and incident on it. The third mirror 15c is installed so as to reflect, toward the fourth mirror 15d, the laser light reflected by the second mirror 15b and incident on it. The fourth mirror 15d is installed so as to reflect, toward the fifth mirror 15e, the laser light reflected by the third mirror 15c and incident on it. The fifth mirror 15e is installed so as to reflect, toward the reflector 13, the laser light reflected by the fourth mirror 15d and incident on it.

[0020] 2 is a diagram showing the propagation path of laser light emitted from laser distance measuring sensor 11 in the direction of first mirror 15a. The laser light emitted from laser distance measuring sensor 11 in the direction of first mirror 15a passes through monitoring area MA and passes through first to fifth mirrors 15a to 15e, i.e., is reflected by the first to fifth mirrors 15a to 15e and is guided to reflector 13 (see arrows). The laser light guided to reflector 13 is reflected (retroreflected) by reflector 13. The laser light reflected by reflector 13 passes through monitoring area MA and is guided to laser distance measuring sensor 11 via the fifth to first mirrors 15e to 15a and is received by laser distance measuring sensor 11 (see block arrows).

[0021] 1, the processing unit 17 stores information relating to the monitoring area MA, the laser distance measuring sensor 11, the reflector 13, and the first to fifth mirrors 15a to 15e. For example, the processing unit 17 stores the position (direction and distance) of each point on the boundary of the monitoring area MA, the position of the reflector 13, and the positions of the first to fifth mirrors 15a to 15e, relative to the position of the laser distance measuring sensor 11.

[0022] Information such as the direction of laser light emission and the distance to the reflection position of the emitted laser light is input to the processing unit 17 from the laser distance measuring sensor 11. In addition, the processing unit 17 receives a detection signal from a train detection unit 51 that detects that a train is approaching a railroad crossing RC, a detection signal from an approach detection unit 52 that detects that a train has entered a railroad crossing RC, and a detection signal from an exit detection unit 53 that detects that a train has exited a railroad crossing RC.

[0023] The processing unit 17 is configured to perform obstacle determination processing on the monitoring area MA, and to output an obstacle detection signal when it determines that an obstacle is present within the monitoring area MA or that there is a possibility that an obstacle is present within the monitoring area MA. Although not particularly limited, in this embodiment, the processing unit 17 performs obstacle determination processing when a detection signal from the train detection unit 51 is input, in other words, when a train approaches the railroad crossing RC and a railroad crossing safety device (such as a railroad crossing alarm or crossing barrier) (not shown) installed on the railroad crossing RC begins to operate. Then, when it determines that an obstacle is present within the monitoring area MA or that there is a possibility that an obstacle is present within the monitoring area MA, the processing unit 17 outputs an obstacle detection signal to the wireless communication unit 19, and transmits the signal from the wireless communication unit 19 to the train approaching the railroad crossing RC, a management center, etc.

[0024] 3 and 4 are flowcharts showing an example of obstacle determination processing performed by (the processing unit 17 of) the obstacle detection device 10. This flowchart starts when a detection signal from the train detection unit 51 is input, that is, when a train approaches a railroad crossing RC.

[0025] In step S11, the processing unit 17 determines whether or not the train has entered the railroad crossing RC. This determination is made, for example, based on whether or not a detection signal has been input from the entry detection unit 52. If the train has not entered the railroad crossing RC, i.e., if a detection signal has not been input from the entry detection unit 52, the processing unit 17 proceeds to processing in step S12. On the other hand, if the train has entered the railroad crossing RC, i.e., if a detection signal has been input from the entry detection unit 52, the processing unit 17 ends this flow. Note that the reason this flow ends when the train has entered the railroad crossing RC is mainly to prevent the train from being judged as an obstacle.

[0026] In step S12, the processing unit 17 receives an input of the direction of emission of the laser light from the laser distance measuring sensor 11 and the distance to the position where the laser light is reflected.

[0027] In step S13, the processing unit 17 determines whether the emission direction of the laser light is the direction of the first mirror 15a, in other words, whether the laser light is laser light that is guided to the reflector 13. If the emission direction of the laser light is not the direction of the first mirror 15a, the processing unit 17 proceeds to the process of step S14. In this case, a normal obstacle determination based on the reflection position of the laser light is performed. On the other hand, if the emission direction of the laser light is the direction of the first mirror 15a, the processing unit 17 proceeds to the process of step S21 (FIG. 4). In this case, an obstacle determination using the reflector 13 is performed.

[0028] In step S14, the processing unit 17 determines whether the reflected position of the laser beam is within the monitoring area MA. If the reflected position of the laser beam is within the monitoring area MA, the processing unit 17 proceeds to the processing of step S15. On the other hand, if the reflected position of the laser beam is not within the monitoring area MA, the processing unit 17 returns to the processing of step S11.

[0029] In step S15, the processing unit 17 determines whether the reflected position of the laser beam is the same as the previous position. If the reflected position of the laser beam is the same as the previous position, the processing unit 17 proceeds to the process of step S16. On the other hand, if the reflected position of the laser beam is different from the previous position, the processing unit 17 stores the reflected position of the laser beam and returns to the process of step S11.

[0030] In step S16, processing unit 17 determines whether the laser beam is reflected at the same position Na times in a row. Na is an integer equal to or greater than 3 and is set in advance. If the laser beam is reflected at the same position Na times in a row, processing unit 17 proceeds to step S17. On the other hand, if the laser beam is not reflected at the same position Na times in a row, processing unit 17 counts up the number of times the laser beam is reflected at the same position and returns to step S11.

[0031] In step S17, the processing unit 17 assigns the reflection positions of the laser beam Na times in succession to meshes for object tracking. Specifically, in this embodiment, the monitoring area MA is divided into N×M meshes, and among these meshes, a mesh corresponding to the reflection positions of the laser beam Na times in succession is identified.

[0032] In step S18, the processing unit 17 determines whether or not the reflection positions of the laser beam Na consecutive times are present within the same mesh for a predetermined period of time or more. If the reflection positions of the laser beam Na consecutive times are present within the same mesh for a predetermined period of time or more, the processing unit 17 proceeds to the processing of step S19. On the other hand, if the reflection positions of the laser beam Na consecutive times are not present within the same mesh for a predetermined period of time or more, the processing unit 17 returns to the processing of step S11.

[0033] In step S19, the processing unit 17 determines that an obstacle is present in the monitoring area MA.

[0034] In step S20, the processing unit 17 outputs an obstacle detection signal. Specifically, the processing unit 17 outputs the obstacle detection signal to the wireless communication unit 19, which then transmits the signal to a train approaching the railroad crossing RC, a management center, etc.

[0035] If the emission direction of the laser light is the direction of first mirror 15a in the process of step S13, processing unit 17 determines in step S21 whether the light reflected by reflector 13 has been received by laser distance measuring sensor 11. This determination is made, for example, based on whether the distance to the reflection position of the laser light matches the distance of the propagation path of the laser light to reflector 13. The distance of the propagation path of the laser light to reflector 13 is the length of the path (see FIG. 2) along which the laser light emitted from laser distance measuring sensor 11 in the direction of first mirror 15a passes through first to fifth mirrors 15a to 15e, i.e., is reflected by first to fifth mirrors 15a to 15e, and reaches reflector 13, and is set in advance as a value including a tolerance. If the distance to the reflection position of the laser light matches the distance of the propagation path of the laser light to reflector 13, processing unit 17 determines that the light reflected by reflector 13 of the laser light emitted from laser distance measuring sensor 11 has been received by laser distance measuring sensor 11. In this case, processing unit 17 returns to the process of step S11. On the other hand, if the distance to the reflection position of the laser light does not match the propagation distance of the laser light to reflector 13, processing unit 17 determines that the reflected light of the laser light emitted from laser distance measuring sensor 11 by reflector 13 is not received by laser distance measuring sensor 11. In this case, processing unit 17 proceeds to the process of step S22.

[0036] In step S22, the processing unit 17 counts up the count value cnt, which indicates the number of times that the laser light emitted from the laser distance measuring sensor 11 and reflected by the reflector 13 is not received by the laser distance measuring sensor 11.

[0037] In step S23, the processing unit 17 determines whether the count value cnt is equal to or greater than Nb. Nb is an integer equal to or greater than 2 and is set in advance. If the count value cnt is equal to or greater than Nb, that is, if the laser distance measuring sensor 11 has not received the laser light reflected by the reflector 13 of the laser light emitted from the laser distance measuring sensor 11 Nb times or more, the processing unit 17 proceeds to step S24. On the other hand, if the count value cnt is less than Nb, the processing unit 17 returns to the processing of step S11.

[0038] In step S24, the processing unit 17 determines that there is a possibility that an obstacle is present within the monitoring area MA, and in step S20, the processing unit 17 outputs an obstacle detection signal.

[0039] As described above, the obstacle detection device 10 according to the embodiment is configured so that the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a passes through the monitoring area MA and is guided to the reflector 13 via the first to fifth mirrors 15a to 15e. The laser light guided to the reflector 13 is reflected by the reflector 13, and the laser light reflected by the reflector 13 passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the fifth to first mirrors 15e to 15a, and is received by the laser distance measuring sensor 11.

[0040] Here, if the laser distance measuring sensor 11 does not receive the reflected light of the laser light from the reflector 13 that is emitted in the direction of the first mirror 15a, there is a possibility that there is an object blocking the laser light along the propagation path of the laser light to the reflector 13, and therefore within the monitoring area MA. In particular, if the laser distance measuring sensor 11 does not receive the reflected light of the laser light from the reflector 13 that is emitted in the direction of the first mirror 15a multiple times, there is a high possibility that the object blocking the laser light will become an obstacle within the monitoring area MA, and objects that block the laser light include not only objects with high reflectivity for laser light but also objects with low reflectivity for laser light.

[0041] Then, when the light reflected by the reflector 13 is not received by the laser distance measuring sensor 11 multiple times, the processing unit 17 of the obstacle detection device 10 determines that there is a possibility that an obstacle is present within the monitoring area MA, and outputs an obstacle detection signal (see steps S21 to S24 and S20 in FIGS. 3 and 4). Therefore, the obstacle detection device 10 according to the embodiment can prevent failure to detect obstacles with low reflectivity of laser light.

[0042] Furthermore, the processing unit 17 of the obstacle detection device 10 determines that the laser distance measuring sensor 11 does not receive the reflected light from the reflector 13 when the distance to the reflection position of the laser light emitted in the direction of the first mirror 15a, i.e., the laser light guided to the reflector 13, does not match the propagation distance of the laser light to the reflector 13. Therefore, when the reflected light of the laser light emitted in the direction of the first mirror 15a by an object other than the reflector 13 is received, the reflected light can be prevented from being erroneously recognized as the reflected light from the reflector 13.

[0043] Furthermore, in addition to the obstacle determination using the reflector 13 as described above, the processing unit 17 of the obstacle detection device 10 also performs a normal obstacle determination based on the reflected position of the laser light. That is, in the obstacle detection device 10, the laser distance measuring sensor 11 is configured to scan a predetermined range including the monitoring area MA with a laser light and receive the reflected light, and the processing unit 17 of the obstacle detection device 10 determines that an obstacle is present in the monitoring area MA when the reflected position of the laser light is within the monitoring area MA, and outputs an obstacle detection signal (see steps S14 to S20 in FIG. 3). Therefore, the obstacle detection device 10 according to the embodiment can stably detect obstacles in the monitoring area MA while suppressing detection omissions of obstacles with low reflectivity of laser light.

[0044] In the above-described embodiment, the obstacle detection device 10 determines whether or not there is an obstacle in a monitoring area MA set for the railroad crossing RC. However, this is not limited to this, and the obstacle detection device 10 may be configured to determine whether or not there is an obstacle in any monitoring area.

[0045] In the above-described embodiment, the processing unit 17 of the obstacle detection device 10 determines whether the train has entered the railroad crossing RC to prevent the train from being mistakenly determined to be an obstacle, and terminates the obstacle detection process when the train has entered the railroad crossing RC. However, this is not limited to this. For example, the processing unit 17 of the obstacle detection device 10 may be configured to perform obstacle determination until the train exits the railroad crossing RC, and to stop outputting the obstacle detection signal from the time the train enters the railroad crossing RC until the time the train exits the railroad crossing RC.

[0046] In the above embodiment, the processing unit 17 of the obstacle detection device 10 determines that there may be an obstacle in the monitoring area MA when the laser distance measuring sensor 11 fails to receive the light reflected by the reflector 13 multiple times, and outputs an obstacle detection signal. However, this is not limited to this. The processing unit 17 may be configured to determine that there may be an obstacle in the monitoring area MA and output an obstacle detection signal when the laser distance measuring sensor 11 fails to receive the light reflected by the reflector 13.

[0047] Furthermore, in the above-described embodiment, the laser distance measuring sensor 11 and the reflector 13 are arranged on one side of the monitoring area MA, the first mirror 15a, the third mirror 15c, and the fifth mirror 15e are arranged on the same side of the monitoring area MA as the laser distance measuring sensor 11 and the reflector 13, and the second mirror 15b and the fourth mirror 15d are arranged on the other side of the monitoring area MA. However, this is not limited to this. Several modified examples are shown below. Note that in the following descriptions of each modified example, the same aspects as those of the above-described embodiment are omitted.

[0048] (First Modification) 5 is a diagram showing a first modified example of the obstacle detection device 10. In the first modified example, the obstacle detection device 10 includes a laser ranging sensor 11, first and second reflectors 13a and 13b, first to third mirrors 15a to 15c, a processing unit 17, and a wireless communication unit 19. The laser ranging sensor 11, the first reflector 13a, and the second reflector 13b are arranged on one side of the monitoring area MA and are spaced apart from each other in a direction intersecting the tracks T1 and T2. The first to third mirrors 15a to 15c are arranged on the other side of the monitoring area MA and are spaced apart from each other in a direction intersecting the tracks T1 and T2.

[0049] In the first modification, the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a passes through the monitoring area MA and is guided to the first reflector 13a via the first mirror 15a and is reflected by the first reflector 13a. The laser light reflected by the first reflector 13a passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the first mirror 15a and is received by the laser distance measuring sensor 11.

[0050] Furthermore, the laser light emitted from the laser distance measuring sensor 11 in the direction of the second mirror 15b passes through the monitoring area MA and is guided to the second reflector 13b via the second mirror 15b and is reflected by the second reflector 13b. The laser light reflected by the second reflector 13b passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the second mirror 15b and is received by the laser distance measuring sensor 11.

[0051] Furthermore, the laser light emitted from the laser distance measuring sensor 11 in the direction of the third mirror 15c passes through the monitoring area MA and is guided to the second reflector 13b via the third mirror 15c and reflected by the second reflector 13b. The laser light reflected by the second reflector 13b passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the third mirror 15c and received by the laser distance measuring sensor 11.

[0052] In the first variant, the processing unit 17 can be configured to output an obstacle detection signal not only when the reflection position of the laser light is within the monitoring area MA, but also when (1) the laser ranging sensor 11 does not receive the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the first mirror 15a by the first reflector 13a, (2) the laser ranging sensor 11 does not receive the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the second mirror 15b by the second reflector 13b, or (3) the laser ranging sensor 11 does not receive the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the third mirror 15c by the second reflector 13b.

[0053] The first modified example also provides the same effects as those of the above-described embodiment.

[0054] (Second Modification) 6 is a diagram showing a second modified example of the obstacle detection device 10. In the second modified example, the obstacle detection device 10 includes a laser ranging sensor 11, a reflector 13, first to fourth mirrors 15a to 15d, a processing unit 17, and a wireless communication unit 19. The laser ranging sensor 11 and the reflector 13 are disposed diagonally opposite each other with a monitoring area MA in between. The first and third mirrors 15a and 15c are disposed on the same side of the monitoring area MA as the laser ranging sensor 11 and are spaced apart from each other in a direction intersecting the tracks T1 and T2. The second and fourth mirrors 15b and 15d are disposed on the same side of the monitoring area MA as the reflector 13 and are spaced apart from each other in a direction intersecting the tracks T1 and T2.

[0055] In the second modified example, the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a passes through the monitoring area MA and is guided to the reflector 13 via the first to fourth mirrors 15a to 15d, and is reflected by the reflector 13. The laser light reflected by the reflector 13 passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the fourth to first mirrors 15d to 15a, and is received by the laser distance measuring sensor 11.

[0056] In the second variant, the processing unit 17 can be configured to output an obstacle detection signal not only when the reflection position of the laser light is within the monitoring area MA, but also when the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the first mirror 15a by the reflector 13 is not received by the laser ranging sensor 11.

[0057] The second modified example also provides the same effects as those of the above-described embodiment.

[0058] In the second modified example, the second mirror 15b and the third mirror 15c can be omitted by adjusting the installation states of the first and fourth mirrors 15a and 15d. In this case, the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a passes through the monitoring area MA and is guided to the reflector 13 via the first and fourth mirrors 15a and 15d and reflected by the reflector 13. The laser light reflected by the reflector 13 passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the first and fourth mirrors 15d and 15a and received by the laser distance measuring sensor 11. The processing unit 17 can be configured to output an obstacle detection signal not only when the reflection position of the laser light is within the monitoring area MA but also when the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a and reflected by the reflector 13 is not received by the laser distance measuring sensor 11.

[0059] (Third Modification) FIG. 7 is a diagram showing a third modified example of the obstacle detection device 10. In the third modified example, the obstacle detection device 10 includes a laser ranging sensor 11, a reflector 13, first to third mirrors 15a to 15c, a processing unit 17, and a wireless communication unit 19. The laser ranging sensor 11 and the reflector 13 are disposed on one side of the monitoring area MA and are spaced apart in a direction intersecting the tracks T1 and T2. The first and third mirrors 15a and 15c are disposed on the other side of the monitoring area MA and are spaced apart in a direction intersecting the tracks T1 and T2. The second mirror 15b is disposed between the laser ranging sensor 11 and the reflector 13 on the one side of the monitoring area MA.

[0060] In the third modified example, the laser light emitted from the laser distance measuring sensor 11 in the direction of the first mirror 15a passes through the monitoring area MA and is guided to the reflector 13 via the first to third mirrors 15a to 15c and is reflected by the reflector 13. The laser light reflected by the reflector 13 passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the third to first mirrors 15c to 15a and is received by the laser distance measuring sensor 11.

[0061] In the third variant, the processing unit 17 can be configured to output an obstacle detection signal not only when the reflection position of the laser light is within the monitoring area MA, but also when the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the first mirror 15a by the reflector 13 is not received by the laser ranging sensor 11.

[0062] The third modified example also provides the same effects as those of the above-described embodiment.

[0063] (Fourth Modification) 8 is a diagram showing a fourth modified example of the obstacle detection device 10. In the fourth modified example, the obstacle detection device 10 includes a laser ranging sensor 11, first and second reflectors 13a and 13b, a mirror 15, a processing unit 17, and a wireless communication unit 19. The laser ranging sensor 11 and the first reflector 13a are arranged on one side of the monitoring area MA, with a railway line T sandwiched between them. The second reflector 13b and the mirror 15 are arranged on the other side of the monitoring area MA, with the railway line T sandwiched between them.

[0064] In the fourth modified example, the laser light emitted from the laser distance measuring sensor 11 in the direction of the mirror 15 passes through the monitoring area MA and is guided to the first reflector 13a via the mirror 15 and reflected by the first reflector 13a. The laser light reflected by the first reflector 13a passes through the monitoring area MA and is guided to the laser distance measuring sensor 11 via the mirror 15 and received by the laser distance measuring sensor 11. The laser light emitted from the laser distance measuring sensor 11 in the direction of the second reflector 13b passes through the monitoring area MA and is reflected by the second reflector 13b, and the laser light reflected by the second reflector 13b is received by the laser distance measuring sensor 11.

[0065] In the fourth variant, the processing unit 17 can be configured to output an obstacle detection signal when, in addition to when the reflection position of the laser light is within the monitoring area MA, (1) the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the mirror 15 by the first reflector 13a is not received by the laser ranging sensor 11, or (2) the reflected light of the laser light emitted from the laser ranging sensor 11 in the direction of the second reflector 13b by the second reflector 13b is not received by the laser ranging sensor 11.

[0066] The fourth modified example also provides the same effects as those of the above-described embodiment.

[0067] The above describes the embodiments of the present invention and their modifications. However, the present invention is not limited to the above-described embodiments and modifications, and it goes without saying that further modifications and changes are possible based on the technical concept of the present invention. [Explanation of symbols]

[0068] 10... Obstacle detection device, 11... Laser distance measurement sensor, 13... Reflector, 13a... First reflector, 13b... Second reflector, 15... Mirror, 15a to 15e... First to fifth mirrors, 17... Processing unit, 19... Wireless communication unit, 51... Train detection unit, 52... Approach detection unit, 53... Exit detection unit, RC... Railroad crossing, T, T1, T2... Railroad tracks

Claims

1. An obstacle detection device comprising a laser ranging sensor, a reflector that retroreflects incident light, and one or more mirrors that reflect the incident light in a direction symmetrical to the surface normal, wherein the laser light emitted from the laser ranging sensor passes through a monitoring area and is guided to the reflector via the one or more mirrors, and wherein the obstacle detection device outputs an obstacle detection signal when the laser light reflected by the reflector is not received by the laser ranging sensor.

2. 2. The obstacle detection device according to claim 1, wherein the laser ranging sensor determines that the reflected light of the laser light by the reflector is not received when the distance to the reflection position of the laser light does not match the distance of the propagation path of the laser light to the reflector via the one or more mirrors.

3. the laser distance measuring sensor and the reflector are disposed diagonally opposite each other across the monitoring area, the one or more mirrors include one or more mirrors arranged on the same side of the monitoring area as the laser distance measuring sensor, and one or more mirrors arranged on the same side of the monitoring area as the reflector. The obstacle detection device according to claim 1 .

4. the laser distance measuring sensor and the reflector are disposed on one side of the monitoring area, the one or more mirrors are mirrors arranged on the other side of the monitoring area, or include one or more mirrors arranged between the laser distance measuring sensor and the reflector on the one side and two or more mirrors arranged on the other side; The obstacle detection device according to claim 1 .

5. An obstacle detection device as described in any one of claims 1 to 4, wherein the laser ranging sensor is configured to scan a laser light within a predetermined range including the monitoring area and receive reflected light of the laser light, and outputs an obstacle detection signal when the reflected position of the laser light is within the monitoring area.

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