Object detection device and object detection method

Abstract

To improve the accuracy of object detection by improving separability between an object to be detected and an object to be excluded.SOLUTION: The object detection device 10 includes the distance measurer 12 that transmits the detection wave and receives the reflected wave of the transmitted detection wave reflected by the object, the extractor 20 that extracts the reflected wave to be used for determining the object detection based on the calculation result of the distance measurer 12, and the determiner 22 that determines the object detection by using the extracted reflected wave. The extracting unit 20 extracts a reflected wave to be used by the determining unit 22 from among the reflected waves of the respective detection waves received by the distance measuring unit 12, on the basis of a restriction distance from the distance measuring unit 12, which is determined in advance on the basis of the detection sensitivity of the distance measuring unit 12, and the position of an object that has reflected each reflected wave. As a result, since the determination of the object detection can be performed in a state where the separability between the object to be detected and the object to be excluded is increased, the accuracy of the object detection can be improved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an object detection device and an object detection method used in the industrial field for detecting an object within a preset detection area. [Background technology]

[0002] Among object detection devices used in industrial applications, devices using so-called time-of-flight (ToF) ranging methods transmit detection waves based on light or radio waves and measure the time it takes for the detection waves to reflect off the object and return, thereby determining the distance to the object. Here, the detection waves reflected by the object and measured by the device are referred to as "reflected waves" or "echoes." Certain ranging methods have the ability to obtain multiple echoes from the same ranging angle direction, which is called "multi-echo." Multi-echoes tend to be obtained particularly when there are disturbances such as rain or snow, and solid objects are present in the environment. In such cases, it is necessary to select the echoes to be used so that objects to be detected (e.g., solid objects) are detected and objects to be removed (e.g., disturbance objects) are removed. Common echo-receiving algorithms include, for example, the following:

[0003] The result obtained by measuring reflected waves using a typical TDC (Time to Digital Converter) circuit is usually a single echo, and even in situations where multiple echoes occur, only one echo is measured for each detected wave. In contrast, if the reflected waves are captured using an ADC (Analog to Digital Converter), it is possible to capture the reflected waves as multiple echoes in situations where multiple echoes occur. There are algorithms that simply adopt the most recent echo from the multiple echoes captured in this way (see, for example, Patent Documents 1 to 3), and algorithms that adopt the most recent echo within the detection area. Another algorithm measures the first and second echoes in order of proximity to the ranging means, and if the first echo matches a pre-registered pattern that indicates a high probability of disturbance, rejects the first echo and adopts the second echo (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-085125 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-021980 [Patent Document 3] Japanese Patent Application Publication No. 2019-219329 [Patent Document 4] Japanese Patent Application Publication No. 08-122437 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, with the single-echo method described above, even in situations where multiple echoes occur, only the time of the first echo is measured, which poses a problem: this must be used as the distance measurement point for the object. More specifically, if an object such as rain or snow is present, this is used as the distance measurement point, and solid objects behind it are not measured. Furthermore, with multiple echoes, the algorithm that simply uses the rearmost echo is based on the assumption that, because front echoes have high transparency and the rearmost echo is a solid object, there is a high probability that the front echo is rain or snow, not a solid object. However, contrary to this assumption, if a solid object to be detected is present within the detection area, this may be measured as a front echo, which could result in the solid object not being detected.

[0006] More specifically, for example, if a person is walking within the detection area and a structure exists behind the person outside the detection area, the structure will be the rearmost echo, while the person (especially a thin, unstable object such as a foot) will be the frontmost echo, resulting in the person's foot not being detected. To address this issue, some algorithms, such as those described above, limit the detection area to employ the rearmost echo in order to improve object detectability. However, this approach has the disadvantage of potentially employing echoes from rain or snow. Furthermore, the algorithm described above, which employs the second echo only when the first echo is present in close proximity, is considered to be effective in preventing the misuse of echoes from rain or snow. However, this algorithm fails to detect solid objects when both the first and second echoes are disturbance objects and the third echo is the solid object to be detected. This situation is likely to occur frequently.

[0007] The present invention has been made in view of the above-mentioned problems, and an object thereof is to improve the separation ability between objects to be detected and objects to be rejected, thereby improving the accuracy of object detection. [Means for solving the problem]

[0008] (Aspects of the invention) The following embodiments of the present invention are examples of the configuration of the present invention, and are described in terms to facilitate understanding of the various configurations of the present invention. Each term does not limit the technical scope of the present invention, and while taking into consideration the best mode for carrying out the invention, some of the components of each term may be replaced or deleted, or other components may be added, and these may also be included in the technical scope of the present invention.

[0009] (1) An object detection device used in the industrial field for detecting objects within a predetermined detection area, comprising: a time-of-flight distance measuring unit that continuously emits detection waves while gradually changing direction so as to cover the detection area, and receives reflected waves from the emitted detection waves reflected by an object each time the detection wave is emitted, and if there are multiple reflected waves for one detection wave, receives those multiple reflected waves and calculates the distance to the object that reflected each of the reflected waves; an extraction unit that extracts reflected waves to be used in determining object detection based on the calculation results of the distance measuring unit; and a determination unit that uses the reflected waves extracted by the extraction unit to determine object detection, wherein the extraction unit extracts the reflected waves to be used in the determination unit from the reflected waves for each detection wave received by the distance measuring unit based on a limited distance from the distance measuring unit that is predetermined based on the detection sensitivity of the distance measuring unit and the position of the object that reflected each of the reflected waves.

[0010] The object detection device described in this section is for detecting objects within a predetermined detection area and includes a distance measurement unit, an extraction unit, and a determination unit. The distance measurement unit is a so-called time-of-flight type that transmits detection waves such as light or radio waves, receives reflected waves (echoes) that hit the object and are reflected, and calculates the distance from the distance measurement unit to the object from the time between the transmission of the detection wave and the reception of the reflected wave. In this case, the distance measurement unit continuously transmits detection waves while gradually changing the transmission direction of the detection waves (ranging angle), thereby measuring the entire detection area. Furthermore, the distance measurement unit is compatible with so-called multi-echo, and if there are multiple reflected waves from one detection wave at each ranging angle, it receives the multiple reflected waves and measures the distance for each.

[0011] The extraction unit extracts reflected waves to be used for determining object detection from the reflected waves for each detection wave received by the distance measurement unit at each distance measurement angle based on the calculation results of the distance measurement unit. More specifically, the extraction unit extracts reflected waves to be used for determining object detection based on a predetermined limit distance from the distance measurement unit and the position of the object that reflected each reflected wave. The limit distance used here is determined based on the detection sensitivity of the distance measurement unit and is the distance to the boundary of a high-sensitivity area close to the distance measurement unit, where disturbance objects such as rain or snow are easily detected due to the characteristic of detection waves that gradually spread and are therefore dense in close range. Therefore, the extraction unit excludes reflected waves from disturbance objects based on the determined limit distance and the positional relationship between the object and the object, and extracts reflected waves to be used for determining object detection.

[0012] The determination unit then uses the reflected waves extracted by the extraction unit as described above from the reflected waves for each detection wave at each distance measurement angle received by the distance measurement unit to determine whether an object has been detected. This allows for determination of whether an object has been detected to be performed with improved rejection of disturbance objects, in other words, with improved separation between objects to be detected and objects to be rejected. This improves the detectability of objects to be detected while suppressing false detection of disturbance objects to be rejected, thereby improving the accuracy of object detection. Consequently, various advantages can be enjoyed depending on how the object detection device described in this section is used in industrial fields.

[0013] (2) In the above paragraph (1), the extraction unit identifies the reflected wave reflected by the object located farthest from the distance measuring unit, among the reflected waves for each detection wave received by the distance measuring unit, as the rearmost reflected wave, and identifies the reflected wave reflected by the object located farthest from the distance measuring unit within the detection area as the rearmost reflected wave within the area, and extracts the rearmost reflected wave within the area as the reflected wave to be used in the judgment unit when the object that reflected the rearmost reflected wave within the area is located at a position greater than the limit distance from the distance measuring unit, and when the object that reflected the rearmost reflected wave within the area is located at a position less than the limit distance from the distance measuring unit and the rearmost reflected wave within the area is the same as the rearmost reflected wave.

[0014] In the object detection device described in this section, when extracting reflected waves to be used in the determination unit from the reflected waves (echoes) for each detection wave received by the distance measurement unit at each distance measurement angle, the extraction unit performs the extraction as follows. Specifically, the extraction unit first identifies, from the reflected waves for each detection wave, the reflected wave reflected by the object located farthest from the distance measurement unit as the rearmost reflected wave based on the calculation results of the distance measurement unit. That is, since the distance measurement unit calculates the distance to the object that reflected each reflected wave, the extraction unit identifies, from the reflected waves for each detection wave, the reflected wave reflected by the object located farthest from the distance measurement unit as the rearmost reflected wave within the detection area based on the positional relationship between a predetermined detection area and the object that reflected each reflected wave.

[0015] If the object that reflected the in-area rearmost reflected wave is located at a distance equal to or greater than the limit distance described in (1) above from the distance measurement unit, the extraction unit determines that the object is unlikely to be a disturbance object and extracts the in-area rearmost reflected wave as the reflected wave to be used in the determination unit. That is, even if multiple reflected waves are generated by a disturbance object within the detection area, if there is a reflected wave from an object to be detected within the detection area behind that, the extraction unit extracts that reflected wave as the reflected wave to be used in the determination unit. Furthermore, even if the object that reflected the in-area rearmost reflected wave is located less than the limit distance from the distance measurement unit, if the in-area rearmost reflected wave is the same as the rearmost reflected wave, there is no reflected wave from behind that object, and that object may be the object to be detected. Therefore, the extraction unit extracts the in-area rearmost reflected wave as the reflected wave to be used in the determination unit. In other words, the extraction unit does not extract any reflected waves that match the reflected waves to be used in the determination unit in cases other than the two above-mentioned cases, including the following patterns:

[0016] First, the extraction unit does not extract the reflected wave if the object that reflected the in-area rearmost reflected wave is located within a limited distance from the distance measurement unit and if a rearmost reflected wave exists in addition to the in-area rearmost reflected wave. In other words, if an object that reflected the in-area rearmost reflected wave exists behind the object that reflected the in-area rearmost reflected wave, which is located within a limited distance from the distance measurement unit, the extraction unit determines that there is no object to be detected and does not extract the reflected wave to be used by the determination unit, because it is highly likely that the object that reflected the in-area rearmost reflected wave is a disturbance object such as rain or snow, and that the rearmost reflected wave was reflected by a structure or other object outside the detection area further behind. In this way, the extraction unit also uses reflected waves caused by structures or other objects outside the detection area to select and discard reflected waves. Furthermore, when identifying the rearmost reflected wave, if the distance measurement unit sends a detection wave but there is no reflected wave in response to it, the extraction unit determines that there is no object that reflects the detection wave and does not extract the reflected wave to be used by the determination unit. Furthermore, when identifying the rearmost reflected wave within the area, even if all of the reflected waves for a single detection wave sent out by the ranging unit at a certain ranging angle are outside the detection area, the extraction unit assumes that no object is present within the detection area and does not extract the reflected wave to be used in the judgment unit.

[0017] The above-described extraction method is based on the following findings: when multiple echoes occur, if the cause of the forward echo is rain or snow, it occurs mainly in the high-sensitivity region close to the ranging unit; if the cause of the forward echo occurs in the detection region farther away, it is primarily due to a solid object to be detected; and two or more echoes can occur in a close-range disturbance. These findings were discovered by the inventors through experiments, etc. This allows for the detection of objects to be detected that would have been undetectable in conventional technology without degrading the performance of rejecting disturbance objects. Moreover, even in cases not considered in conventional technology, where two or more echoes of disturbance objects to be rejected, such as rain, snow, fog, or dust, occur within the same ranging angle and a limited distance, objects to be detected in the detection region further behind the disturbance object can be reliably detected.

[0018] (3) In the above (1) and (2), the object detection device is configured such that the detection area is set at a railroad crossing. The object detection device described in this section is applied to railroad crossings, and a detection area is set at the railroad crossing. This allows for accurate object detection at railroad crossings, while achieving both the ability to remove objects that should be removed, such as rain and snow, and the ability to detect objects that should be detected, such as people and automobiles. This contributes to further improving safety at railroad crossings.

[0019] (4) In the above (1) and (2), the object detection device, wherein the distance measurement unit is configured by a 2D-LiDAR. In the object detection device described in this section, the distance measurement unit is configured with a 2D-LiDAR, which emits light as a detection wave and receives the reflected light as a reflected wave (echo). In this way, by adopting a 2D-LiDAR that supports multi-echo, accurate distance measurement can be performed using a LiDAR with relatively excellent distance measurement performance, while significantly reducing costs compared to adopting a 3D-LiDAR, regardless of whether it is a single echo or multi-echo.

[0020] (5) An object detection method used in the industrial field for detecting objects within a predetermined detection area, which includes: continuously transmitting detection waves while gradually changing direction so as to cover the detection area; and receiving reflected waves from objects each time the transmitted detection wave is transmitted; and, if there are multiple reflected waves for one detection wave, receiving the multiple reflected waves and calculating the distance to the object that reflected each of the reflected waves; and, based on a limited distance from the ranging unit predetermined based on the detection sensitivity of the ranging unit and the position of the object that reflected each of the reflected waves, extracting reflected waves to be used for determining object detection from the reflected waves for each detection wave received by the ranging unit; and using the extracted reflected waves to determine object detection.

[0021] (6) In the above (5), when extracting the reflected wave to be used for determining object detection, among the reflected waves for each detection wave received by the distance measuring unit, the reflected wave reflected by the object located farthest from the distance measuring unit is identified as the rearmost reflected wave, and the reflected wave reflected by the object located farthest from the distance measuring unit within the detection area is identified as the rearmost reflected wave within the area, and the rearmost reflected wave within the area is extracted as the reflected wave to be used for determining object detection when the object that reflected the rearmost reflected wave within the area is located at a position greater than the limit distance from the distance measuring unit, and when the object that reflected the rearmost reflected wave within the area is located at a position less than the limit distance from the distance measuring unit and the rearmost reflected wave within the area is the same as the rearmost reflected wave.

[0022] (7) In the object detection method described above in (5) and (6), the detection area is set to a railroad crossing. (8) In the above (5) and (6), the object detection method uses 2D-LiDAR as the distance measurement unit. The object detection methods described in (5) to (8) are each performed using the object detection devices described in (1) to (4) above, and thereby achieve the same effects as those of the object detection devices described in (1) to (4) above. [Effects of the Invention]

[0023] Since the present invention has the above-described configuration, it is possible to enhance the separability between objects to be detected and objects to be rejected, thereby improving the accuracy of object detection. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a block diagram illustrating an example of a configuration of an object detection device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an image diagram that schematically shows an example of an arrangement in which the object detection device of FIG. 1 is applied to a railroad crossing. [Figure 3]The figures show examples of objects to be detected and objects to be excluded at railroad crossings, where (a) is a planar image including the entire detection area, and (b) is a planar image of the area near the distance measurement unit. [Figure 4] 1 is a flowchart showing an outline of a portion of an example of a procedure of an object detection method according to an embodiment of the present invention. [Figure 5] 1A to 1C are conceptual diagrams showing various cases in which reflected waves used to determine object detection are extracted in an object detection method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, detailed descriptions of parts that are the same as or corresponding to those in the prior art will be omitted, and the same reference numerals will be used throughout the drawings to indicate the same or corresponding parts. FIG. 1 shows a schematic diagram of an example of the configuration of an object detection device 10 according to an embodiment of the present invention. This object detection device 10 is used in various industrial fields to detect objects within a detection area. FIG. 2 shows, in plan view, an example of the layout of the object detection device 10 when applied to a railroad crossing 50, and FIG. 3 shows, in plan view, an example of objects to be detected at the railroad crossing 50. As shown in FIG. 1, the object detection device 10 according to the embodiment of the present invention includes a distance measurement unit 12, an extraction unit 20, and a determination unit 22, and in this embodiment, these units are included in two systems. That is, the object detection device 10 of FIG. 1 includes two distance measurement units 12A and 12B, two extraction units 20A and 20B, and two determination units 22A and 22B.

[0026] Each of the distance measuring units 12A and 12B measures distance using a time-of-flight method. For example, as shown in FIG. 2, the distance measuring units 12A and 12B transmit a detection wave, receive a reflected wave (echo) that reflects off an object 60, and calculate the distance to the object 60 that reflected the reflected wave from the time between transmitting the detection wave and receiving the reflected wave. At the same time, each of the distance measuring units 12A and 12B recognizes the direction of the object 60 that reflected the reflected wave from the direction (distance measuring angle) from which the detection wave was transmitted when the reflected wave was received. In this embodiment, each of the distance measuring units 12 is configured with a 2D-LiDAR 14 (14A, 14B), and is configured to irradiate light as a detection wave and receive the light reflected by the object 60 to measure distance. Each of the distance measuring units 12 continuously transmits detection waves while gradually changing the transmission direction (distance measuring angle) of the detection waves so as to cover a predetermined detection area 40 (see FIGS. 2 and 3).

[0027] For this reason, the 2D-LiDAR 14 constituting the distance measuring unit 12 is installed at a predetermined height suitable for object detection at the railroad crossing 50, so as to continuously emit light while gradually changing the distance measuring angle according to the resolution of the 2D-LiDAR 14, thereby measuring the entire detection area 40. In FIG. 2, the 2D-LiDAR 14A is installed so as to cover the detection area 40A set on the railroad crossing 50, and the 2D-LiDAR 14B is installed so as to cover the detection area 40B set on the railroad crossing 50. The detection areas 40A and 40B are set so as to overlap substantially entirely. In FIG. 3, it can be seen that light is continuously emitted to a portion of the detection area 40 while gradually changing the distance measuring angle. Note that FIG. 3 illustrates only one 2D-LiDAR 14 (distance measuring unit 12).

[0028] Furthermore, each of the distance measuring units 12 receives a reflected wave that is the detection wave reflected back each time the detection wave is transmitted. At this time, if there are multiple reflected waves for one detection wave, the distance measuring unit 12 receives the multiple reflected waves and measures the distance for each of the reflected waves. That is, the distance measuring unit 12 is compatible with multi-echoes, and the 2D-LiDAR 14 constituting the distance measuring unit 12 is configured to receive three or more reflected waves (echoes) and process them in an ADC in this embodiment. Note that the equipment constituting the distance measuring unit 12 is not limited to 2D-LiDAR as long as it performs distance measurement using the time-of-flight method and is compatible with multi-echoes, and may also be a type known as a 3D-LiDAR, laser radar such as millimeter-wave radar, or range sensor.

[0029] 1, each of the extraction units 20 extracts reflected waves (echoes) to be used in the determination unit 22 to determine object detection based on the calculation results of the distance measurement unit 12. In other words, it performs filtering to extract the echo of an object to be detected and eliminate other echoes. The specific extraction method of the extraction unit 20 will be described later, but will be briefly described here. The extraction unit 20 extracts reflected waves to be used in the determination unit 22 from the reflected waves received for each detection wave sent by the distance measurement unit 12 based on a predetermined limit distance 42 (see FIGS. 3(b) and 5) from the distance measurement unit 12 and the position of the object that reflected each reflected wave. In other words, the distance measurement unit 12 measures the distance for each reflected wave and calculates the distance and direction to the object that reflected each reflected wave, and therefore extracts the reflected wave based on the relationship between such object and the predetermined limit distance 42.

[0030] Here, the predetermined limit distance 42 from the distance measuring unit 12 is determined based on the detection sensitivity of the distance measuring unit 12. In this embodiment, it is determined based on the detection performance of the 2D-LiDAR 14 constituting the distance measuring unit 12. That is, the beam light emitted from the 2D-LiDAR 14 gradually diffuses and the beam diameter increases with distance, so the density is high in the area near the 2D-LiDAR 14, and in such an area, even small objects such as rain or snow tend to be easily detected. For this reason, the limit distance 42 from the distance measuring unit 12 (2D-LiDAR 14) is set to a distance that indicates the end of the high sensitivity area 44 (see FIG. 3(b)) where even small objects are easily detected, as described above. Such limit distance 42 may be set arbitrarily depending on the performance of the equipment constituting the distance measuring unit 12, the on-site environment, and the like.

[0031] Meanwhile, each of the determination units 22 uses the reflected waves extracted by the extraction unit 20 to determine whether an object has been detected, and this will be described in more detail later. The object detection device 10 of FIG. 1 has two systems: a distance measurement unit 12, an extraction unit 20, and a determination unit 22, and each system independently performs the above-described processing. That is, the object detection device 10 of FIG. 1 extracts reflected waves in the extraction unit 20A using the measurement results of the distance measurement unit 12A (2D-LiDAR 14A) in the detection area 40A, and then uses the extracted reflected waves to determine whether an object has been detected in the determination unit 22A. At the same time, the object detection device 10 of FIG. 1 extracts reflected waves in the extraction unit 20B using the measurement results of the distance measurement unit 12B (2D-LiDAR 14B) in the detection area 40B, and then uses the extracted reflected waves to determine whether an object has been detected in the determination unit 22B. Here, determination unit 22A and determination unit 22B each have a duplicate CPU and memory, and determination unit 22A compares the determination results and data in a duplicated system to check their validity, and determination unit 22B also compares the determination results and data in a duplicated system to check their validity. Object detection device 10 relays the object detection determination results of determination unit 22A and determination unit 22B to an external device, and further relays the result of combining these two determination results under an OR condition to the external device as the final determination result. To achieve the above operations, extraction units 20A and 20B and determination units 22A and 22B are configured as control devices using fail-safe CPUs.

[0032] 2, as described above, two 2D-LiDARs 14A and 14B are installed to measure detection areas 40A and 40B set at a railroad crossing 50 where a railway (railroad track 52) and a road intersect. Furthermore, FIG. 2 shows two inspection panels 30 used for checking the performance of each of the distance measuring units 12 (2D-LiDARs 14). Also, referring to FIG. 3(a), a state in which various objects exist in the vicinity of the detection area 40 is shown together with a state in which a beam of light is irradiated from one 2D-LiDAR 14 as described above.

[0033] First, within the detection area 40, there are disturbance objects 62, such as rainfall due to environmental factors, and solid objects 60, such as a human leg or part of a bicycle, whose size is relatively close to the beam diameter of the 2D-LiDAR 14. Furthermore, there are disturbance objects 62, such as rainfall, and solid objects 60, such as a human leg, between the 2D-LiDAR 14 and the detection area 40, and two structures 64, such as a pillar or a building, are present far beyond the detection area 40 based on the installation position of the 2D-LiDAR 14. FIG. 3( a) illustrates multiple light beams irradiated in the direction of one of these structures 64. In the state shown in FIG. 3( a), from the perspective of safety at the railroad crossing 50, the solid objects 60 within the detection area 40 and the solid objects 60 in front of the detection area 40 are objects to be detected, and the other disturbance objects 62 and structures 64 are objects to be removed without being detected.

[0034] 3(b) shows an enlarged view of the vicinity of the 2D-LiDAR 14 in FIG. 3(a). In FIG. 3(b), two dashed-dotted lines extending from the 2D-LiDAR 14 indicate the side end positions of the beam light emitted from the 2D-LiDAR 14, and the area between them is the irradiation range of the beam light. Furthermore, a thick arc-shaped dashed line indicates the limit distance 42 from the 2D-LiDAR 14 (distance measurement unit 12) described above, and the roughly sector-shaped area defined by the thick arc-shaped dashed line and the two dashed-dotted lines is the high sensitivity area 44 of the 2D-LiDAR 14. FIG. 3(b) illustrates three beams of light emitted from the 2D-LiDAR 14. As described with reference to FIG. 3(a), solid objects 60, such as a human foot, to be detected and disturbance objects 62, such as rain, to be removed are present within the detection area 40 and between the detection area 40 and the 2D-LiDAR 14. 3(b), a roughly triangular area defined by two dashed dotted lines and the lower edge of the detection area 40 in the drawing is shown as an obstruction area 46, which will be described later. Reference numeral 70 will also be described later.

[0035] Here, the object detection device 10 according to the embodiment of the present invention described above is not limited to the configurations shown in FIGS. 1 to 3, but can have various configurations depending on the situation, application, etc. For example, the distance measurement unit 12, extraction unit 20, and determination unit 22 are not limited to being provided in two systems, but may be provided in one system or three or more systems. Furthermore, when two or more systems are provided, a configuration may be adopted in which part of the distance measurement unit 12, extraction unit 20, or determination unit 22 is shared between the systems. Furthermore, the application of the object detection device 10 is not limited to railroad crossings 50, and the object detection device 10 according to the embodiment of the present invention can be used for various applications in various industrial fields where object detection is required.

[0036] Next, an object detection method according to an embodiment of the present invention, which uses the object detection device 10 shown in FIGS. 1 to 3, will be described in accordance with the flow of the flow diagram shown in FIG. 4, taking as an example a case where object detection is performed at a railroad crossing 50. Please refer to FIGS. 1 to 3 as appropriate for the configuration of the object detection device 10 and the state of the railroad crossing 50. Note that the flow diagram shown in FIG. 4 shows an example of a procedural flow, and the object detection method according to an embodiment of the present invention is not limited to the flow diagram of FIG. 4. For example, some of the steps shown in FIG. 4 may be deleted, changed, rearranged, or added as appropriate, depending on the configuration of the object detection device 10 and the circumstances of the application.

[0037] 4 shows, for one system of the extraction unit 20, the filtering process for extracting reflected waves for object detection in the detection area 40 by the extraction unit 20 in the object detection method according to the embodiment of the present invention. For this reason, it is assumed that the 2D-LiDAR 14 constituting the distance measurement unit 12 is installed as shown in FIG. 2 and that the following process is performed by the 2D-LiDAR 14. Laser light (detection wave) is emitted in a fan shape parallel to the crossing surface at each distance measurement angle according to the resolution. The reflected light (reflected wave, echo) is received at each distance measurement angle where the laser light is emitted, and the amount of reflected light is sampled at high speed by an ADC to obtain the reflected waveform (digital data). Peaks are extracted from the reflected waveform, and for each peak, the distance value of the echo is calculated from the peak time, and the reflection intensity of the echo is calculated from the area of ​​the peak waveform, and these are used as echo information. If there are multiple peaks, they are output as information on the "first echo," "second echo," "third echo," etc. in order of proximity from the 2D-LiDAR 14.

[0038] After the above-described processing is performed by the 2D-LiDAR 14 of each system, the extraction unit 20 of the same system starts processing as shown in FIG. 4 for the echoes obtained at each ranging angle. S10 (determining the maximum number of reflected waves N): From the calculation results of the 2D-LiDAR 14, the number of echoes obtained from the detection waves at the relevant distance measurement angle is determined, and this is set as the maximum number of reflected waves N. At this time, if no echoes are obtained at the relevant distance measurement angle, N becomes zero. S20 (determine maximum reflected wave number N): Determine whether the maximum reflected wave number N determined in S10 above is 1 or greater, in other words, whether one or more echoes have been obtained. If the result is that the maximum reflected wave number N is 1 or greater (YES), proceed to S30; if the maximum reflected wave number N is zero (NO), proceed to S120.

[0039] S30 (Identification of rearmost reflected wave): Since one or more echoes are obtained at the distance measurement angle, the Nth echo, which is the echo with the greatest number of reflected waves and the Nth echo with the furthest distance from the 2D-LiDAR 14, is identified as the rearmost reflected wave obtained at the distance measurement angle. S40 (Input loop variable K): The maximum reflected wave number N determined in S10 above is input as the loop variable K. S50 (determine loop variable K): Determine whether loop variable K is greater than or equal to 1. If loop variable K is greater than or equal to 1 (YES), proceed to S60; if loop variable K is zero (NO), proceed to S120.

[0040] S60 (detection area determination): Determine whether the position of the Kth reflected wave, which is the Kth echo, is outside the preset detection area 40. That is, if the ranging angle at which the Kth reflected wave was obtained and the distance value of the Kth reflected wave calculated by the 2D-LiDAR 14 are known, the position of the Kth reflected wave (the position of the object that reflected the Kth reflected wave) can be determined, and then determine whether it is outside the detection area 40. If the result shows that the position of the Kth reflected wave is outside the detection area 40 (YES), proceed to S70, and if the position of the Kth reflected wave is inside the detection area 40 (NO), proceed to S80.

[0041] S70 (Decrement Loop Variable K): The loop variable K is decremented and the process returns to S50, whereby steps S50 to S70 are repeatedly executed until the condition for exiting the loop process is met in S50 or S60. S80 (identification of rearmost reflected wave within area): The determination in S60 above confirmed that the position of the Kth reflected wave is within the detection area 40, so the Kth reflected wave is identified as the rearmost reflected wave within the area. In other words, the processing in S50 to S70 above confirmed that of the echoes confirmed in order while decrementing the loop variable K from the Kth reflected wave, which is the Nth reflected wave, the rearmost echo within the detection area 40 is the Kth reflected wave related to the current loop variable K, so this echo is identified as the rearmost reflected wave within the area.

[0042] S90 (Determine distance of rearmost reflected wave within region): Determine whether the distance of the rearmost reflected wave within region identified in S80 above is equal to or greater than the predetermined limit distance 42 mentioned in the description of the extraction unit 20 with reference to FIG. 1. The distance value of the echo identified as the rearmost reflected wave within region is calculated by the 2D-LiDAR 14, so this is used for the determination. As a result, if the distance of the rearmost reflected wave within region is equal to or greater than the limit distance 42 (YES), the process proceeds to S110, and if the distance of the rearmost reflected wave within region is shorter than the limit distance 42 (NO), the process proceeds to S100. S100 (Determine rearmost reflected wave within area): Determine whether the rearmost reflected wave within area identified in S80 above is the same as the rearmost reflected wave identified in S30 above. If the rearmost reflected wave within area is the same as the rearmost reflected wave (YES), proceed to S110. If the rearmost reflected wave within area and the rearmost reflected wave are different (NO), proceed to S120.

[0043] S110 (Identification of Extracted Reflected Wave): The in-area rearmost reflected wave identified in S80 above is identified as the reflected wave to be extracted for object detection determination by the determination unit 22, and the process ends. That is, the in-area rearmost reflected wave determined to be farther than the limit distance 42 through S90 above, and the in-area rearmost reflected wave determined to be the same as the rearmost reflected wave through S90 and S100 above, although closer than the limit distance 42, are identified as the extracted reflected wave. In the former case, this indicates that the in-area rearmost reflected wave is caused by an object located within the detection area 40 at a distance greater than the limit distance 42, and such an object is likely to be an object to be detected, so the in-area rearmost reflected wave is extracted. In the latter case, although the object that reflected the in-area rearmost reflected wave is closer than the limit distance 42, there is no object further back that would generate another echo, and therefore the object that reflected the in-area rearmost reflected wave is likely to be an object to be detected, so the in-area rearmost reflected wave is extracted.

[0044] S120 (No Reflected Wave Extracted): It is determined that there is no reflected wave at the relevant distance measurement angle to be used in the determination unit 22 for object detection, and the process ends without extracting a reflected wave. That is, if the process proceeds from S20 to this step, it indicates that no echoes have been obtained at the relevant distance measurement angle. If the process proceeds from S50 to this step, it indicates that all echoes obtained at the relevant distance measurement angle are outside the detection area 40, and therefore no reflected wave is extracted. Also, if the process proceeds from S100 to this step, it indicates that the distance value of the most rearmost reflected wave within the area is less than the limit distance 42, and that a most rearmost reflected wave exists further behind the most rearmost reflected wave within the area. That is, it is determined that no reflected wave is extracted because it is highly likely that the most rearmost reflected wave within the area is caused by a disturbance object 62 such as rain, and that the most rearmost reflected wave was transmitted through the disturbance object 62 and reflected off a structure 64 outside the detection area 40.

[0045] Next, Fig. 5 shows various cases where solid objects 60 such as people or bicycles, disturbance objects 62 such as rain or snow, and structures 64 such as pillars or buildings exist for each ranging angle of the 2D-LiDAR 14. For each case in Fig. 5, how reflected waves are extracted or eliminated by the extraction method shown in Fig. 4 will be explained. Note that in Fig. 5, circles indicate that echoes have been obtained, and echoes indicated by black circles correspond to extracted echoes, while echoes indicated by white circles correspond to echoes that were not extracted and were eliminated.

[0046] First, in the case shown as "case i" in Fig. 5, a detection wave from the 2D-LiDAR 14 is partially reflected by a disturbance object 62 located within the detection region 40 at a distance less than the limit distance 42, and partially passes through the disturbance object 62 and reaches a structure 64 outside the detection region 40, where it is reflected. As a result, an echo from the disturbance object 62 is obtained as a first echo, and an echo from the structure 64 is obtained as a second echo. The second echo is identified as the most rearmost reflected wave within the region (S30 in Fig. 4), and the first echo is identified as the most rearmost reflected wave within the region (S80 in Fig. 4). The distance value of the first echo, which is the most rearmost reflected wave within the region, is less than the limit distance 42 (S90 in Fig. 4), and a second echo of the most rearmost reflected wave exists separately from the first echo of the most rearmost reflected wave within the region (S100 in Fig. 4). Therefore, since it is highly likely that the first echo is an echo of the disturbance object 62 and the second echo is an echo of the structure 64 or the like, neither the first echo nor the second echo is extracted, resulting in no extracted echo (S120 in FIG. 4). As a result, it can be seen that the echo of the disturbance object 62 that is less than the limit distance 42 and the echo of the structure 64 outside the detection area 40 are excluded, and overdetection is prevented in cases where only the echo of the disturbance object 62 is present within the detection area 40.

[0047] Furthermore, in the case shown as "case ii" in FIG. 5, a detection wave from the 2D-LiDAR 14 is partially reflected by a solid object 60 located at or beyond the limit distance 42 within the detection region 40, and partially grazes the solid object 60 and is reflected as far as a structure 64 outside the detection region 40. As a result, an echo from the solid object 60 is obtained as a first echo, and an echo from the structure 64 is obtained as a second echo. The second echo is identified as the most rearmost reflected wave within the region (S30 in FIG. 4), and the first echo is identified as the most rearmost reflected wave within the region (S80 in FIG. 4). Then, because the distance value of the first echo, which is the most rearmost reflected wave within the region, is greater than or equal to the limit distance 42 (S90 in FIG. 4), the first echo, which is the most rearmost reflected wave within the region, is extracted (S110 in FIG. 4). As a result, it can be seen that the echo from the structure 64 outside the detection region 40 is excluded, and the echo from the solid object 60 within the detection region 40 is extracted.

[0048] Furthermore, in the case shown as "case iii" in FIG. 5, a portion of the detection wave from the 2D-LiDAR 14 is reflected by a disturbance object 62 located within the detection region 40 but at a distance less than the limit distance 42, a portion passes through the disturbance object 62 and is reflected by a solid object 60 located within the detection region 40 at a distance greater than the limit distance 42, and a portion of the detection wave grazes the solid object 60 and reaches a structure 64 outside the detection region 40, where it is reflected. As a result, the echo of the disturbance object 62 is obtained as the first echo, the echo of the solid object 60 is obtained as the second echo, and the echo of the structure 64 is obtained as the third echo. Furthermore, the third echo is identified as the most rearward reflected wave within the region (S30 in FIG. 4), and the second echo is identified as the most rearward reflected wave within the region (S80 in FIG. 4). Then, because the distance value of the second echo, which is the most rearward reflected wave within the region, is greater than or equal to the limit distance 42 (S90 in FIG. 4), the second echo, which is the most rearward reflected wave within the region, is extracted (S110 in FIG. 4). As a result, it can be seen that the echoes of the disturbance objects 62 that are less than the limit distance 42 and the echoes of the structures 64 outside the detection area 40 are eliminated, and the echoes of the solid objects 60 inside the detection area 40 are extracted.

[0049] On the other hand, in the case shown as "case iv" in FIG. 5, a portion of the detection wave from the 2D-LiDAR 14 is reflected by a disturbance object 62 located less than the limit distance 42 in front of the detection region 40, and a portion of the detection wave passes through the disturbance object 62 and is reflected by a solid object 60 located less than the limit distance 42 within the detection region 40. As a result, an echo from the disturbance object 62 is obtained as a first echo, and an echo from the solid object 60 is obtained as a second echo. The second echo is identified as the most rearmost reflected wave within the region (S30 in FIG. 4), and the second echo is identified as the most rearmost reflected wave within the region (S80 in FIG. 4). Although the distance value of the second echo, which is the most rearmost reflected wave within the region, is less than the limit distance 42 (S90 in FIG. 4), both the most rearmost reflected wave within the region and the most rearmost reflected wave are the same second echo (S100 in FIG. 4), so the second echo, which is the most rearmost reflected wave within the region, is extracted (S110 in FIG. 4). As a result, it can be seen that the echo of the disturbing object 62 located less than the limit distance 42 is eliminated, and the echo of the solid object 60 located less than the limit distance 42 is extracted.

[0050] On the other hand, in the case shown as "case v" in FIG. 5, a portion of the detection wave from the 2D-LiDAR 14 is reflected by a disturbance object 62 located less than the limit distance 42 in front of the detection region 40, a portion passes through it and is reflected by a disturbance object 62 located less than the limit distance 42, and a further portion passes through it and is reflected by a solid object 60 located at or beyond the limit distance 42 within the detection region 40. As a result, the echo of the disturbance object 62 is obtained as the first echo, the echo of the disturbance object 62 is obtained as the second echo, and the echo of the solid object 60 is obtained as the third echo. Furthermore, the third echo is identified as the rearmost reflected wave (S30 in FIG. 4), and the third echo is identified as the rearmost reflected wave within the region (S80 in FIG. 4). Then, because the distance value of the third echo, which is the rearmost reflected wave within the region, is greater than or equal to the limit distance 42 (S90 in FIG. 4), the third echo, which is the rearmost reflected wave within the region, is extracted (S110 in FIG. 4). This eliminates the echoes of the two disturbance objects 62 that are less than the limit distance 42, and extracts the echo of the solid object 60 within the detection area 40. Even if there are multiple echoes of the disturbance objects 62 at the same distance measurement angle, it can be seen that the echo of the solid object 60 behind them is extracted.

[0051] Here, a brief description of the operation of the determination unit 22 shown in FIG. 1 will be given. In each system, the determination unit 22 receives the information on the reflected waves (echoes) extracted by the extraction unit 20 as input and performs, for example, grouping and tracking. Specifically, in the grouping process, the echo information extracted for adjacent or nearby distance angles is treated as a point cloud, the density of the point cloud is evaluated, and representative coordinates are calculated for point clouds determined to have high density. In the tracking process, position prediction and correction are performed based on the representative coordinates obtained by the grouping process, and instantaneous grouping (noise) is removed by tracking over time. Then, a time count is performed based on the moving speed of the tracked object calculated by the tracking process, and if a predetermined time has passed, the object is confirmed as having been detected. The method of determining object detection by the determination unit 22 is not limited to the above method, and any determination method may be used as long as it utilizes the echo information extracted by the extraction unit 20.

[0052] The object detection device 10 according to the embodiment of the present invention may perform various determinations in addition to determining whether an object has been detected in the detection area 40. For example, the object detection device 10 performs determinations of whether an obstructing object has been detected, whether a check plate has been detected, and whether a setting has been detected. In obstructing object detection, for example, as shown in FIG. 3(b), in an obstructing object area 46 between the 2D-LiDAR 14 and the detection area 40 (railroad crossing 50), the object detection device 10 detects obstructions and monitors the optical sensitivity of the 2D-LiDAR 14. The object detection device 10 then detects obstructions in front of the detection area 40 and dirt 70 adhering to the 2D-LiDAR 14, and notifies of abnormalities depending on the situation.

[0053] In the inspection plate detection, the optical axis deviation and optical sensitivity of the 2D-LiDAR 14 are monitored in the inspection plate detection area including the inspection plate 30 as shown in Figure 2. That is, it is monitored that the inspection plate 30 is always at the same distance and in the same direction from the 2D-LiDAR 14, thereby confirming whether the optical axis of the 2D-LiDAR 14 is deviated, and the reflection level of the inspection plate 30 is monitored, thereby confirming whether the optical level of the 2D-LiDAR 14 is decreasing. Furthermore, the setting detection is performed during maintenance, and is used to specify coordinates using a highly reflective plate when setting the detection area 40, obstruction area 46, and inspection plate detection area for the above-mentioned object detection.

[0054] For this reason, the extraction unit 20 uses the echo information obtained by the distance measurement unit 12 to perform separate filter processing using independent algorithms for each purpose that enhance the detectability of each of the above-mentioned detection targets. That is, the extraction unit 20 performs separate filter processing for detecting an obstruction, a check plate, and a setting, in addition to filter processing for object detection in the detection area 40. Then, the determination unit 22 receives the results of the extraction unit 20 and performs a determination of each detection using grouping processing or the like.

[0055] The above-described embodiment of the present invention provides the following advantageous effects. Specifically, the object detection device 10 according to the embodiment of the present invention is designed to detect an object within a predetermined detection area 40 (see FIGS. 2, 3, and 5). As shown in FIG. 1, the object detection device 10 includes a distance measurement unit 12, an extraction unit 20, and a determination unit 22. The distance measurement unit 12 employs a so-called time-of-flight method, transmitting a detection wave such as light or radio waves, receiving a reflected wave (echo) when the detection wave strikes an object, and calculating the distance from the distance measurement unit 12 to the object based on the time between the transmission of the detection wave and the reception of the reflected wave. The distance measurement unit 12 continuously transmits detection waves while gradually changing the transmission direction (distance measurement angle) of the detection waves, thereby measuring the entire detection area 40. Furthermore, the distance measurement unit 12 supports so-called multi-echo technology. If multiple reflected waves are detected for a single detection wave at each distance measurement angle, the distance measurement unit 12 receives the multiple reflected waves and measures the distance for each of them.

[0056] Based on the calculation results of the distance measurement unit 12, the extraction unit 20 extracts reflected waves to be used for determining object detection from the reflected waves for each detection wave received by the distance measurement unit 12 at each distance measurement angle. More specifically, the extraction unit 20 extracts reflected waves to be used for determining object detection based on a predetermined limit distance 42 from the distance measurement unit 12 (see FIGS. 3(b) and 5) and the position of the object that reflected each reflected wave. The limit distance 42 used here is determined based on the detection sensitivity of the distance measurement unit 12. As shown in FIGS. 3 and 5, this limit distance 42 is the distance to the boundary of a high sensitivity region 44 close to the distance measurement unit 12, where disturbance objects 62, such as rainfall or snowfall, are likely to be detected due to the characteristics of detection waves that gradually spread and are dense in the close range. Therefore, the extraction unit 20 can extract reflected waves to be used for determining object detection by excluding reflected waves from disturbance objects 62 based on the determined limit distance 42 and the positional relationship between the object and the limit distance 42.

[0057] The determination unit 22 then uses the reflected waves extracted by the extraction unit 20 as described above from the reflected waves for each detection wave at each distance measurement angle received by the distance measurement unit 12 to determine whether an object has been detected. This allows for determination of whether an object has been detected with improved exclusion of disturbance objects 62, in other words, with improved separation between objects to be detected and disturbance objects 62 to be excluded. This makes it possible to improve the detectability of objects to be detected while suppressing false detection of disturbance objects 62 to be excluded, thereby improving the accuracy of object detection. Consequently, various advantages can be enjoyed depending on how the object detection device 10 according to the embodiment of the present invention is used in industrial fields.

[0058] Furthermore, in the object detection device 10 according to the embodiment of the present invention, when extracting reflected waves to be used by the determination unit 22 from the reflected waves (echoes) for each detection wave received by the distance measurement unit 12 at each distance measurement angle, the extraction unit 20 performs the extraction as follows. Specifically, as shown in Fig. 4, from among the reflected waves for each detection wave, the extraction unit 20 identifies the reflected wave reflected by the object located farthest from the distance measurement unit 12 as the rearmost reflected wave based on the calculation results of the distance measurement unit 12 (S10 to S30). That is, since the distance to the object that reflected each reflected wave has been calculated by the distance measurement unit 12, the extraction unit 20 identifies, from among the reflected waves for each detection wave, the reflected wave reflected by the object located farthest from the distance measurement unit 12 as the rearmost reflected wave. Furthermore, based on the positional relationship between the predetermined detection area 40 and the object that reflected each of the reflected waves, the extraction unit 20 identifies the reflected wave reflected by the object located farthest from the distance measuring unit 12 within the detection area 40 as the rearmost reflected wave within the area (S40 to S80).

[0059] If the object that reflected the most rearmost in-area reflected wave is located at a position equal to or greater than the limit distance 42 from the distance measuring unit 12, the extraction unit 20 determines that the object is unlikely to be a disturbance object 62 and extracts the most rearmost in-area reflected wave as a reflected wave to be used by the determination unit 22 (S90, S110). That is, even if multiple reflected waves are generated by a disturbance object 62 within the detection area 40, as in "case v" in Figure 5, the extraction unit 20 can extract the reflected wave as a reflected wave to be used by the determination unit 22 if there is a reflected wave from a solid object 60 to be detected within the detection area 40 further to the rear. 5, even if the object that reflected the most rearmost in-area reflected wave is located at a position less than the limit distance 42 from the distance measuring unit 12, if the most rearmost in-area reflected wave is the same as the most rearmost reflected wave, there is no reflected wave from behind the object, and there is a possibility that the object is the object to be detected, so the extraction unit 20 can extract the most rearmost in-area reflected wave as the reflected wave to be used by the determination unit 22 (S90 to S110). In other words, in cases other than the above two patterns, the extraction unit 20 does not extract a reflected wave as there is no reflected wave that corresponds to the reflected wave to be used by the determination unit 22, and this includes the following patterns.

[0060] First, the extraction unit 20 does not extract the reflected wave if the object that reflected the in-area rearmost reflected wave is located at a position less than the limit distance 42 from the distance measurement unit 12 and if a rearmost reflected wave exists in addition to the in-area rearmost reflected wave (S90, S100, S120). That is, for example, as in "case i" in FIG. 5 , if an object that reflected the rearmost reflected wave exists behind the object that reflected the in-area rearmost reflected wave and is located at a position less than the limit distance 42 from the distance measurement unit 12, the extraction unit 20 determines that there is no object to be detected and does not extract the reflected wave to be used by the determination unit 22. In this way, the extraction unit 20 also uses reflected waves caused by structures 64 and the like outside the detection area 40 to select and discard reflected waves.

[0061] Furthermore, when identifying the rearmost reflected wave, if the distance measuring unit 12 sends out a detection wave but there is no reflected wave in response to that detection wave, the extraction unit 20 determines that there is no object that reflects the detection wave and does not extract the reflected wave to be used by the determination unit 22 (S10, S20, S120). Furthermore, when identifying the rearmost reflected wave within the area, even if all reflected waves in response to one detection wave sent out by the distance measuring unit 12 at a certain distance measuring angle are outside the detection area 40, the extraction unit 20 determines that there is no object within the detection area 40 and does not extract the reflected wave to be used by the determination unit 22 (S40 to S70, S120).

[0062] The extraction method described above is based on the following findings: when multiple echoes occur, if the cause of the forward echo is a disturbance object 62, such as rain or snow, it occurs mainly in the high sensitivity region 44 close to the ranging unit 12; if the cause of the forward echo occurs in the detection region 40 farther away, it is primarily due to the solid object 60 to be detected; and that two or more echoes can occur in a short distance. These findings were discovered by the present inventors through experiments. This improves the reliability of the data sent from the extraction unit 20 to the determination unit 22, enabling detection of a solid object 60 to be detected that would have been undetectable in conventional technology without reducing the performance of eliminating the disturbance object 62. Moreover, even in cases not considered in conventional technology, where two or more echoes of a disturbance object 62 to be eliminated, such as rain, snow, fog, or dust, occur within the limited distance 42 at the same ranging angle, the system can stably detect a solid object 60 to be detected in the detection region 40 further behind the disturbance object 62.

[0063] 2 and 3, the object detection device 10 according to the embodiment of the present invention is applied to a railroad crossing 50, and the detection area 40 is set in the railroad crossing 50. This makes it possible to perform accurate object detection at the railroad crossing 50 while achieving both the ability to eliminate disturbance objects 62 that should be eliminated, such as rainfall and snowfall, and the ability to detect solid objects 60 that should be detected, such as people and automobiles. This can contribute to further improving safety at the railroad crossing 50.

[0064] Furthermore, in the object detection device 10 according to the embodiment of the present invention, the distance measurement unit 12 is configured with a 2D-LiDAR 14, which emits light as a detection wave and receives reflected light as a reflected wave (echo). In this way, by employing a 2D-LiDAR 14 that supports multi-echo, it is possible to measure distances accurately using a LiDAR with relatively excellent distance measurement performance, while significantly reducing costs compared to employing a 3D-LiDAR, regardless of whether it is a single echo or multi-echo.

[0065] Additionally, the object detection device 10 according to the embodiment of the present invention has two systems: a distance measurement unit 12, an extraction unit 20, and a determination unit 22. The extraction units 20A and 20B and the determination units 22A and 22B are configured as control devices using fail-safe CPUs. Each of the determination units 22A and 22B has a dual CPU and memory, and the determination results and data are compared in the dual systems in the determination units 22A and 22B to check their validity. This process exposes risky events (missing distance measurement data that should be used) in the echo extraction process, grouping process, and tracking process, which are caused by hardware failures such as bit inversions in the detection area data, and enables transition to a safer state, thereby contributing to the safety of railroad crossings. Furthermore, unlike conventional technology, the object detection device 10 according to the embodiment of the present invention determines whether an object is within the detection area 40 using object detection filtering, which is expected to improve data processing efficiency and contribute to improved system stability by reducing the CPU processing load.

[0066] Furthermore, when the object detection device 10 according to the embodiment of the present invention performs, in addition to determining whether an object is detected within the railroad crossing 50, whether an obstructing object is detected, whether a check plate is detected, or whether a setting is detected, the extractor 20 can employ an echo extraction algorithm specialized for each detection and determination purpose. For example, for object detection within the railroad crossing 50, an algorithm specialized for the purposes of both detecting solid objects 60 and removing disturbance objects 62 can be applied, while for obstructing object detection, a separate algorithm specialized for the purpose of accurately evaluating a reduction in sensitivity of the 2D-LiDAR 14 can be applied. This makes it possible to prevent excessive or non-notification (internalization) of failures or performance degradation due to self-diagnosis without reducing the accuracy of system health self-diagnosis, such as the optical sensitivity of the 2D-LiDAR 14, in order to achieve high object detection performance, thereby contributing to the reliability and safety of railroad crossings.

[0067] On the other hand, the object detection method according to the embodiment of the present invention can be performed using the object detection device 10 according to the embodiment of the present invention as described above, thereby achieving the same effects as those of the object detection device 10 according to the embodiment of the present invention. [Explanation of symbols]

[0068] 10: Object detection device, 12 (12A, 12B): Distance measurement unit, 14 (14A, 14B): 2D-LiDAR, 20 (20A, 20B): Extraction unit, 22 (22A, 22B): Determination unit, 40 (40A, 40B): Detection area, 42: Distance limit, 50: Railroad crossing

Claims

1. An object detection device used in an industrial field for detecting an object within a predetermined detection area, a time-of-flight distance measuring unit that continuously transmits detection waves while gradually changing directions so as to cover the detection area, and receives a reflected wave of the transmitted detection wave reflected by an object each time the detection wave is transmitted, and if there are multiple reflected waves from one detection wave, receives the multiple reflected waves and calculates the distance to the object that reflected each of the reflected waves; an extraction unit that extracts reflected waves to be used for determining object detection based on a calculation result of the distance measurement unit; a determination unit that determines whether an object has been detected by using the reflected wave extracted by the extraction unit, The object detection device is characterized in that the extraction unit extracts the reflected waves to be used in the judgment unit from the reflected waves for each detection wave received by the ranging unit based on a limited distance from the ranging unit, which is predetermined based on the detection sensitivity of the ranging unit, and the position of the object that reflected each of the reflected waves.

2. The extraction unit extracts, from the reflected wave for each detection wave received by the distance measurement unit, A reflected wave reflected by an object located farthest from the distance measuring unit is identified as a rearmost reflected wave, and a reflected wave reflected by an object located farthest from the distance measuring unit within the detection area is identified as a rearmost reflected wave within the area, An object detection device as described in claim 1, characterized in that the object that reflected the rearmost reflected wave within the area is extracted as the reflected wave to be used in the judgment unit when the object that reflected the rearmost reflected wave within the area is located at a position greater than the limit distance from the distance measurement unit, and when the object that reflected the rearmost reflected wave within the area is located at a position less than the limit distance from the distance measurement unit and the rearmost reflected wave within the area is the same as the rearmost reflected wave.

3. 3. An object detection device according to claim 1, wherein the detection area is set at a railroad crossing.

4. 3. The object detection device according to claim 1, wherein the distance measurement unit is configured by 2D-LiDAR.

5. An object detection method used in an industrial field for detecting an object within a predetermined detection area, comprising: a time-of-flight distance measuring unit is provided which continuously transmits detection waves while gradually changing the direction so as to cover the detection area, and receives a reflected wave of the transmitted detection wave reflected by an object each time the detection wave is transmitted, and receives the reflected waves if there are multiple reflected waves for one detection wave, and calculates the distance to the object that reflected each of the reflected waves; extracting reflected waves to be used for determining object detection from the reflected waves of each detection wave received by the distance measuring unit based on a limit distance from the distance measuring unit, the limit distance being determined in advance based on the detection sensitivity of the distance measuring unit, and the position of an object that reflected each of the reflected waves; The object detection method is characterized in that the extracted reflected waves are used to determine whether an object has been detected.

6. When extracting the reflected waves used to determine object detection, among the reflected waves for each detection wave received by the distance measuring unit, A reflected wave reflected by an object located farthest from the distance measuring unit is identified as a rearmost reflected wave, and a reflected wave reflected by an object located farthest from the distance measuring unit within the detection area is identified as a rearmost reflected wave within the area, An object detection method as described in claim 5, characterized in that the rearmost reflected wave within the area is extracted as the reflected wave to be used for determining object detection when the object that reflected the rearmost reflected wave within the area is located at a position greater than the limit distance from the distance measuring unit, and when the object that reflected the rearmost reflected wave within the area is located at a position less than the limit distance from the distance measuring unit and the rearmost reflected wave within the area is the same as the rearmost reflected wave.

7. 7. The object detection method according to claim 5, wherein the detection area is set at a railroad crossing.

8. The object detection method according to claim 5 or 6, characterized in that a 2D-LiDAR is used as the distance measurement unit.

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