Object detection system, control device, object detection method, and object detection program

Abstract

This object detection system detects an object by using a radar and a reflection plate. More specifically, the object detection system emits a radar wave toward the reflection plate, and executes a detection process for detecting the object on the basis of a reflected wave of the radar wave. When the detection position of the object changes in conjunction with a change in the reflecting direction of the reflection plate, the object detection system determines that a propagation path of the radar wave to the object and a propagation path of the reflected wave from the object travel via the reflection plate, and executes a correction process for correcting the detection position of the object on the basis of the propagation paths travelling via the reflection plate.

Description

OBJECT DETECTION SYSTEM, CONTROL DEVICE, OBJECT DETECTION METHOD, AND OBJECT DETECTION PROGRAM

[0001] The present disclosure relates to a technique for detecting objects using radar and reflectors.

[0002] Non-Patent Document 1 discloses a technique relating to frequency sharing and hardware sharing between a radar and a communication system.

[0003] F. Liu, C. Masouros, AP Petropulu, H. Griffiths and L. Hanzo, "Joint Radar and Communication Design: Applications, State-of-the-Art, and the Road Ahead," in IEEE Transactions on Communications, vol. 68, no. 6, pp. 3834-3862, June 2020, doi: 10.1109 / TCOMM.2020.2973976.

[0004] By using radar, it is possible to detect an object and measure its position. Specifically, a radar transceiver emits radar waves and receives the reflected radar waves from the object. Based on the received reflected waves, the object can be detected and its position can be measured. However, there may be an obstruction between the radar transceiver and the object. Such "out-of-line-of-sight objects" cannot be directly detected by radar alone.

[0005] It is possible to use a "reflector" to detect objects beyond the line of sight. By emitting radar waves toward a reflector, it is possible to bypass obstacles and irradiate the radar waves onto objects beyond the line of sight. In other words, it is expected that by using radar and a reflector, it will be possible to detect objects beyond the line of sight.

[0006] However, conventionally, there has been no technology for determining whether a reflected wave received by a radar transceiver is a reflected wave from an object beyond line of sight. In other words, conventionally, it has not been possible to determine whether the propagation path of the radar wave and the propagation path of the reflected wave pass through a reflector. Therefore, even if an object can be detected using a radar and a reflector, it has not been possible to determine whether the object is beyond line of sight. In other words, even if an object can be detected using a radar and a reflector, the detected position (measured position) of the object is not necessarily accurate.

[0007] One object of the present disclosure is to provide a technology that can detect an object using a radar and a reflector and identify the position of the object with high accuracy.

[0008] A first aspect relates to an object detection system that detects an object using a radar and a reflector. The object detection system includes one or more processors. The one or more processors execute a detection process that emits radar waves toward a reflector and detects an object based on the reflected waves of the radar waves. When the detected position of the object changes in conjunction with a change in the reflection direction of the reflector, the one or more processors determine that the propagation path of the radar waves to the object and the propagation path of the reflected waves from the object pass through the reflector, and execute a correction process that corrects the detected position of the object based on the propagation path that passes through the reflector.

[0009] A second aspect relates to a control device for controlling an object detection system including a radar transceiver and a reflector. The control device includes one or more processors. The one or more processors instruct the radar transceiver to emit radar waves toward the reflector, acquire reception information of the reflected radar waves from the radar transceiver, and execute a detection process to detect the object based on the reception information. When the detected position of the object changes in conjunction with a change in the reflection direction of the reflector, the one or more processors determine that the propagation path of the radar waves to the object and the propagation path of the reflected waves from the object pass through the reflector, and execute a correction process to correct the detected position of the object based on the propagation path that passes through the reflector.

[0010] A third aspect relates to an object detection method for detecting an object using a radar and a reflector, the object detection method including: a detection process for emitting radar waves toward a reflector and detecting an object based on the reflected waves of the radar waves; and a correction process for determining, when the detected position of the object changes in conjunction with a change in the reflection direction of the reflector, that the propagation path of the radar waves to the object and the propagation path of the reflected waves from the object pass through the reflector, and correcting the detected position of the object based on the propagation path that passes through the reflector.

[0011] A fourth aspect relates to an object detection program executed by a computer. The object detection program causes a computer to execute the object detection method described above. The object detection program may be recorded on a computer-readable recording medium. The object detection program may be provided via a network.

[0012] According to the present disclosure, a detection process is performed in which radar waves are emitted toward a reflector and an object is detected based on the reflected waves of the radar waves. If the detected position of the object changes in conjunction with a change in the reflection direction of the reflector, it is determined that the propagation path of the radar wave and the reflected wave passes through the reflector. In this case, the detected position of the object is corrected based on the propagation path that passes through the reflector. This makes it possible to accurately identify the position of the object.

[0013] FIG. 1 is a conceptual diagram for explaining an overview of an object detection system. FIG. 1 is a conceptual diagram for explaining an overview of an object detection system according to an embodiment. FIG. 2 is a conceptual diagram for explaining detection position correction processing according to an embodiment. FIG. 3 is a block diagram showing a schematic configuration example of an object detection system according to an embodiment. FIG. 4 is a flowchart showing object detection processing by an object detection system according to an embodiment. FIG. 5 is a block diagram showing a configuration example of an object detection system according to an embodiment. FIG. 6 is a block diagram showing a configuration example of a radar transceiver according to an embodiment. FIG. 7 is a block diagram showing a configuration example of a reflector according to an embodiment. FIG. 8 is a block diagram showing another configuration example of a reflector according to an embodiment. FIG. 9 is a block diagram showing a configuration example of a control device according to an embodiment.

[0014] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0015] 1 is a conceptual diagram for explaining an overview of an object detection system 1. The object detection system 1 detects an object. The object to be detected may be a person, an object, etc., and is not particularly limited.

[0016] The object detection system 1 basically detects objects using radar. To that end, the object detection system 1 includes a radar transceiver 100. The radar transceiver 100 emits radar waves RA. The radar waves RA are reflected by objects. The radar transceiver 100 receives reflected waves RB of the radar waves RA. Based on the reflected waves RB from the object, the object can be detected and its position can be measured.

[0017] However, there is a possibility that an object may be blocking the radar transceiver 100 and the object. Such an object will be referred to as an "out-of-line-of-sight object X" hereinafter. An out-of-line-of-sight object X cannot be directly detected by radar alone.

[0018] According to this embodiment, a reflector 200 that reflects radio waves is used to detect an object X beyond the line of sight. For example, the reflector 200 is a dynamic reflector (RIS: Reconfigurable Intelligent Surface) that can dynamically control the beam. The RIS is composed of a number of reflecting elements and reflects incident radio waves. The reflection characteristics of the RIS, such as the reflection direction, can be dynamically controlled. By using such a reflector 200, it is possible to form a propagation path that bypasses the obstacle.

[0019] More specifically, the radar transceiver 100 emits radar waves RA toward the reflector 200. At least a portion of the radar waves RA is reflected by the reflector 200. The radar waves RA are further reflected by an object X outside of the line of sight. A reflected wave RB of the radar waves RA is reflected by the reflector 200 toward the radar transceiver 100. The radar transceiver 100 receives the reflected wave RB. The object X outside of the line of sight can be detected based on the reflected wave RB from the object X outside of the line of sight. In other words, the object X outside of the line of sight can be detected by using a radar and the reflector 200.

[0020] However, conventionally, there has been no technology for determining whether the reflected wave RB received by the radar transceiver 100 is a reflected wave from an object X outside the line of sight. In other words, conventionally, it has not been possible to determine whether the propagation path of the radar wave RA and the propagation path of the reflected wave RB pass through the reflector 200. Therefore, even if it is possible to detect an object using the radar and the reflector 200, it has not been possible to determine whether the object is an object X outside the line of sight.

[0021] In the example shown in FIG. 1 , the radar transceiver 100 receives a reflected wave RB from an out-of-line-of-sight object X via a reflector 200. Conventionally, the position of the detected object (hereinafter referred to as the "detected position" or the "measured position") is calculated without taking into consideration the presence of the reflector 200. The obtained detected position is an "apparent detected position" and deviates from the actual position of the out-of-line-of-sight object X. As such, conventionally, even if an object could be detected using a radar and a reflector 200, the detected position (measured position) of the object was not necessarily accurate.

[0022] From the above viewpoint, this embodiment proposes a technique that uses a radar and a reflector 200 to detect an object and to accurately identify the position of the object.

[0023] 2 is a conceptual diagram for explaining an overview of an object detection system 1 according to this embodiment. The object detection system 1 emits radar waves RA from a radar transceiver 100 toward a reflector 200. Furthermore, the object detection system 1 detects an object based on reflected waves RB of the radar waves RA and obtains the detected position of the object. The process of emitting radar waves RA toward the reflector 200, detecting an object based on reflected waves RB of the radar waves RA, and obtaining the detected position of the object will be referred to as the "detection process" hereinafter.

[0024] According to this embodiment, the object detection system 1 repeatedly executes the detection process while changing the reflection direction of the reflector 200. The object detection system 1 then checks whether the detected position of the object also changes in conjunction with the change in the reflection direction of the reflector 200. Here, a change in the detected position means a change equal to or greater than a predetermined threshold that takes into account errors, etc. If the detected position of the object changes in conjunction with the change in the reflection direction of the reflector 200, the object detection system 1 determines that the propagation path of the radar wave RA to the object and the propagation path of the reflected wave RB from the object pass through the reflector 200. In other words, if the detected position of the object changes in conjunction with the change in the reflection direction of the reflector 200, the object detection system 1 determines that the object is an "out-of-line-of-sight object X."

[0025] If the detected object is an out-of-line-of-sight object X, the object detection system 1 executes a "detection position correction process" to correct the detected position of the object. In other words, the object detection system 1 corrects the "apparent detected position" to the "actual position of the out-of-line-of-sight object X." This detection position correction process is performed taking into consideration the propagation paths of the radar waves RA and the reflected waves RB that pass through the reflector 200, i.e., the reflection characteristics (reflection direction) of the reflector 200.

[0026] FIG. 3 is a conceptual diagram illustrating the detection position correction process. The measured distance d from the radar transceiver 100 to the non-line-of-sight object X is obtained by the above-described detection process. The measured distance d is the sum of the first distance d1 between the radar transceiver 100 and the reflector 200 and the second distance d2 between the reflector 200 and the non-line-of-sight object X (d = d1 + d2). The installation positions of the radar transceiver 100 and the reflector 200 are known, and the first distance d1 is also known. Therefore, the second distance d2 can be calculated from the measured distance d and the first distance d1. Furthermore, the reflection characteristics (reflection direction) of the reflector 200 are defined by the angle of incidence (θt, φt) and the angle of reflection (θr, φr). Based on the first distance d1, the second distance d2, and the reflection characteristics of the reflector 200, the object detection system 1 corrects the "apparent detected position" to the "actual position of the non-line-of-sight object X." That is, the object detection system 1 executes the detection position correction process based on the propagation path that passes through the reflector 200 .

[0027] If the detected position of the object does not change in conjunction with a change in the reflection direction of the reflector 200, the object detection system 1 determines that the object is a line-of-sight object that exists in a line-of-sight position. In this case, the object detection system 1 uses the detected position of the object as is without performing the above-mentioned detection position correction process.

[0028] FIG. 4 is a block diagram showing a schematic configuration example of an object detection system 1 according to this embodiment. The processing entity for the detection process and the detection position correction process described above is not particularly limited. The detection process and the detection position correction process may be executed by a specific device, or may be executed in a distributed manner by multiple devices. Generally speaking, the object detection system 1 includes one or more processors 10 (hereinafter simply referred to as "processor 10") and one or more storage devices 20 (hereinafter simply referred to as "storage device 20"). The processor 10 executes various processes. Examples of the processor 10 include a central processing unit (CPU), an application specific integrated circuit (ASIC), and a field-programmable gate array (FPGA). The storage device 20 stores various information. Examples of the storage device 20 include a hard disk drive (HDD), a solid state drive (SSD), a volatile memory, and a nonvolatile memory.

[0029] An object detection program 30, which is a computer program, may be used. The object detection program 30 is stored in the storage device 20 and executed by the processor 10. The processor 10 that executes the object detection program 30 works in cooperation with the storage device 20 to realize the functions of the object detection system 1. The object detection program 30 may be recorded on a computer-readable recording medium. The object detection program 30 may be provided via a network.

[0030] The storage device 20 stores reflector information 40, radar measurement information 50, object position information 60, and the like.

[0031] The reflector information 40 includes information such as the installation position and reflection characteristics of the reflector 200. The installation position of the reflector 200 is known information. The reflection characteristics of the reflector 200 include the reflection direction of the radio wave. The reflection direction of the reflector 200 is defined by the incident angle (θt, φt) and the reflection angle (θr, φr). The reflection direction of the reflector 200 may be controlled by the reflector 200 itself or may be remotely controlled.

[0032] The radar measurement information 50 is information used in the above-described detection process using radar. For example, the radar measurement information 50 includes transmission information of the radar waves RA transmitted from the radar transceiver 100. The radar measurement information 50 also includes reception information of the reflected waves RB received by the radar transceiver 100.

[0033] The object position information 60 is information indicating the detected position of an object. When the above-described detection position correction process is performed, the object position information 60 indicates the corrected detected position of the object (out-of-sight object X).

[0034] FIG. 5 is a flowchart showing the object detection process performed by the object detection system 1 according to this embodiment.

[0035] In step S10, the processor 10 sets the reflection direction of the reflector 200 to the first direction. The processor 10 updates the reflector information 40.

[0036] In the following step S20, the processor 10 performs a first detection process. Specifically, the processor 10 acquires information on the installation position of the reflector 200 from the reflector information 40. The installation position of the radar transceiver 100 is also known information. The processor 10 recognizes the direction from the radar transceiver 100 to the reflector 200 based on the installation positions of the radar transceiver 100 and the reflector 200. Then, the processor 10 radiates radar waves RA from the radar transceiver 100 toward the reflector 200. The processor 10 acquires radar measurement information 50 and performs a first detection process based on the radar measurement information 50. The first detection position is the detected position of the object obtained by the first detection process.

[0037] In step S30 after step S20, the processor 10 sets the reflection direction of the reflector 200 to a second direction different from the first direction. The processor 10 updates the reflector information 40.

[0038] In the following step S40, the processor 10 performs a second detection process. Specifically, the processor 10 radiates radar waves RA from the radar transceiver 100 toward the reflector 200. The radiation direction of the radar waves RA is the same as in the first detection process (step S20) described above. The processor 10 acquires radar measurement information 50 and performs a second detection process based on the radar measurement information 50. The second detection position is the detected position of the object obtained by the second detection process.

[0039] In step S50 after step S40, the processor 10 compares the first detection position obtained by the first detection process with the second detection position obtained by the second detection process and determines whether the second detection position has changed from the first detection position. Here, a change in the detection position refers to a change equal to or greater than a predetermined threshold that takes into account errors, etc. In other words, if the difference between the second detection position and the first detection position is equal to or greater than a predetermined threshold, it is determined that the second detection position has changed from the first detection position. If the second detection position has changed from the first detection position (step S50; Yes), it can be said that the detected position of the object has changed in conjunction with a change in the reflection direction of the reflector 200. In this case, the process proceeds to step S60.

[0040] In step S60, the processor 10 determines that the propagation path of the radar wave RA to the object and the propagation path of the reflected wave RB from the object pass through the reflector 200. In other words, the processor 10 determines that the object is an "out-of-line-of-sight object X." The processor 10 then performs a detection position correction process. Specifically, the processor 10 corrects the detected position of the object based on the propagation path that passes through the reflector 200, i.e., the reflection characteristics (reflection direction) of the reflector 200.

[0041] On the other hand, if the second detection position does not change from the first detection position (step S50; No), the processor 10 determines that the object is a line-of-sight object that exists in the line-of-sight position. In this case, the processor 10 uses the detected position of the object as is without performing step S60.

[0042] <Effects> As described above, according to this embodiment, a detection process is performed in which radar waves RA are emitted toward reflector 200 and an object is detected based on the reflected waves RB of the radar waves RA. If the detected position of the object changes in conjunction with a change in the reflection direction of reflector 200, it is determined that the propagation path of the radar waves RA and the reflected waves RB passes through reflector 200. In this case, the detected position of the object is corrected based on the propagation path that passes through reflector 200. This makes it possible to identify the position of the object with high accuracy.

[0043] It should be noted that the smaller the change in the reflection direction of the reflector 200, the more precisely it is possible to check the change in the detected position of the object. Also, the more times the reflection direction of the reflector 200 is changed, the more precisely it is possible to check the change in the detected position of the object. This makes it possible to further improve the accuracy of determining an out-of-line-of-sight object X.

[0044] 6 is a block diagram showing an example of the configuration of an object detection system 1 according to this embodiment. In the example shown in Fig. 6, the object detection system 1 includes a radar transceiver 100, a reflector 200, and a control device 300.

[0045] The radar transceiver 100 has functions to transmit radar waves RA, receive reflected waves RB of the radar waves RA, and perform signal processing on the received reflected waves RB. The radar transceiver 100 is controlled by a control device 300. Note that the frequency band used for the radar waves RA and the frequency band used for the control signal may be different.

[0046] The reflector 200 reflects radio waves. For example, the reflector 200 is a RIS. The number of reflectors 200 is one or more. The reflection characteristics (reflection direction, etc.) of the reflector 200 can be controlled by the control device 300. Alternatively, the reflector 200 itself may set the reflection characteristics. In this case, the reflector 200 feeds back information on the reflection characteristics it has set to the control device 300.

[0047] The control device 300 controls the object detection system 1. The control device 300 is capable of communicating with the radar transceiver 100 and the reflector 200, and can control the radar transceiver 100 and the reflector 200. The communication method may be wired or wireless. The control device 300 may be included in a base station. The base station may include both the control device 300 and the radar transceiver 100.

[0048] For example, the control device 300 includes the processor 10 and the storage device 20 shown in FIG. 4 and performs the object detection process shown in FIG. 5 . More specifically, the control device 300 acquires reflector information 40. The reflection characteristics of the reflector 200 may be controlled by the control device 300 or may be set by the reflector 200 itself. The control device 300 instructs the radar transceiver 100 to radiate radar waves RA toward the reflector 200. The control device 300 also acquires radar measurement information 50 from the radar transceiver 100, including information on the transmission of the radar waves RA and information on the reception of the reflected waves RB. The control device 300 then performs a detection process to detect an object based on the radar measurement information 50. Furthermore, the control device 300 changes the reflection characteristics of the reflector 200. When the detected position of the object changes in conjunction with a change in the reflection direction of the reflector 200, the control device 300 performs a detection position correction process based on the reflection characteristics (reflection direction) of the reflector 200.

[0049] 7 is a block diagram showing an example of the configuration of the radar transceiver 100. The radar transceiver 100 includes an interface 110, a control information acquisition unit 120, a signal generation unit 130, a radar transceiver unit 140, a radar antenna 150, and a quality acquisition unit 160.

[0050] Interface 110 is an interface for exchanging information with control device 300. Control information acquisition unit 120 acquires control information from control device 300 via interface 110. For example, the control information includes information on the installation position of reflector 200. As another example, the control information may include the beam direction of radar waves RA. Signal generation unit 130 generates a radar transmission signal for transmitting radar waves RA based on the control information.

[0051] The radar transceiver 140 transmits radar waves RA via the radar antenna 150 in accordance with the radar transmission signal. The radar transceiver 140 also receives reflected waves RB via the radar antenna 150. The quality acquisition unit 160 performs frequency conversion, detection, amplification, etc. based on the received signal of the reflected waves RB. Radar measurement information 50 is sent to the control device 300 via the interface 110.

[0052] 8 is a block diagram showing an example of the configuration of the reflector 200. The reflector 200 includes a communication unit 210, a control information acquisition unit 220, a weight setting unit 230, and a reflection unit 240.

[0053] The reflecting unit 240 has a function of reflecting radio waves. For example, the reflecting unit 240 is composed of a plurality of reflecting elements. The reflecting unit 240 shifts the phase of the radio waves when the radio waves are reflected by the reflecting elements. By setting a different phase shift amount for each reflecting element as a phase weight, the reflection direction of the radio waves can be dynamically controlled.

[0054] The communication unit 210 communicates with the control device 300. The communication method may be wired or wireless. The control information acquisition unit 220 acquires control information from the control device 300 via the communication unit 210. The control information specifies the reflection characteristics (reflection direction, beam width, etc.) of the reflector 200. The weight setting unit 230 determines weights to be added to the reflection elements that make up the reflector 240 in accordance with the control information, and sets the reflection direction and beam width.

[0055] FIG. 9 is a block diagram showing another example configuration of the reflector 200. In the example shown in FIG. 9, the reflector 200 itself sets the reflection characteristics (reflection direction). More specifically, the reflector 200 includes a communication unit 210, a weight setting unit 230, a reflecting unit 240, and a feedback information generating unit 250. The weight setting unit 230 determines weights to be assigned to the reflecting elements that make up the reflecting unit 240, and sets the reflection direction and beam width. The feedback information generating unit 250 generates feedback information that indicates the set reflection characteristics (reflection direction, beam width). The communication unit 210 transmits the feedback information to the control device 300.

[0056] 10 is a block diagram showing an example of the configuration of the control device 300. The control device 300 includes an interface 310, a communication unit 320, a processing unit 330, a display unit 340, and an operation unit 350.

[0057] The interface 310 is an interface for exchanging information with the radar transceiver 100. The processing unit 330 provides control information to the radar transceiver 100 via the interface 310. The processing unit 330 also receives radar measurement information 50 from the radar transceiver 100 via the interface 310.

[0058] The communication unit 320 communicates with the reflector 200. The communication method may be wired or wireless. The processing unit 330 transmits control information specifying the reflection characteristics of the reflector 200 to the reflector 200 via the communication unit 320. Alternatively, the processing unit 330 receives feedback information indicating the reflection characteristics of the reflector 200 from the reflector 200 via the communication unit 320. In either case, the processing unit 330 holds the reflector information 40.

[0059] The processing unit 330 performs a detection process to detect an object based on the radar measurement information 50. If the detected position of the object changes in conjunction with a change in the reflection direction of the reflector 200, the processing unit 330 performs a detection position correction process. In other cases, the processing unit 330 adopts the detected position of the object without performing the detection position correction process. In this way, the processing unit 330 obtains object position information 60 indicating the detected position of the object.

[0060] The display unit 340 visually displays to the user various types of information in the processing unit 330. The operation unit 350 is used by the user to operate various types of information in the processing unit 330. Note that the display unit 340 and the operation unit 350 may be omitted.

[0061] REFERENCE SIGNS LIST 1... object detection system, 10... processor, 20... storage device, 30... object detection program, 40... reflector information, 50... radar measurement information, 60... object position information, 100... radar transceiver, 200... reflector, 300... control device, RA... radar wave, RB... reflected wave

Claims

1. An object detection system that detects an object using a radar and a reflector, comprising one or more processors, the one or more processors configured to execute a detection process of emitting radar waves toward the reflector and detecting an object based on the reflected waves of the radar waves, and a correction process of determining that the propagation path of the radar wave to the object and the propagation path of the reflected wave from the object pass through the reflector if the detected position of the object changes in conjunction with a change in the reflection direction of the reflector, and correcting the detection position of the object based on the propagation path that passes through the reflector.

2. An object detection system as described in claim 1, wherein the one or more processors are configured to execute a first detection process in which the reflection direction of the reflector is set to a first direction and the detection process is performed; and after the first detection process, a second detection process in which the reflection direction of the reflector is set to a second direction different from the first direction and the detection process is performed, and when the detection position of the object obtained by the second detection process has changed from the detection position of the object obtained by the first detection process, the one or more processors perform the correction process.

3. An object detection system as described in claim 1, wherein, when the detected position of the object does not change in conjunction with the change in the reflection direction of the reflector, the one or more processors determine that the object is present in a line of sight and adopt the detected position of the object without performing the correction processing.

4. A control device for controlling an object detection system including a radar transceiver and a reflector, comprising one or more processors, the one or more processors being configured to execute a detection process for instructing the radar transceiver to radiate radar waves toward the reflector, acquiring reception information of the reflected waves of the radar waves from the radar transceiver, and detecting an object based on the reception information, and a correction process for determining that the propagation path of the radar wave to the object and the propagation path of the reflected wave from the object pass through the reflector when the detection position of the object changes in conjunction with a change in the reflection direction of the reflector, and for correcting the detection position of the object based on the propagation path that passes through the reflector.

5. A method for detecting an object using a radar and a reflector, comprising: a detection process for emitting radar waves toward the reflector and detecting an object based on the reflected waves of the radar waves; and a correction process for determining, when the detected position of the object changes in conjunction with a change in the reflection direction of the reflector, that the propagation path of the radar wave to the object and the propagation path of the reflected wave from the object pass through the reflector, and correcting the detected position of the object based on the propagation path that passes through the reflector.

6. An object detection method as claimed in claim 5, comprising: a first detection process in which the reflection direction of the reflector is set to a first direction and the detection process is performed; and a second detection process in which, after the first detection process, the reflection direction of the reflector is set to a second direction different from the first direction and the detection process is performed, wherein the correction process is performed if the detection position of the object obtained by the second detection process has changed from the detection position of the object obtained by the first detection process.

7. An object detection method as claimed in claim 5, wherein, if the detected position of the object does not change in conjunction with the change in the reflection direction of the reflector, it is determined that the object is present in a line of sight, and the detected position of the object is adopted without performing the correction process.

8. An object detection program that, when executed by a computer, causes the computer to execute the object detection method according to any one of claims 5 to 7.

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