Patent Publication Number: US-11650321-B2

Title: Apparatus and method for detecting tilt of LiDAR apparatus mounted to vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims the benefit of priority from Japanese Patent Application No. 2019-178465, filed Sep. 30, 2019. The entire disclosure of the above application is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a technology for detecting a tilt of a light detection and ranging (LiDAR) apparatus that is mounted to a vehicle. 
     Related Art 
     Technology that enables automatic traveling of a vehicle through use of detection results of a camera, a laser radar, a LiDAR apparatus, and the like, that are mounted to a vehicle, is known. 
     SUMMARY 
     One aspect of the present disclosure provides a detection apparatus that detects a tilt of a LiDAR apparatus that is mounted to a vehicle. The detection apparatus acquires a distance image that is expressed by a detection point group that is detected by the LiDAR apparatus, acquires surroundings information on a periphery of a traveling route of the vehicle, and determines the tilt of the LiDAR apparatus based on the acquired distance image and the acquired surroundings information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG.  1    is an explanatory diagram of an example of a vehicle in which a tilt detection apparatus is mounted according to an embodiment of the present disclosure; 
         FIG.  2    is a block diagram of an overall configuration of the vehicle and the tilt detection apparatus; 
         FIG.  3    is an explanatory diagram of an example of surroundings information; 
         FIG.  4    is an explanatory diagram for explaining a tilt of a LiDAR apparatus; and 
         FIG.  5    is a flowchart of the processing steps in a tilt detection process. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Technology that enables automatic traveling of a vehicle through use of detection results of a camera, a laser radar, a LiDAR apparatus, and the like, that are mounted to a vehicle, is known (for example, U.S. Pat. No. 9,537,959). 
     However, the LiDAR apparatus may become tilted as a result of deterioration over time of a bracket that fixes the LiDAR apparatus to the vehicle, impact that occurs when the vehicle collides with an obstacle, and the like. Consequently, a problem may occur in that a target in the periphery of the vehicle is not accurately recognized. It is thus desired to provide a technology for detecting a tilt of a LiDAR apparatus that is mounted to a vehicle. 
     An exemplary embodiment of the present disclosure provides a detection apparatus that detects a tilt of a LiDAR apparatus that is mounted to a vehicle. The detection apparatus includes: a distance image acquiring unit that acquires a distance image that is expressed by a detection point group that is detected by the LiDAR apparatus; a surroundings information acquiring unit that acquires surroundings information on a periphery of a traveling route of the vehicle; and a detecting unit that determines the tilt of the LiDAR apparatus based on the acquired distance image and the acquired surroundings information. 
     As a result of the detection apparatus according to the above-described exemplary embodiment, the distance image expressed by the detection point group that is detected by the LiDAR apparatus is acquired. The surroundings information on the periphery of the traveling route of the vehicle is acquired. The tilt of the LiDAR apparatus is determined through use of the acquired distance image and the acquired surroundings information. Therefore, the tilt of the LiDAR apparatus can be easily detected. 
     The present disclosure can be implemented according to various embodiments. For example, the present disclosure can be implemented according to embodiments such as a tilt detection apparatus, a tilt detection method, a computer program for implementing the apparatus and method, a storage medium in which the computer program is stored, and the like. 
     A. EMBODIMENT 
     A1. Apparatus Configuration 
     As shown in  FIG.  1    and  FIG.  2   , a vehicle  100  includes a measurement apparatus unit  40 , a tilt detection apparatus  10 , and a driving assistance control apparatus  80 . The vehicle  100  is a vehicle in which switching between autonomous driving and manual driving can be performed. 
     A driver of the vehicle  100  can switch between autonomous driving and manual driving by a predetermined switch that is provided in an instrument panel or the like. “Autonomous driving” refers to driving in which engine control, brake control, and steering control are all automatically performed instead of being performed by the driver, as a result of a driving apparatus  60 , described hereafter, being driven based on states inside and outside a vehicle cabin that are acquired by the measurement apparatus unit  40 , without the driver performing driving operations. 
     The driving apparatus  60  includes an actuator group that is used in driving of the vehicle  100 . “Manual driving” refers to driving in which the driver performs an operation (pressing of an accelerator pedal) for engine control, an operation (pressing of a brake pedal) for brake control, and an operation (rotation of a steering wheel) for steering control. 
     The measurement apparatus unit  40  is mounted on a roof of the vehicle  100 . The measurement apparatus unit  40  is fixed to the vehicle  100  by a fixing mechanism  92  and a frame  93 . Here,  FIG.  1    shows a vehicle width direction LH, a vehicle frontward direction FD, a vehicle rearward direction RD, and a vertically downward direction G. Symbols and arrows that indicate these directions in  FIG.  1    correspond to symbols and arrows that indicate directions in other drawings. 
     The measurement apparatus unit  40  acquires information related to a traveling state of the vehicle  100 , information related to a target in the periphery of the vehicle  100 , and the like. As shown in  FIG.  2   , the measurement apparatus  40  includes at least an imaging apparatus  41 , a LiDAR apparatus  43 , a position sensor  45 , and a six-axis sensor  47 . 
     The imaging apparatus  41  is oriented towards the periphery of the vehicle  100  and captures an image in at least an advancing direction of the vehicle  100 . For example, the imaging apparatus  41  is an imaging apparatus, such as a wide-angle camera or a telescopic camera, that includes an image sensor, such as a charge-coupled device (CCD), or an image sensor array. The imaging apparatus  41  receives visible light and thereby outputs outer appearance information or shape information of a target as image data that is a detection result. 
     The LiDAR apparatus  43  is oriented towards the advancing direction of the vehicle  100 . The LiDAR apparatus  43  emits infrared laser light and receives reflected light that is reflected by a target. The LiDAR apparatus  43  thereby detects a distance and an angle of the target in relation to the vehicle  100  and acquires the target as a detection point group. A detection point refers to a point that indicates a position in which at least a portion of the target identified by the reflected light may be present, within a detectable range of the LiDAR apparatus  43 . 
     In addition, the detection point group refers to a collection of detection points within a predetermined period. The detection point group is expressed as a distance image by three-dimensional coordinates of the detection points. Here, the detection point is meant to include both a distance measurement point that is detected by time of flight (TOF) of light, and a detection point that is expressed by a luminance value that is inputted to a light receiving element that is provided in the LiDAR apparatus  43 . According to the present embodiment, resolution of the LiDAR apparatus  43  is a value that ranges from 0.1 degrees to 0.2 degrees in both a horizontal direction and a vertical direction. 
     The position sensor  45  detects an own position of the vehicle  100 . The own position is expressed by a latitude and a longitude of the vehicle  100 . For example, a global navigation satellite system (GNSS) and a gyro sensor can be given as the position sensor  45 . Here, the own position may include an altitude of the vehicle  100 . 
     The six-axis sensor  47  detects an orientation (advancing direction) of the vehicle  100  and an attitude of the vehicle  100 . For example, a motion sensor that includes a three-axis acceleration sensor and a three-axis gyro sensor can be used as the six-axis sensor  47 . 
     As shown in  FIG.  1   , the tilt detection apparatus  10  and the driving assistance control apparatus  80  are mounted inside the vehicle  100 . The tilt detection apparatus  10  and the driving assistance control apparatus  80  are connected to the measurement apparatus unit  40  by wiring CV. 
     The tilt detection apparatus  10  detects a tilt of the LiDAR apparatus  43  in a vertical direction of the vehicle  100 . As shown in  FIG.  2   , the tilt detection apparatus  10  is configured as a single or a plurality of electronic control units (ECUs) in which a central processing unit (CPU)  20 , a memory  30 , and an input-output interface  11  are mounted. The CPU  20 , the memory  30 , and the input-output interface  11  are connected by a bus  15  so as to be capable of two-way communication. The CPU  20  functions as a detecting unit  21 , a distance image acquiring unit  22 , a surroundings information acquiring unit  23 , and a correcting unit  24  by opening and running a program that is stored in the memory  30 . 
     The detecting unit  21  detects the tilt of the LiDAR apparatus  43  in the vertical direction of the vehicle  100  by collating the distance image generated by the LiDAR apparatus  43  and information (referred to, hereafter, as “surroundings information”) on the periphery of a traveling route of the vehicle  100  in a tilt detection process, described hereafter. 
     According to the present embodiment, the “surroundings information” refers to information that indicates a gradient of the traveling route of the vehicle  100 , and information that indicates positions and shapes of ground objects, such as road facilities and buildings, that are provided in the periphery of the traveling route. For example, the surroundings information includes map information, and coordinate information regarding a captured image of the imaging apparatus  41  and the like. In addition, for example, as the above-described road facilities, guardrails, traffic signs, road information display boards indicating traffic congestion information and guidance information, and footbridges are applicable. Furthermore, the road facilities also include road markings such as boundary lines, stop lines, and crosswalks. 
     Surroundings information SI shown as an example in  FIG.  3    is map information on the periphery of a traveling route Ln of the vehicle  100 . The surroundings information SI includes information that indicates the positions (coordinates) and the shapes of a guardrail Ob 1 , traffic signs Ob 3  and Ob 4 , a road illumination apparatus Ob 5 , a stop line Ob 2 , a building Ob 6 , and the like that are present in the vehicle frontward direction FD. The vehicle frontward direction FD is the advancing direction of the vehicle  100 . 
     In  FIG.  3   , an X axis and a Y axis are set to be parallel to the horizontal direction of the vehicle  100 . A Z axis is set to be parallel to the vertical direction. The X axis is parallel to the advancing direction of the vehicle  100 . A +X direction is the vehicle frontward direction FD and a −X direction is the vehicle rearward direction RD. The Y axis is parallel to the width direction of the vehicle  100 . A+Y direction is the vehicle width direction LH. 
     The detecting unit  21  respectively extracts a specific object from the surroundings information SI and the distance image. The detecting unit  21  then calculates an elevation/depression angle of the LiDAR apparatus  43  by determining an angle between line segments in the horizontal direction of both extracted objects. The detecting unit  21  determines the calculated elevation/depression angle to be the tilt of the LiDAR apparatus  43 . Here, detailed descriptions regarding the tilt of the LiDAR apparatus  43  and a method for detecting the tilt of the LiDAR apparatus  43  will be given hereafter. 
     The distance image acquiring unit  22  acquires the distance image that is generated by the LiDAR apparatus  43 . 
     The surroundings information acquiring unit  23  acquires the surroundings information SI from a traffic management system or the like, through a communication apparatus  65 . Here, the surroundings information acquiring unit  23  may acquire map data from a navigation apparatus  70 , instead of the traffic management system. Alternatively, the surroundings information acquiring unit  23  may acquire a captured image of an area in the advancing direction of the vehicle  10  from the imaging apparatus  41 . 
     The correcting unit  24  corrects the detection result of the LiDAR apparatus  43  using the tilt of the LiDAR apparatus  43  determined by the detecting unit  21 . Specifically, the correcting unit  24  updates an offset correction value  31  with the determined tilt value of the LiDAR apparatus  43 . The offset correction value  31  is stored in the memory  30 . As a result, when the driving assistance control apparatus  80  recognizes a target in the periphery of the vehicle  100  using the detection point group detected by the LiDAR  43 , the position of the detection point group in the vertical direction is corrected with reference to the offset correction value  31 . 
     The driving assistance control apparatus  80  is configured by a single or a plurality of ECUs in which a CPU, a memory, and an interface are mounted (not shown). The driving assistance control apparatus  80  controls the driving apparatus  60 , described hereafter, that is mounted to the vehicle  100 . The driving assistance control apparatus  80  thereby performs driving assistance, that is, braking assistance, steering assistance and driving assistance of the vehicle  100 . 
     In addition to the above-described measurement apparatus unit  40  and the driving assistance control apparatus  80 , a notification apparatus  50 , the driving apparatus  60 , the communication apparatus  65 , and the navigation apparatus  70  are mounted to the vehicle  100 . 
     The notification apparatus  50  notifies an occupant of the vehicle  100  of various types of information through visual information and audio information. The notification apparatus  50  includes a display apparatus  51  and a speaker  53  that are oriented towards the interior of the vehicle cabin of the vehicle  100 . The display apparatus  51  displays characters, images, and the like. The speaker  53  outputs voice, warning sounds, and the like. 
     The driving apparatus  60  includes a driving unit, a steering apparatus, and a brake apparatus (not shown). The driving unit includes at least either of an internal combustion engine and a motor. The driving unit generates driving force for traveling. The steering apparatus includes an electric steering mechanism and the like. The steering apparatus implements steering of the vehicle  100 . The brake apparatus includes a disk brake and the like. The brake apparatus implements braking of the vehicle  100 . 
     The communication apparatus  65  performs exchange of data, such as the surroundings information SI, by performing wireless communication between the vehicle  100  and an external party outside the vehicle  100 . For example, as the external party outside the vehicle  100 , a traffic management system such as an intelligent transport system, a roadside wireless transceiver, and another vehicle that is traveling the periphery of the vehicle  100  are applicable. 
     The navigation apparatus  70  performs route search and route guidance using electronic map data. The electronic map data includes road network data, road data, and the like. 
     A2. Tilt Detection Process 
     Before the tilt detection process is described, the tilt of the LiDAR apparatus  43  will be described with reference to  FIG.  4   . As shown by solid lines, the LiDAR apparatus  43  has a substantially rectangular parallelepiped shape and is fastened to the vehicle  100  by a fixture  432 . A light emitting unit for infrared laser light, a light receiving unit for reflected light that is reflected by a target, and the like are housed inside a casing  431  of the LiDAR apparatus  43 . The LiDAR apparatus  43  is attached to the vehicle  100  such that a lower side of a bottom surface of the casing  431  is parallel with the horizontal direction of the vehicle  100 . A mounted state indicated by the solid lines is an originally correct attitude. 
     The LiDAR apparatus  43   a  that is shown by broken lines indicates a state in which the LiDAR apparatus  43  is tilted in the vertical direction of the vehicle  100 . Specifically, the LiDAR apparatus  43   a  is the LiDAR apparatus  43  that is tilted in an upward direction of the vehicle  100  by an angle θ. A lower side T1a of the bottom surface of the casing of the LiDAR apparatus  43   a  is shifted vertically upward from the horizontal direction of the vehicle  100  by an angle θ and intersects the horizontal direction. Therefore, the tilt of the LiDAR apparatus  43  can be determined by the angle θ being determined. 
     In the tilt detection process according to the present embodiment, the shift in the angle in relation to the horizontal direction of the LiDAR apparatus  43  is detected through use of the surroundings information SI and the distance image. That is, an object that is present in the periphery of the traveling route Ln of the vehicle  100  is respectively extracted from the surroundings information SI and the distance image. An angle of shifting of a side in the horizontal direction of the object that is extracted from the distance image with reference to a side in the horizontal direction of the object that is extracted from the surroundings information SI is detected. The tilt of the LiDAR apparatus  43  is thereby determined. 
     As described above, in the LiDAR apparatus  43  according to the present embodiment, the resolution in the vertical direction is a value that ranges from 0.1 degrees to 0.2 degrees. Therefore, the side extending in the horizontal direction of the object can be accurately detected. 
     The tilt detection process shown in  FIG.  5    is repeatedly performed at a predetermined interval while the vehicle  100  is traveling. The predetermined interval may be several seconds to ten-odd seconds. The tilt detection process is started when a signal that indicates that an ignition switch is switched from off to on is inputted from a high-order ECU that controls the overall vehicle  100 . 
     The detecting unit  21  acquires a current position of the vehicle  100  from the detection result of the position sensor  45  (step S 10 ). The detecting unit  21  acquires the advancing direction of the vehicle  100  from the detection result of the six-axis sensor  47  (step S 15 ). The surroundings information acquiring unit  23  acquires the surroundings information SI (step S 20 ). At this time, the surroundings information acquiring unit  23  acquires the surroundings information SI in which the orientation of the surroundings information SI matches the advancing direction of the vehicle  100 . The distance image acquiring unit  22  acquires the distance image from the detection result of the LiDAR apparatus  43  (step S 25 ). 
     The detecting unit  21  determines a target object of interest (step S 30 ). According to the present embodiment, the “target object of interest” refers to a target object that is present in a position closest to the vehicle  100 , among objects that are present in the periphery of the traveling route Ln of the vehicle. The detecting unit  21  references the surroundings information SI and, among objects that are present in the periphery of the vehicle  100 , such as among road facilities, identifies a road facility that is present in a position closest to the vehicle  100  as the target object of interest. 
     In the surroundings information SI shown as an example in  FIG.  3   , the guardrail Ob 1  can be identified as the target object of interest. Here, when the identified target object of interest cannot be detected in the distance image, the detecting unit  21  may identify a road facility that is present in a position second closest to the vehicle  100  (the stop line Ob 2  or the traffic sign Ob 3  in the example shown in  FIG.  3   ) as the target object of interest 
     The detecting unit  21  respectively detects an angle of the target object of interest in the vertical direction of the vehicle  100  in the surroundings information SI and the distance image (step S 35 ). Specifically, the detecting unit  21  detects the target object of interest from the surroundings information SI. The detecting unit  21  identifies a side of the target object of interest that is parallel to the horizontal direction of the vehicle  100 . The detecting unit  21  then determines an angle that is formed by the identified side and the horizontal direction of the vehicle  100 . 
     More specifically, first, the detecting unit  21  detects a plurality of X coordinates, Y coordinates, and Z coordinates of the detection points (such as representative points) that configure the target object of interest. Using the least squares method, the detecting unit  21  detects a line segment that is parallel to the horizontal direction or an approximate line segment thereof in the target object of interest. Next, with the horizontal direction of the vehicle  100  as reference, the detecting unit  21  determines an angle of the line segment in relation to this reference. 
     Here, the side of the target object of interest that is parallel to the horizontal direction of the vehicle  100  may be a line segment that connects detection points that correspond to terminal points, among the detection points that configure the target object of interest. Alternatively, the side of the target object of interest that is parallel to the horizontal direction of the vehicle  100  may be a line segment that connects a detection point that corresponds to an intermediate point and a detection point that correspond to a terminal point, among the detection points that configure the target object of interest. Moreover, the detecting unit  21  may determine the line segment using an edge extraction process instead of the least squares method. 
     The detecting unit  21  detects the angle of the target object of interest in the distance image through similar steps. Specifically, the detecting unit  21  detects an object that is assumed to be the target object of interest from the distance image. The detecting unit  21  identifies a side of the detected target object of interest that is parallel to the horizontal direction of the vehicle  100 . The detecting unit  21  then determines an angle that is formed by the identified side and the horizontal direction of the vehicle  100 . 
     The detecting unit  21  determines the tilt of the LiDAR apparatus  43  (step S 40 ). Specifically, the detecting unit  21  detects a difference between the angle of the target object of interest in the surroundings information SI and the angle of the target object of interest in the distance image detected at above-described step S 35 , and determines the detected difference to be the tilt of the LiDAR apparatus  43 . 
     The detecting unit  21  determines whether the determined tilt of the LiDAR apparatus  43  is included in a first threshold range (step S 45 ). According to the present embodiment, the “first threshold range” refers to a range in which the angle in the vertical direction of the vehicle  100  ranges from −5 degrees to +5 degrees when the horizontal direction of the vehicle  100  is 0 degrees. When the detecting unit  21  determined that the determined tilt of the LiDAR apparatus  43  is included in the first threshold range (YES at step S 45 ), the correcting unit  24  corrects the position of the detection point group (step S 50 ). Specifically, the correcting unit  24  updates the offset correction value  31  that is stored in the memory  30 . 
     When determined that the determined tilt of the LiDAR apparatus  43  exceeds the first threshold range at step S 45  (NO at step S 45 ), the detecting unit  21  notifies the occupant of the vehicle  100  using the notification apparatus  50  (step S 55 ). For example, the detecting unit  21  enables the notification apparatus  50  to perform notification display or voice guidance that states, “Please have the LiDAR apparatus  43  inspected at an automobile dealership.” 
     The detecting unit  21  determines whether the determined tilt of the LiDAR apparatus  43  is included in a second threshold range (step S 60 ). According to the present embodiment, the “second threshold range” is a range in which the angles in the vertical direction of the vehicle  100  are greater than those of the first threshold range. The “second threshold range” refers to a range in which the angle in the vertical direction of the vehicle  100  ranges from −30 degrees to +30 degrees or, preferably, −25 degrees to +25 degrees. When determined that the determined tilt of the LiDAR apparatus  43  is not included in the second threshold range (NO at step S 60 ), the detecting unit  21  stops autonomous driving of the vehicle  100  (step S 65 ). Specifically, the detecting unit  21  stops execution of autonomous driving of the vehicle  100  by the driving assistance control apparatus  80 . In addition, the detecting unit  21  gives notification to prompt the driver of the vehicle  100  to perform manual driving and notification to prompt inspection of the vehicle  100 , using the notification apparatus  50 . 
     When the detecting unit  21  determines that the determined tilt of the LiDAR apparatus  43  is included in the second threshold range at above-described step S 60  (YES at step S 60 ), or after above-described step S 65  is performed, the tilt detection process is ended. 
     In the tilt detection apparatus  10  according to the present embodiment configured as described above, the distance image expressed by the detection point group that is detected by the LiDAR apparatus  43  is acquired. The surroundings information SI on the periphery of the traveling route Ln of the vehicle  100  is acquired. The tilt of the LiDAR apparatus  43  is determined through use of the acquired distance image and the acquired surroundings information SI. Therefore, the tilt of the LiDAR apparatus  43  can be easily detected. Specifically, the detecting unit  21  determines a target object of interest from the road facilities that are present in the periphery of the traveling route Ln. 
     The detecting unit  21  detects the difference between the angle of the target object of interest in the vertical direction of the vehicle  100  in the surroundings information SI and the angle of the target object of interest in the vertical direction of the vehicle  100  in the distance image. The detecting unit  21  thereby determines the tilt of the LiDAR apparatus  43 . Therefore, the tilt of the LiDAR apparatus  43  can be determined without complicated processes being required. In addition, because the target object of interest is the guardrail Ob 1 , the target object of interest can be easily identified. 
     The correcting unit  24  corrects the position of the detection point group in the vertical direction using the determined tilt of the LiDAR apparatus  43 . Therefore, even if the LiDAR apparatus  43  is tilted in the vertical direction of the vehicle  100  from the attitude at the time of mounting to the vehicle  100 , the position of the detection point group detected by the LiDAR apparatus  43  can be set to a position in which the detection point group should originally be detected. Consequently, occurrence of an issue in that a target in the periphery of the vehicle  100  cannot be accurately detected can be suppressed. 
     In addition, when the determined tilt of the LiDAR apparatus  43  exceeds the first threshold range, the detecting unit  21  notifies the occupant of the vehicle  100  using the notification apparatus  50 . Consequently, the occupant of the vehicle  100  can be made aware that the LiDAR apparatus  43  is tilted from the originally correct attitude and, therefore, inspection of the vehicle  100  is required. 
     In addition, when the determined tilt of the LiDAR apparatus  43  exceeds the second threshold range, the detecting unit  21  stops autonomous driving of the vehicle  100 . 
     Therefore, the detection result of the LiDAR apparatus  43  can be prevented from being used in driving assistance of the vehicle  100 . Consequently, problems occurring in driving assistance of the vehicle  100  can be suppressed. 
     B. OTHER EMBODIMENTS 
     (1) According to the above-described embodiment, the detecting unit  21  may determine the tilt of the LiDAR apparatus  43  by comparing edges in the horizontal direction of a building. Specifically, at above-described step S 30 , the detecting unit  21  identifies the building Ob 6  that is present in a position closest to the vehicle  100  as the target object of interest. Next, at above-described step S 35 , the detecting unit detects the target object of interest from the surroundings information SI and, for example, extracts an edge in the horizontal direction of the target object of interest based on luminance values. 
     In addition, the detecting unit  21  similarly extracts an edge in the horizontal direction of the target object of interest in the distance image, as well. Subsequently, the detecting unit  21  compares the extracted edge in the surroundings information SI and the extracted edge in the distance image, and detects an angle of shifting of the edges. The detecting unit  21  may thereby determine the tilt of the LiDAR apparatus  43 . As a result of a configuration such as this, the tilt of the LiDAR apparatus  43  can be more accurately determined. 
     (2) According to the above-described embodiments, the target object of interest is not limited to guardrails and buildings. The target object of interest may be an arbitrary object that is present on the traveling route Ln of the vehicle  100  and the periphery thereof, such as a road marking such as a lane marker, a crosswalk, or a stop line on the traveling route Ln, or a road facility such as a traffic sign, traffic lights, a footbridge, or a road information display board. 
     (3) According to the above-described embodiments, the detecting unit  21  may determine the tilt of the LiDAR apparatus  43  using past detection values of the angle of a target object of interest in the distance image and the surroundings information SI. Specifically, the detecting unit  21  may store the angles of the target object of interest detected at above-described step S 35  in the memory  30  and, for example, determine the tilt of the LiDAR apparatus  43  using an average value of ten differing angles detected for the target object of interest. 
     At this time, when a detection value that is far from a predetermined reference value is present, the detection value may be excluded. As a result, for example, even in cases in which objects that can be detected differ between the distance image and the surroundings information SI, such as when a road facility is temporarily removed due to construction or the like, the tilt of the LiDAR apparatus  43  can be accurately determined. 
     (4) According to the above-described embodiments, the tilt of the LiDAR apparatus  43  is determined through use of the angle of the target object of interest in the vertical direction of the vehicle  100 . However, the angle of the target object of interest is not limited to that in the vertical direction of the vehicle  100 . The angle of the target object of interest in the advancing direction of the vehicle  100  may also be used. 
     In addition, the CPU  20  of the tilt detection apparatus  10  may omit the correcting unit  24 . In this case, correction of the position of the detection point group (above-described step S 50 ) may be omitted. Furthermore, the occupant of the vehicle  100  may not be notified when the determined tilt of the LiDAR apparatus  43  exceeds the first threshold range. Still further, autonomous driving of the vehicle  100  may not be stopped when the determined tilt of the LiDAR apparatus  43  exceeds the second threshold range. 
     The units such as the control unit and the method thereof described in the present disclosure may be implemented by a dedicated computer that is provided such as to be configured by a processor and a memory, the processor being programmed to provide one or a plurality of functions that are realized by a computer program. 
     Alternatively, the units such as the control unit and the method thereof described in the present disclosure may be implemented by a dedicated computer that is provided by a processor being configured by a single dedicated hardware logic circuit or more. Still alternatively, the units such as the control unit and the method thereof described in the present disclosure may be implemented by a single dedicated computer or more, the dedicated computer being configured by a combination of a processor that is programmed to provide one or a plurality of functions, a memory, and a processor that is configured by a single hardware logic circuit or more. In addition, the computer program may be stored in a non-transitory computer-readable storage medium that can be read by a computer as instructions to be performed by the computer. 
     The present disclosure is not limited to the above-described embodiments. The present disclosure can be implemented through various configurations without departing from the spirit of the disclosure. For example, technical features according to the embodiments that correspond to technical features according to aspects described in the summary of the invention can be replaced and combined as appropriate to solve some or all of the above-described issued or to achieve some or all of the above-described effects. Furthermore, the technical features may be omitted as appropriate unless described as a requisite in the present specification.