Patent Publication Number: US-2021190949-A1

Title: Ranging device

Description:
FIELD 
     The presently disclosed subject matter relates to a ranging device adapted to be mounted on a vehicle. 
     BACKGROUND 
     Patent Document 1 discloses a LiDAR (Light Detecting and Ranging) sensor unit as an example of a distance sensor adapted to be mounted on a vehicle. The LiDAR sensor unit detects a distance to an object that generated reflected light based on a time period from the time when detecting light is emitted to the time when the reflected light is received. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Publication No. 2018-049014 A 
     SUMMARY 
     Technical Problem 
     It is demanded to improve the measurement accuracy of the ranging device mounted on the vehicle as described above. 
     Solution to Problem 
     In order to meet the demand described above, an illustrative aspect of the presently disclosed subject matter provides a ranging device adapted to be mounted on a vehicle, comprising: 
     a light emitting element configured to emit detecting light; 
     a light receiving element; 
     a translucent cover configured to form a part of an outer surface of the vehicle and covering the light emitting element and the light receiving element; and 
     a processor configured to calculate a distance to an object that generated reflected light based on a time period from time when the detecting light is emitted from the light emitting element to time when the reflected light is incident on the light receiving element, at least after it is elapsed a time period from the time when the detecting light is emitted to time when reflected light generated by an inner surface of the translucent cover is incident on the light receiving element. 
     In a case where the light emitting element and the light receiving element are covered by a translucent cover forming a part of the outer surface of the vehicle, the detecting light emitted from the light emitting element may be partially reflected by an inner surface of the translucent cover and incident on the light receiving element as internally reflected light. When a light receiving signal based on the internally reflected light is outputted from the light receiving element, the processor may recognize that an object is present at the position of the translucent cover. 
     According to the above configuration, the reception of the light receiving signal by the processor is started after the elapse of the time period from the time when the detecting light is emitted to the time when the internally reflected light is incident on the light receiving element, so that the distance to the object can be calculated. Therefore, it is possible to eliminate the influence of the internal reflection of the translucent cover on the calculation of the distance to the object performed by the processor. Accordingly, the measurement accuracy of the ranging device is enhanced. 
     The above ranging device may be configured so as to comprise a timer configured to start time measurement based on emission of the detecting light. Here, the processor is configured to calculate the distance at least after the time period from the time when the detecting light is emitted to the time when the reflected light generated by the inner surface of the translucent cover is incident on the light receiving element is measured by the timer. 
     According to such a configuration, since the timer starts measuring the time period based on the emission of the detecting light from the light emitting element, it is possible to more accurately measure the time period. 
     The above ranging device may be configured so as to comprise a timer configured to start time measurement at least after it is elapsed the time period from the time when the detecting light is emitted to the time when the reflected light generated by the inner surface of the translucent cover is incident on the light receiving element. Here, the processor is configured to calculate the distance based on the time period measured by the timer. 
     According to such a configuration, even if the reflected light is incident on the light receiving element before the time period from the time when the detecting light is emitted to the time when the internally reflected light is incident on the light receiving element elapses, the processor cannot calculate the distance based on the received light. This is because the time measurement used for the calculation of the distance is not started by the timer. Since the processor does not have to restrain the acceptance of the output from the light receiving element, it is possible to suppress an increase in the processing load. 
     The above ranging device may be configured so as to comprise a lamp unit disposed in a space defined by the translucent cover, and configured to emit visible light toward the outside of the vehicle. 
     The lamp unit is generally disposed at four corner portions of the vehicle. The four corner portions are also portions where there are few obstacles when detecting information in an outside area of the vehicle. By arranging the light emitting element and the light receiving element so as to share the space defined by the translucent cover with the lamp unit, it is possible to efficiently detect the information in the outside area of the vehicle. On the other hand, the light emitted from the lamp unit may be reflected by the inner surface of the translucent cover. However, as described above, it is also possible to eliminate the influence of such internal reflection on the calculation of the distance to the object performed by the processor. 
     The above ranging device may be configured such that the light emitting element and the light receiving element constitute a part of at least one of a LiDAR sensor unit, a TOF camera unit, and a millimeter wave radar unit. 
     As used herein, the term “light” means an electromagnetic wave having an arbitrary wavelength capable of detecting desired information. For example, the term “light” as used herein includes not only visible light but also ultraviolet light, infrared light, millimeter waves, and microwaves. 
     As used herein, the term “lamp unit” means a constituent unit of a component that can be distributed by itself as a single unit while providing a desired lighting function. 
     As used herein, the term “sensor unit” means a constituent unit of a component that can be distributed by itself as a single unit while providing a desired information detecting function. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a configuration of a left front ranging device according to an embodiment. 
         FIG. 2  illustrates a position of the left front ranging device of  FIG. 1  in a vehicle. 
         FIG. 3A  illustrates a first exemplary configuration of the left front ranging device of  FIG. 1 . 
         FIG. 3B  illustrates an exemplary operation of the left front ranging device of  FIG. 3A . 
         FIG. 4  illustrates an exemplary operation of the left front ranging device of  FIG. 3A . 
         FIG. 5A  illustrates a second exemplary configuration of the left front ranging device of  FIG. 1 . 
         FIG. 5B  illustrates how the left front ranging device of  FIG. 5A  operates. 
         FIG. 6  illustrates how the left front ranging device of  FIG. 5A  operates. 
         FIG. 7A  illustrates a third exemplary configuration of the left front ranging device of  FIG. 1 . 
         FIG. 7B  illustrates how the left front ranging device of  FIG. 7A  operates. 
         FIG. 8  illustrates how the left front ranging device of  FIG. 7A  operates. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Examples of embodiments will be described below in detail with reference to the accompanying drawings. In each of the drawings used in the following description, the scale is appropriately changed in order to make each member have a recognizable size. 
     In the accompanying drawings, an arrow F represents a forward direction of the illustrated structure. An arrow B represents a rearward direction of the illustrated structure. An arrow U represents an upward direction of the illustrated structure. An arrow D represents a downward direction of the illustrated structure. An arrow L represents a leftward direction of the illustrated structure. An arrow R represents a rightward direction of the illustrated structure. The terms “left” and “right” used in the following descriptions represent the left-right directions as viewed from the driver&#39;s seat. 
       FIG. 1  illustrates a configuration of a left front ranging device  1  according to an embodiment. The left front ranging device  1  is disposed in a left front portion LF of the vehicle  100  illustrated in  FIG. 2 . The left front portion LF is an area located on the left of the center in a left-right direction of the vehicle  100  and ahead of the center in a front-rear direction of the vehicle  100 . 
     As illustrated in  FIG. 1 , the left front ranging device  1  includes a housing  11  and a translucent cover  12 . The housing  11  defines an accommodation chamber  13  together with the translucent cover  12 . The translucent cover  12  forms a portion of an outer surface of the vehicle  100 . 
     The left front ranging device  1  includes a LiDAR sensor unit  14 . The LiDAR sensor unit  14  is disposed in the accommodation chamber  13 . 
       FIG. 3A  illustrates a first exemplary configuration of the left front ranging device  1 . The LiDAR sensor unit  14  includes a light emitting element  41  and a light receiving element  42 . The translucent cover  12  covers the light emitting element  41  and the light receiving element  42 . 
     The light emitting element  41  is configured to emit detecting light L 1  toward the outside of the vehicle  100 . As the detecting light L 1 , for example, infrared light having a wavelength of 905 nm can be used. As the light emitting element  41 , a semiconductor light emitting element such as a laser diode or a light emitting diode can be used. 
     The LiDAR sensor unit  14  may appropriately include an optical system (not illustrated) for irradiating the detecting light L 1  in a desired direction. The LiDAR sensor unit  14  may include a scanning mechanism (not illustrated) for changing the irradiating direction of the detecting light L 1  to scan a detection area. 
     The light receiving element  42  is configured to output a light receiving signal S 1  corresponding to the amount of incident light. As the light receiving element  42 , a photodiode, a phototransistor, a photo resistor, or the like can be used. The LiDAR sensor unit  14  may include an amplifier circuit (not illustrated) for amplifying the light receiving signal S 1 . 
     The left front ranging device  1  includes a processor  15 . The processor  15  is disposed in the accommodation chamber  13 . The processor  15  may be incorporated in the LiDAR sensor unit  14 . The processor  15  outputs a control signal S 0  for causing the light emitting element  41  to emit the detecting light L 1  at a desired timing. The processor  15  receives the light receiving signal S 1  outputted from the light receiving element  42 . 
     The processor  15  includes an internal timer  15   a  for measuring time. The processor  15  calculates a distance to an object  200  that generated reflected light L 2  based on a time period from the time when the detecting light L 1  is emitted from the light emitting element  41  to the time when the reflected light L 2  is incident on the light receiving element  42 . The LiDAR sensor unit  14  can obtain information as to the shape of the object  200  associated with the reflected light L 2  by accumulating the data as to the calculated distance in association with the irradiating direction of the detecting light L 1 . 
     In this exemplary configuration, the processor  15  is configured to calculate the distance after a lapse of a time period longer than a time period T 1  from the time t 0  when the detecting light L 1  is emitted to the time when reflected light L 3  reflected by an inner surface  12   a  of the translucent cover  12  is incident on the light receiving element  42 . 
     More specifically, it is configured to perform the calculation of the distance after a lapse of a time period T 2  from the time t 0  to the time when reflected light L 4  is incident on the light receiving element  42 . The reflected light L 4  is reflected by a virtual object  201  that situates at a position distant from the inner surface  12   a  of the translucent cover  12  toward the outside of the vehicle  100  by a distance d. The distance d is set as a value for which the ranging (detection) of an object that situates in an outside area of the vehicle  100  is meaningful. In other words, the distance d is set as a value capable of excluding the detection of an object that is too close to the translucent cover  12 . 
       FIGS. 3B and 4  illustrate exemplary processing for realizing such an operation. First, the processor  15  starts time measurement from the time t 0  when the light emitting element  41  emits the detecting light L 1  (STEP 11 ). The time measurement is performed by the internal timer  15   a  provided in the processor  15 . For example, the time t 0  may be set to a timing at which the processor  15  outputs the control signal S 0  to the light emitting element  41 . 
     The processor  15  determines whether a time period T measured by the internal timer  15   a  has reached T 2  (STEP 12 ). If the measured time period T has not reached T 2  (N in STEP 12 ), this determination processing is repeated. 
     When the measured time period reaches T 2  (Y in STEP 12 ), the processor  15  starts receiving the light receiving signal S 1  outputted from the light receiving element  42  (STEP 13 ). That is, after the elapse of the time period T 2 , the processor  15  can calculate the distance to the object associated with the light receiving signal S 1  based on the time period from the time t 0  to the time when the light receiving signal S 1  is received. The time measurement with the internal timer  15   a  is continued. 
     The processor  15  determines whether the light receiving signal S 1  is received (STEP 14 ). If the light receiving signal S 1  is not received (N in STEP 14 ), this determination processing is repeated to continue the time measurement with the internal timer  15   a.    
     When the light receiving signal S 1  is received (Yin STEP 14 ), the processor  15  stops the time measurement with the internal timer  15   a  (STEP 15 ). In the case of the example illustrated in  FIG. 3A  and  FIG. 3B , the light receiving signal S 1  outputted by the incident of the reflected light L 2  from the object  200  on the light receiving element  42  is received by the processor  15  after the elapse of the time period T 3  from the time t 0 . The processor  15  calculates the distance to the object  200  based on the time period T 3  (STEP 16  in  FIG. 4 ). 
     In  FIG. 3B , a period P 1  represents a period during which time measurement is performed by the internal timer  15   a  of the processor  15 . The period P 2  represents a period during which the processor  15  can receive the light receiving signal S 1  from the light receiving element  42 . In other words, even if the light receiving signal S 1  is outputted by the incident of the reflected light on the light receiving element  42  before the time period T 2  elapses, the processor  15  does not perform the calculation of the distance based on the light receiving signal S 1 . 
     In a case where the LiDAR sensor unit  14  is configured to be disposed in the accommodation chamber  13 , the light emitting element  41  and the light receiving element  42  are covered by the translucent cover  12  forming a part of the outer surface of the vehicle  100 . As a result, the detecting light L 1  emitted from the light emitting element  41  may be partially reflected by the inner surface  12   a  of the translucent cover  12  and incident on the light receiving element  42  as the reflected light L 3 . When the light receiving signal S 1  based on the reflected light L 3  is outputted from the light receiving element  42 , the processor  15  may recognize that an object is present at the position of the translucent cover  12 . 
     According to the above exemplary configuration, the reception of the light receiving signal S 1  by the processor  15  is started after the elapse of the time period T 1  from the time t 0  when the detecting light L 1  is emitted to the time when the reflected light L 3  is incident on the light receiving element  42 , so that the distance to the object can be calculated. Therefore, it is possible to eliminate the influence of the internal reflection of the translucent cover  12  on the calculation of the distance to the object performed by the processor  15 . Accordingly, the measurement accuracy of the left front ranging device  1  is enhanced. 
     More specifically, after the time period T 2  elapses from the time t 0  when the detecting light L 1  is emitted to the time when the reflected light L 4  reflected by the virtual object  201  that situates at a position distant from the inner surface  12   a  of the translucent cover  12  toward the outside of the vehicle  100  by the distance d is incident on the light receiving element  42 , the reception of the light receiving signal S 1  by the processor  15  (i.e., the calculation of the distance to the object) is started. Accordingly, it is possible to avoid a situation in which an object that situates outside the vehicle  100  but is too close to the translucent cover  12  obstructs meaningful ranging. Since the distance d can be relatively freely set regardless of the shape of the inner surface  12   a  of the translucent cover  12 , in particular, in a case where the detecting light L 1  passing through the translucent cover  12  is scanned, the processing load is suppressed. 
       FIG. 5A  illustrates a second exemplary configuration of the left front ranging device  1 . Components that are the same as or equivalent to those in the first exemplary configuration illustrated in  FIG. 3A  are assigned with the same reference symbols, and repetitive descriptions for those will be omitted. 
     The left front ranging device  1  according to the present example further includes a beam splitter  16 , a light receiving element  17 , and a timer  18 . 
     The beam splitter  16  reflects a portion of the detecting light L 1  emitted from the light emitting element  41  as reflected light L 5  toward the light receiving element  17  while allowing passage of another portion of the detecting light L 1 . As long as a similar function can be realized, the beam splitter  16  can be replaced with at least one appropriate optical element. 
     The reflected light L 5  from the beam splitter  16  is incident on the light receiving element  17 . The light receiving element  17  is configured to output a light receiving signal S 2  in response to the incident of the reflected light L 5 . As the light receiving element  17 , a photodiode, a phototransistor, a photo resistor, or the like can be used. That is, it can be detected that the detecting light L 1  is emitted from the light emitting element  41  based on the fact that the light receiving signal S 2  is outputted from the light receiving element  17 . 
     The timer  18  is configured to start time measurement when receiving the light receiving signal S 2  outputted from the light receiving element  17 . That is, the timer  18  is configured to start the time measurement based on the emission of the detecting light L 1  from the light emitting element  41 . The timer  18  is communicably connected to the processor  15 . 
     In this exemplary configuration, the processor  15  is configured to calculate the distance after a lapse of a time period longer than a time period T 1  from the time t 0  when the detecting light L 1  is emitted to the time when reflected light L 3  reflected by an inner surface  12   a  of the translucent cover  12  is incident on the light receiving element  42 . 
       FIGS. 5B and 6  illustrate exemplary processing for realizing such an operation. The timer  18  is in a standby state (N in STEP 21 ) until the light receiving signal S 2  is outputted from the light receiving element  17 . 
     When the light receiving signal S 2  is outputted from the light receiving element  17  in accordance with the emission of the detecting light L 1  from the light emitting element  41  (Y in STEP 21 ), the timer  18  is activated. That is, the timer  18  starts the time measurement substantially from the time t 0  when the light emitting element  41  emits the detecting light L 1  (STEP 22 ). 
     The timer  18  determines whether the measured time period T has reached T 1  (STEP 23 ). If the measured time period T has not reached T 1  (N in STEP 23 ), this determination processing is repeated. 
     When the measured time period T reaches T 1  (Y in STEP 23 ), the timer  18  notifies the processor  15 . In response to this notification, the processor  15  starts reception of the light receiving signal S 1  outputted from the light receiving element  42  (STEP 24 ). That is, after the elapse of the time period T 1 , the processor  15  can calculate the distance to the object associated with the light receiving signal S 1  based on the time period from the time t 0  to the time when the light receiving signal S 1  is received. The time measurement with the timer  18  is continued. 
     The processor  15  determines whether the light receiving signal S 1  is received (STEP 25 ). If the light receiving signal S 1  is not received (N in STEP 25 ), this determination processing is repeated to continue the time measurement with the timer  18 . 
     When the light receiving signal S 1  is received (Y in STEP 25 ), the processor  15  stops the time measurement with the timer  18  (STEP 26 ). In the case of the example illustrated in  FIG. 5A  and  FIG. 5B , the light receiving signal S 1  outputted by the incident of the reflected light L 2  from the object  200  on the light receiving element  42  is received by the processor  15  after the elapse of the time period T 3  from the time t 0 . The processor  15  calculates the distance to the object  200  based on the time period T 3  (STEP 27  in  FIG. 6 ). 
     In  FIG. 5B , a period P 3  represents a period during which the time measurement with the timer  18  is performed. The period P 4  represents a period during which the processor  15  can receive the light receiving signal S 1  from the light receiving element  42 . In other words, even if the light receiving signal S 1  is outputted by the incident of the reflected light on the light receiving element  42  before the time period T 1  elapses, the processor  15  does not perform the calculation of the distance based on the light receiving signal S 1 . 
     According to the present exemplary configuration, the reception of the light receiving signal S 1  by the processor  15  is started after the elapse of the time period T 1  from the time t 0  when the detecting light L 1  is emitted to the time when the reflected light L 3  is incident on the light receiving element  42 , so that the distance to the object can be calculated. Therefore, it is possible to eliminate the influence of the internal reflection of the translucent cover  12  on the calculation of the distance to the object performed by the processor  15 . Accordingly, the measurement accuracy of the left front ranging device  1  is enhanced. 
     In addition, since the timer  18  starts measuring the time period T 1  based on the emission of the detecting light L 1  from the light emitting element  41 , it is possible to more accurately measure the time period T 1 . In a particular case where the detecting light L 1  passing through the translucent cover  12  is scanned, the distance to the inner surface  12   a  of the translucent cover  12  may vary according to the light emitting direction of the detecting light L 1 . Even in such a case, it is possible to accurately set and measure the time period T 1  that changes in accordance with the distance to the inner surface  12   a.    
     The configuration using the beam splitter  16 , the light receiving element  17 , and the timer  18  illustrated in  FIG. 5A  is also applicable to the first exemplary configuration illustrated in  FIG. 3A . That is, the measurement of the time period T 2  with the internal timer  15   a  of the processor  15  may be performed by the timer  18  activated based on the emission of the detecting light L 1  from the light emitting element  41 . 
     Conversely, instead of measuring the time period T 1  using the beam splitter  16 , the light receiving element  17 , and the timer  18  according to the present exemplary configuration, the time period T 1  may be measured by the internal timer  15   a  of the processor  15 . 
       FIG. 7A  illustrates a third configuration of the left front ranging device  1 . Components that are the same as or equivalent to those in the first exemplary configuration illustrated in  FIG. 3A  are assigned with the same reference symbols, and repetitive descriptions for those will be omitted. 
     The left front ranging device  1  according to the present example further includes a timer  19 . The timer  19  is communicably connected to the processor  15 . 
     In this exemplary configuration, the processor  15  is configured to calculate the distance after a lapse of a time period longer than a time period T 1  from the time t 0  when the detecting light L 1  is emitted to the time when reflected light L 3  reflected by an inner surface  12   a  of the translucent cover  12  is incident on the light receiving element  42 . 
       FIGS. 7B and 8  illustrate exemplary processing for realizing such an operation. First, the processor  15  starts time measurement from the time t 0  when the light emitting element  41  emits the detecting light L 1  (STEP 31 ). The time measurement is performed by the internal timer  15   a  provided in the processor  15 . For example, the time t 0  may be set to a timing at which the processor  15  outputs the control signal S 0  to the light emitting element  41 . 
     The processor  15  determines whether the time period T measured by the internal timer  15   a  has reached T 1  (STEP 32 ). If the measured time period T has not reached T 1  (N in STEP 32 ), this determination processing is repeated. 
     When the measured time period T reaches T 1  (Y in STEP 32 ), the processor  15  activates the timer  19  to start time measurement (STEP 33 ). 
     The processor  15  determines whether the light receiving signal S 1  is received (STEP 34 ). If the light receiving signal S 1  is not received (N in STEP 34 ), this determination processing is repeated to continue the time measurement with the timer  19 . 
     When the light receiving signal S 1  is received (Y in STEP 34 ), the processor  15  stops the time measurement with the timer  19  (STEP 35 ). In the case of the example illustrated in  FIG. 7A  and  FIG. 7B , the light receiving signal S 1  outputted by the incident of the reflected light L 2  from the object  200  on the light receiving element  42  is received by the processor  15  after the elapse of the time period T 3  from the time to. The processor  15  calculates the distance to the object  200  based on the time measured by the timer  19  (STEP 36  in  FIG. 8 ). 
     In the above example, the time measured by the timer  19  is (T 3 −T 1 ). For example, the processor  15  may obtain the value of the time period T 3  by adding the time period T 1  measured by the internal timer  15   a  to the time (T 3 −T 1 ) measured by the timer  19 , and calculate the distance to the object  200  corresponding to the value of the time period T 3 . Alternatively, since the time period T 1  is known, the correspondence between the time value measured by the timer  19  and the distance value to the object can be stored in advance in a table or the like. In this case, the processor  15  may directly calculate the distance to the object  200  based on the correspondence with the time measured by the timer  19 . 
     In  FIG. 7B , a period P 5  represents a period during which the time measurement with the timer  19  is performed. The period P 6  represents a period during which the processor  15  can receive the light receiving signal S 1  from the light receiving element  42 . In other words, even if the light receiving signal S 1  is outputted by the incident of the reflected light on the light receiving element  42  before the time period T 1  elapses, the processor  15  cannot perform the calculation of the distance based on the light receiving signal S 1 . This is because the time measurement used for calculating the distance is not started by the timer  19 . 
     According to the present exemplary configuration, the time measurement with the timer  19  is started after the elapse of the time period T 1  from the time t 0  when the detecting light L 1  is emitted to the time when the reflected light L 3  is incident on the light receiving element  42 , so that the distance to the object can be calculated. Therefore, it is possible to eliminate the influence of the internal reflection of the translucent cover  12  on the calculation of the distance to the object performed by the processor  15 . Accordingly, the measurement accuracy of the left front ranging device  1  is enhanced. 
     In addition, the processor  15  does not need to restrain the reception of the light receiving signal S 1  from the light receiving element  42 . Accordingly, it is possible to suppress an increase in the processing load of the processor  15 . 
     As illustrated by dashed lines in  FIG. 7A , the light receiving signal S 1  outputted from the light receiving element  42  can also be inputted to the timer  19 . In this case, the timer  19  may be configured to stop the time measurement in response to the reception of the light receiving signal S 1 , and to notify the processor  15  of the measured time. In this case, since it is possible to suppress the delay of the stop timing of the measurement due to involvement of the processor  15 , the accuracy of the time period measured by the timer  19  is enhanced. 
     As illustrated in  FIG. 1 , the left front ranging device  1  may include a lamp unit  20 . The lamp unit  20  is disposed in the accommodation chamber  13 . The lamp unit  20  is a device for emitting visible light to the outside of the vehicle  100 . Examples of the lamp unit  20  include a headlamp unit, a clearance lamp unit, a direction indicator lamp unit, and a fog lamp unit. 
     The lamp unit  20  is generally disposed at four corner portions of the vehicle  100 . The four corner portions are also portions where there are few obstacles when detecting information in an outside area of the vehicle  100 . By arranging the LiDAR sensor unit  14  so as to share the accommodation chamber  13  with the lamp unit  20 , it is possible to efficiently detect the information in the outside area of the vehicle  100 . On the other hand, the light emitted from the lamp unit  20  may be reflected by the inner surface  12   a  of the translucent cover  12 . However, according to each of the above exemplary configurations, it is also possible to eliminate the influence of such internal reflection on the calculation of the distance to the object performed by the processor  15 . 
     The functions of the processor  15  described above may be realized by a general-purpose microprocessor operating in cooperation with a memory, or may be realized by a dedicated integrated circuit such as a microcontroller, an FPGA, and an ASIC. 
     The above embodiments are mere examples for facilitating understanding of the presently disclosed subject matter. The configuration according to each of the above embodiments can be appropriately modified without departing from the gist of the presently disclosed subject matter. 
     A right front ranging device having a configuration symmetrical with the left front ranging device  1  illustrated in  FIG. 1  relative to the left-right direction may be mounted on a right front portion RF of the vehicle  100  illustrated in  FIG. 2 . The right front portion RF is an area located on the right of the center in the left-right direction of the vehicle  100  and ahead of the center in the front-rear direction of the vehicle  100 . 
     The configuration of the left front ranging device  1  is also applicable to a left rear ranging device. The left rear ranging device is mounted on a left rear portion LB of the vehicle  100  illustrated in  FIG. 2 . The left rear portion LB is an area located on the left of the center in the left-right direction of the vehicle  100  and behind the center in the front-rear direction of the vehicle  100 . The basic configuration of the left rear ranging device may be symmetrical with the left front ranging device  1  relative to the front-rear direction. 
     The configuration of the left front ranging device  1  is also applicable to a right rear ranging device. The right rear ranging device is mounted on a right rear portion RB of the vehicle  100  illustrated in  FIG. 2 . The right rear portion RB is an area located on the right of the center in the left-right direction of the vehicle  100  and behind the center in the front-rear direction of the vehicle  100 . The basic configuration of the right rear ranging device may be symmetrical with the left rear ranging device described above relative to the left-right direction. 
     The LiDAR sensor unit  14  may be replaced with an appropriate sensor unit that may be used for the ranging of an object  200  situates in an outside area of the vehicle  100 . Examples of such a sensor unit include a TOF camera unit and a millimeter wave radar unit. A configuration using plural types of measurement techniques may be incorporated in a single sensor unit. The wavelength of the detecting light L 1  emitted by the light emitting element  41  and the wavelength at which the light receiving element  42  has sensitivity can be appropriately determined according to the detection technique to be used. 
     The present application is based on Japanese Patent Application No. 2018-141097 filed on Jul. 27, 2018, the entire contents of which are incorporated herein by reference.