Patent Publication Number: US-2019179013-A1

Title: Method for a lidar device for detecting a concealed object

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 119 to DE 10 2017 222 258.1, filed in the Federal Republic of Germany on Dec. 8, 2017, the content of which is hereby incorporated by reference herein in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a method for a LIDAR device for detecting a concealed object, a computer program that is configured for carrying out the steps of the method, a machine-readable memory medium on which the computer program is stored, and a LIDAR device for detecting a concealed object. 
     BACKGROUND 
     A method and a device for detecting position information of a target object that is not situated in the visual field of the device is known from WO 2016/063028 A1. The device includes an illumination device for illuminating a scattering surface situated in a viewing direction of the target object, scattered radiation having been scattered by the scattering surface. The device also includes a detection device for detecting reflected radiation. The reflected radiation is the scattered radiation that has been reflected from the target object into the visual field of the detection device. The device also includes a processing device for computing the position information based on the detected reflected radiation. 
     Accordingly, the illumination device emits light pulses which return to the detection device via three diffuse scattering operations (surface, object, surface). Since this is normally only an extremely small portion of the emitted light pulses, high pulse intensities of the emitted light pulses are necessary for reliable detection. 
     SUMMARY 
     The present invention is directed to a method for a LIDAR device for detecting a concealed object, the concealed object in the visual field of the LIDAR device being concealed by an obstacle. The method includes the step of emitting detection radiation in a predefined direction for illuminating a scattering surface, using at least one transmitting unit. The scattering surface is situated in a visual field of the concealed object. The emitted detection radiation is scattered on the scattering surface. The method includes the further step of receiving reflected detection radiation from an image area using a receiving unit. The reflected detection radiation is the detection radiation that has been reflected from the concealed object to the image area. The method includes the further step of detecting the concealed object based on the received detection radiation, using at least one evaluation unit. 
     According to the present invention, the method includes further, chronologically preceding steps. The method includes the chronologically preceding step of emitting a first radiation in the predefined direction using at least one transmitting unit for illuminating the scattering surface. The method also includes the chronologically preceding step of receiving a first radiation using a receiving unit. The method also includes the chronologically preceding step of ascertaining at least one value of the received first radiation using the evaluation unit. 
     The emitted detection radiation can be electromagnetic radiation. The emitted detection radiation can be laser radiation. In particular, the emitted detection radiation can be pulsed laser radiation. The emitted first radiation can be electromagnetic radiation. The emitted first radiation can be laser radiation. In particular, the emitted first radiation can be pulsed laser radiation. The transmitting unit can include a laser device. The laser device can be an individual laser. An individual laser can be a laser diode, for example. The laser device can be a plurality of individual lasers. The transmitting unit can include a pulsed or an unpulsed laser. A pulsed laser can emit laser pulses at a predefined frequency. The transmitting unit for emitting the detection radiation can be the same transmitting unit as the transmitting unit for emitting the first radiation. The transmitting unit for emitting the detection radiation can be different from the transmitting unit for emitting the first radiation. 
     The received first radiation can have been scattered on the scattering surface. The received first radiation can have additionally been diffusely reflected on the scattering surface. The received first radiation can also have been reflected on an unconcealed object in the visual field of the LIDAR device. The received first radiation can also have been directionally reflected on an unconcealed object in the visual field of the LIDAR device. 
     For high temporal resolution, it is advantageous when the receiving unit can be operated in a time-correlated single photon counting (TCSPC) mode. The receiving unit can include a time-resolving light detector. The receiving unit can include a time-resolving light detector array. The receiving unit can include a single photon avalanche diode (SPAD) matrix, for example. The receiving unit for receiving the reflected detection radiation can be the same receiving unit as the receiving unit for receiving the first radiation. The receiving unit for receiving the reflected detection radiation can be different from the receiving unit for receiving the first radiation. 
     The evaluation unit can be a signal processing unit. The evaluation unit can be configured for carrying out, based on the received detection radiation, an evaluation according to a time-of-flight method. The evaluation unit can be configured for carrying out, based on the received first radiation, an evaluation according to a time-of-flight method. The evaluation unit for detecting the concealed object can be the same evaluation unit as the evaluation unit for ascertaining at least one value of the received first radiation. The evaluation unit for detecting the concealed object can be different from the evaluation unit for ascertaining at least one value of the received first radiation. 
     The advantage of the present invention is that the method for recognizing an object that is concealed by an obstacle can be used in road traffic, for example, without endangering the safety of the other road users. The method can be advantageous for use in a vehicle, for example. The LIDAR device can be part of a vehicle, for example. The method can be advantageous for use in a semiautonomous vehicle or in an autonomous vehicle. Objects that enter the detection field of the sensor devices of the vehicle from the side can potentially be recognized during travel. The objects can be recognized at a point in time when they are still concealed by an obstacle. The concealed objects can be recognized even before they actually enter the detection field of the sensor devices of the vehicle. Thus, more time is obtained for countermeasures (braking, seat belt tensioning, activation of the airbag, etc.). 
     In an example embodiment of the present invention, it is provided that the method includes the further, chronologically preceding step of comparing the at least one ascertained value of the received first radiation to at least one predefined value using the evaluation unit. The step of emitting the detection radiation is dependent on the comparison. 
     For recognizing a concealed object, it may be necessary to emit detection radiation having high pulse intensities where the detection radiation is no longer be safe for the eyes. An advantage of this embodiment is that, due to the chronologically preceding steps, a method is provided in which the emission of the detection radiation can be linked to conditions that make it unlikely that other road users will be harmed. Thus, an unconcealed object in a visual field of the LIDAR device can be recognized via the comparison. One condition, for example, can be that detection radiation having high pulse intensity is emitted only when no unconcealed object is recognized in the visual field of the LIDAR device. 
     In an example embodiment of the present invention, it is provided that the at least one ascertained value of the received first radiation is a value of an intensity of the received first radiation. The at least one ascertained value of the received first radiation can also include a value of the distance of an unconcealed object in the visual field of the LIDAR device. For example, at least two values of the received first radiation can also be ascertained. A first value can be a value of the intensity of the received first radiation. A second value can be a value of the distance of an unconcealed object in the visual field of the LIDAR device. 
     An unconcealed object can, for example, be a moving object in the visual field of the LIDAR device. A moving object can be a road user, for example. Another road user could possibly be harmed by the emission of the detection radiation. An unconcealed object can also be a nonmoving object in the visual field of the LIDAR device. A nonmoving object can be reflective, for example. Thus, automotive sheet metal, a rearview mirror, or a car window can be reflective. A nonmoving object can also be directionally reflective, for example. This can be the case with wet conditions or with glistening surfaces. The emitted detection radiation can be reflected on the nonmoving object in such a way that it endangers road users. 
     An advantage of this embodiment is that an unconcealed object in the visual field of the LIDAR device can be reliably recognized in the chronologically preceding steps. The risks described above can be minimized. 
     In an example embodiment of the present invention, it is provided that the power of the emitted detection radiation is different from the power of the emitted first radiation. The difference can be in the range of one to three orders of magnitude. Additionally or alternatively, it is provided that the wavelength of the emitted detection radiation is different from the wavelength of the emitted first radiation. 
     An advantage of this embodiment is that the eye safety of other road users can be ensured. The eye safety of a transmitting unit is stipulated by regulations provided for this purpose. If the transmitting unit includes a laser source, for example the laser safety standard IEC 608251 Ed. 3 is applicable. One variable specifying the eye safety of a laser can accordingly be the power of the laser or the wavelength of the laser. In addition, a correction factor can optionally be taken into account. The correction factor can take the extension of the laser source, for example, into account. Thus, for example, the power of the emitted first radiation of a predefined wavelength can be lower than the power of the emitted detection radiation at the same wavelength. Thus, for example, the intensities of the laser pulses of the emitted first radiation of a predefined wavelength can be less than the intensities of the laser pulses of the emitted detection radiation at the same wavelength. In particular, the emitted first radiation can be safe to the eyes. 
     In an example embodiment of the present invention, it is provided that the method includes the further, chronologically preceding steps of detecting the surroundings and recognizing obstacles and an area concealed by the obstacles, based on the detected surroundings. The step of emitting the first radiation is dependent on the recognition. 
     Detecting the surroundings and recognizing obstacles can take place using the LIDAR device itself. Alternatively or additionally, the detection of the surroundings and the recognition of obstacles can take place using at least one further sensor device that is installed in a vehicle. 
     An advantage of this embodiment is that it can initially be checked whether obstacles are present in the surroundings of the LIDAR device that can potentially conceal objects. The emission of the first radiation can be dependent on the recognition in such a way that first radiation is emitted only when such an obstacle is recognized. The emission of the detection radiation can be dependent on the recognition in such a way that detection radiation is emitted only when such an obstacle is recognized. As a result, the method is applied only when necessary. 
     In addition, an example embodiment of the present invention is directed to a computer program configured for carrying out the described method steps. In addition, an example embodiment of the present invention is directed to a machine-readable memory medium on which the described computer program is stored. 
     An example embodiment of the present invention is directed to a LIDAR device for detecting a concealed object. The concealed object in the visual field of the LIDAR device is concealed by an obstacle. The LIDAR device includes at least one transmitting unit for emitting detection radiation in a predefined direction for illuminating a scattering surface. The scattering surface is situated in a visual field of the concealed object. The emitted detection radiation is scattered on the scattering surface. The LIDAR device also includes at least one receiving unit for receiving reflected detection radiation from an image area. The reflected detection radiation is the detection radiation that has been reflected from the concealed object to the image area. The LIDAR device also includes at least one evaluation unit for detecting the concealed object based on the received detection radiation. 
     According to the present invention, the at least one transmitting unit is also designed for emitting a first radiation in the predefined direction for illuminating the scattering surface. The at least one receiving unit is also designed for receiving a first radiation that is scattered on the surface. The at least one evaluation unit is also designed for ascertaining at least one value of the received first radiation. 
     In an example embodiment, the LIDAR device includes a first transmitting unit and at least one second transmitting unit. The first transmitting unit is designed for emitting the detection radiation, and the second transmitting unit is designed for emitting the first radiation. 
     In an example embodiment, the LIDAR device includes a first receiving unit and at least one second receiving unit. The first receiving unit is designed for receiving the reflected detection radiation, and the second receiving unit is designed for receiving the first radiation that is scattered on the surface. 
     Exemplary embodiments of the present invention are explained in greater detail below with reference to the appended drawings. Identical or functionally equivalent elements are denoted by the same reference numerals in the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a flowchart that illustrates a method according to an example embodiment of the present invention. 
         FIGS. 2A-2B  illustrate use of a method according to an example embodiment of the present invention. 
         FIG. 3  illustrates a LIDAR device according to an example embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates example method  100  for a LIDAR device for detecting a concealed object.  FIGS. 2A-2B  illustrates an example application of the method in a vehicle.  FIG. 2A  illustrates the first part of method  100  up to and including step  106 . The first part of method  100  can optionally also include steps  111 ,  112 , and/or  113 .  FIG. 2B  illustrates the second part of method  100  from step  107  up to and including step  110 . 
       FIG. 2A  shows vehicle  201 , which includes a LIDAR device  300 , as described further below with reference to  FIG. 3 , for detecting a concealed object. Vehicle  201  moves along travel direction  211 , for example. Obstacles  203 - 1  and  203 - 2  are situated in the surroundings of the vehicle. Obstacles  203 - 1  and  203 - 2  can also be nonmoving objects, for example, that are situated in the visual field of LIDAR device  300 . Obstacles  203 - 1  and  203 - 2  can each be a house or a row of houses, for example. Obstacles  203 - 1  and  203 - 2  can also alternatively each be a vehicle, for example. The two obstacles  203 - 1  and  203 - 2  conceal area  202  from the LIDAR device. A concealed object  205  can be situated in area  202 . Concealed object  205  can be another road user, for example. Concealed object  205  can be a pedestrian, for example. Concealed object  205  can be another vehicle, for example. 
     Method  100  shown in  FIG. 1  starts in step  101 . A first radiation is emitted in a predefined direction using at least one transmitting unit of the LIDAR device in step  102 . This first radiation is illustrated by arrow  211  in  FIG. 2A . The emission in a predefined direction can take place, for example, in the direction of a predefined area. In  FIG. 2A  the predefined area is area  204 . This area can be a punctiform area. When the LIDAR device is scanning, area  204  can also have an extension that is predefined by one or multiple scanning angles. This area can be a circular area, for example. This area can be a quadrangular area, for example. Emitted first radiation  211  can be scattered from a surface in the visual field of LIDAR device  300 . The surface can be, for example, a road surface in area  204 . Emitted first radiation  211  can be scattered from a surface in the visual field of LIDAR device  300 . Emitted first radiation  211  can be diffusely reflected from a surface in the visual field of LIDAR device  300 . The scattering surface can be a road surface, for example. This is illustrated in  FIG. 2A  by arrows  209  diffusely emanating in various directions. Separately marked arrow  208  represents radiation that is scattered or reflected back in the direction of LIDAR device  300 . Due to the emission of the first radiation in a predefined direction, in particular a predefined area, the distance of the predefined area from the LIDAR device can also be predefined. The value of this predefined distance can be used as a predefined value in the further method. 
     According to method  100  in  FIG. 1 , the first radiation scattered and/or reflected on the surface in step  103  is received using a receiving unit. For example, the radiation depicted by arrow  208  can be received. At least one value of the received first radiation is ascertained in step  104  of method  100  using an evaluation unit. The at least one value can be a value of the distance of an unconcealed object in the visual field of the LIDAR device. The evaluation unit can ascertain the distance according to a time-of-flight method. Alternatively, the at least one value can be a value of an intensity of the received first radiation. Two values can be ascertained, where a first value can be a value of the distance of an unconcealed object in the visual field of the LIDAR device, and a second value can be a value of the intensity of the received first radiation. 
     A tolerance range can be predefined for the predefined value. The at least one ascertained value is compared to at least one predefined value in step  105 . The value of the distance of an unconcealed object in the visual field of the LIDAR device is compared to a predefined value. The predefined value of the distance may, as described above, be specified from the predefined direction, in particular from the predefined area, in which the first radiation is emitted. Alternatively or additionally, the value of the intensity of the received first radiation is compared to a predefined value. The predefined value of the intensity of the received first radiation can be specified by the operating parameters of the transmitting unit. The predefined value of the intensity of the received first radiation can be specified by the intensity of the laser pulses of the first radiation that are emitted using the transmitting unit. 
     If it is determined in step  105  that the at least one ascertained value differs from the predefined value, the method can be aborted in step  106 . In an example, if it is determined in step  105  that the difference of the at least one ascertained value from the predefined value is so great that the ascertained value is outside the tolerance range of the predefined value, the method can be aborted in step  106 . If the comparison shows, for example, a value of the distance that is outside the tolerance range of the predefined value of the distance, it is to be assumed that an unconcealed object is in the beam path of the first radiation. An unconcealed object can result in particular in the ascertained value of the distance being less than the predefined value of the distance. Since the emission of detection radiation according to step  107  of method  100  could be hazardous in the case of an unconcealed object, the method can be aborted in step  106 . If the comparison shows, for example, a value of the intensity of the received first radiation that is outside the tolerance range of the predefined value of the intensity, this can be attributed to the emitted first radiation not having been diffusely scattered or diffusely reflected, but, rather, directionally reflected. In particular an excessively low value or even the lack of reception of the first radiation can indicate that the emitted first radiation has been directionally reflected. Since the emission of detection radiation according to step  107  of method  100  could be hazardous in the case of a directed reflection, the method can be aborted in step  106 . 
     If it is determined in step  105  that the at least one ascertained value corresponds to the predefined value, the method can be continued in step  107 . In an example, if it is determined in step  105  that the at least one ascertained value is in the tolerance range of the predefined value, the method can be continued in step  107 . 
     The first part of method  100  can optionally also include steps  111  and  112 . Optional step  111  takes place directly after start  101  of method  100 . The surroundings are detected in step  111 . The detection of the surroundings and the recognition of obstacles can take place using the LIDAR device itself. Alternatively or additionally, the detection of the surroundings and the recognition of obstacles can take place using at least one further sensor device that is installed in a vehicle. If obstacles are recognized in subsequent step  112 , based on the detected surroundings, and a concealed area is recognized based on the obstacles, the method is continued in step  102 . If no obstacles and no concealed area are recognized in step  112 , based on the detected surroundings, the method can be aborted in step  113 . However, if obstacles, but no concealed area, are/is recognized in step  112  based on the detected surroundings, the method can be aborted in step  113 . 
     Steps  101 - 106  and steps  111 - 113  of method  100  chronologically precede steps  107 - 110 . The chronologically preceding time period, in particular the time interval between the first part of method  100  and the second part of method  100 , can be small. The emission of the first radiation and the emission of the detection radiation can take place within a small time interval. The small time interval can be in the range of milliseconds. The small time interval can be in the range of 50 ms to 100 ms, for example. 
     As described above, following step  105 , method  100  can continue with step  107 . Detection radiation is emitted in a predefined direction in step  107  for illuminating a scattering surface, using at least one transmitting unit. The power of the detection radiation emitted in step  107  can be different from the power of the first radiation emitted in step  102 . The intensities of the laser pulses of the first radiation emitted in step  102  can be lower than the intensities of the laser pulses of the detection radiation emitted in step  107 . In particular, the first radiation emitted in step  102  can be safe to the eyes. Additionally or alternatively, the wavelength of the emitted detection radiation can be different from the wavelength of the first radiation emitted in step  102 . 
       FIG. 2B  illustrates the second part of method  100  from step  107  up to and including step  110 . The same vehicle  201  with the same LIDAR device  300  is shown as in  FIG. 2A , except with a small time interval, i.e., at a slightly later point in time. Detection radiation  207  is emitted in a predefined direction using a transmitting unit. The same surface of the same area  204  can be illuminated with emitted detection radiation  207  as with emitted first radiation  211 . Although not shown here, emitted detection radiation  207  can also be used to illuminate a surface of a second area that partially overlaps or preferably closely adjoins area  204 . Scattering surface  204  is situated in a visual field of concealed object  205 . Emitted detection radiation  207  is scattered by scattering surface  204 . A portion of the scattered detection radiation can illuminate concealed object  205  in area  202  due to the high intensity of the laser pulses. This is depicted in  FIG. 2B  by marked arrow  209 . At least a portion of scattered detection radiation  209  is reflected, in particular diffusely reflected, from object  205  to image area  206 . This is in turn depicted by arrow  210 - 1 . As shown in  FIG. 2B , image area  206  can be spaced apart from area  204 . As indicated by arrow  210 - 2 , at least a portion of this reflected detection radiation can be received by LIDAR device  300  of vehicle  201 . 
     This corresponds to step  108  of method  100  from  FIG. 1 . The reception of the reflected detection radiation from an image area can take place using a receiving unit. The concealed object is detected in step  109  of method  100  based on the received detection radiation, using at least one evaluation unit. For this purpose, the received detection radiation is evaluated in particular according to a time-of-flight method. In this regard, reference is made to p. 11, 1. 17-p. 14, 1. 24 of WO 2016/063028, the content of which is incorporated by reference herein in its entirety. The evaluation can in particular be based on the evaluation described in WO 2016/063028. Information can be generated during the evaluation. The presence of least one concealed object can be detected and generated as a piece of information. The concealed object can be a nonmoving or a moving object. The size, shape, and alternatively or additionally the movement of at least one moving concealed object can be detected and generated as a piece of information. 
     The generated information can be displayed on a display unit. The display unit can be situated in a vehicle, for example. Information concerning the concealed object can thus be displayed to an occupant of the vehicle. Alternatively or additionally, the generated information can be transmitted to a control unit. This can be, for example, a control unit of a driver assistance system of a vehicle. This also can be, for example, a control unit of an autonomous vehicle. The generated information can be utilized by the control unit. 
     Method  100  from  FIG. 1  ends with step  110 . 
       FIG. 3  shows LIDAR device  300  for detecting a concealed object, as an exemplary embodiment. LIDAR device  300  includes transmitting unit  307 - 1 . Transmitting unit  307 - 1  can include laser  301 - 1 . Transmitting unit  307 - 1  can also include at least one optical component  304 - 1 . An optical component can be a refractive optical element, a diffractive optical element, or a mirror, for example. Transmitting unit  307 - 1  can also include a sampling unit  303 - 1 . It is possible to scan the surroundings of LIDAR device  300  using sampling unit  303 - 1 . LIDAR device  300  also includes at least receiving unit  308 - 1 . Receiving unit  308 - 1  can include detector  302 - 1 . Receiving unit  308 - 1  can also include at least one optical component  304 - 1 . Receiving unit  308 - 1  can also include a sampling unit  303 - 1 . In the example shown, transmitting unit  307 - 1  and receiving unit  308 - 1  include the same optical component  304 - 1  and the same sampling unit  303 - 1 . Alternatively (not shown here), transmitting unit  307 - 1  can include an optical component that is different from a second optical component of receiving unit  308 - 1 . Alternatively (not shown), transmitting unit  307 - 1  can include a sampling unit that is different from a second sampling unit of receiving unit  308 - 1 . LIDAR device  300  also includes control unit  305 . Control unit  305  can be configured for controlling laser  301 - 1 . Control unit  305  can be configured for controlling detector  302 - 1 . Control unit  305  can be configured for controlling a sampling unit  303 - 1 . LIDAR device  300  also includes an evaluation unit  306 . Evaluation unit  306  can obtain data transmitted from detector  302 - 1 . Evaluation unit  306  can be connected to control unit  305 . 
     Transmitting unit  307 - 1  is designed for emitting detection radiation in a predefined direction for illuminating a scattering surface. Transmitting unit  307 - 1  can also be designed for emitting a first radiation in the predefined direction for illuminating the scattering surface. Receiving unit  308 - 1  is designed for receiving reflected detection radiation from an image area. The reflected detection radiation is the detection radiation that has been reflected from the concealed object to the image area. Receiving unit  308 - 1  can also be designed for receiving a first radiation that is scattered on the surface. Data are generated by the receiving unit based on the received reflected detection radiation. These data are transmitted to the evaluation unit. Data are generated by the receiving unit based on the received first radiation. These data are transmitted to the evaluation unit. Evaluation unit  306  is designed for detecting the concealed object based on the received detection radiation. The evaluation unit can also be designed for ascertaining at least one value of the received first radiation. 
     In one variant, LIDAR device  300  can include at least one second transmitting unit in addition to first transmitting unit  307 - 1 . This is transmitting unit  307 - 2  in  FIG. 3 . Transmitting unit  307 - 2  can include laser  301 - 2 . 
     First transmitting unit  307 - 1  can be designed for emitting the detection radiation, and second transmitting unit  307 - 2  can be designed for emitting the first radiation. In addition, the LIDAR device can include a second receiving unit in addition to first receiving unit  308 - 1 . This is receiving unit  308 - 2  in  FIG. 3 . Receiving unit  308 - 2  can include detector  302 - 2 . First receiving unit  308 - 1  can be designed for receiving the reflected detection radiation, and second receiving unit  308 - 2  can be designed for receiving the first radiation scattered on the surface. Similarly as for transmitting unit  307 - 1  and receiving unit  308 - 1 , transmitting unit  307 - 2  and receiving unit  308 - 2  can also include the same at least one optical component  304 - 2 . Transmitting unit  307 - 2  and receiving unit  308 - 2  can also include the same sampling unit  303 - 2 . Alternatively (not shown here), transmitting unit  307 - 2  can include an optical component that is different from a second optical component of receiving unit  308 - 2 . Alternatively (not shown here), transmitting unit  307 - 2  can include a sampling unit that is different from a second sampling unit of receiving unit  308 - 2 . Control unit  305  of LIDAR device  300  can be configured for controlling laser  301 - 2 . Control unit  305  can be configured for controlling detector  302 - 2 . Control unit  305  can be configured for controlling sampling unit  303 - 2 . Evaluation unit  306  can obtain data transmitted from detector  302 - 2 . 
     In one variant, LIDAR device  300  can be connected to a sensor device  309 . Sensor device  309  can be, for example, a further sensor device that is installed in a vehicle. For example, the surroundings can be detected and obstacles recognized using sensor device  309 .