Patent Publication Number: US-2022221564-A1

Title: Cleaning device, lidar sensor set-up and working device

Description:
CROSS REFERENCE 
     The present application claims the benefit under 35 U.S.C. § 119 of German Patent Application No. DE 10 2021 200 098.3 filed on Jan. 8, 2021, which is expressly incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to a cleaning device for a lidar sensor set-up, a lidar sensor set-up as such, as well as a working device. 
     BACKGROUND INFORMATION 
     In working devices and, in particular, in vehicles, lidar sensors are increasingly being used to monitor surroundings. The quality of the monitoring of the surroundings is substantially a function of the quality of the view of the sensor onto the field of view. Upon the installation of a sensor in the outer region of a working mechanism and, in particular, a vehicle, the sensor, along with its window, is subjected to environmental influences, thus, in particular, precipitation, as well, such as rain, dew, frost, snow and ice, but also traces of contamination by dust, insects and the like. Because of this, the clear view of the sensor through the window, through which primary light of the sensor is emitted out into the field of view and secondary light, in particular, from the field of view, is received, may be and become permanently impaired, either due to stubborn dirt, due to damage, and/or due to continuous deterioration of the optical characteristics of the window of the sensor. 
     SUMMARY 
     The cleaning device of the present invention, for a lidar sensor device, may have the advantage that, using simple devices, a deterioration in the optical characteristics of a window of the lidar sensor device, which is possibly permanent and not capable of being eliminated by a cleaning operation, may be reliably detected, so that a prompt, appropriate response is possible. 
     In accordance with an example embodiment of the present invention, this may be achieved by providing a cleaning device for a lidar sensor set-up, which is formed to have a movable cleaning element, and which is configured, for a cleaning operation, to move the cleaning element on and/or along an outer side of a window of the lidar sensor set-up; the outer side facing away from the lidar sensor set-up and facing the field of view of the lidar sensor set-up; the movable cleaning element including an optical element, and the optical element being configured to send back and, in particular, reflect back primary light from a transmitter circuit of the lidar sensor set-up, which is incident upon the optical element, into a receiving path of the lidar sensor set-up. Using these measures, continuous impairment, and/or impairment not eliminable by a cleaning operation, of the optical characteristics of the window, of the optical path, and/or of the light source, in particular, of a laser, of the lidar sensor set-up, may be deduced from a comparison of the intensity of the primary light sent back directly. 
     Preferred further refinements of the present invention are disclosed herein. 
     The optical element may be formed in various ways, as long as it is ensured that primary light of the lidar sensor device, which reaches the optical element from the transmitting path of the lidar sensor device, is sent back completely or partially into the receiving path of the lidar sensor device. 
     According to preferred specific embodiments of the cleaning device according to the present invention, the optical element takes the form of a(n), or is formed to include a(n)
         optically passive element;   reflective element;   mirror;   Lambertian element or Lambertian scattering element;   optically active element;   optical waveguide; or   a combination of them.       

     In this context, the movable cleaning element provided with the optical element may have completely different embodiments, as well, as long as it is ensured that it is suitable for a cleaning operation of the underlying window, and that in this case, it is moved on the outer side of the underlying window, facing away from the lidar sensor set-up. 
     According to other preferred, additional or alternative cleaning devices of the present invention, the movable cleaning element may be formed to include, or may take the form of, a wiper, in particular, including a wiper arm and wiper lip for contacting the outer side of the window, and/or a nozzle for issuing gas, air, and/or liquid. 
     It is particularly advantageous, when according to the present invention, primary light emitted in connection with the cleaning operation and the movement of the cleaning element is reflected directly in front of the outer side of the window by the optical element, and when the reflected light is also detected and evaluated accordingly. 
     Thus, in one embodiment of the cleaning device of the present invention, a control unit and/or an operative connection to a control unit is formed, in particular, with the aid of a control/detection line. 
     In one particularly preferred exemplary embodiment of the cleaning device according to the present invention, in particular, in cooperation with a detection unit of the basic lidar sensor set-up, the control unit is configured to evaluate detected primary light sent back by the optical element. 
     In particular, according to another further refinement of the cleaning device of the present invention, the control unit may be formed
         to determine the intensity of primary light sent back by the optical element;   to compare it to a setpoint intensity;   to compare it to an intensity from an immediately preceding, cleaning operation and/or movement action;   to correlate a particular intensity with   (i) a motion of the cleaning element;   (ii) an angular motion of the cleaning element; and/or   (iii) an angular position of the cleaning element;   to compare it to a threshold intensity value for eye protection;   to compare it to a setpoint laser power value of the intensity; and/or   to output
           a control signal for a cleaning operation; and/or   a warning signal,   
               

     in particular, in each instance, in response to irremovable degradation, defect, and/or contamination. 
     According to a further aspect of the present invention, a lidar sensor set-up, as such, which is formed to include a cleaning device developed in accordance with the present invention, is also provided. 
     In this context, in accordance with an example embodiment of the present invention, the cleaning device is formed, in particular, as an additional element for a housing having a window, as well as transmitting and receiving units in the interior of the housing, which include a light source and detector, respectively, and whose interaction is controlled and/or regulated, in particular, with the aid of the control unit. 
     In addition, the present invention also provides a working device, which is formed to include a lidar sensor set-up developed according to the present invention, and which takes the form of, in particular, a vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific embodiments of the present invention are described in detail below with reference to the figures. 
         FIG. 1  shows a schematic and perspective view of a first general, specific embodiment of the lidar sensor device according to the present invention, where the cleaning device is formed to include an optical element. 
         FIGS. 2 and 3  show, in schematic and sectional plan views, specific embodiments of the lidar sensor device of the present invention that utilize specific embodiments of the proposed cleaning device, which includes an optical element in biaxial and coaxial configurations, respectively, for the transmitting and receiving paths. 
         FIGS. 4 through 6  show, in schematic and sectional side views, specific embodiments of the lidar sensor device according to the present invention, in biaxial form for the transmitting and receiving paths, utilizing specific embodiments of the proposed cleaning device having differently designed optical elements. 
         FIGS. 5 and 8  show, in schematic and sectional side views, specific embodiments of the lidar sensor device according to the present invention, in coaxial form for the transmitting and receiving paths, utilizing specific embodiments of the proposed cleaning device that have differently designed optical elements. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     In the following, exemplary embodiments of the present invention and the technical background are described in detail with reference to  FIGS. 1 through 8 . Identical and equivalent elements and components, as well as elements and components functioning in the same or in an equivalent manner, are denoted by the same reference numerals. The detailed description of the denoted elements and components is not repeated in each case of their appearance. 
     The depicted features and further characteristics may be isolated from each other and combined with each other, as desired, without departing from the essence of the present invention. 
     Initially, reference is made generally to  FIG. 1  and the specific embodiments for the lidar sensor device  1  shown there. 
       FIG. 1  shows a schematic and perspective view of a first general specific embodiment of the lidar sensor device  1  according to the present invention, where a specific embodiment of the cleaning device  100  of the present invention is formed to include an optical element  30  on the moving or movable cleaning element  20  of cleaning device  100 . 
     Substantial components of lidar sensor device  1  may be formed in the interior  10   i  of housing  10 , that is, in particular, transmitter optics including a transmitter unit  41  and corresponding light sources for generating and/or emitting primary light  57  into associated field of view  50 , and receiver optics  42 , which include a receiver unit  42 , and also a detector unit, for receiving and/or detecting secondary light  58  from field of view  50 , or also, for example, in the form of primary light  57 ′ sent back directly and, in particular, reflected back. 
     In this case, housing  10  itself is made up of, for example, a cover plate  12 , a base plate  12 ′, a back wall  13 , and a housing element  11 , in which a window  15  is formed; an inner side or inner surface  15   i  of the window facing interior  10   i  of housing  10 , and an outer side or outer surface  15   a  of the window facing the exterior  10   a  of housing  10 . The primary light  57  generated in interior  10   i  of housing  10  passes through the window set-up having window  15 , from the inside to the outside, and possibly in the direction of field of view  50 ; and secondary light  58  from exterior  10   a  of housing  10  travels inwards, through the viewing set-up having the window, into the interior  10   i  of housing  10 . 
     Window  15  has an outer side  15   a , which is oriented towards or aligned with exterior  10   a  of housing  10 , against which an inner side  15   i  of window  15  is oriented towards and aligned with interior  10   i  of housing  10 . 
     A cleaning device  100  of the present invention is formed on outer side  15   a  of window  15 . This includes a cleaning element  20 , which may be moved by a motion mechanism in a controlled manner, from a position A in the direction of arrow  25 . During the movement, cleaning element  20  is moved parallelly, locally parallelly, and/or in conformance with the surface of outer side  15   a  of window  15  and, in so doing, sweeps over or even contacts the surface of window  15  in highly close proximity to outer side  15   a , if, for example, cleaning element  20  is formed as an arm or wiper arm  21  having a corresponding lip  22  for wiping contact with the surface of window  15 . 
     Finally, cleaning element  20  may be moved in a controllable manner in the direction of double arrow  26 , between the two end positions A, to a plurality or multitude of intermediate positions B between the end positions. During operation, the movement of cleaning element  20  is then preferably connected to a cleaning operation of outer side  15   a  of window  15 . 
     To optically check the condition of window  15 , cleaning element  20  includes an optical element  30 , which is formed and configured in such a manner, that it sends back and, in particular, reflects back primary light  57  coming in from a transmitter path  51  of lidar sensor set-up  1  and, in particular, from interior  10   i  of housing  10 , onto optical element  20 , into a receiving path  52  of lidar sensor set-up  1  and, therefore, into interior  10   i  of housing  10  of lidar sensor set-up  1 . 
     In this context, the event of sending-back or reflecting-back takes place in the region of exterior  10   a  of housing  10  and directly at outer side  15   a  of window  15 . Consequently, primary light  57  is not attenuated at all in the region of exterior  10   a  of housing  10 , which means that an optical condition of window  15  may be deduced from a comparison of the intensity of the primary light  57 ′ to be reflected back directly, to an expected intensity. 
     As is shown, in particular, in further  FIGS. 2 through 8 , to that end, lidar sensor set-up  1  of the present invention includes a suitably formed control unit  40 , which is operatively connected to transmitter unit  41 , receiver unit  42 , and also cleaning device  100 , via a control and/or detection line  45 . In this manner, these components may be controlled, as well as polled or interrogated with regard to their states, that is, in particular, appropriate light sources for emitting primary light  57 , corresponding detector elements for detecting secondary light  58  and, in particular, the primary light  57 ′ reflected back directly by optical element  30 , and a drive unit for moving the moving or movable cleaning element  20  in a controlled manner. 
       FIGS. 2 and 3  show, in schematic and sectional plan views, specific embodiments of the lidar sensor device  1  of the present invention that utilize specific embodiments of the proposed cleaning device  100 , which respectively include an optical element  30  in biaxial and coaxial configurations for transmitting path  51  and receiving path  52 . In this case, cleaning device  100  includes a wiper arm  21 , which may be moved back and forth in a controllable manner in the direction of double arrow  26 , with the aid of a drive unit, and which includes a lip or wiper lip  22  that sweeps over the surface of outer side  15   a  of window  15  in a contacting manner during the back-and-forth movement, in order to clean the window on outer side  15   a  in this manner. 
     Optical element  30 , which takes the form of a reflecting element  31 , e.g., a mirror, in the specific embodiments of  FIGS. 2 and 3 , is additionally formed on wiper arm  21 . 
     Primary light  57  emitted by transmitter unit  41  leaves the interior  10   i  of housing  10  via transmitting path  51  and through inner side  50   i  and outer side  15   a  of window  15 , strikes optical element  30  in the exterior  10   a  of housing  10 , and there, it is reflected back directly, in order to travel, in the form of secondary light  58 , namely, in the form of primary light  57 ′ reflected back directly, through outer side  15   a  and inner side  15   i  of window  15 , from exterior  10   a  into interior  10   i  of housing  10 , consequently, via receiving path  52 , into a detector in receiver unit  42 , in order to be detected there. Corresponding detection signals are sent through control and/or detection line  45  to control unit  40  for evaluation, or are requested by it. Based on the evaluation, the further operation of transmitter unit  41 , receiver unit  42 , and/or cleaning device  100  may then be controlled and/or regulated, using the motion of cleaning element  20 . 
     In the specific embodiment according to  FIG. 2 , transmitting path  51  and receiving path  52  and, therefore, transmitter unit  41  and receiver unit  42 , are formed separately from each other. Thus, it is a biaxial system. 
     In contrast to that, the embodiment shown in  FIG. 3  is a coaxial system. Transmitting path  51  and receiving path  52  coincide optically. 
       FIGS. 4 through 6  show, in schematic and sectional side views, specific embodiments of lidar sensor device  1  of the present invention, in biaxial form for transmitting path  51  and receiving path  52 , utilizing specific embodiments of the proposed cleaning device  100  that have differently designed optical elements  20 . 
     In the specific embodiment of  FIG. 4 , optical element  30  is formed by two mirrors  31  and  33 , which are jointly used in interaction to deflect primary light  57  out of transmitting path  51  and consequently convert it to primary light  57 ′ reflected back directly in the form of secondary light  58 . 
     In the specific embodiment according to  FIG. 5 , optical element  30  is formed by a Lambertian element or scattering element. An advantage of this is that at least a portion of incident primary light  57  from transmitting path  51  is also scattered back in the direction of receiving path  52  in the form of secondary light  58 , in order to be detected in receiver unit  42 . 
     In the specific embodiment according to  FIG. 6 , optical element  30  is formed by a conductor  33 , in which a first and a second mirror  31 ,  32  are formed to respectively couple in and ultimately couple out primary light  57  received from transmitting path  51 . 
       FIGS. 7 and 8  show, in schematic and sectional side views, specific embodiments of lidar sensor device  1  of the present invention in coaxial form for transmitting path  51  and receiving path  52 , utilizing specific embodiments of the proposed cleaning device  100  that have differently designed optical elements  30 , namely, again, in the form of a reflective element or mirror  31  and a Lambertian element  34 , respectively. 
     These and additional features and characteristics of the present invention are elucidated further with the aid of the following explanations: 
     In the next few years, highly and fully automated vehicles (Level 3-5) will be found more and more on our roads. There are different concepts regarding how such an automated vehicle may be implemented. All of these approaches require many different sensors (such as video cameras, lidar, radar, and ultrasonic sensors); in particular, lidar sensors, optical sensors, which generate 3-D point clouds of the surrounding area with the aid of laser light, playing a more and more important role. This optical detection may easily be interfered with by contamination or water drops on the optical glass cover (also referred to as a blockade), which means that a cleaning of the glass is necessary in such cases. This cleaning is often accomplished with the aid of a wiper. For lidar sensor  1 , the challenge is to detect the level of contamination and, through this, to initiate the cleaning interval automatically. At the same time, the intent is to limit the number of cleaning operations to a minimum, in order to maximize the service life of glass cover  15 , since in the case of plastic covers  15 , a cleaning operation may result in microscopically small scratches. The performance of lidar sensor  1  may be simultaneously affected by degradation of the glass cover material due to, for example, microscopically small scratches or discoloration. Lidar sensor  1  must detect such degradation automatically, in order to be able to communicate the current performance to a central evaluation unit. 
     In the case of a lidar sensor  1 , one object of the present invention is, inter alia, to detect contamination, a blockade, and/or degradation of window  15  or glass cover  15  as simply and, nevertheless, reliably as possible, preferably, with the aid of a passive element. 
     In this context, a core aspect of a specific embodiment of the present invention is to form a reflecting element  30  on wiper  20  of a lidar sensor  1 , which allows the degree of a blockade and/or degradation of window  15  to be deduced from the intensity of the laser light reflected by it. 
     The following advantages are yielded individually or in combination in the context of the present invention and its specific embodiments:
         passive method;   no additional electronic components necessary;   cost-effective; and   high degree of validity of the generated data in comparison with indirect methods (point-cloud-based).       

     One specific embodiment of the present invention is made up of a lidar sensor  1  having a wiper as a cleaning device  100 , as is shown in  FIG. 1  in a general manner. 
     During the cleaning operation, wiper  20  travels over glass cover  10  of lidar sensor  1  and cleanses glass cover  10  of water drops and contamination. At the same time, a reflecting reference element  31  in the form of an optical element  30  is mounted on wiper arm  21 . During the cleaning operation, the laser beam, in the form of primary light  57 , is also aimed at reflecting element  31 . The light  57 ′ reflected by reflecting element  31  is measured in receiver  42  of lidar sensor  1 . The transmission of glass cover  15  is determined from the measured light intensity, through which the degree of contamination or the degree of glass cover degradation may be deduced. 
     In particular, reflecting element  31  may be mounted on wiper arm  21  in such a manner, that with regard to specific moving direction  25 ,  26 , reflecting element  31  is still moved over the glass  15 , in front of wiper blade  22 . In this manner, the degree of contamination may be measured before the contamination is removed. Subsequently, the cleaning interval may be reset in light of the measured degree of contamination. The direction of wiper  20  may then be reversed, so that it moves back into its starting position. In this instance, the transmission of glass cover  15  is redetermined. Since glass cover  15  is now already clean, changes in the transmission are now presumably attributable to glass cover degradation, for example, in the form of microscopic scratches, discoloration and the like. 
     In this case, sensor  1  may request a garage visit via control unit  40 , using a warning signal or the like, or possibly call for a higher laser power in primary light  57 , in order to compensate for the loss in transmission, as long as the laser power is still below the limit for eye safety. 
     Different technical implementations are possible as a function of the system architecture of lidar sensor  1  (coaxial, biaxial, macroscanner having a horizontal or vertical configuration, etc.). 
     A Lambertian scattering element  34  in the form of a diffuse scatterer, or one or more mirrors  31 ,  33  ( FIGS. 2 d  and 2 e   ), is effective for a coaxial system. For a biaxial system, reflecting element  20  must deflect light  57  from transmitting path  41  into receiving path  42  of lidar sensor  1 . If transmitting path  41  and receiving path  42  intersect in the region of glass cover  15 , then a Lambertian scattering element  34 , as is shown in  FIG. 5 , is also sufficient in this case. If transmitting path  41  and receiving path  42  do not yet intersect in the region of glass cover  15 , then this may be accomplished, for example, by an optical waveguide  32 , or by reflecting mirrors  31 ,  33 , as is shown in  FIGS. 4 and 6 . 
     Using the wiping across glass cover  15 , one specific embodiment of the present invention also allows contamination and degradation to be localized in the horizontal direction (thus, one-dimensional localization). This may aid in understanding the solid angles, at which lidar sensor  1  possibly has a reduced operating range. 
     As an alternative to a wiper, the reflecting element may also be attached to other cleaning elements  20 , which move across glass cover  10 . For example, an arm having an air nozzle could be used for cleaning the glass cover. 
     The measured reflection may simultaneously be used for monitoring the laser power of the light source of transmitter unit  41 , in order to ensure that lidar sensor  1  operates at a laser power safe for the eyes, and in order to detect possible ageing of the source or laser diode. In addition, possible incorrect adjustment or alignment error of the lidar sensor due to, for example, thermal effects or ageing of adhesive agents may be detected from the position and shape of the laser beam.