Method for determining environmental information relating to a property of an object and / or a surface in the surroundings of a motor vehicle, and motor vehicle comprising a lidar device

Abstract

The invention relates to a method for determining at least one item of environmental information (22) relating to a property of at least one object (6) located in the surroundings (4) of a motor vehicle (1) and / or at least one surface (7) located in the surroundings (4), wherein polarised laser light (3) is generated by means of at least one lidar device (2) of the motor vehicle (1) and emitted into the surroundings (4), wherein the environmental information (22) is determined based on the polarised laser light (3) and backscattered laser light (8), wherein the backscattered laser light (8) is a portion of the polarised laser light (3) that is scattered back from the object (6) and / or the surface (7) to the lidar device (2), wherein, in order to determine the environmental information (22), a polarimetric, coherent phase evaluation is performed in which at least one item of phase information (14) is determined which relates to a phase shift between the polarised laser light (3) and the backscattered laser light (8), wherein the environmental information (22) is determined based on the phase information (14).

Description

[0001] Method for determining environmental information relating to a property of an object and / or a surface in an environment of a motor vehicle, and motor vehicle comprising a lidar device

[0002] DESCRIPTION:

[0003] The present invention relates to a method for determining at least one item of environmental information relating to a property of at least one object located in the environment of a motor vehicle and / or at least one surface located in the environment, wherein polarized laser light is generated by means of at least one lidar device of the motor vehicle and emitted into the environment, wherein the environmental information is determined on the basis of the polarized laser light and a backscattered laser light, wherein the backscattered laser light is a part of the polarized laser light scattered back to the lidar device at the object and / or the surface.

[0004] One method for detecting or determining properties or parameters relating to objects and / or surfaces in the vehicle's environment is information acquisition using Lidar. Lidar refers to a three-dimensional scanning process using laser light. The term "Lidar" is an abbreviation for "Light Detection and Ranging." The obtained results are often used in the control of autonomous vehicles and / or displayed to the driver.

[0005] Lidar devices or sensors often operate according to a scanner principle in which the laser beam sweeps across the surroundings line by line or column, obtaining information regarding the time of flight of the laser light and the distance between the vehicle and the reflection surface from the reflected laser light. This method is known as the time-of-flight method, abbreviated "ToF". Another approach is the FMCW method, where FMCW is an abbreviation for Frequency Modulated Continuous Wave. This method modulates the frequency of the laser light, and the laser light reflected from the object and returned to the lidar device is detected. Based on interference effects relating to the emitted and reflected laser light, the distance to the reflection object and its speed can be determined. Such a concept is known from WO 2021 / 118705 A1.One point addressed in this document concerns the use of polarized laser light. The intensities of the reflected laser light at different polarization planes can be used to detect puddles and ice surfaces.

[0006] There is a need to improve the quality and scope of the data acquired using lidar. The object of the present invention is to provide an improved concept in this regard in connection with a lidar detector of a motor vehicle.

[0007] According to the invention, the object is achieved in a method of the type mentioned at the outset in that a polarimetric, coherent phase evaluation is carried out to determine the ambient information, in which at least one piece of phase information is determined which relates to a phase shift between the polarized laser light and the backscattered laser light, the ambient information being determined on the basis of the phase information.

[0008] The present invention is based on the idea of ​​utilizing another, previously unused source of information to determine environmental information, wherein this source of information is provided by the polarization of the laser light. In this way, a phase or, more precisely, a phase shift of the polarized laser light is measured and determined directly. Reflections occurring during scattering on the object and / or surface cause phase changes, which can also be referred to as phase shifts or phase jumps. The phase changes depend on properties of the object and / or surface, in particular with regard to different polarization directions or planes. In the present invention, the occurring phase shift is used to determine corresponding properties.

[0009] According to the invention, phase information relating to a phase shift between the polarized and backscattered laser light is determined during phase evaluation. Although the backscattered laser light is no longer designated accordingly, it is also polarized under certain conditions relating to properties of the object or surface, in which case the phase shift is detected according to the invention. The term phase shift refers to the difference between the phases of the polarized laser light and the backscattered laser light. The phase shift is typically a modulo value that is usually standardized with respect to the duration of a complete phase transition. It can assume values ​​between 0 and 1, between 0 and 2TT, or between 0 and 360°.

[0010] The use of linearly polarized light is conceivable, in which the electric field vector is always arranged within a plane and oscillates sinusoidally. This plane is also referred to as the polarization direction or polarization plane and includes, in addition to the electric field vector, the direction of propagation of the laser beam. Elliptically, in particular circularly, polarized light is conceivable, in which the tip of the electric field vector rotates elliptically, in particular circularly, around the direction of propagation. An elliptically or circularly polarized light beam can be viewed as a superposition of two linearly polarized light beams with mutually perpendicular polarization planes, with the two polarizations having a phase shift, in the case of circularly polarized light of TT / 2.

[0011] A prerequisite for the method according to the invention is that coherence can be assumed with respect to the laser light, i.e., that the wave field describing the laser light changes in the same way with respect to the instantaneous deflections at different locations, except for a phase shift. The wavelength of the polarized laser light can be located in the near infrared range, for example, between 7800 A and 30000 A, in particular 8500 A, 9050 A, or 15500 A. The wavelength of the polarized laser light can be modulated and, plotted against time in a coordinate system, can be triangular, i.e., linearly increasing and / or decreasing.

[0012] The surroundings of the motor vehicle describe, in particular, the immediate surroundings of the motor vehicle, in which the objects and / or surfaces relevant to the current ferry operation are located. These objects can be moving or immobile objects, such as other road users, obstacles located particularly on or next to the roadway, buildings, curbs, or the like. These surfaces can be road surfaces.

[0013] The phase information can relate to copolarization and / or cross-polarization of the laser light. Phase analysis involves analyzing copolarization or cross-polarization, preferably both. Copolarization means that the lidar device transmits and receives signals in the same polarization plane. Thus, in the case of copolarization, the polarized laser light is linearly polarized along an emitted polarization plane, with the detection of the backscattered laser light relating to a received polarization plane that corresponds to the emitted polarization plane. Cross-polarization means that the lidar device transmits and receives signals in different and mutually perpendicular polarization planes.Thus, in the case of cross-polarization, the polarized laser light is linearly polarized along an emitted polarization plane, with the detection of the backscattered laser light relating to a received polarization plane perpendicular to the emitted polarization plane. In the method according to the invention, it is conceivable for the polarized laser light to be linearly polarized along a first emitted polarization plane and along a second emitted polarization plane, with the first emitted polarization plane and the second emitted polarization plane being perpendicular to one another. In particular, since the change in phase due to the reflection(s) at the object and / or the surface depends on the polarization direction, polarizations in different polarization planes are particularly advantageous for the present purpose.

[0014] The lidar device can comprise two separate lidar devices, each of which can generate linearly polarized laser light and detect the backscattered laser light with respect to the respective polarization plane. Alternatively, the lidar device can be a common lidar device designed and configured to generate laser light with both polarizations. The laser light having the two linear polarizations at an angle to one another can be realized by polarizing the polarized laser light elliptically, in particular circularly.

[0015] It is conceivable that the first emission polarization plane is a horizontal or vertical plane, with the second emission polarization plane being the vertical or horizontal plane. Thus, the first emission polarization plane can be the horizontal plane and the second emission polarization plane can be a vertical plane, or vice versa. The horizontal plane is the plane encompassing the vehicle's longitudinal and transverse directions, and the vertical plane is the plane encompassing the vehicle's longitudinal and vertical directions.

[0016] It is conceivable that the phase information relates to a phase shift between the polarized laser light and the backscattered laser light with respect to the same polarization plane. Thus, the phase shift resulting from the copolarization is detected. Within the scope of the phase evaluation, at least one piece of difference information can be determined, which relates to a difference between a phase shift between the polarized laser light and the backscattered laser light with respect to a first polarization plane and a phase shift between the polarized laser light and the backscattered laser light with respect to a second polarization plane. Specifically, the phase shift with respect to the first polarization plane and the phase shift with respect to the second polarization plane are determined.The difference information concerns the difference between these phase shifts and can be determined by subtracting these values.

[0017] This procedure makes it possible to eliminate any systematic error that might compromise the measurement. The measured phase shift with respect to both polarization planes results from several effects, namely the distance traveled in space, interactions during the backscattering of the laser light from the object or surface, and the systematic error. The phase shift is thus composed of components corresponding to these effects with respect to both polarization planes. The component corresponding to the systematic error is the same for both polarization planes, so that it disappears when the values ​​for the phase shifts are subtracted as described above. Conceivable systematic errors include phase changes that occur due to wave propagation within the lidar device, for example due to corresponding cable lengths or the like.

[0018] It is also conceivable that the phase information relates to a phase shift between the polarized laser light and the backscattered laser light with respect to different polarization planes. Thus, the phase shift resulting from cross-polarization is recorded. Based on this phase information, the number and / or type of reflections occurring during backscattering can be determined. Polarization-maintaining reflections, for example, cause specific phase shifts or jumps that can be determined based on the phase information and allow conclusions to be drawn regarding the number of reflections that have occurred and thus the structure of the object and / or surface.Particularly advantageously, the method according to the invention can be provided for determining at least one piece of amplitude information relating to an amplitude of the polarized laser light and / or the backscattered laser light, based on the polarized laser light and / or the backscattered laser light. The ambient information is additionally determined based on the amplitude information and / or at least one further piece of ambient information is determined based on the amplitude information. The amplitude of the laser light is proportional to its intensity and can be determined indirectly by measuring the intensity of the laser light.

[0019] The amplitude information preferably relates to the copolarization and / or cross-polarization of the laser light. Thus, the amplitude information depends on whether the backscattering is diffuse and thus not polarization-preserving, which depends on the surface properties of the object or surface. Specifically, a ratio, i.e., the quotient, can be determined regarding the amplitudes of the copolarization and the cross-polarization. In the case of diffuse scattering, in which the radiant power incident on the object or surface is not reflected with the same polarization, the linearly polarized laser light is converted into depolarized laser light, which is evident from the ratio of the amplitudes of the cross-polarization and the copolarization.

[0020] It is conceivable that the phase information, and possibly the amplitude information, is determined based on an intermediate frequency provided by a mixer of the lidar device. The mixer has several, typically two, inputs, with a signal relating to the polarized laser light being coupled into one of the inputs and a signal relating to the backscattered laser light being coupled into the other input. The intermediate frequency is generated at an output of the mixer based on the fed-in signals or laser beams and allows the phase information to be determined. If the electric field vector of the polarized laser light oscillates sinusoidally, then information is available with regard to the transmitted signal and thus with regard to the emitted, polarized laser light, not only with regard to the phase, but also with regard to the amplitude, frequency, and polarization direction.This information can also be determined for the backscattered laser light using the mixer, provided that the coherence of the system can be assumed, as is the case here.

[0021] Furthermore, within the scope of the method according to the invention, it is conceivable that at least one piece of optical information relating to the environment is determined by means of an optical sensor, wherein the environmental information is additionally determined based on the optical information and / or at least one further piece of environmental information is determined based on the optical information. Additionally or alternatively, it is conceivable that at least one piece of radar information relating to the environment is determined by means of a radar sensor, wherein the environmental information is additionally determined based on the radar information and / or at least one further piece of environmental information is determined based on the radar information. Lidar and radar sensors, as well as optical sensors, have specific strengths and weaknesses, so that the simultaneous use of these sensor types and the merging of the corresponding sensor data is advantageous.It is conceivable that an image of the surroundings of the motor vehicle captured by the camera is displayed by means of a display device, wherein potential hazards and / or obstacles detected by the lidar and / or radar sensor can be marked in the image.

[0022] It is conceivable that the environmental information, and optionally the amplitude information and / or the additional environmental information, relates to the presence of an obstacle arranged on a roadway and / or an edge of the roadway and / or a condition and / or wetness and / or icy surface of the roadway. It is also conceivable that at least one of these aspects is determined based on the environmental information and / or the additionally mentioned information(s). For example, according to the above description, it is conceivable that the phase information relates to the number of reflections occurring during backscattering. This allows conclusions to be drawn regarding the type and / or condition of the object, whereby an obstacle or an edge arranged on a roadway, such as a curb or the edge of a pothole, can be detected.For example, if a double and / or multiple reflection is detected, the presence of a corresponding object can be inferred.

[0023] It is also conceivable that the phase information relates to the type of reflection occurring during backscattering, i.e., in particular, whether it is a polarization-maintaining or a depolarizing reflection. This allows material parameters of the material forming the object and / or the surface and / or surface parameters of the object and / or the surface, such as surface roughness, to be determined. This allows the condition and / or wetness and / or icing of the road surface to be sensed. Since polarization-maintaining or depolarizing reflection also affects the amplitude information, the results from the phase and amplitude information can be combined, for example, mutually verified.

[0024] Preferably, the environmental information, and optionally the amplitude information and / or the additional environmental information, is used to check whether a hazard condition is met. This condition is met if, based on the environmental information, and optionally the amplitude information and / or the additional environmental information, it is concluded that a potential hazard is present in the environment. Upon fulfillment of the hazard condition, a measure is automatically implemented to reduce or eliminate the hazard. The hazard condition is met, for example, if it turns out that there is an obstacle and / or a pothole and / or a wet patch or puddle and / or an icy surface in front of the motor vehicle.The measure may result in the immediate reduction or elimination of the danger or in the initiation of a further action aimed at reducing or eliminating it, which must be carried out in particular by the user or driver.

[0025] It is conceivable that as a measure a control command used within the framework of at least partially autonomous control of the motor vehicle is generated and / or an output signal is generated and output to an output device, wherein the output signal triggers a warning output for a driver, in particular an acoustic and / or visual warning, issued via the output device. The control command can thus cause the motor vehicle to reduce speed and / or evade the vehicle. The warning output informs the driver of the existing danger so that they can react appropriately. It is conceivable that the image of the surroundings captured by the camera is displayed by means of the display device, which can be a display, wherein the danger spots and / or obstacles can be highlighted in the image by means of colored markings. The markings implement the warning outputs.

[0026] The present invention also relates to a motor vehicle, comprising at least one lidar device by means of which polarized laser light can be generated and emitted into the environment, and an evaluation device which is configured to determine at least one item of environmental information relating to a property of at least one object located in an environment of the motor vehicle and / or at least one surface located in the environment, wherein the evaluation device is configured to determine the environmental information on the basis of the polarized laser light and a backscattered laser light, wherein the backscattered laser light is a part of the polarized laser light scattered back to the lidar device at the object and / or the surface.In this motor vehicle, the invention provides that the evaluation device is further configured to perform a polarimetric, coherent phase evaluation to determine the ambient information. At least one piece of phase information is determined that relates to a phase shift between the polarized laser light and the backscattered laser light. The ambient information is determined based on the phase information. All features, advantages, and aspects explained in connection with the method according to the invention are equally applicable to the motor vehicle according to the invention and vice versa.

[0027] Further advantages and details of the present invention will become apparent from the following exemplary embodiments and the figures, which schematically show:

[0028] Fig. 1 : a view of a motor vehicle according to the invention according to an embodiment,

[0029] Fig. 2: a flowchart of a method according to the invention according to an embodiment, which is carried out during the operation of the motor vehicle of Fig. 1, and

[0030] Fig. 3 - 5: Views of different situations concerning the motor vehicle of Fig. 1 in different environments, in each of which the method according to Fig. 2 is carried out.

[0031] Fig. 1 shows a plan view of a motor vehicle 1 according to the invention according to an exemplary embodiment. The motor vehicle 1 comprises a lidar device 2, by means of which polarized laser light 3 can be generated and emitted. The polarized laser light 3 is emitted into an environment 4 of the motor vehicle 1, for example, toward the front. The motor vehicle 1 comprises an evaluation device 5. The evaluation device 5 is configured to evaluate measurement signals that are detected or generated by the lidar device 2. The evaluation device 5 further functions as a control device configured to generate control signals by means of which the lidar device 2 can be controlled.

[0032] Within the scope of the present invention, the polarized laser light 3 is generated and emitted by the lidar device 2, wherein said light then strikes an object 6, possibly present in the environment 4, and / or a surface 7, possibly present in the environment 4. Due to reflection(s), the polarized laser light 3 is at least partially backscattered, with the backscattered portion returning to the lidar device 2 as backscattered laser light 8. Physical interactions occurring between the polarized laser light 3 and the object 6 and / or the surface 7 during the scattering process may cause a change in the properties with regard to the polarization of the laser light 3, 8. The changed properties can be determined from the backscattered laser light 8 by the lidar device 2 and are used to draw conclusions regarding the properties of the object 6 and / or the surface 7.Specifically, this evaluation involves a polarimetric, coherent phase evaluation based on the polarized laser light 3 and the backscattered laser light 8. Details are explained below.

[0033] Fig. 2 shows a flowchart of a method according to the invention according to an exemplary embodiment, which is carried out during the operation of the motor vehicle 1 of Fig. 1. The evaluation device 5 is configured to carry out the method, i.e., to generate control signals and to evaluate the determined results or information.

[0034] In the first step 9 of the method, the polarized laser light 3 is generated by the lidar device 2 and emitted into the environment 4. The polarized laser light 3 is linearly polarized along a first emission polarization plane 10 and along a second emission polarization plane 11. The polarization planes 10, 11 are perpendicular to one another and perpendicular to the propagation direction 12 of the polarized laser light 3. The first emission polarization plane 10 is a vertical plane, and the second emission polarization plane 11 is a horizontal plane. The polarized laser light 3 is therefore horizontally and vertically polarized. The horizontal and vertical polarization components of the polarized laser light 3 can be in phase, i.e., have a phase shift of 0, or out of phase and thus be elliptically polarized. In the second case, a phase shift TT / 2 is particularly conceivable, so that the laser light 3 is circularly polarized.The backscattered laser light 8 is received in the second step 13 by the lidar device 2, from which phase information 14 and amplitude information 15 are determined. For the sake of clarity, only one of the phase information 14 and one of the amplitude information 15 is indicated in Fig. 2 by a corresponding symbol.

[0035] The phase information 14 describes a phase shift between the polarized laser light 3 and the backscattered laser light 8. The phase information 14 is determined using an intermediate frequency provided by a mixer (not shown in the figures) of the lidar device 2. The mixer has several inputs, with a signal relating to the polarized light 3 being fed into one of the inputs and a signal relating to the backscattered laser light 8 being fed into another of the inputs. The intermediate frequency is generated at the output of the mixer based on the fed-in signals and enables the determination of the phase information 14.

[0036] The phase information 14 relates to both a copolarization and a cross-polarization of the laser light 3, 8. During the evaluation with regard to copolarization, it is provided that the detection of the backscattered laser light 8 relates to a reception polarization plane that corresponds to the respective transmission polarization plane 10, 11. In other words, during the evaluation with regard to copolarization, it is provided that the lidar device 2 transmits and receives signals in the same polarization plane. During the evaluation with regard to cross-polarization, it is provided that the detection of the backscattered laser light 8 relates to a reception polarization plane that is perpendicular to the respective transmission polarization plane 10, 11. In other words, during the evaluation with regard to cross-polarization, it is provided that the lidar device 2 transmits and receives signals in mutually perpendicular polarization planes.

[0037] Phase shifts between the polarized laser light 3 and the backscattered laser light 8 with respect to the same polarization plane 10, 11 are determined as phase information 14. These phase shifts are denoted by PHH and Pvv. Phase shifts between the polarized laser light 3 and the backscattered laser light 8 with respect to different polarization planes 10, 11 are determined as phase information 14. These phase shifts are denoted by PVH and PHV.

[0038] The phase shift PHH describes the difference between the phase of the horizontal polarization of the emitted polarized laser light 3 and the horizontal polarization of the corresponding backscattered laser light 8. The phase shift Pvv describes the difference between the phase of the vertical polarization of the emitted polarized laser light 3 and the vertical polarization of the corresponding backscattered laser light 8. The phase shift PVH describes the difference between the phase of the horizontal polarization of the emitted polarized laser light 3 and the vertical polarization of the corresponding backscattered laser light 8. The phase shift PHV describes the difference between the phase of the vertical polarization of the emitted polarized laser light 3 and the horizontal polarization of the corresponding backscattered laser light 8.

[0039] The amplitude information 15 relates to the amplitude and thus the intensity of the polarized laser light 3 and the backscattered laser light 8. The amplitude information 15 also relates to both the copolarization and the cross-polarization. The amplitude information 15 is also determined using the mixer, which, in addition to the phase information 14, also determines the amplitude information 15. The amplitude information 15 determines the amplitudes with respect to the copolarization and cross-polarization for the horizontal polarization and the vertical polarization of the emitted polarized laser light 3, respectively. For this purpose, intensity coefficients SHH, SVH, SW, SHV are determined, which are elements of the corresponding scattering matrix S, also referred to as the Sinclair matrix.

[0040] The intensity coefficient SHH describes the quotient of the amplitude or intensity of the horizontal polarization of the emitted polarized laser light 3 and the horizontal polarization of the associated backscattered laser light 8. The intensity coefficient Sw describes the quotient of the amplitude or intensity of the vertical polarization of the emitted polarized laser light 3 and the vertical polarization of the associated backscattered laser light 8. The intensity coefficient SVH describes the quotient of the amplitude or intensity of the horizontal polarization of the emitted polarized laser light 3 and the vertical polarization of the associated backscattered laser light 8.The intensity coefficient SHV ​​describes the quotient of the amplitude or intensity of the vertical polarization of the emitted polarized laser light 3 and the horizontal polarization of the corresponding backscattered laser light 8.

[0041] In the third step 16, which is performed simultaneously with the second step 13, optical information 17 and radar information 18 are determined. The optical information 17 is image data of the surroundings 4 and is captured by an optical sensor 19 or a camera of the motor vehicle 1. The radar information 18 is radar data relating to the surroundings 4 and is captured by a radar sensor 20 of the motor vehicle 1.

[0042] In the fourth step 21, environmental information 22 is determined based on information 14, 15, 17, 18, each of which relates to a property of the object 6 or the surface 7. The information 14, 15, 17, 18 complement each other and are also mutually checked for consistency. Details of the environmental information 22 are explained below with reference to Figures 3 to 5.

[0043] Fig. 3 shows the motor vehicle 1 in the environment 4, wherein in the situation shown there, a roadway 23 in front of the motor vehicle 1 has several different surfaces 7, namely a dry and ice-free first surface 24 and a second surface 25 that is icy or has a puddle. Based on the depolarizing properties of the first surface 24 and the polarization-maintaining properties of the second surface 25, conclusions can be drawn about the respective road conditions. The depolarizing properties of the first surface 24 are apparent due to the diffuse scattering of the polarized laser light 3 occurring there on the rough road surface. This can be detected using the amplitude information 14, for example by forming a ratio of the variables SHH, SW, SVH, SHV.In addition, the polarization-maintaining properties of the second surface 25 are evident due to the smooth surface of the ice or puddle, which can also be detected using the amplitude information 14. The evaluation of the phase information 14 also allows the detection of this information, since the polarized laser light 3 is reflected exactly once during scattering on the second surface 25, thus resulting in a specific phase shift or phase jump, which can be identified using the variables PHH, PW, PVH, PHV. In the example shown in Fig. 3, the environmental information 22 relates to the condition and wetness or icing of the surfaces 24, 25 of the roadway 23.

[0044] Furthermore, in step 21, the fulfillment of a hazard condition is checked. In the course of this, the road conditions of the roadway 23 in front of the motor vehicle 1 are analyzed using the environmental information 22. Here, it is determined that in the area of ​​the first surface 24, the condition or roughness of the roadway 23 is such that no hazard exists at this point, and that in the area of ​​the second surface 25 there is icing or a puddle, so that a potential hazard exists at this point, namely that the motor vehicle 1 could skid. The icing present on the second surface 25 means that the hazard condition is fulfilled, and in this case the method continues with the last step 26. Otherwise, i.e. if no hazard exists, the method would continue with the first step 9.

[0045] In the final step 26, a measure is automatically initiated and carried out that reduces or eliminates the danger posed by the icy second surface 25. For this purpose, a control command 27 is generated by the evaluation device 5, which is used within the framework of at least partially autonomous longitudinal and / or lateral guidance of the motor vehicle 1. The control command reduces the speed of the motor vehicle 1 when passing the second surface 25. Furthermore, an output signal 28 is generated by the evaluation device 5 and transmitted to an output device 29 of the motor vehicle 1. This causes a warning to be output to the driver via the output device 29, who is thereby informed of the corresponding danger.The output device 29 is a display by means of which the optical information 17 is output as an image of the environment 4, wherein in the area of ​​the second surface 25 a colored image overlay is displayed as a warning output.

[0046] In the situation shown in Fig. 4, the roadway 23 in front of the motor vehicle 1 has a pothole 30. In the area around the pothole 30, diffuse scattering of the polarized laser light 3 occurs on the rough road surface, which can be detected, as explained above, in particular using the amplitude information 15. In the peripheral area of ​​the pothole 30, there is an edge at which the polarized laser light 3 is doubly reflected during scattering, resulting in a correspondingly specific phase shift or phase jump, which can be determined using the phase information 14. In the example shown in Fig. 4, the environmental information 22 therefore relates to the presence and location of the pothole 30.Subsequently, in step 26, the measures already explained above to reduce the danger posed by the pothole 30, i.e. the output of the control command 27 and the user information 28, are carried out.

[0047] In the situation shown in Fig. 5, an obstacle 31, such as object 6, is located on the roadway 23 in front of the motor vehicle 1. Similar to the case with the pothole 30 as object 6, a polarization change of the laser light 3, 8 specific to this situation results. Thus, multiple reflections, in particular double reflections, occur at the edge of the obstacle 31, which in turn can be recognized from the phase information 14. In the example shown in Fig. 5, the environmental information 22 therefore relates to the presence and position of the object 6 or the obstacle 31. Subsequently, in step 26, the measures already explained above to reduce the danger posed by the pothole 30, i.e. the output of the control command 27 and the user information 28, are carried out.

[0048] Finally, a particularly advantageous aspect that can be realized within the framework of the method according to the invention is explained. This aspect relates to the possibility of eliminating any systematic error that may be present and that burdens the measurement. Such systematic errors are, for example, phase changes that occur due to the wave propagation occurring within the lidar device 2. The phase shifts, in particular the phase shifts PHH and Pvv, arise due to several effects. One of the effects relates to the path traveled in space. Another of the effects relates to the interaction with the object 6 or the surface 7 that takes place during the scattering of the laser light 3, 8. Finally, one of these effects relates to the systematic error, which causes a shift of the same size with regard to PHH and Pvv.During the evaluation of the laser light 3, 8, calculating the difference between these two quantities causes the systematic error components to cancel each other out, and the resulting differential information can be used for further, highly precise evaluation, for example, to determine the distance between the motor vehicle 1 and the object 6 or the surface 7. In this way, highly accurate results can be obtained, allowing even slight changes in distance to be detected. If the object 6 is a wild animal, this procedure can be used to detect, for example, a pulsation of the object 6 caused by the breathing or heartbeat of the wild animal, which in turn can be used for object classification.

Claims

PATENT CLAIMS:

1. A method for determining at least one item of environmental information (22) relating to a property of at least one object (6) located in an environment (4) of a motor vehicle (1) and / or at least one surface (7) located in the environment (4), wherein polarized laser light (3) is generated by means of at least one lidar device (2) of the motor vehicle (1) and emitted into the environment (4), wherein the environmental information (22) is determined on the basis of the polarized laser light (3) and a backscattered laser light (8), wherein the backscattered laser light (8) is a part of the polarized laser light (3) scattered back to the lidar device (2) by the object (6) and / or the surface (7), characterized in that a polarimetric, coherent phase evaluation is carried out to determine the environmental information (22), in which at least one item of phase information (14) is determined,which relates to a phase shift between the polarized laser light (3) and the backscattered laser light (8), wherein the environmental information (22) is determined on the basis of the phase information (14).

2. Method according to claim 1, characterized in that the phase information (14) relates to a copolarization and / or a cross-polarization of the laser light (3, 8).

3. Method according to claim 2, characterized in that the polarized laser light (3) is linearly polarized along a first emission polarization plane (10) and along a second emission polarization plane (11), wherein the first emission polarization plane (10) and the second emission polarization plane (11) are perpendicular to one another.

4. The method according to claim 3, characterized in that the first emission polarization plane (10) is a horizontal or a vertical plane, wherein the second emission polarization plane (11) is the vertical or horizontal plane.

5. Method according to one of claims 2 to 4, characterized in that the phase information (14) relates to a phase shift between the polarized laser light (3) and the backscattered laser light (8) with respect to the same polarization plane (10, 11).

6. The method according to claim 5, characterized in that in the context of the phase evaluation at least one item of difference information is determined which relates to a difference between a phase shift between the polarized laser light (3) and the backscattered laser light (8) with respect to the or a first polarization plane (10) and a phase shift between the polarized laser light (3) and the backscattered laser light (8) with respect to the or a second polarization plane (11).

7. Method according to one of claims 2 to 6, characterized in that the phase information (14) relates to a phase shift between the polarized laser light (3) and the backscattered laser light (8) with respect to different polarization planes (10, 11).

8. Method according to one of claims 5 to 7, characterized in that a number and / or type of reflections occurring during backscattering is determined on the basis of the phase information (14).

9. Method according to one of the preceding claims, characterized in that at least one item of amplitude information (15) relating to an amplitude of the polarized laser light (3) and / or the backscattered laser light (8) is determined on the basis of the polarized laser light (3) and / or the backscattered laser light (8), wherein the environmental information (22) is additionally determined on the basis of the amplitude information (15) and / or at least one further item of environmental information is determined on the basis of the amplitude information (15).

10. Method according to one of the preceding claims, characterized in that the phase information (14) is determined on the basis of an intermediate frequency present on the part of a mixer of the lidar device (2).

11. Method according to one of the preceding claims, characterized in that at least one item of optical information (17) relating to the environment (4) is determined by means of an optical sensor (19) and / or at least one item of radar information (18) relating to the environment (4) is determined by means of a radar sensor (20), wherein the environmental information (22) is additionally determined on the basis of the optical information (17) and / or the radar information (18) and / or at least one further item of environmental information is determined on the basis of the optical information (17) and / or the radar information (18).

12. Method according to one of the preceding claims, characterized in that the environmental information (22) relates to a presence of an obstacle (31) arranged on a roadway (23) and / or an edge of the roadway (23) and / or a condition and / or wetness and / or icing of a surface (24, 25) of the roadway (23).

13. Method according to one of the preceding claims, characterized in that that the environmental information (22) is used to check whether a hazard condition is fulfilled, which is fulfilled if the environmental information (22) is used to conclude that a potential hazard is present in the environment (4), wherein when the hazard condition is fulfilled, a measure is automatically carried out to reduce or eliminate the hazard.

14. The method according to claim 13, characterized in that as a measure, a control command (27) used within the framework of an at least partially autonomous control of the motor vehicle (1) is generated and / or an output signal (28) is generated and output to an output device (29), wherein the output signal (28) causes a warning output for a driver via the output device (29).

15. Motor vehicle comprising at least one lidar device (2) by means of which polarized laser light (3) can be generated and emitted into the environment (4), and an evaluation device (5) which is designed to determine at least one item of environmental information (22) relating to a property of at least one object (6) located in an environment (4) of the motor vehicle (1) and / or at least one surface (7) located in the environment (4), wherein the evaluation device (5) is designed to determine the environmental information (22) on the basis of the polarized laser light (3) and a backscattered laser light (8), wherein the backscattered laser light (8) is a part of the polarized laser light (3) scattered back by the object (6) and / or the surface (7) to the lidar device (2), characterized in that the evaluation device (5) is further designed to determine the environmental information (22) by means of a polarimetric,to carry out coherent phase evaluation, in which at least one phase, sensor information (14) is determined which relates to a phase shift between the polarized laser light (3) and the backscattered laser light (8), wherein the environmental information (22) is determined on the basis of the phase information (14).

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