Method for determining optical cross-talk of a lidar sensor and lidar sensor

Abstract

The present invention relates to a method for determining optical crosstalk of a lidar sensor (10), particularly a spatially resolved lidar sensor (10), and such a lidar sensor (10). The method includes the following steps: transmitting a laser from the lidar sensor (20) to the environment of the lidar sensor (10); receiving a signal from the photodetector (20) of the lidar sensor (10), the signal representing a component of the laser reflected or scattered in the environment of the lidar sensor (10); wherein the photodetector (20) has a first receiving area, the extension scale and position of the first receiving area on the photodetector (20) corresponding to the extension scale and position of the laser imaged onto the photodetector (20) if the scattering of the laser is equal to or less than a predefined threshold; and wherein the photodetector (20) has a second receiving area different from the first receiving area, the second receiving area being directly adjacent to the first receiving area; and the second receiving area being configured to detect a component of the laser imaged onto the photodetector (20) if the scattering of the laser is greater than a predefined threshold, and to obtain information about the degree of optical crosstalk of the lidar sensor (10) based on the component of the laser received in the second receiving area.

Description

Technical Field

[0001] This invention relates to an optical crosstalk method for determining lidar sensors, particularly spatially resolved lidar sensors. The method and such a lidar sensor. Background Technology

[0002] Different types of lidar sensors are known from the prior art, and these lidar sensors are used particularly in partially or even highly automated vehicles for environmental detection. Depending on the technology used, crosstalk of varying intensities may occur in the receiving path of the lidar sensor (e.g., due to scattering on the protective glass of the receiving lidar sensor), and this crosstalk may have a more or less noticeable effect depending on the reflectivity of objects in the environment.

[0003] DE 10 2015 101 902 A1 describes a detector for a lidar system having a row of radiation-sensitive pixels arranged side-by-side. Intervening regions between the pixels are radiation-insensitive due to their construction, in order to reduce crosstalk between pixels.

[0004] EP 2 998 700 B1 describes an electro-optic distance measuring device and a distance measuring method. According to one embodiment, the transmitting beam and receiving beam of the electro-optic distance measuring device are arranged biaxially relative to each other. Since each receiving segment can be assigned a separate signal processing path, electronic crosstalk between signals from different receiving segments can be reduced at least. Summary of the Invention

[0005] According to a first aspect of the invention, a method is proposed for determining the optical crosstalk of a lidar sensor, particularly a spatially resolved lidar sensor. The lidar sensor is configured, for example, as a point scanner, a flash lidar sensor, and preferably as a line scanner. Preferably, the lidar sensor is also a lidar sensor for a vehicle used to scan the environment of the vehicle. In a first step of the method according to the invention, the laser light from the lidar sensor is transmitted to the environment of the lidar sensor. In a second step of the method according to the invention, a signal from the photodetector of the lidar sensor is received, representing the component of the laser light reflected or scattered in the environment of the lidar sensor. The photodetector is preferably configured as a surface detector, but is not limited to such a configuration. Furthermore, the photodetector has a first receiving area, the extent and position of which on the photodetector correspond to the extent and position of the laser light imaged onto the photodetector if the scattering of the laser light is equal to or less than a predefined threshold. Furthermore, the photodetector has a second receiving area, distinct from the first receiving area, directly adjacent to the first receiving area. This second receiving area is configured to detect the component of the laser imaged onto the photodetector if the scattering of the laser exceeds a predefined threshold. Such scattering of the laser can be caused, for example, by the protective glass of the lidar sensor and / or by other optical elements (e.g., lenses) in the transmission and / or reception paths. Other causes of such scattering include, for example, raindrops and / or contamination on the protective glass of the lidar sensor. In addition, the degree of scattering (Ausmaβ) of the laser in the area of ​​the photodetector is related to the reflectivity of objects in the environment of the lidar sensor. Therefore, particularly strongly reflective objects, such as retroreflectors (e.g., traffic signs, traffic guidance devices, etc.), can result in high scattering of the laser on the photodetector. It should be noted that the method according to the invention is based on the assumption that the scattered laser received on the photodetector corresponds substantially to isotropic scattered light, i.e., scattered light that is uniformly scattered in all directions. In the third step of the method according to the invention, information regarding the degree of optical crosstalk of the lidar sensor is obtained based on the component of the laser received in the second receiving region. The steps of at least receiving the signal and obtaining information regarding the degree of optical crosstalk are preferably performed using the analysis and processing unit according to the invention. Therefore, according to the above method, it is possible to achieve a particularly simple and cost-effective method for determining the optical crosstalk of a lidar sensor.

[0006] The dependent claims illustrate preferred extensions of the invention.

[0007] Preferably, when performing environmental identification based on signals from the lidar sensor, and especially based on signal components representing the first receiving area, information regarding the degree of optical crosstalk is taken into account. In other words, based on the method according to the invention, it is possible to evaluate the reliability of the environmental identification, since in the case of high scattering, it can be assumed that false detections of objects in the environment detected by the lidar sensor may occur.

[0008] In an advantageous configuration of this method, a component of the signal representing the second receiving region is used to at least partially compensate for crosstalk in the first receiving region. This provides the advantage that the reliability of the results of downstream processing of the signal can be improved (e.g., in the aforementioned environmental identification), since interference introduced into the useful signal due to scattering can be at least partially eliminated. The acquisition of information regarding the degree of optical crosstalk of the lidar sensor can, in principle, be performed in the context of any lidar system (point scanner, line scanner, flash lidar) of the aforementioned lidar sensor, while crosstalk compensation is generally advantageously applied primarily in the context of line scanners. However, it should not be explicitly excluded that such compensation can also be performed in the context of other lidar systems based on the method according to the invention.

[0009] Particularly advantageously, the lidar sensor is constructed as a spatially resolved line scanner. In other words, the lidar scanner is configured to linearly emit laser light into the environment of the lidar sensor and spatially resolve the echoes generated in the environment by such scan lines along the extension direction of the scan lines in the receiving path of the lidar sensor. In the context of such a line scanner, a first receiving region includes at least one pixel row oriented in the direction in which the scan lines of the lidar sensor are imaged on the photodetector. To at least partially compensate for crosstalk in the first receiving region, for each pixel to be observed in at least one pixel row of the first receiving region, a subset of pixels in the second receiving region adjacent to the corresponding pixel to be observed are determined: these pixels are arranged on an imaginary line extending orthogonally to the pixel row of the first receiving region and intersecting the pixel to be observed. Subsequently, the corresponding brightness value of the corresponding determined pixel in the second receiving region is subtracted from the corresponding brightness value of the pixel row of the first receiving region by subtracting the corresponding brightness values ​​of pixels having the same spacing from the observed pixel. The aforementioned compensation is preferably performed such that the processing steps are iterated progressively for all pixels in the pixel row of the first receiving region or a suitable subset of pixels in the pixel row of the first receiving region (i.e., the corresponding pixel to be observed), wherein the corresponding result of the earlier compensation step is used as the basis for calculation for the corresponding subsequent compensation step. Preferably, after all compensation traversals are completed, the component of the signal of the photodetector representing the first receiving region in the signal is replaced by the corresponding compensated luminance value. Alternatively or additionally, it is possible to consider generating a new signal based on the compensated luminance value, which is then provided to downstream processing. In a particularly simple and thus cost-effective configuration of the photodetector that can be applied in this context, the photodetector, for example, has a single pixel row in the first receiving region and another pixel row arranged parallel to that pixel row, which represents a second receiving region. If the scattering in the pixel row of the second receiving region is higher than a predefined threshold, then in this way, at least the directly adjacent (e.g., above and / or below) pixels of the corresponding pixel to be observed can be compensated by means of the luminance value present in the second region. By using multiple additional parallel rows of pixels in the second region, the additional detected brightness values ​​in the second receiving region can be used to compensate for the additional pixels in the first receiving region that are far from the corresponding observed pixels.

[0010] Advantageously, the brightness value of the second receiving region to be used for corresponding compensation in the first receiving region is extrapolated, at least in part, by means of the predefined scattering characteristics of the lidar sensor. This is particularly advantageous when the second receiving region, as exemplarily described above, has only one pixel row or a small number of parallel pixel rows. In such cases, for example, when using a single pixel row in the second receiving region, it is possible to calculate additional brightness values ​​along virtual (because they are not real) pixel rows in the second receiving region based on the brightness value of the single pixel to be used in the second region for the current compensation traversal. For this purpose, for example, a function and / or lookup table describing the scattering characteristics of the lidar sensor can be used, by means of which additional brightness values ​​can be extrapolated by using or adjusting the brightness values ​​of the pixels in the second region. Furthermore, this extrapolation can also be performed based on multiple pixels in the second region if the second region has more than one pixel in width. The scattering characteristics can be, for example, the average scattering characteristics for multiple lidar sensors constructed similarly or identically, or scattering characteristics individually obtained for each lidar sensor.

[0011] In addition, it can be considered that the first receiving area includes a plurality of parallel rows of pixels, wherein a representative pixel row is selected from the plurality of parallel rows of pixels, and the step of compensating for crosstalk is applied to the representative pixel row. The representative pixel row can be determined, for example, based on the average value of the parallel pixels or the maximum pixel value in the parallel pixel row.

[0012] In an advantageous configuration, crosstalk compensation is applied only to pixels in at least one pixel row that have a predefined minimum scattering among their respective corresponding pixels in the second receiving region. This predefined minimum scattering can be determined, for example, based on the minimum brightness of the pixel in the second receiving region corresponding to the pixel to be observed in the first receiving region and / or based on the average minimum brightness of multiple pixels in the corresponding second receiving region and / or based on the minimum number of illuminated pixels in the respective corresponding second receiving regions.

[0013] Preferably, the face of the photodetector is substantially square, so that optimized or near-complete compensation of the brightness value of the first pixel row can be achieved even under maximum scattering of the scan lines imaged on the photodetector.

[0014] Advantageously, information about the degree of optical crosstalk is used to determine contamination and / or moisture on the protective glass of the lidar sensor. Alternatively or additionally, information about the degree of optical crosstalk is used to determine highly reflective objects (e.g., retroreflectors) in the environment of the lidar sensor, whose reflectivity is higher than a predefined reflectivity.

[0015] Furthermore, advantageously, based on the scattering distribution in the second receiving region, the location and / or extended scale of highly reflective objects in the environment of the lidar sensor can be determined.

[0016] According to a second aspect of the invention, a lidar sensor, particularly a spatially resolved lidar sensor, is provided. The lidar sensor includes an analysis and processing unit, a light emitter, and a photodetector. The analysis and processing unit is configured, for example, as an ASIC, FPGA, processor, digital signal processor, microcontroller, or similar, and is at least connected to the photodetector, and preferably additionally to the light emitter, in an information technology context. The lidar sensor is configured to transmit laser light into the environment of the lidar sensor via the light emitter, while the analysis and processing unit is configured to receive a signal from the photodetector representing a component of the laser light reflected or scattered in the environment of the lidar sensor. The photodetector has a first receiving area, the extension scale and position of which on the photodetector correspond to the extension scale and position of the laser light imaged on the photodetector if the scattering of the laser light is equal to or less than a predefined threshold. Additionally, the photodetector has a second receiving area different from the first receiving area, directly adjacent to the first receiving area, and the second receiving area is configured to detect the component of the laser light imaged on the photodetector if the scattering of the laser light is greater than the predefined threshold. In addition, the analysis and processing unit is configured to determine the degree of optical crosstalk of the lidar sensor based on the component of the laser received in the second receiving area. Attached Figure Description

[0017] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Herein are shown:

[0018] Figure 1 A schematic outline of the components of a lidar sensor according to the present invention is shown;

[0019] Figure 2 A top view of the photodetector of the lidar sensor according to the present invention in the first receiving state is shown;

[0020] Figure 3 A top view of the photodetector of the lidar sensor according to the present invention in the second receiving state is shown. Detailed Implementation

[0021] Figure 1 A schematic outline of the components of a lidar sensor 10 according to the present invention is shown. The lidar sensor 10 includes a light emitter 70, which is configured in conjunction with a transmitting optics 90 to transmit laser light in the form of a scan line through a protective glass 15 of the lidar sensor 10 into the environment of the lidar sensor 10. Components of the transmitted laser light emitted or scattered on an object 80 in the environment of the lidar sensor 10 enter the lidar sensor 10 through the protective window 15 and are imaged onto a photodetector 20 of the lidar sensor 10 by a receiving optics 95, the photodetector being planar in construction. Due to the scattering properties of the protective glass 15, especially in the case of high reflectivity of the object 80, the received laser light includes a scattered light component 100 that may cause crosstalk and thus may lead to a reduction in the spatial resolution accuracy of the lidar sensor 10. The analysis and processing unit 60 according to the present invention is configured as an ASIC, which is connected to the light emitter 70 and the photodetector 20 in terms of information technology. Based on a computer program implemented by the analysis and processing unit 60 that implements the method steps according to the present invention described above, the analysis and processing unit 60 is configured to determine the corresponding degree of crosstalk and, in addition, perform compensation for at least a portion of the crosstalk.

[0022] Figure 2 A top view of the photodetector 20 of the lidar sensor according to the invention is shown in a first receiving state. The photodetector 20 is configured herein as a square photodetector having a first receiving area 30 and a second receiving area 35. The photodetector 20 is configured to receive the scan line imaged onto the photodetector 20 entirely through the pixel row 40 constituting the first receiving area 30 if the scattering of the imaged scan line is equal to or less than a predefined threshold. The second receiving area 35 consists of a plurality of pixels 55, which, in the first receiving state described herein, are not illuminated or are only slightly illuminated due to the currently very low scattering of the scan line.

[0023] Figure 3 A top view of the photodetector 20 of the lidar sensor according to the present invention in a second receiving state is shown. Because... Figure 2 and Figure 3 To avoid repetition, only the differences between the two figures will be described below. Figure 3A second receiving state is illustrated, in which a portion of the scan line imaged onto the photodetector 20 is scattered to such an extent in the region of the uppermost left pixel of the first receiving region 30 that an interfering light component is detected in the second receiving region 35. It should be noted that this is a simplified schematic diagram, which does not show the actual radial scattering near the uppermost left pixel of the second receiving region 35. Using the method described above according to the invention, the brightness information present horizontally relative to the upper left pixel in the second receiving region 35 is algorithmically rotated almost to the direction of the pixel row 40 of the first receiving region 30 (indicated by the shown arrows), and then subtracted pixel-by-pixel from the first receiving region 30 to compensate for the scattering of the scan line.

Claims

1. A method for determining optical crosstalk in a lidar sensor (10), the method comprising: • The laser emitted by the lidar sensor (10) is transmitted (100) into the environment of the lidar sensor (10). • Receive (200) the signal from the photodetector (20) of the lidar sensor (10), the signal representing the component of the laser reflected or scattered in the environment of the lidar sensor (10), wherein, The photodetector (20) has a first receiving area (30) such that if the scattering of the laser is equal to or less than a predefined threshold, the extension scale and position of the first receiving area on the photodetector (20) correspond to the extension scale and position of the laser imaged onto the photodetector (20). The photodetector (20) has a second receiving area (35) that is different from the first receiving area (30). The second receiving area is directly adjacent to the first receiving area (30), and the second receiving area is configured to detect the component of the laser imaged onto the photodetector (20) if the scattering of the laser is greater than the predefined threshold. • Based on the component of the laser received in the second receiving area (35), obtain (300) information about the degree of optical crosstalk of the lidar sensor (10). In this process, based on the brightness value of the pixel in the second receiving area (35) obtained from the component of the laser received in the second receiving area (35), an additional brightness value of the second receiving area (35) is extrapolated, at least in part, by means of the predefined scattering characteristics of the lidar sensor (10). The extrapolated additional brightness value is used to at least partially compensate for optical crosstalk in the first receiving area (30).

2. The method according to claim 1, further comprising: • When performing environmental identification based on the signal from the lidar sensor (10), information about the degree of optical crosstalk is taken into account.

3. The method according to claim 1, wherein, The lidar sensor (10) is a spatially resolved lidar sensor (10).

4. The method according to any one of claims 1 to 3, wherein, The predefined scattering characteristics are described by functions and / or lookup tables.

5. The method according to claim 1, wherein, • The lidar sensor (10) is a spatially resolved line scanner. • The first receiving area (30) includes at least one pixel row (40) oriented in the direction of the scanning line of the lidar sensor (10) on the image of the photodetector (20). • In order to at least partially compensate for optical crosstalk in the first receiving region (30), For each pixel (50) to be observed in at least one pixel row (40) of the first receiving region (30), a plurality of pixels (55) of the second receiving region (35) adjacent to the corresponding pixel (50) are identified. These adjacent pixels are arranged on an imaginary line that extends orthogonally to the pixel row (40) of the first receiving region (30) and intersects with the pixel (50) to be observed. o Thus, subtract the corresponding brightness value of the corresponding adjacent pixel (55) of the second receiving area (35) from the corresponding brightness value of the pixel in the pixel row (40) of the first receiving area (30): subtract the corresponding brightness values ​​of the pixels in the pixel row (40) and the adjacent pixels (55) that have the same spacing as the pixel to be observed (50).

6. The method according to claim 5, wherein, • The first receiving area (30) includes a plurality of parallel rows of pixels (40). • The step of selecting a representative pixel row (40) from the plurality of parallel arranged pixel rows (40) for compensating for optical crosstalk is applied to the representative pixel row.

7. The method according to claim 5 or 6, wherein, The compensation for the optical crosstalk is applied only to the following observed pixels (50) of the at least one pixel row (40): the observed pixels have a predefined minimum scattering in their respective adjacent pixels (55) in the second receiving area (35).

8. The method according to any one of claims 1 to 3, wherein, The face of the photodetector (20) is square.

9. The method according to any one of claims 1 to 3, wherein, Information regarding the degree of optical crosstalk is used to determine: • Contamination and / or moisture on the protective glass of the lidar sensor (10), and / or • The lidar sensor (10) detects highly reflective objects in the environment, where the reflectivity of the object is higher than a predefined reflectivity.

10. The method according to claim 9, wherein, Based on the distribution of scattering in the second receiving region (35), the location and / or extended scale of the highly reflective object are determined.

11. A lidar sensor (10), the lidar sensor comprising: • Analysis and processing unit (60) • Light emitter (70). • Photodetector (20) The analysis and processing unit (60) is configured to, • In conjunction with the light emitter (70), laser light is transmitted into the environment of the lidar sensor (10). • Receive the signal from the photodetector (20), the signal representing the component of the laser reflected or scattered in the environment of the lidar sensor (10), wherein, The photodetector (20) has a first receiving area (30) such that if the scattering of the laser is equal to or less than a predefined threshold, the extension scale and position of the first receiving area on the photodetector (20) correspond to the extension scale and position of the laser imaged onto the photodetector (20). The photodetector (20) has a second receiving area (35) that is different from the first receiving area (30). The second receiving area is directly adjacent to the first receiving area (30), and the second receiving area is configured to detect the component of the laser imaged onto the photodetector (20) if the scattering of the laser is greater than the predefined threshold. The analysis and processing unit (60) is further configured to, • Based on the component of the laser received in the second receiving area (35), information about the degree of optical crosstalk of the lidar sensor (10) is obtained. In this process, based on the brightness value of the pixel in the second receiving area (35) obtained from the component of the laser received in the second receiving area (35), an additional brightness value of the second receiving area (35) is extrapolated, at least in part, by means of the predefined scattering characteristics of the lidar sensor. The extrapolated additional brightness value is used to at least partially compensate for optical crosstalk in the first receiving area (30).

12. The lidar sensor (10) according to claim 11, wherein, The lidar sensor (10) is a spatially resolved lidar sensor (10).

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