DE102022208349A1 - Lidar device and method for operating a lidar device - Google Patents

Abstract

The invention relates to a lidar device (100) with a laser source (101), a detector unit (103), a beam deflection unit (105) for deflecting outgoing laser light (107) from the laser source (101) in predetermined spatial directions (D) and for deflecting from the spatial directions (D) incoming laser light (109) to the detector unit (103), a polarizer (111) for polarizing the outgoing laser light (107) and an evaluation unit (113) for analyzing an intensity of the detected laser light, the beam deflection unit (105) is designed as a facet wheel (117) rotatable about an axis of rotation (115) with a plurality of reflecting facet surfaces (119), with facet surfaces (119) being formed in a beam path (108) of the outgoing laser light (107) by rotation of the facet wheel (117) and can be positioned in a beam path (110) of the incoming laser light (109), a polarization filter (123) for polarizing laser light in a polarization direction (V) being formed on at least one facet surface (121), and wherein the facet surface (121) is positioned via positioning ) a polarization analysis of the incoming laser light (109) can be effected with a polarization filter (123) in the beam path (110) of the incoming laser light (109).

Description

The invention relates to a lidar device and a method for operating a lidar device.

State of the art

Lidar sensors are an essential component for controlling vehicles, especially autonomously controllable vehicles. With highly reflective objects, however, there is a risk of crosstalk effects in which erroneous measured values can be recorded in areas adjacent to the highly reflective object due to the high reflectivity and objects can be falsely detected.

It is therefore an object of the invention to provide an improved lidar device and an improved method for operating a lidar device.

This task is solved by the lidar device and the method for operating a lidar device of the independent claims. Advantageous refinements are the subject of the subordinate claims.

According to one aspect of the invention, a lidar device with a laser source, a detector unit, a beam deflection unit for deflecting outgoing laser light from the laser source in predetermined spatial directions and for deflecting laser light incoming from the spatial directions to the detector unit, a polarizer for polarizing the outgoing laser light and an evaluation unit for analyzing an intensity of the detected laser light, the beam deflection unit being designed as a facet wheel rotatable about an axis of rotation with a plurality of reflecting facet surfaces, facet surfaces being positionable in a beam path of the outgoing laser light and in a beam path of the incoming laser light by rotating the facet wheel, wherein a polarization filter for polarizing laser light in a polarization direction is formed on at least one facet surface, and a polarization analysis of the incoming laser light can be effected by positioning the facet surface with polarization filter in the beam path of the incoming laser light.

In this way, the technical advantage can be achieved that an improved lidar device can be provided, which enables polarization analysis of the detected laser light. For this purpose, the lidar device has a polarizer for polarizing the laser light from the laser source. Furthermore, the lidar device has a polarization filter which is formed on at least one facet surface of the facet wheel of the beam deflection unit. By rotating the facet wheel, the facet surfaces of the facet wheel can be positioned both in the beam path of the outgoing laser light from the laser source and in the beam path of the incoming laser light. By positioning the facet surface with polarization filter in the beam path of the incoming laser light, a polarization analysis of the incoming laser light can be achieved in relation to a polarization direction of the polarization filter. By designing at least one facet surface of the facet wheel without a polarization filter and by positioning the facet surface with polarization filter and the facet surface without polarization filter in the beam path of the incoming laser light one after the other through continuous rotation of the facet wheel, a comparison of the intensity of the facet surface with polarization filter and the Laser light reflected from the facet surface into the detector without a polarization filter can be determined. By comparing the intensities of the laser light, once with reflection on the facet surface with a polarization filter and once without a polarization filter, conclusions can be drawn about the nature of the object reflecting the laser light from the lidar device. In particular, polarization analysis can be used to determine and correct crosstalk effects caused by highly reflective objects. By forming the polarization filter on the facet surface of the facet wheel, a passive analysis element for polarization analysis of the incoming laser light can be realized, which can be switched passively between two polarization states. The analysis element is provided by the facet surfaces of the facet wheel positioned in the beam path of the incoming laser light. By rotating the facet wheel, facet surfaces without a polarization filter and the at least one facet surface with a polarization filter can be positioned one after the other in the beam path of the incoming laser light. The analysis element can thus be connected between an analysis state in which the facet surface with a polarization filter is arranged in the beam path of the incoming laser light, and a state without analysis, in which a facet surface without a polarization filter is arranged in the beam path of the incoming laser light. The connection of the analysis element between The two states mentioned are caused by the rotation of the facet wheel, so that a passive connection of the analysis element is possible. This leads to a robust and technically simple design of the polarization analysis.

For the purposes of the invention, the facet wheel can be designed as a polygonal mirror with several mirror surfaces.

According to one embodiment, a further polarization filter for polarizing laser light in a further polarization direction different from the polarization direction of the polarization filter is formed on at least two further facet surfaces, the two further facet surfaces being arranged adjacent to one another, and the polarizer being in the beam path of the outgoing laser light positioned facet surfaces with polarization filters and/or further facet surfaces with further polarization filters.

In this way, the technical advantage can be achieved that the polarizer for polarizing the laser light from the laser source can also be designed as a passively controllable element. By rotating the facet wheel, the facet surface with polarization filter and the other facet surfaces with further polarization filter can be positioned one after the other in the beam path of the outgoing laser light. Due to the different polarization directions of the different polarization filters, the polarizer can thus be passively connected between two polarization directions, in which a polarization of the outgoing laser light is effected in two different polarization directions. At the same time, by sequentially positioning the different facet surfaces with the different polarization filters in the beam path of the incoming laser light, a passively interconnectable polarization analysis can be achieved again, in which the incoming laser light can be analyzed with respect to the two different polarization directions of the different polarization filters. This in turn enables a robust and technically simple polarization analysis.

According to one embodiment, the facet wheel has a polygonal shape with at least four facet surfaces, the facet wheel having at least two facet surfaces with polarization filters and at least two further facet surfaces with further polarization filters, and wherein the facet surfaces and the further facet surfaces are each arranged adjacent to one another.

In this way, the technical advantage can be achieved that a further precision of the polarization analysis can be achieved by achieving four different polarization combinations by arranging the facet surfaces with polarization filters or further facet surfaces with further polarization filters in the beam paths of the outgoing or incoming laser light by rotating the facet wheel can.

According to one embodiment, the facet wheel further comprises at least one facet surface without a polarization filter.

In this way, the technical advantage can be achieved that by recording the facet surface without a polarization filter, the radiation power of the lidar device and the associated range of the lidar device can be increased.

According to one embodiment, the polarizer is integrated into the laser source.

In this way, the technical advantage can be achieved that a compact and space-saving lidar device is possible.

According to one embodiment, the laser source is designed as an edge emitter.

In this way, the technical advantage can be achieved that a powerful laser source with an integrated polarizer can be provided. According to the invention, the laser light provided by the edge emitter has a preferred polarization direction. An additional polarizer can therefore be dispensed with.

According to one embodiment, the polarization direction of the polarization filter and the further polarization direction of the further polarization filter have a right angle to one another.

In this way, the technical advantage can be achieved that a precise polarization analysis is possible. Highly reflective objects such as retro reflector elements in traffic signs cause the polarization direction of the polarized laser light to rotate by 90 degrees when the laser light is reflected. By aligning the two polarization directions of the two different types of polarization filters at right angles to one another, a precise polarization analysis can be achieved, particularly with regard to laser light reflected by retro-reflector elements. Since such retro-reflector elements are a main cause of crosstalk effects due to their strong reflectivity, crosstalk effects triggered by retro-reflector elements can be precisely detected and thus subsequently corrected by polarization analysis using the two different types of polarization filters of retro-reflector elements.

According to one embodiment, the facet wheel has a third facet surface, wherein a third polarization filter for polarizing laser light in a third polarization direction is formed on the third facet surface, and wherein the third polarization direction forms an angle of 45 degrees to the polarization direction of the polarization filter and to the further polarization direction of the further polarization filter.

In this way, the technical advantage can be achieved that additional material types of the reflective objects can be determined in addition to the retro-reflector elements using the additional polarization filter.

• Polarisieren des ausgehenden Laserlichts der Laserquelle mit dem Polarisator und Positionieren einer Facettenfläche mit Polarisationsfilter im Strahlengang des eingehenden Laserlichts in einem ersten Mess-Frame;
• Drehen des Facettenrads und Positionieren einer weiteren Facettenfläche mit weiterem Polarisationsfilter oder einer Facettenfläche ohne Polarisationsfilter im Strahlengang des eingehenden Laserlichts in einem zweiten Mess-Frame; Vergleichen einer Intensität des im ersten Mess-Frame detektierten Laserlichts und einer Intensität des im zweiten Mess-Frame detektierten Laserlichts; und Ermitteln eines Objekts basierend auf dem in den ersten und zweiten Mess-Frames detektierten Laserlichts, falls die Intensität des im ersten Mess-Frame detektierten Laserlichts gleich der Intensität des im zweiten Mess-Frame detektierten Laserlichts ist; oder
• Identifizieren der gemessenen Intensität als ein Crosstalk-Effekt, falls die Intensität des im ersten Mess-Frame detektierten Laserlichts unterschiedlich zu der Intensität des im zweiten Mess-Frame detektierten Laserlichts ist.

According to a further aspect, a method for operating a lidar device according to one of the preceding embodiments is provided, the method comprising:

• Polarizing the outgoing laser light from the laser source with the polarizer and positioning a facet surface with a polarization filter in the beam path of the incoming laser light in a first measurement frame;
• Rotating the facet wheel and positioning a further facet surface with a further polarization filter or a facet surface without a polarization filter in the beam path of the incoming laser light in a second measurement frame; comparing an intensity of the laser light detected in the first measurement frame and an intensity of the laser light detected in the second measurement frame; and determining an object based on the laser light detected in the first and second measurement frames if the intensity of the laser light detected in the first measurement frame is equal to the intensity of the laser light detected in the second measurement frame; or
• Identifying the measured intensity as a crosstalk effect if the intensity of the laser light detected in the first measurement frame is different from the intensity of the laser light detected in the second measurement frame.

In this way, the technical advantage can be achieved that an improved method for operating a lidar device can be provided, by means of which crosstalk effects can be identified. Through the polarization analysis of the passively operated analysis element, a precise analysis of the polarization direction of the laser light reflected by the respective objects can be effected and the corresponding crosstalk effects can thereby be detected. Passively connecting the analysis element between the two polarization states by rotating the facet wheel enables robust and reliable polarization analysis.

• Positionieren einer Facettenfläche mit Polarisationsfilter im Strahlengang des ausgehenden Laserlichts und Positionieren einer Facettenfläche mit Polarisationsfilter im Strahlengang des eingehenden Laserlichts; wobei das Polarisieren im zweiten Mess-Frame umfasst:
  • Drehen des Facettenrads um die Drehachse und Positionieren einer weiteren Facettenfläche mit weiterem Polarisationsfilter im Strahlengang des ausgehenden Laserlichts und Positionieren einer Facettenfläche mit Polarisationsfilter im Strahlengang des eingehenden Laserlichts; oder
  • Drehen des Facettenrads um die Drehachse und Positionieren einer Facettenfläche mit Polarisationsfilter im Strahlengang des ausgehenden Laserlichts und Positionieren einer weiteren Facettenfläche mit weiterem Polarisationsfilter oder einer Facettenfläche ohne Polarisationsfilter im Strahlengang des eingehenden Laserlichts.

According to one embodiment, the facet wheel comprises at least two facet surfaces with polarization filters and at least two further facet surfaces with further polarization filters, the polarization in the first measurement frame comprising:

• Positioning a facet surface with a polarization filter in the beam path of the outgoing laser light and positioning a facet surface with a polarization filter in the beam path of the incoming laser light; wherein polarizing in the second measurement frame includes:
  • Rotating the facet wheel about the axis of rotation and positioning a further facet surface with a further polarization filter in the beam path of the outgoing laser light and positioning a facet surface with a polarization filter in the beam path of the incoming laser light; or
  • Rotating the facet wheel around the axis of rotation and positioning a facet surface with a polarization filter in the beam path of the outgoing laser light and positioning another facet surface with it another polarization filter or a facet surface without a polarization filter in the beam path of the incoming laser light.

In this way, the technical advantage can be achieved that further precision of the polarization analysis is possible.

• 1 eine schematische Darstellung einer Lidar-Vorrichtung gemäß einer Ausführungsform;
• 2 eine weitere schematische Darstellung einer Lidar-Vorrichtung gemäß einer weiteren Ausführungsform;
• 3 schematische Darstellungen einer Funktionsweise der Lidar-Vorrichtung;
• 4 eine weitere schematische Darstellung einer Lidar-Vorrichtung gemäß einer weiteren Ausführungsform;
• 5 eine weitere schematische Darstellung einer Lidar-Vorrichtung gemäß einer weiteren Ausführungsform;
• 6 weitere schematische Darstellungen einer Funktionsweise der Lidar-Vorrichtung;
• 7 ein Flussdiagramm eines Verfahrens zum Betreiben der Lidar-Vorrichtung.

Embodiments of the invention are explained using the following drawings. Shown in the drawings:

• 1 a schematic representation of a lidar device according to an embodiment;
• 2 a further schematic representation of a lidar device according to a further embodiment;
• 3 schematic representations of how the lidar device works;
• 4 a further schematic representation of a lidar device according to a further embodiment;
• 5 a further schematic representation of a lidar device according to a further embodiment;
• 6 further schematic representations of how the lidar device works;
• 7 a flowchart of a method for operating the lidar device.

1 shows a schematic representation of a lidar device 100 according to an embodiment.

In the embodiment shown, the lidar device 100 comprises a laser source 101 for providing the outgoing laser light 107, a detector unit 103 for detecting the incoming laser light 109 reflected by an object in the vicinity of the lidar device 100, a beam deflection unit 105 by means of which the outgoing laser light 107 can be deflected in a designated spatial direction D and by means of the incoming laser light 109 reflected from said spatial direction D can be deflected into the detector unit 103. The device 100 further comprises an evaluation unit 113, by means of which the incoming laser light 109 detected via the detector unit 103 can be analyzed. The lidar device 100 further comprises a mirror element 131 arranged in the beam path 110 of the incoming laser light 109 between the beam deflection unit 105 and the detector unit 103, by means of which the incoming laser light 109 can be guided from the beam deflection unit 105 into the detector unit 103. Furthermore, the lidar device 100 includes a protective glass 129, by means of which a delimitation of the mentioned components of the lidar device 100 from an environment of the lidar device 100 is possible. The lidar device 100 may further comprise further components, such as a housing, which, however, are not shown in the figures shown for reasons of clarity.

In the embodiment shown, the beam deflection unit 105 is designed as a facet wheel 117 that can be rotated about an axis of rotation 115 and has a plurality of different facet surfaces 119. The facet surfaces 119 are set up to reflect the outgoing laser light 107 as well as the incoming laser light 109. By rotating the facet wheel 117 about the axis of rotation 115, an orientation of the beam path 108 of the outgoing laser light 107 to the respective facet surface 119 can be changed and thus the outgoing laser light 107 can be reflected in variable spatial directions D from the respective facet surface 119. This applies analogously to the facet surface 119 of the facet wheel 117 positioned in the beam path 110 of the incoming laser light 109, which can be variably positioned in its orientation to the beam path 110 by rotating the facet wheel 117, so that incoming laser light 109 is deflected from different spatial directions D to the detector unit 103 and can therefore be detected. The rotation of the facet wheel 117 thus enables a scanning process of the surroundings of the lidar device 100 in different spatial directions D.

In the embodiment shown, the facet wheel 117 is arranged between the laser source 101 and the detector unit 103, so that the outgoing laser light 107 and the incoming laser light 109 are reflected by two different facet surfaces 119 of the facet wheel 117.

In the embodiment shown, the facet wheel 117 is square and has four facet surfaces 119 arranged in pairs opposite one another.

In the embodiment shown, polarization filters 123, 127 are formed on the four facet surfaces 119. A polarization analysis of the incoming laser light 109 is possible via the polarization filters 123, 127. For this purpose, the facet wheel 117 has two facet surfaces 121 with polarization filters 123 and two further facet surfaces 125 with further polarization filters 127. The polarization filters 123 have a polarization direction V, while the further polarization filters 127 have a polarization direction H. The two polarization directions V, H are different according to the invention and, according to one embodiment, have an orientation that is 90 degrees different from one another.

According to the invention, the lidar device 100 has a polarizer 111 for polarizing the outgoing laser light 107 from the laser source 101. In the embodiment shown, the polarizer 111 is provided by the facet surfaces 121 with a polarization filter 123 or further facet surfaces 125 with a further polarization filter 127 that can be positioned in the beam path 108 of the outgoing laser light 107. By rotating the facet wheel 117 about the axis of rotation 115, facet surfaces 121 with polarization filters 123 and further facet surfaces 125 with further polarization filters 127 can be positioned in the beam path 108 of the outgoing laser light 107. This allows the outgoing laser light 107 to be polarized alternately according to the polarization direction V or the polarization direction H of the different polarization filters 123, 127. At the same time, by rotating the facet wheel 117 about the axis of rotation 115, facet surfaces 121 with polarization filters 123 and further facet surfaces 125 with further polarization filters 127 can be positioned in the beam path 110 of the incoming laser light 109. This enables a polarization analysis of the incoming laser light 109 with respect to the different polarization directions V, H.

In the embodiment shown, the facet surfaces 121 with polarization filter 123 are arranged adjacent to one another, while the further facet surfaces 125 with further polarization filter 127 are also arranged adjacent to one another on the facet wheel 117.

By rotating the facet wheel 117 about the axis of rotation 115 by multiples of 90 degrees, various polarization combinations between the polarization direction of the polarization of the outgoing laser light 107 and the analysis direction of the polarization analysis of the incoming laser light 109 can be implemented. In the position of the facet wheel 117 shown and the positioning of the two facet surfaces 121 with polarization filter 123 both in the beam path 108 of the outgoing laser light 107 and in the beam path 110 of the incoming laser light 109, the outgoing laser light 107 is polarized in the polarization direction V and at the same time a polarization analysis of the incoming laser light 109 also with respect to the polarization direction V. When the facet wheel 117 is rotated 90 degrees clockwise, the outgoing laser light 107 is polarized in the polarization direction H and a polarization analysis of the incoming laser light 109 is carried out with respect to the polarization direction V. When the facet wheel 117 is rotated further by 90 Degrees clockwise, the outgoing laser light 107 is polarized in the polarization direction H and a polarization analysis of the incoming laser light 109 is also carried out with respect to the polarization direction H. When the facet wheel 117 is rotated further by 90 degrees in the clockwise direction, the outgoing laser light 107 is polarized in the polarization direction V and one Polarization analysis of the incoming laser light 109 with respect to the polarization direction H.

By comparing the intensities of the incoming laser light 109 detected by the detector unit 103 during these four different positions of the facet wheel 117 by the evaluation unit 113, conclusions can be drawn about the nature of an object in the environment of the lidar device 100, which is used to reflect the laser light of the lidar device 100 led. In particular, various components of the Müller matrix can be calculated with regard to the reflection of a reflecting object and statements can be made regarding the reflectivity or the material properties of the reflecting object. This allows the material properties of the reflecting object to be determined. In addition, signals in the form of detected incoming laser light 109, which indicate the positioning of a reflective one, can be identified as a crosstalk effect and, associated with this, as incorrect object detections.

2 shows a further schematic representation of a lidar device 100 according to a further embodiment.

The embodiment of the lidar device 100 shown is based on the embodiment of the lidar device 100 in 1 . In the 2 Embodiment shown differs from the embodiment in 1 only due to the missing mirror element 131. The functionality of the lidar device 100 shown corresponds to the embodiment in 1 . In the graphics a) and b) there are two different ones Positions of the facet wheel 117 relative to the beam paths 108, 110 of the outgoing and incoming laser light 107, 109 are shown. The two different positions of the facet wheel 117 in graphics a) and b) result in two of the polarization combinations already described above. In graphic a), a polarization of the outgoing laser light 107 in the polarization direction V and a polarization analysis of the incoming laser light 109 in relation to the polarization direction V are achieved. In graphic b), however, a polarization of the outgoing laser light 107 in the polarization direction H and a polarization analysis of the incoming laser light 109 in relation to the polarization direction V are achieved.

3 shows schematic representations of how the lidar device 100 works.

3 shows a graphic representation of the measuring principle of the lidar device 100 according to the invention described above, in which four different polarization combinations between the polarization of the outgoing laser light 107 and the polarization analysis of the incoming laser light 109 are effected by rotating the facet wheel 117 by a multiple of 90 degrees. Graphics a) to d) show four different measurement frames of the lidar device 100, each of which was recorded in different polarization combinations. Graphics a) to d) each show an identical environmental situation of the lidar device 100. In the environmental situation shown, an object 141 is shown in the form of a pedestrian, which is arranged below a reflector element 137 in the form of a reflective traffic sign. Furthermore, laser line signals 135 of the lidar device 100 running along a y-direction are shown in graphics a to d. The laser line signals 135 are arranged parallel to one another along an x-direction. In the embodiment shown, the lidar device 100 is designed as a corresponding line emitter and one of the laser line signals 135 shown is emitted per laser signal emitted. By rotating the facet wheel 117 about the axis of rotation 115, the different laser line signals 135 shown can be emitted at a distance from one another relative to the x-axis shown.

Furthermore, an effect of the reflector element 137 is shown. Reflector elements 137 in the form of reflective traffic signs, which are designed as retro reflectors, lead to disruptive effects in the lidar measurement due to their high reflectivity. On the one hand, the strong reflections from the reflector elements 137 lead to saturation of the detectors of the corresponding lidar device. This leads to the reflector elements 137 not being perceived in the lidar measurement by the respective lidar device 100 due to the saturation of the detector used in each case. This is marked in graphics a) to d) by the hatching shown. Furthermore, the greater reflectivity of the reflector elements 137 leads to crosstalk effects. These lead to false detections of non-existent objects, in which objects are detected in the corresponding lidar measurements due to the high intensity of the reflected laser radiation, which are not positioned at all in the environment of the lidar device 100. This is marked in graphics a) to d) by the bar shown in the y direction above and below the reflector element 137, which represents the crosstalk signals caused by the reflector element 137. In the environmental situation shown, in which the object 141 in the form of the pedestrian is arranged below the reflector element 137, the object 141 is not recognized by the dominant crosstalk effect 139 of the reflector element 137.

The four graphics a) to d) now show four measurement frames that were recorded from the same environmental situation. These four measurement frames each differ in the polarization combination between the polarization direction of the polarization of the outgoing laser light 107 and the analysis direction of the polarization analysis of the incoming laser light 109. In graphic a), the outgoing laser light 107 is polarized in the polarization direction H and the incoming laser light 109 in relation to the Polarization direction H analyzed. This is represented by the letter combination HH in graphic a).

In graphic b), the outgoing laser light 107 is polarized in the polarization direction V, while the incoming laser light 109 is analyzed with respect to the polarization direction H.

In graphic c), the outgoing laser light 107 is polarized in the polarization direction V, while the incoming laser light 109 is analyzed with respect to the polarization direction V.

In graphic d), outgoing laser light 107 is polarized in the polarization direction H, while the incoming laser light 109 is analyzed with respect to the polarization direction V.

The different polarization combinations are achieved as already described above by rotating the facet wheel 117 about the axis of rotation 115 and the corresponding positioning of the facet surfaces 121, 125 with the respective polarization filters 123, 127 in the beam paths 108, 110 of the outgoing and incoming laser light 107, 109.

Graphic f) shows a positioning of the facet wheel 117, which leads to the polarization combination of the measurement frame shown in graphic a). The further positions of the facet wheel 117 can be realized by turning a multiple of 90 degrees clockwise, which leads to the polarization combinations of the measurement frames shown in graphics b to d.

Graphic e) also shows a measurement result corrected in the course of the polarization analysis, in which the saturation of the detector unit 103 was corrected by the strong reflectivity of the reflector element 137 and the crosstalk effects 139 of the reflector element 137 were removed. As a result of the correction carried out, the reflector element 137 can be detected without saturation of the detector unit 103 and the object 141 arranged under the reflector element 137.

The polarization analysis includes the comparison of the intensities detected in the different measurement frames to the different polarization combinations. This can include, for example, an addition or subtraction of the intensities of the different measurement frames of the different polarization combinations. The different combinations of addition and subtraction of the individual intensities of the laser signals detected in the different measurement frames can be based on the first entries of the Müller matrix. It can be calculated for the following four elements of the Müller matrix: $$\begin{array}{l}{\text{<figure-callout id="00" label="m" filenames="DE102022208349A1\_0007.png" state="{{state}}">m</figure-callout>}}_{00}\text{corresponds to HH}+\text{HV}+\text{VH}+\text{VV}\\ {\text{m}}_{01}\text{corresponds to HH}+\text{HV}-\text{VH}-\text{<figure-callout id="10" label="VV m" filenames="DE102022208349A1\_0007.png" state="{{state}}">VV</figure-callout>}& \\ {\text{m}}_{}{}_{10}\text{corresponds to HH}-\text{HV}+\text{VH}-\text{VV}\\ {\text{m}}_{11}\text{corresponds to HH}-\text{HV}-\text{VH}+\text{VV}\end{array}$$

The polarization combinations mentioned correspond to the polarization combinations of the measurement frames shown in graphics a) to e).

4 shows a further schematic representation of a lidar device 100 according to a further embodiment.

4 shows another embodiment of the lidar device 100. The embodiment shown is based on the embodiment in 1 . The embodiment shown differs from the embodiment in 1 by two reflector elements 137 positioned in the beam paths 108 of the outgoing laser light 107 and 110 of the incoming laser light 109. Furthermore, the embodiment shown differs in that the square facet wheel 117 only includes a facet surface 121 with a polarization filter 123. The three further facet surfaces 119 are designed as facet surfaces 133 without a polarization filter. The facet surfaces 133 are therefore only designed as mirror surfaces and are not able to cause polarization of the reflected light.

Furthermore, the embodiment differs from the embodiment in 1 in that the polarizer 111 is integrated into the laser source 101 in the embodiment shown. The laser source 101 can be designed, for example, as an edge emitter with a predetermined polarization direction of the emitted laser light. The predetermined polarization direction of the edge emitter corresponds to the polarization direction V of the polarization filter 123 of the facet surface 121 of the facet wheel 117.

Graphics a) to d) show different positions of the facet wheel 117, in which different facet surfaces 121, 133 of the facet wheel 117 are positioned in the beam paths 108, 110 of the outgoing and incoming laser light 107, 109.

In the embodiment shown, the polarization direction V of the outgoing laser light 107 remains unchanged during the rotation of the facet wheel 117. When the outgoing laser light 107 is reflected from a facet surface 133 without a polarization filter, the polarization direction V of the laser light from the laser source 101 remains unchanged. The same applies to a reflection of the outgoing laser light 107 on the facet surface 121 with polarization filter 123 and the matching polarization direction V of the laser light of the laser source 101 to the polarization direction V of the polarization filter 123, the complete outgoing laser light 107 is reflected on the facet surface 121.

By rotating the facet wheel 117, either the facet surface 121 with polarization filter 123 or the facet surfaces 133 without polarization filter are positioned in the beam path 110 of the incoming laser light 109. In the various measurement frames, an intensity of the laser light with polarization direction V is detected or a laser light is detected without polarization analysis being carried out. Without polarization analysis, the detector unit 103 detects intensity for any polarization directions and in particular of unpolarized laser light. By comparing the laser light detected for the different intensities of the different measurement frames, a conclusion can be drawn about the nature of the object reflecting the laser light.

The tables below show the intensities detected for different types of reflective objects according to the positions of the facet wheel 117 in graphics a) to d). Intensities are given in Table 1 for a retro reflector, in Table 2 for a reflector with a metallic surface and in Table 3 for a non-metallic reflector.

The tables take into account the polarization configurations of graphics a) to d), in which the polarization direction V of the laser light from the laser source 101 corresponds to the polarization direction V of the polarization filter 123.

For a retro reflector, the polarization direction of the reflected laser light is rotated by 90 degrees. The configuration of the 4 Subsequently, when reflected on a retro reflector, the incoming laser light 109 no longer has the polarization direction V of the outgoing laser light 107. For the positions of the facet wheel 117 in graphics a), c) and d), in which a facet surface 133 without a polarization filter is positioned in the beam path of the incoming laser light 109 and thus no polarization analysis of the incoming laser light 109 takes place, 100 percent of the outgoing laser light 107 detected. However, for a position of the facet wheel 117 in graphic b), in which the facet surface 121 with polarization filter 123 is positioned in the beam path 110 of the incoming laser light 109, no intensity is detected by the detector 103. Since the polarization direction V of the polarization filter 123 corresponds to the polarization direction V of the outgoing laser light 107 and since the polarization direction is rotated by 90 degrees when the laser light is reflected at the retro reflector, the incoming laser light 109 has a polarization direction rotated by 90 degrees compared to the polarization direction V of the polarization filter 123. When the incoming laser light 109 hits the polarization filter 123, the full intensity of the incoming laser light 109 is absorbed or transmitted and thus no laser light is reflected into the detector unit 103.

When the laser light is reflected on a metallic surface, however, the polarization direction V of the laser light is retained, so that the incoming laser light 109 continues to have the polarization direction V of the outgoing laser light 107. Since the polarization direction V of the incoming laser light 109 thus corresponds to the polarization direction V of the polarization filter 123, for all positions of the facet wheel 117 in graphics a) to d), 100 percent of the incoming laser light 109 is reflected through the facet surfaces 121 and 133 into the detector unit 103.

However, when the laser light is reflected on a non-metallic surface, the polarization direction V of the outgoing laser light 107 remains and the incoming laser light 109 is unpolarized without a preferred polarization direction. In the positions of the facet wheel 117 in graphics a), c) and d), in which the incoming laser light 109 is reflected into the detector unit 103 on the facet surfaces 133 without a polarization filter, 100% of the incoming laser light 109 is still reflected into the detector unit 103. In the position of the facet wheel 117 in graphic b), however, 50% of the incoming laser light 109 is filtered out by the polarization filter 123 and only 50% is reflected into the detector unit 103.

The polarization analysis can therefore be used to draw conclusions about the surface properties of the reflecting object and thereby carry out the corrective measures described above for the detected intensities of the incoming laser light 109. Table 1 Surface with 90° rotation (eg retro reflector) Position of the facet wheel Polarization of the outgoing laser light Send Reflection @ Target Polarization of incoming laser light Detected intensity relative to the incoming laser light 0° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↺ 0° pole, = 100% ↔ 0° pole, = 100% ↔ 0° pole, = 100% 90° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↺ 0° pole, 100% ↔ 0° pole, = 100% ↕ 90° pole, → 0% 180° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↺ 0° pole, 100% ↔ 0° pole, = 100% ↔ 0° pole, = 100% 270° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↺ 0° pole, 100% ↔ 0° pole, = 100% ↔ 0° pole, = 100% Table 2 Metallic surface with reflection while maintaining the direction of polarization Position of the facet wheel Polarization of the outgoing laser light Send Reflection @ Target Polarization of incoming laser light Detected intensity relative to the incoming laser light 0° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↕ 90° pole. = 100% ↕ 90° pole. = 100% ↕ 90° pole, → 100% 90° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↕ 90° pole. = 100% ↕ 90° pole. = 100% ↕ 90° pole, → 100% 180° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↕ 90° pole. = 100% ↕ 90° pole. = 100% ↕ 90° pole, → 100% 270° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↕ 90° pole. = 100% ↕ 90° pole. = 100% ↕ 90° pole, → 100% Table 3 No metallic surface with unpolarized reflection Position of the facet wheel Polarization of the outgoing laser light Send Reflection @ Target Polarization of incoming laser light Detected intensity relative to the incoming laser light 0° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↔ ↕ non-pol. = 100% ↔ ↕ non-pol. = 100% ↔ ↕ unpolar, = 100% 90° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↔ ↕ non-pol. = 100% ↔ ↕ non-pol. = 100% ↕ 90° pole, → 50% 180° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↔ ↕ non-pol. = 100% ↔ ↕ non-pol. = 100% ↔ ↕ unpolar, = 100% 270° ↕ 90° pole, 100% ↕ 90° pole, → 100% ↔ ↕ non-pol. = 100% ↔ ↕ non-pol. = 100% ↔ ↕ unpolar, = 100%

5 shows a further schematic representation of a lidar device 100 according to a further embodiment.

The embodiment in 5 based on the embodiment in 4 and has all the features described there. The embodiment shown differs only in this from the embodiment in 4 that the facet wheel 117 has two opposing facet surfaces 121 with polarization filter 123.

Through the facet surfaces 133 without polarization filters of the embodiments in 4 and 5 The performance of the lidar device 100 and the associated range of the lidar device 100 can be compared to the embodiment in 1 and 2 improve, since only polarization filtering of the outgoing or incoming laser light 107, 109 is carried out for one or two of the four measurement frames shown. The intensity losses of the outgoing or incoming laser light 107, 109 caused by the polarization filtering of the polarization filters can thus be reduced.

According to one embodiment, the facet wheel 117 may have a polygonal shape other than the square shape shown and include a plurality of facet surfaces. The facet surfaces can be designed as facet surfaces 121 with polarization filter 123, as facet surfaces 125 with another polarization filter 127 or as facet surfaces 133 without polarization filter.

According to one embodiment, the facet wheel 117 may further include a third facet surface with a third polarization filter. The third polarization filter can have a polarization direction that is rotated by 45 degrees to the polarization directions V of the polarization filter 123 and H of the polarization filter 127. The additional polarization direction allows further conclusions to be drawn about the nature of the surface of the reflecting object.

6 shows further schematic representations of how the lidar device 100 works.

Graphic b) shows the surrounding situation of a measurement frame in graphics a) to d) in 3 . Graphic b) is intended to be representative of different measurement frames with different polarization combinations.

Graphic a), on the other hand, shows four intensity angle diagrams for the first four components of the Müller matrix mentioned above. The intensity of the various entries m ₀₀ , m ₀₁ , m ₁₀ and m ₁₁ of the Müller matrix are plotted against a Pol-Dif angle. The angle Pol-Dif describes a difference angle between the polarization direction of the outgoing laser light 107 and the polarization direction of the polarization filter 123, 127 positioned for polarization analysis in the beam path 110 of the incoming laser light 109.

The graphics show intensity values depending on the difference angle Pol-Diff for various object materials such as asphalt 143, wood 145, metallic vehicle paint 147, non-metallic vehicle paint 149, non-reflective traffic sign 151 and retro-reflective traffic sign 153. The analyzes shown can therefore be used to Based on the laser line signal 135 of the graphic b), the reflector element 137 can be recognized as a retro-reflective traffic sign 153, the asphalt 143 of the road. The object 141, on the other hand, does not enable detection due to the diffusely reflecting surface 155.

7 shows a flowchart of a method 200 for operating the lidar device 100.

According to the invention, in a method step 201, the outgoing laser light 107 of the laser source 101 is first polarized with the polarizer 111 in a first measurement frame and a facet surface 121 with a polarization filter 123 is positioned in the beam path 110 of the incoming laser light 109.

According to the embodiment shown, in a method step 211 a facet surface 121 with polarization filter 123 is positioned in the beam path 108 of the outgoing laser light 107 and a facet surface 121 with polarization filter 123 is positioned in the beam path 110 of the incoming laser light 109.

In a further method step 203, a further facet surface 125 with a further polarization filter 127 or a facet surface 133 without a polarization filter is positioned in the beam path 110 of the incoming laser light 109 by rotating the facet wheel 117.

For this purpose, according to the embodiment shown, in a method step 213, the facet wheel 117 is rotated about the axis of rotation 115 in such a way that a further facet surface 125 with a further polarization filter 127 is positioned in the beam path 108 of the outgoing laser light 107 and a facet surface 121 with a polarization filter 123 is positioned in the beam path 110 of the incoming one Laser light 109 is positioned.

Alternatively, in a method step 215, a facet surface 121 with a polarization filter 123 can be positioned in the beam path 108 of the outgoing laser light 107 by rotating the facet wheel 117 and a further facet surface 125 with a further polarization filter 127 or a facet surface 133 without a polarization filter are positioned in the beam path 110 of the incoming laser light 109.

In a further method step 205, intensities of the laser light detected in the first and second measurement frames are compared with one another. This can include, for example, the additions or subtractions described above according to the components of the Müller matrix described.

In a further method step 207, an object 141 is determined based on the laser light detected in the first and second measurement frames if the intensity of the laser light detected in the first measurement frame is equal to the intensity of the laser light detected in the second measurement frame.

Alternatively, in a method step 209, the measured intensity is identified as a crosstalk effect 139 if the intensity of the laser light detected in the first measurement frame is different to the intensity of the laser light detected in the second measurement frame.

Claims (10)

Lidar device (100) with a laser source (101), a detector unit (103), a beam deflection unit (105) for deflecting outgoing laser light (107) from the laser source (101) in predetermined spatial directions (D) and for deflecting out of the spatial directions ( D) incoming laser light (109) to the detector unit (103), a polarizer (111) for polarizing the outgoing laser light (107) and an evaluation unit (113) for analyzing an intensity of the detected laser light, the beam deflection unit (105) being one by one Axis of rotation (115) rotatable facet wheel (117) is formed with a plurality of reflecting facet surfaces (119), with a rotation of the facet wheel (117) facet surfaces (119) in a beam path (108) of the outgoing laser light (107) and in a beam path ( 110) of the incoming laser light (109) can be positioned, a polarization filter (123) being formed on at least one facet surface (121) for polarizing laser light in a polarization direction (V), and wherein the facet surface (121) is positioned with a polarization filter ( 123) a polarization analysis of the incoming laser light (109) can be effected in the beam path (110) of the incoming laser light (109). Lidar device (100). Claim 1 , wherein a further polarization filter (127) is formed on at least two further facet surfaces (125) for polarizing laser light in a further polarization direction (H) that is different from the polarization direction (V) of the polarization filter (123), the two further facet surfaces (125 ) are arranged adjacent to one another, and wherein the polarizer (111) is positioned through the facet surfaces (121) with polarization filters (123) and/or further facet surfaces (125) with further polarization filters (127) positioned in the beam path (108) of the outgoing laser light (107). is formed. Lidar device Claim 2 , wherein the facet wheel (117) has a polygonal shape with at least four facet surfaces (119), the facet wheel (117) having at least two facet surfaces (121) with polarization filters (123) and at least two further facet surfaces (125) with further polarization filters (127). has, and wherein the facet surfaces (121) and the further facet surfaces (125) are each arranged adjacent to one another. Lidar device according to one of the preceding claims, wherein the facet wheel (117) further comprises at least one facet surface (133) without a polarization filter. Lidar device (100) according to one of the preceding claims, wherein the polarizer (111) is integrated into the laser source (101). Lidar device (100). Claim 5 , wherein the laser source (101) is designed as an edge emitter. Lidar device (100) according to one of the above Claims 2 until 6 , wherein the polarization direction (V) of the polarization filter (123) and the further polarization direction (H) of the further polarization filter (127) have a right angle to one another. Lidar device (100) according to one of the above Claims 2 until 7 , wherein the facet wheel (117) has a third facet surface, with a third polarization filter on the third facet surface is designed to polarize laser light in a third polarization direction, and wherein the third polarization direction has an angle of 45 degrees to the polarization direction (V) of the polarization filter (123) and to the further polarization direction (H) of the further polarization filter (127). Method (200) for operating a lidar device (100) according to one of the above Claims 1 until 8th , comprising: polarizing (201) the outgoing laser light (107) of the laser source (101) with the polarizer (111) and positioning a facet surface (121) with a polarization filter (123) in the beam path (110) of the incoming laser light (109) in a first measurement frame; Rotating (203) the facet wheel (117) and positioning a further facet surface (125) with a further polarization filter (127) or a facet surface (133) without a polarization filter in the beam path (110) of the incoming laser light (109) in a second measurement frame; Comparing (205) an intensity of the laser light detected in the first measurement frame and an intensity of the laser light detected in the second measurement frame; and determining (207) an object (141) based on the laser light detected in the first and second measurement frames if the intensity of the laser light detected in the first measurement frame is equal to the intensity of the laser light detected in the second measurement frame; or identifying (209) the measured intensity as a crosstalk effect (139) if the intensity of the laser light detected in the first measurement frame is different from the intensity of the laser light detected in the second measurement frame. Procedure (200) according to Claim 9 wherein the facet wheel (117) comprises at least two facet surfaces (121) with polarization filters (123) and at least two further facet surfaces (125) with further polarization filters (127), and wherein polarizing (201) in the first measurement frame includes: positioning (211 ) a facet surface (121) with a polarization filter (123) in the beam path (108) of the outgoing laser light (107) and positioning a facet surface (121) with a polarization filter (123) in the beam path (110) of the incoming laser light (109); wherein polarizing (203) in the second measurement frame includes: rotating (213) the facet wheel (117) about the axis of rotation (115) and positioning a further facet surface (125) with a further polarization filter (127) in the beam path (108) of the outgoing laser light (107) and positioning a facet surface (121) with a polarization filter (123) in the beam path (110) of the incoming laser light; or rotating (215) the facet wheel (117) about the axis of rotation (115) and positioning a facet surface (121) with a polarization filter (123) in the beam path (108) of the outgoing laser light (107) and positioning a further facet surface (125) with a further polarization filter (127) or a facet surface (133) without a polarization filter in the beam path (110) of the incoming laser light (109).

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