OBJECT RECOGNITION BY AN ACTIVE OPTICAL SENSOR SYSTEM

Abstract

According to a method for object recognition by an active optical sensor system (2), a detector unit (2b) detects light (3b) reflected off an object (4) and generates a sensor signal (5a, 5b, 5c, 5d, 5e, 5f) on the basis thereof. A computing unit (2c) ascertains a first pulse width (D1) defined by a first limit value (G1) for the amplitude of the sensor signal (5a, 5b, 5c, 5d, 5e, 5f) as well as a second pulse width (D2) defined by a corresponding second limit value (G2). The computing unit (2c) ascertains at least one property of the object (4) according to the first pulse width (D1) and according to the second pulse width (D2).

Claims

1. A method for object recognition by an active optical sensor system, comprising: registering light reflected by an object in an environment of the sensor system by a detector unit of the sensor system and generating a sensor signal on the basis of the registered light; determining a first pulse width of a signal pulse of the sensor signal by a computer unit, the first pulse width being established by a predetermined first limit value for an amplitude of the sensor signal; determining a second pulse width of the signal pulse is by the computer unit, the second pulse width being established by a predetermined second limit value for the amplitude of the sensor signal; and determining at least one property of the object by the computer unit as a function of the first pulse width and the second pulse width.

2. The method as claimed in claim 1, wherein the property of the object is determined as a function of a difference between the first pulse width and the second pulse width.

3. The method as claimed in claim 1, wherein the property of the object is determined as a function of a ratio between the first pulse width to the second pulse width.

4. The method as claimed in claim 1, wherein the at least one property contains a reflectivity of the object.

5. The method as claimed in claim 1, wherein the at least one property contains an extent of the object in a radial direction with respect to the sensor system.

6. The method as claimed in claim 1, wherein a classification of the object is carried out by the computer unit as a function of the first and the second pulse width.

7. The method as claimed in claim 1, wherein whether the object is part of a roadway for a motor vehicle or a roadway marking of the roadway is established by means of the computer unit on the basis of the first and the second pulse width.

8. The method as claimed in claim 1, wherein at least one further pulse width of the signal pulse is determined by means of the computer unit, each further pulse width of the at least one further pulse width being established by an associated predetermined further limit value for the amplitude of the sensor signal; and the at least one property of the object is determined by the computer unit as a function of the at least one further pulse width.

9. The method as claimed in claim 1, wherein the second limit value is greater than the first limit value and the first limit value is greater than a predetermined noise level of the detector unit; and/or the second limit value is greater than the first limit value, and the first limit is greater than a predetermined saturation limit value of the detector unit.

10. A method for the at least partially automatic control of a motor vehicle, comprising: determining at least one property of an object in an environment of the motor vehicle by a method for object recognition as claimed in claim 1; and controlling the motor vehicle at least partially automatically as a function of the at least one property of the object.

11. The method as claimed in claim 10, wherein the at least one property of an object is determined by classification of the object carried out by the computer unit as a function of the first and the second pulse width; and the motor vehicle is controlled at least partially automatically as a function of a result of the classification.

12. An active optical sensor system, comprising: a detector unit, which is adapted to register light reflected by an object in an environment of the sensor system and to generate a sensor signal on the basis of the registered light; and a computer unit, which is adapted to determine a first pulse width of a signal pulse of the sensor signal, the first pulse width being established by a predetermined first limit value for an amplitude of the sensor signal; the computer unit is adapted to determine a second pulse width of the signal pulse, the second pulse width being established by a predetermined second limit value for the amplitude of the sensor signal; and the computer unit is adapted to determine at least one property of the object as a function of the first pulse width and the second pulse width .

13. An electronic vehicle guidance system for a motor vehicle, comprising an active optical sensor system as claimed in claim 12; and a control device, which is adapted to generate at least one control signal as a function of the at least one property of the object, in order to control the motor vehicle at least partially automatically.

14.-15. (canceled)

Description

[0071] In the figures:

[0072] FIG. 1 shows a schematic representation of a motor vehicle with an exemplary embodiment of an electronic vehicle guidance system according to the improved concept;

[0073] FIG. 2 shows a schematic representation of sensor signals of a detector unit of an exemplary embodiment of an active optical sensor system according to the improved concept;

[0074] FIG. 3 shows a schematic representation of further sensor signals of a detector unit of a further exemplary embodiment of an active optical sensor system according to the improved concept;

[0075] FIG. 4 shows a schematic representation of further sensor signals of a detector unit of a further exemplary embodiment of an active optical sensor system according to the improved concept;

[0076] FIG. 5 shows a schematic representation of a camera image and a point cloud generated by a further exemplary embodiment of an active optical sensor system according to the improved concept;

[0077] FIG. 6 shows a schematic representation of a camera image and a point cloud generated by a further exemplary embodiment of an active optical sensor system according to the improved concept; and

[0078] FIG. 7 shows a schematic representation of a camera image and a point cloud generated by a further exemplary embodiment of an active optical sensor system according to the improved concept.

[0079] FIG. 1 illustrates a motor vehicle 1 which has an electronic vehicle guidance system 6 according to the improved concept.

[0080] The electronic vehicle guidance system 6 has, in particular, an active optical sensor system 2 according to the improved concept. Optionally, the vehicle guidance system 6 may also have a control device 7.

[0081] The active optical sensor system 2 has an emitter unit 2a, which contains for example an infrared laser. The sensor system 2 furthermore has a detector unit 2b, which contains for example one or more optical detectors, for example APDs.

[0082] The sensor system 2 furthermore has a computer unit 2c. Functions of the computer unit 2c which are described below may also be undertaken in various configurations by the control device 7, or vice versa.

[0083] The emitter unit 2a emits laser pulses 3a into the environment of the motor vehicle 1, where they are partially reflected by an object 4 and at least partially reflected back as reflected pulses 3b in the direction of the sensor system 2, and in particular of the detector unit 2b. The detector unit 2b, in particular the optical detectors of the detector unit 2b, registers the reflected components 3b and, on the basis thereof, generate a time-dependent sensor signal which has an amplitude that is proportional to the radiation intensity or radiation power of the registered light 3b. Corresponding examples of various signal pulses are represented in FIG. 2 to FIG. 4.

[0084] The computer unit 2c determines a first time interval, during which the sensor signal 5a, 5b, 5c, 5d, 5e, 5f exceeds a first limit value G1. This first time interval then corresponds to the first pulse width D1 of the corresponding signal pulse. In the same way, the computer unit 2c determines a second pulse width D2 by corresponding comparison of the sensor signal 5a, 5b, 5c, 5d, 5e, 5f with a second limit value G2, which is greater than the first limit value G1.

[0085] The computer unit 2c or the control device 7 may then determine a property of the object 4, for example a reflectivity or an extent of the object 4, on the basis of the first pulse width D1 and the second pulse width D2.

[0086] In particular, the computer unit 2c or the control device 7 may classify the object 4 as a function of the property, for example the pulse widths D1, D2.

[0087] On the basis of a result of the classification, or on the basis of the property of the object, the control device 7 then for example generates control signals in order to control the motor vehicle 1 at least partially automatically.

[0088] FIG. 2 represents two exemplary sensor signals 5a, 5b, which approximately have the same first pulse width D1. While the sensor signal 5a contains a comparatively steep pulse, the pulse of the sensor signal 5b has a flatter profile. These different pulse shapes are reflected in the different second pulse widths D2. In particular, the second pulse width D2 for the sensor signal 5a is greater than zero, in other words the signal pulse of the sensor signal 5a exceeds the second limit value G2, while this is not the case for the signal pulse of the sensor signal 5b, for which reason the corresponding second pulse width is equal to zero here.

[0089] For example, the sensor signal 5a may correspond to light which has been reflected by an object having a relatively small extent, which is located on a roadway surface. The pulse shape of the sensor signal 5b, on the other hand, is for example typical of a roadway marking on the roadway surface. Correspondingly, small objects may be distinguished from roadway markings because of the different pulse widths D1, D2, which would not be the case when using only the first pulse width D1.

[0090] If APDs are used as optical detectors, for example, a saturation limit value GS may for example be of the order of a few hundreds of mV, for example lying between 100 mV and 1000 mV.

[0091] In the manner described, for example, points on the ground may be distinguished from “genuine” targets.

[0092] FIG. 3 shows two further exemplary sensor signals 5c, 5d, both of which correspond to the case of saturation, that is to say in other words they have signal pulses which reach the saturation limit value GS.

[0093] Accordingly, both the first pulse width D1 and the second pulse width D2 are greater than zero for both signal pulses of the sensor signals 5c, 5d.

[0094] Particularly in cases in which it may be assumed that all signal pulses reach the saturation limit value GS, two limit values G1, G2 and correspondingly two pulse widths D1, D2 are already suitable for reproducing the pulse shape of the sensor signals 5c, 5d sufficiently accurately.

[0095] If the detector unit 2b is operated in such a way that saturation of the pulses is not necessarily ensured, it may be advantageous to insert further limit values between the two limit values G1, G2 and correspondingly to determine further pulse widths, in order to obtain more information relating to the pulse shape.

[0096] FIG. 4 shows a further example of two further sensor signals 5e, 5f. Here again, for example, the sensor signal 5e may correspond to reflections from a roadway marking while the sensor signal 5f may correspond to reflections from a small object on the surface of the roadway.

[0097] Consequently, in this case the two second pulse widths D2 are greater than zero and are approximately equal, or at least similar. However, the first pulse widths D1 differ significantly between the sensor signals 5e, 5f. In this way, conclusions may again be drawn relating to the signal pulse shape, and then also the nature of the object.

[0098] FIG. 5 schematically represents a situation from the view of a motor vehicle 1. A camera image 8 shows a reflector post 4′, which is arranged on a roadway for the motor vehicle 1, as well as a guide post 4″ which is arranged next to the roadway. Corresponding point clouds 9 of the sensor system 2 are furthermore represented. Points of the point cloud are in this case positioned according to their position in the environment of the motor vehicle, and the point cloud 9 in this case indicates all those points which have led to a sensor signal whose maximum amplitude exceeds the first limit value G1.

[0099] FIG. 6 represents the same camera image 8 with a further a further point cloud 9′. The further point cloud 9′ in this case corresponds substantially to the point cloud 9, with the difference that only those points whose corresponding sensor signal exceeds the second limit value G2 are represented. As may readily be seen, the difference in the point clouds 9, 9′ for the guide posts 4″ is relatively small, while there is a significant difference for the reflector posts 4′.

[0100] FIG. 7 represents a further example from the view of the motor vehicle 1. Here, a further camera image 8′ in which V-shaped roadway markings 4m can be seen is shown. The corresponding point cloud 9″ shows the corresponding points. The reflectivity of the roadway markings 4″' is in this case high enough for the corresponding sensor signals to exceed both limit values G1, G2. In this case, however, as explained with reference to FIG. 2 to FIG. 4, the difference between the first pulse width D1 and the second pulse width D2 is more pronounced than would be the case, for example, with other objects on the roadway surface.

[0101] As described, the improved concept provides a possible way of carrying out object recognition by an active optical sensor system with higher reliability and higher accuracy. Correspondingly, functions for automatic or partially automatic vehicle guidance may likewise be carried out with higher accuracy or reliability and safety.