Lane-departure warning system with differentiation between an edge-of-lane marking and a structural boundary of the edge of the lane

1. A driver assistance device for warning a driver of a motor vehicle of a risk of departure from the road or from the lane in which he is driving, said device comprising:

at least one image-transmitting sensor,

a distance-transmitting sensor,

an evaluation device, connected to the image-transmitting sensor and the distance—transmitting sensor, for detecting a structure condition of a road edge and/or a lane edge, comprising:

means for creating a distance profile from measured values of the distance-transmitting sensor to detect discontinuity in the distance profile, and

means for detecting a structural boundary at the region of the edge of lane on the basis of a detected discontinuity in the distance profile to differentiate between the structural boundary and edge-of-lane markings, indicative of a structure condition of the road edge and/or lane edge;

a warning device which is connected to the evaluation device, wherein the warning device varies time points of warning output, indicating a risk of departure from the road or from the lane which the vehicle is in, depending on the structure condition of the road edge and/or the lane edge.

2. The driver assistance device according to claim 1 , further comprising a height-estimating sensor connected to the evaluation device.

3. The driver assistance device according to claim 2 , further comprising:

means for creating a height profile from measured values of the height-estimating sensor, and

means for detecting a structural boundary on the basis of a discontinuity in the height profile.

4. The driver assistance device according to claim 2 , wherein the distance-transmitting sensor and/or the height-estimating sensor are arranged predominantly in a direction transverse to a longitudinal axis of the vehicle.

5. The driver assistance device according to claim 2 , wherein the distance-transmitting sensor and/or the height-estimating sensor are part of another driver assistance device.

6. The driver assistance device according to claim 1 , further comprising a sensor for detecting different reflection behaviour of objects, which, on the basis of the different reflection behaviour of the objects, permits differentiation between the objects, the sensor for detecting different reflection behaviour being connected to the evaluation device.

7. A driver assistance device for warning a driver of a motor vehicle of a risk or departure from the road or from the lane in which he is driving, said device comprising:

at least one image-transmitting sensor,

a height-estimating sensor,

an evaluation device, connected to the image-transmitting sensor and the height-estimating sensor, for detecting a structure condition of a road edge and/or a lane edge, comprising:

means for creating a height profile from measured values of the height-estimating sensor to detect a discontinuity in the height profile, and

means for detecting a structural boundary at the region of the edge of lane on the basis of a detected discontinuity in the height profile to differentiate between the structural boundary and edge-of-lane markings, indicative of a structure condition of the road edge and/or lane edge;

a warning device which is connected to the evaluation device, wherein the warning device varies time points of warning output, indicating a risk of departure from the road or from the lane which the vehicle is in, depending on the structure condition of the road edge and/or the lane edge.

8. A method for operating a driver assistance device for warning a driver of a motor vehicle of a risk of departure from the road or from the lane in which he is driving, the driver assistance device detecting a structure condition of a road edge and/or a lane edge, the method comprising:

creating a distance and/or height profile from measured values of a distant-transmitting and/or height-estimating sensor for detecting the structure condition of the road edge and/or the lane edge, and

detecting a structural boundary at the region of the edge of road/lane on the basis of a discontinuity in such a profile to differentiate between the structural boundary and edge-of-lane markings, indicative of the structure condition of the road edae and/or lane edge,

varying time points of warning output by a warning device depending on the detected structure condition of the road edge and/or the lane edge, wherein

when there is a road/lane marking, warning the driver of the motor vehicle of a risk of departure from the road or from the lane only when the vehicle enters into contact with or passes beyond the marking, and

when there is a structural boundary, warning in advance the driver of the motor vehicle of a risk of departure from the road or from the lane before the vehicle enters into contact with the structural boundary.