DE102010025704A1 - Method for informing rider of vehicle e.g. motor car, about dangerous condition e.g. presence of snow on road surface, involves outputting feedback to rider of vehicle over steering wheel, when condition of road surface is dangerous - Google Patents

Abstract

The method involves emitting light with preset wavelength on a road surface (1a) under a vehicle (60). The light reflected from the road surface is detected. A determination is made that whether dangerous condition of the road surface is present based on the detected reflected light by determining water, snow and/or ice on the road surface. A feedback is output to a rider (66) of the vehicle over a steering wheel (65), when the condition of the road surface is dangerous, where the feedback comprises vibration at or in the steering wheel. An independent claim is also included for a device for informing a rider of a vehicle about a dangerous condition of a road surface.

Description

The present invention relates to warning systems, and more particularly to a method and apparatus for issuing a warning to a driver of a vehicle in dangerous lane conditions.

To warn against road slipperiness or other dangerous road conditions modern motor vehicles usually have standard outdoor temperature sensors with a corresponding display to give the driver or vehicle occupants a visual or audible warning when the outside temperature, for example, under z. B. + 3 ° C drops. This is intended primarily to warn the driver of the occurrence of possible glacial or winter road conditions. However, such warnings are only of a general nature and are independent of the actual road condition, so that they are perceived by the driver and / or a vehicle occupant, if any, only as edge information. In practice, such temperature indications are often ignored.

From the DE 10 2005 018 471 A1 It is known to reduce a steering wheel torque in response to an unstable driving condition. The unstable driving state can be recognized, inter alia, based on the evaluation of the yaw rates. It is also possible to additionally use the lateral acceleration for detecting the unstable driving state. The influencing of the steering wheel torque, however, takes place only when an unstable driving condition already exists.

The DE 10 2007 050 188 A1 also describes the influence of a steering torque to stabilize a vehicle. To determine the steering torque can also be discussed on different coefficients of friction between the road.

However, the devices and methods mentioned in the prior art have the disadvantage that a warning of the driver only takes place when a critical driving situation has already been reached.

The present invention has for its object to overcome these disadvantages.

The object is achieved by a method according to claim 1 and by a device according to claim 7 for informing a driver of a vehicle about a dangerous condition of a road surface. The invention also relates to a vehicle which is equipped with such a device or which carries out the method according to the invention.

The method comprises the steps of emitting light of at least one wavelength onto the road surface 1a under the vehicle, detecting light of the at least one wavelength reflected from a road surface, determining whether there is a dangerous condition of the road surface using the detected reflected light, and outputting a feedback to the driver via a steering wheel when considering the condition of the road surface as was determined dangerously.

The device comprises an optical surface sensor for detecting at least one condition of the road surface and an output device which outputs a feedback to the driver via a steering wheel if the condition of the road surface was determined to be dangerous.

With the optical surface sensor, the nature of the road surface can be detected without contact and the driver can be provided with appropriate information about the steering wheel. The use of the optical surface sensor makes it possible to give the warning of a dangerous road condition as soon as the vehicle is on the dangerous road surface. The information can thus be output to the driver before an unstable driving situation arises, as detected by yaw rate sensors and / or lateral acceleration sensors. An unstable and dangerous driving situation can thus be avoided. The nature of the road surface can be determined to be dangerous if the road surface was determined, for example, as snow-covered, icy and / or wet, that is, the road condition indicates a reduced coefficient of friction. However, the road surface may also include the type of roadway such as concrete, asphalt or roadway dirtiness, or the road surface roughness.

The feedback to the driver can be conveyed, for example, by a vibration of the steering wheel, on or in the steering wheel.

It can also be provided to transmit the feedback by a change in the steering forces or the steering torque on the steering wheel to the driver. For this purpose, for example, be provided on a slippery surface with low coefficient of friction, as on an icy or snow-covered road, provide the steering force or the steering torque noticeably lower. For example, the already occurring effect of a reduction of the steering forces on a road surface with a low coefficient of friction can be additionally reinforced to the driver intuitively convey the feeling of a slippery road surface.

However, it may also be provided to increase the steering forces to z. B. to reduce the risk of oversteer.

The use of an optical surface sensor has the advantage that the actual road surface condition can be measured in a particularly reliable and non-contact manner. Furthermore, the optical surface sensor provides information about the road condition even in a stationary vehicle.

The optical surface sensor may include a light source unit for emitting light of at least one wavelength to the ground and at least one detector for detecting light reflected from the ground.

The surface sensor may comprise a second detector in addition to the first detector, wherein the first detector for detecting diffusely reflected light and the second detector for detecting specularly reflected light are suitable. At least two polarizers can be provided, wherein a first polarizer having a first polarization device is assigned to the first detector. The light source unit may be a Lichtquellenpolarisator and / or the second detector may be associated with a second polarizer whose polarization direction (s) is oriented substantially perpendicular to the first polarization direction of the first polarizer / are. If at least two polarizers or polarization filters are provided, the first polarizer is arranged on the first detector, which transmits only light waves in the first polarization direction to the first detector. If a light source polarizer is provided on the light source unit, its polarization direction is arranged substantially perpendicular to the first polarization direction of the first polarizer, and the light emitted by the sensor is polarized in a direction substantially perpendicular to the first polarization direction, so that polarized at the first detector , Reflected reflected light filtered out and only diffuse reflected light is detected. A similar effect can be achieved if a second polarizer is arranged in front of the second detector whose polarization direction is oriented substantially perpendicular to the first polarization direction. The second polarizer may be used alternatively or in addition to the light source polarizer. It can also be provided to generate already polarized light in the light source unit

The light source unit can be designed to emit light of at least two mutually different wavelengths or to emit a plurality of wavelengths onto the ground or the road surface. For this purpose, the light source unit may for example comprise a plurality of light sources. The use of at least two, preferably three, of different wavelengths makes it possible to operate the sensor in a spectral manner. By the use of wavelengths which z. B. of ice or water are particularly well absorbed, ice or water can be detected on the road surface or road surface, when the reflected light of the absorbed water or ice wavelength is compared with that of a reference wavelength. It is thus possible to implement the principles of spectral analysis and diffuse and specular reflection in a single device or housing. The at least one light source unit, the first detector and possibly the second detector can be arranged for this purpose in a common single and / or one-piece housing, for example directly next to one another.

It is possible to use light in at least three mutually different wavelengths in the infrared range. The light source unit may for this purpose comprise a plurality of light sources. For example, the light source unit may be configured to emit infrared light of the wavelengths 1300 nm, 1460 nm and 1550 nm. While light of wavelength 1460 nm is particularly well absorbed by water, light of wavelength 1550 nm is well absorbed by ice. Light in the range of about 1300 nm can then be used as the reference wavelength. However, other wavelengths may be used. In particular, for the reference wavelength, any other wavelength can be used which is not significantly absorbed by neither ice nor water. As a water-sensitive wavelength, any other wavelength can be used, which is absorbed in water increased. In the same way, each wave length can be chosen as the pseudo-wavelength, which is absorbed in ice. Other interesting wavelengths include z. B. 1190, 1040, 970, 880 and 810 nm in the infrared range, and the visible wavelengths 625, 530 and 470 nm.

The light source unit may be configured to emit light of exactly three different wavelengths. For this purpose, the light source unit can have three light sources, one light source for each wavelength. Only the three wavelengths are used to detect both spectral and specular / diffuse reflected light to detect both the road condition and the type of roadway. Each of the light sources can be controlled individually and switched on and off independently of the other or be adjustable in intensity.

In addition, more than the above two or three different wavelengths may be used. For example, the wavelength 625 nm can also be used to measure the diffused and specularly reflected light.

It may further be provided to modulate the emitted light in intensity or amplitude. The modulation of the intensity or amplitude can be done by turning on and off all or individual light sources of the light source unit. The modulation of the intensity or the switching on and off can be carried out separately for each wavelength of the light source unit or for each light source of the light source unit. For example, the modulation of the amplitude or intensity or the switching on and off for each wavelength with the same frequency, but out of phase and / or with different frequencies. As a result, it can be achieved, for example, that the light of different wavelengths is transmitted offset in time or sequentially. For example, it may be provided to emit light of a first wavelength for a certain time interval, then to turn off the light of the first wavelength and to turn on a second wavelength, etc. In the detectors, light of only one wavelength is then detected. As a result, a spectral analysis or splitting of the incident light at the detectors can be avoided. Mixed forms of different modulation techniques are also applicable, in particular frequency and amplitude modulated optical signal trains with or without interruptions.

The present invention therefore also makes it possible to use simple detectors as the first or second detector. For example, photodiodes can be used. The first detector and the second detector may each comprise one or more photodiodes. At least the first detector may be configured to detect light of all wavelengths emitted by the light source unit. The detector may also alternatively or additionally comprise an opto-electronic chip (eg CCD) or another optical recording device.

The first and second detectors can be used to detect or detect specularly reflected and diffusely reflected light. In addition, at least one of the first and the second detector can also be used for the spectral determination. At least this detector is then designed to detect light of several wavelengths. In this example, the sensor has exactly the first detector and the second detector and no further detectors are provided.

The surface sensor may further comprise an evaluation device which outputs information about the nature of the road surface or the ground.

The surface sensor is also suitable to detect the thickness of a water film on the road surface or the thickness of an ice layer, so that, for example, in a wet roadway above a certain water film thickness, from which, for example, aquaplaning can arise, the information transmitted to the driver becomes.

Also, prior to the delivery of information to the driver, further information can be incorporated. For example, the warning or information can be given to the driver only when the vehicle is moving at a certain speed. Thus, for example, be provided to give the warning in the wet lane only when the water film thickness is greater than, for example, 5 mm or greater than 1 cm and at the same time the driving speed greater than, for example, 60 km / h or 80 km / h, for example. This can ensure that the warning or the information is given to the driver only in such situations, when aquaplaning can actually occur.

In the following, further details and examples of the invention are given by way of example only and not by way of limitation with reference to the attached figures, which show:

1 a vehicle with a device according to the invention;

2 a first example of a device according to the present description;

3 a second example of a device according to the present description; and

4 schematically a method according to the invention.

1 shows an example of a device 9 for the information of a driver 66 of a vehicle 60 about a dangerous condition of a road surface 1a , The vehicle 60 can be any type of motor vehicle, such as a passenger car, a commercial vehicle such as a truck, a bus but also any other vehicle.

As usual with motor vehicles, the driver controls 66 the vehicle 60 over a steering wheel 65 , To facilitate steering, the vehicle is 60 equipped with steering assistance. For this purpose, electrical modifiable power steering systems are common, the description can However, also be applied to other example, mechanical or hydraulic or pneumatic power steering or other controllable steering power assistance. The system is designed by means of a controller 7 to change the steering power. For example, it can be provided that by a manual operation of the controller 7 the steering forces, for example, to park the vehicle 60 can be significantly reduced. Such systems are known to the person skilled in the art.

The vehicle shown 60 is with an optical surface sensor 2 or a sensor 2 equipped, which is at the bottom of the vehicle 60 is arranged so that a transmitted light beam 11 essentially perpendicular to the road surface 1a the roadway 1 is directed.

The sensor 2 Can in the front of the vehicle, especially in the direction of travel 6 in front of the front wheels 63 of the vehicle 60 be arranged, whereby an early warning or information regarding the road surface can be achieved.

The surface sensor 2 , also as a sensor 2 for detecting the condition, in particular a condition and the type of surface of a roadway 1 or road surface 1a is designed to be attached to a motor vehicle 60 to be attached.

The sensor 2 includes in a housing 4 three devices, a light emitting device 10 , a first detector device 20 and a second detector device 30 , The light emitting device 10 has a light-emitting window or a light-emitting aperture 18 in the case 4 on, the first detector device 20 has a first detector window or a first detector opening 28 in the case 4 on and the second Detektoreinrichutung 30 has a second detector window or a second detector opening 38 in the case 4 on. The light emitter opening 18 , the first detector opening 28 and the second detector opening 38 are on the same page 4a of the housing 4 arranged and to the roadway 1 aligned when the sensor 2 ready for use mounted on a vehicle. The sensor 2 is aligned so that the emitted light beam 11 approximately perpendicular to the roadway 1 or road surface 1a falls, ie the optical axis of the light emitter section 10a , or the light emitter axis 11a is substantially perpendicular to the roadway 1 or road surface 1a ,

In the in the 2 and 3 Examples shown are the light emitting device 10 , the first detector device 20 and the second detector device 30 arranged in a row and the light emitting device 10 is between the first detector device 20 and the second detector device 30 arranged.

The light emitter device 10 , the first detector device 20 and the second detector device 30 However, they can also be arranged separately from each other and need not be combined in a housing.

In the light emitting device 10 is a light source unit 12 arranged, which is designed to emit light of several different wavelengths. The light source unit 12 For example, it may comprise one or more light-emitting diodes (LEDs), laser diodes, another suitable light source or a combination thereof, and is capable of emitting light of several mutually different wavelengths. For example, the light source unit 12 Emit light at least with the wavelengths 1300 nm, 1460 nm and 1550 nm. The intended wavelengths, however, can be adapted to the respective application.

The light source unit 12 is in the 2 illustrated example in the direction of the emitted light beam 11 a light source polarizer or light source polarizer 14 downstream of that of the light source unit 12 emitted light is polarized in a predetermined direction.

Furthermore, an emitter optic 16 provided to the emitted light along an emitted light beam 11 to a specific area on the ground or the road surface 1 or the road surface 1a under the vehicle 60 align or focus. The optical axis of the emitter optics 16 can the optical axis 10a of the light emitter section 10 define. The emitter optics 16 may consist of an emitter lens or comprise a plurality of lenses and / or other optical element.

The first detector section 20 includes a first detector 22 For example, one or more photodiodes, designed to light all of the light source unit 10 to detect emitted wavelengths. The first detector 22 may also include a plurality of juxtaposed photodiodes or one or more opto-electronic devices (eg, CCD, CMOS).

At the first detector 22 is a first collectible look 26 and a first polarizer or first polarizing filter 24 arranged. The first collection optics 26 may consist of a single first converging lens or comprise a plurality of lenses and / or further optical elements. The polarization direction of the first polarization filter 24 is perpendicular to that of the light source polarizing filter 14 and thus substantially perpendicular to the predetermined polarization direction. Reflecting reflected light polarized in the predetermined direction is thus filtered out and only diffusely reflected light reaches the first detector 22 , The first detector 22 thus serves as a "scatter detector".

A first axis 20a may be substantially the optical axis of the first collection optics 26 and / or the first detector section 20 correspond and substantially parallel to the emitter axis 10a which essentially corresponds to the optical axis of the emitter optic 16 and / or the light emitter section 10 corresponds, be aligned.

In the second detector section 30 which is on the first detector section 20 opposite side of the light emitter section 10 in the case 4 of the sensor 2 is arranged, is a second detector 32 arranged.

The second detector 32 may also include a photodiode configured to at least light one of the light source unit 12 to detect emitted wavelengths. The second detector 32 however, it may also include a plurality of juxtaposed photodiodes and be configured to detect light of several different wavelengths or wavelength ranges.

The second detector 32 is a second collectible look 36 assigned to the reflected light on the second detector 32 to focus and to detect in this. The second collection optics 36 may consist of a single second converging lens or comprise a plurality of lenses and / or further optical elements. Unlike the first detector 22 , the second detector points 32 im in the 1 example illustrated no polarizer or polarization filter. Since already the emitted light is polarized, this is not necessary. The second detector thus detects diffusely reflected and specularly reflected light which propagates along the second detector beam path 31 is reflected. However, the second detector can also be used 32 a polarizing filter (not shown) whose polarization direction is parallel to that of the emitter polarizer 16 is to only specularly reflected light in the second photodiode 36 to detect.

A second axis 30a may be substantially the optical axis of the second collection optics 36 and or the second detector section 30 correspond and substantially parallel to the emitter axis 10a which essentially corresponds to the optical axis of the emitter optic 16 and / or the light emitter section 10 corresponds, be aligned.

The described sensor can be operated in the visible light range, for example at a wavelength of approximately 625 nm, to measure specularly reflected light and diffusely reflected light. From the ratio of that in the first detector 22 measured diffusely reflected light to that in the second detector 32 additionally measured specularly reflected light can be concluded on the road surface brightness and road surface roughness and thus determine whether the vehicle is located, for example, on an asphalt or concrete pavement.

The described sensor can also be used in the infrared range at different wavelengths. For this purpose, the first detector 22 and / or the second detector 32 be used. For example, infrared light of wavelength 1460 nm is particularly well absorbed by water, so that light of this wavelength in wet conditions only to a small extent to the first detector 22 or the second detector 32 is reflected back. On dry roads, this wavelength is normally reflected. Infrared light of wavelength 1550 nm, on the other hand, is well absorbed by ice. By comparing the reflection of these two wavelengths and considering a reference wavelength can be concluded on ice or water on the road. The reference wavelength, which is not significantly absorbed by neither ice nor water, z. B. 1300 nm, serves as a reference for assessing the absorption of the other two wavelengths. Then, the measured intensity ratios at the wavelengths 1550 nm / 1300 nm with the ratio 1460 nm / 1300 nm can be related in a known manner in order to obtain information on water and ice on the road or a dry road.

The different wavelengths can be transmitted in parallel, but in particular sequentially offset in time. Thus, only light of one wavelength at a time is emitted and detected accordingly. This makes it possible to dispense with a complex spectral analysis or beam splitting.

The sensor 2 also has an evaluation device 50 with which of the first detector 22 and the second detector 32 recorded or determined data are processed. The evaluation device 50 can outside the case 4 be located and, for example, in a different location in the vehicle 60 are located. The evaluation device 50 can with the first detector 22 and the second detector 32 be connected via a cable or a wireless connection. The evaluation device can also be a controller for the light source unit 21 include or connected to a controller. The evaluation unit 50 however, and / or the controller may also be on or in the housing 4 be arranged or integrated in, as with respect to the 2 shown.

With the described sensor 2 Both spectral reflection and specular and diffuse reflection can be measured in a short time sequence with a compact and cost-effective design. On this basis, the roadway type and condition can be concluded. This results in a better and more accurate information about the type and the actual condition of the road 1 or road surface 1a under the vehicle 60 , For the measurement is only the one sensor 2 required.

If only spectral reflection is to be measured, since, for example, the measurement accuracy is sufficient for this, the second detector section can optionally be used 30 be omitted.

The evaluation device 50 can with the controller 7 be connected and to this the determined condition or the determined nature of the road surface 1a output. For example, became a snowy or icy road 1 through the evaluation device 50 determined and this information to the controller 7 passed on, the controller can 7 reduce the steering torque or the steering force by a predetermined value by preferably the steering torque assistance of a power steering is changed accordingly, so that the driver is given the feeling of an unsafe road. The driver feels a lower steering torque and thus interprets unsafe road conditions. Optionally, this information can be combined with a corresponding warning light and / or a warning tone.

The 3 shows another example of a device 9 , The referring to the 3 illustrated and described features, depending on the application with respect to the 2 illustrated and described features are combined or replaced.

The Indian 3 illustrated sensor 2 corresponds to that with respect to the 2 described sensor with the difference that no Lichtquellenpolarisator is provided. The emitted light beam 110 is not polarized in this case. In order to be able to filter out specularly reflected light, there is a second polarizing filter 34 in the beam path in front of the second detector 32 arranged. The polarization direction of the second polarization filter 34 is substantially perpendicular to the polarization direction of the first polarizing filter 24 , All other elements of the sensor 2 can those of with respect to the 1 represented sensor correspond.

I'm in the 3 example shown is the first axis 20b , which is the optical axis of the first collection optics 26 and / or the entire first detector section 20 can correspond, at an angle ☐ to the emitter axis 10a aligned, wherein the angle ☐ is a maximum of about 10 °. Accordingly, the second axis 30b , which is the optical axis of the second collection optics 36 and / or the entire second detector section 30 can correspond, at an angle ☐ to the emitter axis 10a be aligned, wherein the angle ☐ is also a maximum of about 10 °. The point of intersection 40 the emitter axis 10a with the first axis 20b and / or the second axis 30b can on the road surface 1a lie or at a distance of up to 50 cm from the road surface 1a lie.

There is also the possibility of having both a light source polarizer or light source polarizing filter 14 at the light source unit 12 to provide, as with respect to the 1 described as well as a second polarizer or second polarizing filter 34 at the second detector 32 , Typically, then are the polarization directions of the light source polarizing filter 14 and the second polarizing filter 34 aligned parallel to each other. The polarization directions of the light source polarizing filter 14 and the second polarizing filter 34 of the second detector 32 however, are substantially perpendicular to the polarization direction of the first polarizer or first polarizing filter 24 arranged.

In the 3 is also the evaluation device 50 inside the case 4 of the sensor 2 arranged or in the housing 2 shown integrated. It is understood that the evaluation unit also, as in 1 shown outside the sensor 2 can be provided.

The sensor 2 and in particular the emitter optics 16 and the first collection optics 26 or possibly also the second collection optics 36 may be designed to be at a certain height or height above the road surface 1a to be arranged. For example, the sensor 2 102 may be configured at a height h or a distance of about 10 cm to about 1 m from the road surface 1a to be arranged, wherein the distance can be adapted to a particular application. For the use of the sensor 2 in a passenger car, the height h may be in the range of about 10 cm to 40 cm. When using the sensor 2 in a commercial vehicle, omibus or off-road vehicle, the height h may be about 30 cm to about 100 cm, especially in a range of 50 cm to 80 cm.

In addition to the housing 4 of the sensor 2 arranged evaluation device 50 can also control 7 inside the case 4 of the sensor 2 be arranged. The control 7 can with the evaluation device 50 be connected or integrated into this. Thereby, the control signal for the steering torque adjustment directly from the sensor 2 be delivered.

The 4 shows by way of example a method for informing a driver 66 of a vehicle 60 about a dangerous condition of a road surface 1a , The method includes the step 100 acquiring information about the nature of a road surface 1a , Capturing the information 100 includes the emission of light 110 of at least one wavelength, preferably of at least three mutually different wavelengths in the infrared range and the detection 120 from on the road surface 1a reflected light. As described above, the light of the different wavelengths can be offset in time, for example, with different frequency modulated or out-of-phase modulated with the same frequency transmitted and detected accordingly. As a result, the light of all emitted wavelengths and the possibly existing background radiation can be detected with only one detector.

From the ratio of the light intensities of the reflected light of the different wavelengths or the ratio of diffusely reflected and specularly reflected light is in step 150 an information about the condition of the road surface 1a determined, that is, whether the road 1a dry, wet, icy, snowy or has a different texture. Also, in this step, the thickness of a water film or the thickness of a layer of ice on the road surface 1a be determined.

Became an ice-covered or snow-covered road surface 1a recognized, it may optionally be determined by adding further parameters, whether the steering force or the steering torque of the steering 65 should be changed, that is, whether the dangerous situation exists and this information to the driver about the steering torque to be communicated. This decision is made in step 300 ,

Was in step 200 determines the driver about the dangerous nature of the road surface 1a inform in the output step 300 a control signal to the steering 65 issued to change the steering torque or the steering force, especially noticeable to the driver 66 to reduce.

Of course, the other way around, when the steering force or the steering torque is reduced and a dry or wet road surface 1a determined with low risk, the steering force or the steering torque was again increased accordingly.

The foregoing description has been given with regard to the examples shown in the figures. However, one skilled in the art will readily modify or combine the examples given. The person skilled in the art will also find further possible uses of the device according to the invention and of the method according to the invention, for example the attachment to other points of a vehicle.

The person skilled in the art will also consider other than the specified wavelengths in order to adapt the measurement results to different requirements. It is understood that the indicated wavelengths are not limited to the exact values, but may include a wavelength range containing the indicated discrete wavelengths.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005018471 A1 [0003]
• DE 102007050188 A1 [0004]

Claims (16)

Method for informing a driver ( 66 ) of a vehicle ( 60 ) on a dangerous condition of a road surface ( 1a ), the method comprising: emitting light of at least one wavelength onto the road surface ( 1a ) under the vehicle ( 60 ); Detecting on the road surface ( 1a ) reflected light of the at least one wavelength; - Determine ( 200 ) on the basis of the detected reflected light, whether a dangerous condition of the road surface ( 1a ) is present; and - issuing a response ( 300 ) via a steering wheel ( 65 ) to the driver ( 66 ), if the condition of the road surface ( 1a ) was determined to be dangerous. The method of claim 1, wherein said determining ( 200 ), whether the condition of the road surface ( 1a ) is dangerous, a determination of water, snow and / or ice on the road surface ( 1a ). The method of claim 1 or 2, wherein issuing the feedback ( 300 ) comprises a vibration on or in the steering wheel. Method according to one of the preceding claims, wherein the outputting of the feedback ( 300 ) comprises the change of steering forces of the steering wheel. Method according to one of the preceding claims, wherein the emission of light and the detection of on the road surface ( 1a ) reflected light comprises light of three different wavelengths in the infrared range. Method according to one of the preceding claims, wherein detecting on the road surface ( 1a ) reflected light, detecting diffuse reflected and specularly reflected light. Contraption ( 9 ) for the information of a driver ( 66 ) of a vehicle ( 60 ) on a dangerous condition of a road surface ( 1a ), the device ( 9 ) comprises: an optical surface sensor ( 2 ) for determining at least one condition of the road surface ( 1a ), and an output device ( 80 ), which feedback to the driver via a steering wheel ( 66 ) if the condition of the road surface ( 1a ) was determined to be dangerous. Contraption ( 9 ) according to claim 7, wherein the nature of the road surface ( 1a ) includes wet, icy, snowy and / or dry conditions. Contraption ( 9 ) according to claim 7 or 8, wherein the output device ( 80 ) emits a vibration signal to the steering wheel. Contraption ( 9 ) according to one of claims 7 to 9, wherein the output device ( 80 ) can influence the steering force of the steering. Contraption ( 9 ) according to one of claims 7 to 10, wherein the optical surface sensor ( 2 ) comprises: - a light source unit ( 12 ) for emitting light of at least one wavelength to the ground ( 1 ) and - at least a first detector ( 20 . 30 ) from the road surface ( 1a ) to detect reflected light Contraption ( 9 ) according to claim 11, wherein the light source unit ( 12 ) and the at least one detector ( 20 . 30 ) in a housing ( 4 ) are arranged. Apparatus according to claim 11 or 12, further comprising at least a second detector ( 30 ) for detecting specularly reflected light. Contraption ( 9 ) according to one of claims 11 to 13, wherein the light source unit ( 12 ) comprises three light sources for emitting light of three different wavelengths. Contraption ( 9 ) according to one of claims 7 to 14, which for attachment to a vehicle ( 60 ) is suitable with steering assistance. Vehicle ( 60 ) with a device ( 9 ) according to one of claims 7 to 15.

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