The present invention relates to a method for detecting of aquaplaning for a motor vehicle according to the preamble of claim 1, a camera system

according to the preamble of claim 9, and a motor vehicle with a camera system according to the preamble of claim 11.

Wet roads can be a risk for motor vehicles. At high speeds a motor vehicle may lose contact with a wet road which has water thereon. As a result, a wheel loses its capacity to transmit friction to the road surface and thus loses peripheral velocity. This is called hydroplaning or aquaplaning. It is desirable to recognize an aquaplaning condition of a vehicle.

It is an object of the present invention to provide a method for detection of aquaplaning.

This object is achieved by a method for detecting of aquaplaning for a motor vehicle having the features of claim 1, a camera system having the features of claim 9, and a motor vehicle with a camera system having the features of claim 11.

Accordingly, a method for detecting of aquaplaning for a motor vehicle with a time-of-flight camera system comprising transmitting means and receiving means, is provided, wherein the method comprises the following steps: • Illuminating the road in front of the motor vehicle with at least one light beam by transmitting means;

• Receiving at least one light beam reflected by said road by receiving means;

• Determining if there is water on a road on which the motor vehicle is traveling by time-of-flight measurement; and

• Determining, on the basis of the determined information, whether there is a risk of aquaplaning.

Preferably, the method includes; calculating the thickness of a water layer on the road surface. In one advantageous embodiment, the at least one transmitted light beam is modulated infrared light. Preferably, the time-of- flight measurement includes detecting a phase-delay between the transmitted light and the reflected light. In order to determine if water is present it is advantageous, if the time-of-flight measurement includes detecting reflection time differences.

Further it is preferred, if the method includes the following step; Transmitting the determined information and/or the determined risk of aquaplaning to a motor vehicle dynamics control systems. The motor vehicle dynamics control system can this way prepare the driver for the upcoming dangerous situation. It is preferred, that the information is transmitted to the control system of the steering system of the motor vehicle. If a risk of aquaplaning is detected, it is advantageous, if the steering system modifies the steering feel in preparation for the upcoming dangerous situation.

Further a time-of-flight camera system for measurement of water layer thickness on a road surface, is provided, said time-of-flight camera is intended to be carried by a motor vehicle, and that the time-of-flight camera system comprises transmitting means transmitting at least one light beam to a road in front of the motor vehicle as well as receiving means to receive at least one light beam reflected by said road, and means for calculating the thickness of the water layer on the road surface by time-of-flight measurement. Preferably, the at least one transmitted light beam is modulated infrared light.

Furthermore, a motor vehicle with a time-of-flight camera system designed to carry out the above-described method is provided.

A preferred embodiment of the present invention will be described with reference to the drawing.

Figure 1 shows a schematic illustration of a motor vehicle 1 with a time of flight (TOF) camera system 2 arranged in a front section of the motor vehicle 1. The TOF camera system 2 illuminates the road 3 in front of the motor vehicle 1. Preferably, the observed road 3 is illuminated with modulated infrared light. The reflected light features a phase-delay that is, in time-of- flight measurement, detected within the cameras' pixels and directly

translated into a distance value. The water layer height on the road surface is calculated based on phase shift difference between illumination-reflection on water surface and on road surface. The higher the phase shift difference the thicker is the water layer. The light entering the sensor has an ambient component and a reflected component. Distance (depth) information is only embedded in the reflected component. The light source illuminates for a brief period (At), and the reflected energy is sampled at every pixel, in parallel, using two out-of-phase windows, Cl and C2, with the same At. Electrical charges accumulated during these samples, Ql, Q2 and Q3 are measured and used to compute distance using the formula: d_road = l/2*c* At *(Q2/(Q1+Q2)

d_water = l/2*c* At *(Q3/(Q1+Q3).

The calculated water layer height is transmitted to the vehicle dynamics control systems and/or to the steering system of the motor vehicle. Preferably in electromechanical power steering mechanism or steer-by-wire steering systems, the steering feel is modified in preparation for the upcoming dangerous situation, e.g. the steering feel is adjusted to be more direct, but also for the drivetrain system, for e.g. vehicle speed shall not be increased.