Rearview Camera Wet Road Detection via Spray Trail Analysis
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Solution Overview
Problem
Existing driver assistance systems, such as rain sensors and laser scanners, are inadequate for detecting wet road surfaces accurately and reliably, especially when it is not raining, which limits their ability to control vehicle components effectively for safety and efficiency.
Innovation Solution
A method utilizing a rearview camera to detect spray trails caused by the vehicle, which generates a wetness signal for automatic responses, such as activating windshield wipers, headlights, or adjusting vehicle dynamics systems, without the need for additional hardware like laser scanners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rain sensor is used to detect moisture on the windshield, then automatic windshield wiper control is achieved, but the system cannot reliably detect wet road surfaces when it is not raining
Solution Approach 1:
The patent uses spray trails kicked up by the vehicle's own wheels as an intermediary indicator to infer road wetness conditions. Instead of directly measuring road moisture, the system detects the spray pattern generated when wheels contact a wet surface, which serves as a reliable indirect indicator of road conditions even when not raining.
Solution Approach 2:
Instead of detecting rain or moisture directly (as traditional sensors do), the system inverts the approach by detecting the effect of wheel rotation on the environment - specifically the spray trail generated when wheels contact wet road surfaces. This allows detection of road wetness independent of atmospheric conditions.
2Reliability
If a laser scanner is used to detect spray trails and determine visual range, then reliable road wetness information is obtained, but the system becomes complex and expensive
Solution Approach 1:
The patent makes the rearview camera multi-functional by using it not only for its primary purpose of providing rear visibility but also for detecting spray trails to determine road wetness conditions. This eliminates the need for separate dedicated sensors and reduces overall system complexity while maintaining detection reliability.
Solution Approach 2:
Instead of using complex laser scanning technology to detect spray patterns, the system uses a simple camera to capture optical images of the spray trails. The camera creates a visual copy of the spray pattern that can be analyzed by image processing algorithms, providing a simpler and more cost-effective solution than laser-based detection.
3Measurement precision
If additional hardware like laser scanners is added to detect spray trails, then detection accuracy improves, but system cost increases
Solution Approach 1:
The patent replaces expensive, complex laser scanning hardware with inexpensive camera technology that is already commonly available in modern vehicles. The camera provides sufficient measurement precision for spray trail detection at a fraction of the cost of laser scanners, making the system economically viable for mass production.
Solution Approach 2:
The patent substitutes mechanical/optical laser scanning systems with an electronic imaging system using a camera. This replacement maintains the ability to detect and measure spray trails while dramatically reducing system complexity and manufacturing cost, as cameras are standard components in modern vehicles.
Data Source
AI summary
Methods in a driver assistance system of a vehicle for detecting wetness on a road surface as well as a corresponding driver assistance system having a rearview camera are described. The method may include the following: recording an image of an area located behind the rear end of the vehicle, using the rearview camera; evaluating the recorded image for the presence of a spray trail caused by the vehicle; and selectively outputting, based on the evaluation, a wetness signal for triggering an automatic response by the driver assistance system to the wet road surface.