Vehicle Camera Online Calibration Using Vanishing Point Extrapolation
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Solution Overview
Problem
Existing video systems in vehicles face challenges in accurately calibrating camera orientation, especially when only one side of a road or lane marking is visible, which affects the determination of vanishing points and subsequently the camera's pitch and yaw angles, particularly in dynamic driving conditions.
Innovation Solution
A method and system for online calibration that uses time-filtering and recursive filtering to calculate a long-term average vanishing point location from a sequence of images, allowing for the deduction of static yaw and pitch angles of the camera, even when only one side of a road or lane marking is visible, by extrapolating markings and accounting for camera distortion and optical axis location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If both sides of road or lane markings are required to be visible for vanishing point determination, then measurement precision is improved, but adaptability to different driving conditions deteriorates
Solution Approach 1:
The patent divides the vanishing point determination process into two independent phases: first determining the vanishing point direction from single-side markings using orthogonal movement, then refining the location using both sides when available. This segmentation allows the system to adapt to different driving conditions while maintaining precision when possible.
Solution Approach 2:
The patent performs preliminary vanishing point direction determination using only one side of markings before both sides become visible. This preliminary action establishes a baseline that can be refined later, enabling the system to operate effectively in conditions where only single-side markings are initially visible.
2Reliability
If time-filtering methods are used to calculate long-term average vanishing point, then reliability in dynamic conditions is improved, but loss of time increases
Solution Approach 1:
The patent implements periodic updates of the vanishing point location as new markings are detected, rather than requiring complete recalibration. The system continuously refines the vanishing point position by incorporating new measurements periodically, balancing reliability with computational efficiency.
Solution Approach 2:
The patent uses feedback from sequentially detected markings to continuously refine the vanishing point location. Each new marking detection provides feedback that adjusts the current estimate, improving reliability over time without requiring complete recalibration sequences.
3Measurement precision
If recursive filtering is applied to reject outlier measurements, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter being filtered from raw marking coordinates to vanishing point location coordinates. By filtering the derived vanishing point positions rather than individual marking measurements, the system achieves precision improvement with relatively simple filtering logic that tracks the evolving vanishing point location.
Data Source
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AI summary
The present invention relates to video-based driver assistance systems being used in vehicles today to perform a variety of functions, such as lane or road departure warning. These functions often require that parts of the video image be identified as, for example, a traffic sign, a bridge, lane markings, etc. Particularly the present invention relates to a method and system for online calibration of a vehicle video system using vanishing points, evaluated from frames of a camera image contains identified markings or edges on a road. The vanishing points are located by finding or extrapolating at least at one left- and/or right-hand side markings or edges of a road to a point of intersection, whereby a long term average vanishing point location is calculated with time-filtering methods from a sequence of images, even when only one side of a road or lane marking or an edge is visible in any given frame of an image at a time, and from the time-averaged vanishing point location coordinates, the static yaw and pitch angles of the camera are deduced. The present invention relates to also to a method to locate the vanishing points by finding or extrapolating the regularity of repeated road markings, such as dashed patterns and to a method to locate the vanishing point d by using the change in spatial frequency of textures on the surface ahead as an object to determine the camera pitch angle.