Vehicle Camera Extrinsic Calibration via Static Ground Targets
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Solution Overview
Problem
Existing camera calibration methods for vehicles require precise placement, dedicated time, and large surfaces, limiting flexibility and accuracy, especially for extrinsic parameter calibration.
Innovation Solution
A method for extrinsic camera calibration using predetermined patterns on the ground plane, allowing vehicles to drive over markers while cameras capture images, with computation units calculating extrinsic parameters like rotation and mounting height without needing precise vehicle placement or intrinsic parameters, and allowing calibration in various settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional camera calibration methods are used, then accurate extrinsic parameter calibration can be achieved, but precise vehicle placement and large surface areas are required, reducing flexibility
Solution Approach 1:
The calibration method segments the calibration process into two independent parts: intrinsic parameter calibration (using known patterns) and extrinsic parameter calibration (using static ground targets). This segmentation allows extrinsic calibration to be performed independently without requiring precise vehicle placement, as the method uses the known positions of static ground targets to calculate camera extrinsic parameters through coordinate transformation equations.
Solution Approach 2:
The patent introduces a coordinate transformation intermediary that maps between the vehicle coordinate system and the ground target coordinate system. By using this intermediary transformation relationship and the known positions of static ground targets, the method enables accurate extrinsic parameter calibration without requiring the vehicle to be precisely positioned or requiring large calibration surfaces.
2Measurement precision
If traditional calibration methods are used, then accurate calibration can be achieved, but dedicated calibration time is required, reducing productivity
Solution Approach 1:
The patent applies preliminary action by pre-establishing the coordinate system of static ground targets and pre-calculating their positions before vehicle operation. The extrinsic parameter calibration can then be performed quickly by simply capturing images of these pre-positioned targets and applying the pre-established transformation equations, eliminating the need for time-consuming traditional calibration procedures.
3Measurement precision
If intrinsic parameters are calculated during calibration, then complete camera calibration is achieved, but additional computation time and complexity are required
Solution Approach 1:
The patent extracts and separates the extrinsic parameter calibration from the intrinsic parameter calibration process. By taking out the extrinsic calibration as an independent process that uses only static ground target images and pre-known intrinsic parameters, the method simplifies the overall calibration process while maintaining complete calibration accuracy. This extraction eliminates the need for complex simultaneous optimization of both intrinsic and extrinsic parameters.
Data Source
AI summary
A method for deriving extrinsic camera parameters of a vehicle camera. Calibration markers are provided on a flat ground surface and the vehicle is driven past the calibration markers. Marker boundaries are detected and matched to stored pre-determined shape parameters and a marker shape is identified. At least one extrinsic parameter of the camera is derived using the tracked positions of identified marker shape in the video sequence captured while vehicle is moving, wherein the extrinsic parameter is selected from mounting positions and a rotation is selected from both horizontal axis and vertical axis of a vehicle coordinate system.