Fisheye Camera Parameter Estimation via Projection Linearity
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Solution Overview
Problem
Existing methods for estimating the internal parameter of a fisheye-lens camera require photographing a special calibration pattern and prior knowledge of the projection scheme, making the estimation complex and dependent on known three-dimensional points and lens distortion parameters.
Innovation Solution
A camera parameter estimation device and method that generates multiple projection images using different schemes based on the radius of the visual field region of a fisheye-lens camera, selects the most linear projection image to determine the appropriate projection scheme, and outputs the corresponding internal parameter without needing a special calibration pattern or prior knowledge of the projection scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a special calibration pattern with known three-dimensional points is used for internal parameter estimation, then the estimation accuracy can be improved, but the complexity of the estimation process increases and prerequisite knowledge of the projection scheme is required
Solution Approach 1:
The patent extracts only the essential information needed for estimation - specifically, straight lines in the scene - rather than requiring complete calibration patterns with known 3D points. By focusing on line features that can be detected in natural scenes, the method eliminates the need for complex calibration artifacts while maintaining estimation capability
Solution Approach 2:
The method enables the camera system to perform self-calibration using ordinary images of scenes containing straight lines, without requiring external calibration equipment or patterns. The system uses its own imaging data to determine internal parameters, making the process autonomous and eliminating the need for specialized calibration procedures
2Ease of manufacture
If prior knowledge of the projection scheme is required for internal parameter estimation, then the estimation can be performed with available methods, but the versatility and ease of operation are reduced
Solution Approach 1:
The patent employs multiple projection schemes (equidistant, orthographic, stereographic, equisolid angle) and systematically evaluates them by applying each to the captured image and assessing the linearity of transformed straight lines. This parameter-based approach allows the method to adapt to different fisheye lens characteristics without requiring prior knowledge of the specific projection scheme
Solution Approach 2:
The method uses feedback from linearity evaluation to automatically select the appropriate projection scheme. By transforming straight lines under different projection assumptions and measuring how well they remain straight, the system receives feedback that guides it to the correct projection model, eliminating the need for manual specification
Data Source
AI summary
A projection image generation unit 81 applies a plurality of projection schemes that use the radius of a visual field region of a fisheye-lens camera to an image in which an object including a straight line is imaged by the fisheye-lens camera, and generates a plurality of projection images. A projection scheme determination unit 82 selects one of the plurality of projection images on the basis of the linearity of each of the straight lines included in the projection images and determines a projection scheme on the basis of the selected projection image. An output unit 83 outputs an internal parameter of the fisheye-lens camera that corresponds to the determined projection scheme.