Fisheye Image Transformation via Virtual Sphere Mapping
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Solution Overview
Problem
Images captured by fisheye lenses are strongly distorted, making them incompatible with practical applications that require reduced distortion for improved visual effects and compatibility with human visual habits.
Innovation Solution
A fisheye image transformation algorithm based on virtual spheres is introduced, which defines a real camera coordinate system and a virtual camera coordinate system with small and large virtual spheres. The algorithm transforms fisheye images into 3D unit vectors, adjusts the angle of the horizontal or vertical field of view of the virtual camera, and conducts conventional projections to generate a transformed image with reduced line curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fisheye lens is used to capture wide field of view images, then the field of view angle is improved (up to 180 degrees), but the image distortion is strongly increased
Solution Approach 1:
The patent introduces a third dimension by mapping 2D fisheye image coordinates to 3D unit vectors, then transforming between two virtual camera coordinate systems (O-XYZ and O2-X2Y2Z2) with different sphere radii. This dimensional transformation enables the conversion of strongly distorted fisheye images into images with reduced curvature while preserving the wide field of view, effectively resolving the contradiction between FOV and distortion
Solution Approach 2:
The patent uses 3D unit vectors as an intermediary representation between the fisheye image coordinate system and the transformed image coordinate system. By introducing virtual camera coordinate systems with small and large spheres as intermediate transformation spaces, the algorithm mediates the conversion process to reduce image distortion while maintaining the essential viewing characteristics
2Device complexity
If conventional projection is used to transform fisheye images, then the transformation process is simplified, but the line curvature in the transformed image is increased
Solution Approach 1:
The patent introduces dynamic adjustability by allowing the radius ratio n between the large and small virtual spheres to be varied, and by enabling adjustment of the virtual camera's HFOV/VFOV angles. This dynamic parameter control allows optimization of line curvature reduction while maintaining a relatively simple transformation framework, balancing complexity and visual quality
Data Source
AI summary
A fisheye image transformation algorithm based on virtual spheres is provided, comprising: defining a real camera coordinate system O-XYZ and a virtual camera coordinate system O2-X2Y2Z2, wherein a small virtual sphere centered at O with a radius of 1 and a large virtual sphere centered at O2 with a radius of n are defined, the small sphere is internally tangent to the large sphere; transforming a fisheye image to 3D unit vectors in the real camera coordinate system, transforming the 3D unit vectors between the real camera coordinate system and the virtual camera coordinate system according to a relative position between two spheres, and conducting conventional projection of the 3D unit vectors in the virtual camera coordinate system to generate the transformed image; and reducing the line curvature of the transformed image to a certain degree by adjusting the HFOV angle or the VFOV angle of the virtual camera.