Surround View Camera Geometric Calibration via Fisheye Distortion Correction
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Solution Overview
Problem
Multi-camera surround view systems face challenges in producing a seamlessly stitched 360-degree composite view due to fisheye distortion and brightness/color mismatches between camera views, leading to visible seams and geometric errors in the composite bird-eye view.
Innovation Solution
The solution involves a geometric alignment algorithm that corrects fisheye distortion and aligns camera views using a lookup table, a photometric alignment algorithm that adjusts brightness and color, and a synthesis algorithm that generates a seamless composite view by collecting statistics for photometric alignment, reducing memory bandwidth and computational intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If fisheye lenses are used to capture 360-degree views with multiple cameras, then the field of view is improved, but geometric distortion and visibility of seams in the composite view worsen
Solution Approach 1:
The patent applies parameter changes by estimating and correcting fish-eye distortion parameters through geometric alignment. The system transforms distorted fisheye images into undistorted perspectives by calculating correction parameters that map distorted coordinates to corrected coordinates, thereby resolving the geometric accuracy issue while preserving the wide field of view capability
Solution Approach 2:
The patent introduces an intermediary geometric lookup table that stores pre-calculated transformation parameters between different camera views. This intermediary structure enables efficient geometric correction and seamless stitching by providing intermediate transformation data that bridges the gap between distorted fisheye inputs and corrected composite outputs
2Area of stationary object
If multiple cameras are used to capture surrounding views, then the coverage area is improved, but brightness and color mismatches between views worsen
Solution Approach 1:
The patent applies parameter changes by estimating photometric alignment parameters that correct brightness and color mismatches between adjacent camera views. The system calculates correction factors for illumination intensity and color balance, transforming non-uniform multi-camera inputs into a seamlessly blended composite view with uniform appearance across all views
3Manufacturing precision
If geometric alignment and photometric correction are performed in real-time, then the view quality is improved, but computational intensity and memory bandwidth requirements worsen
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing geometric alignment parameters and photometric correction data in lookup tables before real-time processing. During real-time operation, the system simply retrieves pre-computed transformation parameters from memory rather than performing complex calculations, thereby maintaining high stitching accuracy while dramatically reducing computational intensity and memory bandwidth requirements
Data Source
AI summary
A method, apparatus and a system multi-camera image processing method. The method includes performing geometric alignment to produce a geometric output by estimating fish eye distortion correction parameters, performing initial perspective correction on related frame, running corner detection in the overlapping areas, locating the stronger corner, calculating BRIEF descriptors for features and match feature point from two cameras using BRIEF scores, performing checks and rejecting wrong feature matches, finding perspective matrices to minimize distance between matched features; and creating a geometric lookup table.