Fisheye Camera Internal Parameter Estimation Without Calibration Patterns
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Solution Overview
Problem
Existing methods for estimating the internal parameter of a fisheye-lens camera require a special calibration pattern and prior knowledge of a projection scheme, making the estimation process complex and cumbersome.
Innovation Solution
A camera parameter estimation device and method that generates multiple projection images using different schemes, allowing users to select and determine the appropriate projection scheme based on image characteristics, thereby estimating the 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 is used to estimate internal parameters, then measurement precision is improved, but device complexity and ease of operation deteriorate due to requiring special patterns and simultaneous estimation of external and internal parameters
Solution Approach 1:
The invention extracts only the internal parameter estimation from the simultaneous estimation process of external and internal parameters. By using a fisheye lens's unique property of capturing the entire calibration pattern in a single shot, the method separates internal parameter estimation from external parameter estimation, eliminating the need for complex simultaneous optimization while maintaining accuracy.
Solution Approach 2:
The calibration method becomes universal by working with any calibration pattern that can be captured by the fisheye lens, rather than requiring specific special patterns. The method can estimate internal parameters from general scenes or objects within the field of view, making the calibration process applicable to various situations without requiring specialized equipment or patterns.
2Measurement precision
If a special calibration pattern is used, then measurement precision is improved, but device complexity worsens due to requiring prerequisite knowledge of projection schemes
Solution Approach 1:
The method enables self-service by allowing the system to automatically determine the appropriate projection scheme through testing multiple schemes and selecting the one that produces the most linear straight lines in the calibrated image. This eliminates the need for users to have prior knowledge of projection schemes, as the system performs the selection autonomously based on image characteristics.
Solution Approach 2:
The invention applies multiple projection scheme parameters to the same calibration data and evaluates which parameter set produces the best results. By changing the projection scheme parameters (equidistant, orthographic, stereographic, etc.) and comparing the linearity of calibrated straight lines, the method automatically identifies the correct internal parameters without requiring users to pre-specify the projection scheme.
3Ease of operation
If multiple projection schemes are applied and user selection is required, then ease of operation is improved, but loss of time increases due to displaying and selecting from multiple images
Solution Approach 1:
The system provides visual feedback by displaying multiple projection images with different schemes, allowing users to quickly identify the correct scheme based on visual inspection of straight line linearity. This feedback mechanism enables rapid selection without requiring extensive analysis or iteration, reducing the time penalty associated with user selection.
Data Source
AI summary
A projection image generation unit 91 applies a plurality of projection schemes that use the radius of a visual field region of a fisheye-lens camera to an image that is imaged by the fisheye-lens camera to generate a plurality of projection images. A display unit 92 displays the plurality of projection images. A selection acceptance unit 93 accepts a projection image selected by a user from among the plurality of displayed projection images. A projection scheme determination unit 94 determines a projection scheme on the basis of the selected projection image. An output unit 95 outputs an internal parameter of the fisheye-lens camera that corresponds to the determined projection scheme.