Calibration Board Feature Dots for Camera Corner Detection
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Solution Overview
Problem
Existing camera calibration methods using checkerboards face challenges with low accuracy in corner point position detection and are prone to failure when the camera's focal length is reduced, leading to blurred images and detection issues.
Innovation Solution
A calibration board with checkerboard cells arranged on its surface, featuring at least one dot in each cell, with first and second feature dots of different diameters, allowing for improved detection accuracy and anti-blur capabilities through perspective invariant centroids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional checkerboard is used for camera calibration, then the calibration process can be completed, but the corner point detection accuracy is low and the method fails when the camera focal length is reduced causing blurred images
Solution Approach 1:
The patent applies color changes by using dots with different grayscale values (first feature dots with higher grayscale values than second feature dots) to create distinguishable features that maintain detectability under blurred conditions. The grayscale differentiation allows the detection algorithm to identify feature dots even when image sharpness is reduced, thereby maintaining measurement precision and reliability.
Solution Approach 2:
The patent changes the parameter of dot diameter by introducing two types of feature dots with different diameters (first feature dots have larger diameters than second feature dots). This parameter variation creates features with different detection characteristics, allowing the system to maintain accurate corner point detection across varying focal lengths and image sharpness conditions, resolving the contradiction between detection accuracy and reliability under blurred conditions.
2Area of stationary object
If the camera focal length is reduced to increase field of view, then more of the calibration board can be captured, but the acquired image becomes blurred making corner point detection fail
Solution Approach 1:
By using dots with different grayscale values, the patent creates features that remain distinguishable even when the camera captures a larger area with reduced focal length. The grayscale contrast allows the detection algorithm to identify feature dots accurately despite the reduced image sharpness, thereby maintaining measurement precision while expanding field of view coverage.
Solution Approach 2:
The patent introduces feature dots with varying diameter parameters to create features with different detection robustness. The larger first feature dots provide more prominent features that can be reliably detected even when the camera focal length is reduced, allowing the system to maintain corner point detection accuracy while capturing a broader calibration board area.
3Loss of information
If the calibration board is placed to fit the entire field of view, then complete calibration data can be obtained, but the board cannot be blocked and must include all corner points
Solution Approach 1:
The grayscale differentiation of feature dots creates distinctive markers that enable the detection algorithm to identify and locate the calibration board even when only partially visible. This allows the system to obtain sufficient calibration data from partial views, reducing information loss while increasing flexibility in calibration positioning and allowing the board to be blocked or positioned more freely.
Data Source
AI summary
This application discloses a calibration method, a calibration system, and a calibration board. The calibration board includes checkerboard cells arranged on a surface of the calibration board, where at least one dot is arranged in each of the checkerboard cells, the dots of the calibration board include at least a first feature dot and a second feature dot, the first feature dot and the second feature dot are arranged in the checkerboard cells according to a random rule or a specific rule, and a diameter of the first feature dot is greater than a diameter of the second feature dot. The calibration board in this application improves the stability and accuracy of calibration board detection by utilizing characteristics such as a high detection accuracy and a strong anti-blur capability of a dot mark, combining with corner points of checkerboard cells.