3D Calibration Object with Unique Identifiers for Extrinsic Camera Parameters
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Solution Overview
Problem
Conventional 2D patterns for camera calibration are error-prone and limited by viewing angles, making precise estimation of extrinsic camera parameters challenging, especially due to perspective distortion and variable feature point detection accuracy.
Innovation Solution
A 3D calibration object with unique identifiers, such as colored balls, is used to calibrate extrinsic camera parameters by computing positional probabilities and establishing correspondence between 2D pixel coordinates and 3D real-world coordinates, allowing for accurate detection and calibration across various angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If 2D patterns are used for camera calibration, then the calibration process is simple, but the detection accuracy of feature points deteriorates due to perspective distortion and viewing angle limitations
Solution Approach 1:
The patent transitions from 2D calibration patterns to a 3D calibration object with multiple spherical feature points distributed in three-dimensional space. This dimensional change eliminates perspective distortion issues inherent in 2D patterns, as the spherical features can be accurately detected from any viewing angle, thereby improving measurement precision while maintaining calibration simplicity through automated 3D point cloud processing
2Area of stationary object
If 2D patterns are applied to four facades of a 3D calibration box, then coverage is improved, but feature point detection becomes error-prone due to numerous identical feature points
Solution Approach 1:
The patent places spherical feature points with distinct spatial coordinates in 3D space rather than using identical 2D patterns on multiple surfaces. Each spherical feature point has unique local quality defined by its 3D position, allowing reliable identification and detection without confusion from identical features, thereby improving detection reliability while maintaining comprehensive coverage through strategic 3D distribution
3Difficulty of detecting and measuring
If cameras are restricted by viewing angles for 2D pattern discernment, then feature detection is simplified, but calibration versatility deteriorates
Solution Approach 1:
By moving to 3D spherical feature points, the system gains versatility to capture calibration targets from any viewing angle in 360 degrees. The spherical geometry and 3D spatial distribution maintain detection simplicity through consistent feature appearance while eliminating viewing angle restrictions, thereby achieving both simplicity and versatility simultaneously
Data Source
AI summary
Various aspects of a system and a method for extrinsic camera parameters calibration by use of a three dimensional (3D) calibration are disclosed herein. In accordance with an embodiment, the system includes an electronic device, which receives an image, which includes the 3D calibration object with a plurality of unique identifiers. One or more appearance parameters of the 3D calibration object and/or a plurality of intrinsic camera parameters of an image-capturing device that captured the received image, are further received. A positional probability is computed for each of the plurality of unique identifiers distributed in the received image. The plurality of unique identifiers of the 3D calibration object are located in the received image to calibrate the extrinsic camera parameters based on the computed positional probability, the received one or more appearance parameters of the 3D calibration object, and the plurality of intrinsic camera parameters.