Self-Positioning Calibration Plate Using Embedded 2D Codes
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Solution Overview
Problem
Conventional calibration plates for machine vision systems face challenges such as manual calibration requirements, limited motion range, and decreased efficiency due to identical calibration fiducials and increased complexity with 2D DataMatrix codes, which affect accuracy and usability in hand-eye and non-hand-eye calibration processes.
Innovation Solution
A calibration plate with 2D codes embedded within a checkerboard pattern serves as self-positioning fiducials, allowing for automatic calibration of vision system cameras by encoding (X, Y) coordinates and providing unique identifiers for each fiducial, enabling accurate tracking and absolute positioning, even with relative motion between cameras and objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional calibration plates with identical calibration fiducials are used, then manual calibration is required, but automation and efficiency are decreased
Solution Approach 1:
Each calibration fiducial is assigned a unique 2D data code that encodes its specific position and orientation information. This local differentiation allows the vision system to automatically identify and process each fiducial's characteristics without manual intervention, enabling calibration automation while reducing calibration time.
2Loss of information
If 2D DataMatrix codes are embedded in calibration fiducials, then unique identifiers are provided, but complexity and difficulty of detection increase
Solution Approach 1:
The 2D data codes serve multiple functions simultaneously: they provide unique identification for each fiducial, encode position and orientation information, and maintain compatibility with standard vision system cameras. This multi-functionality reduces overall system complexity despite the added information capacity.
3Measurement precision
If calibration fiducials are made distinctive for hand-eye calibration, then motion tracking accuracy is improved, but field of view requirements and motion range are limited
Solution Approach 1:
Multiple identical 2D data code patterns are distributed across the calibration plate at known positions. This allows the vision system to track motion by identifying and comparing code positions across different field of view positions, extending the effective motion range while maintaining tracking accuracy through the repetitive, recognizable code patterns.
Data Source
AI summary
This invention provides a system and method for automatic (non-manual) calibration of one or more cameras employs a tessellating calibration plate having a checkerboard tile pattern and a plurality of 2D codes embedded within the checkerboard pattern. Each 2D code encodes the (X,Y) coordinates that identify tile calibration feature locations in the pattern, and the remaining, surrounding tiles allow measurement of the corner positions as calibration features. One or more vision system camera(s) can be calibrated to a single coordinate system automatically. During calibration, an image of at least a portion of a calibration plate is acquired, the encoded data is decoded for at least one 2D code within the field of view of each camera and then the position of the field of view is determined on the calibration plate for each camera using the 2D code data and the checkerboard tile pattern.