Vision-guided alignment for roll-to-roll testing
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Solution Overview
Problem
Existing systems face challenges in accurately aligning test probes with test pads on flexible substrates during roll-to-roll electrical testing, particularly due to distortion caused by web tension or slippage, leading to unreliable detection of fiducial marks and potential false failure recordings.
Innovation Solution
A vision-guided roll-to-roll electrical testing system that combines a digital imaging system for capturing images of test pads and fiducial marks, a fiducial sensing system for determining fiducial mark positions, and a controller to adjust the test fixture's position based on spatial relationships between features and fiducial marks, ensuring accurate alignment despite variable placement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital imaging system is used to capture images of test pads and fiducial marks, then alignment information can be obtained, but variable placement errors between fiducial marks and features lead to unreliable alignment
Solution Approach 1:
The system segments the alignment task into two independent parts: (1) capturing the spatial relationship between test pads and fiducial marks using a digital imaging system, and (2) sensing fiducial mark positions using a fiducial sensing system. This segmentation allows each subsystem to optimize for its specific function, improving overall alignment reliability despite placement errors.
Solution Approach 2:
The patent introduces an intermediary computational process that uses the captured spatial relationships to predict test pad positions based on sensed fiducial mark positions. This intermediary calculation layer compensates for placement errors by mathematically deriving the expected feature locations, thereby maintaining alignment reliability even when fiducial marks are not precisely aligned with features.
2Ease of operation
If fiducial marks are used for alignment, then positioning reference is provided, but placement errors cause unreliable alignment and potential false failure detection
Solution Approach 1:
The system implements feedback by continuously monitoring the spatial relationships between fiducial marks and test pads through digital imaging. The controller uses this feedback to dynamically adjust alignment calculations and compensate for placement errors, ensuring reliable test results even when initial fiducial mark placement is imperfect.
Solution Approach 2:
The patent performs preliminary capture of spatial relationships between test pads and fiducial marks before the actual alignment operation. This preliminary action allows the system to pre-calculate expected feature positions and prepare compensation strategies, improving both the ease of operation and reliability of the subsequent alignment and testing processes.
3Measurement precision
If vision-guided alignment is implemented, then alignment accuracy improves, but system complexity increases
Solution Approach 1:
The digital imaging system serves multiple functions: capturing test pad positions, detecting fiducial mark locations, and determining spatial relationships between features. This multi-functionality reduces the need for separate specialized components, thereby limiting the increase in system complexity while maintaining high alignment precision.
Data Source
AI summary
A system is used to perform an operation on an article, the article including a plurality of fiducial marks and a set of features. A digital imaging system captures a digital image of the article, which is analyzed to determine spatial relationships between positions of the features and positions of the fiducial marks. The article is positioned in proximity to an instrument and a fiducial sensing system including a plurality of fiducial sensors is used to determine positions of the fiducial marks. Predicted positions of the features are determined responsive to the determined spatial relationships and the determined fiducial mark positions. The position of the instrument or the article is adjusted responsive to the predicted positions of the features, and the instrument is used to perform an operation on the article.