2D Matrix Symbol Image Processing for Donut Effect Correction
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Solution Overview
Problem
Conventional decoding algorithms fail to accurately read two-dimensional (2D) matrix symbols when they are dot-peened onto metal surfaces, resulting in 'donut effects' due to image distortion, where the center of each module has a value opposite to the intended value, and when symbols are marked on metal and covered with paint, changing module polarity.
Innovation Solution
A method involving image processing techniques such as sharpening using Sobel gradient magnitude operators, smoothing with moving windows, and amplification to correct 'donut effects', ensuring the image has a continuous finder pattern and accurately representative data modules, suitable for conventional decoding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional decoding algorithms are used on dot-peened 2D matrix symbols, then the decoding process is simple and fast, but the decoding accuracy fails due to donut effects distorting module centers
Solution Approach 1:
The patent applies preliminary image processing actions (sharpening, smoothing, polarity correction) to the distorted 2D matrix symbol image before decoding. This preprocessing transforms the donut-effect distorted modules into corrected representations with accurate polarity, enabling subsequent conventional decoders to accurately read the symbol without requiring complex specialized decoding logic
Solution Approach 2:
The patent introduces an intermediary image processing step that acts as a mediator between the distorted captured image and the conventional decoder. This intermediary processing stage corrects the donut effects and polarity inversions, transforming the harmful distorted image into a form that conventional decoders can reliably interpret
2Reliability
If paint is applied to metal surfaces to cover marked symbols, then the symbol is protected from wear and corrosion, but the paint changes module polarity and causes decoding failures
Solution Approach 1:
The patent converts the harmful effect of paint-induced polarity changes into a benefit by implementing automatic polarity detection and correction. The system detects regions where paint has altered the expected polarity pattern and flips the polarity interpretation in those regions, thereby recovering the original encoded data despite the presence of protective paint coating
3Measurement precision
If the finder pattern is discontinuous due to donut effects, then the symbol structure is preserved, but conventional locating techniques fail to identify the symbol
Solution Approach 1:
The patent extracts and corrects the distorted finder pattern from the donut-effect distorted image by applying sharpening and smoothing operations. This extraction and correction process isolates the finder pattern from the surrounding data modules, reconstructs its continuous L-shape geometry, and enables conventional locating algorithms to successfully identify and locate the 2D matrix symbol
Data Source
AI summary
A method is presented for processing an image of a two-dimensional (2D) matrix symbol having a plurality of data modules and a discontinuous finder pattern, each distorted by “donut effects”. A resulting processed image contains an image of the 2D matrix symbol having a continuous finder pattern suitable for conventional 2D matrix symbol locating techniques, and having a plurality of data modules, each data module having a center more truly representative of intended data, and suitable for conventional 2D matrix symbol sampling and decoding. The method includes sharpening the distorted image of the 2D matrix symbol to increase a difference between low frequency and high frequency image feature magnitudes, thereby providing a sharpened image, and smoothing the sharpened image using a moving window over the sharpened image so as to provide a smoothed image, the moving window and a module of the 2D matrix code being of substantially similar size.