QR Code Erasure Detection via Reference Matrix Comparison
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Solution Overview
Problem
Existing symbol readers face challenges in accurately identifying erasures in 2D machine-readable symbols, particularly when symbols are partially out of view or damaged, leading to errors in decoding due to incorrect patterns at known locations.
Innovation Solution
The method involves generating a reference matrix by applying the same mask used in encoding to a uniform matrix, allowing for the identification of erasures by comparing unmasked codewords with the reference matrix, either by matching or inversing bit values, thereby facilitating error detection and correction in 2D symbols like QR codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If error codewords are detected by identifying substantial black or white portions in the symbol, then erasure detection is simple and fast, but after unmasking the codewords become unidentifiable and the detection method fails
Solution Approach 1:
The patent performs preliminary action by generating a reference matrix before the actual erasure detection. This reference matrix is created by applying the same mask to a uniform matrix, establishing a baseline pattern that can be compared against the unmasked codeword to identify erasures, thus resolving the contradiction between simple detection and accurate detection after unmasking
Solution Approach 2:
The patent introduces an intermediary approach by using a reference matrix as a mediator between the mask application and erasure detection. This reference matrix serves as a comparison standard that enables accurate erasure identification in unmasked codewords, bridging the gap between the simplicity of pattern-based detection and the accuracy needed after unmasking
2Reliability
If the symbol is partially out of view or damaged, then scanning performance should be improved through error correction, but incorrect patterns at known locations cause decoding errors
Solution Approach 1:
The patent implements feedback by comparing the unmasked codeword against the reference matrix to identify erasures, then using this information to correct decoding errors. This feedback loop allows the system to detect and compensate for incorrect patterns caused by partial viewing or damage, improving overall scanning performance while maintaining pattern accuracy
Solution Approach 2:
The patent performs preliminary action by pre-calculating the reference matrix before actual scanning occurs. This allows the system to be ready to immediately compare against the correct pattern when erasures are detected, enabling rapid error correction without compromising the precision of pattern recognition even when the symbol is partially damaged
Data Source
AI summary
One embodiment of a method for identifying a codeword as an erasure in a Quick Response code (QR code) captured by a bar code reader includes, identifying the scrambling mask used for encoding the data in the QR code. A location of the codeword in the QR code corresponds with a portion of the scrambling mask. The codeword comprises multiple codeword bits and the portion of the scrambling mask comprises multiple mask bits. The method further includes, generating an unscrambled codeword by performing a logical operation between each of the multiple codeword bits and each of the multiple mask bits, generating a reference matrix by applying the scrambling mask to a uniform matrix, and/or comparing the unscrambled codeword with the reference matrix to determine whether the codeword is the erasure.