Barcode Reader Edge Detection Using Phase Waveform Delay
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Solution Overview
Problem
Barcode scanners face challenges in accurately determining signal level transitions due to noise components like thermal and substrate noise, leading to erroneous binary signal levels and incorrect decoding of barcode symbols.
Innovation Solution
The optical reader employs a scan data signal processor with time delay stages generating primary, early, and delayed phase waveforms, along with peak window detection to accurately identify signal transitions and differentiate between barcode elements and noise, thereby enhancing barcode edge detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional signal processing circuits with filters and thresholding devices are used, then noise removal is achieved, but false transitions are generated due to thermal and substrate noise
Solution Approach 1:
The patent segments the signal processing into multiple derivative stages (first derivative, second derivative) with distinct functions. The first derivative identifies potential transitions, while the second derivative confirms valid edges by detecting zero-crossings. This segmentation allows the system to differentiate between noise-induced false transitions and genuine barcode edges, resolving the contradiction between noise removal and false transition generation.
Solution Approach 2:
The patent introduces an intermediary validation mechanism using the second derivative of the scan data signal. This intermediary stage acts as a mediator between the first derivative signal and the final digital output, filtering out false transitions by requiring confirmation through zero-crossing detection. This intermediary layer maintains reliability while preserving noise removal capabilities.
2Reliability
If the laser beam cross-sectional dimensions are reduced to improve depth of modulation, then signal-to-noise ratio improves, but the system becomes more sensitive to barcode edge roughness and printing quality variations
Solution Approach 1:
The patent transforms the scan data signal through derivative operations, changing its mathematical parameters. By converting the original signal into first and second derivatives, the system enhances the visibility of true edges while suppressing noise components. This parameter transformation allows the system to maintain high signal-to-noise ratio while reducing sensitivity to substrate variations and printing quality issues.
3Measurement precision
If multiple derivative stages are added to improve edge detection accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or hardware-based edge detection mechanisms with mathematical signal processing operations. By using software or firmware-based derivative calculations on the scan data signal, the system achieves high measurement precision without proportionally increasing physical device complexity. This substitution allows multiple derivative stages to be implemented with minimal additional hardware overhead.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces errors in barcode decoding by precisely identifying barcode edges and rejecting noise, improving the accuracy and reliability of barcode symbol recognition.
Implementation Method 1
a photodetector for detecting light intensity corresponding to the laser beam scattered off the scanned encoded symbol character and generating an analog electrical signal
Implementation Method 2
a laser source for generating a laser beam along an optical path
Data Source
AI summary
An optical reader for decoding an encoded symbol character of a symbology includes a scan data signal processor having as an input a scan data signal encoding information representative of the encoded symbol character. The scan data signal processor includes a first time delay stage adapted to provide a primary phase waveform from the scan data signal, a second time delay stage adapted to provide an early phase waveform from the scan data signal, and a third time delay stage adapted to provide a delayed phase waveform from the scan data signal. The early phase waveform has a propagation delay less than the primary phase waveform, and the delayed phase waveform has a propagation delay greater than the primary phase waveform. The scan data signal processor further includes a peak window detection stage for generating a peak window timeframe when an amplitude of the primary phase waveform is greater than, less than, or equal to both an amplitude of the early phase waveform and the delayed phase waveform. The optical reader further includes a digitizer circuit adapted to accept, within the peak window timeframe, the scan data signal processor output.