Pulsed Illumination Timing for Optical Code Reading on Reflective Surfaces
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Solution Overview
Problem
Optical codes on highly reflective surfaces, such as electronic display screens, are difficult to decode using general-purpose data readers due to specular reflection, leading to annoying light flicker when switching between illumination and non-illumination modes.
Innovation Solution
The system employs a method to pulse illumination in synchronization with image exposure cycles, ensuring that LED illumination is either within or offset from exposure times to avoid flicker perception, using a processor to analyze image histograms to determine if an LCD screen is present and adjust reading modes accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LED illumination is cycled on and off to read optical codes on reflective surfaces, then decoding capability is improved, but light flicker is produced causing user discomfort
Solution Approach 1:
The patent applies periodic pulsed illumination at a frequency exceeding 50 Hz to read optical codes on reflective surfaces. The illumination is cycled on and off in synchronization with image capture, enabling the reader to alternate between illuminated and non-illuminated states to handle specular reflection while maintaining a high pulse frequency that prevents flicker perception by human vision.
Solution Approach 2:
The patent changes the illumination frequency parameter to exceed 50 Hz, which is above the flicker fusion frequency of human vision. By adjusting the pulse frequency to this higher range, the system maintains the benefits of pulsed illumination for reading reflective surfaces while the flicker effect becomes imperceptible to users.
2Reliability
If illumination is turned off to avoid specular reflection from LCD screens, then reading accuracy is improved, but exposure time must be extended which reduces productivity
Solution Approach 1:
The system uses periodic pulsed illumination synchronized with image capture cycles. The illumination is turned on during specific exposure windows and off during others, allowing the reader to capture images without continuous illumination while maintaining adequate exposure time for accurate reading of reflective surfaces.
Solution Approach 2:
The patent maintains continuous reading capability by cycling illumination and capture operations. The useful action of reading continues without interruption as the system alternates between illuminated and non-illuminated capture cycles, ensuring both reading accuracy and operational efficiency.
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 minimizes the perception of flicker and improves decoding efficiency by optimizing illumination timing, allowing for effective reading of optical codes on reflective surfaces without causing user discomfort.
Implementation Method 1
a first source of illumination, such as a light emitting diode (LED)
Implementation Method 2
imaging device, such as a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) imager
Implementation Method 3
highly, or relatively highly, reflective surfaces... specular reflection
Data Source
AI summary
Methods and systems are disclosed for improved operation of readers of optical codes presented on electronic display screens or other highly reflective surfaces. Certain configurations include controlling image exposure and illumination pulse timing so as to avoid or minimize the perception of flicker of the pulsed illumination by a user or bystander while implementing methods for reading optical codes presented on electronic display screens or other highly reflective surfaces.