2D Barcode Scanner Illumination with Reflection-Avoiding Optics
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Solution Overview
Problem
2D barcode scanners face challenges with insufficient illumination and reflections causing hotspots, which hinder error-free detection, especially for barcodes with special properties outside the visible spectrum and lead to suboptimal illumination over depth ranges.
Innovation Solution
A 2D barcode scanner design featuring external light sources with attachment optics that minimize reflections by redirecting light paths away from the camera, ensuring homogeneous illumination over a depth range, and shifting hotspot locations to less critical areas of the reading window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If external light sources are provided to illuminate the barcode area, then illumination intensity is improved, but light reflections occur on the reading window causing hotspots that impair error-free barcode evaluation
Solution Approach 1:
The patent divides the illumination task among multiple external light sources (at least two) positioned at different locations. Each light source illuminates a specific area of the reading window, and their combined effect provides uniform illumination across the entire area while distributing reflection paths to avoid concentrated hotspots in the camera image.
Solution Approach 2:
The patent positions light sources and reading window at specific angles relative to the camera optical axis. The light sources are arranged outside the optical axis, creating localized illumination zones that reflect away from the camera. This angular arrangement ensures that reflection paths from different areas of the reading window do not converge into the camera lens, eliminating hotspots while maintaining adequate illumination.
2Object-affected harmful factors
If anti-reflective coating is optimized on the reading window, then reflection is reduced for a limited wavelength range, but narrow-band illumination is required which prevents reading barcodes outside the visible spectrum
Solution Approach 1:
Instead of trying to prevent reflections through coating optimization (which limits wavelength range), the patent inverts the approach by geometrically arranging light sources and reading window at angles that direct reflection paths away from the camera. This geometric solution works across all wavelengths without requiring narrow-band illumination, enabling reading of barcodes in visible and near-infrared spectra.
3Object-affected harmful factors
If light sources are arranged to illuminate from the sides at an angle to the optical axis, then hotspot intensity is reduced, but illumination homogeneity over depth is insufficient
Solution Approach 1:
The patent uses multiple light sources positioned at different angular positions relative to the optical axis. Each light source creates a localized illumination zone with its own reflection path that avoids the camera. The superposition of these multiple zones produces uniform illumination across the reading window area and depth range, compensating for the angular arrangement's depth limitations.
Solution Approach 2:
The patent extends the illumination geometry into three-dimensional space by positioning light sources at various heights and angles around the reading window. This spatial distribution creates overlapping illumination cones that maintain homogeneous lighting across the depth range, transforming the two-dimensional angular arrangement into a three-dimensional illumination volume that covers the required depth while keeping reflections away from the camera.
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 solution achieves low-reflection, homogeneous illumination, reducing hotspot intensity and improving barcode detection accuracy across the entire reading window, including areas further away, and supports reading of both visible and near-infrared barcodes.
Implementation Method 1
the reflection paths arising for the external light sources directly or via any deflection mirrors that may be present, from the inside of the reading window back into the camera are not illuminated or are illuminated with a very low intensity
Data Source
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AI summary
A 2D barcode scanner (1) is proposed, comprising a housing (2) with a reading window (3) and a digital camera (4) arranged in the housing (2) for capturing the area of the reading window (3) directly or via a mirror arrangement (8, 9), wherein at least one external light source (5) arranged in the housing (2) is provided for illuminating an area in front of the reading window (3) on the side of the reading window (3) facing away from the digital camera (4), wherein the at least one external light source (5) is provided with an attachment optic (7) by which the light from the at least one external light source (5) is distributed in such a way that the reflection paths arising for the at least one external light source (5) on the inside of the reading window (3) back into the camera (4) are not illuminated or are illuminated with a very low intensity, thereby minimizing light reflections arising on the inside of the reading window (3).which are superimposed on the barcode to be read as very bright spots in the image of the digital camera (4), are avoided or whose intensity is significantly reduced.