Dual-Wavelength Illumination for Indicia Reading
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Solution Overview
Problem
Existing imaging readers using visible illumination light can be bothersome due to their bright and intense nature, causing discomfort to operators and others, while using non-visible infrared light may not effectively read thermally printed symbols, which are crucial in certain applications.
Innovation Solution
The use of a dual-light source system where non-readily visible infrared light and visible light are used to illuminate different fields of view, allowing for the reading of indicia while minimizing eye irritation, with the visible light ensuring readability of thermally printed symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visible illumination light is used to illuminate the indicia, then the indicia can be effectively read, but operators and others experience eye irritation and discomfort
Solution Approach 1:
The illumination system is segmented into multiple independent light sources emitting at different wavelengths (e.g., visible light at 405nm, 530nm, 630nm and infrared at 780nm, 850nm, 940nm). Each wavelength targets different aspects of the indicia, allowing the system to read various indicia types while minimizing eye irritation by using lower intensity visible light combined with non-visible infrared light
Solution Approach 2:
The illumination assembly uses a composite approach by combining multiple LED types with different spectral characteristics (violet, green, red, infrared LEDs) into a single illumination system. This composite light source provides both the visible spectrum needed for reading thermally printed symbols and the infrared spectrum that is less irritating to human eyes
2Object-affected harmful factors
If non-readily visible infrared light is used to illuminate the indicia, then eye irritation is reduced, but thermally printed symbols cannot be effectively read
Solution Approach 1:
The illumination system is segmented into multiple independent light sources emitting at different wavelengths (e.g., visible light at 405nm, 530nm, 630nm and infrared at 780nm, 850nm, 940nm). Each wavelength targets different aspects of the indicia, allowing the system to read various indicia types while minimizing eye irritation by using lower intensity visible light combined with non-visible infrared light
Solution Approach 2:
The illumination assembly is designed with multi-functionality to handle diverse indicia types. By incorporating multiple wavelengths including both visible and infrared, the system can universally read both thermally printed symbols (which require visible light) and other indicia types (which can be read with infrared light), making the system adaptable to various reading scenarios
3Measurement precision
If visible light intensity is increased to improve reading accuracy, then indicia can be read more clearly, but operator discomfort increases
Solution Approach 1:
The illumination system uses pulsed or intermittent illumination rather than continuous high-intensity visible light. The controller activates specific LED wavelengths in sequence or in combination, providing sufficient light for image capture only when needed, thereby reducing overall exposure to visible light and minimizing operator discomfort while maintaining reading accuracy
Solution Approach 2:
The system introduces infrared light as an intermediary that compensates for reduced visible light intensity. By adding infrared wavelengths that are invisible or less visible to humans, the system maintains adequate illumination for reading accuracy without requiring high intensities of visible light that would cause operator discomfort
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 reduces eye irritation from bright visible light while enabling the effective reading of thermally printed symbols by using visible light in conjunction with infrared light, making the system suitable for applications where both comfort and readability are critical.
Implementation Method 1
The illumination assembly includes a first energizable light source, such as one or more (infrared) light emitting diodes for illuminating the field of view with non-readily visible illumination light, and a second energizable light source, such as one or more (red/white) LEDs for illuminating the field of view with visible illumination light
Implementation Method 2
Each imaging sensor includes a sensor array of photocells or light sensors (also known as pixels), which correspond to image elements or pixels over a respective field of view of the imaging sensor
Data Source
AI summary
Infrared light, which is non-readily visible, illuminates at least part of a field of view containing indicia to be electro-optically read. Visible light illuminates another field of view containing the same indicia. The indicia is read by image capture by the illumination light from one of the illuminated fields of view. The use of IR light minimizes an adverse reaction due to only using bright visible light. The use of visible light enables thermally printed indicia, which is not readily readable by IR light, to be read.