Multispectral LED Lighting Modules for Stable Sorting Code Detection
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Solution Overview
Problem
Existing lighting systems for industrial sorting facilities face challenges such as shifting shadows and specular reflections due to different LED colors, complex circuit design for varying driving currents, and ambient noise from switching transients, which affect code detection in high-speed image capture.
Innovation Solution
The solution involves arranging LEDs of different colors non-proportionally on a circuit board to achieve equal irradiance, using common electrical groupings, and employing thermal sinking and reduced switching transients to stabilize current flow, while synchronizing LED flashes with camera captures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LEDs of different colors are used to provide illumination for code detection, then the ability to detect codes under varying lighting conditions is improved, but shifting shadows and specular reflections occur due to different LED colors
Solution Approach 1:
The light bar is divided into multiple independently controllable LED modules, each containing LEDs of different colors (blue, red, infrared). Each module can be activated separately to provide specific wavelength illumination, allowing the system to maintain stable shadow and reflection patterns while offering versatile lighting options for different code types
Solution Approach 2:
The system dynamically switches between different LED color combinations based on the specific detection requirements. By controlling which LED modules are active at any given time, the system adapts illumination to minimize shadow shifting and specular reflection variations while maintaining code detection reliability across different material types
2Illumination intensity
If more LEDs are used to achieve high instantaneous light output for short exposure frames, then adequate illumination is improved, but the width of the light bar increases causing shadow sharpness to decrease
Solution Approach 1:
Multiple LED modules are combined into a single integrated light bar assembly that can be mounted close to the camera. By merging the illumination function into a compact unit positioned near the imaging sensor, the system achieves high instantaneous light output without increasing the effective illumination width that would blur shadow edges
Solution Approach 2:
The system uses periodic flash illumination rather than continuous lighting. By synchronizing LED activation with the camera's short exposure frames, the system delivers high instantaneous light output only when needed for capture, maintaining sharp shadows while reducing overall light bar width requirements
3Illumination intensity
If more LEDs are used to increase light output, then illumination intensity is improved, but heating of the light assembly increases shortening service life
Solution Approach 1:
The LED modules are activated in periodic bursts synchronized with camera exposure rather than continuously. This duty cycling approach maintains high illumination intensity during capture moments while allowing extended cooling periods between flashes, significantly reducing thermal accumulation and extending the service life of the LED assembly
Solution Approach 2:
Different LED modules with different color characteristics are selectively activated based on the specific detection requirements. By using only the necessary LED types for each capture task, the system reduces overall heat generation while maintaining adequate illumination intensity for the intended application
4Illumination intensity
If high current is applied to LEDs to achieve sufficient irradiance, then illumination intensity is improved, but switching transients increase causing ambient noise
Solution Approach 1:
The system pre-charges capacitor energy stores before each LED flash cycle. By accumulating electrical energy in advance and then releasing it in a controlled manner during the flash, the system achieves high instantaneous irradiance while minimizing transient current spikes and electromagnetic interference that would create ambient noise
Solution Approach 2:
Capacitor energy stores act as an intermediary between the power supply and LED load. This intermediate energy storage element smooths out current delivery, providing high instantaneous power for illumination while filtering out high-frequency switching transients that would otherwise create electromagnetic noise interfering with code detection
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 stabilizes illumination, reduces noise interference, and enhances code detection reliability in high-speed image capture, improving sorting efficiency.
Implementation Method 1
Applicant favors light emitting diodes (LEDs) for generating the different colors of light
Implementation Method 2
a monochrome camera system captures a first frame under blue light
Data Source
AI summary
In one aspect, an elongated lighting module includes plural colors of LEDs that flash in a cyclical sequence to provide multi-spectral illumination. Several such modules can be arranged end-to-end to span a conveyor system that transports a stream of plastic waste items in a recycling center, enabling capture of differently-illuminated image frames depicting the items. Each module may include N LEDs of a first color (e.g., red) and M LEDs of a second color (e.g., blue), where N and M are different. Drive circuitry can be simplified by configuring the LEDs in strings of common colors, but with different counts. Electrical noise due to switching transients can be reduced by operating the LEDs at a low current when not being flashed. A great variety of other features and arrangements are also detailed.