LED Luminous Intensity Uniformity Testing via Optical Imaging
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Solution Overview
Problem
Conventional electrical tests fail to detect current leakage and surface defects in light-emitting devices comprising multiple LEDs connected in series and parallel, and cannot measure the uniformity of luminous intensity effectively.
Innovation Solution
A method involving an apparatus with a current source, image receiving device, and image processing unit to drive LEDs with a current density of ≤300 mA/mm², generating an image to determine the luminous intensity of each LED, and using a filter to differentiate defective LEDs based on their luminosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrical tests are used to test light-emitting devices, then the testing process is simple and fast, but defects like current leakage and surface stains cannot be detected
Solution Approach 1:
The patent replaces conventional electrical testing methods with optical imaging technology. By using an image receiving device to capture images of the light-emitting device under test, the system can detect defects such as current leakage and surface stains through visual analysis rather than electrical measurements, thereby improving defect detection capability while maintaining relatively simple implementation
Solution Approach 2:
The patent introduces an image receiving device as an intermediary between the light-emitting device and the testing system. This intermediary captures optical information from the device, allowing indirect detection of defects that cannot be measured by direct electrical testing, thus enhancing reliability without requiring complex electrical test circuits
2Measurement precision
If conventional electrical tests are used, then the testing procedure is simple, but uniformity of luminous intensity cannot be measured
Solution Approach 1:
The patent substitutes electrical measurement methods with optical imaging to measure luminous intensity uniformity. The image receiving device captures the spatial distribution of light emission, and image processing algorithms analyze the uniformity across different regions, enabling precise measurement without complex electrical sensing circuits
Solution Approach 2:
The patent transitions from one-dimensional electrical parameter measurement to two-dimensional spatial light distribution measurement. By capturing images that show the spatial variation of luminous intensity across the device surface, the system can assess uniformity in multiple locations simultaneously, providing comprehensive measurement capability
3Illumination intensity
If high current density is used to drive LEDs, then the luminous intensity is higher for better image generation, but the risk of damaging LEDs and causing false positives increases
Solution Approach 1:
The patent optimizes the current density parameter to a specific range (200-300 mA/mm²) that balances luminous intensity generation with LED safety. This parameter optimization ensures sufficient light emission for clear image capture while staying below thresholds that would cause thermal damage or accelerate degradation, thereby preventing false defect positives
Solution Approach 2:
The patent uses a current density that is sufficient to generate adequate luminous intensity for defect detection but deliberately limits it to avoid excessive action that would damage the LEDs. The chosen current level provides just enough light for reliable imaging without reaching levels that would cause harm, achieving optimal detection sensitivity while protecting the device
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
Enables detection of defects like current leakage and measurement of luminous intensity uniformity, improving the reliability of light-emitting device testing beyond conventional electrical tests.
Implementation Method 1
driving the plurality of the light-emitting diodes with a current; generating an image of the light-emitting device
Data Source
AI summary
Disclosed is a method for testing a light-emitting device comprising the steps of: providing a light-emitting device comprising a plurality of light-emitting diodes; driving the plurality of the light-emitting diodes with a current; generating an image of the light-emitting device; and determining a luminous intensity of each of the light-emitting diodes; wherein the magnitude of the current is determined such that the current density driving each of the light-emitting diodes is smaller than or equal to 300 mA/mm2.