Edge-Sensing Light Sensor for EL Device Variation Detection
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Solution Overview
Problem
There is a need to detect variations and failures in the light output of face-illuminated electroluminescent (EL) devices without obstructing the light path or making the measurement electronics a costly, difficult-to-replace component, as existing solutions either fail to detect shorts or require expensive, integrated units.
Innovation Solution
A system comprising a transparent substrate with EL emitters, a power supply, a light sensor physically separated from the substrate's edge, and a controller that computes light output variations by storing initial and subsequent light readings, allowing for easy replacement of defective components and detecting spatial failures, using total internal reflection to minimize crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light sensors are placed directly on or near the EL device to detect light output, then measurement capability is improved, but the light path to the user is obstructed
Solution Approach 1:
The patent positions light sensors at the edge of the EL device rather than on the face, utilizing the edge dimension to detect light that exits through the side. This spatial reconfiguration allows sensors to monitor light output without blocking the user's view, as sensors are located laterally rather than in the light path.
Solution Approach 2:
The patent uses the EL device substrate and edge structure as intermediaries to guide light from the emitters to the sensors. Light travels through the substrate and exits at the edge where sensors are positioned, allowing indirect measurement without direct obstruction of the user's line of sight.
2Measurement precision
If photodiodes are affixed directly to the light guide or substrate, then measurement integration is improved, but device complexity and replacement difficulty increase
Solution Approach 1:
The patent separates the measurement function from the EL device by positioning light sensors externally at the edge rather than integrating them into the device structure. This segmentation allows the EL device to be replaced independently without the sensors, simplifying maintenance and reducing overall device complexity.
Solution Approach 2:
The patent extracts the light sensing capability from any integrated circuit board or control electronics and places it as a separate, externally positioned sensor at the device edge. This extraction eliminates the need for complex integrated measurement electronics and allows for simpler device replacement.
3Productivity
If multiple EL emitters are closely spaced to increase density, then productivity is improved, but crosstalk between adjacent emitters increases
Solution Approach 1:
The patent positions light sensors to detect light from specific local regions at the device edge, creating localized measurement zones. By strategically placing sensors to monitor particular emitter regions, the system can distinguish between adjacent emitters even when they are closely spaced, reducing crosstalk interference.
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 non-invasive, cost-effective monitoring of EL device output variations and spatial failure detection, decoupling measurement electronics from the substrate for easy replacement, and reducing crosstalk between adjacent emitters, suitable for various substrates like glass and plastic.
Implementation Method 1
using total internal reflection to provide sensor data having reduced crosstalk between multiple adjacent EL emitters
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An apparatus for detecting variations in light output of an electroluminescent (EL) device is described. The EL device includes a transparent substrate having a first edge extending in a first direction and a plurality of EL emitters disposed over the face of the substrate in the first direction, and some of the light emitted by each EL emitter travels through the substrate and out of the first edge. A light sensor physically separated from the first edge senses the light travelling out of the first edge. A controller stored first sensed light at a first time and second sensed light at a later second time and computes a variation in light output of one or more of the EL emitters in the EL device using the stored first sensed light and second sensed light.