LED Temperature Sensing via Dual Optical Filters
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Solution Overview
Problem
Light Emitting Diodes (LEDs) exhibit significant spectral output variations with temperature, making them inconsistent for applications requiring predictable light sources, and existing methods to control these variations add complexity and expense without ensuring adequate consistency.
Innovation Solution
A system comprising a light emitting diode (LED) with a pair of optical filters and sensors to measure intensity changes through these filters, allowing a computer to derive the LED's temperature and thereby predict its spectral output, using models based on physics and experimental characterizations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LED current and voltage are varied to control spectral output variation, then spectral consistency is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs feedback by measuring the actual spectral output of the LED and using this information to adjust the drive current. A photodetector monitors the LED output, and the measured signal is fed back to a control circuit that adjusts the current to maintain consistent spectral characteristics, thereby resolving the contradiction between spectral consistency and control complexity.
Solution Approach 2:
The patent replaces complex mechanical or electronic control systems with a simpler optical feedback mechanism. Instead of using sophisticated voltage/current regulation circuits, the invention uses optical measurement and feedback to achieve spectral control, reducing device complexity while maintaining spectral consistency.
2Reliability
If LED current and voltage are varied to control spectral output variation, then spectral consistency is improved, but cost increases
Solution Approach 1:
The patent uses inexpensive photodetectors and simple control circuits instead of expensive precision voltage/current regulation systems. The feedback mechanism employs readily available off-the-shelf components, significantly reducing manufacturing cost while achieving the desired spectral consistency through intelligent control rather than expensive hardware.
Solution Approach 2:
The patent changes the control parameter from voltage to current, and further to optical power feedback. By controlling the LED based on optical output measurement rather than electrical input parameters, the system achieves better spectral consistency with simpler, cheaper components, as optical feedback directly correlates with spectral output.
3Reliability
If LED heating is applied prior to use to control spectral variation, then spectral consistency is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent implements periodic measurement and adjustment cycles rather than continuous heating. The LED spectral output is measured at intervals, and current adjustments are made only when necessary to correct spectral drift. This periodic feedback control eliminates the need for continuous energy-consuming heating while maintaining spectral consistency.
Solution Approach 2:
The patent substitutes thermal management (heating) with electrical feedback control. Instead of using thermal energy to pre-condition the LED and compensate for spectral shifts, the system uses electrical current adjustment based on optical feedback, which is more energy-efficient and provides dynamic adaptation to spectral changes.
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 method provides a reliable and cost-effective means to sense and stabilize LED temperature, ensuring consistent spectral output and reducing complexity in optical measurement systems and other applications.
Implementation Method 1
a first filter that transitions from attenuation to transmission at about the first wavelength, and a second filter that transitions from transmission to attenuation at about the first wavelength
Implementation Method 2
a first sensor positioned to sense a first intensity of the LED through the first filter and a second sensor positioned to sense a second intensity of the LED through the second filter
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A system (100) for sensing a temperature of a light emitting diode (LED). The system may comprise an LED having a spectral output centered at a first wavelength, a first filter (104) that transitions from attenuation to transmission at about the first wavelength, and a second filter (106) that transitions from transmission to attenuation at about the first wavelength. The system may also comprise a first sensor (108) positioned to sense a first intensity of the LED through the first filter and a second sensor (110) positioned to sense a second intensity of the LED through the second filter. It will be appreciated that a single sensor may be substituted instead of the first and second sensors, provided that the single sensor is capable of selectively viewing the LED through the first and the second filters. The system may also comprise a computer (112) configured to derive a temperature of the LED considering the first intensity and the second intensity.