Tunable LED Spectra for Circadian-Friendly Lighting and High CRI
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Solution Overview
Problem
Existing LED-based illumination products provide excessive circadian stimulation, leading to potential health issues, and lack tunability and effective color rendering across varying light levels, failing to mimic natural light cycles.
Innovation Solution
Designing LED light sources with tunable emission spectra that vary from high to low circadian stimulation while maintaining color rendering index (CRI) above 80 and correlated color temperature (CCT) within a prescribed range, using combinations of LED emission sources and wavelength conversion materials to simulate natural light cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blue-primary phosphor-converted white-emitting LEDs are used, then LED illumination efficiency and brightness are improved, but circadian stimulation becomes excessive leading to health issues
Solution Approach 1:
The patent segments the LED illumination system into multiple independent LED types (first LEDs with peak wavelength 480-530nm, second LEDs with peak wavelength 560-630nm, and optionally third LEDs with peak wavelength 670-750nm). This segmentation allows independent control of each LED type's emission, enabling selective suppression of blue light (440-480nm) that causes excessive circadian stimulation while maintaining overall brightness through contributions from green, yellow-green, and red LEDs.
Solution Approach 2:
The patent applies local quality by assigning different spectral characteristics to different parts of the illumination system. Specifically, the first LEDs (480-530nm peak) provide green light with moderate circadian stimulation, the second LEDs (560-630nm peak) provide yellow-green to red light with low circadian stimulation, and the third LEDs (670-750nm peak) provide deep red light with minimal circadian stimulation. This local spectral differentiation allows the overall system to maintain brightness while reducing harmful blue light content.
2Adaptability or versatility
If illumination products are made tunable, then adaptability to different lighting conditions is improved, but color rendering index deteriorates across the tunable range
Solution Approach 1:
The patent implements dynamics by enabling continuous tuning of the illumination spectrum through independent control of multiple LED types. The relative intensities of first LEDs (480-530nm), second LEDs (560-630nm), and third LEDs (670-750nm) can be dynamically adjusted to achieve different color temperatures and circadian stimulation levels while maintaining CRI≥80. This dynamic control allows adaptation to various lighting conditions (morning, afternoon, evening) without sacrificing color rendering quality.
Solution Approach 2:
The patent uses a composite approach by combining multiple LED types with different spectral characteristics into a single illumination system. The combination of first LEDs (480-530nm peak), second LEDs (560-630nm peak), and third LEDs (670-750nm peak) creates a composite light source that can be tuned across a wide range while maintaining high color rendering. The composite nature of the system allows flexible spectral composition to meet both tunability and CRI requirements.
3Reliability
If blue light content is increased for circadian stimulation, then alertness and cognitive performance are improved, but health risks increase during evening hours
Solution Approach 1:
The patent applies periodic action by enabling time-dependent control of the illumination spectrum. The system can provide high circadian stimulation (including blue light from first LEDs at 480-530nm) during morning and daytime hours to enhance alertness and cognitive performance, then automatically reduce blue light content and shift to predominant yellow-green (second LEDs at 560-630nm) and red (third LEDs at 670-750nm) wavelengths during evening hours to eliminate health risks associated with late-night blue light exposure. This periodic spectral adjustment aligns with natural circadian rhythms.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the spectral composition parameters (peak wavelengths and intensities) of the LED system. During daytime, the system can operate with higher intensity from first LEDs (480-530nm peak) to provide alertness-enhancing blue-green light. During evening hours, the control system modifies the parameters to reduce first LED intensity and increase second LED (560-630nm) and third LED (670-750nm) intensity, thereby changing the spectral parameters to eliminate harmful blue light while maintaining acceptable illumination levels.
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
The solution effectively modulates circadian stimulation, reducing health risks and maintaining desirable light quality, achieving low circadian impact during evening hours and high alertness during the day.
Implementation Method 1
light sources comprising at least one first LED emission source characterized by a first emission, and at least one second LED emission source characterized by a second emission
Implementation Method 2
using combinations of LED emission sources and wavelength conversion materials to simulate natural light cycles
Data Source
AI summary
Methods and apparatus for providing circadian-friendly LED light sources are disclosed. A light source is formed to include a first LED emission (e.g., one or more LEDs emitting a first spectrum) and a second LED emission (e.g., one or more LEDs emitting a second spectrum) wherein the first and second LED emissions are combined in a first ratio and in a second ratio such that while changing from the first ratio to the second ratio the relative circadian stimulation is varied while maintaining a color rendering index above 80.