Circadian-friendly LED light sources
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.
1. A method of using a lighting system to emit emitted light having a relatively high illuminance but a relatively low circadian stimulation, said light system having at least one solid-state lighting emitter, and at least a first and second additional light emitters for cooperating with said lighting emitter such that said emitted light is white light, said method comprising:
applying power to said lighting system thereby causing at least said light emitter and said first and second additional light emitters to emit said emitted light, said emitted light being white light having a spectral power distribution (SPD) and a correlated color temperature (CCT), the lighting system being configured to produce an illuminance, and a circadian stimulation no greater than about 50% of a reference circadian stimulation of a CIE CRI reference illuminant at the same CCT, the reference illuminant having a reference SPD and configured to produce a reference illuminance essentially the same as said illuminance, wherein said circadian stimulation is calculated by integrating said SPD multiplied by a circadian action spectrum, said circadian action spectrum being a gaussian function with a peak at 465 nm and a FWHM of 50 nm, and wherein said reference circadian stimulation is calculated by integrating said reference SPD multiplied by said circadian action spectrum.
2. The method of claim 1 , wherein said circadian stimulation is no greater than about 20% of said reference circadian stimulation.
3. The method of claim 1 , wherein the light emitter comprises at least one light-emitting diode or one laser diode emitting having a peak wavelength in a range 400-430 nm, said first additional light emitter has an emission spectrum having a peak between 500 nm and 550 nm, and said second additional light emitter has an emission spectrum having a peak between 600 nm and 670 nm.
4. The method of claim 1 , wherein said lighting system comprises no light emitting species having a peak emission at a wavelength in a range 440-490 nm.
5. The method of claim 1 , wherein the SPD has a local minimum in a spectral region between 440 nm and 480 nm and a power in the SPD between 440 nm and 480 nm is less than 2% of a power of the SPD between 380 nm and 780 nm.
6. The method of claim 1 , wherein said emitted light has a CRI Ra higher than 80 and a CRI R9 higher than 0.
7. The method of claim 1 , wherein said emitted light has a CRI R9 higher than 80.
8. The method of claim 1 , wherein said certain CCT is at least 2700K and a distance from the Planckian locus Duv which is smaller than +/−0.006.
9. The method of claim 1 , wherein the illuminance is a retinal illuminance.
10. The method of claim 1 , wherein said first and second additional light emitters are phosphor light-converting materials.