Lighting system having reduced melanopic spectral content
A disclosed light-emitting device may provide white light with a cyan gap coinciding with a melanopic sensitivity range and thus having reduced melanopic content. The disclosed light-emitting device may include a light source providing violet or blue light with a peak wavelength under 450 nanometers (nm). The disclosed light-emitting device may include at least one down-converter coupled to and located downstream of the light source and configured with a long-wavelength onset to convert the spectrum of the violet or blue light to generate white light with a spectral power content in a 447-531 nm wavelength range that is less than or equal to 10% of a total spectral power content in a 380-780 nm wavelength range. The disclosed light-emitting device may be incorporated in a light engine system that further includes a control system that controls a drive current to the light-emitting device.
1. A light-emitting device configured to provide white light with a cyan gap coinciding with a melanopic sensitivity range, the light-emitting device comprising:
a light source configured to emit violet or blue light with an emission spectrum having peak wavelength under 450 nm; and
at least one wavelength converter coupled to and located downstream of the light source and configured to absorb at least a portion of violet or blue light emitted by the light source and in response emit light with an emission spectrum at wavelengths longer than those in the light source emission spectrum;
an unabsorbed portion of the violet or blue light emitted by the light source and transmitted through the wavelength converter combined with the emission from the wavelength converter providing a white light emission spectrum from the light emitting device, the white light emission spectrum having a correlated color temperature greater than or equal to 2700 K, comprising a spectral gap in a 447 nm-531 nm wavelength range defined by a long wavelength side of the light source emission spectrum and a short wavelength side of the wavelength converter emission spectrum, and having a spectral power content in the 447-531 nm wavelength range that is less than or equal to 10% of a total spectral power content in a 380 nm-780 nm wavelength range, and a spectral power density value at 447 nm that is greater than a spectral power density value at 500 nm, and the white light emission spectrum having a luminous efficacy of radiation greater than 380 lumens per Watt.
2. The light emitting device of claim 1 , wherein the white light emission spectrum has a spectral power content in the 447-531 nm wavelength range that is less than or equal to 5% of a total spectral power content in a 380 nm-780 nm wavelength range.
3. The light emitting device of claim 1 , wherein the white light emission has a spectral power content between 447 nm and 470 nm greater than a spectral power content of the white light emission between 470 nm and 510 nm.
4. The light emitting device of claim 1 , wherein the white light emission has a spectral power content between 380 nm and 447 nm that is less than a spectral power content between 531 nm and 630 nm.
5. The light emitting device of claim 1 , wherein the light source is configured to emit light with an emission spectrum having peak wavelength less than or equal to 440 nm.
6. The light emitting device of claim 1 , wherein:
the white light emission has a minimum spectral power density value at a wavelength between 480 nm and 490 nm.
7. The light emitting device of claim 1 , wherein the wavelength converter is configured to absorb at least a portion of violet or blue light emitted by the light source and in response emit light with an emission spectrum having a peak in the amber wavelength range and extending into the red wavelength range.
8. The light emitting device of claim 7 , wherein the wavelength converter comprises a nitride-based phosphor.
9. The light emitting device of claim 8 , wherein the a nitride-based phosphor comprises one or more of (Ba,Sr) 2 Si 5 N 8 :Eu, (Sr,Ca)SiAlN 3 :Eu, or (Ba,Sr) 2 Si 5 N 8 :Eu and (Sr,Ca)SiAlN 3 :Eu.
10. The light emitting device of claim 7 , wherein a short wavelength side of the peak in the amber wavelength range forms a long wavelength side of the spectral gap.
11. The light emitting device of claim 1 , wherein the wavelength converter comprises quantum dots configured to absorb at least a portion of the violet or blue light emitted by the light source and in response emit light with an emission spectrum at wavelengths longer than those in the light source emission spectrum.
12. The light emitting device of claim 1 , wherein the light source is a light emitting diode or laser diode.
13. The light emitting device of claim 1 , wherein the wavelength converter is in contact with a light emitting surface of the light source.
14. The light emitting device of claim 13 , wherein the wavelength converter comprises a ceramic plate attached to the light emitting surface of the light source.
15. The light emitting device of claim 1 , wherein the wavelength converter is located at a non-zero distance from a light emitting surface of the light source.
16. A light engine configured to provide white light with tunable spectral content in a range coinciding with a melanopic sensitivity range, the light engine comprising:
a plurality of the light-emitting devices of claim 1 ; and
a control system configured to control drive current to the plurality of light-emitting devices.
17. The light emitting device of claim 16 , wherein the white light emission spectrum of the light-emitting devices has a spectral power content in the 447-531 nm wavelength range that is less than or equal to 5% of a total spectral power content in a 380 nm-780 nm wavelength range.
18. The light emitting device of claim 1 , wherein the violet or blue light has an emission spectrum having peak wavelength greater than 430 nm.
19. The light emitting device of claim 1 , wherein the white light emission spectrum has a first long wavelength peak between 530 nm and 580 nm, a second long wavelength peak between 580 nm and 630 nm, and essentially zero spectral content above wavelength of 690 nm.
20. A light-emitting device comprising:
a light source configured to emit violet or blue light with an emission spectrum having peak wavelength under 450 nm; and
at least one wavelength converter coupled to and located downstream of the light source and configured to absorb at least a portion of violet or blue light emitted by the light source and in response emit light with an emission spectrum at wavelengths longer than those in the light source emission spectrum;
the light source and the at least one wavelength converter configured to emit a white light emission spectrum comprising an unabsorbed portion of the violet or blue light emitted by the light source and transmitted through the wavelength converter combined with the emission from the wavelength converter, the white light emission spectrum having a correlated color temperature greater than or equal to 2700 K, a luminous efficacy of radiation greater than 380 lumens per watt, and comprising a spectrum in a 380 nm 780 nm range having a spectral gap in the 447 nm 531 nm range, with a spectral power content in the spectral gap that is less than or equal to 10% of a total spectral power content over the spectrum in the 380 nm-780 nm range.