Light source with UV LED and UV reflector
A lighting source capable of producing white light using a semiconductor radiation source. The semiconductor radiation source may be an ultraviolet (“UV”) light emitting diode (“LED”) device that emits light at a short wavelength, e.g., near-violet or ultraviolet light. A thin film of phosphor may be deposited or coated on the surface of the UV LED or positioned directly above the UV LED. The lighting source may also include an UV reflector radiationally coupled to the thin phosphor layer that allows visible white light emitted from the thin phosphor to pass through and reflects shorter wavelength light back to the thin phosphor layer.
1 . A lighting source capable of emitting visible light, the lighting source comprising:
a semiconductor radiation source;
a phosphor layer positioned above the surface of the semiconductor radiation source that emits light when excited with radiation from the semiconductor radiation source that is absorbed by the phosphor layer; and
an ultraviolet (“UV”) reflector configured to reflect that portion of the radiation from the semiconductor radiation source that is not absorbed by the thin phosphor layer back to the thin phosphor layer.
2 . The lighting source of claim 1 , wherein the semiconductor radiation source is a UV light-emitting diode (“LED”) capable of emitting a UV light.
3 . The lighting source of claim 2 , wherein the phosphor layer is a thin layer of a phosphor applied directly to the surface of the UV LED.
4 . The lighting source of claim 3 , wherein the thin phosphor layer contains one or more phosphors that emit visible light when excited by UV light emitted by the UV LED.
5 . The lighting source of claim 4 , wherein the phosphor layer comprises a single yellow phosphor that emits white light when excited by UV light.
6 . The lighting source of claim 4 , wherein the phosphor layer comprises a phosphor system selected from the group consisting of garnet-based, silicate-based, oxynitrate-based, nitride-based, sulphide-based, orthosilicate-based, and aluminates and selenide-based phosphor systems.
7 . The lighting source of claim 3 , wherein the UV reflector is configured to reflect light received from the thin phosphor layer having a wavelength less than a predetermined amount back to the thin phosphor layer, and to allow light with a greater wavelength to pass through the UV reflector.
8 . The light source of claim 7 , wherein the predetermined amount has a value in a range of about 380 to 410 nanometers (“nm”).
9 . The light source of claim 2 , wherein the phosphor layer includes a transparent encapsulant in which are suspended one or more phosphors, with the transparent encapsulant being coated upon the surface of the semiconductor radiation source.
10 . The light source of claim 9 , wherein the transparent encapsulant is a transparent epoxy or silicone system.
11 . A method for producing visible light utilizing a semiconductor radiation source and a UV reflector, the method comprising:
emitting light from the semiconductor radiation source;
converting the emitted light to a converted light by exciting a phosphor layer with the emitted light, wherein the converted light has a wavelength that is different from that of the emitted light; and
filtering the converted light through the UV filter.
12 . The method of claim 11 , wherein the step of filtering the converted light further includes:
reflecting light with a wavelength less than a predetermined length back to the phosphor layer; and
allowing light with a wavelength greater than the predetermined length to pass through the UV filter.
13 . The method of claim 12 , further including:
converting the emitted light reflected from the UV filter to a secondarily converted light by exciting the phosphor layer with the reflected light, wherein the secondarily converted light has a wavelength that is different from that of the reflected light; and
re-filtering the secondarily converted light through the UV filter.
14 . The method of claim 13 , wherein the semiconductor radiation source is a UV LED.
15 . The method of claim 12 , wherein the phosphor layer contains one or more phosphors that emit visible light when excited by UV light emitted by the UV LED.
16 . The method of claim 15 , wherein the phosphor layer comprises a single yellow phosphor that emits white light when excited by UV light.
17 . The method of claim 15 , wherein the phosphor layer comprises a phosphor system selected from the group consisting of garnet-based, silicate-based, oxynitrate-based, nitride-based, sulphide-based, orthosilicate-based, and aluminates and selenide-based phosphor systems.
18 . The method of claim 12 , wherein the predetermined amount has a value in a range of about 380 to 410 nanometers (“nm”).
19 . The method of claim 1 1 , wherein the phosphor layer includes a transparent encapsulant in which are suspended one or more phosphors, with the transparent encapsulant being coated upon the surface of the semiconductor radiation source.
20 . The method of claim 19 , wherein the transparent encapsulant is a transparent epoxy or silicone system.