Electronic flash, imaging device and method for producing a flash of light having a wavelength spectrum in the visible range and the infrared range using a fluorescent material
View Patent ↗An electronic flash, imaging device and method for producing a flash of light having a wavelength spectrum in the visible wavelength range and the infrared wavelength range uses a fluorescent material to convert at least some of the original light emitted from one or more light sources of the electronic flash to longer wavelength light to produce the flash of light. The light sources may be configured to generate light having a peak wavelength in an ultraviolet-and-visible wavelength range. The fluorescent material may include any combination of red, green, blue and yellow phosphors.
1. An electronic flash for use in visible light and/or infrared (IR) applications, said electronic flash comprising:
a light source configured to generate original light comprising at least a portion of the visible wavelength spectrum and at least a portion of the ultraviolet wavelength spectrum; and
a wavelength-shifting region optically coupled to said light source to receive said original light, said wavelength-shifting region including a fluorescent material having a wavelength- converting property to convert at least some of said original light to output light encompassing a first wavelength range in the visible wavelength spectrum and a second wavelength range in the infrared wavelength spectrum.
2. The electronic flash of claim 1 wherein said light source includes a light emitting diode (LED) in which is housed a first LED die for emitting light in the at least a portion of the visible wavelength spectrum, and a second LED die for emitting light in the at least a portion of the ultraviolet wavelength spectrum.
3. The electronic flash of claim 2 , wherein the first LED die is configured for emitting light in the at least a portion of the visible wavelength spectrum over a first period of time, and the second LED die is configured for emitting light in the at least a portion of the ultraviolet wavelength spectrum over a second period of time that is different than the first period of time.
4. The electronic flash of claim 2 , wherein the first LED die is configured to emit light at a first amplitude, and the second LED die is configured to emit light at a second amplitude that is different than the first amplitude.
5. The electronic flash of claim 1 , wherein a blue LED is configured to generate the at least a portion of the visible wavelength spectrum, an ultraviolet (UV) LED is configured to generate the at least a portion of the ultraviolet wavelength spectrum, and wherein the fluorescent material is selected to convert the original light emitted by the light source into output light ranging from about 400 nm in the visible wavelength spectrum to about 950 nm in the IR wavelength spectrum.
6. The electronic flash of claim 5 , wherein the fluorescent material is a hybrid phosphor containing a red phosphor and at least one of a) a green phosphor and b) a yellow phosphor.
7. The electronic flash of claim 6 , wherein the red phosphor comprises at least one of a) CAS:Eu 2+ , b) Mn 2+ , c) SrS:Eu 2+ , d) (Zn, Cd)S:Ag, e) Mg 4 GeO 5.5 F:MN 4+ , f) ZnSe:Cu, and g) ZnSeS:Cu,Cl.
8. The electronic flash of claim 6 , wherein the green phosphor comprises at least one of a) SrGa 2 S 4 :Eu 2+ , b) YAG:Ce 3+ , and c) BaSrGa 4 S 7 :Eu.
9. The electronic flash of claim 6 , wherein the yellow phosphor comprises at least one of a) YAG:Ce, b) TAG:Ce, and c) YAG:Ce, Pr.
10. The electronic flash of claim 1 , wherein a red LED is configured to generate the at least a portion of the visible wavelength spectrum, an ultraviolet (UV) LED is configured to generate the at least a portion of the ultraviolet wavelength spectrum, and wherein the fluorescent material is selected to convert the original light emitted by the light source into output light ranging from about 600 nm in the visible wavelength spectrum to about 1500 nm in the IR wavelength spectrum.
11. The electronic flash of claim 10 , wherein the fluorescent material is a red phosphor.
12. The electronic flash of claim 1 , wherein a ultraviolet (UV) LED is configured to generate the at least a portion of the ultraviolet wavelength spectrum, and wherein the fluorescent material is selected to convert the original light emitted by the light source into output light ranging from about 400 nm in the visible wavelength spectrum to about 800 nm in the IR wavelength spectrum.
13. The electronic flash of claim 12 , wherein the fluorescent material is a hybrid phosphor containing a red phosphor, a blue phosphor, and at least one of a) a green phosphor and b) a yellow phosphor.
14. The electronic flash of claim 13 , wherein the blue phosphor comprises BaMg 2 Al 16 O 27 :Eu.
15. The electronic flash of claim 1 , wherein the light source is configured to generate the at least a portion of the visible wavelength spectrum substantially concuffent with the at least a portion of the ultraviolet wavelength spectrum, whereby the first wavelength range in the visible wavelength spectrum and the second wavelength range in the infrared wavelength spectrum are output substantially concuffently from the electronic flash.
16. A method for producing a flash of light containing visible light as well as infrared light, said method comprising:
generating original light comprising at least a portion of the visible wavelength spectrum and at least a portion of the ultraviolet wavelength spectrum;
converting at least some of said original light into converted light by fluorescence; and
emitting said converted light as a component of said flash of light, said flash of light having a wavelength range spanning at least a portion of the visible wavelength spectrum and at least a portion of the infrared wavelength spectrum.
17. The method of claim 16 wherein converting said original light by fluorescence comprises wavelength shifting the at least a portion of the ultraviolet wavelength spectrum to a wavelength in the infrared spectrum.
18. The method of claim 17 wherein said converting comprises using at least one of a fluorescent organic dye, an inorganic phosphor, a hybrid phosphor or a nano-phosphor.
19. A light emitting diode (LED) for dual-purpose use in visible light and/or infrared (IR) applications, the LED comprising:
a first light emitting die for emitting light in at least a portion of the visible wavelength spectrum; and
a second light emitting die for emitting light in at least a portion of the ultraviolet wavelength spectrum; the first and second light emitting dies configured for simultaneously emitting a combination light that encompasses at least a portion of the visible wavelength spectrum and a portion of the ultraviolet wavelength spectrum.
20. The LED of claim 19 , further comprising a fluorescent material having a wavelength-converting property to convert the combination light emitted by the first and second light emitting dies to output light encompassing a first wavelength range in the visible wavelength spectrum and a second wavelength range in the infrared wavelength-spectrum.
21. The LED of claim 20 , further comprising a leadframe on which at least one of the first and the second light emitting dies is mounted.
22. The LED of claim 21 , wherein the leadframe comprises a depressed region for mounting the at least one of the first and the second light emitting dies.
23. The LED of claim 22 , wherein the depressed region is configured as a reflector cup.