White light apparatus with enhanced color contrast

Inactive Publication Date: 2007-10-18
LUMINATION
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0014] In a first aspect, there is provided a lighting apparatus for emitting white light having enhanced red-green color contrast, including a light source emitting radiation with a peak in the range of from about 250 nm to about 500 nm; a phosphor material having a peak emission between 550 and 615 nm; and a filter that prevents a portion of radiation emitted by the phosphor material from being emitted by the apparatus while substantially permitting the emission of radiation from the lighting apparatus in emission wavelengths other than between 550 and 615 nm.
[0015] In a second aspect, there is provided a method for making a lighting apparatus for emitting white light having enhanced red-green color contrast, the method including the steps of providing a light source emitting radiation having a peak emission at from about 250 to 500 nm; providing a phosphor material having a peak emission between 550 and 615 nm radiationally coupled to the light source; and providing a filter that prevents a portion of radiation emitted by the phosphor material from being emitted by the apparatus while substantially permitting the emission of radiation from the lighting apparatus in emission wavelengths other than between 550 and 615 nm.

Problems solved by technology

Until quite recently, LEDs have not been suitable for lighting uses where a bright white light is needed, due to the inherent color of the light produced by the LED.
Incandescent lamps are known to generate a considerable amount of light in the yellow region of the spectrum, leading to “washing out” of the colors of objects illuminated by them.
This deficiency leads to increased red-green color contrast when objects are viewed under this lamp, in comparison to a regular incandescent bulb.
This however reduces the red-green color contrast for test samples of different colors.
Despite the high inherent efficiency, a problem with this solution is its complexity, stemming from the need to use red and green phosphors with sufficient wavelength separation to create the requisite depression in the yellow region, plus an optional variable amount of yellow phosphor to modulate the red-green color contrast enhancement and trade off the latter effect against the loss in luminous efficacy.

Method used

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  • White light apparatus with enhanced color contrast
  • White light apparatus with enhanced color contrast
  • White light apparatus with enhanced color contrast

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[0106] Various LED based light devices based on violet chip with emission maximum near 405 nm and using phosphor blends according to the above embodiments were investigated and compared to identical light sources also including a Nd glass filter of average thickness 1 mm and containing 7.5% Nd2O3 by weight. A summary of photometric characteristics (luminous flux Iv, 1931 CIE coordinates x and y, CCT and CRI values) of these devices is shown in Table 1. The yellow phosphor used in LED samples 1 through 10 was an alkali earth silicate doped with Eu(II) and corresponding to the formula Sr1.66Ca0.30Eu0.04Si0.96O3.92. The blue and green phosphors (Ca,Sr,Ba)5(PO4)3Cl:Eu2+, (Ba0.65Sr0.20Ca0.10Eu0.05)2SiO4 and Sr4Al14O25:Eu2+also used, as needed to achieve the requisite CCTs ranging from 2500 to 7500K prior to filtration. In addition, sample #7 contained a deep red line emitting phosphor (3.5 MgO*0.5 MgF2*GeO2:Mn4+) whereas samples #4-#6 and #8-#10 contained a deep red broadband phosphor (C...

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Abstract

A lighting apparatus for emitting white light including a semiconductor light source emitting radiation with a peak emission between from about 250 nm to about 500 nm and a first phosphor having a peak emission between about 550 and 615 nm, wherein an overall emission spectrum of the lighting apparatus has a depression between about 550 and 615 nm, whereby the red-green color contrast is increased versus a reference illuminant.

Description

[0001] This application is a continuation-in-part of commonly assigned U.S. patent application Ser. No. 11 / 285,122, filed on Nov. 22, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10 / 909,564, filed on Aug. 2, 2004, and claims the benefit of the priority date thereof.BACKGROUND OF THE INVENTION [0002] The present exemplary embodiments relate to lighting devices incorporating one or more phosphors for the conversion of radiation emitted by a light source. They find particular application in conjunction with converting LED-generated ultraviolet (UV), violet or blue radiation into white light for general illumination purposes. It should be appreciated, however, that the invention is also applicable to the conversion of radiation in other applications, such as Hg-based fluorescent lamps, mercury-free gas discharge lamps, metal halide lamps, UV, violet and / or blue lasers, as well as other white light sources for different applications. [0003] Light emitting dio...

Claims

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Application Information

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IPC IPC(8): H01J1/62H01J9/24H01L33/44H01L33/50
CPCC09K11/0883C09K11/665H01L2224/48247C09K11/7731C09K11/7734C09K11/7736C09K11/7738C09K11/7739C09K11/774C09K11/7766C09K11/778C09K11/7786C09K11/7787C09K11/7789C09K11/7794H01L33/44H01L33/507Y02B20/181F21K9/56H01L33/502H01L2224/48091H01L2924/00014H01L2924/12044F21K9/64Y02B20/00C09K11/77342H01L2924/00
InventorRADKOV, EMIL VERGILOVHAUSMANN, ILONA ELISABETHGOODIN, MARISA L.PUBLICOVER, DEREK ALLEN
OwnerLUMINATION