News Column

Patent Issued for Lighting Device Having First, Second and Third Groups of Solid State Light Emitters, and Lighting Arrangement

May 21, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventor Van de Ven, Antony Paul (Sai Kung, CN), filed on August 4, 2009, was published online on May 6, 2014.

The patent's assignee for patent number 8716952 is Cree, Inc. (Durham, NC).

News editors obtained the following quote from the background information supplied by the inventors: "There is an ongoing effort to develop systems that are more energy-efficient. A large proportion (some estimates are as high as twenty-five percent) of the electricity generated in the United States each year goes to lighting. Accordingly, there is an ongoing need to provide lighting which is more energy-efficient.

"Solid state light emitters (e.g., light emitting diodes) are receiving much attention due to their energy efficiency. It is well-known that incandescent light bulbs are very energy-inefficient light sources--about ninety percent of the electricity they consume is released as heat rather than light. Fluorescent light bulbs are more efficient than incandescent light bulbs (by a factor of about 10) but are still less efficient than solid state light emitters, such as light emitting diodes.

"In addition, as compared to the normal lifetimes of solid state light emitters, e.g., light emitting diodes, incandescent light bulbs have relatively short lifetimes, i.e., typically about 750-1000 hours. In comparison, light emitting diodes, for example, have typical lifetimes between 50,000 and 70,000 hours. Fluorescent bulbs have longer lifetimes (e.g., 10,000-20,000 hours) than incandescent lights, but provide less favorable color reproduction. The impact of the need to replace light emitters is particularly pronounced where access is difficult (e.g., vaulted ceilings, bridges, high buildings, traffic tunnels) and/or where change-out costs are extremely high.

"Color reproduction is typically measured using the Color Rendering Index (CRI Ra). CRI Ra is a modified average of the relative measurements of how the color rendition of an illumination system compares to that of a reference radiator when illuminating eight reference colors, i.e., it is a relative measure of the shift in surface color of an object when lit by a particular lamp. The CRI Ra equals 100 if the color coordinates of a set of test colors being illuminated by the illumination system are the same as the coordinates of the same test colors being irradiated by the reference radiator. Daylight has a high CRI (Ra of approximately 100), with incandescent bulbs also being relatively close (Ra greater than 95), and fluorescent lighting being less accurate (typical Ra of 70-80). Certain types of specialized lighting have very low CRI (e.g., mercury vapor or sodium lamps have Ra as low as about 40 or even lower). Sodium lights are used, e.g., to light highways--driver response time, however, significantly decreases with lower CRI Ra values (for any given brightness, legibility decreases with lower CRI Ra).

"Aspects related to the present inventive subject matter can be represented on either the 1931 CIE (Commission International de I'Eclairage) Chromaticity Diagram or the 1976 CIE Chromaticity Diagram. Persons of skill in the art are familiar with these diagrams, and these diagrams are readily available (e.g., by searching 'CIE Chromaticity Diagram' on the internet).

"The CIE Chromaticity Diagrams map out the human color perception in terms of two CIE parameters x and y (in the case of the 1931 diagram) or u' and v' (in the case of the 1976 diagram). For a technical description of CIE chromaticity diagrams, see, for example, 'Encyclopedia of Physical Science and Technology', vol. 7, 230-231 (Robert A Meyers ed., 1987). The spectral colors are distributed around the edge of the outlined space, which includes all of the hues perceived by the human eye. The boundary line represents maximum saturation for the spectral colors. The 1976 CIE Chromaticity Diagram is similar to the 1931 Diagram, except that the 1976 Diagram has been modified such that similar distances on the Diagram represent similar perceived differences in color.

"In the 1931 Diagram, deviation from a point on the Diagram can be expressed either in terms of the x, y coordinates or, alternatively, in order to give an indication as to the extent of the perceived difference in color, in terms of MacAdam ellipses. For example, a locus of points defined as being ten MacAdam ellipses from a specified hue defined by a particular set of coordinates on the 1931 Diagram consists of hues that would each be perceived as differing from the specified hue to a common extent (and likewise for loci of points defined as being spaced from a particular hue by other quantities of MacAdam ellipses).

"Since similar distances on the 1976 Diagram represent similar perceived differences in color, deviation from a point on the 1976 Diagram can be expressed in terms of the coordinates, u' and v', e.g., distance from the point=(.DELTA.u'.sup.2+.DELTA.v'.sup.2).sup.1/2, and the hues defined by a locus of points which are each a common distance from a specified hue consist of hues which would each be perceived as differing from the specified hue to a common extent.

"A series of points that is commonly represented on the CM Diagrams is referred to as the blackbody locus. The chromaticity coordinates (i.e., color points) that lie along the blackbody locus obey Planck's equation: E(.lamda.)=A .lamda..sup.-5/(e.sup.(B/T)-1), where E is the emission intensity, .lamda. is the emission wavelength, T is the color temperature of the blackbody and A and B are constants. The 1976 CIE Diagram includes temperature listings along the blackbody locus. These temperature listings show the color path of a blackbody radiator that is caused to increase to such temperatures. As a heated object becomes incandescent, it first glows reddish, then yellowish, then white, and finally blueish. This occurs because the wavelength associated with the peak radiation of the blackbody radiator becomes progressively shorter with increased temperature, consistent with the Wien Displacement Law. Illuminants that produce light which is on or near the blackbody locus can thus be described in terms of their color temperature.

"The most common type of general illumination is white light (or near white light), i.e., light that is close to the blackbody locus, e.g., within about ten MacAdam ellipses of the blackbody locus on a 1931 CIE Chromaticity Diagram.

"Because light that is perceived as white is necessarily a blend of light of two or more colors (or wavelengths), no single light emitting diode junction has been developed that can produce white light. The emission spectrum of any particular light emitting diode is typically concentrated around a single wavelength (as dictated by the light emitting diode's composition and structure), which is desirable for some applications, but not desirable for others, (e.g., for providing general illumination, such an emission spectrum provides a very low CRI Ra). 'White' solid state light emitting lamps have been produced by providing devices that mix different colors of light, e.g., by using light emitting diodes that emit light of differing respective colors and/or by converting some or all of the light emitted from the light emitting diodes using luminescent material. For example, as is well known, some lamps (referred to as 'RGB lamps') use red, green and blue light emitting diodes, and other lamps use (1) one or more light emitting diodes that generate blue light and (2) luminescent material (e.g., one or more phosphor materials) that emits yellow light in response to excitation by light emitted by the light emitting diode, whereby the blue light and the yellow light, when mixed, produce light that is perceived as white light. While there is a need for more efficient white lighting, there is in general a need for more efficient lighting in all hues.

"Narendran discloses, in 'Color Rendering Properties of LED Light Sources,' Narendran et al., Lighting Research Center, Rennselear Polytechnic Institute, Troy, N.Y. (2002) discloses RGB lamps that include light emitting diodes that emit light having wavelength of about 465 nm, light emitting diodes that emit light having wavelength of about 525 nm and light emitting diodes that emit light having wavelength of about 640 nm. Narendran also discloses RGB lamps that include light emitting diodes that emit light having wavelength of about 465 nm, light emitting diodes that emit light having wavelength of about 525 nm and light emitting diodes that emit light having wavelength of about 615 nm.

"Although the development of light emitting diodes has in many ways revolutionized the lighting industry, some of the characteristics of light emitting diodes have presented challenges, some of which have not yet been fully met.

"Accordingly, for these and other reasons, efforts have been ongoing to develop ways by which solid state light emitters, which may or may not include luminescent material(s), can be used in place of incandescent lights, fluorescent lights and other light-generating devices in a wide variety of applications. In addition, where light emitting diodes (or other solid state light emitters) are already being used, efforts are ongoing to provide solid state light emitters that are improved, e.g., with respect to energy efficiency, color rendering index (CRI Ra), contrast, efficacy (lm/W), and/or duration of service."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "RGB systems typically have low CRI Ra. RGB for natural objects tends to render poor color discrimination for objects (or portions of objects) that are colored red, green and/or blue (i.e., that reflect in those color ranges), as the increased color saturation of these primary colors in the light tends to overpower slight variations in color, with the result that objects that are colored similarly but slightly different tend to look the same.

"The present inventor recognized that with regard to CRI Ra with neutral white and warm white illumination, the dominant wavelength of the green LED can be a limiting factor on the maximum CRI Ra that can be obtained. Currently, if the green LED emits light having a wavelength of about 525 nm, the maximum CRI Ra that is achievable is about 65. If instead a green LED is employed that emits light having a wavelength of about 550 nm, a CRI Ra of about 85 becomes achievable, and if a green LED is employed that emits light having a wavelength in the range of from about 555 nm to about 565 nm, a CRI Ra of about 90 becomes achievable.

"In addition, the present inventor recognized that while an RGB lamp tends to saturate red, green and blue regions on objects being illuminated at the expense of color accuracy and color subtlety, many objects (especially materials printed in cyan, magenta and yellow), reflect colors that are not very close to the saturated colors of an RGB lamp. Objects that reflect such colors can be illuminated by an RGB lamp with excellent contrast, resulting in all colors being illuminated in a very vibrant and attractive way.

"In accordance with one aspect of the present inventive subject matter, there is provided a lighting device comprising:

"a first group of solid state light emitters;

"a second group of solid state light emitters; and

"a third group of solid state light emitters.

"In some embodiments according to the present inventive subject matter, there is provided a lighting device comprising:

"a first group of solid state light emitters;

"a second group of solid state light emitters; and

"a third group of solid state light emitters,

"the first group of solid state light emitters comprising at least a first solid state light emitter, each solid state light emitter in the first group of solid state light emitters emitting light having a dominant wavelength within a range of from about 430 nm to about 490 nm,

"the second group of solid state light emitters comprising at least a second solid state light emitter, each solid state light emitter in the second group of solid state light emitters emitting light having a dominant wavelength within a range of from about 540 nm to about 575 nm, and

"the third group of solid state light emitters comprising at least a third solid state light emitter, each solid state light emitter in the third group of solid state light emitters emitting light having a dominant wavelength within a range of from about 610 nm to about 640 nm.

"In some embodiments according to the present inventive subject matter, there is provided a lighting device comprising:

"a first group of solid state light emitters;

"a second group of solid state light emitters; and

"a third group of solid state light emitters,

"the first group of solid state light emitters comprising at least a first solid state light emitter, each solid state light emitter in the first group of solid state light emitters emitting light having a dominant wavelength within a range of from about 430 nm to about 490 nm,

"the second group of solid state light emitters comprising at least a second solid state light emitter, each solid state light emitter in the second group of solid state light emitters emitting light having a dominant wavelength within a range of from about 525 nm to about 575 nm, and

"the third group of solid state light emitters comprising at least a third solid state light emitter, each solid state light emitter in the third group of solid state light emitters emitting light having a dominant wavelength within a range of from about 610 nm to about 640 nm,

"each solid state light emitter in the first group of solid state light emitters having a dominant wavelength that differs from a dominant wavelength of each solid state light emitter in the second group of solid state light emitters by at least 70 nm,

"each solid state light emitter in the second group of solid state light emitters having a dominant wavelength that differs from a dominant wavelength of each solid state light emitter in the third group of solid state light emitters by at least 70 nm.

"In some embodiments according to the present inventive subject matter, there is provided a lighting arrangement comprising:

"a first group of solid state light emitters;

"a second group of solid state light emitters;

"a third group of solid state light emitters;

"at least a fourth solid state light emitter; and

"at least one item to be illuminated,

"the first group of solid state light emitters comprising at least a first solid state light emitter, each solid state light emitter in the first group of solid state light emitters emitting light having a dominant wavelength within a range of from about 430 nm to about 490 nm,

"the second group of solid state light emitters comprising at least a second solid state light emitter, each solid state light emitter in the second group of solid state light emitters emitting light having a dominant wavelength within a range of from about 525 nm to about 575 nm, and

"the third group of solid state light emitters comprising at least a third solid state light emitter, each solid state light emitter in the third group of solid state light emitters emitting light having a dominant wavelength within a range of from about 610 nm to about 640 nm,

"the fourth solid state light emitter emitting light that has a dominant wavelength that is outside each of the ranges of wavelength for the first, second and third groups of solid state light emitters, and not more than 10 nm different from a dominant wavelength of at least one color on the item to be illuminated.

"In some embodiments according to the present inventive subject matter, there is provided a lighting device comprising:

"a first group of solid state light emitters;

"a second group of solid state light emitters; and

"a third group of solid state light emitters,

"the first group of solid state light emitters comprising at least a first solid state light emitter, each solid state light emitter in the first group of solid state light emitters emitting light having a dominant wavelength within a range of from about 430 nm to about 490 nm,

"the second group of solid state light emitters comprising at least a second solid state light emitter, each solid state light emitter in the second group of solid state light emitters emitting light having a dominant wavelength within a range of from about 525 nm to about 575 nm, and

"the third group of solid state light emitters comprising at least a third solid state light emitter, each solid state light emitter in the third group of solid state light emitters emitting light having a dominant wavelength within a range of from about 610 nm to about 640 nm,

"the lighting device emitting light having a CRI Ra of at least about 70 when at least the first group of solid state light emitters, the second group of solid state light emitters and the third group of solid state light emitters are illuminated.

"In some embodiments according to the present inventive subject matter, including some embodiments that include or do not include any of the features as discussed above, a combination of light emitted by the first group of solid state light emitters, the second group of solid state light emitters and the third group of solid state light emitters is within ten MacAdam ellipses of at least one point on the blackbody locus.

"In some embodiments according to the present inventive subject matter, including some embodiments that include or do not include any of the features as discussed above, light exiting the lighting device is within ten MacAdam ellipses of at least one point on the blackbody locus.

"In some embodiments according to the present inventive subject matter, including some embodiments that include or do not include any of the features as discussed above, the first group of solid state light emitters, the second group of solid state light emitters and the third group of solid state light emitters comprise all of the light emitters in the lighting device.

"In some embodiments according to the present inventive subject matter, including some embodiments that include or do not include any of the features as discussed above, the lighting device further comprises:

"at least a fourth solid state light emitter that emits light that has a dominant wavelength that is outside each of the ranges of wavelength for the first, second and third groups of solid state light emitters, and

"a controller configured to adjust the intensity of light emitted by at least one solid state light emitter selected from among the first group of solid state light emitters, the second group of solid state light emitters, the third group of solid state light emitters and the fourth solid state light emitter, to maintain light emitted by the lighting device within ten MacAdam ellipses of at least one point on the blackbody locus.

"In some embodiments according to the present inventive subject matter, including some embodiments that include or do not include any of the features as discussed above, the lighting device further comprises a controller configured to adjust the intensity of light emitted by at least one solid state light emitter selected from among the first group of solid state light emitters, the second group of solid state light emitters, the third group of solid state light emitters and the fourth solid state light emitter (if provided), to maintain light emitted by the lighting device within ten MacAdam ellipses of at least one point on the blackbody locus.

"In some embodiments according to the present inventive subject matter, including some embodiments that include or do not include any of the features as discussed above, the at least one item to be illuminated (if provided) is printed matter and/or signage.

"The inventive subject matter may be more fully understood with reference to the accompanying drawings and the following detailed description of the inventive subject matter."

For additional information on this patent, see: Van de Ven, Antony Paul. Lighting Device Having First, Second and Third Groups of Solid State Light Emitters, and Lighting Arrangement. U.S. Patent Number 8716952, filed August 4, 2009, and published online on May 6, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=71&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3523&f=G&l=50&co1=AND&d=PTXT&s1=20140506.PD.&OS=ISD/20140506&RS=ISD/20140506

Keywords for this news article include: Cree Inc., Light Bulb, Electronics, Light-emitting Diode.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters