|Publication number||USRE41685 E1|
|Application number||US 11/788,399|
|Publication date||Sep 14, 2010|
|Priority date||Dec 28, 1999|
|Also published as||EP1240674A1, US6666567, WO2001047037A1|
|Publication number||11788399, 788399, US RE41685 E1, US RE41685E1, US-E1-RE41685, USRE41685 E1, USRE41685E1|
|Inventors||Alan Stuart Feldman, Brian David Cull, Dennis Michael Davey|
|Original Assignee||Honeywell International, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (54), Referenced by (22), Classifications (27), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 6,666,567. The reissue applications are application Ser. No. 11/788,399 (the present application), Ser. No. 11/788,398 (filed concurrently herewith), and Ser. No. 11/316,597, all of which are divisional reissues of U.S. Pat. No. 6,666,567.
1. Technical Field
The present invention generally relates to lighting systems, and more particularly, to light sources implementing light emitting diodes (LEDs).
Many industries and applications need backlighting to illuminate an information source. In particular, transmissive liquid crystal displays (LCDs) have become very popular in many electronic media. LCDs are useful in applications such as, but not limited to, displays in avionics, laptop computers, video cameras, and automatic teller machine displays. However, many LCDs require backlighting to illuminate the information being displayed.
Many systems perform the backlighting function in conventional displays. For example, one way to backlight an information source employs an array of conventional straight tubular fluorescent lamps. While these conventional lamps are inexpensive and do not require complex electronic controls, they are sometimes inadequate for particular applications. For instance, in avionics applications, the poor color quality of the phosphors and the short lamp life of these conventional lamps, among other shortcomings, limit their usefulness.
To avoid the various problems with conventional lamps, many manufacturers employ customized lamps, such as tubular serpentine lamps. Unlike conventional fluorescent lamp arrays, custom-made serpentine lamps commonly provide good color characteristics, light luminance uniformity, and long lamp life. These lamps are typically hand made, and consequently, are comparatively costly. Moreover, these lamps. are extremely fragile and difficult to install. Therefore, while custom-made tubular serpentine lamps may meet certain standards for the backlighting function, the high cost and fragility associated with these lamps detract from the advantages they offer.
A third alternative for backlighting information sources is flat fluorescent lamps. An exemplary flat fluorescent lamp, described in U.S. Pat. No. 5,343,116, issued Aug. 30, 1994, to Winsor, comprises a substrate fritted to a transparent cover lid, forming an enclosure. Diffuse channels are formed into the substrate in the interior of the enclosure. Standard phosphors are added to the interior of the enclosure which is further flushed with a material for emitting energy, such as argon or mercury. Energy is emitted in the form of visible light when an electric potential is introduced to the lamp by two electrodes, with one electrode placed at each end of the diffuse channel. Such lamps potentially offer greater ruggedness and lower manufacturing costs than serpentine tubular lamp alternatives. However, these lamps are still costly to manufacture and are difficult to repair.
Yet another alternative for backlighting information sources implements LEDs. The use of LEDs as light sources can be advantageous for several reasons. LEDs have a long life, which reduces the frequency for replacing non-functioning diodes. Further, when it is time to replace an LED, replacement is easier and more cost effective than when replacing a fluorescent light source. Additionally, LEDs are mechanically robust, i.e., they can typically withstand greater shocks and vibration than conventional fluorescent lights. Referring now to
As shown in
Conventional LED lighting systems, however, fail to perform adequately for many backlighting applications, such as avionics, in which strict display performance requirements restrict their use. For example, LEDs typically use power less efficiently than conventional fluorescent lamps to produce comparable light intensity. Further, a conventional fluorescent lamp relies on phosphors which have narrowly defined spectral emission peaks that must be carefully controlled to provide repeatable color output. Control of the phosphor mixture to produce production-quality lamps requires significant investment of time and effort to maintain a uniform mixture, produce an acceptable color point, and ensure color purity based on phosphor chemistry. Moreover, in conventional white LEDs, the spectral emission is dominated by the blue spectral emission, and thus, the resulting “white” light is heavily shifted toward the blue spectrum. This shift limits the usefulness of LED light sources in backlighting applications.
A light source according to various aspects of the present invention comprises LEDs raised above the floor of the optical cavity. The raised LEDs may optionally have a protrusion under the LED for assisting in redirecting light. In another embodiment, adjacent LEDs may be skewed relative to one another to reduce absorption and reflection among the LEDs. In a further embodiment, non-white LEDs may be incorporated into the light source to permit selective color tuning. In an alternative embodiment, a hybrid light source may be created when fluorescent lamps are augmented with LEDs. These LEDs, which may optionally be raised above the floor of the optical cavity, may also optionally have a protrusion beneath. the raised LED.
The subject matter of the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, may best be understood by reference to the following description taken in conjunction with the claims and the accompanying drawings, in which like parts may be referred to by like numerals:
FIG. 4. is a perspective view of an elevated diode in accordance with an exemplary embodiment of the present invention;
The ensuing descriptions are preferred exemplary embodiments only, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the ensuing descriptions provide a convenient description for implementing various exemplary embodiments of light sources according to various aspects of the present invention, it being understood that various changes may be made in the function and arrangement of elements described in the preferred embodiments without departing from the spirit and scope of the invention as set forth in the appended claims.
Referring now to
The power source provides appropriate power supply and control to operate the lamp. The power source may provide power in any appropriate form, such as AC electrical current, and may control the power in any suitable manner, for example in conjunction with a voltage source with current limiting resistance, a constant current source, or a pulse width modulated current source,
LED 400 may be any LED suitable for the application, such as a phosphor-based white LED sold by Nichia Corp, Tokushima, Japan. The color, type, configuration, performance, and other characteristics may be selected according to any appropriate criteria. In the present embodiment, LED 400 includes a diode 402 encased in a translucent rectangular package 404. The LED 400 is raised by a support system 405 such that the base of LED 400 is elevated above the floor 410 of optical cavity 502. For example, the support system 405 suitably comprises a pair of L-brackets 406 and 408 attached to either side of the LED 400 to support the LED 400 above the floor 410. L-brackets 406 and 408 may be affixed to floor 410 according to any suitable technique, such as by an adhesive, fastener or solder. Any support system 405 that raises the LED 400 above floor 410, for example, by using raised, a support matrix, or the like, may be used to support the LED 400.
The support system 405 may further connect the LED 400 to the power source. For example, in the present embodiment, the L-brackets 406 and 408 may be constructed of a suitable electrically conductive material that supports the, LED above the surface of the floor 410, such as copper or beryllium. A lead frame 412 electrically connects the diode 402 with L-brackets 406 and 408. L-brackets 406 and 408 are suitably connected to a printed circuit board which is connected to the power source, for example through control electronics.
In configurations where LEDs 400 are raised above floor 410, as in
In accordance with various aspects of the present invention, the light emitted by the light source may be further enhanced by arranging the LEDs in an array that reduces any absorptive or reflective effects of adjacent LEDs. For example, referring to
Several variations in the orientation of the LEDs may be implemented to enhance light output. For example, referring now to
A light source according to various aspects of the invention may further be configured to exhibit improved spectral characteristics. In accordance with a further embodiment of the present invention, non-white LEDs, preferably, red, green, and blue LEDs, and more preferably red and green LEDs, may be incorporated into the light source as described and constructed in
The non-white LEDs may be configured in the light source in a variety of manners, including, but not limited to, clustering the different LED types together, and by laying down each color in separate rows. Further, non-white LEDs may be randomly dispersed throughout the light source with white LEDs, and may also be used in combination with fluorescent lamps as described below. The non-white LEDs may be mounted directly on the floor of the optical cavity, or as described in detail above, or they may be elevated above the optical cavity floor, and further, they may optionally be elevated above reflective protrusions as described above.
By incorporating non-white LEDs, multiple-wavelength LED light sources are introduced into a diffuse optical cavity to allow color mixing, with the purpose of increasing the color saturation of an LED-based backlight to increase its usefulness in lighting an LCD panel. These emission spectra allow tuning of the color balance of the backlight by actively driving the LEDs or selectively enhancing particular colors to achieve a desired balance. This tunability allows one LED backlight to be used with a wide variety of LCD panels possessing different combinations of color filters. It also allows active tuning of the color balance of an LED-based light source across the color spectrum, limited only by the saturation of the individual color elements comprising the backlight.
LEDs may be interspersed among the fluorescent lamps in a variety of configurations in the hybrid light source. As seen in
It should be appreciated that the present invention is not limited to the configurations described above. For example, referring to
Referring now to
Referring now to
It should be appreciated that in all embodiments of the present invention any number of LEDs and fluorescent lamps may be used according to the particular application or design criteria of the backlight or the display. As such, the drawing figures and the present description are only meant to illustrate exemplary embodiments in accordance with the present invention and are not intended to limit the invention to the configurations illustrated herein.
Thus, a light source incorporating LEDs and fluorescent lamps according to various aspects of the present invention provides several features and advantages, such as light output uniformity. In addition, the above descriptions are preferred exemplary embodiments only, and are not intended to be limiting in any way. Various modifications, substitutions, and other applications of the present embodiments may be made without departing from the spirit and the scope of the invention as set forth in the appended claims.
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|U.S. Classification||362/237, 349/69, 362/231, 362/249.02, 362/97.3, 349/70, 362/236|
|International Classification||H01L33/60, H01L25/13, F21V19/00, H01L33/48, G09F13/04, F21S4/00, F21V9/00|
|Cooperative Classification||H01L2924/0002, H01L33/60, G02F1/133603, G02F1/133608, H01L33/486, G02F1/133604, H01L2924/09701, H01L25/13|
|European Classification||G02F1/1336B5, G02F1/1336B1, H01L33/48C2, H01L25/13, H01L33/60|
|May 23, 2011||FPAY||Fee payment|
Year of fee payment: 8
|May 26, 2015||FPAY||Fee payment|
Year of fee payment: 12
|Jun 9, 2015||IPR||Aia trial proceeding filed before the patent and appeal board: inter partes review|
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Opponent name: CREE, INC.
Effective date: 20150504
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