Patent Application
20080094345
The accompanying drawings illustrate one or more embodiments of the invention and, together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein:
The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like components throughout the views. As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings in
Referring now to
In one embodiment, the substrate 101 has an edge zone 110 and a central zone 150 surrounded by the edge zone 110. In this exemplary embodiment, the central zone 150 has four segments, SC1, SC2, SC3, and SC4, where each segment SCi has a corresponding surface area ACi, i=1, 2, 3, and 4. The surface areas {ACi}, i=1, 2, 3, and 4, can be same, as shown in
The first plurality of light emitting elements 151, 152, 153, . . . are positioned in the central zone 150 of the substrate 101. Specifically, each segments SCi of the central zone 150 of the substrate 101 has one or more of the first plurality of light emitting elements 151, 152, 153, . . . Each of the first plurality of light emitting elements 151, 152, 153, . . . has at least a first LED chip capable of emitting light in a red color, a second LED chip capable of emitting light in a green color, and a third LED chip capable of emitting light in a blue color. Each LED chip associated with the first plurality of light emitting elements 151, 152, 153, . . . in the central zone 150 is characterized by a brightness degree BkC and an area LkC, k=R, G, or B, corresponding to the red color light, the green color light, and the blue color light, respectively. In other words, brightness degree BRC is corresponding to the red color light, brightness degree BGC is corresponding to the green color light, and brightness degree BBC is corresponding to the blue color light, respectively. Similarly, area LRC is corresponding to the red color light, area LGC is corresponding to the green color light, and area LBC is corresponding to the blue color light, respectively.
As shown in
The second plurality of light emitting elements 111, 112, 113, . . . , are positioned in the edge zone 110 of the substrate 101 such that each segment SEj has one or more of the second plurality of light emitting elements. Each of the second plurality of light emitting elements 111, 112, 113 . . . includes at least three LED chips: a first LED chip capable of emitting light in a red color, a second LED chip capable of emitting light in a green color, and a third LED chip capable of emitting light in a blue color. Each LED chip associated with the second plurality of light emitting elements 111, 112, 113, . . . in the edge zone 110 is characterized by a brightness degree BkE and an area LkE, k=R, G, or B, corresponding to the red color light, the green color light, and the blue color light, respectively. As shown in
According to the present invention, the areas, LRC, LGC and LBC, of the at least three LED chips of each of the first plurality of light emitting elements 151, 152, 153, . . . in the central zone 150 of the substrate 101 and these, LRE, LGE and LBE, of the at least three LED chips of each of the second plurality of light emitting elements 111, 112, 113, . . . in the edge zone 110 of the substrate 101 satisfy one of the following relationships:
LRE<LRC, LGE<LGC, and LBE<LBC,
as shown in
Preferably, the number of light emitting elements in a segment is in the range of 1 to 6. However, segments having other numbers of light emitting elements can also be utilized to practice the present invention.
In operation, the brightness degrees, BRC, BGC and BBC, of the at least three LED chips of each of the first plurality of light emitting elements 151, 152, 153, . . . in the central zone 150 of the substrate 101 and these, BRE, BGE and BBE, of the at least three LED chips of each of the second plurality of light emitting elements 111, 112, 113, . . . in the edge zone 110 of the substrate 101, satisfy one of the following relationships:
BRE<BRC, BGE<BGC, and BBE<BBC.
Furthermore, the output power per unit area for these LED chips satisfies:
P
RE
+P
GE
+P
BE
<P
RC
+P
GC
+P
BC,
where PRE, PGE, PBE, represent the output power per unit area corresponding to the red color light, the green color light, and the blue color light, respectively, of the second plurality of light emitting elements 111, 112, 113, . . . in the edge zone 110 of the substrate 101, and PRC, PGC, PBC, represent the output power per unit area corresponding to the red color light, the green color light, and the blue color light, respectively, of the first plurality of light emitting elements 151, 152, 153, . . . in the central zone 150 of the substrate 101, respectively.
The total output power per unit area, PE, by the second plurality of light emitting elements 111, 112, 113, . . . in the edge zone 110 of the substrate 101 is less than its counterpart, PC, by the first plurality of light emitting elements 151, 152, 153, . . . in the central zone 150 of the substrate 101, i.e., PE<PC.
In another embodiment, the substrate has at least a first zone and a second zone. In operation, the first zone has a temperature TH, and the second zone has a temperature TL that is less than TH. The first zone and the second zone of the substrate may or may not be corresponding to the central zone 150 and the edge zone 110 of the substrate 101, as shown in
The first plurality of light emitting elements and the second plurality of light emitting elements are positioned in the first zone, and the second zone of the substrate, respectively. Similar to the embodiment shown in
In operation, the ratio of the output power for the red light to the total output power for the red, green and blue light in the second zone having the temperature TL is less than the ratio of the output power for the red light to the total output power of the red, green and blue light in the first zone having the temperature TH, that is:
where PRH, PGH, PBH, represent the output power per unit area corresponding to the red color light, the green color light, and the blue color light, respectively, of the first plurality of light emitting elements in the first zone having the temperature TH, and PRL, PGL, PBL, represent the output power per unit area corresponding to the red color light, the green color light, and the blue color light, respectively, of the second plurality of light emitting elements in the second zone having the temperature TL, respectively.
Additionally, each of the first plurality of light emitting elements and the second plurality of light emitting elements comprises one or more or at least three LED chips, where each LED chip is capable of emitting light. In one embodiment, the one LED chip is capable of emitting light in a white color. In another embodiment, the at least three LED chips includes at least a first LED chip capable of emitting light in a red color, a second LED chip capable of emitting light in a green color, and a third LED chip capable of emitting light in a blue color. In alternative embodiment, the at least three LED chips may have at least one LED chip capable of emitting light in one color selected from the group of a red color, a blue color, a green color, a brown color, a yellow color, a pink color, a violet color, an indigo color, a reddish orange color, an orange color, a cyan color, a salmon pink color, a mauve color and a white color.
One aspect of the present invention provides a method for controlling brightness of the backlight units disclosed above.
The present invention, among other things, discloses an LED backlight unit includes a substrate having an edge zone and a central zone surrounded by the edge zone, a first plurality of light emitting elements positioned in the central zone of the substrate, a second plurality of light emitting elements positioned in the edge zone of the substrate, and an electronic controlling means for controlling the light emitted from the first plurality of light emitting elements and the second plurality of light emitting elements such that in operation, the output power per unit area by the second plurality of light emitting elements in the edge zone is less than that by the first plurality of light emitting elements in the central zone.
The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.
