SOLAR SPECTRUM-LIKE LED STRUCTURE

Abstract

A solar spectrum-like LED structure, comprising a negative electrode for a three-dimensional integrated package, and a plurality of LED chips and resistors. The negative electrode for a three-dimensional integrated package is a three-dimensional structure comprising a plurality of planes. The plurality of LED chips is installed on the plurality of planes of the negative electrode for the three-dimensional integrated package. Light of different colors emitted by the plurality of LED chips forms a plane light source or a cone light source after being well mixed at an intersection point, thus simulating a solar spectrum. The invention enables manufacturing of a solar spectrum-like LED fluorescent lamp suitable for generating different bands of spectrums for the survival and metabolism of various organisms. In addition, the solar spectrum-like LED fluorescent lamp has a good color-rendering property and visual effect, and can be widely applied in the fields of general lighting, agriculture, animal husbandry and new biological energy sources.

Claims

1. A solar spectrum-like LED structure, comprising: a negative electrode for a three-dimensional integrated package, wherein the negative electrode for a three-dimensional integrated package is a three-dimensional structure comprising a plurality of planes; a plurality of LED chips, wherein the plurality of LED chips are installed on the plurality of planes of the negative electrode for the three-dimensional integrated package, and wherein each plane is correspondingly installed with one LED chip; and a plurality of resistors, wherein an end of each of the plurality of resistors is separately connected to the light-emitting surface of the LED chips, and wherein another end of each of the plurality of resistors is connected to a positive electrode.

2. The solar spectrum-like LED structure according to claim 1, wherein: the negative electrode for a three-dimensional integrated package is a structure designed based on a semi-cylindrical surface having a plurality of planes thereon; lines from the center point of each plane to a center of the designed semi-cylindrical surface are separately perpendicular to each of the corresponding planes; the plurality of LED chips are separately installed on each plane; and each plane is correspondingly installed with one LED chip.

3. The solar spectrum-like LED structure according to claim 2, wherein a computational formula of the design radius of the structure designed based on the semi-cylindrical surface is as follows: $\mathrm{Ra}=\frac{1}{2}.Math.\left(L+M\right)/\sin .Math.\frac{90.Math.°}{n}$ wherein L is a size of the edge of one LED chip, M is a spacing between the LED chips, n is a number of the LED chips, and Ra is a design radius of the electrode designed based on the semi-cylindrical surface.

4. The solar spectrum-like LED structure according to claim 1, wherein: the negative electrode for the three-dimensional integrated package is a structure designed based on a semi-spherical surface having a plurality of planes thereon; apex angles below the plurality of planes are interconnected into a regular polygon; a plane of the regular polygon is parallel to a plane of the designed semi-spherical surface; the apex angles of the regular polygon are located on the designed semi-spherical surface; two top apex angles above the plurality of planes are located on the spherical surface where the plane of the designed semi-spherical surface intersects with the semi-spherical surface; the lines from the center points of the plurality of planes to the center of the designed semi-spherical surface are separately perpendicular to each of the corresponding planes; the plurality of LED chips are separately installed on each plane; and each plane is correspondingly installed with one LED chip.

5. The solar spectrum-like LED structure according to claim 4, wherein a computational formula of the design radius of the structure designed based on the semi-spherical surface is as follows: $\mathrm{Ra}=\frac{1}{2}.Math.\left(L+M\right).Math.\sqrt{{\frac{1}{4}\left[\tan .Math.\frac{90.Math.°\left(n-2\right)}{n}+\sqrt{{\left(\tan .Math.\frac{90.Math.°\left(n-2\right)}{n}\right)}^2+8}\right]}^2+1}$ wherein L is a size of the edge of one LED chip, M is a spacing between the LED chips, n is a number of the LED chips, n≧3, and Ra is a design radius of the electrode designed based on the semi-spherical surface.

6. The solar spectrum-like LED structure according to claim 1, wherein: the negative electrode for a three-dimensional integrated package is a three-dimensional structure comprising a plurality of planes; lines from center points of the plurality of planes to the designed intersection point are separately perpendicular to each of the corresponding planes; the plurality of LED chips are separately installed on each plane; and each plane is correspondingly installed with one LED chip.

7. The solar spectrum-like LED structure according to claim 1, wherein: the plurality of resistors comprises a plurality of variable resistors; and a spectrum of mixed light can be varied by varying a resistance of the plurality of resistors, varying a current through the corresponding LED chips and controlling a proportion of each monochromatic light in the spectrum of mixed light.

8. The solar spectrum-like LED structure according to claim 1, wherein light of a plurality of colors emitted by the plurality of LED chips generates a spectrogram of solar spectrum-like lighting insect-repelling LED fluorescent lamp after being well mixed at a designed intersection point, wherein, in the spectrogram, a radiant flux of wavelengths between 530 nm and 590 nm is greater than 50% of a radiant flux of wavelengths between 380 nm and 780 nm; a main peak wavelength of the spectrum has a minimum value of 581 nm, a maximum value of 601 nm, and a median value of 591 nm, 591 nm; and a radiant flux of wavelengths between 380 nm and 480 nm is less than 25% of the radiant flux of the wavelengths between 380 nm and 780 nm.

9. The solar spectrum-like LED structure according to claim 1, wherein light of a plurality of colors emitted by the plurality of LED chips generates a spectrogram of solar spectrum-like myopia prevention LED fluorescent lamp after being well mixed at a designed intersection point, wherein, in the spectrogram, a radiant flux of wavelengths between 530 nm and 590 nm is greater than 50% of a radiant flux of wavelengths between 380 nm and 780 nm; a main peak wavelength of the spectrum has a minimum value of 550 nm, a maximum value of 570 nm, and a median value of 560 nm, and a radiant flux of wavelengths between 380 nm and 480 nm is less than 25% of the radiant flux of the wavelengths between 380 nm and 780 nm.

10. An LED light source module, wherein the LED light source module applies the LED structure according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The Examples of the present invention will be further described below with reference to the drawings, wherein:

[0023] FIG. 1 is a structure diagram of the solar spectrum-like LED structure of the present invention;

[0024] FIG. 2 is a structure diagram of Example 1 of the solar spectrum-like LED structure of the present invention;

[0025] FIG. 3 is a spectrogram of the solar spectrum-like plant-growing LED fluorescent lamp provided by Example 1 of the solar spectrum-like LED structure of the present invention;

[0026] FIG. 4 is a structure diagram of Example 2 of the solar spectrum-like LED structure of the present invention;

[0027] FIG. 5 is a spectrogram of the solar spectrum-like LED fluorescent lamp provided by Example 2 of the solar spectrum-like LED structure of the present invention;

[0028] FIG. 6 is a structure diagram of Example 3 of the solar spectrum-like LED structure of the present invention;

[0029] FIG. 7 is a spectrogram of the solar spectrum-like lighting insect-repelling LED fluorescent lamp provided by Example 3 of the solar spectrum-like LED structure of the present invention;

[0030] FIG. 8 is a structure diagram of Example 4 of the solar spectrum-like LED structure of the present invention; and

[0031] FIG. 9 is a spectrogram of the solar spectrum-like myopia prevention LED fluorescent lamp provided by Example 4 of the solar spectrum-like LED structure of the present invention.

DETAILED DESCRIPTION

[0032] The present invention will be described in further detail in conjunction with the drawings and specific examples.

[0033] The invention provides a solar spectrum-like LED structure. FIG. 1 is a structure diagram of the solar spectrum-like LED structure of the present invention, which comprises a negative electrode (1) for a three-dimensional integrated package, a plurality of LED chips (2), and a plurality of resistors. The negative electrode (1) for a three-dimensional integrated package is a three-dimensional structure comprising a plurality of planes. The plurality of LED chips (2) are installed on the negative electrode (1) for the three-dimensional integrated package. One end of each of the plurality of resistors is separately connected to the light-emitting surface of the LED chip, and the other end of each of the plurality of resistors is connected to the positive electrode.

[0034] The negative electrode for a three-dimensional integrated package is a structure designed based on a semi-cylindrical surface, a structure designed based on a semi-spherical surface or other arbitrary structure, which is neither a structure designed based on a semi-cylindrical surface nor a structure designed based on a semi-spherical surface and does not block the light continuing to exposure outside. After mixed at the designed intersection point, having a plurality of planes thereon, the lines from the center points of the plurality of planes to the designed intersection point are separately perpendicular to each of the corresponding planes. The plurality of LED chips (2) are separately installed on each plane, and each plane is correspondingly installed with one LED chip.

[0035] Lights of different colors emitted by the plurality of LED chips form a plane light source or a cone light source after being mixed at the designed intersection point. Based on the above designed structure, the lights of different colors emitted by the plurality of LED chips (2) are intersected and well mixed at the designed intersection point, thereby emitting a mixed light having a good stability and color-rendering property.

[0036] The negative electrode for a three-dimensional integrated package is a structure designed based on a semi-cylindrical surface. The size of the LED chip is P*L, P≧L, P and L are the sizes of the edge of the chip, the direction of size L is consistent with the circular arc direction of the designed semi-cylindrical surface, the computational formula of the design radius of the electrode designed based on the semi-cylindrical surface is as follows:

[00003]$\mathrm{Ra}=\frac{1}{2}.Math.\left(L+M\right)/\sin .Math.\frac{90.Math.°}{n}$

wherein, L is the size of the edge of the LED chip, M is the spacing between the LED chips, n is the number of the LED chips, and Ra is the design radius of the electrode designed based on the semi-cylindrical surface.

[0037] The negative electrode for a three-dimensional integrated package is a structure designed based on a semi-spherical surface. The size of the LED chip is P*L, P≧L, P and L are the sizes of the edge of the chip. When P=L, the computational formula of the design radius of the structure designed based on the semi-spherical surface is as follows:

[00004]$\mathrm{Ra}=\frac{1}{2}.Math.\left(L+M\right).Math.\sqrt{{\frac{1}{4}\left[\tan .Math.\frac{90.Math.°\left(n-2\right)}{n}+\sqrt{{\left(\tan .Math.\frac{90.Math.°\left(n-2\right)}{n}\right)}^2+8}\right]}^2+1}$

wherein, L is the size of the edge of the LED chip, M is the spacing between the LED chips, n is the number of the LED chips, n≧3, and Ra is the design radius of the electrode designed based on the semi-spherical surface.

[0038] The plurality of resistors is a plurality of variable resistors. The spectrum of the mixed light can be varied by the manners of varying the resistance value of the plurality of resistors, varying the current through the corresponding LED chips, varying the radiant flux of each LED, and controlling the proportion of each monochromatic light in the mixed light. Thus, a solar spectrum-like LED fluorescent lamp for generating different bands of spectrums suitable for the survival and metabolism of various organisms can be separately manufactured.

Example 1

[0039] FIG. 2 is a structure diagram of Example 1 of the solar spectrum-like LED structure of the present invention, comprising a negative electrode for a three-dimensional integrated package (21) and a plurality of LED chips (22). In order to achieve a solar spectrum-like LED spectrogram required for plant growing, the negative electrode for a three-dimensional integrated package was a structure designed based on a semi-cylindrical surface using eight LED chips with different wavelengths.

[0040] The negative electrode for a three-dimensional integrated package (21) was a structure designed based on the semi-cylindrical surface having a plurality of planes thereon, the lines from the center point of each plane to the center of the designed semi-cylindrical surface were separately perpendicular to each of the corresponding planes. The plurality of LED chips were separately installed on each plane, and each plane was correspondingly installed with one LED chip. The light-emitting surface of the plurality of LED chips (22) were separately faced toward the center of the designed semi-cylindrical surface. The lines from the center point of each light-emitting surface of LED chips (22) to the center of the designed semi-cylindrical surface were separately perpendicular to each of the corresponding light-emitting surfaces, and were intersected at the center of the semi-cylindrical surface. The light of different colors emitted by the plurality of LED chips (22) formed a sector light source at the center of the designed semi-cylindrical surface.

[0041] Eight different LED chips with different wavelengths were normal chips with a size of 0.5×0.5 mm.sup.2, and their wavelength and the corresponding connected multiple resistors are as follows:

TABLE-US-00001 LED11 LED12 LED13 LED14 LED15 LED16 LED17 LED18 wavelength 660 637 615 596 560 516 462 398 (nm) resistors R11 R12 R13 R14 R15 R16 R17 R18

[0042] The spacing between the two planes after the package was M=0.15 mm.

[0043] According to the size of the selected LED chip, the size of the package plane was designed as 0.6×0.6 mm.sup.2, L=0.6 mm, the thickness of the electrode was designed as 1.4 mm. According to the computational formula of radius of the structure designed based on the semi-cylindrical surface, the radius was calculated as R=1.92 mm. Eight square planes of 0.6×0.6 mm.sup.2 were machined on the electrode designed based on the semi-cylindrical surface (21), and the spacing between each two planes was 0.15 mm. The lines from the center points of the eight square planes to the center of the designed semi-cylindrical surface were separately perpendicular to each of the corresponding planes. The substrates of the eight LED chips of LED11-LED18 were separately packaged on eight surfaces of the electrodes, and each plane was correspondingly installed with one LED chip. The light-emitting surfaces of LED11-LED18 were separately faced toward the center of the designed semi-cylindrical surface. The light-emitting surfaces of LED11-LED18 were separately connected to the resistors of R11-R18, and the other end of each of the eight resistors was commonly connected to the positive electrodes of the power source.

[0044] After connecting the line to power, eight lights with different color were emitted by LED chips (22) of LED11-LED18 with eight wavelengths, and mixed at the center of the designed semi-cylindrical surface to form a sector light source. A suitable plant-growing LED spectrum can be obtained by adjusting the resistance values of resistors of R11-R18, respectively, and varying the current of LED11-LED18, respectively, thereby changing the proportions of eight lights in the mixed light. FIG. 3 shows a plant-growing spectrogram of Example 1 of the solar spectrum-like LED structure. An FMS-6000 light-color-electricity integrated test system was used for testing. As can be seen from FIG. 3, the present Example can provide a solar spectrum-like LED spectrum suitable for plant growing.

[0045] It should be noted that the maximum radiant flux of the blue light flux should be the blue light having a wavelength of 440 nm in the spectrogram of the solar spectrum-like LED fluorescent lamp; however, a blue light chip with a wavelength of 440 nm cannot be purchased at home or abroad. However, the present Example can solve this problem well, and provides a solar spectrum-like LED fluorescent lamp suitable for plant growing.

Example 2

[0046] FIG. 4 depicts a structure diagram of Example 2 of the solar spectrum-like LED structure of the present invention, comprising a negative electrode for a three-dimensional integrated package (31) and a plurality of LED chips (32). In order to achieve a solar spectrum-like LED fluorescent lamp spectrogram, the negative electrode for a three-dimensional integrated package is a structure designed based on a semi-cylindrical surface using nine LED chips with different wavelengths.

[0047] Nine different LED chips with different wavelengths are normal chips with a size of 0.625×0.5 mm.sup.2, and their wavelength and the corresponding connected multiple resistors are as follows:

TABLE-US-00002 LED21 LED22 LED23 LED24 LED25 LED26 LED27 LED28 LED29 wavelength 660 635 614 595 572 560 516 462 398 (nm) resistors R22 R22 R23 R24 R25 R26 R27 R28 R29

[0048] The spacing between the two planes after the package was M=0.15 mm. According to the size of the selected LED chip, the size of the package plane is designed as 0.725×0.6 mm.sup.2, L=0.6 mm; the thickness of the electrode is designed as 1.6 mm. According to the computational formula of radius of the structure designed based on the semi-cylindrical surface, the radius was calculated as R=2.16 mm. Nine square planes of 0.75×0.6 mm.sup.2 were machined on the electrode designed based on the semi-cylindrical surface, and the spacing between each two planes was 0.15 mm. The lines from the center points of the nine square planes to the center of the designed semi-cylindrical surface were separately perpendicular to each of the corresponding planes. The substrates of the nine LED chips of LED21-LED29 were separately packaged on nine surfaces of the electrodes, and each plane was correspondingly installed with one LED chip. The light-emitting surfaces of LED21-LED29 were separately faced toward the center of the designed semi-cylindrical surface. The light-emitting surfaces of LED21-LED29 were separately connected to the resistors of R21-R29, and the other end of each of the nine resistors was commonly connected to the positive electrodes of the power source.

[0049] After connecting the line to power, nine lights with different colors were emitted by LED chips (32) of LED21-LED29 with nine wavelengths, and mixed at the center of the designed semi-cylindrical surface to form a sector light source. A spectrum of solar spectrum-like LED fluorescent lamp can be obtained by adjusting the resistance values of resistors of R21-R29, respectively, and varying the current of LED21-LED29, respectively, thereby changing the proportions of nine lights in the mixed light. FIG. 5 is a spectrogram of the solar spectrum-like LED fluorescent lamp provided by Example 2 of the solar spectrum-like LED structure. An FMS-6000 light-color-electricity integrated test system was used for testing.

Example 3

[0050] FIG. 6 illustrates a structure diagram of Example 3 of the solar spectrum-like LED structure of the present invention, comprising a negative electrode for a three-dimensional integrated package (41) and a plurality of LED chips (42). In order to achieve a solar spectrum-like lighting insect-repelling LED spectrum, the negative electrode for a three-dimensional integrated package is a structure designed based on the semi-spherical surface using six LED chips with different wavelengths. One chip is located at the center of the bottom of the electrode, thus, n=5.

[0051] The negative electrode for a three-dimensional integrated package is a structure designed based on the semi-spherical surface having a plurality of planes thereon. The apex angles below the plurality of planes were interconnected into a regular polygon. The plane of the regular polygon was parallel to the plane of the designed semi-spherical surface, and the apex angles of the regular polygon were located on the designed semi-spherical surface. Two top apex angles above the plurality of planes were on the spherical surface where the plane of the designed semi-spherical surface was intersected with the semi-spherical surface. The lines from the center points of the plurality of planes to the center of the designed semi-spherical surface were separately perpendicular to each of the corresponding planes. The plurality of LED chips were separately installed on each plane, and each plane was correspondingly installed with one LED chip. A plurality of lights of different colors emitted by the plurality of LED chips formed a cone light source after being mixed at the center of the designed semi-spherical surface.

[0052] Six different LED chips with different wavelengths are normal chips with a size of 0.5×0.5 mm.sup.2, and their wavelength and the corresponding connected multiple resistors are as follows:

TABLE-US-00003 LED31 LED32 LED33 LED34 LED35 LED36 wavelength 635 613 595 560 518 466 (nm) resistors R31 R32 R33 R34 R35 R36

[0053] A chip is at the center of the bottom, n=5, the spacing between the two planes after the package is M=0.2 mm.

[0054] According to the size of the selected LED chip, the size of the package plane was designed as 0.6×0.6 mm.sup.2. Then, L=0.6 mm. According to the computational formula of radius of the structure designed based on the semi-spherical surface, the radius was calculated as R=0.99 mm. Five square planes of 0.6×0.6 mm.sup.2 were machined on the electrode designed based on the semi-spherical surface. Another square of 0.6×0.6 mm.sup.2 was located at the center of the regular pentagon at the bottom of the electrode, and the minimum spacing between each of the two planes was 0.2 mm. The lines from the center points of the six square planes to the center of the designed semi-spherical surface were separately perpendicular to each of the corresponding planes. The substrates of the six LED chips of LED31-LED36 were separately packaged on six square planes, and each plane was correspondingly installed with one LED chip. The light-emitting surfaces of six LED chips were separately faced toward the center of the designed semi-spherical surface. The light-emitting surfaces of the six LED chips of LED31-LED36 were separately connected to the resistors of R31-R36, and the other end of each of the six resistors was commonly connected to the positive electrodes of the power source.

[0055] After connecting the line to power, six lights with different colors were emitted by LED chips of LED31-LED36 with six wavelengths, and mixed at the center of the designed semi-spherical surface to form a sector light source. A suitable lighting insect-repelling LED fluorescent lamp spectrum can be obtained by adjusting the resistance values of resistors of R31-R36, and varying the current of LED31-LED36, respectively, thereby changing the proportions of six lights in the mixed light. FIG. 7 is a spectrogram of the lighting insect-repelling LED fluorescent lamp provided by Example 3 of the solar spectrum-like LED structure of the present invention. An FMS-6000 light-color-electricity integrated test system was used for testing. It can be seen from FIG. 7 that the main peak wavelength of the spectrum has a minimum value of 581 nm, a maximum value of 601 nm, and a median value of 591 nm. The radiant flux of the wavelength of 530 nm˜590 nm was greater than 50% of the radiant flux of the wavelength of 380 nm˜780 nm, and the radiant flux of the wavelength of 380 nm˜480 nm was less than 25% of the radiant flux of the wavelength of 380 nm˜780 nm. The present Example can provide a suitable lighting insect-repelling LED fluorescent lamp.

Example 4

[0056] FIG. 8 is a structure diagram of Example 4 of the solar spectrum-like LED structure of the present invention, comprising a negative electrode for a three-dimensional integrated package (51) and a plurality of LED chips (52). In order to achieve a solar spectrum-like myopia prevention LED fluorescent lamp spectrum, the negative electrode for a three-dimensional integrated package is a structure designed based on the semi-spherical surface using six LED chips with different wavelengths. There was no chip at the bottom, thus, n=6.

[0057] Six different LED chips with different wavelengths are normal chips with a size of 0.5×0.5 mm.sup.2, and their wavelength and the corresponding connected multiple resistors are as follows:

TABLE-US-00004 LED41 LED42 LED43 LED44 LED45 LED46 wavelength 635 615 596 560 518 467 (nm) resistors R41 R42 R43 R44 R45 R46

[0058] There was no chip located at the bottom, n=6, and the spacing between the two planes after the package was M=0.15 mm.

[0059] According to the size of the selected LED chip, the size of the package plane was designed as 0.6×0.6 mm.sup.2. Then, L=0.6 mm. According to the computational formula of the radius of the structure designed based on the semi-spherical surface, the radius was calculated as R=1.02 mm. Six square planes of 0.6×0.6 mm.sup.2 were machined on the electrode designed based on semi-spherical surface, and the minimum spacing between each of the two planes was 0.15 mm. The lines from the center points of the six square planes to the center of the designed semi-spherical surface were separately perpendicular to each of the corresponding planes. The electrode for a three-dimensional integrated package was connected with the negative electrode. The substrates of the six LED chips of LED41-LED46 were separately packaged on six square planes, and each plane was correspondingly installed with one LED chip. The light-emitting surfaces of six LED chips were separately faced toward the center of the designed semi-spherical surface. The light-emitting surfaces of the six LED chips of LED41-LED46 were separately connected to the resistors of R41-R46, and the other end of each of the six resistors were commonly connected to the same positive electrode of the power source.

[0060] After connecting the line to power, six lights with different colors were emitted by LED chips of LED41-LED46 with six wavelengths, and mixed at the center of the designed semi-spherical surface to form a cone light source. A suitable myopia prevention LED fluorescent lamp spectrum can be obtained by adjusting the resistance values of resistors of R41-R46, and varying the current of LED41-LED46, respectively, thereby changing the proportions of six lights in the mixed light. FIG. 9 illustrates a spectrogram of the myopia prevention LED fluorescent lamp provided by Example 4 of the solar spectrum-like LED structure of the present invention. An FMS-6000 light-color-electricity integrated test system was used for testing. It can be seen from FIG. 9 that the main peak wavelength of the spectrum has a minimum value of 550 nm, a maximum value of 570 nm, and a median value of 560 nm. The radiant flux of the wavelength of 530 nm˜590 nm was greater than 50% of the radiant flux of the wavelength of 380 nm˜780 nm, and the radiant flux of the wavelength of 380 nm˜480 nm was less than 25% of the radiant flux of the wavelength of 380 nm˜780 nm. The present Example can provide a suitable solar spectrum-like myopia prevention LED fluorescent lamp.

[0061] In the description of the invention, it should be noted that the terms “center of the designed semi-spherical surface,” “center of the designed semi-cylindrical surface,” “center,” “upper,” “lower,” “semi-cylindrical surface,” “semi-spherical surface,” “spacing” and the like indicate a directional and positional relationship based on the drawings, and are only for the purpose of describing the invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific shape, a specific shape structure and operation, and, therefore, cannot be construed as limiting the present invention. “Plane” can be a square plane, or a rectangular plane, or the plane of other shapes, depending on the shape of the selected chips. Unless otherwise expressly stipulated and specified, the terms “install,” “package,” “connect,” “connected,” “machined,” “manufacture,” “manufactured” and the like should be understood in a broad sense. For example, the connection may be a mechanical connection or an electrical connection, either a direct connection or indirectly connected through an intermediate medium or an internal connection of the two elements. It will be apparent to those skilled in the art that the specific meaning of the above terms in the present invention may be understood according to the particular situation. In addition, unless otherwise specified, in the description of the present invention, the meaning of “a plurality of” is two or more.

[0062] The specific embodiments of the invention described above are not to be construed as limiting the scope of the invention. Any other changes and modifications that may be made in accordance with the technical concept of the invention are intended to be included within the scope of the appended claims.