Abstract:
A light emitting device includes: a frame having an opening; at least one light emitting diode (LED) disposed on the frame; a reflector disposed on the frame; and a reflective protrusion projecting from the reflector, wherein light emitted from at least one light emitting diode is reflected by the reflector through the opening, wherein the vertical axis of the reflective protrusion is perpendicular to a plane formed by extending the upper surface of the frame, wherein the upper surface of the frame contacts the reflector, and wherein a distance between two LEDs with one LED placed therebetween is greater than a distance between one LED and the reflector. Because a light source is disposed on the frame of the light emitting device, it is possible to easily exchange the light source of the light emitting diode by removing and attaching the frame without disassembling the entire lighting device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation application of U.S. application Ser. No. 12/818,656 filed Jun. 18, 2010, which claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2009-0067429, filed on Jul. 23, 2009, the entirety of which are incorporated by reference in their entirety as if fully set forth herein. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a light emitting device including a light emitting diode. 
         [0004]    2. Description of the Related Art 
         [0005]    A light emitting diode (LED) may constitute a light emitting source by using a compound semiconductor material such as a GaAs based material, AlGaAs based material, GaN based material, InGaN based material, InGaAlP based material and the like. 
         [0006]    LED is packaged and used as a light emitting device emitting various colors. There have been many active researches for utilizing the LED as a light source in the field of the lighting device. 
       SUMMARY 
       [0007]    One aspect of this invention includes a light emitting device. The light emitting device includes: a frame having an opening; at least one light emitting diode (LED) disposed on the frame; a reflector disposed on the frame; and a reflective protrusion projecting from the reflector towards the opening, wherein light emitted from at least one light emitting diode is reflected by the reflector through the opening, wherein a vertical axis of the reflective protrusion is perpendicular to a plane formed by extending an upper surface of the frame, wherein the upper surface of the frame contacts the reflector, and wherein a distance between two LEDs with one LED placed therebetween is greater than a distance between one LED and the reflector. 
         [0008]    Another aspect of this invention includes a light emitting device. The light emitting device includes: a frame formed with an opening therethrough; a heat radiator disposed on an outer portion of the frame; at least one light emitting diode (LED) disposed on the frame; a reflector disposed on the frame; and a reflective protrusion projecting from the reflector towards the opening, wherein the light emitted from the at least one light emitting diode is reflected by the reflector through the opening, wherein a vertical axis of the reflective protrusion is perpendicular to a plane formed by extending an upper surface of the frame, wherein the upper surface of the frame contacts the reflector, and wherein a distance between two opposite LEDs is greater than a distance between one LED and the reflector. 
         [0009]    Another aspect of this invention includes a light emitting device. The light emitting device includes: a circular frame having an opening therethrough; a plurality of light emitting diodes positioned around the circular frame; a dome-shaped reflector comprising an inner reflective surface, the dome-shaped reflector covering the plurality of light emitting diodes and reflecting light emitted from the plurality of light emitting diodes to the opening; and a reflective protrusion projecting from the inner reflective surface of the dome-shaped reflector towards the opening, wherein a vertical axis of the reflective protrusion is perpendicular to a plane formed by extending an upper surface of the frame, wherein the upper surface of the frame contacts the reflector, wherein a distance between two LEDs with one LED placed therebetween is greater than a distance between one LED and the reflector, and wherein a distance between two opposite LEDs is greater than a distance between the two LEDs with one LED placed therebetween. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The embodiment will be described in detail with reference to the following drawings. 
           [0011]      FIG. 1  is an exploded perspective view of a light emitting device according to a first embodiment. 
           [0012]      FIGS. 2   a  and  2   b  area cross sectional view of a light emitting device according to a first embodiment. 
           [0013]      FIG. 3  is a bottom view of a light emitting device according to a first embodiment. 
           [0014]      FIG. 4  is an enlarged view showing only a reflective protrusion of a light emitting device according to a first embodiment. 
           [0015]      FIG. 5  is a cross sectional view of a light emitting device according to a second embodiment. 
           [0016]      FIG. 6  is an exploded diagram showing perspective view of a light emitting device according to a third embodiment. 
           [0017]      FIG. 7  is a cross sectional view of a light emitting device of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0018]    In description of an embodiment, when it is mentioned that each panel, a member, a frame, a sheet, a plate or substrate and the like are formed “on” or “under” each panel, the member, the frame, the sheet, the plate or substrate and the like, it means that the mention includes a case where each panel, a member, a frame, a sheet, a plate or substrate and the like are formed “directly” or “by interposing another layer (indirectly)”. A criterion for “on” and “under” of each component will be described based on the drawings. A size of each component of the drawings is magnified for description thereof. The size of each component does not necessarily mean its actual size. 
         [0019]    Hereinafter, embodiments will be described in a more detailed manner with reference to the accompanying drawings. 
         [0020]      FIG. 1  is an exploded diagram showing perspective view of a light emitting device according to a first embodiment.  FIGS. 2   a  and  2   b  are a cross sectional view of a light emitting device according to a first embodiment.  FIG. 3  is a bottom view of a light emitting device according to a first embodiment.  FIG. 4  is an enlarged view showing only a reflective protrusion of a light emitting device according to a first embodiment. 
         [0021]    The preferred embodiment includes a circular frame, one of ordinary skill in the art will appreciate that the frame can take on any one of a number of shapes. 
         [0022]    Referring to  FIGS. 1 to 4 , a lighting emitting device  100  according to the embodiment includes a frame  110  having an opening  115 , at least one light emitting diode  120  disposed on the frame  110 , a reflector  130  which reflects light irradiated from the light emitting diodes  120  and emits the light through the opening  115 , and at least one reflective protrusion  140  which is formed on a reflective surface  130   a  of the reflector  130  and determines an orientation angle of the light emitted through the opening  115 . 
         [0023]    The reflective protrusion  140  can be integrally formed on the reflector  130 . For another example, the reflective protrusion  140  can be manufactured to be attached to and detached from the reflector  130 . 
         [0024]    The frame  110  has a ring shape surrounding the opening  115 . The frame  110  includes an upper surface  110   a,  a lower surface  110   b,  an inner lateral surface  110   c  surrounding the opening  115 , and an outer lateral surface  110   d.    
         [0025]    The frame  110  can be attached and detached. Therefore, when the frame  110  is applied to a built-in lighting device, the frame  110  having the light emitting diode enables the built-in lighting device to be exchanged without taking out or disassembling the built-in lighting device. Therefore, since a light source is provided to the frame of the light emitting device according to the embodiment, it is possible to easily exchange the light source of the light emitting diode by detaching and attaching the frame without disassembling the entire lighting device. 
         [0026]    The light emitting diodes  120  may be mounted on the upper surface  110   a  of the frame  110  separately from each other by a predetermined interval. 
         [0027]    The light emitting diodes  120  may be arranged along the frame  110  in a line or a plurality of lines. The figures show that the light emitting diodes  120  are arranged in the form of a line. 
         [0028]    Meanwhile, a zener diode (not shown) may be disposed on the frame  110  to protect the light emitting diode  120 . 
         [0029]    The light emitting diode  120  may emit a target light, for example, white light and create a desired light through a mixture of lights from a plurality of the light emitting diodes  120 . Also, the light emitting diode  120  may generate target lights having various colors in accordance with the intention of a user. 
         [0030]    While the light emitting diode  120  emits the light on the upper surface  110   a  of the frame  110 , there is no limit to the light emission type of the light emitting diode  120 . 
         [0031]    The frame  110  supplies an electric power to the light emitting diode  120 . 
         [0032]    The frame  110  may function as a printed circuit board which is electrically coupled to the light emitting diodes  120 . 
         [0033]    The frame  110  may comprises a single layer substrate or a multi layer substrate. A wiring pattern may be formed on the inner surface of the frame  110  or on the lower surface of the frame  110 . There is no limit to the mounting method and mounting pattern of the light emitting diode  120 . 
         [0034]    The reflector  130  is disposed in a light irradiation direction in order to reflect the light irradiated from the light emitting diode  120 . 
         [0035]    The reflector  130  may have a hemisphere shape. The reflector  130  does not necessarily have a hemisphere shape, however, various shapes such as a conical shape, a cylindrical shape, a cannon ball shape and a polygonal shape and the like can be also applied to the reflector  130  in consideration of a reflection efficiency and an optical uniformity. 
         [0036]    The concave surface of the reflector  130  actually functions as the reflective surface  130   a  reflecting the light irradiated from the light emitting diode  120 . 
         [0037]    The reflective surface  130   a  may comprise a material having an excellent optical reflection efficiency. 
         [0038]    The reflector  130  may be coupled to the upper surface  110   a  of the frame  110  where the light emitting diodes  120  are placed inside the reflector  130 . 
         [0039]    Though not shown, the reflector  130  and the frame  110  can be coupled to each other by using fastening means. The fastening means includes a fastening member or an adhesive member. 
         [0040]    At least one reflective protrusion  140  is formed on some areas of the reflective surface  130   a.    
         [0041]    The reflective protrusion  140  is integrally formed with the reflector  130  or is adhered to some areas of the reflective surface  130   a.    
         [0042]    The surface of the reflective protrusion  140  is made of the same material as that of the reflective surface  130   a.    
         [0043]    The reflective protrusion  140  may have a conical shape. 
         [0044]    The reflective protrusion  140  has its bottom surface contacting with the reflector  130  and has its vertex facing the opening  115 . 
         [0045]    The axis of the reflective protrusion  140  may be perpendicular to a plane formed by extending the upper surface  110   a  of the frame  110 . 
         [0046]    The central point of the bottom surface of the reflective protrusion  140  may be the farthest from a plane formed by extending the upper surface  110   a  of the frame  110  in a vertical direction to the plane. 
         [0047]    An orientation angle of the light which is reflected by the reflective surface  130   a  and is emitted through the opening  115  varies according to the height “b” of the reflective protrusion  140  and the diameter “a” of the bottom surface of the reflective protrusion  140 . 
         [0048]    The aforementioned orientation angle of the light refers to a diffusion angle of light emitted through the opening  115  of the frame  110 . An effective lighting area may vary according to the orientation angle of light. 
         [0049]    For example, if the height of the reflective protrusion  140  is increased, the orientation angle of light may be increased, thus the effective lighting area may be increased. Otherwise, if the height of the reflective protrusion  140  is decreased, the orientation angle of light may be decreased and the effective lighting area may be decreased. 
         [0050]    The height “b” of the reflective protrusion  140  from the reflector  130  may be less than a vertical height “c” from the frame  110  to the reflector  130  point which is the farthest from the frame  110 . 
         [0051]    On the other hand, the height “b” of the reflective protrusion  140  from the reflector  130  may be greater than the vertical height “c” from the frame  110  to the reflector  130  point which is the farthest from the frame  110 . 
         [0052]    Meanwhile, in  FIG. 2   b , the preferable width and length of the reflective protrusion  140  will be described based on the orientation angle of the light emitting diode  120 . 
         [0053]    For example, it is assumed that the orientation angle of the light emitting diode  120  is 120°. Since the light emitting diode  120  irradiates light in a vertical direction, the light emitting area of the light emitting diode  120  forms an angle of 30° with the frame  110 . Here, if the radius of the frame  110  is defined as “√3 d”, the lengths of the sides of a triangle area  400  formed by the light emitting area and the frame are defined as “2 d” and “d” respectively. 
         [0054]    When the reflective protrusion  140  has a conical shape, it is preferable that the diameter “x” of the bottom surface of the reflective protrusion  140  is less than ⇄3 d. 
         [0055]    Meanwhile, if the reflector  130  has a constant height “H”, it is preferable that the height “y” of the reflective protrusion  140  is greater than a length difference between the height “H” of the reflector  130  and the vertical length “d” of the triangle area  400 . That is, it is required that a relational expression of y&gt;H−d should be satisfied. If y&lt;H−d, a part of the light irradiated from the light emitting diode  120  is directly incident on the opposite side of the reflector without being reflected by the reflective protrusion  140  and is immediately irradiated to the outside of the frame  110 . As a result, indirect lighting effect is reduced. 
         [0056]    The height “b” of the reflective protrusion  140  may be equal to or greater than 0 mm. The reflective protrusion  140  may be formed to be larger than bumpy patterns formed on the surface of the reflective surface  130   a.  The bumpy patterns are formed for scattering light. 
         [0057]    The lighting emitting device  100  having such a structure can be used as an indirect lighting device. 
         [0058]    The reflective protrusion  140  according to the embodiment makes it possible to obtain a desired effective lighting area by adjusting the orientation angle of light, to improve an optical uniformity and to prevent a glare phenomenon. 
         [0059]    In addition, even if any one of the plurality of the light emitting diodes  120  is disabled, the disabled light rarely affect the entire light. Therefore, there is an effect of lengthening the time period for using the lighting device, thereby reducing the manufacturing cost. 
         [0060]    At least any one among the surface of the reflective protrusion  140  and the reflective surface  130   a  of the reflector  130  may have roughness. A degree of the roughness of the reflective surface  130   a  and a degree of the surface roughness of the reflective protrusion  140  may be different from each other according to the characteristic and design of the lighting. 
         [0061]    The light irradiated from the light emitting diode  120  may be scattered while reflected because of the roughness of the reflective surface  130   a  of the reflector  130  and the roughness of the reflective protrusion  140 , so a lighting uniformity can be improved. 
         [0062]    As a result, in the effective lighting area of the light irradiated from the light emitting device  100 , a hot spot is removed and a luminance distribution of the light is improved. 
         [0063]      FIG. 5  is a cross sectional view of a light emitting device according to a second embodiment. 
         [0064]    Here, regarding a light emitting device  200  shown in  FIG. 5 , the same reference numerals will be assigned to the same elements and structure as those of the first embodiment, and detailed descriptions thereof will be omitted. 
         [0065]    Referring to  FIG. 5 , at least any one among the surface of the reflective protrusion  140  and the reflective surface  130   a  of the reflector  130  may have patterns  210  formed thereon and roughness. The patterns may be a rough patterns or bumpy patterns. A degree of the roughness of the reflective surface  130   a  and a degree of the surface roughness of the reflective protrusion  140  may be different from each other according to the characteristic and design of the lighting. 
         [0066]    The light irradiated from the light emitting diode  120  may be scattered while reflected by the bumpy patterns  210  which are formed on both the reflective surface  130   a  of the reflector  130  and the surface of the reflective protrusion  140 . 
         [0067]    Since the light emitting device  200  does not require a separate diffusion sheet and a separate scattering sheet and the like, it is possible to maintain the light intensity of the light emitting diode  120  of equal to or greater than 90%. 
         [0068]    As a result, in the effective lighting area of the light irradiated from the light emitting device  200 , a hot spot is removed and a luminance distribution of the light is improved. 
         [0069]      FIG. 6  is an exploded perspective view of a light emitting device according to a third embodiment.  FIG. 7  is a cross sectional view of a light emitting device of  FIG. 6 . 
         [0070]    Here, regarding a light emitting device  300  shown in  FIGS. 6 and 7 , the same reference numerals will be assigned to the same elements and structure as those of the first embodiment, and detailed descriptions thereof will be omitted. 
         [0071]    Referring to  FIGS. 6 and 7 , a lighting emitting device  300  according to the embodiment includes a frame  110  having both an opening  115  formed therein and a heat radiator  330  formed on the outer circumference thereof, at least one light emitting diode  120  disposed on the frame  110 , a reflector  130  which reflects light irradiated from the light emitting diodes  120  and emits the light through the opening  115 , and a reflective protrusion  140  which is formed inside the reflector  130  and determines an orientation angle of the light emitted through the opening  115 . 
         [0072]    The frame  110  includes an upper surface  110   a,  a lower surface  110   b,  an inner lateral surface  110   c  and an outer lateral surface  110   d.  The heat radiator  330  is formed to surround the lower part of the outer lateral surface  110   d.    
         [0073]    There is a difference in diameter between the heat radiator  330  and the upper surface  110   a  of the frame  110 . The heat radiator  330  projects out from the outer lateral surface  110   d.    
         [0074]    Since the heat radiator  330  obtains an area for radiating heat, it is possible to overcome the problem of radiation heat of the light emitting diode  120  and to obtain reliability. 
         [0075]    The frame  110  can be integrally formed with the heat radiator  330  or formed to be connected to the heat radiator  330 . 
         [0076]    The reflector  130  may have a hemisphere shape. The concave surface of the reflector  130  forms a reflective surface  130   a.    
         [0077]    The reflective protrusion  140  is formed on some areas of the reflective surface  130   a.  The surface of the reflective protrusion  140  is made of the same material as that of the reflective surface  130   a.    
         [0078]    The reflective protrusion  140  has a conical shape. The reflective protrusion  140  has its bottom surface contacting with the reflective surface  130   a  and has its vertex facing the opening  115 . 
         [0079]    The height “b” of the reflective protrusion  140  from the reflector  130  may be less than a vertical height “c” from the frame  110  to the reflector  130  point which is the farthest from the frame  110 . 
         [0080]    The reflective protrusion  140  according to the embodiment makes it possible to obtain a desired effective lighting area by adjusting the orientation angle of light, to improve an optical uniformity and to prevent a glare phenomenon. 
         [0081]    An orientation angle of the light which is reflected by the reflective surface  130   a  and is emitted through the opening  115  varies according to the height “b” of the reflective protrusion  140  and the diameter “a” of the bottom surface of the reflective protrusion  140 . 
         [0082]    At least any one among the surface of the reflective protrusion  140  and the reflective surface  130   a  of the reflector  130  may have roughness. A degree of the roughness of the reflective surface  130   a  and a degree of the surface roughness of the reflective protrusion  140  may be different from each other according to the characteristic and design of the lighting. 
         [0083]    The light irradiated from the light emitting diode  120  may be scattered while reflected because of the roughness of the reflective surface  130   a  of the reflector  130  and the surface roughness of the reflective protrusion  140 , so a lighting uniformity can be improved. 
         [0084]    As a result, in the effective lighting area of the light irradiated from the light emitting device  300 , a hot spot can be removed and a luminance distribution of the light can be improved. 
         [0085]    The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the foregoing embodiments is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Moreover, unless the term “means” is explicitly recited in a limitation of the claims, such limitation is not intended to be interpreted under 35 USC 112(6).