Abstract:
The present invention provides an LED bulb, which includes a light source portion including at least one LED chip); a housing including a bottom portion supporting the light source portion and a sidewall portion surrounding the light source portion, and opening at one side of a first direction; a base disposed on the other side of the first direction relative to the housing; and a light guide body disposed in a space surrounded by the sidewall portion, and including an incident surface facing the light source portion, a light-emitting surface for making the light from the incident surface emit toward the one side of the first direction, and a peripheral side surface located between the incident surface and the light-emitting surface, wherein the cross-sectional area of the peripheral side surface becomes increasingly larger from a side of the incident surface toward a side of the light-emitting surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a light emitting diode (LED) bulb including LED chip adopted for the light source. 
         [0003]    2. Description of the Related Art 
         [0004]      FIG. 22  shows an example of conventional LED bulb (see Patent Documents 1 and 2, for example). The LED bulb  900  illustrated in the figure includes a plurality of LED modules  901 , a globe  902 , a heat-dissipating element  903  and a base  904 . The LED module  901  is the light emitting device of the LED bulb  900 , and includes at least one LED chip (not shown in the figure) therein. The globe  902  makes the light from the LED modules  901  diffuse and pass through. The heat-dissipating element  903  is the element, e.g., including aluminum, used for dissipating the heat from the LED modules  901 . The base  904  is the portion used for mounting the LED bulb  900  to the incandescent bulb lighting fixture. When being turned on, the LED bulb  900  exhibits the appearance of the incandescent bulb by making the globe  902  illuminate evenly. 
         [0005]    In addition to the incandescent bulb, e.g., the halogen lamp, are the lamp that is mounted on the lighting fixture. The illumination field of the halogen lamp is narrower than that of the incandescent bulb, and the halogen lamp is, e.g., mounted on the indoor lighting fixture which is called down light. Although the LED bulb  900  is adapted for illuminating a wider field, its illumination field is preferably to be limited to a narrower range in order to be used as the down light. 
         [0006]    Patent Document 1: Japanese Patent Publication No. 2010-135308. 
         [0007]    Patent Document 2: Japanese Patent Publication No. 2010-135309. 
       SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0008]    In view of the above-described conventional problems, a technical object of the present invention is to provide an LED bulb which is adapted to be used as a replacement for the halogen lamp. 
       Technical Means for Solving the Problems 
       [0009]    The LED bulb provided by the present invention comprises: a light source portion, comprising at least one LED chip; a housing, comprising a bottom portion supporting the light source portion and a sidewall portion surrounding the light source portion, and opening at one side of a first direction; a base, disposed on the other side of the first direction respective to the housing; and a light guide body, disposed in a space surrounded by the sidewall portion, and comprising an incident surface facing the light source portion, a light-emitting surface for making the light from the incident surface emit toward the side of the first direction, and a peripheral side surface located between the incident surface and the light-emitting surface, wherein the cross-sectional area of the peripheral side surface becomes increasingly larger from a side of the incident surface toward a side of the light-emitting surface. 
         [0010]    In a preferred embodiment of the present invention, the light source portion further comprises a light-transmitting resin covering the LED chip and allowing the light from the LED chip to pass through. 
         [0011]    In a preferred embodiment of the present invention, the light-transmitting resin contains a fluorescent material, the fluorescent material is excited by the light from the LED chip and emits a light having a wavelength that is different from the light from the LED chip. 
         [0012]    In a preferred embodiment of the present invention, the light-transmitting resin is in a shape of dome. 
         [0013]    In a preferred embodiment of the present invention, the light source portion further comprises a lead carrying the LED chip and a case covering at least one part of the lead. 
         [0014]    In a preferred embodiment of the present invention, the incident surface of the light guide body is a recessed surface that is recessed toward the one side of the first direction, and accommodates the light source portion. 
         [0015]    In a preferred embodiment of the present invention, the light-emitting surface of the light guide body comprises a recessed surface overlapping the incident surface as viewed in the first direction and being recessed toward the other side of the first direction. 
         [0016]    In a preferred embodiment of the present invention, the light-emitting surface of the light guide body comprises a plurality of lens surfaces, each being in shape of dome. 
         [0017]    In a preferred embodiment of the present invention, the light source portion further comprises a LED substrate carrying a plurality of LED chips, and a weir portion formed on the LED substrate to surround the LED chips; and the light-transmitting resin is formed in an area surrounded by the weir portion, and comprises a flat light-emitting surface toward the one side of the first direction. 
         [0018]    In a preferred embodiment of the present invention, the light-emitting surface of the light-transmitting resin is located further on the other side of the first direction than the end of weir portion at the one side of the first direction. 
         [0019]    In a preferred embodiment of the present invention, the light guide body further comprises a ring groove surrounding the incident surface and engaging the weir portion. 
         [0020]    In a preferred embodiment of the present invention, the incident surface of the light guide body is a recessed surface that is recessed toward the one side of the first direction and is spaced apart from the light-emitting surface of the light-transmitting resin. 
         [0021]    In a preferred embodiment of the present invention, the incident surface of the light guide body comprises a circular bottom surface and a side surface with a circular cross-section. 
         [0022]    In a preferred embodiment of the present invention, the light-emitting surface of the light guide body comprises a recessed surface overlapping the incident surface as viewed in the first direction and being recessed toward the other side of the first direction. 
         [0023]    In a preferred embodiment of the present invention, the light-emitting surface of the light guide body comprises a plurality of lens surfaces, each being in shape of dome. 
         [0024]    In a preferred embodiment of the present invention, the incident surface of the light guide body is smaller than the light-emitting surface of the light-transmitting resin. 
         [0025]    In a preferred embodiment of the present invention, the incident surface of the light guide body and the light-emitting surface of the light-transmitting resin are in contact with each other. 
         [0026]    In a preferred embodiment of the present invention, the sidewall portion is bright white. 
         [0027]    In a preferred embodiment of the present invention, further comprising a holder having a shape of surrounding a part of the light guide body at the one side of the first direction, and the light guide body being held between the holder and the bottom portion of the housing; wherein the holder is mounted on the housing. 
         [0028]    In a preferred embodiment of the present invention, the housing further comprises a female screw formed on the sidewall portion, and the holder comprises a male screw threadably engaged with the female screw of the housing. 
         [0029]    In a preferred embodiment of the present invention, the housing further comprises a heat-dissipating element constituting the bottom portion and the sidewall portion and being made of metal. 
         [0030]    In a preferred embodiment of the present invention, the heat-dissipating element comprises a plurality of fins. 
         [0031]    In a preferred embodiment of the present invention, further comprising a power source providing electric power to the LED chip; and the housing further comprising a power source accommodating portion mounted on the other side of the first direction relative to the heat-dissipating element, wherein the power source accommodating portion accommodates the power source and is made of resin. 
         [0032]    In a preferred embodiment of the present invention, the sidewall portion of the housing comprises an inner side surface surrounding the peripheral side surface of the light guide body with a gap therebetween. 
         [0033]    In a preferred embodiment of the present invention, the cross-sectional area of the inner side surface becomes increasingly larger toward the one side of the first direction. 
         [0034]    In a preferred embodiment of the present invention, wherein the inner side surface is a bright white surface or a metallic luster surface. 
         [0035]    According to this structure, the light from the light source portion emits toward the one side of the first direction from the light-emitting surface of the light guide body. Therefore, it can emit selectively to the desired field rather than emitting all directions of the periphery of the LED bulb. Therefore, the LED bulb, e.g. is adapted to be used as a replacement for the halogen lamp to be mounted on the lighting fixture such as down light. 
         [0036]    Other features and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a front view showing a LED bulb according to a first embodiment of the present invention; 
           [0038]      FIG. 2  is a plain view showing the LED bulb of  FIG. 1 ; 
           [0039]      FIG. 3  is a bottom view showing the LED bulb of  FIG. 1 ; 
           [0040]      FIG. 4  is a cross-sectional view taken along line IV-IV of  FIG. 1 ; 
           [0041]      FIG. 5  is a cross-sectional view showing a light source portion used in the LED bulb of  FIG. 1 ; 
           [0042]      FIG. 6  is a plain view showing a light source substrate of the light source portion used in the LED bulb of  FIG. 1 ; 
           [0043]      FIG. 7  is a bottom view showing a light source substrate of the light source portion used in the LED bulb of  FIG. 1 ; 
           [0044]      FIG. 8  is a cross-sectional view showing a LED bulb according to a second embodiment of the present invention; 
           [0045]      FIG. 9  is a plain view showing the LED bulb of  FIG. 8 ; 
           [0046]      FIG. 10  is a cross-sectional view showing a LED bulb according to a third embodiment of the present invention; 
           [0047]      FIG. 11  is a plain view showing the LED bulb of  FIG. 10 ; 
           [0048]      FIG. 12  is a front view showing a LED bulb according to a fourth embodiment of the present invention; 
           [0049]      FIG. 13  is a plain view showing the LED bulb of  FIG. 12 ; 
           [0050]      FIG. 14  is a cross-sectional view taken along line XIV-XIV of  FIG. 12 ; 
           [0051]      FIG. 15  is an enlarged cross-sectional view showing main part of the light source portion and the light guide body used in the LED bulb of  FIG. 12 ; 
           [0052]      FIG. 16  is a cross-sectional view showing a LED bulb according to a fifth embodiment of the present invention; 
           [0053]      FIG. 17  is a cross-sectional view showing a LED bulb according to a sixth embodiment of the present invention; 
           [0054]      FIG. 18  is a plain view showing the LED bulb of  FIG. 17 ; 
           [0055]      FIG. 19  is a cross-sectional view showing a LED bulb according to a seventh embodiment of the present invention; 
           [0056]      FIG. 20  is a plain view showing the LED bulb of  FIG. 19 ; 
           [0057]      FIG. 21  is a cross-sectional view showing a LED bulb according to an eighth embodiment of the present invention; and 
           [0058]      FIG. 22  is a plain view showing an example of a conventional LED bulb. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0059]    Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 
         [0060]      FIG. 1  to  FIG. 4  show a LED bulb according to a first embodiment of the present invention. The LED bulb  101  of this embodiment comprises a housing  200 , a light source portion  300 , a light guide body  400 , a power source  500  and a base  600 . The LED bulb  101 , e.g. is used as a replacement for the halogen lamp to be mounted on the lighting fixture such as down light. 
         [0061]    The housing  200  is a primary element of the LED bulb  101 , and in this embodiment, comprises a heat-dissipating element  210  and a power source accommodating portion  220 . The heat-dissipating element  210 , e.g. includes a metal such as aluminum, and includes a bottom portion  201  and a sidewall portion  202  as shown in  FIG. 4 . The bottom portion  201  is a circular plate which supports the light source portion  300 . The sidewall portion  202  is a cylinder which surrounds the bottom portion  201 . A female screw  221  is formed on the inner side of the upper portion of the sidewall portion  202  in the figure. As shown in  FIG. 1 , a plurality of fins  211  are formed on the outer surface of the heat-dissipating element  210 . The inner surface of the sidewall portion  210  is set to dark color such as black. 
         [0062]    The power source accommodating portion  220 , e.g. includes a resin such as polycarbonate, and is a cylinder whose diameter becomes smaller toward the bottom of the figure. The power source accommodating portion  220  is mounted on the heat-dissipating element  210  through spiral engagement caused by the screw (not shown) formed respectively or through adhesion. 
         [0063]    The light source portion  300  is the light source of the LED bulb  101 , and as shown in  FIG. 4 , is supported by the bottom portion  201  of the housing  200  with a light source substrate  370  disposed therebetween. As shown in  FIG. 5 , the light source portion  300  comprises a plurality of LED chips  310 , a light-transmitting resin  320 , a lead  330  and a case  340 . 
         [0064]    The LED chip  310  includes a n-type semiconductor layer, a p-type semiconductor layer and an active layer sandwiched between the n-type semiconductor layer and the p-type semiconductor layer having, e.g. GaN series semiconductor material, and, e.g. emits blue light. The lead  330 , e.g. includes the metal such as Cu alloy or Fe alloy, and carries a plurality of LED chips  310 . The LED chips  310  are connected to the proper portion of the lead  330  by the connecting wires. 
         [0065]    The case  340 , e.g. includes white resin which covers a part of the lead  330 . A portion of the lead  330  exposed from the case  340  is used as a terminal that carries the light source portion  300  on the light source substrate  370 . The light-transmitting resin  320  covers a plurality of LED chips  310 , and is formed on the case  340 . The light-transmitting resin  320  is in a shape of dome, and e.g. includes a transparent epoxy resin containing a fluorescent material. The fluorescent material emits yellow light when excited by the blue light from the LED chip  310 . 
         [0066]    The light source substrate  370  is mounted on the bottom portion  201  of the housing  200  by, e. g. adhesive paste or adhesive film, and includes a substrate  371  and a metal layer  372 , as shown in  FIG. 6  and  FIG. 7 . The substrate  371 , e.g. includes glass epoxy resin or aluminum with surface insulation treatment, and is substantially circular. The metal layer  372  is a plating layer, e.g. laminated by Cu, Ni and Au, and includes a layout pattern  373  and a heat-dissipating pattern  374 . The layout pattern  373  is formed on one side surface of the substrate  371 , and is used for carrying the light source portion  300  and providing electric power to the light source portion  300 . The heat-dissipating pattern  374  is formed on the other side surface of the substrate  371 , and is formed by covering almost the whole area of the surface. 
         [0067]    The light guide body  400 , e.g. includes a transparent epoxy resin, and as shown in  FIG. 4 , is disposed in a space surrounded by the sidewall portion  202  of the housing  200 . The light guide body  400  includes an incident surface  410 , a light-emitting surface  420  and a peripheral side surface  430 . The incident surface  410  is disposed on the bottom portion of the light guide body  400  and corresponds to the light source portion  300 . In this embodiment, the incident surface  410  is a recessed surface that is recessed upward, and accommodates the light source portion  300 . The light from the light source portion  300  is incident to the incident surface  410 . The light-emitting surface  420  is disposed on the top portion of the light guide body  400 , and in this embodiment, is a circular plane. The incident light from the incident surface  410  travels in the light guide body  400 , and then emits out from the light-emitting surface  420 . The peripheral side surface  430  is located between the incident surface  410  and the light-emitting surface  420 , and is a cylinder whose cross-sectional area becomes larger from lower portion toward upper portion. 
         [0068]    The light guide body  400  is pressed to fix to the bottom portion  201  with a light source substrate  370  disposed therebetween. The press is accomplished by a holder  480 . The holder  480  is a ring element, e.g. including resin, and engages the light guide body  400  loosely. A male screw  481  is formed on the holder  480 . When the male screw  481  threadably engages with the female screw  221  of the housing  200 , the holder  480  is mounted on the housing  200 . If the holder  480  is fastened to the housing  200 , the light guide body  400  is held between the holder  480  and the bottom portion  201 . 
         [0069]    The power source  500  provides electric power to the light source portion  300 , and includes a power source substrate  510  and a plurality of electronic components  520 . The power source substrate  510 , e.g. includes a glass epoxy resin, is accommodated in the power source accommodating portion  220  of the housing  200 , and is mounted on the power source accommodating portion. The electronic components  520  is mounted on the power source substrate  510 , and e.g. includes transformer, capacitor, diode, resistor, integrated circuit (IC) chip. 
         [0070]    The base  600  is used to mount the LED bulb  101  on the lighting fixture such as down light, receives the external electric power, and, e.g. complies with the industrial standard such as JIS (Japanese Industrial Standards). The base  600  generally includes a tube portion having insulating material and a screw portion made of metal and mounted on the bottom thereof. 
         [0071]    Further, the operation of the LED bulb  101  is described as follows. 
         [0072]    According to this embodiment, the light from the light source portion  300  emits toward the top of  FIG. 4  from the light-emitting surface  420  of the light guide body  400 . Therefore, it can emit selectively to the desired field rather than emitting all directions of the periphery of the LED bulb  101 . Therefore, the LED bulb  101 , e.g. is adapted to be used as a replacement for the halogen lamp to be mounted on the lighting fixture such as down light. 
         [0073]    Since the light-transmitting resin  320  of the light source portion  300  is in a shape of dome, the light from the LED chip  310  can concentrate upward. Further, the incident surface  410  of the light guide body  400  is a recessed surface that accommodates the light source portion  300  so that almost all light from the light source portion  300  is incident to the light guide body  400 , thereby facilitating the high brightness of the LED bulb  101 . The peripheral side surface  430  guides the light traveling upward obliquely from the light source portion  300  to the light-emitting surface  420  due to the total reflection. 
         [0074]    The heat generated by the light source portion  300  can be conducted to the sidewall portion  202  from the bottom portion  201  rapidly because the housing  200  includes the heat-dissipating element  210  having metal. The fins  211  facilitate dissipating the heat outside. Moreover, the light weight of the LED bulb  101  can be accomplished because the housing  200  includes the power source accommodating portion  220  having resin. 
         [0075]      FIG. 8  to  FIG. 21  show the other embodiments of the present invention. In addition, the same or similar elements of the embodiments in these figures are designated with the same reference numerals. 
         [0076]      FIG. 8  and  FIG. 9  show a LED bulb according to a second embodiment of the present invention. The difference between the LED bulb  102  of this embodiment and the foregoing embodiment is the structure of the light-emitting surface  420  of the light guide body  400 . In this embodiment, the light-emitting surface  420  includes a plurality of lens surfaces  422 . The lens surfaces  422  are in shape of dome with small size respectively, and are arranged in the manner of being adjacent to each other and being evenly spaced apart from each other as shown in  FIG. 9 . 
         [0077]    According to this embodiment, the LED bulb  102  may also be used as a replacement for the halogen lamp. Moreover, the illuminance in the illumination field can be further raised by including the lens surfaces  422 . 
         [0078]      FIG. 10  and  FIG. 11  show a LED bulb according to a third embodiment of the present invention. The difference between the LED bulb  103  of this embodiment and the foregoing embodiment is the structure of the light-emitting surface  420  of the light guide body  400 . In this embodiment, the light-emitting surface  420  includes a recessed surface  421  and a plurality of lens surfaces  422 . The recessed surface  421  is recessed downward from the top end of the light guide body  400 , and has a circular cross-section as shown in  FIG. 11 . The recessed surface  421  of the light-emitting surface  420  overlaps the incident surface  410  from a top view. 
         [0079]    According to this embodiment, the LED bulb  103  may also be used as a replacement for the halogen lamp. Moreover, since the light-emitting surface  420  includes the recessed surface  421 , the light that is incident through the incident surface  410  and travels upward straightly will emit out from the recessed surface  421  rapidly. This embodiment is adapted for restraining the light that travels upward straightly from diffusing undesirably in the light guide body  400 . 
         [0080]      FIG. 12  to  FIG. 15  show a LED bulb according to a fourth embodiment of the present invention. The difference between the LED bulb  104  of this embodiment and the foregoing embodiment is the structures of the housing  200 , the light source portion  300  and the light guide body  400 . 
         [0081]    In this embodiment, the housing  200  is made integrally of metal such as aluminum. As shown in  FIG. 12 , a plurality of fins  211  are formed on the outer surface of the housing  200  longitudinally with a length approximated to the total length of the housing  200 . Further, a recessed portion  203  which opens downward is formed on the housing  200 . The recessed portion  203  accommodates the power source  500 . The sidewall portion  202  of the housing  200  includes an inner side surface  204 . The inner side surface  204  surrounds the peripheral side surface  430  of the light guide body  400  with a gap therebetween. The inner side surface  204  is a cylinder whose cross-sectional becomes larger from the lower portion toward the upper portion, and is in a configuration alongside the peripheral side surface  430  of the light guide body  400 . The inner side surface  204  is a bright white surface with white color or a metallic luster surface formed by metal plating. 
         [0082]    As shown in  FIG. 15 , the light source portion  300  includes a LED substrate  350 , a plurality of LED chips  310 , a weir portion  360  and a light-transmitting resin  320 . The LED substrate  350  includes ceramics, metal such as aluminum with surface insulation treatment or glass epoxy resin, and is rectangular. The LED chips  310  are carried on the LED substrate  350  with e.g. a matrix arrangement. The weir portion  360 , e.g. includes organic silicone resin, and is formed as a ring shape on the LED substrate is  350  to surround the LED chips  310 . The light-transmitting resin  320  is filled in the area surrounded by the weir portion  360  so as to cover the LED chips  310 . The light-transmitting resin  320  has a light-emitting surface  321 . The light-emitting surface  321  is a flat circular surface, and in this embodiment, is located at a position lower than the upper end of the weir portion  360 . The light-transmitting resin  320  is formed by, e.g. injecting a liquid resin material on the LED substrate  350  after finishing the carrying of the LED chips  310  and the formation of the weir portion  360 , and then curing it. 
         [0083]    In this embodiment, the light source substrate  370  includes metal such as aluminum or ceramic. Alternatively, the light source portion  300  may be mounted on the bottom portion  201  directly without the light source substrate  370  disposed therebetween. 
         [0084]    In addition to the incident surface  410 , the light-emitting surface  420  and the peripheral side surface  430 , the light guide body  400  includes a ring groove  440 . The ring groove  440  is formed at the bottom end of the light guide body  400 , and surrounds the incident surface  410 . The ring groove  440  engages the weir portion  360  of the light source portion  300 . When the ring groove  440  engages the weir portion  360 , the incident surface  410  of the light guide body  400  is in contact with the light-emitting surface  321  of the light-transmitting resin  320  of the light source portion  300 . The light guide body  400  is fixed by, e.g. adhering to the housing  200 . 
         [0085]    According to this embodiment, the LED bulb  104  may also be used as a replacement for the halogen lamp. The constitution of connecting the incident surface  410  and the light-emitting surface  321  of the light-transmitting resin  320  of the light source portion  300  can prevent the light from totally reflecting between the light-transmitting resin  320  and the light guide body  400 . The engagement between the ring groove  440  of the light guide body  400  and the weir portion  360  of the light source portion  300  can permit precisely positioning of the light source portion  300  and the light guide body  400 . As shown in  FIG. 15 , since the light-emitting surface  321  of the light-transmitting resin  320  is located at a position lower than the upper end of the weir portion  360 , the connection between the light-emitting surface  321  and the incident surface  410  is secured. The light that is not totally reflected by the peripheral side surface  430  of the light guide body  400  and then passes through the peripheral side surface  430  is incident to the inner side surface  204  of the sidewall portion  202  through the gap. Although the inner side surface  204  is not parallel to the peripheral side surface  430  strictly, the angle therebetween is very small. Therefore, the incident angle of the light that is not totally reflected by the peripheral side surface  430  with respect to the inner side surface  204  is relatively small. Thus, the incident angle of the light that is reflected by the inner side surface  204  with respect to the peripheral side surface  430  is also relatively small. As a result, the light will be incident into the light guide body  400  again. This embodiment is adapted for increasing the proportion of emitting light from the light-emitting surface  420 . 
         [0086]      FIG. 16  shows a LED bulb according to a fifth embodiment of the present invention. The difference between the LED bulb  105  of this embodiment and the foregoing LED bulb  104  is the structure of the light guide body  400 . In this embodiment, the incident surface  410  of the light guide body  400  is a recessed surface that has a bottom surface  411  and a side surface  412 . The bottom surface  411  is at a deep position upward from the lowermost end of the light guide body  400 , and is circular. The side surface  412  is a cylinder whose shape and size in cross section are the same as the bottom surface  411 . In this embodiment, the bottom end of the side surface  412  is consistent with the outer edge of the light-emitting surface  321  because the light-emitting surface  321  of the light-transmitting resin  320  of the light source portion  300  is accommodated in the side surface  412 , or bottom surface  411  and the light-emitting surface  321  have the same shape and size. 
         [0087]    According to this embodiment, the LED bulb  105  may also be used as a replacement for the halogen lamp. Further, the light that reaches at the bottom surface  411  of the incident surface  410  is the light that travels substantially right upward from the light source portion  300 . Such light has a low possibility of being totally reflected by the bottom surface  411 . The light having a relatively greater incident angle with respect to the side surface  412  will be totally reflected by the side surface  412 , and then enters the bottom surface  411 . Therefore, this embodiment is adapted for raising the illuminance in the illumination field, especially the central portion. 
         [0088]      FIG. 17  and  FIG. 18  show a LED bulb according to a sixth embodiment of the present invention. The difference between the LED bulb  106  of this embodiment and the foregoing LED bulbs  104 , 105  is the structure of the light-emitting surface  420  of the light guide body  400 . In this embodiment, the light-emitting surface  420  includes a plurality of lens surfaces  422  as does the foregoing LED bulb  102 . The lens surfaces  422  are in shape of dome with small size respectively, and are arranged in the manner of being adjacent to each other and being evenly spaced apart from each other as shown in  FIG. 18 . 
         [0089]    According to this embodiment, the LED bulb  106  may also be used as a replacement for the halogen lamp. Moreover, the illuminance in the illumination field can be further raised by including the lens surfaces  422 . 
         [0090]      FIG. 19  and  FIG. 20  show a LED bulb according to a seventh embodiment of the present invention. The difference between the LED bulb  107  of this embodiment and the foregoing LED bulbs  104 - 106  is the structure of the light-emitting surface  420  of the light guide body  400 . In this embodiment, the light-emitting surface  420  includes a recessed surface  421  and a plurality of lens surfaces  422  as does the foregoing LED bulb  103 . The recessed surface  421  is recessed downward from the top end of the light guide body  400 , and has a circular cross-section as shown in  FIG. 20 . The recessed surface  421  of the light-emitting surface overlaps the incident surface  410  from a top view. 
         [0091]    According to this embodiment, the LED bulb  107  may also be used as a replacement for the halogen lamp. Moreover, since the light-emitting surface  420  includes the recessed surface  421 , most of the light that is incident to the bottom surface  411  of the incident surface  410  will emit out from the recessed surface  421  rapidly. This embodiment is adapted for restraining the light that travels upward straightly from diffusing undesirably in the light guide body  400 . 
         [0092]      FIG. 21  shows a LED bulb according to an eighth embodiment of the present invention. The difference between the LED bulb  108  of this embodiment and the foregoing embodiments is the structure of the light guide body  400 . In this embodiment, the size of the incident surface  410  of the light guide body  400  is smaller than that of the light-emitting surface  321  of the light-transmitting resin  320  of the light source portion  300 . The light-emitting surface  321  is divided into a central portion connected with the incident surface  410  and a peripheral portion exposed from the incident surface  410 . The size of the light-emitting surface  420  is determined based on the occurrence of a gap between the light-emitting surface  420  and the sidewall portion  202  of the housing  200 . The inner side surface  204  of the sidewall portion  202  of the housing  200  is a bright white surface with white color or a metallic luster surface by disposing a metal film thereon. The opening of the housing  200  is blocked by a light-transmitting mask  490 . 
         [0093]    According to this embodiment, the LED bulb  108  may also be used as a replacement for the halogen lamp. The light coming from a portion of the light-emitting surface  321  of the light-transmitting resin  320  of the light source portion  300  that is in contact with the incident surface  410  of the light guide body  400  emits out from the light-emitting surface  420  toward the central area of the illumination field. On the other hand, the light coming from a portion of the light-emitting surface  321  that is exposed from the incident surface  410  travels in the space between the light guide body  400  and the sidewall portion  202  and is not incident to the light guide body  400 . Then the light will passes through the light-transmitting mask  490  and emits out directly, or be reflected by the inner side surface  204  of the sidewall portion  202  then passes through the light-transmitting mask  490  and emits out directly. Therefore, the illuminance in the outer side within the illumination field can be raised. The preformation of bright white surface or metallic luster surface on the inner side surface of the sidewall portion  202  can facilitate raising the illuminance. 
         [0094]    While several embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention should not be limited to the particular forms as illustrated, and that all modifications which maintain the spirit and scope of the present invention are within the scope defined in the appended claims.