Abstract:
A lens and a lighting fixture utilizing the same provides a plurality of LED light sources as a single light source with a simple configuration. The lens is used with a plurality of light sources in combination and can have a single focus. The lens can include a plurality of light incident portions each disposed so as to face each of the plurality of light sources, the plurality of light incident portions collimating light beams emitted from the plurality of light sources in parallel with a predetermined optical axis while guiding the light beams inside the lens. A light exiting portion can include a refracting surface disposed on optical paths of the collimated light beams guided from the plurality of the light incident portions into the inside of the lens, with the light exiting portions causing the collimated light beams to exit and be converged on the single focus. A lighting fixture can utilize the lens described herein.

Description:
This application claims the priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2009-265117 filed on Nov. 20, 2009, which is hereby incorporated in its entirety by reference. 
     TECHNICAL FIELD 
     The presently disclosed subject matter relates to a lens and a lighting fixture utilizing the same, and in particular, to a lens and a lighting fixture utilizing the same that can provide a single light source even with a plurality of LED light sources. 
     BACKGROUND ART 
     Conventional LED light source apparatuses have been proposed, that can utilize a plurality of LED light sources and which can be handled as a single light source (for example, Japanese Patent Application Laid-Open No. 2002-157904). 
       FIG. 1  is a cross sectional view of such an LED light source apparatus as described in Japanese Patent Application Laid-Open No. 2002-157904. 
     In  FIG. 1 , the light source apparatus can be applied to a vehicle headlamp  200  and can have a plurality of light-converging cylindrical hoods  210  with an inner reflective surface  211  and a plurality of LED light sources  220  that are disposed so as to correspond to the respective light-converging hoods  210 . The LED light sources  220  can be attached to the respective ends of the light-converging hoods  210  so that their optical axes AX 1  cross the axis AX 2  of the light-converging hood  210  at least one point P. When energized, the LED light sources  220  can emit light which can be reflected by the inner reflective surface  211  of the light-converging hoods  210  so as to be projected from the other end  212  of the light-converging hoods  210 . The light-converging hood  210  should be adjusted by the opening angle α as shown in its cross section including the axis X of one light-converging hood  210 , so that a pseudo light source P can be formed at the other end  212 . 
     Since the LED light source apparatus  200  can operate as a pseudo light source P by through a plurality of light-converging hoods  210 , if a certain amount of light intensity is required, the number of LED light sources must increase together with the increased number of the light-converging hoods  210 . In this case, it is difficult to aim the optical axes of large number of LED light sources so as to form a pseudo light source P. A further problem is that the configuration of these light-converging hoods may be complicated. 
     SUMMARY 
     The presently disclosed subject matter was devised in view of these and other problems and features and associated with the conventional art. An aspect of the presently disclosed subject matter can provide a lens and a lighting fixture utilizing the same that can form a plurality of LED light sources as a single light source. 
     According to another aspect of the presently disclosed subject matter, a lens which is capable of being used with a plurality of light sources in combination and which can have a single focus can include: a plurality of light incident portions each disposed so as to face each of the plurality of light sources for collimating light beams emitted from the plurality of light sources in parallel with a predetermined optical axis while guiding the light beams inside the lens; and a light exiting portion including a refracting surface disposed on optical paths of the collimated light beams guided from the plurality of the light incident portions into the inside of the lens, for causing the collimated light beams to exit and be converged on the single focus. 
     According to the presently disclosed subject matter, the light beams emitted from the plurality of light sources can enter the inside of the lens while they are collimated in parallel with a predetermined optical axis (for example, an optical axis of the lens) by the action of the plurality of light incident portions disposed to face the plurality of light sources. Then, the light beams can exit from the refracting surface of the light exiting portion to be converged on the single focus. Since the lens does not utilize any type of converging hood of was used in the conventional art, even if the number of light sources increases, the configuration is not complicated. Accordingly, by utilizing such a lens, a user can utilize a plurality of light sources as a single light source with a simpler configuration than a conventional light source apparatus utilizing a plurality of light-converging hoods. Namely, the lens made in accordance with the principles of the presently disclosed subject matter can gather the light beams (output) emitted from the plurality of light sources, so that a lighting fixture utilizing the lens can serve as a brighter light source. 
     In the lens configured as described above, the light exiting portion can include a center lens portion and a surrounding lens portion arranged to surround the center lens portion. The center lens portion can include a center light exiting surface disposed on at least part of the optical paths of the collimated light beams so that the collimated light beams can exit through the center light exiting surface and be converged on the single focus. The surrounding lens portion can include a surrounding light exiting surface arranged to surround the center light exiting surface and a reflecting surface disposed on at least part of the optical paths of the collimated light beams. The reflecting surface can reflect the collimated light beams reaching there so as to cause the reflected light beams to exit through the surrounding light exiting surface and converge at the single focus. 
     In the lens configured as described above, the light beams emitted from the plurality of light sources can enter the corresponding light incident portions disposed to face the plurality of the light sources so as to be collimated in parallel with the predetermined optical axis by the action of the light incident portions. The collimated light beams entering the inside of the lens and directed to the center lens portion can exit through the center light exiting surface so as to be converged at the single focus. On the other hand, the collimated light beams entering the inside of the lens and directed to the surrounding lens portion can be reflected by the surrounding reflecting surface and exit through the surrounding light exiting surface so as to be converged on a single focus. Accordingly, by utilizing such a lens a user can utilize a plurality of light sources as a single light source with a simpler configuration than a conventional light source apparatus utilizing a plurality of light-converging hoods. Namely, the lens made in accordance with the principles of the presently disclosed subject matter can gather the light beams (output) emitted from the plurality of light sources, so that a lighting fixture utilizing the lens can serve as a brighter light source. 
     In the lens configured as described above, the light incident portions each can be formed of a convex lens surface being convex toward the light source side and configured to collimate the incident light beams with respect to the lens optical axis. 
     Alternatively, the light incident portions each can include a center light incident surface arranged on the respective optical axes, a cylindrical surrounding light incident surface disposed to surround the center light incident surface, and a reflecting surface disposed on the optical paths of the incident light beams from the surrounding light incident surface. 
     In this case, the center light incident surface of the light incident portion may be formed of a convex lens surface being convex toward the light source side and configured to collimate the incident light beams with respect to the lens optical axis, and the reflecting surface may be formed of a revolved parabolic surface to collimate the light beams entering through the surrounding light incident surface. 
     By this configuration, the light gathering performance at the light incident side can be improved, thereby improving the light utilizing efficiency. Accordingly, the same light intensity can be achieved by reduced number of light sources according to the improved light utilizing efficiency, thereby reducing costs. By reducing the number of the used light sources, the entire size can be reduced, and accordingly, the lighting fixture utilizing the lens can be miniaturized. 
     In the lens configured as described above, the center light exiting surface may be formed of a convex lens surface being convex toward the illumination direction and having a focus coinciding with the lens focus with the lens optical axis as a rotation axis. Furthermore, the reflecting surface of the surrounding lens portion may be formed of a revolved parabolic surface with the lens optical axis as a rotation axis and having a focus coinciding with the lens focus. 
     According to still another aspect of the presently disclosed subject matter, a lighting fixture can include a plurality of light sources, and the lens with one of the above-mentioned configurations, wherein the plurality of light sources can face the respective light incident portions. 
     In the lighting fixture configured as described above, the plurality of light sources may be formed of LED light sources. 
     In another exemplary embodiment of the lighting fixture configured as described above, the lighting fixture can further include a second lens disposed in front of the lens and having a focus at or near the single focus of the lens. 
     In still another exemplary embodiment of the lighting fixture configured as described above, the lighting fixture can further include a reflector disposed in front of the lens and having a focus at or near the single focus of the lens. 
     In the conventional LED light source apparatus  200  as shown in  FIG. 1 , a plurality of light-converging hoods  210  can be utilized to form a pseudo light source P. In this case, the light-converging hood  210  must be adjusted by the opening angle α as shown in its cross section including the axis X of one light-converging hood  210 , so that the light can project in the optical axis AX 2  direction to serve as a pseudo light source P derived from the plurality of LED light sources  220 . In this case, the inner surface of the hoods  210  must be subjected to surface treatment such as aluminum deposition or the like to form a uniform reflecting surface, thereby increasing the manufacturing cost in terms of yield or the like. Accordingly, it is difficult to obtain a light source utilizing a plurality of LED light sources just like an incandescent bulb or the like. 
     However, the lens and the lighting fixture utilizing the lens according to the presently disclosed subject matter can project light by the action of the center light exiting surface and the surrounding light exiting surface in the optical axis direction of the lens as a whole. This means the light beams from the plurality of light sources can be utilized as a single light source just like an incandescent bulb or the like (light source that can emit light omnidirectionally). 
     Accordingly, the presently disclosed subject matter can provide a lens and a lighting fixture utilizing the lens that can be configured simpler than the conventional light source apparatus while utilizing a plurality of LED light sources as a single light source. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other characteristics, features, and advantages of the presently disclosed subject matter will become clear from the following description with reference to the accompanying drawings, wherein: 
         FIG. 1  is a cross sectional view of a conventional light source apparatus for a vehicle headlamp; 
         FIG. 2  is a schematic cross sectional view of a lens made in accordance with principles of the presently disclosed subject matter and a plurality of LED light sources in combination to form a lighting fixture made in accordance with principles of the presently disclosed subject matter; 
         FIG. 3  is a schematic cross sectional view of the lens of  FIG. 2  and another lens used in combination to form another lighting fixture made in accordance with principles of the presently disclosed subject matter; 
         FIG. 4  is a schematic cross sectional view of the lens of  FIG. 2  and a reflector R used in combination to form another lighting fixture made in accordance with principles of the presently disclosed subject matter; 
         FIG. 5  is a schematic cross sectional view of a modified example of the lens of the above exemplary embodiment and a plurality of LED light sources used in combination to form a lighting fixture made in accordance with principles of the presently disclosed subject matter; 
         FIG. 6  is a schematic cross sectional view of the modified example of the lens of  FIG. 5  and a plurality of LED light sources used in combination to form a lighting fixture made in accordance with principles of the presently disclosed subject matter; and 
         FIG. 7  is a schematic cross sectional view of another lens made in accordance with principles of the presently disclosed subject matter and a plurality of LED light sources in combination to form another lighting fixture made in accordance with principles of the presently disclosed subject matter 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A description will now be made below to lenses and lighting fixtures utilizing a lens and a plurality of LED light sources in combination with reference to the accompanying drawings in accordance with exemplary embodiments. 
     The lens made in accordance with the principles of the presently disclosed subject matter can be utilized in the field of vehicle headlamps, general-purpose lighting fixtures, game machines, and the like. In these cases, the lens can be utilized singly or in combination with a plurality of light sources including LED light sources, point light sources, and the like. 
       FIG. 2  illustrates a lens  100  according to the present exemplary embodiment. The lens  100  can be a solid lens body formed by injection molding a transparent resin (such as acrylic resins, polycarbonate resins, and the like) or a glass material. The lighting fixture of the present exemplary embodiment can be composed of the lens  100  and a plurality of LED light sources  30 . Each of the LED light sources  30  can be an LED light source formed by packaging one or a plurality of LED chips. In  FIG. 2 , the plurality of LED light sources  30  can be distributed and arranged on a certain plane at a predetermined region so that the respective optical axes AX 1  are directed in the same direction (in  FIG. 2 , the direction is an upward direction as one example). 
     The lens  100  can include a plurality of light incident portions  10  and a light exiting portion  20 . Each of the light incident portions  10  may be disposed to face each of the plurality of LED light sources  30  (each light emission surface). The light incident portions  10  can each have a light incident surface  11 . The light incident surface  11  can receive light beams emitted from the corresponding LED light source  30  and collimate the same with respect to the optical axis AX 1  (namely the main optical axis AX 2 ) of the LED light source  30 . In the exemplary embodiment of  FIG. 2 , the light incident surface  11  can be configured by a convex lens that is convex toward the LED light source. 
     The light exiting portion  20  can be disposed along the optical paths of the collimated light beams entering the inside of the lens through the respective light incident portions  10 . The light exiting portion  20  can include a center lens portion  21  and a surrounding lens portion  22  disposed to surround the center lens portion  21 . The surrounding lens portion  22  can be located adjacent to the center lens portion  21 . 
     The center lens portion  21  can include a center light exiting surface  21   a . The center light exiting surface  21   a  can be disposed on the optical paths of the collimated light beams designated as “Ray 1 ” in  FIG. 2  which are emitted from the LED light sources  30  that are disposed on a center area among the plurality of LED light sources  30  distributedly disposed in the predetermined region. The center light exiting surface  21   a  can be a lens surface that can converge the collimated light beams Ray 1  that reach the center light exiting surface  21   a  at the single focus F. In the exemplary embodiment of  FIG. 2 , the center light exiting surface  21   a  can be formed of a convex lens surface formed using the optical axis AX 2  as a rotation axis and being convex toward the illumination direction. 
     The surrounding lens portion  22  can include a cylindrical surrounding light exiting surface  22   a  disposed to surround the center light exiting surface  21   a  and a reflecting surface  22   b . The reflecting surface  22   b  can be disposed on optical paths of the collimated light beams designated as “Ray 2 ” in  FIG. 2  which are emitted from the LED light sources  30  that are disposed on a surrounding area around the center area among the plurality of LED light sources  30  distributedly disposed in the predetermined region. The reflecting surface  22   b  can totally reflect the collimated light beams Ray 2  so as to cause the reflected light beams to exit through the surrounding light exiting surface  22   a  and be converged at the single focus F. In the exemplary embodiment of  FIG. 2 , the reflecting surface  22   b  may be formed of a revolved parabolic surface formed using the optical axis AX 2  as a rotation axis. 
     Further, as shown in  FIG. 5 , the surface of the lens  100  corresponding to the reflecting surface  22   b  may be subjected to a mirror treatment such as an aluminum deposition  22   b   1  or the like. Alternatively, on the surface of the lens  100  corresponding to the reflecting surface  22   b  a reflective member  23  (shown in  FIG. 6 ) having a mirror finish such as an aluminum deposition can be disposed. By these configurations, the collimated light beams Ray 2  reaching the reflecting surface  22   b  can be prevented from exiting through the reflecting surface  22   b , thereby improving the light utilizing efficiency. 
     Note that in  FIGS. 5 and 6  the aluminum deposition  22   b   1  and the reflecting member  23  are respectively illustrated with a thicker dimension for emphasis than the actual dimensions, and a person skilled in the art can easily recognize that the actual thickness of these layers is very thin when compared with the lens dimension. 
     In the lens  100  configured as described above, the light beams emitted from the plurality of LED light sources  30  can enter the inside of the lens  100  while being collimated by the plurality of light incident portions  10  which are disposed to face the corresponding LED light sources  30 , so that the collimated light beams Ray 1  and Ray 2  are parallel with the optical axis AX 1  of the LED light sources  30 . Then, among the entering light beams, the collimated light beams Ray 1  directed to the center lens portion  21  can exit through the center light exiting surface  21   a  to be converged on the single focus F. On the other hand, the collimated light beams Ray 2  directed to the surrounding lens portion  22  can be totally reflected by the surrounding reflecting surface  22   b  to exit through the surrounding light exiting surface  22   a  and be converged on the single focus F. 
     Since the lens  100  configured as described above does not utilize a converging hood  210  of the type shown in  FIG. 1  with reference to the conventional art, even if the number of light sources  30  increases, the configuration is not so complicated. Accordingly, by utilizing such a lens  100  a user can utilize a plurality of light sources  30  as a single light source with a simpler configuration than a conventional light source apparatus utilizing a plurality of light-converging hoods  210 . Namely, the lens  100  can gather the light beams (output) emitted from the plurality of light sources  30 , so that a lighting fixture utilizing the lens  100  can serve as a brighter light source with the many LED light sources employed. 
       FIG. 3  shows another lighting fixture utilizing the lens of the present exemplary embodiment. The lighting fixture of  FIG. 3  can include the lens  100  of  FIG. 2  and another lens L so as to effectively control the light distribution formed by the light beams from the plurality of LED light sources  30 . The shown lens L can have a focus at or near the focus F of the lens  100  so that the converged light beams can be collimated for projection. In this configuration, all the light beams emitted from the LED light sources  30  arranged in a wide area can be utilized as a single light source for projecting collimated light beams. This can be applied to a lighting fixture with a high intensity. Still another lighting fixture is illustrated in  FIG. 4  wherein the lens of the present exemplary embodiment is utilized. In the lighting fixture of  FIG. 4 , the light beams at the single focus F from the lens  100  can be considered as a light source. When a reflector R having a focus at or near the focus F of the lens  100  is combined with the lens  100 , the plurality of LED light sources  30  arranged in a wide area can be handled as a single light source for light distribution control. 
     Since the lens  100  can have the surrounding lens portion  22 , when compared with the case where a lens has a center lens portion  21  only for forming the single focus F, the light amount and the illumination area for the reflector R can be improved. In other words, the combination of the surrounding lens portion  22  with the center lens portion  21  can result in improved light output and coverage for the reflector R. 
     In the conventional LED light source apparatus  200  as shown in  FIG. 1 , a plurality of light-converging hoods  210  can be utilized to form a pseudo light source P. In this case, the light-converging hood  210  must be subjected to a surface treatment such as aluminum deposition or the like to form a uniform reflecting surface  211  so that the light can project in the optical axis AX 2  direction to serve as a pseudo light source P derived from the plurality of LED light sources  220 . However, depending on the surface treatment, reflecting losses may occur, thereby degrading the light utilization efficiency. Furthermore, since the hood has a narrow opening and a deep inside, it is difficult to form a uniform reflecting surface using surface treatments such as aluminum deposition or the like, thereby increasing the manufacturing cost in terms of yield or the like. 
     However, the lens  100  and the lighting fixture utilizing the lens  100  of the present exemplary embodiment can project light by the action of the center light exiting surface  21   a  and the surrounding light exiting surface  21   b  in the optical axis AX 2  direction without the need for any surface treatment like in the conventional light source apparatus  200 , but with only the specific lens design. Accordingly, the light beams from the plurality of light sources  30  can be utilized as a single light source just like an incandescent bulb or the like (light source that can emit light omnidirectionally). 
     Next, modified examples of the presently disclosed subject matter will be described. 
     In the above exemplary embodiment, the light incident portions  10  have been configured to include a convex lens  11  that is convex toward the LED light source, but the presently disclosed subject matter is not limited to this. For example, the light incident portions  10  each can include, as shown in  FIG. 7 , a center light incident surface  11  arranged on the respective optical axes AX 1  of the LED light sources  30 , a cylindrical surrounding light incident surface  12  disposed to surround the center light incident surface  11 , and a reflecting surface  13  disposed on the optical paths of the incident light beams depicted as “Ray 3 ” in  FIG. 7 , entering through the surrounding light incident surface  12 . In this case, the incident light beams Ray 3  entering through the surrounding incident surface  12  can be reflected by the reflecting surface  12  so as to be collimated in parallel with the lens optical axis AX 1 , and directed to the reflecting surface  22   b  or the center light exiting surface  21   a  of the light exiting portion. The reflecting surface  13  may be formed of a revolved parabolic surface. The light exiting portion of this lens can have the same configuration as that of  FIG. 2 , and a description thereof will be omitted here. 
     This configuration can further improve the light gathering performance at the light incident side, thereby improving the light utilization efficiency. Accordingly, the number of light sources can be reduced by the improved degree, thereby decreasing its cost. Further, depending on the decreased number of light sources, the entire size can be reduced, thereby obtaining more compact lighting fixtures. 
     This modified example of the lens  100  can allow a user to utilize a plurality of light sources  30  as a single light source with a simpler configuration than a conventional light source apparatus utilizing a plurality of light-converging hoods  210 . Namely, the modified example of the lens  100  can gather the light beams (output) emitted from the plurality of light sources  30 , so that the lighting fixture utilizing the lens  100  can serve as a brighter light source with the many LED light sources employed. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the presently disclosed subject matter without departing from the spirit or scope of the presently disclosed subject matter. Thus, it is intended that the presently disclosed subject matter cover the modifications and variations of the presently disclosed subject matter provided they come within the scope of the appended claims and their equivalents. All related art references described above are hereby incorporated in their entirety by reference.