Abstract:
The invention is a lighting unit that can be manufactured repeatedly with a high precision. This problem is solved with a lighting unit having a light source for emitting light. The lighting unit also includes a fiber optic body that defines an optical axis. The fiber optic body extends about the light source to receive and direct the light emitted by the light source. The fiber optic body includes a lateral surface that defines an interface for reflecting a portion of the light impinging thereon to create reflected light. The fiber optic body also includes an optical lens coaxial with the optical axis, the lateral surface and the fiber optic body for refracting another portion of light to create refracted light in a direction parallel with the reflected light.

Description:
BACKGROUND ART  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a lighting unit with at least one light source and at least one fiber-optic body connected downstream from the light source.  
         [0003]     2. Description of the Related Art  
         [0004]     Elements of this invention are known from U.S. Pat. No. 4,698,730. The fiber-optic body of this lighting unit is manufactured by custom production by casting a resin. It has a hemispherical converging lens which forms an acute-angle notch with the hollow cylinder surrounding it. During the process of removing the lighting unit from the mold, there is the risk of breakage of material, which can damage the surface of the workpiece.  
       SUMMARY OF THE INVENTION  
       [0005]     The problem on which the invention is based is to construct a lighting unit that can be manufactured repeatedly with a high precision. This problem is solved with a lighting unit having a light source for emitting light. The lighting unit also includes a fiber optic body that defines an optical axis. The fiber optic body extends about the light source to receive and direct the light emitted by the light source. The fiber optic body includes a lateral surface that defines an interface for reflecting a portion of the light impinging thereon to create reflected light. The fiber optic body also includes an optical lens coaxial with the optical axis, the lateral surface and the fiber optic body for refracting another portion of light to create refracted light in a direction parallel with the reflected light.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     Advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0007]      FIG. 1  is a cross-sectional side view of a lighting unit with a light source and a fiber-optic body;  
         [0008]      FIG. 2  is a cross-sectional side view of a lighting unit with several light-emitting sides;  
         [0009]      FIG. 3  is a cross-sectional side view of an alternative embodiment of the invention with two light sources;  
         [0010]      FIG. 4  is a cross-sectional perspective view of a lighting unit with two fiber-optic bodies. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]      FIG. 1  shows a section through a lighting unit, generally indicated at  2 , with a light source  10  and a fiber-optic body  20 . The light emitted by the light source  10  is conducted through the fiber-optic body  20  downstream from the light source and is emitted into the environment  1  by the fiber-optic body  20 . The fiber-optic body  20  includes an optical lens  27 . The lighting unit  2  defines an optical axis  5  which is perpendicular to the optical lens  27 .  
         [0012]     The light source  10  is, for example, a light-emitting diode  10  which is arranged on the optical axis  5  of the lighting unit  2 . The light-emitting diode  10  consists of electronic parts, e.g., a light-emitting chip  13  and at least two electric terminals  12  connected to the light-emitting chip  13 .  
         [0013]     The light-emitting diode  10  is surrounded by the fiber-optic body  20 . The fiber-optic body  20  is an injection molded plastic part made of PMMA or some other optically clear thermoplastic. It includes a socket  25  and a truncated paraboloid  24  with a transitional edge  23  therebetween.  
         [0014]     The socket  25  has a connecting flange  36  to which a cylindrical section  37  is connected. A notch  38  oriented in the circumferential direction and having an inclined notch base  39  is arranged on the cylindrical section  37 . The light-emitting diode  10  is situated in the socket  25  in such a way that a straight line through the transitional edge  23  and the light-emitting diode  10  forms an angle of approximately 10 degrees with a plane through the light-emitting diode  10  normal to the optical axis  5  of the lighting unit  2 . In other words, the light-emitting diode  10  is set back slightly from a plane perpendicular to the optical axis  5  extending through the transitional edge  23 .  
         [0015]     The truncated paraboloid  24  includes a lateral surface  28  and an light-emitting side  22 . Its diameter increases steadily from the transitional edge  23  on the socket  25  to the light-emitting side  22 . The diameter of the fiber-optic body  20  on the light-emitting side  22  is approximately equal to the length of the lighting unit  2  in the case of the lighting unit  2  depicted in  FIG. 1 .  
         [0016]     The lateral surface  28  of the fiber-optic body  20  is a closed surface. A straight line passing through the light-emitting diode  10  and any point  29  on the lateral surface  28  intersects the normal to the lateral surface  28  at this point  29  at an angle greater than the limiting angle of the total reflection on the interface  31  of the material of the fiber-optic body  20  with the ambient environment  1 . By way of example, the limiting angle is approx. 42 degrees in the case of PMMA.  
         [0017]     The light-emitting side  22  includes a flat ring-shaped surface  43  arranged normal to the optical axis  5  of the lighting unit  2 . As can be seen in the Figures, the flat ring-shaped surface  43  defines an inner diameter. In the embodiment shown, the area content of this ring-shaped surface  43  amounts to approximately three-quarters of the cross-sectional area of the light-emitting side  22 . The optical lens  27  having the shape of a converging lens  27  surrounded by the ring-shaped surface  43  is arranged concentrically with the ring-shaped surface  43  countersunk in a hollow cylinder  47 . The converging lens  27  is in the shape of a section of sphere. For example, the diameter of the base area  26  of the spherical section amounts to approximately four times the height of the spherical section. The distance between the base area  26  and the light source  10  amounts to approximately half the length of the fiber-optic body  20 . It is greater than the distance from the base area  26  to its focal point  33  (shown in  FIG. 2 ). The base area  26  and the surface of the converging lens  27  intersect at a bordering edge  34 . A groove  41  is arranged around this bordering edge  34 . The groove  41  has a constant cross section over its length. For example, it has a planar groove base  42 , which is arranged normal to the optical axis  5 . The groove  41  is bordered by the hollow cylinder  47 , which extends outwardly therefrom. The groove base  42  develops into transitional grooves  51 ,  52  in the adjacent areas.  
         [0018]     In the embodiment of the lighting unit  2  depicted in  FIG. 1 , the bordering edge  34  of the converging lens  27  and the transitional edge  23  between the socket  25  and the truncated paraboloid  24  form peripheral lines on the lateral surface of an imaginary cylinder, which is coaxial with the optical axis  5  of the lighting unit  2 .  
         [0019]     This lighting unit  2  is manufactured in one step in an injection molding process, for example. The injection mold may have a nub near the inserted light-emitting diode. This nub then acts as a flow barrier during injection molding to reduce the rate of flow of the injection-molded material flowing toward the electronic parts. On the workpiece, this nub is designed as a flow notch  38 .  
         [0020]     Rams that can be moved axially, for example, are arranged on the end face of the injection mold. One ram presses and forms the shape of the converging lens  27 . The material is thereby compressed in the fiber-optic body. The converging lens  27  can therefore be manufactured with a high surface quality. When the ram is retracted, the groove  41  prevents damage to the surrounding surfaces of the component.  
         [0021]     After completion of the lighting unit  2 , it can be removed easily from the mold after retracting the ram. The shrinkage of the workpiece in cooling is minor. The functional surfaces, i.e., mainly the converging lens  27  and the ring-shaped surface  43  have a high surface quality. In automated production, the lighting units  2  can be produced in this way repeatedly with a high precision within narrow tolerances of the optical properties.  
         [0022]     The converging lens  27  of the finished lighting unit  2  is inside the outer contour of the fiber-optic body  20 . It is therefore well protected from damage.  
         [0023]     During operation of the lighting unit  2 , light is emitted from the light-emitting diode  10  in the direction of the light-emitting side  22 . The light rays  61  which are emitted within a cone having an angle of 38 degrees to the optical axis  5  pass through the homogeneous optical fiber body  20  and strike the converging lens  27  at an angle between 0 degrees and 15 degrees to the normal. On emerging from the converging lens  27 , the light rays  61  are refracted in the direction of the optical axis  5  such that the light rays  61  are parallel to one another after emerging from the converging lens  27 . The portion of the light rays  61  passing through the optical lens  27  becomes refracted light.  
         [0024]     The light rays  62  which are emitted outside of the above-identified cone strike a point  29  on the lateral surface  28  of the fiber-optic body  20  from the inside. They are reflected there in the direction of the ring-shaped surface  43  which they strike in the normal direction. The reflected light rays  62  then pass through the ring-shaped surface  43  without being refracted. After emerging from the fiber-optic body  20  they are parallel to one another.  
         [0025]     Light rays  63  emitted by the light source  10  at an angle of approximately 75 degrees to the optical axis  5 , for example, strike the lateral surface  28  near the transitional edge  23  where they are reflected and pass through the base of the groove  42  into the environment  1 .  
         [0026]     The lighting unit  2  may also be designed with a converging lens  27  which is a greater distance away from the light-emitting diode  10 . The cone within which the light rays  61  emitted by the light-emitting diodes  10  strike the converging lens  27  becomes more acute. Light rays  62  emitted by the light-emitting diode  10  with this arrangement at an angle of 38 degrees to the optical axis  5 , for example, then strike the lengthened lateral surface  28  where they are reflected. The fiber-optic body  20  used with this design is longer than the fiber-optic body  20  depicted in  FIG. 1 .  
         [0027]     With a reduction in the distance between the converging lens  27  and the light-emitting diode  10 , the fiber-optic body  20  can be designed to be shorter accordingly. If starting from the embodiment depicted in  FIG. 1 , the converging lens  27  is designed with a smaller diameter, then the fiber-optic body  20  must be designed to be longer than that in  FIG. 1 . Conversely, it may also be designed to be shorter in the case of a converging lens  27  having a larger diameter.  
         [0028]     The lighting unit  2  may also have a fiber-optic body  20  which has a smaller outside diameter than the fiber-optic body  20  in  FIG. 1 . This may then be shorter than the fiber-optic body  20  depicted in  FIG. 1 . The illumination area of this lighting unit  2  is brighter in the edge area, for example, than the illumination of the lighting unit depicted in  FIG. 1 .  
         [0029]     A combination of the aforementioned measures is also conceivable. For example, light rays  61  which are emitted by the light-emitting diode  10  in a lighting unit  2  inside a cone with an angle of approximately 35 degrees to the optical axis  5  may strike the converging lens  27 . The maximum diameter of the fiber-optic body  20  is, for example, 1.3 to 1.5 times the length of the fiber-optic body  20 . The maximum wall thickness may amount to approximately one-third of the diameter of the light-emitting side  22 . The fiber-optic body  20  may be designed in a cup shape on its end facing away from the light-emitting side  22 .  
         [0030]      FIG. 2  shows a section through a lighting unit in which the fiber-optic body  20  has multiple light-emitting sides  43 - 46 , wherein an inner-most reflex surface  46  is closest to the optical lens  27 . This lighting unit also includes a light source  10  in the form of a light-emitting diode  10 . This light-emitting diode is integrated into the fiber-optic body  20  so that only the socket  15  with the electric terminals  12  protrudes out of the fiber-optic body  20 . An electronic protective body  14  surrounding the light-emitting diode  10  is part of the fiber-optic body  20 , forming a homogeneous unit with it.  
         [0031]     The fiber-optic body  20  is in the form of a rotationally symmetrical, truncated paraboloid  24  having two parallel end faces  21 ,  22 . The light-emitting diode  10  is arranged at the focal point of the truncated paraboloid  24 . The cross section of the fiber-optic body  20  increases steadily from the end face  21  out of which the socket  15  of the light-emitting diode  10  protrudes, to the light-emitting side  22 , for example. The diameter of the light-emitting side  22 , for example, amounts to approximately 2.7 times the diameter of the opposite end face  21 . The diameter of the light-emitting side  22  is approximately 70% greater than the length of the fiber-optic body  20 .  
         [0032]     The light-emitting side  22  includes, for example, four ring-shaped surfaces  43 ,  44 ,  45 ,  46  arranged concentrically with one another and with the optical axis  5  in a stepped arrangement, extending sequentially with respect to each other. The surface  43  which is the greatest distance away from the optical axis  5  and the surface  46  which is closest to the optical axis  5  are included here. The inside diameter of an exterior surface  43 ,  44 ,  45  corresponds, for example, to the outside diameter of the next surface  44 ,  45 ,  46  toward the inside. The transitions between the steps are in the form of hollow cylinders  47 ,  48 ,  49  whose axes coincide with the optical axis  5  of the lighting unit  2 . The outermost surface  43  of the ring-shaped surfaces  43 - 46  is connected to the lateral surface  28  of the truncated paraboloid  24 . The size of this area  43  amounts to approximately 29% of the cross section of the light-emitting side  22 . The second light-emitting side  44 , the area of which amount to approximately 24% of the cross section of the light-emitting side  22 , is offset in relation to the first light-emitting side  43  by approximately 6% of the length of the fiber-optic body  20  in the direction of the light source  10 . The area of the third light-emitting side  45  amounts to approximately 16% of the cross section of the light-emitting side  22 . This area  45  is offset by approximately 22% of the length of the fiber-optic body  20  with respect to the second light-emitting side  44  in the direction of the light source  10 . The fourth light-emitting side  46  is arranged with an additional offset in the direction of the light source  10  amounting to 13% of the length of the fiber-optic body  20 . Its area amounts to, for example, 14% of the cross-sectional area of the light-emitting side  22 . This fourth ring-shaped light-emitting side  46  borders another hollow cylinder  53 , the length of which is approximately 14% of the length of the fiber-optic body  20 . The groove  41  and the optical lens  27  surrounded by it form the bottom of this hollow cylinder  53 . The groove  41  has a rectangular cross section. Its base area  42  which is arranged normal to the optical axis  5  of the lighting unit  2  amounts to approximately 3% of the cross-sectional area of the light-emitting side  22 . The optical lens  27  is, for example, a converging lens  27  designed like a Fresnel lens. This is a flat lens  27  having a plurality of concentric sections of a converging lens  27 , for example. Its area projected onto a plane normal to the optical axis  5  of the lighting unit  2  amounts to approximately 14% of the area of the light-emitting side  22 . The distance from the base area  26  of the converging lens  27  to the light source  10  amounts to approximately 38% of the length of the fiber-optic body  20 . The focal point  33  of the converging lens  27  is between the light source  10  and the converging lens  27 . In this embodiment, the maximum wall thickness of the workpiece amounts to approximately 40% of the length of the fiber-optic body.  
         [0033]     This lighting unit  2  may be produced in one or two steps. In a two-step production, the electronic protective body  14  may be produced in a first manufacturing step, for example. In the second manufacturing step, this electronic protective body is sheathed to produce the fiber-optic body  20 . With this lighting unit  2 , the light-emitting sides can also be manufactured with a high precision within narrow tolerances.  
         [0034]     During operation of this lighting unit  2 , the light rays  61 ,  62  emitted from the light-emitting diode  10  are directed either in the direction of the Fresnel lens  27  or in the direction of the lateral surface  28 . In passage through the Fresnel lens  27 , the light rays  61  are refracted, for example, such that they are parallel in the environment  1 . The light rays  62  are reflected on the lateral surface  28  and then emerge into the environment  1  unrefracted as parallel light rays  62 .  
         [0035]      FIG. 3  shows a lighting unit  2  with two light sources  10  and a fiber-optic body  20  in the form of a truncated paraboloid  24 . Here again, the light sources  10  are, for example, light-emitting diodes. They are arranged outside of the focal point of the fiber-optic body  20  on its smaller end face  21 . The design of the fiber-optic body  20  is similar to the design of the fiber-optic body  20  depicted in  FIG. 2 . The lateral surface  28  of the fiber-optic body  20  is mirrorized, for example.  
         [0036]     A portion of the light rays  61 ,  62  emitted by the light sources  10  passes through the Fresnel lens  27  while another portion is reflected on the lateral surface  28  of the fiber-optic body  20 . The light rays  61 ,  62  are refracted in their passage through the Fresnel lens  27  and/or the light-emitting sides  43 - 46 .  
         [0037]      FIG. 4  shows a lighting unit  2  with two fiber-optic bodies  20  and one light source  10 . The two fiber-optic bodies  20  are in the form of rotational paraboloids with a section through a central longitudinal plane (see  FIG. 2 ). This imaginary sectional plane is a planar surface  35 . The two fiber-optic bodies  20  are arranged in mirror image to one another, with the smaller end faces  21  of the two fiber-optic bodies  20  being in contact with one another. The light source  10  is arranged in the parting line. The two fiber-optic bodies  20  surround the light source  10 , each surrounding half of it.  
         [0038]     During operation of this lighting unit  2 , the light rays emitted by the light source  10  strike the converging lens  27 , the planar surface  35  and the lateral surface  28  of the two fiber-optic bodies  20 . Depending on the angle of incidence, they are either reflected or they penetrate through the interface.  
         [0039]     Such a lighting unit  2  may be used, for example, as a limiting light on a motor vehicle. It may be mounted with the planar surface  35  on the vehicle body. The light is then emitted both forward and to the rear, for example.  
         [0040]     In all exemplary embodiments, the fiber-optic body  20  may also be an elliptical paraboloid, for example, or it may have any other shape. The lateral surface  28  may also have discontinuous areas.  
         [0041]     The light-emitting sides  43 - 46  may also be arranged at an inclination with respect to the optical axis  5  of the lighting unit. Each light-emitting side  43 - 46  may be composed of a plurality of individual surface elements, e.g., arranged adjacent to one another. The individual surface element is then, for example, a surface area of a curved three-dimensional body. The surface elements may be surface areas of ellipsoids, drums, cylinders, cones, toroids or any other curved three-dimensional bodies. They may also be surface areas of combinations of different bodies and may have both continuous and discontinuous areas, etc. These individual surface elements are then arranged, e.g., in a regular Cartesian arrangement on the light-emitting side  43 - 46 .  
         [0042]     The optical lens  27  may also be a dispersing lens, a planar lens, etc. It may have areas of different curvature. For example, the optical lens  27  may have adjacent area elements arranged regularly or irregularly, e.g., surface areas of curved three-dimensional bodies. The focal point  33  of the optical lens  27  may be located between the lens  27  and the light source  10 , but it may also be situated outside of this area. Instead of a light-emitting diode  10 , the lighting unit may also have one or more other light sources, e.g., a laser diode, a halogen light, an incandescent bulb, etc.  
         [0043]     The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.  
         [0044]     Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.