Abstract:
The invention relates to a lighting device, comprising a light guide ( 11; 31; 43 ), a light source ( 12; 32, 33; 41 ), which couples the light that is emitted into the light guide, and a support ( 10; 20, 21; 22, 23; 30, 35, 38; 40, 42 ) in the form of a shell, consisting of several interconnected sub-shells which enclose the light guide, at least in the area in which the light should be deviated. The invention also relates to a method for producing a lighting device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to International Application No.: PCT/DE00/04270 which was published Jun. 7, 2001. This application further claims priority to German patent application 199957611.4 filed 30 Nov. 1999. 
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates generally to an illumination arrangement having an optical waveguide, a light source, coupled thereto, and a mount for the optical waveguide. 
     BACKGROUND OF THE INVENTION 
     Known illumination arrangements wherein the light source comprises a light-emitting diode or a laser diode, is often used for general illumination or background illumination for liquid-crystal displays (LCD). Herein, the optical waveguide directs light, emitted by the coupled light source, out from the optical waveguide at a waveguide end or at a centrally located window. In the latter example, the surface of the optical waveguide is structured in the window region, e.g. by knobs, grooves, or by some other roughening in order to homogenize the light exit. The optical waveguides are composed of transparent material, such as epoxy resin or polymethyl methacrylate (PMMA). In the course of guiding the light and its internal reflections, it is desirable to have as little light loss as possible, while maintaining cost-effective production and practical and simple assembly. 
     A related art embodiment is shown in  FIG. 5 . Here, a light-emitting diode  50  (LED) is coupled into an optical waveguide  51  which in turn is plugged into a mount  52   a ,  52   b . The mount  52  and LED  50  are mounted on a printed circuit board (PCB)  53 . The light emitted by the LED  50  is internally reflected at bevel  54 . For production engineering reasons, in particular in favor of ease of assembly, the bevel  54  is not covered with a reflective material. During the internal reflection of light at bevel  54 , angled preferably at 45°, light necessarily emerges from the optical waveguide. This light is lost for the envisaged application since it is not guided any further in the optical waveguide. On the other side, the mounts  52   a ,  52   b  simultaneously serve as reflectors which prevent light from emerging from the optical waveguide  51  on these sides. When observing the surface of the optical waveguide from the direction B, for example when the optical waveguide is embodied as LCD background illumination, some regions on the optical waveguide surface appear brighter than others (hot spots) as a result of the light internal reflection at the boundary surface  54  and the direct radiation of the light source. Hot spots are bright surface regions which appear in a light exit window and cannot be corrected by the surface configuration of the optical waveguide in the light exit window. Producing a special reflector for the inclined surface  54  in the form of an injection-molded part is costly and undesirable. 
     SUMMARY OF THE INVENTION 
     An advantage of the present invention is set out in a cost effective and easy to use illumination arrangement which can be produced at reduced engineering and manufacturing costs, be designed for high replication, and preserve, maximize and/or increase board space for component mounting. 
     These and other advantages of the present invention are accomplished by an illumination arrangement, comprising: an optical waveguide; at least one light source for emitting light into the waveguide, the at least one light source coupled to the waveguide; and a housing defining a cavity for accommodating the waveguide and at least one light source therein, the housing further defining contiguous upper, lower and side walls, the upper and lower walls having reflective internal surfaces, and the upper wall defining a window from which light emitted by the waveguide escapes the housing. In addition, these and other advantages of the present invention are accomplished by a method for producing a light emitting component, comprising the steps of: forming a housing having a cavity defined by cooperating bottom, side and top walls, said walls having internal surfaces defining said cavity and external surfaces defining an outer perimeter of said housing, said internal surfaces being light reflecting, said walls being opaque, and said top walls defining rounded corners and a window; forming at least one light emitting source; forming an optical waveguide; forming a printed circuit board having means for facilitating communication of electricity to elements mounted thereon; mounting said waveguide within said cavity; mounting said at least one light emitting source on said board such that electricity is communicated to said light emitting source; mounting said housing over said at least one light emitting source, such that said source is coupled to said waveguide and light emitting from said source is transmitted by said waveguide and out said window. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The novel features believed characteristic of the invention are set out in the claims below. The invention itself, however, as well as other features and advantages thereof, are best understood by reference to the detailed description, which follows, when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  shows a diagrammatic cross section through an illumination arrangement according to the invention, 
         FIGS. 2   a  and  2   b  show side views of a mount for the optical waveguide, 
         FIG. 3  shows a diagrammatic cross section of a special embodiment of the invention, 
         FIGS. 4   a  and  4   b  shows a further, partially perspectively illustrated embodiment of the invention, and 
         FIG. 5  shows a diagrammatic cross-sectional illustration of previously used illumination arrangements. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an illumination arrangement  1  in a cross-sectional illustration. The arrangement comprises a mount  10  or an optical waveguide  11 , into which one or more light sources  12   a ,  12   b  feed light. The light sources  12  are preferably light-emitting diodes (LED) or laser diodes, but other light sources such as incandescent lamps are also possible. The light source  12  and the mount  10  are mounted on a printed circuit board  14 . The mount  10  surrounds the optical waveguide  11  in shell form in the regions in which the light has to be deflected and guided. In order to introduce the optical waveguide into the shell, and to be able to mount it, the mount  10  is formed from a plurality of shell elements. In the example of  FIG. 1 , the mount  10  contains on its top side a window  13  through which an observer B can observe the optical waveguide or the light can be coupled out. The window  13  in the mount  10  is configured in such a way that the illumination arrangement can serve as an element of background illumination for liquid-crystal displays. 
     In accordance with  FIG. 1 , the mount  10  for the optical waveguide  11  simultaneously has the main function of a reflector with the reflector surfaces  16   a ,  16   b , with the aid of which the light beams can be deflected without relatively large light losses arising. The deflection angle is inherently arbitrary, but 90° here. Depending on technical requirements and specifications, the optical waveguide  11  with the mount  10  is constructed in such a way that the optical losses and/or the hot spots are minimized. The mount  10  is shaped in the light deflection region and in the window region  10 , such that light can emerge diffusely through the window  13 . The upper reflector surface  16   a  can be multiply angled or rounded. With respect to the optical waveguide, the lower reflector surface  16   b  is convexly formed or expanded in order that light cannot emerge in a concentrated manner at one location. Both, the optical waveguide  11  and the mount  10  can be produced as injection-molded parts. Transparent material, e.g. PMMA, is used as the optical waveguide. The mount  10  is typically opaque to light and reflective at its inner surfaces in order to reflect back into the optical waveguide the light which emerges at the deflection points of the optical waveguide. 
     According to the invention, the mount  10  is designed in shell form and contains at least two shell elements.  FIG. 2  shows a side view of the arrangement in accordance with  FIG. 1  from viewing direction A. In accordance with  FIG. 2   a ), the mount contains for the optical waveguide two shell elements  20  and  21 , which are designed largely symmetrically with respect to the central line. In the light propagation direction, the optical waveguide has a largely rectangular cross section. During assembly, the optical waveguide is firstly introduced laterally into one of the two shell elements  20  or  21  and then enclosed by the other half-shell  21  or  20 , respectively, at the regions not yet protected. 
     The two half-shells  20  and  21  are connected by a snap-action device  25 ,  26 . In this case, a lug  25  fixed to the half-shell  21  and having an opening is pushed over a knob  26  fixed to the other half-shell  20 . However, the two half-shells can also be connected in any other form which ensures that the two half-shells enclose the optical waveguide. In addition to a releasable connection such as that using the snap-action devices  25 ,  26 , fixed connections, for example by bonding, are also appropriate. In order to prevent the situation where gaps arising at the abutting edge of the two half-shells  20  and  21 , possibly due to material tolerances or due to an aging behavior, lead to the coupling-out of light, it is possible to fold the two shell elements  20  and  21  at their abutting edge, so that the shell elements overlap at the fold and become optically opaque. 
       FIG. 2   b  shows another arrangement for the two shell elements. In this case, the optical waveguide is firstly introduced from the side into a shell element  22 , which encloses the optical waveguide to an extent such that only a cover  23  has to be laterally placed in order to enclose the optical waveguide in the light-guiding region. In this exemplary embodiment, the connection between the shell elements  22  and  23  is effected by a plurality of snap-action devices  27 ,  28 . Projecting knobs are arranged on the shell element  22  and the openings in the lugs  28  can latch into said knobs. The advantage of this arrangement is the releasability of the mount arrangement. In an embodiment of  FIG. 2   a , too, the shell elements  22  and  23  can be provided with a fold, so that no light emerges at the abutting surface. 
     In the arrangement in accordance with  FIG. 1 , it is possible to feed in light from only one light source  12 . Preferably, however, a plurality of light sources  12   a ,  12   b  are provided, which, as in  FIG. 1 , feed light into the optical waveguide from both sides. What is more, further light sources may be arranged perpendicularly to the plane of the drawing. This makes it possible to observe a high light intensity at the window  13 . With the arrangement in accordance with  FIG. 1 , it is possible for the light that is to be couple out, or the observation window  13 , to be arranged remote from the light source  12 . The optical waveguide  11  and the shell mount  10  can be produced extremely favorably by virtue of the production of injection-molded parts, at the same time the light guidance by virtue of the form of the optical waveguide channels and of the shell mount designed as reflectors being effected so optimally that a maximum of light can be utilized for the illumination purposes. The construction in the form of a bridge, means that it is possible to produce a space-saving arrangements wherein, below the mount  10 , in the free space toward the circuit board  14 , components  15  can be arranged on the circuit board. 
       FIG. 3  shows a partial cross section of a further embodiment of the invention. This provides a shell-type mount  30  for the optical waveguide  31 , which in this case are mounted by their side  38  in a planar manner on the circuit board  34 . In contrast to  FIG. 1 , the arrangement contains not only an upwardly radiating LED  32  but a chamber  36  separated from the latter by a partition  35 , arranged in which chamber is an LED or laser diode  33  radiating sideways over the edges. In this construction, a bridge arrangement as illustrated in  FIG. 1  is not provided. The advantage of the arrangement in accordance with  FIG. 3  is that the optical power coupled into the optical waveguide can be considerably higher than in the case of the arrangement in  FIG. 1 . Here, too, the inner surfaces  37  of the mount  30  serve as reflectors. 
       FIG. 4  shows a further, partially perspective exemplary embodiment of the invention, in which the shell elements of the mount are not separated vertically, as illustrated in  FIG. 2 , but horizontally. In this embodiment, the optical waveguide  43  is plugged into the lower shell element  40  from above and subsequently covered by the upper shell element  42 . The lower shell element is mounted on the PCB  45 . The upper shell element can be connected to the lower shell element in the manner described with reference to  FIG. 2 . In the exemplary embodiment, 3 LEDs  41   a  to  41   c  are provided on each circuit-board side of the optical waveguide, but there may also be more or fewer individual light sources. 
     Furthermore, there are a multiplicity of possibilities for producing optical waveguides and associated shell elements which enable virtually arbitrary variation for the coupling-in and coupling-out of light. This is because the optical waveguides are largely completely covered by the shell type mount, except for the coupling-in and coupling-out regions, the inner surfaces of the mount serving as reflector surfaces.