Abstract:
A reading light for a vehicle interior having a light source arranged in a light fixture housing and a lens covering the housing opening and placed in front of the light source in the direction of its light emission. The reading light system includes a second lens and a first lens between the light source and the second lens.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This present invention relates to a reading light for a vehicle interior. In particular, a reading light having a light source arranged in a light fixture housing, which includes a lens disposed in front of the light emitting direction of the light source. 
     2. Related Art 
     German Patent Application 25 07 857 A1 describes a reading light or a seat light for use with vehicles. The reading light includes a light fixture housing that includes a spherical light fixture body pivotally mounted in a receptacle in the light fixture housing. The light fixture body has an incandescent lamp or bulb light source that is surrounded by a reflector. A lens covers an opening in the light fixture housing and is positioned such that it receives light directly emitted from the light source. 
     A disadvantage of known reading light designs is that they are not suitable for light sources having a small beam width or spread factor; for example, light-emitting diodes. Another disadvantage of known reading light designs is that they are not suitable for producing a beam of light having a small beam width because the structural depth of the prior related art reading light devices is too great. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a reading light structure capable of using light-emitting diodes as a light source and which produces a small or narrow beam of light. 
     This object and other objects of the present invention are achieved by providing a reading light, including a light source arranged in a light fixture housing, a second lens placed in front of the light source in the direction of light emission, and a first lens positioned between the light source and the second lens. 
     Due to the use of a lens system including a first lens and a second lens, even light sources having a relatively small beam width may be used. Moreover, the lens system may be constructed with a relatively small structural depth. In addition, the lens system according to the present invention provides a homogeneous plane of illumination. When using light-emitting diodes having arrays of individual so-called dies, the dies are not imaged sharply in the illumination plane which, would lead to a non-homogeneous light distribution in the illumination plane. 
     According to a preferred embodiment of the present invention, the light source is a light-emitting diode arranged at the focal point of the first lens, which is designed as a convergent lens. The first lens is in turn arranged at the focal point of the second lens. The first lens and a holder thereof form the orifice or aperture lens, and the second lens and a holder thereof form the field lens. This arrangement leads to a uniform light distribution or light intensity over an illuminated area. 
     According to another preferred embodiment of the present invention, the light source or the light-emitting diode is arranged between the focal point of the first lens and the first lens. 
     Therefore, because the focal point of the first lens is arranged behind the light-emitting diode or the stop plane, a compact reading light having a very small structural depth may be realized. The arrangement of the focal point behind the plane of the orifice also leads to a virtual object plane, with the result that the beam aperture or light panel may be increased in size, which in turn leads to an increase in efficiency of the light system. The light distribution of the illuminated area may therefore have its maximum at the center and decreases toward an edge thereof. 
     According to another preferred embodiment of the present invention, the second lens is designed as a Fresnel lens. Due to the use of a Fresnel lens, a uniform light intensity of the illuminated area can be achieved. It is also possible to design the second lens as a biconvex lens. 
     Due to the use of light-emitting diodes as the light source, a long lifetime of the light source with a low electric power can be achieved. Furthermore, when using light-emitting diodes, a small light outlet area can be implemented. 
     According to another preferred embodiment of the present invention, the light-emitting diode has a light fixture housing with two pins or two terminals as electric contacts, which may receive a plug that supplies electrical connectivity. 
     Accordingly, since the pins or terminals are used for receiving electricity, supplying electrical power by means of a plug is greatly simplified. 
     According to another preferred embodiment of the present invention, the plug for contacting the light-emitting diode also seals the light fixture housing on its rear side. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 illustrates a cross-sectional view of a reading light according to the present invention having the Fresnel lens as the second lens; 
     FIG. 2 illustrates a cross-sectional view of a reading light according to the present invention having a biconvex lens as the second lens; 
     FIG. 3 illustrates an exterior side view of a reading light according to the present invention; 
     FIG. 4 illustrates an exterior rear view of the reading light illustrated in FIG. 3 as seen from direction IV; 
     FIG. 5 illustrates a side view of a plug according to the present invention; 
     FIG. 6 illustrates a bottom view of the plug illustrated in FIG. 5 as seen from direction VI; 
     FIG. 7 illustrates a top view of the plug illustrated in FIG. 5 as seen from direction VII; 
     FIG. 8 illustrates a beam path diagram of a reading light according to the present invention with a light-emitting diode at the focal point of the first lens; and 
     FIG. 9 illustrates a beam path diagram of a reading light according to the present invention with the focal points of first and second lenses being coincident and positioned behind the light-emitting diode. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As is illustrated in FIGS. 1-7, a reading light  1  includes a light fixture housing  2 , a light source  3 , a first lens  4  and a second lens  5 . The light fixture housing  2  has a spherical light fixture body  6 , which is pivotally mounted in a shell  7 . 
     The light fixture body  6  has a light source  3  on its rear end  8 , the light source  3  is a light-emitting diode  9 . A light panel diaphragm  11  is placed in front of the light-emitting diode  9  in the direction  10  of its light emission. A color filter  12  designed as filter ring  13  is arranged coaxially with light-emitting diode  9 . The first lens  4  is secured by a lens holder  14  of the light-emitting diode  9 , integrally molded on the light fixture body  6 , and the filter ring  13 . The first lens  4  is designed as a convergent lens, preferably a plano-convex lens with a free-form area whose first focal point F 1  is arranged behind the light-emitting diode  9  opposite the direction  10  of emission. However, it is also possible to arrange the light-emitting diode  9  and/or its light panel  11  directly in the first focal point F 1 . 
     The light fixture body  6  has a tube  15  whose rear end  16  connects into the lens holder  14 , and on whose free end  17 , downstream from the first lens  4  facing away from the rear end  16 , the second lens  5  is held in a shoulder  18 . According to a first embodiment, the second lens  5  is a Fresnel lens  19 . According to a second embodiment, the second lens  5  is a biconvex lens  20 . 
     Referring to FIGS. 8 and 9, because the light-emitting diode  9  is arranged at the focal point F 1  of the first lens  4 , a beam aperture stop or light panel  21  is positioned in the plane of the first lens  4 . As a result, a beam angle width or spreading factor of Ω 1  is formed by the beam aperture stop or light panel  21 . The first lens  4  is arranged at a second focal point F 2  of the second lens  5 . A field aperture stop  22  is positioned in the plane of the second lens  5 . An illumination area  23  is thereby illuminated uniformly with parallel light intensity  24  emitted from the dual lens system. 
     If the focal point F 1  of the first lens  4  is arranged behind the light-emitting diode  9 , a virtual object plane  25  with a virtual beam angle width or virtual spreading factor Ω 1  is produced. A field aperture stop  26  is formed at the focal point F 1  in the plane of the first lens  4 . As a result, a real beam angle width or real spreading factor Ω 2  is formed, which is much larger than the virtual beam angle Ω 1 . A beam aperture stop or light panel  28  is shifted in the direction of the second lens  5  so that it increases in size, therefore, the light system efficiency is excellent. In particular, when a biconvex lens  20  is used, the light distribution is maximum at the core and decreases toward the edges. 
     The light-emitting diode  9  has a housing  29  with two pins  30  as electric contacts over which a plug  31  can be placed to provide electrical contact. The plug  31  is designed so that it seals the light fixture housing  2  on its rear side  32  to prevent dust, moisture and the like from entering the lens system. At the same time, the plug  31  forms a twist guard for a cooling body  33  arranged on the rear side  32  of the light fixture housing  2 . 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.