Abstract:
A LED bulb and light module utilizes a LED light source and directs light therefrom in a manner which improves efficiency and illumination. Ideally, the LED bulb is structured to create a virtual image whereby the efficiency of light directed out of the module is greatly improved, even with a single LED light source. The LED bulb generally includes a light pipe receiving light from the LED light source and guides the light downstream to a downstream portion which redirects the light radially outwardly.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a light module for a motor vehicle, and more particularly relates to an LED bulb for use in such a light module. 
     BACKGROUND OF THE INVENTION 
     Modern automotive light modules typically use a filament bulb as their light source. While such modules have a long and successful history, filament bulbs consume a large amount of power and have a relatively short life. In an attempt to overcome these shortcomings, others have proposed to utilize LED light sources to replace the filament bulbs since LED&#39;s consume significantly less power and have a long life span. 
     Unfortunately, LED solutions also have their drawbacks. In particular, automotive light assemblies utilizing LED light sources typically use a large number LED&#39;s, typically eight or more, which thus requires increasing amounts of power over a single LED bulb. Furthermore, these light modules using LED light sources suffer from poor efficiency, that is, the amount of original light from the light source which is actually directed outwardly away from the vehicle to illuminate the surrounding area. 
     Accordingly, there exists a need to provide an automotive light source which utilizes an LED light source to significantly reduce power consumption, have long life, while at the same time efficiently direct the light to provide adequate illumination. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a LED bulb and light module which utilizes a LED light source and directs light therefrom in a manner which improves efficiency and illumination. The LED bulb is structured to create a virtual image whereby the efficiency of light directed out of the module is greatly improved, even with a single LED light source. The LED bulb generally includes a light pipe receiving light from the LED light source which guides the light downstream along a longitudinal axis. A downstream portion of the light pipe defines a first curved surface and a second curved surface. The second curved surface is spaced radially outward of the first curved surface. The first and second curved surfaces redirect the light radially outwardly to define a virtual image of the LED light source. 
     According to more detailed aspects, the LED bulb is plastic molded from a clear optical grade material, whereby the aforementioned components are integrally formed. The first curved surface preferably has a parabolic curvature, while the second curved surface has a spherical curvature. Alternatively, the first and second curved surfaces have a numerically developed free-formed curvature. Light reflects off the first curved surface and passes through the second curved surface. The first curved surface is preferably formed in an end surface of the downstream portion of the light pipe, and the end surface further includes a non-reflecting surface positioned along the longitudinal axis to generate a “hot spot”. The non-reflecting surface may be a flat surface generally perpendicular to the longitudinal axis, or may include a beam spreading structure or a beam focusing structure. 
     According to still more detailed aspects, the light pipe includes an upstream portion and a main body linking the upstream portion to the downstream portion. The upstream portion is structured to collimate light from the LED light source and direct the light longitudinally downstream. The upstream portion preferably defines a recess for receiving the LED light source, and includes a lens adjacent the recess for focusing the light longitudinally downstream. An outer surface of the upstream portion is curved to collimate the light. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a perspective view of an embodiment of a light module for an automobile constructed in accordance with the teachings of the present invention; 
         FIG. 2  is a side view of an LED bulb forming a portion of the light module depicted in  FIG. 1 ; 
         FIG. 3  is a side view of a portion of the light module depicted in  FIG. 1 ; 
         FIG. 4  is a side view of an alternate embodiment of the LED bulb depicted in  FIGS. 1 to 3 ; and 
         FIG. 5  is a side view of another alternate embodiment of the LED bulb depicted in  FIGS. 1 to 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the figures,  FIG. 1  depicts a perspective view of a light module  10  having a LED bulb  20  constructed in accordance with the teachings of the present invention. Among other things, the light module  10  includes a reflector  12  defining a reflective surface  13  which receives light from the LED bulb  20  and directs the light outwardly away from the vehicle. The reflector  12  includes an opening  14  which receives an LED bulb  20 . The bulb  20  is generally defined by a light pipe  22  which extends through the opening  14  in the reflector  12 . The light pipe  22  directs light received from a LED light source  18  ( FIG. 2 ). 
     The details of the LED bulb  20  will now be described with reference to  FIGS. 2 and 3 . The entire light pipe  22  is generally integrally formed, and preferably is formed by injection molding a clear optical grade material, although it will be recognized that the light pipe  22  may be formed in several parts and through other manufacturing techniques. The material must be capable of conducting light in the visible wave length range, and is preferably a plastic such as acrylic or polycarbonate which allows a molding process to be used for producing the part. The first curved surface  42  is coated with a material which reflects light in the visible wavelength range, typically aluminum. The light pipe  22  directs the light utilizing the principles of total internal reflection, standard reflection, and a number of internal surfaces for collimating, focusing, reflecting and directing the light. 
     The light pipe  22  generally includes an upstream portion  24  and a downstream portion  26  connected by a body portion  28 . Light from the LED light source  18  flows downstream from the upstream portion  24  towards the downstream portion  26 , and along a longitudinal axis  15  defined by the light pipe  22 . The main body  28  of the light pipe  22  is generally cylindrical in nature, and includes a plurality of flanges  29  attached to its outer surface for connecting the LED bulb  20  to other structural components of the light module  10  or other support structures of the vehicle. The downstream portion  26  of the light pipe  22  includes a first curved surface  42  and a second curved surface  48  for redirecting the light in the light pipe  22  radially outwardly, as will be described in more detail below. 
     As shown in  FIG. 3 , the upstream portion  24  of the light pipe  22  has a tapered shape in the upstream direction, and generally is structured to collimate the light (light rays indicated by various lined arrows  16 ) from the LED light source  18  and direct the light  16  longitudinally downstream generally parallel with the longitudinal axis  15 . By the term generally, it is meant that the light  16  follows a path which is within 3° of parallel to the longitudinal axis  15 . 
     The upstream portion  24  includes a recess  30  for receiving the LED light source  18 . The recess  30  is defined by a slightly tapering surface  32  which extends longitudinally and ends at an axially facing surface  34  which is structured as a lens that focuses the light  16  longitudinally downstream. The lens  34 , the surface  32  of the recess  40 , and the reflecting surface  36  of the tapered upstream portion  24  all cooperate to direct the light  16  from the LED light source  18  downstream and generally parallel to the longitudinal axis  15 . As such, the upstream end is structured to act as a collimator, which those of skill in the art will recognize can be formed by various other structures or separate devices known in the art. 
     The downstream portion  26  of the light pipe  22  is structured to direct the light  16  radially outwardly from the longitudinal axis  15 , and form a virtual image of the light source  18 , i.e. a virtual focal point  19   a.  The downstream portion  26  includes an end surface  40  that has a first curved surface  42  defined therein. The first curved surface  42  is coated as mentioned above and, acts as a reflector inside the light pipe  22 . In the depicted embodiment, the first curved surface follows a parabolic curvature whereby the virtual image and virtual focal point  19   a  are formed. This virtual imaging of the LED light source  18  improves efficiency and illumination, as described in the commonly assigned co-pending U.S. application Ser. No. 10/945,321, the disclosure of which is incorporated herein in its entirety. 
     The end surface  40  also includes a non-reflecting surface  44  positioned along the longitudinal axis  15  to form a “hot spot” as is known in the art, which approximates such hot spots formed by prior light sources such as incandescent bulbs. The non-reflecting surface  44  is positioned at the peak of the first curved surface  42 , and by virtue of its angling relative to the longitudinal axis  15  and light rays  16 , permits a portion of the light  16   a  to pass therethrough and directly out the light module  10 . In the depicted embodiment, the non-reflecting surface  44  is flat and generally perpendicular to the longitudinal axis  15 . A second flat surface  46  is left around the outer periphery of the end surface  40 , which generally does not transmit any light  16 , except for the occasional incidental light that may occur due to light noise. 
     Light reflected from first curved surface  42  continues through the light pipe  22  in a direction radially outwardly from the longitudinal axis  15 . The outer periphery of the downstream portion  26  of the light pipe  22  defines a second curved surface  48 . As the first curved surface  42  creates a virtual focal point  19   a,  the second curved surface  48  takes a spherical curvature (i.e. circular in a two-dimensional view) so that the light  16  reflected from first curved surface  46  passes through the second curved surface  48  generally undisturbed. It will be recognized by those skilled in the art that the second curved surface  48  may take alternate curvatures, including those refracting the light  16 , depending on the desired application of the light module  10 . 
     A brief summary of the passage of light  16  through the LED bulb  20  will now be given with reference to  FIGS. 2 and 3 . Light  16  is generated by LED light source  18  and originates at a point of origin  19 . Some light  16  follows a path through the lens  34  and is directed longitudinally downstream as shown. The remainder of the light  16  passes through the recess surface  32  and is reflected by the free form curved surface  36  of the upstream portion  24 . Thus, the upstream portion  24  collimates the light  16  and directs the same longitudinally downstream through the body portion  28 . The collimated light rays  16  continue longitudinally downstream until they encounter the end surface  40  of the downstream portion  26 . Light  16  close to the longitudinal axis  15  strikes the flat (non-reflecting) surface  44  and passes directly therethrough to generate the “hot spot”. Light  16  spaced more radially outwardly strikes the first curved surface  42 , and is reflected radially outwardly, and back upstream through second curved surface  48 . It can be seen in  FIGS. 2 and 3  that the light rays  16  exiting the downstream portion  26  of the light pipe  22  are directed towards the reflector  12  and its reflective surface  13  for further redirection of the light rays  16  out of the light module  10  and away from the motor vehicle. 
     It can also be seen from  FIG. 2  that the downstream portion  28  of the LED bulb  20  is positioned in front of the reflective surface  13  ( FIG. 1 ), while the upstream portion  24  extends through the aperture  14  and is positioned behind the reflector  12 . Stated another way, the virtual image and focus point  19   a  needs to be positioned in front of the reflector  12 , allowing the true LED light source  18  to be positioned outside of the cavity and behind the reflector  12 . The virtual image and source point  19   a  is positioned in front of me reflector to direct light toward the reflective surface  13 . 
     Turning to  FIG. 4 , another embodiment of an LED bulb  120  includes a light pipe  122  having an upstream portion  124 , a downstream portion  126  and a main body portion  128 . As in the prior embodiment, the upstream portion  124  includes a recess  130  for receiving an LED light source  118  emitting light  116  from a point of origin  119 . The upstream portion  124  is structured to collimate the light  116  by virtue of the angled wall  132  and lens  134  of the recess  130 , and the curved outer surface  136  of the upstream portion  124 . Flanges  129  on the main body  128  can be used to mount the LED bulb  120 . As in the prior embodiment, the downstream portion  126  includes an end surface  140  defining a first curved surface  142 , while a second curved surface  148  cooperates with the first curved surface  142  to create a virtual image of the LED light source  118  and a small virtual focal area  119   a.    
     However, in the embodiment depicted in  FIG. 4 , the first and second curved surfaces  142 ,  148  follow a free-form curvature. That is, the curvatures are numerically generated, and may not correspond to any equation. Ideally, the first curved surface  142  is structured to redirect the light  116  in a manner to create a small virtual focal area  119   a,  while the second curved surface  148  is given a curvature which permits the reflected light  116  to pass directly therethrough with little to no refraction. However, it will be recognized by those skilled in the art that the free-form curvatures of the first and second curved surfaces  142 ,  148  may collectively generate a small virtual focal area  119   a.  Still further, the first and second curved surfaces  142 ,  148  need not generate a virtual image or a small virtual focal area  119   a,  so long as a substantial portion of the light from the LED light source  118  is redirected radially outwardly from the downstream portion  126  of the light pipe  122 . In this manner, the curvatures of the first and second curved surfaces  142 ,  148  may be controlled and structured to provide a light distribution that approximates the filament bulb that it is intended to replace. It will therefore be recognized by those skilled in the art that numerous variations and structures of the downstream portion  126  of the LED bulb  120  may be generated to replace numerous types of light sources such as filament and incandescent bulbs, and design for the particular application of the motor vehicle such as head lamps, tail lights, turn lights, interior lights, etc. 
     It can also be seen in the embodiment of  FIG. 4  that the end surface  140  of the downstream portion  126  includes a non-reflecting surface  144  that is positioned along the longitudinal axis  115 . Unlike the prior embodiment, a non-reflecting surface  144  includes beam spreading optics, and particularly a plurality of pillows or flutes  146 , rather than the flat surface  44  of the prior embodiment. Here, a “hot spot” can still be created, although the light  116  passing directly through the non-reflecting surface  144  can be spread or diffused. It can thus be seen that controlling the structure of the non-reflecting portion  144  permits further variation of the light distribution provided by the LED bulb  120 . 
     Yet another embodiment of a LED bulb  220  is depicted in  FIG. 5 . The LED bulb  220  includes a light pipe  222  having an upstream portion  224 , a downstream portion  226  and a main body portion  228 . As in the prior embodiment, the upstream portion  224  includes a recess  230  for receiving an LED light source  18  emitting light  216  from a point of origin  219 . The upstream portion  224  is structured to collimate the light  216  by virtue of the angled wall  232  and lens  234  of the recess  230 , and the curved outer surface  236  of the upstream portion  224 . Flanges  229  on the main body  228  can be used to mount the LED bulb  220 . As in the prior embodiment, the downstream portion  226  includes an end surface  240  defining a first curved surface  242  while a second curved surface  248  cooperates with the first curved surface  242  to create a virtual image of the LED light source  218  and a virtual focal area  219   a.    
     As with the embodiment depicted in  FIG. 4 , a first and second curved surfaces  242 ,  248  have been depicted as having free-form curvatures that permit variation of the light distribution while still forming a virtual image and focal area  219   a.  In this embodiment, however, the non-reflective surface  244  includes an optic focusing structure such as a lens. Stated another way, the non-reflecting surface  244  is formed with a curvature to form a lens  245  in the end surface  240  of the light pipe  222 . As with the prior embodiments, a “hot spot” may be created while at the same time permitting variation and control over the light distribution to approximate the various light sources the LED bulb  220  is intended to replace. 
     The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.