Abstract:
A projector optic assembly is disclosed for use with various light emitting sources to collect and direct the rays of light into a high gradient beam pattern. The projector optic assembly includes a light pipe and a projector lens. The light pipe is segregated into several regions including a reflecting region, a funneling region and a transition plane separating the two regions. At the first end of the reflecting region, closest to the light emitting source, is a connecting lens. At the second end of the funneling region is an emitting aperture that is designed to refract light into the high gradient beam pattern.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to an efficient light collection assembly for use with a light emitting source and, more specifically to a projector optic assembly that defines and projects a high gradient beam pattern. The assembly according to the present invention will find utility in vehicle lighting systems, as well as in a variety of non-automotive illumination applications.  
         BACKGROUND  
         [0002]    It is known to use light emitting sources, including light emitting diodes (LEDs), Lambertian emitters, 2π emitters, and fiber optic light guide tips, in a variety of applications, including, but not limited to, vehicular applications. With regard to LED sources, these sources are increasingly finding use in automotive, commercial, and general lighting applications since their light outputs have increased exponentially and their costs have fallen significantly over the past few years. LEDs are attractive due to their small size and the fact that they consume less power relative to incandescent light sources. The popularity of LEDs as light sources is expected to continue and increase as their potential benefits are further developed, particularly with respect to increased light output.  
           [0003]    Today&#39;s LEDs come in different sizes and different emitting cone angles, ranging from 15 degrees (forward emitting or side emitting) to 180 degrees (hemispherical emitting). An emitting cone angle is typically referred to as 2Φ. It is therefore very important to construct efficient light collection assemblies to harness the maximum possible light output from LEDs and to direct it in a predetermined controlled manner.  
           [0004]    For particular applications, one such being a low beam headlight, it is important to project a high gradient beam pattern, such as an automotive low beam hot spot or cutoff, but not limited to these. High gradient beam patterns have a defined beam pattern outline with varying degrees of light intensity within the beam pattern outline.  
           [0005]    Thus, there is a need in the lighting systems field to provide an improved light collection device that can be used with any type of LED to direct the light dispersion in a high gradient beam pattern. This invention provides such an improved LED light collection device.  
         SUMMARY  
         [0006]    The present invention addresses these requirements by providing a projector optic assembly that defines and projects a high gradient beam pattern from a light emitting source, such as a LED. The projector optic assembly includes a light pipe and a projector lens, both of which are positioned along the optical axis defined by the light emitting source. The light pipe includes a reflecting region, a funneling region, and a transition plane or coupling region separating these two regions. Positioned at the first end of the reflecting region is a coupling region. The LED may have its own collecting optics, such as a reflector or lens, in which case, there may be simply a planar or concave hemispherical coupling region without any reflecting region. Positioned at the second end of the funneling region is an emitting aperture. The projector lens is spaced apart from the emitting aperture.  
           [0007]    Constructed according to the teachings of the present invention, the projector optic assembly redirects light into a high gradient beam pattern regardless of the type of light emitting source being used.  
           [0008]    These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description of the invention in combination with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0009]    [0009]FIG. 1 is a perspective view of a projector optic assembly according to one embodiment of the present invention; and  
         [0010]    [0010]FIGS. 2, 2 a  and  2   b  are perspective views, with portions cut away, of alternate embodiments of the image shaping light pipe portion of the projector optic assembly seen in FIG. 1;  
         [0011]    [0011]FIGS. 3 a ,  3   b  and  3   c  are longitudinal sectional views of alternate embodiments of the image shaping light pipe seen in FIG. 2; and  
         [0012]    [0012]FIG. 4 is an end view of just the emitting aperture of the image shaping light pipe. 
     
    
     DETAILED DESCRIPTION  
       [0013]    Referring to the drawings, a projector optic assembly according to one embodiment of the present invention is shown in FIG. 1 and generally designated at  20 . The projector optic assembly  20  includes as its primary components a light pipe  22  and a projector lens  24 .  
         [0014]    The projector optic assembly  20  is used with a light emitting source  26 . Although represented as LEDs in all the figures, the projector optic assembly  20  can be used with a variety of different classes of light emitting sources  26 , including, but not limited to, LEDs, Lambertian emitters, 2π emitters, and fiber optic light guide tips. The projector optic assembly  20  can also be used with different types of light emitting sources within a particular class. The projector optic assembly  20  collects, reflects and refracts the light rays from the source  26  such that they exit the projector optic assembly  20  in a high gradient beam pattern.  
         [0015]    As shown in FIG. 2, the light pipe  22  is constructed as a solid body and is provided with a coupling region  46 , a reflecting region  30 , a funneling region  32 , and a transition plane  34  therebetween. Preferably, the light pipe  22  is designed to reflect all rays of light traveling through it via total internal reflection. Therefore, the index of refraction of the material should be as high as possible, but is likely to be in the range of 1.4-1.8, given the materials available, such as glass, plastics, etc. The light pipe  22  may be composed of one solid material, for example glass or plastic, or may be constructed with a solid outer material, such as glass or plastic, and a fluid or gel material filled interior. There may also be coatings applied to the light pipe  22  in order to enhance the reflective or transmissive properties of the various regions it contains. Further, the overall length of the light pipe is preferably in the range of 30-70 millimeters.  
         [0016]    The reflecting region  30  is generally of a conical shape having a first end  36 , located toward the source  26 , and a second end  34 , located at the transition plane  34 . The reflecting region  30 , while preferred as a conical shape, could be alternatively of a paraboloid shape or ellipsoid shape. In all instances the first end  36  has a first effective cross-sectional diameter  38 , which is less than a second cross-sectional diameter  40  of the second end. The reflecting region  30  may further serve to direct the reflected light in such a way as to create a certain intensity distribution within the subsequent regions of the light pipe this may result in faceting or segmenting of the collection region, either in radial segments, rings, rectangular patches, but not limited to these shapes.  
         [0017]    In an alternative embodiment, the LED may have its own collecting optics, such as a reflector or lens. In that situation, the reflecting region may be omitted in favor of a planar or outwardly convex, refractive, coupling region, or transition plane or coupling region. Such embodiments are seen in FIGS. 3 b  and  3   c  with the LED omitted.  
         [0018]    Referring back to FIGS. 1 and 2, the funneling region  32  is generally conical in shape and has a first end  34  and a second end  42 . The funneling region&#39;s first end  34  has a round cross-section of roughly 40 mm diameter, while the second end  42  has a generally rectangular cross-section of 44 mm by 4 mm.  
         [0019]    A transition plane  34  is defined as the area between the reflecting region  30  and the funneling region  32  by the second end of the reflecting region  30  and the first end of the funneling region  32 . Preferably, the transition plane  34  has approximately a 15-25 millimeter diameter. Therefore, the reflecting region&#39;s second cross-sectional diameter  40  and the funneling region&#39;s first cross-sectional diameter  40  are the same and the transition plane  34  is the widest portion of the light pipe  22 .  
         [0020]    As detailed in both FIGS. 2 and 3 a , a coupling region  46  is formed in the first end  36  of the reflecting region  30 . More specifically, the coupling region  46  is a recessed portion in the first end  36  of the reflecting region  30  that surrounds the light emitting source  26  so that it captures a maximum amount of light being emitted from the light emitting source  26 . Helping in this regard, the entire surface of the coupling region  46  is a refractive surface.  
         [0021]    The coupling region  46  includes two sections: a central concentrating section  48 , which is radially centered on the optical axis defined by the light emitting source  26 , and an outer section  50 , which is radially spaced from the optical axis  28  and which circumferentially surrounds the central concentrating section  48 . Preferably, the central concentrating section  48  is generally hyperbolic or hemispherical in shape and outwardly convex. The outer section  50  defines an inwardly concave hemispherical wall that extends radially outward from an outer circumference  52  of the central concentrating section  48 .  
         [0022]    Further, an emitting aperture  54  is defined in the second end  42  of the funneling region  32 . In general, a goal in designing the emitting aperture  54  is to have as small a surface area as possible for the aperture  54 . The smaller the surface area of the aperture  54 , the more intense the light will be in the projected beam pattern. However, a decreased size of this aperture will normally come at the cost of a wider spread of light from the aperture, causing more light to miss the lens  24 ; therefore there is a practical limit to the size of the aperture  54 .  
         [0023]    The shape of the emitting aperture  54  will vary depending on the desired beam pattern. However, for low beam headlights the shape is preferably a rectangular shape having a modified upper edge. One such shape is illustrated in FIG. 4. The outer perimeter of the emitting aperture  54  includes four edges: an upper edge  56 ; a lower edge  58 ; a left edge  60 ; and a right edge  62  (directional references to be used solely as a clarity aid with reference to the orientation of FIG. 4). In this particular embodiment, the upper edge  56  is stepped and includes first and second parallel surfaces  64  and  66 , and an angled surface  68  extending between the first and second surfaces  64 ,  66 . It is important to note that surface  68  could be angled at other than 90° relative to surfaces  64  and  66  and that other potential cross sectional shapes for the emitting aperture  54 , such as circles, ovals, and squares, could be used, depending on what type beam is to be formed. Further the aperture  54  may be planar or may have a curved surface in order to further shape the intensity distribution to be projected from it.  
         [0024]    The projector lens  24  receives the rays of light exiting from the emitting aperture  54  in the desired beam pattern and projects the rays without altering the outline or gradient of the beam pattern. The projector lens  24  could be any type of lens, including but not limited to, a Fresnel lens as shown in FIG. 1, or any type of aspheric lens. In a preferred embodiment, a cross-sectional area of the projector lens is one square inch (1 in 2 ) and is spaced approximately 30 millimeters from the emitting aperture  54 . There may also be some spreading optics integrated into the projector lens, so as to produce a small amount of spread in the projected beam pattern, usually a horizontal spread. These spreading optics may take the form of flutes, pillows or some similar surface structure, such as a holographic structure.  
         [0025]    As the rays of light are emitted from the light emitting source  26 , they are collected and refracted by the coupling region  46 . The coupling region  46  is designed to refract the rays by generally directing them toward the emitting aperture  54 . A majority of the rays are refracted directly toward the emitting aperture  54 . The other rays are reflected off of the outer walls  70 ,  72  of either the reflecting region  30 , the funneling region  32  or both and are directed toward the emitting aperture  54 . The emitting aperture  54  is designed so that all of the rays that travel through it are refracted into the desired high gradient beam pattern. The high gradient beam pattern travels through the projector lens  24  and is projected over a broader area while retaining its high gradient beam pattern.  
         [0026]    Preferably, numerous projector optic assemblies will be used in combination to achieve a desired intensity level and illumination area for a particular application. For example, twenty such assemblies  20  may be collectively used to define all or a portion of an automotive headlamp assembly.  
         [0027]    As any person skilled in the art of optics will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.