Abstract:
A light for a vehicle. Two or more light guides each project a sheet of light to a common projection lens, but in different directions. Each light guide is selectively actuable by the driver. The projection lens receives the sheets of light, expands them in the horizontal direction, and projects them in the same general direction as received. Thus, the driver can selectively illuminate various regions of the terrain.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a multi-function optical system for forward lighting that utilizes a shared exit optic. The system is high efficiency and maintains a consistent lit appearance between functions and smooth on-road transition between functions. 
         [0003]    2. Description of the Related Art 
         [0004]    Lighting systems of the past included bending light/cornering light or turn signal functions as a separate optical systems from low beam, high beam and/or fog. These separate functions were separated into different optical systems. 
         [0005]    One prior art lighting or signaling devices is known from the patent application WO 2006/096467, which is related to U.S. Provisional Application 60/658,459, and which is incorporated herein by reference. This document discloses a lighting device that comprises a ray guide in the form of solid pieces that are tricky and expensive to produce. Performance in terms of range is reduced because of only moderately satisfactory collimation. In addition, the dimensions of the whole are relatively large. 
         [0006]    In general, many light guide technologies for signal functions have poor efficiency and often require a large number of LEDs and/or light guides or fixtures to produce a desired lit area. In addition, these prior art technologies are either single function or have multi-functions, but the lit aspect for different colors is different. 
         [0007]    Current high-efficiency light guides are intended for forward lighting applications and typically have a single source and a single lit aspect. 
         [0008]    What is needed, therefore, is multi-function optical system for forward lighting that utilizes a shared exit optic having improved efficiency and that is capable of a consistent lit appearance between functions and smooth on-road transition between functions. 
       SUMMARY OF THE INVENTION 
       [0009]    In one embodiment, the system uses multiple high efficiency light guides coupling into a single lens to create on-axis forward lighting (such as low beam, high beam, fog light) and off-axis forward lighting (such as bending light or cornering light) out of a single exit optic. The guides and the exit optic may be made as one piece or as multiple pieces and separated by an air gap. 
         [0010]    An on-axis forward lighting (such as low beam, high beam, fog light) and off-axis forward lighting (such as bending light or cornering light) out of a single exit optic, while maintaining consistent lit appearance and blending beam patterns of different functions to create smooth on-road light (no streaks). One object is to incorporate additional functionality into a low beam system without increasing number of modules (or exit optic elements) in the system. One potential solution was to create a system at a modular level that could perform multiple functions while retaining identical number of exit optics. 
         [0011]    In one aspect, one embodiment comprises a lighting device for a vehicle, comprising a first light guide that projects emits first light rays from a first light source in a first direction, at least one second light guide that projects second light rays from a second light source in a second direction, an elongated projection lens which receives said first light rays and emits them to perform a first light function, and receives said second light rays and emits them to perform a second light function. 
         [0012]    In another aspect, one embodiment comprises an optical device for a vehicle, comprising a first light guide which receives light from a first light source and forms the light into a first beam that performs a first lighting function forward of the vehicle, at least one second light guide which receives light from a second light source and forms the light into a second beam that performs a second lighting function, a lens which i) receives the first beam and transmits the first beam in a first direction forward of the vehicle, and ii) receives the second beam and transmits the second beam in a second direction at an angle that is not parallel to a longitudinal axis of the vehicle. 
         [0013]    In still another aspect, one embodiment comprises a lighting system for a vehicle, comprising a) a first solid, transparent body, which comprises i) a first lens, ii) a first light guide, which transmits a first beam of light to the first lens, which the first lens projects forward of the vehicle, and iii) a second light guide, which transmits a second beam of light to the first lens, which the first lens projects to the left front side of the vehicle, b) a second solid, transparent body, which comprises i) a second lens, ii) a third light guide, which transmits a third beam of light to the second lens, which the second lens projects forward of the vehicle, and iii) a fourth light guide, which transmits a fourth beam of light to the second lens, which the second lens projects to the right front side of the vehicle. 
         [0014]    This invention, including all embodiments shown and described herein, could be used alone or together and/or in combination with one or more of the features covered by one or more of the following list of features:
       The lighting device in which the projection lens, the first light guide, and the at least one second light guide are an integral, monolithic construction of transparent material.   The lighting device in which the first light guide and the at least one second light guide are angularly spaced with a predetermined angle between each adjacent pair of the first light guide and the at least one second light guide.   The lighting device in which all adjacent ones of the first light guide and the at least one second light guide are angularly spaced along an arc an equal distance apart.   The lighting device in which all adjacent ones of the first light guide and the at least one second light guide are angularly spaced along an arc different distances apart.   The lighting device in which the first light guide and the at least one second light guide are parabolic and generally planar light guides.   The lighting device in which the first light function is a forward lighting function defining at least one of a low beam headlight or a part of a low beam headlight, a high beam headlight or a fog light for the vehicle.   The lighting device in which the second light function is a side lighting function defining at least one of a turn signal light or a side light low beam headlight, a high beam headlight or a fog light for the vehicle.   The lighting device in which the second light function is a side lighting function defining at least one of a turn signal light, bending light or a side light for the vehicle.   The lighting device in which the first light guide contains a central plane which bisects the projection lens.   The lighting device in which the first light guide and the at least one second light guide each comprise an exit face that is spaced from an entry face of the elongated projection lens.   The lighting device in which the first light source comprises at least one first LED and the second light source comprises at least one second LED, wherein when the at least one first LED is activated, the first lighting function is performed and when the at least one second LED is activated the second lighting function is performed.   The lighting device in which the at least one first LED and the at least one second LED are activated substantially simultaneously to perform the first and second lighting functions substantially simultaneously.   The optical device in which the at least one of the first light guide or the at least one second light guide comprises a reflective edge which is of generally parabolic shape and positioned so that its focus generally coincides with the first light source, wherein the reflective edge receives light from the first light source, forms it into the first beam, and projects the first beam to the projection lens.   The optical device in which the first light guide comprises a first exit edge spaced from the lens and a first generally parabolic reflective edge having a first focus that generally coincides with the first light source and the second light guide comprises a second exit edge spaced from the lens and a second generally parabolic reflective edge having a second focus that generally coincides with the second light source, wherein the first and second reflective edges of the first and second light guides receive light from the first light source and second light sources, respectively, and emit the first beam through the first exit edge to the lens and emits the second beam through the second exit edge to the lens.   The optical device in which the first beam crosses the second beam inside the lens.   The optical device in which the lens, the first light guide, and the at least one second light guide are an integral, monolithic construction of transparent material.   The optical device in which the first and second light guides are cantilevered from the lens and further comprise a connector which connects the cantilevered light guides together, to thereby stiffen them.   The optical device in which the first beam is wider than the second beam and is effective to form a headlight for a vehicle.   The optical device in which the first light guide and the at least one second light guide are angularly spaced with a predetermined angle between each adjacent pair of the first light guide and the at least one second light guide.   The optical device in which all adjacent ones of the first light guide and the at least one second light guide are angularly spaced along an arc an equal distance apart.   The optical device in which at least one adjacent ones of the first light guide and the at least one second light guide are angularly spaced along an arc different distances apart.   The optical device in which the first light function is a forward lighting function defining at least one of a low beam headlight, a high beam headlight or a fog light for the vehicle.   The optical device in which the second light function is a side lighting function defining at least one of a turn signal light or a side light low beam headlight, a high beam headlight or a fog light for the vehicle.   The optical device in which the first light source comprises at least one first LED and the second light source comprises at least one second LED, wherein when the at least one first LED is activated, the first lighting function is performed and when the at least one second LED is activated the second lighting function is performed, the at least one first LED and the at least one second LED being activated substantially simultaneously.   The optical device in which the at least one first LED and the at least one second LED are activated substantially simultaneously to perform the first and second lighting functions substantially simultaneously.   The optical device as recited in claim  14  wherein the at least one second light guide comprises a second light guide situated adjacent the first light guide and a third light guide situated adjacent the first light guide, the second and third light guides being adapted to perfume the second lighting function, while the first light guide performs the first lighting function, the first lighting function being a forward headlight function.   The lighting system in which the first and second bodies are mirror images of each other.   The lighting system and further comprising a light source for each respective light guide.   The lighting system in which each light guide comprises a curved edge (1) to which the respective light source transmits light, and (2) which reflects the light as a beam of parallel rays.   The lighting system further comprising a plurality of light sources for at least one of said light guides.   The lighting system further comprising a plurality of light sources for each light guide.       
 
         [0046]    These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0047]      FIGS. 1A-1E  are views of one form of the invention; 
           [0048]      FIGS. 2A-2E  are cross-sectional views of one form of the invention, viewed from above, and show various light paths; 
           [0049]      FIGS. 3A and 3B  show how the invention can be incorporated into the surface of a vehicle; 
           [0050]      FIGS. 4 and 5  are high-level schematics which explain processing of light which the invention accomplishes; 
           [0051]      FIGS. 6A-6F  are simulations which illustrate various patterns of light projected by one form of the invention; 
           [0052]      FIG. 6G-6I  illustrates other forms of the invention; 
           [0053]      FIGS. 7, 8, and 9  explain the term critical angle; 
           [0054]      FIGS. 10, 11, 12, 13, 14, 15, and 16  explain the term zone of acceptance; 
           [0055]      FIGS. 17, 18, and 19  illustrate why the LED  16 ,  18  and  20  of  FIGS. 1A-1D  should be located generally centrally within light guide  14 ; 
           [0056]      FIGS. 20 and 21  illustrate two types of entry of light into the light guide  14  from the LED  16 ,  18  and  20 ; 
           [0057]      FIG. 22  defines separation distances between adjacent LEDs  16 ,  18  and  20  and between adjacent light guides  14   a - 14   c;    
           [0058]      FIG. 23  shows an optical coupling medium M; 
           [0059]      FIG. 24  illustrates an approach to reducing vibration in the invention; 
           [0060]      FIGS. 25-30  illustrate an alternate approach to constructing one form of the invention; 
           [0061]      FIG. 31  illustrates another form of the invention; and 
           [0062]      FIG. 32  illustrates a top-down view of a vehicle  40  and illustrates one form of the invention mounted thereon. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0063]      FIGS. 1A-1E  and  FIGS. 2A-2E  illustrate several forms of the invention for use in an optical device, such as a headlamp or turn signal device, for a vehicle. An assembly  10  contains a generally cylindrical lens  12  and a plurality of light guides  14   a ,  14   b  and  14   c.  In the illustration being described, the assembly  10  is constructed of a transparent material. The assembly  10  can be molded as a single unit in a single molding step as shown in  FIGS. 1A-1C  or the plurality of light guides  14   a,    14   b  and  14   c  may be separated from the lens  12  by a predetermined distance PD, as illustrated in  FIGS. 1D and 2A-2E . In one embodiment, the predetermined distance PD is on the order of about 0.5 mm. 
         [0064]      FIGS. 2A-2E  show a simplified overview of an operation of one form of the invention. In the illustration shown in  FIGS. 2A-2E , an optional air space S between ends or exit faces  14   a   1 ,  14   a   2  and  14   a   3  and lens entry face  12   a  of the lens  12  is shown. Each light guide  14   a - 14   c,  when activated, projects light rays LR 1 , LR 2  and LR 3 , respectively, from at least one light-emitting diode (LED)  16 ,  18 ,  20  (as best shown in  FIG. 1C ) through the common projection lens  12 . However, the overall pattern of illumination depends on the combination of LEDs  16 - 20  and their respective light guides  14   a - 14   c  which are activated by a controller and conventional power source (which is only shown schematically in  FIG. 2A  for ease of description). The controller may be provided on the printed circuit board (PCB) with the LEDs  16 - 20 , or provided in the headlamp assembly  10  or elsewhere on the vehicle. For example, in  FIG. 2B , only the light guide  14   a  and LED  16  are activated to generate a forward or first lighting function, such as the central pattern P 1 , as illustrated in  FIG. 2B  and shown in  FIG. 6A . In one embodiment, this pattern P 1  can be used as a high-beam or a low-beam headlight in a vehicle. The light guides  14   a  or  14   c  and their associated LEDs  18  and  20 , respectively, are adapted to provide or generate a second lighting function such as a turn signal, DBL or side lighting function. It should be understood that multiple LEDs or an array of LEDs may be provided to one or more of the light guides  14   a - 14   c  if desired. Also, the LEDs could perform the same or different lighting functions.  FIG. 1E  illustrates the use of multiple LEDs  16   a,    16   b,    18   a,    18   b,    20   a  and  20   b  that could be used with the light guides  14   a - 14   c.    
         [0065]    In  FIG. 2C , light guide  14   b  and LED  18  alone are activated to pass light rays LR 2  and produce pattern P 2  (illustrated on the left side of  FIG. 6C ). This pattern P 2  can be used, for example, to illuminate the left front side of the vehicle or provide a turn signal when making a left turn. In  FIG. 2D , light guide  14   c  and LED  20  alone are activated and produce pattern P 3  on the right side. This pattern P 3  can be used to illuminate the right front side of the vehicle or provide a turn signal when making a right turn. 
         [0066]    Thus, the patterns P 2  and P 3  can be used as turn signal indicators. As another alternate, the patterns P 2  and P 3  can be used as fog lights or used in a dynamic bending lamp or side lighting function. 
         [0067]    The following Table I summarizes some of the functions: 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                   
                 Function 
                   
               
             
          
           
               
                   
                 Middle 
                 Right 
                 Left 
                   
               
               
                   
                 A 
                 B 
                 C 
                   
               
               
                 CASE 
                 14A 
                 14B 
                 14C 
                 LEDs Activated 
               
               
                   
               
             
          
           
               
                 1 
                 Low 
                 Low  
                 Low  
                 All LEDs on  
               
               
                   
                 Beam 
                 Beam 
                 Beam 
                 together for 
               
               
                   
                 (Flat) 
                 (Flat) 
                 (Flat) 
                 Low Beam.  
               
               
                   
                   
                   
                   
                 Each contributes  
               
               
                   
                   
                   
                   
                 to different 
               
               
                   
                   
                   
                   
                 part of Low Beam 
               
               
                 2 
                 Bending 
                 Bending  
                 Bending 
                 LEDs sequenced  
               
               
                   
                 (Side) 
                 (Side) 
                 (Side) 
                 (based on turning 
               
               
                   
                   
                   
                   
                 angle or other 
               
               
                   
                   
                   
                   
                 inputs) 
               
               
                 3 
                 Low 
                 Auxiliary  
                 Auxiliary  
                 High Beam to  
               
               
                   
                 Beam 
                 High 
                 High 
                 supplement 
               
               
                   
                 (Flat) 
                 Beam 
                 Beam 
                 another High 
               
               
                   
                   
                   
                   
                 Beam. 
               
               
                 4 
                 High  
                 Low  
                 Low  
                   
               
               
                   
                 Beam 
                 Beam 
                 Beam 
                   
               
               
                   
                   
                 (Flat) 
                 (Flat) 
                   
               
               
                 5 
                 Fog 
                 Auxiliary  
                 Auxiliary 
                 High Beam  
               
               
                   
                   
                 High 
                 High 
                 to supplement 
               
               
                   
                   
                 Beam 
                 Beam 
                 another  
               
               
                   
                   
                   
                   
                 High Beam. 
               
               
                 6 
                 Fog 
                 Bending  
                 Bending  
                   
               
               
                   
                   
                 (Side) 
                 (Side) 
                   
               
               
                 7 
                 DRL 
                 Low Beam 
                 Low Beam 
                   
               
               
                   
                   
                 (Flat) 
                 (Flat) 
                   
               
               
                 8 
                 DRL 
                 Bending  
                 Bending  
                   
               
               
                   
                   
                 (Side) 
                 (Side) 
                   
               
               
                 9 
                 DRL/Turn 
                 Low  
                 Low  
                 2 LEDs (white,  
               
               
                   
                   
                 Beam 
                 Beam 
                 amber) in 
               
               
                   
                   
                 (Flat) 
                 (Flat) 
                 14a middle  
               
               
                   
                   
                   
                   
                 guide 
               
               
                 10 
                 DRL/Turn 
                 Auxiliary  
                 Auxiliary  
                 2 LEDs (white,  
               
               
                   
                   
                 High 
                 High 
                 amber) in 
               
               
                   
                   
                 Beam 
                 Beam 
                 14a middle 
               
               
                   
                   
                   
                   
                 guide 
               
               
                 11 
                 Stop/Turn 
                 Backup 
                 Backup 
                 2 LEDs (red,  
               
               
                   
                   
                   
                   
                 amber) in 
               
               
                   
                   
                   
                   
                 14a guide 
               
               
                   
               
               
                 Functions can be interchanged between guide locations (14a, 14b, 14c) 
               
               
                 Each Blade can make following patterns: High Beam; Low Beam Flat; Fog and Signal (Stop, Turn, Tail) 
               
             
          
         
       
     
         [0068]    Separate illumination of each light guide  14   a - 14   c  has been described. It should be understood that multiple light guides  14   a - 14   c  can be selectively activated individually or one or more can be activated simultaneously. For example, as in  FIG. 2E , LED  16  and light guide  14   a  can produce pattern P 1  (a headlight beam) while LED  18  and light guide  14   b  can simultaneously produce pattern P 2  for illuminating the left front side of the vehicle during a left turn or to provide a dynamic bending light during a turn. One benefit or advantage of this arrangement is that the overall pattern in  FIG. 2E  is aesthetically pleasing because the light intensity is rather uniformly distributed across the combined patterns P 1  and P 2  without significant gaps or streaks on the roadway which is illuminated. 
         [0069]    Also, an external surface  12   b  of the lens  12  of  FIGS. 1A-1C and 2A-2E  can be adapted to be made conformal with an external surface V 1  ( FIGS. 3A and 3B ) of the vehicle V, as shown in the left side of  FIG. 3B , for styling purposes and to meet aerodynamic requirements. No secondary protective lens is required. In addition, the lens  12  is highly adaptable because it can be curved in multiple dimensions, as indicated by the wire frame sketch in  FIGS. 3A-3B . 
         [0070]    This discussion will return to the structure of the assembly  10  of  FIGS. 1A-1D  and  FIGS. 2A-2E . Each light guide  14   a - 14   c  contains a reflective surface  22  which may bear a reflective coating, such as an aluminum film. The reflective surface  22  is of the parabolic type. The lens  12 , while a single, integral and monolithic unit in one form of the invention, can be conceptually divided into multiple functional sections, two of which lens sections  12   c  and  12   d,  are schematically shown in  FIG. 4 . The light guide  14   a  transmits most of the light from LED  16  (not shown in the figure for ease of illustration) to the lens section  12   c,  which focuses or spreads the rays LR 1  according to the shape of lens section  12   c.  In  FIG. 5 , the light guide  14   c,  for example, transmits its rays LR 3  to both the lens sections  12   c  and  12   d.  The particular allocation of the light between lens sections  12   c  and  12   d  for this light guide  14   c  will depend on the design of the system. Alternately, in one form of the invention, a majority of the light from light guide  14   c  travels through the lens section  12   d.    
         [0071]    As mentioned earlier,  FIGS. 6A through 6F  illustrate simulations illustrating operation of the apparatus of  FIGS. 1A-1C and 2A-2E . In  FIG. 6A , only the light guide  14   a  and LED  16  are illuminated to provide the pattern P 1 , and in  FIG. 6B , only the light guide  14   c  and LED  20  are illuminated to provide the pattern P 4  to provide a bending light to the right. 
         [0072]    In  FIG. 6C , light guides  14   a  and  14   c  and LEDs  16  and  20 , respectively, are illuminated to provide the pattern P 3  to bend light to the left. In  FIG. 6D , the light guide  14   b  and LED  18  are illuminated to provide the pattern P 2 . 
         [0073]    In  FIG. 6E , the light guides  14   a  and  14   b  of  FIGS. 6A and 6B  are illuminated together by LEDs  16  and  18 , respectively, to provide a pattern P 2  that provides a bending light to the left. It is pointed out that the light rays LR 2  of light guide  14   b  cross the light rays LR 1  of light guide  14   a  within the lens  12 . The result is that the projected beams or light rays LR 1  and LR 2  overlap as illustrated in  FIG. 2E  and indicated in  FIG. 6E  to provide the pattern P 2 . 
         [0074]    In  FIG. 6F , all three light guides  14   a,    14   b,  and  14   c  and their associated LEDs  16 ,  18  and  20 , respectively, are illuminated and indicates the uniformity of illumination and a pattern P 5  which is obtained. A plurality of scallops  12   c  in the exit face  12   b  of the lens  12  in  FIG. 1A  promote this uniformity by introducing an amount of scattering into the projected beams or rays LR 1 , LR 2  and LR 3 . 
         [0075]    In one form of the invention, light sources or LEDs  16 ,  18  and  20  are mounted on a single printed-circuit board  34  ( FIGS. 22 and 23 ). These LEDs  16 ,  18  and  20  are properly aligned with entry surfaces  14   a   1  ( FIG. 22 ),  14   a   2  and  14   a   3  of light guides  14   a,    14   b  and  14   c,  respectively, so that during assembly, all light sources or LEDs  16 ,  18  and  20  can be installed by a single process of installing a single circuit board. This alignment process will be explained in more detail later herein. 
         [0076]      FIGS. 6G, 6H and 61  illustrate various embodiments of the invention in which multiple light guides  14   a - 14   e  are present. It should be understood that more or fewer light guides  14   a - 14   e  could be provided, such as the embodiment of  FIG. 6G-6I . Also, multiple LEDs could be used with each light guide  14   a - 14   e.  Also, a device could be provided with the light guide  14   a  in combination with only one of either light guide  14   b  or  14   c  or other light guides, as illustrated in  FIG. 32  and described later herein. 
         [0077]    In the embodiment being described, note that the plurality of light guides, such as light guides  14   a - 14 - c  in  FIGS. 1A and 2A  and light guides  14   a - 14   e  in  FIGS. 6G-6I  are arranged in a generally equally spaced angular arrangement along an arc a predetermined angle PA apart. In the illustration, the predetermined angle is about 30 degrees. It should be understood, however, that they could be unequally spaced apart, such that, for example, the angle PA 1  between light guide  14   a  and light guide  14   c  is larger than the angle PA 2  between light guide  14   a  and light guide  14   b,  as illustrated in  FIG. 6H . The particular spacing may, therefore be varied and at least partly driven by the function to be performed and the environment where the light guides  14   a - 14   e  will be situated. 
       ADDITIONAL CONSIDERATIONS 
       [0078]    1.  FIG. 7  is a view of the light guide  14   a  viewed in the direction of arrow A in  FIG. 1A .  FIG. 7  illustrates the LED  16 . In one form of the invention, the LED  16  should be located generally central or midway between wall  14   a   2  and  14   a   3  to the light guide  14   a  as opposed to being displaced to the left or right in  FIG. 7 , as will now be explained. 
         [0079]      FIG. 7  illustrates Snell&#39;s Law of refraction. The angle A 2  of the transmitted ray follows the sine-function given in the Figure. However, as indicated in  FIG. 8 , when the incident angle A 1  reaches a Critical Angle, the transmitted ray does not exit the light guide  14   a,  but instead travels parallel to the surface of the light guide  14   a  as indicated. Total internal reflection occurs when the incident angle Al exceeds the Critical Angle as illustrated in  FIG. 9 . 
         [0080]    These facts allow one to deduce a Zone of Acceptance ( FIGS. 10-12 ). In  FIGS. 10 and 11 , in order for total internal reflectance to occur, the incoming rays must exceed the Critical Angle. These two Critical Angles are combined into  FIG. 12  which shows the Zone of Acceptance. The angles of the incoming light rays, respectively, should lie within this zone for total internal reflectance to occur. 
         [0081]    It is pointed out that a light ray having less than the Critical Angle will also be reflected internally. However, such a ray will experience both transmission and reflection at each encounter with the surface, as best shown in  FIG. 10 . In this case, if one assumes a reflection coefficient of 0.8, for example, then after ten reflections, the remaining intensity in the ray will be the initial intensity multiplied by 0.8 raised-to-the-tenth-power, which is considered negligible. Such a ray is effectively lost. In contrast, an incident ray at an angle greater than the Critical Angle behaves differently and does not experience this reduction in intensity. 
         [0082]    At this point, a small complication arises, namely, that the Zone of Acceptance has been computed based on rays located within the light guide  14   a,  but the incoming rays outside the light guide  14   a  will be refracted as they enter the light guide  14   a.    FIG. 13  shows the Zone of Acceptance lowered into the light guide  14   a  for ease of explanation.  FIG. 14  shows a ray within the light guide  14   a  at the Critical Angle.  FIG. 15  shows how an incoming ray is refracted according to Snell&#39;s Law to produce the ray of  FIG. 14 . The equations point out that the refraction at the surface causes the Zone of Acceptance to open up somewhat outside the light guide  14   a  because the index of refraction of air is less than that of the light guide  14   a.  Therefore, the actual Zone of Acceptance is adjusted for the incoming refraction of  FIG. 15  and is represented generally by  FIG. 16 . 
         [0083]    Now, the positioning of the LED  16  can be considered. This analysis applies to all the light guides  14   a,    14   b  and  14   c,  but is only described relative to light guide  14   a  for ease of illustration.  FIG. 17  shows the LED  16  positioned on the central axis AX relative to the entry surface  14   a   1  of light guide  14   a.    FIG. 18  shows that LED  16 , but with the Zone of Acceptance boundary ZA superimposed. In  FIG. 18 , as the boundary ZA indicates, the solid rays SR from LED  16  will lie within the Zone of Acceptance and some phantom rays PR (represented by dashed lines in the figure) will not. The phantom rays PR will be lost because they experience the repeated losses of reflection/transmission described above or they simply are directed away from the entry surface  14   a   1  of the light guide  14   a.    
         [0084]    However, if the LED  16  is shifted away from the central axis AX, as illustrated in  FIG. 19 , then all phantom rays PR are still lost because they lack the proper angles. Nothing has changed in this respect. In addition, solid ray R 1  is also lost because it fails to enter the light guide  14   a  entirely. 
         [0085]    Therefore, for maximum optical coupling, the LED  16  should lie on the central axis AX of the light guide  14   a  to avoid loss of rays such as R 1 . 
         [0086]    2. It is possible that future vehicles may be required to significantly reduce power expenditure in their lighting systems and some ways to achieve that reduction will now be considered. 
         [0087]    A gasoline or diesel powered engine of a modern passenger automobile has a power rating in the dozens of kilowatts or a few hundred kilowatts, one kilowatt being about 1.25 horsepower. However, the power consumed by the lighting system of such a vehicle lies in the dozens or hundreds of watts. Thus, the power produced by the engine is roughly one thousand times larger than the power consumed by the lighting system. 
         [0088]    However, electric vehicles are becoming more abundant. Their electric motors generally also have power ratings in the dozens of kilowatts, similar to current gasoline engines. However, under current technology, the electric batteries used to power the electric motors do not possess comparable energy density to that of liquid fuels. Electric power is at a premium in such vehicle. 
         [0089]    Therefore, as the usage of electric vehicles becomes more widespread, it may become important to economize on electric power consumption. In this context, consideration will be given to maximizing the optical coupling between the LED  16  and the light guide  14   a  to reduce losses and to thereby allow usage of less powerful LEDs  16 . The positioning of  FIG. 18  represents one improvement in optical coupling. 
         [0090]      FIG. 20  is a rough graphical rendition of the Fresnel Equations, which indicate the theoretical reflection coefficients for specular reflection for various angles of incidence.  FIG. 20  indicates that the reflection coefficient is minimal and thus the transmission coefficient is maximal at an angle of incidence of zero as measured with respect to the surface normal. 
         [0091]    Therefore, to minimize reflection at the interface IF where the light enters the light guide  14   a,  the light rays should enter perpendicular (as illustrated in  FIG. 20 ) to the surface  14   a   1 . If the LED  16  produces parallel rays, then this is easily accomplished using a flat entry face  14   a   1 . However, if the LED  16  acts as a point source and produces radially directed rays, then the entry face F may be curved so that the rays enter generally perpendicular to the entry face F. In one embodiment, the entry face  14   a   1  in one or more of the light guides  14   a - 14   c  is hemispherical. This is illustrated in  FIG. 21 . 
         [0092]    3. Reflective losses occur where the light from an LED  16 ,  18  or  20  exits the LED  16 ,  18  or  20  and enters the air, for example, at area A 1  in  FIG. 23  and then where light exits the air and enters the light guide surface at area A 2 . These losses can be reduced by an impedance-matching material M shown in  FIG. 23 . The required index of refraction of the matching material M is calculated in a known manner. 
         [0093]    4. In one form of the invention, the LEDs  16 ,  18  and  20  are contained on a single, common printed circuit board (PCB)  34  as illustrated in  FIGS. 23 and 24 . The spacing between adjacent pairs of the LEDs  16 ,  18  and  20  is equal to a distance between the central axes of the corresponding light guides  14   a - 14   c.  In  FIG. 23 , the LEDs  16 ,  18  and  20  are located as shown and mounted on the PCB  34 . The distance D 1  equals the distance D 2  and the distance D 3  equals the distance D 4 . A similar principle applies to the multiple light guides  14   a - 14   c  in other Figures. Thus, the LED to LED distance of an adjacent pair of LEDs  16 ,  18  and  20  is the same as the light guide to light guide distance of the corresponding light guides  14   a - 14   c.    
         [0094]    5.  FIG. 24  is a cross section of one conception of another embodiment of the invention. Light guides  14   a - 14   c,  being cantilevered from the lens  12 , can experience vibration as indicated by the dashed lines. This vibration can be reduced by fastening adjacent light guides  14   a - 14   c  together by using bars  44  near the ends of the light guides  14   a - 14   c.  This connection serves to stiffen the vibrating elements. It also increases the mass of the vibrating elements and thus changes the resonant frequency. Alternately, the light guides  14   a - 14   c  can be fastened to the vehicle structure by brackets or cassettes, one of which is shown schematically by block  46 . 
         [0095]    6.  FIG. 25  indicates the structure of  FIG. 25  being cut or molded into three pieces by the dashed lines.  FIG. 26  indicates that the three pieces are rendered identical in shape.  FIG. 27  conceptually rotates or pivots the three pieces of  FIG. 26  about points P in  FIG. 27 . 
         [0096]      FIG. 28  indicates a shape which can be deduced from  FIG. 27 .  FIG. 29  indicates lens  12  being cut off from the shape of  FIG. 28 .  FIG. 31  indicates three identical shapes of  FIG. 29  assembled into a structure with a lens  12 ′ or a portion of lens  12 ′ added. 
         [0097]    The apparatus of  FIG. 30  provides the benefit of utilizing three copies of a single molded component, namely that of  FIG. 29 , to form one embodiment of the invention. The single molded component is simpler to fabricate compared with the structure of  FIGS. 1A-1C . 
         [0098]    In another embodiment, the assembly  10  in  FIG. 31  can be split, molded or cut along dashed line DL to produce two mirror-image halves on the right side of the Figure. Fabricating a mold for such a half is simpler than fabricating a mold for the entire assembly  10  and the molding process for such a half is simpler as well. 
         [0099]    7. Some characteristics of various embodiments of the invention will be discussed.  FIG. 10  is a schematic exploded view of one form of the invention. The light guide  14   a  can be said to have an exit face  14   a   4  which transmits light into the entry surface  12   a  of projection lens  12 . The exit face  14   a   4  is thin and broad because the thickness TH is less than the height H. It should be understood that various ratios of height H to thickness TH are possible and ratios of height H to thickness TH may be 5 and 50 or any of the values therebetween (e.g., 5 to 50). 
         [0100]    The light guide  14   a  generates a sheet or beam of light rays LR 1  in the example, indicated by arrow  36 . The projection lens  12  receives the sheet or beam and expands it transversely, producing a beam indicated by the dashed arrows  38 . The various patterns were described earlier herein relative to  FIGS. 6A-6F . 
         [0101]    8.  FIG. 32  illustrates one form of and embodiment of the invention. A vehicle  40  contains two assemblies  10  which are mirror-images of each other. Light guide  14   a  and LED  16  in both assemblies  10  together generate the low headlight beam for the vehicle  40 . Light guide  14   c  of the right-hand assembly  10  in  FIG. 32  generates a right turn signal or a right turn headlight, fog light, daytime running light (DRL) or bending light, which illuminates the right front of the vehicle during a right turn. Light guide  14   b  generates a left turn signal, fog light, DRL or bending light or a left turn headlight beam. 
         [0102]    9. In one form of the invention, the lens  12  is symmetrical about an internal axis or plane. This plane or axis can coincide with the central plane of light guide  14   a.  The lens surface  12   b  is conical or curved and may have the scallops  12   c  as mentioned earlier herein. 
         [0103]    10. The light guides  14   a - 14   c  are illustrated as being flat. However, it should be understood that they can be curved and still function properly. 
         [0104]    11. It should also be appreciated that the light guides  14   a - 14   c  do not have to be the same size, one or more of them can be different sizes. 
         [0105]    12. It should also be understood that different colored LEDs  14   a - 14   c  could be used. Also, each light guide may have a plurality of different color LED, such as white, amber, yellow, or other color to facilitate performing different lighting functions, such as the forward lighting function or turn lighting functions mentioned earlier. 
         [0106]    13. Advantageously, the present invention has the following advantages:
       reducing packaging size by placing multiple functions in one optical system and using the same exit optic for all functions;   consistent lit appearance between different functions;   smooth transition between functions on the road (no visible streaks where low beam meets bending light);   all entrance guide may have LEDs that are placed on a single PCB to simplify electronics;   use of separate optical systems for separate functions; and   does not include functions, such as bending or cornering, that are not required to be included.       
 
         [0113]    14. The light guides can be designed to form a plurality of light patterns, such as cut-off, signal, and the like. 
         [0114]    This invention, including all embodiments shown and described herein, could be used alone or together and/or in combination with one or more of the features covered by one or more of the claims set forth herein, including but not limited to one or more of the features or steps mentioned in the bullet list in the Summary of the Invention and the claims. 
         [0115]    While the system, apparatus, process and method herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise system, apparatus, process and method, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.