BACKGROUND 
     1. Field of the Invention 
     The invention relates to a variable adaptive projector system for motor vehicles, and, more particularly, to a structure designed to vary the positions of shields inside the projector lighting unit in order to change the spatial distribution of light on the road. The shields in projector lighting unit can be placed in four defined positions for generating four different beam patterns: a wet road beam function for bad weather; a low beam function (passing beam); a high beam function (driving beam); and a motorway beam function for highway driving. 
     2. Related Technology 
     In order to generate low beam light and high beam light, the prior art headlamps have typically been equipped with either separate lighting units or combined lighting units utilizing two-filament light sources. Another possibility for combining low beam and high beam light involves a mechanism installed inside the lighting unit and providing for movement of an optical element, such as a shield, a light source, part of a reflector or the whole reflector itself. 
     For motorway and wet road (rain or bad weather) beam function, the additional lighting units are needed. The main disadvantages of these additional lighting units consist in higher demands required by the installation of these units in the headlamp, the additional light sources required, the higher power requirements and the higher costs. 
     SUMMARY OF THE INVENTION  
     The above mentioned disadvantages have been eliminated and the providing of low beam, high beam, motorway and wet road light has been solved in accordance with this invention by means of a variable adaptive projector system for motor vehicles. The projector system includes: a reflector, a light source, a basic shield, a wet road shield, a lens and a mechanism for varying the positions of the basic shield and the wet road shield, relative to the reflector, positions for low beam light, motorway light, high beam light and wet road light. 
     For wet road light, the wet road shield is positioned a distance z 3  above the focal point of the ellipsoidal reflector, when
 
 z   3   =b   1   ·β+b   3   ·β   3   +b   5   ·β   5   +b   7   ·β   7 + . . . , for β≈(0÷5),
 
where b 1,3,5,7,  . . . are constants characterizing the aspherical lens. The position of basic shield is shifted a distance z 1  below the focal point of the ellipsoidal reflector, when
 
 z   1   =b   1   ·α+b   3   ·α   3   +b   5   ·α   5   +b   7   ·α   7 + . . . , for α≈(0÷3),
 
where b 1,3,5,7,  . . . are constants characterizing the aspherical lens.
 
     For low beam light, the basic shield is in proximity of the focal point of the reflector and the wet road shield is shifted by distance z 4  above the focal point of the ellipsoidal reflector, when z 4&gt;z   3 . 
     For motorway light, the basic shield is shifted by distance z 1  below the focal point of the ellipsoidal reflector, when
 
 z   1   =b   1   ·α+b   3   ·α   3   +b   5   ·α   5   +b   7   ·α   7 + . . . , for α≈(0÷3),
 
where b 1,3,5,7,  . . . are constants characterizing the aspherical lens. In this mode of operation, the wet road shield is shifted by distance z 4  above the focal point of the ellipsoidal reflector, when z 4 &gt;z 3 .
 
     For high beam light, the basic shield is shifted by distance z 2  below the focal point of the ellipsoidal reflector, when z 2 &gt;z 1 , and the wet road shield is shifted by distance z 4  above the focal point of the ellipsoidal reflector, when z 4 &gt;z 3 . 
     Change of positions of basic shield and wet road shield is advantageously attained by a linear motor. Change of positions of basic shield and wet road shield can be also advantageously attained by a rotational motor. 
     Advantageously, for motorway light and wet road light the variable adaptive projector system is vertically adjusted. 
     The light source can be an arc of discharge lamp, a filament of bulb, or other light source used in the industry. 
     The light source is located within the ellipsoidal reflector in proximity to the reflector&#39;s optical axis so that the reference plane of the light source is generally perpendicular to this optical axis. 
     The basic mechanism used to vary the position of both shields includes a motor connected to the shields via a linkage and a linear or rotational cam, depending on the nature of the output of the motor. The positions of both shields for low beam, high beam, motorway and wet road light are precisely defined on the utilized cam, with the linkages following predefined pathways in or surfaces on the cams. The particular length of the stroke for a linear output motor, or the turning angle for a rotational output motor, are dependent on the specific geometrical arrangement of the whole mechanism, as may be dictated by design criteria beyond the scope of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred, but not limiting, embodiment of the present invention is described below with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an assembly of variable adaptive projector system with rotational motor and cam; 
         FIG. 2  is a perspective view of an assembly of variable adaptive projector system with linear motor and cam; 
         FIGS. 3   a  and  3   b  are, respectively, a schematic view showing the positions of the shields and the shape of the light beam in the low beam light mode of operation; 
         FIGS. 4   a  and  4   b  are, respectively, a schematic view showing the positions of the shields and the shape of the light beam in the motorway light mode of operation; 
         FIGS. 5   a  and  5   b  are, respectively, a schematic view showing the positions of the shields and the shape of the light beam in the wet road light mode of operation; and 
         FIGS. 6   a  and  6   b  are, respectively, a schematic view showing the positions of the shields and the shape of the light beam in the high beam light mode of operation. 
     
    
    
     DETAILED DESCRIPTION  
     Shown in  FIGS. 1 and 2  are perspective views of alternate mechanical constructions of a variable adaptive projector system  10  embodying the principles of the present invention. The system  10  generally includes an ellipsoidal reflector  12 , a light source  14 , an aspherical lens  16 , a basic shield  18 , a wet road shield  20  and a mechanism  22  for varying the positions of the shields  18 ,  20  within and relative to the reflector  12 . Changing the operational mode of the system for low beam, high beam, wet road and motorway light is made by changing the position of the shields  18 ,  20  relative to the reflector  12 . 
     The light source  14  is firmly and conventionally arranged inside the ellipsoidal reflector  12  in the proximity to the optical axis  24  defined by the reflector  12 . Accordingly, the reference plane of the light source  14  is generally perpendicular to the optical axis  24 . 
     As mentioned above, the pattern of the light beam generated by the system  10  can be changed by changing the position of one of both shields  18 ,  20 . The mechanism  22  for varying the position of the shields  18 ,  20  include a motor  26  having an output shaft  28  coupled to the shields  18 ,  20 . Depending on packaging and other considerations in the vehicle itself, the motor  26  of the mechanism  22  may either produce a rotary or a linear output via the output shaft  28 . A rotary configuration is generally illustrated in  FIG. 1 , while a linear configuration is generally illustrated in  FIG. 2 . 
     In the rotary output construction, the output of the motor  26  causes rotation of a rotary cam  30 . The angle of rotation of the output shaft  28 , and therefore the angle of rotation of the cam  30 , determines the relative position of the shields  18 ,  20 . Accordingly, each of the shields  18 ,  20  is coupled via a linkage  32 ,  34  (which in their simplest form may just be bars engaged with the shields and extending to contact the cam) that engages the cam  30  either in a passageway (one for each linkage  32 ,  34  defined in the cam) or on a cam surface. Upon rotation of the cam  30 , the position of the linkages  32 ,  34  are moved, which in turn causes the positions of the shields  18 ,  20  to be altered (such as being moved about a pivot) relative to the optical axis  24 . By properly configuring the cam passageways or surfaces and rotating the cam  30  a predetermined amount, movement of the linkages  32 ,  34  and the resulting positions of the shields  18 ,  20  can be set and controlled as desired. 
     Similarly, for the linear configuration of the  FIG. 2 , the shields  18 ,  20  are coupled via linkages  36 ,  38  (which in their simplest form may just be bars engaged with the shields and extending to contact the cam) to a linearly moveable cam  40  located on the distal end of the output shaft  28 . By properly configuring the cam surfaces and moving the linear cam  40  a predetermined amount, movement of the linkages  36 ,  38  and the resulting positions of the shields  18 ,  20  can be set and controlled as desired. 
     For both of the constructions seen in  FIGS. 1 and 2 , one of ordinary skill in the art will readily appreciate that the specific geometrical arrangement of the cams  30 ,  40  as well as the linkages  32 ,  34 ,  36 ,  38  will be dependent on the specific construction of the system  10  as a whole. Further discussion herein is therefore not necessary. 
     As discussed above, the beam pattern of the light produced by the system  10  can be changed by changing the relative positions of the shields  18 ,  20  relative to the reflector  12 . Changing the beam pattern has various benefits in different driving modes. For example, in what is herein referred to as a wet road light mode of operation, the shields  18 ,  20  can be shifted in the system  10  such that the light rays that would normally illuminate the foreground of the road will be partially obscured. In doing this, the glare perceived by oncoming drivers, as a result of the reflection of light rays from the wet road surface, can be lowered. This is particularly achieved by movement of the wet road shield  20  to the appropriate position in the wet road light mode of operation. 
     The basic shield  18  (a flat or curved member of suitable width and shape) creates the light-dark boundary seen in the beam functions other than high beam light. In these operational modes, the top edge of the basic shield  18  is at or slightly shifted from the focal point F of the projector lighting unit. Owing to this fact, the light rays that generate the hot spot of the high beam light function are partly shielded as seen in the “b” designated figures of  3   b,    4   b  and  5   b.    
     Referring now to  FIGS. 3   a  and  3   b,  for low beam light, the location of the basic shield  18  is such that the top edge of the shield  18  is adjacent the focal plane F of the projector lighting unit  10 . As a consequence, that the part of light rays, reflected from the ellipsoidal reflector  12 , is shielded creating a light-dark boundary of  FIG. 3   b.  The shielded light rays would otherwise generate the hot spot used in the high beam function. In the low beam light operational mode, the position of wet road shield  20  is shifted a distance z 4  above the focal point F of the ellipsoidal reflector  12 , when z 3 &lt;z 4 . 
     For the motorway light operation mode, seen in  FIGS. 4   a  and  4   b,  the basic shield  18  is slightly shifted downward and away from the area of the focal point F of the projector lighting unit  10 . The light rays, those generating the hot spot of high beam function, are partly unshielded and this creates a light-dark boundary for low beam function. As seen in  FIG. 4   a,  the position of basic shield  18  for motorway light function is shifted a distance z 1  below the focal point F of the ellipsoidal reflector  12 , when
 
 z   1   =b   1   ·α+b   3   ·α   3   +b   5   ·α   5   +b   7   ·α   7 + . . . , for α≈(0 to 3),
 
where b 1,3,5,7,  . . . are constants characterizing the aspherical lens  16 , more specifically the mathematical constraints in the polynomial which represents the focal area of the lens  16  and where α is the angle between the beam cut-off (boundary line between light and dark areas) and a horizontal plane. In this mode of operation, the position of wet road shield  20  is shifted by distance z 4  mm above the focal point F of the ellipsoidal reflector, when z 3 &lt;z 4 .
 
     The position of basic shield  18  for the wet road light operational mode is seen in  FIGS. 5   a  and  5   b.  Therein the position of the shield  18  is shifted by distance z 1  below the focal point F of the ellipsoidal reflector  12 , when
 
 z   1   =b   1   ·α+b   3   ·α   3   +b   5   ·α   5   +b   7   ·α   7 + . . . , for α≈(0 to 3),
 
and the position of wet road shield  20  is shifted by distance z 3  above the focal point F of the ellipsoidal reflector  12 , when
 
 z   3   =b   1   ·β+b   3   ·β   3   +b   5   ·β   5   +b   7   ·β   7 + . . . , for β≈(0 to 5),
 
where b 1,3,5,7,  . . . are constants characterizing the aspherical lens  16 , as mentioned above and where β is the angle between the beam cutoff (boundary line between light and dark areas) and a horizontal plane, as mentioned above with reference to α.
 
     If the basic shield  18  is removed from the focal plane F of the projector lighting unit, then the light rays, generating the hot spot of high beam function are unshielded. The position of wet road shield  20  in this high beam mode of operation is such that it is not situated in the area of the focal plane F of the projector lighting unit  10 . 
     In this mode, as seen in  FIGS. 6   a  and  6   b ,  the basic shield  18  is shifted a distance z 2  below the focal point F of the ellipsoidal reflector  12 , when z 2 &gt;z 1 . The position of wet road shield  20  is shifted by a distance z 4  above the focal point F of the ellipsoidal reflector  12 , when z 3 &lt;z 4 . 
     As any person skilled in the art 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.
A variable adaptive projector system for motor vehicles comprises a positioning mechanism for variation the positions of the basic shield ( 3) and the wet road shield ( 4) of the projector lighting unit between the defined positions.