Abstract:
A system for adjusting the direction of a light beam from a headlamp assembly comprises a condenser lens which is movable along an arcuate path. As a vehicle turns a corner, the system moves the condenser lens along the arcuate path, so as to direct the light beam in the direction that the vehicle is moving. Because the condenser lens follows an arcuate path, the light beam is not distorted, allowing for greater angular displacement of the light beam.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to automotive lamps. In particular, the present invention relates to an assembly for moving the light beam pattern of a headlamp. 
     Generally, conventional automotive headlamps utilize a reflector of parabolic shape and an incandescent lamp. However, a projector headlamp, which has recently come into use more widely in the United States, is an automotive headlamp that typically utilizes a reflector of elliptical shape and may include a high intensity discharge gas lamp. A projector headlamp also generally requires the use of a condensing lens, which is located in front of the lamp and the reflector, to focus the light emitted by the assembly into a concentrated beam pattern which meets applicable automotive lighting requirements. 
     In response to changing driving conditions, it can become desirable to move the beam pattern relative to the vehicle. For example, when a vehicle is being driven around a corner, it may be desirable for the beam pattern of that vehicle&#39;s forward lighting system to be adjusted, axially and/or laterally, such that the emitted light better illuminates the area in the direction the vehicle is turning. Additionally, adverse weather conditions or an increase or decrease in a vehicle&#39;s speed may also result in circumstances where adjustment of the vehicle&#39;s forward lighting beam pattern may become desirable. Automotive headlamps that can be adjusted in this manner are generally known in the industry as adaptive front lighting systems (“AFS”). 
     AFS for projector headlamps are generally known in the art. Such systems generally move the emitted light beam pattern by moving the entire projector headlamp assembly. For example, U.S. Pat. No. 6,186,651 (the “&#39;651 patent”) discloses the use of solenoids, motors, cams and such to move the reflector, condenser lens and light shield of the projector headlamp assembly. This method, however, has some significant disadvantages. For example, laterally moving the entire projector lamp distorts the assembly&#39;s beam pattern from its original shape. This can cause the emitted light to become noncompliant with applicable government regulations. Additionally, moving the entire projector lamp requires a large amount of space behind the headlamp to keep the headlamp from swinging into other parts. An additional shortcoming of this approach is that moving the whole assembly requires at least some movement of electrical wires that supply power to the light source. Such movement can eventually result in a complete failure of the assembly. Moreover, when adjustments in the light&#39;s beam pattern are necessary, moving the large mass of the entire headlamp requires a longer than ideal response time or a larger and less efficient means for moving the assembly. 
     It is also generally known to pivot the condenser lens in order to adjust the aim point of the headlamp assembly in the vertical plane. For example, the &#39;651 patent discloses the use of a pivoting condensing lens in conjunction with a pivoting light shield to allow for a single headlamp assembly to provide illumination for both low beam and high beam conditions. While useful for small adjustments in aiming, such as when shifting between low beam illumination and high beam illumination, pivoting the condensing lens around an axis results in unacceptable levels of beam distortion for angles which are desired when a vehicle is turning. 
     It is also generally known to move a condenser lens within a plane that is perpendicular to the horizontal axis of the headlamp. Such a system is disclosed in U.S. Pat. No. 5,915,829 (the “&#39;829 patent”). According to the &#39;829 patent, a lens is mounted within two mountings, both of which are in a plane perpendicular to the horizontal headlamp axis. These mountings are then used to move the lens within the plane perpendicular to the horizontal headlamp axis, so as to control the position of the light beam of the headlight assembly. Although the system disclosed in the &#39;829 patent does allow for some horizontal displacement of a light beam, it is of limited usefulness when a vehicle is turning. Another disadvantage of this system is that as the lens is moved within the mountings, the incidence angle of the light striking the lens increases, causing undesired distortion of the light beam formed by the lens. Thus, the angular displacement of the light beam is limited. 
     Therefore, it is desirable to provide a headlamp assembly that allows for significant angular displacement of the light beam of a headlamp assembly without excessive light beam distortion and without the need to move the entire headlamp assembly. It is further desired that the system be of inexpensive and dependable construction. It is further desired that the headlamp assembly be easily configured to fit within space confines of a variety of vehicle designs. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, a headlamp assembly is provided which overcomes the disadvantages of the prior art by providing a condenser lens that is movable along an arcuate path. One exemplary embodiment of the invention comprises an elliptical reflector having two focal points. A light source is located proximate to the first focal point, and a condenser lens is rotatable around the second focal point. As a vehicle turns, the condenser lens is moved along an arcuate path such that the light beam formed by the headlamp assembly is projected in the direction which the vehicle is turning. 
     The invention provides a headlamp assembly that allows for significant angular displacement of the light beam of a headlamp assembly without excessive light beam distortion and without the need to move the entire headlamp assembly. The invention further provides a headlamp assembly which is inexpensive and of dependable construction. Moreover, it is advantageous that a headlamp assembly according to the present invention can be easily configured to fit within space confines of a variety of vehicle designs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a schematic top plan view of one exemplary embodiment of the invention. 
     FIG. 1B is a schematic top plan view of the embodiment of the invention shown in FIG. 1A with the condenser lens in an alternative position. 
     FIG. 2A is a schematic top plan view of an alternative exemplary embodiment of the invention using a elliptical reflector. 
     FIG. 2B is a schematic top plan view of the alternative embodiment of the invention shown in FIG. 2A with the condenser lens in an alternative position. 
     FIG. 3A is a schematic top plan view of an alternative exemplary embodiment of the invention using a double gimballed mount. 
     FIG. 3B is a schematic front plan view of the alternative embodiment of the invention shown in FIG.  3 A. 
     FIG. 4 is a top plan view of an alternative mounting system for practicing the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1A, a schematic top plan view of one exemplary embodiment of the invention is shown. Headlamp assembly  100 , which is installed in a vehicle, comprises reflector  102  having a reflector axis  104 . Reflector  102  has focal point F 1  and forward-facing reflector opening  106 . Light source  108  is located substantially at focal point F 1 . Condenser lens  110  is disposed forward of reflector opening  106 . For purposes of explanation, point A is positioned at the approximate center of mass of condenser lens  110 . Accordingly, a light beam (not shown) is projected forward from reflector  102  and focused by condenser lens  110  so as to provide illumination in front of the vehicle. 
     Referring now to FIG. 1B, headlamp assembly  100  is shown with condenser lens  110  in an alternate position in accordance with the present invention when the vehicle is turning to the left. The approximate center of mass of condenser lens  110  when condenser lens  110  is in the alternate position is indicated by point B. In this embodiment, the linear distance from F 1  to point A shown in FIG. 1A is equal to the linear distance from F 1  to point B in FIG.  1 B. When condenser lens  110  is in this alternate position, condenser lens  110  focuses the light beam in a direction to the left of the direction of the light beam produced in the configuration of FIG. 1A above. The movement of condenser lens  110  is accomplished by rotating the lens with respect to a point that is not co-located with point A. Accordingly, the path followed by condenser lens  110  from one position to another position about the point of rotation may be described as being arcuate. 
     Those of skill in the art will recognize that the present invention may be practiced with a number of variations. For example, the point of rotation need not be substantially near to the focal point of the reflector. Furthermore, the arcuate path may be of any curvilinear shape such as, but not limited to, generally circular or elliptical. These and other variations being within the scope of the present invention. 
     Moreover, the present invention may be practiced with a variety of headlamp assembly types and configurations. For example, a second exemplary embodiment of the invention is shown in FIG.  2 A. According to this embodiment, headlamp assembly  200 , which is installed in a vehicle, comprises elliptical reflector  202  having a reflector axis  204 . Elliptical reflector  202  has a first focal point F 1 , a second focal point F 2  and forward-facing reflector opening  206 . Light source  208  is located substantially at first focal point F 1  of reflector  202 . Condenser lens  210  is disposed forward of reflector opening  206  and forward of second focal point F 2  of parabolic reflector  202 . For purposes of explanation, point A is positioned at the approximate center of mass of condenser lens  210 . Accordingly, a light beam (not shown) is projected forward from reflector  202  and focused by condenser lens  210  so as to provide illumination in front of the vehicle. 
     Referring now to FIG. 2B, headlamp assembly  200  is shown with condenser lens  210  in an alternate position in accordance with the present invention when the vehicle is turning to the left. The approximate center of mass of condenser lens  210  when condenser lens  210  is in the alternate position is indicated by point B. In this embodiment, the linear distance from F 2  to point A shown in FIG. 2A is equal to the linear distance from F 2  to point B in FIG.  2 B. When condenser lens  210  is in this alternate position, the condenser lens focuses the light beam in a direction to the left of the direction of the light beam produced in the configuration of FIG. 2A above. 
     As will be understood by those of skill in the art, a low beam may be shifted to a high beam by moving the condenser lens in the vertical plane. Accordingly, the present invention may also be used to provide for both high and low beams. Referring to FIG. 3A, headlamp assembly  300  is shown with condenser lens  310 . Condenser lens  310  is mounted to double gimballed mount  320  by mounting brackets  340  as shown in FIG.  3 B. Double gimballed mount  320  functions as a means for moving condenser lens  310  in an arcuate path. Mounting brackets  340  are fixed to inner mount  350 . Inner mount  350  is rotatably connected to outer mount  360  by inner gimbals  355 . Outer mount  360  is connected to reflector  305  by outer gimbals  365 . 
     Thus, movement of the light beam in the left and right direction (horizontal plane) is accomplished by rotating condenser lens  310  about outer gimbals  365 , resulting in condenser lens  310  being moved in an horizontal arcuate path. Moving the light beam between high and low beam positions (vertical plane) is accomplished by rotating condenser lens  310  about inner gimbals  355  resulting in condenser lens  310  being moved in a vertical arcuate path. 
     Referring now to FIG. 4, a schematic top plan view of an alternative exemplary mounting system for practicing the invention is shown. Headlamp assembly  400  includes light source  402 , reflector  404  and condenser lens  406 . Condenser lens  406  is fixedly attached to horizontal lens connector  416  and bracket  408 . Bracket  408  is rotatably connected to reflector  404  at pivot connector  410 . Means for moving condenser lens  406  in an arcuate path in this embodiment is provided by horizontal stepper motor  412  which is fixedly connected to condenser lens mount  414 . Stepper motor  412  comprises drive gear  414  which is operably engaged with horizontal lens connector  416 . 
     Operation of one embodiment of the present invention is explained by reference to FIG.  4 . Stepper motor  412  is responsive to a means for computing angular displacement. The means for computing angular displacement may comprise, for example, a microchip. Input signals to the microchip may include signals related to the direction the vehicle is going such as may be provided with steering wheel position and/or wheel orientation. Additionally, signals related to vehicle speed may be provided, such as accelerator position, engine speed or wheel rotational speed. Additional signals may also include signals responsive to vehicle loading, such as would be desired when compensating light beam position based on vehicle loading. Those of skill in the art will understand that these and other signals, alone or in a variety of combinations, may be provided within the scope of the present invention. 
     In response to the input signals, the means for computing angular displacement generates a control signal to stepper motor  412 . Stepper motor  412  causes drive gear  414  to rotate. Drive gear  414  operates against horizontal lens connector  416 , causing horizontal lens connector  416  to move. Because horizontal lens connector  416  is fixedly attached to condenser lens  406 , condenser lens  406  also moves. The motion of condenser lens  406  is forced into an arcuate path around pivot connector  410 . Thus, means for moving condenser lens  406  comprises the combination of stepper motor  412  and pivot connector  410 . Those of skill in the appropriate art will recognize that a number of alternative embodiments exist for the means for moving condenser lens  406  in an arcuate path. By way of example, but not of limitation, the means for moving may comprise solenoids, motors, cams, gimbals, pivots, tracks, followers, linkages, gears, bearings, pumps, and/or the like. Moreover, the means for moving may include electronic, mechanical, electromechanical, inductive, magnetic, optical, hydraulic, and/or pneumatic devices and/or the like. These and other variants being within the scope of the present invention. 
     As condenser lens  406  is moved in an arcuate path, the light beam formed by condenser lens  406  moves in the same general direction as condenser lens  406 . It has been discovered, that when using an embodiment such that shown in FIG. 4, the light beam can be moved to about sixteen degrees (16°) from the reflector axis without excessive distortion of the light beam when measured at a point twenty-five (25) feet in front of the headlamp assembly. 
     Those of skill in the art will realize that as described herein, the present invention provides significant advantages over the prior art. Embodiments of the invention which may include elliptical reflector headlamp assemblies provide a headlamp assembly that allows for significant angular displacement of the light beam of a headlamp assembly without excessive light beam distortion and without the need to move the entire headlamp assembly. The invention further provides a headlamp assembly which is inexpensive and of dependable construction. Moreover, it is advantageous that a headlamp assembly according to the present invention can be easily configured to fit within space confines of a variety of vehicle designs. The present invention may be practiced to modify the direction of a light beam in response to vehicle motion, loading, varying driving conditions or terrain. Other objects and features of the present invention will be apparent to those of skill in the art in consideration of the above description, the accompanying drawings, and the following claims.