Abstract:
An automobile lamp assembly including a movable glare shield which is moved into the portion of the beam of light produced by a lamp assembly that is associated with the foreground area, thereby reducing the illumination level in the foreground area. The shield may be rotatably moved out of the blocking position to allow for a full illumination pattern when glare is not present.

Description:
BACKGROUND OF THE INVENTION 
     The intensity, beam pattern and beam aim point of vehicle front lamp assemblies are regulated because of the impact they have on various safety issues. Sufficient light is needed under a variety of driving conditions so as to allow the operator of a vehicle to see the road being traveled upon as well as hazards that may present themselves. The concern with adequate lighting is balanced by safety concerns for others. 
     An operator of a vehicle may be blinded by the front lamps of an oncoming vehicle. Similarly, a pedestrian may be blinded by the front lamps of an oncoming vehicle. Typically, the blinding is a result of direct glare. That is, glare resulting from light emitted from the lamp assemblies directly into the eyes of the operator or pedestrian (also referred to as disability glare and discomfort glare). Concern for this type of glare has resulted in regulations regarding the shape of the upper portion of the emitted beam as well as the illumination level in that upper portion. 
     The problem of direct glare has been addressed in a number of ways. The most significant manner of addressing this issue is the use of two different beam patterns, high beam and low beam. Depending upon the situation, such as other traffic in the vicinity, the vehicle operator selects the desired beam in order to decrease the light emitted by the front lamp assemblies (“low beam”) or to increase the light emitted by the front lamp assemblies (“high beam”). Multiple beams may be realized by using multiple light sources and/or moving a cutoff shield, a reflector, the light source and or the lens of the lamp assembly. 
     While the problem of glare for other operators and pedestrians has been given a significant amount of attention, the problem of glare to the operator of the vehicle from the vehicles own front lamps has remained largely unaddressed. Glare to the operator of a vehicle, or reflective glare, typically occurs as a result of wet, snow-covered or icy road conditions. In this environment, light from the lowest portion of the emitted light beam, used to light the road immediately in front of the vehicle or the foreground area, can be reflected back at the vehicle, blinding the operator. 
     The problem of reflective glare can be addressed to some extent by the use of shaped light beams, either by using a square reflector or manufacturing a lamp assembly with a permanent foreground shield that eliminates foreground lighting. However, these approaches unnecessarily eliminate foreground lighting under conditions wherein reflective glare is not a concern (i.e. dry road conditions). Moreover, if a reflective foreground shield is used, the problem of direct glare may be exacerbated. By reflecting a beam back through the main reflector, the emitted beam may not be uniform since the light reflected from the shield will typically not be emitted in a direction parallel to light that has not been reflected by the shield. 
     The potential impact of any solution to the reflective glare issue should take into consideration potential design limitations. By way of example, designers of sports cars frequently attempt to design vehicles with a low-slung, sleek appearance. Such designs may require a headlamp to be mounted at or very near the upper portion of the front of the vehicle, with little if any freeboard above the headlamp. This presents a challenge when reducing reflective glare for headlamps wherein the upper portion of the light beam reflected off the reflector is the primary contributor to reflective glare. In such headlamps, any additional hardware cannot be mounted near the upper part of the headlamp. 
     Therefore, a need exists for an automotive lighting system that provides for the reduction and/or elimination of foreground lighting when reflective glare conditions exist (i.e. when roads are icy, snow-covered or wet), but that also allows more intense illumination of the foreground area when reflective glare conditions do not exist (i.e. when roads are dry). It would be beneficial if the lighting system did not require additional equipment to be placed above the headlamp assembly. It would be further beneficial if the system operated with a variety of light source, shield and reflector configurations. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, a lamp assembly is provided which overcomes the disadvantages of the prior art by providing for reduced illumination of the foreground area when reflective glare is present. According to one embodiment, a rotating shield is located between the reflector and the lens of a lamp assembly. Initially, the shield is placed in a position where it does not block light directed to a forground area from passing out of the lamp assembly. The shield may be opaque, translucent or transparent. When needed or desired, the shield is rotated into the beam of light coming from the reflector, such that illumination in the foreground is reduced. 
     In one embodiment, the shield includes an opaque obstruction generally in the form of a partial epicycloid. When rotated into a blocking position, the shield projects into the beam of light formed by the reflector, reducing the amount of light that is projected into the foreground area of the illumination field of the lamp assembly. In an alternative embodiment, the shield comprises a glass shield with areas of varying degrees of light transparency. In this embodiment, when reflective glare is sensed, the glass shield can be rotated to a position that reduces the emitted light in the foreground area. In another embodiment, a free-formed spreading lens with areas of varying curvatures redirect portions of light in the light beam pattern. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a typical light beam emitted from a lamp assembly onto a measuring screen. 
         FIG. 2  is a diagrammatic side view of a lamp assembly. 
         FIG. 3  is a diagrammatic side view of the lamp assembly of  FIG. 2  with a foreground shield reducing the emitted light beam. 
         FIG. 4  is an illustration of a light beam emitted from a lamp assembly onto a measuring screen with reduced foreground area illumination. 
         FIG. 5  is a plan view of one embodiment of a foreground shield. 
         FIG. 6  is an illustration of the light beam emitted from a lamp assembly with the foreground shield of  FIG. 5  is in its blocking position. 
         FIG. 7  is a perspective view of a lamp assembly with the foreground shield of  FIG. 5 . 
         FIG. 8  shows a second embodiment of the foreground shield that can be utilized to reduce reflective glare. 
         FIG. 9  shows a third embodiment of the foreground shield that can be utilized to reduce reflective glare. 
         FIG. 10  shows a fourth embodiment of the foreground shield that can be utilized to reduce reflective glare. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a view illustrating a typical light beam emitted from a lamp assembly onto a measuring screen. The measuring screen includes vertical axis V and horizontal axis H. A typical light beam is shown by pattern  100 . Pattern  100  includes foreground portion  102 , middle portion  104  and upper portion  106 . Foreground portion  102  is generally bounded on the upper side by dashed line A—A. In operation, foreground portion  102  is directed to the foreground area in front of the vehicle, lighting the road immediately in front of the vehicle. Accordingly, the foreground portion of the emitted beam is the primary contributor to reflective glare. 
     Upper portion  106  is bound on the lower side by horizontal axis H. In a typical passing or low beam pattern in countries that drive in the right hand lane, upper portion  106  is generally limited to the right hand side of the beam pattern as viewed from a vehicle. This is done to avoid direct glare from the lamp assembly to the occupant of an oncoming vehicle and is shown in  FIG. 1 . A non-passing or high beam pattern is not so limited. Thus, as applied to the pattern of  FIG. 1 , the upper portion of a high beam pattern would extend to the left of vertical axis V. 
     Middle portion  104  is typically not a significant contributor to either reflective or direct glare. For purposes of discussion, middle portion  104  is defined to be the portion of the emitted beam of a lamp assembly that is above the foreground portion and below the horizontal axis H. Obviously, the aim point and mounting height of the lamp assembly when used in an operational situation will affect the extent to which each portion discussed above contributes to direct or reflective glare. Accordingly, the shape and size of the above defined portions may vary from embodiment to embodiment. 
       FIG. 2  is a diagrammatic side view of a lamp assembly  200 . Lamp assembly  200  includes lens  202 , reflector  204 , light source  206  and cutoff shield  208 . Light is emitted by light source  206  and reflected by reflector  204  in a forward direction through lens  202 . Cutoff shield  208  defines the upper vertical boundary of the beam of light emitted by lamp assembly  200 . This is shown by light ray  210 , which passes over cutoff shield  208  and represents the uppermost light beam emitted by lamp assembly  200 . Light ray  212  shows the lowest ray of light emitted by lamp assembly  200  into the foreground area  102  (shown in  FIG. 1 ). Light ray  214  shows the lowest ray of light emitted by lamp assembly  200  above the foreground area  102  and into the middle portion  104  of the beam pattern shown in  FIG. 1 . 
     As is well known in the art, variations in the vertical extent of the emitted light beam, such as upper portion  106  of pattern  100  in  FIG. 1 , can be effected by variations in the height of cutoff shield  208  along its length. In certain applications additional light can be emitted by the lamp assembly above light ray  210  by changing the inclination of cutoff shield  208  to a more horizontal state. Thus, a single lamp assembly can provide both low beam and high beam patterns by moving the cutoff shield into and out of a blocking position. 
       FIG. 3  shows lamp assembly  200  of  FIG. 2  with a foreground shield inserted into the forward beam. Specifically, foreground shield  220  has been positioned such that light ray  212  is blocked while light ray  214  is allowed to be emitted from lamp assembly  200 . The resulting beam pattern is shown as pattern  400  of  FIG. 4 .  FIG. 4  shows the measuring screen of  FIG. 1 , along with dashed reference line A—A generally indicating the upper boundary of the foreground portion of pattern  100 . As is shown in  FIG. 4 , if foreground shield  220  is designed properly it can eliminate all the illumination from lamp assembly  200  in the foreground area (the area below dashed line A—A). Accordingly, reflective glare from the foreground area is eliminated. 
     In accordance with one embodiment of the present invention, the foreground shield is rotatable into the forward beam of light so that the shield can be rotated into a position that blocks light during icy, snowy and wet road conditions and rotated into a position that does not block any light during dry road conditions.  FIG. 5  shows a plan view of a rotatable foreground shield  500 . With reference to  FIG. 5 , foreground shield  500  comprises ring  502 , teeth  504  that extend from ring  502 , and protuberance  506  that extends inwardly from ring  502  into a vacant portion  508  of the foreground shield  500 . In this embodiment, protuberance  506  is generally in the shape of a partial epicycloids. This shape affects the emitted light pattern more significantly in the lower center of the pattern than at the lower outer edges of the pattern.  FIG. 6  shows the resulting beam pattern  190  of a lamp assembly that incorporates foreground shield  500 . As shown in  FIG. 6 , the lower center of the foreground portion  102  is eliminated and, thus, reflective glare is substantially reduced. 
       FIG. 7  shows a partial perspective view of a lamp assembly  600  with rotatable foreground shield  500 . As shown in  FIG. 7 , lamp assembly  600  comprises light source  602 . Light from light source  602  is reflected in a forward direction off of reflector  604  through vacant inner portion  508  of foreground shield  500 , over cutoff shield  608  and out through lens  610 . The reflected light travels in a direction generally parallel to optical axis  620  of reflector  604 . 
     Cutoff shield  608  blocks a portion of light from impinging on lens  610 . When foreground shield  500  is placed in the position shown in  FIG. 7  (the “blocking position”), a portion of the light reflected off of reflector  604 , that would otherwise proceed past cutoff shield  608 , is blocked by protuberance  506  of foreground shield  500 . The position of foreground shield  500  is controlled by motor  614  and attached gear  616  which engages teeth  504  of the foreground shield. Foreground shield  500  is thus rotated in a plane generally perpendicular to optical axis  620  in between its blocking position and a position where none of the light that proceeds past cutoff shield  608  is blocked by protuberance  506  (the “pass-through position”). In this embodiment, protuberance  506  is opaque with a black matte finish. Accordingly, light impinging upon protuberance  506  does not contribute appreciably to the light emitted from lamp assembly  600 . 
     As will be appreciated by those of skill in the art, a number of alternative embodiments of rotatable foreground shield may be realized within the scope of the present invention. The following embodiments are provided by way of example, but not of limitation.  FIG. 8  is another embodiment of the rotatable foreground shield  700  with a protuberance  702  that forms a solid horizontal edge  704  across the top portion of the foreground shield. Alternatively,  FIG. 9  shows another embodiment of a rotatable foreground shield  800  with a protuberance  802  that is in the shape of a curved ramp. As shown in  FIG. 9 , the first end  804  of protuberance  802  extends only slightly into the vacant portion  508  of the foreground shields while the second end  806  of the protuberance extends more significantly into the vacant portion of the foreground shield. In this embodiment, the extension into the vacant portion is gradual. However, a series of distinct protuberances of increasing size may also be used. In this embodiment, foreground shield  800  will allow for iterative levels of occlusion as the foreground shield is rotated between its first end  804  that extends only slightly into the light beam and its second end  806  that extends more significantly into the light beam. Thus, as the foreground shield  800  is rotated into the path of the forward beam, an increasing amount impinges the foreground shield. 
     In yet another alternative embodiment shown in  FIG. 10 , a plurality of protuberances are provided. Foreground shield  900  comprises rotating ring  902  and stationary ring  904 . Stationary ring  904  includes cutout  906 . Foreground shield  900  further includes protuberances  908 ,  910  and  912 . The protuberances in this embodiment are of different sizes. Protuberance  908  is the smallest protuberance, and protuberance  912  is the largest. Protuberance  908  is shown in the occluding position, while protuberances  910  and  912  are in non-occluding positions. 
     Protuberances  908 ,  910  and  912  are pivotably connected to rotating ring  902  by spring loaded hinges such as hinge  914 . In operation, hinge  914  biases protuberance  912  against stationary ring  904 . Protuberances  908  and  910  are similarly held against stationary ring  904 . As a protuberance is rotated over cutout  906 , the protuberance is allowed to pivot toward the center of rotating ring  904 . In  FIG. 10 , protuberance  908  is shown pivoted toward the center of ring  904 . As rotating ring  902  moves a protuberance away from cutout  906 , stationary ring  904  acts against the spring biased hinge forcing the protuberance away from the center of rotating ring  904 . Those of skill in the art will appreciate that the embodiment of  FIG. 10  may easily be used in lamps without cutoff shields. 
     In accordance with other embodiments, the protuberance may be translucent, merely reducing the amount of light that passes through lens  610  to illuminate the foreground area. Alternatively, the protuberance may function as a lens, and redirect light passing through protuberance  506  to other portions of the light pattern by providing varying degrees of narrow angle light bending and/or spreading. This allows for a variable amount of illumination to be reduced in the foreground area. These and other embodiments are within the scope of the present invention. 
     Referring back to  FIG. 7 , in operation, foreground shield  500  is initially placed in a pass-through position wherein any light striking protuberance  506  would have, but for the presence of protuberance  506 , struck cutoff shield  608 . In other words, protuberance  506  is located behind cutoff shield  608 . Alternatively, foreground shield  500  could be placed forward of cutoff shield  608 . In this alternate embodiment, the foreground shield is inverted to block foreground lighting as the glare shield is located forward of the reflector focal point. When desired, motor  614  is energized so that gear  616  rotates. Because gear  616  of motor  614  is engaged with teeth  504  of foreground shield  500 , rotation of gear  616  forces foreground shield  500  to rotate. 
     Rotation of foreground shield  500  moves protuberance  506  from behind cutoff shield  608  into a blocking position wherein protuberance  506  extends into the beam of light reflected forward by reflector  604  and passing over cutoff shield  608 . Thus, a portion of the light beam is blocked. Initially, the light blocked is at the edge of the emitted light beam. To avoid shadow areas immediately in front of the vehicle, it is preferred to rotate foreground shield  500  in a direction such that the edge of the emitted light beam away from the center of the vehicle is occluded. When protuberance  506  is rotated into its blocking position (shown in  FIG. 7 ), the light blocked is primarily the light emitted into the foreground area and motor  614  is de-energized. 
     Motor  614  may be energized in response to a sensed reflective glare condition. The energization may be a result of a switch or button activated by a driver. For example, a dedicated circuit may move the glare shield when a driver activates the circuit. Alternatively, activation of the circuit may be in response to activation of a vehicle&#39;s windshield wipers. Other sensors may include, alone or in combination with any of the others, light sensors and moisture sensors. 
     As shown in  FIG. 7 , motor  614  may be mounted below lamp assembly  600 . In many vehicles, the placement of lamp assemblies is constrained by vehicle design. Thus, there may not be room above the lamp assembly for an operating mechanism. As will be appreciated by those of skill in the art, the embodiment of  FIG. 7  allows motor  614  to be mounted in a number of locations, such as above, below and to the side of lamp assembly  600 , without adversely impacting the operation of foreground shield  500 . Additionally, the motor could be located behind reflector  604 , in a position remote from foreground shield  500 . 
     Those of skill in the art will recognize that in accordance with the present invention, the shape and characteristics of the foreground shield could be varied to the desired glare reducing effects. The foreground shield may include as a means for reducing illumination in the foreground area of a headlamp a solid piece of opaque material or generally transparent material having translucent portions. Alternatively, the means for reducing illumination may comprise an area that functions as a filter, such as a color filter or a polarizing filter. Further, the shape of the protuberances of the foreground shield can take a variety of other forms. 
     Moreover, the foreground shield may be moved into and out of the blocking position in a variety of ways. By way of example but not of limitation, the means for receiving motive force may be teeth located on the inner or outer surface of the glare shield ring. Alternatively, the means for receiving motive force may be a bracket or an arm connected to the shield. Additionally, the glare shield may be moved by a worm gear, solenoid, or rack and pinion mechanism. These variations and others are considered to be within the scope of the present invention. 
     Those of skill in the art will realize that as described herein, the present invention provides significant advantages over the prior art. The invention provides a glare shield which reduces and/or eliminates foreground lighting when reflective glare conditions exist, but that also allows more intense illumination of the foreground area when reflective glare conditions do not exist. The glare shield does not require additional equipment to be placed above the headlamp assembly, and can be incorporated into a variety of light source, shield and reflector configurations. 
     While the present invention has been described in detail with reference to certain exemplary embodiments thereof, such are offered by way of non-limiting example of the invention, as other versions are possible. It is anticipated that a variety of other modifications and changes will be apparent to those having ordinary skill in the art and that such modifications and changes are intended to be encompassed within the spirit and scope of the invention as defined by the following claims.