Abstract:
A beam-controllable headlight has a lamp base, a first reflector and a second reflector. A lighting-emitting panel with a light source is mounted on the rear portion of the lamp base. The first reflector is mounted on the rear portion of the lamp base and has a reflective surface facing the rear portion. The second reflector has two end points. A normal of the light-emitting panel passes through one of the end points of the second reflector, and an acute angle is included between the normal of the light-emitting panel and a straight line passing through the other end point and a point on the light-emitting panel defining the normal of the light-emitting panel. Light beams are reflected twice to rule out scattering light generated above a cutoff line of the headlight and enhance brightness under the cutoff line.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a lighting device, and more particularly to a vehicular headlight with reduced glare above a cutoff line of the headlight and enhanced light utilization under the cutoff line. 
         [0003]    2. Description of the Related Art 
         [0004]    Headlights or fog lights of vehicles serve not only for lighting purpose but also for alerting oncoming vehicles or road users to avoid the risk of collision. However, when the beams of headlights or fog lights directly shine into the eyes of oncoming drivers or road users, there is a likelihood that the oncoming drivers or the road users may have accidents caused by glare as a result of the intensified light beams. Hence, cutoff line regulations of headlights or fog lights are well defined by all countries for land transportation means (especially vehicles and motorcycles). To separate a bright area and a dark area in a beam irradiated from a headlight or a fog light with a cutoff line, the bright area is defined to have a specified brightness at a certain distance from the headlight or the fog area such that the driver can clearly identify obstructions on roads. The dark area is defined to have a controlled light output within a specified distance and a specified angle to avoid glare generation resulting in discomfort and possible danger to oncoming drivers and road users. To tackle strong scattering light generated above the cutoff line, a blocking board is mounted between the light source and the headlight cover of a conventional headlight. The blocking board is even painted black or a front portion of the light source is painted black to form an absorbing layer for light absorption and glare avoidance. Despite reduction of scattering light, the foregoing two ways fail to effectively utilize light energy. 
       SUMMARY OF THE INVENTION 
       [0005]    An objective of the present invention is to provide a beam-controllable headlight with reduced glare above a cutoff line of the headlight and enhanced light utilization under the cutoff line. 
         [0006]    To achieve the foregoing objective, the beam-controllable headlight has a lamp base, a first reflector and a second reflector. 
         [0007]    The lamp base has a rear portion, a front portion and a peripheral wall. 
         [0008]    The rear portion has a light-emitting panel. The light-emitting panel is planar and has a light source mounted thereon. 
         [0009]    The peripheral wall is formed on the rear portion and protrudes toward the front portion. 
         [0010]    The first reflector is mounted on the rear portion with a distance to the light-emitting panel less than a distance to the front portion of the lamp base, and has a first reflective surface and two first end points. 
         [0011]    The first reflective surface faces the front portion of the lamp base. 
         [0012]    One of the first end points is connected to the rear portion of the lamp base. The other first end point is connected to the peripheral wall of the lamp base. An acute angle is included between a straight line passing the two first end points of the first reflector and a normal of the light-emitting panel. 
         [0013]    A second reflector is mounted between the rear portion and the front portion of the lamp base and has a second reflective surface and two second end points. 
         [0014]    The second reflective surface faces the rear portion of the lamp base. 
         [0015]    The normal of the light-emitting panel passes through one of the second end points of the second reflector. An acute angle is included between the normal of the light-emitting panel and a straight line passing through the other second end point and a point on the light-emitting panel defining the normal of the light-emitting panel. 
         [0016]    Light beams emitted from the light source are reflected by the second reflector to converge to a focus point of the second reflector, and travel to and are further reflected by the first reflector to parallelly propagate toward the front portion of the lamp base. 
         [0017]    The second reflector serves to reflect and focus light beams of the light source on the first reflector for the first reflector to further collimate the light beams propagating toward the front portion of the lamp base, thereby avoiding generation of scattering light above a cutoff line of the headlight and enhancing light utilization under the cutoff line. 
         [0018]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a perspective view of a first embodiment of a beam-controllable headlight in accordance with the present invention; 
           [0020]      FIG. 2  is an exploded perspective view of the beam-controllable headlight in  FIG. 1 ; 
           [0021]      FIG. 3  is an enlarged side view in partial section of the beam-controllable headlight in  FIG. 1 ; 
           [0022]      FIG. 4  is an operational side view in partial section of the beam-controllable headlight in  FIG. 3 ; 
           [0023]      FIG. 5  is an operational side view in partial section of a second reflector and a light source of a second embodiment of a beam-controllable headlight in accordance with the present invention; and 
           [0024]      FIG. 6  is another operational side view in partial section of the second reflector and the light source in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    With reference to  FIG. 1 , a first embodiment of a beam-controllable headlight in accordance with the present invention can be connected to a front end of a vehicle as a headlight of the vehicle and has a lamp base  10 , a first reflector  20 , a second reflector  30  and a lamp cover  40 . 
         [0026]    With reference to  FIGS. 2 and 3 , the lamp base  10  is bowl-shaped, and has an accommodation space, a rear portion  11 , a front portion  12  and a peripheral wall  13 . The accommodation space is defined within the lamp base  10 . The rear portion  11  has an opening  14  and a light-emitting panel  15 . The opening  14  is formed through the rear portion  11 . The light-emitting panel  15  is planar, is mounted to close the opening  14  for the rear portion  11  to be formed as a closed end, and has a light source  151  mounted thereon. In the present embodiment, the light source  151  is a surface light and a light-emitting diode (LED) light source. The front portion  12  is connected to the lamp cover  40 . The peripheral wall  13  is formed on the rear portion  11  and protrudes toward the front portion  12  of the lamp base  10 . 
         [0027]    The first reflector  20  is mounted on the rear portion  11  of the lamp base  10 . A distance between the first reflector  20  and the light-emitting panel  15  is shorter than a distance between the first reflector  20  and the front portion  12  of the lamp base  10 . In other words, the first reflector  20  is closer to the rear portion  11  than to the front portion  12 . The first reflector  20  has a reflective surface, an arcuate section and two end points P 1 , P 2 . The reflective surface faces the front portion  12 . One of the two end points P 1  is connected to the rear portion  11  of the lamp base  10 . The other end point P 2  is connected to the peripheral wall  13 . An included angle α between a straight line S 1  passing through the two end points P 1 , P 2  of the first reflector  20  and a normal of the light-emitting panel  15  is 60 degrees. In the present embodiment, the first reflector  20  and the rear portion  11  of the lamp base  10  are integrally formed. 
         [0028]    The second reflector  30  is mounted inside the accommodation space of the lamp base  10 , is located between the rear portion  11  and the front portion  12  of the lamp base  10 , and has an arcuate section, a reflective surface and two end points P 3 , P 4 . The reflective surface faces the rear portion  11  of the lamp base  10 . The normal of the light-emitting panel  15  passes through one of the end points P 3  of the second reflector  30 . An included angle between the normal of the light-emitting panel  15  and a straight line passing through the other end point P 4  and a point on the light-emitting panel  15  defining the normal of the light-emitting panel  15  is 60 degrees. In the present embodiment, the second reflector  30  is connected to the rear portion  11  of the lamp base  10  or the light-emitting panel  15  through a connection member  31 . The connection member  31  is parallel to the normal of the light-emitting panel  15 . The second reflector  30  and the rear portion  11  of the lamp base  10  are integrally formed. 
         [0029]    A contour of the lamp cover  40  corresponds to that of a top edge of the front portion of the lamp base  10  to close the lamp base  10 . 
         [0030]    With reference to  FIG. 4 , when in use, the beam-controllable headlight is connected to a vehicular power supply to light up the light source  151  of the light-emitting panel  15 . The light source  151  emits light beams L 1 , L 2 , L 3 , L 4 , L 5 , L 6 , L 7 , L 8 , L 9  and L 10  in a top-down direction. The light beams L 4 , L 5 , L 6  are irradiated to the second reflector  30  in front of the light source  151 , are reflected by the second reflector  30  to travel in a downward direction and converge to a focus point F 1  of the second reflector  30 , which is located under the light source  151  and is closer to the front end  12  of the lamp base  10  than the first reflector  20 . After passing the focus point F 1  of the second reflector  30 , the light beams L 4 , L 5 , L 6  further travel to the first reflector  20  and then are reflected by the first reflector  20  to be eventually irradiated through the lamp cover  40  in the form of collimated light beams parallel to and located below a horizontal line HL. Hence, headlights&#39; light beams that are higher than the horizontal line HL and are directly irradiated to the eyes of oncoming drivers and road users can be effectively avoided, and driving accidents caused by visual impairment resulting from glare can be therefore reduced. A first propagation distance of each light beam L 4 , L 5 , L 6  measured from the second reflector  30  to the focus point F 1  is R 1 . A second propagation distance of each light beam L 4 , L 5 , L 6  measured from the focus point F 1  to the first reflector  20  is R 2 . The first propagation distance R 1  is greater than the second propagation distance R 2 . According to the optical properties of quadratic surfaces, the light beams L 1 , L 2 , L 3 , L 8 , L 9 , L 10  are reflected by the peripheral wall  13  of the lamp base  10  to form collimated light beams parallel to the horizontal line HL. Among all the light beams, the light beams L 8 , L 9 , L 10  are aligned under the horizontal line HL. 
         [0031]    With reference to  FIG. 5 , operation of a second embodiment of a beam-controllable headlight in accordance with the present invention is shown. A distance D 2  between the light source  151  and one of the end points P 3  of the second reflector  30  and a distance D 1  between the light source  151  and the other end point P 4  of the second reflector  30  can be adjusted according to a height of the peripheral wall  13  of the lamp base  10  and a size of the lamp base  10 . An angle between a straight line passing the end point P 4  of the second reflector  30  and a normal of the light source  151  is 60 degrees. When the light source  151  irradiates light beams to a same point on the second reflector  30 , as the light source can be treated as a surface light, a light beam irradiated from a center of the vertical surface light source  151  is taken as a normal. A light divergence angle is defined as an angle between an outmost light beam and the normal of the light source and can be expressed as follows. 
         [0000]    
       
         
           
             
               tan 
                
               
                   
               
                
               θ 
             
             = 
             
               
                 H 
                 / 
                 2 
               
               D 
             
           
         
       
     
         [0032]    where 
         [0033]    θ is a light divergence angle; 
         [0034]    H is a size (height) of the light source; 
         [0035]    D is a distance between the light source and the second reflector. 
         [0036]    When a propagation distance of the light beam L 5  from the light source  151  to the second reflector  30  is 34.41 mm, the light divergence angle of the light beam L 5  is 3.58 degrees. 
         [0037]    As a comparison for adjustment of the second reflector  30 , with reference to  FIG. 6 , supposing that a size H of the light source remains intact, when a propagation distance D 1 ′ of the light beam L 5  from the end point P 4  of the second reflector  30  to the light source  151  is less than the propagation distance D 1  of the light beam L 5  in  FIG. 5  (in other words, the angle between the straight line D 1 ′ and the light source  151  is less than 60 degrees) or when a distance D 2 ′ between the end point P 3  and the light source  151  is less than the distance D 2  in  FIG. 5 , the light divergence angle is approximately 7.46 degrees, which is larger than that in  FIG. 5  because the light beam L 5  propagates shorter distance in  FIG. 6  than in  FIG. 5 . Varying the size of the light source and the distance D 2  between the end point P 3  of the second reflector  30  and the light source  151  and the distance D 1  between the end point P 4  of the second reflector  30  and the light source  151  can adjust the light divergence angle of light beams emitted from the light source  151 . Preferably, the light divergence angle is maintained under 4 degrees as it is efficient for light beams of the light source to be reflected and propagated under the horizontal line HL or the cutoff line. 
         [0038]    Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.