Patent Publication Number: US-7722235-B2

Title: Vehicle headlamp

Description:
This application claims priority from Japanese Patent Application No. 2007-2 91707, filed on Nov. 9, 2007, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   Apparatuses and devices consistent with the present invention relate to a vehicle headlamp which includes a projection-type light source and, more particularly, to a vehicle headlamp that effectively uses light non-reflected light as overhead light distribution. 
   2. Related Art 
   For example, Japanese Patent Application No. JP-A-2003-317513 describes a related art vehicle headlamp. According to a lamp structure of JP-A-2003-317513, the related art vehicle headlamp includes a projection-type light source unit for a high beam. The projection-type light unit includes a projection lens, a light emitting device, and a reflector for reflecting light emitted from the light emitting device such that the light converges to a rear focus of the projection lens. With this lamp structure, light emitted from the light emitting device is reflected twice by a sub-reflecting surface that extends forward from the front edge of the reflector, and an upward sub-reflecting surface that is provided near a rear focus of the projection lens so as to guide the light to the projection lens. Therefore, in addition to the light distribution pattern for the high beam formed by the reflector and the projection lens, the lamp structure provides a light distribution pattern widely diffused outward to the left and right sides. 
   Further, Japanese Patent Application No. JP-A-2004-241349 describes another related art vehicle headlamp. The related art vehicle headlamp includes a translucent member where the projection lens, a cut-off line forming shade, a light emitting device, and a reflector are integrally formed. In the lamp structure, a subreflector is formed on an outer surface between the reflector and the projection lens, and light reflected from the subreflector is radiated forward from the outer surface of the projection lens. Therefore, in addition to the light distribution pattern for a low beam that has a cut-off line corresponding to the cut-off line forming shade, the lamp structure provides a small light distribution pattern, which mainly illuminates a central region of the light distribution pattern. 
   However, the added light distribution patterns described in JP-A-2003-317513 and JP-A-2004-241349 have excessively high luminous flux density (i.e., excessive brightness) as the overhead light distribution used for the light distribution pattern for a low beam. Here, the overhead light distribution denotes light distribution that has low luminous flux density and illuminates a part of an upper portion of the cut-off line of light distribution pattern for a low beam in order to improve the visibility of a road sign or a trade sign provided on the front upper side. The intensity of the overhead light distribution is prescribed in a light distribution standard of a lamp. Accordingly, since the light from the added light distribution patterns in JP-A-2003-317513 and JP-A-2004-241349 becomes glare light against an oncoming vehicle, the lamp structures described above have a disadvantage in that they cannot be used as a headlamp for a low beam. 
   SUMMARY OF THE INVENTION 
   Exemplary embodiments of the present invention address the above disadvantages and other disadvantages not described above. However, the present invention is not required to overcome the disadvantages described above, and thus, an exemplary embodiment of the present invention may not overcome any of the problems described above. 
   Accordingly, it is an aspect of the present invention to provide a vehicle headlamp that can form a low beam having excellent visibility by adding adequate overhead light distribution but that does not become glare light against an oncoming vehicle. 
   According to one or more aspects of the present invention, there is provided a vehicle headlamp. The vehicle headlamp includes at least one projection-type light source unit housed in a lamp chamber. The projection-type light source includes a projection lens; a shade forming a cut-off line; an LED light source for emitting light, wherein the LED light source includes a substrate; an LED chip disposed on the substrate; and a translucent spherical cover member covering the LED chip, and is disposed such that an irradiation center axis of the LED chip is oriented in a direction substantially perpendicular to an optical axis of the projection-type light source unit, and wherein fine concave and convex portions are formed on a region of the cover member except a region corresponding to the reflector so as to diffuse light transmitted through the cover member, a reflector configured to reflect and guide the light emitted from the LED light source such that the light is concentrated near a rear focus of the projection lens; and an optical element configured to guide the diffused light toward a front side of the vehicle headlamp so as to form an overhead light distribution. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of a vehicle headlamp according to a first exemplary embodiment of the present invention; 
       FIG. 2  is a longitudinal sectional view of the vehicle headlamp of  FIG. 1 , taken along line II-II, showing first and second projection-type light source units; 
       FIG. 3  is an enlarged longitudinal sectional view of a third projection-type light source unit of the vehicle headlamp of  FIG. 2 ; 
       FIG. 4  is an enlarged cross-sectional view of an LED module of the projection-type light source unit of  FIG. 3 ; 
       FIGS. 5A to 5C  are front views of light distribution patterns of first, second, and third projection-type light source units, respectively, according to the first exemplary embodiment of the present invention; 
       FIG. 6  is a front view of a light distribution pattern of the vehicle headlamp according to the first exemplary embodiment of the present invention; 
       FIG. 7  is a longitudinal sectional view of a projection-type light source unit according to a second exemplary embodiment of the present invention, showing a light path for an overhead light distribution; and 
       FIG. 8  is a longitudinal sectional view of a projection-type light source unit according to a third exemplary embodiment of the present invention, and showing a light path for an overhead light distribution. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
   Exemplary embodiments of the present invention will now be described with reference to the drawings. 
   As shown in  FIGS. 1 and 2 , a vehicle headlamp  1  includes a light source unit assembly  10 , which is formed by integrating a first projection-type light source unit  10 A, a second projection-type light source unit  10 B, and a third projection-type light source unit  10 C with a lamp bracket  12 . The light source unit assembly  10  is housed in a lamp chamber S that is formed by a container-shaped lamp body  2  and a transparent front cover  4 . The light source unit assembly  10  is supported by an automatic leveling mechanism E so as to be tilted in a vertical direction. The automatic leveling mechanism E is also an aiming mechanism provided between the lamp bracket  12  and the lamp body  2 . 
   That is, the automatic leveling mechanism E includes a pair (i.e., left and right) of aiming screws  21   a  and  21   b , a pair (i.e., left and right) of aiming nuts  22   a  and  22   b , and an actuator  30 . Each of the aiming screws  21   a  and  21   b  is rotatably supported by a through hole formed in the rear wall of the lamp body  2 . The aiming nuts  22   a  and  22   b  are provided on the lamp bracket  12  so as to be engaged with the aiming screws  21  a and  21   b , respectively. The actuator  30  is provided on an inside of the rear wall of the lamp body  2  directly below the aiming screw  21   a  and includes a rotational drive shaft  21   c . The rotational drive shaft  21   c  extends parallel to the aiming screws  21   a  and  21   b , and an aiming nut  22   c  is provided on the lamp bracket  12  so as to be engaged with a screw portion formed at the end of the rotational drive shaft  21   c.    
   The automatic leveling mechanism enables the light source unit assembly  10  to be tilted about a leveling axis Lx which passes through the nuts  22   a  and  22   b  by activating the actuator  30  to rotate the rotational drive shaft  21   c . Further, the actuator  30  rotates the rotational drive shaft  21   c  on the basis of a signal sent from, for example, a centroid position detecting sensor (not shown) that detects the forward and rearward movement of the centroid position of the vehicle, so as to move forward and rearward the aiming nut  22   c  along the rotational drive shaft  21   c . Accordingly, the actuator tilts the vehicle headlamp  1  about the leveling axis Lx so that an optical axis of the vehicle headlamp  1  is always maintained at a constant angle about a driving road surface. 
   Furthermore, the aiming screw  21   b  functions as a horizontal aiming screw that tilts the optical axis of the vehicle headlamp  1  about a vertical tilt axis Ly which is an axis passing through the aiming nuts  22   a  and  22   c , and the aiming screws  21   a  and  21   b  function as vertical aiming screws that tilt the optical axis of the vehicle headlamp  1  about a virtual horizontal tilt axis passing through the aiming nut  22   c . Accordingly, the automatic leveling mechanism E functions as an aiming mechanism. 
   In the light source unit assembly  10 , the first projection-type light source unit  10 A, the second projection-type light source unit  10 B, and the third projection-type light source unit  10 C are integrated in parallel on the front portion of the lamp bracket  12 . The lamp bracket  12  is made of metal having high thermal conductivity such as aluminum and is formed into a substantially rectangular shape. 
   Each of the first projection-type light source unit  10 A, the second projection-type light source unit  10 B, and the third projection-type light source unit  10 C have a same structure. Accordingly, the structure of the projection-type light source units will now be described with reference to the third projection-type light source unit  10 C shown in  FIG. 3 . The third projection-type light source unit  10 C includes a light emitting device  14   c ; a reflector  16   c ; a cut-off line forming shade  17 ; a convex projection lens  18 ; and a subreflector  40   c . The light emitting device  14   c  is provided on the upper surface of a rectangular protrusion  13  protruding forward from the bracket  12 . The reflector  16   c  is made of a resin and provided on the front protrusion  13  so as to cover the light emitting device  14   c . The cut-off line forming shade  17  is made of a resin and fixed to the end of the front protrusion  13  by a screw  13   a . The convex projection lens  18  is made of a resin and provided at the end of front extending portion  17   a  of the shade  17 . The subreflector  40   c  for forming the overhead light distribution is provided between the convex lens  18  and the reflector  16   c . The second projector-type light source unit  10 B comprises a light emitting device  14   b , a reflector  16   b , a cut-off line forming shade  17 , a convex projection lens  18 , and a subreflector  40   b , which are arranged similarly to the third projector-type light source unit  10 C described above. Similarly, the first projector-type light source unit  10 A comprises a light emitting device  14   a , a reflector  16   a , a cut-off line forming shade  17 , a convex projection lens  18 , and a subreflector  40   a , which are arranged similarly to the third projector-type light source unit  10 C described above. Each of the first and second projector-type light source units  10 B and  10 C are similarly configured, and are provided on respective front protrusions  13  which protrude forward from the bracket  12 , as shown in  FIG. 2 . A plurality of radiating fins  12   a  are formed on the front and rear surfaces of the lamp bracket  12  at given positions. 
   As shown in  FIG. 3 , the third projection-type light source unit  10 C has an optical axis Lc that extends forward and rearward. The shade  17  substantially horizontally extends forward so that the upper front edge portion of the shade  17  is positioned near a rear focus F of the projection lens  18 , and an upward reflecting surface  17   b  is formed on the upper surface of the upper front edge portion of the shade  17 . 
   The convex projection lens  18  is provided along the optical axis Lc, and projects an image, which is formed on a focal plane including the rear focus F, on a virtual vertical screen that is positioned on the front side of the vehicle headlamp, as a reverse image. 
   The reflecting surface  16   c   1  of the reflector  16   c  is a substantially elliptical curved surface whose major axis is concentric with the optical axis Lc, and the first focus corresponds to the emission center of the light emitting device  14   c . In this case, the shapes of the vertical cross-section of the reflecting surface  16   c   1  along the optical axis Lc is an elliptical shape that uses a point A positioned slightly ahead of the rear focus F of the lens as a second focus. Further, the eccentricity thereof is gradually increased from a vertical cross-section toward a horizontal cross-section. Accordingly, the reflector  16   c  makes light, which is emitted from the light emitting device  14   c , converge into the point A on the vertical cross-section, and makes the convergence position move forward on the horizontal cross-section. The first projector-type light source unit  10 A comprises an optical axis La and a reflecting surface  16   a   1  of the reflector  16   a , and the second projector-type light source unit  10 B comprises an optical axis Lb and a reflective surface  16   b   1  of the reflector  16   b . Again, the configuration of the first projector-type light source unit  10 A and the second projector-type light source unit  10 B is the same as the third projector-type light source unit  10 C. 
   An aluminum vapor deposition process is used on the upward reflecting surface  17   b  of the resinous shade  17 . The front edge of the upward reflecting surface  17   b  of the resinous shade  17  extends along the focal plane including the rear focus F of the lens  18 . Accordingly, as indicated by reference numeral L 17   b  in  FIG. 3 , a part of the light, which is reflected by the reflector  16   c  and travels toward the point A, is reflected upward by the upward reflecting surface  17   b , then enters the projection lens  18 , and then radiates from the projection lens  18  as downward light. 
   Further, as shown in  FIG. 3 , the subreflector  40   c  is provided between the reflector  16   c  and the convex projection lens  18 , and also is provided at the front edge portion  16   c   1  of the reflector  16   c  so as not to shield light, which is emitted from the light emitting device  14   c , and which is reflected by the reflector  16   c , and which travels toward the projection lens  18 . Furthermore, a slit  19  is formed at the upper edge portion of the convex projection lens  18  to correspond to the subreflector  40   c . As indicated by reference numeral L 40   c  in  FIGS. 3 and 4 , the light, which is emitted from the light emitting device  14   c  and which is reflected by the subreflector  40   c , is distributed forward from the slit  19 . Again, as shown in  FIGS. 2 and 4 , the configuration of the first projector-type light source unit  10 A and the second projector-type light source unit  10 B is the same as the third projector-type light source unit  10 C. 
   In addition, as enlarged in  FIG. 4 , the light emitting device  14   a  ( 14   b ,  14   c ) is formed of a white LED module  50 . In the white LED module, a pair of electrodes  53  and  53  formed by conducting path patterns  52  is exposed on a laminated circuit board  51 . A square LED chip  54  whose side size is about 0.3 to about 3 mm is disposed between the electrodes  53  and  53 , and a transparent cover member  56  that is formed into a hemispherical shape and made of glass is integrated so as to cover the LED chip  54 . The thickness of the cover member is about 0.5 to about 1 mm. 
   Further, as shown in  FIG. 4 , the LED module  50  is disposed such that the irradiation center axis L 50  thereof is oriented toward the upper side so as to be substantially perpendicular to each of the optical axis La (Lb, Lc) of the projection-type light source unit  10 A ( 10 B,  10 C). Fine concave and convex portions  57 , which diffuse light radiated from the cover member  56 , are formed on a region of the outer surface of the cover member  56 , which corresponds to a region between a first outer edge  40   a   1  ( 40   b   1 ,  40   c   1 ) and a second outer edge  40   a   2  ( 40   b   2 ,  40   c   2 ), where the first outer edge  40   a   1  ( 40   b   1 ,  40   c   1 ) corresponds to a front edge portion of the reflector  16   a  ( 16   b ,  16   c ) and the second outer edge  40   a   2  ( 40   b   2 ,  40   c   2 ) corresponds to a front edge portion of the convex projection lens  18  (i.e., a region corresponding to the subreflector  40   a  ( 40   b ,  40   c )). The fine concave and convex portions  57  may be formed on the cover member  56 , for example, by etching a given region of the outer surface of the cover member  56 . 
   Next, a light distribution pattern formed by each of the projection-type light source units  10 A,  10 B, and  10 C will be described hereinafter. 
   The light, which is transmitted through the cover member  56  and travels toward the reflector  16   a  ( 16   b ,  16   c ), of the light emitted from the LED chip  54  is reflected by the reflector  16   a  ( 16   b ,  16   c ) and guided so as to be concentrated on the point A near the rear focus of the projection lens  18 . Further, the convex projection lens  18  projects an image, which is formed on the focal plane including the rear focus F, on a virtual vertical screen that is positioned on the front side of the vehicle headlamp, as a reverse image. As shown in  FIGS. 5A-5C , the reflected light L 17   b  of the upward reflecting surface  17   b  is distributed forward through the projection lens  18 , so that a light distribution pattern for low beam (see reference character Psa (Psb, Psc), which has a clear cut-off line corresponding to the front edge of the cut-off line forming shade, is formed. However, as shown in  FIGS. 5A-5C , the light, which is transmitted through the cover member  56  and travels toward the subreflector  40   a  ( 40   b ,  40   c ), of the light emitted from the LED chip  54  is reflected by the subreflector  40   a  ( 40   b ,  40   c ) and distributed forward from the slit  19  of the convex projection lens  18 , so that an overhead light distribution pattern (see reference character Poha (Pohb, Pohc) for illuminating a given band-like region along the cut-off line of the light distribution pattern Psa (Psb, Psc) is formed. However, when the light emitted from the LED chip  54  is transmitted through the fine concave and convex portions  57  formed on the cover member  56 , the light emitted from the LED chip  54  is changed into diffused light and guided to the subreflector  40   a  ( 40   b ,  40   c ). Accordingly, the overhead light distribution, which is diffused light formed by the subreflector  40   a  ( 40   b ,  40   c ), does not create a strong glare light against oncoming vehicles. 
   If the projection-type light source unit  10 A having the above-mentioned structure is turned on, as shown in  FIG. 5A , a light distribution pattern obtained by combining a light distribution pattern Psa for low beam with an overhead light distribution pattern Poha is formed on the virtual screen positioned 25 meters ahead. The light distribution pattern Psa for low beam has a given cut-off line CLsa substantially corresponding to a horizontal line H-H, and illuminates a substantially central portion of the screen. The overhead light distribution pattern Poha has a given width along the cut-off line CLsa. 
   The shapes of the front edge portions of the shades  17 , the shapes of the reflecting surfaces  16   b   1  and  16   c   1  of the reflectors  16   b  and  16   c , and the shapes of the subreflectors  40   b  and  40   c  of the second and third projection-type light source units  10 B and  10 C, respectively, are slightly different from those of the first projection-type light source unit  10 A. 
   As shown in  FIG. 5B , a light distribution pattern obtained by combining a light distribution pattern Psb for low beam with an overhead light distribution pattern Pohb is formed by the second projection-type light source unit  10 B. The light distribution pattern Psb for low beam has a given cut-off line CLsb that illuminates a region spreading to the left and right sides from a substantially central portion of the screen, and the overhead light distribution pattern Pohb has a given width along the cut-off line CLsb. 
   Further, as shown in  FIG. 5C , a light distribution pattern obtained by combining a light distribution pattern Psc for low beam with an overhead light distribution pattern Pohc is formed by the third projection-type light source unit  10 C. The light distribution pattern Psc for low beam has a given cut-off line CLsc that illuminates a region widely spreading to the left and right sides from a substantially central portion of the screen, and the overhead light distribution pattern Pohc has a given width along the cut-off line CLsc. 
   As described above, the light source unit  10 A is formed as a light concentrating projection-type light source unit that forms the small diffused light distribution pattern shown in  FIG. 5A , the light source unit  10 B is formed as a projection-type light source unit for intermediate diffusion that forms the intermediate diffused light distribution pattern shown in  FIG. 5B , and the light source unit  10 C is formed as a projection-type light source unit for wide diffusion that forms the wide diffused light distribution pattern shown in  FIG. 5C . 
   Further, the light distribution pattern PS for low beam, which is shown in  FIG. 6  and obtained by combining the small, intermediate, and wide diffusion light distribution patterns shown in  FIGS. 5A to 5C , is formed by the light source unit assembly  10  in which the first, second, and third projector-type light source units  10 A,  10 B, and  10 C are integrated. The visibility of the light distribution pattern PS for low beam is improved as much as an overhead light distribution pattern Poh is added, and the overhead light distribution pattern Poh is formed of diffused light having low luminous flux density. Accordingly, light that becomes glare light against the oncoming vehicle is greatly reduced. 
     FIG. 7  is a longitudinal sectional view of a projection-type light source unit according to a second exemplary embodiment of the present invention. 
   In the above-mentioned first exemplary embodiment, the diffused light is radiated from the surface of the cover member  56  of the LED module  50  on which the fine concave and convex portions  57  are formed. Then, the radiated light is reflected by the subreflector  40   a  ( 40   b ,  40   c ) and then is distributed from the slit  19  of the convex projection lens  18  toward the front side of the vehicle headlamp. However, in the second exemplary embodiment, the diffused light is radiated from the surface of the cover member  56  of the LED module  50  on which the fine concave and convex portions  57  are formed. Then, the radiated light is reflected downward by a subreflector  42   a  ( 42   b ,  42   c ) and through an opening  17   c  formed in the extending portion  17   a  of the shade  17 . Once the light is guided through the opening  17   c  to a lower side of the shade  17 , the light is reflected by a second subreflector  43   a  ( 43   b ,  43   c ) so as to be distributed toward the front side of the vehicle headlamp. 
   Other structures of the second exemplary embodiment are the same as those of the first exemplary embodiment, and thus the repeated description will be omitted here. 
     FIG. 8  is a longitudinal sectional view of a projection-type light source unit constituting a main part of a vehicle headlamp according to a third exemplary embodiment of the present invention. 
   In the above-described first and second exemplary embodiments, the diffused light is radiated from the surface of the cover member  56  of the LED module  50  on which the fine concave and convex portions  57  are formed, and is then reflected by the either a subreflector  40   a  ( 40   b ,  40   c ) in the case of the first exemplary embodiment, or the first subreflector  42   a  ( 42   b ,  42   c ) and the second subreflector  43   a  ( 43   b ,  43   c ) in the case of the second exemplary embodiment, and then is distributed toward the front side of the vehicle headlamp. However, in the third exemplary embodiment, the diffused light is radiated from the surface of the cover member  56  of the LED module  50  on which the fine concave and convex portions  57  are formed, then is directly distributed toward the front side of the vehicle headlamp by a Fresnel lens  44 . The Fresnel lens  44  is disposed on the periphery of the convex projection lens  18  and extends in a circular arc shape. 
   Other structures of the third exemplary embodiment are the same as those of the first exemplary embodiment, and thus the repeated description will be omitted here. 
   Meanwhile, in the above-mentioned exemplary embodiments, the fine concave and convex portions  57  are formed on the outer surface of the spherical cover member  56 . However, the position where the fine concave and convex portions are formed is not limited to the outer surface of the cover member, and the fine concave and convex portions  57  may alternatively be formed on the inner surface of the spherical cover member  56  or on both inner and outer surfaces. 
   Further, in the above-mentioned first exemplary embodiment, the fine concave and convex portions  57  on the outer surface of the cover member  56  are formed only on a region of the outer surface of the cover member  56 , which corresponds to a region between an outer edge  40   a   1  ( 40   b   1 ,  40   c   1 ) corresponding to a front edge portion of the reflector  16   a  ( 16   b ,  16   c ) and an outer edge  40   a   2  ( 40   b   2 ,  40   c   2 ) corresponding to a front edge portion of the convex projection lens  18  (i.e., a region corresponding to the subreflector  40   a  ( 40   b ,  40   c )). However, the fine concave and convex portions may be formed a region  58  (shown in  FIG. 4 ) other than the region of the outer surface of the cover member  56  that corresponds to the reflector  16   a  ( 16   b ,  16   c ). 
   Furthermore, as described above, the fine concave and convex portions  57  are formed, for example, by an etching process. If the area to be etched is small, it is easier to form the fine concave and convex portions. However, if the fine concave and convex portions  57  are formed on the region  58  that does not correspond to the reflector, the light, which travels from the cover member  56  toward the region  58  not corresponding to the reflector, becomes diffused light. In other words, if a larger portion of the cover member  56  is provided with the fine concave and convex portions  57 , more light becomes diffused light. Therefore, it is possible to more reliably avoid generating unexpected glare light. 
   In addition, the cover member  56  is made of glass in the above-mentioned exemplary embodiments. However, alternatively, the cover member  56  may be made of a synthetic resin. 
   Further, in the above-described exemplary embodiments, the cover member  56  is formed of a hollow body. However, alternatively, the cover member  56  may be formed of a resin molded solid body integrally formed with an LED chip. Furthermore, if the cover member is formed of the resin molded solid body integrally formed with an LED chip  54 , it is possible to form the fine concave and convex portions only on the outer surface of the cover member  57 . 
   In cases in which the cover member is formed of a resin molded solid body, the light emitted from the LED chip is refracted by the cover member when the light is transmitted through the cover member. Thus, it is difficult to arrange the reflecting surface of the reflector to control the light distribution using the reflector. However, the light emitted from the LED chip is not affected by refraction when the cover member is formed of a hollow glass spherical body (e.g., a thin glass sphere). Thus, when the cover member is formed of a hollow glass spherical bodym, it is easier to control the light distribution using the reflector, and further it is easier to arrange the reflecting surface of the reflector. 
   As discussed above, according to exemplary embodiments of the present invention, there is provided a vehicle headlamp. The vehicle headlamp includes at least one projection-type light source unit housed in a lamp chamber. The projection-type light source includes a projection lens; a shade forming a cut-off line; an LED light source for emitting light, wherein the LED light source includes a substrate; an LED chip disposed on the substrate; and a translucent spherical cover member covering the LED chip, and is disposed such that an irradiation center axis of the LED chip is oriented in a direction substantially perpendicular to an optical axis of the projection-type light source unit, and wherein fine concave and convex portions are formed on a region of the cover member except a region corresponding to the reflector so as to diffuse light transmitted through the cover member, a reflector configured to reflect and guide the light emitted from the LED light source such that the light is concentrated near a rear focus of the projection lens; and an optical element configured to guide the diffused light toward a front side of the vehicle headlamp so as to form an overhead light distribution. 
   Moreover, the cover member may be formed of a resin molded solid body or a hollow glass spherical body. The fine concave and convex portions may be formed on an outer surface of the cover member when the cover member is formed of the resin molded solid body. The fine concave and convex portions may be formed on at least one of an inner surface and an outer surface when the cover member is formed of the hollow glass spherical body. 
   According to the exemplary embodiments of the present invention, a broad overhead light distribution pattern formed by diffused light having a very low luminous flux density is added to a light distribution pattern for a low beam that has a cut-off line. Accordingly, the visibility to the front of the vehicle is improved, and light does not produce glare light against an oncoming vehicle. That is, it is possible to suppress glare light seen by oncoming vehicles without reducing the visibility of the driver of the vehicle using a structure in which fine concave and convex portions are directly formed on the cover member. 
   While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.