Abstract:
Disclosed herein is a plastic compound lens for a headlight. The plastic compound lens includes a first lens part including a first light-incident surface and a first shaped surface and made of a first material, and a second lens part including an inside shaped surface and an outside convex-shaped surface and made of a second material. The second lens part extends to surround the first lens part. The first light-incident surface of the first lens part is formed as any one of plane, convex, concave, and aspherical surfaces, and an aspherical surface including an inflection point. The first shaped surface of the first lens part is formed as a surface of any one of concave, convex and aspherical lenses, and an aspherical lens including an inflection point. The inside shaped surface of the second lens part is formed to correspond to the first shaped surface of the first lens part.

Description:
BACKGROUND 
     1. Technical Field 
       [0001]    The present invention relates generally to a plastic compound lens for a headlight, and more particularly to a plastic compound lens for a headlight, which is capable of correcting chromatic aberration. 
       2. Description of the Related Art 
       [0002]    In general, vehicles have various types of lighting devices. Among these lighting devices, headlights are important lighting devices that ensure the visual field of a driver for driving at night. In connection with this, Korean Patent Application Publication No. 2003-0048708 discloses a headlight structure for a vehicle. 
         [0003]    Aspherical lenses formed by molding and machining glass are used for conventional headlights for vehicles. Glass lenses have the disadvantage of heavier weights, lower productivity and higher manufacturing costs than plastic lenses. Recently, as lamps used for headlights are replaced with LED lamps, it is urgent to deal with this trend by using plastic lenses having cost competitiveness. However, plastic lenses suffer from the occurrence of serious chromatic aberration when white light is generated, and this problem cannot be easily overcome. 
         [0004]    Furthermore, plastic lenses have lower stiffness than glass lenses. When a polycarbonate material is used to deal with such low stiffness, stiffness can be compensated for. However, the plastic lenses have considerably lower Abbe&#39;s numbers than glass lenses, and thus the plastic lenses have the disadvantage of having an insufficient function as optical components. 
         [0005]    Furthermore, when lenses are manufactured using an acrylic material, which is a general plastic optical material, stiffness is low, and thus a yellowing phenomenon may occur when they are exposed to the ultraviolet rays of LED lamps. 
       SUMMARY 
       [0006]    The present invention has been conceived to overcome the above-described problem, and an object of the present invention is to provide a new type of plastic compound lens for a headlight, which is capable of correcting chromatic aberration while providing stiffness and optical characteristics corresponding to those of glass. 
         [0007]    According to an aspect of the present invention, there is provided a plastic compound lens for a headlight, including: a first lens part adapted to include a first light-incident surface on which light is incident and a first shaped surface through which the light is emitted, and made of a first material; and a second lens part adapted to include an inside shaped surface which is coupled onto the first shaped surface, and an outside convex-shaped surface which is formed in a convex shape in a direction opposite the inside shaped surface and which emits the light, incident through the first lens part, to the outside, and made of a second material; wherein the second lens part extends to the first light-incident surface of the first lens part to surround the first lens part; wherein the first light-incident surface of the first lens part is formed as any one of a plane surface, a convex surface, a concave surface, an aspherical surface, and an aspherical surface including an inflection point; wherein the first shaped surface of the first lens part is formed as a surface of any one of a concave lens, a convex lens, an aspherical lens, and an aspherical lens including an inflection point; wherein the inside shaped surface of the second lens part is formed as a surface of any one of a convex lens, a concave lens, an aspherical lens, and an aspherical lens including an inflection point to correspond to the first shaped surface of the first lens part; and wherein the outside convex-shaped surface of the second lens part is formed as any one of a convex aspherical surface, an aspherical surface, and an aspherical surface including an inflection point. 
         [0008]    According to an embodiment, a separation space configured to correct chromatic aberration may be formed by separating the first shaped surface of the first lens and the inside shaped surface of the second lens from each other by a predetermined distance. 
         [0009]    According to an embodiment, the plastic compound lens for a headlight may further include a third lens part coupled onto the first light-incident surface of the first lens, the first lens part, the second lens part, and the third lens part may be integrated with one another, the second lens part and the third lens part may be disposed with the first lens part surrounded by and contained inside the second lens part and the third lens part, the first lens part may be made of a first material, the second lens part and the third lens part may be made of a second material, i.e., an identical material, the third lens part may include a second light-incident surface configured such that light is incident thereon and a light-incident surface-coupled surface coupled onto the first light-incident surface, the second light-incident surface may be formed as any one of a plane surface, a convex surface, a concave surface, an aspherical surface, and an aspherical surface including an inflection point, and the light-incident surface-coupled surface may be formed as any one of a plane surface, a convex surface, a concave surface, an aspherical surface, and an aspherical surface including an inflection point to correspond to the first light-incident surface of the first lens. 
         [0010]    According to an embodiment, the first material may be a material having optical characteristics corresponding to those of flint glass, and the second material may be a material having optical characteristics corresponding to those of crown glass. 
         [0011]    According to an embodiment, the first material may be polycarbonate (PC), and the second material may be an acrylic material (polymethyl methacrylate (PMMA)). 
         [0012]    According to an embodiment, the first material may be an acrylic material (PMMA), and the second material may be a polycarbonate (PC). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIG. 1  is a sectional view showing the sectional configuration of a plastic compound lens according to a preferred embodiment of the present invention; 
           [0015]      FIGS. 2 and 3  are diagrams showing modifications of the plastic compound lens according to the preferred embodiment of the present invention; 
           [0016]      FIG. 4  is a diagram showing an example of the sectional configuration of a plastic compound lens according to another embodiment of the present invention; and 
           [0017]      FIG. 5  is a diagram showing an example of the sectional configuration of a plastic compound lens according to still another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Preferred embodiments of the present invention will be described with reference to the accompanying drawings in order to provide complete understanding of the present invention. The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be interpreted as being limited to the embodiments that will be described in detail below. These embodiments are provided to fully describe the present invention to those having ordinary knowledge in the art to which the present invention pertains. Accordingly, the shapes, sizes and the like of components in the drawings may be exaggerated to make the description obvious. It should be noted that the same components may be designated by the same reference symbols throughout the drawings. Descriptions of well-known functions and configurations that are determined to unnecessarily make the gist of the present invention to be obscure will be omitted. 
         [0019]      FIG. 1  is a sectional view showing the sectional configuration of a plastic compound lens  100  according to a preferred embodiment of the present invention. 
         [0020]    As shown in the drawing, the plastic compound lens  100  according to the present invention is combined into and used in a headlight for a vehicle. The plastic compound lens  100  includes a first lens part  110  configured such that light is incident thereon from a light source (not shown) inside a headlight (not shown), and a second lens part  120  combined with the first lens part  110  and configured to emit light to the outside. 
         [0021]    The first lens part  110  includes a first light-incident surface  111  configured such that light is incident thereon from the light source for a headlight, a first shaped surface  113  formed to be spaced apart from the first light-incident surface  111  by predetermined distances and to be curved toward the first light-incident surface  111 , and a side inclined surface  115  inserted into the second lens part  120 . 
         [0022]    In this case, the first lens part  110  is made of a first material having the optical characteristics of flint glass, whereas the second lens part  120  is made of a second material having the optical characteristics of crown glass. As an example, the first lens part  110  may be made of a polycarbonate (PC) material, whereas the second lens part  120  may be made of an acrylic material (polymethyl methacrylate (PMMA)). 
         [0023]    The first light-incident surface  111  may be formed in a flat shape, as shown in  FIG. 1 , may be formed in a convex shape, as shown in  FIG. 2 , and may be formed in a concave shape, as shown in  FIG. 3 . 
         [0024]    The first shaped surface  113  may be formed in the shape of a surface of a concave lens, as shown in the drawing. In some cases, the first shaped surface  113  may be formed in the shape of a surface of a convex lens, an aspherical lens, or an aspherical lens having an inflection point. 
         [0025]    The optical shapes of the first light-incident surface  111  and the first shaped surface  113  may vary in various manners depending on the optical design by which light is incident and emitted, the manufacturing method by which two different materials are combined with each other, etc. 
         [0026]    The second lens part  120  has an inside shaped surface  121  coupled onto the first shaped surface  113 , and an outside convex-shaped surface  123  formed in a convex shape in a direction opposite the direction of the inside shaped surface  121  and configured to emit light to the outside. 
         [0027]    In this case, the plastic compound lens  100  according to the present invention is configured in the form in which the second lens part  120  surrounds all the regions of the first lens part  110  except for the first light-incident surface  111  of the first lens part  110 . 
         [0028]    In other words, the second lens part  120  is formed in a half-elliptic sectional shape, and has, on the bottom thereof, the inside shaped surface  121  formed to correspond to the first shaped surface  113 . Furthermore, a coupling periphery  125  extending toward the first light-incident surface  111  in a ring shape is provided along the edge of the inside shaped surface  121 . The first lens part  110  is inserted into a space that is formed beside the inside shaped surface  121  inside the coupling periphery  125 . 
         [0029]    The outside convex-shaped surface  123  is formed in the shape of a surface of a convex aspherical lens or an aspherical lens including an inflection point. 
         [0030]    The first coupling protrusion  117  and the second coupling protrusion  128  protrude from the bottoms of the first lens part  110  and the second lens part  120 . The first coupling protrusion  117  and the second coupling protrusion  128  are coupled to the flange of the headlight, thereby fastening the plastic compound lens  100  onto a vehicle. 
         [0031]    The plastic compound lens  100  according to the preferred embodiment of the present invention is configured such that the first shaped surface  113  and the inside shaped surface  121  on which the second lens part  120  is combined with the first lens part  110  are concealed inside the plastic compound lens  100 , thereby reducing defect rate and providing a neat appearance and uniform optical characteristics. 
         [0032]    Furthermore, plastic compound lenses  100 ,  100   a  and  100   b  according to the preferred embodiment of the present invention are each configured such that a first lens part  110  and a second lens part  120  made of a first material and a second material, respectively, having the optical characteristics of flint glass and the optical characteristics of crown glass, respectively, are combined with each other and a first shaped surface  113  and an inside shaped surface  121  are combined and come into contact with each other, as shown in  FIGS. 1, 2 and 3 , thereby being also utilized as an achromatic lens that is composed of two lens superimposed on each other to correct chromatic aberration. 
         [0033]    Furthermore, the polycarbonate material and the acrylic material are used together, and thus effects are achieved in that low stiffness, i.e., the weak point of the acrylic material, can be compensated for and a yellowing phenomenon can be reduced. 
         [0034]    Meanwhile,  FIG. 4  is a diagram showing an example of the sectional configuration of a plastic compound lens  200  according to another embodiment of the present invention. 
         [0035]    The plastic compound lens  100  according to the first preferred embodiment is configured such that the first lens part  110  and second lens part  120  made of different materials are combined with each other. In contrast, the plastic compound lens  200  according to the other embodiment is configured such that a first lens part  210 , a second lens part  220 , and a third lens part  230  are disposed in a superimposed manner. 
         [0036]    In this case, the third lens part  230 , the first lens part  210 , and the second lens part  220  are sequentially disposed from a light source for a headlight (not shown). The light incident on the third lens part  230  passes through the first lens part  210 , and is emitted to the outside via the second lens part  220 . 
         [0037]    The configurations of the first lens part  210  and the second lens part  220  correspond to the configurations of the first lens part  110  and second lens part  120  of the plastic compound lens  100 ,  100   a  or  100   b  according to the above-described first preferred embodiment of the present invention, respectively. 
         [0038]    The third lens part  230  includes a second light-incident surface  231  configured such that light is incident thereon, a light-incident surface-coupled surface  233  coupled onto the first light-incident surface  211 , and a coupling periphery  235  fastened to the flange (not shown) of the headlight. 
         [0039]    The second light-incident surface  231  may be formed as a flat, concave, or convex surface and may be formed as an aspherical surface or an aspherical surface including an inflection point in the same manner as the above-described first light-incident surface  211 . 
         [0040]    The light-incident surface-coupled surface  233  may be formed to correspond to the shape of the first light-incident surface  211 . In other words, as shown in  FIG. 4 , when the first light-incident surface  211  is concave, the light-incident surface-coupled surface  233  is formed in a convex shape. In contrast, when the first light-incident surface  211  is convex, the light-incident surface-coupled surface  233  is formed in a concave shape. 
         [0041]    In this case, in the plastic compound lens  200  according to the other embodiment of the present invention, the second lens part  220  is integrated with the third lens part  230 . A connection region  225  extending across the edge of the second lens part  220  is formed to surround the first lens part  210  while extending to the third lens part  230 . 
         [0042]    The second lens part  220  and the third lens part  230  may be made of the same material, whereas the first lens part  210  may be made of a different material. In this case, the second lens part  220  and the third lens part  230  may be made of a polycarbonate (PC) material, whereas the first lens part  210  may be made of an acrylic material (PMMA). Inversely, the second lens part  220  and the third lens part  230  may be made of an acrylic material (PMMA), whereas the first lens part  210  may be made of a polycarbonate (PC) material. 
         [0043]    When the first lens part  210  is made of a polycarbonate (PC) material and the second lens part  220  and third lens part  230  made of an acrylic material (PMMA) surround the first lens part  210 , the plastic compound lens  200  may be also utilized as an apochromatic lens. 
         [0044]    In this case, the thickness d2 of the first lens part  210 , the thickness d1 of the second lens part  220 , and the thickness d3 of the third lens part  230  are set by taking into consideration the distance to the light source, the material of the first lens part  210  and the second lens part  220 , and the material of the third lens part  230  within a range that can minimize chromatic aberration. 
         [0045]    The apochromatic lens is formed by superimposing three lenses having different refractive indices on each other, and has the advantage of eliminating almost all chromatic aberration compared to the case where the first lens part  110  and the second lens part  120  are combined and utilized as an achromatic lens in the above-described first preferred embodiment. 
         [0046]    Meanwhile, although the second lens part  220  and the third lens part  230  are made of the same material in an integrated manner and the first lens part  210  is made of a different material in the other embodiment of the present invention, this is merely an example. In some cases, the first lens part  210 , the second lens part  220 , and the third lens part  230  may be made of different materials, respectively. 
         [0047]    Meanwhile,  FIG. 5  is a diagram schematically showing the sectional configuration of a plastic compound lens  300  according to still another embodiment of the present invention. 
         [0048]    The plastic compound lenses  100 ,  100   a  and  100   b  according to the above-described first preferred embodiment are each formed such that the first lens part  110  and the second lens part  120  are combined and come into contact with each other. In contrast, in the plastic compound lens  300  according to still another embodiment, a separation space  330  is formed between the first lens part  310  and the second lens part  320 , as shown in  FIG. 5 . 
         [0049]    The configurations of the first lens part  310  and the second lens part  320  correspond to the configurations of the first lens part  110  and second lens part  120  of each of the plastic compound lenses  100 ,  100   a  and  100   b  according to the above-described first preferred embodiment. 
         [0050]    The separation space  330  separates the first shaped surface  313  of the first lens part  310  from the inside shaped surface  321  of the second lens part  320  by a predetermined distance W2. The separation space  330  is formed as an empty space. The separation space  330  formed as an empty space enables the first shaped surface  313  and the inside shaped surface  321  to function as a surface of an independent concave lens and a surface of an independent convex lens, respectively. Accordingly, the plastic compound lens  300  exhibits an effect corresponding to that of an achromatic lens in which the first lens part  310  and second lens part  320  made of different materials are combined together, or an effect corresponding to that of an apochromatic lens in which three lenses are combined together in the actual correction of chromatic aberration. 
         [0051]    The distance W2 of the separation space  330  is set by taking into consideration the thickness W3 of the first lens part  310 , the thickness W1 of the second lens part  320 , the materials of the first lens part  310  and second lens part  320 , the distance to a light source, etc. within a range that can minimize chromatic aberration. 
         [0052]    As described above, the plastic compound lens according to the present invention is configured such that the two lenses made of different materials are combined together and utilized as an achromatic lens, thereby being capable of correcting chromatic aberration. Furthermore, the plastic compound lens according to the present invention is formed by combining an acrylic material and a polycarbonate material, and thus low stiffness, i.e., a problem of the conventional plastic lens, can be compensated for and also a yellowing phenomenon can be minimized. 
         [0053]    Furthermore, the separation space is contained in or the third lens part is added to the plastic compound lens according to the present invention, thereby providing an effect corresponding to that of an apochromatic lens. Accordingly, the effect of eliminating almost all chromatic aberration is achieved. 
         [0054]    The above-described embodiments of the plastic compound lens for a headlight according to the present invention are merely illustrative. It will be readily appreciated by those having ordinary knowledge in the art to which the present invention pertains that various modifications and other equivalent embodiments may be made. Accordingly, it will be apparently understood that the present invention is not limited only to the forms that have been mentioned in the detailed description. Therefore, the true technical range of protection of the present invention should be defined by the technical spirit of the attached claims. Furthermore, it should be appreciated that the present invention includes all modifications, equivalents and substitutions that fall within the spirit and scope of the present invention defined by the attached claims.