Abstract:
There is provided super wide angle lens module, including: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having positive refractive power; and a fifth lens having positive refractive power and having a meniscus shape convex toward an image side, wherein the third lens satisfies Equation 1, 
       d3&gt;1.7   Equation 1
 
     where Nd3 represents a refractive index of the third lens.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2011-0122243 filed on Nov. 22, 2011, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a super wide angle lens module, and more particularly, to a super wide angle lens module that can minimize vignetting in an image projected onto an image sensor. 
         [0004]    2. Description of the Related Art 
         [0005]    A camera is generally used as a device for providing forward or rearward image information from a vehicle in the field of automotive engineering. 
         [0006]    For example, a rearward facing camera may be installed in or on the rear of the vehicle (a trunk or a rear bumper) in order to image an object behind the vehicle and information with regard thereto may be provided to a driver. The rearward facing camera images an object which a vehicle operator may not be able to easily see when the vehicle reverses, to lessen the chance of the vehicle colliding with the object. 
         [0007]    As another example, a forward facing camera may image a traffic situation in front of the vehicle to assist in determining a cause of an accident when a traffic accident occurs. 
         [0008]    Such a monitoring camera includes a super wide angle lens module having a relatively wider angle of view than a general lens module to provide an image having a wide angle of view to a user (that is, a vehicle operator). 
         [0009]    Since the super wide angle lens module is constituted of more lenses (for example, 7 or more) than general lens modules, a wide angle of view (for example, 180° or more) can be implemented. 
         [0010]    However, in the super wide angle lens module, a distortion phenomenon may easily occur, due to the relatively large number of lenses and a vignetting phenomenon in which an edge of an image may be cut off. 
       SUMMARY OF THE INVENTION 
       [0011]    An aspect of the present invention provides a super wide angle lens module that can ensure a wide angle of view with a relatively small number of lenses. 
         [0012]    According to an aspect of the present invention, there is provided a super wide angle lens module, including: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having positive refractive power; and a fifth lens having positive refractive power and having a meniscus shape convex toward an image side, wherein the third lens satisfies Equation 1, 
         [0000]      Nd3&gt;1.7   Equation 1
 
         [0013]    where Nd3 represents a refractive index of the third lens. 
         [0014]    The second lens, the fourth lens, and the fifth lens may be formed of a plastic material 
         [0015]    The second lens may satisfy Equation 2, and the fourth lens may satisfy Equation 3, 
         [0000]      50&lt;V2 &lt;60   Equation 2
 
         [0000]      50&lt;V4&lt;60   Equation 3
 
         [0016]    where V2 represents a dispersion constant (abbe number) of the second lens, and V4 represents a dispersion constant of the fourth lens. 
         [0017]    The super wide angle lens module may further include an stop disposed between the third lens and the fourth lens. 
         [0018]    The stop may satisfy Equation 4, 
         [0000]    
       
         
           
             
               
                 
                   0 
                   &lt; 
                   
                      
                     
                       ds 
                       
                         R 
                          
                         
                             
                         
                          
                         51 
                       
                     
                      
                   
                   &lt; 
                   1.0 
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   4 
                 
               
             
           
         
       
     
         [0019]    where ds represents a distance from the stop to an object-side surface of the fifth lens, and R51 represents a radius of curvature of the object-side surface of the fifth lens. 
         [0020]    At least one surface of the second lens, the fourth lens, and the fifth lens may be aspherical. 
         [0021]    The first lens may have a meniscus shape convex toward an object side. 
         [0022]    The second lens may have an image-side surface having a concave shape. 
         [0023]    The fourth lens may have an image-side surface having a convex shape. 
         [0024]    The first lens may have an object-side surface having a constant curve, including an edge thereof. 
         [0025]    The super wide angle lens module may further include a lens housing including the first to fifth lenses, and the first lens may be disposed such that an object-side surface of the first lens is completely exposed to the outside of the lens housing. 
         [0026]    The first lens may include a protrusion protruding toward the image side, and the lens housing may include a groove into which the protrusion fits. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0028]      FIG. 1  is a cross-sectional view of a lens module according to a first embodiment of the present invention; 
           [0029]      FIG. 2  is a cross-sectional view of a lens module according to a second embodiment of the present invention; 
           [0030]      FIG. 3  is a cross-sectional view of a lens module according to a third embodiment of the present invention; and 
           [0031]      FIG. 4  is a graph illustrating a height difference in an image surface with regard to an angle of view. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0033]    In describing the present invention below, terms indicating components of the present invention are named in consideration of functions thereof. Therefore, the terms should not be understood as limiting technical components of the present invention. 
         [0034]      FIG. 1  is a cross-sectional view of a lens module according to a first embodiment of the present invention,  FIG. 2  is a cross-sectional view of a lens module according to a second embodiment of the present invention,  FIG. 3  is across-sectional view of a lens module according to a third embodiment of the present invention, and  FIG. 4  is a graph illustrating a height difference in an image surface with regard to an angle of view. 
         [0035]    A super wide angle lens module  100  according to the first embodiment of the present invention includes a first lens  10 , a second lens  20 , a third lens  30 , a fourth lens  40 , and a fifth lens  50  and may further selectively include an stop  60  and a filter member  70 . Herein, the first to fifth lenses  10 ,  20 ,  30 ,  40 , and  50  may be sequentially placed from an object side (that is, a subject for photography or an imaging target) to an image side (that is, an image sensor). 
         [0036]    All of the first lens  10 , the second lens  20 , the third lens  30 , the fourth lens  40 , and the fifth lens  50  may be formed of a plastic material. Like this, when all the lenses  10 ,  20 ,  30 ,  40 , and  50  forming the lens module  100  are formed of the plastic material, manufacturing costs of the lens module  100  maybe reduced and mass production thereof maybe facilitated. 
         [0037]    In particular, when the lenses  10 ,  20 ,  30 ,  40 , and  50  are formed of the plastic material, lens surfaces thereof may easily be processed. Therefore, the lens surfaces of the lenses  10 ,  20 ,  30 ,  40 , and  50  may be formed as spherical or aspherical surfaces. 
         [0038]    The first lens  10  may be placed to be closest to the object in the super wide angle lens module  100 . The first lens  10  may have negative refractive power. More specifically, in the first lens  10 , a first surface (an object-side surface)  12  may be convex toward the object side and a second surface (an image-side surface)  14  may be concave toward the image side. More specifically, the first lens  10  may have a cross-sectional shape in which the thickness of the first lens  10  is reduced toward an optical axis (line C-C) from the edge thereof. 
         [0039]    The first lens  10  may have a relatively larger size than the other lenses  20 ,  30 ,  40 , and  50 . More specifically, an effective area A 1  of the second surface  14  of the first lens  10  may be larger than an effective area A 2  of a first surface  22  of the second lens  20 . 
         [0040]    The shape of the first lens  10  may assist in the incidence of light, incident through the first lens  12  and the second surface  14  of the first lens  10 , to the first surface  22  of the second lens  20 . Accordingly, a wide angle of view may be ensured. 
         [0041]    The first lens  10  may have a meniscus shape which is convex toward the object side. Moreover, at least one of the first surface  12  and the second surface  14  of the first lens  10  may be aspherical. However, both the first surface  12  and the second surface  14  may be aspherical as necessary. 
         [0042]    The second lens  20  may be placed in the rear (in the image-side direction) of the first lens  10 . The second lens  20  may have negative refractive power and may be formed of a plastic material like the first lens  10 . 
         [0043]    The first surface (object-side surface)  22  of the second lens  20  may have a concave shape and the second surface (image-side surface)  24  thereof may have a concave shape. However, the first surface  22  of the second lens  20  may be a flat plane as necessary. Alternatively, the first surface  22  of the second lens  20  may be convex on the optical axis and be concave toward the edge thereof as shown in  FIG. 1 . 
         [0044]    The second lens may have at least one aspherical surface. For example, at least one of the first surface  22  and the second surface  24  of the second lens  20  may be aspherical. However, both the first surface  22  and the second surface  24  may be aspherical according to a type of the super wide angle lens module  100  to be manufactured. 
         [0045]    The second lens  20  may have a dispersion constant (abbe number) that satisfies Equation 1. 
         [0000]      50&lt;V2&lt;60   Equation 1
 
         [0000]    (Here, V2 represents a dispersion constant (abbe number) of the second lens.) 
         [0046]    When the dispersion constant of the second lens  20  is larger than 50, the chromatic aberration of the super wide angle lens module  100  may be effectively improved. However, when the dispersion constant of the second lens  20  is larger than 60, it is difficult to manufacture the second lens  20 , and the dispersion constant of the first lens  10  also needs to be increased, and accordingly, manufacturing costs of the super wide angle lens module  100  may increase. 
         [0047]    Accordingly, in the case in which the dispersion constant of the second lens  20  satisfies the numerical range presented in Equation 1, it is useful in the manufacturing of the super wide angle lens module  100 . 
         [0048]    The third lens  30  may be placed in the rear (in the image-side direction) of the second lens  20 . The third lens  30  may have positive refractive power and may be formed of a plastic material like the first lens  10 . 
         [0049]    A first surface (object-side surface)  32  of the third lens  30  may have a convex shape toward the object side and a second surface (image-side surface)  34  thereof may have a concave shape toward the image side. Specifically, the first surface  32  of the third lens  30  may be more convex than the second surface  34  thereof (that is, a radius of curvature of the first surface  32  may be smaller than a radius of curvature of the second surface  34 ). 
         [0050]    The third lens  30  may have at least one aspherical surface. For example, at least one of the first surface  32  and the second surface  34  of the third lens  30  may be aspherical. However, both the first surface  32  and the second surface  34  may be aspherical according to the type of the super wide angle lens module  100  to be manufactured. 
         [0051]    The third lens  30  may have a dispersion constant smaller than that of the second lens  20 . For example, the third lens  30  may have a dispersion constant of 40 or less and as necessary, may have a dispersion constant of 20 or less. As such, when the dispersion constant of the third lens  30  is smaller than the dispersion constant of the second lens  20 , it may be more effective to improve the chromatic aberration. A difference between the dispersion constant of the third lens  30  and the dispersion constant of the second lens  20  may be 20 or more, but 20 or less as necessary. 
         [0052]    The third lens  30  may have refractive index that satisfies Equation 2. That is, the refractive index of the third lens  30  may be greater than 1.7. 
         [0000]      Nd3&gt;1.7   Equation 2
 
         [0000]    (Here, Nd3 represents the refractive index of the third lens  30 .) 
         [0053]    When the refractive index of the third lens  30  satisfies Equation 2 as above, an overall length (a length from the first lens  10  to an image sensor  80  or a length from the first lens  10  to the fifth lens  50 ) of the super wide angle lens module  100  may be minimized. 
         [0054]    Accordingly, the numerical range according to Equation 2 may be used as an important condition to determine the size of the super wide angle lens module  100 . 
         [0055]    Unlike this, when the refractive index of the third lens  30  is 1.7 or less, the overall length of the super wide angle lens module  100  may be extended and the thickness of the third lens  30  maybe increased. Moreover, when the refractive index of the third lens  30  is 1.7 or less, the amount of light passing through the third lens  30  is significantly reduced, and as a result, the resolution of the super wide angle lens module  100  may be deteriorated. 
         [0056]    Meanwhile, although not present in Equation 2, an upper limit of the refractive index of the third lens  30  may be determined according to a material of the third lens  30 . For example, when the third lens  30  is formed of a plastic material, the refractive index of the third lens  30  may be lower than that when the third lens  30  is formed of a glass material. 
         [0057]    The fourth lens  40  may be placed in the rear (in the image-side direction) of the third lens  30 . The fourth lens  40  may have positive refractive power and may be formed of a plastic material like the first lens  10 . 
         [0058]    A first surface (object-side surface)  42  of the fourth lens  40  may have a flat or concave shape and a second surface (image-side surface)  44  thereof may have a convex shape toward the image side. 
         [0059]    The fourth lens  40  may have at least one aspherical surface. For example, at least one of the first surface  42  and the second surface  44  of the fourth lens  40  may be aspherical. However, both the first surface  42  and the second surface  44  may be aspherical according to the type of the super wide angle lens module  100  to be manufactured. 
         [0060]    The fourth lens  40  may have a dispersion constant larger than that of the third lens  30 . For example, the fourth lens  40  may have a dispersion constant of 50 or less. Specifically, the dispersion constant of the fourth lens  40  may have a numerical range that satisfies Equation 3. More specifically, the dispersion constant of the fourth lens  40  may have the same or similar numerical range as that of the dispersion constant of the second lens  20 . 
         [0000]      50&lt;V4&lt;60   Equation 3
 
         [0000]    (Here, V4 represents the dispersion constant of the fourth lens.) 
         [0061]    When the dispersion constant of the fourth lens  40  is larger than 50, the dispersion constant of the fourth lens  40  has a relatively large deviation from the dispersion constant of the third lens  30 , and as a result, it may be effective to improve the chromatic aberration of the super wide angle lens module  100 . 
         [0062]    However, when the dispersion constant of the fourth lens  40  is larger than 60, it may be difficult to manufacture the fourth lens  40 , and as a result, the dispersion constant of the fourth lens  40  may be within the numerical range of Equation 3. More specifically, the dispersion constant of the fourth lens  40  may be equal to the dispersion constant of the second lens  20 . In this case, the improvement effect of the chromatic aberration through the second lens  20 , the third lens  30 , and the fourth lens  40  may be maximized, and the second lens  20  and the fourth lens  40  may be formed of the same material. 
         [0063]    The fifth lens  50  may be placed to be closest to the image in the super wide angle lens module  100 . The fifth lens  50  may have positive refractive power. More specifically, in the fifth lens  50 , a first surface (an object-side surface)  52  may have a concave shape and a second surface (an image-side surface)  54  thereof may be a convex shape toward the image side. More specifically, the fifth lens  50  may have a cross-sectional shape in which the thickness of the fifth lens  50  may be thicker on the optical axis than in the edge of the fifth lens  50 . Moreover, the fifth lens  50  may have a relatively larger size than the fourth lens  40 . 
         [0064]    The shape of the fifth lens  50  may be suitable to project light incident through the fourth lens  40  to the image sensor  80 . Accordingly, vignetting in the image projected onto the image sensor may be suppressed. 
         [0065]    The fifth lens  50  may have a meniscus shape which is convex toward the image side. The meniscus-shaped fifth lens  50  may reduce an incident angle of light so as to prevent light incident in the image sensor  80  from being distorted. 
         [0066]    The fifth lens  50  may have at least one aspherical surface. For example, at least one of the first surface  52  and the second surface  54  of the fifth lens  50  may be aspherical. However, both the first surface  52  and the second surface  54  may be aspherical as necessary. 
         [0067]    The stop  60  may be placed between the third lens  30  and the fourth lens  40 . The stop  60  may control the amount of light incident through the third lens  30 . 
         [0068]    The stop  60  may be formed integrally with the third lens  30  and the fourth lens  40 . For example, the stop  60  may include a light shielding film formed on the second surface  34  of the third lens  30  or on the first surface  42  of the fourth lens  40 . 
         [0069]    In this case, the stop  60  may be covered with black ink or the light shielding film. 
         [0070]    Meanwhile, the stop  60  may satisfy Equation 4. That is, a distance ds from the stop  60  to the first surface  52  of the fifth lens  50  may be determined by a radius of curvature R51 of the first surface  52  of the fifth lens  50 . 
         [0071]    That is, the distance ds may be increased when the radius of curvature R51 of the first surface  52  of the fifth lens  50  is increased and may be reduced when the radius of curvature R51 of the first surface  52  of the fifth lens  50  is reduced. 
         [0000]    
       
         
           
             
               
                 
                   0 
                   &lt; 
                   
                      
                     
                       ds 
                       
                         R 
                          
                         
                             
                         
                          
                         51 
                       
                     
                      
                   
                   &lt; 
                   1.0 
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   4 
                 
               
             
           
         
       
     
         [0000]    (Here, ds represents the distance from the stop to the first surface of the fifth lens, and R51 represents the radius of curvature of the first surface of the fifth lens.) 
         [0072]    However, when the distance ds is equal to or greater than the radius of curvature R51 of the first surface  52 , the overall length of the super wide angle lens module  100  may be significantly extended. Accordingly, when the distance ds is less than the radius of curvature R51, it is effective in miniaturizing the super wide angle lens module  100 . 
         [0073]    The filter member  70  may be placed between the fifth lens  50  and the image sensor  80 . 
         [0074]    The filter member  70  may be an IR filter blocking infrared rays and may be formed of a glass material. Further, the filter member  70  may be integrally formed with the image sensor  80 . Moreover, the filter member  70  may be omitted according to use of the super wide angle lens module  100 . 
         [0075]    The image sensor  80  may be mounted in an apparatus on which the lens module  100  is to be mounted, or in a housing receiving the plurality of lenses  10 ,  20 ,  30 ,  40 , and  50 . 
         [0076]    The image sensor  80  may receive an image of an object through light reflected therefrom incident through the lenses  10 ,  20 ,  30 ,  40 , and  50 . The image sensor  80  may be a CCD or a CMOS and may be formed as a chip scale package (CSP). 
         [0077]    Unlike the related art, since the super wide angle lens module  100  according to the present embodiment is constituted of 5 lenses, the super wide angle lens module  100  may be miniaturized. Moreover, in the super wide angle lens module  100  according to the present embodiment, since the dispersion constants of the second lens  20  and the fourth lens  40  are larger than the dispersion constant of the third lens  30 , chromatic aberration may be improved while a wide angle of view is ensured. 
         [0078]    Next, a lens module according to a second embodiment of the present invention will be described with reference to  FIG. 2 . 
         [0079]    The super wide angle lens module  100  according to the second embodiment may be distinguished from that of the first embodiment in terms of the shape of the first lens  10 . That is, the first surface  12  and the second surface  14  of the first lens  10  may be connected to each other in the super wide angle lens module  100  according to the second embodiment of the present invention. 
         [0080]    The first surface  12  may be a curved surface having a predetermined radius of curvature. More specifically, the first surface  12  may have an aspherical shape in which a curvature of a part through which an optical axis passes is different from that of an edge part. 
         [0081]    The second surface  14  may include a curved portion  14   a  having a predetermined radius of curvature and a flat portion  14   b . The curved portion  14   a  may be formed in a central portion of the second surface  14  and may have a radius of curvature relatively smaller than the radius of curvature of the first surface  12 . Unlike this, the flat portion  14   b  may be formed at an edge portion of the curved portion  14   a  and may be connected to the first surface  12 . 
         [0082]    The first lens  10  may have a cross section in which the first lens is thinner in a part through which the optical axis passes than in the edge portion of the first lens. Moreover, since the first surface  12  and the flat portion  14   b  of the second surface  14  are connected to each other, light incident in a lateral direction of the first lens  10  may pass through the first surface  12 . 
         [0083]    Accordingly, in the first lens  10  according to the present embodiment, since light reflected from things around an object may be ensured, an angle of view of the super wide angle lens module  100  may be more effectively expanded. 
         [0084]    Next, a lens module according to a third embodiment of the present invention will be described with reference to  FIG. 3 . 
         [0085]    The super wide angle lens module  100  according to the third embodiment may be distinguished from the above-mentioned embodiments in terms of the shape of the first lens  10 . That is, the super wide angle lens module  100  shown in  FIG. 3  may include a first lens  10  having a protrusion  16  and a housing  90  having a groove  92 . 
         [0086]    The first lens  10  may include the protrusion  16  protruding toward the image side (that is, toward the image sensor). 
         [0087]    The protrusion  16  may be formed on the flat portion  14   b  in which an effective amount of light (light reflected from a target object to be imaged) is not incident. The protrusion  16  may have a constant circular shape centered around an optical axis (line C-C) or a segmented pillar shape centered around the optical axis. 
         [0088]    The housing  90  may have the groove  92  corresponding to the protrusion  16 . The size of the groove  92  may be enough to fully receive the protrusion  16 . To this end, a cross-sectional size of the groove  92  maybe larger than that of the protrusion  16 . Herein, a spare space generated after the coupling of the groove  92  and the protrusion  16  may be filled with an adhesive. 
         [0089]    In the super wide angle lens module  100 , since the first lens  10  and the housing  90  are coupled to each other through the protrusion  16  and the groove  92 , the edge portion of the first lens  10  may be exposed to the outside, and as a result, an effective amount of light reflected from the object may be ensured to be incident. 
         [0090]    Tables 1 to 5 show numerical values with regard to various Examples of the super wide angle lens module  100  having the above-described configuration. For reference, Tables 1 and 2 are numerical values according to Inventive Example 1, and Tables 3 and 4 are numerical values according to Inventive Example 2. In addition, Table 5 is a calculation value of Equation 4 with regard to Examples 1 and 2. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Surface 
                 Radius of 
                 Thickness 
                   
               
               
                   
                 No. 
                 Curvature 
                 or Distance 
                 Glass code 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 10.94849 
                 0.500000 
                 736.454 
               
               
                   
                  2 
                 3.49580 
                 2.715208 
               
               
                   
                 *3 
                 15.34561 
                 0.500000 
                 534.557 
               
               
                   
                 *4 
                 1.00821 
                 1.297475 
               
               
                   
                  5 
                 2.34309 
                 1.497443 
                 755.275 
               
               
                   
                  6 
                 −7.61563 
                 0.748772 
               
               
                   
                 Stop 
                 INFINITY 
                 0.171813 
               
               
                   
                 *8 
                 −982.07886 
                 0.721722 
                 534.557 
               
               
                   
                 *9 
                 −2.13592 
                 0.986787 
               
               
                   
                 *10  
                 −4.51849 
                 1.276159 
                 534.557 
               
               
                   
                 *11  
                 −1.27699 
                 0.100000 
               
               
                   
                 12 
                 INFINITY 
                 0.400000 
                 516.641 
               
               
                   
                 13 
                 INFINITY 
                 0.100000 
               
               
                   
                 14 
                 INFINITY 
                 0.550000 
                 516.641 
               
               
                   
                 15 
                 INFINITY 
                 0.118942 
               
               
                   
                   
               
             
          
         
       
     
         [0091]    In Table 1, the dispersion constant of the first lens was 45.4, smaller than those of the second and fourth lenses. 
         [0092]    Each of the dispersion constants of the second and fourth lenses was 55.7, satisfying the numerical values presented in Equations 1 and 3. 
         [0093]    The third lens had a dispersion constant of 27.5, smaller than those of the second and fourth lenses in order to improve chromatic aberration. 
         [0094]    However, since the fifth lens did not affect the improvement of the chromatic aberration, the fifth lens had the same dispersion constant (55.7) as those of the second and fourth lenses. 
         [0095]    The refractive index of the third lens was 1.75, satisfying Equation 2. 
         [0096]    A value of |ds/R51| representing the relationship between the stop and the fifth lens was 0.42 (see Table 5), satisfying Equation 4. 
         [0097]    In Inventive Example 1 as described above, although an angle of view (X axis) increases, a difference in height is not significantly decreased due to distortion of light, unlike those of the Comparative Examples as shown in  FIG. 4 , and as a result, the vicinity of the object may be effectively imaged. 
         [0098]    Table 2 shows numerical values for calculating aspherical coefficients of the lenses according to Inventive Example 1, and Equation 5 uses the numerical values thereof. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Surface 
                   
                   
                   
                   
                   
                   
               
               
                 No. 
                 K 
                 A 
                 B 
                 C 
                 D 
                 E 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 3 
                 10.000000 
                 −.743842E−02 
                 0.524045E−03 
                 −.350278E−04 
                 0.143088E−05 
                   
               
               
                 4 
                 −0.781381 
                 0.209206E−01 
                 0.144688E−01 
                 −.576358E−02 
                 0.568103E−03 
               
               
                 8 
                 −982.07886 
                 −.193149E−01 
                 −.817574E−01 
                 −.938745E−01 
                 0.168824E+00 
               
               
                 9 
                 0.000000 
                  0211042E−01 
                 −.848818E−02 
                 −.115809E−01 
                 −.213025E−01 
               
               
                 10 
                 −27.815449 
                 −.848356E−01 
                 −.328496E−02 
                 0.803215E−2  
                 −.644432E−03 
               
               
                 11 
                 −0.000000 
                 0.246656E−01 
                 −.167851E−01 
                 −.232190E−02 
                 0.133101E−02 
                 0.155760E−03 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
           
             
               
                 
                   Z 
                   = 
                   
                     
                       
                         Cr 
                         2 
                       
                       
                         1 
                         + 
                         
                           
                             1 
                             - 
                             
                               
                                 ( 
                                 
                                   1 
                                   + 
                                   k 
                                 
                                 ) 
                               
                                
                               
                                 c 
                                 2 
                               
                                
                               
                                 r 
                                 2 
                               
                             
                           
                         
                       
                     
                     + 
                     
                       Ar 
                       4 
                     
                     + 
                     
                       Br 
                       6 
                     
                     + 
                     
                       Cr 
                       8 
                     
                     + 
                     
                       Dr 
                       10 
                     
                     + 
                     
                       Er 
                       12 
                     
                     + 
                     
                       Fr 
                       14 
                     
                     + 
                     
                       Gr 
                       16 
                     
                     + 
                     
                       Hr 
                       18 
                     
                     + 
                     
                       Jr 
                       20 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   5 
                 
               
             
           
         
       
     
         [0099]    In Equation 5, C represents a curvature (1/r), K represents a conic constant, and r represents a radius of curvature. Moreover, constants A to J represent 4 th  to 20 th  aspherical coefficients. In addition, Z represents a sag at a predetermined position. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Surface 
                 Radius of 
                 Thickness 
                   
               
               
                   
                 No. 
                 Curvature 
                 or Distance 
                 Glass code 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 10.75094 
                 0.500000 
                 672.519 
               
               
                   
                  2 
                 3.44068 
                 2.540762 
               
               
                   
                 *3 
                 11.53410 
                 0.500000 
                 534.557 
               
               
                   
                 *4 
                 0.84232 
                 1.068837 
               
               
                   
                  5 
                 1.68190 
                 1.460719 
                 755.275 
               
               
                   
                  6 
                 −15.40144 
                 0.356907 
               
               
                   
                 Stop 
                 INFINITY 
                 0.291343 
               
               
                   
                 *8 
                 35.63597 
                 0.889986 
                 534.557 
               
               
                   
                 *9 
                 −2.32316 
                 0.490450 
               
               
                   
                 *10  
                 −43.41609 
                 1.093584 
                 534.557 
               
               
                   
                 *11  
                 −1.87276 
                 0.100000 
               
               
                   
                 12 
                 INFINITY 
                 0.400000 
                 516.641 
               
               
                   
                 13 
                 INFINITY 
                 1.000000 
               
               
                   
                 14 
                 INFINITY 
                 0.550000 
                 516.641 
               
               
                   
                 15 
                 INFINITY 
                 0.242643 
               
               
                   
                   
               
             
          
         
       
     
         [0100]    In Table 3, the dispersion constant of the first lens was 51.9, smaller than those of the second and fourth lenses. 
         [0101]    Each of the dispersion constants of the second and fourth lenses was 55.7, satisfying the numerical values presented in Equations 1 and 3. 
         [0102]    The third lens had a dispersion constant of 27.5, smaller than the second and fourth lenses in order to improve chromatic aberration. 
         [0103]    However, since the fifth lens did not affect the improvement of the chromatic aberration, the fifth lens had the same dispersion constant (55.7) as those of the second and fourth lenses. 
         [0104]    The refractive index of the third lens was 1.75, satisfying Equation 2. 
         [0105]    A value of |ds/R51| representing the relationship between the stop and the fifth lens was 0.04 (see Table 5), satisfying Equation 4. 
         [0106]    In Inventive Example 2 as described above, although the angle of view (X axis) increases, a difference in height is not significantly decreased due to distortion of light, unlike those of Comparative Examples as shown in  FIG. 4 , and as a result, the vicinity of the object may be effectively imaged as in Inventive Example 1. 
         [0107]    Table 4 shows numerical values for calculating aspherical coefficients of the lenses according to Inventive Example 2. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Surface 
                   
                   
                   
                   
                   
                   
               
               
                 No. 
                 K 
                 A 
                 B 
                 C 
                 D 
                 E 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 3 
                 10.000000 
                 −.810011E−02 
                 0.628918E−03 
                 −.449682E−04 
                 0.103617E−05 
                   
               
               
                 4 
                 −0.763623 
                 0.295846E−01 
                 0.646521E−02 
                 −.605398E−03 
                 0.401780E−02 
               
               
                 8 
                 0.000000 
                 −.129767E+00 
                 −.780820E−01 
                 0.313971E−01 
                 −.100749E+00 
               
               
                 9 
                 0.000000 
                 −.441848E−02 
                 −.482535E−01 
                 −718921E−02 
                 −.387648E−02 
               
               
                 10 
                 702.228285 
                 0.962675E−02 
                 −.175514E−01 
                 0.200825E−02 
                 0.926691E−03 
               
               
                 11 
                 −1.000000 
                 0.418867E−01 
                 −.140016E−01 
                 −.251153E−03 
                 0.123335E−02 
                 −.135365E−03 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 Equation 
                 Example 1 
                 Example 2 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 |ds/R51| 
                 0.4161 
                 0.038 
               
               
                   
                 V2 
                 55 
                 55 
               
               
                   
                 V4 
                 55 
                 55 
               
               
                   
                   
               
             
          
         
       
     
         [0108]    As set forth above, according to the embodiments of the present invention, there is provided a lens module having an angle of view of 180° or more with a small number of lenses. 
         [0109]    While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.