Abstract:
An optical lens system, sequentially arranged from an object side to an image side along an optical axis, includes: a stop, a first lens element with positive refractive power having a convex object-side surface, a second lens element with negative refractive power, a third lens element with positive refractive power having a concave object-side surface and a convex image-side surface, and a fourth lens element with negative refractive power having a concave image-side surface with both being aspheric. Furthermore, the optical lens system satisfies conditions related to increase the field of view and reduce the total length as well as the sensitivity of assembly tolerance of the optical lens system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical lens system, and more particularly to a four-piece optical lens system applicable to electronic products. 
     2. Description of the Prior Art 
     With the consumer electronic industry continuously growing, the current market demand for small imaging lens system is also increasing. Especially for the imaging lens application in mobile phone, tablet computer and notebook, optical lens system has almost become mainstream in the market. Nowadays, as all types of electronic products are becoming thinner, lighter and easier to carry, the imaging lens system also needs to be further reduced in size in order to fit in the increasingly miniaturized carrier. Fine pixel and good image quality have become basic requirements for optical lens system. In addition, consumers also demand that more persons or views can be recorded on a photograph, therefore, it is becoming increasingly important whether an optical lens system has a wide-angle of view or not. 
     In order to miniaturize the lens system and widen the angle of view, the lens elements of the lens system must have a very short combined focal length so as to form an image within a short distance. As the refractive power of the lens elements increases, the aberration correction will become difficult, and the aberration has to be corrected by arranging more lens elements or using aspheric lens elements. Furthermore, the thickness of the lens elements and the air spaces also need to be minimized, which imposes high requirements on the tolerance during manufacturing and assembling process, making the lens system difficult to manufacture. 
     Conventional arts, such as U.S. Pat. Nos. 7,715,119 and 7,755,853, use glass as the material of the first lens element to provide better aberration, reduce the size of the lens system while improving image quality. However, the manufacturing cost of the glass lens element is high. 
     The lens systems disclosed in U.S. Pat. Nos. 8,405,919, 8,395,691, 8,358,475 and 8,199,418, without using glass lens elements, are capable of providing better image quality simply by adjusting the refractive powers and positions of the lens elements. However, the FOV (field of view) of all these lens systems is less than 76 degrees, and the proportion of the total length to the half of the maximum image height of the lens system (TL/ImgH) is greater than 1.6. Since the image angle is small and the total length is relatively long, all these four lens systems cannot satisfy with the demand for wide-angle shooting and miniaturization. 
     The lens systems disclosed in U.S. Pat. Nos. 8,441,745 and 8,432,622 are capable of wide-angle shooting by using a first lens element with a negative refractive power. However, the total length of these two lens systems is too long to fit in the miniaturized electronic products, such as mobile phone, notebook or tablet computer. 
     The present invention has been made in order to solve the above-mentioned problems. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide an optical lens system applicable to all kinds of electronic products, such as mobile phone, computer, etc, that require the use of micro camera. The optical lens system of the present invention has a wide angle of view, extra short length, high image quality and low sensitivity to assembly tolerance. 
     According to one aspect of the present invention, an optical lens system comprises, in order from an object side to an image side: 
     a stop; 
     a first lens element with a positive refractive power made of plastic having a convex object-side surface; 
     a second lens element with a negative refractive power made of plastic having an aspheric object-side surface and an aspheric image-side surface; 
     a third lens element with a positive refractive power made of plastic having a concave object-side surface and a convex image-side surface; 
     a fourth lens element with a refractive power made of plastic having an aspheric object-side surface and an aspheric concave image-side surface, and at least one inflection point being formed on at least one of the object-side surface and the image-side surface of the fourth lens element; 
     a focal length of the first lens element is f1, a focal length of the optical lens system is f, a maximum effective diameter of the image-side surface of the third lens element is CA_L3S2, a maximum effective diameter of the image-side surface of the fourth lens element is CA_L4S2; and they satisfy the conditions: 
     1&lt;f1/f&lt;1.6; 
     0.4&lt;CA_L3S2/CA_L4S2&lt;0.7. 
     When the condition 1&lt;f1/f&lt;1.6 is satisfied, the distribution of the refractive power of the first lens can be controlled, so that the optical lens system can maintain a wider angle of view, and the sensitivity of the optical lens system assembly can be reduced. 
     When the condition 0.4&lt;CA_L3S2/CA_L4S2&lt;0.7 is satisfied, the total length of the optical lens system would be effectively reduced; Moreover, the occurrence of ghost caused by secondary reflection from the fourth lens element can also be effectively prevented. 
     Preferably, a distance between the object-side surface of the second lens element and the object-side surface of the third lens element along an optical axis is Dr4r6, a distance from the object-side surface of the first lens element to an image plane along the optical axis is TL, and they satisfy the condition: 
     Dr4r6/TL&lt;0.2. 
     When the above condition is satisfied, the total length of the optical lens system can be further reduced. 
     Preferably, a radius of curvature of the object-side surface of the second lens element is R4, a radius of curvature of the image-side surface of the second lens element is R5, and they satisfy the condition: 
     −4&lt;(R4−R5)/(R4+R5)&lt;4. 
     When the above condition is satisfied, the spherical aberrations of the optical lens system can be better balanced, and the sensitivity of assembly tolerance of the optical lens system can also be reduced. 
     Preferably, a focal length of the third lens element is f3, the focal length of the optical lens system is f, and they satisfy the condition: 
     0.3&lt;f3/f&lt;5.5. 
     When the above condition is satisfied, the sensitivity of assembly tolerance of the optical lens system can be reduced, and the back focal length can also be maintained at an appropriate space for placing other components, such as Infrared filter plate and sensor protection glass, as well as for preventing the image degradation caused by dust particles. 
     Preferably, an Abbe number of the third lens element is Vd3, an Abbe number of the second lens element is Vd2, and they satisfy the condition: 
     Vd3−Vd2&gt;25. 
     When the above condition is satisfied, the chromatic aberrations of the optical lens system can be well corrected. 
     Preferably, a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along an optical axis is Dr7r8, a distance from the object-side surface of the first lens element to an image plane along the optical axis is TL, and they satisfy the condition: 
     2.0&lt;Dr7r8×100/TL&lt;13. 
     When the above condition is satisfied, the total length of the optical lens system can be further reduced. 
     Preferably, a distance from the object-side surface of the second lens element to the image-side surface of the third lens element along an optical axis is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: 
     Dr4r7/f&lt;0.6. 
     When the above condition is satisfied, the total length of the optical lens system can be further reduced, and the angle of field of view will be increased too. 
     Preferably, a distance from the object-side surface of the first lens element to an image plane along an optical axis is TL, and a half of the maximum image height of the optical lens system is ImgH, and they satisfy the condition: 
     TL/ImgH&lt;1.6. 
     When the above condition is satisfied, the compact size of the optical lens system can be maintained for its usage in miniaturized electronic products 
     TL and ImgH can further satisfy the condition: 
     TL/ImgH&lt;1.55. 
     Preferably, a maximum field of view of the optical lens system is FOV which satisfies the condition: 
     FOV&gt;80. 
     Therefore, the larger field of view can be provided for wide-range imaging without image distortion. 
     According to another aspect of the present invention, an optical lens system comprises, in order from an object side to an image side: 
     a stop; 
     a first lens element with a positive refractive power made of plastic having a convex object-side surface; 
     a second lens element with a negative refractive power made of plastic having an aspheric object-side surface and an aspheric concave image-side surface; 
     a third lens element with a positive refractive power made of plastic having a concave object-side surface and a convex image-side surface; 
     a fourth lens element with a negative refractive power made of plastic having an aspheric object-side surface and an aspheric concave image-side surface, and at least one inflection point being formed on at least one of the object-side surface and the image-side surface of the fourth lens element; 
     a focal length of the first lens element is f1, a focal length of the optical lens system is f, a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along an optical axis is Dr7r8, a distance from the object-side surface of the first lens element to an image plane along the optical axis is TL, and they satisfy the conditions: 
     1&lt;f1/f&lt;1.6; 
     2.0&lt;Dr7r8×100/TL&lt;13. 
     When the condition 1&lt;f1/f&lt;1.6 is satisfied, the distribution of the refractive power of the first lens can be controlled, so that the optical lens system can maintain a wider angle of view, and the sensitivity of assembly tolerance of the optical lens system can be reduced. 
     When the condition 2.0&lt;Dr7r8×100/TL&lt;13 is satisfied, the total length of the optical lens system can be effectively reduced. 
     Preferably, a distance between the object-side surface of the second lens element and the object-side surface of the third lens element along an optical axis is Dr4r6, a distance from the object-side surface of the first lens element to an image plane along the optical axis is TL, and they satisfy the condition: 
     Dr4r6/TL&lt;0.2. 
     When the above condition is satisfied, the total length of the optical lens system can be further reduced. 
     Preferably, a radius of curvature of the object-side surface of the second lens element is R4, a radius of curvature of the image-side surface of the second lens element is R5, and they satisfy the condition: 
     −4&lt;(R4−R5)/(R4+R5)&lt;4. 
     When the above condition is satisfied, the spherical aberrations of the optical lens system can be better balanced, and the assembly tolerance can also be reduced. 
     Preferably, a focal length of the third lens element is f3, the focal length of the optical lens system is f, and they satisfy the condition: 
     0.3&lt;f3/f&lt;5.5. 
     When the above condition is satisfied, the assembly tolerance can be reduced, and the back focal length can also be maintained at an appropriate space for placing other components, such as Infrared filter plate and sensor protection glass, as well as for preventing the image degradation caused by dust particles. 
     Preferably, an Abbe number of the third lens element is Vd3, an Abbe number of the second lens element is Vd2, and they satisfy the condition: 
     Vd3−Vd2&gt;25. 
     When the above condition is satisfied, the chromatic aberrations of the optical lens system can be well corrected. 
     A maximum effective diameter of the image-side surface of the third lens element is CA_L3S2, a maximum effective diameter of the image-side surface of the fourth lens element is CA_L4S2; and they satisfy the condition: 
     0.4&lt;CA—L3S2/CA—L4S2&lt;0.7. 
     When the condition 0.4&lt;CA_L3S2/CA_L4S2&lt;0.7 is satisfied, the total length of the optical lens system would be further reduced; Moreover, the occurrence of ghost caused by secondary reflection from the fourth lens element can also be effectively prevented. 
     Preferably, a distance from the object-side surface of the second lens element to the image-side surface of the third lens element along an optical axis is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: 
     Dr4r7/f&lt;0.6. 
     When the above condition is satisfied, the total length of the optical lens system can be further reduced, and the angle of field of view will be increased too. 
     Preferably, a distance from the object-side surface of the first lens element to an image plane along an optical axis is TL, and a half of the maximum image height of the optical lens system is ImgH, and they satisfy the condition: 
     TL/ImgH&lt;1.6. 
     When the above condition is satisfied, the compact size of the optical lens system can be maintained for its usage in miniaturized electronic products 
     TL and ImgH can further satisfy the condition: 
     TL/ImgH&lt;1.55. 
     Preferably, a maximum field of view of the optical lens system is FOV which satisfies the condition: 
     FOV&gt;80. 
     Therefore, the larger field of view can be provided for wide-range imaging without image distortion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows an optical lens system cross-sectional view in accordance with the first embodiment; 
         FIG. 1B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the first embodiment; 
         FIG. 2A  shows an optical lens system cross-sectional view in accordance with the second embodiment; 
         FIG. 2B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the second embodiment; 
         FIG. 3A  shows an optical lens system cross-sectional view in accordance with the third embodiment; 
         FIG. 3B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the third embodiment; 
         FIG. 4A  shows an optical lens system cross-sectional view in accordance with the fourth embodiment; 
         FIG. 4B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the fourth embodiment; 
         FIG. 5A  shows an optical lens system cross-sectional view in accordance with the fifth embodiment; 
         FIG. 5B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the fifth embodiment; 
         FIG. 6A  shows an optical lens system cross-sectional view in accordance with the sixth embodiment; 
         FIG. 6B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the sixth embodiment; 
         FIG. 7A  shows an optical lens system cross-sectional view in accordance with the seventh embodiment; 
         FIG. 7B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the seventh embodiment; 
         FIG. 8A  shows an optical lens system cross-sectional view in accordance with the eighth embodiment; 
         FIG. 8B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the eighth embodiment; 
         FIG. 9A  shows an optical lens system cross-sectional view in accordance with the ninth embodiment; 
         FIG. 9B  shows spherical aberration curve, astigmatic field curves and distortion curve of the optical lens system in accordance with the ninth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It is to be noted that in the following embodiments of the present four-piece optical lens system, the terms “convex object-side surface”, “convex image-side surface”, “concave object-side surface” and “concave image-side surface” refer to the surfaces of the lens elements near the optical axis. 
     Referring to  FIG. 1A , which shows an optical lens system cross-sectional view in accordance with a first embodiment of the present invention, and  FIG. 1B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the first embodiment of the present invention. An optical lens system in accordance with the first embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  100 . 
     A first lens element  110  with a positive refractive power made of plastic has a convex object-side surface  111  and a convex image-side surface  112 , and the object-side surface  111  and the image-side surface  112  of the first lens element  110  are aspheric. 
     A second lens element  120  with a negative refractive power made of plastic has a concave object-side surface  121  and a concave image-side surface  122 , and the object-side surface  121  and the image-side surface  122  of the second lens element  120  are aspheric. 
     A third lens element  130  with a positive refractive power made of plastic has a concave object-side surface  131  and a convex image-side surface  132 , and the object-side surface  131  and the image-side surface  132  of the third lens element  130  are aspheric. 
     A fourth lens element  140  with a negative refractive power made of plastic has a convex object-side surface  141  and a concave image-side surface  142 , the object-side surface  141  and the image-side surface  142  of the fourth lens element  140  are aspheric, and at least one inflection point is formed on each of the object-side surface  141  and the image-side surface  142  of the fourth lens element  140 . 
     An IR filter  150  made of glass is located between the image-side surface  142  of the fourth lens element  140  and an image plane  190  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the first embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the first embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.18. 
     In the first embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the first embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=46.1; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=92.2. 
     In the first embodiment of the present optical lens system, the focal length of the first lens element  110  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.14. 
     In the first embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  132  of the third lens element  130  is CA_L3S2, the maximum effective diameter of the image-side surface  142  of the fourth lens element  140  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.55. 
     In the first embodiment of the present optical lens system, a distance between the image-side surface  132  of the third lens element  130  and the object-side surface  141  of the fourth lens element  140  along the optical axis  191  is Dr7r8, a distance from the object-side surface  111  of the first lens element  110  to the image plane  190  along the optical axis  191  is TL, and they satisfy the condition: Dr7r8×100/TL=2.80. 
     In the first embodiment of the present optical lens system, a distance between the object-side surface  121  of the second lens element  120  and the object-side surface  131  of the third lens element  130  along the optical axis  191  is Dr4r6, a distance from the object-side surface  111  of the first lens element  110  to the image plane  190  along the optical axis  191  is TL, and they satisfy the condition: Dr4r6/TL=0.14. 
     In the first embodiment of the present optical lens system, a radius of curvature of the object-side surface  121  of the second lens element  120  is R4, a radius of curvature of the image-side surface  122  of the second lens element  120  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=1.92. 
     In the first embodiment of the present optical lens system, the focal length of the third lens element  130  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=0.53. 
     In the first embodiment of the present optical lens system, an Abbe number of the third lens element  130  is Vd3, an Abbe number of the second lens element  120  is Vd2, and they satisfy the condition: Vd3−Vd2=34.00. 
     In the first embodiment of the present optical lens system, a distance from the object-side surface  121  of the second lens element  120  to the image-side surface  132  of the third lens element  130  along the optical axis  191  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.49. In the first embodiment of the present optical lens system, the distance from the object-side surface  111  of the first lens element  110  to the image plane  190  along the optical axis  191  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.41. 
     The detailed optical data of the first embodiment is shown in table 1, and the aspheric surface data is shown in table 2, wherein the units of the radius of curvature, the thickness and the focal length in table 1 are expressed in mm, and in table 2, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 1 and 2, the surfaces 2 and 3 represent the object-side surface  111  and the image-side surface  112  of the first lens element  110 , respectively, the surfaces 4 and 5 represent the object-side surface  121  and the image-side surface  122  of the second lens element  120 , respectively, the surfaces 6 and 7 represent the object-side surface  131  and the image-side surface  132  of the third lens element  130 , respectively, and the surfaces 8 and 9 represent the object-side surface  141  and the image-side surface  142  of the fourth lens element  140 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 (Embodiment 1) 
               
               
                 f (focal length) = 2.18 mm, Fno = 2.5, HFOV 
               
             
          
           
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe  
                 Focal length 
               
               
                   
               
             
          
           
               
                 0 
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                 Stop 
                 Infinity 
                 −0.04 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 Lens 1 
                 1.90  
                 (ASP) 
                 0.46 
                 Plastic 
                 1.544 
                 56 
                 2.49 
               
               
                 3 
                   
                 −4.30  
                 (ASP) 
                 0.19 
                   
                   
                   
                   
               
               
                 4 
                 Lens 2 
                 −11.22  
                 (ASP) 
                 0.25 
                 Plastic 
                 1.642 
                 22 
                 −4.16 
               
               
                 5 
                   
                 3.54 
                 (ASP) 
                 0.20 
                   
                   
                   
                   
               
               
                 6 
                 Lens 3 
                 −2.25 
                 (ASP) 
                 0.63 
                 Plastic 
                 1.544 
                 56 
                 1.17 
               
               
                 7 
                   
                 −0.54 
                 (ASP) 
                 0.09 
                   
                   
                   
                   
               
               
                 8 
                 Lens 4 
                 1.16 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.533 
                 57 
                 −1.44 
               
               
                 9 
                   
                 0.43 
                 (ASP) 
                 0.41 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                 Infinity 
                 0.50 
                   
                   
                   
                   
               
               
                 12 
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Aspheric Coefficients 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −2.94597 
                 4.110236  
                 5.082019 
                 −100 
               
               
                 A4 = 
                 −0.1068 
                 −0.6184 
                 −1.0323 
                 −0.2496 
               
               
                 A6 = 
                 −0.1494 
                 0.4176 
                 1.5509 
                 −0.0076 
               
               
                 A8 = 
                 −3.0268 
                 −3.0754 
                 −7.0421 
                 1.5572 
               
               
                 A10 = 
                 14.7127 
                 8.1936 
                 29.8128 
                 −3.3844 
               
               
                 A12 = 
                 −43.0601 
                 −4.7856 
                 −42.2724 
                 3.9049 
               
               
                 A14 = 
                 43.9908 
                 −3.7065 
                 17.8407 
                 −1.7616 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 −16.1138 
                 −3.7832 
                 −4.2724 
                 −3.5841 
               
               
                 A4 = 
                 −0.0261 
                 −0.4374 
                 −0.3363 
                 −0.1928 
               
               
                 A6 = 
                 −0.1958 
                 0.5472 
                 0.1914 
                 0.0996 
               
               
                 A8 
                 0.6038 
                 −0.6652 
                 −0.0635 
                 −0.0319 
               
               
                 A10 = 
                 −0.3827 
                 0.6877 
                 0.0189 
                 0.0026 
               
               
                 A12 = 
                 −0.6002 
                 −0.0851 
                 −0.0040 
                 0.0012 
               
               
                 A14= 
                 0.5948 
                 −0.1081 
                 0.0003 
                 −0.0002 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 2A , which shows an optical lens system cross-sectional view in accordance with a second embodiment of the present invention, and  FIG. 2B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the second embodiment of the present invention. An optical lens system in accordance with the second embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  200 . 
     A first lens element  210  with a positive refractive power made of plastic has a convex object-side surface  211  and a convex image-side surface  212 , and the object-side surface  211  and the image-side surface  212  of the first lens element  210  are aspheric. 
     A second lens element  220  with a negative refractive power made of plastic has a concave object-side surface  221  and a concave image-side surface  222 , and the object-side surface  221  and the image-side surface  222  of the second lens element  220  are aspheric. 
     A third lens element  230  with a positive refractive power made of plastic has a concave object-side surface  231  and a convex image-side surface  232 , and the object-side surface  231  and the image-side surface  232  of the third lens element  230  are aspheric. 
     A fourth lens element  240  with a negative refractive power made of plastic has a convex object-side surface  241  and a concave image-side surface  242 , the object-side surface  241  and the image-side surface  242  of the fourth lens element  240  are aspheric, and at least one inflection point is formed on each of the object-side surface  241  and the image-side surface  242  of the fourth lens element  240 . 
     An IR filter  250  made of glass is located between the image-side surface  242  of the fourth lens element  240  and an image plane  290  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the second embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the second embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.2. 
     In the second embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the second embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=45.9; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=91.8. 
     In the second embodiment of the present optical lens system, the focal length of the first lens element  210  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.18. 
     In the second embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  232  of the third lens element  230  is CA_L3S2, the maximum effective diameter of the image-side surface  242  of the fourth lens element  240  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.51. 
     In the second embodiment of the present optical lens system, a distance between the image-side surface  232  of the third lens element  230  and the object-side surface  241  of the fourth lens element  240  along the optical axis  291  is Dr7r8, a distance from the object-side surface  211  of the first lens element  210  to the image plane  290  along the optical axis  291  is TL, and they satisfy the condition: Dr7r8×100/TL=4.36. 
     In the second embodiment of the present optical lens system, a distance between the object-side surface  221  of the second lens element  220  and the object-side surface  231  of the third lens element  230  along the optical axis  291  is Dr4r6, a distance from the object-side surface  211  of the first lens element  210  to the image plane  290  along the optical axis  291  is TL, and they satisfy the condition: Dr4r6/TL=0.14. 
     In the second embodiment of the present optical lens system, a radius of curvature of the object-side surface  221  of the second lens element  220  is R4, a radius of curvature of the image-side surface  222  of the second lens element  220  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=1.61. 
     In the second embodiment of the present optical lens system, the focal length of the third lens element  230  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=0.61. 
     In the second embodiment of the present optical lens system, an Abbe number of the third lens element  230  is Vd3, an Abbe number of the second lens element  220  is Vd2, and they satisfy the condition: Vd3−Vd2=34.00. 
     In the second embodiment of the present optical lens system, a distance from the object-side surface  221  of the second lens element  220  to the image-side surface  232  of the third lens element  230  along the optical axis  291  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.49. 
     In the second embodiment of the present optical lens system, the distance from the object-side surface  211  of the first lens element  210  to the image plane  290  along the optical axis  291  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.41. 
     The detailed optical data of the second embodiment is shown in table 3, and the aspheric surface data is shown in table 4, wherein the units of the radius of curvature, the thickness and the focal length in table 3 are expressed in mm, and in table 4, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 3 and 4, the surfaces 2 and 3 represent the object-side surface  211  and the image-side surface  212  of the first lens element  210 , respectively, the surfaces 4 and 5 represent the object-side surface  221  and the image-side surface  222  of the second lens element  220 , respectively, the surfaces 6 and 7 represent the object-side surface  231  and the image-side surface  232  of the third lens element  230 , respectively, and the surfaces 8 and 9 represent the object-side surface  241  and the image-side surface  242  of the fourth lens element  240 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 3 
               
               
                 (Embodiment 2) 
               
               
                 f (focal length) = 2.2 mm, Fno = 2.5, HFOV = 45.9 deg. 
               
             
          
           
               
                   
                   
                 Curvature  
                   
                   
                   
                   
                   
               
               
                 Surface # 
                   
                 Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 Focal length 
               
               
                   
               
               
                 0 
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                 Stop 
                 Infinity 
                 −0.04 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 Lens 1  
                 1.82 
                 (ASP) 
                 0.46 
                 Plastic 
                 1.544 
                 56 
                 2.60 
               
               
                 3 
                   
                 −5.71 
                 (ASP) 
                 0.20 
                   
                   
                   
                   
               
               
                 4 
                 Lens 2 
                 −14.68 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.642 
                 22 
                 −4.30 
               
               
                 5 
                   
                 3.44 
                 (ASP) 
                 0.19 
                   
                   
                   
                   
               
               
                 6 
                 Lens 3 
                 −2.56 
                 (ASP) 
                 0.62 
                 Plastic 
                 1.544 
                 56 
                 1.34 
               
               
                 7 
                   
                 −0.62 
                 (ASP) 
                 0.14 
                   
                   
                   
                   
               
               
                 8 
                 Lens 4 
                 1.03 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.544 
                 56 
                 −1.73 
               
               
                 9 
                   
                 0.45 
                 (ASP) 
                 0.39 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                 Infinity 
                 0.50 
                   
                   
                   
                   
               
               
                 12 
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
           
               
                 TABLE 4 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −18.5989 
                 69.62838 
                 94.17092 
                 −100 
               
               
                 A4 = 
                 0.2501 
                 −0.5407 
                 −0.9990 
                 −0.2466 
               
               
                 A6 = 
                 −1.3873 
                 0.1642 
                 1.1533 
                 0.0345 
               
               
                 A8 = 
                 2.1390 
                 −1.2215 
                 −7.3480 
                 0.7284 
               
               
                 A10 = 
                 5.7710 
                 0.4835 
                 32.7357 
                 −1.3466 
               
               
                 A12 = 
                 −74.6549 
                 12.6344 
                 −42.8120 
                 2.3236 
               
               
                 A14 = 
                 160.7376 
                 −16.7486 
                 13.4077 
                 −1.5321 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 0.4093 
                 −1.8570 
                 −18.8810 
                 −4.0749 
               
               
                 A4 = 
                 0.0045 
                 0.0823 
                 −0.1255 
                 −0.1772 
               
               
                 A6 = 
                 0.3576 
                 −0.3626 
                 −0.0181 
                 0.1039 
               
               
                 A8 = 
                 −0.4797 
                 0.3080 
                 0.0427 
                 −0.0469 
               
               
                 A10 = 
                 −0.0688 
                 0.5311 
                 −0.0081 
                 0.0108 
               
               
                 A12 = 
                 0.3859 
                 −0.6830 
                 −0.0013 
                 −0.0007 
               
               
                 A14 = 
                 −0.1639 
                 0.2257 
                 0.0003 
                 −0.0001 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 3A , which shows an optical lens system cross-sectional view in accordance with a third embodiment of the present invention, and  FIG. 3B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the third embodiment of the present invention. An optical lens system in accordance with the third embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  300 . 
     A first lens element  310  with a positive refractive power made of plastic has a convex object-side surface  311  and a convex image-side surface  312 , and the object-side surface  311  and the image-side surface  312  of the first lens element  310  are aspheric. 
     A second lens element  320  with a negative refractive power made of plastic has a concave object-side surface  321  and a concave image-side surface  322 , and the object-side surface  321  and the image-side surface  322  of the second lens element  320  are aspheric. 
     A third lens element  330  with a positive refractive power made of plastic has a concave object-side surface  331  and a convex image-side surface  332 , and the object-side surface  331  and the image-side surface  332  of the third lens element  330  are aspheric. 
     A fourth lens element  340  with a negative refractive power made of plastic has a convex object-side surface  341  and a concave image-side surface  342 , the object-side surface  341  and the image-side surface  342  of the fourth lens element  340  are aspheric, and at least one inflection point is formed on each of the object-side surface  341  and the image-side surface  342  of the fourth lens element  340 . 
     An IR filter  350  made of glass is located between the image-side surface  342  of the fourth lens element  340  and an image plane  390  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the third embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the third embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.27. 
     In the third embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the third embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=45; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=90. 
     In the third embodiment of the present optical lens system, the focal length of the first lens element  310  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.19. 
     In the third embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  332  of the third lens element  330  is CA_L3S2, the maximum effective diameter of the image-side surface  342  of the fourth lens element  340  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.55. 
     In the third embodiment of the present optical lens system, a distance between the image-side surface  332  of the third lens element  330  and the object-side surface  341  of the fourth lens element  340  along the optical axis  391  is Dr7r8, a distance from the object-side surface  311  of the first lens element  310  to the image plane  390  along the optical axis  391  is TL, and they satisfy the condition: Dr7r8×100/TL=2.8. 
     In the third embodiment of the present optical lens system, a distance between the object-side surface  321  of the second lens element  320  and the object-side surface  331  of the third lens element  330  along the optical axis  391  is Dr4r6, a distance from the object-side surface  311  of the first lens element  310  to the image plane  390  along the optical axis  391  is TL, and they satisfy the condition: Dr4r6/TL=0.14. 
     In the third embodiment of the present optical lens system, a radius of curvature of the object-side surface  321  of the second lens element  320  is R4, a radius of curvature of the image-side surface  322  of the second lens element  320  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=2.87. 
     In the third embodiment of the present optical lens system, the focal length of the third lens element  330  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=0.68. 
     In the third embodiment of the present optical lens system, an Abbe number of the third lens element  330  is Vd3, an Abbe number of the second lens element  320  is Vd2, and they satisfy the condition: Vd3−Vd2=34.00. 
     In the third embodiment of the present optical lens system, a distance from the object-side surface  321  of the second lens element  320  to the image-side surface  332  of the third lens element  330  along the optical axis  391  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.46. 
     In the third embodiment of the present optical lens system, the distance from the object-side surface  311  of the first lens element  310  to the image plane  390  along the optical axis  391  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.41. 
     The detailed optical data of the third embodiment is shown in table 5, and the aspheric surface data is shown in table 6, wherein the units of the radius of curvature, the thickness and the focal length in table 5 are expressed in mm, and in table 6, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 5 and 6, the surfaces 2 and 3 represent the object-side surface  311  and the image-side surface  312  of the first lens element  310 , respectively, the surfaces 4 and 5 represent the object-side surface  321  and the image-side surface  322  of the second lens element  320 , respectively, the surfaces 6 and 7 represent the object-side surface  331  and the image-side surface  332  of the third lens element  330 , respectively, and the surfaces 8 and 9 represent the object-side surface  341  and the image-side surface  342  of the fourth lens element  340 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 5 
               
               
                 (Embodiment 3) 
               
               
                 f (focal length) = 2.27 mm, Fno = 2.5, HFOV = 45 deg. 
               
             
          
           
               
                 Surface 
                   
                   
                   
                   
                   
                   
                   
               
               
                 # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 Focal length 
               
               
                   
               
               
                 0 
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                 Stop 
                 Infinity 
                 −0.05 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 Lens 1 
                 1.57 
                 (ASP) 
                 0.45 
                 Plastic 
                 1.544 
                 56 
                 2.60 
               
               
                 3 
                   
                 −19.74 
                 (ASP) 
                 0.19 
                   
                   
                   
                   
               
               
                 4 
                 Lens 2 
                 −9.52 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.642 
                 22 
                 −4.80 
               
               
                 5 
                   
                 4.60 
                 (ASP) 
                 0.21 
                   
                   
                   
                   
               
               
                 6 
                 Lens 3 
                 −2.30 
                 (ASP) 
                 0.54 
                 Plastic 
                 1.544 
                 56 
                 1.55 
               
               
                 7 
                   
                 −0.67 
                 (ASP) 
                 0.09 
                   
                   
                   
                   
               
               
                 8 
                 Lens 4 
                 1.34 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.544 
                 56 
                 −2.05 
               
               
                 9 
                   
                 0.55 
                 (ASP) 
                 0.38 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                 Infinity 
                 0.52 
                   
                   
                   
                   
               
               
                 12 
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
           
               
                 TABLE 6 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface 
                   
                   
                   
                   
               
               
                 # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −7.98594 
                 93.92501 
                 −100 
                 −98.693 
               
               
                 A4 = 
                 0.1582 
                 −0.5363 
                 −1.0168 
                 −0.2391 
               
               
                 A6 = 
                 −0.5432 
                 −0.3404 
                 0.7993 
                 −0.3897 
               
               
                 A8 = 
                 −1.1955 
                 −0.1959 
                 −8.4468 
                 1.3254 
               
               
                 A10 = 
                 9.0882 
                 −1.8397 
                 34.0499 
                 −1.2912 
               
               
                 A12 = 
                 −35.4658 
                 8.6366 
                 −24.3843 
                 2.5227 
               
               
                 A14 = 
                 43.9879 
                 3.2015 
                 −14.2950 
                 −1.8293 
               
               
                   
               
               
                 Surface 
                   
                   
                   
                   
               
               
                 # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 −33.7155 
                 −2.8486 
                 −7.7249 
                 −3.9492 
               
               
                 A4 = 
                 0.1286 
                 −0.0513 
                 −0.2390 
                 −0.1965 
               
               
                 A6 = 
                 0.1042 
                 −0.1264 
                 0.0738 
                 0.1217 
               
               
                 A8 = 
                 −0.4516 
                 0.0237 
                 −0.0120 
                 −0.0569 
               
               
                 A10 = 
                 0.2393 
                 0.0759 
                 −0.0001 
                 0.0150 
               
               
                 A12 = 
                 0.3805 
                 −0.8035 
                 0.0000 
                 −0.0017 
               
               
                 A14 = 
                 −0.5146 
                 0.3793 
                 0.0003 
                 0.0000 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 4A , which shows an optical lens system cross-sectional view in accordance with a fourth embodiment of the present invention, and  FIG. 4B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the fourth embodiment of the present invention. An optical lens system in accordance with the fourth embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  400 . 
     A first lens element  410  with a positive refractive power made of plastic has a convex object-side surface  411  and a concave image-side surface  412 , and the object-side surface  411  and the image-side surface  412  of the first lens element  410  are aspheric. 
     A second lens element  420  with a negative refractive power made of plastic has a convex object-side surface  421  and a concave image-side surface  422 , and the object-side surface  421  and the image-side surface  422  of the second lens element  420  are aspheric. 
     A third lens element  430  with a positive refractive power made of plastic has a concave object-side surface  431  and a convex image-side surface  432 , and the object-side surface  431  and the image-side surface  432  of the third lens element  430  are aspheric. 
     A fourth lens element  440  with a negative refractive power made of plastic has a convex object-side surface  441  and a concave image-side surface  442 , the object-side surface  441  and the image-side surface  442  of the fourth lens element  440  are aspheric, and at least one inflection point is formed on each of the object-side surface  441  and the image-side surface  442  of the fourth lens element  440 . 
     An IR filter  450  made of glass is located between the image-side surface  442  of the fourth lens element  440  and an image plane  490  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the fourth embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the fourth embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.35. 
     In the fourth embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the fourth embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=44; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=88. 
     In the fourth embodiment of the present optical lens system, the focal length of the first lens element  410  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.38. 
     In the fourth embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  432  of the third lens element  430  is CA_L3S2, the maximum effective diameter of the image-side surface  442  of the fourth lens element  440  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.56. 
     In the fourth embodiment of the present optical lens system, a distance between the image-side surface  432  of the third lens element  430  and the object-side surface  441  of the fourth lens element  440  along the optical axis  491  is Dr7r8, a distance from the object-side surface  411  of the first lens element  410  to the image plane  490  along the optical axis  491  is TL, and they satisfy the condition: Dr7r8×100/TL=5.34. 
     In the fourth embodiment of the present optical lens system, a distance between the object-side surface  421  of the second lens element  420  and the object-side surface  431  of the third lens element  430  along the optical axis  491  is Dr4r6, a distance from the object-side surface  411  of the first lens element  410  to the image plane  490  along the optical axis  491  is TL, and they satisfy the condition: Dr4r6/TL=0.16. 
     In the fourth embodiment of the present optical lens system, a radius of curvature of the object-side surface  421  of the second lens element  420  is R4, a radius of curvature of the image-side surface  422  of the second lens element  420  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=0.29. 
     In the fourth embodiment of the present optical lens system, the focal length of the third lens element  430  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=0.56. 
     In the fourth embodiment of the present optical lens system, an Abbe number of the third lens element  430  is Vd3, an Abbe number of the second lens element  420  is Vd2, and they satisfy the condition: Vd3−Vd2=34.00. 
     In the fourth embodiment of the present optical lens system, a distance from the object-side surface  421  of the second lens element  420  to the image-side surface  432  of the third lens element  430  along the optical axis  491  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.51. 
     In the fourth embodiment of the present optical lens system, the distance from the object-side surface  411  of the first lens element  410  to the image plane  490  along the optical axis  491  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.41. 
     The detailed optical data of the fourth embodiment is shown in table 7, and the aspheric surface data is shown in table 8, wherein the units of the radius of curvature, the thickness and the focal length in table 7 are expressed in mm, and in table 8, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 7 and 8, the surfaces 2 and 3 represent the object-side surface  411  and the image-side surface  412  of the first lens element  410 , respectively, the surfaces 4 and 5 represent the object-side surface  421  and the image-side surface  422  of the second lens element  420 , respectively, the surfaces 6 and 7 represent the object-side surface  431  and the image-side surface  432  of the third lens element  430 , respectively, and the surfaces 8 and 9 represent the object-side surface  441  and the image-side surface  442  of the fourth lens element  440 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 7 
               
               
                 (Embodiment 4) 
               
               
                 f (focal length) = 2.35 mm, Fno = 2.5, HFOV= 44 deg. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Focal 
               
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 length 
               
               
                   
               
               
                 0 
                 Object 
                 Infinity  
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                 Stop 
                 Infinity 
                 −0.05 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 Lens 1 
                 1.52  
                 (ASP) 
                 0.38 
                 Plastic 
                 1.515 
                 56  
                 3.25 
               
               
                 3 
                   
                 15.29 
                 (ASP) 
                 0.18 
                   
                   
                   
                   
               
               
                 4 
                 Lens 2 
                 4.00 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.642 
                 22  
                 −8.06 
               
               
                 5 
                   
                 2.20 
                 (ASP) 
                 0.26 
                   
                   
                   
                   
               
               
                 6 
                 Lens 3 
                 −2.86 
                 (ASP) 
                 0.60 
                 Plastic 
                 1.544 
                 56 
                 1.31 
               
               
                 7 
                   
                 −0.61 
                 (ASP) 
                 0.17 
                   
                   
                   
                   
               
               
                 8 
                 Lens 4 
                 2.01 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.533 
                 56  
                 −1.51 
               
               
                 9 
                   
                 0.55 
                 (ASP) 
                 0.35 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                 Infinity 
                 0.54 
                   
                   
                   
                   
               
               
                 12 
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
           
               
                 TABLE 8 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −8.09269 
                 −99 
                 −8.1479 
                 −22.419 
               
               
                 A4 = 
                 0.1744 
                 −0.5486 
                 −0.8181 
                 −0.0656 
               
               
                 A6 = 
                 −0.5557 
                 0.1059 
                 0.6910 
                 −0.7216 
               
               
                 A8 = 
                 −1.1135 
                 −3.0728 
                 −8.2166 
                 1.6149 
               
               
                 A10 = 
                 9.1637 
                 9.6926 
                 30.7799 
                 −2.2037 
               
               
                 A12 = 
                 −36.2505 
                 −10.7384 
                 −29.2304 
                 4.7425 
               
               
                 A14 = 
                 43.9886 
                 3.2021 
                 0.0758 
                 −3.8696 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 8.2704 
                 −2.8994 
                 −2.2524 
                 −4.0290 
               
               
                 A4 = 
                 0.2237 
                 −0.0155 
                 −0.3273 
                 −0.2072 
               
               
                 A6 = 
                 0.3469 
                 −0.2971 
                 0.1038 
                 0.1264 
               
               
                 A8 = 
                 −0.7337 
                 0.7861 
                 0.0267 
                 −0.0579 
               
               
                 A10 = 
                 0.4633 
                 0.0980 
                 −0.0148 
                 0.0143 
               
               
                 A12 = 
                 0.1598 
                 −0.7793 
                 0.0002 
                 −0.0011 
               
               
                 A14 = 
                 −0.1991 
                 0.3283 
                 0.0003 
                 −0.0001 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 5A , which shows an optical lens system cross-sectional view in accordance with a fifth embodiment of the present invention, and  FIG. 5B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the fifth embodiment of the present invention. An optical lens system in accordance with the fifth embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  500 . 
     A first lens element  510  with a positive refractive power made of plastic has a convex object-side surface  511  and a concave image-side surface  512 , and the object-side surface  511  and the image-side surface  512  of the first lens element  510  are aspheric. 
     A second lens element  520  with a negative refractive power made of plastic has a concave object-side surface  521  and a concave image-side surface  522 , and the object-side surface  521  and the image-side surface  522  of the second lens element  520  are aspheric. 
     A third lens element  530  with a positive refractive power made of plastic has a concave object-side surface  531  and a convex image-side surface  532 , and the object-side surface  531  and the image-side surface  532  of the third lens element  530  are aspheric. 
     A fourth lens element  540  with a negative refractive power made of plastic has a concave object-side surface  541  and a concave image-side surface  542 , the object-side surface  541  and the image-side surface  542  of the fourth lens element  540  are aspheric, and at least one inflection point is formed on each of the object-side surface  541  and the image-side surface  542  of the fourth lens element  540 . 
     An IR filter  550  made of glass is located between the image-side surface  542  of the fourth lens element  540  and an image plane  590  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the fifth embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the fifth embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.29. 
     In the fifth embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the fifth embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=44.7; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=89.4. 
     In the fifth embodiment of the present optical lens system, the focal length of the first lens element  510  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.13. 
     In the fifth embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  532  of the third lens element  530  is CA_L3S2, the maximum effective diameter of the image-side surface  542  of the fourth lens element  540  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.58. 
     In the fifth embodiment of the present optical lens system, a distance between the image-side surface  532  of the third lens element  530  and the object-side surface  541  of the fourth lens element  540  along the optical axis  591  is Dr7r8, a distance from the object-side surface  511  of the first lens element  510  to the image plane  590  along the optical axis  591  is TL, and they satisfy the condition: Dr7r8×100/TL=6.17. 
     In the fifth embodiment of the present optical lens system, a distance between the object-side surface  521  of the second lens element  520  and the object-side surface  531  of the third lens element  530  along the optical axis  591  is Dr4r6, a distance from the object-side surface  511  of the first lens element  510  to the image plane  590  along the optical axis  591  is TL, and they satisfy the condition: Dr4r6/TL=0.10. 
     In the fifth embodiment of the present optical lens system, a radius of curvature of the object-side surface  521  of the second lens element  520  is R4, a radius of curvature of the image-side surface  522  of the second lens element  520  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=−2.71. 
     In the fifth embodiment of the present optical lens system, the focal length of the third lens element  530  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=0.48. 
     In the fifth embodiment of the present optical lens system, an Abbe number of the third lens element  530  is Vd3, an Abbe number of the second lens element  520  is Vd2, and they satisfy the condition: Vd3−Vd2=34.00. 
     In the fifth embodiment of the present optical lens system, a distance from the object-side surface  521  of the second lens element  520  to the image-side surface  532  of the third lens element  530  along the optical axis  591  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.48. 
     In the fifth embodiment of the present optical lens system, the distance from the object-side surface  511  of the first lens element  510  to the image plane  590  along the optical axis  591  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.41. 
     The detailed optical data of the fifth embodiment is shown in table 9, and the aspheric surface data is shown in table 10, wherein the units of the radius of curvature, the thickness and the focal length in table 9 are expressed in mm, and in table 10, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 9 and 10, the surfaces 2 and 3 represent the object-side surface  511  and the image-side surface  512  of the first lens element  510 , respectively, the surfaces 4 and 5 represent the object-side surface  521  and the image-side surface  522  of the second lens element  520 , respectively, the surfaces 6 and 7 represent the object-side surface  531  and the image-side surface  532  of the third lens element  530 , respectively, and the surfaces 8 and 9 represent the object-side surface  541  and the image-side surface  542  of the fourth lens element  540 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 9 
               
               
                 (Embodiment 5) 
               
               
                 f (focal length) = 2.29 mm, Fno = 2.5, HFOV= 44.7 deg. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Focal 
               
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 length 
               
               
                   
               
               
                 0 
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                 Stop 
                 Infinity 
                 −0.08 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 Lens 1 
                 1.30 
                 (ASP) 
                 0.46 
                 Plastic 
                 1.515 
                 56 
                 2.58 
               
               
                 3 
                   
                 60.00 
                 (ASP) 
                 0.26 
                   
                   
                   
                   
               
               
                 4 
                 Lens 2 
                 −3.58 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.642 
                 22 
                 −3.78 
               
               
                 5 
                   
                 7.77 
                 (ASP) 
                 0.08 
                   
                   
                   
                   
               
               
                 6 
                 Lens 3 
                 −5.19 
                 (ASP) 
                 0.72 
                 Plastic 
                 1.544 
                 56 
                 1.11 
               
               
                 7 
                   
                 −0.57 
                 (ASP) 
                 0.20 
                   
                   
                   
                   
               
               
                 8 
                 Lens 4 
                 −24.57 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.515 
                 57 
                 −1.26 
               
               
                 9 
                   
                 0.67 
                 (ASP) 
                 0.27 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                 Infinity 
                 0.50 
                   
                   
                   
                   
               
               
                 12 
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
           
               
                 TABLE 10 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −6.52568 
                 99 
                 10.68248 
                 77.39232 
               
               
                 A4 = 
                 0.3380 
                 −0.3420 
                 −0.9005 
                 −0.6998 
               
               
                 A6 = 
                 −0.9228 
                 −0.3468 
                 0.6795 
                 1.1302 
               
               
                 A8 = 
                 1.7896 
                 −3.6859 
                 −6.2439 
                 −0.9404 
               
               
                 A10 = 
                 −3.0481 
                 28.5360 
                 18.4839 
                 0.1614 
               
               
                 A12 = 
                 −7.6957 
                 −116.6518 
                 −24.7615 
                 1.0407 
               
               
                 A14 = 
                 14.9845 
                 166.2789 
                 33.4983 
                 −0.5358 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 37.9639 
                 −2.8507 
                 −6.3455 
                 −5.6460 
               
               
                 A4 = 
                 −0.3132 
                 −0.3105 
                 −0.1112 
                 −0.1620 
               
               
                 A6 = 
                 1.0288 
                 0.2880 
                 −0.0266 
                 0.1046 
               
               
                 A8 = 
                 0.0839  
                 −0.2456  
                 0.0074 
                 −0.0649 
               
               
                 A10 = 
                 −2.7897  
                 0.6180 
                 0.0260 
                 0.0228 
               
               
                 A12 = 
                 3.3859  
                 −0.3460 
                 −0.0088 
                 −0.0041 
               
               
                 A14 = 
                 −1.1955  
                 −0.0221 
                 0.0001 
                 0.0003 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 6A , which shows an optical lens system cross-sectional view in accordance with a sixth embodiment of the present invention, and  FIG. 6B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the sixth embodiment of the present invention. An optical lens system in accordance with the sixth embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  600 . 
     A first lens element  610  with a positive refractive power made of plastic has a convex object-side surface  611  and a concave image-side surface  612 , and the object-side surface  611  and the image-side surface  612  of the first lens element  610  are aspheric. 
     A second lens element  620  with a negative refractive power made of plastic has a convex object-side surface  621  and a concave image-side surface  622 , and the object-side surface  621  and the image-side surface  622  of the second lens element  620  are aspheric. 
     A third lens element  630  with a positive refractive power made of plastic has a concave object-side surface  631  and a convex image-side surface  632 , and the object-side surface  631  and the image-side surface  632  of the third lens element  630  are aspheric. 
     A fourth lens element  640  with a negative refractive power made of plastic has a concave object-side surface  641  and a concave image-side surface  642 , the object-side surface  641  and the image-side surface  642  of the fourth lens element  640  are aspheric, and at least one inflection point is formed on each of the object-side surface  641  and the image-side surface  642  of the fourth lens element  640 . 
     An IR filter  650  made of glass is located between the image-side surface  642  of the fourth lens element  640  and an image plane  690  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the sixth embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the sixth embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.24. 
     In the sixth embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the sixth embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=45.3; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=90.6. 
     In the sixth embodiment of the present optical lens system, the focal length of the first lens element  610  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.24. 
     In the sixth embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  632  of the third lens element  630  is CA_L3S2, the maximum effective diameter of the image-side surface  642  of the fourth lens element  640  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.59. 
     In the sixth embodiment of the present optical lens system, a distance between the image-side surface  632  of the third lens element  630  and the object-side surface  641  of the fourth lens element  640  along the optical axis  691  is Dr7r8, a distance from the object-side surface  611  of the first lens element  610  to the image plane  690  along the optical axis  691  is TL, and they satisfy the condition: Dr7r8×100/TL=2.57. 
     In the sixth embodiment of the present optical lens system, a distance between the object-side surface  621  of the second lens element  620  and the object-side surface  631  of the third lens element  630  along the optical axis  691  is Dr4r6, a distance from the object-side surface  611  of the first lens element  610  to the image plane  690  along the optical axis  691  is TL, and they satisfy the condition: Dr4r6/TL=0.12. 
     In the sixth embodiment of the present optical lens system, a radius of curvature of the object-side surface  621  of the second lens element  620  is R4, a radius of curvature of the image-side surface  622  of the second lens element  620  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=0.84. 
     In the sixth embodiment of the present optical lens system, the focal length of the third lens element  630  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=0.39. 
     In the sixth embodiment of the present optical lens system, an Abbe number of the third lens element  630  is Vd3, an Abbe number of the second lens element  620  is Vd2, and they satisfy the condition: Vd3−Vd2=34.00. 
     In the sixth embodiment of the present optical lens system, a distance from the object-side surface  621  of the second lens element  620  to the image-side surface  632  of the third lens element  630  along the optical axis  691  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.53. 
     In the sixth embodiment of the present optical lens system, the distance from the object-side surface  611  of the first lens element  610  to the image plane  690  along the optical axis  691  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.41. 
     The detailed optical data of the sixth embodiment is shown in table 11, and the aspheric surface data is shown in table 12, wherein the units of the radius of curvature, the thickness and the focal length in table 11 are expressed in mm, and in table 12, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 11 and 12, the surfaces 2 and 3 represent the object-side surface  611  and the image-side surface  612  of the first lens element  610 , respectively, the surfaces 4 and 5 represent the object-side surface  621  and the image-side surface  622  of the second lens element  620 , respectively, the surfaces 6 and 7 represent the object-side surface  631  and the image-side surface  632  of the third lens element  630 , respectively, and the surfaces 8 and 9 represent the object-side surface  641  and the image-side surface  642  of the fourth lens element  640 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 11 
               
               
                 (Embodiment 6) 
               
               
                 f (focal length) = 2.24 mm, Fno = 2.5, HFOV= 45.3 deg. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Focal 
               
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 length 
               
               
                   
               
               
                 0 
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                 Stop 
                 Infinity 
                 −0.07 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 Lens 1 
                 1.40 
                 (ASP) 
                 0.46 
                 Plastic 
                 1.515 
                 56 
                 2.77 
               
               
                 3 
                   
                 60.00 
                 (ASP) 
                 0.23 
                   
                   
                   
                   
               
               
                 4 
                 Lens 2 
                 30.35 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.642 
                 22 
                 −4.49 
               
               
                 5 
                   
                 2.62 
                 (ASP) 
                 0.12 
                   
                   
                   
                   
               
               
                 6 
                 Lens 3 
                 −8.23 
                 (ASP) 
                 0.79 
                 Plastic 
                 1.544 
                 56 
                 0.88 
               
               
                 7 
                   
                 −0.47 
                 (ASP) 
                 0.08 
                   
                   
                   
                   
               
               
                 8 
                 Lens 4 
                 −200.00 
                 (ASP) 
                 0.27 
                 Plastic 
                 1.533 
                 57 
                 −0.92 
               
               
                 9 
                   
                 0.49 
                 (ASP) 
                 0.29 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                 Infinity 
                 0.50 
                   
                   
                   
                   
               
               
                 12 
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
           
               
                 TABLE 12 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3  
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −22.7907 
                 99 
                 14.16368 
                 −85.8084 
               
               
                 A4 = 
                 0.9511 
                 −0.4968 
                 −1.0703 
                 −0.3788 
               
               
                 A6 = 
                 −4.8941 
                 1.4297 
                 2.2444 
                 0.7802 
               
               
                 A8 = 
                 19.2690 
                 −17.7137 
                 −12.4252 
                 −1.3881 
               
               
                 A10 = 
                 −50.4540 
                 87.6998 
                 26.9527 
                 1.1588 
               
               
                 A12 = 
                 48.5868 
                 −231.3456 
                 −20.5726 
                 1.1696 
               
               
                 A14 = 
                 14.9857 
                 245.5426 
                 12.1276 
                 −1.4486 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 95.0000 
                 −3.6504 
                 −100.0000 
                 −5.6023 
               
               
                 A4 = 
                 −0.4268 
                 −0.6069 
                 −0.1548 
                 −0.1700 
               
               
                 A6 = 
                 1.5913 
                 1.1270 
                 −0.0984 
                 0.0924 
               
               
                 A8 = 
                 −2.5941 
                 −1.7666 
                 0.0972 
                 −0.0482 
               
               
                 A10 = 
                 3.1098 
                 1.5186 
                 0.0025 
                 0.0150 
               
               
                 A12 = 
                 −2.6266 
                 −0.0247 
                 −0.0088 
                 −0.0023 
               
               
                 A14 = 
                 1.1457 
                 −0.3411 
                 0.0001 
                 0.0001 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 7A , which shows an optical lens system cross-sectional view in accordance with a seventh embodiment of the present invention, and  FIG. 7B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the seventh embodiment of the present invention. An optical lens system in accordance with the seventh embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  700 . 
     A first lens element  710  with a positive refractive power made of plastic has a convex object-side surface  711  and a concave image-side surface  712 , and the object-side surface  711  and the image-side surface  712  of the first lens element  710  are aspheric. 
     A second lens element  720  with a negative refractive power made of plastic has a concave object-side surface  721  and a concave image-side surface  722 , and the object-side surface  721  and the image-side surface  722  of the second lens element  720  are aspheric. 
     A third lens element  730  with a positive refractive power made of plastic has a concave object-side surface  731  and a convex image-side surface  732 , and the object-side surface  731  and the image-side surface  732  of the third lens element  730  are aspheric. 
     A fourth lens element  740  with a negative refractive power made of plastic has a convex object-side surface  741  and a concave image-side surface  742 , the object-side surface  741  and the image-side surface  742  of the fourth lens element  740  are aspheric, and at least one inflection point is formed on each of the object-side surface  741  and the image-side surface  742  of the fourth lens element  740 . 
     An IR filter  750  made of glass is located between the image-side surface  742  of the fourth lens element  740  and an image plane  790  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the seventh embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the seventh embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.32. 
     In the seventh embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the seventh embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=45.4; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=90.8. 
     In the seventh embodiment of the present optical lens system, the focal length of the first lens element  710  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.18. 
     In the seventh embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  732  of the third lens element  730  is CA_L3S2, the maximum effective diameter of the image-side surface  742  of the fourth lens element  740  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.48. 
     In the seventh embodiment of the present optical lens system, a distance between the image-side surface  732  of the third lens element  730  and the object-side surface  741  of the fourth lens element  740  along the optical axis  791  is Dr7r8, a distance from the object-side surface  711  of the first lens element  710  to the image plane  790  along the optical axis  791  is TL, and they satisfy the condition: Dr7r8×100/TL=9.36. 
     In the seventh embodiment of the present optical lens system, a distance between the object-side surface  721  of the second lens element  720  and the object-side surface  731  of the third lens element  730  along the optical axis  791  is Dr4r6, a distance from the object-side surface  711  of the first lens element  710  to the image plane  790  along the optical axis  791  is TL, and they satisfy the condition: Dr4r6/TL=0.13. 
     In the seventh embodiment of the present optical lens system, a radius of curvature of the object-side surface  721  of the second lens element  720  is R4, a radius of curvature of the image-side surface  722  of the second lens element  720  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=1.17. 
     In the seventh embodiment of the present optical lens system, the focal length of the third lens element  730  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=1.44. 
     In the seventh embodiment of the present optical lens system, an Abbe number of the third lens element  730  is Vd3, an Abbe number of the second lens element  720  is Vd2, and they satisfy the condition: Vd3−Vd2=33.00. 
     In the seventh embodiment of the present optical lens system, a distance from the object-side surface  721  of the second lens element  720  to the image-side surface  732  of the third lens element  730  along the optical axis  791  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.38. 
     In the seventh embodiment of the present optical lens system, the distance from the object-side surface  711  of the first lens element  710  to the image plane  790  along the optical axis  791  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.36. 
     The detailed optical data of the seventh embodiment is shown in table 13, and the aspheric surface data is shown in table 14, wherein the units of the radius of curvature, the thickness and the focal length in table 13 are expressed in mm, and in table 14, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 13 and 14, the surfaces 2 and 3 represent the object-side surface  711  and the image-side surface  712  of the first lens element  710 , respectively, the surfaces 4 and 5 represent the object-side surface  721  and the image-side surface  722  of the second lens element  720 , respectively, the surfaces 6 and 7 represent the object-side surface  731  and the image-side surface  732  of the third lens element  730 , respectively, and the surfaces 8 and 9 represent the object-side surface  741  and the image-side surface  742  of the fourth lens element  740 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 13 
               
               
                 (Embodiment 7) 
               
               
                 f (focal length) = 2.32 mm, Fno = 2.5, HFOV= 45.4 deg. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Focal 
               
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 length 
               
               
                   
               
             
          
           
               
                 0 
                   
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                   
                 Stop 
                 Infinity 
                 0.00 
                   
                   
                   
                   
               
             
          
           
               
                 2  
                 (STOP) 
                 Lens 1 
                 1.46 
                 (ASP) 
                 0.37 
                 Plastic 
                 1.544 
                 56 
                 2.74 
               
               
                 3 
                   
                   
                 66.80 
                 (ASP) 
                 0.21 
                   
                   
                   
                   
               
               
                 4 
                   
                 Lens 2 
                 −74.82 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.632 
                 23 
                 −8.65 
               
               
                 5 
                   
                   
                 5.91 
                 (ASP) 
                 0.16 
                   
                   
                   
                   
               
               
                 6 
                   
                 Lens 3 
                 −1.39 
                 (ASP) 
                 0.46 
                 Plastic 
                 1.544 
                 56 
                 3.35 
               
               
                 7 
                   
                   
                 −0.88 
                 (ASP) 
                 0.30 
                   
                   
                   
                   
               
               
                 8 
                   
                 Lens 4 
                 1.02 
                 (ASP) 
                 0.41 
                 Plastic 
                 1.544 
                 56 
                 −5.54 
               
               
                 9 
                   
                   
                 0.66 
                 (ASP) 
                 0.75 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                   
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                   
                 Infinity 
                 0.05 
                   
                   
                   
                   
               
               
                 12 
                   
                 Image 
                 Infinity 
                 — 
                   
                   
                   
                   
               
               
                   
               
             
          
           
               
                 TABLE 14 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −12.5021 
                 50 
                 50 
                 −27.2641 
               
               
                 A4 = 
                 0.3540 
                 −0.4295 
                 −0.6374 
                 0.2354 
               
               
                 A6 = 
                 −0.9333 
                 −0.7532 
                 −0.8272 
                 −1.6647 
               
               
                 A8 = 
                 −1.9698 
                 1.1331 
                 −3.9800 
                 2.2062 
               
               
                 A10 = 
                 15.8309 
                 −4.4645 
                 26.4919 
                 0.4177 
               
               
                 A12 = 
                 −54.0629 
                 11.5903 
                 −24.8465 
                 −0.7447 
               
               
                 A14 = 
                 56.9939 
                 −13.3273 
                 −6.5579 
                 −0.5918 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 −11.7605 
                 −1.2290 
                 −2.8551 
                 −2.5079 
               
               
                 A4 = 
                 0.4949 
                 0.1593 
                 −0.3778 
                 −0.3172 
               
               
                 A6 = 
                 −0.2541 
                 −0.1910 
                 0.1273 
                 0.2278 
               
               
                 A8 = 
                 −0.9931 
                 0.5638 
                 0.0118 
                 −0.1151 
               
               
                 A10 = 
                 0.4248 
                 0.1512 
                 −0.0088 
                 0.0339 
               
               
                 A12 = 
                 2.9780 
                 −0.7067 
                 −0.0006 
                 −0.0050 
               
               
                 A14 = 
                 −3.0805 
                 0.2811 
                 0.0003 
                 0.0003 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 8A , which shows an optical lens system cross-sectional view in accordance with a eighth embodiment of the present invention, and  FIG. 8B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the eighth embodiment of the present invention. An optical lens system in accordance with the eighth embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  800 . 
     A first lens element  810  with a positive refractive power made of plastic has a convex object-side surface  811  and a convex image-side surface  812 , and the object-side surface  811  and the image-side surface  812  of the first lens element  810  are aspheric. 
     A second lens element  820  with a negative refractive power made of plastic has a concave object-side surface  821  and a concave image-side surface  822 , and the object-side surface  821  and the image-side surface  822  of the second lens element  820  are aspheric. 
     A third lens element  830  with a positive refractive power made of plastic has a concave object-side surface  831  and a convex image-side surface  832 , and the object-side surface  831  and the image-side surface  832  of the third lens element  830  are aspheric. 
     A fourth lens element  840  with a negative refractive power made of plastic has a convex object-side surface  841  and a concave image-side surface  842 , the object-side surface  841  and the image-side surface  842  of the fourth lens element  840  are aspheric, and at least one inflection point is formed on each of the object-side surface  841  and the image-side surface  842  of the fourth lens element  840 . 
     An IR filter  850  made of glass is located between the image-side surface  842  of the fourth lens element  840  and an image plane  890  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the eighth embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the eighth embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.32. 
     In the eighth embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the eighth embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=44.9; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=89.8. 
     In the eighth embodiment of the present optical lens system, the focal length of the first lens element  810  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.10. 
     In the eighth embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  832  of the third lens element  830  is CA_L3S2, the maximum effective diameter of the image-side surface  842  of the fourth lens element  840  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.50. 
     In the eighth embodiment of the present optical lens system, a distance between the image-side surface  832  of the third lens element  830  and the object-side surface  841  of the fourth lens element  840  along the optical axis  891  is Dr7r8, a distance from the object-side surface  811  of the first lens element  810  to the image plane  890  along the optical axis  891  is TL, and they satisfy the condition: Dr7r8×100/TL=6.37. 
     In the eighth embodiment of the present optical lens system, a distance between the object-side surface  821  of the second lens element  820  and the object-side surface  831  of the third lens element  830  along the optical axis  891  is Dr4r6, a distance from the object-side surface  811  of the first lens element  810  to the image plane  890  along the optical axis  891  is TL, and they satisfy the condition: Dr4r6/TL=0.13. 
     In the eighth embodiment of the present optical lens system, a radius of curvature of the object-side surface  821  of the second lens element  820  is R4, a radius of curvature of the image-side surface  822  of the second lens element  820  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=−2.13. 
     In the eighth embodiment of the present optical lens system, the focal length of the third lens element  830  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=4.21. 
     In the eighth embodiment of the present optical lens system, an Abbe number of the third lens element  830  is Vd3, an Abbe number of the second lens element  820  is Vd2, and they satisfy the condition: Vd3−Vd2=33.00. 
     In the eighth embodiment of the present optical lens system, a distance from the object-side surface  821  of the second lens element  820  to the image-side surface  832  of the third lens element  830  along the optical axis  891  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.36. 
     In the eighth embodiment of the present optical lens system, the distance from the object-side surface  811  of the first lens element  810  to the image plane  890  along the optical axis  891  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.36. 
     The detailed optical data of the eighth embodiment is shown in table 15, and the aspheric surface data is shown in table 16, wherein the units of the radius of curvature, the thickness and the focal length in table 15 are expressed in mm, and in table 16, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 15 and 16, the surfaces 2 and 3 represent the object-side surface  811  and the image-side surface  812  of the first lens element  810 , respectively, the surfaces 4 and 5 represent the object-side surface  821  and the image-side surface  822  of the second lens element  820 , respectively, the surfaces 6 and 7 represent the object-side surface  831  and the image-side surface  832  of the third lens element  830 , respectively, and the surfaces 8 and 9 represent the object-side surface  841  and the image-side surface  842  of the fourth lens element  840 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 15 
               
               
                 (Embodiment 8) 
               
               
                 f (focal length) = 2.32 mm, Fno = 2.5, HFOV= 44.9 deg. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Focal 
               
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe  
                 length 
               
               
                   
               
             
          
           
               
                 0 
                   
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                   
                 Stop 
                 Infinity 
                 0.00 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 (STOP) 
                 Lens 1 
                 1.48 
                 (ASP) 
                 0.42 
                 Plastic 
                 1.544 
                 56 
                 2.55 
               
               
                 3 
                   
                   
                 −20.00 
                 (ASP) 
                 0.21 
                   
                   
                   
                   
               
               
                 4 
                   
                 Lens 2 
                 −9.8 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.632 
                 23 
                 −11.35 
               
               
                 5 
                   
                   
                 27.08 
                 (ASP) 
                 0.16 
                   
                   
                   
                   
               
               
                 6 
                   
                 Lens 3 
                 −1.11 
                 (ASP) 
                 0.42 
                 Plastic 
                 1.544 
                 56 
                 9.76 
               
               
                 7 
                   
                   
                 −1.04 
                 (ASP) 
                 0.20 
                   
                   
                   
                   
               
               
                 8 
                   
                 Lens 4 
                 0.95 
                 (ASP) 
                 0.53 
                 Plastic 
                 1.544 
                 56 
                 −132.45 
               
               
                 9 
                   
                   
                 0.75 
                 (ASP) 
                 0.75 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                   
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                   
                 Infinity 
                 0.05 
                   
                   
                   
                   
               
               
                 12 
                   
                 Image 
                 Infinity 
                 — 
               
               
                   
               
             
          
           
               
                 TABLE 16 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −12.5021 
                 50 
                 50 
                 −27.2641 
               
               
                 A4 = 
                 0.3360 
                 −0.4388 
                 −0.6263 
                 0.2909 
               
               
                 A6 = 
                 −0.8905 
                 −0.8088 
                 −0.7149 
                 −1.6388 
               
               
                 A8 = 
                 −2.1165 
                 1.3572 
                 −4.0134 
                 2.2328 
               
               
                 A10 = 
                 16.3919 
                 −4.3477 
                 26.6517 
                 0.4410 
               
               
                 Al2 = 
                 −54.0629 
                 11.5904 
                 −25.9038 
                 −0.7969 
               
               
                 A14 = 
                 56.9939 
                 −13.3273 
                 −6.5579 
                 −0.9487 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 −11.7605 
                 −1.0308 
                 −2.3531 
                 −1.9626 
               
               
                 A4 = 
                 0.4788 
                 0.1346 
                 −0.4062 
                 −0.3717 
               
               
                 A6 = 
                 −0.2663 
                 −0.2036 
                 0.1222 
                 0.2532 
               
               
                 A8 = 
                 −0.9284 
                 0.5626 
                 0.0150 
                 −0.1182 
               
               
                 A10 = 
                 0.4750 
                 0.1472 
                 −0.0086 
                 0.0325 
               
               
                 A12 = 
                 2.9267 
                 −0.7024 
                 −0.0007 
                 −0.0047 
               
               
                 A14 = 
                 −3.2343 
                 0.3070 
                 0.0003 
                 0.0003 
               
               
                   
               
             
          
         
       
     
     Referring to  FIG. 9A , which shows an optical lens system cross-sectional view in accordance with a ninth embodiment of the present invention, and  FIG. 9B  shows the spherical aberration curves, the astigmatic field curves, and the distortion curve of the ninth embodiment of the present invention. An optical lens system in accordance with the ninth embodiment of the present invention comprises, in order from the object side to the image side: 
     A stop  900 . 
     A first lens element  910  with a positive refractive power made of plastic has a convex object-side surface  911  and a convex image-side surface  912 , and the object-side surface  911  and the image-side surface  912  of the first lens element  910  are aspheric. 
     A second lens element  920  with a negative refractive power made of plastic has a concave object-side surface  921  and a concave image-side surface  922 , and the object-side surface  921  and the image-side surface  922  of the second lens element  920  are aspheric. 
     A third lens element  930  with a positive refractive power made of plastic has a concave object-side surface  931  and a convex image-side surface  932 , and the object-side surface  931  and the image-side surface  932  of the third lens element  930  are aspheric. 
     A fourth lens element  940  with a positive refractive power made of plastic has a convex object-side surface  941  and a concave image-side surface  942 , the object-side surface  941  and the image-side surface  942  of the fourth lens element  940  are aspheric, and at least one inflection point is formed on each of the object-side surface  941  and the image-side surface  942  of the fourth lens element  940 . 
     An IR filter  950  made of glass is located between the image-side surface  942  of the fourth lens element  940  and an image plane  990  and has no influence on the focal length of the optical lens system. 
     The equation for the aspheric surface profiles of the ninth embodiment is expressed as follows: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 h 
                 ) 
               
             
             = 
             
               
                 
                   ch 
                   2 
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           h 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   h 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   h 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   h 
                   8 
                 
               
               + 
               
                 
                   A 
                   10 
                 
                 ⁢ 
                 
                   h 
                   10 
                 
               
               + 
               
                 
                   A 
                   12 
                 
                 ⁢ 
                 
                   h 
                   12 
                 
               
               + 
               
                 
                   A 
                   14 
                 
                 ⁢ 
                 
                   h 
                   14 
                 
               
               + 
               … 
             
           
         
       
     
     z represents the distance of a point on the aspheric surface at a height h from the optical axis relative to a plane perpendicular to the optical axis at the vertex of the aspheric surface; 
     c is a paraxial curvature equal to 1/R (R: a paraxial radius of curvature); 
     h represents a vertical distance from the point on the curve of the aspheric surface to the optical axis; 
     k represents the conic constant; 
     A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. 
     In the ninth embodiment of the present optical lens system, the focal length of the optical lens system is f, and it satisfies the condition: 
     f=2.28. 
     In the ninth embodiment of the present optical lens system, the f-number of the optical lens system is Fno, and it satisfies the condition: 
     Fno=2.5. 
     In the ninth embodiment of the present optical lens system, half of the maximum field of view of the present optical lens system is HFOV, it satisfies the relation: HFOV=44.9; and the maximum field of view of the present optical lens system is FOV, it satisfies the condition: FOV=89.8. 
     In the ninth embodiment of the present optical lens system, the focal length of the first lens element  910  is f1, the focal length of the optical lens system is f, and they satisfy the condition: 
     f1/f=1.11. 
     In the ninth embodiment of the present optical lens system, the maximum effective diameter of the image-side surface  932  of the third lens element  930  is CA_L3S2, the maximum effective diameter of the image-side surface  942  of the fourth lens element  940  is CA_L4S2, and they satisfy the condition: CA_L3S2/CA_L4S2=0.49. 
     In the ninth embodiment of the present optical lens system, a distance between the image-side surface  932  of the third lens element  930  and the object-side surface  941  of the fourth lens element  940  along the optical axis  991  is Dr7r8, a distance from the object-side surface  911  of the first lens element  910  to the image plane  990  along the optical axis  991  is TL, and they satisfy the condition: Dr7r8×100/TL=4.92. 
     In the ninth embodiment of the present optical lens system, a distance between the object-side surface  921  of the second lens element  920  and the object-side surface  931  of the third lens element  930  along the optical axis  991  is Dr4r6, a distance from the object-side surface  911  of the first lens element  910  to the image plane  990  along the optical axis  991  is TL, and they satisfy the condition: Dr4r6/TL=0.13. 
     In the ninth embodiment of the present optical lens system, a radius of curvature of the object-side surface  921  of the second lens element  920  is R4, a radius of curvature of the image-side surface  922  of the second lens element  920  is R5, and they satisfy the condition: (R4−R5)/(R4+R5)=−1.55. 
     In the ninth embodiment of the present optical lens system, the focal length of the third lens element  930  is f3, the focal length of the optical lens system is f, and they satisfy the condition: f3/f=3.29. 
     In the ninth embodiment of the present optical lens system, an Abbe number of the third lens element  930  is Vd3, an Abbe number of the second lens element  920  is Vd2, and they satisfy the condition: Vd3−Vd2=33.00. 
     In the ninth embodiment of the present optical lens system, a distance from the object-side surface  921  of the second lens element  920  to the image-side surface  932  of the third lens element  930  along the optical axis  991  is Dr4r7, the focal length of the optical lens system is f, and they satisfy the condition: Dr4r7/f=0.37. 
     In the ninth embodiment of the present optical lens system, the distance from the object-side surface  911  of the first lens element  910  to the image plane  990  along the optical axis  991  is TL, and a half of the maximum image height of the present optical lens system is ImgH, and they satisfy the condition: TL/ImgH=1.39. 
     The detailed optical data of the ninth embodiment is shown in table 17, and the aspheric surface data is shown in table 18, wherein the units of the radius of curvature, the thickness and the focal length in table 17 are expressed in mm, and in table 18, k represents the conic constant, and A 4 , A 6 , A 8 , A 10 , A 12 , A 14  . . . : represent the high-order aspheric coefficients. In the tables 17 and 18, the surfaces 2 and 3 represent the object-side surface  911  and the image-side surface  912  of the first lens element  910 , respectively, the surfaces 4 and 5 represent the object-side surface  921  and the image-side surface  922  of the second lens element  920 , respectively, the surfaces 6 and 7 represent the object-side surface  931  and the image-side surface  932  of the third lens element  930 , respectively, and the surfaces 8 and 9 represent the object-side surface  941  and the image-side surface  942  of the fourth lens element  940 , respectively. 
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 TABLE 17 
               
               
                 (Embodiment 9) 
               
               
                 f (focal length) = 2.28 mm, Fno = 2.5, HFOV= 44.9 deg. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Focal 
               
               
                 Surface # 
                   
                 Curvature Radius 
                 Thickness 
                 Material 
                 index 
                 Abbe 
                 length 
               
               
                   
               
             
          
           
               
                 0 
                   
                 Object 
                 Infinity 
                 Infinity 
                   
                   
                   
                   
               
               
                 1 
                   
                 Stop 
                 Infinity 
                 0.00 
                   
                   
                   
                   
               
             
          
           
               
                 2 
                 (STOP) 
                 Lens 1 
                 1.47 
                 (ASP) 
                 0.41 
                 Plastic 
                 1.544 
                 56  
                 2.53 
               
               
                 3 
                   
                   
                 −18.62 
                 (ASP) 
                 0.21 
                   
                   
                   
                   
               
               
                 4 
                   
                 Lens 2 
                 −6.14 
                 (ASP) 
                 0.25 
                 Plastic 
                 1.632 
                 23 
                 −7.97 
               
               
                 5 
                   
                   
                 28.51 
                 (ASP) 
                 0.15 
                   
                   
                   
                   
               
               
                 6 
                   
                 Lens 3 
                 −1.10 
                 (ASP) 
                 0.43 
                 Plastic 
                 1.544 
                 56 
                 7.50 
               
               
                 7 
                   
                   
                 −0.99 
                 (ASP) 
                 0.16 
                   
                   
                   
                   
               
               
                 8 
                   
                 Lens 4 
                 0.92 
                 (ASP) 
                 0.53 
                 Plastic 
                 1.544 
                 56  
                 100.00 
               
               
                 9 
                   
                   
                 0.75 
                 (ASP) 
                 0.79 
                   
                   
                   
                   
               
             
          
           
               
                 10 
                   
                 IR-filter 
                 Infinity 
                 0.21 
                 Glass 
                 1.517 
                 64 
                 — 
               
               
                 11 
                   
                   
                 Infinity 
                 0.05 
                   
                   
                   
                   
               
               
                 12 
                   
                 Image 
                 Infinity 
                 — 
               
               
                   
               
             
          
           
               
                 TABLE 18 
               
               
                 Aspheric Coefficients 
               
             
          
           
               
                 Surface # 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
               
                 k = 
                 −12.4765 
                 −150 
                 35.38507 
                 150.0000 
               
               
                 A4 = 
                 0.3488 
                 −0.4202 
                 −0.6175 
                 0.3006 
               
               
                 A6 = 
                 −0.9049 
                 −0.8163 
                 −0.7122 
                 −1.6340 
               
               
                 A8 = 
                 −1.9941 
                 1.2818 
                 −3.8839 
                 2.1725 
               
               
                 A10 = 
                 15.9424 
                 −4.3731 
                 26.8486 
                 0.3217 
               
               
                 A12 =  
                 −54.0629 
                 11.5906 
                 −26.2274 
                 −0.8158 
               
               
                 A14 = 
                 56.9939 
                 −13.3273 
                 −6.5582 
                 −0.4543 
               
               
                   
               
               
                 Surface # 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
               
                 k = 
                 −12.6153 
                 −0.9810 
                 −2.7816 
                 −2.0940 
               
               
                 A4 = 
                 0.4972 
                 0.1288 
                 −0.3364 
                 −0.3420 
               
               
                 A6 = 
                 −0.3012 
                 −0.1749 
                 0.1128 
                 0.2424 
               
               
                 A8 = 
                 −0.9200 
                 0.5722 
                 0.0108 
                 −0.1168 
               
               
                 A10 = 
                 0.4425 
                 0.1454 
                 −0.0077 
                 0.0332 
               
               
                 A12 = 
                 2.8539 
                 −0.7102 
                 −0.0007 
                 −0.0048 
               
               
                 A14 = 
                 −3.0829 
                 0.2891 
                 0.0003 
                 0.0003 
               
               
                   
               
             
          
         
       
     
     It is to be noted that the tables 1-18 show different data from the different embodiments, however, the data of the different embodiments are obtained from experiments. Therefore, any product of the same structure is deemed to be within the scope of the present invention even if it uses different data. Table 19 lists the relevant data for the various embodiments of the present invention. 
     
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 Embodi- 
                 Embodi- 
                 Embodi- 
                 Embodi- 
                 Embodi- 
                 Embodi- 
                 Embodi- 
                 Embodi- 
                 Embodi- 
               
               
                   
                 ment 
                 ment 
                 ment 
                 ment 
                 ment 
                 ment 
                 ment 
                 ment 
                 ment 
               
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 f 
                 2.18 
                 2.20 
                 2.27 
                 2.35 
                 2.29 
                 2.24 
                 2.32 
                 2.32 
                 2.28 
               
               
                 Fno 
                 2.50 
                 2.50 
                 2.50 
                 2.50 
                 2.50 
                 2.50 
                 2.50 
                 2.50 
                 2.50 
               
               
                 HFOV 
                 46.10 
                 45.90 
                 45.00 
                 44.00 
                 44.70 
                 45.30 
                 45.40 
                 44.90 
                 44.90 
               
               
                 f1/f 
                 1.14 
                 1.18 
                 1.19 
                 1.38 
                 1.13 
                 1.24 
                 1.18 
                 1.10 
                 1.11 
               
               
                 CA_L3S2/ 
                 0.55 
                 0.51 
                 0.55 
                 0.56 
                 0.58 
                 0.59 
                 0.48 
                 0.50 
                 0.49 
               
               
                 CA_L4S2 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Dr7r8x100/ 
                 2.80 
                 4.36 
                 2.80 
                 5.34 
                 6.17 
                 2.57 
                 9.36 
                 6.37 
                 4.92 
               
               
                 TL 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Dr4r6/TL 
                 0.14 
                 0.14 
                 0.14 
                 0.16 
                 0.10 
                 0.12 
                 0.13 
                 0.13 
                 0.13 
               
               
                 (R4 − R5)/  
                 1.92 
                 1.61 
                 2.87 
                 0.29 
                 −2.71 
                 0.84 
                 1.17 
                 −2.13 
                 −1.55 
               
               
                 (R4 + R5) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 f3/f 
                 0.53 
                 0.61 
                 0.68 
                 0.56 
                 0.48 
                 0.39 
                 1.44 
                 4.21 
                 3.29 
               
               
                 Vd3 − Vd2 
                 34.00 
                 34.00 
                 34.00 
                 34.00 
                 34.00 
                 34.00 
                 33.00 
                 33.00 
                 33.00 
               
               
                 Dr4r7/f 
                 0.49 
                 0.49 
                 0.46 
                 0.51 
                 0.48 
                 0.53 
                 0.38 
                 0.36 
                 0.37 
               
               
                 TL/ImgH 
                 1.41 
                 1.41 
                 1.41 
                 1.41 
                 1.41 
                 1.41 
                 1.36 
                 1.36 
                 1.39 
               
               
                 FOV 
                 92.20 
                 91.80 
                 90.00 
                 88.00 
                 89.40 
                 90.60 
                 90.80 
                 89.80 
                 89.80 
               
               
                   
               
             
          
         
       
     
     While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.