Patent Publication Number: US-2020285135-A1

Title: Lens Apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a lens apparatus. 
     Description of the Related Art 
     The current development trend of a projector is toward high brightness and high resolution. Additionally, the projector is developed to have zoom capability in accordance with different application requirements, so that a lens apparatus therein is developed to have large aperture, high resolution and zoom capability. However, the known lens apparatus can&#39;t satisfy such requirements. Therefore, a lens apparatus needs a new structure in order to meet the requirements of large aperture, high resolution and zoom capability at the same time. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a lens apparatus to solve the above problems. The lens apparatus of the invention is provided with characteristics of a decreased F-number, an increased resolution, and a capability to zoom, and still has a good optical performance. 
     The lens apparatus in accordance with the invention includes a first lens group, a second lens group, a third lens group and a fourth lens group. The first lens group includes a first lens with negative refractive power and a second lens with negative refractive power, wherein the first lens includes a convex surface facing an image side and a concave surface facing an objective side. The second lens group includes a third lens with positive refractive power. The third lens group includes a fourth lens with positive refractive power. The fourth lens group includes a fifth lens with negative refractive power, a sixth lens with positive refractive power and a seventh lens with positive refractive power, wherein the seventh lens includes a convex surface facing the image side. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are arranged in order from the image side to the objective side along an optical axis. The lens apparatus satisfies: −2.28&lt;f LG1 /f&lt;−0.59, where f is an effective focal length of the lens apparatus, and f LG1  is an effective focal length of the first lens group. 
     In another embodiment, the second lens includes a concave surface facing the objective side, the fourth lens includes a convex surface facing the image side, the fifth lens includes a concave surface facing the image side, the sixth lens includes a convex surface facing the image side, and the seventh lens includes a convex surface facing the objective side. 
     In yet another embodiment, the second lens includes a convex surface or a concave surface facing the image side, the third lens includes a convex surface or a concave surface facing the image side, the fourth lens includes a convex surface or a flat surface facing the objective side, the fifth lens includes a concave surface or a flat surface facing the objective side, and the sixth lens includes a convex surface or a flat surface facing the objective side. 
     In another embodiment, the first lens group is with negative refractive power and the fourth lens group is with positive refractive power. 
     In yet another embodiment, the second lens comprises a convex surface or a concave surface facing the image side; the third lens comprises a convex surface or a concave surface facing the image side; the fourth lens comprises a convex surface or a flat surface facing the objective side; the fifth lens comprises a concave surface or a flat surface facing the objective side; and the sixth lens comprises a convex surface or a flat surface facing the objective side. 
     In another embodiment, the first lens group further comprises an eighth lens disposed between the image side and the first lens, and the eighth lens is with positive refractive power and comprises a convex surface facing the image side and a concave surface facing the objective side. 
     In yet another embodiment, the second lens group is with positive refractive power, and the third lens group is with positive refractive power. 
     In another embodiment, the second lens comprises a concave surface facing the objective side, and comprises a convex surface or another concave surface facing the image side; the third lens comprises a convex surface or a concave surface facing the image side; the fourth lens comprises a convex surface facing the image side, and comprises another convex surface or a flat surface facing the objective side; the fifth lens comprises a concave surface facing the image side, and comprises another concave surface or a flat surface facing the objective side; the sixth lens comprises a convex surface facing the image side, and comprises another convex surface or a flat surface facing the objective side; and the seventh lens comprises a convex surface facing the objective side. 
     In yet another embodiment, the first lens group further comprises an eighth lens disposed between the image side and the first lens, and the eighth lens is with positive refractive power and comprises a convex surface facing the image side and a concave surface facing the objective side. 
     In another embodiment, the lens apparatus satisfies − 9 . 6 ≤TTL/f LG1 ≤−5.19, 29 mm&lt;f 1 +f 3 &lt;90 mm, or 1.77&lt;f 3 /f&lt;12 where f LG1  is the effective focal length of the first lens group, TTL is a distance between an image side surface of a lens closest to the image side and an objective side surface of the seventh lens along the optical axis, f is the effective focal length of the lens apparatus, f 3  is a focal length of the third lens, and f 1  is a focal length of the first lens. 
     In yet another embodiment, the lens apparatus satisfies 2≤Vd 6 /Vd 3 ≤4, 8.16 mm&lt;|T S1ST −T S3S10 &lt;|22.92 mm, 5.22&lt;T S1ST /T STS15 &lt;8.23, or −2.54&lt;T7ob/f LG1 &lt;−1.3 where Vd 3  is an Abbe number of the third lens, Vd 6  is an Abbe number of the sixth lens, T S1ST  is a distance between an image side surface of a lens closest to the image side and the stop along the optical axis, T S3S10  is a distance between an image side surface of the second lens and an image side surface of the fifth lens along the optical axis, T STS15  is a distance between the stop and an objective side surface of the seventh lens along the optical axis, f LG1  is the effective focal length of the first lens group, and T7ob is a distance between an objective side surface of the seventh lens and an object along the optical axis. 
     In another embodiment, at least one of the first lens group, the second lens group, the third lens group and the fourth lens group is movable along the optical axis, the fifth lens and the sixth lens are cemented together, and the lens apparatus is a projection lens. 
     In yet another embodiment, the lens apparatus satisfies 2≤Vd 6 /Vd 3 ≤4, where Vd 3  is an Abbe number of the third lens, and Vd 6  is an Abbe number of the sixth lens. 
     In another embodiment, the lens apparatus satisfies 29 mm&lt;|f 1 +f 3 &lt;90 mm; and 1.77&lt;f 3 /f&lt;12, where f is the effective focal length of the lens apparatus, f 3  is a focal length of the third lens, and f 1  is a focal length of the first lens. 
     In yet another embodiment, the lens apparatus satisfies −9.6≤TTL/f LG1 ≤−5.19, where f LG1  is the effective focal length of the first lens group, and TTL is a distance between an image side surface of a lens closest to the image side and an objective side surface of the seventh lens along the optical axis. 
     In another embodiment, the fourth lens group further comprises a stop disposed between the fourth lens and the fifth lens, and the lens apparatus satisfies 8.16 mm&lt;|T S1ST −T S3S10 |&lt;22.92 mm, or 5.22&lt;T S1ST  T STS15 &lt;8.23, where T S1ST  is a distance between an image side surface of a lens closest to the image side and the stop along the optical axis, T S3S10  is a distance between an image side surface of the second lens and an image side surface of the fifth lens along the optical axis, and T STS15  is a distance between the stop and an objective side surface of the seventh lens along the optical axis. 
     In yet another embodiment, the lens apparatus satisfies −2.54&lt;T7ob/f LG1 &lt;−1.3, where f LG1  is the effective focal length of the first lens group, and T7ob is a distance between an objective side surface of the seventh lens and an object along the optical axis. 
     In another embodiment, at least one of the first lens group, the second lens group, the third lens group and the fourth lens group is movable along the optical axis, the fifth lens and the sixth lens are cemented together, and the lens apparatus is a projection lens. 
     In yet another embodiment, the lens apparatus satisfies −9.6≤TTL/f LG1 −5.19, where f LG1  is the effective focal length of the first lens group, and TTL is a distance between an image side surface of a lens closest to the image side and an objective side surface of the seventh lens along the optical axis. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a lens layout and optical path diagram of a lens apparatus in accordance with a first embodiment of the invention at a wide-angle end; 
         FIG. 2A  depicts a field curvature diagram of the lens apparatus of  FIG. 1  at the wide-angle end; 
         FIG. 2B  is a distortion diagram of the lens apparatus of  FIG. 1  at the wide-angle end; 
         FIG. 2C  is a relative illumination diagram of the lens apparatus of  FIG. 1  at the wide-angle end; 
         FIG. 2D  is a modulation transfer function diagram of the lens apparatus of  FIG. 1  at the wide-angle end; 
         FIG. 2E  is a modulation transfer function diagram of the lens apparatus of  FIG. 1  at a telephoto end; 
         FIG. 2F  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 1  at the wide-angle end; 
         FIG. 2G  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 1  at the telephoto end; 
         FIG. 3  is a lens layout and optical path diagram of a lens apparatus in accordance with a second embodiment of the invention at a wide-angle end; 
         FIG. 4A  depicts a field curvature diagram of the lens apparatus of  FIG. 3  at the wide-angle end; 
         FIG. 4B  is a distortion diagram of the lens apparatus of  FIG. 3  at the wide-angle end; 
         FIG. 4C  is a relative illumination diagram of the lens apparatus of  FIG. 3  at the wide-angle end; 
         FIG. 4D  is a modulation transfer function diagram of the lens apparatus of  FIG. 3  at the wide-angle end; 
         FIG. 4E  is a modulation transfer function diagram of the lens apparatus of  FIG. 3  at a telephoto end; 
         FIG. 4F  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 3  at the wide-angle end; 
         FIG. 4G  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 3  at the telephoto end; 
         FIG. 5  is a lens layout and optical path diagram of a lens apparatus in accordance with a third embodiment of the invention at a wide-angle end; 
         FIG. 6A  depicts a field curvature diagram of the lens apparatus of  FIG. 5  at the wide-angle end; 
         FIG. 6B  is a distortion diagram of the lens apparatus of  FIG. 5  at the wide-angle end; 
         FIG. 6C  is a relative illumination diagram of the lens apparatus of  FIG. 5  at the wide-angle end; 
         FIG. 6D  is a modulation transfer function diagram of the lens apparatus of  FIG. 6  at the wide-angle end; 
         FIG. 6E  is a modulation transfer function diagram of the lens apparatus of  FIG. 5  at a telephoto end; 
         FIG. 6F  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 5  at the wide-angle end; 
         FIG. 6G  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 5  at the telephoto end; 
         FIG. 7  is a lens layout and optical path diagram of a lens apparatus in accordance with a fourth embodiment of the invention at a wide-angle end; 
         FIG. 8A  depicts a field curvature diagram of the lens apparatus of  FIG. 7  at the wide-angle end; 
         FIG. 8B  is a distortion diagram of the lens apparatus of  FIG. 7  at the wide-angle end; 
         FIG. 8C  is a relative illumination diagram of the lens apparatus of  FIG. 7  at the wide-angle end; 
         FIG. 8D  is a modulation transfer function diagram of the lens apparatus of  FIG. 7  at the wide-angle end; 
         FIG. 8E  is a modulation transfer function diagram of the lens apparatus of  FIG. 7  at a telephoto end; 
         FIG. 8F  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 7  at the wide-angle end; 
         FIG. 8G  is a through focus modulation transfer function diagram of the lens apparatus of  FIG. 7  at the telephoto end. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A lens apparatus in accordance with many embodiments of the invention includes a first lens group, a second lens group, a third lens group and a fourth lens group. The first lens group includes a first lens with negative refractive power and a second lens with negative refractive power, and the first lens includes a convex surface facing an image side and a concave surface facing an objective side. The second lens group includes a third lens with positive refractive power, and the third lens includes a convex surface facing the objective side. The third lens group includes a fourth lens with positive refractive power. The fourth lens group includes a fifth lens with negative refractive power, a sixth lens with positive refractive power and a seventh lens with positive refractive power. The seventh lens includes a convex surface facing the image side. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are arranged in order from the image side to the objective side along an optical axis. 
     In one or more embodiments of the invention, the first lens group is with negative refractive power. 
     In one or more embodiments of the invention, the first lens group can include more lenses. For example, the first lens group can further include an eighth lens with positive refractive power and disposed between the image side and the first lens. 
     In one or more embodiments of the invention, the second lens group is with positive refractive power. 
     In one or more embodiments of the invention, the third lens group is with positive refractive power. 
     In one or more embodiments of the invention, the fourth lens group is with positive refractive power. 
     In one or more embodiments of the invention, the fourth lens group can further include a stop disposed between the third lens group and the fifth lens. 
     In one or more embodiments of the invention, at least one lens of at least one of the first to fourth lens groups can includes a spherical surface. 
     In one or more embodiments of the invention, at least one lens of at least one of the first to fourth lens groups can includes at least one aspheric surface. The aspheric surface sag z of each lens can be calculated by the following formula: 
         z=ch   2 /{1+[1−( k+ 1) c   2   h   2 ] 1/2   }+Ah   4   +Bh   6   +Ch   8   +Dh   10   +Eh   12   +Fh   14   +Gh   16  
 
     where c is a curvature, h is a vertical distance from any points on lens surface to the optical axis, k is a conic constant, and A-G are aspheric coefficients. 
     In one or more embodiments of the invention, all of the lenses of the first lens group are made of glass material, or parts of the lenses are made of glass material. Alternatively, the aspheric lenses in the lens apparatus are made of glass material or plastic material. 
     In one or more embodiments of the invention, the lens apparatus is a zoom lens or a prime lens. 
     The lens apparatus of the invention satisfies at least one of the following conditions: 
       −2.28&lt; f   LG1   /f&lt;− 0.59  (1)
 
       1.5≤ Vd   6   /Vd   3 ≤4.5  (2)
 
       29 mm&lt;| f   1   +f   3 |&lt;90 mm  (3)
 
       −44.4 mm&lt; f   1   +f   3 &lt;90 mm  (4)
 
       1.77&lt; f   3   /f&lt; 12  (5)
 
       −9.6≤TTL/ f   LG1 ≤−5.19  (6)
 
       8.16 mm&lt;| T   S1ST   −T   S3S10 |&lt;22.92 mm  (7)
 
       8.16 mm&lt; T   S1ST   −T   S3S10 &lt;22.92 mm  (8)
 
       5.22&lt; T   S1ST   /T   STS15 &lt;8.23  (9)
 
       −2.54&lt; T 7 ob/f   LG1 &lt;−1.3  (10)
         wherein f is an effective focal length of the lens apparatus, f LG1  is an effective focal length of the first lens group, f 1  is a focal length of the first lens, f 3  is a focal length of the third lens, Vd 3  is an Abbe number of the third lens, Vd 6  is an Abbe number of the sixth lens, TTL is a distance between an image side surface of a lens closest to the image side and an objective side surface of the seventh lens along the optical axis, T S1ST  is a distance between the image side surface of the lens closest to the image side and the stop along the optical axis, T S3S10  is a distance between an image side surface of the second lens and an image side surface of the fifth lens along the optical axis, T STS15  is a distance between the stop and the objective side surface of the seventh lens along the optical axis, and T7ob is a distance between the objective side surface of the seventh lens and an object along the optical axis.       

     By such arrangement, the lens apparatus can be effectively improved to have a reduced diameter, increased brightness, increased resolution and corrected aberration. 
     In the above-described conditions, if the condition (1) is modified to be −1.9&lt;f LG1 /f&lt;−0.74, then a better effect is obtained. 
     In the above-described conditions, if the condition (2) is modified to be 2≤Vd 6 /Vd 3 ≤4 or 2.4≤Vd 6 /Vd 3 ≤3.6, then a better effect is obtained. 
     In the above-described conditions, if the condition (3) is modified to be 37 mm≤f 1 +f 3 ≤75 mm, than a better effect is obtained. 
     In the above-described conditions, if the condition (4) is modified to be −37 mm≤f 1 +f 3 ≤75 mm, then a better effect is obtained. 
     In the above-described conditions, if the condition (5) is modified to be 2.21≤f 3 /f&lt;10.82, then a better effect is obtained. 
     In the above-described conditions, if the condition (6) is modified to be −8≤TTL/f LG1 ≤−5.19, then a better effect is obtained. 
     In the above-described conditions, if the condition (7) is modified to be 10.2 mm≤|T S1ST −T S3S10 |≤19.1 mm, then a better effect is obtained. 
     In the above-described conditions, if the condition (8) is modified to be 10.2 mm≤T S1ST −T S3S10 ≤19.1 mm, then a better effect is obtained. 
     In the above-described conditions, if the condition (9) is modified to be 6≤T S1ST /T STS15 ≤7, then a better effect is obtained. 
     A lens apparatus in accordance with a first embodiment of the invention is described herein. Referring to  FIG. 1 , a lens apparatus  1  includes a first lens group LG 1   1 , a second lens group LG 1   2 , a third lens group LG 1   3 , a fourth lens group LG 1   4 , an optical filter OF 1  and a cover glass CG 1 . The first lens group LG 1   1  is with negative refractive power and includes a first lens L 11  and a second lens L 12 . The second lens group LG 1   2  is with positive refractive power and includes a third lens L 13 . The third lens group LG 1   3  is with positive refractive power and includes a fourth lens L 14 . The fourth lens group LG 1   4  is with positive refractive power and includes a stop ST 1 , a fifth lens L 15 , a sixth lens L 16  and a seventh lens L 17 . The first lens L 11 , the second lens L 12 , the third lens L 13 , the fourth lens L 14 , the stop ST 1 , the fifth lens L 15 , the sixth lens L 16  and the seventh lens L 17  are arranged in order from an image side to an objective side along an optical axis OA 1 . 
     The first lens L 11  can be, for example, with negative refractive power. The first lens L 11  can be, for example, a meniscus lens, an image side surface S 11  thereof can be, for example, a convex surface, and an objective side surface S 12  thereof can be, for example, a concave surface. The image side surface S 11  can be, for example, a spherical surface, and the objective side surface S 12  can be, for example, a spherical surface. 
     The second lens L 12  can be, for example, with negative refractive power. The second lens L 12  can be, for example, a meniscus lens, an image side surface S 13  thereof can be, for example, a convex surface, and an objective side surface S 14  thereof can be, for example, a concave surface. The image side surface S 13  can be, for example, an aspheric surface, and the objective side surface S 14  can be, for example, an aspheric surface. 
     The third lens L 13  can be, for example, with positive refractive power. The third lens L 13  can be, for example, a meniscus lens, an image side surface S 15  thereof can be, for example, a concave surface, and an objective side surface S 16  thereof can be, for example, a convex surface. The image side surface S 15  can be, for example, a spherical surface, and the objective side surface S 16  can be, for example, a spherical surface. 
     The fourth lens L 14  can be, for example, with positive refractive power. The fourth lens L 14  can be, for example, a biconvex lens, an image side surface S 17  thereof can be, for example, a convex surface, and an objective side surface S 18  thereof can be, for example, a convex surface. The image side surface S 17  can be, for example, a spherical surface, and the objective side surface S 18  can be, for example, a spherical surface. 
     The fifth lens L 15  can be, for example, with negative refractive power. The fifth lens L 15  can be, for example, a biconcave lens, an image side surface S 110  thereof can be, for example, a concave surface, and an objective side surface S 111  thereof can be, for example, a concave surface. The image side surface S 110  can be, for example, a spherical surface, and the objective side surface S 111  can be, for example, a spherical surface. 
     The sixth lens L 16  can be, for example, with positive refractive power. The sixth lens L 16  can be, for example, a planoconvex lens, an image side surface S 112  thereof can be, for example, a convex surface, and an objective side surface S 113  thereof can be, for example, a flat surface. The image side surface S 112  can be, for example, a spherical surface, and the objective side surface S 113  can be, for example, a spherical surface. 
     The seventh lens L 17  can be, for example, with positive refractive power. The seventh lens L 17  can be, for example, a biconvex lens, an image side surface S 114  thereof can be, for example, a convex surface, and an objective side surface S 115  thereof can be, for example, a convex surface. The image side surface S 114  can be, for example, an aspheric surface, and the objective side surface S 115  can be, for example, an aspheric surface. 
     An objective side surface S 116  of the optical filter OF 1  can be, for example, a flat surface, and an image side surface S 117  of the optical filter OF 1  can be, for example, a flat surface. 
     An objective side surface S 118  of the cover glass CG 1  can be, for example, a flat surface, and an image side surface S 119  of the cover glass CG 1  can be, for example, a flat surface. 
     By the design of the above lenses, the stop ST 1  and at least one of the conditions (1)-(10) satisfied, the lens apparatus  1  is able to have the lens diameter effectively reduced, brightness and resolution effectively increased, and aberration effectively corrected. 
     During operation, light from an object IS 1  travels to the image side finally. By changing a distance D 1   G1G2  between the first lens group LG 1   1  and the second lens group LG 1   2 , a distance D 1   G2G3  between the second lens group LG 1   2  and the third lens group LG 1   3  and a distance D 1   G3G4  between the third lens group LG 1   3  and the fourth lens group LG 1   4 , the effective focal length of the lens apparatus  1  can be adjusted. When the first lens group LG 1   1  is moved along the optical axis OA 1  to change the distance D 1   G1G2  and/or the distance D 1   G2G3 , the lens apparatus  1  is focusing. In order to achieve the above purposes and effectively enhance the optical performance, the lens apparatus  1  in accordance with the first embodiment of the invention is provided with the optical specifications shown in Table 1, which include curvature of each lens surface, distance between adjacent surface, refractive index of each lens, Abbe number of each lens and focal length of each lens. Table 1 shows that the lens apparatus  1  at a wide-angle end has the effective focal length equal to 9.7 mm and F-number equal to 1.94, and the lens apparatus  1  at a telephoto end has the effective focal length equal to 11.6 mm and F-number equal to 2.04. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Focal  
                   
               
               
                 Surface  
                 Curvature  
                 Distance  
                   
                   
                 Length  
                   
               
               
                 Number  
                 (mm −1 )  
                 (mm)  
                 Nd  
                 Vd  
                 (mm)  
                 Remark 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S11  
                 0.03  
                 3.7  
                 1.74  
                 45.00  
                 −55.531  
                 The First  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L11  
               
               
                 S12  
                 0.06  
                 8.1  
                   
                   
                   
                   
               
               
                 S13  
                 0.02  
                 2.2  
                 1.60  
                 60.00  
                 −29.056  
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L12  
               
               
                 S14  
                 0.08  
                 24.8  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 D1 G1G2    
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 21.0  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S15  
                 −0.02  
                 4.9  
                 1.76  
                 27.00  
                 104.935  
                 The Third  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L13  
               
               
                 S16  
                 −0.03  
                 21.3  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 D1 G2G3    
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 13.1  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S17  
                 0.04  
                 4.7  
                 1.62  
                 60.00  
                 33.214  
                 The Fourth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L14  
               
               
                 S18  
                 −0.01  
                 12.9  
                   
                   
                   
                   
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D1 G3G4    
               
               
                   
                   
                 14.5  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S19  
                 0.00  
                 1.6  
                   
                   
                   
                 The Stop  
               
               
                   
                   
                   
                   
                   
                   
                 ST1  
               
               
                 S110  
                 −0.05  
                 1.0  
                 1.75  
                 28.00  
                 −16.403  
                 The Fifth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L15  
               
               
                 S111  
                 0.03  
                 0.1  
                   
                   
                   
                   
               
               
                 S112  
                 0.06  
                 3.5  
                 1.50  
                 81.00  
                 33.33  
                 The Sixth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L16  
               
               
                 S113  
                 0.00  
                 2.0  
                   
                   
                   
                   
               
               
                 S114  
                 0.02  
                 4.2  
                 1.60  
                 60.00  
                 24.931  
                 The Seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L17  
               
               
                 S115  
                 −0.05  
                 17.9  
                   
                   
                   
                   
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                   
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 19.6  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S116  
                 0.00  
                 2.0  
                 1.52  
                 58.00  
                   
                 The Optical  
               
               
                   
                   
                   
                   
                   
                   
                 Filter OF1  
               
               
                 S117  
                 0.00  
                 1.0  
                   
                   
                   
                   
               
               
                 S118  
                 0.00  
                 1.1  
                 1.51  
                 62.00  
                   
                 The Cover  
               
               
                   
                   
                   
                   
                   
                   
                 Glass CG1  
               
               
                 S119  
                 0.00  
                 0.7 
               
               
                   
               
            
           
         
       
     
     Table 2 shows that the optical specifications of the aspheric surface of each lens shown in Table 1, wherein k is a conic constant and A-G are aspheric coefficients. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 S13 
                 S14 
                 S114 
                 S115 
               
               
                   
               
             
            
               
                 k 
                 −0.52 
                 −1.1 
                 7.35 
                 0.3 
               
               
                 A 
                  4.87E−06 
                  2.56E−05 
                 −7.16E−05  
                 2.59E−05 
               
               
                 B 
                 −2.45E−08 
                 −8.36E−08 
                 2.13E−07 
                 4.22E−07 
               
               
                 C 
                 −2.17E−10 
                 −3.14E−10 
                 −8.13E−09  
                 −9.26E−09  
               
               
                 D 
                  1.37E−12 
                  9.96E−13 
                 1.23E−10 
                 1.43E−10 
               
               
                 E 
                 −7.32E−16 
                 −2.34E−16 
                 0.00E+00 
                 0.00E+00 
               
               
                 F 
                 −1.51E−17 
                 −2.72E−17 
                 0.00E+00 
                 0.00E+00 
               
               
                 G 
                  3.48E−20 
                  1.06E−19 
                 0.00E+00 
                 0.00E+00 
               
               
                   
               
            
           
         
       
     
     Table 3 shows the optical specifications of the lens apparatus  1  and calculated values corresponding to the conditions (1)-(10). It can be seen from Table 3 that the lens apparatus  1  can meet requirements of the conditions (1)-(10). 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
             
            
               
                 f LG1   
                 −18.3 
                 mm 
                 TTL (The Wide- 
                 95 
                 mm 
                 TTL (The 
                 84.6 
                 mm 
               
               
                   
                   
                   
                 Angle End) 
                   
                   
                 Telephoto End) 
               
               
                 T S1ST  (The Wide- 
                 82.6 
                 mm 
                 T S1ST  (The 
                 72.2 
                 mm 
                 T S3S10  (The Wide- 
                 72.4 
                 mm 
               
               
                 Angle End) 
                   
                   
                 Telephoto End) 
                   
                   
                 Angle End) 
               
               
                 T S3S10  (The 
                 62 
                 mm 
                 T STS15  (The Wide- 
                 12.4 
                 mm 
                 T STS15  (The 
                 12.4 
                 mm 
               
               
                 Telephoto End) 
                   
                   
                 Angle End) 
                   
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 f LG1 /f (The Wide- 
                 −1.89 
                 f LG1 /f (The 
                 −1.58 
                 Vd 6 /Vd 3   
                 3 
               
               
                 Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 |f 1  + f 3 | 
                 49.40 
                 mm 
                 f 1  + f 3   
                 49.40 
                 mm 
                 f 3 /f (The Wide- 
                 10.82 
               
               
                   
                   
                   
                   
                   
                   
                 Angle End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 f 3 /f (The 
                  9.05 
                 TTL/f LG1  (The 
                 −5.19 
                 TTL/f LG1  (The 
                 −4.62 
               
               
                 Telephoto End) 
                   
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 |T S1ST  − T S3S10 | 
                 10.2 
                 mm 
                 |T S1ST  − T S3S10 | 
                 10.2 
                 mm 
                 T S1ST  − T S3S10   
                 10.2 
                 mm 
               
               
                 (The Wide-Angle 
                   
                   
                 (The Telephoto 
                   
                   
                 (The Wide-Angle 
               
               
                 End) 
                   
                   
                 End) 
                   
                   
                 End) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 T S1ST  − T S3S10 (The 
                 10.2 
                 mm 
                 T S1ST /T STS15  (The 
                  6.66 
                 T S1ST /T STS15   
                 5.82 
               
               
                 Telephoto End) 
                   
                   
                 Wide-Angle End) 
                   
                 (The Telephoto 
               
               
                   
                   
                   
                   
                   
                 End) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 T7ob (The Wide- 
                 22.7 
                 mm 
                 T7ob (The 
                 24.4 
                 mm 
                 T7ob/f LG1  (The 
                 −1.24 
               
               
                 Angle End) 
                   
                   
                 Telephoto End) 
                   
                   
                 Wide-Angle End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 T7ob/f LG1  (The 
                 −1.33 
                   
                   
                   
                   
               
               
                 Telephoto End) 
               
               
                   
               
            
           
         
       
     
     It can be seen from  FIGS. 2A-2G  that the lens apparatus  1  also meets the requirements of optical performance. 
     It can be seen from  FIG. 2A  that a field curvature of the lens apparatus  1  at the wide-angle end ranges from −0.03 mm to 0.06 mm. It can be seen from  FIG. 2B  that a distortion of the lens apparatus  1  at the wide-angle end ranges from −2.1% to 0%. It can be seen from  FIG. 2C  that a relative illumination of the lens apparatus  1  at the wide-angle end ranges from 0.92 to 1.0. It can be seen from  FIG. 2D  that a modulation transfer function of the lens apparatus  1  at the wide-angle end ranges from 0.49 to 1.0. It can be seen from  FIG. 2E  that a modulation transfer function of the lens apparatus  1  at the telephoto end ranges from 0.41 to 1.0. It can be seen from  FIG. 2F  that the modulation transfer function of the lens apparatus  1  at the wide-angle end ranges from 0 to 0.72 as a focus shift ranges between −0.05 mm and 0.05 mm. It can be seen from  FIG. 2G  that the modulation transfer function of the lens apparatus  1  at the telephoto end ranges from 0 to 0.67 as a focus shift ranges between −0.05 mm and 0.05 mm. 
     It is obvious that the field curvature and the distortion of the lens apparatus  1  can be corrected effectively, and the relative illumination, the resolution and the depth of focus of the lens apparatus  1  can meet the requirements. Therefore, the lens apparatus  1  is capable of good optical performance. 
     Referring to  FIG. 3 ,  FIG. 3  is a lens layout and optical path diagram of a lens apparatus in accordance with a second embodiment of the invention. A lens apparatus  2  includes a first lens group LG 2   1 , a second lens group LG 2   2 , a third lens group LG 2   3 , a fourth lens group LG 2   4 , an optical filter OF 2  and a cover glass CG 2 . The first lens group LG 2   1  includes a first lens L 21  and a second lens L 22 . The second lens group LG 2   2  includes a third lens L 23 . The third lens group LG 2   3  includes a fourth lens L 24 . The fourth lens group LG 2   4  includes a stop ST 2 , a fifth lens L 25 , a sixth lens L 26  and a seventh lens L 27 . The first lens L 21 , the second lens L 22 , the third lens L 23 , the fourth lens L 24 , the stop ST 2 , the fifth lens L 25 , the sixth lens L 26  and the seventh lens L 27  are arranged in order from an image side to an objective side along an optical axis OA 2 . 
     The difference between the second embodiment and the first embodiment as shown in  FIG. 1  is described herein. An image side surface S 21  of the first lens L 21  can be, for example, an aspheric surface, and an objective side surface S 22  of the first lens L 21  can be, for example, an aspheric surface. An image side surface S 23  of the second lens L 22  can be, for example, a concave surface and a spherical surface, and an objective side surface S 24  of the second lens L 22  can be, for example, a spherical surface. An image side surface S 25  of the third lens L 23  can be, for example, a convex surface. An image side surface S 28  of the fourth lens L 24  can be, for example, a flat surface. The other elements of the lens apparatus  2  of the second embodiment as shown in  FIG. 3  are similar to those of the lens apparatus  1  as shown in  FIG. 1 , and therefore the descriptions thereof are omitted. 
     By the design of the above lenses, the stop ST 2  and at least one of the conditions (1)-(10) satisfied, the lens apparatus  2  is able to have the lens diameter effectively reduced, brightness and resolution effectively increased, and aberration effectively corrected. 
     During operation, light from an object IS 2  travels to the image side finally. By changing a distance D 2   G1G2  between the first lens group LG 2   1  and the second lens group LG 2   2 , a distance D 2   G2G3  between the second lens group LG 2   2  and the third lens group LG 2   3  and a distance D 2   G3G4  between the third lens group LG 2   3  and the fourth lens group LG 2   4 , the effective focal length of the lens apparatus  2  can be adjusted. When the first lens group LG 2   1  is moved along the optical axis OA 2  to change the distance D 2   G1G2 , the lens apparatus  2  is focusing. 
     In order to achieve the above purposes and effectively enhance the optical performance, the lens apparatus  2  of the second embodiment of the invention is provided with the optical specifications shown in Table 4, which include curvature of each lens surface, distance between adjacent surface, refractive index of each lens, Abbe number of each lens and effective focal length of each lens. Table 4 shows that the lens apparatus  2  at a wide-angle end has the effective focal length equal to 12.0 mm and F-number equal to 1.94, and the lens apparatus  2  at a telephoto end has the effective focal length equal to 15.4 mm and F-number equal to 2.13. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Effective 
                   
               
               
                   
                   
                   
                   
                   
                 Focal  
                   
               
               
                 Surface  
                 Curvature  
                 Distance  
                   
                   
                 Length  
                   
               
               
                 Number  
                 (mm −1 )  
                 (mm)  
                 Nd  
                 Vd  
                 (mm)  
                 Remark 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S21  
                 0.02  
                 4.3  
                 1.52  
                 56.00  
                 −71.073  
                 The First  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L21  
               
               
                 S22  
                 0.05  
                 15.6  
                   
                   
                   
                   
               
               
                 S23  
                 −0.04  
                 1.8  
                 1.75  
                 28.00  
                 −16.168  
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L22  
               
               
                 S24  
                 0.04  
                 11.0  
                   
                   
                   
                 The  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D2 G1G2    
               
               
                   
                   
                 9.9  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S25  
                 0.01  
                 5.2  
                 1.76  
                 27.00  
                 34.041  
                 The Third  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L23  
               
               
                 S26  
                 −0.03  
                 19.0  
                   
                   
                   
                 The  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D2 G2G3    
               
               
                   
                   
                 3.4  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S27  
                 0.03  
                 4.7  
                 1.60  
                 60.00  
                 55.556  
                 The Fourth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L24  
               
               
                 S28  
                 0.00  
                 18.0  
                   
                   
                   
                 The  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D2 G3G4    
               
               
                   
                   
                 21.5  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S29  
                 0.00  
                 1.4  
                   
                   
                   
                 The Stop  
               
               
                   
                   
                   
                   
                   
                   
                 ST2  
               
               
                 S210  
                 −0.06  
                 1.2  
                 1.80  
                 25.00  
                 −17.695  
                 The Fifth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L25 
               
               
                 S211  
                 0.01  
                 0.1  
                   
                   
                   
                   
               
               
                 S212  
                 0.04  
                 4.2  
                 1.50  
                 81.00  
                 50  
                 The Sixth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L26  
               
               
                 S213  
                 0.00  
                 1.3  
                   
                   
                   
                   
               
               
                 S214  
                 0.02  
                 3.4  
                 1.51  
                 64.00  
                 40.327  
                 The Seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L27  
               
               
                 S215  
                 −0.03  
                 19.7  
                   
                   
                   
                   
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                   
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 23.2  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S216  
                 0.00  
                 2.0  
                 1.52  
                 58.00  
                   
                 The Optical  
               
               
                   
                   
                   
                   
                   
                   
                 Filter OF2  
               
               
                 S217  
                 0.00  
                 1.0  
                   
                   
                   
                   
               
               
                 S218  
                 0.00  
                 1.1  
                 1.51  
                 62.00  
                   
                 Cover Glass  
               
               
                   
                   
                   
                   
                   
                   
                 CG2 
               
               
                 S219  
                 0.00  
                 0.7 
               
               
                   
               
            
           
         
       
     
     Table 5 shows that the optical specifications of the aspheric surface of each lens shown in Table 4, wherein k is a conic constant and A-G are aspheric coefficients. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 S21 
                 S22 
                 S214 
                 S215 
               
               
                   
               
             
            
               
                 k 
                 3.5 
                 0.5 
                 8.13 
                 0 
               
               
                 A 
                  3.35E−05 
                  3.08E−05 
                 −3.61E−05  
                 4.36E−05 
               
               
                 B 
                 −9.17E−08 
                 −1.05E−07 
                 2.27E−07 
                 3.33E−07 
               
               
                 C 
                  1.72E−10 
                 −1.30E−10 
                 1.18E−10 
                 1.89E−09 
               
               
                 D 
                 −1.47E−14 
                 −1.69E−13 
                 3.21E−11 
                 −2.36E−11  
               
               
                 E 
                 −2.11E−16 
                  5.34E−15 
                 −4.85E−13  
                 1.19E−12 
               
               
                 F 
                 −1.91E−20 
                 −1.02E−17 
                 9.04E−15 
                 −1.38E−14  
               
               
                 G 
                  5.24E−22 
                 −4.35E−20 
                 −3.93E−17  
                 9.32E−17 
               
               
                   
               
            
           
         
       
     
     Table 6 shows the optical specifications of the lens apparatus  2  and calculated values corresponding to the conditions (1)-(10). It can be seen from Table 6 that the lens apparatus  2  can meet requirements of the conditions (1)-(10). 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                 f LG1   
                 −11.4 
                 mm 
                 TTL (The Wide- 
                 91.2 
                 mm 
                 TTL (The 
                 78.2 mm 
               
               
                   
                   
                   
                 Angle End) 
                   
                   
                 Telephoto End) 
               
               
                 T S1ST  (The Wide- 
                 79.6 
                 mm 
                 T S1ST  (The 
                 66.6 
                 mm 
                 T S3S10  (The Wide- 
                 61.1 mm 
               
               
                 Angle End) 
                   
                   
                 Telephoto End) 
                   
                   
                 Angle End) 
               
               
                 T S3S10  (The 
                 47.9 
                 mm 
                 T STS15  (The Wide- 
                 11.6 
                 mm 
                 T STS15  (The 
                 11.6 mm 
               
               
                 Telephoto End) 
                   
                   
                 Angle End) 
                   
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 f LG1 /f (The 
                 −0.95 
                 f LG1 /f (The 
                 −0.74 
                 Vd 6 /Vd 3   
                 3 
               
               
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 |f 1  + f 3 | 
                 37.03 
                 mm 
                 f 1  + f 3   
                 −37.032 
                 mm 
                 f 3 /f (The Wide- 
                 2.84 
               
               
                   
                   
                   
                   
                   
                   
                 Angle End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 f 3 /f (The 
                  2.21 
                 TTL/f LG1  (The 
                 −8.00 
                 TTL/f LG1  (The 
                 −6.86 
               
               
                 Telephoto End) 
                   
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 |T S1ST  − T S3S10 | 
                 18.5 
                 mm 
                 |T S1ST  − T S3S10 | 
                 18.7 
                 mm 
                 T S1ST  − T S3S10   
                 18.5 mm 
               
               
                 (The Wide-Angle 
                   
                   
                 (The Telephoto 
                   
                   
                 (The Wide-Angle 
               
               
                 End) 
                   
                   
                 End) 
                   
                   
                 End) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 T S1ST  − T S3S10   
                 18.7 
                 mm 
                 T S1ST /T STS15  (The 
                  6.86 
                 T S1ST /T STS15   
                 5.74 
               
               
                 (The Telephoto 
                   
                   
                 Wide-Angle End) 
                   
                 (The Telephoto 
               
               
                 End) 
                   
                   
                   
                   
                 End) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 T7ob (The Wide- 
                 24.5 
                 mm 
                 T7ob (The 
                 28.0 
                 mm 
                 T7ob/f LG1  (The 
                 −2.14 
               
               
                 Angle End) 
                   
                   
                 Telephoto End) 
                   
                   
                 Wide-Angle End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 T7ob/f LG1  (The 
                 −2.45 
                   
                   
                   
                   
               
               
                 Telephoto End) 
               
               
                   
               
            
           
         
       
     
     The lens apparatus  2  can also meet the requirements of optical performance as seen in  FIGS. 4A-4G . It can be seen from  FIG. 4A  that a field curvature of the lens apparatus  2  at the wide-angle end ranges from −0.03 mm to 0.04 mm. It can be seen from  FIG. 4B  that a distortion of the lens apparatus  2  at the wide-angle end ranges from −0.8% to 0%. It can be seen from  FIG. 4C  that a relative illumination of the lens apparatus  2  at the wide-angle end ranges from 0.53 to 1.0. It can be seen from  FIG. 4D  that a modulation transfer function of the lens apparatus  2  at the wide-angle end ranges from 0.58 to 1.0. It can be seen from  FIG. 4E  that a modulation transfer function of the lens apparatus  2  at the telephoto end ranges from 0.38 to 1.0. It can be seen from  FIG. 4F  that the modulation transfer function of the lens apparatus  2  at the wide-angle end ranges from 0 to 0.70 as a focus shift ranges between −0.05 mm and 0.05 mm. It can be seen from  FIG. 4G  that the modulation transfer function of the lens apparatus  2  at the telephoto end ranges from 0 to 0.68 as a focus shift ranges between −0.05 mm and 0.05 mm. 
     It is obvious that the field curvature and the distortion of the lens apparatus  2  can be corrected effectively, and the relative illumination, the resolution and the depth of focus of the lens apparatus  2  can meet the requirements. Therefore, the lens apparatus  2  is capable of good optical performance. 
     In another embodiment of the invention, the fifth lens and the sixth lens of the fourth lens group can be designed to be a cemented lens. 
     Referring to  FIG. 5 ,  FIG. 5  is a lens layout and optical path diagram of a lens apparatus in accordance with a third embodiment of the invention. A lens apparatus  3  includes a first lens group LG 3   1 , a second lens group LG 3   2 , a third lens group LG 3   3 , a fourth lens group LG 3   4 , an optical filter OF 3  and a cover glass CG 3 . The first lens group LG 3   1  includes a first lens L 31  and a second lens L 32 . The second lens group LG 3   2  includes a third lens L 33 . The third lens group LG 3   3  includes a fourth lens L 34 . The fourth lens group LG 3   4  includes a stop ST 3 , a fifth lens L 35 , a sixth lens L 36  and a seventh lens L 37 . The fifth lens L 35  and the sixth lens L 36  are cemented together. The first lens L 31 , the second lens L 32 , the third lens L 33 , the fourth lens L 34 , the stop ST 3 , the fifth lens L 35 , the sixth lens L 36  and the seventh lens L 37  are arranged in order from an image side to an objective side along an optical axis OA 3 . 
     The difference between the third embodiment and the first embodiment as shown in  FIG. 1  is described herein. An image side surface S 31  of the first lens L 31  can be, for example, an aspheric surface, and an objective side surface S 32  of the first lens L 31  can be, for example, an aspheric surface. An image side surface S 33  of the second lens L 32  can be, for example, a concave surface and a spherical surface, and an objective side surface S 34  of the second lens L 32  can be, for example, a spherical surface. An image side surface S 35  of the third lens L 33  can be, for example, a convex surface. The other elements of the lens apparatus  3  of the third embodiment as shown in  FIG. 5  are similar to those of the lens apparatus  1  as shown in  FIG. 1 , and therefore the descriptions thereof are omitted. 
     By the design of the above lenses, the stop ST 3  and at least one of the conditions (1)-(10) satisfied, the lens apparatus  3  is able to have the lens diameter effectively reduced, brightness and resolution effectively increased, and aberration effectively corrected. 
     During operation, light from an object IS 3  travels to the image side finally. By changing a distance D 3   G1G2  between the first lens group LG 3   1  and the second lens group LG 3   2 , a distance D 3   G2G3  between the second lens group LG 3   2  and the third lens group LG 3   3  and a distance D 3   G3G4  between the third lens group LG 3   3  and the fourth lens group LG 3   4 , the effective focal length of the lens apparatus  3  can be adjusted. When the first lens group LG 3   1  is moved along the optical axis OA 3  to change the distance D 3   G1G2 , the lens apparatus  3  is focusing. 
     In order to achieve the above purposes and effectively enhance the optical performance, the lens apparatus  3  of the third embodiment of the invention is provided with the optical specifications shown in Table 7, which include curvature of each lens surface, distance between adjacent surface, refractive index of each lens, Abbe number of each lens and focal length of each lens. Table 7 shows that the lens apparatus  3  at a wide-angle end has the effective focal length equal to 15.4 mm and F-number equal to 1.94, and the lens apparatus  3  at a telephoto end has the effective focal length equal to 18.5 mm and F-number equal to 2.05. The fifth lens L 35  and the sixth lens L 36  are cemented together. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 7 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Focal  
                   
               
               
                 Surface  
                 Curvature  
                 Distance  
                   
                   
                 Length  
                   
               
               
                 Number  
                 (mm −1 )  
                 (mm)  
                 Nd  
                 Vd  
                 (mm)  
                 Remark 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S31  
                 0.05  
                 3.9  
                 1.52  
                 64.00  
                 −42.5  
                 The First  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L31  
               
               
                 S32  
                 0.10  
                 11.5  
                   
                   
                   
                   
               
               
                 S33  
                 −0.01  
                 1.7  
                 1.49  
                 81.00  
                 −48.9  
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L32  
               
               
                 S34  
                 0.03  
                 19.5  
                   
                   
                   
                 The Distance  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 D3 G1G2    
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 14.7  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S35  
                 0.01  
                 3.5  
                 1.78  
                 47.00  
                 56.8  
                 The Third  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L33  
               
               
                 S36  
                 −0.01  
                 13.0 
                   
                   
                   
                 The Distance  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 D3 G2G3    
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 6.3  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S37  
                 0.04  
                 4.6  
                 1.49  
                 81.00  
                 44.3  
                 The Fourth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L34 
               
               
                 S38  
                 −0.01  
                 11.8  
                   
                   
                   
                   
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 The Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D3 G3G4    
               
               
                   
                   
                 14.3  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S39  
                 0.00  
                 1.0  
                   
                   
                   
                 The Stop ST3  
               
               
                 S310  
                 −0.04  
                 1.0  
                 1.75  
                 27.00  
                 −19.7  
                 The Fifth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L35 
               
               
                 S311  
                 0.03  
                 0.0  
                   
                   
                   
                   
               
               
                 S312  
                 0.03  
                 2.2  
                 1.49  
                 81.00  
                 43.86  
                 The Sixth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L36  
               
               
                 S313  
                 0.00  
                 4.3  
                   
                   
                   
                   
               
               
                 S314  
                 0.02  
                 3.3  
                 1.67  
                 55.00  
                 25.7  
                 The Seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L37 
               
               
                 S315  
                 −0.03  
                 21.8  
                   
                   
                   
                   
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                   
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 24.2  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S316  
                 0.00  
                 2.0  
                 1.52  
                 58.00  
                   
                 The Optical  
               
               
                   
                   
                   
                   
                   
                   
                 Filter OF3  
               
               
                 S317  
                 0.00  
                 1.0  
                   
                   
                   
                   
               
               
                 S318  
                 0.00  
                 1.1  
                 1.51  
                 62.00  
                   
                 Cover Glass  
               
               
                   
                   
                   
                   
                   
                   
                 CG3 
               
               
                 S319  
                 0.00  
                 0.7 
               
               
                   
               
            
           
         
       
     
     Table 8 shows that the optical specifications of the aspheric surface of each lens shown in Table 7, wherein k is a conic constant and A-G are aspheric coefficients. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 Surface 
                   
                   
                   
                   
               
               
                 Number 
                 S31 
                 S32 
                 S314 
                 S315 
               
               
                   
               
             
            
               
                 k 
                 −3.84 
                 −0.8 
                 −9.01 
                 −4.9 
               
               
                 A 
                 −5.95E−06 
                 −5.27E−05  
                 −3.87E−07 
                 −1.49E−05 
               
               
                 B 
                  5.40E−09 
                 1.19E−07 
                 −3.57E−08 
                  2.08E−07 
               
               
                 C 
                  1.68E−10 
                 4.80E−10 
                  3.19E−09 
                 −6.85E−09 
               
               
                 D 
                 −4.38E−13 
                 −2.79E−12  
                 −2.20E−10 
                  1.09E−10 
               
               
                 E 
                 −1.53E−15 
                 2.38E−15 
                  6.11E−12 
                 −8.54E−13 
               
               
                 F 
                  8.16E−18 
                 −1.73E−17  
                 −8.76E−14 
                 −2.99E−15 
               
               
                 G 
                 −9.32E−21 
                 1.75E−19 
                  4.96E−16 
                  5.75E−17 
               
               
                   
               
            
           
         
       
     
     Table 9 shows the optical specifications of the lens apparatus  3  and calculated values corresponding to the conditions (1)-(10). It can be seen from Table 9 that the lens apparatus  3  can meet requirements of the conditions (1)-(10). 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 9 
               
               
                   
               
             
            
               
                 f LG1   
                 −20.6 
                 mm 
                 TTL (The Wide- 
                 81.3 mm 
                 TTL (The 
                 72.3 mm 
               
               
                   
                   
                   
                 Angle End) 
                   
                 Telephoto End) 
               
               
                 T S1ST  (The Wide- 
                 69.5 
                 mm 
                 T S1ST  (The 
                 60.5 mm 
                 T S3S10  (The Wide- 
                 55.1 mm 
               
               
                 Angle End) 
                   
                   
                 Telephoto End) 
                   
                 Angle End) 
               
               
                 T S3S10  (The 
                 46.1 
                 mm 
                 T STS15  (The Wide- 
                 11.8 mm 
                 T STS15  (The 
                 11.8 mm 
               
               
                 Telephoto End) 
                   
                   
                 Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 f LG1 /f (The 
                 −1.34 
                 f LG1 /f (The 
                 −1.11 
                 Vd 6 /Vd 3   
                  1.72 
               
               
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 |f 1  + f 3 | 
                 14.3 
                 mm 
                 f 1  + f 3   
                 14.3 mm 
                 f 3 /f (The Wide- 
                  3.69 
               
               
                   
                   
                   
                   
                   
                 Angle End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 f 3 /f (The 
                  3.07 
                 TTL/f LG1  (The 
                 −3.95 
                 TTL/f LG1  (The 
                 −3.51 
               
               
                 Telephoto End) 
                   
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 |T S1ST  − T S3S10 | 
                 14.4 
                 mm 
                 |T S1ST  − T S3S10 | 
                 14.4 mm 
                 T S1ST  − T S3S10   
                 14.4 mm 
               
               
                 (The Wide-Angle 
                   
                   
                 (The Telephoto 
                   
                 (The Wide-Angle 
               
               
                 End) 
                   
                   
                 End) 
                   
                 End) 
               
               
                 T S1ST  − T S3S10   
                 14.4 
                 mm 
                 T S1ST /T STS15  (The 
                  5.89 
                 T S1ST /T STS15   
                 5.13 
               
               
                 (The Telephoto 
                   
                   
                 Wide-Angle End) 
                   
                 (The Telephoto 
               
               
                 End) 
                   
                   
                   
                   
                 End) 
               
               
                 T7ob (The Wide- 
                 26.6 
                 mm 
                 T7ob (The 
                 29.0 mm 
                 T7ob/f LG1  (The 
                 −1.29 
               
               
                 Angle End) 
                   
                   
                 Telephoto End) 
                   
                 Wide-Angle End) 
               
            
           
           
               
               
               
               
               
               
            
               
                 T7ob/f LG1  (The 
                 −1.40 
                   
                   
                   
                   
               
               
                 Telephoto End) 
               
               
                   
               
            
           
         
       
     
     The lens apparatus  3  can also meet the requirements of optical performance as seen in  FIGS. 6A-6G . It can be seen from  FIG. 6A  that a field curvature of the lens apparatus  3  at the wide-angle end ranges from −0.04 mm to 0.08 mm. It can be seen from  FIG. 6B  that a distortion of the lens apparatus  3  at the wide-angle end ranges from −0.8% to 0%. It can be seen from  FIG. 6C  that a relative illumination of the lens apparatus  3  at the wide-angle end ranges from 0.48 to 1.0. It can be seen from  FIG. 6D  that a modulation transfer function of the lens apparatus  3  at the wide-angle end ranges from 0.52 to 1.0. It can be seen from  FIG. 6E  that a modulation transfer function of the lens apparatus  3  at the telephoto end ranges from 0.48 to 1.0. It can be seen from  FIG. 6F  that the modulation transfer function of the lens apparatus  3  at the wide-angle end ranges from 0 to 0.62 as a focus shift ranges between −0.05 mm and 0.05 mm. It can be seen from  FIG. 6G  that the modulation transfer function of the lens apparatus  3  at the telephoto end ranges from 0 to 0.64 as a focus shift ranges between −0.05 mm and 0.05 mm. 
     It is obvious that the field curvature and the distortion of the lens apparatus  3  can be corrected effectively, and the relative illumination, the resolution and the depth of focus of the lens apparatus  3  can meet the requirements. Therefore, the lens apparatus  3  is capable of good optical performance. 
     Referring to  FIG. 7 ,  FIG. 7  is a lens layout and optical path diagram of a lens apparatus in accordance with a fourth embodiment of the invention. A lens apparatus  4  includes a first lens group LG 4   1 , a second lens group LG 4   2 , a third lens group LG 4   3 , a fourth lens group LG 4   4 , an optical filter OF 4  and a cover glass CG 4 . The first lens group LG 4   1  includes an eighth lens L 48 , a first lens L 41  and a second lens L 42 . The second lens group LG 4   2  includes a third lens L 43 . The third lens group LG 4   3  includes a fourth lens L 44 . The fourth lens group LG 4   4  includes a stop ST 4 , a fifth lens L 45 , a sixth lens L 46  and a seventh lens L 47 . The eighth lens L 48 , the first lens L 41 , the second lens L 42 , the third lens L 43 , the fourth lens L 44 , the stop ST 4 , the fifth lens L 45 , the sixth lens L 46  and the seventh lens L 47  are arranged in order from an image side to an objective side along an optical axis OA 4 . 
     The difference between the fourth embodiment and the first embodiment as shown in  FIG. 1  is described herein. The eighth lens L 48  can be, for example, a meniscus lens and with positive refractive power. An image side surface S 41  of the eighth lens L 48  can be, for example, a convex surface, and an objective side surface S 42  of the eighth lens L 48  can be, for example, a concave surface. The image side surface S 41  can be, for example, a spherical surface, and the objective side surface S 42  can be, for example, a spherical surface. An image side surface S 45  of the second lens L 42  can be, for example, a concave surface and a spherical surface, and an objective side surface S 46  of the second lens L 42  can be, for example, a spherical surface. An objective side surface S 415  of the sixth lens L 46  can be, for example, a convex surface. In the present of other embodiment, the fifth lens L 45 , the sixth lens L 46  and the seventh lens L 47  can, for example, include at least one aspheric surface. The other elements of the lens apparatus  4  of the fourth embodiment as shown in  FIG. 7  are similar to those of the lens apparatus  1  as shown in  FIG. 1 , and therefore the descriptions thereof are omitted. 
     During operation, light from an object IS 4  travels to the image side finally. By changing a distance D 4   G1G2  between the first lens group LG 4   1  and the second lens group LG 4   2 , a distance D 4   G2G3  between the second lens group LG 4   2  and the third lens group LG 4   3  and a distance D 4   G3G4  between the third lens group LG 4   3  and the fourth lens group LG 4   4 , the effective focal length of the lens apparatus  4  can be adjusted. When the first lens group LG 4   1  is moved along the optical axis OA 4  to change the distance D 4   G1G2 , the lens apparatus  4  is focusing. 
     By the design of the above lenses, the stop ST 4  and at least one of the conditions (1)-(10) satisfied, the lens apparatus  4  is able to have the lens diameter effectively reduced, brightness and resolution effectively increased, and aberration effectively corrected. 
     In order to achieve the above purposes and effectively enhance the optical performance, the lens apparatus  4  of the fourth embodiment of the invention is provided with the optical specifications shown in Table 10, which include curvature of each lens surface, distance between adjacent surface, refractive index of each lens, Abbe number of each lens and effective focal length of each lens. Table 10 shows that the lens apparatus  4  at a wide-angle end has the effective focal length equal to 12.0 mm and F-number equal to 1.94, and the lens apparatus  4  at a telephoto end has the effective focal length equal to 14.4 mm and F-number equal to 2.07. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Effective 
                   
               
               
                   
                   
                   
                   
                   
                 Focal  
                   
               
               
                 Surface  
                 Curvature  
                 Distance  
                   
                   
                 Length  
                   
               
               
                 Number  
                 (mm −1 )  
                 (mm)  
                 Nd  
                 Vd  
                 (mm)  
                 Remark 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S41  
                 0.01  
                 8.0  
                 1.58  
                 62.00  
                 172.414  
                 The Eighth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L48  
               
               
                 S42  
                 0.0012  
                 0.2  
                   
                   
                   
                   
               
               
                 S43  
                 0.02  
                 3.6  
                 1.71  
                 64.00  
                 −38.68  
                 The First  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L41  
               
               
                 S44  
                 0.06  
                 8.3  
                   
                   
                   
                   
               
               
                 S45  
                 −0.02  
                 1.8  
                 1.65  
                 34.00  
                 −21.542  
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L42  
               
               
                 S46  
                 0.05  
                 15.0  
                   
                   
                   
                 The  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D4 G1G2    
               
               
                   
                   
                 13.1  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S47  
                 −0.01  
                 5.6  
                 1.80  
                 27.00  
                 113.682  
                 The Third  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L43  
               
               
                 S48  
                 −0.02  
                 18.8  
                   
                   
                   
                 The  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D4 G2G3    
               
               
                   
                   
                 11.4  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S49  
                 0.04  
                 6.0  
                 1.72  
                 52.00  
                 28.941  
                 The Fourth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L44  
               
               
                 S410  
                 −0.01  
                 10.4  
                   
                   
                   
                 The  
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                 Distance  
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                 D4 G3G4    
               
               
                   
                   
                 11.7  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S411  
                 0.00  
                 1.0  
                   
                   
                   
                 The Stop  
               
               
                   
                   
                   
                   
                   
                   
                 ST4  
               
               
                 S412  
                 −0.04  
                 1.0  
                 1.74  
                 28.00  
                 −33.784  
                 The Fifth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L45  
               
               
                 S413  
                 0.05  
                 0.1  
                   
                   
                   
                   
               
               
                 S414  
                 0.07  
                 4.0  
                 1.50  
                 81.00  
                 25.597  
                 The Sixth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L46  
               
               
                 S415  
                 −0.01  
                 1.6  
                   
                   
                   
                   
               
               
                 S416  
                 0.03  
                 4.2  
                 1.60  
                 60.00  
                 29.155  
                 The Seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L47  
               
               
                 S417  
                 −0.03  
                 19.2  
                   
                   
                   
                   
               
               
                   
                   
                 (The Wide-  
                   
                   
                   
                   
               
               
                   
                   
                 Angle End)  
                   
                   
                   
                   
               
               
                   
                   
                 21.4  
                   
                   
                   
                   
               
               
                   
                   
                 (The  
                   
                   
                   
                   
               
               
                   
                   
                 Telephoto  
                   
                   
                   
                   
               
               
                   
                   
                 End)  
                   
                   
                   
                   
               
               
                 S418  
                 0.00  
                 2.0  
                 1.52  
                 58.00  
                   
                 The Optical  
               
               
                   
                   
                   
                   
                   
                   
                 Filter OF4  
               
               
                 S419  
                 0.00  
                 1.0  
                   
                   
                   
                   
               
               
                 S420  
                 0.00  
                 1.1  
                 1.51  
                 62.00  
                   
                 Cover Glass  
               
               
                   
                   
                   
                   
                   
                   
                 CG4 
               
               
                 S421  
                 0.00  
                 0.7 
               
               
                   
               
            
           
         
       
     
     Table 11 shows the optical specifications of the lens apparatus  4  and calculated values corresponding to the conditions (1)-(10). It can be seen from Table 11 that the lens apparatus  4  can meet requirements of the conditions (1)-(10). 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 11 
               
               
                   
               
             
            
               
                 f LG1   
                 −15.9 mm 
                 TTL (The Wide- 
                 89.6 mm 
                 TTL (The 
                 81.6 mm 
               
               
                   
                   
                 Angle End) 
                   
                 Telephoto End) 
               
               
                 T S1ST  (The Wide- 
                 77.7 mm 
                 T S1ST  (The 
                 69.7 mm 
                 T S3S10  (The Wide- 
                 58.6 mm 
               
               
                 Angle End) 
                   
                 Telephoto End) 
                   
                 Angle End) 
               
               
                 T S3S10  (The 
                 50.6 mm 
                 T STS15  (The Wide- 
                 11.9 mm 
                 T STS15  (The 
                 23.6 mm 
               
               
                 Telephoto End) 
                   
                 Angle End) 
                   
                 Telephoto End) 
               
               
                 f LG1 /f (The 
                 −1.33 
                 f LG1 /f (The 
                 −1.10 
                 Vd 6 /Vd 3   
                 3 
               
               
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
               
                 |f 1  + f 3 | 
                 75.00 mm 
                 f 1  + f 3   
                 75.00 mm 
                 f 3 /f (The Wide- 
                 9.47 
               
               
                   
                   
                   
                   
                 Angle End) 
               
               
                 f 3 /f (The 
                  7.89 
                 TTL/f LG1  (The 
                 −5.64 
                 TTL/f LG1  (The 
                 −5.13 
               
               
                 Telephoto End) 
                   
                 Wide-Angle End) 
                   
                 Telephoto End) 
               
               
                 |T S1ST  − T S3S10 | 
                 19.1 mm 
                 |T S1ST  − T S3S10 | 
                 19.1 mm 
                 T S1ST  − T S3S10   
                 19.1 mm 
               
               
                 (The Wide- 
                   
                 (The Telephoto 
                   
                 (The Wide-Angle 
               
               
                 Angle End) 
                   
                 End) 
                   
                 End) 
               
               
                 T S1ST  − T S3S10   
                 19.1 mm 
                 T S1ST /T STS15   
                  6.53 
                 T S1ST /T STS15   
                 2.95 
               
               
                 (The Telephoto 
                   
                 (The Wide-Angle 
                   
                 (The Telephoto 
               
               
                 End) 
                   
                 End) 
                   
                 End) 
               
               
                 T7ob (The Wide- 
                 24.0 mm 
                 T7ob (The 
                 26.2 mm 
                 T7ob/f LG1  (The 
                 −1.50 
               
               
                 Angle End) 
                   
                 Telephoto End) 
                   
                 Wide-Angle End) 
               
               
                 T7ob/f LG1  (The 
                 −1.64 
               
               
                 Telephoto End) 
               
               
                   
               
            
           
         
       
     
     The lens apparatus  4  can also meet the requirements of optical performance as seen in  FIGS. 8A-8G . It can be seen from  FIG. 8A  that a field curvature of the lens apparatus  4  at the wide-angle end ranges from −0.05 mm to 0.06 mm. It can be seen from  FIG. 8B  that a distortion of the lens apparatus  4  at the wide-angle end ranges from −4% to 0%. It can be seen from  FIG. 8C  that a relative illumination of the lens apparatus  4  at the wide-angle end ranges from 0.64 to 1.0. It can be seen from  FIG. 8D  that a modulation transfer function of the lens apparatus  4  at the wide-angle end ranges from 0.43 to 1.0. It can be seen from  FIG. 8E  that a modulation transfer function of the lens apparatus  4  at the telephoto end ranges from 0.28 to 1.0. It can be seen from  FIG. 8F  that the modulation transfer function of the lens apparatus  4  at the wide-angle end ranges from 0 to 0.69 as a focus shift ranges between −0.05 mm and 0.05 mm. It can be seen from  FIG. 8G  that the modulation transfer function of the lens apparatus  4  at the telephoto end ranges from 0 to 0.68 as a focus shift ranges between −0.05 mm and 0.05 mm. 
     It is obvious that the field curvature and the distortion of the lens apparatus  4  can be corrected effectively, and the relative illumination, the resolution and the depth of focus of the lens apparatus  4  can meet the requirements. Therefore, the lens apparatus  4  is capable of good optical performance. 
     Although the objective side surface S 42  of the eighth lens L 48  of the above-described lens apparatus  4  is a concave surface, the invention is not limited thereto. That is to say, the objective side surface of the eighth lens can be adjusted according to the requirement of actual application. In other embodiments of the invention, the objective side surface of the eighth lens can be designed as a flat surface. If it is desired to improve the wide-angle performance of the lens apparatus, the value of the curvature of the objective side surface of the eighth lens can be increased. If it is desired to improve the telephoto performance of the lens apparatus, the effective focal length of the lens apparatus can be slightly increased and the objective side surface of the eighth lens can be designed as a convex surface.