Patent Publication Number: US-2022229274-A1

Title: Lens Assembly

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a lens assembly. 
     Description of the Related Art 
     The current development trend of a lens assembly is toward miniaturization and high resolution. Additionally, the lens assembly is developed to have resistance to severe environment temperature variation in accordance with different application requirements. However, the known lens assembly can&#39;t satisfy such requirements. Therefore, the lens assembly needs a new structure to meet the requirements of miniaturization, high resolution, and resistance to severe environment temperature variation at the same time. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a lens assembly to solve the above problems. The lens assembly of the invention is provided with characteristics of a shortened total lens length, a smaller F-number, a high resolution, a resistance to severe environment temperature variation, and still has a good optical performance. 
     The assembly in accordance with an exemplary embodiment of the invention includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The first lens is a meniscus lens with negative refractive power and includes a convex surface facing an objective side as well as a concave surface facing an image side. The second lens is with negative refractive power. The third lens is with refractive power. The fourth lens is with positive refractive power. The fifth lens is with positive refractive power and includes a convex surface facing the image side. The sixth lens is with refractive power. The seventh lens is with positive refractive power. The eighth lens is with negative refractive power and includes a concave surface facing the objective side. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are arranged in order from the object side to the image side along an optical axis. 
     In another exemplary embodiment, the third lens is with positive refractive power. The fourth lens includes a convex surface facing the image side. The sixth lens is with positive refractive power. The seventh lens includes a convex surface facing the objective side. 
     In another exemplary embodiment, the fourth lens is a meniscus lens and further includes a concave surface facing the image side. The fifth lens is a meniscus lens and further includes a concave surface facing the objective side. The seventh lens is a biconvex lens and further includes a convex surface facing the image side. 
     In another exemplary embodiment, the second lens is a meniscus lens and includes a convex surface facing the objective side as well as a concave surface facing the image side. The third lens is a biconvex lens and includes a convex surface facing the objective side as well as another convex surface facing the image side. The sixth lens is a meniscus lens and includes a concave surface facing the objective side as well as a convex surface facing the image side. The eighth lens is a meniscus lens and further includes a convex surface facing the image side. 
     In another exemplary embodiment, the second lens is a meniscus lens and includes a convex surface facing the objective side as well as a concave surface facing the image side. The third lens is a meniscus lens and includes a convex surface facing the objective side as well as a concave surface facing the image side. The sixth lens is a biconvex lens and includes a convex surface facing the objective side as well as another convex surface facing the image side. The eighth lens is a biconcave lens and further includes a concave surface facing the image side. 
     In another exemplary embodiment, the fourth lens is a biconvex lens and further includes another convex surface facing the objective side. The fifth lens is a biconvex lens and further includes another convex surface facing the objective side. The seventh lens is a meniscus lens and further includes a concave surface facing the image side. The eighth lens is a biconcave lens and further includes another concave surface facing the image side. 
     In another exemplary embodiment, the second lens is a meniscus lens and includes a concave surface facing the objective side as well as a convex surface facing the image side. The third lens is a meniscus lens and includes a concave surface facing the objective side as well as a convex surface facing the image side. The sixth lens is a meniscus lens and includes a convex surface facing the objective side as well as a concave surface facing the image side. 
     The lens assembly of the invention can further include a stop disposed between the fourth lens and the fifth lens. 
     In yet another exemplary embodiment, the lens assembly satisfies at least one of the following conditions: 0.05&lt;GAP5678/T5678&lt;0.25, −2.0&lt;f1/f&lt;−1.7, wherein GAP5678 is a sum of an air interval from the fifth lens to the eighth lens along the optical axis, T5678 is a sum of a lens thickness of the fifth lens to the eighth lens along the optical axis, f is an effective focal length of the lens assembly, and f 1  is an effective focal length of the first lens. 
     In yet another exemplary embodiment, the lens assembly satisfies at least one of the following conditions: 1.0&lt;D1/D7&lt;1.1, 0.02&lt;GAP5678/TTL&lt;0.06, wherein D1 is a larger one of an optical effective diameter of the objective surface and the image surface of the first lens, D7 is a larger one of an optical effective diameter of the objective surface and the image surface of the seventh lens, GAP5678 is a sum of an air interval from the fifth lens to the eighth lens along the optical axis, and TTL is an interval from the objective surface of the first lens to the image plane 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 diagram of a lens assembly in accordance with a first embodiment of the invention; 
         FIG. 2A  is a longitudinal aberration diagram of the lens assembly in accordance with the first embodiment of the invention; 
         FIG. 2B  is a field curvature diagram of the lens assembly in accordance with the first embodiment of the invention; 
         FIG. 2C  is a distortion diagram of the lens assembly in accordance with the first embodiment of the invention; 
         FIG. 3  is a lens layout diagram of a lens assembly in accordance with a second embodiment of the invention; 
         FIG. 4A  is a longitudinal aberration diagram of the lens assembly in accordance with the second embodiment of the invention; 
         FIG. 4B  is a field curvature diagram of the lens assembly in accordance with the second embodiment of the invention; 
         FIG. 4C  is a distortion diagram of the lens assembly in accordance with the second embodiment of the invention; 
         FIG. 5  is a lens layout diagram of a lens assembly in accordance with a third embodiment of the invention; 
         FIG. 6A  is a longitudinal aberration diagram of the lens assembly in accordance with the third embodiment of the invention; 
         FIG. 6B  is a field curvature diagram of the lens assembly in accordance with the third embodiment of the invention; 
         FIG. 6C  is a distortion diagram of the lens assembly in accordance with the third embodiment of the invention; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     The invention provides a lens assembly including a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The first lens is a meniscus with negative refractive power and includes a convex surface facing an object side as well as a concave surface facing an image side. The second lens is with negative refractive power. The third lens is with refractive power. The fourth lens is with positive refractive power. The fifth lens is with positive refractive power and includes a convex surface facing the image side. The sixth lens is with refractive power. The seventh lens is with positive refractive power. The eighth lens is with negative refractive power and includes a concave surface facing the objective side. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are arranged in order from the object side to then image side along an optical axis. 
     Referring to Table 1, Table 3, and Table 5, wherein Table 1, Table 3, and Table 5 show the parameters of the lenses in accordance with the first embodiment to the third embodiment of the invention respectively. 
       FIG. 1 ,  FIG. 3 , and  FIG. 5  are the lens layout diagram of the lens assembly in accordance with the first embodiment, the second embodiment, and the third embodiment of the invention respectively. The first lenses L 11 , L 21 , L 31  are meniscus lenses with negative refractive power and are made of glass. The objective surfaces thereof S 11 , S 21 , S 31  are convex. The image surfaces thereof S 12 , S 22 , S 32  are concave. Both of the objective surfaces S 11 , S 21 , S 31  and the image surfaces S 12 , S 22 , S 32  thereof are spherical surfaces. 
     The second lenses L 12 , L 22 , L 32  are meniscus lenses with negative refractive power and are made of glass. Both the objective surfaces S 13 , S 23 , S 33  and the image surfaces S 14 , S 24 , S 34  thereof are spherical surfaces. 
     The third lenses L 13 , L 23 , L 33  are with positive refractive power and are made of glass. Both the objective surfaces S 15 , S 25 , S 35  and the image surfaces S 16 , S 26 , S 36  thereof are spherical surfaces. 
     The fourth lenses L 14 , L 24 , L 34  are with positive refractive power and are made of glass. The image surfaces thereof S 18 , S 28 , S 38  are convex. Both the objective surfaces S 17 , S 27 , S 37  and the image surfaces S 18 , S 28 , S 38  thereof are spherical surfaces. 
     The fifth lenses L 15 , L 25 , L 35  are with positive refractive power, and are made of glass. The image surfaces thereof S 111 , S 211 , S 311  are convex. Both the objective surfaces S 110 , S 210 , S 310  and image surfaces S 111 , S 211 , S 311  thereof are spherical surfaces. 
     The sixth lenses L 16 , L 26 , L 36  are with positive refractive power and are made of glass. Both the objective surfaces S 112 , S 212 , S 312  and the image surfaces thereof S 113 , S 213 , S 313  are spherical surfaces. 
     The seventh lenses L 17 , L 27 , L 37  are with positive refractive power and are made of glass. The objective surface thereof S 114 , S 214 , S 314  are convex. Both the objective surfaces S 114 , S 214 , S 314  and the image surfaces thereof S 115 , S 215 , S 315  are spherical surfaces. 
     The eighth lenses L 18 , L 28 , L 38  are with negative refractive power and are made of glass. The objective surfaces thereof S 116 , S 216 , S 316  are concave. Both the objective surfaces S 116 , S 216 , S 316  and the image surfaces S 117 , S 217 , S 317  thereof are spherical surfaces. 
     In addition, the lens assemblies  1 ,  2 ,  3  satisfy at least one of the following conditions: 
       0.05&lt;GAP 5678   /T   5678 &lt;0.25  (1)
 
       −2.0 &lt;f   1   /f&lt;− 1.7  (2)
 
       1.0 &lt;D   1   /D   7 &lt;1.1  (3)
 
       0.02&lt;GAP 5678 /TTL&lt;0.06  (4)
 
     For the first embodiment to the third embodiment, GAP5678 is a sum of an air interval from the fifth lenses L 15 , L 25 , L 35  to the eighth lenses L 18 , L 28 , L 38  along the optical axes OA 1 , OA 2 , OA 3 . T5678 is a sum of a lens thickness of the fifth lenses L 15 , L 25 , L 35  to the eighth lenses L 18 , L 28 , L 38  along the optical axes OA 1 , OA 2 , OA 3 . f 1  is an effective focal length of the first lenses L 11 , L 21 , L 31 . f is an effective focal length of the lens assembly  1 ,  2 ,  3 . D 1  is a larger one of optical effective diameter of objective surfaces S 11 ,  521 , S 31  and the image surfaces  512 , S 22 , S 32  of the first lenses L 11 , L 21 , L 31 . D 7  is a larger one of optical effective diameter of the objective surfaces S 114 , S 214 , S 314  and the image surfaces S 115 , S 215 , S 315  of the seventh lenses L 17 , L 27 , L 37 . TTL is an interval from the objective surfaces S 11 , S 21 , S 31  of the first lens to the image plane IMA 1 , IMA 2 , IMA 3  along the optical axes OA 1 ,  0 A 2 ,  0 A 3  respectively. With the lens assemblies  1 ,  2 ,  3  satisfying at least one of the above conditions (1)-(4), total lens length can be effectively shorten, the resolution can be effectively increased, the environmental temperature change can be effectively resisted, the aberration can be effectively corrected. 
     The total lens length of the lens assemblies can be effectively shorten when the equation (1) 0.05&lt;GAP5678/T5678&lt;0.25 is satisfied. The field of view of the lens assemblies can be effectively increased when the equation (2) −2.0&lt;f1/f&lt;−1.7 is satisfied. The diameter can be effectively reduced when the equation (3) 1.0&lt;D1/D7&lt;1.1 is satisfied. The total lens length of the lens assemblies can be effectively shorten when the equation (4) 0.02&lt;GAP5678/TTL&lt;0.06 is satisfied. By the design that all of the lenses of the lens assemblies are made of glass with spherical surfaces, the environmental temperature change can be effectively resisted. It makes the lens assemblies  1 ,  2 ,  3  can still have a good optical properties under high or low temperature. It makes the cost of the production thereof can be effectively reduced. It makes the lens assemblies  1 ,  2 ,  3  not easy to be damaged and can still have good optical properties even after long term use. 
     A detailed description of the lens assembly in accordance with the first embodiment of the invention is as follows. Referring to  FIG. 1 , the lens assembly  1  includes a first lens L 11 , a second lens L 12 , a third lens L 13 , a fourth lens L 14 , a stop ST 1 , a fifth lens L 15 , a sixth lens L 16 , a seventh lens L 17 , an eighth lens L 18 , an optical filter OF 1 , and a cover glass CG 1 , all of which are arranged in order from an object side to an image side along an optical axis OA 1 . In operation, an image of light rays from the object side is formed at an image plane IMA 1 . According to paragraphs [0029]-[0038], wherein: 
     The second lens L 12  is a meniscus lens, the objective surface S 13  thereof is convex, and the image surface S 14  thereof is concave. The third lens L 13  is a biconvex lens, the objective surface S 15  thereof is convex, and the image surface S 16  thereof is also convex. The fourth lens L 14  is a meniscus lens, and the objective surface S 17  thereof is concave. The fifth lens L 15  is a meniscus lens, and the objective surface S 110  thereof is concave. The sixth lens L 16  is a meniscus lens, the objective surface S 112  thereof is concave, and the image surface S 113  thereof is convex. The seventh lens L 17  is a biconvex lens, and the image surface S 115  thereof is convex. The eighth lens L 18  is a meniscus lens, and the image surface S 117  thereof is convex. 
     Both the objective surface S 118  and the image surface S 119  of the optical filter OF 1  are flat surfaces. 
     Both the objective surface S 120  and the image surface S 121  of the cover glass CG 1  are flat surfaces. 
     With the above design of the lenses and the stop ST 1  and at least any one of the conditions (1)-(4) satisfied, the lens assembly  1  can have an effective shorter total lens length, an effective increased resolution, an effective resisted environmental temperature change, and is capable of an effective corrected aberration. 
     Table 1 shows the optical specification of the lens assembly  1  in  FIG. 1 . 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Effective Focal Length = 2.959 mm 
                 F-number = 1.34 
               
               
                 Total Lens Length = 19.004 mm 
                 Field Of View = 148 Degrees 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sur- 
                 Radius 
                   
                   
                   
                 Effective 
                   
               
               
                 face 
                 of 
                 Thick- 
                   
                   
                 Focal 
                   
               
               
                 Num- 
                 Curvature 
                 ness 
                   
                   
                 Length  
                   
               
               
                 ber 
                 (mm) 
                 (mm) 
                 Nd 
                 Vd 
                 (mm) 
                 Remark 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S11 
                 33.442 
                 0.400 
                 1.62 
                 60.4 
                 −5.312 
                 The First Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L11 
               
               
                 S12 
                 2.948 
                 1.529 
                   
                   
                   
                   
               
               
                 S13 
                 7.609 
                 1.297 
                 1.65 
                 55.9 
                 −24.391 
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L12 
               
               
                 S14 
                 4.778 
                 0.527 
                   
                   
                   
                   
               
               
                 S15 
                 44.310 
                 1.042 
                 2 
                 25.4 
                 12.587 
                 The Third Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L13 
               
               
                 S16 
                 −16.704 
                 0.831 
                   
                   
                   
                   
               
               
                 S17 
                 −9.684 
                 0.818 
                 1.9 
                 37.4 
                 16.517 
                 The Fourth s 
               
               
                   
                   
                   
                   
                   
                   
                 Len L14 
               
               
                 S18 
                 −6.046 
                 −0.369 
                   
                   
                   
                   
               
               
                 S19 
                 ∞ 
                 2.591 
                   
                   
                   
                 Stop ST1 
               
               
                 S110 
                 −16.253 
                 1.726 
                 1.76 
                 52.3 
                 13.213 
                 The Fifth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L15 
               
               
                 S111 
                 −6.398 
                 0.100 
                   
                   
                   
                   
               
               
                 S112 
                 −199.235 
                 1.297 
                 1.88 
                 40.8 
                 25.407 
                 The sixth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L16 
               
               
                 S113 
                 −19.869 
                 0.089 
                   
                   
                   
                   
               
               
                 S114 
                 8.398 
                 3.077 
                 1.77 
                 49.6 
                 7.635 
                 The seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L17 
               
               
                 S115 
                 −15.882 
                 0.376 
                   
                   
                   
                   
               
               
                 S116 
                 −11.229 
                 0.474 
                 1.99 
                 16.5 
                 −11.904 
                 The eighth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L18 
               
               
                 S117  
                 −2959.847 
                 1.822 
                   
                   
                   
                   
               
               
                 S118 
                 ∞ 
                 0.300 
                 1.52 
                 64.2 
                   
                 optical filter OF1 
               
               
                 S119 
                 ∞ 
                 0.500 
                   
                   
                   
                   
               
               
                 S120 
                 ∞ 
                 0.500 
                 1.52 
                 64.2 
                   
                 cover glass CG1 
               
               
                 S121 
                 ∞ 
                 0.076 
               
               
                   
               
            
           
         
       
     
     Table 2 shows the parameters and condition values for conditions (1)-(4) in accordance with the first embodiment of the invention. It can be seen from Table 2 that the lens assembly  1  of the first embodiment satisfies the conditions (1)-(4). 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 GAP 5678   
                 0.565 mm 
                 T 5678   
                 6.573 mm 
                 D 1   
                 8.662 mm 
               
               
                 D 7   
                 8.440 mm 
               
               
                 GAP 5678 /T 5678   
                 0.086 
                 f 1 /f 
                 −1.795 
                 D 1 /D 7   
                 1.026 
               
               
                 GAP 5678 /TTL 
                 0.030 
               
               
                   
               
            
           
         
       
     
     Besides, by the above arrangements of the lenses and the stop ST 1 , the lens assembly  1  of the first embodiment can meet the requirements of optical performance. It can be seen from  FIG. 2A  that the longitudinal aberration in the lens assembly  1  of the first embodiment ranges from −0.01 mm to 0.05 mm. It can be seen from  FIG. 2B  that the field curvature of tangential direction and sagittal direction in the lens assembly  1  of the first embodiment ranges from −0.04 mm to 0.05 mm. It can be seen from  FIG. 2C  that the distortion in the lens assembly  1  of the first embodiment ranges from −70% to 0%. 
     It is obvious that the longitudinal aberration, the field curvature, and the distortion of the lens assembly  1  of the first embodiment can be corrected effectively. Therefore, the lens assembly  1  of the first embodiment is capable of good optical performance. 
     Referring to  FIG. 3 , the lens assembly  2  includes a first lens L 21 , a second lens L 22 , a third lens L 23 , a fourth lens L 24 , a stop ST 1 , a fifth lens L 25 , a sixth lens L 26 , a seventh lens L 27 , an eighth lens L 28 , an optical filter OF 2 , and a cover glass CG 2 , all of which are arranged in order from an object side to an image side along an optical axis OA 2 . In operation, an image of light rays from the object side is formed at an image plane IMA 2 . According to paragraphs [0029]-[0038], wherein: 
     The second lens L 22  is a meniscus lens, the objective surface S 23  thereof is convex, and the image surface S 24  thereof is concave. The third lens L 23  is a meniscus lens, the objective surface S 15  thereof is convex, and the image surface S 16  thereof is concave. The fourth lens L 24  is a meniscus lens, and the objective surface S 27  thereof is concave. The fifth lens L 25  is a meniscus lens, and the objective surface S 210  thereof is concave. The sixth lens L 26  is a biconvex lens, the objective surface S 212  thereof is convex, and the image surface S 213  thereof is convex. The seventh lens L 27  is a biconvex lens, and the image surface S 215  thereof is convex. The eighth lens L 28  is a biconcave lens, and the image surface S 217  thereof is concave. 
     Both the objective surface S 218  and the image surface S 219  of the optical filter OF 2  are flat surfaces. 
     Both an objective surface S 220  and an image surface S 221  of the cover glass CG 2  are flat surfaces. 
     With the above design of the lenses and the stop ST 2  and at least any one of the conditions (1)-(4) satisfied, the lens assembly  2  can have an effective shorter total lens length, an effective increased resolution, an effective resisted environmental temperature change, and is capable of an effective corrected aberration. 
     Table 3 shows the optical specification of the lens assembly  2  in  FIG. 3 . 
     
       
         
           
               
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Effective Focal Length = 2.953 mm 
                 F-number = 1.34 
               
               
                 Total Lens Length = 18.995 mm 
                 Field Of View = 148 Degrees 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sur- 
                 Radius  
                   
                   
                   
                 Effective 
                   
               
               
                 face 
                 of 
                 Thick- 
                   
                   
                 Focal 
                   
               
               
                 Num- 
                 Curvature 
                 ness 
                   
                   
                 Length 
                   
               
               
                 ber 
                 (mm) 
                 (mm) 
                 Nd 
                 Vd 
                 (mm) 
                 Remark 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S21 
                 25.923 
                 0.400 
                 1.65 
                 55.9 
                 −5.376 
                 The First Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L21 
               
               
                 S22 
                 3.017 
                 2.171 
                   
                   
                   
                   
               
               
                 S23 
                 9.524 
                 0.411 
                 1.68 
                 55.6 
                 −14.747 
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L22 
               
               
                 S24 
                 4.751 
                 0.241 
                   
                   
                   
                   
               
               
                 S25 
                 7.402 
                 1.221 
                 1.99 
                 16.5 
                 19.858 
                 The Third Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L23 
               
               
                 S26 
                 11.312 
                 0.901 
                   
                   
                   
                   
               
               
                 S27 
                 −116.270 
                 1.009 
                 1.83 
                 42.7 
                 9.88 
                 The Fourth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L24 
               
               
                 S28 
                 −7.571 
                 −0.310 
                   
                   
                   
                   
               
               
                 S29 
                 ∞ 
                 3.005 
                   
                   
                   
                 Stop ST2 
               
               
                 S210 
                 −15.504 
                 1.397 
                 1.66 
                 57.4 
                 17.078 
                 The Fifth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L25 
               
               
                 S211 
                 −6.686 
                 0.093 
                   
                   
                   
                   
               
               
                 S212 
                 27.362 
                 1.673 
                 1.88 
                 40.9 
                 12.48 
                 The sixth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L26 
               
               
                 S213 
                 −17.253 
                 0.092 
                   
                   
                   
                   
               
               
                 S214 
                 8.591 
                 2.499 
                 1.69 
                 54.9 
                 9.688 
                 The seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L27 
               
               
                 S215 
                 −24.697 
                 0.550 
                   
                   
                   
                   
               
               
                 S216 
                 −12.036 
                 0.400 
                 1.99 
                 16.5 
                 −11.34 
                 The eighth Lens 
               
               
                   
                   
                   
                   
                   
                   
                 L28 
               
               
                 S217 
                 92.057 
                 1.867 
                   
                   
                   
                   
               
               
                 S218 
                 ∞ 
                 0.300 
                 1.52 
                 64.2 
                   
                 optical filter OF2 
               
               
                 S219 
                 ∞ 
                 0.500 
                   
                   
                   
                   
               
               
                 S220 
                 ∞ 
                 0.500 
                 1.52 
                 64.2 
                   
                 cover glass CG2 
               
               
                 S221 
                 ∞ 
                 0.076 
               
               
                   
               
            
           
         
       
     
     Table 4 shows the parameters and condition values for conditions (1)-(4) in accordance with the second embodiment of the invention. It can be seen from Table  4  that the lens assembly  2  of the second embodiment satisfies the conditions (1)-(4). 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
             
            
               
                 GAP 5678   
                 0.735 mm 
                 T 5678   
                 5.969 mm 
                 D 1   
                 8.659 mm 
               
               
                 D 7   
                 8.408 mm 
               
               
                 GAP 5678 /T 5678   
                 0.123 
                 f 1 /f 
                 −1.820 
                 D 1 /D 7   
                 1.030 
               
               
                 GAP 5678 /TTL 
                 0.039 
               
               
                   
               
            
           
         
       
     
     Besides, by the above arrangements of the lenses and the stop ST 2 , the lens assembly  2  of the second embodiment can meet the requirements of optical performance. It can be seen from  FIG. 4A  that the longitudinal aberration in the lens assembly  2  of the second embodiment ranges from −0.01 mm to 0.05 mm. It can be seen from  FIG. 4B  that the field curvature of tangential direction and sagittal direction in the lens assembly  2  of the second embodiment ranges from −0.04 mm to 0.05 mm. It can be seen from  FIG. 4C  that the distortion in the lens assembly  2  of the second embodiment ranges from −70% to 0%. 
     It is obvious that the longitudinal aberration, the field curvature, and the distortion of the lens assembly  2  of the second embodiment can be corrected effectively. The resolution and the depth of focus of the lens assembly  2  of the second embodiment can also meet the requirements. Therefore, the lens assembly  2  of the second embodiment is capable of good optical performance. 
     Referring to  FIG. 5 , the lens assembly  3  includes a first lens L 31 , a second lens L 32 , a third lens L 33 , a fourth lens L 34 , a stop ST 3 , a fifth lens L 35 , a sixth lens L 36 , a seventh lens L 37 , an eighth lens L 38 , an optical filter OF 3 , and a cover glass CG 3 , all of which are arranged in order from an object side to an image side along an optical axis OA 3 . In operation, an image of light rays from the object side is formed at an image plane IMA 3 . According to paragraphs [0029]-[0038], wherein: 
     The second lens L 32  is a meniscus lens, the objective surface S 33  thereof is concave and the image surface S 34  thereof is convex. The third lens L 33  is a meniscus lens, the objective surface S 35  thereof is concave, and the image surface S 36  thereof is convex. The fourth lens L 34  is a biconvex lens, and the objective surface S 37  thereof is convex. The fifth lens L 25  is a biconvex lens, and the objective surface S 310  thereof is convex. The sixth lens L 36  is a meniscus lens, the objective surface S 312  thereof is convex, and the image surface S 313  thereof is concave. The seventh lens L 37  is a meniscus lens, and the image surface S 315  thereof is concave. The eighth lens L 38  is a biconcave lens, and the image surface S 317  thereof is concave. 
     Both the objective surface S 318  and the image surface S 319  of the optical filter OF 3  are flat surfaces. 
     Both an objective surface S 320  and an image surface S 321  of the cover glass CG 3  are flat surfaces; 
     With the above design of the lenses and the stop ST 3  and at least any one of the conditions (1)-(4) satisfied, the lens assembly  3  can have an effective shorter total lens length, an effective increased resolution, an effective resisted environmental temperature change, and is capable of an effective corrected aberration. 
     Table 5 shows the optical specification of the lens assembly  3  in  FIG. 5 . 
     
       
         
           
               
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Effective Focal Length = 2.884 mm 
                 F-number = 1.33 
               
               
                 Total Lens Length = 21.199 mm 
                 Field Of View = 146 Degrees 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sur- 
                 Radius  
                   
                   
                   
                 Effective 
                   
               
               
                 face 
                 of 
                 Thick- 
                   
                   
                 Focal 
                   
               
               
                 Num- 
                 Curvature 
                 ness 
                   
                   
                 Length 
                   
               
               
                 ber 
                 (mm) 
                 (mm) 
                 Nd 
                 Vd 
                 (mm) 
                 Remark 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 S31 
                 17.775 
                 0.400 
                 1.7 
                 52.4 
                 −5.525 
                 The First  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L31 
               
               
                 S32 
                 3.110 
                 2.889 
                   
                   
                   
                   
               
               
                 S33 
                 −4.350 
                 0.400 
                 1.59 
                 61.3 
                 −29.726 
                 The Second  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L32 
               
               
                 S34 
                 −6.016 
                 0.063 
                   
                   
                   
                   
               
               
                 S35 
                 −21.630 
                 3.702 
                 2.05 
                 26.9 
                 11.363 
                 The Third  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L33 
               
               
                 S36 
                 −8.180 
                 0.380 
                   
                   
                   
                   
               
               
                 S37 
                 40.286 
                 0.817 
                 1.88 
                 41 
                 16.69 
                 The Fourth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L34 
               
               
                 S38 
                 −22.117 
                 0.306 
                   
                   
                   
                   
               
               
                 S39 
                 ∞ 
                 4.763 
                   
                   
                   
                 Stop ST3 
               
               
                 S310 
                 29.615 
                 1.323 
                 1.62 
                 57.1 
                 20.042 
                 The Fifth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L35 
               
               
                 S311 
                 −20.585 
                 0.095 
                   
                   
                   
                   
               
               
                 S312 
                 11.520 
                 1.305 
                 1.88 
                 41 
                 16.697 
                 The sixth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L36 
               
               
                 S313 
                 55.028 
                 0.091 
                   
                   
                   
                   
               
               
                 S314 
                 6.453 
                 1.761 
                 1.62 
                 56.9 
                 13.995 
                 The seventh  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L37 
               
               
                 S315 
                 23.463 
                 0.840 
                   
                   
                   
                   
               
               
                 S316 
                 −31.573 
                 0.455 
                 1.99 
                 16.5 
                 −16.235 
                 The eighth  
               
               
                   
                   
                   
                   
                   
                   
                 Lens L38 
               
               
                 S317 
                 29.475 
                 0.322 
                   
                   
                   
                   
               
               
                 S318 
                 ∞ 
                 0.210 
                 1.52 
                 64.2 
                   
                 optical filter  
               
               
                   
                   
                   
                   
                   
                   
                 OF3 
               
               
                 S319 
                 ∞ 
                 0.500 
                   
                   
                   
                   
               
               
                 S320 
                 ∞ 
                 0.500 
                 1.52 
                 64.2 
                   
                 cover glass  
               
               
                   
                   
                   
                   
                   
                   
                 CG3 
               
               
                 S321 
                 ∞ 
                 0.076 
               
               
                   
               
            
           
         
       
     
     Table 6 shows the parameters and condition values for conditions (1)-(4) in accordance with the third embodiment of the invention. It can be seen from Table  6  that the lens assembly  3  of the third embodiment satisfies the conditions (1)-(4). 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                 GAP 5678   
                 1.027 mm 
                 T 5678   
                 4.844 mm 
                 D 1   
                 8.500 mm 
               
               
                 D 7   
                 8.267 mm 
               
               
                 GAP 5678 /T 5678   
                 0.212 
                 f 1 /f 
                 −1.916 
                 D 1 /D 7   
                 1.028 
               
               
                 GAP 5678 /TTL 
                 0.048 
               
               
                   
               
            
           
         
       
     
     Besides, by the above arrangements of the lenses and the stop ST 3 , the lens assembly  3  of the third embodiment can meet the requirements of optical performance. It can be seen from  FIG. 6A  that the longitudinal aberration in the lens assembly  3  of the third embodiment ranges from −0.02 mm to 0.03 mm. It can be seen from  FIG. 6B  that the field curvature of tangential direction and sagittal direction in the lens assembly  3  of the third embodiment ranges from −0.04 mm to 0.05 mm. It can be seen from  FIG. 6C  that the distortion in the lens assembly  3  of the third embodiment ranges from −70% to 0%. 
     It is obvious that the longitudinal aberration, the field curvature, and the distortion of the lens assembly  3  of the third embodiment can be corrected effectively. Therefore, the lens assembly  3  of the third embodiment is capable of good optical performance. 
     While the invention has been described by way of example and in terms of the preferred embodiment(s), it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.