Imaging lens

Abstract

To provide an imaging lens having an excellent optical characteristic, while satisfying requirements for reduction in height and a small F number.SOLUTION: The imaging lens comprises a first lens having negative refractive power, a second lens having positive refractive power, a third lens having positive refractive power, a fourth lens having negative refractive power, a fifth lens having positive refractive power, and a sixth lens having negative refractive power, arranged in order from an object side to an image side. The first lens has a biconcave shape on a paraxial axis. The second lens has a convex surface on the object side on the paraxial axis. The fourth lens has a concave surface on the image side on the paraxial axis. The fifth lens has a convex surface on the object side on the paraxial axis. The sixth lens has a concave surface on the image side on the paraxial axis. The zoom lens satisfies a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an imaging lens that forms an image of a subject on a solid-state imaging element such as a CCD sensor or a C-MOS sensor used in an imaging device. [Background technology]

[0002] In recent years, camera functions have been installed in a variety of products, including home appliances, information terminal devices, and automobiles. It is expected that the development of various products incorporating camera functions will continue in the future.

[0003] The imaging lenses mounted on such devices are required to be compact yet have high resolution performance.

[0004] As a conventional imaging lens aiming at high performance, for example, an imaging lens as disclosed in Patent Document 1 below is known.

[0005] Patent Document 1 discloses an imaging lens that is composed of, in order from the object side, a first lens having negative refractive power, a second lens having positive refractive power, a third lens having positive refractive power, a fourth lens having negative refractive power, a fifth lens having positive refractive power, and a sixth lens having negative refractive power, and that is configured so that the angle of view of the imaging lens, the relationship between the focal length of the fifth lens and the focal length of the sixth lens, and the relationship between the paraxial radius of curvature of the object-side surface of the third lens and the paraxial radius of curvature of the image-side surface of the third lens satisfy certain conditions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] China Patent Application Publication No. 111007648 Summary of the Invention [Problem to be solved by the invention]

[0007] When attempting to reduce the height and F-number with the lens configuration described in Patent Document 1, it is extremely difficult to correct aberrations in the peripheral areas, and good optical performance cannot be obtained.

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide an imaging lens that has high resolving power with various aberrations well corrected, while satisfying in a well-balanced manner the requirements for a low height and a low F-number.

[0009] Regarding the terms used in the present invention, the convex, concave, and flat surfaces of a lens are defined as the shapes in the paraxial direction. The refractive power is defined as the refractive power in the paraxial direction. The pole is defined as a point on an aspheric surface other than on the optical axis where the tangent plane intersects the optical axis perpendicularly. The total optical length is defined as the distance on the optical axis from the object-side surface of the optical element located closest to the object to the imaging surface. The total optical length and back focus are the distances obtained by converting the thicknesses of an IR cut filter, a cover glass, etc., placed between the imaging lens and the imaging surface into air. [Means for solving the problem]

[0010] An imaging lens according to the present invention is composed of, arranged in order from the object side to the image side, a first lens having negative refractive power, a second lens having positive refractive power, a third lens having positive refractive power, a fourth lens having negative refractive power, a fifth lens having positive refractive power, and a sixth lens having negative refractive power, wherein the first lens is biconcave in the paraxial direction, the second lens has a convex surface on the object side in the paraxial direction, the fourth lens has a concave surface on the image side in the paraxial direction, the fifth lens has a convex surface on the object side in the paraxial direction, and the sixth lens has a concave surface on the image side in the paraxial direction.

[0011] The first lens has negative refractive power and is biconcave in the paraxial direction, thereby suppressing chromatic aberration, coma, astigmatism, and distortion.

[0012] The second lens has positive refractive power and has a convex surface on the object side in the paraxial direction, thereby providing excellent correction for spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0013] The third lens has a positive refractive power, thereby achieving a low height and effectively correcting spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0014] The fourth lens has negative refractive power and is concave on the image side paraxially, thereby suppressing chromatic aberration, coma, astigmatism, curvature of field, and distortion.

[0015] The fifth lens has positive refractive power and has a convex surface on the object side in the paraxial direction, thereby suppressing spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0016] The sixth lens has negative refractive power and is concave on the image side at paraxial direction to effectively correct chromatic aberration, astigmatism, curvature of field, and distortion. Also, by making the image side concave at paraxial direction, the back focus is secured while maintaining a low height.

[0017] In the imaging lens having the above configuration, it is preferable that the object-side surface of the first lens is formed as an aspheric surface having a pole at a position other than on the optical axis.

[0018] By forming an aspheric surface having a pole point at a position other than on the optical axis on the object side surface of the first lens, it becomes possible to more effectively correct astigmatism, curvature of field, and distortion.

[0019] In the imaging lens having the above configuration, it is preferable that the second lens has a concave surface on the image side paraxially.

[0020] By making the image-side surface of the second lens a concave surface paraxially, coma, curvature of field, and distortion can be effectively corrected.

[0021] In the imaging lens having the above configuration, it is preferable that the image-side surface of the fourth lens is formed as an aspheric surface having a pole at a position other than on the optical axis.

[0022] By forming an aspheric surface having a pole point at a position other than on the optical axis on the image-side surface of the fourth lens, it becomes possible to more effectively correct astigmatism, curvature of field, and distortion.

[0023] In the imaging lens having the above configuration, it is preferable that the sixth lens has a convex surface on the object side paraxially.

[0024] By making the object-side surface of the sixth lens a convex surface on the paraxial direction, it becomes possible to satisfactorily correct astigmatism, curvature of field, and distortion.

[0025] In the imaging lens having the above configuration, it is preferable that the object-side surface of the sixth lens is formed as an aspheric surface having a pole at a position other than on the optical axis.

[0026] By forming an aspheric surface having a pole point at a position other than on the optical axis on the object side surface of the sixth lens, it becomes possible to more effectively correct astigmatism, curvature of field, and distortion.

[0027] In the imaging lens having the above configuration, it is preferable that the image-side surface of the sixth lens is formed as an aspheric surface having a pole at a position other than on the optical axis.

[0028] By forming an aspheric surface having a pole point at a position other than on the optical axis on the image side surface of the sixth lens, it becomes possible to more effectively correct astigmatism, curvature of field, and distortion.

[0029] By adopting the above-mentioned configuration, the imaging lens of the present invention achieves a low height with a total-to-diagonal ratio (the ratio of the total optical length to the diagonal length of the effective imaging surface of the image sensor) of 1.05 or less, and a low F-number of 2.4 or less.

[0030] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (1). (1) 5.75 <f3 / T3<14.50 Here, f3 is the focal length of the third lens, and T3 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.

[0031] By satisfying the range of conditional expression (1), a low height can be achieved and spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0032] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (2). (2) - 5.9 <r1 / r2<-0.9 Here, r1 is the paraxial radius of curvature of the object-side surface of the first lens, and r2 is the paraxial radius of curvature of the image-side surface of the first lens.

[0033] By satisfying the range of conditional expression (2), coma, astigmatism, and distortion can be corrected satisfactorily.

[0034] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (3). (3)11 <r4 / (T2 / T1)<255 where r4 is the paraxial radius of curvature of the image-side surface of the second lens, T2 is the distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens, and T1 is the distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens.

[0035] By satisfying the range of conditional expression (3), a low height can be achieved and coma, curvature of field, and distortion can be favorably corrected.

[0036] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (4). (4)-15 <r6 / T3<-3 Here, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and T3 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.

[0037] By satisfying the range of conditional expression (4), a low height can be achieved and spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0038] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (5). (5)-35.5 <r9 / r10<-4.9 Here, r9 is the paraxial radius of curvature of the object-side surface of the fifth lens, and r10 is the paraxial radius of curvature of the image-side surface of the fifth lens.

[0039] By satisfying the range of conditional expression (5), coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0040] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (6). (6) -36<(T1 / f1)×100<-9 Here, T1 is the distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens, and f1 is the focal length of the first lens.

[0041] By satisfying the range of conditional expression (6), a low height can be achieved and chromatic aberration, coma, astigmatism, and distortion can be favorably corrected.

[0042] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (7). (7)-3.5<(T5 / f6)×100<-0.5 Here, T5 is the distance on the optical axis from the surface of the fifth lens on the image side to the surface of the sixth lens on the object side, and f6 is the focal length of the sixth lens.

[0043] By satisfying the range of conditional expression (7), a low height can be achieved and chromatic aberration, astigmatism, curvature of field, and distortion can be favorably corrected.

[0044] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (8). (8) 0.7 <T4 / T5<4.5 Here, T4 is the distance on the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens, and T5 is the distance on the optical axis from the image-side surface of the fifth lens to the object-side surface of the sixth lens.

[0045] By satisfying the range of conditional expression (8), a low height can be achieved and coma, astigmatism, and distortion can be favorably corrected.

[0046] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (9). (9)-2.5 <f1 / f<-0.5 Here, f1 is the focal length of the first lens, and f is the focal length of the entire imaging lens system.

[0047] By satisfying the range of conditional expression (9), chromatic aberration, coma, astigmatism, and distortion can be corrected satisfactorily.

[0048] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (10). (10)1 <f2 / f<8 Here, f2 is the focal length of the second lens, and f is the focal length of the entire imaging lens system.

[0049] By satisfying the range of conditional expression (10), it becomes possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0050] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (11). (11)-7 <r1 / f<-1 Here, r1 is the paraxial radius of curvature of the object side surface of the first lens, and f is the focal length of the entire imaging lens system.

[0051] By satisfying the range of conditional expression (11), coma, astigmatism, and distortion can be corrected satisfactorily.

[0052] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (12). (12)0.40 <r2 / f<1.65 Here, r2 is the paraxial radius of curvature of the image-side surface of the first lens, and f is the focal length of the entire imaging lens system.

[0053] By satisfying the range of conditional expression (12), coma, astigmatism, and distortion can be corrected satisfactorily.

[0054] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (13). (13)-2.3 <r2 / r1 / D1<-0.3 Here, r2 is the paraxial radius of curvature of the image-side surface of the first lens, r1 is the paraxial radius of curvature of the object-side surface of the first lens, and D1 is the thickness of the first lens on the optical axis.

[0055] By satisfying the range of conditional expression (13), a low height can be achieved and coma, astigmatism, and distortion can be favorably corrected.

[0056] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (14). (14)20 <r4 / T2<450 Here, r4 is the paraxial radius of curvature of the image-side surface of the second lens, and T2 is the distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens.

[0057] By satisfying the range of conditional expression (14), a low height can be achieved and coma, curvature of field, and distortion can be favorably corrected.

[0058] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (15). (15)15 <r5 / T2<250 Here, r5 is the paraxial radius of curvature of the object-side surface of the third lens, and T2 is the distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens.

[0059] By satisfying the range of conditional expression (15), a low height can be achieved and spherical aberration, astigmatism, curvature of field, and distortion can be favorably corrected.

[0060] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (16). (16)-28.0<(r6 / |r7|)×100<-0.2 Here, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and r7 is the paraxial radius of curvature of the object-side surface of the fourth lens.

[0061] By satisfying the range of conditional expression (16), it becomes possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0062] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (17). (17)3<|r7| / f<430 Here, r7 is the paraxial radius of curvature of the object side surface of the fourth lens, and f is the focal length of the entire imaging lens system.

[0063] By satisfying the range of conditional expression (17), coma, astigmatism, and distortion can be corrected satisfactorily.

[0064] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (18). (18)0.5 <r8 / f<3.0 Here, r8 is the paraxial radius of curvature of the image-side surface of the fourth lens, and f is the focal length of the entire imaging lens system.

[0065] By satisfying the range of conditional expression (18), coma, astigmatism, curvature of field, and distortion can be corrected satisfactorily.

[0066] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (19). (19)1.8 <r9 / f<14.5 Here, r9 is the paraxial radius of curvature of the object side surface of the fifth lens, and f is the focal length of the entire imaging lens system.

[0067] By satisfying the range of conditional expression (19), coma, astigmatism, curvature of field, and distortion can be corrected satisfactorily.

[0068] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (20). (20)8.5 <r9 / (T3+D4)<72.5 where r9 is the paraxial radius of curvature of the object-side surface of the fifth lens, T3 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens, and D4 is the thickness on the optical axis of the fourth lens.

[0069] By satisfying the range of conditional expression (20), a low height can be achieved and coma, astigmatism, and distortion can be favorably corrected.

[0070] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (21). (21)-1.2 <r10 / D5<-0.3 Here, r10 is the paraxial radius of curvature of the image-side surface of the fifth lens, and D5 is the thickness of the fifth lens on the optical axis.

[0071] By satisfying the range of conditional expression (21), a low height can be achieved and good correction of astigmatism, curvature of field, and distortion can be achieved.

[0072] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (22). (22)5 <r11 / (T4+T5)<24 where r11 is the paraxial radius of curvature of the object-side surface of the sixth lens, T4 is the distance on the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens, and T5 is the distance on the optical axis from the image-side surface of the fifth lens to the object-side surface of the sixth lens.

[0073] By satisfying the range of conditional expression (22), a low height can be achieved and coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0074] According to the present invention, it is possible to obtain an imaging lens having high resolution and in which various aberrations are well corrected while satisfying the requirements for a low height and a low F-number in a well-balanced manner. [Brief description of the drawings]

[0075] [Figure 1] 1 is a diagram showing a schematic configuration of an imaging lens according to a first embodiment of the present invention. [Diagram 2] 4A to 4C are diagrams illustrating spherical aberration, astigmatism, and distortion of the imaging lens according to the first embodiment of the present invention. [Diagram 3] FIG. 11 is a diagram showing a schematic configuration of an imaging lens according to a second embodiment of the present invention. [Figure 4] 5A to 5C are diagrams illustrating spherical aberration, astigmatism, and distortion of the imaging lens according to the second embodiment of the present invention. [Diagram 5] FIG. 11 is a diagram showing a schematic configuration of an imaging lens according to a third embodiment of the present invention. [Figure 6] 11A to 11C are diagrams illustrating spherical aberration, astigmatism, and distortion of the imaging lens according to Example 3 of the present invention. [Figure 7] FIG. 11 is a diagram showing a schematic configuration of an imaging lens according to a fourth embodiment of the present invention. [Figure 8] 11A to 11C are diagrams illustrating spherical aberration, astigmatism, and distortion of the imaging lens according to Example 4 of the present invention. [Figure 9] FIG. 11 is a diagram showing a schematic configuration of an imaging lens according to a fifth embodiment of the present invention. [Figure 10] 13A to 13C are diagrams illustrating spherical aberration, astigmatism, and distortion of the imaging lens according to Example 5 of the present invention. [Figure 11]FIG. 13 is a diagram showing a schematic configuration of an imaging lens according to a sixth embodiment of the present invention. [Figure 12] 13 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 6 of the present invention. [Figure 13] FIG. 13 is a diagram showing a schematic configuration of an imaging lens according to a seventh embodiment of the present invention. [Figure 14] 13 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 7 of the present invention. FIG. [Figure 15] FIG. 13 is a diagram showing a schematic configuration of an imaging lens according to an eighth embodiment of the present invention. [Figure 16] 13 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 8 of the present invention. FIG. [Figure 17] FIG. 13 is a diagram showing a schematic configuration of an imaging lens according to a ninth embodiment of the present invention. [Figure 18] 13 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 9 of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0077] 1, 3, 5, 7, 9, 11, 13, 15, and 17 are schematic configuration diagrams of imaging lenses according to Examples 1 to 9 of the embodiments of the present invention, respectively. Details of the embodiments of the present invention will be described below with reference to FIG.

[0078] As shown in FIG. 1, the imaging lens according to the present invention is composed of, arranged in order from the object side to the image side, a first lens L1 having negative refractive power, a second lens L2 having positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having negative refractive power, a fifth lens L5 having positive refractive power, and a sixth lens L6 having negative refractive power, wherein the first lens L1 is biconcave in the paraxial direction, the second lens L2 has a convex surface on the object side in the paraxial direction, the fourth lens L4 has a concave surface on the image side in the paraxial direction, the fifth lens L5 has a convex surface on the object side in the paraxial direction, and the sixth lens L6 has a concave surface on the image side in the paraxial direction.

[0079] In addition, a filter IR such as an infrared cut filter or a cover glass is disposed between the sixth lens L6 and the imaging surface IMG (that is, the imaging surface of the imaging element). Note that this filter IR can be omitted.

[0080] The aperture stop ST is disposed between the second lens L2 and the third lens L3, which facilitates correction of distortion. The position of the aperture stop ST is not limited to between the second lens L2 and the third lens L3. It may be disposed appropriately according to the specifications of the image sensor.

[0081] The first lens L1 has negative refractive power and is biconcave paraxially, thereby suppressing chromatic aberration, coma, astigmatism, and distortion.

[0082] In addition, the aspheric surface formed on the object-side surface of the first lens L1 has a pole point at a position other than on the optical axis X. This makes it possible to more effectively suppress astigmatism, curvature of field, and distortion.

[0083] The second lens L2 has positive refractive power and is a meniscus shape with a convex surface on the object side on the paraxial line, thereby providing excellent correction for spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0084] The third lens L3 has positive refractive power and a paraxial biconvex shape, which allows for a low height and excellent correction of spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0085] The fourth lens L4 has a negative refractive power and is a meniscus shape with a concave image side on the paraxial line. Therefore, chromatic aberration, coma aberration, astigmatism, field curvature, and distortion are well corrected. The shape of the fourth lens L4 is not limited to the shape according to the present numerical example 1. The shape of the fourth lens L4 may be a reverse meniscus shape, that is, a meniscus shape with a convex image side on the paraxial line. Furthermore, it may be a biconcave shape on the paraxial line. In this case, the negative refractive power on both sides is advantageous for correcting chromatic aberration.

[0086] In addition, the aspheric surface formed on the image-side surface of the fourth lens L4 has a pole point at a position other than on the optical axis X. Therefore, astigmatism, curvature of field, and distortion are corrected more satisfactorily.

[0087] The fifth lens L5 has positive refractive power and is biconvex on the paraxial direction, thereby providing excellent correction for spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0088] The sixth lens L6 has negative refractive power and is a meniscus shape with a concave surface on the image side at paraxial position. Therefore, chromatic aberration, astigmatism, curvature of field, and distortion aberration are corrected well. In addition, by making the image side concave at paraxial position, the back focus is secured while maintaining a low height.

[0089] In addition, the aspheric surface formed on the object side surface of the sixth lens L6 has a pole point at a position other than on the optical axis X. Therefore, astigmatism, field curvature, and distortion are corrected more satisfactorily.

[0090] Furthermore, the aspheric surface formed on the image-side surface of the sixth lens L6 has a pole point at a position other than on the optical axis X. Therefore, astigmatism, field curvature, and distortion are corrected more satisfactorily.

[0091] In the imaging lens according to this embodiment, it is preferable that each of the first lens L1 to the sixth lens L6 is composed of a single lens. A composition consisting of only single lenses can make extensive use of aspherical surfaces. In this embodiment, by forming appropriate aspherical surfaces on all lens surfaces, various aberrations are corrected satisfactorily. In addition, since the number of steps can be reduced compared to the case of using cemented lenses, it is possible to manufacture the lens at low cost.

[0092] Furthermore, the imaging lens according to this embodiment is easy to manufacture by using plastic materials for all the lenses, enabling mass production at low cost.

[0093] The lens material is not limited to plastic materials. It is possible to aim for even higher performance by using glass materials. It is also preferable to form all lens surfaces aspheric, but depending on the required performance, spherical surfaces, which are easier to manufacture, may be used.

[0094] The imaging lens of this embodiment exerts favorable effects by satisfying the following conditional expressions (1) to (22). (1) 5.75 <f3 / T3<14.50 (2) - 5.9 <r1 / r2<-0.9 (3)11 <r4 / (T2 / T1)<255 (4)-15 <r6 / T3<-3 (5)-35.5 <r9 / r10<-4.9 (6) -36<(T1 / f1)×100<-9 (7)-3.5<(T5 / f6)×100<-0.5 (8) 0.7 <T4 / T5<4.5 (9)-2.5 <f1 / f<-0.5 (10)1 <f2 / f<8 (11)-7 <r1 / f<-1 (12)0.40 <r2 / f<1.65 (13)-2.3 <r2 / r1 / D1<-0.3 (14)20 <r4 / T2<450 (15)15 <r5 / T2<250 (16)-28.0<(r6 / |r7|)×100<-0.2 (17)3<|r7| / f<430 (18)0.5 <r8 / f<3.0 (19)1.8 <r9 / f<14.5 (20)8.5 <r9 / (T3+D4)<72.5 (21)-1.2 <r10 / D5<-0.3 (22)5 <r11 / (T4+T5)<24 however, D1: Thickness of the first lens L1 on the optical axis X D4: Thickness of the fourth lens L4 on the optical axis X D5: Thickness of the fifth lens L5 on the optical axis X T1: the distance on the optical axis X from the image-side surface of the first lens L1 to the object-side surface of the second lens L2 T2: the distance on the optical axis X from the image-side surface of the second lens L2 to the object-side surface of the third lens L3 T3: the distance on the optical axis X from the image-side surface of the third lens L3 to the object-side surface of the fourth lens L4 T4: the distance on the optical axis X from the image-side surface of the fourth lens L4 to the object-side surface of the fifth lens L5 T5: the distance on the optical axis X from the image-side surface of the fifth lens L5 to the object-side surface of the sixth lens L6 f: focal length of the entire imaging lens system f1: focal length of the first lens L1 f2: focal length of second lens L2 f3: focal length of the third lens L3 f6: focal length of the sixth lens L6 r1: paraxial radius of curvature of the object side surface of the first lens L1 r2: paraxial radius of curvature of the image-side surface of the first lens L1 r4: paraxial radius of curvature of the image-side surface of the second lens L2 r5: paraxial radius of curvature of the object-side surface of the third lens L3 r6: Paraxial curvature radius of the image side surface of the third lens L3 r7: Paraxial radius of curvature of the object side surface of the fourth lens L4 r8: Paraxial curvature radius of the image side surface of the fourth lens L4 r9: paraxial radius of curvature of the object side surface of the fifth lens L5 r10: Paraxial curvature radius of the image side surface of the fifth lens L5 r11: Paraxial radius of curvature of the object side surface of the sixth lens L6 It is not necessary to satisfy all of the above conditional expressions. By satisfying each conditional expression individually, it is possible to obtain the effect corresponding to each conditional expression.

[0095] Moreover, the imaging lens of this embodiment exerts more preferable effects by satisfying the following conditional expressions (1a) to (22a). (1a)6.5 <f3 / T3<12.5 (2a)-5.7 <r1 / r2<-1.2 (3a)16 <r4 / (T2 / T1)<210 (4a)-13.5 <r6 / T3<-4.5 (5a)-30.0 <r9 / r10<-5.8 (6a) -30.0<(T1 / f1)×100<-13.5 (7a)-2.9<(T5 / f6)×100<-1.1 (8a)1.1 <T4 / T5<3.6 (9a)-2.0 <f1 / f<-0.9 (10a)2.0. <f2 / f<6.5 (11a)-5.9 <r1 / f<-1.5 (12a) 0.60 <r2 / f<1.50 (13a)-2.0 <r2 / r1 / D1<-0.5 (14a)30 <r4 / T2<370 (15a)21 <r5 / T2<200 (16a)-23.0<(r6 / |r7|)×100<-0.4 (17a) 4.5<|r7| / f<350.0 (18a) 0.9 <r8 / f<2.3 (19a)2.4 <r9 / f<12.0 (20a)9.5 <r9 / (T3+D4)<52.5 (21a)-1.0 <r10 / D5<-0.5 (22a)7 <r11 / (T4+T5)<20 However, the symbols in each conditional expression are the same as those explained in the previous paragraph. Note that only the lower limit value or only the upper limit value of each of the conditional expressions (1a) to (22a) may be applied to the corresponding conditional expressions (1) to (22).

[0096] In this embodiment, the aspheric shape adopted for the aspheric surface of the lens surface is expressed by Formula 1, where Z is the axis in the optical axis direction, H is the height in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic coefficient, and A4, A6, A8, A10, A12, A14, A16, A18, and A20 are aspheric coefficients.

[0097]

number

[0098] Next, examples of the imaging lens according to this embodiment are shown. In each example, f denotes the focal length of the entire imaging lens system, Fno denotes the F-number, ω denotes the half angle of view, ih denotes the maximum image height, and TTL denotes the total optical length. Also, i denotes the surface number counted from the object side, r denotes the paraxial radius of curvature, d denotes the distance between lens surfaces on the optical axis (surface spacing), Nd denotes the refractive index of the d-line (reference wavelength), and νd denotes the Abbe number for the d-line. Aspheric surfaces are indicated by adding an asterisk (*) after the surface number i.

[0099] Example 1

[0100] Basic lens data is shown in Table 1 below.

[0101] [Table 1]

[0102] The imaging lens of Example 1 achieves a total length to diagonal ratio of 0.94 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0103] FIG. 2 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 1. The spherical aberration diagram shows the amount of aberration for each wavelength of the F-line (486 nm), d-line (588 nm), and C-line (656 nm). The astigmatism diagram also shows the amount of aberration for the d-line (solid line) at the sagittal image plane S and the amount of aberration for the d-line (broken line) at the tangential image plane T (the same applies to FIGS. 4, 6, 8, 10, 12, 14, 16, and 18). As shown in FIG. 2, it can be seen that each aberration is well corrected.

[0104] Example 2

[0105] Basic lens data is shown in Table 2 below.

[0106] [Table 2]

[0107] The imaging lens of Example 2 achieves a total length to diagonal ratio of 0.95 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0108] Fig. 4 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 2. As shown in Fig. 4, it can be seen that each aberration is well corrected.

[0109] Example 3

[0110] Basic lens data is shown in Table 3 below.

[0111] [Table 3]

[0112] The imaging lens of Example 3 achieves a total length to diagonal ratio of 0.96 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0113] Fig. 6 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 3. As shown in Fig. 6, it can be seen that each aberration is well corrected.

[0114] Example 4

[0115] Basic lens data is shown in Table 4 below.

[0116] [Table 4]

[0117] The imaging lens of Example 4 achieves a total length to diagonal ratio of 0.94 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0118] Fig. 8 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 4. As shown in Fig. 8, it can be seen that each aberration is well corrected.

[0119] Example 5

[0120] Basic lens data is shown in Table 5 below.

[0121] [Table 5]

[0122] The imaging lens of Example 5 achieves a total length to diagonal ratio of 0.94 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0123] Fig. 10 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 5. As shown in Fig. 10, it can be seen that each aberration is well corrected.

[0124] Example 6

[0125] Basic lens data is shown in Table 6 below.

[0126] [Table 6]

[0127] The imaging lens of Example 6 achieves a total length to diagonal ratio of 0.94 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0128] Fig. 12 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 6. As shown in Fig. 12, it can be seen that each aberration is well corrected.

[0129] Example 7

[0130] Basic lens data is shown in Table 7 below.

[0131] [Table 7]

[0132] The imaging lens of Example 7 achieves a total length to diagonal ratio of 0.95 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0133] Fig. 14 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 7. As shown in Fig. 14, it can be seen that each aberration is well corrected.

[0134] Example 8

[0135] Basic lens data is shown in Table 8 below.

[0136] [Table 8]

[0137] The imaging lens of Example 8 achieves a total length to diagonal ratio of 0.71 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0138] Fig. 16 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 8. As shown in Fig. 16, it can be seen that each aberration is well corrected.

[0139] Example 9

[0140] Basic lens data is shown in Table 9 below.

[0141] [Table 9]

[0142] The imaging lens of Example 9 achieves a total length to diagonal ratio of 0.95 and an F-number of 2.2. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (22).

[0143] Fig. 18 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 9. As shown in Fig. 18, it can be seen that each aberration is well corrected.

[0144] Table 10 shows the values ​​of conditional expressions (1) to (22) according to Examples 1 to 9.

[0145] [Table 10] [Industrial Applicability]

[0146] When the imaging lens according to the present invention is applied to a product equipped with a camera function, it is possible to contribute to a reduction in the height and F-number of the camera, and to improve the performance. [Explanation of symbols]

[0147] ST aperture stop L1 First lens L2 Second lens L3 Third lens L4 4th lens L5 5th lens L6 6th lens IR Filter IMG Imaging surface

Claims

1. Arranged in order from the object side to the image side, a first lens having a negative refractive power; a second lens having a positive refractive power; a third lens having a positive refractive power; a fourth lens having a negative refractive power; a fifth lens having a positive refractive power; and a sixth lens having a negative refractive power, the first lens is paraxially biconcave; The second lens has a convex surface on the object side in a paraxial direction. the fourth lens has a paraxial concave surface on the image side, The fifth lens has a convex surface on the object side in a paraxial direction. the sixth lens has a paraxial concave surface on the image side, An imaging lens characterized by satisfying the following conditional expressions (1), (2), and (7'): (1) 5.75<f3 / T3<14.50 (2) -5.9<r1 / r2<-0.9 (7')-3.5<(T5 / f6)×100≦-1.70 however, f3: focal length of the third lens T3: the distance on the optical axis from the image side surface of the third lens to the object side surface of the fourth lens r1: paraxial radius of curvature of the object side surface of the first lens r2: paraxial radius of curvature of the image side surface of the first lens T5: the distance on the optical axis from the image side surface of the fifth lens to the object side surface of the sixth lens f6: focal length of the sixth lens

2. 2. The imaging lens according to claim 1, wherein the second lens has a concave surface on the image side in a paraxial direction.

3. 2. The imaging lens according to claim 1, wherein the sixth lens has a convex surface on the object side in a paraxial direction.

4. 2. The imaging lens according to claim 1, wherein the following conditional expression (3) is satisfied: (3) 11<r4 / (T2 / T1)<255 however, r4: paraxial radius of curvature of the image side surface of the second lens T2: the distance on the optical axis from the image side surface of the second lens to the object side surface of the third lens T1: distance on the optical axis from the image side surface of the first lens to the object side surface of the second lens

5. 2. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied: (4) -15<r6 / T3<-3 however, r6: paraxial radius of curvature of the image side surface of the third lens T3: the distance on the optical axis from the image side surface of the third lens to the object side surface of the fourth lens

6. 2. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied: (5) -35.5<r9 / r10<-4.9 however, r9: paraxial radius of curvature of the object side surface of the fifth lens r10: paraxial radius of curvature of the image side surface of the fifth lens

Images