Imaging lens

Abstract

To provide an image capturing lens which satisfies requirements of a low height and low F-number, and yet offers good optical characteristics.SOLUTION: An image capturing lens provided herein consists of a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive or negative refractive power, a fourth lens having positive refractive power, a fifth lens, and a sixth lens having negative refractive power arranged in order from the object side to the image side, where the first lens has an object-side surface that is convex near an optical axis and the sixth lens has an image-side surface that is concave near the optical axis. The image capturing lens satisfies predetermined conditional expressions.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 composed of, in order from the object side, a first lens, a second lens having a positive refractive index, a third lens having a negative refractive index, a fourth lens, a fifth lens, and a sixth lens, in which the relationship between the focal length of the first lens and the focal length of the second lens, and the paraxial radius of curvature of the object-side surface of the second lens and the paraxial radius of curvature of the image-side surface of the second lens satisfy certain conditions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] China Patent Publication No. 110346908 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 positive refractive power, a second lens having negative refractive power, a third lens having positive or negative refractive power, a fourth lens having positive refractive power, a fifth lens, and a sixth lens having negative refractive power, in which the first lens has a convex surface facing the object side in a paraxial direction, and the sixth lens has a concave surface facing the image side in a paraxial direction.

[0011] The first lens has positive refractive power, and has aspheric surfaces formed on both sides, and has a convex surface on the object side in the paraxial direction, thereby suppressing spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0012] The second lens has negative refractive power and has aspheric surfaces on both sides, thereby providing excellent correction for chromatic aberration, astigmatism, curvature of field, and distortion.

[0013] The third lens has a positive or negative refractive power and has aspherical surfaces on both sides. When it has a positive refractive power, it effectively corrects spherical aberration, astigmatism, curvature of field, and distortion. When it has a negative refractive power, it effectively corrects chromatic aberration, astigmatism, curvature of field, and distortion.

[0014] The fourth lens has positive refractive power and has aspheric surfaces on both sides, thereby achieving a low height and providing excellent correction for coma, astigmatism, curvature of field, and distortion.

[0015] The fifth lens has aspheric surfaces on both sides, which effectively corrects astigmatism, field curvature, and distortion.

[0016] The sixth lens has negative refractive power and is aspherical on both sides to effectively correct chromatic aberration, astigmatism, curvature of field, and distortion. In addition, the image side is concave on the paraxial line to ensure a low back focus while maintaining a low profile.

[0017] In the imaging lens having the above configuration, it is preferable that the first lens has a concave surface on the image side paraxially.

[0018] By making the image-side surface of the first lens a paraxial concave surface, it becomes possible to satisfactorily correct astigmatism and distortion.

[0019] In the imaging lens having the above configuration, it is preferable that the second lens has a convex surface on the object side in the paraxial direction.

[0020] By making the object-side surface of the second lens a convex surface in the paraxial direction, it becomes possible to satisfactorily correct astigmatism, curvature of field, and distortion.

[0021] In the imaging lens having the above configuration, it is preferable that the second lens has a concave surface on the image side paraxially.

[0022] By making the image-side surface of the second lens a concave surface paraxially, it becomes possible to satisfactorily correct astigmatism, curvature of field, and distortion.

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

[0024] By making the image-side surface of the fourth lens a convex surface on the paraxial direction, coma, astigmatism, curvature of field, and distortion can be effectively corrected.

[0025] In the imaging lens having the above configuration, it is preferable that the sixth lens has a convex surface on the object side paraxially.

[0026] 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.

[0027] 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.

[0028] By forming an aspheric shape 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, field curvature, and distortion.

[0029] 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.

[0030] By forming an aspheric shape 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.

[0031] 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 0.7 or less, and a low F-number of 2.0 or less.

[0032] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (1). (1) 11.00<νd3<26.00 Here, νd3 is the Abbe number for the d-line of the third lens.

[0033] Conditional expression (1) defines an appropriate range for the Abbe number of the third lens element with respect to the d-line. By satisfying the range of conditional expression (1), favorable correction of chromatic aberration becomes possible.

[0034] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (2). (2) 0.10<(r2 / |r6|)×100<100.00 Here, r2 is the paraxial radius of curvature of the image-side surface of the first lens, and r6 is the paraxial radius of curvature of the image-side surface of the third lens.

[0035] Conditional expression (2) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the first lens and the paraxial radius of curvature of the image-side surface of the third lens. Satisfying the range of conditional expression (2) enables good correction of astigmatism, field curvature, and distortion.

[0036] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (3). (3) 1.60<(|r5 / r6|)×100 Here, r5 is the paraxial radius of curvature of the object-side surface of the third lens, and r6 is the paraxial radius of curvature of the image-side surface of the third lens.

[0037] Conditional expression (3) defines an appropriate range for 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. Satisfying the range of conditional expression (3) enables good correction of astigmatism, field curvature, and distortion.

[0038] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (4). (4) 0.50 <r11 / (T4+D5+T5)<6.75 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, D5 is the thickness of the fifth lens on the optical axis, 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.

[0039] Conditional expression (4) defines the relationship between the paraxial radius of curvature of the object-side surface of the sixth lens, the axial distance from the image-side surface of the fourth lens to the object-side surface of the fifth lens, the axial thickness of the fifth lens, and the axial distance from the image-side surface of the fifth lens to the object-side surface of the sixth lens within an appropriate range. By satisfying the range of conditional expression (4), a low height can be achieved and good correction of coma, astigmatism, curvature of field, and distortion can be achieved.

[0040] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (5). (5)0.05<(r2 / r4 / |r6|)×100<7.00 Here, r2 is the paraxial radius of curvature of the image side surface of the first lens, r4 is the paraxial radius of curvature of the image side surface of the second lens, and r6 is the paraxial radius of curvature of the image side surface of the third lens.

[0041] Conditional expression (5) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the first lens, the paraxial radius of curvature of the image-side surface of the second lens, and the paraxial radius of curvature of the image-side surface of the third lens. Satisfying the range of conditional expression (5) enables good correction of astigmatism, field curvature, and distortion.

[0042] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (6). (6)-5.00 <r3 / f2<-1.00 Here, r3 is the paraxial radius of curvature of the object side surface of the second lens, and f2 is the focal length of the second lens.

[0043] Conditional expression (6) defines an appropriate range for the paraxial radius of curvature of the object-side surface of the second lens and the focal length of the second lens. Satisfying the range of conditional expression (6) enables favorable correction of chromatic aberration, astigmatism, field curvature, and distortion.

[0044] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (7). (7)3.25 <r3 / (T2 / T1)<11.50 where r3 is the paraxial radius of curvature of the object-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 first lens.

[0045] Conditional expression (7) defines the relationship between the paraxial radius of curvature of the object-side surface of the second lens, 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 the distance on the optical axis from the image-side surface of the first lens to the object-side surface of the first lens within an appropriate range. Satisfying the range of conditional expression (7) enables a low height to be achieved and good correction of astigmatism, field curvature, and distortion aberrations to be achieved.

[0046] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (8). (8) 33.00<νd4<77.00 Here, νd4 is the Abbe number for the d-line of the fourth lens.

[0047] Condition (8) defines an appropriate range for the Abbe number of the fourth lens for the d-line. By satisfying the range of condition (8), favorable correction of chromatic aberration becomes possible.

[0048] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (9). (9)7.75 <f4 / D4<90.00 Here, f4 is the focal length of the fourth lens, and D4 is the thickness of the fourth lens on the optical axis.

[0049] Condition (9) defines an appropriate range for the focal length of the fourth lens and the thickness of the fourth lens on the optical axis. By satisfying the range of condition (9), a low height can be achieved and coma, astigmatism, curvature of field, and distortion can be effectively corrected.

[0050] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (10). (10) 8.00<(f1 / f4)×100<65.00 Here, f1 is the focal length of the first lens, and f4 is the focal length of the fourth lens.

[0051] Condition (10) defines an appropriate range for the relationship between the focal length of the first lens and the focal length of the fourth lens. By satisfying the range of condition (10), a low height can be achieved and spherical aberration, coma, astigmatism, curvature of field, and distortion can be effectively corrected.

[0052] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (11). (11) 9.50<|r6| / r12 Here, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and r12 is the paraxial radius of curvature of the image-side surface of the sixth lens.

[0053] Conditional expression (11) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the third lens and the paraxial radius of curvature of the image-side surface of the sixth lens. Satisfying the range of conditional expression (11) enables good correction of astigmatism, field curvature, and distortion.

[0054] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (12). (12) 1.50 <r3 / r4<9.00 Here, r3 is the paraxial radius of curvature of the object-side surface of the second lens, and r4 is the paraxial radius of curvature of the image-side surface of the second lens.

[0055] Conditional expression (12) defines an appropriate range for the relationship between the paraxial radius of curvature of the object-side surface of the second lens and the paraxial radius of curvature of the image-side surface of the second lens. Satisfying the range of conditional expression (12) enables good correction of astigmatism, field curvature, and distortion.

[0056] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (13). (13) 0.30<(r4 / |r6|)×100<38.75 Here, r4 is the paraxial radius of curvature of the image-side surface of the second lens, and r6 is the paraxial radius of curvature of the image-side surface of the third lens.

[0057] Conditional expression (13) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the second lens and the paraxial radius of curvature of the image-side surface of the third lens. Satisfying the range of conditional expression (13) enables good correction of astigmatism, field curvature, and distortion.

[0058] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (14). (14)-2.50 <r8 / r11<-0.40 Here, r8 is the paraxial radius of curvature of the image-side surface of the fourth lens, and r11 is the paraxial radius of curvature of the object-side surface of the sixth lens.

[0059] Conditional expression (14) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the fourth lens and the paraxial radius of curvature of the object-side surface of the sixth lens. Satisfying the range of conditional expression (14) enables good correction of coma, astigmatism, curvature of field, and distortion.

[0060] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (15). (15) 1.00 <r11 / r12<4.50 Here, r11 is the paraxial radius of curvature of the object-side surface of the sixth lens, and r12 is the paraxial radius of curvature of the image-side surface of the sixth lens.

[0061] Conditional expression (15) defines an appropriate range for the relationship between the paraxial radius of curvature of the object-side surface of the sixth lens and the paraxial radius of curvature of the image-side surface of the sixth lens. Satisfying the range of conditional expression (15) enables good correction of astigmatism, field curvature, and distortion.

[0062] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (16). (16)2.30 <r3 / f<14.00 Here, r3 is the paraxial radius of curvature of the object side surface of the second lens, and f is the focal length of the entire imaging lens system.

[0063] Condition (16) defines an appropriate range for the paraxial radius of curvature of the object-side surface of the second lens. Satisfying the range of condition (16) enables favorable correction of astigmatism, field curvature, and distortion.

[0064] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (17). (17) 10.00 <r4 / T2<30.00 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.

[0065] Conditional expression (17) defines an appropriate range for the paraxial radius of curvature of the image-side surface of the second lens and the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens. Satisfying the range of conditional expression (17) enables a low height and good correction of astigmatism, field curvature, and distortion.

[0066] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (18). (18)2.10<|r5| / f Here, r5 is the paraxial radius of curvature of the object side surface of the third lens, and f is the focal length of the entire imaging lens system.

[0067] Condition (18) defines an appropriate range for the paraxial radius of curvature of the object-side surface of the third lens. Satisfying the range of condition (18) enables favorable correction of astigmatism, curvature of field, and distortion.

[0068] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (19). (19)47.00<|r6| / D3 Here, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and D3 is the thickness of the third lens on the optical axis.

[0069] Condition (19) defines an appropriate range for the paraxial radius of curvature of the image-side surface of the third lens and the axial thickness of the third lens. Satisfying the range of condition (19) enables a low height and good correction of astigmatism, field curvature, and distortion.

[0070] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (20). (20)0.20 <r11 / f<1.35 Here, r11 is the paraxial radius of curvature of the object side surface of the sixth lens, and f is the focal length of the entire imaging lens system.

[0071] Condition (20) defines an appropriate range for the paraxial radius of curvature of the object-side surface of the third lens. Satisfying the range of condition (20) enables favorable correction of astigmatism, curvature of field, and distortion.

[0072] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (21). (21)4.15<|r6| / r11 Here, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and r11 is the paraxial radius of curvature of the object-side surface of the sixth lens.

[0073] Conditional expression (21) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the third lens and the paraxial radius of curvature of the object-side surface of the sixth lens. Satisfying the range of conditional expression (21) enables good correction of astigmatism, field curvature, and distortion.

[0074] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (22). (22) 18.50<|r6| / (T2+D3) where r6 is the paraxial radius of curvature of the image-side surface of the third 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 D3 is the thickness on the optical axis of the third lens.

[0075] Conditional expression (22) defines the relationship between the paraxial radius of curvature of the image-side surface of the third lens, 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 the thickness on the optical axis of the third lens within an appropriate range. Satisfying the range of conditional expression (22) enables a low height to be achieved and good correction of astigmatism, field curvature, and distortion aberrations.

[0076] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (23). (23)0.32 <r12 / r11<1.00 Here, r12 is the paraxial radius of curvature of the image-side surface of the sixth lens, and r11 is the paraxial radius of curvature of the object-side surface of the sixth lens.

[0077] Conditional expression (23) defines an appropriate range for the relationship between the paraxial radius of curvature of the image-side surface of the sixth lens and the paraxial radius of curvature of the object-side surface of the sixth lens. Satisfying the range of conditional expression (23) enables good correction of astigmatism, field curvature, and distortion.

[0078] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (24). (24)2.50 <r11 / D6<12.00 Here, r11 is the paraxial radius of curvature of the object side surface of the sixth lens, and D6 is the thickness of the sixth lens on the optical axis.

[0079] Moreover, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (25). (25)0.75 <r4 / (T2 / T1)<3.50 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. Effect of the Invention

[0080] 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]

[0081] [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

[0082] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0083] 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 embodiment of the present invention, respectively.

[0084] The imaging lens of this embodiment is composed of, arranged in order from the object side to the image side, a first lens L1 having positive refractive power, a second lens L2 having negative refractive power, a third lens L3 having positive or negative refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5, and a sixth lens L6 having negative refractive power, in which the first lens L1 has a convex surface facing the object side in the paraxial direction, and the sixth lens L6 has a concave surface facing the image side in the paraxial direction.

[0085] 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.

[0086] The aperture stop ST is disposed on the object side of the first lens L1, which facilitates correction of various aberrations and facilitates control of the angle at which light rays with high image height enter the imaging element.

[0087] The first lens L1 has positive refractive power and is a meniscus shape with a convex surface on the object side and a concave surface on the image side on the paraxial line. In addition, both sides are aspheric. This suppresses spherical aberration, coma, astigmatism, curvature of field, and distortion.

[0088] The second lens L2 has negative refractive power, and is a meniscus shape with a convex surface on the object side and a concave surface on the image side on the paraxial line. In addition, both sides are aspheric. Therefore, chromatic aberration, astigmatism, curvature of field, and distortion aberration are well corrected.

[0089] The third lens L3 has a positive refractive power in Examples 1, 3, 4, 5, 6, and 9 shown in Figs. 1, 5, 7, 9, 11, and 17, and has a negative refractive power in Examples 2, 7, and 8 shown in Figs. 3, 13, and 15. When the third lens L3 has a positive refractive power, it is possible to correct spherical aberration, astigmatism, curvature of field, and distortion aberration well. When the third lens L3 has a negative refractive power, it is possible to correct chromatic aberration, astigmatism, curvature of field, and distortion aberration well.

[0090] Regarding the shape of the third lens L3, Example 1 shown in FIG. 1 has a biconvex shape with a convex object side and a convex image side on the paraxial line. Example 2, Example 3, Example 4, Example 5, Example 8, and Example 9 shown in FIG. 3, FIG. 5, FIG. 7, FIG. 9, FIG. 15, and FIG. 17 have a meniscus shape with a convex object side and a concave image side. Example 6 and Example 7 shown in FIG. 11 and FIG. 13 have a meniscus shape with a concave object side and a convex image side. Note that aspheric surfaces are formed on both sides in all examples. Here, when the third lens L3 has a biconvex shape on the paraxial line, it is possible to make good corrections to spherical aberration, astigmatism, curvature of field, and distortion. When the third lens L3 has a meniscus shape with a convex object side and a concave image side on the paraxial line, it is possible to make good corrections to astigmatism, curvature of field, and distortion. When the third lens L3 has a meniscus shape with a concave surface on the object side and a convex surface on the image side on the paraxial line, it becomes possible to satisfactorily correct astigmatism, curvature of field, and distortion.

[0091] The fourth lens L4 has positive refractive power, and is a meniscus shape with a concave surface on the object side and a convex surface on the image side on the paraxial line. In addition, both sides are aspheric. Therefore, coma, astigmatism, curvature of field, and distortion are well corrected.

[0092] The fifth lens L5 has substantially no refractive power, and the object-side and image-side surfaces are formed as flat surfaces in the paraxial direction. In addition, aspheric surfaces are formed on both sides. Therefore, astigmatism, field curvature, and distortion are well corrected by the aspheric surfaces formed on both sides without affecting the focal length of the entire imaging lens system.

[0093] The refractive power of the fifth lens L5 may be negative as in Example 6 and Example 9 shown in FIG. 11 and FIG. 17. In this case, it is advantageous for correcting chromatic aberration. Furthermore, the refractive power of the fifth lens L5 may be positive as in Example 7 and Example 8 shown in FIG. 13 and FIG. 15. In this case, it is advantageous for correcting spherical aberration.

[0094] The shape of the fifth lens L5 may be a meniscus shape with a convex object side and a concave image side on the paraxial line, as in Example 6, Example 7, and Example 8 shown in Figs. 11, 13, and 15. In this case, good correction of astigmatism, curvature of field, and distortion is possible. The shape of the fifth lens L5 may be a meniscus shape with a concave object side and a convex image side on the paraxial line, as in Example 9 shown in Fig. 17. In this case, good correction of astigmatism, curvature of field, and distortion is possible.

[0095] The sixth lens L6 has negative refractive power and is a meniscus concave shape with a convex surface on the object side and a concave surface on the image side on the paraxial line. In addition, aspheric surfaces are formed on both sides. Therefore, chromatic aberration, astigmatism, curvature of field, and distortion aberration are corrected. By making the surface on the image side of the sixth lens L6 a concave surface on the paraxial line, the back focus is secured while maintaining a low height.

[0096] 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, curvature of field, and distortion are well corrected.

[0097] 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.

[0098] 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 man-hours can be reduced compared to the case of using cemented lenses, it is possible to manufacture the lens at low cost.

[0099] Furthermore, the imaging lens according to this embodiment is made of a plastic material, which makes it easy to manufacture and allows for mass production at low cost.

[0100] 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.

[0101] The imaging lens of this embodiment exerts favorable effects by satisfying the following conditional expressions (1) to (25). (1) 11.00<νd3<26.00 (2) 0.10<(r2 / |r6|)×100<100.00 (3) 1.60<(|r5 / r6|)×100 (4) 0.50 <r11 / (T4+D5+T5)<6.75 (5)0.05<(r2 / r4 / |r6|)×100<7.00 (6)-5.00 <r3 / f2<-1.00 (7)3.25 <r3 / (T2 / T1)<11.50 (8) 33.00<νd4<77.00 (9)7.75 <f4 / D4<90.00 (10) 8.00<(f1 / f4)×100<65.00 (11) 9.50<|r6| / r12 (12) 1.50 <r3 / r4<9.00 (13) 0.30<(r4 / |r6|)×100<38.75 (14)-2.50 <r8 / r11<-0.40 (15) 1.00 <r11 / r12<4.50 (16)2.30 <r3 / f<14.00 (17) 10.00 <r4 / T2<30.00 (18)2.10<|r5| / f (19)47.00<|r6| / D3 (20)0.20 <r11 / f<1.35 (21)4.15<|r6| / r11 (22) 18.50<|r6| / (T2+D3) (23)0.32 <r12 / r11<1.00 (24)2.50 <r11 / D6<12.00 (25)0.75 <r4 / (T2 / T1)<3.50 however, νd3: Abbe number for the d line of the third lens L3 νd4: Abbe number for the d line of the fourth lens L4 D3: Thickness of the third lens L3 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 D6: Thickness of the sixth lens L6 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 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 f4: focal length of the fourth lens L4 r2: paraxial radius of curvature of the image-side surface of the first lens L1 r3: paraxial radius of curvature of the object side surface of the second lens L2 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 r8: Paraxial curvature radius of the image side surface of the fourth lens L4 r11: Paraxial radius of curvature of the object side surface of the sixth lens L6 r12: Paraxial curvature radius of the image-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.

[0102] Moreover, the imaging lens of this embodiment exerts more preferable effects by satisfying the following conditional expressions (1a) to (22a). (1a) 15.50<νd3<23.00 (2a) 0.40<(r2 / |r6|)×100<65.00 (3a)2.20<(|r5 / r6|)×100<300.00 (4a) 1.75 <r11 / (T4+D5+T5)<5.30 (5a)0.08<(r2 / r4 / |r6|)×100<6.25 (6a)-4.00 <r3 / f2<-1.20 (7a)3.95 <r3 / (T2 / T1)<10.25 (8a) 45.00<νd4<67.00 (9a) 10.75 <f4 / D4<74.00 (10a) 12.50<(f1 / f4)×100<53.00 (11a) 10.50<|r6| / r12<1000.00 (12a)2.30 <r3 / r4<7.20 (13a)0.50<(r4 / |r6|)×100<35.50 (14a)-2.00 <r8 / r11<-0.50 (15a) 1.50 <r11 / r12<3.50 (16a)2.65 <r3 / f<11.50 (17a) 11.00 <r4 / T2<25.00 (18a) 2.70<|r5| / f<550.00 (19a)57.00<|r6| / D3<4000.00 (20a) 0.50 <r11 / f<1.20 (21a) 4.65<|r6| / r11<350.00 (22a)25.00<|r6| / (T2+D3)<2000.00 (23a) 0.35 <r12 / r11<0.75 (24a)3.70 <r11 / D6<10.50 (25a) 0.90 <r4 / (T2 / T1)<2.85 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 (25a) may be applied to the corresponding conditional expressions (1) to (25).

[0103] 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.

[0104]

number

[0105] 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.

[0106] Example 1

[0107] Basic lens data is shown in Table 1 below.

[0108] [Table 1]

[0109] The imaging lens of Example 1 achieves a total length to diagonal ratio of 0.62 and an F-number of 1.80. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0110] 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.

[0111] Example 2

[0112] Basic lens data is shown in Table 2 below.

[0113] [Table 2]

[0114] The imaging lens of Example 2 achieves a total length to diagonal ratio of 0.62 and an F-number of 1.80. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0115] 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.

[0116] Example 3

[0117] Basic lens data is shown in Table 3 below.

[0118] [Table 3]

[0119] The imaging lens of Example 3 achieves a total length to diagonal ratio of 0.64 and an F-number of 1.80. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0120] 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.

[0121] Example 4

[0122] Basic lens data is shown in Table 4 below.

[0123] [Table 4]

[0124] The imaging lens of Example 4 achieves a total length to diagonal ratio of 0.64 and an F-number of 1.80. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0125] 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.

[0126] Example 5

[0127] Basic lens data is shown in Table 5 below.

[0128] [Table 5]

[0129] The imaging lens of Example 5 achieves a total length to diagonal ratio of 0.64 and an F-number of 1.90. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0130] 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.

[0131] Example 6

[0132] Basic lens data is shown in Table 6 below.

[0133] [Table 6]

[0134] The imaging lens of Example 6 achieves a total length to diagonal ratio of 0.62 and an F-number of 1.80. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0135] Fig. 12 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 6. As shown in Fig. 10, it can be seen that each aberration is well corrected.

[0136] Example 7

[0137] Basic lens data is shown in Table 7 below.

[0138] [Table 7]

[0139] The imaging lens of Example 7 achieves a total length to diagonal ratio of 0.62 and an F-number of 1.90. Also, as shown in Table 13, the imaging lens satisfies conditional expressions (1) to (25).

[0140] 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.

[0141] Example 8

[0142] Basic lens data is shown in Table 8 below.

[0143] [Table 8]

[0144] The imaging lens of Example 8 achieves a total length to diagonal ratio of 0.62 and an F-number of 1.90. Also, as shown in Table 10, the imaging lens satisfies conditional expressions (1) to (25).

[0145] 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.

[0146] Example 9

[0147] Basic lens data is shown in Table 9 below.

[0148] [Table 9]

[0149] The imaging lens of Example 9 achieves a total length to diagonal ratio of 0.65 and an F-number of 1.90. Also, as shown in Table 13, the imaging lens satisfies conditional expressions (1) to (22).

[0150] 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.

[0151] Table 10 shows the values ​​of conditional expressions (1) to (25) according to Examples 1 to 9.

[0152] [Table 10] [Industrial Applicability]

[0153] 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]

[0154] 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 positive refractive power; a second lens having a negative refractive power; a third lens having a positive or negative refractive power; a fourth lens having a positive refractive power; A fifth lens; and a sixth lens having a negative refractive power, the first 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'), (3), (4), (6) and (9a). (1) 11.00<νd3<26.00 (2') 0.10<(r2 / |r6|)×100<=33.02 (3) 1.60<(|r5 / r6|)×100 (4) 0.50<r11 / (T4+D5+T5)<6.75 (6) -5.00<r3 / f2<-1.00 (9a) 10.75<f4 / D4<74.00 however, νd3: Abbe number of the third lens for the d line r2: paraxial radius of curvature of the image side surface of the first lens r6: paraxial radius of curvature of the image side surface of the third lens r5: paraxial radius of curvature of the object side surface of the third lens r11: paraxial radius of curvature of the object side surface of the sixth lens T4: The distance on the optical axis from the image side surface of the fourth lens to the object side surface of the fifth lens D5: Thickness of the fifth lens on the optical axis 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 r3: paraxial radius of curvature of the object side surface of the second lens f2: focal length of the second lens f4: focal length of the fourth lens D4: Thickness of the fourth lens on the optical axis

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

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

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

5. 2. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied: (5) 0.05<(r2 / r4 / |r6|)×100<7.00 however, r2: paraxial radius of curvature of the image side surface of the first lens r4: paraxial radius of curvature of the image side surface of the second lens r6: paraxial radius of curvature of the image side surface of the third lens

6. 2. The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied: (7) 3.25<r3 / (T2 / T1)<11.50 however, r3: paraxial radius of curvature of the object 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 first lens

Images