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 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 the object side to the image side, where the first lens is a meniscus-shaped lens with an object-side surface that is convex near an optical axis, the fourth lens has an image-side surface that is convex near the optical axis, the fifth lens has an image-side surface that is concave near the 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 device such as a CCD sensor or a C-MOS sensor used in an imaging apparatus.

Background Art

[0002] In recent years, camera functions have been mounted on various products such as home appliances, information terminal devices, and automobiles. In the future, it is considered that various product developments integrating camera functions will proceed.

[0003] The imaging lens mounted on such devices is required to have high resolution performance while being small.

[0004] As a conventional imaging lens aiming at high performance, for example, an imaging lens as described 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 negative refractive power, a third lens having a negative refractive power, a fourth lens, a fifth lens, and a sixth lens, and configured such that the relationship between the focal length of the first lens and the focal length of the entire imaging lens and the relationship between the paraxial curvature radius of the object-side surface of the fourth lens and the thickness on the optical axis of the fourth lens satisfy certain conditions.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When attempting to reduce the thickness and the F-number in the lens configuration described in Patent Document 1, it is extremely difficult to correct aberrations in the peripheral portion, and it is impossible to obtain good optical performance.

[0008] The present invention has been made in view of the above-described problems, and an object thereof is to provide an imaging lens that has high resolution with various aberrations well corrected while satisfactorily meeting the requirements for thickness reduction and low F-number in a well-balanced manner.

[0009] Regarding the terms used in the present invention, the convex surface, concave surface, and flat surface of the lens surface are defined to refer to the shapes in the paraxial region. The refractive power is defined to refer to the refractive power in the paraxial region. The vertex is defined as a point on the aspherical surface other than on the optical axis where the tangent plane intersects the optical axis perpendicularly. The overall optical length is defined as the distance on the optical axis from the object-side surface of the optical element located on the most object side to the imaging surface. Note that the overall optical length and the back focus are distances obtained by converting the thickness of an IR cut filter, cover glass, etc. disposed between the imaging lens and the imaging surface into air.

Means for Solving the Problems

[0010] The imaging lens according to the present invention is composed of a first lens having a positive refractive power, a second lens having a negative 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, which are arranged in order from the object side toward the image side. The first lens has a meniscus shape with a convex object side in the paraxial region, the fourth lens has a convex image side in the paraxial region, the fifth lens has a concave image side in the paraxial region, and the sixth lens has a concave image side in the paraxial region.

[0011] The first lens has a positive refractive power and suppresses spherical aberration, astigmatism, field curvature, and distortion by having a meniscus shape with a convex object side in the paraxial region.

[0012] By having a negative refractive power, the second lens corrects chromatic aberration, coma aberration, astigmatism, field curvature, and distortion well.

[0013] By having a positive refractive power, the third lens reduces the lens height and corrects spherical aberration, coma aberration, astigmatism, field curvature, and distortion well.

[0014] The fourth lens has a negative refractive power and is convex on the image side in the paraxial region, thereby correcting chromatic aberration, coma aberration, astigmatism, field curvature, and distortion well.

[0015] The fifth lens has a positive refractive power and is concave on the image side in the paraxial region, thereby correcting spherical aberration, coma aberration, astigmatism, field curvature, and distortion well.

[0016] The sixth lens has a negative refractive power and is concave on the image side in the paraxial region, thereby correcting chromatic aberration, astigmatism, field curvature, and distortion well. Also, by being concave on the image side in the paraxial region, the back focus is ensured while maintaining the low lens height.

[0017] In addition, in the imaging lens having the above configuration, it is desirable that the image-side surface of the first lens is formed with an aspherical surface having an apex at a position other than on the optical axis.

[0018] By forming an aspherical surface having an apex at a position other than on the optical axis on the image-side surface of the first lens, better correction of astigmatism, field curvature, and distortion becomes possible.

[0019] In addition, in the imaging lens having the above configuration, it is desirable that the object side of the third lens is convex in the paraxial region.

[0020] By making the object-side surface of the third lens convex in the paraxial region, good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion becomes possible.

[0021] Further, in the imaging lens having the above-described configuration, it is desirable that the surface on the object side of the third lens has an aspherical surface having a pole at a position other than on the optical axis.

[0022] By forming an aspherical surface having a pole at a position other than on the optical axis on the surface on the object side of the third lens, better correction of spherical aberration, field curvature, and distortion aberration becomes possible.

[0023] Further, in the imaging lens having the above-described configuration, it is desirable that the third lens has a convex surface on the image side in the paraxial region.

[0024] By making the surface on the image side of the third lens convex in the paraxial region, good correction of spherical aberration, coma aberration, spherical aberration, field curvature, and distortion aberration becomes possible.

[0025] Further, in the imaging lens having the above-described configuration, it is desirable that the sixth lens has a convex surface on the object side in the paraxial region.

[0026] By making the surface on the object side of the sixth lens convex in the paraxial region, good correction of spherical aberration, field curvature, and distortion aberration becomes possible.

[0027] Further, in the imaging lens having the above-described configuration, it is desirable that the surface on the object side of the sixth lens has an aspherical surface having a pole at a position other than on the optical axis.

[0028] By forming an aspherical surface having a pole at a position other than on the optical axis on the surface on the object side of the sixth lens, better correction of spherical aberration, field curvature, and distortion aberration becomes possible.

[0029] Further, in the imaging lens having the above-described configuration, it is desirable that the surface on the object side of the sixth lens has an aspherical surface having a pole at a position other than on the optical axis.

[0030] By forming an aspherical surface having a pole at a position other than on the optical axis on the surface on the image side of the sixth lens, better correction of spherical aberration, field curvature, and distortion aberration becomes possible.

[0031] By adopting the above-described configuration, the imaging lens of the present invention achieves a low-profile design with an overall length-to-diagonal ratio (the ratio of the overall optical length to the diagonal length of the effective imaging surface of the imaging device) of 0.9 or less, and an F-number of 2.0 or less, realizing a low F-number design.

[0032] In the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (1). (1) -42 < (r2 / r4 / r6) × 100 < -21 Here, r2 is the paraxial curvature radius of the image-side surface of the first lens, r4 is the paraxial curvature radius of the image-side surface of the second lens, and r6 is the paraxial curvature radius of the image-side surface of the third lens.

[0033] By satisfying the range of conditional expression (1), good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion aberration becomes possible.

[0034] In the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (2). (2) 0.3 < r5 / f < 1.6 Here, r5 is the paraxial curvature radius of the object-side surface of the third lens, and f is the focal length of the entire imaging lens system.

[0035] By satisfying the range of conditional expression (2), good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion aberration becomes possible.

[0036] In the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (3). (3) 6.85 < (D5 / f5) × 100 < 10.75 Here, D5 is the thickness on the optical axis of the fifth lens, and f5 is the focal length of the fifth lens.

[0037] By satisfying the range of conditional expression (3), a low-profile design is achieved, and good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion aberration becomes possible.

[0038] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (4). (4) -24 < f4 / D4 < -9 However, f4 is the focal length of the fourth lens, and D4 is the thickness on the optical axis of the fourth lens.

[0039] By satisfying the range of the conditional expression (4), it is possible to reduce the height and achieve good correction of chromatic aberration, coma aberration, astigmatism, field curvature, and distortion aberration.

[0040] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (5). (5) -0.9 < r5 / r6 < -0.2 However, r5 is the paraxial curvature radius of the object-side surface of the third lens, and r6 is the paraxial curvature radius of the image-side surface of the third lens.

[0041] By satisfying the range of the conditional expression (5), it is possible to achieve good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion aberration.

[0042] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (6). (6) -0.35 < r3 / f2 < -0.10 However, r3 is the paraxial curvature radius of the object-side surface of the second lens, and f2 is the focal length of the second lens.

[0043] By satisfying the range of the conditional expression (6), it is possible to achieve good correction of chromatic aberration, coma aberration, astigmatism, field curvature, and distortion aberration.

[0044] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (7). (7) 4.0 < r5 / T2 < 19.1 However, r5 is the paraxial curvature radius 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.

[0045] By satisfying the range of conditional expression (7), the lens can be made thinner while enabling good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion.

[0046] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (8). (8) 0.7 < r9 / D5 < 3.4 However, r9 is the paraxial curvature radius of the object-side surface of the fifth lens, and D5 is the thickness on the optical axis of the fifth lens.

[0047] By satisfying the range of conditional expression (8), the lens can be made thinner while enabling good correction of coma aberration, astigmatism, field curvature, and distortion.

[0048] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (9). (9) -8.5 < (T5 / f6) × 100 < -2.5 However, 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, and f6 is the focal length of the sixth lens.

[0049] By satisfying the range of conditional expression (9), the lens can be made thinner while enabling good correction of chromatic aberration, astigmatism, field curvature, and distortion.

[0050] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (10). (10) 0.02 < T4 / T5 < 0.09 However, 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.

[0051] By satisfying the range of conditional expression (10), the lens can be made thinner while enabling good correction of coma aberration, astigmatism, and distortion.

[0052] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (11). (11) 5.75 < f3 / D3 < 12.00 However, f3 is the focal length of the third lens, and D3 is the thickness on the optical axis of the third lens.

[0053] By satisfying the range of the conditional expression (11), the height can be reduced, and it becomes possible to achieve good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion.

[0054] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (12). (12) 2.0 < f3 / (D3 + T3) < 6.5 However, f3 is the focal length of the third lens, D3 is the thickness on the optical axis 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.

[0055] By satisfying the range of the conditional expression (12), the height can be reduced, and it becomes possible to achieve good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion.

[0056] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (13). (13) 0.5 < f5 / f < 2.6 However, f5 is the focal length of the fifth lens, and f is the focal length of the entire imaging lens system.

[0057] By satisfying the range of the conditional expression (13), it becomes possible to achieve good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion.

[0058] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (14). (14) 0.4 < f1 / f5 < 1.0 However, f1 is the focal length of the first lens, and f5 is the focal length of the fifth lens.

[0059] By satisfying the range of conditional expression (14), it becomes possible to achieve good correction of spherical aberration, coma aberration, astigmatism, field curvature, and distortion aberration.

[0060] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (15). (15) 14.5 < r2 / T2 < 25.0 However, r2 is the paraxial curvature radius of the image-side surface of the first lens, and T2 is the on-axis distance from the image-side surface of the second lens to the object-side surface of the third lens.

[0061] By satisfying the range of conditional expression (15), it is possible to reduce the height and achieve good correction of astigmatism, field curvature, and distortion aberration.

[0062] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (16). (16) 0.20 < r3 / f < 0.86 However, f3 is the focal length of the third lens, and f is the focal length of the entire imaging lens system.

[0063] By satisfying the range of conditional expression (16), it becomes possible to achieve good correction of coma aberration, astigmatism, field curvature, and distortion aberration.

[0064] In addition, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (17). (17) 1.0 < r3 / (T2 / T1) < 5.5 However, r3 is the paraxial curvature radius of the object-side surface of the second lens, T2 is the on-axis distance from the image-side surface of the second lens to the object-side surface of the third lens, and T1 is the on-axis distance from the image-side surface of the first lens to the object-side surface of the second lens.

[0065] By satisfying the range of conditional expression (17), it is possible to reduce the height and achieve good correction of coma aberration, astigmatism, field curvature, and distortion aberration.

[0066] In addition, for the imaging lens with the above configuration, it is desirable to satisfy the following conditional expression (18). (18) -0.5 < r8 / f < -0.1 However, r8 is the paraxial curvature radius of the image side surface of the fourth lens, and f is the focal length of the entire imaging lens system.

[0067] By satisfying the range of the conditional expression (18), it becomes possible to achieve good correction of coma aberration, spherical aberration, field curvature, and distortion aberration.

[0068] In addition, for the imaging lens with the above configuration, it is desirable to satisfy the following conditional expression (19). (19) 1.00 < r10 / D5 < 5.15 However, r10 is the paraxial curvature radius of the image side surface of the fifth lens, and D5 is the thickness on the optical axis of the fifth lens.

[0069] By satisfying the range of the conditional expression (19), it becomes possible to reduce the height and achieve good correction of coma aberration, spherical aberration, field curvature, and distortion aberration.

[0070] In addition, for the imaging lens with the above configuration, it is desirable to satisfy the following conditional expression (20). (20) 0.30 < r11 / f < 0.95 However, r11 is the paraxial curvature radius of the object side surface of the sixth lens, and f is the focal length of the entire imaging lens system.

[0071] By satisfying the range of the conditional expression (20), it becomes possible to achieve good correction of spherical aberration, field curvature, and distortion aberration.

[0072] In addition, for the imaging lens with the above configuration, it is desirable to satisfy the following conditional expression (21). (21) -0.60 < r11 / f6 < -0.15 However, r11 is the paraxial curvature radius of the object side surface of the sixth lens, and f6 is the focal length of the sixth lens.

[0073] By satisfying the range of conditional expression (21), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, field curvature, and distortion.

[0074] Also, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (22). (22) 1.50 < r11 / (T4 + T5) < 5.25 However, r11 is the paraxial curvature radius of the object-side surface of the sixth lens, T4 is the on-axis distance from the image-side surface of the fourth lens to the object-side surface of the fifth lens, and T5 is the on-axis distance from the image-side surface of the fifth lens to the object-side surface of the sixth lens.

[0075] By satisfying the range of conditional expression (22), it is possible to reduce the thickness and achieve good correction of spherical aberration, field curvature, and distortion.

[0076] According to the present invention, it is possible to obtain an imaging lens with high resolution in which various aberrations are well corrected while satisfying the requirements of thickness reduction and low F-number in a well-balanced manner.

Brief Description of the Drawings

[0077]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0078] Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

[0079] FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 respectively show schematic configuration diagrams of the imaging lenses according to Examples 1 to 5 of the embodiments of the present invention. Hereinafter, the details of the embodiments of the present invention will be described with reference to FIG. 1.

[0080] As shown in FIG. 1, the imaging lens according to the present invention includes a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, a third lens L3 having a positive refractive power, a fourth lens L4 having a negative refractive power, a fifth lens L5 having a positive refractive power, and a sixth lens L6 having a negative refractive power, which are arranged in order from the object side to the image side. The first lens L1 has a meniscus shape with a convex surface on the object side in the paraxial region, the fourth lens L4 has a convex surface on the image side in the paraxial region, the fifth lens L5 has a concave surface on the image side in the paraxial region, and the sixth lens L6 has a concave surface on the image side in the paraxial region.

[0081] In addition, a filter IR such as an infrared cut filter or a cover glass is arranged between the sixth lens L6 and the imaging surface IMG (that is, the imaging surface of the imaging device). Note that this filter IR can be omitted.

[0082] Since the aperture stop ST is arranged on the object side of the first lens L1, it facilitates the correction of various aberrations and the control of the angle when high image height rays enter the imaging device.

[0083] The first lens L1 has a positive refractive power and has a meniscus shape with a convex surface on the object side in the paraxial region. Therefore, it suppresses spherical aberration, astigmatism, field curvature, and distortion.

[0084] In addition, the aspherical surface formed on the image side surface of the first lens L1 has a pole at a position other than on the optical axis X. Therefore, it suppresses astigmatism, field curvature, and distortion better.

[0085] The second lens L2 has a negative refractive power and has a meniscus shape with a concave surface on the image side in the paraxial region. Therefore, it corrects chromatic aberration, coma aberration, astigmatism, field curvature, and distortion.

[0086] The third lens L3 has a positive refractive power and has a biconvex shape in the paraxial region. Therefore, it aims to reduce the thickness and corrects spherical aberration, coma aberration, astigmatism, field curvature, and distortion well. The shape of the third lens L3 is not limited to the shape according to the present numerical example 1. The shape of the third lens L3 may be any shape as long as its refractive power is positive. As the shape of the third lens L3, a meniscus shape with a convex surface on the image side in the paraxial region or a meniscus shape with a concave surface on the image side may be used.

[0087] In addition, the aspherical surface formed on the object side surface of the third lens L3 has a pole at a position other than on the optical axis X. Therefore, it corrects astigmatism, field curvature, and distortion better.

[0088] The fourth lens L4 has a negative refractive power and has a meniscus shape with a convex surface on the image side in the paraxial region. Therefore, it corrects chromatic aberration, coma aberration, astigmatism, field curvature, and distortion well.

[0089] The fifth lens L5 has a positive refractive power and has a meniscus shape with a concave surface on the image side in the paraxial region. Therefore, it corrects spherical aberration, coma aberration, astigmatism, field curvature, and distortion well.

[0090] The sixth lens L6 has a negative refractive power and has a meniscus shape with a concave image side in the paraxial region. Therefore, it corrects chromatic aberration, spherical aberration, field curvature, and distortion well. Also, by making the image side concave in the paraxial region, it secures the back focus while maintaining a low profile.

[0091] In addition, the aspherical surface formed on the object side surface of the sixth lens L6 has a vertex at a position other than on the optical axis X. Therefore, it corrects spherical aberration, field curvature, and distortion even better.

[0092] Furthermore, the aspherical surface formed on the image side surface of the sixth lens L6 has a vertex at a position other than on the optical axis X. Therefore, it corrects spherical aberration, field curvature, and distortion even better.

[0093] In the imaging lens according to this embodiment, it is preferable that all of the first lens L1 to the sixth lens L6 are each composed of a single lens. A configuration of only single lenses allows for extensive use of aspherical surfaces. In this embodiment, by forming appropriate aspherical surfaces on all lens surfaces, good correction of various aberrations is achieved. Also, since the number of man-hours can be reduced compared to the case of adopting cemented lenses, it is possible to manufacture at low cost.

[0094] Also, the imaging lens according to this embodiment facilitates manufacturing and enables mass production at low cost by adopting a plastic material for all lenses.

[0095] Note that the lens material to be adopted is not limited to plastic materials. By adopting a glass material, it is also possible to aim for further high performance. Also, although it is desirable to form all lens surfaces as aspherical surfaces, depending on the required performance, spherical surfaces that are easy to manufacture may be adopted.

[0096] The imaging lens in this embodiment exhibits preferable effects by satisfying the following conditional expressions (1) to (22). (1) -42 < (r2 / r4 / r6) × 100 < -21 (2) 0.3 < r5 / f < 1.6 (3) 6.85 < (D5 / f5) × 100 < 10.75 (4) -24 < f4 / D4 < -9 (5) -0.9 < r5 / r6 < -0.2 (6) -0.35 < r3 / f2 < -0.10 (7) 4.0 < r5 / T2 < 19.1 (8) 0.7 < r9 / D5 < 3.4 (9) -8.5 < (T5 / f6) × 100 < -2.5 (10) 0.02 < T4 / T5 < 0.09 (11) 5.75 < f3 / D3 < 12.00 (12) 2.0 < f3 / (D3 + T3) < 6.5 (13) 0.5 < f5 / f < 2.6 (14) 0.4 < f1 / f5 < 1.0 (15) 14.5 < r2 / T2 < 25.0 (16) 0.20 < r3 / f < 0.86 (17) 1.0 < r3 / (T2 / T1) < 5.5 (18) -0.5 < r8 / f < -0.1 (19) 1.00 < r10 / D5 < 5.15 (20) 0.30 < r11 / f < 0.95 (21) -0.60 < r11 / f6 < -0.15 (22) 1.50 < r11 / (T4 + T5) < 5.25 However, D3: Thickness on the optical axis X of the third lens L3 D4: Thickness on the optical axis X of the fourth lens L4 D5: Thickness on the optical axis X of the fifth lens L5 T1: 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: 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: 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: 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: 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 the second lens L2 f3: Focal length of the third lens L3 f4: Focal length of the fourth lens L4 f5: Focal length of the fifth lens L5 f6: Focal length of the sixth lens L6 r2: Paraxial curvature radius of the image-side surface of the first lens L1 r3: Paraxial curvature radius of the object-side surface of the second lens L2 r4: Paraxial curvature radius of the image-side surface of the second lens L2 r5: Paraxial curvature radius 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 r9: Paraxial curvature radius 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 curvature radius of the object-side surface of the sixth lens L6 Note that it is not necessary to satisfy all of the above conditional expressions. By satisfying each conditional expression individually, the operational effects corresponding to each conditional expression can be obtained.

[0097] In addition, the imaging lens in this embodiment exhibits more preferable effects by satisfying the following conditional expressions (1a) to (22a). (1a) -40 < (r2 / r4 / r6) × 100 < -28 (2a) 0.6 < r5 / f < 1.4 (3a) 7.2 < (D5 / f5) × 100 < 9.5 (4a) -22 < f4 / D4 < -14 (5a) -0.8 < r5 / r6 < -0.4 (6a) -0.3 < r3 / f2 < -0.2 (7a) 10.0 < r5 / T2 < 18.5 (8a) 1.7 < r9 / D5 < 3.2 (9a) -7.8 < (T5 / f6) × 100 < -4.5 (10a) 0.025 < T4 / T5 < 0.080 (11a) 6.5 < f3 / D3 < 10.00 (12a) 3.5 < f3 / (D3 + T3) < 5.8 (13a) 1.2 < f5 / f < 2.1 (14a) 0.60 < f1 / f5 < 0.95 (15a) 16.5 < r2 / T2 < 23.5 (16a) 0.50 < r3 / f < 0.84 (17a) 2.0 < r3 / (T2 / T1) < 4.5 (18a) -0.45 < r8 / f < -0.25 (19a) 2.75 < r10 / D5 < 4.90 (20a) 0.5 < r11 / f < 0.85 (21a) -0.45 < r11 / f6 < -0.20 (22a) 3.0 < r11 / (T4 + T5) < 4.9 However, the signs of each conditional expression are the same as those described in the previous paragraph. Note that only the lower limit value or the upper limit value of each of the conditional expressions (1a) to (22a) may be applied to the corresponding conditional expressions (1) to (22), respectively.

[0098] In this embodiment, the aspherical shape adopted for the aspherical surface of the lens is represented by Equation 1 when the axis in the optical axis direction is Z, the height in the direction orthogonal to the optical axis is H, the paraxial radius of curvature is R, the conic coefficient is k, and the aspherical coefficients are A4, A6, A8, A10, A12, A14, A16, A18, A20.

[0099]

Number

[0100] Next, an example of the imaging lens according to this embodiment is shown. In each example, f represents the focal length of the entire imaging lens system, Fno represents the F-number, ω represents the semi-field angle, ih represents the maximum image height, and TTL represents the overall optical length. Also, i represents the surface number counted from the object side, r represents the paraxial curvature radius, d represents the distance between lens surfaces on the optical axis (surface interval), Nd represents the refractive index of the d-line (reference wavelength), and νd represents the Abbe number with respect to the d-line. For an aspherical surface, an asterisk (*) symbol is added after the surface number i for indication.

[0101] (Example 1)

[0102] The basic lens data is shown in Table 1 below.

[0103] [Table 1]

[0104] The imaging lens of Example 1 realizes an overall length to diagonal ratio of 0.77 and an F-number of 1.8. Also, as shown in Table 6, it satisfies the conditional expressions (1) to (22).

[0105] Figure 2 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 1. The spherical aberration diagram shows the aberration amounts for each wavelength of the F-line (486 nm), d-line (588 nm), and C-line (656 nm). Also, the astigmatism diagram shows the aberration amount of the d-line on the sagittal image plane S (solid line) and the aberration amount of the d-line on the tangential image plane T (dashed line) respectively (the same also applies in Figures 4, 6, 8, and 10). As shown in Figure 2, it can be seen that each aberration is well corrected.

[0106] (Example 2)

[0107] The basic lens data is shown in Table 2 below.

[0108] [Table 2]

[0109] The imaging lens of Example 2 realizes a full-length diagonal ratio of 0.77 and an F-number of 1.8. Also, as shown in Table 6, it satisfies conditional expressions (1) to (22).

[0110] Figure 4 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 2. As shown in Figure 4, it can be seen that each aberration is well corrected.

[0111] (Example 3)

[0112] The basic lens data is shown in Table 3 below.

[0113] [Table 3]

[0114] The imaging lens of Example 3 realizes a full-length diagonal ratio of 0.77 and an F-number of 1.8. Also, as shown in Table 6, it satisfies conditional expressions (1) to (22).

[0115] Figure 6 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 3. As shown in Figure 6, it can be seen that each aberration is well corrected.

[0116] (Example 4)

[0117] The basic lens data is shown in Table 4 below.

[0118] [Table 4]

[0119] The imaging lens of Example 4 realizes a full-length diagonal ratio of 0.77 and an F-number of 1.8. Also, as shown in Table 6, it satisfies conditional expressions (1) to (22).

[0120] FIG. 8 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 4. As shown in FIG. 8, it can be seen that each aberration is well corrected.

[0121] (Example 5)

[0122] The basic lens data is shown in Table 5 below.

[0123] [Table 5]

[0124] The imaging lens of Example 5 realizes a full-length diagonal ratio of 0.77 and an F-number of 1.8. Also, as shown in Table 6, it satisfies the conditional expressions (1) to (22).

[0125] FIG. 10 shows the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 5. As shown in FIG. 10, it can be seen that each aberration is well corrected.

[0126] Table 6 shows the values of the conditional expressions (1) to (22) according to Examples 1 to 5.

[0127] [Table 6] [Industrial Applicability]

[0128] When the imaging lens according to the present invention is applied to a product having a camera function, it is possible to achieve high performance while contributing to the reduction in the thickness and the reduction in the F-number of the camera. [Description of Reference Numerals]

[0129] ST Aperture stop L1 First lens L2 Second lens L3 Third lens L4 Fourth 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 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 has a meniscus shape with a convex surface on the object side in a paraxial direction, the fourth lens has a paraxial convex surface facing the image side, The fifth lens has a paraxial concave surface on the image side. 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') and (19): (1) -42<(r2 / r4 / r6)×100<-21 (2) 0.3<r5 / f<1.6 (3')6.85<(D5 / f5)×100≦8.63 (19) 1.00<r10 / D5<5.15 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 r5: paraxial radius of curvature of the object side surface of the third lens f: focal length of the entire imaging lens system D5: Thickness of the fifth lens on the optical axis f5: focal length of the fifth lens r10: paraxial radius of curvature of the image side surface of the fifth lens

2. 2. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied: (4) -24<f4 / D4<-9 however, f4: focal length of the fourth lens D4: Thickness of the fourth lens on the optical axis

3. 2. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied: (5) -0.9<r5 / r6<-0.2 however, r5: paraxial radius of curvature of the object side surface of the third lens r6: paraxial radius of curvature of the image side surface of the third lens

4. 2. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied: (6) -0.35<r3 / f2<-0.10 however, r3: paraxial radius of curvature of the object side surface of the second lens f2: focal length of the second lens

5. 2. The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied: (7) 4.0<r5 / T2<19.1 however, r5: paraxial radius of curvature of the object side surface of the third 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

6. 2. The imaging lens according to claim 1, wherein the following conditional expression (8) is satisfied: (8) 0.7<r9 / D5<3.4 however, r9: paraxial radius of curvature of the object side surface of the fifth lens D5: Thickness of the fifth lens on the optical axis

Images