Imaging lens

Abstract

To provide an imaging lens suitable for in-vehicle camera systems, which has a compact configuration, a wide angle of view, a bright optical system with a small F-number, and can accommodate larger image sensors while achieving good resolution performance. [Solution] Starting from the object side, the lens consists of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power, and a sixth lens with positive refractive power. An imaging lens characterized by satisfying the following conditional equation. -2.3 <f3 / f2<-1.6 (1) -2.3 < (r6 + r5) / (r6 - r5) < -1.8 (2)

Description

Technical Field

[0001] The present invention relates to an imaging lens suitable for an in-vehicle camera.

Background Art

[0002] In recent years, technological development related to in-vehicle cameras has been active. For the optical system used in such in-vehicle cameras, it is required to have a compact configuration with a short overall lens length, a wide angle of view, a bright optical system with a small F-number, and good resolution performance. Conventionally, a lens unit composed of six lenses has been known as an optical system for in-vehicle use (for example, Patent Document 1, Patent Document 2, and Patent Document 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in in-vehicle cameras, coping with a wide traffic environment is required, and it is required to have a high resolution and a wide dynamic range so as to be able to acquire information in scenes with large brightness differences such as backlight and tunnel entrances and exits. Therefore, the need for using a larger image sensor is increasing.

[0005] In order to satisfy the requirements of these in-vehicle cameras, for the optical system, while maintaining the characteristics of being compact, having a wide angle of view, and having a low F-number, it is required to achieve both compatibility with a larger image sensor and good resolution performance.

[0006] The present invention aims to solve the above-mentioned problems of the conventional invention and achieve the following objectives. Specifically, the present invention aims to provide an imaging lens that has a compact configuration, a wide angle of view and a bright optical system with a small F-number, and that can be used with larger image sensors and achieve good resolution performance. [Means for solving the problem]

[0007] The means for solving the above problems are as follows: That is, the imaging lens of the present invention consists of, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, a third lens having positive refractive power, a fourth lens having positive refractive power, a fifth lens having negative refractive power, and a sixth lens having positive refractive power. An imaging lens characterized by satisfying the following conditional equation. -2.3 <f3 / f2<-1.6 (1) -2.3 < (r6 + r5) / (r6 - r5) < -1.8 (2) Here, f2 is the focal length of the second lens. f3 is the focal length of the third lens. r5 is the radius of curvature of the object-side surface of the third lens. r6 is the radius of curvature of the image-side surface of the third lens. That is the case.

[0008] Furthermore, condition (1) is more preferably one that satisfies the following condition. -2.3 <f3 / f2<-2.0 (1-1)

[0009] Furthermore, condition (2) is more preferably one that satisfies the following condition. -2.3<(r6+r5) / (r6-r5)<-2.0 (2-1)

[0010] Furthermore, it is preferable that the imaging lens of the present invention satisfies the following conditional equation. -17 <f123 / f<-8 (3) Here, f is the focal length of the entire imaging lens system, f123 is the combined focal length of the first, second, and third lenses, is as follows.

[0011] Also, in the imaging lens of the present invention, it is preferable to satisfy the following conditional expression. 0.5 < r10 / r11 < 1.3 (4) Here, r10 is the radius of curvature of the image-side surface of the fifth lens, r11 is the radius of curvature of the object-side surface of the sixth lens, is as follows.

[0012] Also, the conditional expression (4) more preferably satisfies the following conditional expression. 0.70 < r10 / r11 < 0.73 (4-1)

[0013] Also, in the imaging lens of the present invention, the object-side surface of the second lens is concave near the optical axis and is configured such that the negative power becomes weaker than the center at the effective diameter end, and it is preferable to satisfy the following conditional expression. -0.97 < (r4 + r3) / (r4 - r3) < -0.83 (5) Here, r3 is the radius of curvature of the object-side surface of the second lens, r4 is the radius of curvature of the image-side surface of the second lens, is as follows.

[0014] Also, in the imaging lens of the present invention, it is preferable to satisfy the following conditional expression. -0.25 < (r8 + r7) / (r8 - r7) < -0.15 (6) Here, r7 is the radius of curvature of the object-side surface of the fourth lens, r8 is the radius of curvature of the image-side surface of the fourth lens, is as follows.

Effects of the Invention

[0015] According to the present invention, a compact configuration provides a bright optical system with a wide angle of view and a small F-number, achieving both compatibility with larger image sensors and good resolution performance. [Brief explanation of the drawing]

[0016] [Figure 1] This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 1 of the present invention. [Figure 2] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 1 is in focus at an object distance of 400 mm. [Figure 3] This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 2 of the present invention. [Figure 4] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 2 is in focus at an object distance of 400 mm. [Figure 5] This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 3 of the present invention. [Figure 6] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 3 is in focus at an object distance of 400 mm. [Figure 7] This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 4 of the present invention. [Figure 8] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 4 is in focus at an object distance of 400 mm. [Figure 9] This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 5 of the present invention. [Figure 10] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 5 is in focus at an object distance of 400 mm. [Figure 11]This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 6 of the present invention. [Figure 12] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 6 is in focus at an object distance of 400 mm. [Figure 13] This is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Embodiment 7 of the present invention. [Figure 14] This figure shows (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) when the imaging lens according to Example 7 is in focus at an object distance of 400 mm. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a cross-sectional view along the optical axis showing an example of the optical configuration of an imaging lens according to an embodiment of the present invention. The optical configuration in Figure 1 corresponds to the optical configuration of the first embodiment.

[0018] The imaging lens of the present invention is configured by arranging, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, a third lens having positive refractive power, an aperture diaphragm, a fourth lens having positive refractive power, a fifth lens having negative refractive power, and a sixth lens having positive refractive power.

[0019] In all the following embodiments, in the optical configuration cross-sectional diagrams, FL represents various filters such as bandpass filters, CG represents the cover glass, and I represents the imaging surface of the image sensor.

[0020] Furthermore, in the imaging lens of the present invention, it is preferable that the first lens L1 and the fourth lens L4 are both made of glass, and the other lenses are made of plastic, from the viewpoint of low cost and stability of optical performance against changes in ambient temperature.

[0021] An image sensor such as a CCD is positioned on the imaging surface I of the imaging lens of the present invention. A dual bandpass filter FL is positioned in the space between the sixth lens L6 and the cover glass CG, having transmission areas in both the visible light region and the near-infrared light region, enabling continuous day and night imaging.

[0022] Furthermore, the imaging lens used in this implementation satisfies the following condition. -2.3 <f3 / f2<-1.6 (1) -2.3 < (r6 + r5) / (r6 - r5) < -1.8 (2) Here, f2 is the focal length of the second lens. f3 is the focal length of the third lens. r5 is the radius of curvature of the object-side surface of the third lens. r6 is the radius of curvature of the image-side surface of the third lens. That is the case.

[0023] Conditional equation (1) is a conditional equation for achieving a compact and wide-angle optical system while effectively correcting field curvature and chromatic aberration. If the range exceeds that of conditional equation (1), the power of the second lens becomes too weak, making wide-angle correction difficult. Conversely, if the range falls below that of conditional equation (1), the power of the second lens becomes too strong, making correction of field curvature difficult and undesirable. Also, the power of the third lens becomes too weak, making correction of chromatic aberration difficult and undesirable.

[0024] Furthermore, condition (1) is more preferably one that satisfies the following condition. -2.3 <f3 / f2<-2.0 (1-1)

[0025] Conditional equation (2) is a conditional equation designed to achieve a wide-angle optical system while simultaneously correcting distortion and chromatic aberration. If the range exceeds that of conditional equation (2), the power of the third lens becomes too strong, resulting in strong negative distortion, which is undesirable. Conversely, if the range falls below that of conditional equation (2), the power of the third lens becomes too weak, making it difficult to correct chromatic aberration, which is also undesirable.

[0026] Furthermore, condition (2) is more preferably one that satisfies the following condition. -2.3<(r6+r5) / (r6-r5)<-2.0 (2-1)

[0027] Furthermore, the imaging lens of this embodiment more preferably satisfies the following conditional expression. -17 <f123 / f<-8 (3) Here, f is the focal length of the entire imaging lens system. f123 is the combined focal length of the first, second, and third lenses. That is the case.

[0028] Condition (3) is a condition for achieving a wide-angle optical system while effectively correcting field curvature and chromatic aberration. If the range falls below that of condition (3), the negative refractive power of the first and second lenses becomes weak, making wide-angle correction difficult. If the range exceeds that of condition (3), the negative refractive power of the first and second lenses becomes too strong, making it difficult to correct field curvature, and the positive refractive power of the third lens becomes weak, making it difficult to correct chromatic aberration, which is undesirable.

[0029] Furthermore, the imaging lens of this embodiment more preferably satisfies the following conditional expression. 0.5 <r10 / r11<1.3 (4) Here, r10 is the radius of curvature of the image-side surface of the fifth lens. r11 is the radius of curvature of the object-side surface of the sixth lens. That is the case.

[0030] Condition (4) is a condition for ensuring the image circle while correcting field curvature. If the range falls below that of condition (4), the radius of curvature of the image-side surface of the fifth lens becomes too small, resulting in increased field curvature, which is undesirable. If the range exceeds that of condition (4), the radius of curvature of the object-side surface of the sixth lens becomes too small, resulting in strong negative distortion, making it difficult to enlarge the image circle, which is also undesirable.

[0031] Furthermore, condition (4) is more preferably one that satisfies the following condition. 0.70 <r10 / r11<0.73 (4-1)

[0032] Furthermore, the imaging lens of this embodiment is more preferably configured such that the object-side surface of the second lens is concave near the optical axis and the negative power is weaker at the effective diameter end than at the center. The following conditions must be met. -0.97<(r4+r3) / (r4-r3)<-0.83 (5) Here, r3 is the radius of curvature of the object-side surface of the second lens. r4 is the radius of curvature of the image-side surface of the second lens. That is the case.

[0033] Condition (5) is a condition for achieving wide-angle optical systems while effectively correcting field curvature. If the range falls below that of condition (5), the power of the second lens becomes too strong, making distortion correction difficult and undesirable. Conversely, if the range exceeds that of condition (5), the power of the second lens becomes too weak, making wide-angle correction difficult and undesirable. Furthermore, since the object-side surface of the second lens is concave near the optical axis and the negative power is weaker at the effective aperture end than at the center, this condition is designed to achieve both wide-angle correction and distortion correction.

[0034] Furthermore, the imaging lens of this embodiment more preferably satisfies the following conditional expression. -0.25<(r8+r7) / (r8-r7)<-0.15 (6) Here, r7 is the radius of curvature of the object-side surface of the fourth lens. r8 is the radius of curvature of the image-side surface of the fourth lens. That is the case.

[0035] By setting the shaping factor of the fourth lens L4 within the range of condition equation (6), it becomes possible to effectively correct spherical aberration in the fourth lens L4 and effectively correct coma aberration in the peripheral areas, even with an optical system with a small F-number. [Examples]

[0036] Next, specific numerical examples of the imaging lens of the present invention are shown. The symbols used in each example are as follows.

[0037] f: Focal length of the entire imaging lens system (Effective Focal Length) FNO: F-number TTL: Optical total length r: paraxial radius of curvature d(D): Thickness of the lens or air gap on the optical axis nd: Refractive index of lens material relative to the d line νd: Abbe number of lens material Φimg: Image circle of the imaging lens Furthermore, in each embodiment, the surfaces marked with an asterisk (*) after each surface number are surfaces with an aspherical shape.

[0038] Furthermore, the aspherical shape is expressed by the following equation (I), where z is the direction of the optical axis, y is the direction perpendicular to the optical axis, K is the conicity coefficient, and A4, A6, A8, A10... are the aspherical coefficients. z=(y 2 / r) / [1+{1-(1+K)(y / r) 2} 1 / 2 ]+A4y 4 +A6y 6 +A8y 8 +A10y 10 ...(I) In the aspherical coefficient, E represents a power of 10, for example, 2.3 × 10⁻⁶. -2 This will be represented as 2.3E-002. Furthermore, the symbols for these specifications are the same in the numerical data of the examples described later.

[0039] (Example 1) Next, the imaging lens according to Example 1 will be described. Figure 1 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 1.

[0040] Figure 2 shows the (A) astigmatism (AS), (B) distortion (DT), and (C) chromatic aberration (LC) of the imaging lens according to Example 1 when the object distance is 400 mm and in focus. The vertical axis in the graph represents the image height. The symbols and conditions in the aberration diagram are the same as those in the examples described later.

[0041] As shown in Figure 1, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object side and the image side, a fifth lens L5 with a negative refractive power with a concave surface facing both the object side and the image side, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object side and the image side.

[0042] The overall specifications of the imaging lens in Example 1 are shown below. f: 0.92mm f1: -6.0987mm f2 : -2.958mm f3: 6.279mm f4: 2.671mm f5 : -1.876mm f6: 1.996mm FNO: 2.40 TTL: 13.148mm Φimg: 3.947mm Table 1 shows the surface data of the imaging lens for Example 1. The upper row of Table 1 shows the central radius of curvature (r), thickness (d), refractive index (nd), and Abbe number (νd) for each surface, with the central radius of curvature and thickness in mm. These symbols are also common to the numerical data of the examples described later.

[0043] [Table 1]

[0044] The aspherical data of the imaging lens in Example 1 is shown below. 3rd page K=0 A4=5.821E-02, A6=-1.506E-02, A8=1.724E-03, A10=-7.313E-05, A12=-4.687E-08, A14=2.805E-08 Side 4 K=0 A4=4.265E-02, A6=3.982E-02, A8=-5.040E-02, A10=1.281E-02, A12=-9.403E-04, A14=9.189E-06 5th page K=0 A4=-1.616E-02, A6=-2.332E-02, A8=1.013E-02, A10=-9.425E-04, A12=-7.256E-05 Page 6 K=0 A4=-1.670E-02, A6=1.255E-02, A8=-6.085E-03, A10=3.064E-03, A12=-8.894E-04, A14=9.443E-05 Side 7 K=0 A4=-2.658E-02, A6=4.011E-02, A8=-8.568E-02 Side 8 K=0 A4=3.105E-04, A6=1.773E-02, A8=-2.413E-02 9th page K=0 A4=-1.140E-01, A6=1.376E-01, A8=-1.263E-01, A10=-8.719E-03, A12=4.374E-02 Side 10 K=0 A4=-1.645E-01, A6=1.040E-01, A8=-4.400E-02, A10=-8.177E-03, A12=7.152E-03 Page 11 K=0 A4=-8.115E-02, A6=4.148E-02, A8=-1.945E-03, A10=-1.701E-03, A12=3.683E-04 Side 12 K=0 A4=4.245E-02, A6=-3.911E-03, A8=2.155E-02, A10=-1.599E-02, A12=6.969E-03

[0045] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 1 are shown below. (1) f3 / f2 = -2.123 (2)(r6+r5) / (r6-r5)=-2.208 (3) f123 / f = -12.903 (4) r10 / r11 = 0.710 (5)(r4+r3) / (r4-r3)=-0.848 (6)(r8+r7) / (r8-r7)=-0.214 In the imaging lens of Example 1, the first and fourth lenses are made of glass material, and the other lenses are made of plastic material.

[0046] (Example 2) Next, we will describe the imaging lens according to Example 2. Figure 3 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 2.

[0047] As shown in Figure 3, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object and image sides, a fifth lens L5 with a negative refractive power with a concave surface facing both the object and image sides, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object and image sides.

[0048] The overall specifications of the imaging lens in Example 2 are shown below. f: 0.94mm f1: -6.133mm f2 : -2.956mm f3: 6.503mm f4 : 2.425mm f5 : -1.749mm f6: 2.027mm FNO: 2.00 TTL: 13.242mm Φimg: 3.947mm The surface data of the imaging lens in Example 2 is shown below.

[0049] [Table 2]

[0050] The aspherical data of the imaging lens in Example 2 is shown below. 3rd page K=0 A4=5.777E-02, A6=-1.510E-02, A8=1.723E-03, A10=-7.304E-05, A12=-4.927E-08, A14=2.176E-08 Side 4 K=0 A4=4.298E-02, A6=4.178E-02, A8=-5.068E-02, A10=1.276E-02, A12=-9.314E-04, A14=-3.066E-06 Page 5 K=0 A4=-1.370E-02, A6=-2.381E-02, A8=1.012E-02, A10=-9.589E-04, A12=-1.698E-05 Page 6 K=0 A4=-1.324E-02, A6=1.210E-02, A8=-6.353E-03, A10=3.411E-03, A12=-1.028E-03, A14=1.462E-04 Page 7 K=0 A4=-8.455E-04, A6=-6.156E-03, A8=1.842E-02 Page 8 K=0 A4=1.897E-02, A6=2.875E-02, A8=-1.562E-02 Page 9 K=0 A4=-1.320E-01, A6=1.472E-01, A8=-1.122E-01, A10=9.937E-03, A12=7.676E-03 Page 10 K=0 A4=-1.709E-01, A6=9.511E-02, A8=-3.665E-02, A10=-4.334E-03, A12=3.148E-03 Page 11 K=0 A4=-7.924E-02, A6=3.881E-02, A8=-3.743E-03, A10=-1.038E-03, A12=3.314E-04 Page 12 K=0 A4=4.014E-02, A6=-2.932E-03, A8=2.091E-02, A10=-1.623E-02, A12=6.434E-03

[0051] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 2 are shown below. (1) f3 / f2 = -2.200 (2)(r6+r5) / (r6-r5)=-2.274 (3) f123 / f = -10.134 (4) r10 / r11 = 0.695 (5)(r4+r3) / (r4-r3)=-0.850 (6)(r8+r7) / (r8-r7)=-0.160 In the imaging lens of Example 2, the first and fourth lenses are made of glass material, while the other lenses are made of plastic material.

[0052] (Example 3) Next, we will describe the imaging lens according to Example 3. Figure 5 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 3.

[0053] As shown in Figure 5, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object and image sides, a fifth lens L5 with a negative refractive power with a concave surface facing both the object and image sides, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object and image sides.

[0054] The overall specifications of the imaging lens in Example 3 are shown below. f: 0.96mm f1: -5.638mm f2 : -3.243mm f3: 5.759mm f4: 2.614mm f5 : -1.874mm f6: 1.991mm FNO: 2.00 TTL: 12.673mm Φimg: 3.953mm The surface data of the imaging lens in Example 3 is shown below.

[0055] [Table 3]

[0056] The aspherical data for the imaging lens of Example 3 is shown below. 3rd page K=0 A4=5.725E-02, A6=-1.513E-02, A8=1.723E-03, A10=-7.304E-05, A12=-4.852E-08, A14=1.600E-08 Side 4 K=0 A4=4.828E-02, A6=4.236E-02, A8=-5.055E-02, A10=1.277E-02, A12=-9.394E-04, A14=-1.533E-05 5th page K=0 A4=-1.359E-02, A6=-2.418E-02, A8=9.823E-03, A10=-1.025E-03, A12=3.387E-05 Page 6 K=0 A4=-1.499E-02, A6=1.258E-02, A8=-6.063E-03, A10=3.163E-03, A12=-1.184E-03, A14=5.183E-04 Side 7 K=0 A4=-2.107E-02, A6=3.904E-02, A8=-1.906E-02 Side 8 K=0 A4=1.213E-03, A6=3.420E-02, A8=4.062E-03 9th page K=0 A4=-1.323E-01, A6=1.515E-01, A8=-1.097E-01, A10=1.313E-02, A12=1.991E-02 Side 10 K=0 A4=-1.681E-01, A6=9.599E-02, A8=-3.791E-02, A10=-8.229E-03, A12=6.010E-03 Page 11 K=0 A4=-8.198E-02, A6=3.721E-02, A8=-4.275E-03, A10=-7.293E-04, A12=4.937E-04 Side 12 K=0 A4=3.631E-02, A6=-1.726E-03, A8=2.153E-02, A10=-1.605E-02, A12=6.357E-03

[0057] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 3 are shown below. (1) f3 / f2 = -1.776 (2)(r6+r5) / (r6-r5)= -1.889 (3) f123 / f = -16.344 (4) r10 / r11 = 0.711 (5)(r4+r3) / (r4-r3)=-0.935 (6)(r8+r7) / (r8-r7)=-0.184 In the imaging lens of Example 3, the first and fourth lenses are made of glass material, while the other lenses are made of plastic material.

[0058] (Example 4) Next, we will describe the imaging lens according to Example 4. Figure 7 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 4.

[0059] As shown in Figure 7, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object and image sides, a fifth lens L5 with a negative refractive power with a concave surface facing both the object and image sides, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object and image sides.

[0060] The overall specifications of the imaging lens in Example 4 are shown below. f: 0.95mm f1: -6.072mm f2 : -3.051mm f3: 6.285mm f4: 2.628mm f5 : -1.862mm f6: 1.965mm FNO: 2.00 TTL: 13.692mm Φimg: 3.931mm The surface data of the imaging lens in Example 4 is shown below.

[0061] [Table 4]

[0062] The aspherical data for the imaging lens of Example 4 is shown below. 3rd page K=0 A4=5.715E-02, A6=-1.511E-02, A8=1.720E-03, A10=-7.284E-05, A12=-8.654E-08, A14=2.457E-08 Side 4 K=0 A4=4.313E-02, A6=4.158E-02, A8=-5.066E-02, A10=1.277E-02, A12=-9.299E-04, A14=2.479E-06 Page 5 K=0 A4=-1.281E-02, A6=-2.399E-02, A8=9.882E-03, A10=-1.021E-03, A12=1.035E-05 Page 6 K=0 A4=-1.605E-02, A6=1.220E-02, A8=-6.132E-03, A10=3.257E-03, A12=-1.153E-03, A14=2.176E-04 Page 7 K=0 A4=-3.547E-02, A6=3.307E-02, A8=-1.801E-02 Page 8 K=0 A4=-4.156E-03, A6=2.119E-02, A8=-8.070E-03 Page 9 K=0 A4=-1.322E-01, A6=1.506E-01, A8=-1.150E-01, A10=1.021E-02, A12=2.350E-02 Page 10 K=0 A4=-1.690E-01, A6=9.694E-02, A8=-3.637E-02, A10=-7.129E-03, A12=5.506E-03 Page 11 K=0 A4=-8.394E-02, A6=3.678E-02, A8=-4.557E-03, A10=-9.809E-04, A12=5.862E-04 Page 12 K=0 A4=3.894E-02, A6=-2.948E-03, A8=2.106E-02, A10=-1.622E-02, A12=6.328E-03

[0063] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 4 are shown below. (1) f3 / f2 = -2.060 (2)(r6+r5) / (r6-r5)= -2.191 (3) f123 / f = -11.102 (4) r10 / r11 = 0.713 (5)(r4+r3) / (r4-r3)=-0.883 (6)(r8+r7) / (r8-r7)=-0.239 In the imaging lens of Example 4, the first and fourth lenses are made of glass material, and the other lenses are made of plastic material.

[0064] (Example 5) Next, we will describe the imaging lens according to Example 5. Figure 9 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 5.

[0065] As shown in Figure 9, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object side and the image side, a fifth lens L5 with a negative refractive power with a concave surface facing both the object side and the image side, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object side and the image side.

[0066] The overall specifications of the imaging lens in Example 5 are shown below. f: 0.87mm f1: -5.856mm f2 : -3.483mm f3: 6.792mm f4: 2.210mm f5 : -1.895mm f6: 2.005mm FNO: 2.40 TTL: 12.982mm Φimg: 3.984mm The surface data of the imaging lens in Example 5 is shown below.

[0067] [Table 5]

[0068] The aspherical data of the imaging lens in Example 5 is shown below. 3rd page K=0 A4= 5.756E-02, A6= -1.535E-02, A8= 1.733E-03, A10= -7.537E-05, A12= 5.587E-08 Side 4 K = -1.496E+00 A4= 4.867E-02, A6= 6.254E-02, A8= -5.036E-02, A10= 8.756E-03, A12= -2.497E-06 5th page K = -3.534E+01 A4= -9.954E-04, A6= -2.455E-02, A8= 8.363E-03, A10= -7.893E-04, A12= 2.372E-05 Page 6 K = 7.968E-02 A4= -4.476E-03, A6= 4.138E-03, A8= -5.407E-03, A10= 9.506E-03, A12= -3.039E-03 Side 7 K=0 A4= -2.605E-02, A6= -1.166E-03, A8= -2.358E-03 Side 8 K=0 A4= -7.597E-03, A6= 2.903E-03, A8= -2.041E-04 9th page K=0 A4= -1.310E-01, A6= 9.819E-02, A8= -3.578E-02, A10= 3.871E-03, A12= 9.181E-04 Side 10 K = -2.079E+00 A4= -1.208E-01, A6= 9.499E-02, A8= -3.506E-02, A10= 5.358E-03, A12= 1.190E-04 Page 11 K = -1.472E+00 A4= -5.728E-02, A6= 1.851E-02, A8= -2.631E-03, A10= 7.325E-05, A12= 4.988E-06 Side 12 K = -1.351E+00 A4= 1.471E-02, A6= 2.148E-03, A8= -1.256E-03, A10= 1.913E-04, A12= 4.053E-05

[0069] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 5 are shown below. (1) f3 / f2 = -1.950 (2) (r6+r5) / (r6-r5)=-1.851 (3) f123 / f = -8.384 (4) r10 / r11 = 0.728 (5)(r4+r3) / (r4-r3)=-0.899 (6)(r8+r7) / (r8-r7)=-0.235 In the imaging lens of Example 5, the first and fourth lenses are made of glass material, and the other lenses are made of plastic material.

[0070] (Example 6) Next, the imaging lens according to Example 6 will be described. Figure 11 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 6.

[0071] As shown in Figure 11, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object and image sides, a fifth lens L5 with a negative refractive power with a concave surface facing both the object and image sides, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object and image sides.

[0072] The overall specifications of the imaging lens in Example 6 are shown below. f: 0.93mm f1: -6.685mm f2 : -2.945mm f3: 6.380mm f4: 2.654mm f5 : -1.869mm f6: 1.998mm FNO: 2.00 TTL: 13.190mm Φimg: 3.946mm The surface data of the imaging lens in Example 6 is shown below.

[0073] [Table 6]

[0074] The aspherical data of the imaging lens in Example 6 is shown below. 3rd page K=0 A4=5.756E-02, A6=-1.535E-02, A8=1.733E-03, A10=-7.537E-05, A12=5.587E-08 Side 4 K = -1.496E+00 A4=4.867E-02, A6=6.254E-02, A8=-5.036E-02, A10=8.756E-03, A12=-2.497E-06 Page 5 K=-3.534E+01 A4=-9.954E-04, A6=-2.455E-02, A8=8.363E-03, A10=-7.893E-04, A12=2.372E-05 Page 6 K=7.968E-02 A4=-4.476E-03, A6=4.138E-03, A8=-5.407E-03, A10=9.506E-03, A12=-3.039E-03 Page 7 K=0 A4=-2.605E-02, A6=-1.166E-03, A8=-2.358E-03 Page 8 K=0 A4=-7.597E-03, A6=2.903E-03, A8=-2.041E-04 Page 9 K=0 A4=-1.310E-01, A6=9.819E-02, A8=-3.578E-02, A10=3.871E-03, A12=9.181E-04 Page 10 K=-2.079E+00 A4=-1.208E-01, A6=9.499E-02, A8=-3.506E-02, A10=5.358E-03, A12=1.190E-04 Page 11 K = -1.472E + 00 A4=-5.728E-02, A6=1.851E-02, A8=-2.631E-03, A10=7.325E-05, A12=4.988E-06 Page 12 K = -1.351E + 00 A4=1.471E-02, A6=2.148E-03, A8=-1.256E-03, A10=1.913E-04, A12=4.053E-05

[0075] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 6 are shown below. (1) f3 / f2 = -2.166 (2)(r6+r5) / (r6-r5)= -2.275 (3) f123 / f = -12.784 (4) r10 / r11 = 0.718 (5)(r4+r3) / (r4-r3)=-0.843 (6)(r8+r7) / (r8-r7)=-0.201 In the imaging lens of Example 6, the first and fourth lenses are made of glass material, and the other lenses are made of plastic material.

[0076] (Example 7) Next, the imaging lens according to Example 7 will be described. Figure 13 is a cross-sectional view along the optical axis showing the optical configuration of the imaging lens according to Example 7.

[0077] As shown in Figure 13, this imaging lens consists of, in order from the object side, a negative meniscus first lens L1 with a convex surface facing the object side, a second lens L2 whose object-side surface is concave near the optical axis and whose negative power is weaker at the effective diameter end than at the center, and which has a negative refractive power with a concave surface facing the image side, a positive meniscus third lens L3 with a concave surface facing the object side, an aperture diaphragm S, a fourth lens L4 with a positive refractive power with a convex surface facing both the object and image sides, a fifth lens L5 with a negative refractive power with a concave surface facing both the object and image sides, and a sixth lens L6 with a positive refractive power with a convex surface facing both the object and image sides.

[0078] The overall specifications of the imaging lens in Example 7 are shown below. f: 0.97mm f1: -5.230mm f2 : -3.321mm f3: 5.654mm f4: 2.608mm f5 : -1.875mm f6: 1.986mm FNO: 2.00 TTL: 12.659mm Φimg: 3.935mm The surface data of the imaging lens in Example 7 is shown below.

[0079] [Table 7]

[0080] The aspherical data of the imaging lens in Example 7 is shown below. 3rd page K=0 A4= 5.744E-02, A6= -1.512E-02, A8= 1.724E-03, A10= -7.285E-05, A12= -2.435E-09, A14= 2.806E-08 Side 4 K=0 A4= 4.642E-02, A6= 4.234E-02, A8= -5.047E-02, A10= 1.281E-02, A12= -9.293E-04, A14= -1.383E-05 5th page K=0 A4= -1.360E-02, A6= -2.444E-02, A8= 9.661E-03, A10= -1.112E-03, A12= 3.354E-05 Page 6 K=0 A4= -1.536E-02, A6= 1.242E-02, A8= -6.863E-03, A10= 2.497E-03, A12= -1.641E-03, A14= 1.693E-03 Side 7 K=0 A4= -2.125E-02, A6= 3.713E-02, A8= -2.089E-02 Side 8 K=0 A4= 3.208E-03, A6= 3.591E-02, A8= 2.815E-03 9th page K=0 A4= -1.342E-01, A6= 1.495E-01, A8= -1.101E-01, A10= 1.470E-02, A12= 2.428E-02 Side 10 K=0 A4= -1.684E-01, A6= 9.602E-02, A8= -3.785E-02, A10= -8.162E-03, A12= 6.030E-03 Page 11 K=0 A4= -8.149E-02, A6= 3.731E-02, A8= -4.271E-03, A10= -7.329E-04, A12= 4.981E-04 Side 12 K=0 A4= 3.567E-02, A6= -2.125E-03, A8= 2.140E-02, A10= -1.611E-02, A12= 6.345E-03

[0081] The values ​​corresponding to the conditional equations (1) to (6) for the imaging lens in Example 7 are shown below. (1) f3 / f2 = -1.702 (2)(r6+r5) / (r6-r5)= -1.822 (3) f123 / f = -15.864 (4) r10 / r11 = 0.712 (5)(r4+r3) / (r4-r3)=-0.969 (6)(r8+r7) / (r8-r7)=-0.183 In the imaging lens of Example 7, the first and fourth lenses are made of glass material, while the other lenses are made of plastic material. [Explanation of Symbols]

[0082] L1 First Lens L2 Second Lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens FL bandpass filter (dual-pass filter) CG cover glass I. Imaging surface S Aperture diaphragm

Claims

1. Starting from the object side, the lens consists of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, a fourth lens with positive refractive power, a fifth lens with negative refractive power, and a sixth lens with positive refractive power. An imaging lens characterized by satisfying the following conditional equation. -2.3<f3 / f2<-1.6 (1) -2.3<(r6+r5) / (r6-r5)<-1.8 (2) Here, f2 is the focal length of the second lens. f3 is the focal length of the third lens. r5 is the radius of curvature of the object-side surface of the third lens. r6 is the radius of curvature of the image-side surface of the third lens. That is the case.

2. The imaging lens according to claim 1, characterized in that it satisfies the following conditional expression. -17<f123 / f<-8 (3) Here, f is the focal length of the entire imaging lens system. f123 is the combined focal length of the first, second, and third lenses. That is the case.

3. The imaging lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression. 0.5<r10 / r11<1.3 (4) Here, r10 is the radius of curvature of the image-side surface of the fifth lens. r11 is the radius of curvature of the object-side surface of the sixth lens. That is the case.

4. The object-side surface of the second lens is concave near the optical axis, and the negative power is weaker at the effective diameter end than at the center. The imaging lens according to claim 1, characterized in that it satisfies the following conditional expression. -0.97<(r4+r3) / (r4-r3)<-0.83 (5) Here, r3 is the radius of curvature of the object-side surface of the second lens. r4 is the radius of curvature of the image-side surface of the second lens. That is the case.

5. The imaging lens according to claim 1 or 4, characterized in that it satisfies the following conditional expression. -0.25<(r8+r7) / (r8-r7)<-0.15 (6) Here, r7 is the radius of curvature of the object-side surface of the fourth lens. r8 is the radius of curvature of the image-side surface of the fourth lens. That is the case.

Images