Imaging lens

Abstract

To provide a compact imaging lens which has a wide angle and furthermore has excellent optical characteristics.SOLUTION: An imaging lens is comprised of a first to a sixth lens arranged in this order from an object side to an image side, the first lens L1 has negative refractive power; the second lens L2 has negative refractive power, the third lens L3 has positive or negative refractive power, the fourth lens L4 has positive refractive power, the fifth lens L5 has positive refractive power, and the sixth lens L6 has negative refractive power. The second lens L2 has an object-side surface which is convex near an optical axis and the sixth lens L6 has an object-side surface which is concave near the optical axis. The imaging lens satisfies the following conditional expressions: 0.05<D34 / D45<0.20 ...(1), 1.00<T1 / T2<2.85 ...(2), where D34 represents an optical axial distance from an image-side surface of the third lens L3 to an object-side surface of the fourth lens L4, D45 represents an optical axial distance from an image-side surface of the fourth lens L4 to an object-side surface of the fifth lens L5, T1 represents the thickness on the optical axis, of the first lens L1, and T2 represents the thickness on the optical axis, of the second lens L2.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 CMOS sensor. [Background technology]

[0002] More and more automobiles are being equipped with onboard cameras, and their functions, such as obstacle detection and driver monitoring, are continually evolving to improve vehicle safety and provide a more comfortable driving experience for the driver.

[0003] The imaging lenses installed in such vehicle-mounted cameras are required to have a wide angle of view and high resolution. In addition, vehicle-mounted cameras are becoming smaller in size in order to install multiple vehicle-mounted cameras on one vehicle, and so further miniaturization is also required for the imaging lenses.

[0004] As an imaging lens having a wide angle of view and high resolution, for example, an imaging lens as disclosed in Patent Document 1 below is known.

[0005] Patent Document 1 discloses an imaging lens including, in order from the object side, a first lens having negative refractive power with a convex surface on the object side and a concave surface on the image side, a second lens having refractive power, a third lens having positive refractive power, a fourth lens having convex surfaces on the object side and the image side and having positive refractive power, a fifth lens having refractive power, and a sixth lens having refractive power. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] China Patent Application Publication No. 112444938 Summary of the Invention [Problem to be solved by the invention]

[0007] The lens described in Patent Document 1 has a maximum angle of view of 140° or more, but since the total optical length exceeds 25 mm, it is difficult to satisfy the recent demand for compactness.

[0008] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an imaging lens that has good optical characteristics despite its wide angle, and is also capable of meeting the miniaturization specifications that have been required in recent years. [Means for solving the problem]

[0009] The imaging lens according to the present invention is composed of 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 positive refractive power, and a sixth lens having negative refractive power, which are arranged in this order from the object side to the image side. The second lens has a convex surface on the object side in the paraxial direction, and the sixth lens has a concave surface on the object side in the paraxial direction. In this specification, the convex, concave, and flat surfaces of the lens refer to the shape in the paraxial direction, and the refractive power refers to the refractive power in the paraxial direction unless otherwise specified.

[0010] The first lens has a negative refractive power, thereby achieving a wide angle and effectively correcting chromatic aberration, coma aberration, astigmatism, and curvature of field.

[0011] The second lens has negative refractive power and has a convex surface on the object side in the paraxial direction, thereby providing excellent correction for chromatic aberration, spherical aberration, coma aberration, astigmatism, and curvature of field.

[0012] The third lens has a positive refractive power, and thereby effectively corrects chromatic aberration, spherical aberration, coma aberration, astigmatism, and curvature of field.

[0013] The fourth lens has a positive refractive power, thereby achieving a low height and providing excellent correction for chromatic aberration, spherical aberration, astigmatism, and curvature of field.

[0014] The fifth lens has a positive refractive power, thereby achieving a low height and providing excellent correction for chromatic aberration, spherical aberration, coma, and curvature of field.

[0015] The sixth lens has negative refractive power and is concave on the object side paraxially, thereby ensuring an appropriate back focus and providing excellent correction for chromatic aberration, spherical aberration, coma, and field curvature.

[0016] In the imaging lens having the above configuration, it is desirable that the first lens has a meniscus shape with a convex surface on the object side on the paraxial line.

[0017] By making the first lens have a meniscus shape with a convex surface on the object side paraxially, it is possible to capture a wide range of light beams while suppressing the occurrence of various aberrations.

[0018] In the imaging lens having the above configuration, it is preferable that the second lens has a meniscus shape paraxially.

[0019] By making the second lens have a meniscus shape on the paraxial line, chromatic aberration, spherical aberration, coma aberration, astigmatism, and curvature of field can be corrected satisfactorily.

[0020] In the imaging lens having the above configuration, it is desirable that the third lens has a meniscus shape with a concave surface on the image side on the paraxial line.

[0021] By making the third lens have a meniscus shape with a concave surface on the image side paraxially, it becomes possible to satisfactorily correct spherical aberration, coma aberration, astigmatism, curvature of field, and distortion aberration.

[0022] In the imaging lens having the above configuration, it is desirable that the fourth lens has a biconvex shape on the paraxial surface.

[0023] By making the fourth lens have a biconvex shape on the paraxial line, the positive refractive power is strengthened to reduce the height, and good correction of chromatic aberration, spherical aberration, astigmatism, and curvature of field is possible.

[0024] In the imaging lens having the above configuration, it is desirable that the fifth lens has a biconvex shape paraxially.

[0025] By making the fifth lens have a biconvex shape on the paraxial line, the positive refractive power is strengthened to reduce the height, and good correction of chromatic aberration, spherical aberration, coma, and curvature of field is possible.

[0026] In the imaging lens having the above configuration, it is desirable that the sixth lens has a convex surface on the image side paraxially.

[0027] By forming the image-side surface of the sixth lens to be a convex surface on the paraxial line, chromatic aberration, spherical aberration, coma, and field curvature can be effectively corrected.

[0028] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (1). (1) 0.05 <D34 / D45<0.20 Here, D34 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens, and D45 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.

[0029] By satisfying the range of conditional expression (1), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0030] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (2). (2) 1.00 <T1 / T2<2.85 Here, T1 is the thickness of the first lens on the optical axis, and T2 is the thickness of the second lens on the optical axis.

[0031] By satisfying the range of conditional expression (2), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0032] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (3). (3) 0.16 <R3f / R3r<0.55 Here, R3f is the paraxial radius of curvature of the object-side surface of the third lens, and R3r is the paraxial radius of curvature of the image-side surface of the third lens.

[0033] By satisfying the range of conditional expression (3), chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be corrected satisfactorily.

[0034] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (4). (4) 0.04 <T6 / bf<0.18 Here, T6 is the thickness of the sixth lens on the optical axis, and bf is the back focus.

[0035] By satisfying the range of conditional expression (4), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0036] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (5). (5) 1.60 <R1f / D12<5.30 Here, R1f is the paraxial radius of curvature of the object-side surface of the first lens, and D12 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.

[0037] By satisfying the range of conditional expression (5), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0038] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (6). (6) 4.30 <R1f / T1<14.30 Here, R1f is the paraxial radius of curvature of the object-side surface of the first lens, and T1 is the thickness of the first lens on the optical axis.

[0039] By satisfying the range of conditional expression (6), a low height can be achieved and chromatic aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0040] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (7). (7) -0.70 <R2f / f2<-0.09 Here, R2f 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.

[0041] By satisfying the range of conditional expression (7), chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be corrected satisfactorily.

[0042] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (8). (8)3.50 <T5 / T6<15.00 Here, T5 is the thickness of the fifth lens on the optical axis, and T6 is the thickness of the sixth lens on the optical axis.

[0043] By satisfying the range of conditional expression (8), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0044] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (9). (9) 1.30 <f4 / f<5.00 Here, f4 is the focal length of the fourth lens, and f is the focal length of the entire imaging lens system.

[0045] By satisfying the range of conditional expression (9), a low height can be achieved and chromatic aberration, spherical aberration, astigmatism, and curvature of field can be favorably corrected.

[0046] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (10). (10)0.80 <f5 / f<2.75 Here, f5 is the focal length of the fifth lens, and f is the focal length of the entire imaging lens system.

[0047] By satisfying the range of conditional expression (10), a low height can be achieved and chromatic aberration, spherical aberration, coma, and curvature of field can be favorably corrected.

[0048] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (11). (11)-4.80 <f6 / f<-1.40 Here, f6 is the focal length of the sixth lens, and f is the focal length of the entire imaging lens system.

[0049] By satisfying the range of conditional expression (11), an appropriate back focus can be ensured, and chromatic aberration, spherical aberration, coma, and curvature of field can be favorably corrected.

[0050] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (12). (12)-1.45 <f1 / f5<-0.80 Here, f1 is the focal length of the first lens, and f5 is the focal length of the fifth lens.

[0051] By satisfying the range of conditional expression (12), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0052] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (13). (13) 1.70 <f3 / f4<7.00 Here, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

[0053] By satisfying the range of conditional expression (13), chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be corrected satisfactorily.

[0054] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (14). (14)0.80 <T2 / D23<4.00 Here, T2 is the thickness of the second lens on the optical axis, and D23 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.

[0055] By satisfying the range of conditional expression (14), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0056] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (15). (15)0.88 <D23 / D34<4.44 Here, D23 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 D34 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.

[0057] By satisfying the range of conditional expression (15), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0058] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (16). (16)0.11 <D23 / D45<0.41 Here, D23 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 D45 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.

[0059] By satisfying the range of conditional expression (16), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0060] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (17). (17)6.0 <R2f / D23<34.0 Here, R2f is the paraxial radius of curvature of the object-side surface of the second lens, and D23 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.

[0061] By satisfying the range of conditional expression (17), chromatic aberration, spherical aberration, astigmatism, and curvature of field can be corrected satisfactorily.

[0062] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (18). (18)0.98 <D12 / f<2.88 Here, D12 is the distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens, and f is the focal length of the entire imaging lens system.

[0063] By satisfying the range of conditional expression (18), a low height can be achieved and chromatic aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0064] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (19). (19)-4.75 <R1f / f1<-1.45 Here, R1f is the paraxial radius of curvature of the object side surface of the first lens, and f1 is the focal length of the first lens.

[0065] By satisfying the range of conditional expression (19), the angle of view can be increased, and chromatic aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0066] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (20). (20)-2.15 <R5r / f<-0.55 Here, R5r is the paraxial radius of curvature of the image-side surface of the fifth lens, and f is the focal length of the entire imaging lens system.

[0067] By satisfying the range of conditional expression (20), a low height can be achieved and chromatic aberration, spherical aberration, coma, and curvature of field can be favorably corrected.

[0068] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (21). (21)-2.30 <R6f / f<-0.55 Here, R6f 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.

[0069] By satisfying the range of conditional expression (21), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0070] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (22). (22)0.10 <R4f / R3r<0.36 Here, R4f is the paraxial radius of curvature of the object-side surface of the fourth lens, and R3r is the paraxial radius of curvature of the image-side surface of the third lens.

[0071] By satisfying the range of conditional expression (22), chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be corrected satisfactorily.

[0072] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (23). (23)0.65 <R2f / R2r<2.75 Here, R2f is the paraxial radius of curvature of the object-side surface of the second lens, and R2r is the paraxial radius of curvature of the image-side surface of the second lens.

[0073] By satisfying the range of conditional expression (23), chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be corrected satisfactorily.

[0074] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (24). (24)-3.10 <R5f / R5r<-0.70 Here, R5f is the paraxial radius of curvature of the object-side surface of the fifth lens, and R5r is the paraxial radius of curvature of the image-side surface of the fifth lens.

[0075] By satisfying the range of conditional expression (24), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0076] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (25). (25)0.10 <R6f / R6r<0.70 Here, R6f is the paraxial radius of curvature of the object-side surface of the sixth lens, and R6r is the paraxial radius of curvature of the image-side surface of the sixth lens.

[0077] By satisfying the range of conditional expression (25), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0078] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (26). (26)0.78 <R1r / T1<2.70 Here, R1r is the paraxial radius of curvature of the image-side surface of the first lens, and T1 is the thickness of the first lens on the optical axis.

[0079] By satisfying the range of conditional expression (26), the angle of view can be increased, and chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0080] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (27). (27) 1.50 <R3f / T3<9.00 Here, R3f is the paraxial radius of curvature of the object side surface of the third lens, and T3 is the thickness of the third lens on the optical axis.

[0081] By satisfying the range of conditional expression (27), chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be corrected satisfactorily.

[0082] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (28). (28)-13.20 <R4r / T4<-1.70 Here, R4r is the paraxial radius of curvature of the image-side surface of the fourth lens, and T4 is the thickness of the fourth lens on the optical axis.

[0083] By satisfying the range of conditional expression (28), a low height can be achieved and chromatic aberration, spherical aberration, astigmatism, and curvature of field can be favorably corrected.

[0084] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (29). (29)0.80 <R5f / T5<2.60 Here, R5f is the paraxial radius of curvature of the object side surface of the fifth lens, and T5 is the thickness of the fifth lens on the optical axis.

[0085] By satisfying the range of conditional expression (29), a low height can be achieved and chromatic aberration, spherical aberration, coma, and curvature of field can be favorably corrected.

[0086] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (30). (30)-14.70 <R6f / T6<-2.80 Here, R6f is the paraxial radius of curvature of the object side surface of the sixth lens, and T6 is the thickness of the sixth lens on the optical axis.

[0087] By satisfying the range of conditional expression (30), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0088] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (31). (31)-26.80 <R5r / D56<-7.55 Here, R5r is the paraxial radius of curvature of the image-side surface of the fifth lens, and D56 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.

[0089] By satisfying the range of conditional expression (31), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0090] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (32). (32)-300.0 <f23 / f<-8.0 Here, f23 is the composite focal length of the second and third lenses, and f is the focal length of the entire imaging lens system.

[0091] By satisfying the range of conditional expression (32), chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be corrected satisfactorily.

[0092] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (33). (33)3.2 <f23 / f1<130.0 Here, f23 is the combined focal length of the second and third lenses, and f1 is the focal length of the first lens.

[0093] By satisfying the range of conditional expression (33), the angle of view can be increased, and chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be favorably corrected.

[0094] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (34). (34) 55°<ω<100° Here, ω is the half angle of view.

[0095] By satisfying the range of conditional expression (34), it is possible to make the imaging lens smaller and to achieve a wider angle.

[0096] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (35). (35)13<νd2<28 Here, νd2 is the Abbe number for the d-line of the second lens.

[0097] By satisfying the range of conditional expression (35), chromatic aberration can be corrected satisfactorily.

[0098] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (36). (36)39<νd3<72 Here, νd3 is the Abbe number for the d-line of the third lens.

[0099] By satisfying the range of conditional expression (36), chromatic aberration can be corrected satisfactorily.

[0100] According to the present invention, it is possible to obtain an imaging lens that has a wide angle and high resolution while satisfying the demand for compactness. In addition, since the imaging lens according to the present invention satisfactorily corrects various aberrations, the number of lenses can be reduced, and by reducing the amount of lens material used, an environmentally friendly imaging lens can be provided. [Brief description of the drawings]

[0101] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an imaging lens according to a first embodiment of the present invention. [Diagram 2] 3A to 3C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the imaging lens according to the first embodiment of the present invention. [Diagram 3] FIG. 11 is a cross-sectional view showing a schematic configuration of an imaging lens according to a second embodiment of the present invention. [Figure 4] 5A to 5C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 2 of the present invention. [Diagram 5] FIG. 11 is a cross-sectional view showing a schematic configuration of an imaging lens according to a third embodiment of the present invention. [Figure 6] 10A to 10C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 3 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0102] An embodiment of the present invention will be described in detail below with reference to the drawings. Figures 1, 3, and 5 are cross-sectional views showing the schematic configurations of imaging lenses according to Examples 1 to 3 of this embodiment. Since the basic lens configuration is the same in all the examples, the imaging lens according to this embodiment will be described here with reference to the cross-sectional view of Example 1.

[0103] As shown in FIG. 1, the imaging lens of this embodiment is composed of, in order from the object side to the image side, a first lens L1 having negative refractive power, a second lens L2 having negative refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having positive refractive power, and a sixth lens L6 having negative refractive power.

[0104] Between the sixth lens L6 and the imaging surface IMG, a filter FL such as a low-pass filter or a band-pass filter that cuts off a specific wavelength range, and a cover glass CG are arranged. The filter FL and the cover glass CG can be omitted. Instead of arranging various filters such as the filter FL, a coating that has the same effect as the various filters may be applied to the lens surface of any of the lenses.

[0105] The first lens L1 has negative refractive power and is a meniscus shape with a convex surface on the object side at the paraxial position. This allows the imaging lens to capture a wide range of light rays while suppressing the occurrence of various aberrations, thereby widening the angle of view. In addition, chromatic aberration, coma aberration, astigmatism, and curvature of field are well corrected.

[0106] The second lens L2 has negative refractive power and is a meniscus shape with a convex surface on the object side on the paraxial line, thereby providing excellent correction for chromatic aberration, spherical aberration, coma aberration, astigmatism, and field curvature.

[0107] The third lens L3 has positive refractive power and is a meniscus shape with a concave surface on the image side paraxially, thereby providing excellent correction for chromatic aberration, spherical aberration, coma aberration, astigmatism, and curvature of field.

[0108] The fourth lens L4 has positive refractive power and is biconvex with convex surfaces on both the object side and the image side on the paraxial line, thereby achieving a low profile of the imaging lens while providing excellent correction for chromatic aberration, spherical aberration, astigmatism, and curvature of field.

[0109] The fifth lens L5 has positive refractive power and is biconvex with convex surfaces on both the object side and the image side on the paraxial line, thereby achieving a low profile of the imaging lens while providing excellent correction for chromatic aberration, spherical aberration, coma, and curvature of field.

[0110] The sixth lens L6 has negative refractive power and is a meniscus shape with a concave surface on the object side at the paraxial line, which ensures an appropriate back focus and effectively corrects chromatic aberration, spherical aberration, coma, and field curvature.

[0111] In the imaging lens according to the present embodiment, the aperture stop ST is disposed between the third lens L3 and the fourth lens L4, thereby effectively correcting distortion. It also has the effect of blocking stray light that is not necessary for imaging. The position of the aperture stop ST is not limited to between the third lens L3 and the fourth lens L4, and may be disposed appropriately according to the specifications of the imaging element.

[0112] The imaging lens according to this embodiment is configured such that a second lens L2 having a weak negative refractive power and a third lens L3 having a weak positive refractive power are arranged behind a first lens L1 having a strong negative refractive power. This allows a bundle of light rays from a wide range to be taken in by the first lens L1, and the second lens L2 and the third lens L3 to refract the bundle of light into a state close to parallel light, while correcting various aberrations occurring in the first lens L1, thereby realizing an optical system with fewer aberrations.

[0113] In the imaging lens according to the present embodiment, the first lens L1 is preferably made of a glass material. For example, in an imaging lens mounted on an in-vehicle camera, the first lens L1, which is disposed closest to the object, is in direct contact with the outside air, and is therefore preferably made of a material with high water resistance, heat resistance, weather resistance, etc. By forming the first lens L1 from a glass material, stable optical characteristics can be obtained even when used in a harsh environment.

[0114] In the imaging lens according to this embodiment, the second lens L2 to the sixth lens L6 are preferably made of a plastic material. By using a plastic material, it is possible to form an aspheric shape with high precision, and it is also possible to achieve weight reduction and cost reduction.

[0115] In the imaging lens according to the present embodiment, it is desirable to form all lens surfaces aspheric surfaces, but depending on the required performance, spherical surfaces, which are easier to manufacture, may be used. When spherical surfaces are used, manufacturing costs can be reduced.

[0116] In the imaging lens according to this embodiment, all of the first lens L1 to the sixth lens L6 are each composed of a single lens. A configuration consisting of only single lenses can make extensive use of aspherical surfaces that are effective in correcting aberrations. In this embodiment, appropriate aspherical surfaces are formed on the lens surfaces of the first lens L1 to the sixth lens L6, thereby achieving good correction of various aberrations. In addition, since the number of steps can be reduced compared to the case of using cemented lenses, the manufacturing costs can be suppressed.

[0117] In order to suppress axial chromatic aberration, lateral chromatic aberration, spherical aberration, and sensitivity to assembly errors, the fifth lens L5 having a positive refractive power and the sixth lens L6 having a negative refractive power may be cemented together.

[0118] The imaging lens of this embodiment exerts favorable effects by satisfying the following conditional expressions (1) to (36). (1) 0.05 <D34 / D45<0.20 (2) 1.00 <T1 / T2<2.85 (3) 0.16 <R3f / R3r<0.55 (4) 0.04 <T6 / bf<0.18 (5) 1.60 <R1f / D12<5.30 (6) 4.30 <R1f / T1<14.30 (7) -0.70 <R2f / f2<-0.09 (8)3.50 <T5 / T6<15.00 (9) 1.30 <f4 / f<5.00 (10)0.80 <f5 / f<2.75 (11)-4.80 <f6 / f<-1.40 (12)-1.45 <f1 / f5<-0.80 (13) 1.70 <f3 / f4<7.00 (14)0.80 <T2 / D23<4.00 (15)0.88 <D23 / D34<4.44 (16)0.11 <D23 / D45<0.41 (17)6.0 <R2f / D23<34.0 (18)0.98 <D12 / f<2.88 (19)-4.75 <R1f / f1<-1.45 (20)-2.15 <R5r / f<-0.55 (21)-2.30 <R6f / f<-0.55 (22)0.10 <R4f / R3r<0.36 (23)0.65 <R2f / R2r<2.75 (24)-3.10 <R5f / R5r<-0.70 (25)0.10 <R6f / R6r<0.70 (26)0.78 <R1r / T1<2.70 (27) 1.50 <R3f / T3<9.00 (28)-13.20 <R4r / T4<-1.70 (29)0.80 <R5f / T5<2.60 (30)-14.70 <R6f / T6<-2.80 (31)-26.80 <R5r / D56<-7.55 (32)-300.0 <f23 / f<-8.0 (33)3.2 <f23 / f1<130.0 (34) 55°<ω<100° (35)13<νd2<28 (36)13<νd3<28 however, R1f: paraxial radius of curvature of the object-side surface of the first lens L1 R1r: paraxial radius of curvature of the image-side surface of the first lens L1 R2f: paraxial radius of curvature of the object side surface of the second lens L2 R2r: paraxial radius of curvature of the image-side surface of the second lens L2 R3f: paraxial radius of curvature of the object-side surface of the third lens L3 R3r: paraxial radius of curvature of the image-side surface of the third lens L3 R4f: paraxial radius of curvature of the object-side surface of the fourth lens L4 R4r: paraxial radius of curvature of the image-side surface of the fourth lens L4 R5f: Paraxial radius of curvature of the object-side surface of the fifth lens L5 R5r: Paraxial curvature radius of the image-side surface of the fifth lens L5 R6f: Paraxial radius of curvature of the object-side surface of the sixth lens L6 R6r: Paraxial curvature radius of the image-side surface of the sixth lens L6 D12: 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 D23: 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 D34: The distance on the optical axis X from the image-side surface of the third lens L3 to the object-side surface of the fourth lens L4 D45: 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 D56: 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 T1: Thickness of the first lens L1 on the optical axis X T2: Thickness of the second lens L2 on the optical axis X T3: Thickness of the third lens L3 on the optical axis X T4: Thickness of the fourth lens L4 on the optical axis X T5: Thickness of the fifth lens L5 on the optical axis X T6: Thickness of the sixth lens L6 on the optical axis X f: focal length of the entire imaging lens system f1: focal length of the first lens L1 f2: focal length of second lens L2 f3: focal length of the third lens L3 f4: focal length of the fourth lens L4 f5: focal length of the fifth lens L5 f6: focal length of the sixth lens L6 f23: The combined focal length of the second lens L2 and the third lens L3 bf: back focus ω: Half angle of view νd2: Abbe number for the d line of the second lens L2 νd3: Abbe number for the d line of the third lens L3 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.

[0119] Moreover, the imaging lens of this embodiment exerts more preferable effects by satisfying the following conditional expressions (1a) to (36a). (1a) 0.07 <D34 / D45<0.17 (2a)1.40 <T1 / T2<2.35 (3a) 0.24 <R3f / R3r<0.45 (4a) 0.06 <T6 / bf<0.15 (5a)2.40 <R1f / D12<4.40 (6a)6.50 <R1f / T1<11.90 (7a)-0.58 <R2f / f2<-0.13 (8a)5.35 <T5 / T6<12.50 (9a)2.00 <f4 / f<4.10 (10a)1.20 <f5 / f<2.25 (11a)-3.90 <f6 / f<-2.10 (12a)-1.30 <f1 / f5<-0.92 (13a)2.55 <f3 / f4<5.80 (14a)1.20 <T2 / D23<3.30 (15a)1.30 <D23 / D34<3.70 (16a) 0.16 <D23 / D45<0.34 (17a)9.0 <R2f / D23<28.3 (18a)1.25 <D12 / f<2.40 (19a)-4.00 <R1f / f1<-2.20 (20a)-1.80 <R5r / f<-0.85 (21a)-1.90 <R6f / f<-0.85 (22a) 0.16 <R4f / R3r<0.30 (23a) 0.95 <R2f / R2r<2.20 (24a)-2.60 <R5f / R5r<-1.05 (25a) 0.15 <R6f / R6r<0.58 (26a)1.15 <R1r / T1<2.25 (27a)2.20 <R3f / T3<7.50 (28a)-10.90 <R4r / T4<-2.50 (29a)1.20 <R5f / T5<2.15 (30a)-12.25 <R6f / T6<-4.15 (31a)-23.30 <R5r / D56<-11.30 (32a)-230.0 <f23 / f<-10.5 (33a)4.7 <f23 / f1<110.0 (34a) 65°<ω<90° (35a)15<νd2<24 (36a)15<νd3<24 However, the symbols in each conditional expression are the same as those explained in the previous paragraph. Note that, for the conditional expressions (1a) to (36a), the lower limit value and the upper limit value of the corresponding conditional expression (1) to (36) may be applied as the respective lower limit value and upper limit value.

[0120] In this embodiment, the aspheric shape adopted for the aspheric surface of the lens surface is expressed by Equation 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 An is the n-th aspheric coefficient.

[0121]

number

[0122] Next, examples of the imaging lens according to this embodiment are shown. In each example, f is the focal length of the entire imaging lens system, Fno is the F-number, ω is the half angle of view, ih is the maximum image height, and TTL is the total optical length. Here, the total optical length is the distance on the optical axis from the object side surface of the optical element located closest to the object side to the imaging plane IMG. The values ​​of the total optical length and back focus are the distances obtained by converting the thicknesses of the filter FL, cover glass CG, etc., arranged between the imaging lens and the imaging plane IMG into air.

[0123] Additionally, i is the surface number counted from the object side, r is the paraxial radius of curvature, d is the distance between the lens surfaces on the optical axis X (surface spacing), Nd is the refractive index at the reference wavelength d line (588 nm), and νd is the Abbe number for the reference wavelength d line. Note that aspheric surfaces are indicated by adding an asterisk (*) after the surface number i.

[0124] Example 1 Basic lens data [Table 1]

[0125] [Table 2]

[0126] FIG. 2 is an aberration diagram showing 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), C-line (656 nm), and near-infrared light of 940 nm. The astigmatism diagram and distortion diagram show the amount of aberration at the reference wavelength d-line (588 nm). The astigmatism diagram also shows the amount of aberration (solid line) at the sagittal image plane S and the amount of aberration (broken line) at the tangential image plane T. As shown in FIG. 2, the imaging lens of Example 1 can correct each aberration well.

[0127] In addition, as shown in FIG. 2, the imaging lens according to the first embodiment can satisfactorily correct aberrations not only in the visible light region but also in the near-infrared region, and therefore can exhibit high resolution performance even when photographing in a dark environment, such as at night.

[0128] Example 2 Basic lens data [Table 3]

[0129] [Table 4]

[0130] FIG. 4 is an aberration diagram showing the spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 2. 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 and distortion diagram show the amount of aberration at the reference wavelength d-line (588 nm). The astigmatism diagram also shows the amount of aberration (solid line) at the sagittal image plane S and the amount of aberration (broken line) at the tangential image plane T (same as in FIG. 6). As shown in FIG. 4, the imaging lens of Example 2 can also correct each aberration well.

[0131] Example 3 Basic lens data [Table 5]

[0132] [Table 6]

[0133] As shown in FIG. 6, the imaging lens according to the third embodiment can also satisfactorily correct each aberration.

[0134] Values ​​(values ​​corresponding to the conditional expressions) (1) to (36) according to the first to third embodiments are shown below.

[0135] [Table 7] [Industrial Applicability]

[0136] When the imaging lens according to the present invention is applied to a product such as an in-vehicle camera, the camera can be made smaller while achieving a wider angle and higher performance. [Explanation of symbols]

[0137] X optical axis ST aperture stop L1 First lens L2 Second lens L3 Third lens L4 4th lens L5 5th lens L6 6th lens FL Filter CG cover glass IMG Imaging surface

Claims

1. Arranged in order from the object side to the image side, a first lens having a negative refractive power; a second lens having a negative refractive power; a third lens having a positive refractive power; a fourth lens having a positive refractive power; a fifth lens having a positive refractive power; and a sixth lens having a negative refractive power, the second lens has a paraxial convex surface facing the object side, the sixth lens has a paraxial concave surface on the object side, An imaging lens characterized by satisfying the following conditional expressions (1) and (2): (1) 0.05<D34 / D45<0.20 (2) 1.00<T1 / T2<2.85 however, D34: The distance on the optical axis from the image side surface of the third lens to the object side surface of the fourth lens D45: The distance on the optical axis from the image side surface of the fourth lens to the object side surface of the fifth lens T1: thickness of the first lens on the optical axis T2: Thickness of the second lens on the optical axis

2. 2. The imaging lens according to claim 1, wherein the following conditional expression (3) is satisfied: (3) 0.16<R3f / R3r<0.55 however, R3f: paraxial radius of curvature of the object side surface of the third lens R3r: paraxial radius of curvature of the image side surface of the third lens

3. 2. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied: (4) 0.04<T6 / bf<0.18 however, T6: Thickness of the sixth lens on the optical axis bf: back focus

4. 2. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied: (5) 1.60<R1f / D12<5.30 however, R1f: paraxial radius of curvature of the object side surface of the first lens D12: The distance on the optical axis from the image side surface of the first lens to the object side surface of the second lens

5. 2. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied: (6) 4.30<R1f / T1<14.30 however, R1f: paraxial radius of curvature of the object side surface of the first lens T1: thickness of the first lens on the optical axis

6. 2. The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied: (7) -0.70<R2f / f2<-0.09 however, R2f: paraxial radius of curvature of the object side surface of the second lens f2: focal length of the second lens

7. 2. The imaging lens according to claim 1, wherein the following conditional expression (8) is satisfied: (8) 3.50<T5 / T6<15.00 however, T5: Thickness of the fifth lens on the optical axis T6: Thickness of the sixth lens on the optical axis

Images