Imaging lens

Abstract

To provide an imaging lens which has a wide angle of view and yet is compact, has a small F-number, and can be well corrected for aberrations over a visible to near-infrared wavelength range.SOLUTION: An imaging lens is provided, comprising: a first lens L1 having negative refractive power; a second lens L2 having positive refractive power; a third lens L3 having positive refractive power; a fourth lens L4 having positive refractive power; a fifth lens L5 having negative refractive power; and a sixth lens L6 having positive refractive power which are arranged in order from the object side to the image side, the second lens L2 has an image-side surface which is concave near an optical axis and the fifth lens L5 has an image-side surface which is convex near the optical axis. The imaging lens satisfies the following conditional expression: 1.10<D12 / f<3.55 ...(1), where D12 represents a distance on an optical axis X from an image-side surface of the first lens L1 to an object-side surface of the second lens L2, and f represents a focal length of the entire imaging lens system.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] In recent years, the number of automobiles equipped with onboard cameras has been increasing, 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] Imaging lenses installed in vehicle-mounted cameras are required to be compact and have a wide angle of view. They are also required to have a small F-number and high resolution performance in the visible to near-infrared light range so that they can be used not only in bright environments such as daytime but also in dark environments such as nighttime.

[0004] As an imaging lens that aims to be small in size, have a small F-number, and have good performance in the visible light to near-infrared light range, for example, an imaging lens as disclosed in Patent Document 1 below is known.

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

[0006] [Patent Document 1] JP 2010-72622 A Summary of the Invention [Problem to be solved by the invention]

[0007] The imaging lens of Patent Document 1 has a bright F-number of 1.50 to 2.0, and aberrations are well corrected in the visible light to near infrared light range. However, the total optical length is 16 mm or more, and the total angle of view is approximately 43 to 58°, making it difficult to meet the specifications for miniaturization and wide angle that are currently required.

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide an imaging lens that satisfies the demands for compactness and a wide angle, while having a small F-number and high resolving power with various aberrations well corrected in the wavelength region from visible light to near-infrared light. [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 positive 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, which are arranged in this order from the object side to the image side. The second lens has a concave surface on the image side in the paraxial direction, and the fifth lens has a convex surface on the image 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, spherical aberration, coma aberration, astigmatism, and curvature of field.

[0011] The second lens has positive refractive power and has a concave surface on the image side paraxially, 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 thus effectively corrects chromatic aberration and astigmatism.

[0013] The fourth lens has a positive refractive power, thereby enabling the imaging lens to have a low profile and providing good correction for chromatic aberration, spherical aberration, coma, and astigmatism.

[0014] The fifth lens has negative refractive power and has a convex surface on the image side in the paraxial direction, thereby providing excellent correction for chromatic aberration, spherical aberration, coma aberration, astigmatism, and curvature of field.

[0015] The sixth lens has a positive refractive power, thereby enabling the imaging lens to have a low profile and providing excellent correction for chromatic aberration, spherical aberration, coma, and curvature of field.

[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 desirable that the second lens has a convex surface on the object side paraxially.

[0019] By forming the object-side surface of the second lens as a convex surface paraxially, it becomes possible to satisfactorily correct chromatic aberration, spherical aberration, coma aberration, astigmatism, and curvature of field while suppressing the occurrence of various aberrations.

[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 object side paraxially.

[0021] By forming the object-side surface of the third lens as a concave surface in the paraxial direction, it is possible to effectively correct chromatic aberration and astigmatism, and by forming the third lens as a meniscus shape in the paraxial direction, it is possible to effectively correct field curvature and distortion.

[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 chromatic aberration and astigmatism can be effectively corrected.

[0024] In the imaging lens having the above configuration, it is desirable that the fifth lens has a concave surface on the object side paraxially.

[0025] By forming the object-side surface of the fifth lens as a concave surface paraxially, it becomes possible to satisfactorily correct chromatic aberration, spherical aberration, coma aberration, astigmatism, curvature of field, and distortion aberration.

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

[0027] By forming the object-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)1.10 <D12 / f<3.55 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.

[0029] By satisfying the range of conditional expression (1), a low height can be achieved and chromatic aberration, spherical aberration, coma, 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) 0.50 <T1 / f<1.95 Here, T1 is the thickness of the first lens on the optical axis, and f is the focal length of the entire imaging lens system.

[0031] By satisfying the range of conditional expression (2), a low height can be achieved and chromatic aberration, spherical aberration, coma, 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) 0.20 <D23 / f<0.85 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 f is the focal length of the entire imaging lens system.

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

[0034] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (4). (4) 1.00 <T6 / bf<4.30 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), an appropriate back focus can be ensured and chromatic aberration, spherical aberration, coma, and curvature of field can be favorably corrected.

[0036] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (5). (5) 1.20 <T1 / T2<4.20 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.

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

[0038] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (6). (6) 0.30 <R1r / T1<1.60 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.

[0039] By satisfying the range of conditional expression (6), chromatic aberration, spherical aberration, coma, curvature of field, and distortion can be corrected satisfactorily.

[0040] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (7). (7) 0.35 <R6f / T6<1.40 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.

[0041] By satisfying the range of conditional expression (7), chromatic aberration, spherical aberration, coma, 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)2.35 <D12 / T2<8.55 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 T2 is the thickness of the second lens on the optical axis.

[0043] By satisfying the range of conditional expression (8), a low height can be achieved, and the occurrence of various aberrations can be suppressed while favorable correction of field curvature and distortion can be achieved.

[0044] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (9). (9) 0.35 <T2 / D23<1.25 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.

[0045] By satisfying the range of conditional expression (9), chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be corrected satisfactorily.

[0046] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (10). (10)0.25 <T4 / T6<0.80 Here, T4 is the thickness of the fourth lens on the optical axis, and T6 is the thickness of the sixth lens on the optical axis.

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

[0048] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (11). (11)2.10 <T4 / D45<10.80 Here, T4 is the thickness of the fourth lens on the optical axis, 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.

[0049] By satisfying the range of conditional expression (11), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0050] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (12). (12)0.07 <R1r / R1f<0.30 Here, R1r is the paraxial radius of curvature of the image-side surface of the first lens, and R1f is the paraxial radius of curvature of the object-side surface of the first lens.

[0051] By satisfying the range of conditional expression (12), it is possible to take in a wide range of light beams while suppressing the occurrence of various aberrations, and also to make favorable correction for curvature of field and distortion.

[0052] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (13). (13)-0.35 <R2r / R3f<-0.07 Here, R2r is the paraxial radius of curvature of the image-side surface of the second lens, and R3f is the paraxial radius of curvature of the object-side surface of the third lens.

[0053] By satisfying the range of conditional expression (13), it becomes possible to satisfactorily correct curvature of field and distortion.

[0054] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (14). (14)2.30 <R3f / R3r<8.50 Here, R3f is the paraxial radius of curvature on the object side of the third lens, and R3r is the paraxial radius of curvature on the image side of the third lens.

[0055] By satisfying the range of conditional expression (14), chromatic aberration and distortion can be corrected satisfactorily.

[0056] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (15). (15)-2.30 <R5r / R6f<-0.64 Here, R5r is the paraxial radius of curvature on the image side of the fifth lens, and R6f is the paraxial radius of curvature on the object side of the sixth lens.

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

[0058] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (16). (16)-0.25 <R6f / R6r<-0.05 Here, R6f is the paraxial radius of curvature on the object side of the sixth lens, and R6r is the paraxial radius of curvature on the image side of the sixth lens.

[0059] By satisfying the range of conditional expression (16), chromatic aberration, spherical aberration, coma, and curvature of field can be corrected satisfactorily.

[0060] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (17). (17)0.20 <R1r / D12<0.70 Here, R1r is the paraxial radius of curvature of the image-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.

[0061] By satisfying the range of conditional expression (17), a low height can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be favorably corrected.

[0062] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (18). (18)1.55 <R2r / D23<4.90 Here, R2r is the paraxial radius of curvature of the image-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.

[0063] By satisfying the range of conditional expression (18), chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be corrected satisfactorily.

[0064] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (19). (19)-22.80 <R6r / bf<-6.40 Here, R6r is the paraxial radius of curvature of the image side surface of the sixth lens, and bf is the back focus.

[0065] By satisfying the range of conditional expression (19), an appropriate back focus can be ensured, and chromatic aberration, spherical aberration, coma, 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)-7.10 <R6r / f6<-1.80 Here, R6r is the paraxial radius of curvature of the image-side surface of the sixth lens, and f6 is the focal length of the sixth lens.

[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)-19.0 <R3f / f<-4.0 Here, R3f is the paraxial radius of curvature of the object side surface of the third lens, and f is the focal length of the entire imaging lens system.

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

[0070] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (22). (22)-4.80 <R3f / f3<-1.00 Here, R3f is the paraxial radius of curvature of the object side surface of the third lens, and f3 is the focal length of the third lens.

[0071] By satisfying the range of conditional expression (22), chromatic aberration 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)0.55 <R5r / f5<1.80 Here, R5r is the paraxial radius of curvature of the image-side surface of the fifth lens, and f5 is the focal length of the fifth lens.

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

[0074] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (24). (24)0.35 <D23 / bf<1.45 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 bf is the back focus.

[0075] By satisfying the range of conditional expression (24), chromatic aberration, spherical aberration, coma, astigmatism, 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 <R2r / f2<0.40 Here, R2r is the paraxial radius of curvature of the image-side surface of the second lens, and f2 is the focal length of the second lens.

[0077] By satisfying the range of conditional expression (25), chromatic aberration, spherical aberration, coma, astigmatism, 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)-3.70 <f1 / f<-1.35 Here, f1 is the focal length of the first lens, and f is the focal length of the entire imaging lens system.

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

[0080] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (27). (27)3.10 <f2 / f<12.50 Here, f2 is the focal length of the second lens, and f is the focal length of the entire imaging lens system.

[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)1.80 <f3 / f<6.30 Here, f3 is the focal length of the third lens, and f is the focal length of the entire imaging lens system.

[0083] By satisfying the range of conditional expression (28), chromatic aberration and astigmatism can be corrected satisfactorily.

[0084] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (29). (29)0.90 <f6 / f<3.00 Here, f6 is the focal length of the sixth lens, and f is the focal length of the entire imaging lens system.

[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)-700 <f45 / f<-12 Here, f45 is the combined focal length of the fourth and fifth lenses, and f is the focal length of the entire imaging lens system.

[0087] By satisfying the range of conditional expression (30), coma, astigmatism, and distortion can be corrected satisfactorily.

[0088] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (31). (31)-350 <f45 / f6<-7 However, f45 is the combined focal length of the fourth and fifth lenses, and f6 is the focal length of the sixth lens.

[0089] By satisfying the range of conditional expression (31), it becomes possible to satisfactorily correct curvature of field and distortion.

[0090] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (32). (32) 60°<ω<120° Here, ω is the half angle of view.

[0091] By satisfying the range of conditional expression (32), it is possible to make the imaging lens smaller and to achieve a wider angle.

[0092] It is desirable for the imaging lens having the above configuration to satisfy the following conditional expression (33). (33)13<νd2<28 Here, νd2 is the Abbe number for the d-line of the second lens.

[0093] By satisfying the range of condition (33), chromatic aberration can be corrected satisfactorily.

[0094] According to the present invention, it is possible to obtain an imaging lens that has a wide angle, yet is small in size, has a small F-number, and has high resolution with various aberrations well corrected in the wavelength region from visible light to near infrared light. Furthermore, since the imaging lens according to the present invention well 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]

[0095] [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

[0096] 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.

[0097] 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 positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having negative refractive power, and a sixth lens L6 having positive refractive power.

[0098] 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.

[0099] The first lens L1 has negative refractive power and is a meniscus shape with a convex surface on the object side in the paraxial direction. 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, spherical aberration, coma aberration, astigmatism, and curvature of field are well corrected.

[0100] The second lens L2 has positive refractive power and is a meniscus shape with a concave surface on the image side paraxially, which effectively corrects chromatic aberration, spherical aberration, coma, astigmatism, and field curvature while suppressing the occurrence of various aberrations.

[0101] The third lens L3 has positive refractive power and is a meniscus shape with a concave surface on the object side paraxially, thereby providing excellent correction for chromatic aberration and astigmatism.

[0102] 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 effectively correcting chromatic aberration, spherical aberration, coma, and astigmatism.

[0103] The fifth lens L5 has negative refractive power and is a meniscus shape with a convex surface on the image side paraxially, thereby providing excellent correction for chromatic aberration, spherical aberration, coma aberration, astigmatism, curvature of field, and distortion.

[0104] The sixth lens L6 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 effectively correcting chromatic aberration, spherical aberration, coma, and curvature of field.

[0105] In the imaging lens according to this embodiment, the aperture stop ST is disposed between the second lens L2 and the third lens L3, 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 second lens L2 and the third lens L3, and may be disposed appropriately according to the specifications of the imaging element.

[0106] In the imaging lens according to this embodiment, it is preferable that all of the first lens L1 to the sixth lens L6 are 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.

[0107] Furthermore, when a camera or other device equipped with an imaging lens is used in a harsh environment, it is desirable to form the first lens L1, which is positioned closest to the object, from a material that has high water resistance, heat resistance, weather resistance, etc., such as a glass material.

[0108] 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.

[0109] 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.

[0110] The imaging lens of this embodiment exerts favorable effects by satisfying the following conditional expressions (1) to (33). (1)1.10 <D12 / f<3.55 (2) 0.50 <T1 / f<1.95 (3) 0.20 <D23 / f<0.85 (4) 1.00 <T6 / bf<4.30 (5) 1.20 <T1 / T2<4.20 (6) 0.30 <R1r / T1<1.60 (7) 0.35 <R6f / T6<1.40 (8)2.35 <D12 / T2<8.55 (9) 0.35 <T2 / D23<1.25 (10)0.25 <T4 / T6<0.80 (11)2.10 <T4 / D45<10.80 (12)0.07 <R1r / R1f<0.30 (13)-0.35 <R2r / R3f<-0.07 (14)2.30 <R3f / R3r<8.50 (15)-2.30 <R5r / R6f<-0.64 (16)-0.25 <R6f / R6r<-0.05 (17)0.20 <R1r / D12<0.70 (18)1.55 <R2r / D23<4.90 (19)-22.80 <R6r / bf<-6.40 (20)-7.10 <R6r / f6<-1.80 (21)-19.0 <R3f / f<-4.0 (22)-4.80 <R3f / f3<-1.00 (23)0.55 <R5r / f5<1.80 (24)0.35 <D23 / bf<1.45 (25)0.10 <R2r / f2<0.40 (26)-3.70 <f1 / f<-1.35 (27)3.10 <f2 / f<12.50 (28)1.80 <f3 / f<6.30 (29)0.90 <f6 / f<3.00 (30)-700 <f45 / f<-12 (31)-350 <f45 / f6<-7 (32) 60°<ω<120° (33)13<νd2<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 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 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 T1: Thickness of the first lens L1 on the optical axis X T2: Thickness of the second lens L2 on the optical axis X T4: Thickness of the fourth lens L4 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 f5: focal length of the fifth lens L5 f6: focal length of the sixth lens L6 f45: The composite focal length of the fourth lens L4 and the fifth lens L5 bf: back focus ω: Half angle of view νd2: Abbe number for the d line of the second lens L2 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.

[0111] Moreover, the imaging lens of this embodiment exerts more preferable effects by satisfying the following conditional expressions (1a) to (33a). (1a) 1.55 <D12 / f<2.95 (2a) 0.75 <T1 / f<1.60 (3a) 0.30 <D23 / f<0.70 (4a) 1.50 <T6 / bf<3.55 (5a) 1.80 <T1 / T2<3.60 (6a) 0.47 <R1r / T1<1.32 (7a) 0.55 <R6f / T6<1.17 (8a)3.50 <D12 / T2<7.10 (9a) 0.55 <T2 / D23<1.10 (10a) 0.40 <T4 / T6<0.72 (11a)3.10 <T4 / D45<9.70 (12a) 0.10 <R1r / R1f<0.23 (13a)-0.28 <R2r / R3f<-0.10 (14a)3.50 <R3f / R3r<7.60 (15a)-1.90 <R5r / R6f<-0.95 (16a)-0.20 <R6f / R6r<-0.09 (17a) 0.30 <R1r / D12<0.58 (18a)2.35 <R2r / D23<4.40 (19a)-18.90 <R6r / bf<-9.60 (20a)-5.90 <R6r / f6<-2.70 (21a)-15.7 <R3f / f<-6.0 (22a)-4.00 <R3f / f3<-1.55 (23a) 0.80 <R5r / f5<1.60 (24a) 0.54 <D23 / bf<1.20 (25a) 0.15 <R2r / f2<0.33 (26a)-3.00 <f1 / f<-1.66 (27a)4.75 <f2 / f<10.35 (28a)2.75 <f3 / f<5.23 (29a)1.36 <f6 / f<2.50 (30a)-580 <f45 / f<-19 (31a)-288 <f45 / f6<-10 (32a) 70°<ω<105° (33a)16<νd2<23 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 (33a), the lower limit value and the upper limit value of the corresponding conditional expression (1) to (33) may be applied as the respective lower limit value and upper limit value.

[0112] 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.

[0113]

number

[0114] 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 X from the object-side surface of the optical element located closest to the object 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.

[0115] 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.

[0116] Example 1 Basic lens data [Table 1]

[0117] [Table 2]

[0118] 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 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 (the same applies to FIG. 4 and FIG. 6). As shown in FIG. 2, the imaging lens of Example 1 can correct each aberration well.

[0119] Example 2 Basic lens data [Table 3]

[0120] [Table 4]

[0121] As shown in FIG. 4, the imaging lens according to the second embodiment can also satisfactorily correct each aberration.

[0122] Example 3 Basic lens data [Table 5]

[0123] [Table 6]

[0124] As shown in FIG. 6, the imaging lens according to the third embodiment can also satisfactorily correct each aberration.

[0125] Values ​​(values ​​corresponding to the conditional expressions) (1) to (33) according to the first to third embodiments are shown below.

[0126] [Table 7] [Industrial Applicability]

[0127] 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]

[0128] 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 positive refractive power; a third lens having a positive refractive power; a fourth lens having a positive refractive power; a fifth lens having a negative refractive power; and a sixth lens having a positive refractive power, the second lens has a paraxial concave surface on the image side, the fifth lens has a paraxial convex surface on the image side, An imaging lens characterized by satisfying the following conditional expression (1): (1) 1.10<D12 / f<3.55 however, 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 f: focal length of the entire imaging lens system

2. 2. The imaging lens according to claim 1, wherein the following conditional expression (2) is satisfied: (2) 0.50<T1 / f<1.95 however, T1: thickness of the first lens on the optical axis f: focal length of the entire imaging lens system

3. 2. The imaging lens according to claim 1, wherein the following conditional expression (3) is satisfied: (3) 0.20<D23 / f<0.85 however, D23: The distance on the optical axis from the image side surface of the second lens to the object side surface of the third lens f: focal length of the entire imaging lens system

4. 2. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied: (4) 1.00<T6 / bf<4.30 however, T6: Thickness of the sixth lens on the optical axis bf: back focus

5. 2. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied: (5) 1.20<T1 / T2<4.20 however, T1: thickness of the first lens on the optical axis T2: Thickness of the second lens on the optical axis

6. 2. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied: (6) 0.30<R1r / T1<1.60 however, R1r: paraxial radius of curvature of the image side surface of the first lens T1: thickness of the first lens on the optical axis

7. 2. The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied: (7) 0.35<R6f / T6<1.40 however, R6f: paraxial radius of curvature of the object side surface of the sixth lens T6: Thickness of the sixth lens on the optical axis

Images