JP2025040465A - Imaging lens - Google Patents

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

The present invention relates to an imaging lens that forms an image of a subject on a solid-state imaging element such as a CCD sensor or a CMOS sensor.

An increasing number of cars 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 drivers.

The imaging lenses installed in such vehicle-mounted cameras are required to have a wide angle of view and high resolution performance. Furthermore, vehicle-mounted cameras are becoming smaller in size in order to install multiple vehicle-mounted cameras on a single vehicle, and there is a demand for imaging lenses to become even smaller as well.

As an example of an imaging lens that has a wide angle of view and high resolution, the imaging lens described in Patent Document 1 below is known.

Patent document 1 discloses an imaging lens that includes, 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 image side and having positive refractive power, a fifth lens having refractive power, and a sixth lens having refractive power.

Chinese Patent Publication No. 112444938

The lens described in Patent Document 1 has a maximum angle of view of more than 140°, but the total optical length exceeds 25 mm, making it difficult to meet the compact specifications required in recent years.

The present invention was made in consideration of the above-mentioned problems, and aims to provide an imaging lens that has a wide angle, good optical characteristics, and can also meet the specifications for miniaturization that have been required in recent years.

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, 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.

The first lens has negative refractive power, which allows for a wider angle of view and effectively corrects chromatic aberration, coma, astigmatism, and field curvature.

The second lens has negative refractive power and is convex on the object side at the paraxial position, providing excellent correction for chromatic aberration, spherical aberration, coma, astigmatism, and field curvature.

The third lens has a positive refractive power, which effectively corrects chromatic aberration, spherical aberration, coma, astigmatism, and field curvature.

The fourth lens has positive refractive power, which allows for a low profile and provides excellent correction for chromatic aberration, spherical aberration, astigmatism, and field curvature.

The fifth lens has positive refractive power, which allows for a low profile and effectively corrects chromatic aberration, spherical aberration, coma, and field curvature.

The sixth lens has negative refractive power and is concave on the object side at the paraxial line, ensuring an appropriate back focus and providing excellent correction for chromatic aberration, spherical aberration, coma, and field curvature.

In an 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 when paraxially aligned.

By making the first lens a meniscus shape with a convex surface on the object side at the paraxial position, it becomes possible to capture a wide range of light beams while suppressing the occurrence of various aberrations.

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

By making the second lens a meniscus shape at the paraxial position, it is possible to provide good correction of chromatic aberration, spherical aberration, coma aberration, astigmatism, and field curvature.

In an 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 paraxially.

By making the third lens a meniscus shape with a concave surface on the image side at the paraxial position, it is possible to provide good correction of spherical aberration, coma, astigmatism, field curvature, and distortion.

In an imaging lens having the above configuration, it is desirable for the fourth lens to have a biconvex shape on the paraxial plane.

By making the fourth lens paraxially biconvex, the positive refractive power is strengthened, making the lens lower in height, and good correction of chromatic aberration, spherical aberration, astigmatism, and curvature of field is possible.

In an imaging lens having the above configuration, it is preferable that the fifth lens has a biconvex shape on the paraxial plane.

By making the fifth lens paraxially biconvex, the positive refractive power is strengthened, making the lens lower in height, and good correction of chromatic aberration, spherical aberration, coma, and curvature of field is possible.

In an imaging lens with the above configuration, it is desirable for the sixth lens to have a convex surface on the image side paraxially.

By forming the image-side surface of the sixth lens as a convex surface paraxially, it becomes possible to provide good correction of chromatic aberration, spherical aberration, coma, and field curvature.

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.

By satisfying the range of conditional expression (1), a low profile can be achieved and good correction of chromatic aberration, spherical aberration, coma, astigmatism, field curvature, and distortion can be achieved.

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.

By satisfying the range of conditional expression (2), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, astigmatism, field curvature, and distortion.

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.

By satisfying the range of conditional expression (3), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (4), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

By satisfying the range of conditional expression (5), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (6), a low profile can be achieved and good correction of chromatic aberration, coma, astigmatism, field curvature, and distortion can be achieved.

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.

By satisfying the range of conditional expression (7), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (8), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, astigmatism, field curvature, and distortion.

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.

By satisfying the range of conditional expression (9), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (10), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

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

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.

By satisfying the range of conditional expression (12), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

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

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.

By satisfying the range of conditional expression (14), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (15), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, astigmatism, field curvature, and distortion.

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.

Satisfying the range of conditional expression (16) makes it possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (17), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (18), it is possible to achieve a low profile and good correction of chromatic aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (19), a wider angle can be achieved and chromatic aberration, coma, astigmatism, and curvature of field can be effectively corrected.

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.

By satisfying the range of conditional expression (20), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

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

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.

By satisfying the range of conditional expression (22), it becomes possible to satisfactorily correct chromatic aberration, spherical aberration, coma, astigmatism, field curvature, and distortion.

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.

By satisfying the range of conditional expression (23), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (24), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

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

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.

By satisfying the range of conditional expression (26), a wider angle can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field can be effectively corrected.

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.

By satisfying the range of conditional expression (27), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (28), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, astigmatism, and curvature of field.

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.

By satisfying the range of conditional expression (29), it is possible to achieve a low profile and good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

By satisfying the range of conditional expression (30), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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.

By satisfying the range of conditional expression (31), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, and curvature of field.

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 lens and the third lens, and f is the focal length of the entire imaging lens system.

By satisfying the range of conditional expression (32), it becomes possible to achieve good correction of chromatic aberration, spherical aberration, coma, astigmatism, field curvature, and distortion.

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 composite focal length of the second and third lenses, and f1 is the focal length of the first lens.

By satisfying the range of conditional expression (33), a wider angle can be achieved and chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be effectively corrected.

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.

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

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.

By satisfying the range of conditional expression (35), chromatic aberration can be effectively corrected.

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.

By satisfying the range of conditional expression (36), chromatic aberration can be effectively corrected.

The present invention makes it possible to obtain an imaging lens that has a wide angle, high resolution, and satisfies the demand for compactness. In addition, the imaging lens according to the present invention effectively corrects various aberrations, so the number of lenses can be reduced, and by reducing the amount of lens material used, an environmentally friendly imaging lens can be provided.

1 is a cross-sectional view showing a schematic configuration of an imaging lens according to a first embodiment of the present invention. 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. FIG. 11 is a cross-sectional view showing a schematic configuration of an imaging lens according to a second embodiment of the present invention. 5A to 5C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 2 of the present invention. FIG. 11 is a cross-sectional view showing a schematic configuration of an imaging lens according to a third embodiment of the present invention. 11A to 11C are aberration diagrams showing spherical aberration, astigmatism, and distortion of the imaging lens according to Example 3 of the present invention.

An embodiment of the present invention will now be described in detail 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 of the examples, the imaging lens according to this embodiment will now be described with reference to the cross-sectional view of Example 1.

As shown in FIG. 1, the imaging lens according to 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.

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 between the sixth lens L6 and the imaging surface IMG. Note that the filter FL and the cover glass CG can be omitted. Also, 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 one of the lenses.

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 a wide range of light rays to be captured while suppressing the occurrence of various aberrations, thereby achieving a wide-angle imaging lens. In addition, chromatic aberration, coma aberration, astigmatism, and field curvature are well corrected.

The second lens L2 has negative refractive power and is a meniscus shape with a convex surface on the object side at the paraxial position. This provides excellent correction for chromatic aberration, spherical aberration, coma, astigmatism, and field curvature.

The third lens L3 has positive refractive power and is a meniscus shape with a concave surface on the image side at the paraxial position. This provides excellent correction for chromatic aberration, spherical aberration, coma, astigmatism, and field curvature.

The fourth lens L4 has positive refractive power and is biconvex with convex surfaces on both the object side and the image side at the paraxial position. This allows for good correction of chromatic aberration, spherical aberration, astigmatism, and curvature of field while reducing the height of the imaging lens.

The fifth lens L5 has positive refractive power and is biconvex with convex surfaces on both the object side and the image side at the paraxial position. This allows for good correction of chromatic aberration, spherical aberration, coma, and curvature of field while reducing the height of the imaging lens.

The sixth lens L6 has negative refractive power and is a meniscus shape with a concave surface on the object side at the paraxial position. This ensures an appropriate back focus and provides good correction for chromatic aberration, spherical aberration, coma, and field curvature.

In the imaging lens according to this 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. Note that 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 as appropriate according to the specifications of the imaging element.

The imaging lens according to this embodiment is configured such that a second lens L2 with a weak negative refractive power and a third lens L3 with a weak positive refractive power are arranged behind a first lens L1 with a strong negative refractive power. This allows a light beam from a wide range to be taken in by the first lens L1, and then refracted to a state close to parallel light by the second lens L2 and the third lens L3, while also correcting the various aberrations that occur in the first lens L1, thereby realizing an optical system with fewer aberrations.

In the imaging lens according to this embodiment, the first lens L1 is preferably formed from a glass material. For example, in an imaging lens mounted on an in-vehicle camera, the first lens L1, which is positioned closest to the object, is in direct contact with the outside air, so it is desirable for the first lens L1 to be 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 harsh environments.

In the imaging lens according to this embodiment, it is preferable that the second lens L2 to the sixth lens L6 are each formed from a plastic material. By using a plastic material, it is possible to form an aspheric shape with high precision, and to achieve weight reduction and cost reduction.

It is desirable for all lens surfaces of the imaging lens according to this embodiment to be aspheric, but depending on the required performance, spherical surfaces, which are easier to manufacture, may also be used. When spherical surfaces are used, manufacturing costs can be reduced.

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 aspheric surfaces, which are effective in correcting aberrations. In this embodiment, appropriate aspheric 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, the number of steps can be reduced compared to when a cemented lens is used, thereby suppressing manufacturing costs.

In addition, 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.

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 fourth lens L4 R5r: paraxial radius of curvature of the image side surface of the fourth lens L4 paraxial radius of curvature R5r of the object-side surface of the fifth lens L5: paraxial radius of curvature R6f of the image-side surface of the sixth lens L6: paraxial radius of curvature R6r of the image-side surface of the sixth lens L6: paraxial radius of curvature D12: 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: distance D23 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: distance D34 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: 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: 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 on the optical axis X of the first lens L1; T2: Thickness on the optical axis X of the second lens L2; T3: Thickness on the optical axis X of the third lens L3; T4: Thickness on the optical axis X of the fourth lens L4; T5: Thickness on the optical axis X of the fifth lens L5; T6: Thickness on the optical axis X of the sixth lens L6 Thickness f on the optical axis X: focal length f1 of the entire imaging lens system: focal length f2 of the first lens L1: focal length f3 of the second lens L2: focal length f4 of the third lens L3: focal length f5 of the fourth lens L4: focal length f6 of the fifth lens L5: focal length f23 of the sixth lens L6: composite focal length bf of the second lens L2 and the third lens L3: 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, and by satisfying each conditional expression individually, it is possible to obtain an effect corresponding to each conditional expression.

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 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 expressions (1) to (36) may be applied as the respective lower limit value and upper limit value.

In this embodiment, the aspheric shape used 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.

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 to the imaging plane IMG. Note that 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., placed between the imaging lens and the imaging plane IMG into air.

In addition, 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. Aspheric surfaces are indicated by adding an asterisk (*) after the surface number i.

Example 1
Basic lens data

Figure 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 for 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 (dashed line) at the tangential image plane T. As shown in Figure 2, the imaging lens of Example 1 can correct each aberration well.

In addition, as shown in FIG. 2, the imaging lens according to the first embodiment can effectively 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.

Example 2
Basic lens data

Figure 4 is an aberration diagram showing the spherical aberration (mm), astigmatism (mm), and distortion (%) for 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 (dashed line) at the tangential image plane T (the same applies to Figure 6). As shown in Figure 4, the imaging lens of Example 2 can also correct each aberration well.

Example 3
Basic lens data

As shown in FIG. 6, the imaging lens according to the third embodiment can also effectively correct each aberration.

The following are values (conditional formula corresponding values) corresponding to conditional formulas (1) to (36) in Examples 1 to 3.

When the imaging lens according to the present invention is applied to products such as vehicle-mounted cameras, the camera can be made smaller while achieving a wider angle and higher performance.

X Optical axis ST Aperture diaphragm L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens L6 Sixth lens FL Filter CG Cover glass IMG Imaging surface

Claims (7)

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: Distance on the optical axis from the image side surface of the third lens to the object side surface of the fourth lens D45: 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 on the optical axis of the first lens T2: Thickness on the optical axis of the second lens 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 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 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: distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens 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 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 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