JP7846589B2 - Imaging lens and imaging device - Google Patents

Description

This disclosure relates to imaging lenses and imaging devices.

Imaging lenses used in cameras, including surveillance cameras and in-vehicle cameras, are required to be highly resistant to environmental changes and to have good image formation performance across the entire image area. In addition, due to the often limited mounting space for imaging lenses in cameras, they must also be small and lightweight.

As a single-focus imaging lens capable of meeting the above requirements, the technologies described in Patent Documents 1 and 2 have been proposed. For example, Patent Document 1 discloses a lens unit that can be used effectively even in harsh environments with a wide required temperature range and has high chromatic aberration correction accuracy. For example, Patent Document 2 discloses a lens unit that can be used over a wide temperature and wavelength range and is highly compact.

Japanese Patent Publication No. 2008-008960 Japanese Patent Publication No. 2013-047753

For example, in-vehicle cameras are now used not only for conventional visual applications but also for sensing applications to detect objects, requiring even higher performance. With the increasing pixel count of solid-state image sensors such as CCDs (Charge Coupled Devices) and CMOS (Complementary Metal-Oxide Semiconductor Devices), the imaging lenses used in these cameras are also required to have correspondingly superior optical performance.

In light of the above-mentioned problems, the purpose of this disclosure is to provide an imaging lens and imaging device that are compact, lightweight, and inexpensive due to their six-element configuration, while possessing high optical performance through the appropriate setting of the lens shape.

A National lens according to one embodiment of this disclosure is
(1)
It is an imaging lens,
The device comprises, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, a third lens having positive refractive power, an aperture diaphragm, a fourth lens having positive refractive power, a fifth lens having negative refractive power, and a sixth lens having positive refractive power.
If D4 is the on-axial distance from the image side of the second lens to the object side of the third lens, f is the focal length of the imaging lens with respect to the d line, and D3 is the on-axial thickness of the second lens, then the conditional equation is:
D4/f<0.08 (1)
0.12<D3/f<0.23 (2)
It satisfies the condition.

(2)
The imaging lens described in (1) above,
If the focal length of the first lens with respect to the d line is f1, then the conditional equation is,
-1.5<f1/f<-1.2 (3)
It may satisfy this condition.

(3)
The imaging lens described in (1) or (2) above,
If the refractive index of the second lens is N2,
N2/f<0.33 (4)
It may satisfy this condition.

(4)
An imaging lens as described in any one of (1) to (3) above,
Each of the two surfaces of the second lens may be a concave surface.

(5)
An imaging lens as described in any one of (1) to (4) above,
If R3 is the radius of curvature of the object side of the second lens and R4 is the radius of curvature of the image side of the second lens, then the conditional equation is:
-1<(R3+R4)/(R3-R4)<-0.82 (5)
It may satisfy this condition.

(6)
An imaging lens as described in any one of (1) to (5) above,
If R2 is the radius of curvature of the image surface of the first lens, then the conditional equation is:
0.77<R2/f<0.9 (6)
It may satisfy this condition.

(7)
An imaging lens as described in any one of (1) to (6) above,
If the Abbe number of the fifth lens is ν5, then the conditional equation is:
4.8<ν5/f<5.5 (7)
It may satisfy this condition.

(8)
An imaging lens as described in any one of (1) to (7) above,
If the focal length of the second lens with respect to the d line is f2, then the conditional equation is,
-3.8<f2/f<-2 (8)
It may satisfy this condition.

(9)
An imaging lens as described in any one of (1) to (8) above,
If the focal length of the third lens with respect to the d line is f3, then the conditional equation is,
1.6<f3/f<3.1 (9)
It may satisfy this condition.

(10)
An imaging lens as described in any one of (1) to (9) above,
If Da is the total length of the imaging lens along its axis, then the conditional equation is:
Da/f<5.2 (10)
It may satisfy this condition.

(11)
An imaging lens as described in any one of (1) to (10) above,
If the focal length of the fourth lens with respect to the d line is f4, then the conditional equation is,
1.2<f4/f<1.8 (11)
It may satisfy this condition.

(12)
An imaging lens as described in any one of (1) to (11) above,
If fg is the combined focal length of the fourth lens, the fifth lens, and the sixth lens with respect to the d line, then the conditional equation is:
1.4<fg/f<1.8 (12)
It may satisfy this condition.

(13)
An imaging lens as described in any one of (1) to (12) above,
If the focal length of the fifth lens with respect to the d line is f5, then the conditional equation is,
-2.0<f5/f<-1.1 (13)
It may satisfy this condition.

(14)
An imaging lens as described in any one of (1) to (13) above,
If the focal length of the sixth lens with respect to the d line is f6, then the conditional equation is,
1.45<f6/f<1.8 (14)
It may satisfy this condition.

(15)
An imaging lens as described in any one of (1) to (14) above,
Each of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens may be made of glass material.

(16)
An imaging lens as described in any one of (1) to (15) above,
Each of the six surfaces of the sixth lens may be aspherical.

(17)
An imaging lens as described in any one of (1) to (16) above,
The fourth lens and the fifth lens may be formed as a cemented lens.

(18)
An imaging lens as described in any one of (1) to (17) above,
The object side surface of the first lens may be concave.

(19)
An imaging lens as described in any one of (1) to (18) above,
If W is the half-angle of view of the light ray incident at the highest image height position on the image plane, then the conditional equation is:
48 < W (15)
It may satisfy this condition.

An imaging apparatus according to one embodiment of the present disclosure,
(20)
The imaging lens comprises, in order from the object side, a first lens with negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, an aperture diaphragm, a fourth lens with positive refractive power, a fifth lens with negative refractive power, and a sixth lens with positive refractive power.
An image sensor that converts an optical image formed through the aforementioned imaging lens into an electrical signal,
Equipped with,
If D4 is the on-axial distance from the image side of the second lens to the object side of the third lens, f is the focal length of the imaging lens with respect to the d line, and D3 is the on-axial thickness of the second lens, then the conditional equation is:
D4/f<0.08 (16)
0.12<D3/f<0.23 (17)
It satisfies the condition.

According to one embodiment of this disclosure, an imaging lens and imaging device can be provided that are compact, lightweight, and inexpensive due to their six-element configuration, while possessing high optical performance by appropriately setting the shape of the lenses.

This is a lens configuration diagram of the imaging lens according to Embodiment 1 of the present disclosure. Figure 1 is a graph showing the astigmatism of the imaging lens. Figure 1 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 2 of the present disclosure. Figure 3 is a graph showing the astigmatism of the imaging lens. Figure 3 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 3 of the present disclosure. Figure 5 is a graph showing the astigmatism of the imaging lens. Figure 5 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 4 of the present disclosure. Figure 7 is a graph showing the astigmatism of the imaging lens. Figure 7 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 5 of the present disclosure. Figure 9 is a graph showing the astigmatism of the imaging lens. Figure 9 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 6 of the present disclosure. Figure 11 is a graph showing the astigmatism of the imaging lens. Figure 11 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 7 of the present disclosure. Figure 13 is a graph showing the astigmatism of the imaging lens. Figure 13 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 8 of the present disclosure. Figure 15 is a graph showing the astigmatism of the imaging lens. Figure 15 is a graph showing the distortion aberration of the imaging lens. This is a lens configuration diagram of the imaging lens according to Embodiment 9 of the present disclosure. Figure 17 is a graph showing the astigmatism of the imaging lens. Figure 17 is a graph showing the distortion aberration of the imaging lens.

The following describes in detail an imaging lens 10 and imaging device 1 according to one embodiment of this disclosure, with reference to the attached drawings. More specifically, the configuration and function of the imaging lens 10 and imaging device 1 common to each embodiment described later will be explained. In each attached drawing showing the configuration of the imaging lens 10 and imaging device 1, the "object side" corresponds to the left side and the "image side" corresponds to the right side. The figures used in the following description are schematic, and the dimensional ratios shown in the drawings do not necessarily correspond to actual dimensions.

The lens configuration of the imaging lens 10 and imaging device 1 according to one embodiment will be mainly described with reference to Figure 1, which will be described later and shows the configuration of the imaging lens 10 and imaging device 1 of Embodiment 1.

The imaging device 1 comprises an imaging lens 10 and an image sensor 20 that converts the optical image formed through the imaging lens 10 into an electrical signal. The image sensor 20 includes, for example, a solid-state image sensor such as a CCD or CMOS. An image plane 21 is formed on the surface of the image sensor 20. The imaging device 1 images an object by having the imaging lens 10 form an image of the object onto the image plane 21 of the image sensor 20.

The imaging lens 10 has, arranged in order from the object side, a first lens 110, a second lens 120, a third lens 130, an aperture diaphragm 170, a fourth lens 140, a fifth lens 150, a sixth lens 160, a first flat plate 180a, and a second flat plate 180b. The fourth lens 140 and the fifth lens 150 are formed as a cemented lens. The imaging lens 10 is a six-element fixed-focus imaging lens. Each of the first lens 110, second lens 120, third lens 130, fourth lens 140, fifth lens 150, and sixth lens 160 is made of glass material.

The first lens 110 has a spherical shape. Each of its two surfaces is concave. The second lens 120 has a spherical shape. Each of its two surfaces is concave. The third lens 130 has a spherical shape. Each of its two surfaces is convex. The fourth lens 140 has a spherical shape. Each of its two surfaces is convex. The fifth lens 150 has a spherical shape. Each of its two surfaces is concave. Each of its two surfaces is aspherical. The first flat plate 180a includes optical components such as an IR (Infrared) cut filter. The second flat plate 180b includes optical components such as LID glass, which is placed relative to the image sensor 20. The LID glass is a cover glass used for the image sensor 20 as an image sensor.

The imaging lens 10 is substantially composed of a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160. In this disclosure, "substantially composed" means that the imaging lens 10 substantially consists of six lenses, the first to sixth lenses 110 to 160, but the imaging lens 10 may also have other optical elements, such as lenses that substantially do not have power, as well as other optical elements other than lenses, including an aperture and cover glass. For example, in addition to the first to sixth lenses 110 to 160, the imaging lens 10 includes an aperture diaphragm 170, and first and second flat plates 180a and 180b.

The imaging lens 10 comprises, in order from the object side, a first lens 110 with negative refractive power, a second lens 120 with negative refractive power, a third lens 130 with positive refractive power, an aperture diaphragm 170, a fourth lens 140 with positive refractive power, a fifth lens 150 with negative refractive power, and a sixth lens 160 with positive refractive power.

In a wide-angle imaging lens 10, a short focal length is necessary to obtain a wide field of view. However, due to the mechanical constraints of the imaging lens 10, the back focus must be longer than the focal length. Therefore, a lens with negative refractive power is placed in front of the imaging lens 10, causing the light incident on the imaging lens 10 from the object side to diverge once, and then being focused by a lens with positive refractive power behind it. This allows the principal point of the lens system to be positioned behind the imaging lens 10, thereby securing a back focus longer than the focal length.

More specifically, the first lens 110 and the second lens 120, which have negative refractive power, diverge the light, and the third lens 130, the fourth lens 140, and the sixth lens 160, which have positive refractive power, focus the light. By positioning the first lens 110 and the second lens 120, which are negative refractive lenses, closest to the object in the imaging lens 10, sufficient negative refractive power can be obtained to position the principal point behind the image. By positioning the third lens 130, which has positive refractive power, before the aperture diaphragm 170, good correction of chromatic aberration is possible. By positioning the fourth lens 140 and the sixth lens 160, which have positive refractive power, after the aperture diaphragm 170, the angle of incidence of light to the image plane 21 can be reduced, and aberrations can be corrected well.

The aperture diaphragm 170 is positioned between the third lens 130 and the fourth lens 140. If the aperture diaphragm 170 were positioned closer to the image than the fourth lens 140, the imaging lens 10 would become larger, which is undesirable. Furthermore, if the aperture diaphragm 170 were positioned closer to the object than the third lens 130, it would be difficult to widen the angle of the imaging lens 10, which is also undesirable. Therefore, by positioning the aperture diaphragm 170 between the third lens 130 and the fourth lens 140 as described above, the imaging lens 10 can achieve good correction of various aberrations and a compact lens system.

The functions of the imaging lens 10 and imaging device 1 according to one embodiment will be mainly described.

The imaging lens 10 satisfies the following conditions (1) and (2).
D4/f<0.08 (1)
0.12<D3/f<0.23 (2)
However, D4 is the on-axial distance from the image side of the second lens 120 to the object side of the third lens 130. That is, D4 is the distance from the image side of the second lens 120 to the object side of the third lens 130 on the optical axis Ax of the imaging lens 10 shown in Figure 1. f is the focal length of the imaging lens 10 with respect to the d line (wavelength λ = 587.56 nm). D3 is the on-axial thickness of the second lens 120. That is, D3 is the distance from the object side of the second lens 120 to the image side of the second lens 120 on the optical axis Ax of the imaging lens 10 shown in Figure 1.

Conditional equation (1) relates the axial distance between the second lens 120 and the third lens 130 to the focal length of the imaging lens 10. When the value of D4/f exceeds the upper limit of 0.08, the gap between the negative lens group (composed of the first lens 110 and the second lens 120) and the positive lens group (composed of the third lens 130 through the sixth lens 160) becomes too wide. This makes correcting axial chromatic aberration difficult. When conditional equation (1) is satisfied, correcting axial chromatic aberration becomes easier.

Conditional equation (2) relates the axial thickness of the second lens 120 to the focal length of the imaging lens 10. When the value of D3/f is less than or equal to the lower limit of 0.12, the refractive power of the concave second lens 120 decreases, resulting in field curvature. When the value of D3/f is greater than or equal to the upper limit of 0.23, the optical path length of the light passing through the second lens 120 increases, leading to significant axial chromatic aberration. When conditional equation (2) is satisfied, the occurrence of field curvature and axial chromatic aberration is suppressed.

The imaging lens 10 may further satisfy the following condition (3).
-1.5<f1/f<-1.2 (3)
However, f1 is the focal length of the first lens 110 with respect to the d line.

Conditional equation (3) relates the focal length of the first lens 110 to the focal length of the imaging lens 10. If the value of f1/f exceeds the upper limit of -1.2, the refractive power of the first lens 110 as a concave lens in the imaging lens 10 becomes too large, resulting in significant field curvature. When conditional equation (3) is satisfied, the occurrence of field curvature is suppressed. By keeping the value of f1/f above the lower limit of -1.5, the refractive power of the first lens 110 does not become too small, allowing for good correction of axial chromatic aberration.

The imaging lens 10 may further satisfy the following condition (4).
N2/f<0.33 (4)
However, N2 is the refractive index of the second lens 120.

Conditional equation (4) relates the refractive index of the second lens 120 to the focal length of the imaging lens 10. If the value of N2/f exceeds the upper limit of 0.33, the refractive power of the concave second lens 120 becomes too large, causing the image plane 21 to tilt towards the image. When conditional equation (4) is satisfied, the tilting of the image plane 21 towards the image is suppressed.

The imaging lens 10 has a concave surface on each of its two sides, allowing for the easy formation of a flat receiving portion that can contact the first lens 110 and spacers without requiring any additional processing of the second lens 120. This enables a configuration with low tolerance sensitivity. As shown in Figure 1, the flat receiving portion is formed on the second lens 120 in the region furthest from the optical axis Ax, where the first lens 110 and the second lens 120 are in contact with each other.

For example, if the lens surface is convex, it is necessary to additionally form a flat receiving portion in the region furthest from the optical axis on the outer circumference of the lens. If such a flat receiving portion does not exist in the convex lens, the receiving position of the convex lens relative to the concave lens will be unstable, causing the optical axis of the convex lens to shift. As a result, when incorporating the convex lens into the lens system, it may not fit within the assembly tolerances. Since it is not easy to additionally form a flat receiving portion on the outer circumference of a convex lens surface, it is desirable that the second lens 120 has a concave lens surface with a flat receiving portion formed as a result of normal machining.

The imaging lens 10 may further satisfy the following condition (5).
-1<(R3+R4)/(R3-R4)<-0.82 (5)
However, R3 is the radius of curvature of the object side of the second lens 120, and R4 is the radius of curvature of the image side of the second lens 120.

Conditional equation (5) relates the radii of curvature of each surface of the second lens 120. If the value of (R3 + R4) / (R3 - R4) is less than or equal to the lower limit of -1, the difference in the absolute values of the radii of curvature of the two concave surfaces of the second lens 120 becomes large, resulting in astigmatism. If the value of (R3 + R4) / (R3 - R4) is greater than or equal to the upper limit of -0.82, the difference in the absolute values of the radii of curvature of the two concave surfaces of the second lens 120 becomes small, making it difficult to correct axial chromatic aberration. When conditional equation (5) is satisfied, correction of axial chromatic aberration becomes easier, and the occurrence of astigmatism is suppressed.

The imaging lens 10 may further satisfy the following condition (6).
0.77<R2/f<0.9 (6)
However, R2 is the radius of curvature of the image surface of the first lens 110.

Conditional equation (6) relates the radius of curvature of the image surface of the first lens 110 to the focal length of the imaging lens 10. If the R2/f value exceeds the upper limit of 0.9, focusing becomes difficult at the first lens 110, which is the concave lens located closest to the object, resulting in spherical aberration. If the R2/f value falls below the lower limit of 0.77, the shape of the first lens 110 becomes difficult to manufacture. In addition, the refractive power of the concave lens 110 becomes too large, causing the image plane 21 to tilt towards the image side. By satisfying conditional equation (6), the occurrence of spherical aberration and the tilting of the image plane 21 towards the image side are suppressed.

The imaging lens 10 may further satisfy the following condition (7).
4.8<ν5/f<5.5 (7)
However, ν5 is the Abbe number of the fifth lens 150.

Conditional equation (7) relates the Abbe number of the fifth lens 150 to the focal length of the imaging lens 10. When the value of ν5/f is above the upper limit of 5.5, the occurrence of axial chromatic aberration in the concave fifth lens 150 is reduced, making correction of the entire optical system difficult. Conversely, when the value of ν5/f is below the lower limit of 4.8, axial chromatic aberration becomes significant, resulting in overcorrection. When conditional equation (7) is satisfied, correction of axial chromatic aberration in the entire optical system becomes possible.

The imaging lens 10 may further satisfy the following condition (8).
-3.8<f2/f<-2 (8)
However, f2 is the focal length of the second lens 120 with respect to the d line.

Conditional equation (8) relates the focal length of the second lens 120 to the focal length of the imaging lens 10. When the f/2/f value is less than the upper limit of -2, the refractive power of the second lens 120 as a concave lens is appropriately suppressed, resulting in good correction of astigmatism. When the f/2/f value is below the lower limit of -3.8, the axial chromatic aberration generated in the second lens 120 weakens, making it difficult to correct axial chromatic aberration across the entire imaging lens 10. When conditional equation (8) is satisfied, correction of axial chromatic aberration across the entire imaging lens 10 becomes easier.

The imaging lens 10 may further satisfy the following condition (9).
1.6<f3/f<3.1 (9)
However, f3 is the focal length of the third lens 130 with respect to the d line.

Conditional equation (9) relates the focal length of the third lens 130 to the focal length of the imaging lens 10. If the f3/f value is 3.1 or higher (the upper limit), the refractive power of the third lens 130, a convex lens located in front of the aperture 170, becomes too small, causing field curvature. If the f3/f value is 1.6 or lower (the lower limit), the refractive power of the third lens 130, a convex lens in the imaging lens 10, becomes too large, making it difficult to correct the axial chromatic aberration generated by this convex lens. When conditional equation (9) is satisfied, field curvature is suppressed, and the correction of axial chromatic aberration generated by this convex lens becomes easier.

The imaging lens 10 may further satisfy the following condition (10).
Da/f<5.2 (10)
However, Da is the total length of the imaging lens 10 along the optical axis Ax. That is, Da is the distance from the side surface of the object on the first lens 110 to the image plane 21 along the optical axis Ax of the imaging lens 10 shown in Figure 1.

Conditional equation (10) relates the total length of the imaging lens 10 to its focal length. When the Da/f value is smaller than the upper limit of 5.2, the optical path ratio between the optical axis Ax and positions away from the optical axis Ax increases in each air lens, thus suppressing astigmatism. In addition, this leads to miniaturization of the imaging lens 10 in both the overall length and radial directions, improving the design flexibility of the camera housing.

The imaging lens 10 may further satisfy the following condition (11).
1.2<f4/f<1.8 (11)
However, f4 is the focal length of the fourth lens 140 with respect to the d line.

Conditional equation (11) relates the focal length of the fourth lens 140 to the focal length of the imaging lens 10. When the value of f4/f exceeds the upper limit of 1.8, the refractive power of the convex fourth lens 140 decreases, causing the image plane 21 to tilt towards the image side, making image field curvature correction difficult. When the value of f4/f falls below the lower limit of 1.2, the refractive power of the positive fourth lens 140 becomes too large, making axial chromatic aberration correction by the negative fifth lens 150 difficult. When conditional equation (11) is satisfied, image field curvature correction becomes easier, and axial chromatic aberration correction by the negative fifth lens 150 also becomes easier.

The imaging lens 10 may further satisfy the following condition (12).
1.4<fg/f<1.8 (12)
However, fg is the combined focal length of the fourth lens 140, the fifth lens 150, and the sixth lens 160 with respect to the d line.

Conditional equation (12) relates the combined focal length of the fourth lens 140 to the sixth lens 160 to the focal length of the imaging lens 10. When the fg/f value exceeds the upper limit of 1.8, focusing becomes difficult by the fourth lens 140, fifth lens 150, and sixth lens 160, which are located on the image side of the aperture diaphragm 170, resulting in astigmatism. When the fg/f value is 1.4 or less, the lower limit of 1.4, focusing becomes easier, but the refractive power of the lens group located on the image side of the aperture diaphragm 170 is too great, causing the image plane 21 in the meridional direction to tilt towards the object. By satisfying conditional equation (12), the occurrence of astigmatism and the tilting of the image plane 21 in the meridional direction towards the object are suppressed.

The imaging lens 10 may further satisfy the following condition (13).
-2.0<f5/f<-1.1 (13)
However, f5 is the focal length of the fifth lens 150 with respect to the d line.

Conditional equation (13) relates the focal length of the fifth lens 150 to the focal length of the imaging lens 10. When the value of f5/f is greater than or equal to the upper limit of -1.1, the refractive power of the fifth lens 150 increases, and lateral chromatic aberration is significantly generated in the reverse direction by the fifth lens 150, which is a concave lens on the image side of the aperture diaphragm 170. When the value of f5/f is less than or equal to the lower limit of -2.0, the refractive power of the negative fifth lens 150, which cancels out the axial chromatic aberration generated by the positive fourth lens 140, decreases, making correction of axial chromatic aberration difficult. When conditional equation (13) is satisfied, the generation of lateral chromatic aberration in the reverse direction is suppressed, and correction of axial chromatic aberration becomes easier.

The imaging lens 10 may further satisfy the following condition (14).
1.45<f6/f<1.8 (14)
However, f6 is the focal length of the sixth lens 160 with respect to the d line.

Conditional equation (14) relates the focal length of the sixth lens 160 to the focal length of the imaging lens 10. When the value of f6/f exceeds the upper limit of 1.8, the refractive power of the sixth lens 160, the convex lens closest to the image plane 21, decreases, causing the image plane 21 to tilt towards the object, making image field curvature correction difficult. When conditional equation (14) is satisfied, image field curvature correction becomes easier. By keeping the value of f6/f greater than the lower limit of 1.45, the refractive power of the sixth lens 160 does not become excessively large, allowing for a lower tolerance sensitivity. This prevents the image plane 21 from tilting towards the image, making image field curvature correction easier.

The imaging lens 10 is designed so that the first lens 110, second lens 120, third lens 130, fourth lens 140, fifth lens 150, and sixth lens 160 are each made of glass material, thereby suppressing yellowing due to ultraviolet light and changes in optical properties due to temperature changes.

The imaging lens 10 has aspherical surfaces on both sides of the sixth lens 160. This means that the sixth lens 160 closest to the image plane 21 has an aspherical shape, allowing for easy adjustment of the angle of light incidence to the image sensor 20. As a result, correction of spherical aberration and astigmatism becomes easier.

The imaging lens 10 is formed by combining the fourth lens 140 and the fifth lens 150 as a cemented lens. This allows the fourth lens 140 and the fifth lens 150, which have high axial misalignment sensitivity, to be configured as a cemented lens, enabling the realization of an optical system with low tolerance sensitivity. In addition, the use of cemented lenses in the imaging lens 10 reduces the number of components, thereby reducing the workload for assembly into the imaging lens 10.

The imaging lens 10, with its concave object-side surface on the first lens 110, allows for easy formation of a retaining structure, such as a retainer, without requiring additional processing of the first lens 110. Furthermore, when light reflected from the image plane 21 of the imaging lens 10 is incident on the object-side surface of the first lens 110, the re-reflected light tends to diverge rather than converge. Therefore, it is possible to suppress the occurrence of ghosting caused by such re-reflected light re-imaging at the image plane 21.

The imaging lens 10 may further satisfy the following condition (15).
48 < W (15)
However, W is the half-angle of view of the light ray incident at the maximum image height position on the image plane 21.

Conditional equation (15) is an equation relating to the field of view of the entire imaging lens 10 system. If the value of W falls below the lower limit of 48, it becomes difficult to secure the imaging range that an imaging device 1, for example, used in an in-vehicle camera, should satisfy. When conditional equation (15) is satisfied, the imaging range that an imaging device 1, for example, used in an in-vehicle camera, should satisfy can be easily secured.

(Examples)
Next, the lens configuration of the embodiment relating to the imaging lens 10 of this disclosure will be mainly described. More specifically, Embodiments 1 to 9 with specific numerical values for the imaging lens 10 will be shown. Embodiments 1 to 9 have the characteristics of the embodiment described above with respect to the positive or negative refractive power of each lens, the surface shape, and the parameters shown in conditional equations (1) to (15).

In Examples 1 to 9, the focal length f of the imaging lens 10, the total length Da of the imaging lens 10 on the optical axis Ax, and the F-number and image height are as shown in Table 1. In the data for each example in Table 1, the values derived from the lens specifications, including the focal length f, are also values relative to the d line unless otherwise specified.

In Examples 1 to 9, the parameter values included in each of the conditional expressions (1) to (15) are as shown in Table 2 below.

In the basic lens data for each embodiment, the number i (where i is a natural number) in the lens specifications is the surface number assigned sequentially from the object side to all the lenses included in the imaging lens 10, the aperture diaphragm 170, and each surface of the first plate 180a and the second plate 180b. Ri is the radius of curvature of the i-th surface. Di is the distance between the i-th surface and the (i+1)-th surface on the optical axis Ax. Nd is the refractive index for the d-line. νd is the Abbe number for the d-line.

In all the specifications listed below, the units of length, such as the radius of curvature Ri and interplanar spacing Di, are millimeters (mm) unless otherwise specified, and their notation in each table is omitted. However, since the imaging lens 10 achieves equivalent optical performance in both proportional magnification and proportional reduction, this is not limited to these units.

The aspherical shape of the lens described in the following embodiment is expressed by the following equation (16), i.e., the aspherical equation, where k is the cone coefficient, A is the 4th-order aspherical coefficient, B is the 6th-order aspherical coefficient, C is the 8th-order aspherical coefficient, and D is the 10th-order aspherical coefficient, with the direction from the object side to the image side being positive, k being the cone coefficient, A being the 4th-order aspherical coefficient, B being the 6th-order aspherical coefficient, C being the 8th-order aspherical coefficient, and D being the 10th-order aspherical coefficient. Here, h represents the height of the ray, c is the reciprocal of the central radius of curvature, and Z is the depth from the tangent plane to the vertex of the surface.

(16)
The aspherical data in each of the following examples shows the aspherical coefficient and other factors that give the aspherical shape of the lens surface marked with * in the basic lens data.

(Example 1)
Figure 1 is a lens configuration diagram of the imaging lens 10 according to Embodiment 1 of the present disclosure. Figure 1 shows the lens configuration of the imaging lens 10 according to Embodiment 1 in an optical cross-section.

As shown in Figure 1, in the imaging lens 10 of Embodiment 1, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

In Figure 1, D1 corresponds to the axial thickness of the first lens 110 and is the distance along the optical axis Ax between surfaces S1 and S2. D2 is the axial distance between surfaces S2 and S3. D3 corresponds to the axial thickness of the second lens 120 and is the distance along the optical axis Ax between surfaces S3 and S4. D4 is the axial distance between surfaces S4 and S5. D5 corresponds to the axial thickness of the third lens 130 and is the distance along the optical axis Ax between surfaces S5 and S6. D6 is the axial distance between surfaces S6 and S7. D7 is the axial distance between surfaces S7 and S8.

D8 corresponds to the axial thickness of the fourth lens 140 and is the distance on the optical axis Ax between plane S8 and plane S9. D9 corresponds to the axial thickness of the fifth lens 150 and is the distance on the optical axis Ax between plane S9 and plane S10. D10 is the axial distance between plane S10 and plane S11. D11 corresponds to the axial thickness of the sixth lens 160 and is the distance on the optical axis Ax between plane S11 and plane S12. D12 is the axial distance between plane S12 and plane S13. D13 corresponds to the axial thickness of the first flat plate 180a and is the distance on the optical axis Ax between plane S13 and plane S14. D14 is the axial distance between plane S14 and plane S15. D15 corresponds to the axial thickness of the second plate 180b and is the distance along the optical axis Ax between plane S15 and plane S16. D16 is the axial distance between plane S16 and the image plane 21.

The above explanation regarding the interplanar spacing Di also applies to the following other embodiments. The interplanar spacing Di is shown only in Figure 1; its illustration is omitted in the other drawings.

Table 3 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 1. In Table 3, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 4 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 1. The aspherical data shown in Table 4 is for each of the surfaces S11 and S12 of the sixth lens 160.

Figures 2A and 2B show the aberration diagrams of the imaging lens 10 in Figure 1.

Figure 2A is a graph showing the astigmatism of the imaging lens 10 in Figure 1. In Figure 2A, the vertical axis represents the incident height on the entrance pupil normalized to a pupil diameter of 1, and the horizontal axis represents the shift in the image formation position. Each line in the graph represents the astigmatism (mm) for light of each wavelength shown on the right of the graph. "S" represents the value on the sagittal image plane, and "T" represents the value on the tangential image plane.

Figure 2B is a graph showing the distortion aberration of the imaging lens 10 in Figure 1. In Figure 2B, the vertical axis represents the incident height on the entrance pupil normalized to a pupil diameter of 1, and the horizontal axis represents the shift in the image formation position. Each line in the graph represents the distortion aberration (%) for light of each wavelength shown on the right of the graph.

As shown in Figures 2A and 2B, according to Embodiment 1, various aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

The above explanation regarding the aberration diagrams also applies to the aberration diagrams shown in other embodiments; therefore, further explanation is omitted below.

(Example 2)
Figure 3 is a lens configuration diagram of the imaging lens 10 according to Embodiment 2 of this disclosure. Figure 3 shows the lens configuration of the imaging lens 10 according to Embodiment 2 in an optical cross-section.

As shown in Figure 3, in the imaging lens 10 of Embodiment 2, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 5 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 2. In Table 5, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 6 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 2. The aspherical data shown in Table 6 is for each of the surfaces S11 and S12 of the sixth lens 160.

Figures 4A and 4B are aberration diagrams of the imaging lens 10 shown in Figure 3. Figure 4A is a graph showing the astigmatism of the imaging lens 10 in Figure 3. Figure 4B is a graph showing the distortion of the imaging lens 10 in Figure 3. As shown in Figures 4A and 4B, according to Embodiment 2, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 3)
Figure 5 is a lens configuration diagram of the imaging lens 10 according to Embodiment 3 of the present disclosure. Figure 5 shows the lens configuration of the imaging lens 10 according to Embodiment 3 in an optical cross-section.

As shown in Figure 5, in the imaging lens 10 of Embodiment 3, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 7 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 3. In Table 7, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 8 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 3. The aspherical data shown in Table 8 is for surfaces S11 and S12 of the sixth lens 160, respectively.

Figures 6A and 6B are aberration diagrams of the imaging lens 10 shown in Figure 5. Figure 6A is a graph showing the astigmatism of the imaging lens 10 in Figure 5. Figure 6B is a graph showing the distortion of the imaging lens 10 in Figure 5. As shown in Figures 6A and 6B, according to Embodiment 3, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 4)
Figure 7 is a lens configuration diagram of the imaging lens 10 according to Embodiment 4 of the present disclosure. Figure 7 shows the lens configuration of the imaging lens 10 according to Embodiment 4 in an optical cross-section.

As shown in Figure 7, in the imaging lens 10 of Embodiment 4, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 9 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 4. In Table 9, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 10 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 4. The aspherical data shown in Table 10 are for surfaces S11 and S12 of the sixth lens 160, respectively.

Figures 8A and 8B are aberration diagrams of the imaging lens 10 shown in Figure 7. Figure 8A is a graph showing the astigmatism of the imaging lens 10 in Figure 7. Figure 8B is a graph showing the distortion of the imaging lens 10 in Figure 7. As shown in Figures 8A and 8B, according to Embodiment 4, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 5)
Figure 9 is a lens configuration diagram of the imaging lens 10 according to Embodiment 5 of the present disclosure. Figure 9 shows the lens configuration of the imaging lens 10 according to Embodiment 5 in an optical cross-section.

As shown in Figure 9, in the imaging lens 10 of Embodiment 5, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 11 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 5. In Table 11, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 12 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 5. The aspherical data shown in Table 12 are for surfaces S11 and S12 of the sixth lens 160, respectively.

Figures 10A and 10B are aberration diagrams of the imaging lens 10 shown in Figure 9. Figure 10A is a graph showing the astigmatism of the imaging lens 10 shown in Figure 9. Figure 10B is a graph showing the distortion of the imaging lens 10 shown in Figure 9. As shown in Figures 10A and 10B, according to Embodiment 5, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 6)
Figure 11 is a lens configuration diagram of the imaging lens 10 according to Embodiment 6 of the present disclosure. Figure 11 shows the lens configuration of the imaging lens 10 according to Embodiment 6 in an optical cross-section.

As shown in Figure 11, in the imaging lens 10 of Embodiment 6, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 13 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 6. In Table 13, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 14 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 6. The aspherical data shown in Table 14 is for each of the surfaces S11 and S12 of the sixth lens 160.

Figures 12A and 12B are aberration diagrams of the imaging lens 10 shown in Figure 11. Figure 12A is a graph showing the astigmatism of the imaging lens 10 in Figure 11. Figure 12B is a graph showing the distortion of the imaging lens 10 in Figure 11. As shown in Figures 12A and 12B, according to Embodiment 6, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 7)
Figure 13 is a lens configuration diagram of the imaging lens 10 according to Embodiment 7 of the present disclosure. Figure 13 shows the lens configuration of the imaging lens 10 according to Embodiment 7 in an optical cross-section.

As shown in Figure 13, in the imaging lens 10 of Embodiment 7, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 15 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 7. In Table 15, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 16 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 7. The aspherical data shown in Table 16 are for surfaces S11 and S12 of the sixth lens 160, respectively.

Figures 14A and 14B are aberration diagrams of the imaging lens 10 shown in Figure 13. Figure 14A is a graph showing the astigmatism of the imaging lens 10 in Figure 13. Figure 14B is a graph showing the distortion of the imaging lens 10 in Figure 13. As shown in Figures 14A and 14B, according to Example 7, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 8)
Figure 15 is a lens configuration diagram of the imaging lens 10 according to Embodiment 8 of the present disclosure. Figure 15 shows the lens configuration of the imaging lens 10 according to Embodiment 8 in an optical cross-section.

As shown in Figure 15, in the imaging lens 10 of Embodiment 8, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 17 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 8. In Table 17, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 18 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 8. The aspherical data shown in Table 18 is for each of the surfaces S11 and S12 of the sixth lens 160.

Figures 16A and 16B are aberration diagrams of the imaging lens 10 shown in Figure 15. Figure 16A is a graph showing the astigmatism of the imaging lens 10 in Figure 15. Figure 16B is a graph showing the distortion of the imaging lens 10 in Figure 15. As shown in Figures 16A and 16B, according to Embodiment 8, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

(Example 9)
Figure 17 is a lens configuration diagram of the imaging lens 10 according to Embodiment 9 of the present disclosure. Figure 17 shows the lens configuration of the imaging lens 10 according to Embodiment 9 in an optical cross-section.

As shown in Figure 17, in the imaging lens 10 of Embodiment 9, the first lens 110 is a biconcave lens having negative refractive power and a spherical shape. The second lens 120 is a biconcave lens having negative refractive power and a spherical shape. The third lens 130 is a biconvex lens having positive refractive power and a spherical shape. The fourth lens 140 is a biconvex lens having positive refractive power and a spherical shape. The fifth lens 150 is a biconcave lens having negative refractive power and a spherical shape. The sixth lens 160 is a biconvex lens having positive refractive power and an aspherical shape.

Table 19 shows the basic lens data, including the specifications of the imaging lens 10 according to Example 9. In Table 19, for surfaces S11 and S12, which are aspherical surfaces indicated by *, the value of the radius of curvature Ri represents the paraxial radius of curvature.
* indicates an aspherical surface.

Table 20 shows the aspherical data, including the aspherical coefficient, of the imaging lens 10 according to Example 9. The aspherical data shown in Table 20 is for surfaces S11 and S12 of the sixth lens 160, respectively.

Figures 18A and 18B are aberration diagrams of the imaging lens 10 shown in Figure 17. Figure 18A is a graph showing the astigmatism of the imaging lens 10 shown in Figure 17. Figure 18B is a graph showing the distortion of the imaging lens 10 shown in Figure 17. As shown in Figures 18A and 18B, according to Embodiment 9, aberrations such as astigmatism and distortion are well corrected, and an imaging lens 10 with excellent imaging performance is obtained.

According to the imaging lens 10 and imaging device 1 of one embodiment of this disclosure described above, the six-element configuration allows for compactness, lightness, and low cost, while achieving high optical performance by appropriately setting the lens shape. As a result, it is possible to realize a compact imaging lens 10 and imaging device 1 with high optical performance that can be mounted on cameras, including surveillance cameras and in-vehicle cameras.

The imaging lens 10 can easily correct axial chromatic aberration by satisfying condition (1). The imaging lens 10 can suppress the occurrence of field curvature and axial chromatic aberration by satisfying condition (2).

The imaging lens 10 can suppress the occurrence of field curvature by satisfying condition (3). In addition, the imaging lens 10 can effectively correct axial chromatic aberration.

The imaging lens 10 can suppress the tilting of the image plane 21 toward the image side by satisfying condition (4).

The imaging lens 10, with each of its two concave surfaces, allows for the easy formation of a flat receiving portion that can contact the first lens 110 and spacers on a flat surface without requiring any additional processing of the second lens 120.

The imaging lens 10, by satisfying condition (5), can easily correct axial chromatic aberration and suppress the occurrence of astigmatism.

The imaging lens 10 can suppress the occurrence of spherical aberration and the tilt of the image plane 21 toward the image side by satisfying condition (6).

The imaging lens 10 can correct axial chromatic aberration throughout the entire optical system by satisfying condition (7).

By satisfying condition (8), the imaging lens 10 can easily correct axial chromatic aberration across its entirety.

By satisfying condition (9), the imaging lens 10 suppresses the occurrence of field curvature and allows for easy correction of axial chromatic aberration generated in the third lens 130.

The imaging lens 10 can suppress astigmatism by satisfying condition (10). In addition, the imaging lens 10 enables miniaturization in both the overall length and radial directions, improving the design flexibility of the camera housing.

The imaging lens 10, by satisfying condition (11), allows for easy correction of field curvature, and also allows for easy correction of axial chromatic aberration caused by the negative fifth lens 150.

The imaging lens 10, by satisfying condition (12), can suppress the occurrence of astigmatism and the tilt of the image plane 21 toward the object in the meridional direction.

By satisfying condition (13), the imaging lens 10 suppresses the occurrence of lateral chromatic aberration in the reverse direction, and axial chromatic aberration can also be easily corrected.

The imaging lens 10 can easily correct field curvature by satisfying condition (14). In addition, the imaging lens 10 can also have a low tolerance sensitivity.

The imaging lens 10 is designed so that the first lens 110, second lens 120, third lens 130, fourth lens 140, fifth lens 150, and sixth lens 160 are each made of glass material, thereby suppressing yellowing due to ultraviolet light and changes in optical properties due to temperature changes.

The imaging lens 10 allows for easy adjustment of the angle of incidence of light to the image sensor 20 because each of the six surfaces of the sixth lens 160 is aspherical. As a result, the imaging lens 10 can easily correct spherical aberration and astigmatism.

The imaging lens 10, with its fourth lens 140 and fifth lens 150 formed as a cemented lens, enables the realization of an optical system with low tolerance sensitivity. In addition, the imaging lens 10 reduces the workload associated with its assembly.

The imaging lens 10, having a concave surface on the object-side of the first lens 110, allows for easy formation of a retaining structure, such as a retainer, without requiring any additional processing of the first lens 110. Furthermore, the imaging lens 10 can suppress the generation of ghosting.

By satisfying condition (15), the imaging lens 10 can easily ensure the imaging range that an imaging device 1, such as one used in an in-vehicle camera, must meet.

It will be apparent to those skilled in the art that this disclosure can be implemented in other predetermined forms besides the embodiments described above, without deviating from its spirit or essential features. Therefore, the prior description is illustrative and not limiting. The scope of the disclosure is defined not by the prior description but by the added claims. Any modifications within the scope of their equivalents are included therein.

For example, the shape, size, arrangement, orientation, and number of each component described above are not limited to those shown in the above description and drawings. The shape, size, arrangement, orientation, and number of each component may be configured arbitrarily, as long as they can achieve their function.

Although an imaging lens 10 according to one embodiment has been described, this disclosure is not limited to the imaging lens 10 of each embodiment described above, and various modifications are possible without departing from the spirit of the invention. For example, the specifications of the imaging lens 10 in each embodiment are illustrative, and various parameters can be changed within the scope of this disclosure.

1. Imaging device 10: Imaging lens 110, First lens 120, Second lens 130, Third lens 140, Fourth lens 150, Fifth lens 160, Sixth lens 170, Aperture diaphragm 180a, First plate 180b, Second plate 20, Image sensor 21: Image plane Ax, Optical axis Di, Planar spacing Da, Total length Ri, Radius of curvature Si

Claims (18)

It is an imaging lens,
Starting from the object side, it consists of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, an aperture diaphragm, a fourth lens with positive refractive power, a fifth lens with negative refractive power, and a sixth lens with positive refractive power.
If D4 is the on-axial distance from the image side of the second lens to the object side of the third lens, f is the focal length of the imaging lens with respect to the d line, D3 is the on-axial thickness of the second lens, f3 is the focal length of the third lens with respect to the d line , and Da is the total length of the imaging lens on the axis, then the conditional equation is:
D4/f<0.08 (1)
0.12<D3/f<0.23 (2)
1.6<f3/f<3.1 (9)
Da/f<5.2 (10)
An imaging lens that satisfies the requirements. It is an imaging lens,
Starting from the object side, it consists of a first lens with negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, an aperture diaphragm, a fourth lens with positive refractive power, a fifth lens with negative refractive power, and a sixth lens with positive refractive power.
If D4 is the on-axial distance from the image side of the second lens to the object side of the third lens, f is the focal length of the imaging lens with respect to the d line, D3 is the on-axial thickness of the second lens, f3 is the focal length of the third lens with respect to the d line, and f6 is the focal length of the sixth lens with respect to the d line, then the conditional equation is:
D4/f<0.08 (1)
0.12<D3/f<0.23 (2)
1.6<f3/f<3.1 (9)
1.45<f6/f<1.8 (14)
An imaging lens that satisfies the requirements. It is an imaging lens,
Starting from the object side, the lens consists of a first lens with a concave surface and negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, an aperture diaphragm, a fourth lens with positive refractive power, a fifth lens with negative refractive power, and a sixth lens with positive refractive power.
If D4 is the on-axial distance from the image side of the second lens to the object side of the third lens, f is the focal length of the imaging lens with respect to the d line, D3 is the on-axial thickness of the second lens, and f3 is the focal length of the third lens with respect to the d line, then the conditional equation is:
D4/f<0.08 (1)
0.12<D3/f<0.23 (2)
1.6<f3/f<3.1 (9)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If the focal length of the first lens with respect to the d line is f1, then the conditional equation is,
-1.5<f1/f<-1.2 (3)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If the refractive index of the second lens is N2,
N2/f<0.33 (4)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
Each of the two surfaces of the second lens is concave.
Imaging lens. An imaging lens according to any one of claims 1 to 3 ,
If R3 is the radius of curvature of the object side of the second lens and R4 is the radius of curvature of the image side of the second lens, then the conditional equation is:
-1<(R3+R4)/(R3-R4)<-0.82 (5)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If R2 is the radius of curvature of the image surface of the first lens, then the conditional equation is:
0.77<R2/f<0.9 (6)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If the Abbe number of the fifth lens is ν5, then the conditional equation is:
4.8<ν5/f<5.5 (7)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If the focal length of the second lens with respect to the d line is f2, then the conditional equation is,
-3.8<f2/f<-2 (8)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If the focal length of the fourth lens with respect to the d line is f4, then the conditional equation is,
1.2<f4/f<1.8 (11)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If fg is the combined focal length of the fourth lens, the fifth lens, and the sixth lens with respect to the d line, then the conditional equation is:
1.4<fg/f<1.8 (12)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
If the focal length of the fifth lens with respect to the d line is f5, then the conditional equation is,
-2.0<f5/f<-1.1 (13)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
Each of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens is formed of glass material.
Imaging lens. An imaging lens according to any one of claims 1 to 3 ,
Each of the six surfaces of the aforementioned sixth lens is aspherical.
Imaging lens. An imaging lens according to any one of claims 1 to 3 ,
The fourth lens and the fifth lens are formed as a cemented lens.
Imaging lens. An imaging lens according to any one of claims 1 to 3 ,
If W is the half-angle of view of the light ray incident at the highest image height position on the image plane, then the conditional equation is:
48 < W (15)
An imaging lens that satisfies the requirements. An imaging lens according to any one of claims 1 to 3 ,
An image sensor that converts an optical image formed through the aforementioned imaging lens into an electrical signal,
Equipped with ,
Imaging device.