Imaging lens and imaging device

Abstract

The objective is to provide an imaging lens and imaging device that have high angular resolution near the optical axis and a wide field of view. [Solution] To achieve this objective, an imaging lens was adopted that consists of a total of L lenses, arranged in order from the object side, including a first lens with a concave surface on the image side and negative refractive power, a second lens with a concave surface on the object side and positive refractive power, and a second L lens with positive refractive power that is positioned closest to the image side, where L satisfies 6 ≤ L ≤ 8, the aperture is positioned between the first lens and the L lens, the lens group positioned closer to the object than the aperture is designated as the first lens group, and the lens group positioned closer to the image than the aperture is designated as the second lens group, satisfying a predetermined conditional equation.

Description

[Technical Field]

[0001] The present invention relates to an imaging lens and an imaging device equipped with said imaging lens. [Background technology]

[0002] Small imaging devices using solid-state image sensors, such as digital still cameras and digital video cameras, are widely used. The imaging optics in these small imaging devices require further miniaturization, weight reduction, and cost reduction. Among the imaging lenses used in the imaging optics of such small imaging devices, lenses for mobile devices such as automotive lenses and drones (small unmanned aircraft, unmanned aerial vehicles) require detailed resolution at a distance near the optical axis, even if it means sacrificing resolution at the periphery, and also require a wide field of view.

[0003] In this way, by making the angular resolution near the optical axis higher than that of the peripheral area, objects near the optical axis can be imaged with high resolution, and by widening the field of view, a wide area can be imaged. By applying such an imaging lens to an in-vehicle lens or an imaging lens for a mobile object such as a drone, it becomes possible to accurately detect distant objects in front of the moving object such as a vehicle or drone, and to recognize objects around the moving object (obstacles, traffic lights, road signs, etc.) over a wide area. In the specification of this invention, "near the optical axis" refers to a range of about 20% of the image height including the optical axis, and "periphery" refers to a range outside of the range of about 70% of the image height including the optical axis.

[0004] As an example of such an imaging lens, in Example 12 of Patent Document 1, an imaging lens is proposed that consists of a total of six lenses, in the order from the object side: a lens with negative refractive power, a lens with positive refractive power, a lens with positive refractive power, a lens with positive refractive power, a lens with negative refractive power, and a lens with positive refractive power, with a field of view of 100°.

[0005] Furthermore, in Example 1 of Patent Document 2, an imaging lens is proposed that consists of a total of six lenses, arranged in the following order from the object side: a lens with negative refractive power, a lens with positive refractive power, a lens with positive refractive power, a lens with positive refractive power, a lens with negative refractive power, and a lens with positive refractive power, with a field of view of 126°. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-173807 [Patent Document 2] Japanese Patent Publication No. 2019-035989 [Patent Document 3] Japanese Patent Publication No. 2022-131903 [Patent Document 4] Japanese Patent Publication No. 2022-040489 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the imaging lens in Patent Document 1, for example in Example 9, has a relatively short telephoto ratio of 4.08 when the total length is normalized by the focal length, but the field of view is 100°, which is not sufficiently wide. Also, the imaging lens in Patent Document 2, for example in Example 3, has a strong refractive power of the second lens with f / f2 = 0.1538, which cancels out the negative refractive power of the first lens, resulting in a field of view of 126°, which is not sufficiently wide. Furthermore, the large effective diameter of the first lens is disadvantageous for miniaturization. Also, the imaging lens in Patent Document 3, for example in Example 1, has a relatively long telephoto ratio of 6.50 when the total length is normalized by the focal length, but the field of view is 132.00°, which is not sufficiently wide. In addition, the imaging lens in Patent Document 4, for example in Example 1, has a relatively long telephoto ratio of 6.75 when the total length is normalized by the focal length, but the field of view is 109.76°, which is not sufficiently wide.

[0008] The present invention has been made in view of such circumstances. The present invention is suitable as an imaging lens when high resolution is required in a surveillance camera that requires higher resolution at the center than at the periphery, or in an in-vehicle camera in which a camera with a built-in lens is arranged in front of the traveling direction. The present invention solves the above-described problems, enables widening the angle of view while increasing the angular resolution near the optical axis, and reduces the effective diameter of the first lens while keeping the entrance pupil small, and can reduce the angle CRA of the chief ray incident on the image plane and maintain a high peripheral light quantity. An object of the present invention is to provide an imaging lens and an imaging device.

Means for Solving the Problems

[0009] As a result of intensive research to solve the above-described problems, the inventors have conceived the following imaging lens and imaging device.

[0010] The imaging lens according to the present invention is composed of a total of L lenses including a first lens having a concave surface on the image side and a negative refractive power, a second lens having a concave surface on the object side and a positive refractive power, and a lens L having a positive refractive power arranged on the most image side, where L satisfies 6 ≤ L ≤ 8, and the aperture stop is arranged between the first lens and the lens L, and the lens group arranged on the object side of the aperture stop is defined as the first lens group, and the lens group arranged on the image side of the aperture stop is defined as the second lens group. An imaging lens that satisfies the following conditional expressions is adopted. 0.000 < f / f2 < 0.147 ·····(1) However, f: Focal length of the imaging lens f2: Focal length of the second lens

[0011] The imaging device according to the present invention adopts an imaging device characterized by including the above-described imaging lens and an imaging element that converts an optical image formed by the imaging lens into an electrical signal.

Effects of the Invention

[0012] The imaging lens according to the present invention makes it possible to widen the field of view while maintaining resolution and to increase the angular resolution near the optical axis. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view of the imaging lens of Example 1. [Figure 2] This is an aberration diagram for Example 1 when an object at infinity is in focus. [Figure 3] This is a cross-sectional view of the imaging lens of Example 2. [Figure 4] This is an aberration diagram for Example 2 when an object at infinity is in focus. [Figure 5] This is a cross-sectional view of the imaging lens of Example 3. [Figure 6] This is an aberration diagram for Example 3 when an object at infinity is in focus. [Figure 7] This is a cross-sectional view of the imaging lens of Example 4. [Figure 8] This is an aberration diagram for Example 4 when an object at infinity is in focus. [Figure 9] This is a cross-sectional view of the imaging lens of Example 5. [Figure 10] This is an aberration diagram for Example 5 when an object at infinity is in focus. [Figure 11] This is a cross-sectional view of the imaging lens of Example 6. [Figure 12] This is an aberration diagram for Example 6 when an object at infinity is in focus. [Modes for carrying out the invention]

[0014] The following describes embodiments of the imaging lens and imaging device according to the present invention. It should be noted that the following description merely illustrates one aspect and should not be interpreted as limiting the scope of the description below.

[0015] 1. Embodiment of an imaging lens 1-1.Optical configuration The imaging lens according to the present invention is substantially composed of a total of L lenses, including, in order from the object side, a first lens with a concave surface on the image side and negative refractive power, a second lens with a concave surface on the object side and positive refractive power, and a second L lens with positive refractive power that is positioned closest to the image, where L satisfies 6 ≤ L ≤ 8. Here, "substantially composed" means that the optical elements that substantially constitute the imaging lens are the total of L lenses from the first lens to the second L lens as described above, but it is permissible to include other lenses that do not have substantial refractive power, or optical elements other than lenses such as apertures and cover glasses. In the imaging lens, the aperture is positioned between the first lens and the second L lens. The group of lenses positioned closer to the object than the aperture is called the first lens group, and the group of lenses positioned closer to the image than the aperture is called the second lens group. That is, the first lens group includes the first lens and multiple lenses positioned closer to the object than the aperture, and the second lens group includes the second L lens and multiple lenses positioned closer to the image than the aperture.

[0016] In this imaging lens, the lens group consists of one or more lenses. The lens group may be configured to change its spacing during focusing, or its spacing may be fixed. In this case, the lenses may be configured to move along the optical axis, or they may be fixed.

[0017] In order to widen the field of view while maintaining resolution and to increase the angular resolution near the optical axis, it is preferable to increase the negative distortion aberration.

[0018] 1-1-1. Lens Configuration (1) First lens and second lens The imaging lens, by arranging a first lens with a concave surface on the image side and a second lens with a concave surface on the object side in that order, achieves a wide field of view while reducing the diameter of the first lens relative to the field of view. By arranging the first and second lenses with such surface shapes on the object side of the imaging lens, it becomes easy to obtain an imaging lens with higher angular resolution near the optical axis than at the periphery. Here, "angular resolution" is defined as "the number of pixels on the image sensor per degree of imaging field of view." Also, "field of view" refers to the field of view when focused at infinity.

[0019] To obtain the above-described functions and effects, it is preferable that the first lens has a meniscus shape with a concave surface on the image side. Furthermore, it is preferable that the first lens has negative refractive power. In lenses with a wide angle of view, the incident height of the principal ray (distance from the optical axis at the point of incidence) to the peripheral image height (e.g., 100% image height, 70% image height, etc.) tends to be largest at the first lens. Therefore, by making the image side of the first lens concave as described above and increasing its curvature, it is possible to correct coma aberration well from near the center of the optical axis to the periphery, while keeping peripheral distortion within an appropriate range.

[0020] To obtain a sufficiently wide field of view while ensuring high angular resolution near the optical axis, it is necessary to increase negative distortion. Therefore, it is preferable that the second lens has a concave shape on the object side, as this can compensate for the negative power of the first lens. Furthermore, it is preferable that the image plane side is convex in order to compensate for the positive refractive power of the third lens. For this reason, it is preferable that the second lens has a meniscus shape. It is also preferable that the second lens has positive refractive power, as this is advantageous in keeping the entrance pupil small and reducing the effective diameter of the first lens. The third lens is a lens positioned adjacent to the image side of the second lens.

[0021] (2) L lens The L-lens is the lens positioned closest to the image sensor in the imaging lens. Furthermore, the L-lens has positive refractive power. This helps suppress vignetting, which is common when widening the field of view, and reduces the decrease in peripheral light intensity.

[0022] Furthermore, while the lens surface shape of the L lens is not particularly limited, it is preferable, for example, that the object-side surface of the L lens has a small curvature. When light incident on the imaging lens is reflected at the image plane and then incident on the object surface of the L lens, it is possible to prevent the re-reflected light from being strongly focused onto the image plane. In other words, by focusing the re-reflected light at a location different from the image plane, it is possible to prevent focus onto the image plane and suppress the increase in ghost illumination. Moreover, it is preferable that the image-side surface of the L lens has a small curvature, as this makes the above-mentioned effect easier to achieve.

[0023] (3) The position of the aperture and the lenses before and after the aperture In this imaging lens, the aperture is the aperture diaphragm that defines the diameter of the light beam of the imaging lens, that is, the aperture diaphragm that defines the Fno (F number) of the lens. In this imaging lens, the aperture is positioned between the first lens and the L lens. Here, it is preferable that the lenses before and after the aperture, that is, the lens positioned furthest towards the image in the first lens group and the lens positioned furthest towards the object in the second lens group, have positive refractive power. By positioning the aperture between lenses with positive refractive power, the distance between the lenses before and after the aperture can be minimized, thereby shortening the overall optical length. Furthermore, by positioning the aperture between positive lenses, it becomes possible to make the effective diameters of the lenses before and after the aperture relatively small, and aberrations occurring between the first lens group and the second lens group can be well corrected.

[0024] (4) Air lens Since air can be considered an optical material with a refractive index of approximately 1, the shape of the air between lenses is considered a lens made of that air and is called an air lens. In this imaging lens, the air lens has a positive meniscus shape with the convex surface facing the object. Having this shape increases the degree of freedom in aberration correction. In particular, it is effective in correcting spherical aberration while excessively correcting distortion to increase angular resolution. In this case, the refractive power Φa of the air lens is defined by the following equation (29). Also, the focal length fa' of the air lens is expressed by the following equation (30).

[0025] Φa=((1-Nf) / Rf)+((Nr-1) / Rr)-D×((1-Nf) / Rf)×((Nr-1) / Rr) ····(29) however, Rf: Radius of curvature of the air lens on the side surface of the object. Nf: Refractive index of the d line on the side surface of an air lens Rr: Radius of curvature on the image surface of the air lens Nr: Refractive index of the d line on the image side of an air lens D: Center thickness of the air lens (distance along the optical axis between the object-side lens surface and the image-side lens surface)

[0026] fa'=1 / Φa ·····(30)

[0027] 1-1-2. Lens group configuration The first lens group, the second lens group, and the aperture will be explained in more detail below.

[0028] (1) First lens group a) Lens composition The first lens group includes a first lens and a second lens, and is preferably composed of four or fewer lenses. More preferably, it is composed of three or fewer lenses. This is because composing the first lens group with fewer lenses makes it easier to reduce the diameter and weight of the imaging lens.

[0029] b) Refractive force It is preferable that the first lens group as a whole has a negative refractive power. Having a negative refractive power in the first lens group allows for a negative-leading optical configuration, making it easier to achieve a wide angle of view while reducing the diameter of the first lens relative to the angle of view.

[0030] c) Lenses with positive refractive power When the first lens group as a whole has negative refractive power, it is preferable that the first lens group includes at least one lens with positive refractive power. By configuring the first lens group, which has negative refractive power as a whole, to include a lens with positive refractive power, field curvature and chromatic aberration can be improved, and coma aberration generated by the first lens can be corrected, making it easier to realize an imaging lens with high optical performance.

[0031] In the first lens group, it is preferable that the lens positioned closest to the image has a positive refractive power. For example, if the first lens group consists of three lenses, it is preferable that the third lens has a positive refractive power. Also, if the first lens group consists of four lenses, it is preferable that the fourth lens, positioned fourth from the object side, has a positive refractive power. This makes it possible to effectively correct distortion and astigmatism generated in the first lens, which is advantageous for increasing the resolution at the peripheral image height and widening the angle of view. In particular, if the third lens has a positive refractive power, it is advantageous for improving Fno and positively correcting spherical aberration.

[0032] When the lens positioned furthest towards the image in the first lens group has a positive refractive power, it is preferable that the Abbe number of that lens on the d line is less than 65. Furthermore, it is preferable that the Abbe number of that lens on the d line is greater than 23, and more preferably greater than 44. By positioning a lens with such dispersion characteristics furthest towards the image in the first lens group, i.e., on the object side of the aperture, chromatic aberration can be effectively corrected.

[0033] Furthermore, it is preferable that the image-side of the lens positioned closest to the image in the first lens group be convex. Since this lens is positioned immediately before the aperture, making the image-side of this lens convex allows for control of both the ray angle between the axial rays and the optical axis, and the ray angle between the peripheral rays and the optical axis, thereby reducing these ray angles after passing through the lens immediately after the aperture. As a result, these ray angles incident on the second lens group are also reduced, suppressing fluctuations in the incident angle of view due to widening the field of view and providing an advantage in aberration correction. In this case, the lens with positive refractive power positioned closest to the object is placed in the second lens group.

[0034] d) Lenses with negative refractive power When the first lens group as a whole has negative refractive power, it is preferable that the first lens group includes at least one lens with negative refractive power. When the first lens group consists of three or more lenses, it is preferable for the first or second lens to have negative refractive power in order to widen the angle of view. In particular, by having the first lens, which is positioned closest to the object in the imaging lens, have negative refractive power, it becomes easier to widen the angle of view while keeping the diameter of the first lens small relative to the angle of view. In this case, by including two lenses with negative refractive power in the first lens group, the negative refractive power of the first lens group can be distributed to the two lenses, making it easier to suppress spherical aberration and chromatic aberration occurring in the first lens group and realize an imaging lens with high optical performance.

[0035] Furthermore, positioning the entrance pupil as close to the object as possible is preferable for miniaturizing the imaging lens in the radial direction. In the first lens group, by placing at least one lens with negative refractive power on the object side of the lens with positive refractive power, it becomes easier to position the entrance pupil on the object side, thereby enabling miniaturization in the radial direction.

[0036] e) Aspheric lenses The diameter of the lenses constituting the first lens group is generally larger than that of the lenses constituting the second lens group. Also, wide-angle lenses tend to have insufficient correction of field curvature. Therefore, if the lens positioned on the object side within the first lens group is an aspherical lens, field curvature can be corrected more effectively than if the lens positioned on the image side within the first lens group were an aspherical lens.

[0037] (2) Second lens group a) Lens composition The object-facing surface of the lens positioned closest to the object in the second lens group may be convex or concave. When the object-facing surface in the second lens group is convex, distortion at low image heights can be made relatively large, while keeping the difference in angular resolution between the edges and the center small. On the other hand, when the object-facing surface in the second lens group is concave, distortion at low image heights can be kept small, while keeping the angular resolution at the center of the image large.

[0038] b) Refractive force It is preferable that the second lens group has a positive refractive power as a whole. If the first lens group has a negative refractive power as a whole and the second lens group has a positive refractive power as a whole, astigmatism generated in the first lens group can be well corrected by the second lens group, and an imaging lens with high optical performance can be obtained while achieving a wider angle of view.

[0039] c) Lenses with positive refractive power When the second lens group has positive refractive power, it is preferable that the second lens group includes at least two lenses with positive refractive power. By including at least two lenses with positive refractive power in the second lens group, it is possible to effectively correct astigmatism and other aberrations generated by the first lens while suppressing excessive curvature of each lens surface. Furthermore, by including at least two lenses with positive refractive power, image field curvature can also be effectively corrected.

[0040] In the second lens group, the lens positioned closest to the object, that is, the lens positioned immediately after the aperture, preferably has a positive refractive power. By positioning the lens with the strongest positive refractive power closest to the object in the second lens group, negative distortion can be obtained, allowing for a wider angle of view while maintaining high angular resolution near the optical axis. In this case, by making the lens positioned closest to the image in the first lens group a lens with a convex surface on the image side, angle of view fluctuations can be effectively suppressed when positional changes or displacements occur due to assembly variations or temperature changes, and focal position fluctuations can also be effectively suppressed.

[0041] Furthermore, in the second lens group, the lens positioned closest to the object has a small difference between the incident angle of off-axis rays and the incident angle of on-axis rays. Therefore, the lens positioned closest to the object in the second lens group can correct on-axis chromatic aberration more effectively than off-axis chromatic aberration. For this reason, it is preferable that the positive refractive power lenses included in the second lens group have low dispersion, and for good chromatic aberration correction, the Abbe number on the d line is preferably greater than 53, and more preferably greater than 63.

[0042] As mentioned above, the L lens, which is positioned closest to the image sensor in the second lens group, has a positive refractive power.

[0043] d) Lenses with negative refractive power When the second lens group has positive refractive power, it is preferable that the second lens group includes at least one lens with negative refractive power. By having at least one lens with negative refractive power in the second lens group, chromatic aberration can be corrected well.

[0044] Furthermore, positioning the exit pupil as close to the object as possible is preferable for making the angle of incidence on the image plane at the peripheral image height of the imaging lens vertical and increasing the peripheral light intensity. By placing at least one lens with negative refractive power on the object side of the lens with positive refractive power behind the second lens group, it becomes advantageous for bringing the angle of incidence on the principal ray to the image plane closer to vertical, and the peripheral light intensity can be increased.

[0045] Furthermore, in the second lens group, by placing a lens with negative refractive power on the image side of a lens with positive refractive power, axial and near-axial chromatic aberration can be effectively corrected.

[0046] In the second lens group, the lens having negative refractive power preferably has a refractive index greater than 1.60 at the d line, and more preferably greater than 1.65. This is because a larger refractive index for the lens having negative refractive power is preferable for miniaturizing the imaging lens.

[0047] e) Resin lenses When resin lenses are used among the L lenses that make up the imaging lens, it is preferable to place all of them in the second lens group. By placing all the resin lenses on the image side of the aperture, it is possible to suppress changes in the angle of view due to changes in ambient temperature and to suppress changes in the focal position more effectively compared to when the resin lenses are placed on the object side of the aperture.

[0048] 1-1-3. Number of lenses and their configuration The imaging lens consists of lenses numbered from 1st to Lst, in order from the object side, where L satisfies the condition 6 ≤ L ≤ 8.

[0049] When L=6, i.e., when the imaging lens is composed of six lenses, the refractive power of each lens is preferably negative, positive, positive, negative, positive, in that order from the object side. The aperture is preferably positioned between the third and fourth lenses, which are lenses with positive refractive power, in order to reduce the aperture diameter for the purpose of facilitating aberration correction. The first lens with negative refractive power and the second lens with positive refractive power widen the angle of view and reduce the diameter of the first lens. The subsequent third lens with positive refractive power corrects coma aberration and axial chromatic aberration, and reduces the aperture diameter. The fourth lens with positive refractive power following the aperture allows for correction of field curvature and distortion. The fifth lens with negative refractive power is advantageous for correcting axial and peripheral chromatic aberration and for bringing the angle of incidence of the principal ray to the image plane closer to perpendicular. The sixth lens, which has the most positive refractive power on the image side, is advantageous for correcting image field curvature and bringing the angle of incidence of the principal ray onto the image plane closer to perpendicular.

[0050] When L=7, i.e., when the imaging lens is composed of 7 lenses, the refractive power of each lens is preferably negative positive positive positive negative positive, or negative positive positive negative positive negative positive, in order from the object side. The aperture is preferably positioned between the 4th and 5th lenses, which are lenses with positive refractive power, in order to reduce the aperture diameter for the purpose of facilitating aberration correction. The 1st lens with negative refractive power and the 2nd lens with positive refractive power widen the angle of view and reduce the diameter of the 1st lens. The subsequent 3rd lens with positive refractive power corrects coma aberration and axial chromatic aberration, and reduces the aperture diameter. The 5th lens with positive refractive power following the aperture allows for correction of field curvature and distortion. The 6th lens with negative refractive power following is advantageous for correcting axial and peripheral chromatic aberration and for bringing the angle of incidence of the principal ray to the image plane closer to perpendicular. The seventh lens, which has the most positive refractive power on the image side, is advantageous for correcting image field curvature and bringing the angle of incidence of the principal ray onto the image plane closer to perpendicular.

[0051] When L=8, i.e., when the imaging lens is composed of 8 lenses, the refractive power of each lens is preferably negative positive positive positive negative positive positive, or negative positive positive negative positive negative positive, in order from the object side. The aperture is preferably positioned between the 4th and 5th lenses, which are lenses with positive refractive power, in order to reduce the aperture diameter for the purpose of facilitating aberration correction. The 1st lens with negative refractive power and the 2nd lens with positive refractive power widen the angle of view and reduce the diameter of the 1st lens. The subsequent 3rd lens with positive refractive power corrects coma aberration and axial chromatic aberration, and reduces the aperture diameter. The 5th lens with positive refractive power following the aperture allows for correction of field curvature and distortion. The 6th lens with negative refractive power follows, which is advantageous for correcting axial and peripheral chromatic aberration and bringing the angle of incidence of the principal ray to the image plane closer to perpendicular. The seventh and eighth lenses, which have positive refractive power, are advantageous in correcting field curvature and bringing the angle of incidence of the principal ray onto the image plane closer to perpendicular.

[0052] 1-2. Conditional expression The imaging lens preferably employs the configuration described above and satisfies one or more of the following conditional equations.

[0053] 1-2-1. Conditional expression (1) 0.000 <f / f2<0.147 ·····(1) however, f: Focal length of the imaging lens f2: Focal length of the second lens

[0054] Conditional equation (1) is an equation that defines the ratio of the focal length of the imaging lens to the focal length of the second lens. In conditional equation (1), if the value of "f / f2" satisfies the upper limit, the refractive power of the second lens can be kept small, which is effective in keeping the field curvature underexposed. If the value of "f / f2" exceeds the upper limit, the refractive power of the second lens increases and cancels out the negative refractive power of the first lens, which is advantageous in obtaining a sufficiently wide angle of view.

[0055] On the other hand, when the "f / f2" value satisfies the lower limit, the refractive power of the second lens can be kept relatively large, which is advantageous in keeping the entrance pupil small and maintaining a small effective diameter of the first lens.

[0056] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (1) is more preferably 0.005, but may also be set to 0.010, 0.015, or 0.030. Also, the upper limit of conditional expression (1) is more preferably 0.145, but may also be set to 0.140, 0.130, or 0.120.

[0057] When adopting these preferred lower or upper limits, you may substitute the equals sign (≦) with the inequality sign (<), or vice versa. The same applies to the other conditional expressions described later.

[0058] 1-2-2. Conditional expression (2) -2.00 <RgLf / RgLr<-0.52 ·····(2) however, RgLf: Radius of curvature on the object side of the L lens RgLr: Radius of curvature on the image side of the L lens

[0059] In condition (2), when the value of "RgLf / RgLr" satisfies the upper limit, the object-side radius of curvature of the L lens can be kept large relative to the absolute value of the image-side radius of curvature. This prevents harmful reflected light rays reflected from the image plane and further reflected from the object side of the L lens from converging near the image plane, thus resulting in good ghost suppression. It also makes it easier to keep the field curvature underexposed. Furthermore, it makes it easier to maintain high peripheral illumination by reducing the angle CRA of the principal rays incident on the image plane. It is also effective in reducing the principal rays of peripheral light. In addition, regarding aberration correction, distortion is large and is an effective element in ensuring angular resolution (in Seidel third-order aberration), and is advantageous in correcting field curvature that occurs when distortion is increased by the first lens alone.

[0060] On the other hand, if the value of "RgLf / RgLr" in condition (2) satisfies the lower limit, the radius of curvature on the image side of the L lens can be kept large relative to the absolute value of the object-side radius of curvature, and this is also advantageous for maintaining over-curvature of the image field.

[0061] Furthermore, in order to obtain the above effect, the lower limit of conditional equation (2) is more preferably -1.97, but may also be set to -1.96, -1.93, or -1.90. Also, the upper limit of conditional equation (2) is more preferably -0.53, but may also be set to -0.54, -0.56, or -0.60.

[0062] 1-2-3. Conditional expression (3) 4.10 <OAL / f<9.00 ·····(3) however, OAL: Total length from the first lens to the image plane f: Focal length of the imaging lens

[0063] In condition (3), if the value of "OAL / f" satisfies the upper limit, it is effective in shortening the overall length of the imaging lens. By shortening the overall length and miniaturizing the camera, the camera can be placed closer to the human eye's line of sight, which is advantageous for sensing using image information similar to human vision.

[0064] On the other hand, if the value of "OAL / f" in condition (3) satisfies the lower limit, it prevents the overall length of the imaging lens from being excessively shortened, which is advantageous for field curvature when increasing resolution, increasing Fno, and widening the angle of view.

[0065] Furthermore, in order to obtain the above effect, the lower limit of conditional equation (3) is more preferably 4.25, but may also be set to 4.40, 4.55, or 4.70. Also, the upper limit of conditional equation (3) is more preferably 8.0, but may also be set to 6.50, 6.25, or 6.10.

[0066] 1-2-4. Conditional expression (4) 7.70 <RgLf-DairLF<100.00 ·····(4) however, RgLf: Radius of curvature of the object side of the L lens DairLF: The sum of the air-equivalent distances along the optical axis from the vertex of the object's side surface to the image plane of the L lens.

[0067] In condition (4), if the value of "RgLf-DairLF" satisfies the upper limit, the radius of curvature of the object side of the L lens does not become excessively large, which is advantageous for correcting various aberrations.

[0068] On the other hand, when the value of "RgLf-DairLF" in condition (4) satisfies the lower limit, the radius of curvature of the object side surface of the L lens is within an appropriate range, which is advantageous in suppressing ghosting. This prevents light incident on the imaging lens from being reflected at the image plane, and then the re-reflected light that is reflected again by the object side surface of the L lens from entering the image plane.

[0069] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (4) is more preferably 7.85, but may also be set to 8.00, 8.15, or 8.30. Also, the upper limit of conditional expression (4) is more preferably 87.50, but may also be set to 75.00, 62.50, or 50.00.

[0070] 1-2-5. Conditional expression (5) 0.90 <fs / f<2.80 ·····(5) however, fs: The focal length of the lens located adjacent to the image side of the aperture. f: Focal length of the imaging lens

[0071] In condition (5), when the value of "fs / f" satisfies the upper limit, the value of fs can be prevented from becoming too large, which is advantageous for correcting spherical aberration. Furthermore, the presence of a lens with positive refractive power before the aperture is advantageous for correcting field curvature and distortion.

[0072] On the other hand, if the value of "fs / f" in condition (5) satisfies the lower limit, the value of fs can be prevented from becoming too small, which allows for a reduction in the angle of the principal rays passing through the aperture in the peripheral area, thus being advantageous for widening the field of view.

[0073] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (5) is more preferably 1.00, but may also be set to 1.10, 1.20, or 1.30. Also, the upper limit of conditional expression (5) is more preferably 2.50, but may also be set to 2.20, 1.90, or 1.60.

[0074] 1-2-6. Conditional expression (6) 4.5 <f×tan(θ) / Yh<5.5 ·····(6) however, f: Focal length of the imaging lens θ: Maximum half-angle of view when the imaging lens is in focus at infinity. Yh: Maximum image height

[0075] In condition (6), if the value of "f × tan(θ) / Yh" satisfies the upper limit, the projection method approaches perspective projection (central projection), which is preferable because it reduces the difference in image distortion between the center and periphery of the screen.

[0076] On the other hand, if the value of "f × tan(θ) / Yh" in condition (6) satisfies the lower limit, it is preferable because, when the diagonal angle of view is the same, the area per unit angle of view at the center of the screen increases, and the angular resolution increases. It is also preferable because the peripheral light intensity increases.

[0077] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (6) is more preferably 4.6, but may also be set to 4.7, 4.8, or 4.9. Also, the upper limit of conditional expression (6) is more preferably 5.4, but may also be set to 5.3, 5.2, or 5.1.

[0078] 1-2-7. Conditional expression (7) 1.67 <Ng1<1.88 ·····(7) however, Ng1: Refractive index of the d line of the first lens

[0079] In condition (7), it is preferable that the value of "Ng1" in this condition satisfies the upper limit, as this tends to reduce the distortion.

[0080] On the other hand, when the value of "Ng1" in condition (7) satisfies the lower limit, it is preferable because, when the diagonal field of view is the same, the area per unit field of view at the center of the screen tends to increase and the angular resolution tends to increase.

[0081] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (7) is more preferably 1.68, but may also be set to 1.70, 1.72, or 1.74. Also, the upper limit of conditional expression (7) is more preferably 1.87, but may also be set to 1.86, 1.85, or 1.84.

[0082] 1-2-8. Conditional expression (8) 1.55 <Ng2<1.90 ·····(8) however, Ng2: Refractive index of the d line of the second lens

[0083] In conditional equation (8), it is preferable that the value of "Ng2" satisfies the upper limit, as this allows for sufficient correction of spherical aberration and suppression of long-wavelength axial chromatic aberration.

[0084] On the other hand, it is preferable that the value of "Ng2" in condition (8) satisfies the lower limit, as this can make spherical aberration negative and suppress axial chromatic aberration at short wavelengths.

[0085] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (8) is more preferably 1.56, but may also be set to 1.57, 1.58, or 1.59. Also, the upper limit of conditional expression (8) is more preferably 1.86, but may also be set to 1.83, 1.80, or 1.77.

[0086] 1-2-9. Conditional expression (9) 0.50 <f1G / f<2.00 ·····(9) however, f1G: Focal length of the first lens group f: Focal length of the imaging lens

[0087] In condition (9), if the value of "f1G / f" satisfies the upper limit, the refractive power of the entire first lens group can be prevented from becoming too large, which is advantageous for widening the angle of view and improving angular resolution, and is also preferable because it allows for a smaller diameter for the first lens.

[0088] On the other hand, if the value of "f1G / f" in condition (9) satisfies the lower limit, the refractive power of the entire first lens group can be prevented from becoming too small, which is advantageous and desirable for correcting aberrations such as chromatic aberration.

[0089] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (9) is more preferably 0.80, but may also be set to 0.90, 1.00, or 1.10. Also, the upper limit of conditional expression (9) is more preferably 1.90, but may also be set to 1.75, 1.60, or 1.45.

[0090] 1-2-10. Conditional expression (10) 4.5 <OAL / Yh<7.0 ·····(10) however, OAL: Total length from the first lens to the image plane Yh: Maximum image height

[0091] In condition (10), if the value of "OAL / Yh" satisfies the upper limit, it is advantageous for miniaturizing the imaging lens in the optical axis direction.

[0092] On the other hand, if the value of "OAL / Yh" in condition (10) satisfies the lower limit, the size of the optical axis direction of the imaging lens is permissible, which is advantageous for correcting various aberrations such as field curvature and chromatic aberration.

[0093] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (10) is more preferably 4.6, but may also be set to 4.7, 4.8, or 4.9. Also, the upper limit of conditional expression (10) is more preferably 6.8, but may also be set to 6.7, 6.6, or 6.5.

[0094] 1-2-11. Conditional expression (11) -4.5 <FAir / f<-0.1 ·····(11) however, FAir: In the second lens group, the distance between lenses (distance parallel to the optical axis) is narrower at the periphery than at the center, resulting in a negative refractive power due to the air between the lenses. f: Focal length of the imaging lens

[0095] Conditional equation (11) is an equation that defines the refractive power of the air lens with negative refractive power included in the second lens group. If the air lens has a shape close to biconvex, then "FAir / f" in conditional equation (11) will be a value close to zero.

[0096] More specifically, the air lens in the second lens group is preferably an air lens that has a negative power due to the spacing becoming narrower from the center to the periphery, and has a spacing of 2 / 3 or less of the axial spacing at half the height of the effective diameter of the larger of the two surfaces, and has a spacing shape that enables face contact or edge contact.

[0097] In condition (11), if the value of "FAir / f" satisfies the upper limit, the refractive power of FAir can be prevented from becoming too large, which is advantageous for correcting coma aberration.

[0098] On the other hand, if the value of "FAir / f" in condition (11) satisfies the lower limit, it is possible to prevent the refractive power of FAir from becoming too small, which is advantageous in increasing distortion and improving angular resolution.

[0099] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (11) is more preferably -4.3, but may also be set to -4.1, -3.9, or -3.7. Also, the upper limit of conditional expression (11) is more preferably -0.3, but may also be set to -0.5, -1.0, -1.5, -2.0, or -2.2.

[0100] 1-2-12. Conditional expression (12) -5.00<(RAf+RAr) / (RAf-RAr)<-1.00 ····(12) however, RAf: Radius of curvature on the object side of an air lens. RAr: Radius of curvature on the image plane side of an air lens (Air).

[0101] Conditional equation (12) represents the shape factor of the air lens.

[0102] In condition (12), if the value of "(RAf+RAr) / (RAf-RAr)" satisfies the upper limit, it is advantageous in increasing distortion and improving angular resolution.

[0103] On the other hand, if the value of "(RAf+RAr) / (RAf-RAr)" in condition (12) satisfies the lower limit, it is advantageous for correcting coma aberration.

[0104] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (12) is more preferably -4.75, but may also be set to -4.40, -4.05, or -3.70. Also, the upper limit of conditional expression (12) is more preferably -1.20, but may also be set to -1.50, -1.80, or -2.10.

[0105] 1-2-13. Conditional expression (13) 0.40 <Dg2 / f<1.70 ·····(13) however, Dg2: Center thickness of the second lens f: Focal length of the imaging lens

[0106] In condition (13), if the value of "Dg2 / f" satisfies the upper limit, the central thickness of the second lens does not become excessively large, which is advantageous for shortening the overall length of the imaging lens.

[0107] On the other hand, it is preferable that the value of "Dg2 / f" in condition (13) satisfies the lower limit, as this allows for good correction of the coma aberration generated in the first lens.

[0108] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (13) is more preferably 0.44, but may also be set to 0.45, 0.46, or 0.47. Also, the upper limit of conditional expression (13) is more preferably 1.66, but may also be set to 1.62, 1.58, or 1.54.

[0109] 1-2-14. Conditional expression (14) 1.44 <NgL<1.70 ·····(14) however, NgL: Refractive index of the d line of the L lens

[0110] In condition (14), if the value of "NgL" satisfies the upper limit, the refractive index of the L lens can be kept from being too high, which is advantageous for correcting field curvature.

[0111] On the other hand, if the value of "NgL" in condition (14) satisfies the lower limit, the refractive index of the L lens can be prevented from being too low, making it possible to secure refractive power even with a small radius of curvature, which is advantageous for miniaturizing the imaging lens.

[0112] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (14) is more preferably 1.45, but may also be set to 1.46, 1.47, or 1.48. Also, the upper limit of conditional expression (14) is more preferably 1.68, but may also be set to 1.65, 1.62, or 1.59.

[0113] 1-2-15. Conditional expression (15) 1.20 <Rg1f / f<2.40 ·····(15) however, Rg1f: Radius of curvature on the object side of the first lens f: Focal length of the imaging lens

[0114] When the value of "Rg1f / f" in condition (15) satisfies the upper limit, it is possible to prevent Rg1f from becoming too large, which is advantageous for shortening the overall length of the imaging lens.

[0115] On the other hand, if the value of "Rg1f / f" in condition (15) satisfies the lower limit, Rg1f can be prevented from becoming too small, which is advantageous for aberration correction because the angle of incidence of light rays to the side of the object of the first lens does not become large.

[0116] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (15) is more preferably 1.24, but may also be set to 1.28, 1.32, or 1.36. Also, the upper limit of conditional expression (15) is more preferably 2.30, but may also be set to 2.20, 2.10, or 2.00.

[0117] 1-2-16. Conditional expression (16) -3.20 <f12 / f<-1.30 ·····(16) however, f12: Combined focal length of the first and second lenses f: Focal length of the imaging lens

[0118] When the value of "f12 / f" in condition (16) satisfies the upper limit, the combined refractive power of the first and second lenses can be prevented from becoming too large, which is advantageous for shortening the overall length of the imaging lens.

[0119] On the other hand, if the value of "f12 / f" in condition (16) satisfies the lower limit, the combined refractive power of the first and second lenses can be prevented from becoming too small, which is advantageous for widening the angle of view.

[0120] Furthermore, in order to obtain the above effect, the lower limit of conditional equation (16) is more preferably -3.10, but may also be set to -3.00, -2.90, or -2.80. Also, the upper limit of conditional equation (16) is more preferably -1.40, but may also be set to -1.52, -1.64, or -1.76.

[0121] 1-2-17. Conditional expression (17) 2.3 <fL / f<7.0 ·····(17) however, fL: Focal length of the L lens f: Focal length of the imaging lens

[0122] In condition (17), when the value of "fL / f" satisfies the upper limit, the refractive power of the L lens can be relatively increased, thus ensuring a large amount of peripheral light.

[0123] On the other hand, if the value of "fL / f" in condition (17) satisfies the lower limit, the refractive power of the L lens can be relatively reduced, which is advantageous for increasing the size of the image sensor.

[0124] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (17) is more preferably 2.4, but may also be set to 2.5, 2.6, or 2.7. Also, the upper limit of conditional expression (17) is more preferably 6.7, but may also be set to 6.4, 6.1, or 5.8.

[0125] 1-2-18. Conditional expression (18) 33.0 <Vg1<58.0 ·····(18) however, Vg1: Abbe number of the d line of the first lens

[0126] In condition (18), if the value of "Vg1" satisfies the upper limit, the Abbe number of the first lens can be kept from becoming too large, which is preferable because it increases the options for increasing the refractive index of the first lens.

[0127] On the other hand, if the value of "Vg1" in condition (18) satisfies the lower limit, the Abbe number of the first lens can be kept from being too small, which reduces the dispersion of the first lens and is advantageous for achromatic imaging.

[0128] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (18) is more preferably 35.0, but may also be set to 36.5, 38.0, or 39.5. Also, the upper limit of conditional expression (18) is more preferably 55.0, but may also be set to 52.5, 50.0, or 47.5.

[0129] 1-2-19. Conditional expression (19) 20.0 <Vg2<75.0 ·····(19) however, Vg2: Abbe number of the d line of the second lens

[0130] In condition (19), if the value of "Vg2" satisfies the upper limit, the Abbe number of the second lens can be kept from becoming too large, which is advantageous for achromaticity within the first lens group, which has a negative refractive power overall.

[0131] On the other hand, if the value of "Vg2" in condition (19) satisfies the lower limit, the Abbe number of the second lens can be kept from being too small, which allows for positive correction of long-wavelength magnification color in image height. This is advantageous for correcting chromatic aberration that has been excessively generated in the first lens.

[0132] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (19) is more preferably 22.0, but may also be set to 23.8, 25.6, or 27.4. Also, the upper limit of conditional expression (19) is more preferably 74.0, but may also be set to 68.0, 62.0, or 56.0.

[0133] 1-2-20. Conditional expression (20) 1.50 <NgL2<1.88 ·····(20) however, NgL2: When the lens adjacent to the object side of the L lens is called the L2 lens, the refractive index of the d line of the L2 lens.

[0134] In condition (20), if the value of "NgL2" satisfies the upper limit, the refractive index of the L2 lens can be kept from being too high, which is advantageous for correcting field curvature.

[0135] On the other hand, if the value of "NgL2" in condition (20) satisfies the lower limit, the refractive index of the L2 lens can be prevented from being too small. This makes it possible to secure refractive power even with a small radius of curvature for the L2 lens, which is advantageous for miniaturization.

[0136] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (20) is more preferably 1.53, but may also be set to 1.56, 1.62, or 1.68. Also, the upper limit of conditional expression (20) is more preferably 1.82, but may also be set to 1.80, 1.78, or 1.76.

[0137] 1-2-21. Conditional expression (21) 22.0 <VgL2<65.0 ·····(21) however, VgL2: When the lens adjacent to the object side of the L lens is called the L2 lens, the Abbe number of the d line of the L2 lens.

[0138] In condition (21), if the value of "VgL2" satisfies the upper limit, the Abbe number is kept low, which is advantageous for color correction when the L2 lens has negative refractive power. Furthermore, if the L2 lens has positive refractive power, it becomes possible to share the refractive power and color correction with the L lens.

[0139] On the other hand, if the value of "VgL2" in condition (21) satisfies the lower limit, the Abbe number is maintained at a high level, which is advantageous for color correction when the L2 lens has positive refractive power. Furthermore, if the L2 lens has negative refractive power, it becomes possible to share the refractive power and color correction with the L lens.

[0140] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (21) is more preferably 23.5, but may also be set to 27.0, 30.5, or 34.0. Also, the upper limit of conditional expression (21) is more preferably 62.0, but may also be set to 59.0, 56.0, or 53.0.

[0141] 1-2-22. Conditional expression (22) 55 <VgL<80 ·····(22) however, VGL: Abbe number of the d line of the L lens

[0142] In condition (22), if the value of "VgL" satisfies the upper limit, the Abbe number can be kept from being too high, which increases the degree of freedom in the refractive index of the L lens and is advantageous in increasing the refractive power of the L lens.

[0143] On the other hand, when the value of "VgL" in condition (22) satisfies the lower limit, the Abbe number is maintained at a high level, which is advantageous for color correction when the L lens has positive refractive power.

[0144] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (22) is more preferably 56, but may also be set to 58, 60, or 62. Also, the upper limit of conditional expression (22) is more preferably 77, but may also be set to 75, 73, or 71.

[0145] 1-2-23. Conditional expression (23) 0.65 <BF / f<0.90 ·····(23) however, BF: Back focus, indicating the distance from the vertex of the image lateral surface of the L lens to the image plane. f: Focal length of the imaging lens

[0146] In condition (23), if the value of "BF / f" satisfies the upper limit, it is possible to prevent BF from becoming too large, which is advantageous for shortening the overall length of the imaging lens.

[0147] On the other hand, if the value of "BF / f" in condition (23) satisfies the lower limit, the BF can be prevented from being too small, which is advantageous for securing space for the parallel plane plate placed in the BF area and for securing space for mounting the image sensor.

[0148] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (23) is more preferably 0.67, but may also be set to 0.70, 0.73, or 0.76. Also, the upper limit of conditional expression (23) is more preferably 0.89, but may also be set to 0.87, 0.85, or 0.83.

[0149] 1-2-24. Conditional expression (24) -1.75 <f1 / f<-1.00 ·····(24) however, f1: Focal length of the first lens f: Focal length of the imaging lens

[0150] In conditional equation (24), if the value of "f1 / f" satisfies the upper limit, the absolute value of the refractive power of the first lens can be kept from becoming too large, which is advantageous for shortening the overall length of the imaging lens.

[0151] On the other hand, if the value of "f1 / f" in condition (24) satisfies the lower limit, the absolute value of the refractive power of the first lens can be prevented from being too small, which is advantageous for widening the angle of view.

[0152] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (24) is more preferably -1.70, but may also be set to -1.63, -1.56, or -1.49. Also, the upper limit of conditional expression (24) is more preferably -1.10, but may also be set to -1.20, -1.30, or -1.40.

[0153] 1-2-25. Conditional expression (25) 1.00 <f3 / f<3.00 ·····(25) however, f3: Focal length of the third lens f: Focal length of the imaging lens

[0154] In condition (25), if the value of "f3 / f" satisfies the upper limit, the absolute value of the focal length of the third lens can be kept from becoming too large, which is advantageous for correcting coma aberration.

[0155] On the other hand, if the value of "f3 / f" in condition (25) satisfies the lower limit, the absolute value of the focal length of the third lens can be prevented from being too small, which is advantageous for shortening the overall length of the imaging lens.

[0156] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (25) is more preferably 1.15, but may also be set to 1.30, 1.45, or 1.60. Also, the upper limit of conditional expression (25) is more preferably 2.90, but may also be set to 2.70, 2.50, or 2.30.

[0157] 1-2-26. Conditional expression (26) -0.80 <f / FL2<0.21 ·····(26) however, f: Focal length of the imaging lens FL2: When the lens adjacent to the object side of the L lens is called the L2 lens, the focal length of the L2 lens.

[0158] In conditional equation (26), if the value of "f / FL2" satisfies the upper limit, the refractive power of the L2 lens can be prevented from becoming too large, which is advantageous in suppressing an increase in the effective diameter of the second lens group.

[0159] On the other hand, if the value of "f / FL2" in condition (26) satisfies the lower limit, the negative refractive power of the L2 lens can be prevented from being too small, which is advantageous for correcting coma aberration from the axial to the periphery.

[0160] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (26) is more preferably -0.78, but may also be set to -0.75, -0.72, or -0.69. Also, the upper limit of conditional expression (26) is more preferably 0.20, but may also be set to 0.19, 0.18, 0.17, 0.16, or 0.15.

[0161] 1-2-27. Conditional expression (27) 0.01 <f1G / f2G<1.00 ·····(27) however, f1G: Focal length of the first lens group f2G: Focal length of the second lens group

[0162] In conditional equation (27), if the value of "f1G / f2G" satisfies the upper limit, the combined refractive power of the second lens group can be prevented from becoming too large. This is advantageous in that it suppresses the increase in the effective diameter of the second lens group, reduces the back focus, allows for a relatively small overall length of the imaging lens, and reduces the angle of the principal ray entering the image plane.

[0163] On the other hand, if the value of "f1G / f2G" in condition (27) satisfies the lower limit, the combined refractive power of the second lens group can be prevented from being too small, which is advantageous in that the angle of the principal ray entering the image plane can be reduced. It is also advantageous for correcting coma aberration from the axial to the periphery.

[0164] Furthermore, in order to obtain the above effect, the lower limit of conditional expression (27) is more preferably 0.05, but may also be set to 0.08, 0.09, or 0.10. Also, the upper limit of conditional expression (27) is more preferably 0.90, but may also be set to 0.80, 0.70, 0.60, 0.50, or 0.40.

[0165] 2. Embodiment of an Imaging Device The imaging device according to the present invention is an imaging device comprising the imaging lens according to the present invention described above and an image sensor that converts the optical image formed by the imaging lens into an electrical signal.

[0166] Here, the image sensor is provided on the image plane side of the imaging lens and is not particularly limited as long as it can convert an optical image into an electrical signal, but solid-state image sensors such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors can also be used. Such solid-state image sensors are preferred for the image sensor in this imaging device. Furthermore, the imaging device may be a fixed-lens type imaging device in which the lens is fixed to the housing, or it may be a lens-interchangeable type imaging device such as an SLR camera or a mirrorless interchangeable-lens camera.

[0167] It is more preferable that the imaging device includes an image processing unit that electrically processes the image data acquired by the image sensor to change the shape of the image, and an image correction program holding unit that holds image correction data and image correction programs used to process the image data in the image processing unit. When a lens is miniaturized, distortion or chromatic aberration is more likely to occur. In this case, it is preferable to store data for correcting distortion or chromatic aberration in advance in the image correction data holding unit, and then use the above data in the image processing unit to correct distortion or chromatic aberration. With such an imaging device, the lens can be miniaturized even further, a beautiful image can be obtained, and the imaging device can be miniaturized.

[0168] The imaging lens according to the present invention, which is incorporated into the imaging device, has high angular resolution near the optical axis and can achieve a wide field of view relative to its focal length. Therefore, by applying this imaging device to a sensing camera on a mobile device such as a vehicle or drone, it becomes possible to accurately detect distant objects in front of the moving object and to recognize objects (obstacles, traffic lights, road signs, etc.) over a wide area around the moving object.

[0169] The embodiments of the present invention described above are one aspect of the present invention and can be modified as appropriate without departing from the spirit of the present invention. Furthermore, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. [Examples]

[0170] (1) Optical configuration of the imaging lens Figure 1 shows a cross-sectional view of the imaging lens of Embodiment 1 of the present invention when it is in focus at infinity. The imaging lens of Embodiment 1 is composed of, in order from the object side, a first lens L1 having negative refractive power, a second lens L2 having positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having negative refractive power, and a sixth lens L6 having positive refractive power. That is, Embodiment 1 has an L=6 configuration, and the sixth lens L6 is the L lens. When focusing from an object at infinity to a nearby object, all lenses are moved along the optical axis toward the object. Furthermore, it is assumed that, as in pan-focus, not only the lens group but also the spacing between the lenses does not change.

[0171] The aperture diaphragm S is located on the image side of the third lens L3. That is, the first lens group consists of the first lens L1 to the third lens L3, and the second lens group consists of the fourth lens L4 to the sixth lens L6.

[0172] In the first lens group, the first lens L1 is a meniscus lens with its concave surface facing the image side, the second lens L2 is a meniscus lens with its concave surface facing the object side, and the third lens L3 is a biconvex lens. In the second lens group, the fourth lens L4 is a biconvex lens, the fifth lens L5 is a biconcave lens, and the sixth lens L6 is a biconvex lens. The fourth and fifth lenses are cemented lenses. The fifth and sixth lenses are in face / edge contact. All of the lenses from the first L1 to the sixth L6 are made of glass.

[0173] In Figure 1, "IMG" represents the imaging plane, specifically the imaging surface of a solid-state image sensor such as a CCD sensor or CMOS sensor, or the film surface of a silver halide film. Furthermore, the object side of the imaging plane "IMG" is equipped with parallel plates that have virtually no refractive power, such as a cover glass "CG" or an infrared shielding filter "IRCF". These points are the same in the cross-sectional lens diagrams shown in other embodiments, so further explanation is omitted below.

[0174] (2) Numerical Examples Next, we will describe a numerical example that applies the specific numerical values ​​of Example 1. Table 1 shows the surface data of the imaging lens of Example 1. In Table 1, the 13th and 14th surfaces are the surface data of the infrared shielding filter IRCF, and the 15th and 16th surfaces are the surface data of the cover glass CG. In Table 1, "surface number" is the order of the lens surfaces counted from the object side to the image plane side, "r" is the radius of curvature of each lens surface (mm), "d" is the spacing between lens surfaces on the optical axis (mm), "Nd" is the refractive index at the d line (wavelength λ = 587.56 nm), and "νd" is the Abbe number at the d line. In the "r" column, "INF" means infinity, and it means that the surface is a plane. Also, a surface with "*" after the surface number indicates that it is an aspherical surface, and "S" indicates that the surface is an aperture diaphragm. The sign of the radius of curvature is positive when it is convex towards the object side. Unless otherwise specified, "refractive index," "Abbe number," "focal length," and "refractive power of the lens" refer to their respective values ​​at the d-line (wavelength λ = 587.56 nm).

[0175] Table 2 shows the specifications of the imaging lens. "f" is the focal length (mm), "FNo" is the F-number, "θ" is the half-angle of view (°), and "CRA" is the angle of the principal rays incident on the image plane (°).

[0176] Table 3 shows the aspheric coefficients for each aspheric surface. These aspheric coefficients are the values ​​obtained when each aspheric shape is defined by the following equation (28). Note that in Table 3, "E-xx" is "×10 -xx It means "...".

[0177] x(Y)=(CY2 ) / [1 + {1 - (1 + k)·(CY) 2} 1 / 2 + A4Y 4 + A6Y 6 + A8Y 8 + A 10 Y 10 + A 12 Y 12 + A 14 Y 14 ···(28) However, Y: Distance from the optical axis in the direction perpendicular to the optical axis x(Y): Displacement in the optical axis direction at Y C: Curvature at the surface vertex k: Conic constant A4: Fourth-order aspheric coefficient A6: Sixth-order aspheric coefficient A8: Eighth-order aspheric coefficient A 10 : Tenth-order aspheric coefficient A 12 : Twelfth-order aspheric coefficient A 14 : Fourteenth-order aspheric coefficient

[0178] Table 4 shows the focal lengths of each lens. Note that the unit of length in Table 4 is all "mm".

[0179] Also, Table 25 shows the numerical values in Conditional Expressions (1) to (27), and Table 26 shows the values of each parameter used to obtain the numerical values of each conditional expression. Note that the unit of length is all "mm", and the unit of the angle of view is all "°".

[0180] The matters regarding each of the above-mentioned tables are the same in the tables shown in other embodiments, so the description will be omitted below.

[0181] [Table 1] Surface number r d Nd νd 1* 11.375 2.000 1.85135 40.10 2* 4.538 3.796 3 -19.423 8.888 1.75520 27.53 4 -15.388 3.601 5* 16.740 5.001 1.59201 67.02 6* -15.282 0.100 7S INF 0.000 8 15.005 5.026 1.61997 63.88 9 -10.181 1.310 1.74077 27.76 10 10.471 1.576 11* 18.901 6.823 1.59201 67.02 12* -30.872 1.120 13 INF 0.500 1.51680 64.20 14 INF 2.174 15 INF 0.500 1.51680 64.20 16 INF 1.008

[0182] [Table 2] f 7.28 FNo 1.60 θ 78.65 CRA 18.2

[0183] [Table 3] Face number k A4A6A8A 10 1 0.00000E+00 -1.14425E-03 1.42408E-05 -1.14944E-07 3.76274E-10 2 -2.40000E+00 8.89550E-04 -1.54371E-05 6.80040E-07 -2.42556E-09 5 0.00000E+00 -3.58033E-05 6.34544E-07 -1.29919E-08 3.43369E-10 6 0.00000E+00 1.15512E-05 9.94474E-07 -6.70179E-09 2.41043E-10 11 0.00000E+00 -3.90113E-04 2.80861E-06 -2.59335E-07 4.85402E-09 12 0.00000E+00 -4.19366E-04 -2.16899E-06 2.13708E-07 -6.46614E-09 Face number A 12 A 14 1 0.00000E+00 0.00000E+00 2 0.00000E+00 0.00000E+00 5 0.00000E+00 0.00000E+00 6 0.00000E+00 0.00000E+00 11 0.00000E+00 0.00000E+00 12 8.54805E-11 -2.78735E-13

[0184] [Table 4] Lens focal length L1 -10.246 L2 50.355 L3 14.326 L4 10.593 L5 -6.785 L6 20.867

[0185] Figure 2 shows the longitudinal aberration diagram for Example 1 when the image is focused at infinity. From left to right, the figures represent spherical aberration (mm), astigmatism (mm), and distortion (%).

[0186] In the spherical aberration diagram, the vertical axis shows the ratio to the open aperture F-number, and the horizontal axis shows the defocus. "FNO" indicates the open aperture F-number. The solid line represents the spherical aberration at the d line (wavelength 587.56 nm), the dashed line represents the spherical aberration at the g line (wavelength 435.84 nm), and the dotted line represents the spherical aberration at the C line (wavelength 656.28 nm).

[0187] In the astigmatism diagram, the vertical axis represents the half-angle of view θ(°) at infinity focus, and the horizontal axis represents the defocus. The astigmatism values ​​are shown at the d-line, with the solid line X representing the sagittal image plane of the d-line and the dashed line Y representing the meridional image plane of the d-line.

[0188] In the distortion diagram, the vertical axis represents the half-angle of view θ (°) at infinity focus, and the horizontal axis represents the distortion (%). The distortion value shown is at the d line.

[0189] The same applies to the longitudinal aberration diagrams shown in other embodiments, so we will omit further explanation below. [Examples]

[0190] (1) Optical configuration of the imaging lens Figure 3 shows a cross-sectional view of the imaging lens of Embodiment 2 of the present invention when it is in focus at infinity. The imaging lens of Embodiment 2 is composed of, in order from the object side, a first lens L1 having negative refractive power, a second lens L2 having positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having negative refractive power, and a sixth lens L6 having positive refractive power. That is, Embodiment 2 has an L=6 configuration, and the sixth lens L6 is the L lens. It is assumed that the spacing between the lens groups does not change when focusing, and that the entire lens group extends. It is also assumed that the spacing between the lenses does not change in the case of pan focus. Furthermore, it is assumed that the spacing between adjacent lens groups changes for the purpose of aberration correction.

[0191] The aperture diaphragm S is located on the image side of the third lens L3. That is, the first lens group consists of the first lens L1 to the third lens L3, and the second lens group consists of the fourth lens L4 to the sixth lens L6.

[0192] In the first lens group, the first lens L1 is a meniscus lens with its concave surface facing the image side, the second lens L2 is a meniscus lens with its concave surface facing the object side, and the third lens L3 is a biconvex lens. In the second lens group, the fourth lens L4 is a biconvex lens, the fifth lens L5 is a biconcave lens, and the sixth lens L6 is a biconvex lens. The fourth and fifth lenses are cemented lenses. All of the lenses from the first lens L1 to the sixth lens L6 are made of glass.

[0193] (2) Numerical Examples Next, we will describe a numerical example in which the specific numerical values ​​of Example 2 are applied. Table 5 shows the surface data of the imaging lens of Example 2. Note that the 13th and 14th surfaces in Table 5 are the surface data of the infrared shielding filter IRCF, and the 15th and 16th surfaces are the surface data of the cover glass CG. Table 6 shows the specifications of the imaging lens. Table 7 shows the aspheric coefficient of each aspherical surface. Table 8 shows the focal length of each lens. Furthermore, Table 25 shows the numerical values ​​in conditional equations (1) to (27), and Table 26 shows the values ​​of each parameter used to determine the numerical values ​​of each conditional equation.

[0194] Furthermore, Figure 4 shows the longitudinal aberration diagram when the object at infinity is in focus in Example 2. From left to right, these are spherical aberration (mm), astigmatism (mm), and distortion (%).

[0195] [Table 5] Face number rd Nd νd 1* 13.714 2.065 1.74397 44.85 2* 4.527 3.665 3 -20.301 9.912 1.75520 27.58 4 -16.821 2.353 5* 16.302 4.299 1.52293 64.10 6* -13.266 0.100 7S INF 0.000 8 12.878 4.376 1.62041 60.32 9 -10.190 1.310 1.75520 27.58 10 11.243 1.508 11* 18.624 7.612 1.48749 70.40 12* -25.707 1.119 13 INF 0.500 1.51680 64.20 14 INF 2.173 15 INF 0.500 1.51680 64.20 16 INF 0.914

[0196] [Table 6] f 7.13 FNo 1.60 θ 78.65 CRA 19.3

[0197] [Table 7] Face number k A4A6A8A 10 1 0.00000E+00 -9.20291E-04 1.17115E-05 -8.81601E-08 2.60390E-10 2 -2.40000E+00 1.36590E-03 -4.91960E-06 -1.29723E-07 2.82506E-08 5 0.00000E+00 -5.59300E-05 9.51352E-07 8.02363E-09 -4.09985E-10 6 0.00000E+00 2.31563E-05 -1.95264E-06 1.29342E-07 -1.94066E-09 11 0.00000E+00 -4.71186E-04 2.12406E-07 4.88236E-08 -1.28281E-09 12 0.00000E+00 -4.49499E-04 2.59843E-06 9.09329E-08 -4.51265E-09 Side number A 12 A 14 1 0.00000E+00 0.00000E+00 2 0.00000E+00 0.00000E+00 5 0.00000E+00 0.00000E+00 6 0.00000E+00 0.00000E+00 11 0.00000E+00 0.00000E+00 12 8.54805E-11 -2.78735E-13

[0198] [Table 8] Lens Focal Length L1 -10.046 L2 58.38 L3 14.721 L4 9.887 L5 -6.896 L6 23.475

Example

[0199] (1) Optical Configuration of Imaging Lens FIG. 5 shows a lens cross-sectional view at infinity focus of the imaging lens of Example 3 according to the present invention. The imaging lens of Example 3 includes, in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a positive refractive power, a third lens L3 having a positive refractive power, a fourth lens L4 having a positive refractive power, a fifth lens L5 having a negative refractive power, and a sixth lens L6 having a positive refractive power. That is, Example 3 has a configuration of L = 6, and the sixth lens L6 is the L-th lens. When focusing from an infinite object to a close object, it is performed by moving all the lenses in the object-side direction along the optical axis.

[0200] The aperture stop S is disposed on the image side of the third lens L3. That is, the first lens group is composed of the first lens L1 to the third lens L3, and the second lens group is composed of the fourth lens L4 to the sixth lens L6.

[0201] In the first lens group, the first lens L1 is a meniscus lens with its concave surface facing the image side, the second lens L2 is a meniscus lens with its concave surface facing the object side, and the third lens L3 is a biconvex lens. In the second lens group, the fourth lens L4 is a biconvex lens, the fifth lens L5 is a biconcave lens, and the sixth lens L6 is a biconvex lens. The fourth and fifth lenses are cemented lenses. All of the lenses from the first lens L1 to the sixth lens L6 are made of glass.

[0202] (2) Numerical Examples Next, we will describe a numerical example in which the specific numerical values ​​of Example 3 are applied. Table 9 shows the surface data of the imaging lens of Example 3. Note that the 13th and 14th surfaces in Table 9 are the surface data of the infrared shielding filter IRCF, and the 15th and 16th surfaces are the surface data of the cover glass CG. Table 10 shows the specifications of the imaging lens. Table 11 shows the aspheric coefficient of each aspherical surface. Table 12 shows the focal length of each lens. Furthermore, Table 25 shows the numerical values ​​in conditional equations (1) to (27), and Table 26 shows the values ​​of each parameter used to determine the numerical values ​​of each conditional equation.

[0203] Furthermore, Figure 6 shows the longitudinal aberration diagram when the object at infinity is in focus in Example 3. From left to right, these are spherical aberration (mm), astigmatism (mm), and distortion (%).

[0204] [Table 9] Face number rd Nd νd 1* 13.967 2.000 1.74397 44.85 2* 4.557 3.695 3 -18.667 10.800 1.75481 27.95 4 -16.978 1.134 5* 18.146 6.000 1.49543 65.79 6* -12.135 0.100 7S INF 0.000 8 13.116 5.380 1.62041 60.32 9 -9.000 1.310 1.75520 27.58 10 10.997 1.547 11* 30.529 6.982 1.58543 62.28 12* -15.595 1.119 13 INF 0.500 1.51680 64.20 14 INF 2.173 15 INF 0.500 1.51680 64.20 16 INF 1.571

[0205] [Table 10] f 7.00 FNo 1.60 θ 78.65 CRA 16.9

[0206] [Table 11] Face number k A4A6A8A 10 1 0.00000E+00 -8.96580E-04 1.19783E-05 -1.00849E-07 3.67547E-10 2 -2.27824E+00 1.26719E-03 -6.75450E-06 1.33479E-07 1.94523E-08 5 0.00000E+00 -4.25866E-05 -5.72906E-07 2.44311E-08 -7.56722E-10 6 0.00000E+00 1.50058E-05 2.29484E-08 2.09744E-08 -6.06757E-10 11 0.00000E+00 -3.62801E-04 -1.57523E-06 -8.14074E-08 4.10265E-09 12 0.00000E+00 -2.62647E-04 -4.22964E-06 2.69933E-07 -6.96151E-09 Side number A 12 A 14 1 0.00000E+00 0.00000E+00 2 0.00000E+00 0.00000E+00 5 0.00000E+00 0.00000E+00 6 0.00000E+00 0.00000E+00 11 0.00000E+00 0.00000E+00 12 8.54805E-11 -2.78735E-13

[0207] [Table 12] Lens focal length L1 -9.996 L2 66.279 L3 15.709 L4 9.487 L5 -6.374 L6 18.676 [Examples]

[0208] (1) Optical configuration of the imaging lens Figure 7 shows a cross-sectional view of the imaging lens of Embodiment 4 of the present invention when it is focused at infinity. The imaging lens of Embodiment 4 is composed of, in order from the object side, a first lens L1 having negative refractive power, a second lens L2 having positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having negative refractive power, and a sixth lens L6 having positive refractive power. That is, Embodiment 4 has an L=6 configuration, and the sixth lens L6 is the L lens. When focusing from an object at infinity to a nearby object, all lenses are moved along the optical axis toward the object.

[0209] The aperture diaphragm S is located on the image side of the third lens L3. That is, the first lens group consists of the first lens L1 to the third lens L3, and the second lens group consists of the fourth lens L4 to the sixth lens L6.

[0210] In the first lens group, the first lens L1 is a meniscus lens with its concave surface facing the image side, the second lens L2 is a meniscus lens with its concave surface facing the object side, and the third lens L3 is a biconvex lens. In the second lens group, the fourth lens L4 is a biconvex lens, the fifth lens L5 is a biconcave lens, and the sixth lens L6 is a biconvex lens. The fourth and fifth lenses are cemented lenses. All of the lenses from the first lens L1 to the sixth lens L6 are made of glass.

[0211] (2) Numerical Examples Next, we will describe a numerical example in which the specific numerical values ​​of Example 4 are applied. Table 13 shows the surface data of the imaging lens of Example 4. Note that the 13th and 14th surfaces in Table 13 are the surface data of the infrared shielding filter IRCF, and the 15th and 16th surfaces are the surface data of the cover glass CG. Table 14 shows the specifications of the imaging lens. Table 15 shows the aspheric coefficient of each aspherical surface. Table 16 shows the focal length of each lens. Furthermore, Table 25 shows the numerical values ​​in conditional equations (1) to (27), and Table 26 shows the values ​​of each parameter used to determine the numerical values ​​of each conditional equation.

[0212] Furthermore, Figure 8 shows the longitudinal aberration diagram when the object at infinity is in focus in Example 4. From left to right, these are spherical aberration (mm), astigmatism (mm), and distortion (%).

[0213] [Table 13] Face number rd Nd νd 1* 9.602 2.000 1.71476 47.34 2* 3.880 4.377 3 -10.446 3.897 1.67623 31.68 4 -10.186 3.301 5* 13.609 4.476 1.54468 65.07 6* -9.909 0.100 7S INF 0.000 8 12.805 4.160 1.66994 52.29 9 -9.000 1.110 1.75520 27.58 10 8.195 0.902 11* 16.658 5.086 1.48749 70.40 12* -21.044 1.119 13 INF 0.500 1.51680 64.20 14 INF 2.173 15 INF 0.500 1.51680 64.20 16 INF 1.006

[0214] [Table 14] f 7.00 FNo 1.60 θ 78.65 CRA 25.3

[0215] [Table 15] Face number k A4A6A8A 10 1 0.00000E+00 -1.24694E-03 1.32321E-05 -8.94377E-08 4.11973E-12 2 -2.20794E+00 1.61981E-03 1.25386E-05 -1.37423E-06 9.15787E-08 5 0.00000E+00 -1.93207E-04 7.81816E-07 -6.61781E-08 1.22817E-09 6 0.00000E+00 3.67711E-05 3.21929E-06 -1.07868E-07 1.93578E-09 11 0.00000E+00 -7.94041E-04 2.75678E-05 -2.01930E-06 4.69042E-08 12 0.00000E+00 -6.31250E-04 -1.16149E-06 1.55029E-07 -6.11390E-09 Side number A 12 A 14 1 0.00000E+00 0.00000E+00 2 0.00000E+00 0.00000E+00 5 0.00000E+00 0.00000E+00 6 0.00000E+00 0.00000E+00 11 0.00000E+00 0.00000E+00 12 8.54805E-11 -2.78735E-13

[0216] [Table 16] Lens focal length L1 -10.665 L2 85.872 L3 11.285 L4 8.543 L5 -5.526 L6 19.956 [Examples]

[0217] (1) Optical configuration of the imaging lens Figure 9 shows a cross-sectional view of the imaging lens of Embodiment 5 of the present invention when it is focused at infinity. The imaging lens of Embodiment 5 is composed of, in order from the object side, a first lens L1 having negative refractive power, a second lens L2 having positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having positive refractive power, a sixth lens L6 having negative refractive power, and a seventh lens L7 having positive refractive power. In other words, Embodiment 5 has an L=7 configuration, and the seventh lens L7 is the L lens. When focusing from an object at infinity to a nearby object, all lenses are moved along the optical axis toward the object.

[0218] The aperture diaphragm S is located on the image side of the fourth lens L4. That is, the first lens group consists of the first lens L1 to the fourth lens L4, and the second lens group consists of the fifth lens L5 to the seventh lens L7.

[0219] In the first lens group, the first lens L1 is a meniscus lens with its concave surface facing the image side, the second lens L2 is a meniscus lens with its concave surface facing the object side, the third lens L3 is a biconvex lens, and the fourth lens L4 is a biconvex lens. In the second lens group, the fifth lens L5 is a biconvex lens, the sixth lens L6 is a biconcave lens, and the seventh lens L7 is a biconvex lens. The fifth and sixth lenses are cemented lenses. All of the lenses from the first lens L1 to the seventh lens L7 are made of glass.

[0220] (2) Numerical Examples Next, we will describe a numerical example in which the specific numerical values ​​of Example 5 are applied. Table 17 shows the surface data of the imaging lens of Example 5. Note that the 15th and 16th surfaces in Table 17 are the surface data of the infrared shielding filter IRCF, and the 17th and 18th surfaces are the surface data of the cover glass CG. Table 18 shows the specifications of the imaging lens. Table 19 shows the aspheric coefficient of each aspherical surface. Table 20 shows the focal length of each lens. Furthermore, Table 25 shows the numerical values ​​in conditional equations (1) to (27), and Table 26 shows the values ​​of each parameter used to determine the numerical values ​​of each conditional equation.

[0221] Furthermore, Figure 10 shows the longitudinal aberration diagram when the object at infinity is in focus in Example 5. From left to right, these are spherical aberration (mm), astigmatism (mm), and distortion (%).

[0222] [Table 17] Face number rd Nd νd 1* 10.558 2.000 1.74397 44.85 2* 4.021 4.174 3 -12.714 5.583 1.58983 60.26 4 -13.029 0.100 5 59.711 4.500 1.75319 27.66 6 -61.579 0.543 7* 16.643 4.188 1.48749 70.40 8* -13.033 0.100 9S INF 0.000 10 11.303 4.160 1.62263 59.88 11 -9.000 1.110 1.75520 27.58 12 9.121 0.902 13* 18.402 6.222 1.62041 60.32 14* -34.023 1.119 15 INF 0.500 1.51680 64.20 16 INF 2.173 17 INF 0.500 1.51680 64.20 18 INF 1.008

[0223] [Table 18] f 7.06 FNo 1.60 θ 78.65 CRA 23.3

[0224] [Table 19] Surface number k A4A6A8A 10 1 0.00000E+00 -1.19617E-03 1.39902E-05 -1.08533E-07 3.00148E-10 2 -2.04900E+00 1.24638E-03 -4.14566E-06 2.49176E-08 2.68817E-08 7 0.00000E+00 -1.00274E-05 -1.78419E-06 6.89992E-08 -1.87935E-09 8 0.00000E+00 -9.78344E-05 2.54004E-06 -4.30295E-08 -7.15465E-11 13 0.00000E+00 -7.75082E-04 1.21690E-05 -1.10041E-06 2.80554E-08 14 0.00000E+00 -5.44541E-04 -2.00419E-06 1.76189E-07 -5.20975E-09 Face number A 12 A 14 1 0.00000E+00 0.00000E+00 2 0.00000E+00 0.00000E+00 7 0.00000E+00 0.00000E+00 8 0.00000E+00 0.00000E+00 13 0.00000E+00 0.00000E+00 14 8.54805E-11 -2.78735E-13

[0225] [Table 20] Lens focal length L1 -10.037 L2 159.929 L3 40.901 L4 15.72 L5 8.734 L6 -5.844 L7 20.166 [Examples]

[0226] (1) Optical configuration of the imaging lens Figure 11 shows a cross-sectional view of the imaging lens of Embodiment 6 of the present invention when it is focused at infinity. The imaging lens of Embodiment 6 is composed of, in order from the object side, a first lens L1 having negative refractive power, a second lens L2 having positive refractive power, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, a fifth lens L5 having positive refractive power, a sixth lens L6 having negative refractive power, a seventh lens L7 having positive refractive power, and an eighth lens L8 having positive refractive power. In other words, Embodiment 6 has an L=8 configuration, and the eighth lens L8 is the L lens. When focusing from an object at infinity to a nearby object, all lenses are moved along the optical axis toward the object.

[0227] The aperture diaphragm S is located on the image side of the fourth lens L4. That is, the first lens group consists of the first lens L1 to the fourth lens L4, and the second lens group consists of the fifth lens L5 to the eighth lens L8.

[0228] In the first lens group, the first lens L1 is a meniscus lens with its concave surface facing the image side, the second lens L2 is a meniscus lens with its concave surface facing the object side, the third lens L3 is a biconvex lens, and the fourth lens L4 is a biconvex lens. In the second lens group, the fifth lens L5 is a biconvex lens, the sixth lens L6 is a biconcave lens, the seventh lens L7 is a biconvex lens, and the eighth lens L8 is a biconvex lens. The fifth and sixth lenses are cemented lenses. All of the lenses from the first L1 to the seventh L7 are made of glass.

[0229] (2) Numerical Examples Next, we will describe a numerical example in which the specific numerical values ​​of Example 6 are applied. Table 21 shows the surface data of the imaging lens of Example 6. Note that the 17th and 18th surfaces in Table 21 are the surface data of the cover glass CG. Table 22 shows the specifications of the imaging lens. Table 23 shows the aspheric coefficient of each aspherical surface. Table 24 shows the focal length of each lens. Furthermore, Table 25 shows the numerical values ​​in conditional equations (1) to (27), and Table 26 shows the values ​​of each parameter used to determine the numerical values ​​of each conditional equation.

[0230] Furthermore, Figure 12 shows the longitudinal aberration diagram when the object at infinity is in focus in Example 6. From left to right, these are spherical aberration (mm), astigmatism (mm), and distortion (%).

[0231] [Table 21] Face number rd Nd νd 1* 10.504 2.000 1.74397 44.85 2* 3.974 4.180 3 -13.861 6.575 1.61876 60.41 4 -15.463 0.100 5 122.418 2.856 1.75520 27.58 6 -38.027 1.867 7* 17.239 3.950 1.48749 70.40 8* -15.158 0.100 9S INF 0.000 10 11.563 4.337 1.62041 60.32 11 -9.000 1.110 1.75520 27.58 12 10.285 0.902 13* 33.537 4.434 1.62041 60.32 14* -63.862 0.100 15 60.000 2.000 1.49712 69.36 16 -31.645 1.965 17 INF 1.000 1.51680 64.20 18 INF 3.006

[0232] [Table 22] f 7.01 FNo 1.60 θ 78.65 CRA 21.5

[0233] [Table 23] Face number k A4A6A8A 10 1 0.00000E+00 -1.19553E-03 1.38196E-05 -1.14408E-07 3.65691E-10 2 -2.04878E+00 1.32680E-03 -1.66476E-05 5.32779E-07 9.87310E-09 7 0.00000E+00 3.63562E-05 -1.56932E-06 8.51137E-08 -1.84672E-09 8 0.00000E+00 -9.26304E-05 8.69022E-07 4.34499E-08 -1.33792E-09 13 0.00000E+00 -9.04324E-04 5.40618E-06 -6.89325E-07 2.14533E-08 14 0.00000E+00 -5.14039E-04 -2.37276E-06 1.76880E-07 -4.68310E-09 Face number A 12 A 14 1 0.00000E+00 0.00000E+00 2 0.00000E+00 0.00000E+00 7 0.00000E+00 0.00000E+00 8 0.00000E+00 0.00000E+00 13 0.00000E+00 0.00000E+00 14 8.54805E-11 -2.78735E-13

[0234] [Table 24] Lens focal length L1 -9.883 L2 380.097 L3 38.715 L4 17.234 L5 8.874 L6 -6.202 L7 36.072 L8 41.98

[0235] [Table 25] Conditional Expression Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 (1) f / f2 0.145 0.122 0.106 0.082 0.044 0.018 (2) RgLf / RgLr -0.612 -0.724 -1.958 -0.792 -0.541 -1.896 (3) OAL / f 5.959 5.960 6.397 4.955 5.500 5.778 (4) RgLf-DairLF 9.651 8.542 20.596 8.275 9.599 50.197 (5) fs / f 1.453 1.386 1.354 1.219 1.235 1.267 (6) f×tan(θ) / Yh 5.215 5.090 4.975 4.914 4.994 5.027 (7) Ng1 1.851 1.744 1.744 1.715 1.744 1.744 (8) Ng2 1.755 1.755 1.755 1.676 1.590 1.619 (9) f1G / f 1.222 1.308 1.389 1.197 1.320 1.411 (10) OAL / Yh 6.260 6.111 6.411 4.905 5.533 5.851 (11) fAir / f -3.667 -3.551 -2.953 -2.321 -2.968 -3.570 (12) (RAf+RAr) / (RAf-RAr) -3.484 -4.046 -2.126 -2.937 -2.965 -1.885 (13) Dg2 / f 1.220 1.390 1.542 0.556 0.790 0.938 (14) NgL 1.592 1.487 1.585 1.487 1.620 1.497 (15) Rg1f / f 1.561 1.923 1.994 1.370 1.493 1.499 (16) f12 / f -2.875 -2.695 -2.697 -2.234 -1.875 -1.758 (17) fL / f 2.863 3.291 2.666 2.848 2.852 5.992 (18) Vg1 40.104 44.850 44.850 47.342 44.850 44.850 (19) Vg2 27.530 27.579 27.948 31.676 60.256 60.408 (20) NgL2 1.741 1.755 1.755 1.755 1.755 1.620 (21) VgL2 27.761 27.579 27.579 27.579 27.579 60.323 (22) VgL 67.022 70.405 62.277 70.405 60.323 69.357 (23) BF / f 0.728 0.744 0.838 0.757 0.750 0.852 (24) f1 / f -1.406 -1.409 -1.427 -1.522 -1.420 -1.411 (25) f3 / f 1.966 2.064 2.242 1.611 2.224 2.460 (26) f / fL2 -0.607 -0.578 -0.591 -0.716 -0.695 0.194 (27) f1G / f2G 0.144 0.179 0.269 0.434 0.108 0.166

[0236] [Table 26] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 f 7.288 7.132 7.006 7.006 7.070 7.006 f1 -10.246 -10.046 -9.996 -10.665 -10.037 -9.883 f2 50.355 58.380 66.279 85.872 159.929 380.098 f3 14.326 14.721 15.709 11.285 15.720 17.234 f12 -20.950 -19.221 -18.896 -15.655 -13.255 -12.315 fs 10.593 9.887 9.487 8.543 8.734 8.874 fL2 -12.013 -12.336 -11.846 -9.787 -10.173 36.072 fL 20.867 23.475 18.676 19.956 20.166 41.980 f1G 8.904 9.331 9.729 8.386 9.329 9.885 f2G 61.764 52.146 36.185 77.767 56.049 41.114 Yh 6.937 6.956 6.991 7.077 7.028 6.918 OAL 43.426 42.505 44.818 34.713 38.885 40.481 BF 5.305 5.306 5.870 5.305 5.304 5.971 Ng1 1.851 1.744 1.744 1.715 1.744 1.744 Ng2 1.755 1.755 1.755 1.676 1.590 1.619 NgL2 1.741 1.755 1.755 1.755 1.755 1.620 NgL 1.592 1.487 1.585 1.487 1.620 1.497 RgLf 18.901 18.624 30.529 16.658 18.402 60.000 RgLr -30.872 -25.707 -15.595 -21.044 -34.023 -31.645 DairLF 9.250 10.082 9.933 8.383 8.803 9.803 Vg1 40.104 44.850 44.850 47.342 44.850 44.850 Vg2 27.530 27.579 27.948 31.676 60.256 60.408 VgL 67.022 70.405 62.277 70.405 60.323 69.357 VgL2 27.761 27.579 27.579 27.579 27.579 60.323 Dg2 8.888 9.912 10.800 3.897 5.583 6.575 fAir -26.725 -25.324 -20.688 -16.260 -20.986 -25.010 θ 78.650 78.650 78.650 78.650 78.650 78.650 RAf 10.471 11.243 10.997 8.195 9.121 10.285 RAr 18.901 18.624 30.529 16.658 18.402 33.537 Rg1f 11.375 13.714 13.967 9.602 10.558 10.504

[0237] (summary) The imaging lens according to the first aspect of the present invention is characterized by comprising a total of L lenses, including, in order from the object side, a first lens having a concave surface on the image side and negative refractive power, a second lens having a concave surface on the object side and positive refractive power, and a second L lens having positive refractive power that is positioned closest to the image side, wherein L satisfies 6 ≤ L ≤ 8, the aperture is positioned between the first lens and the L lens, the lens group positioned closer to the object than the aperture is the first lens group, the lens group positioned closer to the image than the aperture is the second lens group, and the following conditional equation is satisfied. 0.000 <f / f2<0.147 ·····(1) however, f: Focal length of the imaging lens f2: Focal length of the second lens

[0238] In the first embodiment, the imaging lens according to the second aspect of the present invention may satisfy the following condition. -2.00 <RgLf / RgLr<-0.52 ·····(2) however, RgLf: Radius of curvature of the object side of the aforementioned L lens RgLr: Radius of curvature on the image side of the aforementioned L lens

[0239] The imaging lens according to the third aspect of the present invention may satisfy the following conditional expression in the first and second aspects. 4.10 <OAL / f<9.00 ·····(3) however, OAL: Total length from the first lens to the image plane

[0240] The imaging lens according to the fourth aspect of the present invention may satisfy the following condition in the first to third aspects. 7.70 <RgLf-DairLF<100.00 ·····(4) however, RgLf: Radius of curvature of the object side of the aforementioned L lens DairLF: The sum of the air-equivalent distances along the optical axis from the vertex of the object's side surface to the image plane of the aforementioned L lens.

[0241] The imaging lens according to the fifth aspect of the present invention may satisfy the following condition in the first to fourth aspects. 0.90 <fs / f<2.80 ·····(5) however, fs: The focal length of the lens positioned adjacent to the image side of the aperture.

[0242] The imaging lens according to the sixth aspect of the present invention may satisfy the following condition in the first to fifth aspects. 4.5 <f×tan(θ) / Yh<5.5 ·····(6) however, θ: Maximum half-angle of view when the imaging lens is focused at infinity. Yh: Maximum image height

[0243] The imaging lens according to the seventh aspect of the present invention may satisfy the following condition in the first to sixth aspects. 1.67 <Ng1<1.88 ·····(7) however, Ng1: Refractive index of the d line of the first lens.

[0244] The imaging lens according to the eighth aspect of the present invention may satisfy the following condition in the first to seventh aspects. 1.55 <Ng2<1.90 ·····(8) however, Ng2: Refractive index of the d line of the second lens.

[0245] The imaging lens according to the ninth aspect of the present invention may satisfy the following conditional expression in the first to eighth aspects. 0.50 <f1G / f<2.00 ·····(9) however, f1G: Focal length of the first lens group

[0246] The imaging lens according to the tenth aspect of the present invention may satisfy the following condition in the first to ninth aspects. 4.5 <OAL / Yh<7.0 ·····(10) however, OAL: Total length from the first lens to the image plane Yh: Maximum image height

[0247] The imaging lens according to the eleventh aspect of the present invention may satisfy the following condition in the first to tenth aspects. -4.5 <FAir / f<-0.1 ·····(11) however, FAir: In the second lens group, the focal length of the air lens Air, which has a negative refractive power due to the air between the lenses, where the distance between the lenses (distance parallel to the optical axis) is narrower at the periphery than at the center.

[0248] In the twelfth aspect of the present invention, the imaging lens may satisfy the following condition in the eleventh aspect. -5.00<(RAf+RAr) / (RAf-RAr)<-1.00 ····(12) however, RAf: Radius of curvature of the air lens Air on the object side. RAr: Radius of curvature on the image plane side of the aforementioned air lens Air.

[0249] The imaging lens according to the thirteenth aspect of the present invention may satisfy the following conditional expression in the first to twelfth aspects. 0.40 <Dg2 / f<1.70 ·····(13) however, Dg2: Center thickness of the second lens mentioned above

[0250] The imaging lens according to the fourteenth aspect of the present invention is as follows, in the first to thirteenth aspects: 1.44 <NgL<1.70 ·····(14) however, NgL: Refractive index of the d line of the aforementioned L lens

[0251] The imaging lens according to the fifteenth aspect of the present invention may satisfy the following conditional expression in the first to fourteenth aspects. 1.20 <Rg1f / f<2.40 ·····(15) however, Rg1f: Radius of curvature of the object side of the first lens.

[0252] The imaging lens according to the sixteenth aspect of the present invention may satisfy the following condition in the first to fifteenth aspects. -3.20 <f12 / f<-1.30 ·····(16) however, f12: Combined focal length of the first and second lenses

[0253] The imaging device according to the first aspect of the present invention is characterized by comprising an imaging lens according to the first to sixteenth aspects, and an image sensor that converts an optical image formed by the imaging lens into an electrical signal. [Industrial applicability]

[0254] The imaging lens according to the present invention can widen the field of view while maintaining resolution and increase the angular resolution near the optical axis. In other words, it is suitable for imaging lenses for mobile devices such as vehicles and drones, which are required to accurately detect distant objects in front of the moving object in the direction of travel, and to recognize objects around the moving object (obstacles, traffic lights, road signs, etc.) over a wide range. [Explanation of Symbols]

[0255] L1 First Lens L2 Second Lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens L8 8th lens S Aperture diaphragm IRCF Infrared Shielding Filter CG cover glass IMG imaging plane

Claims

1. Starting from the object side, A first lens having a concave surface on the image side and negative refractive power, A second lens having a concave surface on the object side and positive refractive power, It consists of a total of L lenses, including the L lens, which is positioned closest to the image and has positive refractive power. L satisfies 6 ≤ L ≤ 8, The aperture is positioned between the first lens and the L lens. An imaging lens characterized in that a group of lenses positioned closer to the object than the aperture is designated as the first lens group, and a group of lenses positioned closer to the image than the aperture is designated as the second lens group, and the following conditional equation is satisfied. 0.000<f / f2<0.147 (1) however, f: Focal length of the imaging lens f2: Focal length of the second lens

2. The imaging lens according to claim 1, satisfying the following conditional expression. -2.00<RgLf / RgLr<-0.52 (2) however, RgLf: Radius of curvature of the object side of the L lens. RgLr: Radius of curvature on the image side of the L lens.

3. The imaging lens according to claim 1, satisfying the following conditional expression. 4.10<OAL / f<9.00 (3) however, OAL: Total length from the first lens to the image plane

4. The imaging lens according to claim 1, satisfying the following conditional expression. 7.70<RgLf-DairLF<100.00 (4) however, RgLf: Radius of curvature of the object side of the L lens. DirLF: The sum of the air-equivalent distances along the optical axis from the vertex of the surface of the object side of the L lens to the image plane.

5. The imaging lens according to claim 1, satisfying the following conditional expression. 0.90<fs / f<2.80 (5) however, fs: The focal length of the lens positioned adjacent to the image side of the aperture.

6. The imaging lens according to claim 1, satisfying the following conditional expression. 4.5<f×tan(θ) / Yh<5.5 (6) however, θ: Maximum half-angle of view when the imaging lens is focused at infinity. Yh: Maximum image height

7. The imaging lens according to claim 1, satisfying the following conditional expression. 1.67<Ng1<1.88 (7) however, Ng1: Refractive index of the d line of the first lens

8. The imaging lens according to claim 1, satisfying the following conditional expression. 1.55<Ng2<1.90 (8) however, Ng2: Refractive index of the d line of the second lens.

9. The imaging lens according to claim 1, satisfying the following conditional expression. 0.50<f1G / f<2.00 (9) however, f1G: Focal length of the first lens group

10. The imaging lens according to claim 1, satisfying the following conditional expression. 4.5<OAL / Yh<7.0 (10) however, OAL: Total length from the first lens to the image plane Yh: Maximum image height

11. The imaging lens according to claim 1, satisfying the following conditional expression. -4.5<FAir / f<-0.1 (11) however, FAIR: The focal length of the air lens Air in the second lens group, which has a negative refractive power due to the air between the lenses, where the distance between the lenses (distance parallel to the optical axis) is narrower at the periphery than at the center.

12. The imaging lens according to claim 11, satisfying the following conditional expression. -5.00<(RAf+RAr) / (RAf-RAr)<-1.00 (12) however, RAf: Radius of curvature of the air lens Air on the object side. RAr: Radius of curvature of the image plane side of the air lens Air.

13. The imaging lens according to claim 1, satisfying the following conditional expression. 0.40<Dg2 / f<1.70 (13) however, Dg2: Center thickness of the second lens

14. The imaging lens according to claim 1, satisfying the following conditional expression. 1.44<NgL<1.70 (14) however, NgL: Refractive index of the d line of the L lens.

15. The imaging lens according to claim 1, satisfying the following conditional expression. 1.20<Rg1f / f<2.40 (15) however, Rg1f: Radius of curvature of the object side of the first lens

16. The imaging lens according to claim 1, satisfying the following conditional expression. -3.20<f12 / f<-1.30 (16) however, f12: Combined focal length of the first lens and the second lens

17. An imaging device comprising an imaging lens as described in claim 1, and an image sensor that converts an optical image formed by the imaging lens into an electrical signal.

Images