Imaging lens and imaging apparatus

Abstract

To provide an imaging lens that maintains favorable optical performance by correcting various aberrations including chromatic aberration in the medium infrared wavelength range, and an imaging apparatus comprising the imaging lens.SOLUTION: An imaging lens includes a plurality of lenses and a stop. Assuming that a refractive index of each lens included in the imaging lens at a wavelength of 4000 nm is N4, at least one lens of the plurality of lenses is an LA lens that satisfies N4<1.5, and at least one lens of the plurality of lenses is an LB lens that satisfies 2<N4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology of the present disclosure relates to an imaging lens and an imaging device. [Background technology]

[0002] Conventionally, infrared light has been used in imaging with FA (Factory Automation) cameras, MV (Machine Vision) cameras, surveillance cameras, vehicle-mounted cameras, etc. For example, a lens system described in Patent Document 1 below is known as an infrared camera lens system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-287950 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for imaging lenses that maintain good optical performance in the mid-infrared wavelength range by correcting various aberrations including chromatic aberration.

[0005] The present disclosure provides an imaging lens in which various aberrations including chromatic aberration are corrected in the mid-infrared wavelength range to maintain good optical performance, and an imaging device including this imaging lens. [Means for solving the problem]

[0006] One aspect of the present disclosure is an imaging lens including a plurality of lenses and an aperture, in which, when the refractive index of each lens included in the imaging lens at a wavelength of 4000 nm is N4, at least one of the plurality of lenses is N4<1.5 (1A) At least one of the plurality of lenses is an LA lens that satisfies the conditional formula (1A) represented by 2 <N4 (1B) This is an LB lens that satisfies conditional formula (1B) expressed by:

[0007] In the above aspect, it is preferable that at least one LA lens is disposed on the object side of the aperture stop.

[0008] In the above aspect, it is preferable that at least one LB lens is disposed on the object side of the aperture stop.

[0009] In the above aspect, it is preferable that at least one LA lens is disposed on the image side of the aperture stop.

[0010] In the above aspect, it is preferable that at least one LB lens is disposed on the image side of the aperture stop.

[0011] The imaging lens of the above embodiment may be configured to include at least two aspheric lenses.

[0012] All of the lenses included in the imaging lens of the above aspect N4<5 (1C) It is preferable that conditional formula (1C) be satisfied.

[0013] If the sum of the distance on the optical axis from the lens surface of the imaging lens closest to the object side to the lens surface of the imaging lens closest to the image side and the back focus of the imaging lens in the air equivalent distance at a wavelength of 4000 nm is taken as TL, and the focal length of the imaging lens at a wavelength of 4000 nm is taken as f, the imaging lens of the above embodiment is TL / f<20 (2) It is preferable to satisfy conditional expression (2) expressed as follows:

[0014] When the back focus of the imaging lens at a wavelength of 4000 nm in air equivalent distance is Bf and the focal length of the imaging lens at a wavelength of 4000 nm is f, the imaging lens of the above embodiment is 0.3 <Bf / f (3) It is preferable to satisfy conditional expression (3) expressed as follows:

[0015] If the refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3 and the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, the imaging lens of the above embodiment has the following refractive index: 100<(N4-1) / (N3-N5)<400 (4A) It is preferable that the optical system includes at least one aspheric lens that satisfies conditional formula (4A) expressed as follows:

[0016] At least one of the lenses included in the imaging lens has a concave lens surface, and at least one of the lenses included in the imaging lens has a convex lens surface. If the refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3 and the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, then At least one of the lenses having the concave lens surface is 0<(N4-1) / (N3-N5)<180 (4B) Satisfying conditional formula (4B) expressed by At least one of the lenses having a convex lens surface is 180<(N4-1) / (N3-N5)<400 (4C) It is preferable that conditional formula (4C) be satisfied.

[0017] If the refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3 and the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, the imaging lens of the above embodiment has the following refractive index: 0<(N4-1) / (N3-N5)<250 (4D) It is preferable that the optical fiber includes at least one spherical lens which satisfies conditional formula (4D) represented by the following formula (4D):

[0018] The imaging lens of the above embodiment preferably includes at least three lenses.

[0019] If TL is the sum of the distance on the optical axis from the lens surface of the imaging lens closest to the object side to the lens surface of the imaging lens closest to the image side and the back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm, and Y is the maximum image height of the imaging lens, then the imaging lens of the above embodiment is 0.5 <TL / 2Y<20 (5) It is preferable to satisfy conditional expression (5) expressed as follows:

[0020] If the composite focal length of all lenses on the object side of the aperture at a wavelength of 4000 nm is fF, and the composite focal length of all lenses on the image side of the aperture at a wavelength of 4000 nm is fR, the imaging lens of the above embodiment is |fF / fR|<40 (6) It is preferable to satisfy conditional expression (6) expressed as follows:

[0021] The LA lens is preferably constructed from a crystalline material.

[0022] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive or negative refractive power, a second lens having positive refractive power, and a third lens having negative refractive power.

[0023] It is preferable that a negative lens is disposed adjacent to the image side of the aperture. In a configuration in which a negative lens is disposed adjacent to the image side of the aperture, a positive lens may be disposed adjacent to the image side of the negative lens.

[0024] Another aspect of the present disclosure is an imaging device including the imaging lens of the above aspect of the present disclosure and an imaging element that captures an image formed by the imaging lens of the above aspect.

[0025] In addition, in this specification, "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, the following may be included: a lens that has substantially no refractive power, optical elements other than lenses such as an aperture, a filter, and a cover glass, and mechanical parts such as a lens flange, a lens barrel, an image sensor, and an image stabilization mechanism.

[0026] In this specification, the mid-infrared wavelength region refers to a wavelength band of 3000 nm to 5000 nm. The unit of wavelength, "nm," is nanometer. In this specification, an aspherical lens is a lens with at least one lens surface having an aspherical shape, and a spherical lens is a lens with two lens surfaces, one on the object side and one on the image side, having a spherical shape. In this specification, a compound aspherical lens (a lens in which a lens (e.g., a spherical lens) and an aspherical film formed on the lens are integrally configured to function as a single aspherical lens as a whole) is not considered as a cemented lens, but is treated as a single lens. The radius of curvature, sign of refractive power, and surface shape of a lens including an aspherical surface are those in the paraxial region, unless otherwise specified.

[0027] The "focal length" used in the conditional expressions is the paraxial focal length. The "distance on the optical axis" used in the conditional expressions is the geometric distance unless otherwise specified. The values ​​used in the conditional expressions are values ​​when the lens is focused on an object at infinity unless otherwise specified. Effect of the Invention

[0028] According to the present disclosure, it is possible to provide an imaging lens in which various aberrations including chromatic aberration are corrected in the mid-infrared wavelength range and good optical performance is maintained, and an imaging device including this imaging lens. [Brief description of the drawings]

[0029] [Figure 1] 1 is a cross-sectional view showing a configuration of an imaging lens according to an embodiment and a light beam, which corresponds to the imaging lens of Example 1. FIG. [Diagram 2] 1 is a cross-sectional view showing a configuration of an imaging lens according to a first embodiment. [Diagram 3] 3A to 3C are diagrams showing various aberrations of the imaging lens of Example 1. [Figure 4] FIG. 11 is a cross-sectional view showing the configuration of an imaging lens according to a second embodiment. [Diagram 5] 6A to 6C are diagrams showing various aberrations of the imaging lens of Example 2. [Figure 6] FIG. 11 is a cross-sectional view showing the configuration of an imaging lens according to a third embodiment. [Figure 7] 11A to 11C are diagrams showing various aberrations of the imaging lens of Example 3. [Figure 8] FIG. 11 is a cross-sectional view showing the configuration of an imaging lens according to a fourth embodiment. [Figure 9] 11A to 11C are diagrams showing various aberrations of the imaging lens of Example 4. [Figure 10] FIG. 11 is a cross-sectional view showing the configuration of an imaging lens according to a fifth embodiment. [Figure 11] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 5. [Figure 12] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to a sixth embodiment. [Figure 13] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 6. [Figure 14] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to a seventh embodiment. [Figure 15] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 7. [Figure 16] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to an eighth embodiment. [Figure 17] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 8. [Figure 18] FIG. 13 is a cross-sectional view showing the configuration of an imaging lens according to a ninth embodiment. [Figure 19] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 9. [Figure 20] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to a tenth embodiment. [Figure 21] 21A to 21C are diagrams showing various aberrations of the imaging lens of Example 10. [Figure 22] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to an eleventh embodiment. [Figure 23] 13A to 13C are diagrams showing various aberrations of the imaging lens of Example 11. [Figure 24] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to a twelfth embodiment. [Diagram 25] 23A to 23C are diagrams showing various aberrations of the imaging lens of Example 12. [Figure 26] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to a thirteenth embodiment. [Figure 27] 23A to 23C are diagrams showing various aberrations of the imaging lens of Example 13. [Figure 28] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens of Example 14. [Figure 29] 21A to 21C are diagrams showing various aberrations of the imaging lens of Example 14. [Diagram 30] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens of Example 15. [Diagram 31] 21A to 21C are diagrams showing various aberrations of the imaging lens of Example 15. [Diagram 32] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to a sixteenth embodiment. [Diagram 33] 21A to 21C are diagrams showing various aberrations of the imaging lens of Example 16. [Diagram 34] FIG. 21 is a cross-sectional view showing the configuration of an imaging lens according to a seventeenth embodiment. [Diagram 35] 21A to 21C are diagrams showing various aberrations of the imaging lens of Example 17. [Diagram 36] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to an eighteenth embodiment. [Figure 37] 21A to 21C are diagrams showing various aberrations of the imaging lens of Example 18. [Figure 38] FIG. 23 is a cross-sectional view showing the configuration of an imaging lens according to a nineteenth embodiment. [Figure 39] 23A to 23C are diagrams showing various aberrations of the imaging lens of Example 19. [Diagram 40] 1 is a schematic diagram illustrating the configuration of an imaging device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, in order to avoid redundancy, the same symbols are used in formulas for which the same definitions are used, and duplicate explanations of the symbols will be omitted.

[0031] Fig. 1 shows a cross-sectional view of the configuration of an imaging lens according to an embodiment of the present disclosure and light beams. In Fig. 1, an on-axis light beam B0 and an off-axis light beam B1 with a maximum half angle of view are shown as light beams. In Fig. 1, the left side is the object side and the right side is the image side, and a state in which an object at infinity is focused is shown. The example shown in Fig. 1 corresponds to the imaging lens of Example 1 described later.

[0032] In Fig. 1, assuming that the imaging lens is applied to an imaging device, an example is shown in which a parallel plate-like optical member PP is disposed between the imaging lens and an image surface Sim. The optical member PP is a member assuming various filters and / or cover glass, etc. The optical member PP is a member that does not have refractive power. It is also possible to configure an imaging device without the optical member PP.

[0033] The imaging lens of the present disclosure includes multiple lenses and an aperture stop St. As an example, the imaging lens in Fig. 1 is a fixed focal length lens, and is composed of lenses L1 to L3, an aperture stop St, and lenses L4 to L7, in that order from the object side to the image side along the optical axis Z. Note that the aperture stop St in Fig. 1 does not indicate the size or shape, but indicates the position in the optical axis direction.

[0034] In the formulas in the following specification, the refractive index of each lens included in the imaging lens at a wavelength of 4000 nm is N4. In the technology of the present disclosure, a lens that satisfies the following conditional formula (1A) is called an LA lens, and a lens that satisfies the following conditional formula (1B) is called an LB lens. N4<1.5 (1A) 2 <N4 (1B)

[0035] In addition, in the technology of the present disclosure, v4 defined by the following formula is conveniently called the Abbe number. ν4=(N4-1) / (N3-N5) Here, the refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is denoted as N3, and the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is denoted as N5. The above Abbe number represents the degree of dispersion.

[0036] Among the multiple lenses included in the imaging lens of the present disclosure, at least one is an LA lens and at least one is an LB lens. Since an optical material with a relatively low refractive index used in the mid-infrared wavelength region has a small Abbe number and a large dispersion, it is easy to correct chromatic aberration by using at least one LA lens that satisfies conditional formula (1A). Furthermore, an optical material with a relatively high refractive index used in the mid-infrared wavelength region has a large Abbe number and a small dispersion, it is easy to correct various aberrations while suppressing the occurrence of chromatic aberration by using at least one LB lens that satisfies conditional formula (1B). According to the technology of the present disclosure, by combining an LA lens and an LB lens, it is easy to provide an imaging lens in which various aberrations including chromatic aberration are well corrected in a wide wavelength region of 3000 nm to 5000 nm.

[0037] As an example, in the imaging lens of FIG. 1, lenses L2, L3, and L5 to L7 are LA lenses, and lenses L1 and L4 are LB lenses.

[0038] At least one of the LA lenses included in the imaging lens preferably satisfies the following conditional formula (1A-1). By ensuring that the corresponding value of conditional formula (1A-1) is not equal to or less than the lower limit, it becomes easy to strengthen the refractive power of the lens that corrects chromatic aberration, and therefore it becomes easy to improve the effect of correcting chromatic aberration. At least one of the LA lenses included in the imaging lens more preferably satisfies the following conditional formula (1A-2), even more preferably satisfies the following conditional formula (1A-3), and even more preferably satisfies the following conditional formula (1A-4). 1.2 <N4<1.5 (1A-1) 1.2 <N4<1.47 (1A-2) 1.2 <N4<1.45 (1A-3) 1.3 <N4<1.42 (1A-4)

[0039] At least one of the LB lenses included in the imaging lens preferably satisfies the following conditional formula (1B-1), more preferably satisfies the following conditional formula (1B-2), even more preferably satisfies the following conditional formula (1B-3), and even more preferably satisfies the following conditional formula (1B-4). By ensuring that the corresponding value of conditional formula (1B-3) is not equal to or greater than the upper limit, it becomes possible to select a material that can be practically used. Also, by ensuring that the corresponding value of conditional formula (1B-4) is not equal to or greater than the upper limit, it becomes easy to prevent the cost of materials from increasing. 2.1 <N4 (1B-1) 2.4 <N4 (1B-2) 2.45 <N4<5 (1B-3) 2.45 <N4<4.5 (1B-4)

[0040] It is preferable that at least one LA lens is disposed on the object side of the aperture diaphragm St. By disposing the LA lens on the object side of the aperture diaphragm St, it becomes easy to correct chromatic aberration on the object side of the aperture diaphragm St, and therefore it becomes easy to suppress overall chromatic aberration.

[0041] It is preferable that at least one LB lens is disposed on the object side of the aperture diaphragm St. By disposing the LB lens on the object side of the aperture diaphragm St, it becomes easy to suppress chromatic aberration that occurs on the object side of the aperture diaphragm St, and therefore it becomes easy to suppress overall chromatic aberration.

[0042] It is preferable that at least one LA lens is disposed on the image side of the aperture diaphragm St. By disposing the LA lens on the image side of the aperture diaphragm St, it becomes easy to correct chromatic aberration on the image side of the aperture diaphragm St, and therefore it becomes easy to suppress overall chromatic aberration.

[0043] It is preferable that at least one LB lens is disposed on the image side of the aperture diaphragm St. By disposing an LB lens on the image side of the aperture diaphragm St, it becomes easy to suppress chromatic aberration that occurs on the image side of the aperture diaphragm St, and therefore it becomes easy to suppress overall chromatic aberration.

[0044] It is preferable that at least two LB lenses are disposed on the image side of the aperture stop St. In this case, it becomes easier to suppress chromatic aberration occurring on the image side of the aperture stop St, and therefore it becomes easier to suppress overall chromatic aberration.

[0045] The LA lens is preferably made of a crystalline material, which provides high transmittance in the wavelength range of 3000 nm to 5000 nm and a stable refractive index, making it easy to stably manufacture lenses with good performance.

[0046] It is preferable that at least one lens made of a crystalline material is disposed on the object side of the aperture stop St. In this case, it becomes easy to correct chromatic aberration on the object side of the aperture stop St, making it easy to suppress overall chromatic aberration.

[0047] It is preferable that at least one lens made of a crystalline material is disposed on the image side of the aperture stop St. In this case, it becomes easy to correct chromatic aberration on the image side of the aperture stop St, making it easy to suppress overall chromatic aberration.

[0048] It is preferable to dispose at least two lenses on the image side of the aperture stop St. In this case, various aberrations occurring on the image side of the aperture stop St can be easily and satisfactorily corrected, which is advantageous for improving performance.

[0049] The imaging lens includes at least two lenses made of crystal materials on the image side of the aperture stop St, and it is preferable that at least two of the lenses made of crystal materials are made of different types of crystal materials. In this case, it becomes easier to correct chromatic aberration in the lens on the image side of the aperture stop St more effectively, and it becomes easier to correct chromatic aberration overall.

[0050] The imaging lens preferably includes at least one aspherical lens. By using an aspherical lens, it becomes easier to correct various aberrations well. The imaging lens more preferably includes at least two aspherical lenses. By using an aspherical lens, it becomes easier to correct various aberrations well.

[0051] It is preferable that all lenses included in the imaging lens satisfy the following conditional formula (1C). By making the corresponding value of conditional formula (1C) not equal to or greater than the upper limit, it becomes possible to select a material that can be practically used. It is more preferable that all lenses included in the imaging lens satisfy the following conditional formula (1C-1), it is even more preferable that they satisfy the following conditional formula (1C-2), it is even more preferable that they satisfy the following conditional formula (1C-3), and it is even more preferable that they satisfy the following conditional formula (1C-4). By making the corresponding value of conditional formula (1C-1) not equal to or greater than the upper limit, it becomes easy to suppress an increase in the cost of materials. By making the corresponding value of conditional formula (1C-3) not equal to or less than the lower limit, it becomes easy to strengthen the refractive power of each lens, which makes it easy to make the lens compact and correct chromatic aberration. N4<5 (1C) N4<4.5 (1C-1) N4<4 (1C-2) 1.2 <N4<3 (1C-3) 1.3 <N4<3 (1C-4)

[0052] It is preferable that the imaging lens satisfies the following conditional formula (2). Here, f is the focal length of the imaging lens at a wavelength of 4000 nm. Also, TL is the sum of the distance on the optical axis from the lens surface of the imaging lens closest to the object to the lens surface of the imaging lens closest to the image, and the back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm. By making sure that the corresponding value of conditional formula (2) is not equal to or greater than the upper limit, it is advantageous for miniaturization. It is more preferable that the imaging lens satisfies the following conditional formula (2-1), more preferably the following conditional formula (2-2), and even more preferably the following conditional formula (2-3). By making sure that the corresponding value of conditional formula (2-1) is not equal to or less than the lower limit, it is easy to prevent the angle of view from becoming too narrow. TL / f<20 (2) 0.5 <TL / f<15 (2-1) 0.8 <TL / f<12 (2-2) 1 <TL / f<9 (2-3)

[0053] It is preferable that the imaging lens satisfies the following conditional formula (3). Here, the back focus of the imaging lens in the air-equivalent distance at a wavelength of 4000 nm is taken as Bf. By making sure that the corresponding value of conditional formula (3) is not equal to or less than the lower limit, it becomes easy to prevent the angle of view from becoming too narrow. It is more preferable that the imaging lens satisfies the following conditional formula (3-1), and it is even more preferable that the imaging lens satisfies the following conditional formula (3-2). By making sure that the corresponding value of conditional formula (3-1) is not equal to or more than the upper limit, it becomes easy to prevent the overall length from becoming too long because the back focus does not become too long. 0.3 <Bf / f (3) 0.4 <Bf / f<5 (3-1) 0.45 <Bf / f<3 (3-2)

[0054] It is preferable that the imaging lens includes at least one lens that satisfies the following conditional formula (4A). The corresponding value of conditional formula (4A) is the Abbe number of the technology of the present disclosure. By making the corresponding value of conditional formula (4A) not equal to or less than the lower limit, the Abbe number does not become too small, and therefore the dispersion does not become too large, thereby making it possible to suppress the amount of chromatic aberration. By making the corresponding value of conditional formula (4A) not equal to or more than the upper limit, the Abbe number does not become too large, and therefore the dispersion does not become too small, thereby being advantageous for reducing the cost of materials. It is more preferable that at least one of the lenses that satisfy conditional formula (4A) included in the imaging lens satisfies at least one of the following conditional formulas (4A-1) and (4A-2). 100<(N4-1) / (N3-N5)<400 (4A) 150<(N4-1) / (N3-N5)<200 (4A-1) 130<(N4-1) / (N3-N5)<180 (4A-2)

[0055] At least one of the lenses included in the imaging lens and satisfying conditional formula (4A) is preferably an aspherical lens. In this case, in addition to the effect of conditional formula (4A) above, the effect of making it easier to effectively correct various aberrations is obtained. It is more preferable that at least one of the aspherical lenses included in the imaging lens and satisfying conditional formula (4A) above satisfies at least one of conditional formula (4A-1) and conditional formula (4A-2).

[0056] It is preferable that the imaging lens includes at least one lens that satisfies the following conditional formula (4B). The corresponding value of conditional formula (4B) is the Abbe number of the technique of the present disclosure. By using a lens with large dispersion that satisfies conditional formula (4B), it becomes easy to correct chromatic aberration. At least one of the lenses that satisfies conditional formula (4B) included in the imaging lens more preferably satisfies the following conditional formula (4B-1), even more preferably satisfies the following conditional formula (4B-2), and even more preferably satisfies the following conditional formula (4B-3). 0<(N4-1) / (N3-N5)<180 (4B) 80<(N4-1) / (N3-N5)<180 (4B-1) 120<(N4-1) / (N3-N5)<180 (4B-2) 140<(N4-1) / (N3-N5)<180 (4B-3)

[0057] Furthermore, it is preferable that the imaging lens includes at least one lens that satisfies the following conditional formula (4C). The corresponding value of conditional formula (4C) is the Abbe number of the technology of the present disclosure. By using a lens with small dispersion that satisfies conditional formula (4C), it becomes easy to suppress the occurrence of chromatic aberration. It is more preferable that at least one of the lenses that satisfies conditional formula (4C) included in the imaging lens satisfies the following conditional formula (4C-1), and even more preferable that it satisfies the following conditional formula (4C-2). 180<(N4-1) / (N3-N5)<400 (4C) 180<(N4-1) / (N3-N5)<300 (4C-1) 180<(N4-1) / (N3-N5)<220 (4C-2)

[0058] At least one of the lenses included in the imaging lens has a concave lens surface, and at least one of the lenses has a convex lens surface. It is preferable that at least one of the lenses having a concave lens surface satisfies the above conditional formula (4B), and at least one of the lenses having a convex lens surface satisfies the above conditional formula (4C). By combining a lens having a concave lens surface and a large dispersion with a lens having a convex lens surface and a small dispersion, it becomes easy to correct chromatic aberration. In chromatic aberration correction using the above combination, overcorrection can be suppressed by preventing the difference between the Abbe number of the lens having a concave lens surface and the Abbe number of the lens having a convex lens surface from becoming too large, and undercorrection can be suppressed by preventing the difference from becoming too small.

[0059] In the above combination, it is more preferable that the lens having a concave lens surface satisfies the above conditional formula (4B-1), more preferably the above conditional formula (4B-2), and even more preferably the above conditional formula (4B-3).In addition, in the above combination, it is more preferable that the lens having a convex lens surface satisfies the above conditional formula (4C-1), and even more preferably the above conditional formula (4C-2).

[0060] The imaging lens preferably includes at least one spherical lens that satisfies the following conditional formula (4D). The corresponding value of conditional formula (4D) is the Abbe number of the technology of the present disclosure. By making the corresponding value of conditional formula (4D) not equal to or less than the lower limit, the Abbe number does not become too small, and therefore the dispersion does not become too large, which makes it easy to suppress the occurrence of chromatic aberration. By making the corresponding value of conditional formula (4D) not equal to or more than the upper limit, the Abbe number does not become too large, and therefore the dispersion does not become too small, which is advantageous for reducing the cost of materials. At least one of the spherical lenses that satisfies conditional formula (4D) included in the imaging lens more preferably satisfies the following conditional formula (4D-1), even more preferably satisfies the following conditional formula (4D-2), even more preferably satisfies the following conditional formula (4D-3), and even more preferably satisfies the following conditional formula (4D-4). 0<(N4-1) / (N3-N5)<250 (4D) 0<(N4-1) / (N3-N5)<200 (4D-1) 5<(N4-1) / (N3-N5)<100 (4D-2) 10<(N4-1) / (N3-N5)<80 (4D-3) 15(N4-1) / (N3-N5)<50 (4D-4)

[0061] It is preferable that the imaging lens satisfies the following conditional formula (5). Here, the maximum image height of the imaging lens is Y. As an example, the maximum image height Y is shown in FIG. 1. By making the corresponding value of conditional formula (5) not equal to or less than the lower limit, TL does not become too small, which makes it easy to arrange the lenses, and this is advantageous for improving performance. By making the corresponding value of conditional formula (5) not equal to or more than the upper limit, this is advantageous for miniaturization. It is more preferable that the imaging lens satisfies the following conditional formula (5-1), even more preferable that it satisfies the following conditional formula (5-2), even more preferable that it satisfies the following conditional formula (5-3), even more preferable that it satisfies the following conditional formula (5-4), and even more preferable that it satisfies the following conditional formula (5-5). 0.5 <TL / 2Y<20 (5) 0.5 <TL / 2Y<18 (5-1) 0.8 <TL / 2Y<15 (5-2) 1 <TL / 2Y<14 (5-3) 1.5 <TL / 2Y<12 (5-4) 1.5 <TL / 2Y<8.5 (5-5)

[0062] It is preferable that the imaging lens satisfies the following conditional formula (6). Here, the composite focal length at a wavelength of 4000 nm of all lenses on the object side of the aperture stop St is fF. The composite focal length at a wavelength of 4000 nm of all lenses on the image side of the aperture stop St is fR. By satisfying the numerical range of conditional formula (6), it is possible to properly maintain the balance between the refractive power of the group on the object side of the aperture stop St and the refractive power of the group on the image side, which makes it easy to correct spherical aberration and curvature of field. In order to more properly maintain the above balance, it is more preferable that the imaging lens satisfies the numerical range of the following conditional formula (6-1), it is even more preferable that the imaging lens satisfies the numerical range of the following conditional formula (6-2), it is even more preferable that the imaging lens satisfies the numerical range of the following conditional formula (6-3), and it is even more preferable that the imaging lens satisfies the numerical range of the following conditional formula (6-4). |fF / fR|<40 (6) 0.1<|fF / fR|<30 (6-1) 0.15<|fF / fR|<20 (6-2) 0.4<|fF / fR|<19 (6-3) 1<|fF / fR|<15 (6-4)

[0063] The lens group consisting of all the lenses located on the object side of the aperture stop St may be configured to have positive refractive power as a whole, which makes it easier to make the lens system compact.

[0064] Alternatively, the lens group consisting of all the lenses on the object side of the aperture stop St may be configured to have negative refractive power as a whole. In this case, it is easy to achieve a wide angle.

[0065] It is preferable that the lens group consisting of all the lenses located on the image side of the aperture stop St has a positive refractive power as a whole, which makes it easier to make the lens system compact.

[0066] A negative lens may be arranged adjacent to the image side of the aperture stop St. In this case, it becomes easier to correct axial chromatic aberration and lateral chromatic aberration well. A negative lens may be arranged adjacent to the image side of the aperture stop St, and a positive lens may be arranged adjacent to the image side of the negative lens. In this case, it becomes easier to correct axial chromatic aberration and lateral chromatic aberration well.

[0067] The imaging lens may be configured to include, in succession from the object side to the image side, an aperture stop St, a negative lens, a positive lens, and a negative lens. In this case, it becomes easier to effectively correct the axial chromatic aberration and the chromatic aberration of magnification. Alternatively, the imaging lens may be configured to include, in succession from the object side to the image side, an aperture stop St, a negative lens, a positive lens, and a positive lens. In this case, it becomes easier to effectively correct the spherical aberration in addition to the axial chromatic aberration and the chromatic aberration of magnification.

[0068] The imaging lens may be configured to include, in succession from the object side to the image side, an aperture stop St, a negative lens, a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens. In this case, it becomes easy to effectively correct various aberrations by combining the negative lens and the positive lens.

[0069] The imaging lens preferably includes at least three lenses. By including three or more lenses, it becomes easier to correct various aberrations and chromatic aberrations by combining them.

[0070] The number of lenses included in the imaging lens may be 12 or less. In this case, miniaturization is easy. To achieve even greater miniaturization, the number of lenses included in the imaging lens is preferably 9 or less, more preferably 7 or less, and even more preferably 4 or less.

[0071] The lens closest to the object side of the imaging lens may be configured to be a positive lens. This is advantageous for miniaturizing the lens system and correcting distortion aberration. When the lens closest to the object side of the imaging lens is a positive lens, this lens closest to the object side may be configured to be an LA lens. This makes it easy to suppress chromatic aberration while miniaturizing the lens system. Alternatively, when the lens closest to the object side of the imaging lens is a positive lens, this lens closest to the object side may be configured to be an LB lens. This makes it easy to suppress various aberrations such as field curvature while miniaturizing the lens system.

[0072] The lens closest to the object side of the imaging lens may be configured to be a negative lens. This is advantageous for achieving a wider angle. When the lens closest to the object side of the imaging lens is a negative lens, this lens closest to the object side is preferably an LB lens. By arranging a negative lens made of a material with a refractive index of more than 2 at a wavelength of 4000 nm closest to the object side, it becomes easy to achieve a long back focus while widening the angle of the lens system.

[0073] The second lens from the object side of the imaging lens may be configured to be a positive lens. In this case, it is advantageous for correcting the curvature of field. Alternatively, the second lens from the object side of the imaging lens may be configured to be a negative lens. In this case, it is advantageous for achieving a wide angle and ensuring a long back focus.

[0074] The third lens from the object side of the imaging lens may be configured to be a positive lens. In this case, it is advantageous for correcting spherical aberration and curvature of field. Alternatively, the third lens from the object side of the imaging lens may be configured to be a negative lens. In this case, it is advantageous for correcting axial chromatic aberration and chromatic aberration of magnification.

[0075] The fourth lens from the object side of the imaging lens may be configured to be a positive lens. In this case, it is advantageous for correcting spherical aberration and curvature of field. Alternatively, the fourth lens from the object side of the imaging lens may be configured to be a negative lens. In this case, it is advantageous for correcting axial chromatic aberration and chromatic aberration of magnification.

[0076] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive or negative refractive power, a second lens having positive refractive power, and a third lens having negative refractive power. In this case, it is easy to realize a lens system that is compact yet has excellent correction of spherical aberration and curvature of field.

[0077] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive or negative refractive power, a second lens having positive refractive power, a third lens having negative refractive power, and a fourth lens having positive refractive power. In this case, it becomes easy to effectively correct various aberrations by combining the negative lens and the positive lens.

[0078] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, a fourth lens having positive or negative refractive power, and a fifth lens having positive refractive power. In this case, it becomes easy to effectively correct various aberrations by combining the negative lens and the positive lens.

[0079] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive refractive power, a second lens having positive or negative refractive power, a third lens having negative refractive power, a fourth lens having positive refractive power, and a fifth lens having positive refractive power. In this case, it becomes easy to effectively correct various aberrations by combining the negative lens and the positive lens.

[0080] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive refractive power, a second lens having positive refractive power, a third lens having negative refractive power, a fourth lens having positive or negative refractive power, a fifth lens having positive refractive power, and a sixth lens having positive refractive power. In this case, it becomes easy to effectively correct various aberrations by combining the negative lens and the positive lens.

[0081] The imaging lens may be configured to include, in succession from the object side to the image side, a first lens having positive refractive power, a second lens having positive refractive power, a third lens having negative refractive power, a fourth lens having positive or negative refractive power, a fifth lens having positive refractive power, a sixth lens having positive refractive power, and a seventh lens having negative refractive power. In this case, it becomes easy to effectively correct various aberrations by combining the negative lens and the positive lens.

[0082] The imaging lens may be configured to include, in order from the object side to the image side, a first lens having negative refractive power, a second lens having positive or negative refractive power, a third lens having positive refractive power, a fourth lens having positive or negative refractive power, a fifth lens having negative refractive power, a sixth lens having positive refractive power, a seventh lens having negative refractive power, an eighth lens having positive refractive power, a ninth lens having negative refractive power, a tenth lens having positive refractive power, an eleventh lens having negative refractive power, and a twelfth lens having positive refractive power. In this case, various aberrations can be easily corrected by combining the negative lens and the positive lens.

[0083] Note that the example shown in Fig. 1 is just one example, and as illustrated above, various modifications are possible within the scope of the gist of the technology of the present disclosure. For example, the number of LA lenses, the number of LB lenses, and the total number of lenses in the entire system included in the imaging lens may be different from those in the example of Fig. 1. The position of the aperture stop St may be different from that in the example of Fig. 1.

[0084] The above-mentioned preferred and possible configurations can be arbitrarily combined, and are preferably selectively adopted as appropriate according to the required specifications. The conditional expressions that the imaging lens preferably satisfies are not limited to the conditional expressions written in the form of an expression, and include all conditional expressions obtained by arbitrarily combining the lower and upper limits of the conditional expressions listed as preferred.

[0085] As an example, a preferred embodiment of the imaging lens of the present disclosure includes at least one LA lens, at least one LB lens, and an aperture stop St.

[0086] Next, examples of the imaging lens of the present disclosure will be described with reference to the drawings. Note that the reference symbols attached to the lenses in the cross-sectional views of each example are used independently for each example to avoid the explanation and the drawings becoming complicated due to an increase in the number of digits of the reference symbols. Therefore, even if common reference symbols are attached in the drawings of different examples, they do not necessarily have the same configuration.

[0087] [Example 1] A cross-sectional view of the configuration of the imaging lens of Example 1 is shown in Fig. 2. Compared to Fig. 1, light beams are not shown in Fig. 2, but the basic illustration method in Fig. 2 is the same as in Fig. 1, so some overlapping explanations will be omitted here. The imaging lens of Example 1 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L7.

[0088] Table 1 shows basic lens data of the imaging lens of Example 1. The table of basic lens data is described as follows. The "Sn" column shows the surface numbers when the surface closest to the object is the first surface and the numbers increase by one toward the image side. The "R" column shows the radius of curvature of each surface. The "D" column shows the surface distance on the optical axis between each surface and its adjacent surface on the image side. The "N4" column shows the refractive index of each component at a wavelength of 4000 nm. The "N3" column shows the refractive index of each component at a wavelength of 3000 nm. The "N5" column shows the refractive index of each component at a wavelength of 5000 nm. The "Material" column shows the material name of each component. The "(N4-1) / (N3-N5)" column shows the corresponding values ​​of the above conditional expressions (4A), (4B), (4C), and (4D), that is, the Abbe numbers in the technology of the present disclosure.

[0089] In the basic lens data table, the sign of the radius of curvature of a surface with a convex shape facing the object side is positive, and the sign of the radius of curvature of a surface with a convex shape facing the image side is negative. In the column for the surface number of the surface corresponding to the aperture stop St, the surface number and the word (St) are entered. The basic lens data table also shows the optical member PP. The value in the bottom row of the D column in the table is the distance between the surface closest to the image side in the table and the image plane Sim.

[0090] Table 2 shows the specifications of the imaging lens of Example 1 at a wavelength of 4000 nm. The table of specifications shows the focal length f, the back focus Bf in air equivalent distance, the F-number FNo., the maximum total angle of view 2ω, and the maximum image height Y. In the maximum total angle of view column, [°] indicates that the unit is degrees.

[0091] In the data in each table, the angle unit is degrees and the length unit is mm (millimeters), but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table shown below, values ​​are rounded to a predetermined number of decimal places.

[0092] [Table 1]

[0093] [Table 2]

[0094] FIG. 3 shows the aberration diagrams of the imaging lens of Example 1 in a state where the lens is focused on an object at infinity. From the left, FIG. 3 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In the spherical aberration diagram, the aberrations at wavelengths of 4000 nm, 3000 nm, and 5000 nm are shown by solid lines, long dashed lines, and short dashed lines, respectively. In the astigmatism diagram, the aberrations at wavelengths of 4000 nm in the sagittal direction are shown by solid lines, and the aberrations at wavelengths of 4000 nm in the tangential direction are shown by short dashed lines. In the distortion diagram, the aberrations at wavelengths of 4000 nm are shown by solid lines. In the lateral chromatic aberration diagram, the aberrations at wavelengths of 3000 nm and 5000 nm are shown by long dashed lines and short dashed lines, respectively. In the spherical aberration diagram, the value of the F-number is shown after "FNo.=". In other aberration diagrams, the value of the maximum half angle of view is shown after "ω=".

[0095] The symbols, meanings, description methods, and illustration methods of each piece of data related to the above-mentioned Example 1 are basically the same in the following Examples unless otherwise specified, so duplicated explanations will be omitted below.

[0096] [Example 2] 4 shows a cross-sectional view of the configuration of the imaging lens of Example 2. The imaging lens of Example 2 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L7.

[0097] Regarding the imaging lens of Example 2, basic lens data is shown in Table 3, specifications are shown in Table 4, and various aberration diagrams are shown in FIG.

[0098] [Table 3]

[0099] [Table 4]

[0100] [Example 3] 6 shows a cross-sectional view of the configuration of the imaging lens of Example 3. The imaging lens of Example 3 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L7.

[0101] Regarding the imaging lens of Example 3, basic lens data is shown in Table 5, specifications are shown in Table 6, and various aberration diagrams are shown in FIG.

[0102] [Table 5]

[0103] [Table 6]

[0104] [Example 4] 8 shows a cross-sectional view of the configuration of the imaging lens of Example 4. The imaging lens of Example 4 is composed of, in order from the object side to the image side, lenses L1 and L2, an aperture stop St, and lenses L3 and L5.

[0105] Regarding the imaging lens of Example 4, basic lens data is shown in Table 7, specifications are shown in Table 8, and each aberration diagram is shown in FIG.

[0106] [Table 7]

[0107] [Table 8]

[0108] [Example 5] 10 shows a cross-sectional view of the configuration of the imaging lens of Example 5. The imaging lens of Example 5 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L6.

[0109] Regarding the imaging lens of Example 5, basic lens data is shown in Table 9, specifications are shown in Table 10, and each aberration diagram is shown in FIG.

[0110] [Table 9]

[0111] [Table 10]

[0112] [Example 6] 12 shows a cross-sectional view of the configuration of the imaging lens of Example 6. The imaging lens of Example 6 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L6.

[0113] For the imaging lens of Example 6, basic lens data is shown in Table 11, specifications in Table 12, and various aberration diagrams in Fig. 13. In the table of basic lens data, the abbreviation of the manufacturer of the material is written in parentheses under the material name "K-FIR98UV". "Sumita Optical" refers to Sumita Optical Glass Co., Ltd. Similarly, in the "Material" column of the table of basic lens data for the following examples, the abbreviation or name of the manufacturer of some materials is written in parentheses under the material name.

[0114] [Table 11]

[0115] [Table 12]

[0116] [Example 7] 14 shows a cross-sectional view of the configuration of the imaging lens of Example 7. The imaging lens of Example 7 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L6.

[0117] Regarding the imaging lens of Example 7, basic lens data is shown in Table 13, specifications are shown in Table 14, and various aberration diagrams are shown in FIG.

[0118] [Table 13]

[0119] [Table 14]

[0120] [Example 8] 16 shows a cross-sectional view of the configuration of the imaging lens of Example 8. The imaging lens of Example 8 is composed of, in order from the object side to the image side, an aperture stop St and lenses L1 to L3.

[0121] The imaging lens of Example 8 includes an aspheric lens. Regarding the imaging lens of Example 8, basic lens data is shown in Table 15, specifications are shown in Table 16, aspheric coefficients are shown in Table 17, and each aberration diagram is shown in FIG.

[0122] In the basic lens data, the aspheric surface numbers are marked with an *, and the paraxial radius of curvature value is given in the column for the radius of curvature of the aspheric surface. In Table 17, the Sn row shows the aspheric surface numbers, and the KA and Am rows show the numerical values ​​of the aspheric coefficients for each aspheric surface. Note that m in Am is an integer between 3 and 20 (m=3, 4, 5, ..., 20). The numerical values ​​of the aspheric coefficients in Table 17, "E±n" (n: integer), are expressed as "×10 ±n " KA and Am are aspheric coefficients in the aspheric equation expressed below. Zd = C × h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (the length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the apex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial curvature radius KA, Am: Aspheric coefficients In the aspheric surface formula, Σ means the summation with respect to m. The above description of the aspheric surface is similar to that of other embodiments having an aspheric surface.

[0123] [Table 15]

[0124] [Table 16]

[0125] [Table 17]

[0126] [Example 9] A cross-sectional view of the configuration of the imaging lens of Example 9 is shown in Fig. 18. The imaging lens of Example 9 is composed of, in order from the object side to the image side, a lens L1, an aperture stop St, and lenses L2 to L4.

[0127] Concerning the imaging lens of Example 9, basic lens data is shown in Table 18, specifications are shown in Table 19, aspheric coefficients are shown in Table 20, and each aberration diagram is shown in FIG.

[0128] [Table 18]

[0129] [Table 19]

[0130] [Table 20]

[0131] [Example 10] 20 shows a cross-sectional view of the configuration of the imaging lens of Example 10. The imaging lens of Example 10 is composed of an aperture stop St and lenses L1 to L3.

[0132] For the imaging lens of Example 10, basic lens data is shown in Table 21, specifications in Table 22, aspheric coefficients in Table 23, and various aberration diagrams in Fig. 21. "Chengdu Guangming" in the basic lens data refers to Chengdu Guangming Optoelectronics Co., Ltd.

[0133] [Table 21]

[0134] [Table 22]

[0135] [Table 23]

[0136] [Example 11] 22 shows a cross-sectional view of the configuration of the imaging lens of Example 11. The imaging lens of Example 11 is composed of, in order from the object side to the image side, a lens L1, an aperture stop St, and lenses L2 to L4.

[0137] Concerning the imaging lens of Example 11, basic lens data is shown in Table 24, specifications are shown in Table 25, aspheric coefficients are shown in Table 26, and each aberration diagram is shown in FIG.

[0138] [Table 24]

[0139] [Table 25]

[0140] [Table 26]

[0141] [Example 12] 24 shows a cross-sectional view of the configuration of the imaging lens of Example 12. The imaging lens of Example 12 is composed of, in order from the object side to the image side, lenses L1 to L6, an aperture stop St, and lenses L7 to L12.

[0142] Regarding the imaging lens of Example 12, basic lens data is shown in Table 27, specifications are shown in Table 28, and various aberration diagrams are shown in FIG.

[0143] [Table 27]

[0144] [Table 28]

[0145] [Example 13] 26 shows a cross-sectional view of the configuration of the imaging lens of Example 13. The imaging lens of Example 13 is composed of, in order from the object side to the image side, lenses L1 to L6, an aperture stop St, and lenses L7 to L12.

[0146] For the imaging lens of Example 13, basic lens data is shown in Table 29, specifications are shown in Table 30, and each aberration diagram is shown in Fig. 27. "Isuzu Precision Glass" in the basic lens data refers to Isuzu Precision Glass Co., Ltd.

[0147] [Table 29]

[0148] [Table 30]

[0149] [Example 14] 28 shows a cross-sectional view of the configuration of the imaging lens of Example 14. The imaging lens of Example 14 is composed of, in order from the object side to the image side, lenses L1 to L3, an aperture stop St, and lenses L4 to L9.

[0150] Regarding the imaging lens of Example 14, basic lens data is shown in Table 31, specifications are shown in Table 32, and each aberration diagram is shown in FIG.

[0151] [Table 31]

[0152] [Table 32]

[0153] [Example 15] A cross-sectional view of the configuration of the imaging lens of Example 15 is shown in Fig. 30. The imaging lens of Example 15 is composed of, in order from the object side to the image side, lenses L1 to L2, an aperture stop St, and lenses L3 to L8.

[0154] Regarding the imaging lens of Example 15, basic lens data is shown in Table 33, specifications are shown in Table 34, and each aberration diagram is shown in FIG.

[0155] [Table 33]

[0156] [Table 34]

[0157] [Example 16] 32 shows a cross-sectional view of the configuration of the imaging lens of Example 16. The imaging lens of Example 16 is composed of, in order from the object side to the image side, a lens L1, an aperture stop St, and lenses L2 to L4.

[0158] Concerning the imaging lens of Example 16, basic lens data is shown in Table 35, specifications are shown in Table 36, aspheric coefficients are shown in Table 37, and each aberration diagram is shown in FIG.

[0159] [Table 35]

[0160] [Table 36]

[0161] [Table 37]

[0162] [Example 17] 34 shows a cross-sectional view of the configuration of the imaging lens of Example 17. The imaging lens of Example 17 is composed of, in order from the object side to the image side, a lens L1, an aperture stop St, and lenses L2 to L4.

[0163] Concerning the imaging lens of Example 17, basic lens data is shown in Table 38, specifications are shown in Table 39, aspheric coefficients are shown in Table 40, and each aberration diagram is shown in FIG.

[0164] [Table 38]

[0165] [Table 39]

[0166] [Table 40]

[0167] [Example 18] A cross-sectional view of the configuration of the imaging lens of Example 18 is shown in Fig. 36. The imaging lens of Example 18 is composed of, in order from the object side to the image side, a lens L1, an aperture stop St, and lenses L2 to L5.

[0168] Regarding the imaging lens of Example 18, basic lens data is shown in Table 41, specifications are shown in Table 42, and each aberration diagram is shown in FIG.

[0169] [Table 41]

[0170] [Table 42]

[0171] [Example 19] A cross-sectional view of the configuration of the imaging lens of Example 19 is shown in Fig. 38. The imaging lens of Example 19 is composed of, in order from the object side to the image side, a lens L1, an aperture stop St, and lenses L2 to L3.

[0172] Concerning the imaging lens of Example 19, basic lens data is shown in Table 43, specifications are shown in Table 44, aspheric coefficients are shown in Table 45, and each aberration diagram is shown in FIG.

[0173] [Table 43]

[0174] [Table 44]

[0175] [Table 45]

[0176] Table 46 shows values ​​corresponding to conditional formulas (2), (3), (5), and (6) for the imaging lenses of Examples 1 to 19. The corresponding values ​​for the Examples shown in Table 46 may be used as upper or lower limits to set preferred ranges for the conditional formulas.

[0177] [Table 46]

[0178] In the imaging lenses of Examples 1 to 19, various aberrations including chromatic aberration are corrected in the mid-infrared wavelength range, and good optical performance is maintained.

[0179] Next, an imaging device according to an embodiment of the present disclosure will be described. Fig. 40 shows a schematic configuration diagram of an imaging device 100 according to an embodiment of the present disclosure. The imaging device 100 is configured to include an imaging lens 1 according to an embodiment of the present disclosure. Examples of the imaging device 100 include a camera for FA (Factory Automation), a camera for MV (Machine Vision), a surveillance camera, and an in-vehicle camera.

[0180] The imaging device 100 includes an imaging lens 1, a filter 2, an imaging element 3, and a signal processing unit 5. Note that the imaging lens 1 is conceptually illustrated in FIG.

[0181] The imaging element 3 captures an optical image formed by the imaging lens 1 and converts it into an electrical signal. For example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) can be used as the imaging element 3. The imaging element 3 is disposed so that its imaging surface coincides with the image surface of the imaging lens 1. Although only one imaging element 3 is shown in FIG. 40, a so-called three-plate imaging device having three imaging elements may also be used. The signal processing unit 5 performs arithmetic processing on the output signal from the imaging element 3.

[0182] Although the technology of the present disclosure has been described above with reference to the embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, surface spacing, refractive index, aspheric coefficient, etc. of each lens are not limited to the values ​​shown in the above examples, and may take other values.

[0183] Regarding the above-mentioned embodiments and examples, the following supplementary notes are further disclosed. [Appendix 1] An imaging lens including a plurality of lenses and an aperture, If the refractive index of each lens included in the imaging lens at a wavelength of 4000 nm is N4, At least one of the lenses N4<1.5 (1A) The LA lens satisfies conditional formula (1A) expressed by: At least one of the lenses 2 <N4 (1B) The imaging lens is an LB lens that satisfies the conditional formula (1B) expressed by: [Appendix 2] The imaging lens according to claim 1, wherein at least one of the LA lenses is disposed on the object side of the aperture. [Appendix 3] The imaging lens according to claim 1 or 2, wherein at least one of the LB lenses is disposed on the object side of the aperture stop. [Appendix 4] The imaging lens according to any one of Supplementary Note 1 to Supplementary Note 3, wherein at least one of the LA lenses is disposed on the image side of the aperture stop. [Appendix 5] The imaging lens according to any one of Supplementary Note 1 to Supplementary Note 4, wherein at least one of the LB lenses is disposed on the image side of the aperture stop. [Appendix 6] 6. The imaging lens according to any one of claims 1 to 5, comprising at least two aspheric lenses. [Appendix 7] All lenses included in the imaging lens N4<5 (1C) The imaging lens according to any one of claims 1 to 6, which satisfies conditional formula (1C) represented by: [Appendix 8] TL is the sum of the distance on the optical axis from the lens surface of the imaging lens closest to the object side to the lens surface of the imaging lens closest to the image side and the back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm, If the focal length of the imaging lens at a wavelength of 4000 nm is f, then TL / f<20 (2) The imaging lens according to any one of claims 1 to 7, which satisfies conditional expression (2) represented by: [Appendix 9] The back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm is Bf, If the focal length of the imaging lens at a wavelength of 4000 nm is f, then 0.3 <Bf / f (3) The imaging lens according to any one of claims 1 to 8, which satisfies conditional expression (3) represented by: [Appendix 10] The refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3, If the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, 100<(N4-1) / (N3-N5)<400 (4A) The imaging lens according to any one of claims 1 to 9, comprising at least one aspheric lens which satisfies conditional formula (4A) represented by: [Appendix 11] At least one of the plurality of lenses is a lens having a concave lens surface, and at least one of the plurality of lenses is a lens having a convex lens surface, The refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3, If the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, At least one of the lenses having a concave lens surface is 0<(N4-1) / (N3-N5)<180 (4B) Satisfying conditional formula (4B) expressed by At least one of the lenses having a convex lens surface is 180<(N4-1) / (N3-N5)<400 (4C) The imaging lens according to any one of claims 1 to 10, which satisfies conditional formula (4C) represented by: [Appendix 12] The refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3, If the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, 0<(N4-1) / (N3-N5)<250 (4D) 12. The imaging lens according to claim 1, further comprising at least one spherical lens which satisfies conditional formula (4D) represented by: [Appendix 13] 13. The imaging lens according to any one of claims 1 to 12, comprising at least three lenses. [Appendix 14] TL is the sum of the distance on the optical axis from the lens surface of the imaging lens closest to the object side to the lens surface of the imaging lens closest to the image side and the back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm, If the maximum image height of the imaging lens is Y, 0.5 <TL / 2Y<20 (5) The imaging lens according to any one of claims 1 to 13, which satisfies conditional expression (5) represented by: [Appendix 15] The composite focal length of all the lenses on the object side of the aperture at a wavelength of 4000 nm is fF. If the composite focal length of all the lenses on the image side of the aperture at a wavelength of 4000 nm is fR, |fF / fR|<40 (6) The imaging lens according to any one of claims 1 to 14, which satisfies conditional expression (6) represented by: [Appendix 16] 16. The imaging lens according to claim 1, wherein the LA lens is made of a crystalline material. [Appendix 17] The imaging lens according to any one of Appendix 1 to Appendix 16, including, in succession from the object side to the image side, a first lens having positive or negative refractive power, a second lens having positive refractive power, and a third lens having negative refractive power. [Appendix 18] The imaging lens according to any one of claims 1 to 17, further comprising a negative lens disposed adjacent to the image side of the aperture. [Appendix 19] 19. The imaging lens according to claim 18, further comprising a positive lens disposed adjacent to the negative lens on an image side. [Appendix 20] An imaging lens according to any one of Supplementary Note 1 to Supplementary Note 19; and an imaging element for capturing an image formed by the imaging lens. [Explanation of symbols]

[0184] 1 Imaging lens 2. Filters 3. Image sensor 5. Signal Processing Section 100 Imaging device B0 On-axis luminous flux B1 Off-axis luminous flux L1~L12 lenses PP Optical Components Sim image plane St aperture stop Y Maximum image height Z optical axis

Claims

1. An imaging lens including a plurality of lenses and an aperture, When the refractive index of each lens included in the imaging lens at a wavelength of 4000 nm is N4, At least one of the plurality of lenses N4<1.5 (1A) The LA lens satisfies the conditional formula (1A) expressed by: At least one of the plurality of lenses 2<N4 (1B) The imaging lens is an LB lens that satisfies the conditional formula (1B) expressed by:

2. The imaging lens according to claim 1 , wherein at least one of the LA lenses is disposed on the object side of the aperture stop.

3. 2. The imaging lens according to claim 1, wherein at least one of the LB lenses is disposed on the object side of the aperture stop.

4. The imaging lens according to claim 1 , wherein at least one of the LA lenses is disposed on the image side of the aperture stop.

5. 2. The imaging lens according to claim 1, wherein at least one of the LB lenses is disposed on the image side of the aperture stop.

6. The imaging lens of claim 1 , comprising at least two aspheric lenses.

7. All lenses included in the imaging lens N4<5 (1C) 2. The imaging lens according to claim 1, which satisfies conditional formula (1C) represented by:

8. TL is the sum of the distance on the optical axis from the lens surface closest to the object side of the imaging lens to the lens surface closest to the image side of the imaging lens and the back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm, If the focal length of the imaging lens at a wavelength of 4000 nm is f, then TL / f<20 (2) 2. The imaging lens according to claim 1, which satisfies conditional expression (2) expressed by:

9. The back focus of the imaging lens in terms of an air-equivalent distance at a wavelength of 4000 nm is Bf, If the focal length of the imaging lens at a wavelength of 4000 nm is f, then 0.3<Bf / f (3) 2. The imaging lens according to claim 1, which satisfies conditional expression (3) expressed by:

10. The refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3, When the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, 100<(N4-1) / (N3-N5)<400 (4A) 2. The imaging lens according to claim 1, comprising at least one aspheric lens which satisfies conditional expression (4A) represented by:

11. At least one of the plurality of lenses is a lens having a concave lens surface, and at least one of the plurality of lenses is a lens having a convex lens surface, The refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3, When the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, At least one of the lenses having a concave lens surface is 0<(N4-1) / (N3-N5)<180 (4B) and satisfying conditional formula (4B) represented by At least one of the lenses having a convex lens surface is 180<(N4-1) / (N3-N5)<400 (4C) 2. The imaging lens according to claim 1, which satisfies conditional formula (4C) represented by:

12. The refractive index of each lens included in the imaging lens at a wavelength of 3000 nm is N3, When the refractive index of each lens included in the imaging lens at a wavelength of 5000 nm is N5, 0<(N4-1) / (N3-N5)<250 (4D) 2. The imaging lens according to claim 1, comprising at least one spherical lens which satisfies conditional formula (4D) expressed by:

13. The imaging lens of claim 1 comprising at least three lenses.

14. TL is the sum of the distance on the optical axis from the lens surface closest to the object side of the imaging lens to the lens surface closest to the image side of the imaging lens and the back focus of the imaging lens in terms of the air equivalent distance at a wavelength of 4000 nm, If the maximum image height of the imaging lens is Y, 0.5<TL / 2Y<20 (5) 2. The imaging lens according to claim 1, which satisfies conditional expression (5) expressed by:

15. The composite focal length of all the lenses on the object side of the aperture at a wavelength of 4000 nm is fF. If the composite focal length of all the lenses on the image side of the aperture at a wavelength of 4000 nm is fR, |fF / fR|<40 (6) 2. The imaging lens according to claim 1, which satisfies conditional expression (6) expressed by:

16. The imaging lens according to claim 1 , wherein the LA lens is made of a crystalline material.

17. 2. The imaging lens according to claim 1, comprising, in succession from the object side to the image side, a first lens having positive or negative refractive power, a second lens having positive refractive power, and a third lens having negative refractive power.

18. The imaging lens according to claim 1 , further comprising a negative lens disposed adjacent to the image side of the aperture.

19. 20. The imaging lens according to claim 18, further comprising a positive lens disposed adjacent to the image side of the negative lens.

20. The imaging lens according to any one of claims 1 to 19, and an imaging element for capturing an image formed by the imaging lens.

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