Near-infrared imaging lens system, camera module, on-vehicle system, and mobile vehicle

Abstract

To provide a near-infrared imaging lens system which is bright, offers superior imaging performance, and can be miniaturized, and to provide a camera module, on-vehicle system, and mobile vehicle.SOLUTION: A near-infrared imaging lens system 11 consists of a first group G1 having positive power, a second group G2 having negative power, and a third group G3 having positive power in order from an object side to an image side. The first group G1 consists of at least three or more lenses, where all the lenses constituting the first group G1 have object-side surfaces that are convex toward the object side and have positive power except for the final lens L1e of the first group G1, and the final lens L1e has an image-side surface that is concave toward the image side. The second group G2 consists of a biconcave lens L2 having negative power. The third group G3 consists of at least two or more lenses and comprises, in order from the object side to the image side, a first lens L31 with positive power having an image-side surface that is convex toward the image side and a second lens L32 with positive power having an object-side surface that is convex toward the object side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a near-infrared imaging lens system, and more particularly to a large-diameter, narrow-angle near-infrared imaging lens system, a camera module, an in-vehicle system, and a mobile object. [Background technology]

[0002] In recent years, there has been a trend toward requiring cameras mounted on vehicles to have sensing functions in order to realize autonomous driving, etc. There is also a trend toward requiring distance measurement functions known as Lidar (light detection and ranging). Lidar measures distance by measuring the time it takes for a near-infrared laser beam of approximately 905 nm to be irradiated onto an object and the reflected light to be received by an imaging optical system. The near-infrared imaging lens system used for such distance measurement must be bright because the intensity of light reaching the imaging lens system from a distant object is attenuated. Furthermore, such near-infrared imaging lens systems must have high resolution for accurate distance measurement. Furthermore, such near-infrared imaging lens systems must be compact in order to be installed on vehicles. Patent Document 1 describes a so-called double Gauss type imaging lens system that has a relatively large aperture with an F-number of about 1.8. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5966728 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the imaging lens system described in Patent Document 1 still has a large F-number and is not bright enough. Furthermore, because the imaging lens system described in Patent Document 1 is a double Gauss type, the opposing concave surfaces with large curvatures before and after the aperture stop cause significant sagittal coma aberration at off-axial angles of view, resulting in insufficient resolution. Specifically, the occurrence of sagittal coma aberration significantly widens the spot diameter, potentially causing light from a single object point to leak into multiple pixels on the image sensor, leading to erroneous recognition. Furthermore, in the imaging lens system described in Patent Document 1, if the overall length is shortened relative to the focal length in order to achieve compactness, the curvature of the lens surfaces must be increased, resulting in particularly strong sagittal coma aberration. This presents a problem in that it is difficult to achieve a compact design suitable for in-vehicle applications.

[0005] The present invention has been made in view of the above problems, and aims to provide a near-infrared imaging lens system, camera module, in-vehicle system, and mobile object that is bright, has excellent imaging performance, and can be made compact. [Means for solving the problem]

[0006] A near-infrared imaging lens system according to one embodiment comprises, in order from the object side to the image side, a first lens unit having positive power, a second lens unit having negative power, and a third lens unit having positive power, the first group is made up of at least three lenses, all of the lenses constituting the first group have object-side surfaces convex toward the object side, all of the lenses in the first group except for a final lens located closest to the image side have positive power, and the image-side surface of the final lens in the first group has a concave surface facing toward the image side, the second lens group is made up of a biconcave lens having negative power, The third group is composed of at least two lenses, and includes, in order from the object side to the image side, a first lens having a convex image-side surface facing the image side and positive power, and a second lens having a convex object-side surface facing the object side and positive power.

[0007] A camera module according to another embodiment includes the near-infrared imaging lens system described above, and an image sensor that converts light focused through the near-infrared imaging lens system into an electrical signal.

[0008] An in-vehicle system according to another embodiment is an in-vehicle system mounted on a vehicle, The above camera module, an information processing device that processes a captured image output from the imaging element of the camera module and recognizes an object in the captured image; Equipped with.

[0009] A moving body according to another embodiment is a moving body equipped with the above-described in-vehicle system, the in-vehicle system further includes an output device that outputs information to an occupant; The information processing device is configured to output the recognition information of the object to the output device. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a near-infrared imaging lens system, a camera module, an in-vehicle system, and a mobile object that are bright, have excellent imaging performance, and can be made compact. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 1. FIG. [Figure 2] 2A to 2C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 1. [Figure 3] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 2. [Figure 4] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 2. [Figure 5] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 3. [Figure 6]10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 3. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 4. [Figure 8] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 4. [Figure 9] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 5. [Figure 10] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 5. [Figure 11] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 6. [Figure 12] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 6. [Figure 13] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 7. [Figure 14] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 7. [Figure 15] FIG. 10 is a cross-sectional view showing the configuration of a near-infrared imaging lens system according to Example 8. [Figure 16] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, and distortion in the near-infrared imaging lens system of Example 8. [Figure 17] 1 is a schematic diagram of a vehicle equipped with an in-vehicle system including a camera module according to an embodiment of the present invention. [Figure 18] 18 is a block diagram showing the configuration of an imaging device that constitutes the in-vehicle system of FIG. 17. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment can realize a highly reliable system, particularly in a sensing system, and contributes to the development of resilient infrastructure. The target is "9. Industry, innovation and infrastructure" of the Sustainable Development Goals (SDGs) advocated by the United Nations, which states, "9.1 Develop quality, reliable, sustainable and resilient infrastructure, including regional and transborder infrastructure, to support economic development and human well-being, with a focus on affordable and equitable access for all." (Embodiment 1) The near-infrared imaging lens system of the first embodiment comprises, in order from the object side to the image side, a first lens unit having positive power, a second lens unit having negative power, and a third lens unit having positive power. The first group is made up of at least three lenses, all of which have convex object-side surfaces facing the object side, all of which have positive power except for the final lens element located closest to the image side, and all of which have concave image-side surfaces facing the image side of the final lens element in the first group. The second lens group is made up of a biconcave lens having negative power. The third group is made up of at least two lenses, and includes, in order from the object side to the image side, a first lens having positive power and a convex surface on its image side facing the image side, and a second lens having positive power and a convex surface on its object side facing the object side.

[0013] This makes it possible to provide a near-infrared imaging lens that is bright with an F-number of about 1.2 to 1.4, has excellent imaging performance, and can be made compact. Specifically, the first group is composed of at least three lenses, and the object-side surfaces of all the lenses constituting the first group are convex toward the object, thereby enabling sufficient correction of spherical aberration. More specifically, the multiple lenses in the first group can gradually bend light rays toward the optical axis, thereby suppressing the occurrence of spherical aberration. Furthermore, among adjacent lenses, spherical aberration occurring in the object-side lens can be corrected by the image-side lens. Furthermore, by having the lenses other than the final lens in the first group have positive power, the height of the axial marginal rays passing through the image side surface of the final lens is reduced, thereby suppressing the occurrence of field curvature at the final lens. Furthermore, by having the image side surface of the final lens facing concave toward the image side, field curvature at the final lens can be corrected. Here, the axial marginal rays refer to the outermost rays of light that pass through the aperture stop. Furthermore, because the lens in the second group has a biconcave shape, the lens can have a sufficiently strong negative power without the need to make either the object-side or image-side surface of the lens in the second group extremely curvature-rich. Since the curvature of either the object-side or image-side surface of the lens in the second group does not need to be extremely sharp, the occurrence of aberrations in the lens can be suppressed. Furthermore, the lens in the second group facilitates aberration correction for the entire lens system and also reduces sensitivity to manufacturing errors. In addition, the image side surface of the first lens in the third group is convex toward the image side, which helps to suppress the occurrence of field curvature, and the object side surface of the second lens in the third group is convex toward the object side, which helps to suppress the occurrence of spherical aberration. Therefore, it is possible to suppress the occurrence of aberrations and easily correct aberrations in the entire lens system, thereby achieving excellent imaging performance. Furthermore, because the occurrence of aberrations is suppressed and aberration correction for the entire lens system can be easily performed, the F-number can be reduced and the overall length of the lens system can be shortened, which means that the lens can be brighter and more compact.

[0014] Furthermore, when the radius of curvature of the object-side surface of the lens in the second group is R2f, the radius of curvature of the image-side surface is R2r, the radius of curvature of the image-side surface of the final lens in the first group is R1er, and the focal length of the entire optical system is F, it is preferable that the following formula (1') and formula (2) be satisfied: 0.2<|R2f| / |R2r|<3.0 (1') 0.1 <R1er / F<1···(2) It is more preferable that the following formulas (1) and (2) be satisfied. 0.2<|R2f| / |R2r|<2.5 (1) 0.1 <R1er / F<1···(2) By satisfying the above formulas (1') and (2), it is possible to balance the curvatures of the three surfaces - the image-side surface of the final lens in the first group, the object-side surface of the lens in the second group, and the image-side surface of the lens in the second group - and to distribute power in a balanced manner among these three surfaces, thereby enabling effective correction of field curvature. Specifically, if the upper and lower limits of the above formula (1') are not satisfied, the negative power of the second lens group cannot be distributed in a balanced manner to the object-side and image-side surfaces of the second lens group, making it difficult to suppress the occurrence of aberrations in the second lens group and also making it difficult to correct aberrations throughout the entire lens system. Furthermore, the positive power of the lenses other than the final lens in the first group reduces the height of the axial marginal ray passing through the image-side surface of the final lens, thereby suppressing the occurrence of field curvature at the final lens. However, if the radius of curvature R1er of the image-side surface of the final lens in the first group satisfies the above formula (2), the field curvature at the final lens can be corrected. More specifically, if the radius of curvature R1er of the image-side surface of the final lens in the first group exceeds the upper limit of the above formula (2), the curvatures of the object-side and image-side surfaces of the lenses in the second group become too sharp, making it difficult to suppress the occurrence of aberrations at the second lens group and increasing the likelihood of manufacturing errors. Furthermore, it becomes difficult to correct the field curvature at the image-side surface of the final lens in the first group. On the other hand, if the radius of curvature R1er of the image-side surface of the final lens in the first group falls below the lower limit of the above formula (2), the curvature of the image-side surface of the final lens in the first group becomes too sharp, resulting in overcorrection of aberrations and increasing the likelihood of manufacturing errors.

[0015] Furthermore, when the focal length of the lens in the second group is f2 and the focal length of the entire optical system is F, it is preferable that the following formula (3') be satisfied. 0.6<|f2| / F<3 (3') It is more preferable that the following formula (3) be satisfied. 1<|f2| / F<3 (3) If the focal length f2 of the second lens group exceeds the upper limit of the above formula (3'), the power of the second lens group will be too weak. To achieve a balance between the second lens group, which has negative power, and the first and third lens groups, which have positive power, the powers of the first and third lens groups will also be too weak. As a result, the overall length of the optical system will be too long to achieve the desired focal length and sufficiently correct aberrations throughout the optical system, making it difficult to miniaturize the optical system. On the other hand, if the focal length f2 of the second lens group falls below the lower limit of the above formula (3'), the power of the second lens group will be too strong. To achieve a balance between the second lens group, which has negative power, and the first and third lens groups, which have positive power, the powers of the first and third lens groups will also be too strong. As a result, aberrations in the second lens group will be over-corrected, and manufacturing errors will be more likely to occur.

[0016] Furthermore, when the thickness of the final lens in the first group at the central optical axis is t1e and the focal length of the entire optical system is F, it is preferable that the following formula (4) be satisfied. 0.1 <t1e / F<0.5···(4) By ensuring that the thickness t1e of the final lens in the first group at the central optical axis satisfies the lower limit of the above formula (4), i.e., by increasing the thickness t1e of the final lens to a certain extent, it is possible to ensure sufficient refractive power without making the curvature of the object-side surface of the final lens too sharp. This reduces the occurrence of spherical aberration and makes the lens less likely to decenter. Furthermore, if the thickness t1e of the final lens in the first group at the central optical axis falls below the lower limit of the above formula (4), it becomes difficult to sufficiently correct spherical aberration and off-axis aberration. On the other hand, by ensuring that the thickness t1e of the final lens in the first group at the central optical axis satisfies the upper limit of the above formula (4), i.e., by not increasing the thickness t1e of the final lens too much, it is possible to ensure the compactness of the entire optical system.

[0017] Furthermore, when the radius of curvature of the object-side surface of the final lens in the first group is R1ef and the focal length of the entire optical system is F, it is preferable that the following formula (5) be satisfied. 0.1 <R1ef / F<1···(5) If the radius of curvature R1ef of the object-side surface of the final lens in the first group exceeds the upper limit of equation (5) above, the positive power cannot be appropriately shared between the final lens and the lenses other than the final lens in the first group, making it difficult to sufficiently correct spherical aberration. Furthermore, in order to sufficiently correct spherical aberration, the thickness t1e of the final lens at the central optical axis becomes too large, which affects the compactness of the entire optical system and increases manufacturing costs and the weight of the entire optical system. On the other hand, if the radius of curvature R1ef of the object-side surface of the final lens in the first group falls below the lower limit of equation (5) above, the curvature of the object-side surface of the final lens becomes too sharp, resulting in severe spherical aberration and making manufacturing errors more likely to occur.

[0018] Furthermore, when the radius of curvature of the object side surface of the final lens in the first group is R1ef and the radius of curvature of the image side surface of the final lens in the first group is R1er, it is preferable that the following formula (6) be satisfied. 1 <R1ef / R1er<1.8···(6) If the radius of curvature R1ef of the object-side surface and the radius of curvature R1er of the image-side surface of the final lens in the first group satisfy the above-mentioned formula (6), the curvatures of the object-side and image-side surfaces of the final lens can be balanced, and spherical aberration and field curvature can be suitably corrected. Specifically, if the radius of curvature R1ef and the radius of curvature R1er of the object-side surface of the final lens in the first group exceed the upper limit of the above formula (6), the curvature of the object-side surface of the final lens will be too gentle, resulting in an excessively thick thickness t1e of the final lens, or the curvature of the image-side surface of the final lens will be too steep, resulting in overcorrection of field curvature and increased susceptibility to manufacturing errors.On the other hand, if the radius of curvature R1ef and the radius of curvature R1er of the object-side surface of the final lens in the first group fall below the lower limit of the above formula (6), the curvature of the object-side surface of the final lens will be too steep, resulting in significant spherical aberration, or the curvature of the image-side surface of the final lens will be too gentle, resulting in insufficient correction of field curvature.

[0019] Furthermore, when the rate of change of the refractive index with temperature of the lens in the second group is dn2 / dt and the average of the rates of change of the refractive index with temperature of the lens in the first group and the lens in the third group is dN / dt, it is preferable that the following equations (7) and (8) be satisfied: dn2 / dt>4×10 -6 ···(7) dN / dt<4×10 -6 ···(8) By satisfying the above formula (8), the rate of change with temperature of the refractive index of the lenses in the first and third groups, which have positive power, is made small, and by satisfying the above formula (7), the rate of change with temperature of the refractive index of the lens in the second group, which has negative power, is made large to a certain extent. Therefore, even if the barrel and intermediate ring holding the lenses in the first to third groups are made of a metal or the like having a higher linear expansion coefficient than glass, and the expansion of the barrel and intermediate ring due to temperature changes causes the position of the image sensor to shift away from the lens groups, the shift can be offset by the change in focal length caused by the change in the refractive index of the lens in the second group. This makes it possible to provide an imaging lens system that is resistant to temperature changes.

[0020] (Embodiment 2) The near-infrared imaging lens system according to the second embodiment has the same lens configuration as the near-infrared imaging lens system according to the first embodiment, and therefore a description thereof will be omitted.

[0021] Furthermore, in the second embodiment, when the refractive index of the first lens in the third group at 905 nm is n31 and the refractive index of the second lens in the third group at 905 nm is n32, it is preferable that the following expressions (9) and (10) be satisfied: n31≧1.67 (9) n32≧1.70 (10) By satisfying the above formulas (9) and (10), the occurrence of ghosts can be suppressed. Specifically, ghosts occur when light reflected from the sensor surface of the image sensor is reflected again by a lens located close to the image sensor and then enters the sensor surface of the image sensor. Therefore, by having a relatively large refractive index for the first and second lenses of the third group located close to the image sensor, the reflectance at the interface between the AR coating and the lens surface can be reduced. This makes it possible to suppress the reflection of ghost light at the interface between the AR coating and the lens surface of the first and second lenses, thereby suppressing the occurrence of ghosts.

[0022] Furthermore, when the radius of curvature of the object-side surface of the first lens in the third group is R31f, the focal length of the entire optical system is F, the thickness of the second lens in the third group at the central optical axis is t32, and the total length of the entire optical system is TTL, it is preferable that the following equations (11) and (12) be satisfied. -3.2 <R31f / F<2.0···(11) 0.24 <t32 / TTL<0.28···(12) Because the refractive index of the first lens in the third group is relatively large, the power of the first lens can be increased, allowing the curvature of the lens surface of the first lens to be gentle. However, if the curvature of the lens surface of the first lens is gentle, ghost light reflected from the lens surface is likely to be imaged on the sensor surface of the image sensor. Therefore, by ensuring that the radius of curvature R31f of the object-side surface of the first lens in the third group satisfies the above formula (11), ghost light can be prevented from being imaged on the sensor surface of the image sensor. Furthermore, by having the radius of curvature R31f of the object-side surface of the first lens in the third group satisfy the above formula (11), the curvatures of the object-side and image-side surfaces of the first lens become sharper, allowing the positive power of the first lens to be strengthened and the positive power of the second lens in the third group to be correspondingly reduced. This allows the thickness t32 of the second lens at the central optical axis to be thin. Specifically, the thickness t32 of the second lens can satisfy the above formula (12), contributing to the miniaturization of the optical system.

[0023] Furthermore, when the focal length of the first lens in the third group is f31, the focal length of the second lens in the third group is f32, and the focal length of the entire optical system is F, it is preferable that the following equations (13) and (14) be satisfied: 1.63 <f31 / F<1.91···(13) 0.71 <f32 / F<0.77···(14) Because the refractive index of the first lens in the third group is relatively large and the curvatures of the object-side and image-side surfaces of the first lens are steep, the positive power of the first lens can be strengthened, and the positive power of the second lens in the third group can be weakened accordingly. Specifically, by making the focal length f31 of the first lens in the third group and the focal length f32 of the second lens in the third group satisfy the above-mentioned formulas (13) and (14), a favorable balance is achieved between the positive power of the first lens and the positive power of the second lens.

[0024] Furthermore, when the total thickness of the lenses constituting the third group at the central optical axis is tG3 and the total thickness of the lenses in the entire optical system at the central optical axis is tE, it is preferable that the following equation (15) be satisfied: tG3 / tE≧0.34 (15) If the total thickness tG3 of the lenses constituting the third group at the central optical axis satisfies the above formula (15), the thickness of the lenses constituting the third group can be made relatively thicker than those of the other groups, and the intensity of ghost light that passes through the lenses constituting the third group can be attenuated.

[0025] It is also preferable that the third group has at least one lens element formed from a glass material having a transmittance of 99.7% or less for light rays of 905 nm at a thickness of 10 mm. This makes it possible to attenuate the intensity of ghost light that passes through the lens in the third group.

[0026] (Example) Next, Examples 1 to 5 corresponding to the near-infrared imaging lens system of the first embodiment and Examples 6 to 8 corresponding to the near-infrared imaging lens system of the second embodiment will be described with reference to the drawings. Example 1 FIG. 1 is a cross-sectional view showing the configuration of a near-infrared imaging lens system 11 according to a first embodiment. The near-infrared imaging lens system 11 according to Example 1 comprises, in order from the object side to the image side, a first lens unit G1 having positive power, a second lens unit G2 having negative power, and a third lens unit G3 having positive power. The image plane of the near-infrared imaging lens system 11 is indicated by IMG.

[0027] The first group G1 consists of, in order from the object side to the image side, a first lens L11, a second lens L12, and a final lens L1e. All of the object-side surfaces S2, S4, and S6 of the first lens L11, the second lens L12, and the final lens L1e convexly face the object side. The image-side surface S3 of the first lens L11 faces a concave surface toward the image side. The image-side surface S5 of the second lens L12 faces a concave surface toward the image side. The image-side surface S7 of the final lens L1e faces a concave surface toward the image side. The first lens L11 and the second lens L12 have positive power, and the final lens L1e has negative power. The first lens L11, the second lens L12, and the final lens L1e are glass lenses.

[0028] The second group G2 is made of a glass lens L2, which is biconcave and has negative power.

[0029] The third lens group G3 consists, in order from the object side to the image side, of a first lens 31 having positive power and a second lens 32 having positive power. The object-side surface S10 of the first lens L31 is concave toward the object side, and the image-side surface S11 of the first lens L31 is convex toward the image side. The object-side surface S12 of the second lens L32 is convex toward the object side, and the image-side surface S13 of the second lens 32 is concave toward the image side. The first lens L31 and the second lens L32 are glass lenses.

[0030] The aperture stop STOP is an aperture that determines the F-number (F-number, Fno) of the lens system, and is located on the object side of the first group G1.

[0031] Table 1 shows lens data for each lens surface in the near-infrared imaging lens system 11 of Example 1. In Table 1, the lens data includes the glass material, the refractive index n for 905 nm light, the curvature of each surface, the radius of curvature (mm) of each surface, the surface spacing (mm) at the central optical axis, and the effective diameter (mm). The refractive indices shown in Table 1 are values ​​when the ambient temperature t (°C), which is the temperature around the near-infrared imaging lens system 11, is 25 (°C). In Table 1, for example, "3.8297E-05" corresponds to "3.8297×10 -5 " The same applies to the following tables.

[0032] [Table 1]

[0033] Next, aberrations will be described with reference to the drawings. Fig. 2 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 1. As shown in Fig. 2, the near-infrared imaging lens system 11 of Example 1 has a half angle of view of 12.0° and an F-number of 1.4. In the longitudinal aberration diagram of Figure 2(A), the horizontal axis indicates the position where the light ray intersects with the optical axis OA, and the vertical axis indicates the height of the light ray passing through the entrance pupil. Figure 2(A) also shows the simulation results for a 905 nm light ray. In the field curvature diagram of Figure 2(B), the horizontal axis represents the distance along the optical axis OA, and the vertical axis represents the image height (angle of view). In the field curvature diagram of Figure 2(B), Sag represents the image formation position of the sagittal ray bundle, and Tan represents the image formation position of the tangential ray bundle. Figure 2(B) also shows the simulation results for light with a wavelength of 905 nm. In the distortion diagram of Figure 2(C), the horizontal axis represents the amount of image distortion (%) and the vertical axis represents the image height (angle of view). Figure 2(C) also shows the results of a simulation using light with a wavelength of 905 nm. FIG. 2 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion when the environmental temperature t (° C.) is 25 (° C.).

[0034] Example 2 3 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 2. The near-infrared imaging lens system 11 according to Example 2 has the same lens configuration as Example 1. Hereinafter, characteristic data of the near-infrared imaging lens system 11 according to Example 2 will be described.

[0035] Table 2 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 2. The items shown in Table 2 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0036] [Table 2]

[0037] 4 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 2. The explanation of each aberration diagram shown in FIG. 4 is the same as that in FIG. 2, and therefore will not be repeated.

[0038] Example 3 FIG. 5 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 3. Similar to Example 1, the near-infrared imaging lens system 11 according to Example 3 is composed of, in order from the object side to the image side, a first group G1, a second group G2, and a third group G3. The first group G1 and the second group G2 of Example 3 have the same lens configuration as Example 1, while the lens configuration of the third group G3 of Example 3 differs from Example 1. The near-infrared imaging lens system 11 according to Example 3 differs from Example 1 in that an aperture stop STOP is disposed between the second lens L12 of the first group G1 and the final lens L1e. Therefore, a description of the lens configurations of the first group G1 and the second group G2 of Example 3 will be omitted.

[0039] The third lens group G3 consists, in order from the object side to the image side, of a first lens 31 having positive power, a second lens 32 having positive power, and a third lens 33 having positive power. The object-side surface S11 of the first lens L31 faces a convex surface toward the object side, and the image-side surface S12 of the first lens L31 faces a convex surface toward the image side. The object-side surface S13 of the second lens L32 faces a convex surface toward the object side, and the image-side surface S14 of the second lens L32 faces a convex surface toward the image side. The object-side surface S15 of the third lens L33 faces a concave surface toward the object side, and the image-side surface S16 of the third lens L33 faces a convex surface toward the image side. The first lens L31, the second lens L32, and the third lens L33 are glass lenses.

[0040] The characteristic data of the near-infrared imaging lens system 11 according to Example 3 will be described below. Table 3 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 3. The items shown in Table 3 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0041] [Table 3]

[0042] Fig. 6 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 3. The explanation of each aberration diagram shown in Fig. 6 is the same as that in Fig. 2, and therefore will not be repeated. As shown in Fig. 6, the near-infrared imaging lens system 11 of Example 3 has a half angle of view of 12.0° and an F-number of 1.2.

[0043] Example 4 7 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 4. Similar to Example 1, the near-infrared imaging lens system 11 according to Example 4 is composed of, in order from the object side to the image side, a first group G1, a second group G2, and a third group G3. The first group G1 and the second group G2 of Example 4 have the same lens configuration as Example 1, while the lens configuration of the third group G3 of Example 4 is different from Example 1. Therefore, a description of the lens configurations of the first group G1 and the second group G2 of Example 4 will be omitted.

[0044] The third lens group G3 consists, in order from the object side to the image side, of a first lens 31 having positive power, a second lens 32 having positive power, and a third lens 33 having positive power. The object-side surface S10 of the first lens L31 is concave toward the object side, and the image-side surface S11 of the first lens L31 is convex toward the image side. The object-side surface S12 of the second lens L32 is convex toward the object side, and the image-side surface S13 of the second lens L32 is concave toward the image side. The object-side surface S14 of the third lens L33 is convex toward the object side, and the image-side surface S15 of the third lens L33 is concave toward the image side. The first lens L31, the second lens L32, and the third lens L33 are glass lenses.

[0045] Hereinafter, the characteristic data of the near-infrared imaging lens system 11 according to Example 4 will be described. Table 4 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 4. The items shown in Table 4 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0046] [Table 4]

[0047] 8 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 4. The explanation of each aberration diagram shown in FIG. 8 is the same as that in FIG. 2, and therefore will not be repeated.

[0048] Example 5 9 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 5. Similar to Example 1, the near-infrared imaging lens system 11 according to Example 5 is composed of, in order from the object side to the image side, a first group G1, a second group G2, and a third group G3. The second group G2 and the third group G3 of Example 5 have the same lens configuration as Example 1, while the lens configuration of the first group G1 of Example 5 is different from that of Example 1. Therefore, a description of the lens configurations of the second group G2 and the third group G3 of Example 5 will be omitted.

[0049] The first group G1 consists of, in order from the object side to the image side, a first lens L11, a second lens L12, a third lens L13, and a final lens L1e. The object-side surfaces S2, S4, S6, and S8 of all the lenses constituting the first group G1, namely the first lens L11, the second lens L12, the third lens L13, and the final lens L1e, face convexly toward the object side. The image-side surface S3 of the first lens L11 faces concavely toward the image side. The image-side surface S5 of the second lens L12 faces concavely toward the image side. The image-side surface S7 of the third lens L13 faces concavely toward the image side. The image-side surface S9 of the final lens L1e faces concavely toward the image side. The first lens L11, the second lens L12, and the third lens L13 have positive power, and the final lens L1e has negative power. The first lens L11, the second lens L12, the third lens L13, and the final lens L1e are glass lenses.

[0050] Hereinafter, the characteristic data of the near-infrared imaging lens system 11 according to Example 5 will be described. Table 5 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 5. The items shown in Table 5 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0051] [Table 5]

[0052] Fig. 10 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 5. The explanation of each aberration diagram shown in Fig. 10 is the same as that in Fig. 2, and therefore will not be repeated. As shown in Fig. 10, the near-infrared imaging lens system 11 of Example 5 has a half angle of view of 12.0° and an F-number of 1.2.

[0053] Example 6 11 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 6. The near-infrared imaging lens system 11 according to Example 6 has the same lens configuration as Example 1. Hereinafter, characteristic data of the near-infrared imaging lens system 11 according to Example 6 will be described.

[0054] Table 6 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 6. The items shown in Table 6 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0055] [Table 6]

[0056] 12 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 6. The explanation of each aberration diagram shown in Fig. 12 is the same as that in Fig. 2, and therefore will not be repeated.

[0057] Example 7 13 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 7. The near-infrared imaging lens system 11 according to Example 7 has the same lens configuration as Example 1. Hereinafter, characteristic data of the near-infrared imaging lens system 11 according to Example 7 will be described.

[0058] Table 7 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 7. The items shown in Table 7 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0059] [Table 7]

[0060] 14 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 7. The explanation of each aberration diagram shown in FIG. 14 is the same as that in FIG. 2, and therefore will not be repeated.

[0061] Example 8 15 is a cross-sectional view showing a near-infrared imaging lens system 11 according to Example 8. The near-infrared imaging lens system 11 according to Example 8 has the same lens configuration as Example 1. Hereinafter, characteristic data of the near-infrared imaging lens system 11 according to Example 8 will be described.

[0062] Table 8 shows lens data for each lens surface of the near-infrared imaging lens system 11 according to Example 8. The items shown in Table 8 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0063] [Table 8]

[0064] 16 shows diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the near-infrared imaging lens system 11 of Example 8. The explanation of each aberration diagram shown in Fig. 16 is the same as that in Fig. 2, and therefore will not be repeated.

[0065] Tables 9 and 10 show the focal length f11 of the first lens L11 in the first group G1, the focal length f12 of the second lens L12, the focal length f13 of the third lens L13, the focal length f1e of the final lens L1e, the focal length f2 of the lens L2 in the second group G2, the focal length f31 of the first lens L31 in the third group G3, the focal length f32 of the second lens L32, the focal length f33 of the third lens L33, the focal length F of the entire optical system of the near-infrared imaging lens system 11, the overall length TTL of the optical system of the near-infrared imaging lens system 11, |R2f| / | The following table shows the values ​​of R2r|, R1er / F, |f2| / F, t1e / F, R1ef / F, R1ef / R1er, dn2 / dt, dN / dt, the refractive index n31 of the first lens L31 in the third group G3 at 905 nm, the refractive index n32 of the second lens L32 in the third group G3 at 905 nm, R31f / F, t32 / TTL, f31 / F, f32 / F, tG3 / tE, the transmittance (%) of 905 nm light at a 10 mm thickness of the first lens L31 and the second lens L32 in the third group G3, and TTL / F. In Tables 9 and 10, the focal length, the thickness at the central optical axis of the lens, and the overall length of the optical system are all in mm. The focal lengths shown in Tables 9 and 10 were calculated using light with a wavelength of 905 nm. In addition, in Tables 9 and 10, the units of dn2 / dt and dN / dt are both 1 / K.

[0066] [Table 9]

[0067] [Table 10]

[0068] In Examples 1 to 8, the near-infrared imaging lens system 11 comprises, in order from the object side to the image side, a first group G1 having positive power, a second group G2 having negative power, and a third group G3 having positive power. The first group G1 comprises at least three lenses L11, L12, . . . , L1e. The object-side surfaces of all the lenses L11, L12, . . . , L1e convex toward the object side of the first group G1. All the lenses except the final lens L1e, which is located closest to the image side of the first group G1, The outer lenses L11, L12, ... have positive power, and the image-side surface of the final lens L1e in the first group G1 faces concave toward the image side. The second group G2 is composed of a biconcave lens L2 with negative power. The third group G3 is composed of at least two lenses L31, L32, ..., which, in order from the object side to the image side, include a first lens L31 with positive power and a convex surface toward the image side, and a second lens L32 with positive power and a convex surface toward the object side. As a result, the near-infrared imaging lens systems 11 according to Examples 1 to 8 can suppress the occurrence of aberrations and easily correct aberrations throughout the lens system, thereby achieving excellent imaging performance. Furthermore, because the occurrence of aberrations is suppressed and aberration correction throughout the lens system is easily performed, the F-number can be reduced, and the overall length of the lens system can be shortened. This means that the lens system can be brighter and more compact. In fact, the near-infrared imaging lens systems 11 according to Examples 1 to 8 suitably reduce various aberrations, have excellent imaging performance, and achieve high resolution, as shown in Figures 2, 4, 6, 8, 10, 12, 14, and 16. Furthermore, the near-infrared imaging lens systems 11 according to Examples 1 to 8 have F-numbers of about 1.2 to 1.4, making them bright lens systems.

[0069] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above formulas (1') and (2). This makes it possible to balance the curvatures of three surfaces: the image side surface of the final lens L1e in the first group G1, the object side surface of the lens L2 in the second group G2, and the image side surface of the lens L2 in the second group G2; and to distribute power in a balanced manner to these three surfaces. This makes it possible to effectively correct field curvature.

[0070] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above formula (3'), which makes it possible to reduce the size of the near-infrared imaging lens system 11 and to suppress the occurrence of manufacturing errors.

[0071] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above formula (4). This eliminates the need to make the thickness t1e of the final lens too thick, making it possible to reduce the size of the near-infrared imaging lens system 11 and suppress the occurrence of spherical aberration. Lens decentering is less likely to occur.

[0072] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above formula (5), which makes it possible to sufficiently correct spherical aberration without increasing the thickness t1e of the final lens, and also to suppress the occurrence of manufacturing errors.

[0073] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above formula (6), which makes it possible to achieve a balance between the curvatures of the object-side and image-side surfaces of the final lens L1e in the first group G1, and to suitably correct spherical aberration and curvature of field.

[0074] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above expressions (7) and (8), thereby making it possible to provide a near-infrared imaging lens system 11 that is resistant to temperature changes.

[0075] Furthermore, in Examples 1 to 8, the near-infrared imaging lens system 11 satisfies the above formulas (9) and (10), which makes it possible to suppress reflection of ghost light at the interfaces between the AR coatings and the lens surfaces of the first lens L31 and the second lens L32, thereby making it possible to suppress the occurrence of ghosts.

[0076] Furthermore, in Examples 6 to 8, the near-infrared imaging lens system 11 satisfies the above expressions (11) and (12). When the radius of curvature R31f of the object-side surface of the first lens L31 in the third group G3 satisfies the above expression (11), ghost light can be prevented from forming an image on the sensor surface of the image sensor, and when the above expression (12) is satisfied, the thickness t32 of the second lens L32 at the central optical axis can be reduced, which can contribute to the miniaturization of the optical system.

[0077] In Examples 6 to 8, the near-infrared imaging lens system 11 satisfies the above expressions (13) and (14), thereby achieving a favorable balance between the positive power of the first lens L31 and the positive power of the second lens L32 in the third group G3.

[0078] Furthermore, in Examples 6 to 8, the near-infrared imaging lens system 11 satisfies the above formula (15), which allows the lenses L31 and L32 constituting the third group G3 to be made thicker than the other groups, thereby attenuating the intensity of ghost light passing through the lenses L31 and L32 constituting the third group G3.

[0079] In Examples 1 to 8, the third group G3 has a first lens L31 made of a glass material with a transmittance of 99.7% or less for light rays of 905 nm at a thickness of 10 mm, which makes it possible to attenuate the intensity of ghost light passing through the first lens L31 of the third group G3.

[0080] In addition, in Examples 1 to 8, the value of TTL / F satisfies the following formula (16). 1.25 <TTL / F<1.8···(16) When the value of TTL / F satisfies the above formula (16), the total optical system length TTL is short relative to the overall focal length F of the near-infrared imaging lens system 11, and the near-infrared imaging lens system 11 can be made compact.

[0081] (Embodiment 3) FIG. 17 is a schematic diagram of a vehicle 40 equipped with an in-vehicle system including an imaging device 50 including a near-infrared imaging lens system 11 according to the first or second embodiment and an imaging element that converts light collected through the near-infrared imaging lens system 11 into an electrical signal. As shown in the figure, the imaging device 50 can be mounted on the vehicle 40, and FIG. 17 illustrates an example of the mounting position of the imaging device 50 on the vehicle 40. The imaging device 50 mounted on the vehicle 40 can also be called an in-vehicle camera and can be installed in various locations on the vehicle 40. For example, the first imaging device 50a may be installed on or near the front bumper as a camera that monitors the front of the vehicle 40 while the vehicle 40 is traveling. The second imaging device 50b that monitors the front of the vehicle 40 may be installed near an inner rearview mirror inside the vehicle 40. The third imaging device 50c may be installed on the dashboard or in the instrument panel as a camera that monitors the driver's driving status. The fourth imaging device 50d may be installed at the rear of the vehicle 40 to monitor the rear of the vehicle 40. The imaging devices 50a and 50b can be called front cameras. The third imaging device 50c can be called an in-camera. The fourth imaging device 50d can be called a rear camera. The imaging device 50 is not limited to these, and includes imaging devices installed in various positions, such as a left side camera that captures images of the left rear side and a right side camera that captures images of the right rear side.

[0082] An image signal of an image captured by the imaging device 50 may be output to an information processing device 42 and / or a display device 43, etc., within the vehicle 40. The information processing device 42 and the display device 43, together with the imaging device 50, constitute an in-vehicle system. The information processing device 42 within the vehicle 40 includes a device that processes the image signal acquired by the imaging device 50 and recognizes various objects in the captured image to assist the driver in driving. The information processing device 42 may include, but is not limited to, a navigation system, a collision damage mitigation braking system, a vehicle-to-vehicle distance control system, a lane departure warning system, etc. The display device 43 displays an image processed and output by the information processing device 42, but can also receive an image signal directly from the imaging device 50. The display device 43 may be, but is not limited to, a liquid crystal display (LCD), an organic electroluminescence (EL) display, or an inorganic EL display. The display device 43 can display to the driver an image signal output from the imaging device 50, which captures an image from a position difficult for the driver to view, such as a rear camera.

[0083] Fig. 18 shows the configuration of an imaging device 50 that constitutes the in-vehicle system of Fig. 17. As shown in the figure, the imaging device 50 according to one embodiment includes a control unit 52, a storage unit 54, and a camera module 30.

[0084] The control unit 52 controls the camera module 30 and processes the electrical signal output from the image sensor 12 of the camera module 30. The control unit 52 may be configured as, for example, a processor. The control unit 52 may also include one or more processors. The processor may include a general-purpose processor that loads a specific program to execute a specific function, and a dedicated processor specialized for a specific process. The dedicated processor may include an application-specific integrated circuit (IC). An application-specific IC is also called an application-specific integrated circuit (ASIC). The processor may include a programmable logic device. A programmable logic device is also called a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The control unit 52 may be either a system-on-a-chip (SoC) or a system in a package (SiP) in which one or more processors work together.

[0085] The storage unit 54 stores various information or parameters related to the operation of the imaging device 50. The storage unit 54 may be configured with, for example, a semiconductor memory or the like. The storage unit 54 may function as a work memory for the control unit 52. The storage unit 54 may store captured images. The storage unit 54 may store various parameters, etc., used by the control unit 52 to perform detection processing based on the captured images. The storage unit 54 may be included in the control unit 52.

[0086] The camera module 30 captures an image of a subject formed via the near-infrared imaging lens system 11 with the image sensor 12 and outputs the captured image. The image captured by the camera module 30 is also referred to as a captured image.

[0087] The imaging element 12 may be configured, for example, as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device). The imaging element 12 has an imaging surface on which a plurality of pixels are arranged. Each pixel outputs a signal specified by a current or voltage according to the amount of incident light. The signal output by each pixel is also referred to as imaging data.

[0088] The imaging data may be read by the camera module 30 for all pixels and imported into the control unit 52 as a captured image. A captured image read out for all pixels is also referred to as a maximum captured image. The imaging data may be read by the camera module 30 for some pixels and imported as a captured image. In other words, the imaging data may be read out from pixels in a predetermined capture range. The imaging data read out from pixels in the predetermined capture range may be imported as a captured image. The predetermined capture range may be set by the control unit 52. The camera module 30 may acquire the predetermined capture range from the control unit 52. The imaging element 12 may capture an image of a predetermined capture range from the subject image formed via the near-infrared imaging lens system 11.

[0089] It should be noted that the present invention is not limited to the above-described embodiments and can be modified as appropriate without departing from the spirit and scope of the present invention. For example, the applications of the near-infrared imaging lens system of the present invention are not limited to vehicle-mounted cameras and surveillance cameras, and it can also be used for other applications, such as being mounted on small electronic devices such as mobile phones. [Explanation of symbols]

[0090] 11 Near-infrared imaging lens system 12 Image sensor 30 Camera Module 40 Vehicles (moving objects) 42 Information processing equipment (processing equipment) 43 Display device (output device) 50 Imaging device 52 Control section G1 Group 1 G2 2nd group G3 3rd group L11: First lens in the first group L12: Second lens in the first group L13: Third lens in the first group L1e: The final lens in the first group L2 2nd group of lenses L31: First lens in the third group L32 2nd lens in the 3rd group L33: 3rd lens in 3rd group STOP Aperture IMG Image plane OA optical axis

Claims

1. The lens comprises, in order from the object side to the image side, a first lens unit having positive power, a second lens unit having negative power, and a third lens unit having positive power, the first group is made up of at least three or more lenses, all of the lenses constituting the first group have object-side surfaces convex toward the object side, all of the lenses in the first group except for a final lens located closest to the image side have positive power, and the image-side surface of the final lens in the first group has a concave surface facing toward the image side, the second lens group is made up of a biconcave lens having negative power, the third group includes at least two or more lenses, and includes, in order from the object side to the image side, a first lens having a convex surface on its image side facing the image side and positive power, and a second lens having a convex surface on its object side facing the object side and positive power, a radius of curvature of the object-side surface of the first lens in the third group is R31f, a focal length of the entire optical system is F, a thickness of the second lens in the third group at the central optical axis is t32, and a total length of the entire optical system is TTL, the following expressions (11) and (12) are satisfied: -3.2<R31f / F<2.0...(11) 0.24<t32 / TTL<0.28...(12)

2. The lens comprises, in order from the object side to the image side, a first lens unit having positive power, a second lens unit having negative power, and a third lens unit having positive power, the first group is made up of at least three or more lenses, all of the lenses constituting the first group have object-side surfaces convex toward the object side, all of the lenses in the first group except for a final lens located closest to the image side have positive power, and the image-side surface of the final lens in the first group has a concave surface facing toward the image side, the second lens group is made up of a biconcave lens having negative power, the third group includes at least two or more lenses, and includes, in order from the object side to the image side, a first lens having a convex surface on its image side facing the image side and positive power, and a second lens having a convex surface on its object side facing the object side and positive power, a focal length of the first lens in the third group being f31, a focal length of the second lens in the third group being f32, and a focal length of the entire optical system being F, the near-infrared imaging lens system satisfying the following expressions (13) and (14): 1.63<f31 / F<1.91...(13) 0.71<f32 / F<0.77...(14)

3. 3. The near-infrared imaging lens system according to claim 1, wherein the following formulas (1) and (2) are satisfied, where R2f is the radius of curvature of the object-side surface of the lens in the second group, R2r is the radius of curvature of the image-side surface of the lens, R1er is the radius of curvature of the image-side surface of the final lens in the first group, and F is a focal length of the entire optical system: 0.2<|R2f| / |R2r|<2.5...(1) 0.1<R1er / F<1...(2)

4. 3. The near-infrared imaging lens system according to claim 1, wherein the following formula (3) is satisfied, where f2 is the focal length of the second lens group and F is the focal length of the entire optical system: 1<|f2| / F<3...(3)

5. 3. The near-infrared imaging lens system according to claim 1, wherein the following formula (4) is satisfied, where t1e is a thickness of the final lens in the first group at the central optical axis and F is a focal length of the entire optical system: 0.1<t1e / F<0.5...(4)

6. 3. The near-infrared imaging lens system according to claim 1, wherein the following formula (5) is satisfied, where R1ef is the radius of curvature of the object-side surface of the final lens in the first group, and F is the focal length of the entire optical system: 0.1<R1ef / F<1...(5)

7. 3. The near-infrared imaging lens system according to claim 1, wherein the following formula (6) is satisfied, where R1ef is a radius of curvature of the object-side surface of the final lens in the first group, and R1er is a radius of curvature of the image-side surface of the final lens in the first group: 1<R1ef / R1er<1.8...(6)

8. 3. The near-infrared imaging lens system according to claim 1, wherein the following formulas (7) and (8) are satisfied, where dn2 / dt is a rate of change of refractive index with temperature of the lens in the second group, and dN / dt is an average value of the rates of change of refractive index with temperature of the lenses in the first group and the third group: dn2 / dt>4×10 －６ ・・・(7) dN / dt<4×10 －６ ・・・(8)

9. 3. The near-infrared imaging lens system according to claim 1, wherein the following expressions (9) and (10) are satisfied, where n31 is a refractive index of the first lens in the third group at 905 nm and n32 is a refractive index of the second lens in the third group at 905 nm: n31≧1.67 (9) n32 ≧ 1.70 (10)

10. 3. The near-infrared imaging lens system according to claim 1, wherein the following formula (15) is satisfied, where tG3 is a total thickness of the lenses constituting the third group at the central optical axis, and tE is a total thickness of the lenses in the entire optical system at the central optical axis: tG3 / tE≧0.34...(15)

11. 3. The near-infrared imaging lens system according to claim 1, wherein the third group has at least one lens formed from a glass material having a transmittance of 99.7% or less for light rays of 905 nm at a thickness of 10 mm.

12. 12. A camera module comprising: a near-infrared imaging lens system according to claim 1; and an imaging element that converts light focused through the near-infrared imaging lens system into an electrical signal.

13. An in-vehicle system mounted on a vehicle, a camera module according to claim 12; an information processing device that processes a captured image output from the imaging element of the camera module and recognizes an object in the captured image; An in-vehicle system comprising:

14. A moving body equipped with the in-vehicle system according to claim 13, the in-vehicle system further includes an output device that outputs information to an occupant; The mobile body is characterized in that the information processing device is configured to output the recognition information of the object to the output device.

Images