Imaging lens systems, camera modules, in-vehicle systems, mobile objects

Abstract

To provide an imaging lens system which can offer high resolution and can be miniaturized, and a camera module, in-vehicle system, and mobile object.SOLUTION: An imaging lens system is comprised of: a first lens L1 with negative power and having a concave surface on the image side; a second lens L2 with negative power and having a concave surface on the image side; a third lens L3 with positive power and having a convex surface on the image side; an aperture stop STOP; a fourth lens L4 with positive power and having a convex surface on the object side; a fifth lens L5 and a sixth lens L6 which constitute a cemented lens and one of which has negative power and the other having positive power, wherein the lenses and the aperture stop arranged in order from the object side to the image side, and the imaging lens system satisfies conditional expressions (1)-(4), where f1, f3, f4, and f respectively represent focal lengths of the first lens L1, third lens L3, fourth lens L4, and entire optical system, and νd4 represents an Abbe number of the fourth lens L4 for the d-ray.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an imaging lens system, a camera module, an in-vehicle system, and a moving body. [Background technology]

[0002] In recent years, sensing functions have been increasingly required for vehicle-mounted cameras and surveillance cameras, and imaging elements are becoming larger and with higher resolution. Accordingly, imaging lens systems mounted on vehicle-mounted cameras and the like are also becoming larger. Specifically, the diameter of the first lens (the lens closest to the object) of the imaging lens system tends to become larger. For example, Patent Document 1 describes an imaging lens system consisting of six lenses mounted on vehicle-mounted cameras and the like, in which the diameter (effective diameter) of the first lens is approximately three times the diagonal length of the imaging element, making it a relatively large optical system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-057562 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, in recent years, due to the demand for omnidirectional sensing around the vehicle, in-vehicle cameras are increasingly being mounted in spatially limited locations such as side mirrors. This has led to a demand for smaller in-vehicle cameras. Furthermore, in some cases, in-vehicle cameras are mounted in place of side mirrors, creating a demand for even smaller in-vehicle cameras. The imaging lens system described in Patent Document 1 is a relatively large optical system, making it difficult to meet the demand for smaller in-vehicle cameras.

[0005] The present invention has been made in consideration of the above problems, and has as its object to provide an imaging lens system, a camera module, an in-vehicle system, and a mobile body that are compact and capable of achieving high resolution. [Means for solving the problem]

[0006] An imaging lens system of one embodiment includes, in order from the object side to the image side, a first lens having a concave surface on its image side facing the image side and negative power, a second lens having a concave surface on its image side facing the image side and negative power, a third lens having a convex surface on its image side facing the image side and positive power, a stop, a fourth lens having a convex surface on its object side facing the object side and positive power, and fifth and sixth lenses forming a cemented lens, one of which has negative power and the other has positive power, When the focal length of the first lens is defined as f1, the focal length of the fourth lens as f4, the Abbe number of the fourth lens at the d-line as νd4, the focal length of the third lens as f3, and the focal length of the entire optical system as f, the following conditional expressions (1) to (4) are satisfied. -5.0 <f1 / f<-3.0···(1) 2.7 <f4 / f<3.1···(2) νd4>60 (3) 6.0 <f3 / f<10.0···(4) [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an imaging lens system, a camera module, an in-vehicle system, and a mobile body that can achieve high resolution and are miniaturized. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a first embodiment. [Figure 2] 2A to 2C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, distortion, and chromatic aberration of magnification in the imaging lens system of Example 1. [Figure 3]FIG. 10 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a second embodiment. [Figure 4] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, distortion, and chromatic aberration of magnification in the imaging lens system of Example 2. [Figure 5] FIG. 10 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a third embodiment. [Figure 6] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, distortion, and chromatic aberration of magnification in the imaging lens system of Example 3. [Figure 7] FIG. 10 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a fourth embodiment. [Figure 8] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, distortion, and chromatic aberration of magnification in the imaging lens system of Example 4. [Figure 9] FIG. 10 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a fifth embodiment. [Figure 10] 10A to 10C are diagrams showing spherical aberration (longitudinal aberration), curvature of field, distortion, and chromatic aberration of magnification in the imaging lens system of Example 5. [Figure 11] 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 12] 12 is a block diagram showing the configuration of an imaging device that constitutes the in-vehicle system of FIG. 11. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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 "9.1 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," which is one of the Sustainable Development Goals (SDGs) advocated by the United Nations. Furthermore, this embodiment makes it possible to reduce the volume of the glass material used for the first lens, and to correct aberrations that occur when the diameter of the first lens is reduced without increasing the number of lenses that make up the imaging lens system, and it targets the Sustainable Development Goal proposed by the United Nations, which states, in "Goal 12. Ensure sustainable consumption and production patterns," that it aims to achieve Goal 12.8: By 2030, ensure that people everywhere have the relevant information and awareness for sustainable development and lifestyles in harmony with nature. (Embodiment 1: Imaging lens system) The imaging lens system according to the first embodiment includes a first lens having a concave image-side surface facing the image side and negative power, a second lens having a concave image-side surface facing the image side and negative power, a third lens having a convex image-side surface facing the image side and positive power, a stop, a fourth lens having a convex object-side surface facing the object side and positive power, and fifth and sixth lenses forming a cemented lens, one of which has negative power and the other has positive power, When the focal length of the first lens is defined as f1, the focal length of the fourth lens as f4, the Abbe number of the fourth lens at the d-line as νd4, the focal length of the third lens as f3, and the focal length of the entire optical system as f, the following conditional expressions (1) to (4) are satisfied: -5.0 <f1 / f<-3.0···(1) 2.7 <f4 / f<3.1···(2) νd4>60 (3) 6.0 <f3 / f<10.0···(4)

[0010] This makes it possible to achieve high resolution and provide a compact imaging lens system. Specifically, by ensuring that the power of the first lens is relatively strong enough to satisfy conditional expression (1), the diameter of the first lens can be made small, thereby enabling the optical system to be made compact. More specifically, if the value of f1 / f is −3.0 or greater, the focal length of the first lens is too long relative to the focal length of the entire optical system. In other words, the power of the first lens is too weak, the diameter of the first lens becomes large, and the imaging lens system cannot be reliably made compact. On the other hand, if the value of f1 / f is −5.0 or less, the focal length of the first lens is too short relative to the focal length of the entire optical system. In other words, the power of the first lens is too strong. While the diameter of the first lens can be made small, the lateral chromatic aberration generated in the first lens becomes too large, deteriorating the imaging performance of the imaging lens system. The value of f1 / f is more preferably −3.15 or greater and −3.70 or less. Furthermore, by ensuring that the power of the fourth lens satisfies conditional expression (2), high resolution can be achieved with greater certainty. Specifically, if the value of f4 / f is 3.1 or greater, the focal length of the fourth lens is too long relative to the focal length of the entire optical system. In other words, the power of the fourth lens is too weak, which increases the overall length of the optical system, making it difficult to reliably reduce the size of the imaging lens system. On the other hand, if the value of f4 / f is 2.7 or less, the focal length of the fourth lens is too short relative to the focal length of the entire optical system. In other words, the power of the fourth lens is too strong, which shortens the overall length of the optical system. This increases the error sensitivity of the imaging performance and makes it more susceptible to manufacturing errors. The value of f4 / f is more preferably 2.75 or greater and 2.95 or less. Furthermore, if the Abbe number νd4 of the fourth lens satisfies conditional expression (3), it is possible to correct lateral chromatic aberration occurring in the first lens, thereby achieving high resolution. Specifically, if the Abbe number νd4 of the fourth lens is 60 or less, it is not possible to sufficiently correct lateral chromatic aberration occurring in the first lens. The Abbe number νd4 of the fourth lens is more preferably greater than 63, and even more preferably greater than 68. Furthermore, by satisfying conditional expression (4), the distance from the entrance pupil to the aperture stop (the distance on the optical axis from the object-side surface of the first lens to the aperture stop) can be shortened, thereby enabling the miniaturization of the optical system. Specifically, if the value of f3 / f is 10.0 or greater, the focal length of the third lens is too long relative to the focal length of the entire optical system. In other words, the power of the third lens is too weak, widening the gap between the first lens and the aperture stop. This necessitates increasing the diameter of the first lens, making it impossible to miniaturize the imaging lens system. On the other hand, if the value of f3 / f is 6.0 or less, the focal length of the third lens is too short relative to the focal length of the entire optical system. In other words, the power of the third lens is too strong, narrowing the gap between the first lens and the aperture stop. While the diameter of the first lens can be reduced, the magnification chromatic aberration generated in the first lens becomes too large, deteriorating the imaging performance of the imaging lens system. The value of f3 / f is more preferably 6.5 or greater and 9.5 or less, and even more preferably 8.0 or greater and 9.0 or less. Therefore, it is possible to provide a compact imaging lens system that can achieve high resolution.

[0011] Furthermore, when the distance on the optical axis from the object side surface of the first lens to the image plane of the image sensor is defined as TTL and the focal length of the entire optical system is defined as f, it is preferable that the imaging lens system satisfy the following conditional expression (5): 9 <TTL / f<11···(5) By satisfying the above conditional expression (5), it is possible to reliably reduce the size of the imaging lens system. Specifically, if the value of TTL / f is 11 or greater, it is not possible to reliably reduce the size of the imaging lens system. On the other hand, if the value of TTL / f is 9 or less, it is necessary to reduce the size of each lens, which increases the difficulty of manufacturing, reduces the manufacturing yield, and increases the cost of parts. The value of TTL / f is more preferably 9.3 or greater and 10.5 or less, and even more preferably 9.5 or greater and 10.0 or less.

[0012] Furthermore, when the focal length of the fifth lens is defined as f5 and the focal length of the entire optical system is defined as f, it is preferable that the imaging lens system satisfies the following conditional expression (6): 10.0<|f5 / f|<30.0 (6) By satisfying the above conditional expression (6), it is possible to appropriately correct axial chromatic aberration that occurs when the fourth lens uses a glass material that satisfies conditional expressions (2) and (3). Specifically, if the value of |f5 / f| is 30.0 or greater, the power of the fifth lens is too weak, making it impossible to sufficiently correct axial chromatic aberration, and the resolution performance of the imaging lens system deteriorates. On the other hand, if the value of |f5 / f| is 10.0 or less, the power of the fifth lens is too strong, making excessive correction of axial chromatic aberration, and the resolution performance of the imaging lens system deteriorates. The value of |f5 / f| is more preferably 13.0 or greater and 28.5 or less, and even more preferably 14.5 or greater and 22.0 or less.

[0013] Furthermore, when the d-line refractive index of the first lens is defined as nd1, it is preferable that the following conditional expression (7) be satisfied. nd1>1.8 (7) By satisfying the above conditional expression (7), it is possible to reduce the diameter of the first lens. Specifically, if the value of nd1 is 1.8 or less, the power of the first lens is too weak, making it impossible to reduce the diameter of the first lens. The value of nd1 is more preferably 1.83 or more, and even more preferably 1.84 or more.

[0014] Preferably, the first and fourth lenses are glass lenses, and the second, third, fifth, and sixth lenses are plastic lenses. By using a glass lens as the first lens, it is possible to provide an imaging lens system that is highly weather resistant. Furthermore, by using a glass lens for the fourth lens, an imaging lens system can be provided in which focus shift due to changes in environmental temperature is reduced. Specifically, by using a glass lens for the fourth lens, a glass material having a temperature coefficient of refractive index relative to the d-line, dnd4 / dT, of less than 0 can be selected for the fourth lens. This allows the change in distance (focus shift amount) from the object-side lens surface of the first lens to the image plane of the imaging element, which is caused by expansion and contraction of the lens barrel in the optical axis direction due to changes in environmental temperature, to be offset by the focus shift amount due to temperature changes in the fourth lens itself. In particular, in an imaging lens system for vehicle use, when the temperature is high, the lens barrel expands in the optical axis direction, causing the image plane of the imaging element to move away from the imaging lens system. However, when the fourth lens becomes hot, the focal point of the fourth lens shifts toward the image side, thereby maintaining the imaging performance of the imaging lens system. On the other hand, by using plastic lenses for the second, third, fifth and sixth lenses, it is possible to reduce manufacturing costs.

[0015] It is also preferable that the object side and image side surfaces of the second lens have aspheric shapes, and that the object side surface of the second lens has an inflection point. Reducing the diameter of the first lens has the disadvantage that it becomes difficult to adjust the relationship between the angle of view and the image height of the image formed on the imaging element (hereinafter referred to as "angle of view characteristics"). However, by providing an inflection point on the object-side surface of the second lens, it becomes possible to easily adjust the angle of view characteristics. This makes it possible to suppress the reduction in peripheral illumination, which is a problem in wide-angle imaging lens systems. Specifically, by providing an inflection point on the object-side surface of the second lens, it becomes possible, for example, to intentionally form an image so that the magnification at the periphery is small on the image formation plane, thereby suppressing the reduction in peripheral illumination.

[0016] (Embodiment 2: Camera Module) The camera module according to the second embodiment includes the imaging lens system described above and an imaging element disposed at the focal position of the imaging lens system and converting light collected through the imaging lens system into an electrical signal, thereby achieving high resolution and providing a compact camera module.

[0017] Next, examples corresponding to the imaging lens system according to the first embodiment and the camera module according to the second embodiment will be described with reference to the drawings. Example 1 1 is a cross-sectional view showing the configuration of a camera module 10 of Example 1. Specifically, camera module 10 includes an imaging lens system 11 and an imaging element 12. Imaging lens system 11 and imaging element 12 are housed in a housing (not shown).

[0018] The imaging element 12 is an element that converts received light into an electrical signal, and is, for example, a CCD image sensor or a CMOS image sensor. The imaging element 12 is disposed at the imaging position (focal position) of the imaging lens system 11.

[0019] The imaging lens system 11 according to Example 1 comprises, in order from the object side to the image side, a front group Gf consisting of a first lens L1, a second lens L2, and a third lens L3, and a rear group Gr consisting of an aperture stop (STOP) and a fourth lens L4, a fifth lens L5, and a sixth lens L6. The imaging plane of the imaging lens system 11 is indicated by IMG. The first lens L1 and the fourth lens L4 are glass lenses. The second lens L2, the third lens L3, the fifth lens L5, and the sixth lens L6 are plastic lenses. If necessary, an optical filter (such as an infrared cut filter or a visible / infrared bandpass filter) may be disposed between the imaging lens system 11 and the imaging element 12. In this specification, an example in which an infrared cut filter (IRCF) is disposed between the imaging lens system 11 and the imaging element 12 will be described.

[0020] The first lens L1 is a glass lens having negative power. The object-side surface S1 of the first lens L1 has a spherical shape with a convex surface facing the object side. The image-side surface S2 of the first lens L1 has a spherical shape with a concave surface facing the image side.

[0021] The second lens L2 is a plastic lens with negative power. The object-side surface S3 of the second lens L2 has an aspheric shape with an inflection point. Specifically, the object-side surface S3 of the second lens L2 has a shape in which the central portion is concave toward the object side and the peripheral portion is convex toward the object side. In addition, the image-side surface S4 of the second lens L2 has an aspheric shape with a concave surface toward the image side.

[0022] The third lens L3 is a plastic lens with positive power. The object-side surface S5 of the third lens L3 has an aspheric shape with a concave surface facing the object side. The image-side surface S6 of the third lens L3 has an aspheric shape with a convex surface facing the image side.

[0023] The aperture stop STOP is an aperture that determines the F-number (F-number, Fno) of the lens system, and is disposed between the third lens L3 and the fourth lens L4.

[0024] The fourth lens L4 is a glass lens having positive power. The object-side surface S9 of the fourth lens L4 has a spherical shape with a convex surface facing the object side. The image-side surface S10 of the fourth lens L4 also has a spherical shape with a convex surface facing the image side.

[0025] The fifth lens L5 is a plastic lens having negative power. The object-side surface S11 of the fifth lens L5 has an aspheric shape with a convex surface facing the object side. The image-side surface S12 of the fifth lens L5 has an aspheric shape with a concave surface facing the image side.

[0026] The sixth lens L6 is a plastic lens with positive power. The object-side surface S13 of the sixth lens L6 has an aspheric shape with a convex surface facing the object side. The image-side surface S14 of the sixth lens L6 also has an aspheric shape with a convex surface facing the image side.

[0027] The fifth lens L5 and the sixth lens L6 form a cemented lens. That is, the image-side surface S12 of the fifth lens L5 and the object-side surface S13 of the sixth lens L6 are in contact with each other. The fifth lens L5 and the sixth lens L6 are cemented together with an adhesive layer having an axial thickness of 0.020 mm.

[0028] The infrared cut filter (IRCF) is a filter for cutting light in the infrared region. When designing the imaging lens system 11, the infrared cut filter is treated as an integral part of the imaging lens system 11. However, the infrared cut filter is not an essential component of the imaging lens system 11. The infrared cut filter is disposed on the image side of the sixth lens L6. Furthermore, a sensor cover glass may be placed between the infrared cut filter and the imaging element 12 to prevent dust from adhering to the imaging element 12.

[0029] Table 1 shows lens data for each lens surface in the imaging lens system 11 of Example 1. Table 1 presents the lens data, including the radius of curvature (mm) of each surface, the surface spacing (mm) at the central optical axis, the effective diameter (mm), the refractive index nd for the d-line, and the Abbe number vd for the d-line. In Table 1, surfaces marked with an asterisk (*) are aspherical.

[0030] [Table 1]

[0031] The aspherical shape used on the lens surface is expressed by the following equation, where z is the amount of sag, c is the reciprocal of the radius of curvature, k is the conic coefficient, r is the ray height from the optical axis OA, and the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th orders are α4, α6, α8, α10, α12, α14, and α16, respectively.

number

[0032] Table 2 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 1. In Table 2, for example, "-2.843E-03" represents "-2.843×10 -3 The same applies to the numerical expressions in the following tables.

[0033] [Table 2]

[0034] Next, aberrations will be described with reference to the drawings. Fig. 2 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system 11 of Example 1. As shown in Fig. 2, the imaging lens system 11 of Example 1 has an F-number of 2.0 and a half angle of view of 103°. In the longitudinal aberration diagram of Fig. 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. Fig. 2(A) also shows the simulation results for the d-line, C-line, and F-line. In the field curvature diagram of Fig. 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 Fig. 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. Fig. 2(B) also shows the simulation results using the d-line. In the distortion diagram of Figure 2(C), the horizontal axis represents image distortion (%) and the vertical axis represents image height (angle of view). Figure 2(C) also shows the results of a simulation using d-line light. In the lateral chromatic aberration diagram of Figure 2(D), the horizontal axis represents the amount of lateral chromatic aberration, and the vertical axis represents the image height (angle of view). Figure 2(D) also shows simulation results for the d-line, C-line, and F-line.

[0035] Example 2 3 is a cross-sectional view showing a camera module 10 according to Example 2. The imaging lens system 11 according to Example 2 has the same lens configuration as Example 1, and therefore its description will be omitted. The characteristic data of the imaging lens system 11 according to Example 2 will be described below.

[0036] Table 3 shows lens data for each lens surface of the imaging lens system 11 according to Example 2. The items shown in Table 3 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0037] [Table 3]

[0038] Table 4 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 2. In Table 4, the aspherical shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0039] [Table 4]

[0040] 4 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the 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.

[0041] Example 3 5 is a cross-sectional view showing a camera module 10 according to Example 3. The imaging lens system 11 according to Example 3 has the same lens configuration as Example 1, and therefore its description will be omitted. Below, characteristic data of the imaging lens system 11 according to Example 3 will be described.

[0042] Table 5 shows lens data for each lens surface of the imaging lens system 11 according to Example 3. The items shown in Table 5 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0043] [Table 5]

[0044] Table 6 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 3. In Table 6, the aspherical shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0045] [Table 6]

[0046] 6 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the 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. Example 4 7 is a cross-sectional view showing a camera module 10 according to Example 4. The imaging lens system 11 according to Example 4 has the same lens configuration as Example 1, and therefore its description will be omitted. The characteristic data of the imaging lens system 11 according to Example 4 will be described below.

[0047] Table 7 shows lens data for each lens surface of the imaging lens system 11 according to Example 4. The items shown in Table 7 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0048] [Table 7]

[0049] Table 8 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 4. In Table 8, the aspherical shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0050] [Table 8]

[0051] 8 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the 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. Example 5 9 is a cross-sectional view showing a camera module 10 according to Example 5. The imaging lens system 11 according to Example 5 differs from Example 1 in that the object side surface S3 of the second lens L2 has a convex shape facing the object side. The other configurations of the imaging lens system 11 according to Example 5 are the same as those of Example 1, and therefore descriptions thereof will be omitted. Below, characteristic data of the imaging lens system 11 according to Example 5 will be described.

[0052] Table 9 shows lens data for each lens surface of the imaging lens system 11 according to Example 5. The items shown in Table 9 are the same as those in Table 1, and therefore the explanation thereof will be omitted.

[0053] [Table 9]

[0054] Table 10 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 5. In Table 10, the aspherical shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0055] [Table 10]

[0056] 10 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the 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.

[0057] Table 11 shows the total optical length (TTL) of the imaging lens system 11, the focal length (f) of the entire optical system of the imaging lens system 11, the focal length (f) of the first lens L1, the focal length (f2) of the second lens L2, the focal length (f3) of the third lens L3, the focal length (f4) of the fourth lens L4, the focal length (f5) of the fifth lens L5, the focal length (f6) of the sixth lens L6, the values ​​of (f1 / f), (f2 / f), (f3 / f), (f4 / f), (f5 / f), (f6 / f), the value of (TTL / f), the d-line refractive index (nd1) of the first lens L1, and the Abbe number (νd4) of the d-line of the fourth lens. In Table 11, the focal lengths and total optical lengths are all in mm. The focal lengths and total optical lengths shown in Table 11 were calculated using light with a wavelength of 550 nm.

[0058] [Table 11]

[0059] In Examples 1 to 5, the power of the first lens L1 is relatively strong enough to satisfy conditional expression (1), which allows the aperture of the first lens L1 to be small, thereby enabling the optical system to be made compact. Specifically, because the value of f1 / f is smaller than -3.0, the aperture of the first lens can be made small, ensuring the miniaturization of the imaging lens system 11. Furthermore, because the value of f1 / f is greater than -5.0, the chromatic aberration of magnification occurring in the first lens L1 is kept within a suitable range, preventing deterioration of the imaging performance of the imaging lens system 11. In fact, in Examples 1 to 5, the chromatic aberration of magnification can be suitably reduced, as shown in FIGS. 2(D), 4(D), 6(D), 8(D), and 10(D).

[0060] Furthermore, by making the power of the fourth lens L4 satisfy conditional expression (2), high resolution can be achieved more reliably. Specifically, because the value of f4 / f is greater than 2.7, it is possible to prevent the error sensitivity of the imaging performance from becoming high and to avoid the likelihood of manufacturing errors occurring. Furthermore, because the value of f4 / f is less than 3.1, it is possible to avoid the overall length of the optical system from becoming long, and it is possible to reliably reduce the size of the imaging lens system 11.

[0061] Furthermore, when the Abbe number νd4 of the fourth lens L4 satisfies conditional expression (3), it is possible to correct the chromatic aberration of magnification that occurs in the first lens L1, thereby achieving high resolution. In fact, in Examples 1 to 5, as shown in Figures 2(D), 4(D), 6(D), 8(D), and 10(D), it is possible to suitably reduce the chromatic aberration of magnification.

[0062] Furthermore, since the power of the third lens L3 satisfies conditional expression (4), the distance from the entrance pupil to the aperture stop can be shortened, thereby enabling a compact optical system. Specifically, since the value of f3 / f is less than 10.0, the distance between the first lens L1 and the aperture stop is prevented from widening, the diameter of the first lens L1 can be reduced, and the imaging lens system 11 can be made smaller. Furthermore, since the value of f3 / f is greater than 6.0, the lateral chromatic aberration occurring in the first lens L1 can be prevented from becoming too large, thereby preventing deterioration of the imaging performance of the imaging lens system 11. Therefore, it is possible to provide an imaging lens system 11 that can achieve high resolution and is compact. In fact, in the imaging lens systems 11 according to Examples 1 to 5, the diameter (effective diameter) of the first lens L1 is slightly less than twice the diagonal length of the image sensor 12, thereby enabling a compact imaging lens system 11. Furthermore, as shown in FIGS. 2, 4, 6, 8, and 10, the imaging lens systems 11 according to Examples 1 to 5 suitably reduce spherical aberration, field curvature, distortion, and chromatic aberration of magnification, and are excellent in imaging performance and achieve high resolution.

[0063] Furthermore, in Examples 1 to 5, the imaging lens system 11 satisfies the above conditional expression (5), which ensures that the imaging lens system can be made compact.

[0064] Furthermore, in Examples 1 to 5, the imaging lens system 11 satisfies the above-mentioned conditional expression (6). This makes it possible to suitably correct the longitudinal chromatic aberration caused by the fourth lens L4. In fact, as shown in Figures 2, 4, 6, 8, and 10, the imaging lens systems 11 according to Examples 1 to 5 suitably reduce spherical aberration, field curvature, and distortion, and are able to achieve excellent imaging performance and high resolution.

[0065] Furthermore, in Examples 1 to 5, the imaging lens system 11 satisfies the above conditional expression (7), which allows the diameter of the first lens L1 to be reduced.

[0066] In Examples 1 to 5, the first lens L1 and the fourth lens L4 are glass lenses, and the second lens L2, the third lens L3, the fifth lens L5, and the sixth lens L6 are plastic lenses. By using a glass lens for the first lens L1, it is possible to provide an imaging lens system 11 with excellent weather resistance. By using a glass lens for the fourth lens L4, it is possible to provide an imaging lens system 11 in which focus shift due to changes in environmental temperature is reduced. Table 12 shows the amount of focus shift (μm) associated with changes in environmental temperature at the focal length f of the imaging lens system 11 in Examples 1 to 5. Table 12 also shows the amount of focus shift from the focal length f at a room temperature of 25°C. The material of the barrel and housing used to calculate the amount of focus shift at the focal length f shown in Table 10 is RenyXL1027U manufactured by Mitsubishi Engineering-Plastics Corporation. [Table 12] Furthermore, by using plastic lenses for the second lens L2, the third lens L3, the fifth lens L5, and the sixth lens L6, it is possible to reduce manufacturing costs.

[0067] In addition, in Examples 1 to 5, the object-side surface S3 and the image-side surface S4 of the second lens L2 have aspheric shapes, and the object-side surface S3 of the second lens L2 has an inflection point, which makes it easier to adjust the angle of view characteristics and makes it possible to suppress the reduction in peripheral light intensity that is a problem in wide-angle imaging lens systems.

[0068] Furthermore, the camera module 10 is equipped with an imaging lens system 11, which is miniaturized and has sufficient resolution required for image recognition in autonomous driving, thereby enabling the camera module 10 to be miniaturized and achieve high-precision sensing.

[0069] (Embodiment 3) FIG. 11 is a schematic diagram of a vehicle 40 equipped with an in-vehicle system including an imaging device 50 including an imaging lens system 11 according to the first or second embodiment and an imaging element 12 that converts light collected through the 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. 11 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.

[0070] 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 device, 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 a driver or other occupant, 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.

[0071] Fig. 12 shows the configuration of an imaging device 50 that constitutes the in-vehicle system of Fig. 11. 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 10.

[0072] The control unit 52 controls the camera module 10 and processes the electrical signal output from the image sensor 12 of the camera module 10. 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 an SoC (system-on-a-chip) or a SiP (system in a package) in which one or more processors work together.

[0073] 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.

[0074] As described above, the camera module 10 captures an image of a subject formed via the imaging lens system 11 with the imaging element 12 and outputs the captured image. The image captured by the camera module 10 is also referred to as a captured image.

[0075] 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.

[0076] The imaging data may be read by the camera module 10 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 10 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 10 may acquire the predetermined capture range from the control unit 52. The image sensor 12 may capture an image of a predetermined capture range from the subject image formed via the imaging lens system 11.

[0077] It should be noted that the present invention is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the spirit of the present invention. For example, the applications of the 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 purposes, such as being mounted on small electronic devices such as mobile phones. [Explanation of symbols]

[0078] 10 Camera Module 11 Imaging lens system 12 Image sensor 40 Vehicles (moving objects) 42 Information processing equipment (processing equipment) 43 Display device (output device) 50 Imaging device 52 Control section L1 First lens L2 Second lens L3 Third lens L4 4th lens L5 Fifth lens L6 6th lens STOP Aperture Gf front group Gr rear group IRCF Infrared Cut Filter IMG Image plane OA optical axis

Claims

1. and a fourth lens element having a convex surface on its object side facing the object side and positive power; a fifth lens element and a sixth lens element, which constitute a cemented lens, one of which has negative power and the other has positive power; When the focal length of the first lens is defined as f1, the focal length of the fourth lens is defined as f4, the Abbe number of the fourth lens at the d-line is defined as νd4, the focal length of the third lens is defined as f3, the focal length of the fifth lens is defined as f5, and the focal length of the entire optical system is defined as f, the following conditional expressions (1) to (4) and (6) are satisfied: Imaging lens system. -5.0<f1 / f<-3.0...(1) 2.7<f4 / f<3.1...(2) νd4>60...(3) 6.0<f3 / f<10.0...(4) 10.0<|f5 / f|<30.0...(6)

2. 2. The imaging lens system according to claim 1, wherein the following conditional expression (5) is satisfied, where TTL is defined as a distance on the optical axis from the object-side surface of the first lens to an image plane of an imaging element, and f is defined as a focal length of the entire optical system: 9<TTL / f<11...(5)

3. 2. The imaging lens system according to claim 1, wherein the following conditional expression (7) is satisfied when the d-line refractive index of the first lens is defined as nd1. nd1>1.8...(7)

4. 3. The imaging lens system according to claim 2, wherein the following conditional expression (7) is satisfied when the d-line refractive index of the first lens is defined as nd1. nd1>1.8...(7)

5. the first lens and the fourth lens are glass lenses, the second lens, the third lens, the fifth lens, and the sixth lens are plastic lenses. The imaging lens system according to claim 1 .

6. the first lens and the fourth lens are glass lenses, the second lens, the third lens, the fifth lens, and the sixth lens are plastic lenses.

3. The imaging lens system according to claim 2.

7. the first lens and the fourth lens are glass lenses, the second lens, the third lens, the fifth lens, and the sixth lens are plastic lenses.

4. The imaging lens system according to claim 3.

8. 2. The imaging lens system according to claim 1, wherein the object-side and image-side surfaces of the second lens have aspheric shapes, and the object-side surface of the second lens has an inflection point.

9. 3. The imaging lens system according to claim 2, wherein the object-side and image-side surfaces of the second lens have aspherical shapes, and the object-side surface of the second lens has an inflection point.

10. 4. The imaging lens system according to claim 3, wherein the object-side and image-side surfaces of the second lens have aspherical shapes, and the object-side surface of the second lens has an inflection point.

11. 6. The imaging lens system according to claim 5, wherein the object-side and image-side surfaces of the second lens have aspherical shapes, and the object-side surface of the second lens has an inflection point.

12. 12. A camera module comprising: the imaging lens system according to claim 1; and an imaging element that converts light collected through the 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