Imaging lens system, camera module, on-vehicle system, and moving body

Abstract

To provide an imaging lens system having sufficient brightness for a sensing function in bad weather such as night, rain, or fog, with a high resolution, a camera module, an on-vehicle system, and a moving body.SOLUTION: An imaging lens system 11 comprises a front group Gf, an aperture diaphragm STOP, and a rear group Gr, and comprises: a first lens L1 that has negative power and has an image-side surface having a concave surface facing an image side; a second lens L2 that has an object-side surface having a concave surface facing an object side; a third lens L3 that has positive power and has an image-side surface having a convex surface facing the image side; a fourth lens L4 and a fifth lens L5 one of which has negative power and the other of which has positive power and constitute a cemented lens; and a sixth lens L6 that has positive power. When a refractive index of the first lens L1 is defined as nd1, focal lengths of the second lens L2 and the entire optical system are defined as f2 and f, and the Abbe number of the third lens L3 is defined as νd3, the following conditional expressions are satisfied: nd1>1.7...(1), |f2 / f|>8...(2), νd3<55...(3).SELECTED DRAWING: Figure 2

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, cameras mounted on vehicles are increasingly required to have a sensing function for detecting people and objects. In addition, the camera must be bright enough to enable sensing at night and in bad weather such as rain and fog. For this reason, there is a demand for imaging lenses with small F-numbers, high brightness, and high resolution. Patent Document 1 describes a lens system for an in-vehicle sensing camera having an F-number of 1.60 to 1.63 and consisting of six lenses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7126868 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the imaging lens system described in Patent Document 1 has an F-number of 1.60 to 1.63, which is relatively dark and may be insufficient for sensing at night or in bad weather.

[0005] The present invention has been made in consideration of these problems, and has an object to provide an imaging lens system, a camera module, an in-vehicle system, and a moving body that have sufficient brightness for sensing functions at night and in bad weather such as rain and fog, and have high resolution. [Means for solving the problem]

[0006] An imaging lens system of one embodiment is composed of substantially six lenses, which are, in order from the object side to the image side, a front group, an aperture stop, and a rear group, and which comprises a first lens having a negative power and whose image side surface is concave toward the image side, a second lens having a concave surface toward the object side, a third lens having a positive power and whose image side surface is convex toward the image side, a fourth lens, a fifth lens, and a sixth lens having positive power, the fourth lens and the fifth lens constitute a cemented lens, one of which has a negative power and the other of which has a positive power; When the refractive index of the first lens with respect to the d-line is defined as nd1, the focal length of the second lens is defined as f2, the focal length of the entire optical system is defined as f, and the Abbe number of the third lens with respect to the d-line is defined as νd3, the following conditional expressions (1) to (3) are satisfied. nd1>1.7 (1) |f2 / f|>8 ···(2) νd3<55 (3) Effect 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 have sufficient brightness for sensing functions at night and in bad weather such as rain and fog, and have high resolution. [Brief description of the drawings]

[0008] [Figure 1] 10 is a cross-sectional view illustrating a distance ET12 parallel to the optical axis between an image side surface of an edge portion of a first lens and an object side surface of an edge portion of a second lens. [Diagram 2] 1 is a cross-sectional view showing a configuration of a camera module and an imaging lens system according to a first embodiment. [Diagram 3] 3A to 3C are diagrams showing spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system of Example 1. [Figure 4] FIG. 11 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a second embodiment. [Diagram 5]11A to 11C are diagrams showing spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system of Example 2. [Figure 6] FIG. 11 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a third embodiment. [Figure 7] 11A to 11C are diagrams showing spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system of Example 3. [Figure 8] FIG. 11 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a fourth embodiment. [Figure 9] 11A to 11C are diagrams showing spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system of Example 4. [Figure 10] FIG. 11 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a fifth embodiment. [Figure 11] 13A to 13C are diagrams showing spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system of Example 5. [Figure 12] FIG. 13 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to a sixth embodiment. [Figure 13] 13 is a diagram showing spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system of Example 6. FIG. [Figure 14] 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 15] 15 is a block diagram showing a configuration of an imaging device that constitutes the in-vehicle system of FIG. 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment 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 ensures healthy lives and promotes welfare for all people of all ages, and targets "3.6 By 2020, halve the number of global road traffic fatalities and injuries." in "3. Health and well-being for all" of the Sustainable Development Goals (SDGs) advocated by the United Nations. In addition, this embodiment contributes to the development of resilient infrastructure, and targets "9. Build resilient infrastructure, promote industry, innovation and infrastructure, and promote economic development and human welfare, with a focus on affordable and equitable access for all." in "9. Infrastructure and infrastructure." in the Sustainable Development Goals (SDGs) advocated by the United Nations. (Embodiment 1: Imaging lens system) The imaging lens system according to the first embodiment is composed of substantially six lenses, which are, in order from the object side to the image side, a front group, an aperture stop, and a rear group, and which include a first lens having a negative power and a concave surface on the image side facing the image side, a second lens having a concave surface on the object side facing the object side, a third lens having a positive power and a convex surface on the image side facing the image side, a fourth lens, a fifth lens, and a sixth lens having positive power. the fourth lens and the fifth lens, one of which has negative power and the other of which has positive power, constitute a cemented lens; When the refractive index of the first lens with respect to the d-line is defined as nd1, the focal length of the second lens is defined as f2, the focal length of the entire optical system is defined as f, and the Abbe number of the third lens with respect to the d-line is defined as νd3, the following conditional expressions (1) to (3) are satisfied. nd1>1.7 (1) |f2 / f|>8 ···(2) νd3<55 (3)

[0010] This makes it possible to provide an imaging lens system that has sufficient brightness for sensing functions at night and in bad weather such as rain and fog, and has high resolution. Specifically, when the F-number (Fno) is lowered, the diameter of the light beam incident on the imaging lens system becomes larger, and therefore aberration correction is required. By satisfying the above conditional formula (1), various aberrations such as field curvature and distortion can be corrected, and a bright imaging optical system with high resolution can be realized. More specifically, when the value of nd1 is 1.7 or less, the refractive index of the first lens is too small, and various aberrations such as field curvature and distortion in the peripheral area within the effective diameter of the first lens cannot be sufficiently corrected, making it difficult to realize a bright imaging lens system with high resolution. The value of nd1 is more preferably 1.75 or more, 1.76 or more, and even more preferably 1.77 or more. Moreover, by satisfying the above conditional formula (2), it is possible to realize a high-resolution, bright imaging optical system that can suppress the occurrence of chromatic aberration in the second lens. More specifically, when the value of |f2 / f| is 8 or less, the negative power of the second lens is too strong, and it is not possible to sufficiently suppress the occurrence of chromatic aberration in the second lens, making it difficult to realize a bright, high-resolution imaging lens system. The value of |f2 / f| is more preferably 20 or more, 25 or more, and further preferably 55 or more. Moreover, by satisfying the above conditional expression (3), the chromatic aberration occurring in the first lens can be corrected in the third lens, and a bright and high-resolution imaging lens system can be realized. Usually, the higher the refractive index of a glass material, the smaller the Abbe number. The first lens has negative power, a high refractive index, a small Abbe number, and a large dispersion, and thus generates large chromatic aberration. Therefore, by reducing the Abbe number of the third lens having positive power and increasing the dispersion, the chromatic aberration occurring in the first lens can be offset by the chromatic aberration occurring in the third lens. The value of νd3 is more preferably 50 or less, and even more preferably 45 or less. Therefore, when the imaging lens system satisfies conditional expressions (1) to (3), it is possible to provide an imaging lens system that has sufficient brightness for sensing functions at night and in bad weather such as rain and fog, and has high resolution.

[0011] Furthermore, when the focal length of the first lens is defined as f1, it is preferable to satisfy the following conditional expression (4). -2.2 <f1 / f<-1.7 ···(4) When the imaging lens system satisfies the above conditional formula (4), the first lens can appropriately correct field curvature and distortion, thereby realizing a bright imaging lens system with high resolution. Specifically, when the value of f1 / f is -1.7 or more, the focal length of the first lens is too short with respect to the focal length of the entire optical system, in other words, the negative power of the first lens is too strong, and the field curvature and distortion are overcorrected. The value of f1 / f is more preferably -1.85 or less, and even more preferably -1.9 or less. When the value of f1 / f is -2.2 or less, the focal length of the first lens is too long with respect to the focal length of the entire optical system, in other words, the negative power of the first lens is too weak, and the field curvature and distortion cannot be sufficiently corrected. The value of f1 / f is more preferably -2.1 or more, and even more preferably -1.95 or more.

[0012] Furthermore, when the focal length of the sixth lens in the imaging lens system is defined as f6, it is preferable that the imaging lens system satisfies the following conditional expression (5). f6 / f>3 ···(5) When the imaging lens system satisfies the above conditional formula (5), the sixth lens can appropriately correct the curvature of field, and a bright imaging lens system with high resolution can be realized. Specifically, when the value of f6 / f is 3 or less, the focal length of the first lens is too short with respect to the focal length of the entire optical system, in other words, the positive power of the sixth lens is too strong, and the curvature of field is overcorrected. The value of f6 / f is more preferably 3.2 or more, 3.3 or more, 6.7 or more, 9.9 or more, and further preferably 46.0 or more.

[0013] Furthermore, when the composite focal length of the fourth lens and the fifth lens is defined as f45, it is preferable that the imaging lens system satisfies the following conditional expression (6). |f45 / f|>5 ···(6) When the imaging lens system satisfies the above conditional formula (6), the longitudinal chromatic aberration and the lateral chromatic aberration can be suitably corrected, and a bright imaging lens system with high resolution can be realized. Specifically, when the value of |f45 / f| is 5 or less, the combined focal length of the cemented lens is too short with respect to the focal length of the entire optical system, in other words, the power of the cemented lens is too strong, and the longitudinal chromatic aberration and the lateral chromatic aberration are overcorrected. The value of |f45 / f| is more preferably 10 or more, and further preferably 15 or more.

[0014] Furthermore, when the Abbe number for the d-line of the cemented lens having negative power is defined as νdn, it is preferable that the imaging lens system satisfies the following conditional expression (7): νdn<22 (7) When the imaging lens system satisfies the above conditional formula (7), the axial chromatic aberration and the lateral chromatic aberration can be suitably corrected, and a bright imaging lens system with high resolution can be realized. Specifically, when the Abbe number νdn of the lens having negative power in the cemented lens is 22 or more, the dispersion of the lens having negative power becomes small, and the axial chromatic aberration and the lateral chromatic aberration cannot be sufficiently corrected in the cemented lens. The value of νdn is more preferably 21 or less, 20 or less, and further preferably 18 or less.

[0015] The sixth lens is preferably an aspherical lens, which can correct various aberrations such as lateral aberration and curvature of field, thereby achieving a bright and high-resolution imaging lens system.

[0016] In addition, the imaging lens system has a linear expansion coefficient of the fourth lens at temperatures between -30°C and 70°C of A4(10 -7 K), and the linear expansion coefficient of the fifth lens at -30°C to 70°C is A5 (10 -7 K), it is preferable that the following conditional expression (8) is satisfied: |A4-A5|<15 ···(8) When the imaging lens system satisfies the above conditional expression (8), it is possible to suppress stress generated in the adhesive on the cemented surface between the fourth lens L4 and the fifth lens L5, and it is possible to prevent the cemented lens from peeling off due to temperature changes. The value of |A4-A5| is preferably 10 or less, and more preferably 5 or less.

[0017] Moreover, when the half angle of view of the imaging lens system is defined as ω, it is preferable that the imaging lens system satisfies the following conditional expression (9): ω>45° (9) When the imaging lens system satisfies the above conditional expression (9), a bright, high-resolution imaging lens system with a wide angle of view can be realized. The value of ω is preferably 66° or more, 67° or more, 68° or more, and more preferably 86° or more.

[0018] Moreover, when the distance parallel to the optical axis of the imaging lens system between the image side surface of the edge portion of the first lens and the object side surface of the edge portion of the second lens is defined as ET12, it is preferable that the imaging lens system satisfies the following conditional expression (10): Here, the distance ET12 is the distance between the object side surface SE1 of the edge portion of the first lens L1 and the image side surface SE2 of the edge portion of the second lens L2, as shown in Fig. 1, and is the distance parallel to the optical axis OA. ET12≧0.8 (10) When the imaging lens system satisfies the above conditional expression (10), a cleaning device for removing water droplets, dust, etc. adhering to the object side surface of the first lens and a heater for melting snow adhering to the object side of the first lens can be disposed between the image side surface of the edge portion of the first lens and the object side surface of the edge portion of the second lens. Water droplets, dust, and snow adhering to the object side surface of the first lens in bad weather adversely affect sensing. By disposing the cleaning device and heater, a bright and high-resolution imaging lens system can be realized even in bad weather. The value of ET12 is preferably 1.0 or more, and more preferably 1.2 or more.

[0019] (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. This makes it possible to provide a high-resolution camera module that has sufficient brightness for sensing functions at night and in bad weather such as rain and fog.

[0020] 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 2 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).

[0021] 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 an image forming position (focal position) of the imaging lens system 11.

[0022] The imaging lens system 11 according to the first embodiment is composed of, in order from the object side to the image side, a front group Gf composed of a first lens L1 and a second lens L2, an aperture stop (STOP), and a rear group Gr composed of a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6. The imaging surface of the imaging lens system 11 is indicated by IMG. The first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5 are spherical glass lenses. The third lens L3 and the sixth lens L6 are aspherical glass lenses. If necessary, an optical filter (such as an infrared transmission filter, a visible / infrared bandpass filter, or an infrared cut 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.

[0023] The first lens L1 is a meniscus 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.

[0024] The second lens L2 is a meniscus lens having negative power. The object side surface S3 of the second lens L2 has a spherical shape with a concave surface facing the object side. The image side surface S4 of the second lens L2 has a spherical shape with a convex surface facing the image side.

[0025] The aperture STOP is an aperture that determines the F-number (F number, Fno) of the lens system. The aperture STOP is disposed between the second lens L2 and the third lens L3.

[0026] The third lens L3 has a positive power. The object side surface S7 of the third lens L3 has an aspheric shape with a convex surface facing the object side. The image side surface S8 of the third lens L3 has an aspheric shape with a convex surface facing the image side.

[0027] The fourth lens L4 is a meniscus lens having negative 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 has a spherical shape with a concave surface facing the image side.

[0028] The fifth lens L5 has a positive power. The object side surface S11 of the fifth lens L5 has a spherical shape with a convex surface facing the object side. The image side surface S12 of the fifth lens L5 has a spherical shape with a convex surface facing the image side.

[0029] The sixth lens L6 has a positive power. An object side surface S13 of the sixth lens L6 has an aspheric shape with a convex surface facing the object side. In addition, an image side surface S14 of the sixth lens L6 has an aspheric shape with a convex surface facing the image side.

[0030] 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 being integrated with 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.

[0031] Table 1 shows lens data for each lens surface in the imaging lens system 11 of Example 1. In Table 1, the lens data includes the radius of curvature (mm) of each surface, the surface spacing (mm) on the optical axis OA, the refractive index nd for the d-line, the Abbe number νd for the d-line, and the effective beam radius (mm). In Table 1, a surface marked with an "*" indicates that it is an aspheric surface. In the imaging lens system 11 of Example 1, the F-number is 1.37, and the total angle of view (2ω) is 134.3°.

[0032] [Table 1]

[0033] The aspheric shape used on the lens surface is expressed as follows: Z is the amount of sag, c is the inverse of the radius of curvature, k is the cone coefficient, and r is the ray height from the optical axis OA. The aspheric coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th orders are α4, α6, α8, and α 10 , α 12 , α 14 , α 16 Then, it is expressed by the following equation.

number

[0034] Table 2 shows aspheric coefficients for defining the aspheric shape of the lens surface that is made aspheric in the imaging lens system 11 of Example 1. Note that in Table 2, for example, "-3.733774E-05" corresponds to "-3.733774×10-5 The same applies to the numerical expressions in the following tables.

[0035] [Table 2]

[0036] Next, aberration will be described with reference to the drawings. Fig. 3 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system 11 of the first embodiment. In the longitudinal aberration diagram of Fig. 3(A), the horizontal axis indicates the position where the light ray intersects with the optical axis OA, and the vertical axis indicates the passing height of the light ray on the entrance pupil. Fig. 3(A) also shows the simulation results for the d-line. In the field curvature diagram of Fig. 3(B), the horizontal axis indicates the distance in the optical axis OA direction, and the vertical axis indicates the image height (angle of view). In the field curvature diagram of Fig. 3(B), Sag indicates the image formation position of the sagittal ray bundle, and Tan indicates the image formation position of the tangential ray bundle. Fig. 3(B) also shows the simulation results for the d-line. In the distortion diagram of Fig. 3(C), the horizontal axis represents image distortion (%) and the vertical axis represents image height (angle of view), Fig. 3(C) also shows the simulation results for the d-line. In addition, in the magnification chromatic aberration diagram of Fig. 3(D), the horizontal axis indicates the amount of magnification chromatic aberration, and the vertical axis indicates the image height (angle of view). Fig. 3(D) also shows simulation results for the d-line, C-line, and F-line.

[0037] Example 2 4 is a cross-sectional view showing a camera module 10 according to Example 2. In the imaging lens system 11 according to Example 2, the sixth lens L6 is a meniscus lens having a positive power, the object side surface S13 has an aspheric shape with a convex surface facing the object side, and the image side surface S14 has an aspheric shape with a concave surface facing the image side. The configuration of the imaging lens system 11 according to Example 2 other than the sixth lens L6 is the same as that of Example 1, so the description thereof will be omitted. Hereinafter, characteristic data of the imaging lens system 11 according to Example 2 will be described.

[0038] 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 their explanation will be omitted. Furthermore, in the imaging lens system 11 of Example 2, the F-number is 1.40, and the total angle of view (2ω) is 134.6°.

[0039] [Table 3]

[0040] Table 4 shows aspheric coefficients for defining the aspheric shape of the lens surface that is made aspheric in the imaging lens system 11 of Example 2. In Table 4, the aspheric shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0041] [Table 4]

[0042] 5 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. 5 is the same as that in FIG. 3, and therefore will not be repeated.

[0043] Example 3 6 is a cross-sectional view showing a camera module 10 according to Example 3. In the imaging lens system 11 according to Example 3, the sixth lens L6 is a meniscus lens having a positive power, the object side surface S13 has an aspheric shape with a concave surface facing the object side, and the image side surface S14 has an aspheric shape with a convex surface facing the image side. The configuration of the imaging lens system 11 according to Example 3 other than the sixth lens L6 is the same as that of Example 2, so the description thereof will be omitted. Hereinafter, characteristic data of the imaging lens system 11 according to Example 3 will be described.

[0044] 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 their explanation will be omitted. Furthermore, in the imaging lens system 11 of Example 3, the F-number is 1.40, and the total angle of view (2ω) is 137.8°.

[0045] [Table 5]

[0046] Table 6 shows aspheric coefficients for defining the aspheric shape of the lens surface that is made aspheric in the imaging lens system 11 of Example 3. In Table 6, the aspheric shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0047] [Table 6]

[0048] 7 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. 7 is the same as that in FIG. 3, and therefore will not be repeated.

[0049] Example 4 8 is a cross-sectional view showing a camera module 10 according to Example 4. In the imaging lens system 11 according to Example 4, an aperture (STOP) is disposed between the third lens L3 and the fourth lens L4. Since the configuration of the imaging lens system 11 according to Example 4 other than the arrangement position of the aperture is the same as that of Example 1, the description thereof will be omitted. Hereinafter, characteristic data of the imaging lens system 11 according to Example 4 will be described.

[0050] 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 their explanation will be omitted. Furthermore, in the imaging lens system 11 of Example 4, the F-number is 1.37, and the total angle of view (2ω) is 134.4°.

[0051] [Table 7]

[0052] Table 8 shows aspheric coefficients for defining the aspheric shape of the lens surface that is made aspheric in the imaging lens system 11 of Example 4. In Table 8, the aspheric shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0053] [Table 8]

[0054] 9 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. 9 is the same as that in FIG. 3, and therefore will not be repeated.

[0055] Example 5 10 is a cross-sectional view showing a camera module 10 according to Example 5. In the imaging lens system 11 according to Example 5, the first lens L1 to the fifth lens L5 are spherical glass lenses, and the sixth lens L6 is an aspheric glass lens. In the imaging lens system 11 according to Example 5, the third lens L3 has a positive power, the object side surface S5 of the third lens L3 has a spherical shape with a convex surface facing the object side, and the image side surface S6 of the third lens L3 has a spherical shape with a convex surface facing the image side. In the imaging lens system 11 according to Example 5, the fourth lens L4 has a positive power, the object side surface S9 of the fourth lens L4 has a spherical shape with a convex surface facing the object side, and the image side surface S10 of the fourth lens L4 has a spherical shape with a convex surface facing the image side. In the imaging lens system 11 according to Example 5, the fifth lens L5 has a negative power, the object side surface S11 of the fifth lens L5 has a spherical shape with a concave surface facing the object side, and the image side surface S12 of the fifth lens L5 has a spherical shape with a concave surface facing the image side. In the imaging lens system 11 according to Example 5, the sixth lens L6 is a meniscus lens having a positive power, the object side surface S13 of the sixth lens L6 has an aspheric shape with a convex surface facing the object side, and the image side surface S14 of the sixth lens L6 has an aspheric shape with a concave surface facing the image side. The other configurations of the imaging lens system 11 according to Example 5 are the same as those of Example 4, so the description thereof will be omitted. Hereinafter, characteristic data of the imaging lens system 11 according to Example 5 will be described.

[0056] 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 their explanation will be omitted. Furthermore, in the imaging lens system 11 of Example 5, the F-number is 1.40, and the total angle of view (2ω) is 133.1°.

[0057] [Table 9]

[0058] Table 10 shows aspheric coefficients for defining the aspheric shape of the lens surface that is made aspheric in the imaging lens system 11 of Example 5. In Table 10, the aspheric shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0059] [Table 10]

[0060] Fig. 11 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. 11 is the same as that in Fig. 3, and therefore will not be repeated.

[0061] Example 6 12 is a cross-sectional view showing a camera module 10 according to Example 6. In the imaging lens system 11 according to Example 6, the second lens L2, the fourth lens L4, and the fifth lens L5 are spherical glass lenses, and the first lens L1, the third lens L3, and the sixth lens L6 are aspheric glass lenses. In the imaging lens system 11 according to Example 6, the first lens L1 is a meniscus lens having negative power, the object side surface S1 of the first lens L1 has an aspheric shape with a convex surface facing the object side, and the image side surface S2 of the first lens L1 has an aspheric shape with a concave surface facing the image side. In the imaging lens system 11 according to Example 6, the third lens L3 has positive power, the object side surface S5 of the third lens L3 has an aspheric shape with a convex surface facing the object side, and the image side surface S6 of the third lens L3 has an aspheric shape with a convex surface facing the image side. Other configurations of the imaging lens system 11 according to Example 6 are omitted since it has the same lens configuration as Example 5. Hereinafter, characteristic data of the imaging lens system 11 according to Example 6 will be described.

[0062] Table 11 shows lens data for each lens surface of the imaging lens system 11 according to Example 6. The items shown in Table 11 are the same as those in Table 1, and therefore their explanation will be omitted. Furthermore, in the imaging lens system 11 of Example 6, the F-number is 1.28, and the total angle of view (2ω) is 173.1°.

[0063] [Table 11]

[0064] Table 12 shows aspheric coefficients for defining the aspheric shape of the lens surface that is made aspheric in the imaging lens system 11 of Example 6. In Table 12, the aspheric shape adopted for the lens surface is expressed by the same formula as in Example 1.

[0065] [Table 12]

[0066] Fig. 13 shows diagrams of spherical aberration (longitudinal aberration), field curvature, distortion, and lateral chromatic aberration in the imaging lens system 11 of Example 6. The explanation of each aberration diagram shown in Fig. 13 is the same as that in Fig. 3, and therefore will not be repeated.

[0067] Table 13 shows the F value of the imaging lens system 11, the total angle of view (2ω), the focal length f of the entire optical system of the imaging lens system 11, the focal length f1 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 refractive index nd1 of the first lens L1 for the d-line, the value of |f2 / f|, the Abbe number νd3 of the third lens L3 for the d-line, the value of f1 / f, the value of f6 / f, the value of |f45 / f|, the value of νdn, the value of |A4-A5|, and the value of ET12. In Table 13, the unit of focal length is mm. The focal lengths shown in Table 13 were calculated using the d-line.

[0068] [Table 13]

[0069] In Examples 1 to 6, the imaging lens system 11 satisfies conditional expressions (1) to (3), so that the imaging lens system 11 has sufficient brightness for sensing functions in bad weather such as at night and in rain or fog, and has high resolution. Specifically, in Examples 1 to 6, the F-number is 1.28 to 1.40, and the imaging lens system 11 has sufficient brightness. Also, in Examples 1 to 6, as shown in Figs. 3, 5, 7, 9, 11, and 13, various aberrations can be suitably reduced. Therefore, in Examples 1 to 6, the imaging lens system 11 has high resolution. Also, in Examples 1 to 6, the half angle of view (ω) is about 66.6° to about 86.6°, and the imaging lens system 11 has a wide angle of view sufficient for sensing a vehicle.

[0070] In Examples 1 to 6, the value of f1 / f satisfies the above conditional expression (4), so that the curvature of field and distortion can be suitably corrected in the first lens L1. In fact, in Examples 1 to 6, various aberrations can be suitably reduced, as shown in Figures 3, 5, 7, 9, 11, and 13.

[0071] In addition, in Examples 1 to 6, the value of f6 / f satisfies the above conditional expression (5), so that the field curvature can be suitably corrected in the sixth lens L6. In fact, in Examples 1 to 6, as shown in Figures 3(B), 5(B), 7(B), 9(B), 11(B), and 13(B), the field curvature can be suitably reduced.

[0072] In addition, in Examples 1 to 6, the value of |f45 / f| satisfies the above conditional expression (6), so that the axial chromatic aberration and lateral chromatic aberration can be suitably corrected in the cemented lens composed of the fourth lens L4 and the fifth lens L5. In fact, in Examples 1 to 6, the lateral chromatic aberration can be suitably reduced, as shown in Figures 3(D), 5(D), 7(D), 9(D), 11(D), and 13(D).

[0073] In addition, in Examples 1 to 6, the value of vdn satisfies the above conditional expression (7), so that the longitudinal chromatic aberration and the lateral chromatic aberration can be suitably corrected in the cemented lens composed of the fourth lens L4 and the fifth lens L5. In fact, in Examples 1 to 6, the lateral chromatic aberration can be suitably reduced, as shown in Figs. 3(D), 5(D), 7(D), 9(D), 11(D), and 13(D).

[0074] In addition, in Examples 1 to 6, since the sixth lens L6 is an aspheric lens, various aberrations such as lateral aberration and curvature of field can be suitably corrected in the sixth lens L6. In fact, in Examples 1 to 6, various aberrations can be suitably reduced as shown in Figs. 3, 5, 7, 9, 11, and 13.

[0075] In addition, in Examples 1 to 6, the value of |A4-A5| satisfies the above-mentioned conditional formula (8), so that stress generated in the adhesive on the cemented surface between the fourth lens L4 and the fifth lens L5 can be suppressed, and peeling of the cemented lens due to temperature change can be suppressed.

[0076] In addition, in Examples 1 to 6, the value of the half angle of view ω satisfies the above conditional expression (9), and the imaging lens system 11 has a wide angle of view that is sufficient for sensing a vehicle.

[0077] In addition, in Examples 1 to 6, the value of ET12 satisfies the above conditional formula (10), so that a cleaning device for removing water droplets, dust, etc. adhering to the object-side surface of the first lens can be disposed between the image-side surface SE1 of the edge portion of the first lens L1 and the object-side surface SE2 of the edge portion of the second lens L2, thereby realizing a bright and high-resolution imaging lens system.

[0078] Furthermore, by providing the camera module 10 with the imaging lens system 11, it is possible to provide a high-resolution camera module 10 that has sufficient brightness for sensing functions even at night or in bad weather such as rain or fog.

[0079] (Embodiment 3) FIG. 14 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 into an electrical signal. As shown in the figure, the imaging device 50 can be mounted on the vehicle 40, and FIG. 14 is an example of an arrangement illustrating a 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 places on the vehicle 40. For example, the first imaging device 50a may be arranged on or near the front bumper as a camera that monitors the front when the vehicle 40 is traveling. The second imaging device 50b that monitors the front may be arranged near an inner rearview mirror inside the vehicle 40. The third imaging device 50c may be arranged on the dashboard or in the instrument panel as a camera that monitors the driving situation of the driver. The fourth imaging device 50d may be installed at the rear of the vehicle 40 for rear monitoring 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 the left rear side and a right side camera that captures the right rear side.

[0080] 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 in 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 in 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 includes, but is not limited to, a navigation device, a collision damage mitigation brake device, a vehicle distance control device, and a lane departure warning device. 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 employ, but is not limited to, a liquid crystal display (LCD), an organic EL (Electro-Luminescence) display, and an inorganic EL display. The display device 43 can display an image signal output from the imaging device 50, which captures an image at a position that is difficult for the driver to view, such as a rear camera, to a passenger such as the driver.

[0081] Fig. 15 shows the configuration of an imaging device 50 constituting the in-vehicle system of Fig. 14. 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.

[0082] The control unit 52 controls the camera module 10 and processes an electrical signal output from the image sensor 12 of the camera module 10. The control unit 52 may be configured as a processor, for example. The control unit 52 may 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 integrated circuit (ASIC) may also be called an application-specific integrated circuit (ASIC). The processor may include a programmable logic device. The programmable logic device may also be 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) in which one or more processors work together, or a system in a package (SiP).

[0083] The storage unit 54 stores various information or parameters related to the operation of the imaging device 50. The storage unit 54 may be composed of, 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 and the like for 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.

[0084] As described above, the camera module 10 captures an object image 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 called a captured image.

[0085] The imaging element 12 may be composed of, for example, 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 called imaging data.

[0086] The imaging data may be read by the camera module 10 for all pixels and taken into the control unit 52 as a captured image. The 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 taken into the control unit 52 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 taken into the capture image. The predetermined capture range may be set by the control unit 52. The camera module 10 may obtain the predetermined capture range from the control unit 52. The imaging element 12 may capture an image of a predetermined capture range of a subject image formed via the imaging lens system 11.

[0087] 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 imaging lens system of the present invention is not limited to use in vehicle-mounted cameras and surveillance cameras, and can also be used for other purposes, such as being mounted on small electronic devices such as mobile phones. [Explanation of symbols]

[0088] 10 Camera Module 11 Imaging lens system 12 Image sensor 40 Vehicles (mobile objects) 42 Information processing device (processing device) 43 Display device (output device) 50 Imaging device 52 Control section L1 First lens L2 Second lens L3 Third lens L4 4th lens L5 5th lens L6 6th lens STOP Squeeze Gf front group Gr rear group IRCF Infrared Cut Filter IMG Image plane OA optical axis

Claims

1. The optical system is substantially composed of six lenses, which are, in order from the object side to the image side, a front group, an aperture stop, and a rear group, and which comprise a first lens having a negative power and a concave surface on its image side facing the image side, a second lens having a concave surface on its object side facing the object side, a third lens having a positive power and a convex surface on its image side facing the image side, a fourth lens, a fifth lens, and a sixth lens having positive power, the fourth lens and the fifth lens, one of which has a negative power and the other of which has a positive power, constitute a cemented lens; The optical system is characterized in that, when the refractive index of the first lens with respect to the d-line is defined as nd1, the focal length of the second lens is defined as f2, the focal length of the entire optical system is defined as f, and the Abbe number of the third lens with respect to the d-line is defined as νd3, the optical system satisfies the following conditional expressions (1) to (3): Imaging lens system. nd1>1.7...(1) |f2 / f|>8...(2) νd3<55...(3)

2. When the focal length of the first lens is defined as f1, the following conditional expression (4) is satisfied:

2. The imaging lens system according to claim 1. -2.2<f1 / f<-1.7...(4)

3. 2. The imaging lens system according to claim 1, wherein when the focal length of the sixth lens is defined as f6, the following conditional expression (5) is satisfied: f6 / f>3...(5)

4. 2. The imaging lens system according to claim 1, wherein the following conditional expression (6) is satisfied when a composite focal length of the fourth lens and the fifth lens is defined as f45: |f45 / f|>5...(6)

5. 2. The imaging lens system according to claim 1, wherein when the Abbe number for the d-line of the cemented lens having negative power is defined as νdn, the following conditional expression (7) is satisfied: νdn<22...(7)

6. The imaging lens system of claim 1 , wherein the sixth lens is an aspheric lens.

7. The linear expansion coefficient of the fourth lens at a temperature of -30°C to 70°C is A4 (10 －７ K), the linear expansion coefficient of the fifth lens at -30°C or more and 70°C or less is A5 (10 －７ 2. The imaging lens system according to claim 1, wherein the following conditional expression (8) is satisfied when F(f)=F(f) / F(f) / F(f) / F(f) / F(f) |A4-A5|<15...(8)

8. 2. The imaging lens system according to claim 1, wherein the following conditional expression (9) is satisfied when a half angle of view of the imaging lens system is defined as ω: ω>45°...(9)

9. 2. The imaging lens system according to claim 1, wherein, when a distance parallel to an optical axis of the imaging lens system between an image side surface of an edge portion of the first lens and an object side surface of an edge portion of the second lens is defined as ET12, the imaging lens system satisfies the following conditional expression (10): ET12≧0.8 ... (10)

10. 10. 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.

11. An in-vehicle system installed in a vehicle, A camera module according to claim 10; 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:

12. A moving body equipped with the in-vehicle system according to claim 11, The in-vehicle system further includes an output device for outputting information to an occupant. The mobile body is characterized in that the information processing device is configured to output recognition information of the object to the output device.

Images