Imaging lens system, camera module, in-vehicle system, and mobile object

Abstract

The present invention provides an imaging lens system that has brightness and an angle of view sufficient for monitoring the inside of a vehicle at night, that have a small sensor incident angle, and that are less affected by environmental temperature changes, and also provides a camera module, an in-vehicle system, and a mobile object. An imaging lens system (11), which is constituted of a front group Gf, an aperture stop STOP, and a rear group Gr, substantially including five lenses, comprises: a first lens (L1) having a negative power with a concave image-side face facing an image side; the aperture stop STOP; a second lens (L2) having a positive power with a convex image-side face facing the image side; a third lens (L3) having a power; a fourth lens (L4) having a power; and a fifth lens (L5) having a power. When the focal length of the first lens (L1) is defined as f1, the focal length of the entire optical system is defined as f, and the combined focal length of the third lens (L3), the fourth lens (L4), and the fifth lens (L5) is defined as f345, conditional expressions (1) and (2) are satisfied.　(1): -1.5 < f1 / f < -0.8 (2): f345 / f > 2

Description

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

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

[0002] Patent Document 1 describes an imaging optical system consisting of five lenses, with an F-number of 1.9 and a total angle of view of 118°, as an imaging lens system that can be mounted in a wide variety of imaging devices, such as a camera device for photography, an in-vehicle camera device, a stereo camera device, an inspection camera device, and a surveillance camera device.

[0003] Japanese Patent Application Laid-Open No. 2021-060506

[0004] However, the imaging lens system described in Patent Document 1 has an F-number of 1.9, which is insufficient in brightness for monitoring the interior of a vehicle at night or for sensing at night or in bad weather. Furthermore, the imaging lens system described in Patent Document 1 has a total angle of view of 118°, which is too narrow for monitoring the driver, front passenger, and rear seat passengers inside the vehicle. Furthermore, the angle of incidence of the chief ray onto the image sensor (hereinafter referred to as the "sensor incident angle") becomes large in a bright optical system with a small F-number. If the sensor incident angle is large, incident light may enter the wiring layer or the like at the periphery of the image sensor and not reach the light receiving surface (imaging surface) of the image sensor, resulting in a decrease in the amount of light received by the image sensor. However, Patent Document 1 does not mention the sensor incident angle.

[0005] The present invention has been made in consideration of the above problems, and aims to provide an imaging lens system, a camera module, an in-vehicle system, and a mobile body that have sufficient brightness and angle of view for monitoring the interior of a vehicle at night, have a small sensor incident angle, and are less affected by changes in environmental temperature.

[0006] An imaging lens system according to one embodiment is substantially composed of five lenses, including, in order from the object side to the image side, a front group, an aperture stop, and a rear group, and the five lenses include a first lens having a negative power and a concave surface on the image side facing the image side, the aperture stop, a second lens having a positive power and a convex surface on the image side facing the image side, a third lens having power, a fourth lens having power, and a fifth lens having power, and satisfies the following conditional expressions (1) and (2), where f1 is the focal length of the first lens, f is the focal length of the entire optical system, and f345 is the composite focal length of the third lens, the fourth lens, and the fifth lens. -1.5<f1 / f<-0.8 (1) f345 / f>2 (2)

[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 and angle of view for monitoring the interior of a vehicle at night, have a small sensor incident angle, and are less affected by changes in environmental temperature.

[0008] FIG. 1 is a cross-sectional view illustrating a sensor incident angle CRA and a collection angle Θ. FIG. 2 is a cross-sectional view illustrating the configuration of a camera module and an imaging lens system according to Example 1. FIG. 3 is a diagram illustrating spherical aberration (longitudinal aberration) in the imaging lens system according to Example 1. FIG. 4 is a diagram illustrating curvature of field in the imaging lens system according to Example 1. FIG. 5 is a diagram illustrating distortion aberration in the imaging lens system according to Example 1. FIG. 6 is a cross-sectional view illustrating the configuration of a camera module and an imaging lens system according to Example 2. FIG. 7 is a diagram illustrating spherical aberration (longitudinal aberration) in the imaging lens system according to Example 2. FIG. 8 is a diagram illustrating curvature of field in the imaging lens system according to Example 2. FIG. 9 is a diagram illustrating distortion aberration in the imaging lens system according to Example 2. FIG. 10 is a cross-sectional view illustrating the configuration of a camera module and an imaging lens system according to Example 3. FIG. 11 is a diagram illustrating spherical aberration (longitudinal aberration) in the imaging lens system according to Example 3. FIG. 12 is a diagram illustrating curvature of field in the imaging lens system according to Example 3. FIG. 13 is a diagram illustrating distortion aberration in the imaging lens system according to Example 3. FIG. 14 is a cross-sectional view illustrating the configuration of a camera module and an imaging lens system according to Example 4. FIG. 15 is a diagram illustrating spherical aberration (longitudinal aberration) in the imaging lens system according to Example 4. 12 is a diagram of field curvature in the imaging lens system of Example 4. FIG. 13 is a diagram of distortion aberration in the imaging lens system of Example 4. FIG. 14 is a cross-sectional view showing the configuration of a camera module and an imaging lens system according to Example 5. FIG. 15 is a diagram of spherical aberration (longitudinal aberration) in the imaging lens system of Example 5. FIG. 16 is a diagram of field curvature in the imaging lens system of Example 5. FIG. 17 is a diagram of distortion aberration in the imaging lens system of Example 5. FIG. 18 is a schematic diagram of a vehicle on which an in-vehicle system including a camera module according to an embodiment of the present invention is mounted. FIG. 19 is a block diagram showing the configuration of an imaging device constituting the in-vehicle system of FIG.

[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. Industry, innovation and infrastructure" of the Sustainable Development Goals (SDGs) advocated by the United Nations, which states, "9.1 Develop quality, reliable, sustainable and resilient infrastructure, including regional and transborder infrastructure, to support economic development and human well-being, with a focus on affordable and equitable access for all." (Embodiment 1: Imaging Lens System) The imaging lens system according to embodiment 1 is composed of substantially five lenses, namely, in order from the object side to the image side, a front group, an aperture stop, and a rear group, and comprises a first lens having negative power and a concave surface on its image side facing the image side, the aperture stop, a second lens having positive power and a convex surface on its image side facing the image side, a third lens having power, a fourth lens having power, and a fifth lens having power, and satisfies the following conditional expressions (1) and (2), where f1 is the focal length of the first lens, f is the focal length of the entire optical system, and f345 is the combined focal length of the third lens, the fourth lens, and the fifth lens. -1.5<f1 / f<-0.8 (1) f345 / f>2 (2)

[0010] This makes it possible to provide an imaging lens system that has sufficient brightness and angle of view for monitoring the interior of a vehicle at night, a small sensor incident angle, and reduced influence of environmental temperature changes. Specifically, when the angle of view of the imaging lens system is widened, the diameter of light incident on the imaging lens system becomes thicker, increasing the effective beam radius of the lens, and requiring aberration correction, particularly in the peripheral area within the effective beam radius of the lens. Here, the "effective beam radius" refers to the distance from the optical axis to the maximum peripheral ray passing through the lens surface. Similarly, when the F-number (F number, Fno) is small, the effective beam radius of the lens becomes large, and requiring aberration correction, particularly in the peripheral area within the effective beam radius of the lens. By satisfying the above conditional expression (1), various aberrations such as field curvature and distortion can be corrected, and an imaging lens system with high resolution, sufficient brightness, and angle of view can be realized. More specifically, when the value of f1 / f is −0.8 or greater, the power of the first lens is too strong, resulting in overcorrection of various aberrations such as field curvature and distortion in the peripheral area within the effective beam radius of the first lens. On the other hand, if the value of f1 / f is −1.5 or less, the power of the first lens is too weak, making it impossible to sufficiently correct various aberrations, such as curvature of field and distortion, in the peripheral area within the effective beam radius of the first lens. The upper limit of f1 / f is more preferably −0.9 or −1.0, and even more preferably −1.1. The lower limit of f1 / f is more preferably −1.4, and even more preferably −1.3. Furthermore, by satisfying the above conditional expression (2), the amount of focus shift of the third, fourth, and fifth lenses due to changes in environmental temperature can be suppressed, thereby reducing the effects of changes in environmental temperature. More specifically, if the value of f345 / f is 2 or less, the power of the third, fourth, and fifth lenses is too strong, making it impossible to sufficiently suppress the amount of focus shift of the third, fourth, and fifth lenses due to changes in environmental temperature, making it difficult to realize an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view. The lower limit of f345 / f is more preferably 3.0, 3.1, or 3.2, and even more preferably 3.5. Furthermore, by disposing the aperture stop between the first lens and the second lens, the angle of incidence on the sensor can be reduced, and a decrease in the amount of light at the periphery of the image sensor can be prevented.Here, the sensor incident angle and the collection angle will be explained with reference to FIG. 1 . As shown in FIG. 1 , the sensor incident angle is the angle CRA between the chief ray CR of light incident on the image sensor and the perpendicular to the light receiving surface (imaging surface) RS of the image sensor, and it increases from the center of the image sensor (the intersection P with the optical axis) toward the periphery. The collection angle is the angle Θ between the lower ray LR (or upper ray UR) of light collected at the intersection P between the image sensor and the optical axis and the chief ray CR. If the numerical aperture is defined as NA, the refractive index of the medium through which light propagates as n, and the collection angle as Θ, then NA = n × sin Θ holds, and since the F-number = 1 / (2 × NA), the F-number = 1 / (2n × sin Θ). Therefore, as the F-number decreases, the collection angle Θ increases. When the collection angle Θ is large and the sensor incident angle CRA is also large, in the peripheral portion, light incident on the image sensor is incident on the wiring layer of the image sensor, etc., and does not reach the light-receiving surface RS of the image sensor, resulting in a decrease in the amount of light received by the image sensor. In other words, the sensor incident angle CRA increases toward the periphery of the image sensor, resulting in a decrease in the amount of light received by the image sensor. However, in the imaging lens system according to embodiment 1, by disposing the aperture stop between the first lens and the second lens, the sensor incident angle can be reduced, thereby preventing a decrease in the amount of light in the peripheral portion of the image sensor. Therefore, by satisfying conditional expressions (1) and (2) and disposing the aperture stop between the first lens and the second lens, it is possible to provide an imaging lens system that has sufficient brightness and angle of view for monitoring the interior of a vehicle at night, has a small sensor incident angle, and is less affected by changes in environmental temperature.

[0011] Furthermore, when the focal length of the second lens is defined as f2, the imaging lens system preferably satisfies the following conditional expression (3): 1.0<f2 / f<1.7 (3) When the imaging lens system satisfies the above conditional expression (3), the second lens can appropriately correct spherical aberration, lateral aberration, and the like, thereby achieving an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view. Specifically, when the value of f2 / f is 1.0 or less, the focal length of the second lens is too short relative to the focal length of the entire optical system. In other words, the positive power of the second lens is too strong, resulting in overcorrection of spherical aberration, lateral aberration, and the like. On the other hand, when the value of f2 / f is 1.7 or more, the focal length of the second lens is too long relative to the focal length of the entire optical system. In other words, the positive power of the second lens is too weak, resulting in insufficient correction of spherical aberration, lateral aberration, and the like. The lower limit of f2 / f is more preferably 1.3, and even more preferably 1.4. The upper limit of f2 / f is more preferably 1.6, and even more preferably 1.5.

[0012] Furthermore, when the composite focal length of the first lens and the second lens is defined as f12, it is preferable that the imaging lens system satisfy the following conditional expression (4): f12 / f<2 (4) When the imaging lens system satisfies the above conditional expression (4), the amount of focus shift of the first lens and the second lens due to changes in environmental temperature can be suppressed, and the effects of changes in environmental temperature can be alleviated. More specifically, when the value of f12 / f is 2 or greater, the power of the first lens and the second lens is too strong, making it impossible to sufficiently suppress the amount of focus shift of the first lens and the second lens due to changes in environmental temperature, making it difficult to realize an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view. The upper limit of f12 / f is more preferably 1.7, 1.6, or 1.5, and even more preferably 1.4.

[0013] Furthermore, when the focal length of the third lens is defined as f3, it is preferable that the imaging lens system satisfy the following conditional expression (5): -10<f3 / f<-3 (5) When the imaging lens system satisfies the above conditional expression (5), lateral aberration and curvature of field can be suitably corrected, and an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view can be realized. Specifically, when the value of f3 / f is -3 or greater, 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, resulting in overcorrection of lateral aberration and curvature of field. On the other hand, when the value of f3 / f is -10 or less, 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, resulting in insufficient correction of lateral aberration and curvature of field. The lower limit of f3 / f is more preferably -9, and even more preferably -8. The upper limit of f3 / f is more preferably -4, and even more preferably -5.

[0014] Furthermore, when the focal length of the fourth lens is defined as f4, it is preferable that the imaging lens system satisfy the following conditional expression (6): 2<f4 / f<10 (6) When the imaging lens system satisfies the above conditional expression (6), lateral aberration and curvature of field can be suitably corrected, and an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view can be realized. Specifically, when the value of f4 / f is 2 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, resulting in overcorrection of lateral aberration and curvature of field. On the other hand, when the value of f4 / f is 10 or more, 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, resulting in insufficient correction of lateral aberration and curvature of field. The lower limit of f4 / f is more preferably 3, and even more preferably 4. The upper limit of f4 / f is more preferably 7, and even more preferably 6.

[0015] Furthermore, when the focal length of the fifth lens is defined as f5, it is preferable that the imaging lens system satisfy the following conditional expression (7): 3<f5 / f<15 (7) When the imaging lens system satisfies the above conditional expression (7), lateral aberration and curvature of field can be suitably corrected, and an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view can be realized. Specifically, when the value of f5 / f is 3 or less, the focal length of the fifth lens is too short relative to the focal length of the entire optical system. In other words, the power of the fifth lens is too strong, resulting in overcorrection of lateral aberration and curvature of field. On the other hand, when the value of f5 / f is 15 or more, the focal length of the fifth lens is too long relative to the focal length of the entire optical system. In other words, the power of the fifth lens is too weak, resulting in insufficient correction of lateral aberration and curvature of field. The lower limit of f5 / f is more preferably 3.5, and even more preferably 4. The upper limit of f5 / f is more preferably 11, and even more preferably 10.

[0016] It is also preferable that the first and second lenses are glass lenses, and the third, fourth, and fifth lenses are plastic lenses. By using a glass lens for the first lens, it is possible to provide an imaging lens system that is scratch-resistant, resistant to oil stains, and has excellent weather resistance. Furthermore, by using glass lenses with a relatively small linear expansion coefficient for the first and second lenses, the power of the first and second lenses can be made stronger than that of the other lenses, and the first and second lenses can compensate for the amount of focus shift caused by changes in environmental temperature. On the other hand, by using plastic lenses for the third, fourth, and fifth lenses, it is possible to reduce manufacturing costs.

[0017] In addition, in the imaging lens system, it is preferable that the first lens has the largest negative power, which makes it possible to compensate for the amount of focus shift of other lenses having positive power due to changes in the temperature of the environment.

[0018] In addition, in the imaging lens system, it is preferable that the second lens has the largest positive power, which allows the second lens to compensate for the amount of focus shift caused by temperature changes in the environment of the other lenses having negative power.

[0019] The second lens is preferably an aspherical lens, which can correct various aberrations such as spherical aberration and lateral aberration, thereby realizing an imaging lens system with high resolution, sufficient brightness, and a sufficient angle of view.

[0020] Furthermore, when the distance on the optical axis between the image-side surface of the fifth lens and the light-receiving surface of the image sensor is defined as BFL, it is preferable that the imaging lens system satisfies the following conditional expression (8): BFL / f>0.9 (8) When the imaging lens system satisfies the above conditional expression (8), a sufficient distance can be secured between the imaging lens system and the image sensor, making it easier to assemble the imaging lens system and the image sensor. The lower limit of BFL / f is more preferably 1.0 or 1.1, and even more preferably 1.2 or 1.25.

[0021] Furthermore, when the design wavelength of the imaging lens system is defined as WL, it is preferable that the imaging lens system satisfies the following conditional expression (9): 800 nm<WL<1000 nm (9) When the imaging lens system satisfies the above conditional expression (9), it is possible to detect infrared light, enabling sensing at night or in bad weather.

[0022] Furthermore, 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 (10): ω>60° (10) When the imaging lens system satisfies the above conditional expression (10), an imaging lens system having a wide angle of view, high resolution, sufficient brightness, and sufficient angle of view can be realized. The lower limit of ω is more preferably 70°.

[0023] Furthermore, when the sensor incident angle of the imaging lens system is defined as CRA, it is preferable that the imaging lens system satisfies the following conditional expression (11): CRA<5° (11) When the imaging lens system satisfies the above conditional expression (11), the sensor incident angle can be made small over the entire image sensor, and a decrease in the amount of light can be prevented particularly in the peripheral part of the image sensor.

[0024] (Embodiment 2: Camera Module) A camera module according to embodiment 2 includes the above-described imaging lens system and an imaging element that is disposed at the focal position of the imaging lens system and converts light collected through the imaging lens system into an electrical signal. This makes it possible to provide a camera module that has sufficient brightness and angle of view for monitoring the interior of a vehicle at night, has a small sensor incident angle, and is less susceptible to changes in environmental temperature.

[0025] Next, examples corresponding to the imaging lens system according to embodiment 1 and the camera module according to embodiment 2 will be described with reference to the drawings. (Example 1) Fig. 2 is a cross-sectional view showing the configuration of a camera module 10 according to example 1. Specifically, the camera module 10 includes an imaging lens system 11 and an imaging element 12. The imaging lens system 11 and the imaging element 12 are housed in a housing (not shown).

[0026] The image sensor 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 image sensor 12 is disposed at the image forming position (focal position) of the imaging lens system 11.

[0027] The imaging lens system 11 according to Example 1 includes, in order from the object side to the image side, a front group Gf including a first lens L1, an aperture stop (STOP), and a rear group Gr including a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The image plane of the imaging lens system 11 is indicated by IMG. The first lens L1 and the second lens L2 are glass lenses. The third lens L3, the fourth lens L4, and the fifth lens L5 are plastic lenses. Note that an optical filter (such as an infrared transmission filter or a visible / infrared bandpass filter) is disposed between the imaging lens system 11 and the image sensor 12 as needed. This specification will be described using an example in which an infrared transmission filter (FILTER) is disposed between the imaging lens system 11 and the image sensor 12.

[0028] 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.

[0029] The aperture stop STOP is an aperture that determines the F-number (F-number, Fno) of the lens system. The aperture stop STOP is disposed between the first lens L1 and the second lens L2.

[0030] The second lens L2 is a biconvex lens having positive power. The object-side surface S5 of the second lens L2 has an aspheric shape with a convex surface facing the object side. The image-side surface S6 of the second lens L2 has an aspheric shape with a convex surface facing the image side.

[0031] The third lens L3 is a meniscus lens having negative power. The object-side surface S7 of the third lens L3 has an aspheric shape with a concave 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.

[0032] The fourth lens L4 is a biconvex lens having positive power. The object-side surface S9 of the fourth lens L4 has an aspheric shape with the convex surface facing the object side. The image-side surface S10 of the fourth lens L4 also has an aspheric shape with the convex surface facing the image side.

[0033] The fifth lens L5 is a meniscus lens having positive 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.

[0034] The infrared transmission filter (FILTER) is a filter that transmits light in the near-infrared region and blocks light in the visible light region. When designing the imaging lens system 11, the infrared transmission filter is treated as an integral part of the imaging lens system 11. However, the infrared transmission filter is not an essential component of the imaging lens system 11. The infrared transmission filter is disposed on the image side of the fifth lens L5. Furthermore, a sensor cover glass may be disposed between the infrared transmission filter and the imaging element 12 to prevent dust from adhering to the imaging element 12.

[0035] 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) on the optical axis OA, the refractive index n850 for a light beam of 850 nm, the refractive index nd for the d-line, the Abbe number vd for the d-line, and the effective beam radius (mm). In Table 1, surfaces marked with an asterisk (*) are aspherical. The imaging lens system 11 of Example 1 has an F-number of 1.30 and a half angle of view (ω) of 73.6°.

[0036]

[0037] The aspherical shape adopted for the lens surface is as follows: Z is the sag amount, c is the inverse 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 respectively α ４ , α ６ , α ８ , α １０ , α １２ , α １４ , α １６ When this is the case, it is expressed by the following equation:

[0038] 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, "-1.326785E-03" corresponds to "-1.326785×10 －３ The same applies to the numerical expressions in the following tables.

[0039]

[0040] Next, aberrations will be described with reference to the drawings. FIGS. 3A, 3B, and 3C show spherical aberration diagrams (longitudinal aberration diagrams), field curvature diagrams, and distortion diagrams for the imaging lens system 11 of Example 1. In the longitudinal aberration diagram of FIG. 3A, the horizontal axis indicates the position where a light ray intersects with the optical axis OA, and the vertical axis indicates the height at which the light ray passes through the entrance pupil. FIG. 3A also shows simulation results for light rays of 850 nm. In the field curvature diagram of FIG. 3B, the horizontal axis indicates the distance in the direction of the optical axis OA, and the vertical axis indicates the image height (angle of view). In the field curvature diagram of FIG. 3B, Sag indicates the image formation position for a sagittal ray bundle, and Tan indicates the image formation position for a tangential ray bundle. FIG. 3B also shows simulation results for light rays of 850 nm. In the distortion diagram of FIG. 3C, the horizontal axis indicates the image distortion aberration (%), and the vertical axis indicates the image height (angle of view). FIG. 3C shows the simulation results for 850 nm light.

[0041] Example 2 Figure 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 fourth lens L4 is a meniscus lens having positive power, the object-side surface S9 has an aspherical shape with a concave surface facing the object side, and the image-side surface S10 has an aspherical shape with a convex surface facing the image side. Since the configuration of the imaging lens system 11 according to Example 2 other than the fourth lens L4 is the same as that of Example 1, a description thereof will be omitted. Below, characteristic data of the imaging lens system 11 according to Example 2 will be described.

[0042] 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, the imaging lens system 11 of Example 2 has an F-number of 1.30 and a half angle of view (ω) of 73.4°.

[0043]

[0044] 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.

[0045]

[0046] 5A, 5B, and 5C show diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the imaging lens system 11 of Example 2. The explanations for the aberration diagrams shown in Figures 5A, 5B, and 5C are the same as those for Figures 3A, 3B, and 3C, and therefore will not be repeated.

[0047] Example 3 Figure 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 fifth lens L5 is a biconvex lens having positive power, the object-side surface S11 has an aspherical shape with the convex surface facing the object side, and the image-side surface S12 has an aspherical shape with the convex surface facing the image side. The configuration of the imaging lens system 11 according to Example 3, other than the fifth lens L5, is the same as that of Example 2, and therefore a description thereof will be omitted. Below, characteristic data of the imaging lens system 11 according to Example 3 will be described.

[0048] 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, the imaging lens system 11 according to Example 3 has an F-number of 1.31 and a half angle of view (ω) of 73.4°.

[0049]

[0050] 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.

[0051]

[0052] 7A, 7B, and 7C show diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the imaging lens system 11 of Example 3. The explanations for the aberration diagrams shown in Figures 7A, 7B, and 7C are the same as those for Figures 3A, 3B, and 3C, and therefore will not be repeated.

[0053] Example 4 Figure 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, the fifth lens L5 is a meniscus lens having positive power, the object-side surface S11 has an aspherical shape with a concave surface facing the object side, and the image-side surface S12 has an aspherical shape with a convex surface facing the image side. Since the configuration of the imaging lens system 11 according to Example 4, other than the fifth lens L5, is the same as that of Example 2, the characteristic data of the imaging lens system 11 according to Example 4 will be described below.

[0054] 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, the imaging lens system 11 of Example 4 has an F-number of 1.31 and a half angle of view (ω) of 73.4°.

[0055]

[0056] 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.

[0057]

[0058] 9A, 9B, and 9C show diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the imaging lens system 11 of Example 4. The explanations for the aberration diagrams shown in Figures 9A, 9B, and 9C are the same as those for Figures 3A, 3B, and 3C, and therefore will not be repeated.

[0059] Example 5 FIG. 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 third lens L3 is a biconcave lens having negative power, the object-side surface S7 has an aspherical shape with a concave surface facing the object side, and the image-side surface S6 has an aspherical shape with a concave surface facing the image side. In addition, in the imaging lens system 11 according to Example 5, the fourth lens L4 is a biconvex lens having positive power, the object-side surface S9 has an aspherical shape with a convex surface facing the object side, and the image-side surface S10 of the fourth lens L4 has an aspherical shape with a convex surface facing the image side. The other components of the imaging lens system 11 according to Example 5 are similar to those of Example 4, and therefore description thereof will be omitted. Below, characteristic data of the imaging lens system 11 according to Example 5 will be described.

[0060] Table 9 shows lens data for each lens surface of the imaging lens system 11 according to Example 5. In Table 9, the refractive index n940 for light rays with a wavelength of 940 nm is presented instead of the refractive index n850 for light rays with a wavelength of 850 nm. The other items shown in Table 9 are the same as those in Table 1, and therefore their explanation will be omitted. Furthermore, the imaging lens system 11 of Example 5 has an F-number of 1.30 and a half angle of view (ω) of 73.6°.

[0061]

[0062] 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.

[0063]

[0064] 11A, 11B, and 11C show diagrams of spherical aberration (longitudinal aberration), field curvature, and distortion in the imaging lens system 11 of Example 5. The explanations for the aberration diagrams shown in Figures 11A, 11B, and 11C are the same as those for Figures 3A, 3B, and 3C, and therefore will not be repeated.

[0065] Table 11 shows the F-number 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 value of f1 / f, the value of f345 / f, the value of f2 / f, the value of f12 / f, the value of f3 / f, the value of f4 / f, the value of f5 / f, the value of BFL / f, the value of WL, the value of the half angle of view (ω), and the value of the sensor incident angle CRA. In Table 11, the focal lengths are in mm. The focal lengths shown in Table 11 were calculated using the d-line.

[0066]

[0067] In Examples 1 to 5, the imaging lens system 11 satisfies conditional expressions (1) and (2), thereby providing an imaging lens system 11 that has sufficient brightness and angle of view for monitoring the interior of a vehicle at night, a small sensor incident angle, and reduced influence of environmental temperature changes. Specifically, in Examples 1 to 5, the F-number is 1.30 to 1.31, and the imaging lens system 11 has sufficient brightness. Furthermore, in Examples 1 to 5, various aberrations are suitably reduced as shown in FIGS. 3A, 3B, 3C, 5A, 5B, 5C, 7A, 7B, 7C, 9A, 9B, 9C, 11A, 11B, and 11C. Therefore, in Examples 1 to 5, the imaging lens system 11 has high resolution. Furthermore, in Examples 1 to 5, the half angle of view (ω) is 73.4° to 73.6°, and the imaging lens system 11 has a wide angle of view that is sufficient for sensing the interior of a vehicle, particularly the interior of the vehicle. In addition, in Examples 1 to 5, the sensor incident angle CRA was 1.90° to 4.90°, and the sensor incident angle was able to be kept sufficiently small.

[0068] Furthermore, in Examples 1 to 5, the value of f2 / f satisfies the above-mentioned conditional expression (3), so that various aberrations such as spherical aberration and lateral aberration can be suitably corrected in the second lens L2. In fact, in Examples 1 to 5, various aberrations can be suitably reduced, as shown in Figures 3A, 3B, 3C, 5A, 5B, 5C, 7A, 7B, 7C, 9A, 9B, 9C, 11A, 11B, and 11C.

[0069] Furthermore, in Examples 1 to 5, the value of f12 / f satisfies the above-mentioned conditional expression (4), thereby enabling sufficient suppression of focus shift due to changes in environmental temperature. Table 12 shows the focus shift (μm) associated with changes in environmental temperature for the focal length f of the imaging lens system 11 in Examples 1 to 5. Table 12 also shows the focus shift on the optical axis from the focal length f at a room temperature of 25°C. The material of the barrel and housing used to calculate the focus shift amount for the focal length f shown in Table 12 was XYRON XP640 manufactured by Asahi Kasei Corporation. As shown in Table 12, in Examples 1 to 5, the focus shift amount due to changes in environmental temperature was sufficiently suppressed. The focus shift amount for the focal length f shown in Table 12 was calculated using the design wavelength. The design wavelength was 850 nm in Examples 1 to 4, and 940 nm in Example 5.

[0070] Furthermore, in Examples 1 to 5, the value of f3 / f satisfies the above-mentioned conditional expression (5), and therefore various aberrations such as lateral aberration and curvature of field can be suitably corrected in the third lens L3. In fact, in Examples 1 to 5, various aberrations can be suitably reduced, as shown in Figures 3A, 3B, 3C, 5A, 5B, 5C, 7A, 7B, 7C, 9A, 9B, 9C, 11A, 11B, and 11C.

[0071] Furthermore, in Examples 1 to 5, the value of f4 / f satisfies the above-mentioned conditional expression (6), and therefore, various aberrations such as lateral aberration and curvature of field can be suitably corrected in the fourth lens L4. In fact, in Examples 1 to 5, various aberrations can be suitably reduced, as shown in Figures 3A, 3B, 3C, 5A, 5B, 5C, 7A, 7B, 7C, 9A, 9B, 9C, 11A, 11B, and 11C.

[0072] Furthermore, in Examples 1 to 5, the value of f5 / f satisfies the above-mentioned conditional expression (7), and therefore, various aberrations such as lateral aberration and curvature of field can be suitably corrected in the fifth lens L5. In fact, in Examples 1 to 5, various aberrations can be suitably reduced, as shown in Figures 3A, 3B, 3C, 5A, 5B, 5C, 7A, 7B, 7C, 9A, 9B, 9C, 11A, 11B, and 11C.

[0073] Furthermore, in Examples 1 to 5, the second lens L2 is an aspherical lens, so that various aberrations such as spherical aberration and lateral aberration can be suitably corrected in the second lens L2. In fact, in Examples 1 to 5, various aberrations can be suitably reduced, as shown in Figures 3A, 3B, 3C, 5A, 5B, 5C, 7A, 7B, 7C, 9A, 9B, 9C, 11A, 11B, and 11C.

[0074] Furthermore, in Examples 1 to 5, the value of BFL / f satisfies the above-mentioned conditional expression (8), so that a sufficient distance can be secured between the imaging lens system and the image sensor, facilitating the assembly of the imaging lens system and the image sensor.

[0075] Furthermore, in Examples 1 to 5, the value of WL satisfies the above conditional expression (9), so that infrared light can be detected, enabling sensing at night or in bad weather.

[0076] In addition, in Examples 1 to 5, the value of the half angle of view ω satisfies the above conditional expression (10), and the imaging lens system 11 has a wide enough angle of view for sensing the interior of a vehicle, particularly the interior of a vehicle.

[0077] Furthermore, in Examples 1 to 5, the value of the sensor incident angle CRA satisfies the above-mentioned conditional expression (11), so that the sensor incident angle can be made small over the entire image sensor, and a decrease in the amount of light, particularly in the peripheral part of the image sensor, can be prevented.

[0078] Furthermore, by providing the camera module 10 with the imaging lens system 11, it is possible to provide a camera module 10 that has sufficient brightness and angle of view for monitoring the interior of a vehicle at night, has a small sensor incident angle, and is less affected by changes in environmental temperature.

[0079] Third Embodiment FIG. 12 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. 12 is an example of an arrangement illustrating 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 disposed 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 disposed near an inner rearview mirror inside the vehicle 40. The third imaging device 50c may be disposed on the dashboard, in the instrument panel, or the like 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 images the left rear side and a right side camera that images the right rear side.

[0080] Image signals of images captured by the imaging device 50 may be output to an information processing device 42 and / or a display device 43 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 image signals acquired by the imaging device 50 and recognizes various objects in the captured images to assist the driver in driving. Examples of the information processing device 42 include, but are not limited to, a navigation system, a collision damage mitigation braking system, a vehicle-to-vehicle distance control system, and a lane departure warning system. The display device 43 displays images processed and output by the information processing device 42, but can also receive image signals 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 image signals output from the imaging device 50, which captures images from positions difficult for the driver to view, such as a rear camera, to occupants such as the driver.

[0081] Fig. 13 shows the configuration of an imaging device 50 that constitutes the in-vehicle system of Fig. 12. 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 the electrical signals 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). A PLD may include a field-programmable gate array (FPGA). The control unit 52 may be either a system-on-a-chip (SoC) or a system-in-a-package (SiP) in which one or more processors work together.

[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 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.

[0084] 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.

[0085] 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.

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

[0087] 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 applications, such as being mounted on small electronic devices such as mobile phones.

[0088] This application claims priority based on Japanese Patent Application No. 2023-216444, filed December 22, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0089] It is possible to provide an imaging lens system, a camera module, an in-vehicle system, and a mobile body that have sufficient brightness and angle of view for monitoring the interior of a vehicle at night, have a small sensor incident angle, and are less affected by changes in environmental temperature.

[0090] REFERENCE SIGNS LIST 10 camera module 11 imaging lens system 12 imaging element 40 vehicle (moving body) 42 information processing device (processing device) 43 display device (output device) 50 imaging device 52 control unit L1 first lens L2 second lens L3 third lens L4 fourth lens L5 fifth lens STOP aperture Gf front group Gr rear group FILTER infrared transmission filter IMG imaging surface OA optical axis

Claims

1. An imaging lens system substantially consisting of five 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 negative power and whose image side surface faces the image side with a concave surface facing the image side, the aperture stop, a second lens having positive power and whose image side surface faces the image side with a convex surface facing the image side, a third lens having power, a fourth lens having power, and a fifth lens having power, characterized in that, when the focal length of the first lens is defined as f1, the focal length of the entire optical system is defined as f, and the composite focal length of the third lens, the fourth lens, and the fifth lens is defined as f345, the imaging lens system satisfies the following conditional expressions (1) and (2): -1.5<f1 / f<-0.8 ... (1) f345 / f>2 ... (2) 2. The imaging lens system according to claim 1, characterized in that, when the focal length of the second lens is defined as f2, the following conditional expression (3) is satisfied: 1.0<f2 / f<1.7 (3) 3. The imaging lens system according to claim 1, wherein when a composite focal length of the first lens and the second lens is defined as f12, the following conditional expression (4) is satisfied: f12 / f<2 (4) 4. The imaging lens system according to claim 1, wherein, when the focal length of the third lens is defined as f3, the following conditional expression (5) is satisfied: −10<f3 / f<−3 (5) 5. The imaging lens system according to claim 1, wherein the following conditional expression (6) is satisfied when the focal length of the fourth lens is defined as f4: 2<f4 / f<10 (6) 6. The imaging lens system according to claim 1, wherein the following conditional expression (7) is satisfied when the focal length of the fifth lens is defined as f5: 3<f5 / f<15 (7) 7. The imaging lens system according to claim 1, wherein the first lens and the second lens are glass lenses, and the third lens, the fourth lens and the fifth lens are plastic lenses.

8. The imaging lens system according to claim 1, wherein in said imaging lens system, said first lens has the largest negative power.

9. The imaging lens system according to claim 1, wherein in said imaging lens system, said second lens has the greatest positive power.

10. The imaging lens system of claim 1, wherein said second lens is an aspheric lens.

11. The imaging lens system according to claim 1, wherein the following conditional expression (8) is satisfied when the distance on the optical axis between the image side surface of the fifth lens and the light receiving surface of the image sensor is defined as BFL: BFL / f>0.9 (8) 12. The imaging lens system according to claim 1, wherein the imaging lens system satisfies the following conditional expression (9), where WL is a design wavelength of the imaging lens system: 800 nm<WL<1000 nm (9) 13. The imaging lens system according to claim 1, wherein the imaging lens system satisfies the following conditional expression (10) when a half angle of view of the imaging lens system is defined as ω: ω>60° (10) 14. The imaging lens system according to claim 1, wherein the imaging lens system satisfies the following conditional expression (11) when the incident angle to a sensor of the imaging lens system is defined as CRA: CRA<5° (11) 15. A camera module comprising the imaging lens system according to any one of claims 1 to 14, and an imaging element for converting light focused through said imaging lens system into an electrical signal.

16. An in-vehicle system to be mounted in a vehicle, comprising: a camera module as described in claim 15; and an information processing device that processes an image output from the imaging element of the camera module and recognizes objects in the image.

17. A moving body equipped with the on-board system described in claim 16, wherein the on-board system further comprises an output device for outputting information to an occupant, and the information processing device is configured to output recognition information of the object to the output device.

Images