WO2021157527A1

WO2021157527A1 - Imaging lens system and imaging device

Info

Publication number: WO2021157527A1
Application number: PCT/JP2021/003547
Authority: WO
Inventors: 由多可牧野; 隆杉山
Original assignee: マクセル株式会社
Priority date: 2020-02-03
Filing date: 2021-02-01
Publication date: 2021-08-12

Abstract

The purpose of the present invention is to provide an imaging lens system and an imaging device that are capable of suppressing the change of a focal position due to temperature change.　An imaging lens system (11) comprises at least power lenses (L1)-(L5) that satisfy |fi/F| < 20.0 when the focal length of an i-th (i is a positive integer) lens disposed at an i-th position in order from the object side to the image side is denoted by fi, and the focal length of the entire optical system is denoted by F. The power lenses (L1)-(L5) are disposed such that, when the change rate of a refractive index Nd with respect to the d line of the i-th lens due to temperature change is denoted by (dNd/dt)i, and Pdi = (dNd/dt)i/fi, the signs of the value of Pdi are alternated in order from the object side to the image side, and the half angle of view is 50° or more.

Description

Imaging lens system and imaging device

The present invention relates to an image pickup lens system and an image pickup apparatus, for example, an image pickup lens system and an image pickup apparatus for in-vehicle use or surveillance.

Cameras mounted on vehicles are required to have an imaging optical system having a wide angle of view so that a wide imaging range can be obtained. For example, Patent Document 1 describes an imaging lens system having a wide angle of view using a plastic lens. Specifically, Patent Document 1 describes, in order from the object side to the image side, a first lens L1 which is a glass lens, a second lens L2 which is a plastic lens, a third lens L3 which is a glass lens, and a plastic lens. An imaging lens system including the fourth lens L4 is described.

JP-A-2007-101920

On the other hand, in-vehicle cameras are placed in a harsh usage environment, so an imaging optical system that suppresses focus shift (change in focal position) due to temperature changes is required. However, since the lens system described in Patent Document 1 uses a plastic lens, there is a problem that the focal position is likely to change due to a temperature change.

In particular, in an imaging lens system used for sensing in automatic driving, if a focus shift occurs due to a temperature change, a problem will occur in the accuracy of the sensing. For example, in an in-vehicle optical system, it is necessary to keep the focus shift within ± 20 μm in the temperature range of −40 ° C. to 105 ° C. in order to suppress an error in image recognition in automatic driving. However, the lens system described in Patent Document 1 does not satisfy the requirements of the optical system used for sensing.

On the other hand, by using glass lenses for all the lenses used in the imaging lens system, it is possible to suppress out-of-focus due to temperature changes. However, glass lenses are generally more expensive than plastic lenses, which increases the cost.

The present invention has been made in view of such problems, and an object of the present invention is to provide an image pickup lens system and an image pickup apparatus capable of suppressing a change in a focal position due to a temperature change.

In the image pickup lens system of one embodiment, the focal length of the i-th lens (i is a positive integer) arranged in order from the object side to the image side is set to fi, and the focal length of the entire optical system is set to fi. When F is set, at least 5 power lenses satisfying | fi / F | <20.0 are provided.
When the rate of change of the refractive index Nd of the d-line of the i-th lens due to a temperature change is (dNd / dt) i and Pdi = (dNd / dt) i / fi, the code of the value of the Pdi is an object. The power lenses are arranged so as to switch alternately from the side to the image side.

According to the present invention, it is possible to provide an image pickup lens system and an image pickup apparatus capable of suppressing a change in the focal position due to a temperature change.

It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 1. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 1. It is a curvature of field view in the image pickup lens system of Example 1. FIG. It is a distortion aberration diagram in the image pickup lens system of Example 1. FIG. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 2. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 2. It is a curvature of field view in the image pickup lens system of Example 2. FIG. It is a distortion aberration diagram in the image pickup lens system of Example 2. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 3. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 3. It is a curvature of field view in the image pickup lens system of Example 3. FIG. It is a distortion aberration diagram in the image pickup lens system of Example 3. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 4. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 4. It is a curvature of field view in the image pickup lens system of Example 4. It is a distortion aberration diagram in the image pickup lens system of Example 4. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 5. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 5. It is a curvature of field view in the image pickup lens system of Example 5. It is a distortion aberration diagram in the image pickup lens system of Example 5. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 6. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 6. It is a curvature of field view in the image pickup lens system of Example 6. It is a distortion aberration diagram in the image pickup lens system of Example 6. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 7. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 7. It is a curvature of field view in the image pickup lens system of Example 7. It is a distortion aberration diagram in the image pickup lens system of Example 7. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 8. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 8. It is a curvature of field view in the image pickup lens system of Example 8. It is a distortion aberration diagram in the image pickup lens system of Example 8. It is sectional drawing which shows the structure of the image pickup lens system which concerns on Example 9. FIG. It is a spherical aberration diagram (longitudinal aberration diagram) in the image pickup lens system of Example 9. It is a curvature of field view in the image pickup lens system of Example 9. It is a distortion aberration diagram in the image pickup lens system of Example 9. It is sectional drawing of the image pickup apparatus which concerns on Embodiment 2. FIG.

Hereinafter, the optical lens and the imaging device according to the present embodiment will be described.
(Embodiment 1: Imaging lens system)
In the image pickup lens system of the first embodiment, the focal length of the i-th lens (i is a positive integer) arranged in order from the object side to the image side is fi, and the focal length of the entire optical system is fi. When F is, at least five power lenses satisfying | fi / F | <20.0 are provided. Here, the power lens means a lens having a relatively large power and satisfying | fi / F | <20.0.
Further, in the image pickup lens system of the first embodiment, the rate of change of the refractive index Nd of the d-line of the i-th lens due to a temperature change is set to (dNd / dt) i, and Pdi = (dNd / dt) i / fi. In this case, the power lens is arranged so that the positive and negative signs of the Pdi value are alternately switched from the object side to the image side in order. Here, the d-line is a light ray having a wavelength of 588 nm.
As a result, the change in the focal position due to the temperature change of the power lenses arranged adjacent to each other can be canceled out from each other.
Specifically, the present inventors have determined that the amount of change in the focal position due to a temperature change in the image pickup lens system is the value of Pdi of the power lens constituting the image pickup lens system, that is, the power lens constituting the image pickup lens system. It was noted that it mainly depends on the value obtained by multiplying the rate of change (dNd / dt) i of the refractive index due to the temperature change of the lens by the power (1 / f).
More specifically, when the value of (dNd / dt) i is positive in a power lens having positive power, Pdi is positive, and the focal position of the power lens is higher than the focal position at room temperature at high temperature. Displace to the object side. On the other hand, when the value of (dNd / dt) i is negative in a power lens having positive power, Pdi becomes negative and the focal position of the power lens is displaced to the image side of the focal position at room temperature at high temperature. do.
Further, when the value of (dNd / dt) i is positive in a power lens having negative power, Pdi becomes negative, and the focal position of the power lens is displaced to the image side of the focal position at room temperature at high temperature. do. On the other hand, when the value of (dNd / dt) i is negative in a power lens having negative power, Pdi becomes positive, and the focal position of the power lens is displaced toward the object side from the focal position at room temperature at high temperature. do.
Therefore, the positive and negative signs of the Pdi value of the power lenses arranged from the object side to the image side are alternately switched, so that the changes in the focal position due to the temperature change of the power lenses arranged adjacent to each other cancel each other out. can do.

For example, from the object side to the image side, even if several lenses having a positive Pdi value continue and then several lenses having a negative Pdi value continue, the temperature of the entire imaging lens system as a whole. It is possible to suppress the displacement of the focal length due to the change. However, if lenses having the same Pdi code continue, the fluctuation due to the temperature change of the position of the light beam in each lens becomes large, which increases the aberration and lowers the resolution. For example, if a lens having a positive Pdi value continues, the displacement of the position of the light beam becomes cumulatively large when the temperature changes, and a specific angle of view emitted from the image-side surface of the lens group having a positive Pdi value. Since the fluctuation of the position where the light beam is incident on the object-side surface of the adjacent lens becomes large, the aberration correction that should be performed in the adjacent lens is not sufficiently performed. Therefore, it is preferable that the power lenses arranged from the object side to the image side are arranged so that the positive and negative signs of the Pdi value are alternately switched.

Further, in the image pickup lens system, generally, a lens having a predetermined power required to finally obtain a desired all-system focal length F at the same time as performing various corrections and a power for the purpose of correction only are relatively large. It consists of a weak lens. Since a lens with relatively weak power does not contribute to the fluctuation of the focal position when the temperature changes, it is not necessary to consider the sign of Pdi. Therefore, in the image pickup lens system according to the first embodiment, only the power lens having a relatively strong power satisfying | fi / F | <20.0, the sign of the Pdi value is directed from the object side to the image side. They are arranged so as to switch in order of negative, positive, negative, ..., Or positive, negative, positive, ...

Further, the half angle of view of the image pickup lens system according to the first embodiment is 50 ° or more, and the image pickup lens system according to the first embodiment is a wide angle of view image pickup lens system. Here, the semi-angle of view of the optical system means an angle formed by a light ray passing through the center of the pupil and reaching a position (diagonal point) of the diagonal length of the sensor with the optical axis on the object side.

Further, in the image pickup lens system according to the first embodiment, it is preferable that ^{the power lens satisfies | Pdi | <1.5 × 10-5.}
When the absolute value of Pdi of a certain power lens becomes larger than the upper limit value, the fluctuation of the focal position due to the temperature change of the power lens becomes too large, and the temperature change of the power lens is caused by another power lens adjacent to the power lens. It becomes difficult to correct the fluctuation of the focal position. Therefore, the absolute value of Pdi of each power lens is preferably smaller than ^{1.5 × 10-5.}

Further, in the image pickup lens system of the first embodiment, the value of (dNd / dt) i at 25 ° C. is larger than 0 (1 / K) and 9 × 10 ^-6 (9 × 10 -6) in order from the object side to the image side. The value of (dNd / dt) i at 25 ° C. on the image side of the first lens group in which two lenses composed of materials of less than 1 / K) are arranged adjacent to each other and the first lens group. It consists of a second lens group in which four lenses composed of only materials of -8 × 10 ^{-5 (1 / K) or less are arranged adjacent to each other.}
When the combined focal length of the second lens group is defined as fr and the focal length of the entire lens system is defined as F, the following equation (1) is satisfied.
fr / F> 3.5 ・・・ (1)

As described above, according to the image pickup lens system of the first embodiment, it is possible to provide an image pickup lens system capable of reducing aberrations and suppressing changes in the focal position due to temperature changes at a level required for image recognition in automatic driving. can.

The above effects will be explained in more detail. In general, it is difficult to calculate the combined focal lengths of a plurality of lenses with a combination other than adjacent lenses. Furthermore, if the temperature characteristics are included, it cannot be calculated in reality.

For example, in the image pickup lens described in Patent Document 1, since the first lens is glass, the second lens is plastic, the third lens is glass, and the fourth lens is plastic, it is necessary for image recognition in automatic operation. It is difficult to achieve aberration correction at the level. On the other hand, in the image pickup lens system of the first embodiment, a plurality of lenses in the first lens group have the same temperature characteristics as each other, and a plurality of lenses in the second lens group have the same temperature characteristics as each other. Therefore, it is possible to realize an imaging lens system capable of reducing aberrations and suppressing changes in the focal position due to temperature changes.

The present inventor has focused on the fact that the sum of the powers (1 / f) × (dNd / dt) i of each lens is dominant in the amount of change in the focal position due to the temperature change. Then, in the image pickup lens system of the first embodiment, the first lens group having a positive value of the temperature change rate (dNd / dt) i of the refractive index and ^{less than 9.0 × 10-6} (1 / K) and (dNd). / Dt) The second lens group has a negative i value and is ^{divided into a second lens group of −8.0 × 10 -5} (1 / K) or less, and the absolute value of the (dNd / dt) i value is large. By increasing the combined focal length of (specifically, 3.2 times or more the focal length of the entire optical system), the amount of change in the focal position due to the temperature change in the entire imaging lens system can be reduced.

Specifically, by increasing the combined focal length of the second lens group, which has a large absolute value of the temperature change rate of the refractive index, by 1.8 to 3.8 times that of the first lens group, the focal length shifts due to the temperature change. Can cancel each other out and be made smaller (specifically, the amount of change in the focal length due to a temperature change from −40 ° C. to 105 ° C. is ± 0.02 mm).

In addition, since the first lens group having a positive value of the temperature change rate (dNd / dt) i of the refractive index and the second lens group having a negative value are not mixed, it is possible to collect lenses having a close dNd / Dt in the group. , The fluctuation of light rays at the time of temperature change is reduced, and the spherical aberration at the time of temperature change is improved.

The image pickup lens system of the first embodiment may satisfy the following equation (2).
fr / F ≧ 4.1 ・・・ (2)

In the image pickup lens system of the first embodiment, the value of the temperature change rate (dNd / dt) i of the refractive index of all the materials constituting the two lenses of the first lens group is 3.0 × 10 ^−. The temperature change rate of the refractive index of all the materials constituting the four lenses of the second lens group, which is ⁶ (1 / K) or more and 8.2 × ^{10-6 (1 / K) or less.} The value of dNd / dt) i may be -12 × 10 ^-5 (1 / K) or more and −8.5 × 10 ^-5 (1 / K) or less.

Further, the image pickup lens system according to the first embodiment has a first lens having a negative power and a concave surface on the image side in order from the object side toward the image side, and has a positive power on the object side. The first lens and the second lens are composed of a second lens having a convex surface, a third lens having a positive power, a fourth lens having a negative power, a fifth lens having a positive power, and a sixth lens. In the meantime, it is preferable to provide an aperture arranged at any one of the second lens and the third lens, and between the third lens and the fourth lens.
Here, the first lens to the fifth lens are power lenses having a relatively large power satisfying | fi / F | <20.0, and the sixth lens is mainly for the purpose of aberration correction, | fi / F. It is a lens having a relatively weak power that does not satisfy | <20.0.
Normally, the image pickup lens system used for sensing of automatic operation, which is required to have a wide angle of view and high resolution, has a concave surface on the image side to realize a wide angle of view in order from the object side to the image side. It is composed of one or two lenses, one or two condensing lenses, a concave lens and a convex lens for correcting chromatic aberration, and an aberration correction lens having a relatively small power mainly for the purpose of correcting aberrations, if necessary. In other words, the imaging lens system requires at least five or more power lenses. However, as the number of power lenses constituting the image pickup lens system increases, the cumulative value of the change in the focal position due to the temperature change increases accordingly. Therefore, the image pickup lens system according to the first embodiment is preferably composed of the five power lenses of the first to fifth lenses described above and one sixth lens for aberration correction.

Further, in the image pickup lens system according to the first embodiment, the first lens and the second lens are made of a glass material having a d-line refractive index Nd of 1.7 or more, and the third to sixth lenses are d. It is preferable that the line is made of a glass material having a refractive index Nd of less than 1.7. By forming the third lens to the sixth lens with a relatively inexpensive glass material having a d-line refractive index Nd of less than 1.7, the cost of the imaging lens system can be reduced.

In the image pickup lens system of the first embodiment, the first lens group has a first lens having a concave shape and negative power on the image side and a convex shape and positive power on the object side in order from the object side to the image side. Consists of a second lens with
The second lens group consists of a third lens having a positive power, a fourth lens having a negative power, a fifth lens having a positive power, and a sixth lens in order from the object side to the image side. ,
A diaphragm arranged at any one of the first lens and the second lens, between the second lens and the third lens, and between the third lens and the fourth lens is provided. You may.

Further, in the image pickup lens system according to the first embodiment, when the combined focal lengths of the third lens, the fourth lens, the fifth lens, and the sixth lens are f (3 to 6), the following equation (3) is used. It is preferable to satisfy. Since the second lens group includes a third lens, a fourth lens, a fifth lens, and a sixth lens, fr = f (3 to 6).
f (3-6) /F> 3.5 ・・・ (3)
Since the third lens to the sixth lens are made of a glass material having a refractive index Nd of less than 1.7, for example, plastic, the rate of change (dNd / dt) i of the refractive index due to a temperature change is large. Therefore, in order to reduce the influence of (dNd / dt) i on the value of Pdi, it is preferable that the combined focal length f (3 to 6) of the third lens to the sixth lens is relatively large. Therefore, by satisfying the above equation (3), it is possible to suppress the fluctuation of the focal position due to the temperature change in the third lens to the sixth lens while forming the third lens to the sixth lens with a relatively inexpensive glass material. can.

Further, in the image pickup lens system according to the first embodiment, it is preferable that the following equation (4) is satisfied when the thickness of the second lens on the optical axis is d2.
0.63 <d2 / F <0.9 ... (4)
Spherical aberration can be suitably corrected when the thickness of the second lens on the optical axis satisfies the above equation (4), that is, is relatively thick.

Further, in the image pickup lens system according to the first embodiment, the fourth lens and the fifth lens may be joined to each other.
When the fourth lens and the fifth lens form a junction lens, chromatic aberration can be suitably corrected.

In the image pickup lens system of the first embodiment, the total thickness (center thickness) on the optical axis of the lenses constituting the first lens group is ΣA, and the sum of the thicknesses (center thickness) on the optical axis of the lenses constituting the second lens group is ΣA. When defined as the total thickness ΣB, the following equation (5) may be satisfied.
0.9 ≤ ΣB / ΣA ≤ 1.8 ... (5)

Next, an example corresponding to the image pickup lens system of the first embodiment will be described with reference to the drawings.
(Example 1)
FIG. 1 is a cross-sectional view showing the configuration of the image pickup lens system 11 of the first embodiment. Specifically, in the image pickup lens system 11 according to the first embodiment, the first lens L1, the second lens L2, the third lens L3, the aperture stop (STOP), and the fourth lens are arranged in this order from the object side to the image side. It is composed of L4, a fifth lens L5, and a sixth lens L6. The image plane of the image pickup lens system 11 is indicated by IMG.

The first lens L1 is a spherical glass lens having a negative power. The object-side lens surface S1 of the first lens L1 has a concave surface facing the object side. The image-side lens surface S2 of the first lens L1 has a concave curved surface portion.

The second lens L2 is a spherical glass lens having positive power. The object-side lens surface S3 of the second lens L2 has a convex surface facing the object side. Further, the image-side lens surface S4 of the second lens L2 has a convex surface facing the image side.

The third lens L3 is an aspherical plastic lens having positive power. The object-side lens surface S5 of the third lens L3 has a convex surface facing the object side. Further, the image side lens surface S6 of the third lens L3 has a convex surface facing the image surface side.

Aperture STOP is an aperture that determines the F value (Fno) of the lens system. The aperture STOP is arranged between the third lens L3 and the fourth lens L4.

The fourth lens L4 is an aspherical plastic lens having negative power. The object-side lens surface S9 of the fourth lens L4 has a concave surface facing the object side. Further, the image side lens surface S10 of the fourth lens L4 has a concave surface facing the image surface side.

The fifth lens L5 is an aspherical plastic lens having positive power. The object-side lens surface S11 of the fifth lens L5 has a convex curved surface portion. Further, the image side lens surface S12 of the fifth lens L5 has a convex surface facing the image surface side.

The fourth lens L4 and the fifth lens L5 form a junction lens. That is, the image-side lens surface S10 of the fourth lens L4 and the object-side lens surface S11 of the fifth lens L5 are in contact with each other. For example, it is preferable that the fourth lens L4 and the fifth lens L5 are joined by an adhesive layer having an axial thickness of 0.02 mm.

The sixth lens L6 is an aspherical plastic lens having positive power. The object-side lens surface S13 of the sixth lens L6 has a convex curved surface portion. Further, the image side lens surface S14 of the sixth lens L6 has a concave curved surface portion.

The IR cut filter 12 is a filter for cutting light in the infrared region. The IR cut filter 12 is treated integrally with the image pickup lens system 11 at the time of designing the image pickup lens system 11. However, the IR cut filter 12 is not an essential component of the image pickup lens system 11.

Table 1 shows the lens data of each lens surface in the image pickup lens system 11 of Example 1. In Table 1, as lens data, the radius of curvature (mm) of each surface, the surface spacing (mm) on the central optical axis, the refractive index Nd with respect to the d line, the Abbe number Vd with respect to the d line, and the refraction at a wavelength of 588 nm at 25 ° C. The rate of temperature change dNd / dt (1 / K) is presented. The refractive index on the d-line and the Abbe number on the d-line shown in Table 1 are values when the environmental temperature t (° C.), which is the ambient temperature of the image pickup lens system 11, is 25 (° C.). Further, in Table 1, the surfaces marked with "*" indicate that they are aspherical surfaces. Further, in Table 1, for example, "-4.9E-06" means "-4.9 × ^10-6 ". The numerical expressions are the same for the following table.

The aspherical shape adopted for the lens surface is 3rd, 4th, 5th, 6th, where z is the sag amount, c is the inverse of the radius of curvature, k is the conical coefficient, and r is the ray height from the optical axis Z. Next, 7th, 8th, 9th, 10th, 12th, 14th, and 16th aspherical coefficients are A3, A4, A5, A6, A7, A8, A9, A10, A12, A14, A16, respectively. Then, it is expressed by the following equation.

Table 2 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the first embodiment.

Next, the aberration will be described with reference to the drawings. 2A, 2B, and 2C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of the first embodiment, respectively. As shown in FIGS. 2A, 2B, and 2C, in the image pickup lens system 11 of the first embodiment, the half angle of view is 52.0 ° and the F number is 2.0.
Further, in the longitudinal aberration diagram of FIG. 2A, the horizontal axis indicates the position where the light ray intersects the optical axis Z, and the vertical axis indicates the height at the pupil diameter. Further, FIG. 2A shows the simulation results with light rays of 455 nm, 502 nm, 546 nm, 614 nm, and 661 nm.
Further, in the curvature of field diagram of FIG. 2B, the horizontal axis indicates the distance in the optical axis Z direction, and the vertical axis indicates the image height (angle of view). Further, in the curvature of field diagram of FIG. 2B, Sag shows the curvature of field on the sagittal plane, and Tan shows the curvature of field on the tangent plane. Further, FIG. 2B shows a simulation result using a light beam having a wavelength of 546 nm.
Further, in the distortion diagram of FIG. 2C, the horizontal axis represents the amount of distortion (%) of the image, and the vertical axis represents the image height (angle of view). Further, FIG. 2C shows a simulation result using a light beam having a wavelength of 546 nm.
2A, 2B, and 2C show a spherical aberration diagram (longitudinal aberration diagram), an image curvature diagram, and a distortion aberration diagram when the environmental temperature t (° C.) is 25 (° C.).

(Example 2)
FIG. 3 is a cross-sectional view showing the image pickup lens system 11 according to the second embodiment. Since the configuration of the image pickup lens system 11 according to the second embodiment is the same as that of the first embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the second embodiment will be described.

Table 3 shows the lens data of each lens surface of the imaging lens system 11 according to the second embodiment. Since the items shown in Table 3 are the same as those in Table 1, the description thereof will be omitted.

Table 4 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the second embodiment. In Table 4, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

4A, 4B, and 4C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of the second embodiment. Since the description of each aberration diagram shown in FIGS. 4A, 4B, and 4C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 3)
FIG. 5 is a cross-sectional view showing the image pickup lens system 11 according to the third embodiment. The configuration of the image pickup lens system 11 according to the third embodiment is the same as that of the first embodiment except that the aperture STOP is also arranged between the first lens L1 and the second lens L2. Omit. Hereinafter, the characteristic data of the image pickup lens system 11 according to the third embodiment will be described.

Table 5 shows the lens data of each lens surface of the image pickup lens system 11 according to the third embodiment. Since the items shown in Table 5 are the same as those in Table 1, the description thereof will be omitted.

Table 6 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the third embodiment. In Table 6, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

6A, 6B, and 6C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of the third embodiment. Since the description of each aberration diagram shown in FIGS. 6A, 6B, and 6C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 4)
FIG. 7 is a cross-sectional view showing the image pickup lens system 11 according to the fourth embodiment. Since the configuration of the image pickup lens system 11 according to the fourth embodiment is the same as that of the first embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the fourth embodiment will be described.

Table 7 shows the lens data of each lens surface of the image pickup lens system 11 according to the fourth embodiment. Since the items shown in Table 7 are the same as those in Table 1, the description thereof will be omitted.

Table 8 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the fourth embodiment. In Table 8, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

8A, 8B, and 8C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of the fourth embodiment. Since the description of each aberration diagram shown in FIGS. 8A, 8B, and 8C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 5)
FIG. 9 is a cross-sectional view showing the image pickup lens system 11 according to the fifth embodiment. Since the configuration of the image pickup lens system 11 according to the fifth embodiment is the same as that of the first embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the fifth embodiment will be described.

Table 9 shows the lens data of each lens surface of the image pickup lens system 11 according to the fifth embodiment. Since the items shown in Table 9 are the same as those in Table 1, the description thereof will be omitted.

Table 10 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the fifth embodiment. In Table 10, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

10A, 10B, and 10C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of Example 5. Since the description of each aberration diagram shown in FIGS. 10A, 10B, and 10C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 6)
FIG. 11 is a cross-sectional view showing the image pickup lens system 11 according to the sixth embodiment. Since the configuration of the image pickup lens system 11 according to the sixth embodiment is the same as that of the first embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the sixth embodiment will be described.

Table 11 shows the lens data of each lens surface of the imaging lens system 11 according to the sixth embodiment. Since the items shown in Table 11 are the same as those in Table 1, the description thereof will be omitted.

Table 12 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the sixth embodiment. In Table 12, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

12A, 12B, and 12C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of the sixth embodiment. Since the description of each aberration diagram shown in FIGS. 12A, 12B, and 12C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 7)
FIG. 13 is a cross-sectional view showing the image pickup lens system 11 according to the seventh embodiment. Since the configuration of the image pickup lens system 11 according to the seventh embodiment is the same as that of the third embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the seventh embodiment will be described.

Table 13 shows the lens data of each lens surface of the image pickup lens system 11 according to the seventh embodiment. Since the items shown in Table 13 are the same as those in Table 1, the description thereof will be omitted.

Table 14 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the seventh embodiment. In Table 14, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

14A, 14B, and 14C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of Example 7. Since the description of each aberration diagram shown in FIGS. 14A, 14B, and 14C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 8)
FIG. 15 is a cross-sectional view showing the image pickup lens system 11 according to the eighth embodiment. Since the configuration of the image pickup lens system 11 according to the eighth embodiment is the same as that of the third embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the eighth embodiment will be described.

Table 15 shows the lens data of each lens surface of the image pickup lens system 11 according to the eighth embodiment. Since the items shown in Table 15 are the same as those in Table 1, the description thereof will be omitted.

Table 16 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the eighth embodiment. In Table 16, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

16A, 16B, and 16C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of Example 8. Since the description of each aberration diagram shown in FIGS. 16A, 16B, and 16C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

(Example 9)
FIG. 17 is a cross-sectional view showing the image pickup lens system 11 according to the ninth embodiment. Since the configuration of the image pickup lens system 11 according to the ninth embodiment is the same as that of the first embodiment, the description thereof will be omitted. Hereinafter, the characteristic data of the image pickup lens system 11 according to the ninth embodiment will be described.

Table 17 shows the lens data of each lens surface of the image pickup lens system 11 according to the ninth embodiment. Since the items shown in Table 17 are the same as those in Table 1, the description thereof will be omitted.

Table 18 shows the aspherical coefficient for defining the aspherical shape of the lens surface which is the aspherical surface in the image pickup lens system 11 of the ninth embodiment. In Table 18, the aspherical shape adopted for the lens surface is represented by the same formula as in Example 1.

18A, 18B, and 18C show a spherical aberration diagram (longitudinal aberration diagram), an image plane curvature diagram, and a distortion aberration diagram in the image pickup lens system 11 of the ninth embodiment. Since the description of each aberration diagram shown in FIGS. 18A, 18B, and 18C is the same as that of FIGS. 2A, 2B, and 2C, the description thereof will be omitted.

As shown in the longitudinal aberration diagrams of FIGS. 2A, 4A, 6A, 8A, 10A, 12A, 14A, 16A, and 18A, according to the imaging lens system 11 of Examples 1 to 9, the wavelengths are 455 nm, 502 nm, 546 nm, and 614 nm. , 661 nm longitudinal aberration is well corrected. Therefore, the image pickup lens system 11 has a high resolution.

Further, as shown in the curvature of field of FIGS. 2B, 4B, 6B, 8B, 10B, 12B, 14B, 16B, and 18B, the curvature of field is good according to the image plane curvatures 11 of Examples 1 to 9. It has been corrected to. Therefore, the image pickup lens system 11 has a high resolution.

Further, as shown in the distortion aberration diagrams of FIGS. 2C, 4C, 6C, 8C, 10C, 12C, 14C, 16C, and 18C, according to the image pickup lens system 11 of Examples 1 to 9, the distortion aberration is satisfactorily corrected. Has been done. Therefore, the image pickup lens system 11 has a high resolution.

Table 19, the focal length _{f 1} of the first lens L1, the focal length _{f 2} of the second lens L2, the focal length _{f 3} of the third lens L3, the focal length _{f 4} of the fourth lens L4, the focus of the fifth lens L5 Distance f ₅ _{, focal distance f 6} of the sixth lens L6, synthetic focal distance f (1-2) of the first lens L1 to the second lens L1, synthetic focal distance f (3) of the third lens L3 to the sixth lens L6. ~ 6), F2 / F1 (F2 / F1 = f (3 ~ 6) / f (1 ~ 2)) values, focal distance F of the entire optical system of the imaging lens system 11, | f1 / F | ~ | f6 The value of / F |, the value of f (3 to 6) / F, the thickness d1 to d6 of the first lens L1 to the sixth lens L6 on the optical axis, the value of d2 / F, and the value of the first lens group. Total thickness on the optical axis of the lens ΣA, total thickness on the optical axis of the lenses constituting the second lens group ΣB, ΣB / ΣA values, temperature change rate of the refractive index of the first lens L1 (dNd) / Dt) 1, Temperature change rate of the refractive index of the second lens L2 (dNd / dt) 2, Temperature change rate of the refractive index of the third lens L3 (dNd / dt) 3, Temperature of the refractive index of the fourth lens L4 Change rate (dNd / dt) 4, temperature change rate of refractive index of fifth lens L5 (dNd / dt) 5, temperature change rate of refractive index of sixth lens L6 (dNd / dt) 6, first lens L1 Pd1, Pd2 of the second lens L2, Pd3 of the third lens L3, Pd4 of the fourth lens L4, Pd5 of the fifth lens L5, Pd6 of the sixth lens L6, Pdi of the first lens L1 to the sixth lens L6. The total ΣPdi shows the focal position of the imaging lens system 11 at −40 ° C. and the focal position of 105 ° C. when the focal position of the imaging lens system 11 at 25 ° C. is used as a reference (0 mm). In Table 19, the unit of the focal length and the thickness of the first lens L1 to the sixth lens L6 on the optical axis is mm. The unit of the temperature change rate of the refractive index is 1 / K. The unit of (dNd / dt) 1 to (dNd / dt) 6 is 1 / K, and the unit of Pd1 to Pd6 is 1 / K · mm. The various focal lengths and focal positions in Table 19 were calculated using light rays having a wavelength of 546 nm. In Examples 1 to 9, since the second lens group includes the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6, fr = f (3 to 6).

As shown in Table 19, in Examples 1 to 9, the first lens L1 to the fifth lens L5, which are power lenses satisfying | fi / F | <20.0, have Pdi values on the object side. The lenses are arranged so as to switch alternately from negative to positive, negative, and so on toward the image side. As a result, the change in the focal position due to the temperature change of the power lenses arranged adjacent to each other can be canceled out from each other, and the change in the focal position due to the temperature change in the focal length F of the entire optical system of the imaging lens system 11 can be suppressed. .. In fact, as shown in Table 19, in Examples 1 to 9, the change in the focal position due to the temperature change in the focal length F of the entire optical system of the imaging lens system 11 is suppressed within 20 μm.

Further, in Examples 1 to 9, the half angle of view of the image pickup lens system 11 is 50 ° or more, and the image pickup lens system 11 having a wide angle of view can be realized.

Further, as shown in Table 19, in Examples 1 to 9, the first lens L1 to the fifth lens L5, which are power lenses satisfying | fi / F | <20.0, are | Pdi | <1.5. It satisfies ^{× 10-5.} As a result, it is possible to more reliably correct the fluctuation of the focal position due to the temperature change of the power lenses L1 to L5.

Further, in Examples 1 to 9, the image pickup lens system 11 is composed of five power lenses of the first lens L1 to the fifth lens L5 and one sixth lens L6 for aberration correction. As a result, it is possible to suppress the number of lenses constituting the image pickup lens system 11 and suppress the cumulative value of the fluctuation of the focal position due to the temperature change while realizing high resolution while having a wide angle of view. In fact, in Examples 1 to 9, as shown in FIGS. 2, 4, 6, 8, 10, 12, 14, 16 and 18, various aberrations can be suitably reduced and high resolution can be realized, and Table 19 shows. As shown, the fluctuation of the focal position due to the temperature change of the image pickup lens system 11 can be suppressed.

Further, in Examples 1 to 9, the first lens L1 and the second lens L2 are made of a glass material having a d-line refractive index Nd of 1.7 or more, and the third lens L3 to the sixth lens L6 are d. The line is made of a glass material having a refractive index Nd of less than 1.7. As a result, the cost of the image pickup lens system 11 can be reduced by forming the third lens to the sixth lens with a relatively inexpensive glass material.

Further, as shown in Table 19, in Examples 1 to 9, the values of f (3 to 6) / F satisfy the above equations (1) to (3). As a result, it is possible to suppress fluctuations in the focal position due to temperature changes in the third lens L3 to the sixth lens L6 while forming the third lens L3 to the sixth lens L6 with a relatively inexpensive glass material.

Further, as shown in Table 19, in Examples 1 to 9, the value of d2 / F satisfies the above formula (4). Since the thickness d2 on the optical axis of the second lens L2 is relatively thick, spherical aberration can be suitably corrected. In fact, in Examples 1-9, spherical aberrations at wavelengths of 455 nm, 502 nm, 546 nm, 614 nm, and 661 nm are satisfactorily corrected, as shown in FIGS. 2A, 4A, 6A, 8A, 10A, 12A, 14A, 16A, and 18A. , A high-resolution image pickup lens system 11 can be realized.

Further, in Examples 1 to 9, the fourth lens L4 and the fifth lens L5 are joined to each other. As a result, chromatic aberration can be suitably corrected.

(Embodiment 2: Application Example to Imaging Device)
In FIG. 19, the image pickup device 21 includes an image pickup lens system 11 and an image pickup element 22. The image pickup lens system 11 and the image pickup element 22 are housed in a housing (not shown). The image pickup lens system 11 is the image pickup lens system 11 described in the first embodiment described above.

The image sensor 22 is an element that converts the received light into an electric signal, and for example, a CCD image sensor or a CMOS image sensor is used. The image pickup device 22 is arranged at the imaging position of the image pickup lens system 11.

As described above, according to the image pickup device of the second embodiment, it is possible to provide an image pickup device capable of reducing aberrations and suppressing changes in the focal position due to temperature changes at a level required for image recognition in automatic driving.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit. For example, Example 2 may be applied to Examples 1 to 9. For example, the application of the image pickup lens system of the present invention is not limited to an in-vehicle camera or a surveillance camera, and can be used for other applications such as mounting on a small electronic device such as a mobile phone.

This application claims priority based on Japanese application Japanese Patent Application No. 2020-015791 filed on February 3, 2020 and Japanese application Japanese Patent Application No. 2021-001775 filed on January 8, 2021. Incorporate all of the disclosure here.

It is possible to provide an imaging lens system and an imaging device capable of suppressing a change in the focal position due to a temperature change.

11 Imaging lens system 12 IR cut filter 21 Imaging device 22 Imaging element L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens STOP Aperture IMG imaging surface

Claims

When the focal length of the i-th lens (i is a positive integer) arranged in order from the object side to the image side is fi and the focal length of the entire optical system is F, | fi / Have at least 5 power lenses that satisfy F | <20.0,
When the rate of change of the refractive index Nd of the d-line of the i-th lens due to a temperature change is (dNd / dt) i and Pdi = (dNd / dt) i / fi, the code of the value of the Pdi is an object. An imaging lens system in which the power lens is arranged so as to switch alternately from the side to the image side.
The imaging lens system according to claim 1, wherein the power lens satisfies | Pdi | <1.5 × 10-5.
From the object side to the image side, the value of (dNd / dt) i at 25 ° C. was larger than 0 (1 / K) and was composed only of materials less than 9 × 10-6 (1 / K). The value of (dNd / dt) i at 25 ° C. is -8 × 10-5 (1 / K) on the image side of the first lens group in which two or more lenses are arranged adjacent to each other and the image side of the first lens group. ) Consists of a second lens group in which four or more lenses composed of only the following materials are arranged adjacent to each other.
The imaging lens system according to claim 1 or 2, wherein the composite focal length of the second lens group is defined as fr and the focal length of the entire lens system is defined as F, which satisfies the following equation (1).
fr / F> 3.5 ・・・ (1)
The imaging lens system according to claim 3, which satisfies the following formula (2).
fr / F ≧ 4.1 ・・・ (2)
The (dNd / dt) i of all the materials constituting the two lenses of the first lens group at 25 ° C. is 3.0 × 10 -6 (1 / K) or more and 8.2 × 10 It is -6 (1 / K) or less, and (dNd / dt) i of all the materials constituting the four lenses of the second lens group at 25 ° C. is -12 × 10 -5 (1 / K). The imaging lens system according to claim 3 or 4, which is the above and is −8.5 × 10-5 (1 / K) or less.
From the object side to the image side, a first lens having a negative power and a concave surface on the image side, a second lens having a positive power and a convex surface on the object side, and a second lens having a positive power. It consists of 3 lenses, a 4th lens with negative power, a 5th lens with positive power, and a 6th lens.
A claim that includes an aperture arranged at any one of the first lens and the second lens, between the second lens and the third lens, and between the third lens and the fourth lens. The imaging lens system according to 1 or 2.
The first lens group has a first lens having a negative power and having a concave surface on the image side and a second lens having a positive power and having a convex surface on the object side in order from the object side to the image side. Consists of
The second lens group comprises a third lens having a positive power, a fourth lens having a negative power, a fifth lens having a positive power, and a sixth lens in order from the object side to the image side.
A claim that includes an aperture arranged at any one of the first lens and the second lens, between the second lens and the third lens, and between the third lens and the fourth lens. The imaging lens system according to any one of 3 to 5.
The first lens and the second lens are made of a glass material having a d-line refractive index Nd of 1.7 or more, and the third lens to the sixth lens have a d-line refractive index Nd of 1.7. The imaging lens system according to claim 6 or 7, which is made of less than a glass material.
The imaging lens system according to claim 6 or 8, wherein the half angle of view is 50 ° or more.
Claims 6, 8 and 9 satisfy the following formula (3) when the combined focal lengths of the third lens, the fourth lens, the fifth lens and the sixth lens are f (3 to 6). The imaging lens system according to any one of the above.
f (3-6) /F> 3.5 ・・・ (3)
The imaging lens system according to any one of claims 6 to 10, which satisfies the following formula (4) when the thickness of the second lens on the optical axis is d2.
0.63 <d2 / F <0.9 ... (4)
The imaging lens system according to any one of claims 6 to 11, wherein the fourth lens and the fifth lens are joined to each other.
When the total thickness on the optical axis of the lenses constituting the first lens group is defined as ΣA and the total thickness on the optical axis of the lenses constituting the second lens group is defined as ΣB, the following equation (5) The imaging lens system according to any one of claims 3 to 5, or 7.
0.9 ≤ ΣB / ΣA ≤ 1.8 ... (5)
The imaging lens system according to any one of claims 1 to 13.
An image pickup device including an image pickup element arranged at a focal position of the image pickup lens system.