JP2015060201A - Imaging lens system and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens system easy to be manufactured and having a sufficient aberration correction capability.SOLUTION: An imaging lens system 101 according to the present invention includes, in order from an object side to an image side: a first lens L1 having negative power and having a meniscus shape with a concave surface on the image side; a second lens L2 having negative power and having a concave surface on the image side; a third lens L3 having positive power and having a convex surface on the object side; a fourth lens L4 having negative power; a fifth lens L5 having positive power; and a sixth lens L6 having positive power. The fourth lens L4 and the fifth lens L5 of the imaging lens system 101 are bonded to each other by an adhesive layer provided between an image-side lens surface S9 of the fourth lens L4 and an object-side lens surface S10 of the fifth lens L5, and a conditional expression of 0.9≤R/f≤1.3 is satisfied if assuming that a focal length of the entire lens system 101 is f and a curvature radius of the image-side lens surface S9 of the fourth lens L4 is R.

Description

  The present invention relates to an imaging lens system and an imaging apparatus.

  As an optical system for surveillance applications, there are a surveillance camera lens system for ensuring safety indoors and outdoors, an in-vehicle camera lens system for exterior and interior surveillance, and the like. An optical system for monitoring is required to have a very wide field of view and high resolution. In particular, an imaging lens system for a vehicle-mounted camera is also required to be compact.

  Patent Document 1 describes a wide-angle lens system having a wide angle and high resolution. In this wide-angle lens system, a negative first lens, a negative second lens, a positive third lens, a negative fourth lens, a positive fifth lens, and a positive sixth lens are sequentially arranged from the object side. Consists of. In this wide-angle lens system, the image side lens surface of the fourth lens and the object side lens surface of the fifth lens are cemented. By using a cemented lens, the number of parts when assembling the lens system can be reduced, which contributes to cost reduction.

Japanese Patent No. 5045300

  Bonding of a cemented lens is an operation that takes time in manufacturing a lens system in which a plurality of lenses are combined. On the cemented surface of the cemented lens, the concave surface and the convex surface are bonded together with an adhesive or the like.

When the curvature of the cemented surface of the cemented lens is tight, there are problems that it takes time to fit the convex surface into the concave surface, and that the cemented surface is easily damaged when the lenses are fitted together.
On the other hand, if the curvature of the joint surface is loosened so that it can be easily fitted, the lens surface is hardly damaged. However, if the curvature of the joint surface is relaxed, it becomes difficult to perform sufficient aberration correction.

  The present invention has been made to solve these problems, and an object of the present invention is to provide an imaging lens system that is easy to manufacture and has sufficient aberration correction capability.

The imaging lens system of the present invention is
From the object side to the image side,
A meniscus first lens having negative power and having a concave surface facing the image side;
A second lens having negative power and having a concave surface facing the image side;
A third lens having positive power and having a convex surface facing the object side;
A fourth lens having negative power;
A fifth lens having positive power;
An imaging lens system comprising a sixth lens having positive power,
The fourth lens and the fifth lens are bonded together by an adhesive layer between the image side lens surface of the fourth lens and the object side lens surface of the fifth lens;
The focal length of the entire lens system is f,
The radius of curvature of the image-side lens surface of the fourth lens is R _4i
The following conditional expression (1) is satisfied.
0.9 ≦ R _4i /f≦1.3 (1)

  If the lower limit of conditional expression (1) is not reached, the radius of curvature of the image-side lens surface of the fourth lens becomes small, so that it is not easy to join the object-side lens surface of the fifth lens, and workability to manufacture a cemented lens. Decreases and the cost increases. On the other hand, if the upper limit of conditional expression (1) is exceeded, it will be difficult to correct chromatic aberration, and the resolution of the imaging lens system will be reduced.

The imaging lens system described above is
The image side lens surface of the fourth lens and the object side lens surface of the fifth lens are aspherical,
The image side lens surface of the fourth lens and the object side lens surface of the fifth lens are not in contact with each other,
The length of the foot of the perpendicular drawn from the lens surface to the optical axis is the height from the optical axis, and the sag amount at the height corresponding to the effective diameter of the object side lens surface of the fifth lens is Sg2H,
The sag amount at the same height as the effective diameter of the object side lens surface of the fifth lens on the image side lens surface of the fourth lens is Sg1H,
And when
The following conditional expression (2) is satisfied.
Sg1H ≦ Sg2H (2)

  In the imaging lens system of the present invention, the image side lens surface of the fourth lens and the object side lens surface of the fifth lens, which are cemented surfaces of the two lenses constituting the cemented lens, have different aspheric shapes. Yes. With this configuration, it becomes easy to correct various aberrations such as spherical aberration and chromatic aberration using the cemented lens, so that the resolving power of the imaging lens system can be increased.

  Further, since the conditional expression (2) is satisfied, the thickness of the adhesive layer between the image side lens surface of the fourth lens and the object side lens surface of the fifth lens having different aspherical shapes can be increased. . That is, the interval between the cemented surfaces of the two lenses constituting the cemented lens can be increased. Thereby, it is possible to prevent or suppress an accident such as bringing the joint surfaces into contact with each other during the bonding operation of bonding the two lenses. Therefore, it becomes easy to manufacture the cemented lens.

  Moreover, since the space | interval of the joint surface of a 4th lens and a 5th lens is wide, it becomes easy for a resin adhesive to wrap around between joint surfaces. Thereby, it is possible to prevent bubbles from remaining between the two lenses. Therefore, it becomes easy to manufacture the cemented lens.

The imaging lens system described above is
The focal length of the entire lens system is f,
The combined focal length of the fourth lens and the fifth lens is f ₄₅ ,
The following conditional expression (3) is satisfied.
2.8 ≦ f ₄₅ /f≦3.7 (3)
Here, f ₄₅ is a combined focal length by the fourth lens, the fifth lens, and the adhesive layer.

For conditional expression (3), more preferably,
3.0 ≦ f ₄₅ /f≦3.4
It is good to do.

  If the upper limit of conditional expression (3) is exceeded, the power of the cemented lens becomes relatively weak, and the correction of chromatic aberration becomes insufficient. On the other hand, if the lower limit of conditional expression (3) is not reached, the power of the cemented lens becomes relatively strong, and the radius of curvature of each surface of the cemented lens becomes small, making it difficult to perform processing and cementing operations. At the same time, it becomes difficult to maintain the back focus.

The imaging lens system described above is
The focal length of the entire lens system is f,
The distance from the object side lens surface of the first lens to the image side lens surface of the sixth lens is OL.
The following conditional expression (4) is satisfied.
7.0 ≦ OL / f ≦ 12 (4)

For conditional expression (4), more preferably,
8.0 ≦ OL / f ≦ 11
It is good to do.

  If the upper limit of conditional expression (4) is exceeded, it will be difficult to make the total optical length of the lens system compact. On the other hand, if the lower limit of conditional expression (4) is not reached, the focal length of the entire lens system becomes smaller than the distance from the forefront surface to the rearmost surface of the lens. In this case, since the power of each lens is increased, the curvature is increased, which is disadvantageous in terms of manufacturing such as processing, molding, and bonding.

The imaging lens system described above is
The focal length of the third lens is f ₃ ,
The combined focal length of the fourth lens and the fifth lens is f _45.
The following conditional expression (5) is satisfied.
0.8 ≦ f ₄₅ / f ₃ ≦ 1.4 (5)
Here, f ₄₅ is a combined focal length by the fourth lens, the fifth lens, and the adhesive layer.

For conditional expression (5), more preferably,
0.85 ≦ f ₄₅ / f ₃ ≦ 1.35
It is good to do.

  By satisfying conditional expression (5), it is possible to satisfactorily correct spherical aberration, coma aberration, axial chromatic aberration, and lateral chromatic aberration in the imaging lens system. If the lower limit of conditional expression (5) is not reached, the positive power of the third lens becomes relatively weak with respect to the combined focal length of the fourth lens and the fifth lens. As a result, the correction of chromatic aberration is insufficient, and the resolving power decreases. On the other hand, if the upper limit of conditional expression (5) is exceeded, the positive power of the third lens becomes relatively strong. For this reason, the correction of chromatic aberration becomes excessive, and the spherical aberration and the coma aberration are deteriorated, so that the resolution is lowered.

The imaging lens system described above is
The combined focal length of the first lens and the second lens is f ₁₂
The following conditional expression (6) is satisfied.
−1.4 ≦ f ₁₂ /f≦−1.0 (6)

For conditional expression (6), more preferably,
−1.35 ≦ f ₁₂ /f≦−1.1
It is good to do.

  If the lower limit of conditional expression (6) is not reached, the negative power of the first lens and the second lens becomes weak. For this reason, since it becomes difficult to bend a light beam with a large angle of view, it is difficult to achieve a super wide angle. Further, the back focus is insufficient, and the curvature of field is insufficiently corrected. On the contrary, if the upper limit of conditional expression (6) is exceeded, the negative power of the first lens and the second lens becomes strong. For this reason, the curvatures of the image-side lens surface of the first lens and the image-side lens surface of the second lens become strong, making manufacturing difficult. Further, the field curvature is excessively corrected, and the spherical aberration is excessively corrected in the positive direction, so that the resolution is lowered.

The imaging lens system described above is
The focal length of the entire lens system is f,
The combined focal length of the first lens and the second lens is f ₁₂
The focal length of the third lens is f ₃
The following conditional expression (7) is satisfied.
−2.8 ≦ f ₃ / f ₁₂ ≦ −2.0 (7)

For conditional expression (7), more preferably,
−2.6 ≦ f ₃ / f ₁₂ ≦ −2.2
It is good to do.

  By satisfying conditional expression (7), axial chromatic aberration and lateral chromatic aberration can be corrected in the imaging lens system, and good resolution characteristics can be obtained. If the lower limit of conditional expression (7) is not reached, the positive power of the third lens becomes relatively weak with respect to the combined power of the first lens and the second lens, resulting in insufficient correction of chromatic aberration. On the other hand, if the upper limit of conditional expression (7) is exceeded, the positive power of the third lens L3 becomes relatively strong, the chromatic aberration is excessively corrected, and it is difficult to ensure the back focus.

The imaging lens system described above is
The focal length of the first lens is f ₁ ,
Focal length f ₂ of the second lens
The following conditional expression (8) is satisfied.
1.9 ≦ f ₁ / f ₂ ≦ 2.4 (8)

For conditional expression (8), more preferably,
2.0 ≦ f ₁ / f ₂ ≦ 2.3
It is good to do.

  Conditional expression (8) defines the ratio of the focal lengths of the first lens and the second lens. If the upper limit of conditional expression (8) is exceeded, the negative power of the first lens becomes weak. Then, it is disadvantageous for widening the angle, and the effective diameter of the first lens is increased and the size is increased. In addition, the back focus is shortened. On the other hand, if the lower limit of conditional expression (8) is not reached, the negative power of the first lens becomes relatively strong. Then, it becomes difficult to correct the curvature of field, and the resolving power decreases.

The imaging lens system described above is
The Abbe number of the first lens is ν ₁ ,
The Abbe number of the second lens is ν ₂ ,
The Abbe number of the third lens is ν ₃ ,
The Abbe number of the fourth lens is ν ₄ ,
The Abbe number of the fifth lens is ν ₅ ,
The Abbe number of the sixth lens is ν ₆
In this case, all of the following conditional expressions (9) to (14) are satisfied.
ν ₁ ≧ 40 (9)
ν ₂ ≦ 50 (10)
ν ₃ ≦ 35 (11)
ν ₄ ≦ 35 (12)
ν ₅ ≦ 50 (13)
ν ₆ ≧ 50 (14)

  By satisfying conditional expressions (9) to (14), axial chromatic aberration and lateral chromatic aberration are appropriately corrected, and high resolution can be achieved.

The imaging lens system described above is
The chief ray incident angle at the maximum angle of view is φ _H
The following conditional expression (15) is satisfied.
φ _h ≦ 16 ° (15)

  By satisfying conditional expression (15), it is possible to efficiently guide the incident light beam particularly from the wide angle of view side to each pixel of the image sensor, and to suppress shading generated in the image sensor.

Furthermore, the imaging lens system described above is
The object side lens surface may be convex toward the object side in the vicinity of the optical axis of the second lens.
By adopting this configuration, it becomes easy to correct distortion.

In addition, the imaging lens system described above is
The fourth lens and the fifth lens may be plastic lenses.
By using many plastic lenses, it is possible to provide an imaging lens system that is lightweight and inexpensive.

Furthermore, the imaging lens system described above is
The first lens is a glass lens;
The second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens may be plastic lenses.
By making all but the first lens a plastic lens, it is possible to further reduce the weight and reduce the manufacturing cost.

In addition, the imaging lens system described above is
The first lens and the third lens are glass lenses;
The second lens, the fourth lens, the fifth lens, and the sixth lens may be plastic lenses.

  When a glass material having a high refractive index is used for the third lens, the focus shift of the imaging lens system with respect to temperature changes is suppressed as compared with the case where all the lenses other than the first lens are plastic lenses. As a result, in an imaging apparatus that does not have an autofocus mechanism, it can be expected to further suppress deterioration in imaging performance at high temperatures and low temperatures.

The imaging apparatus of the present invention
The imaging lens system described above;
And an imaging device arranged at an imaging position of the imaging lens system.

  According to the present invention, it is possible to provide an imaging lens system that is easy to manufacture and has sufficient aberration correction capability.

1 is a diagram illustrating a configuration of an imaging apparatus according to a first embodiment. FIG. 6 is a schematic diagram for explaining conditions of sag amounts of a fourth lens and a fifth lens of the imaging lens system according to the first embodiment. 1 is a diagram illustrating a configuration of an imaging lens system according to Example 1. FIG. FIG. 4 is an aberration diagram of the imaging lens system of Example 1. 6 is a diagram illustrating a configuration of an imaging lens system of Example 2. FIG. 6 is an aberration diagram of the imaging lens system of Example 2. FIG. 6 is a diagram illustrating a configuration of an imaging lens system according to Example 3. FIG. 6 is an aberration diagram of the imaging lens system of Example 3. FIG. 6 is a diagram illustrating a configuration of an imaging lens system of Example 4. FIG. FIG. 6 is an aberration diagram of the imaging lens system of Example 4. 6 is a diagram illustrating a configuration of an imaging lens system of Example 5. FIG. FIG. 10 is an aberration diagram of the imaging lens system according to Example 5.

[Embodiment 1]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of an imaging apparatus 100 according to the present embodiment. The imaging apparatus 100 includes an imaging lens system 101, a cover glass 102, and an imaging element 103.

The image sensor 103 is an element that converts received light into an electrical signal. For example, a CCD image sensor or a CMOS image sensor is used. The image sensor 103 is disposed at the imaging position of the imaging lens system 101.
The cover glass 102 is provided on the image sensor 103 in order to protect the image sensor 103 from foreign matter.

  The imaging lens system 101 includes, in order from the object side to the image side, a first lens L1 having negative power, a second lens L2 having negative power, a third lens L3 having positive power, and a diaphragm. And a fourth lens L4 having negative power, a fifth lens L5 having positive power, and a sixth lens L6 having positive power. As shown in FIG. 1, the lens surfaces of the imaging lens system 101 are represented as S1 to S13, and the surfaces of the cover glass 102 are represented as S14 and S15.

  The first lens L1 is a meniscus lens having a concave surface facing the image side. The second lens L2 has at least one aspherical surface and has a concave surface facing the image side. The third lens L3 has a convex surface facing the object side.

  In the fourth lens L4, the image side lens surface S9 has an aspherical shape, and a concave surface is directed to the image side. In the fifth lens L5, the object side lens surface S10 has an aspherical shape, and has a convex surface facing the object side. The image side lens surface S9 of the fourth lens L4 and the object side lens surface S10 of the fifth lens L5 are arranged so as not to contact each other and are joined by an adhesive layer. The sixth lens L6 has at least one lens surface having an aspheric shape. For example, a resin adhesive is used as the adhesive layer.

  The imaging lens system 101 can improve telecentricity by disposing the sixth lens L6 having at least one aspherical surface and having positive power on the most image side of the lens system.

The imaging lens system 101 according to this embodiment includes:
The length of the foot of the perpendicular line dropped from the lens surface to the optical axis z is the height from the optical axis, and the sag amount at the height H corresponding to the effective diameter of the object side lens surface S10 of the fifth lens L5 is Sg2H,
The sag amount at the same height H as the effective diameter of the object side lens surface S10 of the fifth lens L5 in the image side lens surface S9 of the fourth lens L4 is Sg1H,
And when
The following conditional expression (1) is satisfied.
Sg1H ≦ Sg2H (1)

  The lens sag amount and the above-described parameters Sg1H and Sg2H will be described with reference to FIG. The length of the leg of the perpendicular line dropped from an arbitrary position on the lens surface to the optical axis z is defined as a height h from the optical axis z. A perpendicular drawn from the lens surface to the optical axis z is directed in a direction (y-axis direction) orthogonal to the optical axis z. The sag amount of the lens surface at the height h from the optical axis z is the light when the plane perpendicular to the optical axis z including the intersection of the lens surface and the optical axis z (z-axis direction) is used as a reference plane. This is the distance in the z-axis direction from the reference surface to the lens surface at the position of the height h from the axis z.

  In FIG. 2, the reference surface of the image side lens surface S9 of the fourth lens L4 is P1, and the reference surface of the object side lens surface S10 of the fifth lens L5 is P2. If the height from the optical axis z corresponding to the effective diameter of the object side lens surface S10 of the fifth lens L5 is H, Sg2H is the distance from the reference surface P2 to the lens surface S10 at the height H. Sg1H is the distance from the reference surface P1 to the lens surface S9 at the same height H as Sg2H.

Consider the thickness of the adhesive layer between the image side lens surface S9 of the fourth lens L4 and the object side lens surface S10 of the fifth lens L5 constituting the cemented lens. When the thickness of the adhesive layer in the direction along the optical axis z of the imaging lens system 101 is D,
The thickness D of the adhesive layer preferably satisfies the following conditions.
20 μm ≦ D ≦ 100 μm (16)

  At the time of designing the imaging lens system 101, the thickness D of the adhesive layer is set to 20 μm, and refraction by the adhesive layer between the joint surfaces is also taken into consideration. If an adhesive is used in the manufacturing stage without considering the presence of the adhesive layer in the design stage in advance, there is a tendency for the shift of the field curvature on the tangential surface to the plus side to increase due to the influence of the adhesive layer between the joint surfaces. is there. By considering the shift of the tangential surface to the plus side of the curvature of field in advance at the time of design, it is possible to perform a design that suppresses the shift of the curvature of field to the plus side.

  Further, if the thickness D of the adhesive layer is 100 μm or less, the shift of the curvature of field on the tangential surface to the plus side due to the increase in the distance between the fourth lens L4 and the fifth lens L5, It is possible to keep within the correction range.

  As described above, the configuration of this embodiment can provide the imaging lens system 101 that is easy to manufacture and has sufficient aberration correction capability.

The cemented surface of the cemented lens is usually a spherical surface, and in this case, the curvature radii of the two surfaces to be cemented are often equal. Accordingly, when spherical cemented lenses are used, an aspherical surface can be used only for two surfaces that are not cemented, and the degree of freedom in lens design is reduced from four surfaces to three surfaces.
In the imaging lens system 101 of the present embodiment, since a cemented lens obtained by cementing two lenses having different cemented surfaces is used, there is a degree of freedom for four surfaces in the lens design, and the resolving power can be increased. Furthermore, since aspheric surfaces can be used for all four surfaces, the resolving power can be further increased. However, an imaging lens system including a cemented lens in which spherical surfaces are bonded to each other is not excluded from the present invention.

Hereinafter, examples of the imaging lens system 101 of the present invention will be described.
In the imaging lenses 101 of Examples 1, 3, and 5, the first lens L1 is a glass lens, and the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are It is a plastic lens.

  In the imaging lenses 101 of Examples 2 and 4, the first lens L1 and the third lens L3 are glass lenses, and the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are plastic lenses. is there.

(Example 1)
FIG. 3 is a diagram illustrating a configuration of the imaging lens system 101 according to the first embodiment.
The imaging lens system 101 according to the first exemplary embodiment includes, in order from the object side to the image side, a first lens L1 having a negative power, a second lens L2 having a negative power, and a third lens having a positive power. L3, a stop, a fourth lens L4 having negative power, a fifth lens L5 having positive power, and a sixth lens L6 having positive power.

  The first lens L1 is a spherical meniscus lens having negative power. The object side lens surface S1 and the image side lens surface S2 of the first lens L1 are spherical surfaces each having a positive curvature. The object side lens surface S1 has a convex surface facing the object side, and the image side lens surface S2 has a concave surface facing the image side.

  The second lens L2 is an aspheric lens having negative power. The object side lens surface S3 and the image side lens surface S4 are aspherical surfaces having a positive curvature. The object side lens surface S3 has a convex surface facing the object side, and the image side lens surface S4 has a concave surface facing the image side.

  The third lens L3 is an aspheric lens having positive power. The object side lens surface S5 is an aspherical surface having a positive curvature, and the image side lens surface S6 is an aspherical surface having a negative curvature. The object side lens surface S5 includes a convex curved surface portion protruding toward the object side, and the image side lens surface S6 includes a convex curved surface portion protruding toward the image side.

  The fourth lens L4 is an aspheric lens having negative power. The object side lens surface S8 and the image side lens surface S9 are aspherical surfaces each having a positive curvature. The object side lens surface S8 includes a convex curved surface portion protruding toward the object side, and the image side lens surface S9 includes a convex curved surface portion protruding toward the object side.

  The fifth lens L5 is an aspheric lens having positive power. The object side lens surface S10 is an aspherical surface having a positive curvature, and the image side lens surface S11 is an aspherical surface having a negative curvature. The object side lens surface S10 includes a convex curved surface portion protruding toward the object side, and the image side lens surface S11 includes a convex curved surface portion protruding toward the image side.

  The sixth lens L6 is an aspheric lens having positive power. The object side lens surface S12 is an aspherical surface having a positive curvature, and the image side lens surface S13 is an aspherical surface having a negative curvature. The object side lens surface S12 includes a convex curved surface portion protruding toward the object side, and the image side lens surface S13 includes a convex curved surface portion protruding toward the image side.

  Table 1 shows lens data of each lens surface of the imaging lens system 101. The lens data includes the radius of curvature, surface spacing, refractive index, and Abbe number of each surface. A surface marked with “*” indicates an aspherical surface.

  The aspherical shape adopted for the lens surface is 4th, 6th, 8th, 10th, where Y is the sag amount, c is the reciprocal of the radius of curvature, K is the conic coefficient, and h is the height of the ray from the optical axis. The twelfth, fourteenth, and sixteenth aspherical coefficients are represented by the following equations when A4, A6, A8, A10, A12, A14, and A16 are used.

Table 2 shows the aspheric coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 101 of Example 1. In Table 2, for example, “−2.1058E-03” means “−2.1058 × 10 ⁻³ ”.

  4A to 4C are a longitudinal aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens system 101 according to the first embodiment. In the longitudinal aberration diagram of FIG. 4A, the horizontal axis indicates the position where the light beam intersects the optical axis z, and the vertical axis indicates the height at the pupil diameter. FIG. 4A shows a simulation result using a plurality of light beams having different wavelengths (436 nm, 546 nm, and 656 nm). In the field curvature diagram of FIG. 4B, the horizontal axis indicates the distance in the optical axis z direction, and the vertical axis indicates the image height (field angle). In FIG. 4B, Sag indicates the field curvature in the sagittal plane, and Tan indicates the field curvature in the tangential plane. In the distortion diagram of FIG. 4C, the horizontal axis indicates the amount of image distortion (%), and the vertical axis indicates the image height (field angle). FIG. 4B and FIG. 4C show simulation results using light rays having a wavelength of 546 nm.

(Example 2)
FIG. 5 is a diagram illustrating a configuration of the imaging lens system 101 according to the second embodiment.
In the imaging lens system 101 of the second embodiment, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 have the same shape as the imaging lens system 101 of the first embodiment. I am doing.

  The sixth lens L6 is an aspheric lens having positive power. The object side lens surface S12 is an aspherical surface having a positive curvature, and the image side lens surface S13 is also an aspherical surface having a positive curvature. The object side lens surface S12 and the image side lens surface S13 include a convex curved surface portion protruding toward the object side.

  Table 3 shows lens data of each lens surface of the imaging lens system 101. A surface marked with “*” indicates an aspherical surface.

  Table 4 shows the aspheric coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 101 of the present embodiment.

  6A to 6C are a longitudinal aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens system 101 according to the second embodiment.

Example 3
FIG. 7 is a diagram illustrating a configuration of the imaging lens system 101 according to the third embodiment.
In the imaging lens system 101 according to the third embodiment, the first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5 have the same shape as the imaging lens system 101 according to the first embodiment.

  The third lens L3 is an aspheric lens having positive power. The object side lens surface S5 and the image side lens surface S6 are aspherical surfaces having a positive curvature. The object side lens surface S5 and the image side lens surface S6 include a convex curved surface portion protruding toward the object side.

  The sixth lens L6 is an aspheric lens having positive power. The object side lens surface S12 and the image side lens surface S13 are aspherical surfaces having a positive curvature. The object side lens surface S12 and the image side lens surface S13 include a convex curved surface portion protruding toward the object side.

  Table 5 shows lens data of each lens surface of the imaging lens system 101. A surface marked with “*” indicates an aspherical surface.

  Table 6 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 101 of the present embodiment.

  8A to 8C are a longitudinal aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens system 101 of Example 3. FIG.

Example 4
FIG. 9 is a diagram illustrating a configuration of the imaging lens system 101 according to the fourth embodiment.
In the imaging lens system 101 of Example 4, the first lens L1, the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 have the same shape as the imaging lens system 101 of Example 1. I am doing.

  The third lens L3 is an aspheric lens having positive power. The object side lens surface S5 and the image side lens surface S6 are aspherical surfaces having a positive curvature. The object side lens surface S5 and the image side lens surface S6 include a convex curved surface portion protruding toward the object side.

  Table 7 shows lens data of each lens surface of the imaging lens system 101. A surface marked with “*” indicates an aspherical surface.

  Table 8 shows the aspheric coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 101 of the present embodiment.

  10A to 10C are a longitudinal aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens system 101 according to the fourth embodiment.

(Example 5)
FIG. 11 is a diagram illustrating a configuration of the imaging lens system 101 according to the fifth embodiment.
The imaging lens system 101 of Example 5 has the same shape as the imaging lens system 101 of Example 1.

  Table 9 shows lens data of each lens surface of the imaging lens system 101. A surface marked with “*” indicates an aspherical surface.

  Table 10 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 101 of the present embodiment.

  12A to 12C are a longitudinal aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens system 101 of the fifth embodiment.

Table 11 shows the result of calculating the characteristic values of the imaging lens systems 101 of Examples 1 to 5. In the imaging lens system 101, the F number is FNo. , The total field angle (maximum field angle) is 2ω, the distance from the object side lens surface S1 of the first lens L1 to the imaging surface of the imaging lens system 101 is TL, and the object side lens surface S1 of the first lens L1 is The distance to the image side lens surface S13 of the lens L6 is OL, the focal length of the entire lens system is f, the focal length of the first lens L1 is f ₁ , the focal length of the second lens L2 is f ₂ , and the third lens L3 The focal length is f ₃ , the focal length of the fourth lens L4 is f ₄ , the focal length of the fifth lens L5 is f ₅ , the focal length of the sixth lens L6 is f ₆ , and the first lens L1 and the second lens L2 The combined focal length f ₁₂ , the combined focal length of the third lens L 3, the fourth lens L 4, and the fifth lens L 5 (including the adhesive layer) is f ₃₄₅ , and the combined focal length of the fourth lens L 4 and the fifth lens L 5 ( comprising an adhesive layer) to _{f 45,} the image of the fourth lens L4 The radius of curvature R _4i of the lens surfaces _S9, these characteristic values when the main light beam incidence angle in the horizontal viewing angle was phi _h, and are as shown in Table 11. The total angle of view 2ω, chief ray incident angle φ _h , and various focal lengths were calculated using light rays with a wavelength of 546 nm.

  Table 12 shows the calculation results of the characteristic values that are the parameters of the conditional expressions (1) to (16) in the imaging lens systems 101 of Examples 1 to 5.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the application of the imaging lens system 101 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 in a small electronic device such as a mobile phone.

DESCRIPTION OF SYMBOLS 100 Imaging device 101 Imaging lens 102 Cover glass 103 Image pick-up element L1-L6 1st lens-6th lens S1-S13 Lens surface S14, S15 Surface of cover glass

Claims (15)

From the object side to the image side,
A meniscus first lens having negative power and having a concave surface facing the image side;
A second lens having negative power and having a concave surface facing the image side;
A third lens having positive power and having a convex surface facing the object side;
A fourth lens having negative power;
A fifth lens having positive power;
An imaging lens system comprising a sixth lens having positive power,
The fourth lens and the fifth lens are bonded together by an adhesive layer between the image side lens surface of the fourth lens and the object side lens surface of the fifth lens;
The focal length of the entire lens system is f,
The radius of curvature of the image-side lens surface of the fourth lens is R _4i
An imaging lens system satisfying the following conditional expression (1):
0.9 ≦ R _4i /f≦1.3 (1) The imaging lens system according to claim 1,
The image side lens surface of the fourth lens and the object side lens surface of the fifth lens are aspherical,
The image side lens surface of the fourth lens and the object side lens surface of the fifth lens are not in contact with each other,
The length of the foot of the perpendicular drawn from the lens surface to the optical axis is the height from the optical axis, and the sag amount at the height corresponding to the effective diameter of the object side lens surface of the fifth lens is Sg2H,
The sag amount at the same height as the effective diameter of the object side lens surface of the fifth lens on the image side lens surface of the fourth lens is Sg1H,
And when
An imaging lens system satisfying the following conditional expression (2):
Sg1H ≦ Sg2H (2) The imaging lens system according to claim 1 or 2,
The focal length of the entire lens system is f,
The combined focal length of the fourth lens and the fifth lens is f ₄₅ ,
An imaging lens system satisfying the following conditional expression (3):
2.8 ≦ f ₄₅ /f≦3.7 (3)
Here, f ₄₅ is a combined focal length by the fourth lens, the fifth lens, and the adhesive layer. The imaging lens system according to any one of claims 1 to 3,
The focal length of the entire lens system is f,
The distance from the object side lens surface of the first lens to the image side lens surface of the sixth lens is OL.
An imaging lens system satisfying the following conditional expression (4):
7.0 ≦ OL / f ≦ 12 (4) The imaging lens system according to any one of claims 1 to 4,
The focal length of the third lens is f ₃ ,
The combined focal length of the fourth lens and the fifth lens is f _45.
An imaging lens system satisfying the following conditional expression (5):
0.8 ≦ f ₄₅ / f ₃ ≦ 1.4 (5)
Here, f ₄₅ is a combined focal length by the fourth lens, the fifth lens, and the adhesive layer. The imaging lens system according to any one of claims 1 to 5,
The focal length of the entire lens system is f,
The combined focal length of the first lens and the second lens is f ₁₂
An imaging lens system satisfying the following conditional expression (6):
−1.4 ≦ f ₁₂ /f≦−1.0 (6) The imaging lens system according to any one of claims 1 to 6,
The combined focal length of the first lens and the second lens is f ₁₂
The focal length of the third lens is f ₃
An imaging lens system satisfying the following conditional expression (7):
−2.8 ≦ f ₃ / f ₁₂ ≦ −2.0 (7) The imaging lens system according to any one of claims 1 to 7,
The focal length of the first lens is f ₁ ,
Focal length f ₂ of the second lens
An imaging lens system satisfying the following conditional expression (8):
1.9 ≦ f ₁ / f ₂ ≦ 2.4 (8) The imaging lens system according to any one of claims 1 to 8,
The Abbe number of the first lens is ν ₁ ,
The Abbe number of the second lens is ν ₂ ,
The Abbe number of the third lens is ν ₃ ,
The Abbe number of the fourth lens is ν ₄ ,
The Abbe number of the fifth lens is ν ₅ ,
The Abbe number of the sixth lens is ν ₆
An imaging lens system satisfying all of the following conditional expressions (9) to (14).
ν ₁ ≧ 40 (9)
ν ₂ ≦ 50 (10)
ν ₃ ≦ 35 (11)
ν ₄ ≦ 35 (12)
ν ₅ ≦ 50 (13)
ν ₆ ≧ 50 (14) In the imaging lens system according to any one of claims 1 to 9,
The chief ray incident angle at the maximum angle of view is φ _H
An imaging lens system satisfying the following conditional expression (15):
φ _h ≦ 16 ° (15) The imaging lens system according to any one of claims 1 to 10,
An imaging lens system, wherein an object side lens surface is convex toward the object side in the vicinity of an optical axis of the second lens. The imaging lens system according to any one of claims 1 to 11,
The imaging lens system, wherein the fourth lens and the fifth lens are plastic lenses. The imaging lens system according to any one of claims 1 to 12,
The first lens is a glass lens;
The imaging lens system, wherein the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are plastic lenses. The imaging lens system according to any one of claims 1 to 12,
The first lens and the third lens are glass lenses;
The imaging lens system, wherein the second lens, the fourth lens, the fifth lens, and the sixth lens are plastic lenses. The imaging lens system according to any one of claims 1 to 14,
An imaging device comprising: an imaging element disposed at an imaging position of the imaging lens system.

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