WO2011052370A1

WO2011052370A1 - Imaging lens

Info

Publication number: WO2011052370A1
Application number: PCT/JP2010/067842
Authority: WO
Inventors: 永悟佐野; 麻衣子西田
Original assignee: コニカミノルタオプト株式会社
Priority date: 2009-10-26
Filing date: 2010-10-12
Publication date: 2011-05-05

Abstract

Provided is an imaging lens configured with four lenses, wherein each aberration is effectively corrected even though the size of the imaging lens is smaller than conventional imaging lenses. An imaging lens for forming an image to be taken on a photoelectric conversion unit of a solid-state image sensor is provided, from the object side, with: a double-convex first lens which has a positive refractive power; a second lens which has a negative refractive power and a concave surface facing the image side; a meniscus-shaped third lens which has a positive refractive power and a convex surface facing the image side; and a fourth lens, at least one surface of which is an aspheric surface, and which has a negative refractive power and a concave surface facing the image side. Further, an aperture stop is provided between the first lens and the second lens, and the following condition is fulfilled: -2.50 <f2/f< -1.50 (f2 represents the focal length of the second lens, and f represents the focal length of the entire imaging lens system).

Description

Imaging lens

The present invention relates to an imaging lens for forming a subject image on a photoelectric conversion unit of a solid-state imaging device.

In recent years, with the improvement and miniaturization of imaging devices using solid-state imaging devices such as CCD (Charged Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors, mobile phones equipped with imaging devices and Portable information terminals are becoming popular. In addition, there is an increasing demand for higher performance and miniaturization of imaging lenses mounted on these imaging devices. As an imaging lens for such an application, a four-lens imaging lens has been proposed because it can achieve higher performance than a two- or three-lens configuration.

As this four-lens imaging lens, in order from the object side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a first lens having a positive refractive power. A so-called reverse Ernostar type imaging lens that is configured by four lenses and aims at high performance is disclosed (for example, see Patent Document 1).

In addition, the first lens having positive refractive power, the second lens having negative refractive power, the third lens having positive refractive power, and the fourth lens having negative refractive power are arranged in order from the object side. A so-called telephoto type imaging lens that aims to reduce the overall lens length (distance on the optical axis from the most object-side lens surface of the entire imaging lens system to the image-side focal point) has been disclosed (for example, Patent Documents). 2).

Japanese Patent Laid-Open No. 2004-341013 JP 2002-365530 A

However, since the imaging lens described in Patent Document 1 is an inverted Ernostar type, the fourth lens is a positive lens, and the main lens of the optical system is larger than the case where the fourth lens is a negative lens as in the telephoto type. Since the point position becomes the image side and the back focus becomes long, this is a disadvantageous type for downsizing. Further, of the four lenses, only one lens has a negative refractive power, and it is difficult to correct the Petzval sum, and good performance cannot be ensured at the periphery of the image.

In addition, the imaging lens disclosed in Patent Document 2 has a narrow imaging angle of view and insufficient aberration correction. Further, if the entire lens length is shortened, it is difficult to cope with an increase in the number of pixels of the imaging element due to performance degradation. There is a problem.

The present invention has been made in view of such a problem, and an object thereof is to provide a four-lens imaging lens in which various aberrations are favorably corrected while being smaller than a conventional type.

Here, although it is a scale of a small imaging lens, the present invention aims at miniaturization at a level satisfying the following expression. By satisfying this range, the entire imaging apparatus can be reduced in size and weight.

L / 2Y <1.10
However,
L: Distance on the optical axis from the lens surface closest to the object side to the image-side focal point of the entire imaging lens system 2Y: Diagonal length of the imaging surface of the solid-state imaging device (diagonal length of the rectangular effective pixel region of the solid-state imaging device)
Here, the image-side focal point refers to an image point when a parallel light beam parallel to the optical axis is incident on the imaging lens.

When a parallel plate such as an optical low-pass filter, an infrared cut filter, or a seal glass of a solid-state image sensor package is disposed between the image-side surface of the imaging lens and the image-side focal position, the imaging lens is parallel. The flat plate portion is calculated as the above L value after the air conversion distance. Further, the following conditional expression is more desirable.

L / 2Y <1.00

The above object is achieved by the invention described below.

1. An imaging lens for forming a subject image on a photoelectric conversion unit of a solid-state imaging device,
From the object side,
A biconvex first lens having positive refractive power;
A second lens having negative refractive power and having a concave surface facing the image side;
A third meniscus lens having positive refractive power and having a convex surface facing the image side;
A fourth lens having at least one surface formed as an aspherical surface and having a negative refractive power and a concave surface facing the image side;
An imaging lens having an aperture stop between the first lens and the second lens and satisfying the following conditional expression:

-2.50 <f2 / f <-1.50 (1)
However,
f2: Focal length of the second lens f: Focal length of the entire imaging lens system The basic configuration of the present invention is a biconvex first lens having positive refractive power and negative refraction in order from the object side. A second lens having a concave surface on the image side with a force, a meniscus third lens having a positive refractive power and a convex surface on the image side, and at least one surface is formed as an aspheric surface, And a fourth lens having negative refractive power and having a concave surface facing the image side. In order from the object side, a positive lens group composed of a first lens, a second lens, and a third lens and a negative fourth lens with a concave surface facing the image side are arranged to reduce the overall length of the imaging lens. This is an advantageous configuration.

Furthermore, by using two of the four lens elements as negative lenses, it is possible to easily correct the Petzval sum by increasing the diverging surface and to ensure good imaging performance up to the periphery of the screen. Can be obtained. In addition, by setting the fourth lens arranged closest to the image side to at least one aspherical surface, various aberrations at the peripheral portion of the screen can be corrected satisfactorily.

In addition, by arranging an aperture stop between the first lens and the second lens, the refraction angle of the peripheral marginal ray passing through the object side surface of the first lens does not become too large, and the imaging lens can be downsized and good. It is possible to achieve both aberration correction.

Conditional expression (1) is a conditional expression for appropriately setting the focal length of the second lens. If the value of conditional expression (1) exceeds the lower limit, the negative refracting power of the second lens can be maintained moderately, and both the shortening of the total lens length and good correction of axial chromatic aberration and curvature of field are compatible. can do.

On the other hand, when the value falls below the upper limit, the negative refractive power of the second lens does not become too large, and the occurrence of lateral chromatic aberration due to excessively jumping up the light rays in the peripheral portion can be suppressed.

Also, the following conditional expression is more desirable.

-2.40 <f2 / f <-1.50
2. 2. The imaging lens according to 1, wherein the following conditional expression is satisfied.

2.00 ≦ (r3 + r4) / (r3-r4) ≦ 5.00 (2)
However,
r3: radius of curvature of the object side surface of the second lens r4: radius of curvature of the image side surface of the second lens Conditional expression (2) is a condition for appropriately setting the shape of the second lens. Within the range of the conditional expression (2), the second lens has a shape having a negative refractive power stronger on the image side surface than on the object side surface.

When the value of conditional expression (2) exceeds the lower limit, the refractive power of the image side surface of the second lens can be increased, and correction of coma aberration, field curvature, astigmatism, and chromatic aberration can be easily performed. . On the other hand, the curvature of the object side surface of the second lens becomes gentle, and the aberration of the off-axis light beam passing near the periphery of this surface can be suppressed. On the other hand, by being below the upper limit, it is possible to suppress the negative refracting power of the image side surface of the second lens from becoming too strong, and to correct aberrations in a balanced manner. In addition, the radius of curvature of the image-side surface does not become too small, and the shape has no problem in lens processing.

Also, the following conditional expression is more desirable.

2.10 <(r3 + r4) / (r3-r4) <4.80
3. 3. The imaging lens as described in 1 or 2 above, wherein the following conditional expression is satisfied.

15 <ν2 <27 (3)
However,
ν2: Abbe number of the second lens Conditional expression (3) is a conditional expression for appropriately setting the Abbe number of the second lens and correcting chromatic aberration satisfactorily.

By using a material with relatively large dispersion for the negative second lens, the axial chromatic aberration can be corrected well, but the image side surface of the second lens is a strong divergent surface, so that the incident of peripheral rays The angle becomes large and chromatic aberration of magnification occurs.

When the value of the conditional expression (3) is below the lower limit, the longitudinal chromatic aberration can be sufficiently corrected, but the lateral chromatic aberration generated by the peripheral light beam also becomes large. On the other hand, if the upper limit is exceeded, the lateral chromatic aberration of the peripheral luminous flux can be kept small, but the longitudinal chromatic aberration cannot be corrected.

Also, the following conditional expression is more desirable.

20 <ν2 <27
4). 4. The imaging lens according to any one of 1 to 3, wherein the following conditional expression is satisfied.

0.35 <f3 / f <0.65 (4)
However,
f3: Focal length of the third lens f: Focal length of the entire imaging lens Conditional expression (4) is a conditional expression for appropriately setting the focal length of the third lens. When the value of conditional expression (4) exceeds the lower limit, the focal length of the third lens does not become too small, and generation of higher-order spherical aberration and coma aberration can be suppressed. On the other hand, by being below the upper limit, the focal length of the third lens can be maintained moderately, and a reduction in the overall length of the imaging lens can be achieved.

Also, the following conditional expression is more desirable.

0.40 <f3 / f <0.62
5. 5. The imaging lens according to any one of 1 to 4, wherein the following conditional expression is satisfied.

0.70 <f1 / f <1.05 (5)
However,
f1: Focal length of the first lens f: Focal length of the entire imaging lens Conditional expression (5) appropriately sets the focal length of the first lens, and appropriately achieves shortening of the entire length of the imaging lens and aberration correction. Is a conditional expression.

When the value of conditional expression (5) is less than the upper limit, the refractive power of the first lens can be maintained moderately, and the synthetic principal point of the first lens to the third lens can be arranged closer to the object side. The overall length of the imaging lens can be shortened. On the other hand, by exceeding the lower limit, the refractive power of the first lens does not become unnecessarily large, and high-order spherical aberration and coma aberration generated in the first lens can be suppressed to be small.

Also, the following conditional expression is more desirable.

0.75 <f1 / f <0.95
6). 6. The imaging lens according to any one of 1 to 5, wherein the following conditional expression is satisfied.

-1.00 <(r1 + r2) / (r1-r2) <-0.50 (6)
However,
r1: radius of curvature of the object side surface of the first lens r2: radius of curvature of the image side surface of the first lens Conditional expression (6) is a condition for appropriately setting the shape of the first lens. Within the range of this conditional expression, the first lens has a shape having a positive refractive power stronger on the image side surface than on the object side surface. When the value of conditional expression (6) is less than the upper limit, the positive refractive power of the image side surface of the first lens does not become too strong, and the peripheral portion of the image side surface of the second lens has excessive negative refraction. Generation of coma, curvature of field, and chromatic aberration due to force can be suppressed. By exceeding the lower limit, a space is created on the object side in the periphery of the first lens, and the arrangement of the diaphragm becomes easy, so that the overall length can be easily shortened.

Also, the following conditional expression is more desirable.

−0.95 <(r1 + r2) / (r1−r2) <− 0.52
7). The imaging lens according to any one of 1 to 6, wherein the following conditional expression is satisfied.

−0.70 <f4 / f <−0.40 (7)
However,
f4: Focal length of the fourth lens f: Focal length of the entire imaging lens Conditional expression (7) is a conditional expression for appropriately setting the focal length of the fourth lens. When the value of conditional expression (7) is less than the upper limit, the negative refractive power of the fourth lens does not increase more than necessary, and the light beam that forms an image on the periphery of the imaging surface of the solid-state imaging device is excessively raised. Thus, the telecentric characteristics of the image-side light beam can be easily ensured. On the other hand, by exceeding the lower limit, the negative refracting power of the fourth lens can be appropriately maintained, and the overall length of the lens is shortened and various off-axis aberrations such as field curvature and distortion are corrected well. Can do.

Also, the following conditional expression is more desirable.

-0.68 <f4 / f <-0.42
8). The image side surface of the fourth lens is formed as an aspherical surface, has a negative refractive power in the vicinity of the optical axis, and has a inflection point because the negative refractive power becomes weaker toward the periphery. 8. The imaging lens according to any one of 1 to 7 above.

The negative refracting power becomes weaker as the image side surface of the fourth lens goes from the optical axis to the periphery, and the telecentric characteristics of the image-side light beam can be easily secured by making the aspherical shape having an inflection point. Further, the image side surface of the second lens need not excessively weaken the negative refracting power at the periphery of the lens, and it is possible to satisfactorily correct off-axis aberrations.

Here, the “inflection point” is a point on the aspheric surface where the tangent plane of the aspherical vertex is a plane perpendicular to the optical axis in the curve of the lens cross-sectional shape within the effective radius.

9. 9. The imaging lens according to any one of 1 to 8, wherein the fourth lens has a biconcave shape.

By making the fourth lens a biconcave shape, the peripheral portion of the fourth lens does not protrude greatly in the image plane direction, and is disposed between the fourth lens and the solid-state imaging device, an optical low-pass filter, The back focus can be shortened while avoiding contact with a parallel plate such as an infrared cut filter or a seal glass of a solid-state image sensor package or a substrate of a solid-state image sensor, which is advantageous for shortening the overall length of the imaging lens. It becomes composition.

10. 10. The imaging lens according to any one of 1 to 9, wherein all the lenses are made of a plastic material.

Recently, for the purpose of downsizing the entire solid-state imaging device, even a solid-state imaging device having the same number of pixels has been developed with a small pixel pitch and consequently a small imaging surface size. In such an imaging lens for a solid-state imaging device having a small imaging surface size, it is necessary to relatively shorten the focal length of the entire system, so that the curvature radius and the outer diameter of each lens are considerably reduced. Therefore, compared to glass lenses manufactured by time-consuming polishing, all lenses are made of plastic lenses manufactured by injection molding, so that even lenses with small radii of curvature and outer diameters are inexpensive. Mass production is possible. In addition, since the plastic lens can lower the press temperature, it is possible to suppress the wear of the molding die, and as a result, the number of replacements and maintenance times of the molding die can be reduced, and the cost can be reduced.

According to the imaging lens of the present invention, it is possible to obtain an effect that various aberrations are corrected satisfactorily while having a four-lens configuration and being smaller than the conventional type.

2 is a cross-sectional view of an imaging lens of Example 1. FIG. FIG. 3 is an aberration diagram of the imaging lens of Example 1. 6 is a cross-sectional view of an imaging lens of Example 2. FIG. 6 is an aberration diagram of the imaging lens of Example 2. FIG. 6 is a cross-sectional view of an imaging lens of Example 3. FIG. 6 is an aberration diagram of the imaging lens of Example 3. FIG. 6 is a cross-sectional view of an imaging lens of Example 4. FIG. FIG. 6 is an aberration diagram of the imaging lens of Example 4. 6 is a cross-sectional view of an imaging lens of Example 5. FIG. FIG. 10 is an aberration diagram of the imaging lens of Example 5. 6 is a cross-sectional view of an imaging lens of Example 6. FIG. 10 is an aberration diagram of the imaging lens of Example 6. FIG. 10 is a cross-sectional view of an imaging lens of Example 7. FIG. 10 is an aberration diagram of the imaging lens of Example 7. FIG. 10 is a cross-sectional view of an imaging lens of Example 8. FIG. 10 is an aberration diagram of the imaging lens of Example 8. FIG. 10 is a cross-sectional view of an imaging lens of Example 9. FIG. 10 is an aberration diagram of the imaging lens of Example 9. FIG.

Examples of the imaging lens of the present invention are shown below. Symbols used in each example are as follows.

f: Focal length of the entire imaging lens system fB: Back focus F: F number 2Y: Diagonal length of the imaging surface of the solid-state imaging device ENTP: Entrance pupil position (distance from the first surface to the entrance pupil position)
EXTP: exit pupil position (distance from imaging surface to exit pupil position)
H1: Front principal point position (distance from first surface to front principal point position)
H2: Rear principal point position (distance from the final surface to the rear principal point position)
R: radius of curvature D: axial distance between axes Nd: refractive index of lens material with respect to d-line νd: Abbe number of lens material Also, in each example, the surface where “*” is written after each surface number is aspherical It is a surface having

The shape of the aspherical surface is expressed by the following formula 1, where the vertex of the surface is the origin, the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.

However,
Ai: i-th order aspheric coefficient R: radius of curvature K: conic constant Further, in the aspheric coefficient, a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is used by E (for example, 2.5E-02). It shall represent.

[Example 1]
The overall specifications of the imaging lens are shown below.

f = 3.26mm
fB = 0.36mm
F = 2.45
2Y = 4.536mm
ENTP = 0.41mm
EXTP = −2.23mm
H1 = -0.43mm
H2 = -2.89mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 0.98
2 (*) 1.958 0.55 1.54470 56.2 0.88
3 (*) -6.692 0.02 0.72
4 (Aperture) ∞ 0.05 0.62
5 (*) 2.392 0.30 1.63200 23.4 0.68
6 (*) 1.453 0.74 0.71
7 (*) -2.539 0.62 1.54470 56.2 0.97
8 (*) -0.735 0.05 1.23
9 (*) -83.072 0.47 1.54470 56.2 1.77
10 (*) 0.915 0.60 1.93
11 ∞ 0.30 1.51630 64.1 2.19
12 ∞ 2.26
All the lenses are made of a plastic material.

The aspheric coefficient is shown below.

2nd surface K = -0.26814E + 01, A4 = -0.11747E-01, A6 = -0.17618E-01, A8 = -0.18096E + 00, A10 = 0.26150E + 00, A12 = -0.15102E + 00
3rd surface K = 0.27630E + 02, A4 = 0.60811E-02, A6 = -0.15114E + 00, A8 = 0.11782E + 00, A10 = 0.67109E-01, A12 = -0.13453E + 00
5th surface K = -0.12093E + 02, A4 = 0.14326E + 00, A6 = 0.55269E-01, A8 = -0.68445E + 00, A10 = 0.12947E + 01, A12 = -0.50101E + 00
6th surface K = -0.59109E + 01, A4 = 0.24783E + 00, A6 = -0.15038E + 00, A8 = 0.21536E + 00, A10 = -0.71892E + 00, A12 = 0.11219E + 01
7th surface K = -0.31719E + 01, A4 = -0.33897E-01, A6 = -0.20382E + 00, A8 = 0.31602E + 00, A10 = -0.18128E + 00, A12 = -0.13936E-02
8th surface K = -0.45298E + 01, A4 = -0.31995E + 00, A6 = 0.39754E + 00, A8 = -0.42892E + 00, A10 = 0.34598E + 00, A12 = -0.10483E + 00
9th surface K = -0.50000E + 02, A4 = -0.15384E + 00, A6 = 0.86586E-01, A8 = -0.49242E-02, A10 = -0.85682E-02, A12 = 0.27935E-02, A14 = -0.27890E-03
10th surface K = -0.89315E + 01, A4 = -0.13200E + 00, A6 = 0.66980E-01, A8 = -0.31101E-01, A10 = 0.89225E-02, A12 = -0.14659E-02, A14 = 0.11392E-03
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 2.844
2 5 -6.688
3 7 1.694
4 9 -1.658
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = −2.05
(2) (r3 + r4) / (r3-r4) = 4.10
(3) ν2 = 23.4
(4) f3 / f = 0.52
(5) f1 / f = 0.87
(6) (r1 + r2) / (r1-r2) = − 0.55
(7) f4 / f = −0.51
1 is a cross-sectional view of the imaging lens of Example 1. FIG. In FIG. 1, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a sealing glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 2 is an aberration diagram (spherical aberration, astigmatism, distortion, meridional coma) of the imaging lens of Example 1.

[Example 2]
The overall specifications of the imaging lens are shown below.

f = 3.26mm
fB = 0.28mm
F = 2.46
2Y = 4.536mm
ENTP = 0.35mm
EXTP = -2.32mm
H1 = −0.48mm
H2 = -2.97mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 0.94
2 (*) 1.781 0.47 1.54470 56.2 0.82
3 (*) -18.198 0.02 0.67
4 (Aperture) ∞ 0.05 0.62
5 (*) 2.618 0.30 1.63200 23.4 0.68
6 (*) 1.578 0.80 0.71
7 (*) -3.296 0.71 1.54470 56.2 1.05
8 (*) -0.763 0.20 1.26
9 (*) -13.100 0.32 1.54470 56.2 1.87
10 (*) 0.939 0.60 2.02
11 ∞ 0.30 1.51630 64.1 2.50
12 ∞ 2.50
All the lenses are made of a plastic material.

The aspheric coefficient is shown below.

2nd surface K = -0.15459E + 01, A4 = -0.28791E-02, A6 = -0.24289E-01, A8 = -0.11838E + 00, A10 = 0.20184E + 00, A12 = -0.14321E + 00
3rd surface K = 0.47814E + 02, A4 = 0.96387E-02, A6 = -0.13456E + 00, A8 = 0.77628E-01, A10 = 0.77298E-01, A12 = -0.10311E + 00
5th surface K = -0.14118E + 02, A4 = 0.13980E + 00, A6 = 0.43187E-01, A8 = -0.57737E + 00, A10 = 0.10821E + 01, A12 = -0.48591E + 00
6th surface K = -0.56003E + 01, A4 = 0.22057E + 00, A6 = -0.11437E + 00, A8 = 0.30521E + 00, A10 = -0.89179E + 00, A12 = 0.10503E + 01
7th surface K = 0.28826E + 01, A4 = -0.37862E-01, A6 = -0.24223E + 00, A8 = 0.46212E + 00, A10 = -0.36944E + 00, A12 = 0.12434E + 00
8th surface K = -0.45017E + 01, A4 = -0.34542E + 00, A6 = 0.39522E + 00, A8 = -0.44197E + 00, A10 = 0.31771E + 00, A12 = -0.81224E-01
9th surface K = 0.11884E + 02, A4 = -0.15197E + 00, A6 = 0.88924E-01, A8 = -0.51121E-02, A10 = -0.86921E-02, A12 = 0.27123E-02, A14 = -0.25245E-03
10th surface K = -0.82395E + 01, A4 = -0.12508E + 00, A6 = 0.67661E-01, A8 = -0.30945E-01, A10 = 0.90430E-02, A12 = -0.14549E-02, A14 = 0.99735E-04
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 3.002
2 5 -7.072
3 7 1.660
4 9 -1.596
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = -2.17
(2) (r3 + r4) / (r3-r4) = 4.03
(3) ν2 = 23.4
(4) f3 / f = 0.51
(5) f1 / f = 0.92
(6) (r1 + r2) / (r1-r2) = − 0.82
(7) f4 / f = −0.49
FIG. 3 is a cross-sectional view of the imaging lens of the second embodiment. In FIG. 3, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a sealing glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 4 is an aberration diagram (spherical aberration, astigmatism, distortion, meridional coma) of the imaging lens of Example 2.

[Example 3]
The overall specifications of the imaging lens are shown below.

f = 3.26mm
fB = 0.34mm
F = 2.46
2Y = 4.536mm
ENTP = 0.43mm
EXTP = -2.24mm
H1 = -0.44mm
H2 = -2.92mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 1.00
2 (*) 1.636 0.53 1.54470 56.2 0.86
3 (*) -17.079 0.04 0.68
4 (Aperture) ∞ 0.05 0.60
5 (*) 3.649 0.30 1.63200 23.4 0.66
6 (*) 1.906 0.70 0.69
7 (*) -2.108 0.67 1.54470 56.2 0.88
8 (*) -0.705 0.05 1.14
9 (*) -1000.000 0.49 1.54470 56.2 1.76
10 (*) 0.885 0.60 1.96
11 ∞ 0.30 1.51630 64.1 2.22
12 ∞ 2.29
All the lenses are made of a plastic material.

The aspheric coefficient is shown below.

2nd surface K = -0.16817E + 01, A4 = 0.83191E-02, A6 = 0.30773E-01, A8 = -0.23470E + 00, A10 = 0.31437E + 00, A12 = -0.18225E + 00
3rd surface K = -0.50000E + 02, A4 = 0.55720E-01, A6 = -0.20957E + 00, A8 = 0.84907E-01, A10 = 0.24816E + 00, A12 = -0.32181E + 00
5th surface K = 0.57301E + 01, A4 = 0.13291E + 00, A6 = -0.14000E + 00, A8 = -0.23532E + 00, A10 = 0.92288E + 00, A12 = -0.63012E + 00
6th surface K = -0.12286E + 02, A4 = 0.32160E + 00, A6 = -0.26249E + 00, A8 = 0.12941E + 00, A10 = 0.10177E-01, A12 = 0.18198E + 00
7th surface K = -0.47352E + 00, A4 = -0.49541E-01, A6 = -0.19155E + 00, A8 = 0.10745E + 00, A10 = 0.34955E-01, A12 = -0.17517E + 00
8th surface K = -0.42581E + 01, A4 = -0.36830E + 00, A6 = 0.44957E + 00, A8 = -0.49955E + 00, A10 = 0.29701E + 00, A12 = -0.57079E-01
9th surface K = 0.50000E + 02, A4 = -0.13819E + 00, A6 = 0.69622E-01, A8 = -0.22948E-02, A10 = -0.74642E-02, A12 = 0.23681E-02, A14 = -0.23298E-03
10th surface K = -0.83990E + 01, A4 = -0.12725E + 00, A6 = 0.66635E-01, A8 = -0.31867E-01, A10 = 0.97193E-02, A12 = -0.17419E-02, A14 = 0.14169E-03
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 2.769
2 5 -6.765
3 7 1.664
4 9 -1.622
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = −2.08
(2) (r3 + r4) / (r3-r4) = 3.19
(3) ν2 = 23.4
(4) f3 / f = 0.51
(5) f1 / f = 0.85
(6) (r1 + r2) / (r1-r2) = − 0.83
(7) f4 / f = −0.50
FIG. 5 is a cross-sectional view of the imaging lens of the third embodiment. In FIG. 5, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a sealing glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 6 is an aberration diagram (spherical aberration, astigmatism, distortion, meridional coma) of the imaging lens of Example 3.

[Example 4]
The overall specifications of the imaging lens are shown below.

f = 3.23mm
fB = 0.53mm
F = 2.45
2Y = 4.536mm
ENTP = 0.37mm
EXTP = −2.04mm
H1 = -0.46mm
H2 = -2.7mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 0.96
2 (*) 1.851 0.48 1.54470 56.2 0.86
3 (*) -6.817 0.02 0.73
4 (Aperture) ∞ 0.07 0.61
5 (*) 3.453 0.30 1.63200 23.4 0.65
6 (*) 1.691 0.70 0.70
7 (*) -2.856 0.73 1.54470 56.2 0.97
8 (*) -0.800 0.20 1.25
9 (*) 4.249 0.31 1.54470 56.2 1.73
10 (*) 0.764 0.40 1.93
11 ∞ 0.30 1.51630 64.1 2.50
12 ∞ 2.50
All the lenses are made of a plastic material.

The aspheric coefficient is shown below.

2nd surface K = -0.16936E + 01, A4 = -0.19458E-01, A6 = -0.64258E-01, A8 = 0.59439E-02, A10 = -0.68961E-01
3rd surface K = 0.30000E + 02, A4 = 0.17943E-01, A6 = -0.22199E + 00, A8 = 0.43212E + 00, A10 = -0.72780E + 00, A12 = 0.48883E + 00
5th surface K = -0.29400E + 02, A4 = 0.16648E + 00, A6 = -0.11830E + 00, A8 = -0.38545E + 00, A10 = 0.15951E + 01, A12 = -0.16489E + 01
6th surface K = -0.11087E + 02, A4 = 0.33129E + 00, A6 = -0.28693E + 00, A8 = 0.53007E-01, A10 = 0.52475E + 00, A12 = -0.63855E + 00
7th surface K = 0.73287E + 01, A4 = 0.10229E + 00, A6 = -0.54248E + 00, A8 = 0.11071E + 01, A10 = -0.91218E + 00, A12 = 0.35166E + 00
8th surface K = -0.55600E + 01, A4 = -0.39762E + 00, A6 = 0.51162E + 00, A8 = -0.66716E + 00, A10 = 0.56491E + 00, A12 = -0.16848E + 00
9th surface K = -0.89159E + 00, A4 = -0.38884E + 00, A6 = 0.21604E + 00, A8 = -0.18315E-01, A10 = -0.22847E-01, A12 = 0.84676E-02, A14 = -0.93280E-03
10th surface K = -0.61692E + 01, A4 = -0.19043E + 00, A6 = 0.10570E + 00, A8 = -0.42066E-01, A10 = 0.10037E-01, A12 = -0.12388E-02, A14 = 0.56813E-04
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 2.726
2 5 -5.612
3 7 1.811
4 9 -1.767
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = -1.74
(2) (r3 + r4) / (r3-r4) = 2.92
(3) ν2 = 23.4
(4) f3 / f = 0.56
(5) f1 / f = 0.84
(6) (r1 + r2) / (r1-r2) = − 0.57
(7) f4 / f = −0.55
FIG. 7 is a sectional view of the imaging lens of Example 4. In FIG. 7, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a sealing glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 8 is an aberration diagram (spherical aberration, astigmatism, distortion, meridional coma) of the imaging lens of Example 4.

[Example 5]
The overall specifications of the imaging lens are shown below.

f = 3.26mm
fB = 0.35mm
F = 2.46
2Y = 4.536mm
ENTP = 0.34mm
EXTP = -2.28mm
H1 = -0.43mm
H2 = -2.9mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 0.94
2 (*) 1.940 0.46 1.54470 56.2 0.84
3 (*) -10.409 0.02 0.70
4 (Aperture) ∞ 0.05 0.63
5 (*) 2.242 0.30 1.63200 23.4 0.69
6 (*) 1.453 0.80 0.71
7 (*) -3.043 0.62 1.54470 56.2 1.03
8 (*) -0.762 0.05 1.25
9 (*) -35.685 0.50 1.54470 56.2 1.76
10 (*) 0.934 0.60 1.96
11 ∞ 0.30 1.51630 64.1 2.19
12 ∞ 2.25
All the lenses are made of a plastic material.

The aspheric coefficient is shown below.

2nd surface K = -0.22834E + 01, A4 = -0.13804E-01, A6 = -0.34432E-01, A8 = -0.15941E + 00, A10 = 0.25524E + 00, A12 = -0.15999E + 00
3rd surface K = 0.50000E + 02, A4 = -0.51938E-02, A6 = -0.15543E + 00, A8 = 0.11091E + 00, A10 = 0.92223E-01, A12 = -0.14237E + 00
5th surface K = -0.99582E + 01, A4 = 0.14153E + 00, A6 = 0.37260E-01, A8 = -0.63606E + 00, A10 = 0.13793E + 01, A12 = -0.74559E + 00
6th surface K = -0.54972E + 01, A4 = 0.24332E + 00, A6 = -0.19087E + 00, A8 = 0.38562E + 00, A10 = -0.91366E + 00, A12 = 0.11017E + 01
7th surface K = -0.33134E + 01, A4 = -0.31725E-01, A6 = -0.18905E + 00, A8 = 0.31784E + 00, A10 = -0.23541E + 00, A12 = 0.65441E-01
8th surface K = -0.45046E + 01, A4 = -0.31538E + 00, A6 = 0.39716E + 00, A8 = -0.43879E + 00, A10 = 0.33688E + 00, A12 = -0.94144E-01
9th surface K = -0.30678E + 02, A4 = -0.15297E + 00, A6 = 0.87441E-01, A8 = -0.49381E-02, A10 = -0.85921E-02, A12 = 0.27727E-02, A14 = -0.27462E-03
10th surface K = -0.82268E + 01, A4 = -0.12639E + 00, A6 = 0.66957E-01, A8 = -0.31217E-01, A10 = 0.89964E-02, A12 = -0.14562E-02, A14 = 0.10592E-03
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 3.042
2 5 -7.668
3 7 1.703
4 9 -1.663
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = −2.35
(2) (r3 + r4) / (r3-r4) = 4.69
(3) ν2 = 23.4
(4) f3 / f = 0.52
(5) f1 / f = 0.93
(6) (r1 + r2) / (r1-r2) = − 0.69
(7) f4 / f = −0.51
FIG. 9 is a sectional view of the imaging lens of Example 5. In FIG. 9, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a seal glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 10 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the imaging lens of Example 5.

[Example 6]
The overall specifications of the imaging lens are shown below.

f = 3.17mm
fB = 0.37mm
F = 2.76
2Y = 4.536mm
ENTP = 0.4mm
EXTP = -2.39mm
H1 = -0.07mm
H2 = -2.8mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 0.89
2 (*) 1.618 0.46 1.54470 56.2 0.78
3 (*) -33.861 0.05 0.64
4 (Aperture) ∞ 0.05 0.52
5 (*) 3.363 0.30 1.81360 25.7 0.53
6 (*) 1.736 0.71 0.60
7 (*) -3.530 0.87 1.54470 56.2 0.99
8 (*) -0.645 0.05 1.21
9 (*) 6.995 0.42 1.54470 56.2 1.76
10 (*) 0.653 0.61 2.00
11 ∞ 0.30 1.51630 64.1 2.09
12 ∞ 2.15
The first lens, the third lens, and the fourth lens are made of a plastic material, and the second lens is made of a glass material.

The aspheric coefficient is shown below.

2nd surface K = -0.12464E + 01, A4 = 0.10586E-01, A6 = 0.88035E-02, A8 = -0.23667E + 00, A10 = 0.36470E + 00, A12 = -0.50904E + 00
3rd surface K = 0.30000E + 02, A4 = -0.12331E + 00, A6 = 0.10511E-01, A8 = 0.12380E-01, A10 = -0.93159E + 00, A12 = 0.12984E + 01
5th surface K = -0.19486E + 02, A4 = -0.69825E-01, A6 = 0.53173E-01, A8 = -0.25869E + 00, A10 = 0.98527E-01, A12 = 0.60041E + 00
6th surface K = -0.11408E + 02, A4 = 0.21915E + 00, A6 = -0.26489E + 00, A8 = 0.24070E + 00, A10 = -0.11393E + 00, A12 = 0.23080E + 00
7th surface K = 0.44499E + 01, A4 = -0.49461E-01, A6 = -0.77497E-01, A8 = 0.51106E-01, A10 = 0.81568E-01, A12 = -0.50913E-01
8th surface K = -0.38423E + 01, A4 = -0.30757E + 00, A6 = 0.36250E + 00, A8 = -0.44299E + 00, A10 = 0.30040E + 00, A12 = -0.72127E-01
9th surface K = 0.57434E + 01, A4 = -0.15398E + 00, A6 = 0.81711E-01, A8 = -0.68951E-02, A10 = -0.65231E-02, A12 = 0.21392E-02, A14 = -0.21119E-03
10th surface K = -0.54509E + 01, A4 = -0.10992E + 00, A6 = 0.66389E-01, A8 = -0.29163E-01, A10 = 0.78016E-02, A12 = -0.10827E-02, A14 = 0.56328E-04
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 2.847
2 5 -4.809
3 7 1.310
4 9 -1.355
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = −1.52
(2) (r3 + r4) / (r3-r4) = 3.13
(3) ν2 = 25.7
(4) f3 / f = 0.41
(5) f1 / f = 0.90
(6) (r1 + r2) / (r1-r2) = − 0.91
(7) f4 / f = −0.43
FIG. 11 is a sectional view of the imaging lens of Example 6. In FIG. 11, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a sealing glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 12 is an aberration diagram (spherical aberration, astigmatism, distortion, and meridional coma) of the imaging lens of Example 6.

[Example 7]
The overall specifications of the imaging lens are shown below.

f = 3.23mm
fB = 0.32mm
F = 2.44
2Y = 4.536mm
ENTP = 0.47mm
EXTP = -2.28mm
H1 = -0.3mm
H2 = -2.91mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 1.04
2 (*) 1.482 0.55 1.54470 56.2 0.87
3 (*) -16.482 0.05 0.73
4 (Aperture) ∞ 0.10 0.58
5 (*) 6.389 0.30 1.81360 25.7 0.60
6 (*) 2.396 0.50 0.67
7 (*) -2.042 0.87 1.54470 56.2 0.84
8 (*) -0.811 0.05 1.19
9 (*) 13.433 0.63 1.54470 56.2 1.89
10 (*) 1.038 0.55 2.13
11 ∞ 0.30 1.51630 64.1 2.29
12 ∞ 2.33
The first lens, the third lens, and the fourth lens are made of a plastic material, and the second lens is made of a glass material.

The aspheric coefficient is shown below.

2nd surface K = -0.10804E + 01, A4 = 0.28140E-01, A6 = 0.29499E-01, A8 = -0.19556E + 00, A10 = 0.33356E + 00, A12 = -0.35312E + 00
3rd surface K = -0.30000E + 02, A4 = 0.44782E-01, A6 = -0.18092E + 00, A8 = 0.91452E-01, A10 = -0.40545E + 00, A12 = 0.39078E + 00
5th surface K = 0.26447E + 02, A4 = 0.83473E-01, A6 = -0.14020E + 00, A8 = -0.43089E + 00, A10 = 0.99821E + 00, A12 = -0.76003E + 00
6th surface K = -0.15122E + 02, A4 = 0.25350E + 00, A6 = -0.17470E + 00, A8 = -0.12759E + 00, A10 = 0.34579E + 00, A12 = -0.10690E + 00
7th surface K = -0.24691E + 00, A4 = -0.24837E-01, A6 = -0.24649E + 00, A8 = 0.37275E + 00, A10 = -0.63155E-01, A12 = -0.89487E-01
8th surface K = -0.35974E + 01, A4 = -0.31950E + 00, A6 = 0.37727E + 00, A8 = -0.46761E + 00, A10 = 0.36505E + 00, A12 = -0.96939E-01
9th surface K = 0.22700E + 02, A4 = -0.15327E + 00, A6 = 0.82030E-01, A8 = -0.44748E-02, A10 = -0.84313E-02, A12 = 0.25452E-02, A14 = -0.22761E-03
10th surface K = -0.66779E + 01, A4 = -0.12047E + 00, A6 = 0.68020E-01, A8 = -0.32607E-01, A10 = 0.91571E-02, A12 = -0.13546E-02, A14 = 0.78449E-04
Single lens data of the imaging lens is shown below.

Lens Start surface Focal length (mm)
1 2 2.523
2 5 -4.876
3 7 1.979
4 9 -2.104
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = −1.51
(2) (r3 + r4) / (r3-r4) = 2.20
(3) ν2 = 25.7
(4) f3 / f = 0.61
(5) f1 / f = 0.78
(6) (r1 + r2) / (r1-r2) = − 0.83
(7) f4 / f = −0.65
FIG. 13 is a cross-sectional view of the imaging lens of the seventh embodiment. In FIG. 13, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a seal glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 14 is an aberration diagram (spherical aberration, astigmatism, distortion, meridional coma) of the imaging lens of Example 7.

[Example 8]
The overall specifications of the imaging lens are shown below.

f = 3.17mm
fB = 0.41mm
F = 2.4
2Y = 4.536mm
ENTP = 0.44mm
EXTP = -2.44mm
H1 = 0.08mm
H2 = -2.76mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 1.01
2 (*) 1.699 0.51 1.54470 56.2 0.88
3 (*) -434.783 0.05 0.76
4 (Aperture) ∞ 0.05 0.60
5 (*) 2.123 0.31 1.94590 18.0 0.63
6 (*) 1.415 0.60 0.66
7 (*) -3.219 0.97 1.54470 56.2 1.02
8 (*) -0.590 0.05 1.25
9 (*) 3.743 0.30 1.54470 56.2 1.69
10 (*) 0.567 0.65 1.92
11 ∞ 0.30 1.51630 64.1 2.07
12 ∞ 2.13
The first lens, the third lens, and the fourth lens are made of a plastic material, and the second lens is made of a glass material.

The aspheric coefficient is shown below.
2nd surface K = -0.15740E + 01, A4 = 0.22067E-02, A6 = 0.17900E-01, A8 = -0.21202E + 00, A10 = 0.25851E + 00, A12 = -0.22485E + 00
3rd surface K = -0.30000E + 02, A4 = -0.16112E + 00, A6 = 0.85149E-01, A8 = 0.25673E-01, A10 = -0.44441E + 00, A12 = 0.35822E + 00
5th surface K = -0.16785E + 01, A4 = -0.10537E + 00, A6 = 0.12390E + 00, A8 = -0.10139E + 00, A10 = -0.63288E-01, A12 = 0.11374E + 00
6th surface K = -0.59936E + 01, A4 = 0.22146E + 00, A6 = -0.19877E + 00, A8 = 0.36513E + 00, A10 = -0.48228E + 00, A12 = 0.27550E + 00
7th surface K = 0.10547E + 01, A4 = -0.40014E-01, A6 = -0.15612E + 00, A8 = 0.25747E + 00, A10 = -0.77319E-01, A12 = -0.57611E-02
8th surface K = -0.44372E + 01, A4 = -0.35401E + 00, A6 = 0.41169E + 00, A8 = -0.46487E + 00, A10 = 0.30460E + 00, A12 = -0.76778E-01
9th surface K = -0.24612E + 02, A4 = -0.18034E + 00, A6 = 0.10193E + 00, A8 = -0.11323E-01, A10 = -0.86089E-02, A12 = 0.33135E-02, A14 = -0.37994E-03
10th surface K = -0.56557E + 01, A4 = -0.12507E + 00, A6 = 0.70810E-01, A8 = -0.29853E-01, A10 = 0.80872E-02, A12 = -0.12687E-02, A14 = 0.83659E-04
Single lens data of the imaging lens is shown below.
Lens Start surface Focal length (mm)
1 2 3.109
2 5 -5.705
3 7 1.175
4 9 -1.269
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = -1.80
(2) (r3 + r4) / (r3-r4) = 5.00
(3) ν2 = 18.0
(4) f3 / f = 0.37
(5) f1 / f = 0.98
(6) (r1 + r2) / (r1-r2) = − 0.99
(7) f4 / f = −0.41
FIG. 15 is a cross-sectional view of the imaging lens of the eighth embodiment. In FIG. 15, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a seal glass of a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 16 is an aberration diagram of the imaging lens of Example 8 (spherical aberration, astigmatism, distortion, and meridional coma).

[Example 9]
The overall specifications of the imaging lens are shown below.

f = 3.18mm
fB = 0.09mm
F = 2.2
2Y = 4.536mm
ENTP = 0.6mm
EXTP = -1.79mm
H1 = -1.61mm
H2 = -3.1mm
The surface data of the imaging lens is shown below.
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.00 1.23
2 (*) 1.351 0.67 1.54470 56.2 0.97
3 (*) -22.251 0.05 0.78
4 (Aperture) ∞ 0.05 0.61
5 (*) 9.025 0.30 1.92290 21.3 0.63
6 (*) 3.008 0.38 0.67
7 (*) -5.952 1.19 1.54470 56.2 0.82
8 (*) -0.976 0.30 1.32
9 (*) -2.049 0.30 1.54470 56.2 1.66
10 (*) 1.411 0.35 1.96
11 ∞ 0.30 1.51630 64.1 2.20
12 ∞ 2.20
The first lens, the third lens, and the fourth lens are made of a plastic material, and the second lens is made of a glass material.

The aspheric coefficient is shown below.
2nd surface K = -0.96907E + 00, A4 = 0.24019E-01, A6 = 0.84796E-01, A8 = -0.22271E + 00, A10 = 0.28774E + 00, A12 = -0.17442E + 00
3rd surface K = -0.30000E + 02, A4 = 0.84287E-01, A6 = -0.18816E + 00, A8 = 0.20886E + 00, A10 = -0.30122E + 00, A12 = 0.16373E + 00
5th surface K = 0.30000E + 02, A4 = 0.11403E + 00, A6 = -0.65865E-01, A8 = -0.31411E + 00, A10 = 0.93783E + 00, A12 = -0.83395E + 00
6th surface K = -0.10302E + 02, A4 = 0.17911E + 00, A6 = -0.14445E + 00, A8 = 0.47641E + 00, A10 = -0.79293E + 00, A12 = 0.68086E + 00
7th surface K = 0.17802E + 02, A4 = -0.85831E-01, A6 = -0.87201E-01, A8 = 0.35773E-03, A10 = 0.16761E + 00, A12 = -0.19170E + 00
8th surface K = -0.55360E + 01, A4 = -0.35963E + 00, A6 = 0.42612E + 00, A8 = -0.43422E + 00, A10 = 0.26144E + 00, A12 = -0.57313E-01
9th surface K = 0.28252E + 00, A4 = -0.23522E + 00, A6 = 0.15611E + 00, A8 = -0.24606E-02, A10 = -0.12016E-01, A12 = 0.17307E-02, A14 = 0.12003E-03
10th surface K = -0.13695E + 02, A4 = -0.13749E + 00, A6 = 0.70698E-01, A8 = -0.28906E-01, A10 = 0.74311E-02, A12 = -0.12460E-02, A14 = 0.10580E-03
Single lens data of the imaging lens is shown below.
Lens Start surface Focal length (mm)
1 2 2.362
2 5 -5.009
3 7 1.977
4 9 -1.489
Values corresponding to conditional expressions (1) to (7) are shown below.
(1) f2 / f = −1.57
(2) (r3 + r4) / (r3-r4) = 2.00
(3) ν2 = 21.3
(4) f3 / f = 0.62
(5) f1 / f = 0.74
(6) (r1 + r2) / (r1-r2) = − 0.89
(7) f4 / f = −0.46
FIG. 17 is a cross-sectional view of the imaging lens of Example 9. In FIG. 17, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, S is an aperture stop, F is an optical low-pass filter, an IR cut filter, or a sealing glass for a solid-state image sensor. A parallel plate assuming I and the like, I is an imaging surface. FIG. 18 is an aberration diagram of the imaging lens of Example 9 (spherical aberration, astigmatism, distortion, and meridional coma).

Here, since the plastic material has a large refractive index change at the time of temperature change, if all of the first lens to the fourth lens are made of plastic lenses, the image point position of the entire imaging lens changes when the ambient temperature changes. Have the problem of doing.

Recently, it has been found that the temperature change of the plastic material can be reduced by mixing inorganic fine particles in the plastic material. More specifically, mixing fine particles with a transparent plastic material generally causes light scattering and lowers the transmittance, so it was difficult to use as an optical material. By making it smaller than the wavelength, it is possible to substantially prevent scattering. The refractive index of the plastic material decreases with increasing temperature, but the refractive index of inorganic particles increases with increasing temperature. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 20 nanometers or less in a plastic material as a base material, a plastic material with extremely low temperature dependency of the refractive index is obtained. For example, by dispersing fine particles of niobium oxide (Nb ₂ O ₅ ) in acrylic, the refractive index change due to temperature change can be reduced. In the present invention, by using a plastic material in which such inorganic particles are dispersed in the positive lens (L1) having a relatively large refractive power, or all the lenses (L1 to L4), the temperature change of the entire imaging lens system It is possible to suppress the image point position fluctuation at the time.

In recent years, as a method for mounting an image pickup apparatus at a low cost and in large quantities, a reflow process (heating process) is performed on a substrate on which solder has been potted in advance, with an IC chip or other electronic component and an optical element placed on the substrate. A technique has been proposed in which an electronic component and an optical element are simultaneously mounted on a substrate by melting solder.

In order to perform mounting using such a reflow process, it is necessary to heat the optical element together with the electronic component to about 200 to 260 degrees, but at such a high temperature, a lens using a thermoplastic resin is thermally deformed. However, there is a problem that the optical performance deteriorates due to discoloration. As one of the methods for solving such a problem, a technology has been proposed that uses a glass mold lens having excellent heat resistance performance and achieves both miniaturization and optical performance in a high temperature environment. Since the cost is higher than the lens using the lens, there has been a problem that it is impossible to meet the demand for cost reduction of the imaging device.

Therefore, by using an energy curable resin as the material of the imaging lens, since the optical performance degradation when exposed to high temperatures is small compared to a lens using a thermoplastic resin such as polycarbonate or polyolefin, It is effective for the reflow process, is easier to manufacture than a glass mold lens, is inexpensive, and can achieve both low cost and mass productivity of an imaging apparatus incorporating an imaging lens. The energy curable resin refers to both a thermosetting resin and an ultraviolet curable resin.

Also, the plastic lens of the present invention may be formed using the above-mentioned energy curable resin.

In the present embodiment, the principal ray incident angle of the light beam incident on the imaging surface of the solid-state imaging device is not necessarily designed to be sufficiently small in the periphery of the imaging surface. However, recent techniques have made it possible to reduce shading by reviewing the arrangement of the color filters of the solid-state imaging device and the on-chip microlens array. Specifically, if the pitch of the arrangement of the color filters and the on-chip microlens array is set slightly smaller than the pixel pitch of the imaging surface of the imaging device, the color filter or Since the on-chip microlens array is shifted to the optical axis side of the imaging lens, the obliquely incident light beam can be efficiently guided to the light receiving portion of each pixel. Thereby, the shading which generate | occur | produces with a solid-state image sensor can be restrained small. The present embodiment is a design example aiming at further miniaturization with respect to the portion where the requirement is relaxed.

L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens S Aperture stop F Parallel plate I Imaging surface

Claims

An imaging lens for forming a subject image on a photoelectric conversion unit of a solid-state imaging device,
From the object side,
A biconvex first lens having positive refractive power;
A second lens having negative refractive power and having a concave surface facing the image side;
A third meniscus lens having positive refractive power and having a convex surface facing the image side;
A fourth lens having at least one surface formed as an aspheric surface and having negative refractive power and a concave surface facing the image side;
An imaging lens having an aperture stop between the first lens and the second lens and satisfying the following conditional expression:
-2.50 <f2 / f <-1.50
However,
f2: focal length of the second lens f: focal length of the entire imaging lens system
The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
2.00 ≦ (r3 + r4) / (r3-r4) ≦ 5.00
However,
r3: radius of curvature of the object side surface of the second lens r4: radius of curvature of the image side surface of the second lens
The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
15 <ν2 <27
However,
ν2: Abbe number of the second lens
The imaging lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.35 <f3 / f <0.65
However,
f3: focal length of the third lens f: focal length of the entire imaging lens system
5. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
0.70 <f1 / f <1.05
However,
f1: Focal length of the first lens f: Focal length of the entire imaging lens system
6. The imaging lens according to claim 1, wherein the following conditional expression is satisfied.
−1.00 <(r1 + r2) / (r1−r2) <− 0.50
However,
r1: radius of curvature of the object side surface of the first lens r2: radius of curvature of the image side surface of the first lens
The imaging lens according to any one of claims 1 to 6, wherein the following conditional expression is satisfied.
-0.70 <f4 / f <-0.40
However,
f4: focal length of the fourth lens f: focal length of the entire imaging lens system
The image side surface of the fourth lens is formed as an aspherical surface, has a negative refractive power in the vicinity of the optical axis, and has a inflection point because the negative refractive power becomes weaker toward the periphery. The imaging lens according to any one of claims 1 to 7.
9. The imaging lens according to claim 1, wherein the fourth lens has a biconcave shape.
10. The imaging lens according to claim 1, wherein all the lenses are made of a plastic material.