CN112444953B

CN112444953B - Image pickup lens

Info

Publication number: CN112444953B
Application number: CN202010924135.2A
Authority: CN
Inventors: 德能康熙; 关根幸男; 镰田健一
Original assignee: Tokyo Visionary Optics Co Ltd
Current assignee: Tokyo Visionary Optics Co Ltd
Priority date: 2019-09-04
Filing date: 2020-09-04
Publication date: 2023-05-19
Anticipated expiration: 2040-09-04
Also published as: CN112444953A

Abstract

The invention provides an imaging lens which can meet the requirements of low back and low F value and has good optical characteristics. The imaging lens includes, in order from an object side toward an image side: a first lens having positive optical power with its convex surface facing the object side in the paraxial region; a second lens having negative optical power in a paraxial region; a third lens having negative optical power in a paraxial region; a fourth lens having positive optical power in a paraxial region; and a fifth lens having negative optical power in a paraxial region; a predetermined conditional expression is satisfied.

Description

Image pickup lens

Technical Field

The present invention relates to an imaging lens for imaging an image of a subject on a solid-state imaging element using a CCD sensor or a C-MOS sensor for an imaging device.

Background

In recent years, a camera function is commonly mounted in various products such as home appliances, information terminal apparatuses, and automobiles. Prediction is also being carried out in the future, and development of commodities incorporating camera functions is being carried out.

An imaging lens mounted in such a device needs to be small and high resolution.

As conventional imaging lenses aimed at high performance, for example, the following patent document 1 is known.

Patent document 1 (japanese patent application laid-open No. 109407284) discloses an imaging lens including, in order from the object side: a first lens with a convex surface facing the object side and having positive optical power; a second lens having negative optical power; the third lens, the concave surface faces the image side, have negative focal power; a fourth lens having positive or negative optical power; and a fifth lens having a concave surface facing the object side and having negative optical power; the relationship between the total optical length and the focal length of the entire system and the relationship between the focal length of the entire system and the half value of the image height satisfy certain conditions.

Disclosure of Invention

Problems to be solved by the invention

When the lens structure described in patent document 1 is intended to achieve low back and low F-number, it is very difficult to correct aberrations in the peripheral portion, and good optical performance cannot be obtained.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging lens having high resolution capable of satisfying the requirements for low back and low F-number in a balanced manner and capable of satisfactorily correcting each aberration.

In the term used in the present invention, the convex, concave, and plane of the lens surface refer to the shape near the optical axis (paraxial). Optical power refers to paraxial optical power unless otherwise indicated. The pole refers to a point on an aspherical surface other than the optical axis where the tangential plane perpendicularly intersects the optical axis. The optical total length is a distance on the optical axis from the object side surface of the optical element located on the most object side to the image pickup surface. The total optical length and the back focal length are distances obtained by converting the thickness of an IR cut filter, a cover glass, or the like disposed between the imaging lens and the imaging surface into air.

Means for solving the problems

The imaging lens of the present invention includes, in order from an object side toward an image side: a first lens having positive optical power with its convex surface facing the object side in the paraxial region; a second lens having negative optical power in a paraxial region; a third lens having negative optical power in a paraxial region; a fourth lens having positive optical power in a paraxial region; and a fifth lens having negative optical power in a paraxial region.

By enhancing the optical power, the first lens achieves a low back. In addition, the first lens favorably suppresses spherical aberration and distortion by having the convex surface facing the object side in the paraxial region.

The second lens corrects spherical aberration and chromatic aberration well.

The third lens corrects chromatic aberration and coma well.

The fourth lens realizes low back, and well corrects astigmatism, field curvature and distortion.

The fifth lens favorably corrects chromatic aberration, astigmatism, field curvature, and distortion.

In the imaging lens having the above configuration, the convex surface of the second lens is preferably directed toward the object side in the paraxial region. By adopting such a shape, coma, astigmatism, and distortion can be corrected.

In the imaging lens having the above configuration, the third lens preferably has a concave surface facing the image side in the paraxial region. By adopting such a shape, astigmatism and distortion can be corrected.

In the imaging lens having the above configuration, the fifth lens preferably has a concave surface facing the object side in the paraxial region. By adopting such a shape, astigmatism, field curvature, and distortion can be corrected.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (1) is satisfied,

(1)9.0＜νd4＜29.0

wherein,,

νd4: and the fourth lens has a dispersion coefficient relative to d-line.

The condition (1) specifies the dispersion coefficient of the fourth lens with respect to the d-line within an appropriate range. By satisfying the range of the conditional expression (1), chromatic aberration can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (2) is satisfied,

(2)2.8＜r1×|r2|/f＜9.5

wherein,,

r1: the paraxial radius of curvature of the object-side surface of the first lens,

r2: the paraxial radius of curvature of the image-side surface of the first lens,

f: focal length of the whole system of the imaging lens.

The condition (2) defines a relationship between a paraxial radius of curvature of an object side surface of the first lens and an image side surface of the first lens and a focal length of the imaging lens system as a whole within an appropriate range. By satisfying the range of conditional expression (2), the back can be reduced, and spherical aberration, coma, astigmatism, and distortion can be suppressed.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (3) is satisfied,

(3)-2.5＜r3/r7＜-0.1

wherein,,

r3: the paraxial radius of curvature of the object-side surface of the second lens,

r7: paraxial radius of curvature of an object side surface of the fourth lens.

The condition (3) defines a relationship between a paraxial radius of curvature of an object side surface of the second lens and a paraxial radius of curvature of an object side surface of the fourth lens in an appropriate range. By satisfying the conditional expression (3), astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (4) is satisfied,

(4)3.0＜(D4/f4)×100＜13.0

wherein,,

d4: the thickness on the optical axis of the fourth lens,

f4: focal length of the fourth lens.

The conditional expression (4) specifies the relationship between the thickness on the optical axis of the fourth lens and the focal length of the fourth lens in an appropriate range. By satisfying the range of the conditional expression (4), the back can be reduced, and astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (5) is satisfied,

(5)1.5＜|r2|/f＜7.0

wherein,,

f: focal length of the whole system of the imaging lens.

The condition (5) defines a paraxial radius of curvature of the image side surface of the first lens in an appropriate range. By satisfying the range of conditional expression (5), spherical aberration, coma, astigmatism, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (6) is satisfied,

(6)-20.0＜|r2|/r8＜-3.5

wherein,,

r8: paraxial radius of curvature of the image-side surface of the fourth lens.

The condition (6) defines a relationship between a paraxial radius of curvature of an image side surface of the first lens and a paraxial radius of curvature of an image side surface of the fourth lens in an appropriate range. By satisfying the range of conditional expression (6), coma, astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (7) is satisfied,

(7)0.0＜|r5|/r6＜18.0

wherein,,

r5: the paraxial radius of curvature of the object-side surface of the third lens,

r6: paraxial radius of curvature of the image side surface of the third lens.

The conditional expression (7) defines a relationship between a paraxial radius of curvature of an object side surface of the third lens and a paraxial radius of curvature of an image side surface of the third lens in an appropriate range. By satisfying the conditional expression (7), coma, astigmatism, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (8) is satisfied,

(8)0.0＜|r5|/r6/r1＜12.0

wherein,,

r6: the paraxial radius of curvature of the image-side surface of the third lens,

r1: paraxial radius of curvature of the object side of the first lens.

The condition (8) defines a relationship between a paraxial radius of curvature of an object side surface of the third lens and an image side surface of the third lens and a paraxial radius of curvature of an object side surface of the first lens in an appropriate range. By satisfying the conditional expression (8), spherical aberration, coma, astigmatism, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (9) is satisfied,

(9)0.5＜f4/f＜3.0

wherein,,

f4: the focal length of the fourth lens is set,

f: focal length of the whole system of the imaging lens.

The conditional expression (9) defines the focal length of the fourth lens in an appropriate range. By satisfying the range of the conditional expression (9), the back can be reduced, and astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (10) is satisfied,

(10)47.0＜νd3＜67.0

wherein,,

νd3: the third lens has a dispersion coefficient with respect to d-line.

The conditional expression (10) specifies the dispersion coefficient of the third lens with respect to the d-line within an appropriate range. By satisfying the range of the conditional expression (10), chromatic aberration can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (11) is satisfied,

(11)1.0＜(T2/f)×100＜18.0

wherein,,

t2: the distance on the optical axis from the image side surface of the second lens to the object side surface of the third lens,

f: focal length of the whole system of the imaging lens.

The conditional expression (11) defines a distance on the optical axis from the image side surface of the second lens to the object side surface of the third lens in an appropriate range. By satisfying the range of the conditional expression (11), the back surface can be reduced, the incident angle of the light beam to the object side surface of the third lens can be appropriately controlled, and astigmatism and distortion can be satisfactorily corrected.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (12) is satisfied,

(12)0.05＜D3/(T3-T2)＜1.35

wherein,,

d3: the thickness on the optical axis of the third lens,

t3: the distance on the optical axis from the image side surface of the third lens to the object side surface of the fourth lens,

t2: the distance on the optical axis from the image side surface of the second lens to the object side surface of the third lens.

The condition (12) defines a relationship between the thickness of the third lens on the optical axis and the distance between the image side surface of the third lens and the object side surface of the fourth lens and the distance between the image side surface of the second lens and the object side surface of the third lens in an appropriate range. By satisfying the range of the conditional expression (12), the third lens is arranged at the optimum position, and each aberration correction function of the lens becomes more effective. As a result, the back can be reduced, and astigmatism and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (13) is satisfied,

(13)1.2＜D4/T4＜13.0

wherein,,

d4: the thickness on the optical axis of the fourth lens,

t4: an image side surface of the fourth lens element extends to an object side surface of the fifth lens element.

The conditional expression (13) defines a relationship between the thickness on the optical axis of the fourth lens element and the distance on the optical axis from the image side surface of the fourth lens element to the object side surface of the fifth lens element within an appropriate range. By satisfying the range of the conditional expression (13), the back surface can be reduced, the incident angle of the light beam to the object side surface of the fifth lens can be appropriately controlled, and astigmatism and distortion can be satisfactorily corrected.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (14) is satisfied,

(14)0.5＜(T4/f)×100＜6.5

wherein,,

t4: the distance on the optical axis from the image side surface of the fourth lens to the object side surface of the fifth lens,

f: focal length of the whole system of the imaging lens.

Conditional expression (14) defines a distance on the optical axis from the image side surface of the fourth lens element to the object side surface of the fifth lens element within an appropriate range. By satisfying the range of the conditional expression (14), the back can be reduced, and astigmatism and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (15) is satisfied,

(15)-6.00＜|r2|/r3/r8＜-0.55

wherein,,

r8: paraxial radius of curvature of the image-side surface of the fourth lens.

The condition (15) defines a relationship between a paraxial radius of curvature of an image side surface of the first lens and a paraxial radius of curvature of an object side surface of the second lens and a paraxial radius of curvature of an image side surface of the fourth lens in an appropriate range. By satisfying the conditional expression (15), spherical aberration, coma, astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (16) is satisfied,

(16)-200.0＜r7/T2＜-3.0

wherein,,

r7: the paraxial radius of curvature of the object-side surface of the fourth lens,

The conditional expression (16) defines a relationship between a paraxial radius of curvature of an object-side surface of the fourth lens element and a distance on an optical axis from an image-side surface of the second lens element to an object-side surface of the third lens element within an appropriate range. By satisfying the range of the conditional expression (16), the back can be reduced, and astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (17) is satisfied,

(17)-35.0＜r7/(T3-T2)＜-1.5

wherein,,

Conditional expression (17) defines a relationship between a paraxial radius of curvature of an object-side surface of the fourth lens element and a distance on an optical axis from an image-side surface of the third lens element to the object-side surface of the fourth lens element and a distance on an optical axis from the image-side surface of the second lens element to the object-side surface of the third lens element in an appropriate range. By satisfying the range of the conditional expression (17), the optical power of the object side surface of the fourth lens is maintained, the third lens is arranged at the optimal position, and the respective aberration correction functions of the lenses become more effective. As a result, the back can be reduced, and astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (18) is satisfied,

(18)0.15＜f1/f4＜0.80

wherein,,

f1: the focal length of the first lens is chosen,

f4: focal length of the fourth lens.

Conditional expression (18) specifies the relationship between the focal length of the first lens and the focal length of the fourth lens in an appropriate range. By satisfying the range of the conditional expression (18), the optical power of the first lens and the optical power of the fourth lens can be appropriately balanced. As a result, the back can be reduced, and spherical aberration, coma, astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (19) is satisfied,

(19)-1.3＜f2/f4＜-0.3

wherein,,

f2: the focal length of the second lens is chosen,

f4: focal length of the fourth lens.

Conditional expression (19) specifies the relationship between the focal length of the second lens and the focal length of the fourth lens in an appropriate range. By satisfying the range of the conditional expression (19), the optical power of the second lens and the optical power of the fourth lens can be appropriately balanced. As a result, chromatic aberration, spherical aberration, coma, astigmatism, curvature of field, and distortion can be corrected well.

In the imaging lens having the above configuration, it is preferable that the following conditional expression (20) is satisfied,

(20)0.0≤r10/f5＜2.3

wherein,,

r10: the paraxial radius of curvature of the image-side surface of the fifth lens,

f5: focal length of the fifth lens.

The conditional expression (20) defines a relationship between a paraxial radius of curvature of an image side surface of the fifth lens and a focal length of the fifth lens in an appropriate range. By satisfying the range of the conditional expression (20), chromatic aberration, astigmatism, field curvature, and distortion can be corrected well.

ADVANTAGEOUS EFFECTS OF INVENTION

The invention can obtain an imaging lens which can well meet the requirements of low back and low F value, well correct various aberrations and has high resolution.

Drawings

Fig. 1 is a diagram showing a schematic configuration of an imaging lens according to embodiment 1 of the present invention.

Fig. 2 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 1 of the present invention.

Fig. 3 is a diagram showing a schematic configuration of an imaging lens according to embodiment 2 of the present invention.

Fig. 4 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 2 of the present invention.

Fig. 5 is a diagram showing a schematic configuration of an imaging lens according to embodiment 3 of the present invention.

Fig. 6 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 3 of the present invention.

Fig. 7 is a diagram showing a schematic configuration of an imaging lens according to embodiment 4 of the present invention.

Fig. 8 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 4 of the present invention.

Fig. 9 is a diagram showing a schematic configuration of an imaging lens according to embodiment 5 of the present invention.

Fig. 10 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 5 of the present invention.

Fig. 11 is a diagram showing a schematic configuration of an imaging lens according to embodiment 6 of the present invention.

Fig. 12 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 6 of the present invention.

Fig. 13 is a diagram showing a schematic configuration of an imaging lens according to embodiment 7 of the present invention.

Fig. 14 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 7 of the present invention.

Fig. 15 is a diagram showing a schematic configuration of an imaging lens according to embodiment 8 of the present invention.

Fig. 16 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens according to embodiment 8 of the present invention.

Fig. 17 is a diagram showing a schematic configuration of an imaging lens according to embodiment 9 of the present invention.

Fig. 18 is a view showing spherical aberration, astigmatism, and distortion of the imaging lens in embodiment 9 of the present invention.

Description of the reference numerals

ST: an aperture diaphragm,

L1: a first lens,

L2: a second lens,

L3: a third lens,

L4: a fourth lens,

L5: a fifth lens,

ih: maximum image height,

IR: an optical filter,

IMG: an imaging surface.

Detailed Description

Embodiments according to the present invention will be described in detail below with reference to the drawings.

Fig. 1, 3, 5, 7, 9, 11, 13, 15, and 17 are schematic configuration diagrams of imaging lenses according to examples 1 to 9 of the embodiment of the present invention, respectively. Hereinafter, an embodiment of the present invention will be described in detail mainly with reference to fig. 1.

As shown in fig. 1, the imaging lens of the present embodiment includes, in order from an object side toward an image side: the first lens L1 has positive focal power with the convex surface facing the object side in the paraxial region; the second lens L2 has a convex surface facing the object side in the paraxial region and has negative focal power; the third lens L3 has negative focal power at the concave surface of the paraxial region facing the image side; a fourth lens L4 having positive optical power in a paraxial region; and a fifth lens L5 having negative optical power with its concave surface facing the object side in the paraxial region.

An optical filter IR such as an infrared cut filter or cover glass is disposed between the fifth lens L5 and the image pickup surface IMG (i.e., the image pickup surface of the image pickup device). In addition, the filter IR can be omitted.

The aperture stop ST is disposed between the second lens L2 and the third lens L3, and is easy to correct distortion. The position of the aperture stop ST is not limited to the position between the second lens L2 and the third lens L3. The aperture stop ST may be disposed between the first lens L1 and the second lens L2 as in embodiment 3 and embodiment 4 shown in fig. 5 and 7. The aperture stop ST may be disposed on the object side of the first lens L1 as in embodiment 5, embodiment 7, embodiment 8, and embodiment 9 shown in fig. 9, 13, 15, and 17.

The first lens L1 has positive optical power and has a meniscus shape with a convex surface facing the object side and a concave surface facing the image side in the paraxial region. Therefore, the back is reduced, and spherical aberration, coma, astigmatism, and distortion are suppressed.

As shown in embodiment 2, embodiment 3, embodiment 4, embodiment 5, embodiment 6, embodiment 7, and embodiment 8 shown in fig. 3, fig. 5, fig. 7, fig. 9, fig. 11, fig. 13, and fig. 15, the shape of the first lens L1 may be a biconvex shape with the convex surface facing the object side and the convex surface facing the image side in the paraxial region. In this case, the back is reduced by having positive optical power on both surfaces.

The second lens L2 has negative optical power, and has a meniscus shape with a convex surface facing the object side and a concave surface facing the image side in the paraxial region. Thus, spherical aberration, chromatic aberration, coma, astigmatism, and distortion are well corrected.

The third lens L3 has negative optical power, and has a meniscus shape with a convex surface facing the object side and a concave surface facing the image side in the paraxial region. Therefore, chromatic aberration, coma, astigmatism, and distortion are well corrected.

As shown in fig. 3, 9, 11, 13, 15, and 17, in example 2, 5, 6, 7, 8, and 9, the shape of the third lens L3 may be a biconcave shape in which the concave surface faces the object side and the concave surface faces the image side in the paraxial region. In this case, the chromatic aberration can be corrected more favorably by having negative optical power on both surfaces.

The fourth lens L4 has positive optical power and has a meniscus shape with a concave surface facing the object side and a convex surface facing the image side in the paraxial region. Therefore, the back is reduced, and astigmatism, field curvature, and distortion are well corrected.

The fifth lens L5 has negative optical power and has a meniscus shape with a concave surface facing the object side and a convex surface facing the image side in the paraxial region. In addition, both sides are formed as aspherical surfaces. Therefore, chromatic aberration, astigmatism, field curvature, and distortion are well corrected.

As in embodiment 2 shown in fig. 3, the fifth lens L5 may have a concave surface facing the object side and a flat surface facing the image side in the paraxial region. At this time, astigmatism, curvature of field, and distortion are well corrected by the image surface forming an aspherical surface.

In the imaging lens of the present embodiment, it is preferable that all of the first lens L1 to the fifth lens L5 are constituted by respective individual lenses. An aspherical surface can be used more by being constituted by only a single lens. In the present embodiment, each aberration is well corrected by forming an appropriate aspherical surface on all lens surfaces. In addition, the man-hours can be reduced compared with the case of using a cemented lens, so that the manufacturing can be performed at low cost.

In addition, the imaging lens of the present embodiment is easy to manufacture by using a plastic material for all lenses, and can be mass-produced at low cost.

The lens material used is not limited to plastic material. By using a glass material, higher performance can be expected. In addition, although all lens surfaces are preferably formed as aspherical surfaces, spherical surfaces that are easy to manufacture may be employed depending on the required performance.

The imaging lens in the present embodiment satisfies the following conditional expressions (1) to (20), thereby exhibiting preferable effects.

(1)9.0＜νd4＜29.0

(2)2.8＜r1×|r2|/f＜9.5

(3)-2.5＜r3/r7＜-0.1

(4)3.0＜(D4/f4)×100＜13.0

(5)1.5＜|r2|/f＜7.0

(6)-20.0＜|r2|/r8＜-3.5

(7)0.0＜|r5|/r6＜18.0

(8)0.0＜|r5|/r6/r1＜12.0

(9)0.5＜f4/f＜3.0

(10)47.0＜νd3＜67.0

(11)1.0＜(T2/f)×100＜18.0

(12)0.05＜D3/(T3-T2)＜1.35

(13)1.2＜D4/T4＜13.0

(14)0.5＜(T4/f)×100＜6.5

(15)-6.00＜|r2|/r3/r8＜-0.55

(16)-200.0＜r7/T2＜-3.0

(17)-35.0＜r7/(T3-T2)＜-1.5

(18)0.15＜f1/f4＜0.80

(19)-1.3＜f2/f4＜-0.3

(20)0.0≤r10/f5＜2.3

Wherein,,

νd3: the third lens L3 has an abbe number with respect to d-line,

νd4: the fourth lens L4 has an abbe number with respect to d-line,

d3: the thickness on the optical axis X of the third lens L3,

d4: the thickness on the optical axis X of the fourth lens L4,

t2: the distance on the optical axis X from the image side surface of the second lens element L2 to the object side surface of the third lens element L3,

t3: the distance on the optical axis X from the image side surface of the third lens element L3 to the object side surface of the fourth lens element L4,

t4: the distance on the optical axis X from the image side surface of the fourth lens element L4 to the object side surface of the fifth lens element L5,

f: the focal length of the entire system of the imaging lens,

f1: the focal length of the first lens L1,

f2: the focal length of the second lens L2,

f4: the focal length of the fourth lens L4,

f5: the focal length of the fifth lens L5,

r1: the paraxial radius of curvature of the object-side surface of the first lens L1,

r2: the paraxial radius of curvature of the image-side surface of the first lens L1,

r3: the paraxial radius of curvature of the object-side surface of the second lens L2,

r5: the paraxial radius of curvature of the object-side surface of the third lens L3,

r6: the paraxial radius of curvature of the image-side surface of the third lens L3,

r7: the paraxial radius of curvature of the object-side surface of the fourth lens L4,

r8: the paraxial radius of curvature of the image-side surface of the fourth lens L4,

r10: the paraxial radius of curvature of the image-side surface of the fifth lens L5,

further, it is not necessary to satisfy all of the above-described conditional expressions, and by satisfying each conditional expression individually, an operational effect corresponding to each conditional expression can be obtained.

In the present embodiment, the imaging lens satisfies the following conditional expressions (1 a) to (20 a), thereby exhibiting a more preferable effect.

(1a)18.0＜νd4＜22.0

(2a)2.88≤r1×|r2|/f≤9.20

(3a)-2.36≤r3/r7≤-0.14

(4a)3.16≤(D4/f4)×100≤11.81

(5a)1.79≤|r2|/f≤6.41

(6a)-19.87≤|r2|/r8≤-4.29

(7a)1.12≤|r5|/r6≤15.66

(8a)0.07≤|r5|/r6/r1≤11.04

(9a)0.71≤f4/f≤2.69

(10a)55.0＜νd3＜60.0

(11a)3.17≤(T2/f)×100≤15.23

(12a)0.19≤D3/(T3-T2)≤1.25

(13a)1.4≤D4/T4≤12.29

(14a)0.69≤(T4/f)×100≤6.06

(15a)-4.40≤|r2|/r3/r8≤-0.64

(16a)-181.02≤r7/T2≤-3.75

(17a)-32.82≤r7/(T3-T2)≤-2.62

(18a)0.16≤f1/f4≤0.63

(19a)-1.12≤f2/f4≤-0.33

(20a)0≤r10/f5≤1.91

The signs of the respective conditional expressions are the same as those described in the preceding paragraph. In addition, only the upper limit value or the lower limit value of each of the conditional expressions (1 a) to (20 a) may be applied to the corresponding conditional expression (1) to (20).

In the present embodiment, the aspherical shape employed on the aspherical surface of the lens surface is expressed by the mathematical expression 1, where Z is the axis in the optical axis direction, H is the height in the direction orthogonal to the optical axis, R is the paraxial radius of curvature, k is the conic coefficient, and A4, A6, A8, a10, a12, a14, a16, a18, and a20 are the aspherical coefficients.

[ mathematics 1]

Next, an example of an imaging lens according to the present embodiment is described. In each embodiment, F represents a focal length of the entire system of the imaging lens, fno represents an F value, ω represents a half field angle, ih represents a maximum image height, and TTL represents an optical total length. In addition, i denotes a surface number counted from the object side, r denotes a paraxial radius of curvature, d denotes a distance (surface interval) between lens surfaces on the optical axis, nd denotes a refractive index of d-line (reference wavelength), and vd denotes a dispersion coefficient with respect to d-line. The aspherical surface is denoted by an asterisk (asterisk) following the surface number i.

Example 1

The basic lens data are shown in table 1 below.

TABLE 1

Example 1

Unit mm

f＝5.80

Fno＝2.60

ω(°)＝24.0

ih＝2.65

TTL＝5.26

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 1 satisfies the conditional expressions (1) to (20).

Fig. 2 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 1. The spherical aberration diagram shows the amounts of aberration for each wavelength with respect to the F-line (486 nm), d-line (588 nm), and C-line (656 nm). The astigmatic diagram shows the aberration amount of the d-line on the sagittal image surface S (solid line) and the aberration amount of the d-line on the meridional image surface T (broken line) (the same applies to fig. 4, 6, and 8). As shown in fig. 2, it is known that each aberration is well corrected.

Example 2

The basic lens data are shown in table 2 below.

TABLE 2

Example 2

Unit mm

f＝5.86

Fno＝2.60

ω(°)＝24.0

ih＝2.65

TTL＝5.23

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 2 satisfies conditional expressions (1) to (20).

Fig. 4 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 2. As shown in fig. 4, it is known that each aberration is well corrected.

Example 3

The basic lens data are shown in table 3 below.

TABLE 3

Example 3

Unit mm

f＝6.10

Fno＝2.60

ω(°)＝22.7

ih＝2.65

TTL＝5.26

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 3 satisfies conditional expressions (1) to (20).

Fig. 6 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 3. As shown in fig. 6, it is clear that each aberration is well corrected.

Example 4

The basic lens data are shown in table 4 below.

TABLE 4

Example 4

Unit mm

f＝6.10

Fno＝2.60

ω(°)＝22.7

ih＝2.65

TTL＝5.26

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 4 satisfies conditional expressions (1) to (20).

Fig. 8 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 4. As shown in fig. 8, it is clear that each aberration is well corrected.

Example 5

The basic lens data are shown in table 5 below.

TABLE 5

Example 5

Unit mm

f＝7.21

Fno＝2.40

ω(°)＝14.7

ih＝2.04

TTL＝5.96

Surface data

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Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 5 satisfies conditional expressions (1) to (20).

Fig. 10 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 5. As shown in fig. 10, it is known that each aberration is well corrected.

Example 6

The basic lens data are shown in table 6 below.

TABLE 6

Example 6

Unit mm

f＝5.82

Fno＝2.60

ω(°)＝24.1

ih＝2.65

TTL＝5.23

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 6 satisfies conditional expressions (1) to (20).

Fig. 12 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 6. As shown in fig. 12, it is clear that each aberration is well corrected.

Example 7

The basic lens data are shown in table 7 below.

TABLE 7

Example 7

Unit mm

f＝7.21

Fno＝2.40

ω(°)＝14.7

ih＝2.04

TTL＝5.96

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 7 satisfies the conditional expressions (1) to (20).

Fig. 14 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 7. As shown in fig. 4, it is known that each aberration is well corrected.

Example 8

The basic lens data are shown in table 8 below.

TABLE 8

Example 8

Unit mm

f＝7.21

Fno＝2.4

ω(°)＝15.8

ih＝2.04

TTL＝5.96

Surface data

Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 8 satisfies conditional expressions (1) to (20).

Fig. 16 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 8. As shown in fig. 16, it is clear that each aberration is well corrected.

Example 9

The basic lens data are shown in table 9 below.

TABLE 9

Example 9

Unit mm

f＝6.65

Fno＝2.4

ω(°)＝17.0

ih＝2.06

TTL＝5.80

Surface data

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Composing lens data

Aspherical data

As shown in table 10, the imaging lens of example 9 satisfies conditional expressions (1) to (20).

Fig. 18 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 9. As shown in fig. 18, it is clear that each aberration is well corrected.

Table 10 shows values of conditional expressions (1) to (20) related to examples 1 to 9.

TABLE 10

Industrial applicability

When the imaging lens according to the present invention is applied to a product having a camera function, the camera can be reduced in back and F value, and the performance of the camera can be improved.

Claims

1. An imaging lens comprising, in order from an object side toward an image side:

a first lens having positive optical power in a paraxial region, the object-side surface being a convex surface;

the second lens is provided with negative focal power in a paraxial region, the object side surface is a convex surface, and the image side surface is a concave surface;

a third lens having negative optical power in a paraxial region, the image side surface being a concave surface;

the fourth lens is provided with positive focal power in a paraxial region, the object side surface is a concave surface, and the image side surface is a convex surface; and

a fifth lens element having negative refractive power in a paraxial region, the object-side surface being a concave surface;

the following conditional expressions (1), (2), (3), (11) and (20) are satisfied:

(1)9.0＜νd4＜29.0

(2)2.8＜r1×|r2|/f＜9.5

(3)-2.5＜r3/r7＜-0.1

(11)1.0＜(T2/f)×100＜18.0

(20)0.0≤r10/f5＜2.3

wherein,,

νd4: the fourth lens has a dispersion coefficient with respect to d-line,

f: the focal length of the entire system of the imaging lens,

f5: focal length of the fifth lens.

2. The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied:

(4)3.0＜(D4/f4)×100＜13.0

wherein,,

d4: the thickness on the optical axis of the fourth lens,

f4: focal length of the fourth lens.

3. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied:

(5)1.5＜|r2|/f＜7.0

wherein,,

f: focal length of the whole system of the imaging lens.

4. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied:

(6)-20.0＜|r2|/r8＜-3.5

wherein,,

r8: paraxial radius of curvature of the image-side surface of the fourth lens.

5. The imaging lens according to claim 1, wherein the following conditional expression (7) is satisfied:

(7)0.0＜|r5|/r6＜18.0

wherein,,

r6: paraxial radius of curvature of the image side surface of the third lens.

6. The imaging lens according to claim 1, wherein the following conditional expression (8) is satisfied:

(8)0.0＜|r5|/r6/r1＜12.0

wherein,,

r1: paraxial radius of curvature of the object side of the first lens.

7. The imaging lens according to claim 1, wherein the following conditional expression (9) is satisfied:

(9)0.5＜f4/f＜3.0

wherein,,

f4: the focal length of the fourth lens is set,

f: focal length of the whole system of the imaging lens.