JP2006301221A - Imaging lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain reduction in thickness and size while securing high optical performance, regarding an imaging lens used for a camera for a mobile phone or the like. <P>SOLUTION: The imaging lens includes, in order from an object side, a 1st lens 1 having positive refractive index, an aperture diaphragm SD, a 2nd meniscus lens 2 having positive refractive index and also having a concave face on the object side, a 3rd lens 3 having negative refractive index, and also, where the surface on the image field side is concave on the image field side near the optical axis, and also, the surface becomes convex on the image field side as it comes close to the peripheral part, and all the 1st to 3rd lenses 1 to 3 are molded of resin material, and also, both surfaces of all the 1st to 3rd lenses 1 to 3 are aspherical, and the 1st to 3rd lenses 1 to 3 are constituted so that the abbe's numbers ν1, ν2 and ν3 may satisfy the following inequalities; ¾ν1-ν2¾<20, ¾ν2-ν3¾<20 and ¾ν1-ν3¾<20. By having such the constitution, the high optical performance is attained while attaining the reduction in weight and cost. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a small imaging lens used in a digital still camera or the like using a solid-state imaging device such as a CCD, and more particularly to a digital still camera, an in-vehicle camera, a mobile phone, a PDA, a portable personal computer, or the like. The present invention relates to an ultra-small imaging lens suitable for a mobile camera or the like that is mounted or used as an accessory.

In recent years, with the widespread use of digital still cameras and the like, there is an increasing demand for high performance, low cost, and compactness as imaging lenses used in electronic imaging devices. For example, many lens configurations that satisfy high performance, low cost, and compactness employ a retrofocus type in which the exit angle is reduced while sufficiently ensuring the back focus.
Further, along with the downsizing of the image pickup device, the entire image pickup apparatus has been further reduced in size. As an image pickup lens used in these small image pickup apparatuses, a single lens that has been conventionally compact and emphasizes portability or Many are composed of two lenses.
On the other hand, since these imaging lenses are required to have high optical performance as compared with the conventional lenses, it is difficult to obtain sufficient optical performance with one or two lenses. Therefore, development of an imaging lens having a three-lens configuration with an increased number of lenses is underway (see, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

JP-A-4-153612 Japanese Patent Laid-Open No. 5-188284 Japanese Patent Laid-Open No. 9-288235 Japanese Patent Laid-Open No. 10-48516

  However, the imaging lenses disclosed in Patent Documents 1 to 3 use a high-refractive index glass lens having a refractive index of 1.7 or more, which increases the cost. Further, the imaging lens disclosed in Patent Document 4 is not sufficient in terms of miniaturization because the power of the first lens is small.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to use a resin material (plastic) that is easy to process, with a configuration of 3 elements in 3 groups, and the overall length of the lens is back focus. 3mm or less, F-number is about 2.8, the lens brightness is about 2.8, high optical performance can be secured for an image sensor of about 300,000 pixels, low cost, ultra-compact, single focus It is to provide an imaging lens.

The imaging lens of the present invention includes, in order from the object side to the image plane side, a first lens having a positive refractive index, an aperture stop having a predetermined aperture, a meniscus having a positive refractive index and a concave shape on the object side. A second lens having a shape, and a third lens having a negative refractive index and having a concave surface on the image surface side in the vicinity of the optical axis and a convex shape on the image surface side toward the periphery. The first lens, the second lens, and the third lens are all made of a resin material, both the object side and the image side are both aspheric, and the Abbe number of the first lens is When ν1, the Abbe number of the second lens is ν2, and the Abbe number of the third lens is ν3, the following conditional expressions (1), (2), (3)
(1) | ν1-ν2 | <20
(2) | ν2-ν3 | <20
(3) | ν1-ν3 | <20
It is characterized by satisfying.

According to this configuration, since all of the first lens to the third lens are formed of a resin material (plastic), a complicated shape can be easily processed as compared with a glass lens (for example, an aspheric surface can be easily formed). ), A compact configuration can be achieved as much as the degree of freedom of aberration correction is increased, and weight reduction and cost reduction can be achieved. Moreover, the production cost can be further reduced by satisfying conditional expressions (1), (2), and (3).
In addition, since both the object side and the image plane side of the first lens to the third lens are all aspherical surfaces, it is possible to reduce spherical aberration, astigmatism, coma aberration, etc. while achieving thinning in the optical axis direction. Aberrations can be corrected well, and high optical performance can be obtained. In other words, in order to obtain the same optical performance with a spherical shape, the third lens requires two or more lenses, which makes it difficult to reduce the thickness. However, the reduction in thickness is achieved by making both surfaces aspherical. In addition, various aberrations can be corrected while mainly correcting coma aberration on the upper ray side. In addition, by making the both surfaces of the first lens and the second lens aspherical surfaces, it is possible to correct various aberrations such as spherical aberration, astigmatism, and coma aberration that occur when the total length of the lens is short while achieving thinning. can do.
Further, in the third lens, the image surface side surface is formed in a concave shape on the image surface side in the vicinity of the optical axis and is formed in a convex shape on the image surface side toward the peripheral portion. In addition, the outer diameter can be reduced, and the lens can be reduced in size.

In the above configuration, the Abbe number ν1 of the first lens, the Abbe number ν2 of the second lens, and the Abbe number ν3 of the third lens are the following conditional expressions (4), (5), (6)
(4) 30 <ν1 <60
(5) 30 <ν2 <60
(6) 30 <ν3 <60
A configuration that satisfies the above can be adopted.
According to this configuration, as the first lens to the third lens, by using a lens made of a material whose Abbe numbers ν1, ν2, and ν3 are in the range of 30 to 60, the degree of freedom in selecting a plastic material is increased.

In the above configuration, when the focal length of the first lens is f1, the focal length of the entire lens system is f, and the distance from the object side surface of the first lens to the image plane is TL, the following conditional expressions (7), ( 8)
(7) 0.95 <f1 / f <1.05
(8) TL / f <1.35
A configuration that satisfies the above can be adopted.
According to this configuration, it is possible to achieve shortening and downsizing of the entire lens while ensuring telecentricity, and it is possible to satisfactorily correct various aberrations, particularly distortion.

In the above configuration, when the distance on the optical axis from the image side surface of the third lens to the image plane is D7 and the focal length of the entire lens system is f, the following conditional expression (9)
(9) 2.05 <f / D7 <2.17
A configuration that satisfies the above can be adopted.
According to this configuration, it is possible to satisfactorily correct various aberrations, particularly distortion, while ensuring the back focus necessary for a camera lens including an image sensor such as a CCD.

In the above configuration, when the distance on the optical axis from the aperture stop to the object side surface of the third lens is D3 and the focal length of the entire lens system is f, the following conditional expression (10)
(10) f / D3> 5.2
A configuration that satisfies the above can be adopted.
According to this configuration, the overall lens length can be shortened, and various aberrations, particularly astigmatism and distortion can be favorably corrected while achieving a reduction in thickness and size.

  According to the imaging lens having the above-described configuration, it is a configuration of 3 elements in 3 groups, particularly, the total length of the lens is 3 mm or less without including the back focus, the lens brightness with an F number of about 2.8, and 300,000 pixels. A high optical performance suitable for an image sensor of a certain degree can be ensured, and a lightweight, small, thin, and inexpensive imaging lens can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
1 and 2 show an embodiment of an imaging lens according to the present invention. FIG. 1 is a schematic configuration diagram, and FIG. 2 is an optical path diagram.
As shown in FIG. 1, the imaging lens includes, in order from the object side to the image plane side, a first lens 1 having a positive refractive index, an aperture stop SD having a predetermined aperture, and a first lens having a positive refractive index. It is formed by two lenses 2 and a third lens 3 having negative refractive power. An image plane P is disposed behind the third lens 3.

  Here, in the configuration in which the first lens 1, the aperture stop SD, the second lens 2, the third lens 3, and the image plane P are sequentially arranged along the optical axis L from the object side to the image plane side. As shown in FIG. 1, each surface is Si (i = 1-7), the radius of curvature of each surface Si is Ri (i = 1-7), and the refractive index with respect to the d-line is Ni (i = 1-3). The Abbe number is represented by νi (i = 1 to 3), and the distance (thickness, air spacing) on each optical axis L from the first lens 1 to the image plane P is represented by Di (i = 1 to 7). Further, the focal length of the first lens 1 is denoted by f1, the focal length of the entire lens system is denoted by f, and the distance from the first lens 1 (the object-side surface S1) to the image plane P is denoted by TL.

The first lens 1 is a meniscus plastic lens formed of a resin material and having a positive refractive power and an object-side surface S1 having a convex shape and an image-side surface S2 having a concave shape. Further, both the object side and image side S1 and S2 are formed as aspherical surfaces.
The second lens 2 is a meniscus plastic lens formed of a resin material and having a positive refractive power, the object side surface S4 being concave and the image side surface S5 being convex. Both the object side and image surface side surfaces S4 and S5 are formed as aspherical surfaces.
The third lens 3 is formed of a resin material, and the object-side surface S6 is convex in the vicinity of the optical axis L so as to have a negative refractive index. It is a plastic lens formed such that the side surface S7 is concave in the vicinity of the optical axis L and convex toward the periphery. In addition, both the object side and the image surface side S6 and S7 are formed as aspherical surfaces.

  Thus, since all of the first lens 1 to the third lens 3 are formed of a resin material (plastic), a complicated shape can be easily processed as compared with a glass lens, for example, an aspherical surface can be easily formed. Thus, a compact configuration can be achieved as much as the degree of freedom of aberration correction is increased, and weight reduction and cost reduction can be achieved.

In addition, the object side and image plane side surfaces S1, S2, S4, S5, S6, and S7 of the first lens 1 to the third lens 3 are all aspherical, thereby achieving a reduction in the thickness in the optical axis direction L. On the other hand, various aberrations such as spherical aberration, astigmatism and coma can be corrected well, and high optical performance can be secured.
That is, by making both surfaces S1, S2 of the first lens 1 and both surfaces S4, S5 of the second lens 2 aspherical, while achieving a reduction in thickness and shortening the total lens length TL, spherical aberration and astigmatism. Various aberrations such as coma can be corrected. Further, in the third lens 3, it is difficult to reduce the thickness because two or more lenses are required to obtain the same optical performance with a spherical shape. However, by making both surfaces S6 and S7 aspherical. In addition to achieving a reduction in thickness, various aberrations can be corrected while correcting mainly the coma aberration on the upper ray side.
Further, in the third lens 3, the surface S7 on the image plane side is formed to be concave on the image plane side in the vicinity of the optical axis L and to be convex on the image plane side toward the periphery. The injection angle and the outer diameter can be reduced, and the lens can be miniaturized.

Here, the expression representing the aspheric surfaces of the first lens 1 to the third lens 3 is defined by the following expression.
Z = Cy ² / [1+ (1-εC ² y ² ) ^1/2 ] + Dy ⁴ + Ey ⁶ + Fy ⁸ + Gy ¹⁰ + Hy ¹²
Where Z: distance from the tangent plane at the apex of the aspheric surface to a point on the aspheric surface whose height from the optical axis L is y, y: height from the optical axis, C: curvature at the apex of the aspheric surface ( 1 / R), ε: conic constant, D, E, F, G, H: aspheric coefficients.

The Abbe number ν1 of the first lens 1, the Abbe number ν2 of the second lens 2, and the Abbe number ν3 of the third lens 3 are the following conditional expressions (1), (2), (3)
(1) | ν1-ν2 | <20
(2) | ν2-ν3 | <20
(3) | ν1-ν3 | <20
It is formed to satisfy.
Thus, by satisfying the conditional expressions (1), (2), and (3), the resin material approximated as the material of the first lens 1, the second lens 2, and the third lens 3 is used to produce The cost can be reduced, and the production cost can be further reduced when resin materials having the same Abbe number are used.

Here, in the above configuration, the Abbe number ν1 of the first lens 1, the Abbe number ν2 of the second lens 2, and the Abbe number ν3 of the third lens 3 are preferably the following conditional expressions (4), (5 ), (6)
(4) 30 <ν1 <60
(5) 30 <ν2 <60
(6) 30 <ν3 <60
It may be formed so as to satisfy
Thus, by satisfying the conditional expressions (4), (5), (6), the first lens 1 to the third lens 3 can be made of materials whose Abbe numbers ν1, ν2, ν3 are in the range of 30-60. Since a lens is used, the degree of freedom in selecting a plastic material is increased, and specifications according to requirements can be appropriately selected.

In the above configuration, the focal length f1 of the first lens 1, the focal length f of the entire lens system, and the distance TL from the object-side surface S1 of the first lens 1 to the image plane P are preferably as follows. Formula (7), (8)
(7) 0.95 <f1 / f <1.05
(8) TL / f <1.35
It may be formed so as to satisfy
Conditional expression (7) relates to the focal length of the first lens 1. If the value of f1 / f is greater than or equal to the upper limit value of conditional expression (7), the power of the first lens 1 becomes too small to make correction of field curvature difficult, and the exit angle becomes large and telecentricity deteriorates. Therefore, it is not preferable. On the other hand, if the value of f1 / f is less than or equal to the lower limit value of conditional expression (7), the power of the first lens 1 is increased and it becomes difficult to correct curvature of field.
Conditional expression (8) defines the total lens length TL. If the value of TL deviates from this range, it is impossible to maintain a reduction in thickness and size, and balance with aberration correction cannot be achieved.
Therefore, by satisfying conditional expressions (7) and (8), it is possible to achieve shortening and downsizing of the entire lens while ensuring telecentricity, and correct various aberrations, particularly distortion aberrations. can do.

In the above configuration, the distance D7 on the optical axis L from the image plane side surface S7 to the image plane P of the third lens 3 and the focal length f of the entire lens system are preferably the following conditional expression (9 )
(9) 2.05 <f / D7 <2.17
It may be formed so as to satisfy
Conditional expression (9) is a conditional expression for ensuring the back focus necessary for the CCD camera lens. When the value of f / D7 becomes equal to or greater than the lower limit value of conditional expression (9) and the back focus becomes long, the power of the first lens 1 needs to be reduced, and the generated negative distortion aberration increases. On the other hand, when the value of f / D7 becomes equal to or greater than the upper limit value of conditional expression (9) and the back focus is shortened, there is sufficient space for arranging an infrared cut filter, a pass filter, and the like necessary for the CCD camera lens. It will disappear.
Therefore, by satisfying conditional expression (9), it is possible to satisfactorily correct various aberrations, particularly distortion, while ensuring the back focus necessary for a camera lens including an image sensor such as a CCD.

Furthermore, in the above configuration, the distance D3 on the optical axis L from the aperture stop SD to the object-side surface S6 of the third lens 3 is preferably the following conditional expression (10):
(10) f / D3> 5.2
It may be formed so as to satisfy
Conditional expression (10) defines an appropriate lens interval in the optical axis direction L between the aperture stop SD and the third lens 3. If the value of f / D3 deviates from the conditional expression (10), the distance to the exit pupil becomes long and the angle of the light ray incident on the image sensor becomes small, so that the telecentricity is good, but the total lens length becomes longer compared with the first. The outer diameter of the three lenses 3 is increased, which is not preferable in terms of thinning and size reduction, and correction of astigmatism and distortion is particularly difficult.
Therefore, by satisfying conditional expression (10), it is possible to satisfactorily correct various aberrations, particularly astigmatism and distortion, while achieving a reduction in thickness and size.

  Next, specific numerical examples of the imaging lens will be described below as Example 1 and Example 2.

Numerical data of conditional expressions (1) to (10) in the first embodiment, main specifications of the first lens 1 to the third lens 3, and various numerical data (setting values) are as follows.
<Value of conditional expression>
(1) | ν1-ν2 | = 0
(2) | ν2-ν3 | = 0
(3) | ν1-ν3 | = 0
(4) ν1 = 56.3
(5) ν2 = 56.3
(6) ν3 = 56.3
(7) f1 / f = 2.99 / 3.05 = 0.98
(8) TL / f = 4.09 / 3.05 = 1.34
(9) f / D7 = 3.05 / 1.42 = 2.16
(10) f / D3 = 3.05 / 0.52 = 5.86

<Specification specifications>
Object distance = 60 cm, focal length (f) = 3.05 mm, F number = 2.8, exit pupil position = 3.08 mm, total lens length (TL) = 2.67 mm, back focus (air conversion) = 1.42 mm , Angle of view (2ω) = 59.6 °, distortion (maximum value) = 0.7%
<Curvature radius (aspheric surface)>
R1 = 1.405 mm, R2 = 10.688 mm, R3 = ∞, R4 = −0.733 mm, R5 = −0.668 mm, R6 = 10.309 mm, R7 = 1.920 mm
<Spacing on the optical axis>
D1 = 0.723 mm, D2 = 0.03 mm, D3 = 0.521 mm, D4 = 0.653 mm, D5 = 0.1 mm, D6 = 0.649 mm, D7 = 1.415 mm
<Refractive index (Nd)>
N1 = 1.525120, N2 = 1.525120, N3 = 1.525120
<Abbe number (νd)>
ν1 = 56.3, ν2 = 56.3, ν3 = 56.3

<Numerical data of aspheric coefficient>
<S1 surface>
ε = 1.569750, D = −0.027411, E = −0.015690, F = 3.128559 × 10 ⁻³ , G = −0.082494, H = 0.0
<S2 surface>
ε = 0.0, D = −0.046949, E = −0.039756, F = −0.298975, G = 0.468340, H = 0.0
<S4 surface>
ε = 1.155032, D = 0.132550, E = −0.741721, F = 2.638360, G = 2.38630, H = 0.0
<S5 surface>
ε = 0.205194, D = 0.223262, E = −0.602969, F = 0.343112, G = 1.132828, H = −0.914784
<S6 surface>
ε = 83.027704, D = −0.145034, E = −0.152657, F = 0.28520, G = −0.144927, H = 0.0
<S7 surface>
ε = -20.178419, D = -0.175560, E = 0.047230, F = -6.30438 × 10 ⁻³ , G = −2.11672 × 10 ⁻³ , H = 0.0

The aberration diagram regarding the spherical aberration, astigmatism, distortion (distortion) and lateral chromatic aberration in Example 1 is as shown in FIG. In FIG. 3, S represents the aberration on the sagittal plane, and M represents the aberration on the meridional plane.
According to the lens specifications according to Example 1, the lens has a total lens length (TL) of 2.67 mm and an F number of 2.8, and spherical aberration, astigmatism, distortion, and lateral chromatic aberration are corrected well. In addition, a thin and small imaging lens with high optical performance can be obtained.

Numerical data of conditional expressions (1) to (10) in the second embodiment, main specification specifications of the first lens 1 to the third lens 3, and various numerical data (setting values) are as follows.
<Value of conditional expression>
(1) | ν1-ν2 | = 0
(2) | ν2-ν3 | = 0
(3) | ν1-ν3 | = 0
(4) ν1 = 30.3
(5) ν2 = 30.3
(6) ν3 = 30.3
(7) f1 / f = 3.00 / 2.94 = 1.02
(8) TL / f = 3.96 / 2.94 = 1.34
(9) f / D7 = 2.94 / 1.43 = 2.06
(10) f / D3 = 2.94 / 0.56 = 5.25

<Specification specifications>
Object distance = 60 cm, focal length (f) = 2.94 mm, F number = 2.8, exit pupil position = 3.06 mm, total lens length (TL) = 2.53 mm, back focus (air equivalent) = 1.43 mm , Angle of view (2ω) = 61.2 °, distortion (maximum value) = 1.3%
<Curvature radius (aspheric surface)>
R1 = 1.473 mm, R2 = 7.756 mm, R3 = ∞, R4 = −0.751 mm, R5 = −0.669 mm, R6 = 6.572 mm, R7 = 1.609 mm
<Spacing on the optical axis>
D1 = 0.631 mm, D2 = 0.02 mm, D3 = 0.558 mm, D4 = 0.648 mm, D5 = 0.15 mm, D6 = 0.526 mm, D7 = 1.427 mm
<Refractive index (Nd)>
N1 = 1.58816, N2 = 1.58816, N3 = 1.58816
<Abbe number (νd)>
ν1 = 30.3, ν2 = 30.3, ν3 = 30.3

<Numerical data of aspheric coefficient>
<S1 surface>
ε = 1.861270, D = −0.041055, E = −3.81910 × 10 ⁻³ , F = −0.050460, G = −0.071008, H = 0.0
<S2 surface>
ε = −29.0, D = −0.031846, E = −0.077220, F = −0.206572, G = 0.274801, H = 0.0
<S4 surface>
ε = 1.173842, D = 0.144696, E = −0.857322, F = 2.984905, G = 1.23926, H = 0.0
<S5 surface>
ε = 0.177073, D = 0.249530, E = -0.571912, F = 0.247541, G = 1.029140, H = -0.790010
<S6 surface>
ε = −49.0, D = −0.137607, E = −0.142134, F = 0.288550, G = −0.150011, H = 0.0
<S7 surface>
ε = −15.864269, D = −0.1966603, E = 0.061710, F = −3.990309 × 10 ⁻³ , G = −5.99701 × 10 ⁻³ , H = 0.0

The aberration diagram regarding the spherical aberration, astigmatism, distortion (distortion) and lateral chromatic aberration in Example 2 is as shown in FIG. In FIG. 4, S represents the aberration on the sagittal plane, and M represents the aberration on the meridional plane.
According to the lens specifications according to the second embodiment, the lens has a total lens length (TL) of 2.53 mm, an F number of 2.8, and spherical aberration, astigmatism, distortion, and lateral chromatic aberration are well corrected. In addition, a thin and small imaging lens with high optical performance can be obtained.

  As described above, since the imaging lens of the present invention can ensure high optical performance that can correspond to an imaging element of about 300,000 pixels with a small size and a thin shape, a digital still camera, an in-vehicle camera, a portable information terminal ( It can be applied as an imaging lens for a mobile camera of a mobile phone, a PDA, a portable personal computer, etc., and is also useful as an imaging lens for a fixed camera or a camera used for other purposes. is there.

It is a schematic block diagram which shows one Embodiment of the imaging lens which concerns on this invention. FIG. 2 is an optical path diagram of the imaging lens shown in FIG. 1. FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration in Example 1. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration in Example 2.

Explanation of symbols

L optical axis TL total lens length f focal length f1 of entire lens system first focal length 1 first lens 2 second lens 3 third lens SD aperture stop P image plane ν1 Abbe number ν1 of first lens ν2 of second lens Abbe number ν3 Abbe number D3 of the third lens Distance on the optical axis from the aperture stop to the object side surface of the third lens D7 Distance on the optical axis from the image side surface of the third lens to the image plane

Claims (5)

In order from the object side to the image surface side, a first lens having a positive refractive index, an aperture stop having a predetermined aperture, a second meniscus lens having a positive refractive index and concave on the object side, negative A third lens that has a refractive index of 2 and a concave surface on the image surface side in the vicinity of the optical axis and a convex shape on the image surface side toward the periphery,
The first lens, the second lens, and the third lens are all made of a resin material, both the object side and the image side are both aspherical, and the Abbe number of the first lens is ν1. An imaging lens satisfying the following conditional expressions (1), (2), and (3) when the Abbe number of the second lens is ν2 and the Abbe number of the third lens is ν3.
(1) | ν1-ν2 | <20
(2) | ν2-ν3 | <20
(3) | ν1-ν3 | <20 The Abbe number ν1 of the first lens, the Abbe number ν2 of the second lens, and the Abbe number ν3 of the third lens satisfy the following conditional expressions (4), (5), and (6). The imaging lens according to claim 1.
(4) 30 <ν1 <60
(5) 30 <ν2 <60
(6) 30 <ν3 <60 When the focal length of the first lens is f1, the focal length of the entire lens system is f, and the distance from the object side surface of the first lens to the image plane is TL, the following conditional expressions (7) and (8) The imaging lens according to claim 1, wherein:
(7) 0.95 <f1 / f <1.05
(8) TL / f <1.35 The following conditional expression (9) is satisfied, where D7 is the distance on the optical axis from the image plane side surface of the third lens to the image plane, and f is the focal length of the entire lens system. The imaging lens according to any one of 1 to 3.
(9) 2.05 <f / D7 <2.17 The following conditional expression (10) is satisfied, where D3 is the distance on the optical axis from the aperture stop to the object side surface of the third lens, and f is the focal length of the entire lens system. The imaging lens according to any one of 1 to 4.
(10) f / D3> 5.2

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