JP2000321489A - Image pickup lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup lens capable of maintaining desired optical performance, properly setting the power of a 1st lens and the power of a 2nd lens while a large back focus distance is secured, and being easily manufactured. SOLUTION: This image pickup lens is composed of a 1st lens consisting of a concave lens and a 2nd lens 2 consisting of a convex lens. The 1st surface of the 1st lens 1 is made aspherical, the value of the focal length of the 2nd lens 2 to the total focal length is 1.0 to 1.2, the surface interval between the 1st lens 1 and 2nd lens 2 is 0.5 to 1 time the focal length of the whole lens system, and the focal length of the 2nd lens is 0.25 to 0.9 time the focal length of the 1st lens 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an imaging lens,
In particular, it is used for an image pickup device (for example, a CCD camera) using an image pickup device such as a CCD or a CMOS mounted on a portable computer or a videophone, etc. It relates to an imaging lens.

[0002]

2. Description of the Related Art In recent years, the progress of multimedia has been remarkable,
For example, the demand for a camera using an image pickup device such as a CCD or a CMOS for mounting on a portable computer, a videophone or the like, for example, a CCD camera has been remarkably increased. Since such a CCD camera needs to be mounted in a limited installation space, it is desired that the CCD camera be small and lightweight.

[0003] Therefore, the imaging lens used in such a CCD camera is also required to be small and lightweight.

Conventionally, a two-lens system using two lenses has been used as such an imaging lens.

[0005] Such a conventional two-lens lens system imaging lens is disclosed in, for example, JP-A-10-104511 and JP-B-7-50246.

In the imaging lens disclosed in each of these publications, a first lens and a second lens are sequentially arranged from the object side, and the first lens is provided with a central radius of curvature of the first surface and the second surface. A concave meniscus lens having the same sign is used, and the second lens is a convex lens. With such a configuration, it is possible to secure the back focus distance while shortening the focal length.

[0007]

However, in the conventional imaging lens disclosed in Japanese Patent Application Laid-Open No. 10-104511, the radius of center curvature of the second surface of the first lens is relatively small. Therefore, there is a problem that the production becomes extremely difficult. Also, if an attempt is made to dispose a stop closer to the image plane side than the second lens in order to correct the chromatic aberration of magnification, the diameter of the first lens becomes large, and the first lens becomes large.
There is also a problem that the manufacture of the second surface of the lens becomes more difficult. Further, in this conventional imaging lens, it is difficult to manufacture the second surface of the first lens, and therefore, there is also a problem that it is hardly possible to cope with a wide angle (short focus) of the imaging lens. .

Further, the imaging lens disclosed in Japanese Patent Publication No. 7-50246 has a fatal problem that the entire length of the optical system of the lens becomes long due to its structure. In the case of an optical system having such a configuration,
When stray light enters the lens system of the imaging lens from outside the angle of view, a ghost occurs. Therefore, the shape of the first surface of the first lens near the optical axis is required to be close to a plane. However, if an attempt is made to arrange the stop on the image plane side with respect to the second lens, the diameter of the first lens becomes large,
Increasing the diameter of the first lens leads to a convex shape of the first surface of the first lens, which also has a problem that the performance of the imaging lens is reduced. In addition, the power of the first lens is greatly related to the occurrence of each aberration such as distortion, and when the first surface of the first lens has an extremely convex shape, distortion and the like can be eliminated. It has the problem of disappearing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and appropriately sets the powers of a first lens and a second lens while maintaining a desired optical performance and a large back focus distance. It is an object of the present invention to provide an imaging lens which can be manufactured easily.

[0010]

According to a first aspect of the present invention, there is provided an imaging lens comprising a first lens comprising a concave lens and a second lens comprising a convex lens. The first surface of the lens is formed in an aspherical shape, and (1) 1.0 ≦ f ₂ /fl≦1.2 (2) 0.5 fl <D ₂ <fl (3) 0.25 <| f ₂ | / | F ₁ | <0.9 where fl: focal length of the entire lens system f ₁ : focal length of the first lens f ₂ : focal length of the second lens D ₂ : surface of the first and second lenses It is characterized by satisfying the condition of interval.

According to the first aspect of the present invention, the equations (1), (2) and (3) are obtained while maintaining a desired optical performance and a large back focus distance. This is a condition for appropriately setting the powers of the first lens and the second lens, and is a condition represented by Expression (1).
In this case, if f ₂ / fl is smaller than 1.0, the second lens becomes a convex lens having a strong power, and the center radius of curvature of the second surface of the second lens tends to be small. This leads to deterioration of various aberrations. When the value of f ₂ / fl exceeds 1.2, the distance between the first lens and the second lens is increased in order to obtain a desired focal length. I will. Further, when the distance between the first lens and the second lens is increased as described above, the effective diameter of the second surface of the first lens increases, so that the depth of the concave surface of the second surface (the depth in the optical axis direction) )
Becomes large, making the production difficult. Equation (2)
In the case D ₂ is less than 0.5Fl, lens interval becomes too narrow, short focusing That is, it is impossible to properly correspond to the wide angle. Further, when D ₂ is fl or more, it is impossible to reduce the size of the entire optical system, and the first lens is increased in size, and it is difficult to manufacture the second surface of the first lens. Further, in equation (3), | f ₂
When | / | f ₁ | is 0.25 or less, a large back focus distance cannot be secured, and various filters such as a low-pass filter cannot be inserted. Also, | f ₂ | / | f ₁
Is 0.9 or more, the power of the first lens is too strong, making it difficult to manufacture the first lens, and furthermore, distortion is likely to occur.

In the present invention, by satisfying the conditions of the above equations, the desired optical performance is maintained, and the power of the first lens and the second lens is appropriately set while the back focus distance is kept large. And each lens can be easily manufactured. In particular, even when the stop for correcting the chromatic aberration of magnification is arranged closer to the image side than the second lens, the first lens can be easily manufactured, and the diameter of the first lens can be increased. Alternatively, it is possible to easily cope with a wide angle.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the basic structure of an image pickup lens according to the present invention, which comprises a first lens 1 composed of a concave lens and a second lens 2 composed of a convex lens.
At least the first surface of the lens 1 and the second lens 2 located on the object side of the first lens 1 is formed in an aspherical shape. Each of the first lens 1 and the second lens 2
Satisfies the following conditions.

(1) 1.0 ≦ f ₂ /fl≦1.2 (2) 0.5 fl <D ₂ <fl (3) 0.25 <| f ₂ | / | f ₁ | <0.9 , Fl is the focal length of the entire lens system, f ₁ is the focal length of the first lens 1, f ₂ is the focal length of the second lens 2, D ₂
Is the surface distance between the first lens 1 and the second lens 2.

Further, on the second surface side of the first lens 1 and the second surface side of the second lens 2, a light amount limiting plate 3 is provided.
And a diaphragm 4 are provided, respectively, and the second lens 2
On the second surface side, a cover glass 5 and a CCD substrate 6 on which a CCD as an image sensor is mounted are sequentially disposed.

The light amount limiting plate 3 and the stop 4 are not always required, and an optical system can be configured without disposing them. However, it is more desirable to configure the optical system by arranging the stop 4 at an appropriate position.

The first lens 1 may be a concave lens having concave surfaces on both sides or a concave lens having a meniscus shape. Further, the second lens 2 may be a convex lens having convex surfaces on both sides or a convex lens having a meniscus shape. Further, the diaphragm 4 may be arranged on the first surface side of the second lens 2.

In this embodiment, equations (1) and (2)
And equation (3) are conditions for maintaining the desired optical performance and properly setting the powers of the first lens 1 and the second lens 2 with a large back focus distance secured. .

In the formula (1), when f ₂ / fl is smaller than 1.0, the second lens 2 becomes a convex lens having a high power, and the radius of curvature of the center of the second surface of the second lens 2 becomes small. Is difficult, and various aberrations are worsened. When the value of f ₂ / fl exceeds 1.2,
Since the distance between the first lens 1 and the second lens 2 is increased,
If the entire optical system is enlarged and the distance between the first lens 1 and the second lens 2 is increased, the first
It is necessary to reduce the radius of curvature of the center of the second surface of the lens 1, which makes the manufacturing difficult.

In the equation (2), D ₂ is 0.5f
If it is less than 1, the lens interval becomes too narrow, and it is not possible to properly cope with short focus, that is, wide angle. Further, D ₂ is not less than fl, can not reduce the size of the entire optical system, moreover, the first lens 1 becomes difficult to produce large.

Further, in equation (3), | f ₂ | / | f
_{When 1} | is 0.25 or less, a large back focus distance cannot be secured, and various filters such as a low-pass filter cannot be inserted. When | f ₂ | / | f ₁ | is 0.9 or more, the power of the first lens 1 is too strong, so that it is difficult to manufacture the first lens 1 and further, distortion is likely to occur.

In the present embodiment, by satisfying the conditions of the above equations, the desired optical performance is maintained, and the power of the first lens 1 and the second lens 2 is reduced while the back focus distance is kept large. It can be set appropriately and each lens can be easily manufactured. In particular, the diaphragm 4 for correcting chromatic aberration is connected to the second lens 2.
Even when the first lens 1 is disposed on the image side, the first lens 1 can be easily manufactured.
It is possible to easily cope with enlargement of the diameter or wide angle.

The optical system according to the present embodiment is extremely suitable for a wide-angle optical system having a diagonal length of an image plane of 10 mm or less and a diagonal angle of view of about 50 to 100 °.

[0025]

FIG. 2 to FIG. 1 show an embodiment of the present invention.
This will be described with reference to FIG.

[0026] In the present embodiment, fl is the focal length of the entire system, f ₁ is the focal length of the first lens 1, f ₂ is the second
Focal length of lens 2, Bf is back focus distance, F
Is the F number, 2ω is the angle of view, D ₂ is the first lens 1 and the second
The surface spacing with the lens 2, r is the radius of curvature of the lens or the like, d is the lens thickness or air spacing, and nd is the refractive index.

The shape of the aspherical surface of the lens has a Z axis in the optical axis direction and an X axis in a direction perpendicular to the optical axis, the light traveling direction is positive, and k, a, b, c, and d are non-spherical. When the spherical coefficient is used, it is expressed by the following equation.

[0028] <Embodiment 1> FIG. 2 shows a first embodiment of the present invention. In this embodiment, an image pickup lens having the structure shown in FIG. Aperture 4 on side
Is arranged. In this embodiment, the light amount limiting plate 3 is disposed between the first lens 1 and the second lens 2, but this is not always required. The imaging lens of the first embodiment is set under the following conditions.

The back focus distance Bf in this embodiment is an air-equivalent distance from the diaphragm 4 to the CCD surface (image pickup surface).

Fl = 3.825 mm, F = 2.80, 2ω = 60.9 °, D ₂ = 3.15 mm, f ₁ = −5.77 mm, f ₂ = 3.91 mm, Bf = 6.384 mm Surface Curvature radius r Distance d Refractive index nd Abbe number νd 1 (first lens first surface) -17.000 1.1500 1.49405 57.8 2 (first lens second surface) 3.500 3.1500 3 (light quantity limiting plate) 0.000 0.0000 4 (second lens) 1st surface) 14.558 1.2500 1.49405 57.8 5 (2nd lens 2nd surface) -2.161 0.0000 6 (aperture) 0.000 0.1000 7 (cover glass 1st surface) 0.000 1.9500 1.51633 64.28 (2nd cover glass surface) 0.000 4.9983 9 ( CCD surface) 0.000 kab 1 -1.301171e + 003 2.716762e-002 -2.112726e-003 2 5.048659e + 000 6.977649e-002 -1.395315e-002 4 2.597277e + 001 -4.310376e-003 9.984627e-004 5 -4.812487e-001 4.041928e-003 7.702718e-004 cd 1 1.698224e-004 0.000000e + 000 2 1.031676e-002 0.000000e + 000 4 0.000000e +000 0.000000e + 000 5 0.000000e + 000 0.000000e + 000 Under such conditions, f ₂ /fl=1.022 was achieved, thereby satisfying the expression (1).

D ₂ /fl=0.824 was achieved, thereby satisfying the expression (2).

| F ₂ | / | f ₁ | = 0.678 was achieved, thereby satisfying the expression (3).

FIG. 3 shows the results of measuring the spherical aberration, astigmatism, and distortion of the imaging lens of Example 1.

According to the measurement results, each of the spherical aberration, astigmatism, and distortion is a substantially satisfactory value, and it can be seen that sufficient optical characteristics can be obtained.

<Embodiment 2> FIG. 4 shows a second embodiment of the present invention. In this embodiment, an aperture 4 is arranged between a first lens 1 and a second lens 2. is there. The imaging lens of the second embodiment is set under the following conditions.

Note that the back focus distance Bf in the present embodiment is an air-equivalent distance from the second surface of the second lens 2 to the CCD surface (imaging surface).

Fl = 3.828 mm, F = 2.80, 2ω = 61.0 °, D ₂ = 3.50 mm, f ₁ = −5.18 mm, f ₂ = 4.17 mm, Bf = 7.251 mm Surface Curvature radius r Distance d Refractive index nd Abbe number νd 1 (first lens first surface) -15.000 1.0000 1.49405 57.8 2 (first lens second surface) 3.150 3.4300 3 (aperture) 0.000 0.0000 4 (second lens first) Surface) -400.000 1.5000 1.49405 57.8 5 (second lens second surface) -2.050 0.0000 6 (cover glass first surface) 0.000 1.9500 1.51633 64.2 7 (cover glass second surface) 0.000 5.9660 8 (CCD surface) 0.000 kab 1 -7.590375e + 002 3.075588e-002 -3.226287e-003 2 3.621909e + 000 6.235259e-002 -2.439978e-003 4 1.032651e + 005 -1.196471e-002 -5.057308e-003 5 1.859306e-001 7.683247 e-003 1.872035e-003 cd 1 2.379159e-004 0.000000e + 000 2 2.390750e-003 0.000000e + 000 4 0.000000e + 000 0.000000e + 000 5 0.000000e + 000 0.000000e + 000 Under such conditions, f ₂ /fl=1.089 was achieved, thereby satisfying the expression (1).

D ₂ /fl=0.914 was achieved, thereby satisfying the expression (2).

| F ₂ | / | f ₁ | = 0.805 was achieved, thereby satisfying the expression (3).

FIG. 5 shows the measurement results of the spherical aberration, astigmatism, and distortion of the imaging lens of the second embodiment.

According to the measurement results, each of the spherical aberration, astigmatism, and distortion is almost a satisfactory value, and it can be seen that sufficient optical characteristics can be obtained.

<Embodiment 3> FIG. 6 shows a third embodiment of the present invention. In this embodiment, a diaphragm 4 is arranged between a first lens 1 and a second lens 2. It is. The imaging lens of the third embodiment is set under the following conditions.

Note that the back focus distance Bf in the present embodiment is an air-equivalent distance from the second surface of the second lens 2 to the CCD surface (imaging surface).

Fl = 3.824 mm, F = 2.80, 2ω = 61.6 °, D ₂ = 3.15 mm, f ₁ = −8.19 mm, f ₂ = 3.91 mm, Bf = 5.629 mm Surface Curvature radius r Distance d Refractive index nd Abbe number νd 1 (first lens first surface) -16.331 1.1500 1.49405 57.8 2 (first lens second surface) 5.500 3.1500 3 (aperture) 0.000 0.0000 4 (second lens first surface) Surface) 15.227 1.2500 1.49405 57.8 5 (second lens second surface) -2.152 0.0000 6 (cover glass first surface) 0.000 1.9500 1.51633 64.2 7 (cover glass second surface) 0.000 4.3429 8 (CCD surface) 0.000 kab1 -1.867982e + 003 2.160295e-002 -1.722846e-003 2 1.106169e + 001 6.177410e-002 -1.689733e-002 4 -1.003437e + 002 -8.879210e-003 7.027934e-004 5 5.117326e-001 1.619541e -002 -3.115484e-003 cd 1 1.561908e-004 0.000000e + 000 2 6.649701e-003 0.000000e + 000 4 -3.170700e-003 0.000000e + 000 5 1.891826e-003 0.000000e + 000 Under such conditions, f ₂ /fl=1.022 was achieved, thereby satisfying the expression (1).

D ₂ /fl=0.824 was achieved, thereby satisfying the expression (2).

| F ₂ | / | f ₁ | = 0.577 was achieved, thereby satisfying the expression (3).

FIG. 7 shows the measurement results of the spherical aberration, astigmatism, and distortion of the imaging lens of the third embodiment.

According to the measurement results, each of the spherical aberration, astigmatism, and distortion is almost a satisfactory value, and it can be seen that sufficient optical characteristics can be obtained.

<Embodiment 4> FIG. 8 shows a fourth embodiment of the present invention. In this embodiment, a diaphragm 4 is arranged between a first lens 1 and a second lens 2. is there. The imaging lens of the fourth embodiment is set under the following conditions.

The back focus distance Bf in this embodiment is the air-equivalent distance from the second surface of the second lens 2 to the CCD surface (imaging surface).

Fl = 3.824 mm, F = 2.80, 2ω = 60.6 °, D ₂ = 3.50 mm, f ₁ = −6.49 mm, f ₂ = 3.90 mm, Bf = 6.083 mm Surface Curvature radius r Distance d Refractive index nd Abbe number νd 1 (first lens first surface) 12.000 1.1500 1.49405 57.8 2 (first lens second surface) 2.450 3.5000 3 (aperture) 0.000 0.0000 4 (second lens first surface) 13.592 1.2500 1.49405 57.8 5 (2nd lens second surface) -2.178 0.0000 6 (1st cover glass surface) 0.000 1.9500 1.51633 64.2 7 (2nd cover glass surface) 0.000 4.7974 8 (CCD surface) 0.000 kab 1 1.942014 e + 000 2.117529e-002 -1.282694e-003 2 1.779039e + 000 3.270540e-002 9.230374e-004 4 -5.236163e + 001 -3.888274e-003 -9.698204e-004 5 -5.067513e-002 8.864262e- 003 1.560999e-004 cd 1 1.674928e-004 0.000000e + 000 2 4.261772e-003 0.000000e + 000 4 0.000000e + 000 0.000000e + 000 5 0.000000e + 000 0. 000000e + 000 Under such conditions, f ₂ /fl=1.020 was achieved, thereby satisfying the expression (1).

D ₂ /fl=0.915 was achieved, thereby satisfying the expression (2).

| F ₂ | / | f ₁ | = 0.601 was achieved, thereby satisfying the expression (3).

FIG. 9 shows the measurement results of the spherical aberration, astigmatism, and distortion of the imaging lens of the fourth embodiment.

According to the measurement results, each of the spherical aberration, astigmatism, and distortion is almost a satisfactory value, and it can be seen that sufficient optical characteristics can be obtained.

<Embodiment 5> FIG. 10 shows a fifth embodiment of the present invention. In this embodiment, an aperture 4 is arranged between a first lens 1 and a second lens 2. is there. The imaging lens of the fifth embodiment is set under the following conditions.

The back focus distance Bf in the present embodiment is the air-equivalent distance from the second surface of the second lens 2 to the CCD surface (imaging surface).

Fl = 3.824 mm, F = 2.80, 2ω = 61.5 °, D ₂ = 3.40 mm, f ₁ = −6.71 mm, f ₂ = 4.03 mm, Bf = 6.334 mm Surface Curvature radius r Distance d Refractive index nd Abbe number νd 1 (first lens first surface) 100.000 1.0000 1.49405 57.8 2 (first lens second surface) 3.200 3.3300 3 (aperture) 0.000 0.0700 4 (second lens first surface) ) -190.000 1.5000 1.49405 57.8 5 (2nd lens 2nd surface) -1.975 0.0000 6 (1st cover glass surface) 0.000 1.9500 1.51633 64.2 7 (2nd cover glass surface) 0.000 5.0478 8 (CCD surface) 0.000 kab1 -1.012596e + 003 3.049228e-002 -2.915189e-003 2 3.410804e + 000 4.073944e-002 4.178761e-003 4 2.885193e + 004 -1.495966e-002 -6.789103e-003 5 1.366334e-001 8.741288e- 003 4.421911e-004 cd 1 2.556826e-004 0.000000e + 000 2 7.666546e-004 0.000000e + 000 4 0.000000e + 000 0.000000e + 000 5 0.000000e + 000 0.000000e + 000 Under such conditions, f ₂ /fl=1.054 was achieved, thereby satisfying the expression (1).

D ₂ /fl=0.889 was achieved, thereby satisfying the expression (2).

| F ₂ | / | f ₁ | = 0.601 was achieved, thereby satisfying the expression (3).

FIG. 11 shows the measurement results of the spherical aberration, astigmatism, and distortion of the imaging lens of the fifth embodiment.

According to the measurement results, all of the spherical aberration, astigmatism, and distortion are almost satisfactory values, and it can be seen that sufficient optical characteristics can be obtained.

<Embodiment 6> FIG. 12 shows a sixth embodiment of the present invention. In this embodiment, a stop 4 is arranged between a first lens 1 and a second lens 2. is there. The imaging lens of the sixth embodiment is set under the following conditions.

Note that the back focus distance Bf in the present embodiment is an air-equivalent distance from the second surface of the second lens 2 to the CCD surface (imaging surface).

Fl = 3.824 mm, F = 2.80, 2ω = 60.3 °, D ₂ = 3.15 mm, f ₁ = −8.19 mm, f ₂ = 4.05 mm, Bf = 6.082 mm Surface Curvature radius r Distance d Refractive index nd Abbe number νd 1 (first lens first surface) -30.674 1.5000 1.49405 57.8 2 (first lens second surface) 4.733 3.0500 3 (aperture) 0.000 0.1000 4 (second lens first surface) Surface) -17.411 1.7500 1.49405 57.8 5 (second lens second surface) -1.856 0.0000 6 (cover glass first surface) 0.000 1.9500 1.51633 64.2 7 (cover glass second surface) 0.000 4.6960 8 (CCD surface) 0.000 kab 1 -1.945808e + 003 1.529210e-002 -1.026370e-003 2 6.594317e + 000 3.257940e-002 -2.746300e-003 4 2.484845e + 002 -2.011230e-002 -4.706800e-003 5 -4.433800e-002 5.302160e-003 1.069550e-003 cd 1 7.185974e-005 -4.184540e-007 2 1.398160e-003 1.082900e-005 4 3.338890e-004 -2.432540e-004 5 -4.727260e- 004 1.835900e-005 Under such conditions, f ₂ /fl=1.059 was achieved, thereby satisfying the expression (1).

D ₂ /fl=0.824 was achieved, thereby satisfying the expression (2).

| F ₂ | / | f ₁ | = 0.495 was achieved, thereby satisfying the expression (3).

FIG. 13 shows the measurement results of the spherical aberration, astigmatism, and distortion of the imaging lens of the sixth embodiment.

According to the measurement results, each of the spherical aberration, astigmatism, and distortion is almost a satisfactory value, indicating that sufficient optical characteristics can be obtained.

The present invention is not limited to the above-described embodiment, but can be variously modified as needed.

[0071]

As described above, the imaging lens according to the first aspect of the invention maintains desired optical performance by satisfying the conditions of the expressions (1), (2) and (3). In addition, the power of the first lens and the second lens 2 can be appropriately set while the back focus distance is kept large, and each lens can be easily manufactured. In particular, even when the stop for correcting the chromatic aberration of magnification is arranged on the image side of the second lens 2, the first stop may be used.
The lens can be easily manufactured, and the first
This has the effect that it is possible to easily cope with an increase in the lens diameter or a wide angle.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram showing a first embodiment of the imaging lens of the present invention.

FIG. 3 is an explanatory diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of FIG. 2;

FIG. 4 is a schematic configuration diagram showing a second embodiment of the imaging lens of the present invention.

FIG. 5 is an explanatory diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of FIG. 4;

FIG. 6 is a schematic configuration diagram showing a third embodiment of the imaging lens of the present invention.

FIG. 7 is an explanatory diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of FIG. 6;

FIG. 8 is a schematic configuration diagram showing a fourth embodiment of the imaging lens of the present invention.

FIG. 9 is an explanatory diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of FIG. 8;

FIG. 10 is a schematic configuration diagram showing a fifth embodiment of the imaging lens of the present invention.

FIG. 11 is an explanatory diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of FIG. 10;

FIG. 12 is a schematic configuration diagram showing a sixth embodiment of the imaging lens of the present invention.

FIG. 13 is an explanatory diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of FIG. 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st lens 2 2nd lens 3 Light quantity limiting plate 4 Aperture 5 Cover glass 6 CCD board

Continued on the front page F term (reference) 2H087 KA03 LA03 PA02 PA17 PB02 QA02 QA03 QA07 QA17 QA19 QA21 QA32 QA34 QA42 RA05 RA12 RA13 RA35 RA42 UA01

Claims (1)

[Claims] 1. A first lens comprising a concave lens and a second lens comprising a convex lens, wherein at least the first lens
The first surface of the lens is formed in an aspherical shape, and (1) 1.0 ≦ f ₂ /fl≦1.2 (2) 0.5 fl <D ₂ <fl (3) 0.25 <| f ₂ | / | F ₁ | <0.9 where fl: focal length of the entire lens system f ₁ : focal length of the first lens f ₂ : focal length of the second lens D ₂ : surface of the first and second lenses An imaging lens characterized by satisfying a condition of a distance.