KR100791641B1 - Imaging lens - Google Patents

Abstract

Disclosed are an imaging lens in which the aberration is corrected well, and at the same time, the optical length is short and sufficient back focus is secured. The disclosed imaging lens has an aperture diaphragm S1, a first lens L1, a second lens L2, and a third lens L3, and has an aperture diaphragm, a first lens, and a second lens from an object side toward an image side. And a third lens. The first lens is a lens having positive refractive power toward the convex surface on the object side and the image side. The second lens is a lens having negative refractive power of a meniscus shape toward the convex surface toward the image side. The third lens is a lens having positive refractive power toward the convex surface on the object side and the image side. Both surfaces of the first lens are aspherical, at the same time both surfaces of the second lens are aspherical, and both surfaces of the third lens are aspheric.

Description

Imaging lens {IMAGING LENS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging lens, and more particularly, to an image input device, a digital camera, a surveillance CCD camera, an inspection device, or the like of a mobile phone or personal computer using a CCD (Charge Coupled Devices) or a CMOS (Complementary Metal Oxide Semiconductor) as an imaging device. An imaging lens suitable for mounting.

In the above-described imaging lens, the optical length defined by the distance from the object-side incident surface of the imaging lens to the imaging surface (image pickup surface such as CCD) must be short. That is, in lens design, a study is required to reduce the ratio of the optical length to the combined focal length of the imaging lens. Thereafter, an imaging lens having a short optical length and a small ratio of the optical length to the focal length is called a compact lens.

For example, in a cellular phone, at least this optical length should be shorter than the thickness of the cellular phone base. On the other hand, the back focus defined by the distance from the image emitting surface of the imaging lens to the imaging surface is preferably as long as possible. In other words, in the lens design, the ratio of the back focus to the focal length needs to be as large as possible. This is because it is necessary to insert a component such as a filter or cover glass between the imaging lens and the imaging surface.

In addition to the above, it is naturally required that as the imaging lens, distortion of the aberration image is not conscious of vision and corrected to a small enough extent as required from the integration density of the imaging device (also called pixels). It is necessary to correct the aberration well, and hereinafter, an image in which such aberration is well corrected is referred to as a "good image".

Disclosed below are three imaging lenses suitable for use in an imaging device using a solid-state imaging device such as a CCD and a CMOS, which are represented by a portable computer, a videophone, and the like. All of these lenses have a wide angle of view and can be miniaturized and lightweight.

Among them, an image pickup lens capable of obtaining an image in which aberrations are well corrected while ensuring a wide angle of view is disclosed as the first three-piece lens (see Patent Document 1, for example).

However, these three lens shapes arranged in sequence from the object side as the first, second and third lenses have a meniscus lens having a positive refractive power in which the first lens faces the front side toward the image side, and the second lens has an object. The meniscus lens which has negative refractive power toward the ear surface toward the side, and the 3rd lens are comprised by the lens which has positive refractive power, and it has a structure which optical length becomes too long with respect to the length of a back focus. As a result, it cannot be called a compact lens.

As the second to fourth three-component lenses, an imaging lens in which aberrations are well-corrected while securing a wide field of view and a short focus is disclosed, respectively (for example, Patent Document 2, Patent Document 3, See Patent Document 4).

The refractive power of these three lenses arranged in order from the object side in the same manner as the above-mentioned imaging lens in the same manner as the above-described imaging lens is that the first lens has positive refractive power, the second lens has negative refractive power, 3 The lens is positive refractive power. And although the combined focal length as the imaging lens is set short, the back focus is long and the optical length is too long with respect to the combined focal length. In addition, since the lens is made of glass material, the lens has a high cost.

As the fifth three-element lens, an aspherical lens is used, and a miniaturized imaging lens is disclosed by appropriately setting power distribution and planar shape (see Patent Document 5, for example).

However, this imaging lens has the refractive power of these three lenses arranged in order from the object side as the first, second and third lenses, such that the first lens has negative refractive power, the second lens has positive refractive power, and the third lens It has a configuration having negative refractive power, and as a result, it is an imaging lens having a long optical length with respect to the combined focal length. In addition, since the lens is made of glass material, the lens has a high cost.

As a sixth three-element lens, a pair of meniscus-shaped lenses facing each other in the rear surface are made of plastic lenses each having at least one aspherical surface, and the all-lens system is made of a three-lens configuration to reduce size and reduce cost. An image pickup lens capable of easily achieving a suppression of focus movement due to a temperature change while achieving the above is disclosed (see Patent Document 6, for example).

However, this imaging lens has the refractive powers of these three lenses arranged as the first, second and third lenses in order from the object side, respectively, the first lens has a weak refractive power, the second lens has a weak refractive power, and the third lens. Since the structure has a positive refractive power, the refractive power of the first lens and the second lens cannot be completely supplemented with only the third lens. As a result, the back focus for the combined focal length becomes long, and the optical length becomes long. Furthermore, since the third lens becomes a lens made of a glass material, low cost cannot be achieved.

As the seventh three-element lens, the whole lens system is divided into two groups, the front group has positive refractive power, and the rear group has a telephoto type with a lens structure having negative refractive power. (For example, refer patent document 7).

However, in this lens system, the refractive power of these three lenses arranged as the first, second and third lenses in order from the object side, respectively, the first lens is negative refractive power, the second lens is positive refractive power, and the third lens is negative It has refractive power and has a wide space between the second lens and the third lens. As a result, the optical length is long with respect to the combined focal length, and the third lens has a large diameter, which is suitable for mounting to an image input device, a digital camera, a surveillance CCD camera, or an inspection device of a mobile phone or a personal computer. Not.

As an eighth three-element lens, two positive lenses and both surfaces become aspherical on the object side, and the negative power gradually decreases as it moves from the center of the lens to the periphery, and the negative side has the positive power on the peripheral side. An imaging lens in which a negative lens is directed toward the lens is disclosed (see Patent Document 8, for example).

However, in this lens system, as the lens corresponding to the third lens moves from the center of the lens to the periphery, the negative power gradually weakens, and the position where the power is changed to the positive power ranges from 0.7 times to 1.0 times the effective diameter of the lens from the center of the lens. It is a feature that exists. In the lens disclosed as an embodiment, the position at which the positive power is changed is 0.96 times and 0.97 times the effective diameter of the lens from the center of the lens, respectively, and is set mostly in the periphery of the lens.

When the position where the power is changed to positive power is set at the periphery of the lens, the light incident on the vicinity of the intersection point between the lens optical axis and the image pickup surface and the periphery portion approximates the angle of incidence to the image pickup element at a right angle, but the intersection between the lens optical axis and the image pickup surface and the lens periphery In the intermediate position of, the angle of incidence to the image pickup device is greatly different from the right angle. Therefore, at an intermediate position with the lens peripheral portion that occupies an important part of the image, the angle of incidence of the light falls off from the right angle so that the incident light enters the image pickup device from the inclination direction of the image pickup device, and the amount of reflection on the incident surface increases, resulting in photoelectricity of the image pickup device. The light energy reaching the conversion surface becomes small, thereby causing a problem that the image of this part is dark.

A ninth three-element lens comprising: an aperture stop from the object side, a biconvex first lens having positive refractive power, a second lens having negative refractive power and facing the concave surface toward the object side, and the object side An imaging lens in which a meniscus-shaped third lens is arranged facing a convex surface is disclosed (see Patent Document 9, for example).

This lens system is designed to obtain a good image when the aperture stop is arranged on the object side of the first lens. By arranging the aperture stop on the object side of the first lens, the position of the entrance pupil can be formed close to the object side. This has the feature that the chief ray can be incident on the image plane at an angle close to normal. When the chief ray enters the image plane at an oblique angle, shading occurs to reduce the amount of incident light to a pixel (image pickup device) arranged on the image plane, causing a problem that the image is dark at the periphery of the screen.

This problem is due to the fact that when light rays enter the image pickup device from the oblique direction of the image pickup device, the amount of reflection on the screen of the image pickup device increases and the light energy reaching the photoelectric conversion surface of the image pickup device becomes smaller. That is, by arranging the aperture stop on the object side of the first lens, it is possible to design an imaging lens in which shading is unlikely to occur.

For a lens system designed based on such a design guideline, a different aperture between the first lens and the second lens for the purpose of preventing flare, which is a phenomenon in which image contrast is reduced, or smear, which is an image blur phenomenon. If you place it, the following happens: That is, the chief ray incident at a large incidence angle with respect to the optical axis of the imaging lens in the chief ray passing through the aperture stop is blocked by the cross axis. As a result, a portion of the chief rays as described above are blocked instead of blocking the stray light that causes flare or smear that degrades the image quality. In some cases, the amount of light around the image is reduced, thereby darkening the periphery of the image. The problem arises.

In addition, this lens system is characterized in that the lens corresponding to the third lens is a meniscus lens having positive refractive power, and the back focus with respect to the optical length is relatively short. Therefore, if the back focus is increased in order to insert components such as a filter, cover glass, etc. between the imaging lens and the imaging surface, the optical length also becomes long, resulting in an excessively large lens system.

A tenth three-element lens comprising a first lens, an aperture, and a plastic material having positive refractive power in which the object-side surface is convex in order from the object side, and concave toward the object-side with at least one surface aspherical. Disclosed is an imaging lens in which a second lens having positive or negative refractive power toward the (i) surface and a third lens having positive refractive power toward the convex surface toward the object side with both surfaces aspherical (for example) are disclosed. , Patent Document 10).

The tenth three-element lens is designed to obtain a good image on the premise that an aperture is set between the first lens and the second lens and that the aperture functions as an aperture stop. Therefore, when a shutter or the like is placed on the object side of the second lens, the incidence opening of the lens becomes narrow due to this shutter. That is, since this shutter or the like functions as a practical aperture, a part of the chief ray incident on the aperture is blocked. Since the chief ray incident at a large angle with respect to the optical axis of the lens is a ray forming the periphery of the image, the ray may be blocked by a shutter or the like provided on the object side of the first lens, which may cause a problem of darkening the periphery of the image. .

In addition, also in this lens system, a lens corresponding to the third lens is a meniscus lens having positive refractive power, similarly to the ninth three-element lens. Therefore, also in this lens system, if the back focus is lengthened in the same way as in the ninth three-element lens, the optical length also becomes long, and the lens system becomes too large.

An eleventh three-component lens, comprising: a first lens having positive refractive power in the form of a glass material from the object side and a convex surface in the object side at the same time; an aperture, a plastic material and at least one surface Is a aspherical surface and at the same time has a meniscus-shaped second lens having positive refractive power toward the concave surface toward the object side, a plastic material, aspherical on both sides, and at the same time toward the convex surface toward the object side; An imaging lens in which a third lens having negative refractive power is disposed is disclosed (see Patent Document 11, for example).

Since the basic configuration of the eleventh three-element lens is the same as that of the tenth three-element lens, there is the same problem as described above as the tenth three-element lens.

A twelfth three-element lens comprising: a first lens having positive refractive power in which at least one surface is aspherical in shape from the object side and has a biconvex surface shape, an aperture, and an aspheric shape in at least one surface And a meniscus-shaped second lens having positive refractive power toward the concave surface toward the object side, and having both surfaces aspherical and positive or negative at the same time, and the surface on the object side is a convex surface. An imaging lens in which a third lens made of a plastic material of a shape is disposed is disclosed (see Patent Document 12, for example).

The basic configuration of the twelfth three-element lens is the same as that of the tenth and eleventh three-element lens. Therefore, there is a problem as described above, such as the tenth and eleventh three-component lenses.

A thirteenth three-component lens comprising a first lens having mainly positive refractive power toward the convex surface from the object side to the object side, and a meniscus shape having negative refractive power toward the convex surface toward the image side. Disclosed is an imaging lens in which a second lens and a third lens having positive refractive power toward a convex surface are disposed on an object side. Then, an imaging lens in which an aperture is disposed on an object side of a first lens and an imaging lens in which an aperture is disposed between a first lens and a second lens are disclosed (see Patent Document 13, for example).

That is, an imaging lens designed so as to obtain a good image on the premise that the aperture disposed on the object side of the first lens functions as an aperture stop, and the aperture disposed between the first lens and the second lens functions as an aperture stop. Disclosed is an imaging lens designed to obtain a good image on the premise of making it possible.

As described above, another aperture is arranged between the first lens and the second lens with respect to the imaging lens designed to obtain a good image on the premise that the aperture disposed on the object side of the first lens functions as an aperture stop. If the main beam is incident at a large angle of incidence with respect to the optical axis of the main lens in the main beam of light passing through the aperture stop, the further stop will be blocked. Similarly, when the diaphragm disposed between the first lens and the second lens functions as an aperture diaphragm, the diaphragm is arranged on the object side of the first lens with respect to the imaging lens designed to obtain a good image. Therefore, the chief ray entering at a large angle of incidence with respect to the optical axis of the imaging lens in the chief ray passing through the aperture stop is blocked by the further arranged aperture.

As a result, as described above, part of the chief rays as described above is blocked instead of blocking stray light that causes flare or smear that degrades image quality, so that the amount of light around the image is reduced in some cases. This causes a problem that the periphery of the image becomes dark.

Patent Document 13 discloses an embodiment in which an imaging lens in which an aperture diaphragm is arranged on the object side of the first lens and an imaging lens in which the aperture diaphragm is arranged between the first lens and the second lens are independently designed. . That is, the shapes of the first to third lenses and the arrangement of these lenses are designed so that a good image for each can be obtained depending on the position where the aperture stops are arranged. Therefore, there is no disclosure of an imaging lens in which an aperture is disposed on the object side of the first lens and an aperture stop is also arranged between the first lens and the second lens. That is, no imaging lens is provided with an aperture for the purpose of preventing flare or smear in addition to the aperture stop for determining the entrance pupil position to further improve the performance of the lens.

Also in the thirteenth elementary lens, the lens corresponding to the third lens is a meniscus lens having a positive refractive power, similarly to the ninth elemental lens of the ninth element described above. Therefore, also in this lens system, when the back focus is lengthened in the same way as in the ninth three-component lens, the optical length also becomes long, which causes the lens system to become too large.

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-075006

Patent Document 2: Japanese Patent Application Laid-Open No. 2003-149548

Patent Document 3: Japanese Patent Application Laid-Open No. 2002-221659

Patent Document 4: Japanese Patent Application Laid-Open No. 2002-244030

Patent Document 5: Japanese Patent Application Laid-Open No. 2003-149545

Patent Document 6: Japanese Patent Application Laid-Open No. 10-301022

Patent Document 7: Japanese Patent Application Laid-Open No. 10-301021

Patent Document 8: Japanese Patent Application Laid-Open No. 2003-322792

Patent Document 9: Japanese Patent Application Laid-Open No. 2004-004566

Patent Document 10: Japanese Patent Application Laid-Open No. 2004-302058

Patent Document 11: Japanese Patent Application Laid-Open No. 2004-302059

Patent Document 12: Japanese Patent Application Laid-Open No. 2004-302060

Patent Document 13: Japanese Patent Application Laid-Open No. 2005-004045

It is therefore an object of the present invention to provide an imaging lens which has a short optical length and a long back focus, which is suitable for mounting in a camera using a CCD or CMOS as an imaging device, and which can obtain a good image. The short optical length specifically means that the ratio of the optical length to the focal length is small. The long back focus means that the ratio of the back focus to the focal length is large.

In addition, by realizing all the lenses (three pieces) constituting the imaging lens of the present invention with a plastic material, it is possible to provide an imaging lens with low cost and weight reduction. Here, the plastic material is a plastic material that is plastically deformed and molded by heat and pressure or both, and refers to a material that is transparent to visible light as a polymer material capable of forming a lens.

In order to achieve the above object, the imaging lens of the first invention includes an aperture stop S1, a first lens L1, a second lens L2, and a third lens L3, and the image side is positioned from the object side. Toward the aperture diaphragm S1, the first lens L1, the second lens L2, and the third lens L3. The first lens L1 is a lens having positive refractive power toward the obverse plane on the object side and the image side. The second lens L2 is a lens having negative meniscus-shaped negative refractive power that is directed toward the ear plane toward the image side. The third lens L3 is a lens having positive refractive power toward the rear surface toward the object side and the image side.

Both surfaces of the first lens L1 are aspherical, both surfaces of the second lens L2 are aspherical, and both surfaces of the third lens L3 are aspheric.

The imaging lens satisfies the following conditions (1-1) to (1-7).

0.55 <| r ₂ / r ₃ | <0.70 (1-1)

0.08 <d ₃ / f <0.12 (1-2)

0.140 ≤ d ₄ / f <0.270 (1-3)

0.24 <d ₆ / f <0.40 (1-4)

0.90 <L / 2Y <1.10 (1-5)

0.40 <b _f / f <0.52 (1-6)

2.70 <F _NO <3.60 (1-7)

only,

f: Composite focusing distance of the imaging lens

r ₂ : radius of curvature (optical axis curvature radius) near the object-side optical axis of the first lens L1

r ₃ : radius of curvature (optical axis curvature radius) in the vicinity of the optical axis of the image-side surface of the first lens L1

d ₃ : Optical axis gap between the first lens L1 and the second lens L2

d ₄ : Center thickness of the second lens L2

d ₆ : center thickness of third lens L3

L: Distance from the object side surface of the first lens L1 to the image surface (in air)

2Y: Approx. (Effective screen diagonal length)

b _f : Distance on the optical axis from the image side surface of the third lens L3 to the image surface (in air)

F _NO : F-number

to be.

The back focus b _f defined as the distance from the image emitting surface of the imaging lens to the imaging surface is here the optical axis distance from the image side surface of the third lens L3 to the image surface. The image height 2Y is the diagonal length of the effective screen, that is, the diagonal length in the rectangular light receiving surface of the solid-state image sensor provided on the image surface of the imaging lens.

The imaging lens of the second invention includes a first lens L1, an aperture stop S2, a second lens L2, and a third lens L3, and the first lens L1 faces from the object side toward the image side. And the aperture diaphragm S2, the second lens L2, and the third lens L3. The first lens L1 is a lens having positive refractive power toward the obverse plane on the object side and the image side. The second lens L2 is a lens having negative meniscus-shaped negative refractive power that is directed toward the ear plane toward the image side. The third lens L3 is a lens having positive refractive power toward the rear surface toward the object side and the image side.

Both surfaces of the first lens L1 are aspherical, both surfaces of the second lens L2 are aspherical, and both surfaces of the third lens L3 are aspheric.

The imaging lens satisfies the following conditions (2-1) to (2-7).

0.55 <| r ₁ / r ₂ | <0.70 (2-1)

0.08 <D ₃ / f <0.12 (2-2)

0.140 ≤ d ₄ / f <0.270 (2-3)

0.24 <d ₆ / f <0.40 (2-4)

0.90 <L / 2Y <1.10 (2-5)

0.40 <b _f / f <0.52 (2-6)

2.70 <F _NO <3.60 (2-7)

only,

f: Composite focusing distance of the imaging lens

r ₁ : radius of curvature (optical axis curvature radius) in the vicinity of the object-side optical axis of the first lens (L1)

r ₂ : radius of curvature (optical axis curvature radius) in the vicinity of the optical axis of the image-side surface of the first lens L1

D ₃ : Optical axis gap between the first lens L1 and the second lens L2

d ₄ : Center thickness of the second lens L2

d ₆ : center thickness of third lens L3

L: Distance from the object side surface of the first lens L1 to the image surface (in air)

2Y: Approx. (Effective screen diagonal length)

b _f : Distance on the optical axis from the image side surface of the third lens L3 to the image surface (in air)

F _NO : F-number

The back focus b _f defined as the distance from the image emitting surface of the imaging lens to the imaging surface is here the optical axis distance from the image side surface of the third lens L3 to the image surface. The image height 2Y is the diagonal length of the effective screen, that is, the diagonal length in the rectangular light receiving surface of the solid-state image sensor provided on the image surface of the imaging lens.

In addition, in the imaging lens of the second aspect of the invention, the aperture stop S2 is disposed between the first lens L1 and the second lens L2, whereby an optical axis of the first lens L1 and the second lens L2 is formed. The interval D ₃ is defined as follows. That is, the interval D ₃ is the sum of the interval from the image side surface of the first lens L1 to the aperture stop S2 and the interval from the aperture stop S2 to the object side surface of the second lens L2.

The imaging lens of the third invention includes an aperture stop S1, a first lens L1, an aperture stop S2, a second lens L2, and a third lens L3, and faces from the object side to the image side. The aperture stop S2, the first lens L1, the aperture stop S2, the second lens L2 and the third lens L3 are arranged in this order. The first lens L1 is a lens having positive refractive power toward the obverse plane on the object side and the image side. The second lens L2 is a lens having negative meniscus-shaped negative refractive power that is directed toward the ear plane toward the image side. The third lens L3 is a lens having positive refractive power toward the rear surface toward the object side and the image side.

Both surfaces of the first lens L1 are aspherical, both surfaces of the second lens L2 are aspherical, and both surfaces of the third lens L3 are aspheric.

The imaging lens satisfies the following conditions (3-1) to (3-7).

0.55 <| r ₂ / r ₃ | <0.70 (3-1)

0.08 <D ₃ / f <0.12 (3-2)

0.140 ≤ d ₄ / f <0.270 (3-3)

0.24 <D ₆ / f <0.40 (3-4)

0.90 <L / 2Y <1.10 (3-5)

0.40 <b _f / f <0.52 (3-6)

2.70 <F _NO <3.60 (3-7)

only,

f: Composite focusing distance of the imaging lens

r ₂ : radius of curvature (optical axis curvature radius) near the object-side optical axis of the first lens L1

r ₃ : radius of curvature (optical axis curvature radius) in the vicinity of the optical axis of the image-side surface of the first lens L1

D ₃ : Optical axis gap between the first lens L1 and the second lens L2

D ₄ : center thickness of the second lens L2

D ₆ : center thickness of the third lens L3

L: Distance from the object side surface of the first lens L1 to the image surface (in air)

2Y: Approx. (Effective screen diagonal length)

b _f : Distance on the optical axis from the image side surface of the third lens L3 to the image surface (in air)

F _NO : F-number

The back focus b _f defined as the distance from the image emitting surface of the imaging lens to the imaging surface is here the optical axis distance from the image side surface of the third lens L3 to the image surface. The image height 2Y is the diagonal length of the effective screen, that is, the diagonal length in the rectangular light receiving surface of the solid-state image sensor provided on the image surface of the imaging lens.

In the imaging lens of the third invention, the aperture diaphragm S2 is disposed between the first lens L1 and the second lens L2 in the same manner as the imaging lens of the second invention. The optical-axis spacing D ₃ of the second lens L2 is defined as follows, similarly to the imaging lens of the second invention. That is, the interval D ₃ is the sum of the interval from the image side surface of the first lens L1 to the aperture stop S2 and the interval from the aperture stop S2 to the object side surface of the second lens L2.

In the imaging lenses of the first to third inventions, the refractive index of the material of the second lens L2 is higher than the refractive index of the material of the first lens L1 and the third lens L3, and the second lens L2 It is preferable that the Abbe number of the raw material is smaller than the Abbe number of the raw material of the first lens L1 and the third lens L3.

In the imaging lenses of the first to third inventions, the first lens L1, the second lens L2, and the third lens L3 are lenses formed of a material having an Abbe number in the range of 30 to 60. It is preferable. The first lens L1 and the third lens L3 are lenses formed of cycloolefin resin as a material, and the second lens L2 is a lens formed of polycarbonate as a material.

Effects of the Invention

The first lens L1 is a lens having positive refractive power toward the rear surface toward the object side and the image side, and the second lens L2 is a lens having negative meniscus-shaped refractive power facing the rear surface toward the image side. The optical length L can be shortened by making the third lens L3 a lens having positive refractive power toward the convex surface on the object side and the image side.

In the imaging lens obtained by satisfying the conditional formulas (1-1) to (1-7), the conditional formulas (2-1) to (2-7) and the conditional formulas (3-1) to (3-7) The effect is as follows.

The conditional expressions (1-1), (2-1), and (3-1) described above correspond to the optical axial curvature radius of the first surface (object side surface) of the first lens L1 and that of the second surface (image side surface). Conditional formula that determines the ratio of the optical axis curvature radius. If the ratio is larger than the lower limit provided by the conditional expressions (1-1), (2-1) and (3-1), the back focus b _f of the imaging lens is set between a cover glass or a filter between the imaging lens and the imaging surface. It becomes sufficient to insert a component, and it can set to the length of the range which does not impair the compactness of the apparatus which mounts this imaging lens. In addition, spherical aberration does not become too large, and the processing of the first surface of the first lens L1 is also easy.

The ratio between the optical axis radius of curvature of the first surface (object side) of the first lens L1 and the optical axis radius of curvature of the second surface (image side) is expressed by the conditional formulas (1-1), (2-1), and (3 If it is smaller than the upper limit provided by -1), the back focus can be shortened, so that the compactness of the imaging lens can be achieved. Further, spherical aberration and astigmatism do not become excessively large as positive values. Moreover, the distortion aberration takes a negative value but its absolute value does not become too large. For this reason, it becomes possible by the 2nd lens L2 and the 3rd lens L3 to correct these aberrations so that they may enter a required range.

The conditional expressions (1-2), (2-2), and (3-2) described above capture a range of values to be taken by the optical axis spacing d ₃ of the first lens L1 and the second lens L2. It is a conditional expression determined by standardizing on the combined focal length f of the lens. Here, in the second and the third imaging lens of the invention, and denote the d is ₃ to D _3. This is because, as described above, in the imaging lenses of the second and third inventions, the aperture stop S2 is disposed between the first lens L1 and the second lens L2. That is, the interval D ₃ is the sum of the interval from the image side surface of the first lens L1 to the aperture diaphragm S2 and the interval from the aperture diaphragm S2 to the object side surface of the second lens L2. In order to distinguish it from the case of the first imaging lens in which S2) is not disposed, d ₃ Instead of D ₃ I write it and distinguish it. However, since the physical meanings are the same, in the following description, in particular, when it is not necessary to distinguish both, d ₃ And D ₃ may be commonly expressed as d ₃ without distinguishing between them.

If the value of d ₃ / f is larger than the lower limit defined by the conditional formulas (1-2), (2-2) and (3-2), the value of the spherical aberration does not increase excessively to a positive value, and the distortion The value of the aberration never becomes excessively large. In addition, when the value of d ₃ / f is smaller than the upper limit defined by the conditional formulas (1-2), (2-2) and (3-2), the diameters of the second lens L2 and the third lens L3 are determined. It is not necessary to increase the size so that it is difficult to compact.

The conditional formulas (1-3), (2-3), and (3-3) described above are the center thicknesses d of the second lens L2.₄Is a conditional expression for determining the range of values to be taken as the standardized focal length f of the imaging lens. However, in the imaging lens of the third invention, this d₄D₄It is written as. In the imaging lens of the third invention, the diaphragm S1 is disposed on the object side of the first lens L1, and the diaphragm S2 is disposed between the first lens L1 and the second lens L2. Correspondingly to the configuration described above, it is conveniently distinguished for the following description. However, since the physical meanings are the same, in the following description, in particular, when it is not necessary to distinguish the two, d₄ And D₄Do not write distinctly d in common₄Some may say

If the value of d ₄ / f is larger than the lower limit specified by the conditional formulas (1-3), (2-3) and (3-3), the center thickness required for processing as a resin lens can be sufficiently secured. have. In addition, when the value of d ₄ / f is smaller than the upper limit defined by the conditional formulas (1-3), (2-3) and (3-3), it is possible to sufficiently reduce the image distortion and obtain a good image. .

The conditional expressions (1-4), (2-4), and (3-4) described above indicate the range of values that the center thickness d ₆ of the third lens L3 should take. Conditional expression determined by standardization.

Here, in the imaging lens of the third aspect of the invention, and is indicated by the d ₆ D _6. In the same manner as described above with respect to d _4, in the imaging lens of the third invention, the diaphragm S1 is arranged on the object side of the first lens L1, and the first lens L1 and the second lens are arranged. Corresponding to the configuration in which the diaphragm S2 is arranged between (L2), it is conveniently distinguished and used for the following description. However, since the physical meanings are the same, as in the case of d ₄ above, d ₆ And D ₆ may be commonly expressed as d ₆ without distinguishing between them.

When d ₆ / f is larger than the lower limits defined by the conditional formulas (1-4), (2-4) and (3-4), the outer peripheral thickness of the third lens L3 is plasticized when the resin lens is formed. It can be ensured to the extent that the gate required in order to contain formation resin along with a casting mold can be arrange | positioned. That is, when the center thickness d ₆ of the third lens L3 is thin, the outer peripheral portion thickness of the third lens L3 is also thinned by that much. However, when d ₆ / f is set to be larger than the lower limits defined by the conditional formulas (1-4), (2-4) and (3-4), the gate whose outer peripheral portion thickness of the third lens L3 is required as the resin lens is used. It can be secured enough to arrange.

When d ₆ / f is smaller than the upper limits defined by the conditional formulas (1-4), (2-4) and (3-4), the outer periphery of the third lens L3 loses the compactness of the imaging lens. You don't have to be big enough to throw it away. Then, the distortion aberration can be sufficiently reduced to obtain a good image.

The above conditional expressions (1-5), (2-5), and (3-5) are conditional expressions that define the range of values that the ratio of the optical length L to the height (effective screen diagonal length) 2Y should take. . If the ratio of L / 2Y is greater than the lower limits of the conditional formulas (1-5), (2-5) and (3-5), the thickness of the first lens L1, the second lens L2, and the third lens L3 Can be ensured to be more than the thickness required at the time of lens formation. That is, when the first lens (L1), the second lens (L2) and the third lens (L3) are made of a resin material, if the thickness of the lens is thin during injection molding, the resin material is injected into the mold evenly and widely. It is difficult to do Therefore, when the lens is formed of a resin material, the thickness of the lens needs to be somewhat thick. If the ratio of L / 2Y is larger than the lower limits of the conditional formulas (1-5), (2-5) and (3-5), the thickness of the lens can be sufficiently secured.

If the ratio of L / 2Y is smaller than the upper limits of the conditional expressions (1-5), (2-5) and (3-5), the first lens L1, the second lens L2, and the third lens L3 It is possible to ensure that the peripheral light quantity ratio of the imaging lens is not too small without securing the external shape large enough to impair the compactness.

The conditional expressions (1-6), (2-6), and (3-6) described above are conditional expressions defined by standardizing the range of values to be taken by the back focus b _f by the combined focal length f of the imaging lens. If the back focus falls within the ranges given by the conditional formulas (1-6), (2-6) and (3-6), an optical part such as a filter required for an image input device such as a mobile phone is used as a third lens ( It is possible to insert between the upper surface of L3) and the imaging surface.

The above conditional expressions (1-7), (2-7) and (3-7) give conditions defining the range of values to be taken by the aperture ratio (F number) of the imaging lens. If the aperture ratio exceeds the lower limits of the conditional expressions (1-7), (2-7) and (3-7), it is possible to obtain a sufficient resolution as the imaging lens, and also to sufficiently secure the surrounding light quantity ratio. . If the aperture ratio is less than the upper limit of the conditional expressions (1-7), (2-7) and (3-7), the lens possesses sufficient brightness as the imaging lens, and the CCD can be used for an imaging device using a CCD or a CMOS. The light reception sensitivity of CMOS does not need to be so high that the noise level has to be a problem.

Therefore, for each of the above-described imaging lenses of the first to third inventions, conditional expressions (1-1) to (1-7), conditional expressions (2-1) to (2-7) and conditional expressions (3-1) to (3-7) By setting the lens structure that satisfies each of the seven conditions, the above-mentioned problem can be solved and a compact imaging lens capable of obtaining a small and good image can be provided.

The imaging lens of the first aspect of the invention is characterized in that an aperture stop S1 for determining incident pupil is disposed on the entire surface of the first lens L1, that is, on the object side of the first lens L1. As a result, the incident pupil can be made closer to the object side, and the chief ray can be incident on the image plane at an angle close to the vertical, thereby preventing shading.

The imaging lens of the second aspect of the invention is characterized in that an aperture stop S2 for determining incident pupil is disposed between the first lens L1 and the second lens L2. As a result, the diaphragm S2 also possesses a function of removing the flare generated in the first lens L1. Since the third lens L3 has a large aperture, before the stray light that causes the flare generated in the first lens L1 enters the third lens L3, rather than blocking after passing through the third lens L3. It is much more effective to block.

In addition, in order to change the aperture ratio (F number) of the imaging lens, the size of the aperture stop may be changed. The imaging lens of the second aspect of the invention has a configuration in which the aperture stop S2 is disposed between the first lens L1 and the second lens L2, so that changing the aperture ratio only needs to be replaced by the aperture stop S2. However, like the imaging lens of the first invention, in order to arrange the aperture stop on the front surface of the first lens L1, the barrel goes back to the step of manufacturing a barrel for fixing the first to third lenses constituting the imaging lens. The size of the opening must be set so that the leading edge of X serves as the aperture stop S1. That is, it is necessary to correct the barrel design of the imaging lens every time the aperture ratio is changed, and to make and change a mold for barrel production of the imaging lens each time.

As described above, the imaging lens of the first invention and the imaging lens of the second invention each have different characteristics.

The imaging lens of the third aspect of the present invention is an imaging lens provided with an early opening for the purpose of preventing flare or smear in addition to the aperture stop for determining incident pupil. That is, in the case where both the diaphragm S1 and the diaphragm S2 are disposed, when the diaphragm aberration is calculated as the aperture diaphragm S1 and the diaphragm aberration as the diaphragm S2 as the aperture diaphragm The characteristic of the imaging lens of the third aspect of the present invention is that the value obtained in the above can obtain a good image in either case. In the calculation of these aberrations, the shapes and the constituent materials of the first to third lenses L1 to L3 were made the same, and the mutual spacing between the lenses was calculated in the same manner.

In Examples 11 and 12 described later, aberrations were calculated for each case under the assumption that the diaphragm S1 functions as an aperture diaphragm and the diaphragm S2 functions as an aperture diaphragm. In either case, it was confirmed that a good image could be obtained.

That is, the imaging lens of the third aspect of the invention is an imaging lens having a feature that sufficient brightness is ensured up to the periphery of an image, and that stray light, which causes flare or smear, which degrades image quality, can be effectively blocked.

The refractive index of the material of the second lens L2 is higher than that of the first lens L1 and the third lens L3, and the Abbe number of the material of the second lens L2 is the first lens L1 and the third lens. If it is smaller than the material Abbe number of the lens L3, it is possible to effectively reduce color and spherical aberration.

When the second lens L2 is formed of polycarbonate, and the first lens L1 and the third lens L3 are formed of cycloolefin plastic, the material refractive index of the second lens L2 is the first lens L1. ) And the material refractive index of the third lens L3, and the material Abbe number of the second lens L2 may be smaller than the material Abbe number of the first lens L1 and the third lens L3.

Since the refractive index of cycloolefin plastics is 1.5304 and the refractive index of polycarbonate is 1.5839, the Abbe number of cycloolefin plastics is 56.2 and the Abbe number of polycarbonates is 30.0, so these materials can be used for the imaging lens of the present invention.

Cycloolepin-based plastic or polycarbonate material is known to be a suitable material for forming a lens by the injection molding method, a conventionally established manufacturing technique. Of course, it is not limited to a specific plastic material, The plastic material and mold glass material which Abbe number exists in the range of 30-60 can be used.

In Examples 1 to 12, which will be described later, the first lens L1 and the third lens L3 are made of cycloolefin plastic, and the second lens L2 is made of polycarbonate.

1 is a cross-sectional view of an imaging lens of the first invention.

2 is a sectional view of an imaging lens of Example 1;

3 is a distortion aberration diagram of the imaging lens of Example 1. FIG.

4 is an astigmatism diagram of the imaging lens of Example 1. FIG.

5 is a color / spherical aberration diagram of the imaging lens of Example 1. FIG.

6 is a sectional view of an imaging lens of Example 2. FIG.

7 is a distortion aberration diagram of the imaging lens of Example 2. FIG.

8 is an astigmatism diagram of the imaging lens of Example 2. FIG.

9 is a color / spherical aberration diagram of the imaging lens of Example 2. FIG.

10 is a sectional view of an imaging lens of Example 3. FIG.

11 is a distortion aberration diagram of the imaging lens of Example 3. FIG.

12 is an astigmatism diagram of the imaging lens of Example 3. FIG.

FIG. 13 is a color / spherical aberration diagram of the imaging lens of Example 3. FIG.

14 is a sectional view of an imaging lens of Example 4. FIG.

15 is a distortion aberration diagram of the imaging lens of Example 4. FIG.

16 is an astigmatism diagram of the imaging lens of Example 4. FIG.

17 is a chromatic / spherical aberration diagram of the imaging lens of Example 4. FIG.

18 is a sectional view of an imaging lens of Example 5. FIG.

19 is a distortion aberration diagram of the imaging lens of Example 5. FIG.

20 is an astigmatism diagram of the imaging lens of Example 5. FIG.

21 is a chromatic / spherical aberration diagram of the imaging lens of Example 5. FIG.

Fig. 22 is a sectional view of the imaging lens of the second invention.

Fig. 23 is a sectional view of an imaging lens of Example 6;

24 is a distortion aberration diagram of the imaging lens of Example 6. FIG.

25 is an astigmatism diagram of the imaging lens of Example 6. FIG.

26 is a chromatic / spherical aberration diagram of the imaging lens of Example 6. FIG.

27 is a sectional view of an imaging lens of Example 7. FIG.

28 is a distortion aberration diagram of the imaging lens of Example 7. FIG.

29 is an astigmatism diagram of the imaging lens of Example 7. FIG.

30 is a chromatic / spherical aberration diagram of the imaging lens of Example 7. FIG.

31 is a sectional view of an imaging lens of Example 8. FIG.

32 is a distortion aberration diagram of the imaging lens of Example 8. FIG.

33 is an astigmatism diagram of the imaging lens of Example 8. FIG.

34 is a chromatic / spherical aberration diagram of the imaging lens of Example 8. FIG.

35 is a sectional view of an imaging lens of Example 9;

36 is a distortion aberration diagram of the imaging lens of Example 9. FIG.

37 is an astigmatism diagram of the imaging lens of Example 9. FIG.

38 is a chromatic / spherical aberration diagram of the imaging lens of Example 9. FIG.

39 is a sectional view of an imaging lens of Example 10;

40 is a distortion aberration diagram of the imaging lens of Example 10;

41 is an astigmatism diagram of the imaging lens of Example 10. FIG.

42 is a chromatic / spherical aberration diagram of the imaging lens of Example 10;

43 is a cross-sectional view of the imaging lens of the third invention.

44 is a sectional view [A] of the imaging lens of Example 11. FIG.

45 is a distortion aberration diagram [A] of the imaging lens of Example 11. FIG.

46 is an astigmatism diagram [A] of the imaging lens of Example 11. FIG.

FIG. 47 is a chromatic / spherical aberration diagram [A] of the imaging lens of Example 11. FIG.

48 is a sectional view [B] of the imaging lens of Example 11. FIG.

49 is a distortion aberration diagram [B] of the imaging lens of Example 11. FIG.

50 is an astigmatism diagram [B] of the imaging lens of Example 11. FIG.

Fig. 51 is a color / spherical aberration diagram [B] of the imaging lens of the eleventh embodiment.

52 is a sectional view [A] of the imaging lens of Example 12. FIG.

53 is a distortion aberration diagram [A] of the imaging lens of Example 12. FIG.

54 is an astigmatism diagram [A] of the imaging lens of Example 12. FIG.

55 is a chromatic / spherical aberration diagram [A] of the imaging lens of Example 12. FIG.

56 is a sectional view [B] of the imaging lens of Example 12;

57 is a distortion aberration diagram [B] of the imaging lens of Example 12. FIG.

58 is an astigmatism diagram [B] of the imaging lens of Example 12. FIG.

59 is a color / spherical aberration diagram [B] of the imaging lens of Example 12. FIG.

[Description of the code]

10; imaging device

S1, S2; opening aperture

L1; first lens

L2; second lens

L3; third lens

r _i ; radius of curvature on the optical axis of the i-th plane

d _i ; Distance from the intersection of the i th plane to the optical axis

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described with reference to drawings. Here, these drawings are only schematically showing the shape, size and arrangement of the components to the extent that the present invention can be understood, and the numerical conditions and other conditions described below are simply good examples, the present invention It is not limited only to the embodiment of the invention.

1, 22 and 43 are block diagrams of the imaging lenses of the first to third inventions, respectively. Symbols such as surface numbers and surface intervals defined in FIGS. 1, 22, and 43 are shown in FIGS. 2, 6, 10, 14, 18, 23, 27, 31, 35, and 39. 44, 48, 52, and 56 shall be used in common.

Counting from the object side, the first, second and third lenses are represented by L1, L2 and L3, respectively. Aperture is represented by S1 and S2. Also, within the range of no misunderstanding, r _i (i = 1,2,3, ..., 9) is used as a variable representing the value of the optical axis radius of curvature, or a symbol identifying a lens, a cover glass, or an imaging surface ( For example, r ₁ may be used to mean the object-side surface of the first lens.

Parameters such as r _i (i = 1,2,3, ..., 9) and d _i (i = 1,2,3, ..., 8) shown in these figures are shown in Tables 1 to 3 shown below. In Table 12, specific values are given. The subscript i is assigned in correspondence with the surface number of each lens, the thickness of the lens, the lens surface spacing, and the like sequentially from the object side toward the image side.

In other words,

r _i is the radius of curvature of the optical axis of the i-th plane,

d _i is the distance from the i th plane to the i + 1 th plane,

N _i is the material refractive index of the lens

ν _i is the material Abbe number of the lens consisting of the i th plane and the i + 1 th plane

Respectively.

In FIG. 1, FIG. 22 and FIG. 43, the opening part of a stop is shown by the line segment. This is because the intersection of the aperture surface and the optical axis must be clearly shown in order to define the distance from the lens surface to the aperture surface. 2, 6, 10, 14, 18, 23, 27, 31, 35, 39, 44, 48, which are cross-sectional views of the imaging lenses of Examples 1 to 12, respectively. In FIG. 52 and FIG. 56, the diaphragm main body which opens the aperture of a diaphragm, and cuts off the light by two straight lines which made the end of an opening point as opposed to FIG. 1, FIG. 22, and FIG. 43 is shown. This is because it is necessary to open the aperture opening to reflect the actual state of the aperture in order to write light rays such as the chief ray.

The optical length L is the distance from the aperture S1 to the imaging surface in the imaging lenses of the first and third inventions, and from the intersection of the object side surface of the first lens and the optical axis to the imaging surface in the imaging lens of the second invention. Distance. The back focus b _f is the distance from the image side surface of the third lens L3 to the imaging surface on the optical axis.

Aspheric data is shown with the face number in each column of Tables 1-12. Since the surfaces of the diaphragms S1 and S2 and the imaging surface are flat, they are indicated by ∞.

The aspherical surface used in the present invention is given by the following equation.

Z = ch ² / [1 + [1-(1 + k) c ² h ² ] ^+1/2 ] + A ₀ h ⁴ + B ₀ h ⁶ + C ₀ h ⁸ + D ₀ h ¹⁰

only,

Z: Depth from tangent plane to vertex

c: paraxial curvature of the face

h: height of the optical axis

k: conical constant

A ₀ : 4th aspherical coefficient

B ₀ : 6th aspherical coefficient

C ₀ : 8th aspherical coefficient

D ₀ : 10th aspherical coefficient

to be.

In Tables 1-12 in this specification, the numerical value which showed the aspherical coefficient is an exponential display, for example, "e-1" means "10e-1 power". The value indicated as the focal length f is the combined focal length of the lens system composed of the first to third lenses.

Hereinafter, Examples 1 to 12 will be described with reference to FIGS. 2 to 59, respectively.

3, 7, 11, 15, 19, 24, 28, 32, 36, 40, 45, 49, 53 and 57, the distortion aberration curves from the optical axis The aberration (the percentage of dissatisfaction of the tangent condition is indicated in percentage on the horizontal axis) with respect to the distance (the maximum distance from the optical axis in the image plane on the vertical axis is expressed as a percentage). The astigmatism curves shown in FIGS. 4, 8, 12, 16, 20, 25, 29, 33, 37, 41, 46, 50, 54, and 58 are distortion aberrations. The aberration amount (in mm) is represented on the horizontal axis with respect to the distance from the optical axis indicated on the vertical axis in the form of a curve, and the aberration amount (in mm) on the meridional plane and the sagittai plane. Indicates. In the color and spherical aberration curves shown in FIGS. 5, 9, 13, 17, 21, 26, 30, 34, 38, 42, 47, 51, 55, and 59, The aberration amount (in mm units) is represented by the horizontal axis with respect to the incident height h (F-number) of the vertical axis.

In the color and spherical aberration curve, C line (light having a wavelength of 656.3 nm), d line (light having a wavelength of 587.6 nm), e line (light having a wavelength of 546.1 nm), F line (light having a wavelength of 486.1 nm), and g line The aberration value for (light of wavelength 435.8 nm) is shown. The refractive index is the refractive index in the d line (light of 587.6 nm).

Below, the curvature radius (in mm), lens surface spacing (in mm), refractive index of the lens material, Abbe's number of lens material, focal length, numerical aperture and aspheric coefficient of the constituent lenses according to Examples 1 to 12 are shown below. Tables 1 to 12 list and publish. In Examples 1 to 12, the focal lengths of the first lens L1, the second lens L2, and the third lens L3 are represented by f ₁ , f ₂ , and f ₃ . In Examples 1 to 12, in any case, f ₁ and f ₃ are positive values and f ₂ is negative values. That is, the first lens and the third lens are lenses having positive refractive power, and the second lens is a lens having negative refractive power.

The value r _i (i = 1,2,3, ..., 9) of the radius of curvature on the optical axis is a positive value for the convex on the object side and a negative value for the convex on the upper side. It is indicated by. From the provision of the curvature radius value of the curved surface constituting the lens, the first lens is a convex lens facing the convex surface toward the object side and the image side, and the second lens is a meniscus toward the convex surface toward the image side. It is read that the lens and the third lens are convex lenses facing the convex surface on the object side and the image side.

Below, the characteristic of each Example is shown. In Examples 1 to 12, Xenox E48R (Xenox is a registered trademark of Xeon Co., Ltd., Japan), which is a cycloolefin based plastic material of the first lens L1 and the third lens L3. Is a product number). In addition, polycarbonate was used as a material for the second lens L2.

The refractive index of xenox E48R with respect to d line is 1.5304, and the refractive index of polycarbonate with d line is 1.5869. In addition, the Abbe number of Xenox E48R is 56.0 and the Abbe number of polycarbonate is 30.9.

In addition, both surfaces of each of the first lens L1, the second lens L2, and the third lens L3 were aspherical.

<1st invention>

As shown in FIG. 1, the imaging lens of the first invention includes an aperture stop S1, a first lens L1, a second lens L2, and a third lens L3, and faces from the object side toward the image side. And the aperture diaphragm S1, the first lens L1, the second lens L2, and the third lens L3. Curvature radius (mm unit), lens surface spacing (mm unit), refractive index of lens material, Abbe's number of lens material, focal length, numerical aperture of lens constituting the first to fifth embodiments of the imaging lens And aspheric coefficients are listed and published in Tables 1 to 5, respectively.

Example 1

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.421 mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.689 mm.

(C) The optical axis spacing d _{3 of} the first lens L1 and the second lens L2 is d _3. = 0.0901.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1445 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3032 mm.

(F) The optical length L is L = 1.282mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.30 mm.

(H) The back focus b _f is b _f = 0.482 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.9.

therefore,

(1-1) │r ₂ / r ₃ │ = │0.421 / -0.689│ = 0.611,

(1-2) d ₃ / f = 0.0901 / 1.00 = 0.0901,

(1-3) d ₄ / f = 0.1445 / 1.00 = 0.1445,

(1-4) d ₆ / f = 0.3032 / 1.00 = 0.3032,

(1-5) L / 2Y = 1.282 / 1.30 = 0.9862,

(1-6) b _f / f = 0.482 / 1.00 = 0.482,

(1-7) F _NO = 2.9,

By doing so, the lens of Example 1 satisfies all of the following conditional formulas (1-1) to (1-7).

0.55 <｜ r ₂ / r ₃ ｜ <0.70 (1-1)

0.08 <d ₃ / f <0.12 (1-2)

0.140 ≤ d ₄ / f <0.270 (1-3)

0.24 <d ₆ / f <0.40 (1-4)

0.90 <L / 2Y <1.10 (1-5)

0.40 <b _f / f <0.52 (1-6)

2.70 <F _NO <3.60 (1-7)

Subsequently, in the first invention, the seven equations from (1-1) to (1-7) are indicated as conditional expressions.

As shown in Table 1, the diaphragm S1 is provided in the intersection position of the 1st surface (object side surface) of the 1st lens L1, and an optical axis. That is, the diaphragm surface may indicate that there is a plane, so r ₁ = ∞ as showed in Table 1, the aperture diaphragm (S1) to the position of the surface r ₁ is disposed. The numerical aperture (F number) is 2.90.

2 is a cross-sectional view of the imaging lens of Example 1. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.482mm.

Distortion aberration curve 20 shown in Fig. 3, astigmatism curve shown in Fig. 4 (aberration curve 22 for the major journal surface and aberration curve 24 for the sagittal plane), color, spherical aberration curve (Fig. 5) Curve 26, aberration curve 28 for d line, aberration curve 30 for e line, aberration curve 32 for F line, and aberration curve 34 for g line, respectively, are shown graphically.

The vertical axis of the aberration curves of FIGS. 3 and 4 indicates the image height as a percentage of the distance from the optical axis. 3 and 4, 100% corresponds to 0.651 mm. In addition, the vertical axis | shaft of the aberration curve of FIG. 5 has shown the incident height h (F-number), and the maximum corresponds to 2.9. 5 represents the magnitude of the aberration.

The distortion aberration is the maximum of the aberration amount at 0.4527% at the position of 80% of the height (0.5208 mm), and the absolute value of the aberration is within 0.4527% in the range of 0.651mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the surface of the mary journal is at a maximum of 0.0875 mm at the position of 100% of the height (0.651 mm), and the absolute value of the aberration is within 0.0875 mm within the range of 0.651 mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 34 with respect to the g line reaches a maximum of 0.0421 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0421 mm.

Example 2

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.436 mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.659 mm.

(C) The optical axis spacing d _{3 of} the first lens L1 and the second lens L2 is d _3. = 0.0925.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1479 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3173 mm.

(F) The optical length L is L = 1.288 mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.32 mm.

(H) The back focus b _f is b _f = 0.460 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.78.

therefore,

(1-1) │r ₂ / r ₃ │ = │0.436 / -0.659│ = 0.6616,

(1-2) d ₃ / f = 0.0925 / 1.00 = 0.0925,

(1-3) d ₄ / f = 0.1479 / 1.00 = 0.1479,

(1-4) d ₆ / f = 0.3173 / 1.00 = 0.3173,

(1-5) L / 2Y = 1.288 / 1.32 = 0.9758,

(1-6) b _f / f = 0.460 / 1.00 = 0.460,

(1-7) F _NO = 2.78,

By doing so, the lens of Example 2 satisfies all of the following conditional formulas (1-1) to (1-7).

0.55 <｜ r ₂ / r ₃ ｜ <0.70 (1-1)

0.08 <d ₃ / f <0.12 (1-2)

0.140 ≤ d ₄ / f <0.270 (1-3)

0.24 <d ₆ / f <0.40 (1-4)

0.90 <L / 2Y <1.10 (1-5)

0.40 <b _f / f <0.52 (1-6)

2.70 <F _NO <3.60 (1-7)

Subsequently, in the first invention, the seven equations from (1-1) to (1-7) are indicated as conditional expressions. As shown in Table 2, the diaphragm S1 is provided in the intersection position of the 1st surface (object side surface) of the 1st lens L1, and an optical axis. That is, the diaphragm surface may indicate that there is a plane, so r ₁ = ∞ as showed in Table 2, the aperture diaphragm (S1) to the position of the surface r ₁ is disposed. The numerical aperture (F number) is 2.78.

6 is a sectional view of the imaging lens of Example 2. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.460mm.

Distortion aberration curve 36 shown in FIG. 7, astigmatism curve shown in FIG. 8 (aberration curve 38 for the major journal surface and aberration curve 40 for the sagittal plane), color and spherical aberration curve shown in FIG. 9 (aberration for C line) Curve 42, aberration curve 44 for d line, aberration curve 46 for e line, aberration curve 48 for F line, and aberration curve 50 for g line, respectively, are shown graphically.

The vertical axis of the aberration curves of Figs. 7 and 8 indicates the image height by what percentage of the distance from the optical axis. 7 and 8, 100% corresponds to 0.660 mm. In addition, the vertical axis of the aberration curve of FIG. 9 represents the incident height h (F-number), and the maximum corresponds to 2.78. 9 represents the magnitude of the aberration.

The distortion aberration is the maximum of the aberration amount at 0.5607% at the position of 80% of the height (0.5280mm), and the absolute value of the aberration is within 0.5607% in the range of 0.660mm or less.

As for astigmatism, the absolute value of the aberration amount on the surface of the journal is maximum at 0.0249mm at the position of 100% of the height (0.660mm), and the absolute value of the aberration is within 0.0249mm within the range of 0.660mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 50 with respect to the g line reaches a maximum of 0.0764 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0764 mm.

Example 3

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.415 mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.671 mm.

(C) The optical axis spacing d _{3 of} the first lens L1 and the second lens L2 is d _3. = 0.0875.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1400 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.2980 mm.

(F) The optical length L is L = 1.274mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.24 mm.

(H) The back focus b _f is b _f = 0.488 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.80.

therefore,

(1-1) │r ₂ / r ₃ │ = │0.415 / -0.671│ = 0.6185,

(1-2) d ₃ / f = 0.0875 / 1.00 = 0.0875,

(1-3) d ₄ / f = 0.1400 / 1.00 = 0.1400,

(1-4) d ₆ / f = 0.2980 / 1.00 = 0.2980,

(1-5) L / 2Y = 1.274 / 1.24 = 1.0274,

(1-6) b _f / f = 0.488 / 1.00 = 0.488,

(1-7) F _NO = 2.80,

By doing so, the lens of Example 3 satisfies all of the following Conditional Expressions (1-1) to (1-7).

0.55 <｜ r ₂ / r ₃ ｜ <0.70 (1-1)

0.08 <d ₃ / f <0.12 (1-2)

0.140 ≤ d ₄ / f <0.270 (1-3)

0.24 <d ₆ / f <0.40 (1-4)

0.90 <L / 2Y <1.10 (1-5)

0.40 <b _f / f <0.52 (1-6)

2.70 <F _NO <3.60 (1-7)

As shown in Table 3, the diaphragm S1 is provided in the intersection position of the 1st surface (object side surface) of the 1st lens L1, and an optical axis. That is, the diaphragm surface may indicate that there is a plane, so r ₁ = ∞ as showed in Table 3, the aperture for the location of the surface r ₁ (S ₁₎ are arranged. The numerical aperture (F number) is 2.80.

FIG. 10 is a sectional view of the imaging lens of Example 3. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.488mm.

Distortion aberration curve 52 shown in Fig. 11, astigmatism curve shown in Fig. 12 (aberration curve 54 for the primary surface and aberration curve 56 for the sagittal plane), and color and spherical aberration curve shown in Fig. 13 (aberration for C line) Curve 58, aberration curve 60 for d line, aberration curve 62 for e line, aberration curve 64 for F line, and aberration curve 66 for g line, respectively.

The vertical axis of the aberration curves of Figs. 11 and 12 indicates the image height as a percentage of the distance from the optical axis. In FIG. 11 and FIG. 12, 100% corresponds to 0.620 mm. In addition, the vertical axis of the aberration curve in FIG. 13 indicates the incidence height h (F-number), and the maximum corresponds to 2.80. 13 represents the magnitude of the aberration.

The distortion aberration has a maximum of 0.3991% of the absolute value of the aberration at the position of 100% of the height (0.620 mm), and the absolute value of the aberration amount falls within 0.3991% of the range of 0.620mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the surface of the main journal is at a maximum of 0.0221 mm at the position of 100% of the height (0.620 mm), and the absolute value of the aberration is within 0.0221 mm within the range of 0.620 mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 66 with respect to the g line reaches a maximum of 0.0781mm at 100% of the incident height h, and the absolute value of the aberration amount is within 0.0781mm.

Example 4

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.416 mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.671 mm.

(C) The optical axis spacing d _{3 of} the first lens L1 and the second lens L2 is d _3. = 0.0875.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1400 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3008 mm.

(F) The optical length L is L = 1.274mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.26 mm.

(H) The back focus b _f is b _f = 0.485 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.80.

therefore,

(1-1) │ r ₂ / r ₃ │ = │0.416 / -0.671│ = 0.6200,

(1-2) d ₃ / f = 0.0875 / 1.00 = 0.0875,

(1-3) d ₄ / f = 0.1400 / 1.00 = 0.1400,

(1-4) d ₆ / f = 0.3008 / 1.00 = 0.3008,

(1-5) L / 2Y = 1.274 / 1.26 = 1.0111,

(1-6) b _f / f = 0.485 / 1.00 = 0.485,

(1-7) F _NO = 2.80,

By doing so, the lens of Example 4 satisfies all of the following conditional formulas (1-1) to (1-7).

0.55 <｜ r ₂ / r ₃ ｜ <0.70 (1-1)

0.08 <d ₃ / f <0.12 (1-2)

0.140 ≤ d ₄ / f <0.270 (1-3)

0.24 <d ₆ / f <0.40 (1-4)

0.90 <L / 2Y <1.10 (1-5)

0.40 <b _f / f <0.52 (1-6)

2.70 <F _NO <3.60 (1-7)

As shown in Table 4, the diaphragm S1 is provided in the intersection position of the 1st surface (object side) of the 1st lens L1, and an optical axis. That is, the diaphragm surface may indicate that there is a plane, so as showed in Table 4 r ₁ = ∞, if r aperture diaphragm (S1) at a position of ₁ is arranged. The numerical aperture (F number) is 2.80.

FIG. 14 is a sectional view of the imaging lens of Example 4. FIG. The back focus for focal length 1.00mm can be secured to 0.485mm long enough.

Distortion aberration curve 68 shown in Fig. 15, astigmatism curve shown in Fig. 16 (aberration curve 70 for the major journal surface and aberration curve 72 for the sagittal plane), color, spherical aberration curve shown in Fig. 17 (aberration for C line) Curve 74, aberration curve 76 for d line, aberration curve 78 for e line, aberration curve 80 for F line, and aberration curve 82 for g line, respectively, are shown graphically.

The vertical axis of the aberration curves of Figs. 15 and 16 shows the image as a percentage of the distance from the optical axis. In FIG. 15 and FIG. 16, 100% corresponds to 0.630 mm. In addition, the vertical axis of the aberration curve in FIG. 17 indicates the incident height h (F-number), and the maximum corresponds to 2.80. 17 represents the magnitude of the aberration.

Distortion aberration is the maximum of the aberration amount is 0.8777% at the position of 100% of the height (0.630mm), and the absolute value of the aberration is within 0.8777% in the range of 0.630mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the surface of the mary journal is at the maximum of 0.1033mm at the position of 100% of the height (0.630mm), and the absolute value of the aberration is within 0.1033mm within the range of 0.630mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 82 with respect to the g line reaches a maximum of 0.0278 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0278 mm.

Example 5

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.436 mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.661 mm.

(C) The optical axis spacing d _{3 of} the first lens L1 and the second lens L2 is d _3. = 0.0927.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1483 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3183 mm.

(F) The optical length L is L = 1.289 mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.24 mm.

(H) The back focus b _f is b _f = 0.459 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 3.40.

therefore,

(1-1) │r ₂ / r ₃ │ = │0.436 / -0.661│ = 0.6596,

(1-2) d ₃ / f = 0.0927 / 1.00 = 0.0927,

(1-3) d ₄ / f = 0.1483 / 1.00 = 0.1483,

(1-4) d ₆ / f = 0.3183 / 1.00 = 0.3183,

(1-5) L / 2Y = 1.289 / 1.24 = 1.0395,

(1-6) b _f / f = 0.459 / 1.00 = 0.459,

(1-7) F _NO = 3.40,

By doing so, the lens of Example 5 satisfies all of the following Conditional Expressions (1-1) to (1-7).

0.55 <｜ r ₂ / r ₃ ｜ <0.70 (1-1)

0.08 <d ₃ / f <0.12 (1-2)

0.140 ≤ d ₄ / f <0.270 (1-3)

0.24 <d ₆ / f <0.40 (1-4)

0.90 <L / 2Y <1.10 (1-5)

0.40 <b _f / f <0.52 (1-6)

2.70 <F _NO <3.60 (1-7)

As shown in Table 5, the diaphragm S1 is provided in the intersection position of the 1st surface (object side surface) of the 1st lens L1, and an optical axis. That is, the diaphragm surface may indicate that there is a plane, so r ₁ = ∞ as showed in Table 5, the aperture diaphragm (S1) to the position of the surface r ₁ is disposed. The numerical aperture (F number) is 3.40.

18 is a sectional view of the imaging lens of Example 5. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.459mm.

Distortion aberration curve 84 shown in FIG. 19, astigmatism curve shown in FIG. 20 (aberration curve 86 for the major journal surface and aberration curve 88 for the sagittal plane), and color and spherical aberration curve shown in FIG. 21 (aberration for C line) Curve 90, aberration curve 92 for d line, aberration curve 94 for e line, aberration curve 96 for F line, and aberration curve 98 for g line, respectively, are shown graphically.

The vertical axis of the aberration curves of FIGS. 19 and 20 indicates the image height as a percentage of the distance from the optical axis. In Figs. 19 and 20, 100% corresponds to 0.620 mm. In addition, the vertical axis of the aberration curve in FIG. 21 represents the incident height h (F-number), and the maximum corresponds to 3.40. 21 represents the magnitude of the aberration.

The distortion aberration is at an absolute value of 1.2363% at a maximum of 80% (0.496 mm), and the absolute value of the aberration is within 1.2363% within a range of 0.620 mm or less.

As for astigmatism, the absolute value of the aberration of the aberration is about 0.0404 mm at the maximum 100% (0.620 mm) position, and the absolute value of the aberration is within 0.0404 mm within the range of 0.620 mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 90 with respect to the g line reaches a maximum of 0.0232 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0232 mm.

<2nd invention>

The imaging lens of the second invention has a first lens L1, an aperture stop S2, a second lens L2 and a third lens L3, as shown in Fig. 22, from the object side toward the image side. And the first lens L1, the aperture stop S2, the second lens L2, and the third lens L3 in this order. Curvature radius (mm unit), lens surface spacing (mm unit), refractive index of lens material, Abbe number of lens material, focal length, numerical aperture of lens constituting the sixth to tenth embodiments of the imaging lens of the second invention And aspheric coefficients are listed and published in Tables 6 to 10, respectively.

Example 6

(A) The object-side curvature radius r ₁ of the first lens L1 is r ₁ = 0.421 mm.

(B) The image-side curvature radius r ₂ of the first lens L1 is r ₂ = −0.689 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.0901 mm.

However, D ₃ is d ₂ in FIG. 22. + d ₃ , where d ₂ = 0 mm.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1445 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3032 mm.

(F) The optical length L is L = 1.282mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.30 mm.

(H) The back focus b _f is b _f = 0.482 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.90.

therefore,

(2-1) │ r ₁ / r ₂ │ = │0.421 / -0.689│ = 0.611,

(2-2) D ₃ / f = 0.0901 / 1.00 = 0.0901,

(2-3) d ₄ / f = 0.1445 / 1.00 = 0.1445,

(2-4) d ₆ / f = 0.3032 / 1.00 = 0.3032,

(2-5) L / 2Y = 1.282 / 1.30 = 0.9862,

(2-6) b _f / f = 0.482 / 1.00 = 0.482,

(2-7) F _NO = 2.90,

By doing so, the lens of Example 6 satisfies all of the following Conditional Expressions (2-1) to (2-7).

0.55 <| r ₁ / r ₂ | <0.70 (2-1)

0.08 <D ₃ / f <0.12 (2-2)

0.140 ≤ d ₄ / f <0.270 (2-3)

0.24 <d ₆ / f <0.40 (2-4)

0.90 <L / 2Y <1.10 (2-5)

0.40 <b _f / f <0.52 (2-6)

2.70 <F _NO <3.60 (2-7)

Subsequently, in the second invention, as the conditional formula, seven formulas from (2-1) to (2-7) are indicated.

As shown in Table 6, the diaphragm S2 is provided in the position between the 1st lens L1 and the 2nd lens L2. That is, the diaphragm surface may indicate that there is a plane, so r ₃ = ∞ as showed in Table 6, the aperture (S2) on the side where r ₃ is arranged. The numerical aperture (F number) is 2.90.

23 is a cross sectional view of the imaging lens of Example 6. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.482mm.

Distortion aberration curve 120 shown in Fig. 24, astigmatism curve shown in Fig. 25 (aberration curve 122 for the major journal surface and aberration curve 124 for the sagittal plane), and color and spherical aberration curve (C line aberration shown in Fig. 26). Curve 126, aberration curve 128 for d line, aberration curve 130 for e line, aberration curve 132 for F line, and aberration curve 132 for g line, respectively.

The vertical axis of the aberration curves of Figs. 24 and 25 shows the image as a percentage of the distance from the optical axis. In FIG. 24 and FIG. 25, 100% corresponds to 0.649 mm. In addition, the vertical axis of the aberration curve in FIG. 26 indicates the incident height h (F-number), and the maximum corresponds to 2.90. The horizontal axis in FIG. 26 indicates the magnitude of the aberration.

The distortion aberration is at the absolute value of 1.1701% at the maximum 100% (0.649 mm) position, and the absolute value of the aberration is within 1.1707% within the range of 0.649 mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the surface of the mary journal is maximum at 0.0571mm at the 100% elevation (0.649mm height) position, and the absolute value of the aberration amount is within 0.0571mm within the range of 0.649mm or less elevation. .

As for color and spherical aberration, the absolute value of the aberration curve 134 with respect to the g line reaches a maximum of 0.0581 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0581 mm.

Example 7

(A) The object-side curvature radius r ₁ of the first lens L1 is r ₁ = 0.436 mm.

(B) The image-side curvature radius r ₂ of the first lens L1 is r ₂ = −0.659 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.0925 mm.

However, D ₃ is d ₂ in FIG. 22. + d ₃ , where d ₂ = 0 mm.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1479 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3173 mm.

(F) The optical length L is L = 1.288 mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.32 mm.

(H) The back focus b _f is b _f = 0.460 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.78.

therefore,

(2-1) │r ₁ / r ₂ │ = │0.436 / -0.659│ = 0.6616,

(2-2) D ₃ / f = 0.0925 / 1.00 = 0.0925,

(2-3) d ₄ / f = 0.1479 / 1.00 = 0.1479,

(2-4) d ₆ / f = 0.3173 / 1.00 = 0.3173,

(2-5) L / 2Y = 1.288 / 1.32 = 0.9758,

(2-6) b _f / f = 0.460 / 1.00 = 0.460,

(2-7) F _NO = 2.78,

By doing so, the lens of Example 7 satisfies all of the following Conditional Expressions (2-1) to (2-7).

0.55 <| r ₁ / r ₂ | <0.70 (2-1)

0.08 <D ₃ / f <0.12 (2-2)

0.140 ≤ d ₄ / f <0.270 (2-3)

0.24 <d ₆ / f <0.40 (2-4)

0.90 <L / 2Y <1.10 (2-5)

0.40 <b _f / f <0.52 (2-6)

2.70 <F _NO <3.60 (2-7)

As shown in Table 7, the diaphragm S2 is provided in the position between the 1st lens L1 and the 2nd lens L2. That is, since the diaphragm plane is flat, it is shown in Table 7 as r ₃ = ∞, and it indicates that the diaphragm S2 is disposed at the position of the plane r ₃ . The numerical aperture (F number) is 2.78.

27 is a sectional view of the imaging lens of Example 7. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.460mm.

The distortion aberration curve 136 shown in FIG. 28, the astigmatism curve shown in FIG. 29 (aberration curve 138 for the main surface, and the aberration curve 140 for the sagittal plane), and the color and spherical aberration curves shown in FIG. Curve 142, aberration curve 144 for d line, aberration curve 146 for e line, aberration curve 148 for F line, and aberration curve 150 for g line, respectively.

The vertical axis of the aberration curves of Figs. 28 and 29 indicates the image height as a percentage of the distance from the optical axis. In FIG. 28 and FIG. 29, 100% corresponds to 0.660 mm. The vertical axis of the aberration curve in Fig. 30 represents the incident height h (F-number), and the maximum corresponds to 2.78. 30 represents the magnitude of the aberration.

The distortion aberration is at an absolute value of 0.9205% at a position of 80% of elevation (0.528 mm), and an absolute value of aberration is within 0.9205% of the range of 0.660mm or less.

As for astigmatism, the absolute value of the aberration of the aberration is about 0.0608mm at the 100% height (0.660mm), and the absolute value of the aberration is within 0.0608mm within the range of 0.660mm or less. .

As for the chromatic and spherical aberration, the absolute value of the aberration curve 150 with respect to the g line reaches a maximum of 0.0733mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0733mm.

Example 8

(A) The object-side curvature radius r ₁ of the first lens L1 is r ₁ = 0.415 mm.

(B) The image-side curvature radius r ₂ of the first lens L1 is r ₂ = −0.671 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.0875 mm.

However, D ₃ is d ₂ in FIG. 22. + d ₃ , where d ₂ = 0 mm.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1400 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.2980 mm.

(F) The optical length L is L = 1.274mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.24 mm.

(H) The back focus b _f is b _f = 0.488 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.80.

therefore,

(2-1) │r ₁ / r ₂ │ = │0.415 / -0.671│ = 0.6185,

(2-2) D ₃ / f = 0.0875 / 1.00 = 0.0875,

(2-3) d ₄ / f = 0.1400 / 1.00 = 0.1400,

(2-4) d ₆ / f = 0.2980 / 1.00 = 0.2980,

(2-5) L / 2Y = 1.274 / 1.24 = 1.0274,

(2-6) b _f / f = 0.488 / 1.00 = 0.488,

(2-7) F _NO = 2.80,

By doing so, the lens of Example 8 satisfies all of the following Conditional Expressions (2-1) to (2-7).

0.55 <| r ₁ / r ₂ | <0.70 (2-1)

0.08 <D ₃ / f <0.12 (2-2)

0.140 ≤ d ₄ / f <0.270 (2-3)

0.24 <d ₆ / f <0.40 (2-4)

0.90 <L / 2Y <1.10 (2-5)

0.40 <b _f / f <0.52 (2-6)

2.70 <F _NO <3.60 (2-7)

As shown in Table 8, the diaphragm S2 is provided in the position between the 1st lens L1 and the 2nd lens L2. That is, the diaphragm surface may indicate that there is a plane, so r ₃ = ∞ as showed in Table 8, the aperture (S2) on the side where r ₃ is arranged. The numerical aperture (F number) is 2.80.

31 is a sectional view of the imaging lens of Example 8. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.488mm.

The aberration aberration curve 152 shown in FIG. 32, the astigmatism curve shown in FIG. 33 (aberration curve 154 for the primary surface and the aberration curve 156 for the sagittal surface), and the color and spherical aberration curve (C line) shown in FIG. Curve 158, aberration curve 160 for d line, aberration curve 162 for e line, aberration curve 164 for F line, and aberration curve 166 for g line, respectively, are shown graphically.

The vertical axis of the aberration curves of Figs. 32 and 33 shows the image as a percentage of the distance from the optical axis. In FIG. 32 and FIG. 33, 100% corresponds to 0.620 mm. In addition, the vertical axis of the aberration curve in Fig. 34 represents the incident height h (F-number), and the maximum corresponds to 2.80. 34 represents the magnitude of the aberration.

Distortion aberration is the maximum of the aberration amount is 0.5260% at the position of 70% of the height (0.434 mm), and the absolute value of the aberration is within 0.5260% within the range of 0.620mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the main journal surface is maximum at 0.0558mm at the 100% elevation (0.620mm) position, and the absolute value of the aberration amount is within 0.0558mm in the range below 0.620mm. .

As for color and spherical aberration, the absolute value of the aberration curve 166 with respect to the g line reaches a maximum of 0.0781 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0781 mm.

Example 9

(A) The object-side curvature radius r ₁ of the first lens L1 is r ₁ = 0.416 mm.

(B) The image-side curvature radius r ₂ of the first lens L1 is r ₂ = −0.671 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.0875 mm.

However, D ₃ is d ₂ in FIG. 22. + d ₃ , where d ₂ = 0 mm.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1400 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3008 mm.

(F) The optical length L is L = 1.274mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.26 mm.

(H) The back focus b _f is b _f = 0.485 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.80.

therefore,

(2-1) │r ₁ / r ₂ │ = │0.416 / -0.671│ = 0.6200,

(2-2) D ₃ / f = 0.0875 / 1.00 = 0.0875,

(2-3) d ₄ / f = 0.1400 / 1.00 = 0.1400,

(2-4) d ₆ / f = 0.3008 / 1.00 = 0.3008,

(2-5) L / 2Y = 1.274 / 1.26 = 1.0111,

(2-6) b _f / f = 0.485 / 1.00 = 0.485,

(2-7) F _NO = 2.80,

By doing so, the lens of Example 9 satisfies all of the following Conditional Expressions (2-1) to (2-7).

0.55 <| r ₁ / r ₂ | <0.70 (2-1)

0.08 <D ₃ / f <0.12 (2-2)

0.140 ≤ d ₄ / f <0.270 (2-3)

0.24 <d ₆ / f <0.40 (2-4)

0.90 <L / 2Y <1.10 (2-5)

0.40 <b _f / f <0.52 (2-6)

2.70 <F _NO <3.60 (2-7)

As shown in Table 9, the diaphragm S2 is provided in the position between the 1st lens L1 and the 2nd lens L2. That is, since the diaphragm plane is a plane, it is represented by Table ₃ as r ₃ = ∞, and it indicates that the diaphragm S ₂ is disposed at the position of the plane r ₃ . The numerical aperture (F number) is 2.80.

35 is a sectional view of the imaging lens of Example 9; The back focus for focal length 1.00mm can be secured to 0.485mm long enough.

Distortion aberration curve 168 shown in FIG. 36, astigmatism curve shown in FIG. 37 (aberration curve 170 for the primary surface and aberration curve 172 for the sagittal plane), and color and spherical aberration curve (C line aberration shown in FIG. 38) Curve 174, aberration curve 176 for d line, aberration curve 178 for e line, aberration curve 180 for F line, and aberration curve 182 for g line, respectively.

The vertical axis of the aberration curves of Figs. 36 and 37 shows the image as a percentage of the distance from the optical axis. In FIG. 36 and FIG. 37, 100% corresponds to 0.630 mm. In addition, the vertical axis of the aberration curve in FIG. 38 represents the incident height h (F-number), and the maximum corresponds to 2.80. 38 represents the magnitude of the aberration.

The distortion aberration is at an absolute value of 0.7085% at the position of 80% of the height (0.504mm), and the absolute value of the aberration is within 0.7085% in the range of 0.630mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the surface of the journal at the 100% height (0.630 mm) is 0.0948 mm, and the absolute value of the aberration is within 0.0948 mm within the range of 0.630 mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 182 with respect to the g line reaches a maximum of 0.0278 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0278 mm.

Example 10

(A) The object-side curvature radius r ₁ of the first lens L1 is r ₁ = 0.436 mm.

(B) The image-side curvature radius r ₂ of the first lens L1 is r ₂ = −0.661 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.0927 mm.

However, D ₃ is d ₂ in FIG. 22. + d ₃ , where d ₂ = 0 mm.

(D) The center thickness d ₄ of the second lens L2 is d ₄ = 0.1483 mm.

(E) The center thickness d ₆ of the third lens L3 is d ₆ = 0.3183 mm.

(F) The optical length L is L = 1.289 mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.24 mm.

(H) The back focus b _f is b _f = 0.459 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 3.40.

therefore,

(2-1) │r ₁ / r ₂ │ = │0.436 / -0.661│ = 0.6596,

(2-2) D ₃ / f = 0.0927 / 1.00 = 0.0927,

(2-3) d ₄ / f = 0.1483 / 1.00 = 0.1483,

(2-4) d ₆ / f = 0.3183 / 1.00 = 0.3183,

(2-5) L / 2Y = 1.289 / 1.24 = 1.0395,

(2-6) b _f / f = 0.459 / 1.00 = 0.459,

(2-7) F _NO = 3.40,

By doing so, the lens of Example 10 satisfies all of the following Conditional Expressions (2-1) to (2-7).

0.55 <| r ₁ / r ₂ | <0.70 (2-1)

0.08 <D ₃ / f <0.12 (2-2)

0.140 ≤ d ₄ / f <0.270 (2-3)

0.24 <d ₆ / f <0.40 (2-4)

0.90 <L / 2Y <1.10 (2-5)

0.40 <b _f / f <0.52 (2-6)

2.70 <F _NO <3.60 (2-7)

As shown in Table 10, the diaphragm S2 is provided in the position between the 1st lens L1 and the 2nd lens L2. That is, the diaphragm surface may indicate that there is a plane, so r ₃ = ∞ as showed in Table 10, the aperture (S2) on the side where r ₃ is arranged. The numerical aperture (F number) is 3.40.

39 is a sectional view of the imaging lens of Example 10. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.459mm.

Distortion aberration curve 184 shown in Fig. 40, astigmatism curve shown in Fig. 41 (aberration curve 186 for the main surface and aberration curve 188 for the sagittal plane), and color and spherical aberration curve (C line aberration shown in Fig. 42). Curve 190, aberration curve 192 for d line, aberration curve 194 for e line, aberration curve 196 for F line, and aberration curve 198 for g line, respectively, are shown graphically.

The vertical axis of the aberration curves of Figs. 40 and 41 shows the image as a percentage of the distance from the optical axis. In FIG. 40 and FIG. 41, 100% corresponds to 0.620 mm. In addition, the vertical axis of the aberration curve in FIG. 42 indicates the incident height h (F-number), and the maximum corresponds to 3.40. 42 represents the magnitude of the aberration.

The distortion aberration is at the maximum 80% (0.496 mm), and the absolute value of the aberration is 1.5860%, and the absolute value of the aberration is within 1.5860% in the range of 0.620 mm or less.

As for astigmatism, the absolute value of the aberration amount with respect to the surface of the journal is maximum at 0.0571mm at the position of 100% of the height (0.620mm), and the absolute value of the aberration is within 0.0571mm within the range of 0.620mm or less. .

As for color and spherical aberration, the absolute value of the aberration curve 198 with respect to the g line reaches a maximum of 0.0233 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0233 mm.

<Third invention>

The imaging lens of the third invention has an aperture stop S1, a first lens L1, an aperture stop S2, a second lens L2 and a third lens L3, as shown in FIG. The aperture diaphragm S1, the first lens L1, the aperture diaphragm S2, the second lens L2 and the third lens L3 are arranged in this order from the object side toward the image side. Curvature radius (mm unit), lens surface spacing (mm unit), refractive index of lens material, Abbe number of lens material, focal length, numerical aperture of lens constituting the eleventh and twelfth embodiments of the imaging lens of the third invention And aspheric coefficients are listed and published in Tables 11 to 12, respectively.

Example 11

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.405mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.720 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.0883 mm.

However, D ₃ is d ₃ in FIG. 43 + d ₄ , where d ₃ = 0 mm.

(D) The center thickness D ₄ of the second lens L2 is D _4. = 0.1417 mm.

However, D ₄ is the same as d ₅ in FIG. 43.

(E) The center thickness D ₆ of the third lens L3 is D _6. = 0.2497 mm.

However, D ₆ is the same as d in Fig. ₇ 43.

(F) The optical length L is L = 1.252 mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.26 mm.

(H) The back focus b _f is b _f = 0.509 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.80.

therefore,

(3-1) │r ₂ / r ₃ │ = │0.405 / -0.720│ = 0.5625,

(3-2) D ₃ / f = 0.0883 / 1.00 = 0.0883,

(3-3) D ₄ / f = 0.1417 / 1.00 = 0.1414,

(3-4) D ₆ / f = 0.2497 / 1.00 = 0.2497,

(3-5) L / 2Y = 1.252 / 1.26 = 0.9937,

(3-6) b _f / f = 0.509 / 1.00 = 0.509,

(3-7) F _NO = 2.80,

By doing so, the lens of Example 11 satisfies all of the following Conditional Expressions (3-1) to (3-7).

0.55 <| r ₂ / r ₃ | <0.70 (3-1)

0.08 <D ₃ / f <0.12 (3-2)

0.140 ≤ D ₄ / f <0.270 (3-3)

0.24 <D ₆ / f <0.40 (3-4)

0.90 <L / 2Y <1.10 (3-5)

0.40 <b _f / f <0.52 (3-6)

2.70 <F _NO <3.60 (3-7)

Subsequently, in the third aspect of the invention, seven expressions are indicated as (3-1) to (3-7) as the conditional expressions.

As shown in Table 11, the diaphragm S1 is provided in the intersection position of the 1st surface (object side) of an 1st lens L1, and an optical axis, and the diaphragm S2 is made of the 1st lens L1 and 1st. It is provided in the position between two lenses L2. That is, since the diaphragm plane is a flat surface, r ₁ = ∞ and r ₄ = ∞ in Table 11, and the diaphragm S1 is disposed at the surface r ₁ and the diaphragm S2 is disposed at the surface r ₄ , respectively. (See FIG. 43). The numerical aperture (F number) is 2.80.

[Calculation of Aberration Using Aperture S1 as Aperture Aperture]

44 is a sectional view [A] of the imaging lens of Example 11. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.509mm.

When the aberration is calculated using the aperture S1 as the aperture diaphragm, the aberration is imputed under the condition that all chief rays entering the aperture S1 pass through the optical axis (center of the aperture) on which the aperture S1 is placed. It means to calculate. In FIG. 44, the position indicated by the point P is the optical axis (center of the iris) on which the diaphragm S1 is placed, and is the passage position of the chief ray incident on the diaphragm S1. As shown in FIG. 44, it turns out that the main chief ray which penetrates this point P passes through the diaphragm S1.

In order to distinguish it from the case where the aberration was calculated using the diaphragm S2 described later as an aperture diaphragm, the symbol of [A] is appropriately attached to each aberration, aberration curve, and aberration diagram as necessary.

Distortion aberration curve [A] 220 shown in FIG. 45, astigmatism curve [A] shown in FIG. 46 (aberration curve 222 for the main journal surface and aberration curve 224 for the sagittal plane), and color and spherical aberration curve shown in FIG. [A] (aberration curve 226 for C line, aberration curve 228 for d line, aberration curve 230 for e line, aberration curve 232 for F line and aberration curve 234 for g line), respectively. have.

The vertical axis of the aberration curve [A] of FIGS. 45 and 46 shows an image as what percentage of distance from an optical axis. In FIG. 45 and FIG. 46, 100% corresponds to 0.630 mm. In addition, the vertical axis of the aberration curve A in FIG. 47 represents the incident height h (F-number), and the maximum corresponds to 2.80. 47 represents the magnitude of the aberration.

The distortion aberration [A] has a maximum of 1.075% of the absolute value of the aberration at the position of 100% of the elevation (up to 0.630mm), and the absolute value of the aberration is within 1.075% within the range of 0.630mm or less.

In the astigmatism [A], the absolute value of the aberration amount with respect to the main journal surface is at a maximum of 0.0214 mm at the position of 100% of the height (0.630 mm), and the absolute value of the aberration amount is 0.0214 mm in the range of 0.630 mm or less. Is within.

As for color and spherical aberration [A], the absolute value of the aberration curve 234 with respect to the g line reaches the maximum at 0.0491 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0491 mm.

[Calculation of Aberration Using Aperture S2 as Aperture Aperture]

FIG. 48 is a sectional view [B] of the imaging lens of Example 11. FIG. The same drawing as in FIG. 44 but the shape of the light beams is different. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.509mm.

When the aberration is calculated using the aperture S2 as the aperture diaphragm, the aberration is impaired under the condition that all chief rays of light incident on the aperture S2 pass through the optical axis (center of the aperture) on which the aperture S2 is placed. It means to calculate. In FIG. 48, the position shown by the point P is an optical axis image (center of aperture) in which the diaphragm S2 was put, and is the passage position of the chief ray which injects into the diaphragm S2. As shown in FIG. 48, it turns out that the main chief ray which penetrates this point P passes through the diaphragm S2.

In order to distinguish it from the case where the above-mentioned aberration was calculated using the aperture S1 as the aperture diaphragm, the symbol of [B] is appropriately attached to each aberration, aberration curve, and aberration diagram as necessary.

Distortion aberration curve [B] 236 shown in FIG. 49, astigmatism curve [B] shown in FIG. 50 (aberration curve 238 for the primary surface and aberration curve 240 for the sagittal plane), and color and spherical aberration curve shown in FIG. [B] graphs aberration curve 242 for line C, aberration curve 244 for line d, aberration curve 246 for line e, aberration curve 248 for line F, and aberration curve 250 for line g. have.

The vertical axis of the aberration curve [B] in FIGS. 49 and 50 indicates the image height as a percentage of the distance from the optical axis. In FIG. 49 and FIG. 50, 100% corresponds to 0.630 mm. Moreover, the vertical axis | shaft of the aberration curve B of FIG. 51 has shown the incidence height h (F-number), and the maximum corresponds to 2.80. The horizontal axis in FIG. 51 represents the magnitude of the aberration.

Distortion aberration [B] has a maximum of 1.3965% of the aberration amount at the position of 100% of the height (0.630 mm), and an absolute value of the aberration amount is within 1.3965% of the range of 0.630mm or less.

In the astigmatism [B], the absolute value of the aberration amount with respect to the main journal surface is at a maximum of 0.0631 mm at the 100% elevation (0.630 mm), and the absolute value of the aberration amount is 0.0631 mm in the range of 0.630 mm or less. Are within.

As for color and spherical aberration [B], at 100% of the incident height h, the absolute value of the aberration curve 250 with respect to the g line reaches a maximum of 0.0491 mm, and the absolute value of the aberration amount falls within 0.0491 mm.

Example 12

(A) The object-side curvature radius r ₂ of the first lens L1 is r ₂ = 0.585 mm.

(B) The image-side curvature radius r ₃ of the first lens L1 is r ₃ = -0.837 mm.

(C) The optical axis spacing D _{3 of} the first lens L1 and the second lens L2 is D _3. = 0.1149 mm.

However, D ₃ is d ₃ in FIG. 43 + d ₄ , where d ₃ = 0 mm.

(D) The center thickness D ₄ of the second lens L2 is D _4. = 0.2532 mm.

However, D ₄ is the same as d ₅ in FIG. 43.

(E) The center thickness D ₆ of the third lens L3 is D _6. = 0.3952 mm.

However, D ₆ is the same as d in Fig. ₇ 43.

(F) The optical length L is L = 1.531 mm.

(G) The image height (effective screen diagonal length) 2Y is 2Y = 1.42 mm.

(H) The back focus b _f is b _f = 0.519 mm.

(I) aperture ratio (F number) (F _NO ) is F _NO = 2.80.

therefore,

(3-1) │r ₂ / r ₃ │ = │0.585 / -0.837│ = 0.6989,

(3-2) D ₃ / f = 0.1149 / 1.00 = 0.1149,

(3-3) D ₄ / f = 0.2532 / 1.00 = 0.2532,

(3-4) D ₆ / f = 0.3952 / 1.00 = 0.3952,

(3-5) L / 2Y = 1.531 / 1.42 = 1.0782,

(3-6) b _f / f = 0.519 / 1.00 = 0.519,

(3-7) F _NO = 2.80,

By doing so, the lens of Example 12 satisfies all of the following Conditional Expressions (3-1) to (3-7).

0.55 <| r ₂ / r ₃ | <0.70 (3-1)

0.08 <D ₃ / f <0.12 (3-2)

0.140 ≤ D ₄ / f <0.270 (3-3)

0.24 <D ₆ / f <0.40 (3-4)

0.90 <L / 2Y <1.10 (3-5)

0.40 <b _f / f <0.52 (3-6)

2.70 <F _NO <3.60 (3-7)

Subsequently, in the third aspect of the invention, seven expressions are indicated as (3-1) to (3-7) as the conditional expressions.

As shown in Table 12, the diaphragm S1 is provided at the intersection of the first surface (object side) of the first lens L1 and the optical axis, and the diaphragm S2 is formed of the first lens L1 and the first lens. It is provided in the position between two lenses L2. That is, since the diaphragm surface is flat, r ₁ = ∞ and r ₄ = ∞ in Table 12, and the diaphragm S1 is disposed at the surface r ₁ and the diaphragm S2 is disposed at the surface r ₄ , respectively. (See FIG. 43). The numerical aperture (F number) is 2.80.

[Calculation of Aberration Using Aperture S1 as Aperture Aperture]

52 is a sectional view [A] of the imaging lens of Example 12. FIG. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.519mm.

As in the eleventh embodiment, the result of calculating the aberration when the aberration was calculated using the aperture S1 as the aperture stop will be described. In FIG. 52, the position indicated by the point P is the optical axis (center of the iris) on which the diaphragm S1 is placed, and is the passage position of the chief ray incident on the diaphragm S1. As shown in FIG. 52, it turns out that the main chief ray which penetrates this point P passes through the diaphragm S1.

Here, in order to distinguish it from the case where the aberration was calculated using the aperture S2 described later as an aperture diaphragm, the aberration, aberration curve, and aberration diagram of the aberration diagram will be described as appropriate.

Distortion aberration curve [A] 252 shown in FIG. 53, astigmatism curve [A] shown in FIG. 54 (aberration curve 254 for the primary surface and aberration curve 256 for the sagittal plane), and color and spherical aberration curve shown in FIG. Graph [A] (aberration curve 258 for line C, aberration curve 260 for line d, aberration curve 262 for line e, aberration curve 264 for line F, and aberration curve 266 for line g), respectively. have.

The vertical axis of the aberration curve [A] of FIGS. 53 and 54 shows the image as a percentage of the distance from the optical axis. In FIG. 53 and FIG. 54, 100% corresponds to 0.710 mm. Moreover, the vertical axis | shaft of the aberration curve A of FIG. 55 has shown the incidence height h (F-number), and the maximum corresponds to 2.80. 55 represents the magnitude of the aberration.

The distortion aberration [A] has a maximum of 3.2531% of absolute value of aberration at a position of 80% of elevation (0.568mm of elevation), and an absolute value of aberration of within 3.2531% of the range of 0.630mm or less of elevation.

In the astigmatism [A], the absolute value of the aberration amount with respect to the main surface is 0.0515 mm at the position of 100% of the height (0.710 mm) and the absolute value of the aberration is 0.0515 mm in the range of 0.710 mm or less. Are within.

As for color and spherical aberration [A], the absolute value of the aberration curve 266 with respect to the g line reaches a maximum of 0.0380 mm at 100% of the incident height h, and the absolute value of the aberration amount falls within 0.0380 mm.

[Calculation of Aberration Using Aperture S2 as Aperture Aperture]

56 is a sectional view [B] of the imaging lens of Example 12. FIG. The same drawing as in Fig. 52 but the shape of the light beams is different. The back focus for the focal length of 1.00mm can be secured to a sufficient length of 0.519mm.

As in the eleventh embodiment, the result of calculating the aberration when the aberration is calculated using the aperture S2 as the aperture stop will be described. In FIG. 56, the position indicated by the point P is the optical axis (center of the iris) on which the iris S2 is placed, and is the passage position of the chief ray incident on the iris S2. As shown in FIG. 56, it turns out that the main chief ray which penetrates this point P passes through the diaphragm S2.

Here, in order to distinguish the aberration from the case where the above-mentioned diaphragm S1 is used as the aperture diaphragm and the aberration is calculated, the description of the aberration, the aberration curve, and the aberration diagram as appropriate is appropriately described.

Distortion aberration curve [B] 268 shown in FIG. 57, astigmatism curve [B] shown in FIG. 58 (aberration curve 270 for the main journal surface, and aberration curve 272 for the sagittal plane), and color and spherical aberration curve shown in FIG. (B) (aberration curve 274 for line C, aberration curve 276 for line d, aberration curve 278 for line e, aberration curve 280 for line F, and aberration curve 282 for line g), respectively. have.

The vertical axis of the aberration curve [B] in FIGS. 57 and 58 indicates the image height as a percentage of the distance from the optical axis. In FIG. 57 and FIG. 58, 100% corresponds to 0.710 mm. In addition, the vertical axis of the aberration curve B in FIG. 59 indicates the incident height h (F-number), and the maximum corresponds to 2.80. The abscissa in Fig. 59 indicates the magnitude of the aberration.

Distortion aberration [B] has a maximum of 3.3733% of absolute value of aberration at a position of 80% of elevation (0.568mm of elevation), and an absolute value of aberration within 3.3733% of range of 0.710mm or less of elevation.

In the astigmatism [B], the absolute value of the aberration amount with respect to the main journal surface is at a maximum of 0.1629 mm at the 100% elevation (0.710 mm), and the absolute value of the aberration amount is 0.1629 mm in the range of 0.710 mm or less. Are within.

As for color and spherical aberration [B], at 100% of the incident height h, the absolute value of the aberration curve 282 with respect to the g line reaches a maximum of 0.0379 mm, and the absolute value of the aberration amount falls within 0.0379 mm.

As described above, in the imaging lens of the third aspect of the invention, the shapes of the first to third lenses and the constituent materials thereof are the same, and the mutual spacing between the lenses is the same, and both the aperture S1 and the aperture S2 are In the case of all arrangements, it is confirmed that a good image can be obtained in any case in which the values obtained in the case where the aberration S1 is calculated as the aperture diaphragm and the case where the aperture S2 is calculated as the aperture diaphragm are calculated. Could.

In addition, as is apparent from the description of the imaging lenses of the first to third inventions, each of the constituent lenses of the imaging lenses is defined by the conditional formulas (1-1) to (1-7) and the conditional formulas (2-1) to (2-7). And by designing to satisfy conditional formula (3-1)-(3-7), the subject which this invention is going to solve is solved. That is, it is possible to obtain an imaging lens in which the aberration is well corrected, a sufficient back focus can be obtained and the optical length is kept short.

Meanwhile, in the above-described embodiment, a plastic material of Xenox E48R is used for the first lens L1 and the third lens L3 and polycarbonate is used for the second lens L2. It goes without saying that a material other than glass can be used as long as it is a material that satisfies the conditions described in Examples and the like even if it is not a plastic material as well as a plastic material.

As described above, according to the imaging lenses of the first to third inventions, the aberration is well corrected, a good image can be obtained despite the short optical length, and the back focus can also be sufficiently secured.

From the above description, the imaging lens of the present invention is not only used as a lens for a camera embedded in a mobile phone, a personal computer or a digital camera, but also a camera lens and an image recognition function embedded in a personal digital assistant (PDA). It may be applied as a lens for a camera embedded in a toy provided with a camera, a lens for a camera embedded in a surveillance, inspection or security device.

Claims (6)

An aperture stop S1, a first lens L1, a second lens L2, and a third lens L3; The aperture diaphragm S1, the first lens L1, the second lens L2, and the third lens L3 are arranged in an order from the object side toward the image side; The first lens (L1) is a lens having a positive refractive power toward the rear surface toward the object side and the image side, The second lens (L2) is a lens having a negative meniscus-shaped refractive power toward the image plane toward the image side, The third lens (L3) is a lens having a positive refractive power toward the rear surface toward the object side and the image side, Both surfaces of the first lens L1 are aspherical, simultaneously both surfaces of the second lens L2 are aspherical, and both surfaces of the third lens L3 are aspheric, An imaging lens, which satisfies the following conditions. 0.55 <| r ₂ / r ₃ | <0.70 (1-1) 0.08 <d ₃ / f <0.12 (1-2) 0.140 ≤ d ₄ / f <0.270 (1-3) 0.24 <d ₆ / f <0.40 (1-4) 0.90 <L / 2Y <1.10 (1-5) 0.40 <b _f / f <0.52 (1-6) 2.70 <F _NO <3.60 (1-7) only, f: Composite focusing distance of the imaging lens r ₂ : radius of curvature (optical axis curvature radius) near the object-side optical axis of the first lens L1 r ₃ : radius of curvature (optical axis curvature radius) in the vicinity of the optical axis of the image-side surface of the first lens L1 d ₃ : Optical axis gap between the first lens L1 and the second lens L2 d ₄ : Center thickness of the second lens L2 d ₆ : center thickness of third lens L3 L: Distance on the optical axis from the object side surface of the first lens L1 to the image surface (optical length) 2Y: Approx. (Effective screen diagonal length) b _f : Distance on the optical axis from the image side surface of the third lens L3 to the image surface F _NO : F-number A first lens L1, an aperture stop S2, a second lens L2, and a third lens L3; The first lens L1, the aperture stop S2, the second lens L2, and the third lens L3 are arranged in an order from an object side toward an image side; The first lens (L1) is a lens having a positive refractive power toward the rear surface toward the object side and the image side, The second lens (L2) is a lens having a negative meniscus-shaped refractive power toward the image plane toward the image side, The third lens (L3) is a lens having a positive refractive power toward the rear surface toward the object side and the image side, Both surfaces of the first lens L1 are aspherical, at the same time both surfaces of the second lens L2 are aspherical, and both surfaces of the third lens L3 are aspheric. An imaging lens, which satisfies the following conditions. 0.55 <| r ₁ / r ₂ | <0.70 (2-1) 0.08 <D ₃ / f <0.12 (2-2) 0.140 ≤ d ₄ / f <0.270 (2-3) 0.24 <d ₆ / f <0.40 (2-4) 0.90 <L / 2Y <1.10 (2-5) 0.40 <b _f / f <0.52 (2-6) 2.70 <F _NO <3.60 (2-7) only, f: Composite focusing distance of the imaging lens r ₁ : radius of curvature (optical axis curvature radius) in the vicinity of the object-side optical axis of the first lens (L1) r ₂ : radius of curvature (optical axis curvature radius) in the vicinity of the optical axis of the image-side surface of the first lens L1 D ₃ : Optical axis gap between the first lens L1 and the second lens L2 d ₄ : Center thickness of the second lens L2 d ₆ : center thickness of third lens L3 L: Distance on the optical axis from the object side surface of the first lens L1 to the image surface (optical length) 2Y: Approx. (Effective screen diagonal length) b _f : Distance on the optical axis from the image side surface of the third lens L3 to the image surface F _NO : F-number An aperture stop S1, a first lens L1, an aperture stop S2, a second lens L2, and a third lens L3, The aperture diaphragm S2, the first lens L1, the aperture diaphragm S2, the second lens L2, and the third lens L3 are arranged in an order from the object side toward the image side. , The first lens (L1) is a lens having a positive refractive power toward the rear surface toward the object side and the image side, The second lens (L2) is a lens having a negative meniscus-shaped refractive power toward the image plane toward the image side, The third lens (L3) is a lens having a positive refractive power toward the rear surface toward the object side and the image side, Both surfaces of the first lens L1 are aspherical, simultaneously both surfaces of the second lens L2 are aspherical, and both surfaces of the third lens L3 are aspheric, An imaging lens, which satisfies the following conditions. 0.55 <| r ₂ / r ₃ | <0.70 (3-1) 0.08 <D ₃ / f <0.12 (3-2) 0.140 ≤ d ₄ / f <0.270 (3-3) 0.24 <D ₆ / f <0.40 (3-4) 0.90 <L / 2Y <1.10 (3-5) 0.40 <b _f / f <0.52 (3-6) 2.70 <F _NO <3.60 (3-7) only, f: Composite focusing distance of the imaging lens r ₂ : radius of curvature (optical axis curvature radius) near the object-side optical axis of the first lens L1 r ₃ : radius of curvature (optical axis curvature radius) in the vicinity of the optical axis of the image-side surface of the first lens L1 D ₃ : Optical axis gap between the first lens L1 and the second lens L2 D ₄ : center thickness of the second lens L2 D ₆ : center thickness of the third lens L3 L: Distance on the optical axis from the object side surface of the first lens L1 to the image surface (optical length) 2Y: Approx. (Effective screen diagonal length) b _f : Distance on the optical axis from the image side surface of the third lens L3 to the image surface F _NO : F-number The refractive index of the raw material of the said 2nd lens L2 is higher than the refractive index of the raw material of the said 1st lens L1 and the said 3rd lens L3, The said 2nd The Abbe number of the raw material of the lens (L2) is smaller than the Abbe number of the raw material of the said 1st lens (L1) and the said 3rd lens (L3). The first lens L1, the second lens L2 and the third lens L3 constituting the imaging lens according to any one of claims 1 to 3, having an Abbe number of 30 to 60. An imaging lens formed of a material which is a value within the range of. The lens according to any one of claims 1 to 3, wherein the first lens (L1) and the third lens (L3) constituting the imaging lens are lenses made of a cycloolefin plastic. And the second lens (L2) is a lens made of polycarbonate.

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