JPH10115776A - Image pickup lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup lens which is easily produced and has optically complete performance and whose constitution is simplified by obtaining a combined lens consisting of at least two positive lenses and at least one negative lens and having plural combined surfaces and making the refractive index of the positive lens larger than that of the negative lens. SOLUTION: This image pickup lens is obtained by combining and integrating three lenses, that is, the positive lens having both convex shapes r1 and r2 , the negative lens having both concave shapes r2 and r3 and the positive lens having the convex shape r3 on an object side and a plane shape r4 on an image surface side in order from the object side, and a diaphragm surface is set on the first surface of the lens. The combined lens includes the positive lens and the negative lens adjacently and satisfies conditions (1) Np -Nn >0.1 (2) 1.5f<TL>4f when the refractive indexes of the positive lens and the negative lens adjacent to each other are defined as Np and Nr , respectively. Provided that TL is the length of the entire lens system and (f) is the focal distance of the entire system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup lens for performing electronic image pickup such as a video camera and an image pickup apparatus using the same.

[0002]

2. Description of the Related Art In recent years, cameras for performing electronic imaging, such as those used in home video cameras, videophones, and door phones with cameras, have become widespread. Low cost is a major issue. A lens system used in these cameras generally has a fixed focal length and has about 3 to 6 lenses. FIG. 17 shows an example of such a lens system. Such a lens system is generally provided with a low-pass filter or an infrared cut filter (F) for eliminating moiré as shown in FIG. It is arranged in.

A conventional lens system used in these cameras is disclosed in Japanese Patent Laid-Open Publication No.
As disclosed in JP-A-191716, a lens using an aspherical single lens, and as disclosed in JP-A-61-277913, a lens composed of a single axial type gradient index lens (axial type GRIN lens), etc. is there.

[0004]

A conventional lens system having about 3 to 6 lenses has a large number of lenses and a complicated lens frame structure for fixing the lenses. There is a disadvantage that the performance tends to deteriorate due to the eccentricity of the lens. In addition, there is a disadvantage that the cost is increased.

Further, the conventional lens systems disclosed in Japanese Patent Application Laid-Open Nos. 4-191716 and 61-277913 have a simple lens configuration, but the optical performance of the lens system is not sufficient. There are drawbacks. In particular, correction of chromatic aberration and curvature of field cannot be said to be sufficient. Further, it is conceivable that an imaging lens is constituted by one radial type GRIN lens which is said to have a high aberration correction capability, but the radial type GRIN lens has a drawback that it is technically difficult to manufacture a lens material.

An object of the present invention is to provide an imaging lens which is easy to manufacture, has sufficient optical performance, and has a simple structure.

[0007]

The basic structure of an image pickup lens according to the present invention is a cemented lens having at least two positive lenses and at least one negative lens and having a plurality of cemented surfaces. It is characterized in that the refractive index is larger than the refractive index of the negative lens.

The lens system according to the present invention comprises, in order from the object side, a positive lens having a convex surface on the object side, a negative lens having a concave surface on the image side, and a positive lens having a convex surface on the object side. Are bonded and integrated, and the refractive index of the two positive lenses is larger than the refractive index of the negative lens. A lens system having a more desirable configuration can be obtained.

In order to solve the above-mentioned problem, it is conceivable that the imaging lens is constituted by only one lens element. If the imaging lens can be composed of only one lens element as described above, there is an advantage that a lens frame structure for holding the imaging lens can be simplified, and assembling and adjustment become easy. As a result, it is possible to reduce the cost, size and weight as a whole, including the lens barrel and the assembly adjustment, and to minimize the influence of assembly errors and maintain good optical performance.

As described above, a method of forming the imaging lens with one lens includes a method of forming an aspheric single lens, a method of forming one axial type GRIN lens,
A method using one radial type GRIN lens is conceivable.

However, as described above, there is a problem that the optical performance is not sufficient when the imaging lens is constituted by an aspherical single lens and when an imaging lens is constituted by one axial type GRIN lens. In particular, in both cases, correction of chromatic aberration and curvature of field is not sufficient. Further, when an imaging lens is constituted by one radial type GRIN lens, the optical performance is quite good, but there is a problem that the production of the material is technically difficult.

According to the present invention, a lens system composed of one lens component is constituted by using only a homogeneous lens which has been established in terms of manufacturing technology.

As a well-known lens composed of a single lens component composed of a homogeneous lens, there is known a lens composed of one lens component in which two lenses called an achromat are joined. However, since the normal achromat focuses only on the correction of chromatic aberration and spherical aberration, the curvature of field is large, and it is difficult to use it as it is for an imaging lens. On the other hand, if an attempt is made to favorably correct the curvature of field by achromatization, on the contrary, the spherical aberration will worsen. In other words, it is difficult to correct chromatic aberration, spherical aberration, and field curvature in a conventional achromat.

In the present invention, first, a lens component in which three lenses are joined and integrated is used. Conventionally, there are three cemented lenses, but these are mainly used for correcting the secondary spectrum with a microscope objective lens or the like. Since low-dispersion glass is used, the refractive index of the positive lens is used. And the field curvature is not sufficiently corrected.

As described above, the imaging lens of the present invention has at least two positive lenses and at least one positive lens.
One cemented lens component in which two negative lenses are cemented, such that the refractive index of the positive lens is larger than the refractive index of the negative lens, which allows chromatic aberration, spherical aberration,
Various aberrations such as curvature of field are corrected well.

In the imaging lens of the present invention, the cemented lens includes a positive lens and a negative lens adjacent to each other, and the refractive indices of the adjacent positive and negative lenses are N _p and N, respectively. _{When n} , the following conditions (1) and (2)
Is preferably satisfied.

(1) N _P −N _n > 0.1 (2) 1.5f <TL <4f where TL is the length of the entire lens system, and f is the focal length of the entire system.

In the imaging lens of the present invention, as described above, as described above, as described above, in order from the object side, a positive lens having a convex surface on the object side, a negative lens having a concave surface on the image side, and a positive lens having a convex surface on the object side surface. Consisting of three lenses,
It is desirable to form a lens system in which the two positive lenses have a configuration in which the refractive indexes of the two positive lenses are larger than the refractive index of the negative lens. In the lens system having a more desirable configuration, the above conditions (1) and (2) are satisfied.
It is even more desirable to satisfy

First, in the case where the lens system of the present invention is composed of three lenses, it is necessary to make the overall length of the lens system extremely long and to properly correct spherical aberration and chromatic aberration at each cemented surface. Positive power of three lenses in order from the object side,
It is desirable to arrange in the order of negative power and positive power. In this case, considering the correction of the field curvature and the spherical aberration, it is preferable that the refractive indexes of the two positive lenses be larger than the refractive indexes of the negative lenses, and that the two cemented surfaces each have a positive power.

In other words, in order to keep the Petzval sum to a small value and keep the image plane good, it is necessary to increase the refractive index of the positive lens and decrease the refractive index of the negative lens, as can be seen from the equation for giving the Petzval sum. There is. At this time, in the actual glass range, the image surface tends to slightly tilt in the negative direction in the lens system of the present invention as in the ordinary imaging lens. Therefore, it is necessary to properly balance the spherical aberration with the tilt of the image plane, and it is desirable that the spherical aberration of the entire lens system is slightly lower. Therefore, the positive power required for the entire lens system is distributed to the first surface, the second surface (joining surface), and the third surface (joining surface), so that each surface has a positive power. As a result, the positive power of each surface does not become extremely large, and the occurrence of spherical aberration on each surface can be suppressed to a small value. Can be balanced. In this case, the first lens of the positive lens has a biconvex shape, the second lens of the negative lens has a biconcave shape, and the third lens of the positive lens has a convex shape on the object side surface.

As a special case, the image side of the first lens and the object side of the second lens may be a flat surface or a surface convex to the object side. At this time, the cemented surface between the first lens and the second lens becomes powerless or negative power. However, by dispersing the power between the first lens surface and the third lens surface (joint surface), the amount of generated spherical aberration is allowed. Can be kept within.

Further, in the lens system of the present invention, it is desirable to satisfy the above condition (1) in order to favorably correct the field curvature. In order to properly correct the field curvature, it is necessary to reduce the Petzval sum, and it is necessary to increase the refractive index of the positive lens and decrease the refractive index of the negative lens. It is desirable to make the difference in the refractive index indicated by the condition. When the value exceeds the range of the condition (1), it becomes difficult to sufficiently correct the field curvature.

As described above, as a lens system according to the present invention, in order from the object side, a positive lens having a convex surface facing the object side, a negative lens having a concave surface facing the image side, and a positive lens having a convex surface facing the object side. A lens system comprising a lens component, particularly a biconvex positive lens, a biconcave negative lens, and a positive lens convex on the object side, which is a lens component obtained by cementing a first positive lens, a second negative lens, and a third positive lens. It is desirable that the following conditions (1A) and (1B) are satisfied.

(1A) N ₁ −N ₂ > 0.1 (1B) N ₃ −N ₂ > 0.1 where N ₁ , N ₂ and N ₃ are the first lens, the second lens and the third lens, respectively. Is the refractive index of

In the above conditions (1A) and (1B), N
₁ and N ₃ are the refractive indices N _p and N ₂ of the positive lens in the condition (1).
It is equivalent to the refractive index N _n of the negative lens, if the lens system of the present invention using the cemented lens of the three lenses, the condition (1A), thus satisfying the (1B).

In the lens system of the present invention having the above-described configuration, it is desirable that the condition (2) is satisfied in order to provide a predetermined power in the entire system while keeping the amount of aberration generated on each surface small. . If this condition (2) is satisfied, the spacing between the surfaces can be made sufficiently large, and the aberrations can be balanced without extremely increasing the refractive power of each surface. If the lower limit of the condition is exceeded, the height of the light beam on each surface does not change much and becomes close to thin, so that it is difficult to balance the aberrations. If the upper limit is exceeded, the lens system becomes too large, which is not preferable.

In the lens system of the present invention, it is desirable to satisfy the following condition (3) in order to satisfactorily correct chromatic aberration.

[0028] _{(3) V p -V n>} 5 , however, V _p, is V _n is the Abbe number of the positive lens, a negative lens of the adjacent.

If the above condition (3) is not satisfied, it becomes difficult to correct chromatic aberration. However, when a single color is used as in a laser optical system or the like, the condition (3) need not be satisfied.

The condition (3) is satisfied by the first lens of the positive lens, the second lens of the negative lens, and the third lens of the positive lens as described above.
In the case of a lens system composed of three lenses having a configuration in which the lenses are cemented, the Abbe numbers of the first, second, and third lenses are V ₁ ,
It is apparent that V ₂ and V ₃ can be expressed as the following conditions (3A) and (3B).

(3A) V ₁ −V ₂ > 5 (3B) V ₃ −V ₂ > 5 In the imaging lens of the present invention, coma and astigmatism are caused by setting the stop surface close to the first surface of the lens system. And by adjusting the power distribution of each surface.
At this time, distortion occurs in a slightly negative direction, that is, barrel-shaped distortion occurs, which is also a practically allowable amount.

In order to satisfactorily correct coma and astigmatism by adjusting the power of each surface as described above, it is desirable to satisfy the following conditions (4), (5) and (6).

(4) 0.4φ <φ ₁ <1.2φ (5) -0.3φ <φ ₂ <0.5φ (6) 0 <φ ₃ <0.6φ where φ is the overall lens system Power, φ ₁ is the power of the first surface, φ ₂ is the power of the second surface, and φ ₃ is the power of the third surface.

If these conditions are exceeded, it becomes difficult to achieve a good balance of the aberrations, and the optical performance deteriorates. That is, when the lower limits of the conditions (4), (5), and (6) are exceeded, it becomes difficult to obtain the power of the entire system.
If the power of the entire system is forcibly obtained, the power of the other surface becomes large, and the coma and astigmatism deteriorate as a whole. When the value exceeds the upper limit of the condition (4), astigmatism deteriorates. When the value exceeds the upper limit of the condition (5), coma aberration and spherical aberration deteriorate. When the value exceeds the upper limit of the condition (6), the coma becomes worse. Furthermore, the upper limit of the condition (5) and the condition (6)
If the upper limit is exceeded, the curvature of the cemented surface will be too steep to make the lens difficult to process, resulting in high costs.

With the above arrangement, the lens system of the present invention has
An aberration level sufficient for practical use as an imaging lens can be obtained.

Although the description has been given of the case of a three-element cemented lens, even if the number of lenses is increased to four or more, an optically equivalent or higher effect can be obtained.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the above-described imaging lens of the present invention and an imaging apparatus using the imaging lens will be described.

First, each embodiment of the imaging lens of the present invention will be described.

In Example 1, as shown in FIG. 1, in order from the object side, a biconvex positive lens, a biconcave negative lens, and a positive lens having a convex object side surface and a flat image surface side are used. This is an imaging lens in which two lenses are joined and integrated, and the aperture surface is set on the first surface of the lens. In this embodiment, the best image for an object at infinity can be formed at a distance of 0.7 from the final lens surface. The lens data is shown below. f = 6 mm, F / 2.0, maximum image height 1.8 mm, angle of view 2ω = 35.0 ° r ₁ = 6.4277 (aperture) d ₁ = 4.5173 n ₁ = 1.72916 ν ₁ = 54.68 r ₂ = −4.3411 d ₂ = 3.0845 n ₂ = 1.56732 ν ₂ = 42.83 r ₃ = 3.2588 d ₃ = 3.1426 n ₃ = 1.77250 ν ₃ = 49.60 r ₄ = ∞ LT = 1.79f φ ₁ = 0.681 φ, φ ₂ = 0.224 φ, φ ₃ = 0.378 φ This lens FIG. 7 shows the state of aberration of the system, and each aberration is well corrected. FIG. 7 shows a case where the object distance is infinity.

In the second embodiment, as shown in FIG. 2, three lenses of a biconvex positive lens, a biconcave negative lens, and a biconvex positive lens are joined and integrated in order from the object side. In the imaging lens, the aperture surface is set on the first lens surface. This embodiment is configured so that the best image for an object at infinity is formed at a distance of 0.9 from the final lens surface, and the lens data is as follows. f = 5 mm, F / 2.0, maximum image height 1.8 mm, angle of view 2ω = 41.9 ° r ₁ = 7.2706 (aperture) d ₁ = 3.6851 n ₁ = 1.81600 ν ₁ = 46.62 r ₂ = -3.7802 d ₂ = 2.0474 n ₂ = 1.59270 ν ₂ = 35.30 r ₃ = 4.1993 d ₃ = 3.5654 n ₃ = 1.81600 ν ₃ = 46.62 r ₄ = -13.7422 LT = 1.86f φ ₁ = 0.561 φ, φ ₂ = 0.295 φ, φ ₃ = 0.266 φ The aberration state of the lens system is as shown in FIG. 8, and each aberration is well corrected. FIG. 8 shows a case where the object distance is infinity.

The third embodiment has the configuration shown in FIG. 3 and includes, in order from the object side, a biconvex positive lens, a biconcave negative lens, and a positive lens having a convex object side surface and a flat image surface side. This is an imaging lens in which two lenses are joined and integrated, and the aperture surface is set on the first surface of the lens. In this embodiment, the distance 2
The best image for an object of 80 mm is configured just on the final surface of the lens, and the lens data is shown below. f = 4.5 mm, F / 1.8, maximum image height 1.8 mm, angle of view 2ω = 47.6 ° r ₁ = 5.3757 (aperture) d ₁ = 3.7197 n ₁ = 1.81600 ν ₁ = 46.62 r ₂ = −3.9287 d ₂ = 2.8910 n ₂ = 1.59270 ν ₂ = 35.30 r ₃ = 2.4461 d ₃ = 2.7989 n ₃ = 1.81600 ν ₃ = 46.62 r ₄ = ∞ LT = 2.09f φ ₁ = 0.683 φ, φ ₂ = 0.256 φ, φ ₃ = 0.411 φ This lens The aberration of the system is as shown in FIG. 9, and each aberration is well corrected. FIG. 9 shows a case where the object distance is infinite.

The fourth embodiment is shown in FIG. 4 and includes, in order from the object side, a biconvex positive lens, a biconcave negative lens, and a positive lens having a convex object side surface and a flat image surface side. The aperture surface is set closer to the object side than the first lens surface. This example is
It is configured such that the best image for an object at a distance of 13000 mm can be formed exactly on the final surface of the lens. The lens data is shown below. f = 10 mm, F / 1.0, maximum image height 1.8 mm, angle of view 2ω = 20.7 ° r ₁ = (aperture) d ₁ = 1.0000 r ₂ = 11.2828 (aspherical surface) d ₂ = 5.4246 n ₁ = 1.78650 ν ₁ = 50.00 r ₃ = -7.6604 d ₃ = 6.2000 n ₂ = 1.59270 ν ₂ = 35.30 r ₄ = 8.2280 d ₄ = 7.8489 n ₃ = 1.786650 ν ₃ = 50.00 r ₅ = ∞ Aspheric coefficient P = 1, A ₄ = -9.5047 × 10 ^-5 , A ₆ = -4.6575 × 10 ^-6 LT = 1.95f φ ₁ = 0.697 φ, φ ₂ = 0.253 φ, φ ₃ = 0.236 φ The aberration situation of this lens system is as shown in FIG.
Each aberration is well corrected. FIG. 10 shows a case where the object distance is infinite.

The fourth embodiment has a very bright lens system of F / 1.0. To achieve this caliber ratio,
An aspherical surface is used for the first lens surface, and a very bright lens system of F / 1.0 is used.

The aspherical surface used in this embodiment has the origin at the intersection with the optical axis, the x axis in the optical axis direction, and the y axis in a plane perpendicular to the x axis.
When taking the axis, it is represented by the following equation.

Where r is the radius of curvature of the reference spherical surface, p, A
_2i is a coefficient representing an aspheric surface.

When the aperture of the lens is made extremely large as in the fourth embodiment, even if the positive power required for the entire system is dispersed on three surfaces, the amount of spherical aberration is shifted toward the underside of the field curvature. It is much lower than the amount of falling.
In order to correct this, it is effective to introduce an aspherical surface. The positive power is large on the first lens surface near the stop so that the positive power decreases from the optical axis toward the periphery. Is effective. Thereby, the spherical aberration on the under side can be corrected, and the amount of curvature of field can be well balanced.

In Example 5, as shown in FIG. 5, in order from the object side, a meniscus-shaped positive lens with a convex surface facing the object side, a meniscus-shaped negative lens with a concave surface facing the image side, and a convex object side surface. An imaging lens formed by joining three lenses of a positive lens having a shape and a flat image surface side, and an aperture surface is set between a first lens of a positive meniscus lens and a second lens of a negative meniscus lens. ing. In addition, the fifth embodiment
In the figure, the image side of the lens system is filled with resin.

The fifth embodiment is configured so that the best image for an object at a distance of 280 mm can be formed in the resin 1.0 mm behind the final surface of the lens. Here, the thickness of the resin is set to 1.0 mm. In this case, the end face of the resin becomes an image forming plane.
The lens data of the fifth embodiment is as follows. f = 6 mm, F / 2.0, maximum image height 1.8 mm, angle of view 2ω = 33.9 ° r ₁ = 4.6104 d ₁ = 4.4456 n ₁ = 1.72916 ν ₁ = 54.68 r ₂ = 4.6314 (aperture) d ₂ = 2.1242 n ₂ = 1.56732 ν ₂ = 42.83 r ₃ = 2.8562 d ₃ = 3.1426 n ₃ = 1.777250 ν ₃ = 49.60 r ₄ = ∞ d ₄ = 1.0000 n ₄ = 1.49216 ν ₄ = 57.50 r ₅ = ∞ LT = 1.62f φ ₁ = 0.949 φ, φ ₂ = -0.210 φ, φ ₃ = 0.431 φ The aberration situation of this lens system is as shown in FIG.
Each aberration is well corrected. FIG. 11 shows a case where the object distance is infinity.

In the fifth embodiment, the stop is set between the first lens and the second lens, and the stop is provided with chromium oxide on one of the joining surfaces before joining the first lens and the second lens. It can be configured by providing a light-shielding portion on which is vapor-deposited.

Embodiment 6 is as shown in FIG. 6, in which, in order from the object side, a positive lens having a convex object side surface and a flat image surface side, and a negative lens having a flat object side surface and a concave image surface side. This is an imaging lens in which three lenses of a positive lens and a biconvex positive lens are joined and integrated, and the aperture surface is set on the object-side surface of the first lens. In this example, the image side of the lens system is filled with resin. In this embodiment, the distance is 530 mm
The best image for the object is formed in the resin 1.0 mm behind the final surface of the lens. Here, if the thickness of the resin is set to 1.0 mm, the end face of the resin becomes the image forming surface. The lens data is shown below. f = 5 mm, F / 2.0, maximum image height 1.8 mm, angle of view 2ω = 35.0 ° r ₁ = 6.4067 (aperture) d ₁ = 4.5095 n ₁ = 1.81600 ν ₁ = 46.62 r ₂ = ∞ d ₂ = 2.7438 n ₂ = 1.53172 ν ₂ = 48.91 r ₃ = 4.2264 d ₃ = 3.9189 n ₃ = 1.88300 ν ₃ = 40.78 r ₄ = -30.4102 d ₄ = 1.0000 n ₄ = 1.49216 ν ₄ = 57.50 r ₅ = ∞ LT = 2.23f φ ₁ = 0.637 φ, φ ₂ = 0, φ ₃ = 0.416 φ The aberration situation of this lens system is as shown in FIG.
Each aberration is well corrected. FIG. 12 shows a case where the object distance is infinity.

In the sixth embodiment, since the joint surface between the first lens and the second lens is a flat surface, there is an advantage that lens processing and joining are easy and the cost is low.

Of the embodiments described above, the first, third, fourth, and fifth embodiments have the most image-side surface (the image-side surface of the third lens) being flat. In addition, the image plane is located near this plane, which is very convenient when an image pickup apparatus is configured by integrating a lens system with an image pickup device such as a CCD.

FIG. 13 shows an example of an image pickup apparatus in which an image pickup lens and an image pickup element are integrated by using the lens system according to the first embodiment of the present invention. In this figure, 1 is a lens system,
2 is an imaging chip of the imaging device, 3 is an imaging surface of the imaging device, 4
Reference numeral denotes a ceramic substrate of the image sensor, in which a flat portion, which is the final surface of the lens system, is directly adhered to the ceramic substrate 4 of the image sensor from which the protective glass has been removed. Example 1
The best image for an object at infinity is formed at a position 0.7 mm behind the final lens surface. Therefore, if the distance between the final lens surface and the imaging surface is set to 0.7 mm, an image of an object at infinity can be captured by the integrated imaging device. At this time,
Due to the depth of field, even an object located on the lens side from infinity can be imaged in a considerably wide range.

FIG. 14 shows an example of a device integrated with an image pickup device using the lens system according to the third or fourth embodiment of the present invention. FIG. 14 (A) is a side view, and FIG. ) Is a plan view. In the figure, 5 is a lens system, 6 is an imaging chip of the imaging device, 7 is an imaging surface of the imaging device, 8 is a ceramic substrate of the imaging device, 9 is a connection portion of the imaging chip, and a plane portion which is a final surface of the lens system. Is directly adhered to the imaging chip 6 of the imaging device from which the protective glass has been removed. In the lens system according to the third embodiment, the best image for an object at a distance of 280 mm can be formed just near the final surface of the lens. In the case of the lens system of Example 5, the best image for an object at a distance of 13000 mm can be formed just near the final surface of the lens. Therefore, an image of an object at a predetermined distance can be captured by the imaging device directly bonded to and integrated with the imaging chip. At this time, an object around a predetermined distance can be imaged in a considerably wide range depending on the depth of field. In addition, at the time of bonding, the image side portion of the lens is machined in a step shape as shown in the figure in order to avoid interference with the connection portion as the outer shape of the lens.

FIG. 15 shows a configuration in which the lens and the image pickup element are integrated with resin by using a lens system according to the fifth or sixth embodiment of the present invention. In this figure, 10 is a lens system, 11 is an imaging chip of an imaging device, 12 is an imaging surface of the imaging device, 13 is a ceramic substrate of the imaging device, and a resin 1 is provided between the lens system and the imaging chip.
It is filled with 4. In the lens system of Example 5, the distance 2
Best image for object at 80mm is 1mm from lens system
Can only be in the resin behind. Therefore, if the thickness of the resin is adjusted to 1 mm, an image of an object at a distance of 280 mm can be captured. At this time, an object at a distance of about 280 mm can be imaged in a considerably wide range depending on the depth of field.

As in the fifth embodiment, by employing a configuration in which the space between the lens system and the image pickup device is filled with resin, the marginal rays can be prevented from having a large angle behind the lens. Can be taken.

The lens system of the sixth embodiment has a distance 530
The best image for an object in mm is formed in the resin 1 mm behind the lens system. Therefore, if the thickness of the resin is adjusted to 1 mm, an image of an object at a distance of 530 mm can be captured. At this time, an object at a distance of about 530 mm can be imaged in a considerably wide range depending on the depth of field. In the sixth embodiment, the lens surface (final lens surface) in contact with the resin has a curvature. However, if the resin is used, the integration of the imaging lens and the imaging element is easy.

As described above, the lens system of the present invention is suitable for forming an image pickup apparatus in which the lens system and the image pickup element are integrated. , And can be easily integrated with the image sensor.

At this time, a low-pass filter or an infrared cut filter which is conventionally disposed behind the imaging lens is changed as follows so that an imaging optical system having such a filter function, an optical system, and an imaging device are connected. An integrated imaging device can be configured.

First, in order to provide the function of an infrared cut filter, for example, as shown in FIG. 16 (B)
A method of applying a coating 16 for cutting infrared light on the lens surface as shown in FIG.

In order to provide a function of a low-pass filter, aberrations and diffraction blur of the lens system are increased to a pixel pitch at which moire is generated, or moire is eliminated on the first surface of the lens. For constructing a diffraction pattern for this purpose.

The imaging lens according to the present invention has the structure described in the claims, and the structure described in each of the following items can also achieve the object of the present invention.

(1) The lens system according to claim 1, 2 or 3, wherein the following conditions (4), (5),
An imaging lens which satisfies (6).

(4) 0.4φ <φ ₁ <1.2φ (5) -0.3φ <φ ₂ <0.5φ (6) 0 <φ ₃ <0.6φ (2) Claims Item 4. The imaging lens according to Item 1, 2 or 3, wherein each cemented surface has a positive power or is a powerless lens.

(3) In the lens system according to claim 1, in order from the object side, a positive lens having a convex surface on the object side, a negative lens having a concave surface on the image side, and a convex lens on the object side. An imaging lens comprising a three-lens lens and a positive lens having three lenses joined together and integrated, wherein the refractive index of the two positive lenses is larger than the refractive index of the negative lens .

(4) In the lens system described in claims 1, 2 or 3 or (1), (2) or (3), the surface closest to the image is a plane. An imaging lens, characterized in that:

(5) The lens closest to the object in the lens system described in claim 1, 2 or 3 or the lens system described in (1), (2), (3) or (4). An imaging lens characterized in that the object-side surface is an aspheric surface whose positive power decreases from the optical axis toward the periphery.

(6) The lens system according to claim 1, 2 or 3 or (1), (2), (3), (4) or (5), wherein at least An imaging lens, wherein an infrared light cut function is provided inside or on a surface of one lens.

(7) Claims 1, 2 or 3 of the claims or the above (1), (2), (3), (4),
An imaging lens according to (5) or (6), wherein a function of a low-pass filter is provided inside or on at least one of the lenses.

(8) Claims 1, 2 or 3 of the claims or the above (1), (2), (3), (4),
(5) An imaging apparatus, wherein the imaging lens described in (6) or (7) is integrated with an imaging element.

(9) The lens system described in (8) above, wherein the outer peripheral portion near the image-side surface of the lens system is processed to be smaller than the outer shape of the entire lens system. Imaging device.

(10) The image pickup apparatus according to the above item (8), wherein the image pickup lens and the image pickup element are integrated with a resin.

[0073]

The imaging lens of the present invention is a homogeneous lens, and therefore easy to manufacture, and has sufficient optical performance. Further, the imaging lens is integrated as one lens component by joining, so that the lens barrel structure and the assembly adjustment are simplified, and the influence of an assembly error is small. Since the number of lenses can be three, the conventional three to three lenses can be used.
Compared with the six-lens configuration, the total number of components including the periphery of the lens system is greatly reduced, and it is possible to reduce the size and cost of the lens system. Further, by integrating the image pickup lens of the present invention and the image pickup device, an image pickup apparatus having a simple configuration can be configured.

[Brief description of the drawings]

FIG. 1 is a sectional view of Embodiment 1 of an imaging lens of the present invention.

FIG. 2 is a sectional view of Embodiment 2 of the imaging lens of the present invention.

FIG. 3 is a cross-sectional view of Embodiment 3 of the imaging lens of the present invention.

FIG. 4 is a sectional view of Embodiment 4 of the imaging lens of the present invention.

FIG. 5 is a sectional view of Embodiment 5 of the imaging lens of the present invention.

FIG. 6 is a sectional view of Embodiment 6 of the imaging lens of the present invention;

FIG. 7 is an aberration curve diagram according to the first embodiment of the present invention.

FIG. 8 is an aberration curve diagram according to the second embodiment of the present invention.

FIG. 9 is an aberration curve diagram according to the third embodiment of the present invention.

FIG. 10 is an aberration curve diagram according to the fourth embodiment of the present invention.

FIG. 11 is an aberration curve diagram according to the fifth embodiment of the present invention.

FIG. 12 is an aberration curve diagram according to the sixth embodiment of the present invention.

FIG. 13 is a diagram illustrating an example of a configuration of an imaging apparatus in which an imaging lens and an imaging element are integrated.

FIG. 14 is a diagram illustrating another example of the configuration of an imaging apparatus in which an imaging lens and an imaging element are integrated.

FIG. 15 is a diagram showing still another example of the configuration of an imaging apparatus in which an imaging lens and an imaging element are integrated.

FIG. 16 is a diagram illustrating an example of an imaging device having an infrared cut filter function.

FIG. 17 is a diagram showing a configuration of a conventional imaging lens.

Claims (3)

[Claims] At least two positive lenses and at least one positive lens
An imaging lens comprising a cemented lens composed of two negative lenses, wherein the cemented lens has a plurality of cemented surfaces, and a refractive index of the positive lens is larger than a refractive index of the negative lens. 2. The cemented lens includes a positive lens and a negative lens adjacent to each other. When the refractive indices of the adjacent positive and negative lenses are N _p and N _n , respectively, 2. The imaging lens according to claim 1, wherein a condition is satisfied. _{(1) N P -N n>} 0.1 (2) 1.5f <TL <4f However, TL is the whole lens system length, f is the focal length of the entire lens system. 3. The imaging lens according to claim 2, wherein the following condition is satisfied. _{(3) V p -V n>} 5 , however, V _p, is V _n is the Abbe number of the positive lens, a negative lens of the adjacent.