JP6016092B2 - Imaging lens, imaging device, and information device - Google Patents

Description

  The present invention is used as an imaging optical system in various cameras including a so-called silver salt camera, in particular, a digital camera, a video camera, a surveillance camera, and the like, and is used to improve a single-focus imaging lens for imaging a subject image. In particular, an imaging lens suitable as an imaging optical system in an imaging apparatus using electronic imaging means such as a digital camera and a digital video camera, an imaging apparatus such as a camera using such an imaging lens, and an imaging function The present invention relates to an information device such as a portable information terminal device.

In recent years, digital still cameras and digital video cameras have been widely used as imaging devices using solid-state imaging devices such as CCD (charge-coupled device) imaging devices and CMOS (complementary metal oxide semiconductor) imaging devices. A digital camera used for capturing an image, that is, a still image, is widely used as an imaging apparatus that replaces a conventional silver salt camera using a so-called silver salt film.
Solid-state imaging devices used in this type of imaging apparatus have a higher number of pixels, and accordingly, an imaging lens used as an imaging lens is required to have higher optical performance. In addition, the portability of imaging devices has been taken into account, and the downsizing has progressed, and the market has demanded imaging devices that have both high performance and compactness. It has been. Furthermore, the photographing speed has been increased, and a brighter lens is required as an imaging lens suitable for high-speed photographing.
As for the angle of view of the imaging lens for digital cameras, a certain wide angle is preferred so that it can be easily taken with a snapshot, etc., and equivalent to 35 mm in the case of 35 mm (so-called Leica) film photography. The half angle of view corresponding to the focal length: 32 degrees is one of the guidelines for the required angle of view.

Moreover, the price of some glass materials is rising with the recent surge in rare metals. For this reason, the company has made a dramatic breakthrough in situations where it is required to compete for design and development in order to reduce both the degree of freedom of glass materials used by reducing the cost of glass materials for optical systems and to achieve both high performance and compactness. There is a need to design and develop different optical systems.
More recently, along with the increase in the number of pixels of an image sensor as an image sensor for converting an optical image formed by an imaging lens into electrical image data, compact and high-performance optical systems have been put on the market. ing. In addition, camera-equipped portable information terminal devices such as mobile phones have been equipped with image sensors having a pixel number of 8 megapixels or more and a high-performance imaging lens corresponding thereto, and are close to digital cameras. It has been commercialized to a level that is not.
As an imaging lens mounted as an imaging lens for a camera function in this type of portable information terminal device, lenses using resin as a lens material are mainly used. An example of such an imaging lens is disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-295112, Japanese Patent No. 4616566). An example in which an inner focus type optical system is used as an imaging lens for a camera function of a portable information terminal device is disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2008-76953) and the like.

On the other hand, an example of using an inner focus type optical system employing a resin material for an imaging lens of a digital camera is disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2011-22427). Furthermore, even in the zoom lens, an example using an optical system employing a resin material is disclosed in Patent Document 4 (JP-equitable 1-24284) and the like. An example in which an optical system using a resin material for an imaging lens is used in a simple camera called a “lens-attached film” (also referred to as a “single-use camera” or the like) that has been widely used. (JP-A-8-338944) and the like. Further, as an example of a so-called photographic lens, that is, an imaging lens in a camera, an example using an optical system in which resin lenses are used for all lenses is disclosed in Patent Document 6 (Japanese Patent Laid-Open No. 2-101417).
That is, the optical systems as the imaging lenses disclosed in Patent Documents 1 to 6 are all imaging lenses using resin lenses, and in particular, the optical systems of Patent Document 2 and Patent Document 3 are: This is an inner focus type optical system in which the entire length of the optical system does not change during focus adjustment, that is, focusing.

Patent Document 1 shows an optical system for a camera function in a portable information terminal device, which has a wide angle of three lenses, an open F value equivalent to F2.4, and a 35 mm equivalent focal length equivalent to 32 mm. It is configured as a system optical system. Patent Document 2 also shows an optical system for a camera function in a portable information terminal device, which has four lenses, an open F value equivalent to F3.5, and a 35 mm equivalent focal length equivalent to 35 mm. It is configured as a wide-angle optical system. The optical system shown in Patent Document 3 is an inner focus type optical system in which the number of lenses is seven and a resin material lens is adopted as a part of the optical system, and the open F value is equivalent to F2.8. The optical system has a 35 mm equivalent focal length equivalent to 40 mm.
The optical systems of Patent Document 1 and Patent Document 2 described above are high performance with a small number of lenses, 3 and 4, but both are for portable information terminal devices in which the size of an image sensor as an image sensor is small. In the configuration, when the size of the image sensor is increased, it is not easy to obtain sufficient optical performance with a configuration of 3 to 4 lenses. The optical system of Patent Document 3 is bright and high-performance with an open F value of F2.8, but the total length of the optical system is 3.6 times the image height ratio, which is sufficient in terms of compactness. is not.

  The optical system disclosed in Patent Document 4 is a zoom lens, and the entire optical system is made of a resin material. However, the total length of the optical system is large, and there is a surface with large chromatic aberration. Is not enough. Patent Document 5 shows an optical system composed of two resin lenses, but is a type in which the open F value is dark and the imaging surface is also curved, and is used in the optical system of a high-performance digital camera. Inappropriate to do. The optical system of the photographic lens disclosed in Patent Document 6 is also composed of four lenses, but the open F value is as dark as F4.0 and the total length of the optical system is large.

As described above, the optical systems of Patent Document 1 and Patent Document 2 have a small number of lenses of 3 and 4 and high performance, but both are small in size of an image sensor as an image sensor. When the size of the image sensor is increased, it is considered that there is room for improvement in terms of optical performance when the number of lenses is three to four. In addition, the optical system of Patent Document 3 is bright and high-performance with an open F value of F2.8, but the total length of the optical system is equivalent to 3.6 times the image height ratio, and in terms of compactness, There is room for improvement.
The optical system disclosed in Patent Document 4 is a zoom lens, and the entire optical system is made of a resin material. However, the overall length of the optical system is large, and there is a large chromatic aberration, so there is room for improvement. It is believed that there is. Patent Document 5 shows an optical system composed of two resin lenses, but is a type in which the open F value is dark and the imaging surface is also curved, and is used in the optical system of a high-performance digital camera. If so, there is room for improvement. The optical system of the photographic lens disclosed in Patent Document 6 is also composed of four lenses, but there is room for improvement because the open F value is dark as F4.0 and the total length of the optical system is large. it is conceivable that.
The present invention has been made in view of the above-described circumstances, and is a so-called rear focus type optical system that can perform focusing without changing the entire length of the optical system, and has a wide angle of about 32 to 33 degrees. Thus, the F value is as bright as about F2.5, the total length of the optical system is as small as about 2.3 times the image height, and there is little variation in distortion during focusing, resulting in high performance. An object of the present invention is to provide an image lens and a small and high-performance imaging device and information device using such an imaging lens.

In order to achieve the above-described object, the imaging lens according to the present invention provides
A first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power are sequentially arranged from the object side to the image plane side to form an optical image of the object. In an imaging lens comprising an optical system for imaging,
The first lens group has at least two lenses,
The second lens group has, in order from the object side to the image plane side, a lens having a positive refractive power, a lens having the weakest refractive power in the second lens group, and a negative refractive power. a lens made up of a lens having a positive refractive power, of four lenses,
The entire optical system is composed of seven or less lenses,
The at least two lenses in the second lens group are moved from the object side to the image plane side as focusing lenses to perform focusing from the infinity side to the short distance side.

According to the present invention, it is a so-called rear focus type optical system that can perform focusing without changing the entire length of the optical system, a half angle of view is a wide angle of about 32 to 33 degrees, and an F value is equivalent to F2.5. An imaging lens capable of obtaining high performance with a small and bright optical system and having a total optical system length as small as about 2.3 times the image height, and with little variation in distortion during focusing. It is possible to provide a small-sized and high-performance imaging apparatus and information apparatus using the.
That is, according to the imaging lens according to the present invention,
A first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power are sequentially arranged from the object side to the image plane side to form an optical image of the object. In an imaging lens comprising an optical system for imaging,
The first lens group has at least two lenses,
The second lens group has, in order from the object side to the image plane side, a lens having a positive refractive power, a lens having the weakest refractive power in the second lens group, and a negative refractive power. a lens made up of a lens having a positive refractive power, of four lenses,
The entire optical system is composed of seven or less lenses,
By moving the image plane side from the object side at least two lenses in the second lens group as a focusing lens, by the infinite side is configured to perform the focusing on the close range side,
This is a so-called rear focus type optical system, which has a wide angle of half angle of view of about 32 to 33 degrees, an F value as bright as about F2.5, and the entire length of the optical system is about 2.3 times the image height. A small size and high performance can be obtained.

It is sectional drawing along the optical axis which shows the structure of the optical system of the imaging lens in Example 1 which concerns on the 1st Embodiment of this invention. Aberrations indicating spherical aberration, astigmatism, distortion aberration, and coma aberration for d-line and g-line when the imaging lens according to Example 1 of the present invention shown in FIG. 1 is focused on an object at infinity. FIG. Spherical aberration and astigmatism about d-line and g-line when the imaging lens according to Example 1 of the present invention shown in FIG. 1 is focused at an imaging magnification of about −1/20 times (shooting distance≈500 mm). It is an aberration curve diagram showing various aberrations of aberration, distortion and coma. It is sectional drawing along the optical axis which shows the structure of the optical system of the imaging lens in Example 2 which concerns on the 2nd Embodiment of this invention. Aberrations indicating spherical aberration, astigmatism, distortion aberration, and coma aberration for d-line and g-line when the imaging lens according to Example 2 of the present invention shown in FIG. 4 is focused on an object at infinity. FIG. Spherical aberration and astigmatism with respect to d-line and g-line when the imaging lens according to Example 2 of the present invention shown in FIG. 4 is focused at an imaging magnification of about −1/20 times (imaging distance≈500 mm). FIG. 6 is an aberration curve diagram showing various aberrations such as distortion and coma. It is sectional drawing along the optical axis which shows the structure of the optical system of the imaging lens in Example 3 which concerns on the 3rd Embodiment of this invention. Aberrations showing various aberrations of spherical aberration, astigmatism, distortion aberration, and coma aberration with respect to the d-line and the g-line when the imaging lens according to Example 3 of the present invention shown in FIG. 7 is focused on an object at infinity. FIG. Spherical aberration and astigmatism with respect to d-line and g-line when the imaging lens according to Example 3 of the present invention shown in FIG. 7 is focused at an imaging magnification of about −1/20 times (imaging distance≈500 mm). FIG. 6 is an aberration curve diagram showing various aberrations such as distortion and coma. It is sectional drawing along the optical axis which shows the structure of the optical system of the imaging lens in Example 4 which concerns on the 4th Embodiment of this invention. Aberrations indicating spherical aberration, astigmatism, distortion aberration, and coma aberration with respect to the d-line and the g-line when the imaging lens according to Example 4 of the present invention illustrated in FIG. 10 is focused on an object at infinity. FIG. Spherical aberration and astigmatism with respect to d-line and g-line when the imaging lens according to Example 4 of the present invention shown in FIG. 10 is focused at an imaging magnification of about −1/20 times (imaging distance≈500 mm). FIG. 6 is an aberration curve diagram showing various aberrations such as distortion and coma. It is sectional drawing along the optical axis which shows the structure of the optical system of the imaging lens in Example 5 which concerns on the 5th Embodiment of this invention. Aberrations showing spherical aberration, astigmatism, distortion aberration, and various coma aberrations with respect to d-line and g-line when the imaging lens according to Example 5 shown in FIG. 13 is focused on an object at infinity. FIG. Spherical aberration and astigmatism with respect to d-line and g-line when the imaging lens according to Example 5 of the present invention shown in FIG. 13 is focused at an imaging magnification of about −1/20 times (imaging distance≈500 mm). FIG. 6 is an aberration curve diagram showing various aberrations such as distortion and coma. It is sectional drawing along the optical axis which shows the structure of the optical system of the imaging lens in Example 6 which concerns on the 6th Embodiment of this invention. Aberrations indicating spherical aberration, astigmatism, distortion, and coma aberration for d-line and g-line when the imaging lens according to Example 6 of the present invention illustrated in FIG. 16 is focused on an object at infinity. FIG. Spherical aberration and astigmatism with respect to d-line and g-line in the state where the imaging lens according to Example 6 of the present invention shown in FIG. 16 is focused at an imaging magnification of about −1/20 times (imaging distance≈500 mm). FIG. 6 is an aberration curve diagram showing various aberrations such as distortion and coma. The structure of an example of the relative support structure of the lens which has positive refractive power and the lens which has negative refractive power in the 1st lens group of the imaging lens which concerns on Example 7 which concerns on the 7th Embodiment of this invention. It is sectional drawing along the optical axis shown. Another example of a relative support structure of a lens having a positive refractive power and a lens having a negative refractive power in the first lens group of the imaging lens according to Example 8 according to the eighth embodiment of the invention. It is typical sectional drawing along the optical axis which shows a structure. Schematic cross section along the optical axis showing the configuration of an example of the relative support structure of two adjacent focusing lenses in the second lens group of the imaging lens according to Example 9 according to the ninth embodiment of the present invention FIG. The model along the optical axis which shows the structure of another example of the relative support structure of two adjacent focusing lenses in the 2nd lens group of the imaging lens which concerns on Example 10 which concerns on the 10th Embodiment of this invention. FIG. It is the perspective view seen from the front side which shows typically the external appearance structure of the digital camera as an imaging device which concerns on the 11th Embodiment of this invention, ie, the object side which is a to-be-photographed object, (a) of this invention. The imaging lens constructed using the imaging lens according to the first embodiment is retracted in the body of the digital camera, and (b) shows the imaging lens protruding from the body of the digital camera. Each is shown. It is the perspective view seen from the back side which showed the external appearance structure of the digital camera of FIG. 23, ie, the photographer side. FIG. 25 is a block diagram schematically illustrating a functional configuration of the digital camera of FIGS. 23 and 24.

Hereinafter, based on an embodiment of the present invention, an imaging lens, an imaging device, and an information device concerning the present invention are explained in detail with reference to drawings. Before describing specific numerical examples, first, a fundamental embodiment of the present invention will be described.
The first to sixth embodiments of the present invention are embodiments as an imaging lens constituting an optical system for forming an optical image of an object.
The imaging lens according to the first embodiment of the present invention is an imaging optical system that actively employs a resin material, and is configured as a so-called rear focus type in which the entire length of the optical system does not change with focusing. It is an optical system, has a wide angle of half angle of view of about 32 degrees to about 33 degrees, F value is as bright as about F2.5, and the total length of the optical system is about 2.2 times the image height. This is a high-performance imaging lens system in which a change in distortion due to the lens is small, and a reduction in cost can be achieved by using a resin material as a glass material of the optical system.

That is, the imaging lens according to the first embodiment of the present invention is
A first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power are sequentially arranged from the object side to the image plane side to form an optical image of the object. An imaging lens comprising an optical system for imaging,
The first lens group has at least two lenses,
The second lens group has, in order from the object side to the image plane side, a lens having a positive refractive power, a lens having the weakest refractive power in the second lens group, and a negative refractive power. a lens made up of a lens having a positive refractive power, of four lenses,
The entire optical system is composed of seven or less lenses,
By moving the at least two lenses in the second lens group from the object side to the image plane side as focusing lenses, focusing from the infinity side to the short distance side is achieved. The imaging lens is a high performance (corresponding to claim 1).
As described above, when the lenses of the first lens group are, for example, a combination of a negative lens and a positive lens, by disposing at least those two lenses closer to the object side than the aperture stop, positive spherical aberration can be reduced. At least four lenses are arranged as the second lens group on the image plane side of the aperture stop, and negative spherical aberration is generated by the most object side lens among them, thereby effectively correcting the spherical aberration. To do.

In addition, such a lens configuration can effectively correct other aberrations such as aberration, astigmatism, and coma. With respect to changes in various aberrations caused by the movement of the focusing lens, in this case, in particular, an increase in the astigmatism, it is possible to effectively suppress an increase in the astigmatism by using two focusing lenses. It becomes possible. Further, the focusing speed can be improved by setting the number of focusing lenses to two.
In addition, the imaging lens described above is
By forming at least one of the at least two lenses as a focusing lens to be moved for focusing into a negative meniscus lens concave on the object side, a higher performance imaging lens may be used. 2).
With such a configuration, it is possible to effectively correct sagittal and tangential astigmatism, in particular .

In such a configuration, in particular, it is possible to suppress an increase in astigmatic difference accompanying focusing as much as possible.
The imaging lens described above is
At the time of focusing, the at least two lenses as the focusing lens may be moved integrally in synchronism with each other, so that a higher-performance imaging lens may be provided (corresponding to claim 3 ).
In such a configuration, an increase in astigmatism accompanying focusing can be suppressed as much as possible. Although it is possible to move the two lenses individually to further reduce fluctuations in various aberrations due to focusing, as described above, at least two lenses as the focusing lens are simultaneously used. That is, by moving them in synchronism with each other, it is possible to realize a reduction in the number of parts in the mechanism parts, simplification of the mechanism parts, and the like, and many merits can be obtained.
The imaging lens described above is
When performing focusing, the most object-side lens and the most image-side lens in the second lens group may be fixed lenses that do not move, so that a higher-performance imaging lens may be provided (corresponding to claim 4 ). .

Such a configuration is the best condition of the focusing lens in the above-described imaging lens. In particular, with respect to the lens closest to the object side in the second lens group, the positive lens generated by the lens in front of the aperture stop (object side) is positive. It is possible to correct spherical aberration. By the way, if the lens closest to the object side of the second lens is moved as a focus group, the spherical aberration at the time of focusing at a short distance will be affected. Therefore, the lens closest to the object side of the second lens is brought into focus. It is desirable to use a fixed lens that does not move. In addition, the lens closest to the image plane in the second lens group efficiently corrects distortion and astigmatism. If these lenses are moved with focusing, distortion and astigmatism will occur. Since influences appear, it is desirable to use these as fixed lenses.
In addition, the imaging lens described above is
By adopting a configuration that satisfies the following conditional expression [1], a higher-performance imaging lens may be provided (corresponding to claim 5 ).
[1] 2.1 <| f / ff | <2.7
Here, f represents the focal length of the entire optical system when the photographing distance is set to infinity, and ff represents the combined focal length of the lens group constituting the focusing lens that moves during focusing. Conditional expression [1] is an optimum conditional expression for the focal length of the focusing lens. If | f / ff | in conditional expression [1] is below the lower limit, the field curvature tends to increase, and such a configuration is not desirable. Further, when | f / ff | in the conditional expression [1] exceeds the upper limit, coma increases, and such a configuration is not desirable.

In addition, the imaging lens described above is
By adopting a configuration that satisfies the following conditional expression [2], a higher performance imaging lens may be provided (corresponding to claim 6 ).
[2] 8.5 <| ΔDf / β | <12.5
Here, ΔDf is a moving distance of the focusing lens in a focusing operation for focusing from an infinite shooting distance to a close object (image forming magnification β), and β is an image forming magnification when focusing on a close object. Is shown. If | ΔDf / β | in conditional expression [2] is below the lower limit, the amount of change in magnification due to focusing increases, so the amount of focus movement associated with the focusing operation from infinity to a short distance object decreases, and the focusing speed However, such a configuration is not desirable because the resolution needs to be finely controlled. If | ΔDf / β | in conditional expression [2] exceeds the upper limit, the amount of change in magnification due to focusing decreases, the amount of movement increases with focusing from infinity to a close object, and focusing speed increases. Such a configuration is not desirable because it slows down.

The imaging lens described above is
By adopting a configuration that satisfies the following conditional expression [3], a compact and high-performance imaging lens may be provided (corresponding to claim 7 ).
[3] 2.2 <L / Y ′ <2.5
Here, L represents the distance from the most object-side surface of the first lens group to the image plane, and Y ′ represents the maximum image height. Conditional expression [3] regulates the total length of the imaging lens that best exhibits the effects of the present invention. If L / Y ′ in the conditional expression [3] exceeds the upper limit, the total length of the optical system becomes large, which is advantageous in terms of optical performance, but such a configuration is not desirable in terms of compactness. In addition, when L / Y ′ in conditional expression [3] is below the lower limit, various aberrations occur and optical performance is not achieved, so such a configuration is not desirable.
The imaging lens described above is
By adopting a configuration that satisfies the following conditional expression [4], a higher performance imaging lens may be provided (corresponding to claim 8 ).
[4] 1.0 [mm] <| (AX1-AX2) / β | <1.6 [mm]
Here, AX1 is the axial chromatic aberration of the g-line with respect to the d-line at an imaging distance of infinity, β is the imaging magnification when focusing on a close object, and AX2 is with respect to the d-line at the imaging magnification β The axial chromatic aberration of the g line is shown respectively. If | (AX1-AX2) / β | in the conditional expression [4] is below the lower limit, the longitudinal chromatic aberration is improved, but the lateral chromatic aberration is increased, and such a configuration is not desirable. . Also, if | (AX1-AX2) / β | in conditional expression [4] exceeds the upper limit, the longitudinal chromatic aberration increases, and such a configuration is not desirable.

The imaging lens described above is
The most image side lens of the first lens group and the most object side lens of the second lens group are biconvex lenses, and the aperture stop is disposed between the two consecutive biconvex lenses. By adopting a configuration that satisfies the conditional expression [5], a higher performance imaging lens may be provided (corresponding to claim 9 ).
[5] 0.7 <f1p / f2p <1.1
Here, f1p represents the focal length of the biconvex lens disposed adjacent to the object side of the aperture stop, and f2p represents the focal length of the biconvex lens disposed adjacent to the image plane side of the aperture stop. ing. If f1p / f2p in the conditional expression [5] falls below the lower limit or exceeds the upper limit and falls outside the range between the upper limit and the lower limit, particularly coma aberration and lateral chromatic aberration tend to increase. Such a configuration is not desirable.
The imaging lens described above is
By arranging a positive lens having a convex shape on the image plane side closest to the image plane side of the second lens group and satisfying the following conditional expression [6], a higher performance imaging lens can be obtained. It is also possible (corresponding to claim 10 ).
[6] 0.7 <f2pi / f <1.0
Here, f2pi represents the focal length of the positive lens closest to the image plane in the second lens group, and f represents the focal length of the entire optical system when the photographing distance is infinity. If f2pi / f in the conditional expression [6] is below the lower limit, sagittal coma and astigmatism are greatly generated and, in addition, distortion is affected. Such a configuration is not desirable. When f2pi / f in conditional expression [6] exceeds the upper limit, astigmatism and lateral chromatic aberration are greatly generated, such a configuration is not desirable.

The above-mentioned imaging lens,
Before SL positive lens on the most image side of the negative lens and the second lens group on the most image side of the second lens group, by adopting a configuration that satisfies the following condition (7), a higher performance It may be an imaging lens (corresponding to claim 11 ).
[7] 1.6 <| f2pi / f2ni | <2.0
Here, f2pi represents the focal length of the positive lens closest to the image plane in the second lens group, and f2ni represents the focal length of the negative lens closest to the image plane in the second lens group. If | f2pi / f2ni | in the conditional expression [7] is below the lower limit, astigmatism occurs greatly, and the curvature of field increases accordingly, such a configuration is not desirable. Further, if | f2pi / f2ni | in the conditional expression [7] exceeds the upper limit, lateral chromatic aberration is greatly generated, and such a configuration is not desirable.

The imaging lens described above is
The first lens group closer to the object side than the aperture stop is arranged with a lens having a negative refractive power and a lens having a positive refractive power sequentially from the object side to the image plane side. By adopting a configuration that satisfies the following conditional expression [8], a compact and high-performance imaging lens may be provided (corresponding to claim 12 ).
[8] 0.7 <| f1p / f1n | <1.1
Here, f1p represents the focal length of the lens having the positive refractive power of the first lens group, and f1n represents the focal length of the lens having the negative refractive power of the first lens group. If | f1p / f1n | in the conditional expression [8] is below the lower limit, the spherical aberration and the longitudinal chromatic aberration increase, and such a configuration is not desirable. If | f1p / f1n | in conditional expression [8] exceeds the upper limit, spherical aberration and axial chromatic aberration at an infinite shooting distance are improved, but spherical aberration and axial aberration when focusing on an object at a close distance are improved. Such a configuration is undesirable because of the increased chromatic aberration.

The imaging lens described above may be a more compact and high-performance imaging lens by satisfying the following conditional expression [9] (corresponding to claim 13 ).
[9] 0.5 <LD1 / LD2 <0.9
Here, LD1 is the maximum effective diameter of the lens having the largest diameter in the first lens group on the object side from the aperture stop, and LD2 is the maximum diameter in the second lens group on the image plane side from the aperture stop. The maximum effective diameter of a large lens is shown respectively. Conditional expression [9] regulates the lens diameter of the imaging lens that best exhibits the effects of the present invention. When LD1 / LD2 of the conditional expression [9] exceeds the upper limit or falls below the lower limit and falls outside the range between the upper limit and the lower limit, at least one lens of the first lens group and the second lens group Such a configuration is not desirable because the diameter increases, the lens barrel diameter increases, and further downsizing becomes difficult.

Furthermore, the imaging lens described above is
The first lens group may be a high-performance imaging lens by including at least one lens made of a resin material (corresponding to claim 14 ).

  In such a configuration, by using a resin material for the first lens group, the cost merit is large compared to the case of using a glass material, and the resin material can reduce the weight of the lens. It is possible to reduce the weight of the entire optical system.

The imaging lens described above is
The second lens group may be a high-performance imaging lens by including at least one lens made of a resin material (corresponding to claim 15 ).
In such a configuration, by using a resin material for the second lens group, the cost merit is large compared to the case of using a glass material, and the resin material can be configured to reduce the weight of the lens. It is possible to reduce the weight of the entire optical system.

The imaging lens described above is
All the lenses constituting the entire lens system may be made of a resin material so as to be a high-performance imaging lens (corresponding to claim 16 ).
In such a configuration, a resin material is used for the entire optical system, and aberrations are sufficiently corrected for aberrations (see Examples 1 to 6). By using a resin material, there are advantages such as good moldability, weight reduction, cost reduction, and easy processing of an aspherical shape as compared with the case of using a glass material.
The imaging lens described above is
The resin material constituting the lens composed of the resin material may be a high-performance imaging lens by using two types of resin materials, a cycloolefin resin material and a polyester resin material. (Corresponding to claim 17 ).
In such a configuration, there is a cost merit of promoting unification of component materials by using two kinds of resin materials as the resin material.

The imaging lens described above is
The first lens group includes a negative lens and a positive lens adjacent to each other, and both the negative lens and the positive lens have the same material for the lens optical portion and the lens peripheral portion constituting the support mechanism near the lens outer periphery. in is one body, the lens peripheral portion in contact with the annular line contact manner of those in each other, by the structure where mutual support, (corresponding to claim 18) may be a high-performance imaging lens.
In such a configuration, the lens optical portion and the lens outer periphery are formed by forming a conical inclined surface portion at the lens peripheral portion in the vicinity of the outer periphery of the lens and abutting them in line contact to support each other (see FIG. 19). It is possible to reduce the number of lens mechanism parts by integrating the peripheral part of the lens constituting the nearby support mechanism part, and to suppress shift deviation between the lens surfaces.
The imaging lens described above is
The first lens group includes a negative lens and a positive lens adjacent to each other, and both the negative lens and the positive lens have the same material for the lens optical portion and the lens peripheral portion constituting the support mechanism near the lens outer periphery. It is also possible to provide a high-performance imaging lens by adopting a configuration in which they are integrated with each other and are in mutual contact with each other at the periphery of the lens in a surface contact manner in an annular band shape (corresponding to claim 19 ). ).

In such a configuration, the negative lens and the positive lens of the first lens group can be made of a resin material, and the lens optical portion and the lens peripheral portion can be structurally integrated. In this case, the number of parts of the lens mechanism parts can be reduced by adopting a structure in which plane portions formed in an annular belt shape are in contact with each other in a surface contact manner (see FIG. 20), and the positive lens It is possible to suppress tilt shift of the lens surface of the negative lens.
The imaging lens described above is
Adjacent each lens of the focusing lens is moved for focusing is an body both the lens periphery portion constituting the supporting mechanism of the lens optic portion and the lens outer periphery is the same material, the lens periphery portion to each other In this case, a high-performance imaging lens may be obtained by abutting in an annular line contact and supporting each other (corresponding to claim 20 ).
In such a configuration, the adjacent lenses of the focusing lens are made of a resin material, and a conical inclined surface portion is formed in the lens peripheral portion in the vicinity of the outer periphery of the two adjacent lenses so that the lenses are brought into line contact with each other. To support each other (see FIG. 21). In this way, the optical part of the lens and the peripheral part for the supporting mechanism in the vicinity of the outer periphery can be integrated to reduce the number of parts of the mechanism parts, and the shift between two adjacent lens surfaces can be achieved. The shift can be suppressed.

The imaging lens described above is
Adjacent each lens of the focusing lens is moved for focusing is an body both the lens periphery portion constituting the supporting mechanism of the lens optic portion and the lens outer periphery is the same material, the lens periphery portion to each other In this case, a high-performance imaging lens may be obtained by adopting an annular belt-like surface-contacting and mutual support structure (corresponding to claim 21 ).
In such a configuration, the adjacent lenses of the focusing lens are made of resin material, and the planar portions formed in an annular band shape are in surface contact with each other at the peripheral portion constituting the support mechanism near the outer periphery of the two adjacent lenses. To support each other (see FIG. 22). In this way, the optical part of the lens and the peripheral part for the support mechanism in the vicinity of the outer periphery can be integrated to reduce the number of mechanical parts, and the tilt deviation between two adjacent lens surfaces can be reduced. It becomes possible to suppress.
The imaging lens described above is
A high-performance imaging lens may be obtained by inserting an annular light-shielding mask as a fixed stop between adjacent lenses of the focusing lens that is moved for focusing (corresponding to claim 22 ). .

With such a configuration, it is possible to suppress the generation of harmful ghost flare by shielding stray light in the focusing lens with the light shielding mask in accordance with the change in the light path of the focusing lens. In particular, at the peripheral part of the vicinity of the outer diameter of the two adjacent lenses, the flat surface portions formed in an annular belt shape are brought into contact with each other in a surface contact manner so that they can be easily supported on the contact portions. It is possible to sandwich a light shielding mask (see FIG. 22), and it is possible to efficiently suppress harmful stray light in the focusing lens.
The imaging lens described above is
By providing a shutter space for disposing a mechanical shutter between the lenses and satisfying the following conditional expression [10], a higher performance imaging lens may be provided (corresponding to claim 23 ). To do).
[10] SD> 3.0 [mm]
Here, SD represents the dimension in the optical axis direction of the shutter space provided between the lenses. In this case, a shutter space is provided between the lenses before and after the aperture stop, that is, between the first lens group and the second lens group. It is most efficient to provide a shutter before and after the aperture stop where the diameter of the beam bundle is the largest, and a shutter space of at least 3.0 mm is secured.

Furthermore, the other imaging lens according to the first embodiment of the present invention is:
In seven following lens comprising an imaging lens of the entire system of the optical system,
An aperture stop is arranged between the lenses of the optical system,
Said opening the object side than the diaphragm, have each at least one and a lens having a lens and a negative refractive power having a positive refractive power, and a total of three following lens,
From the object side to the image plane side, the image plane side of the aperture stop is sequentially a lens having a positive refractive power, a lens having the weakest refractive power among the lenses on the image plane side of the aperture stop , A lens having a negative refractive power and a lens having a positive refractive power are arranged and configured.
In focusing, the lens having the weakest refractive power and the lens having a negative refractive power located on the image plane side with respect to the aperture stop are moved as the focusing lens from the object side to the image plane side, and are moved to infinity. By using a rear focus type optical system that performs a focusing operation from the side to the short distance side, a bright, small, and high-performance imaging lens may be provided (corresponding to claim 24 ).

  As described above, by combining a negative lens and a positive lens and arranging at least two lenses closer to the object side than the aperture stop, positive spherical aberration is generated, and after the aperture stop, that is, on the image plane side The negative lens generates negative spherical aberration and corrects it. The lens arrangement on the image plane side from the aperture stop, in order from the object side to the image plane side, a single lens having a positive refractive power, a lens having a weak refractive power, a negative lens having a concave shape on the object side, and A modification in which a positive lens having a convex shape is arranged on the image surface side, and an aberration correction lens is arranged between a so-called triplet type first lens and a second lens as a “positive-weak refractive power-negative-positive” arrangement. Configure as a triplet type. Regarding focusing, aberration variation due to focusing is minimized as much as possible by moving a lens having a weak refractive power and a negative lens having a concave shape on the object side as a focusing lens during focusing. Further, the focusing speed can be improved by configuring the focusing lens with two lenses. As for the aberration fluctuation generated by the movement of these two lenses, for example, astigmatism change at a short distance, the generation of astigmatism is kept small until the image height is about 0.8 Y '. (Refer to the aberration diagrams of the respective examples) High performance can be obtained even at a short distance. As a bright, compact, high-performance imaging lens, it is desirable that the entire optical system has a lens structure of 6 to 7 lenses.

The second embodiment of the present invention is an embodiment as an imaging device such as a so-called digital camera or an information device having an imaging function.
That is, the imaging apparatus according to the second embodiment of the present invention is configured by using the above-described imaging lens as an imaging optical system (corresponding to claim 25 ).
With such a configuration, a small and high-performance imaging device can be realized.
An information device according to the second embodiment of the present invention has an imaging function, and is configured using the imaging lens described above as an imaging optical system (corresponding to claim 26 ).
With such a configuration, a small and high-performance information device having an imaging function can be realized.

Next, specific examples based on the above-described embodiment of the present invention will be described in detail. Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6 described below are the first embodiment, the second embodiment, and the third embodiment of the present invention. The fourth embodiment corresponds to the fourth embodiment and the fifth embodiment, and is an example of a specific configuration based on specific numerical examples of the imaging lens, and the seventh embodiment is an embodiment. Implementation related to a specific support structure in a focusing lens of a lens having a positive refractive power and a lens having a negative refractive power in the first lens group in the imaging lens of Examples 1 to 6. The eighth embodiment is an embodiment of an imaging apparatus or information apparatus using a lens unit configured to have an imaging lens as shown in Examples 1 to 6 as an imaging optical system. It is a form.
1 to 3 are diagrams for explaining an imaging lens in Example 1 according to the first embodiment of the present invention, and FIGS. 4 to 6 illustrate a second embodiment of the present invention. FIG. 7 to FIG. 9 are for explaining the imaging lens in Example 3 according to the third embodiment of the present invention. FIGS. 10 to 12 are for explaining the imaging lens in Example 4 according to the fourth embodiment of the present invention, and FIGS. 13 to 15 illustrate the fifth embodiment of the present invention. FIG. 16 to FIG. 18 are for explaining the imaging lens in Example 6 according to the sixth embodiment of the present invention. belongs to.

Aberrations in the imaging lenses of Examples 1 to 6 are corrected at a high level, and spherical aberration, astigmatism, curvature of field, and lateral chromatic aberration are sufficiently corrected. By forming the imaging lens as in the present invention, the half angle of view is 32 to 33 degrees and the F value (F number) is as large as about F2.5, but very good imaging performance. It is clear from the respective Examples 1 to 6 that the above can be secured.
The meanings of symbols common to Examples 1 to 6 are as follows.
f: Focal length of the entire optical system F: F value (F number)
R: radius of curvature (for aspheric surfaces, paraxial radius of curvature / curvature C = 1 / R)
D: Surface interval Nd: Refractive index νd: Abbe number SD: Shutter space [mm]
ω: Half angle of view [degree]
In Examples 1 to 6, some lens surfaces are aspherical. In order to form an aspherical surface, each lens surface is directly aspherical like a so-called molded aspherical lens, and a resin that forms an aspherical surface on the lens surface of a spherical lens like a so-called hybrid aspherical lens. There is a configuration in which an aspheric surface is obtained by laying a thin film, any of which may be used. In such an aspherical shape, the displacement X in the optical axis direction at the position of the height H from the optical axis when the vertex of the surface is used as a reference, the cone coefficient is k, fourth order, sixth order, eighth order, The aspherical coefficients of the 10th order,... Are defined as C4, C6, C8, C10,.

FIG. 1 schematically shows a lens configuration of a longitudinal section when an optical system of an imaging lens according to Example 1 of the present invention is focused at infinity.
That is, the optical system of the image forming lens of Example 1 according to the first embodiment of the present invention, as shown in FIG. 1, sequentially from the object side to the image plane side, the first lens L1, 2 lens L2, 3rd lens L3, aperture stop AD, 4th lens L4, 5th lens L5, 6th lens L6, and 7th lens L7 are arranged, and 1st lens L1-7th lens L7 are In either case, a cemented lens is not configured, and a seven-lens configuration is used.
Focusing on the lens group configuration, the first lens L1 to the third lens L3 constitute a first lens group Gr1 having a positive refractive power, and the fourth lens L4 to the seventh lens L7 have a positive refractive power. A two-lens group Gr2 is configured. That is, the optical system of the imaging lens shown in FIG. 1 has a configuration in which the first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are sequentially arranged from the object side to the image plane side. .

Specifically, the first lens group Gr1 is a negative lens having a negative meniscus shape that is concave on the object side with a concave surface formed with an aspheric surface on the object side sequentially from the object side to the image surface side. And a second lens L2 composed of a biconcave negative lens having a concave surface having a slightly larger curvature on the object side and a concave surface formed with an aspheric surface on the image surface side. And a third lens L3 made of a biconvex positive lens having a convex surface having a slightly larger curvature than the image surface side on the object side and a convex surface formed by forming an aspheric surface on the image surface side. The one lens group Gr1 is configured to exhibit a positive refractive power. An aperture stop AD is disposed between the first lens group Gr1 and the second lens group Gr2.
The second lens group Gr2 is a biconvex shape in which, from the object side to the image surface side, a convex surface formed with an aspheric surface is sequentially directed toward the object side, and a convex surface having a slightly larger curvature than the object side is directed toward the image surface side. A fourth lens L4 made up of a positive lens, a fifth lens L5 made up of a negative meniscus negative lens having a negative refractive power that forms an aspherical surface on the object side and forms a convex shape on the object side, and an aspheric surface on the object side A concave lens formed by forming a negative lens having a negative meniscus shape on the object side and a convex surface formed by forming an aspheric surface on the image surface side, and a convex surface formed on the image surface side. A seventh lens L7 made of a positive lens having a positive meniscus shape is arranged, and the second lens group Gr2 is configured to exhibit a positive refractive power.

Further, a back insertion glass BG is disposed behind the first lens group Gr1 and the second lens group Gr2, that is, on the image plane side.
As in a so-called digital still camera, in an imaging optical system using a solid-state imaging device such as a CCD (charge coupled device) imaging device or a CMOS (complementary metal oxide semiconductor) imaging device, a back insertion glass, a low-pass filter, red At least one of an outer cut glass and a cover glass for protecting the light receiving surface of the solid-state imaging device is inserted. Are shown as one plane parallel plate. In addition, in Example 2 to Example 6, the back insertion glass BG is equivalently shown as one plane parallel plate, but the back insertion glass, low pass filter, It represents at least one of infrared cut glass and cover glass.

The first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are supported substantially integrally by an appropriate support frame or the like, except for a focusing lens described later, at least when used. That is, for focusing from a state where the shooting distance is infinite to an object at a short distance, two lenses of the fifth lens L5 and the sixth lens L6 in the second lens group Gr2 are used as focusing lenses. Focusing is performed by moving integrally from the object side to the image plane side along the optical axis relative to the lens.
FIG. 1 also shows the surface number of each optical surface in the optical system of the imaging lens. 1 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, FIG. 4, FIG. 7, FIG. 10, FIG. 13 and FIG. 16 or the like are not necessarily in a common configuration with the embodiments corresponding to them.
In Example 1, the focal length f, the half angle of view ω [degrees], and the open F value F of the entire system are f = 23.52 mm, ω = 31.91 degrees, and F = 2.58 (that is, F2). 58), the radius of curvature of the optical surface (paraxial radius of curvature for an aspheric surface) R in each optical element in Example 1, R between adjacent optical surfaces, refractive index Nd, Abbe number νd, and lens The optical properties of the materials and the like are as shown in Table 1 below.

In Table 1, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. “INF” represents infinity (∞). The same applies to the other Examples 2 to 6.
That is, in Table 1, the first surface that is the optical surface on the object side of the first lens L1 marked with “*”, the fourth surface that is the optical surface on the image plane side of the second lens L2, and the third lens. The sixth surface which is the optical surface on the image plane side of L3, the eighth surface which is the optical surface on the object side of the fourth lens L4, the tenth surface which is the optical surface on the object side of the fifth lens L5, and the sixth lens L6. The twelfth surface which is the optical surface on the object side and the fifteenth surface which is the optical surface on the image surface side of the seventh lens L7 are aspherical surfaces, and the aspherical parameter (aspherical coefficient) in equation [11] is Table 2 below. In the aspheric parameter, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”. The same applies to the other embodiments.

  In Example 1, since the fifth lens L5 and the sixth lens L6 of the second lens group Gr2 are used as focusing lenses and moved from the object side to the image plane side during focusing, the second lens group Gr2 shown in Table 1 is used. The variable distance D9 between the fourth lens L4 and the fifth lens L5 and the variable distance D13 between the sixth lens L6 and the seventh lens L7 of the second lens group Gr2 change the imaging magnification. When the object distance changes from infinity (INF) to an imaging magnification of −1/20 (imaging distance≈500 mm), it changes as shown in Table 3 below.

  The values corresponding to the conditional expressions [1] to [10] described in the first embodiment are as shown in the following table. However, the numerical values of the conditional expression [2] and the conditional expression [4] are calculated as the imaging magnification β = −1 / 20.

Therefore, the numerical values related to the conditional expressions [1] to [10] described in the first embodiment are within the ranges of the conditional expressions, respectively, and satisfy the conditional expressions [1] to [10]. doing.
FIG. 2 shows various aberrations in the d-line and g-line when the imaging lens according to Example 1 is focused on an object at infinity, that is, each of spherical aberration, astigmatism, distortion aberration, and coma aberration. FIG. 3 shows aberration curves, and FIG. 3 shows the d-line and g-line when the imaging lens according to Example 1 is focused on an object with an imaging magnification of about −1/20 times (shooting distance≈500 mm). Each aberration curve diagram of various aberrations, that is, spherical aberration, astigmatism, distortion aberration and coma aberration is shown.
2 and 3, the broken line in spherical aberration represents a sine condition, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration curve diagrams according to other examples.

FIG. 4 is a second example of the present invention, and schematically shows a lens configuration of a longitudinal section when the optical system of the imaging lens according to the second embodiment is in focus at infinity.
That is, as shown in FIG. 4, the optical system of the imaging lens according to Example 2 of the present invention sequentially has a first lens L1, a second lens L2, and a third lens from the object side to the image plane side. L3, aperture stop AD, fourth lens L4, fifth lens L5, sixth lens L6, and seventh lens L7 are arranged, and the first lens L1 to the seventh lens L7 are all composed of cemented lenses. It is not a seven-sheet configuration.
Focusing on the lens group configuration, the first lens L1 to the third lens L3 constitute a first lens group Gr1 having a positive refractive power, and the fourth lens L4 to the seventh lens L7 have a positive refractive power. A two-lens group Gr2 is configured. That is, the imaging lens optical system shown in FIG. 4 has a configuration in which the first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are sequentially arranged from the object side to the image plane side. .

More specifically, the first lens group Gr1 is a positive meniscus having a positive meniscus shape that is convex on the image side with the concave surface formed with an aspheric surface facing the object side sequentially from the object side to the image surface side. A first lens L1 made of a lens, a second lens L2 made of a biconcave negative lens having a concave surface having a larger curvature than the image surface side on the object side and an aspheric surface formed on the image surface side, and the image surface side And a third lens L3 made of a biconvex positive lens having a convex surface with a larger curvature than the object-side surface and an aspheric surface formed on the image surface side, and positive refraction as the first lens group Gr1. It is configured to show power. An aperture stop AD is disposed between the first lens group Gr1 and the second lens group Gr2.
The second lens group Gr2 is a biconvex lens having a convex surface formed with an aspheric surface on the object side and a convex surface having a larger curvature than the object side surface in order from the object side to the image surface side. A fourth lens L4 composed of a positive lens having a shape, a fifth lens L5 composed of a negative meniscus negative lens having a negative refractive power that forms an aspherical surface on the object side and has a convex shape on the object side, and a non-lens on the object side. A sixth lens L6, which is a negative lens having a negative meniscus shape that is concave on the object side with the concave surface that forms a spherical surface, and a convex surface that forms an aspheric surface on the image surface side are directed toward the image surface side. A seventh lens L7, which is a positive lens having a positive meniscus shape with a convex surface having a larger curvature than the object-side surface, is arranged so as to exhibit positive refractive power as the second lens group Gr2.

Further, a back insertion glass BG substantially the same as that of the first embodiment (FIG. 1) is disposed behind the first lens group Gr1 and the second lens group Gr2, that is, on the image plane side.
The first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are supported substantially integrally by an appropriate support frame or the like, except for a focusing lens described later, at least when used. That is, for focusing from a state where the shooting distance is infinite to an object at a short distance, two lenses of the fifth lens L5 and the sixth lens L6 in the second lens group Gr2 are used as focusing lenses. Focusing is performed by moving integrally from the object side to the image plane side along the optical axis relative to the lens.
FIG. 4 also shows the surface numbers of the optical surfaces in the optical system of the imaging lens. Note that each reference symbol shown in FIG. 4 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol. Therefore, FIG. 1, FIG. 7, FIG. 13 and FIG. 16 or the like are not necessarily in a common configuration with the embodiments corresponding to them.
In Example 2, the focal length f of the entire system, the half angle of view ω [degrees], and the open F value F are respectively f = 23.51 mm, ω = 31.81 degrees, and F = 2.59 (that is, F2 59), the radius of curvature of the optical surface (paraxial curvature radius for an aspheric surface) R in each optical element in Example 2, surface spacing D of adjacent optical surfaces, refractive index Nd, Abbe number νd, and lens The optical characteristics of the materials and the like are as shown in Table 5 below.

In Table 5, the lens surface with the surface number indicated by adding “*” to the surface number is an aspherical surface. “INF” represents infinity (∞). The same applies to other examples, that is, Example 1 and Examples 3 to 6.
That is, in Table 5, the first surface, which is the object-side optical surface of the first lens L1, marked with “*”, the fourth surface, which is the optical surface of the second lens L2, and the third lens. The sixth surface which is the optical surface on the image plane side of L3, the eighth surface which is the optical surface on the object side of the fourth lens L4, the tenth surface which is the optical surface on the object side of the fifth lens L5, and the sixth lens L6. The twelfth surface which is the optical surface on the object side and the fifteenth surface which is the optical surface on the image surface side of the seventh lens L7 are aspherical surfaces, and the aspherical parameter (aspherical coefficient) in equation [11] is Table 6 below. In the aspheric parameter, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”. The same applies to the other embodiments.

  In Example 2, the fifth lens L5 and the sixth lens L6 of the second lens group Gr2 are used as focusing lenses and moved during focusing. Therefore, the fourth lens L4 and the fourth lens L4 of the second lens group Gr2 shown in Table 5 are moved. The variable distance D9 between the fifth lens L5 and the variable distance D13 between the sixth lens L6 and the seventh lens L7 of the second lens group Gr2 changes the imaging magnification and the object distance is infinite (INF ) And an imaging magnification of −1/20 (imaging distance≈500 mm).

  The values corresponding to the conditional expressions [1] to [10] described in the second embodiment are as shown in Table 8 below. Also in this case, as in the case of the first embodiment, the numerical values of the conditional expression [2] and the conditional expression [4] are calculated as the imaging magnification β = −1 / 20.

Therefore, the numerical values related to the conditional expressions [1] to [10] described in the second embodiment are within the ranges of the conditional expressions, respectively, and satisfy the conditional expressions [1] to [10]. doing.
FIG. 5 shows various aberrations in d-line and g-line when the imaging lens according to Example 2 is focused on an object at infinity, that is, spherical aberration, astigmatism, distortion aberration, and coma aberration. FIG. 6 is an aberration curve diagram, and FIG. 6 shows the d-line and g-line in the state where the imaging lens according to Example 2 is focused on an object with an imaging magnification of about −1/20 times (shooting distance≈500 mm). Each aberration curve diagram of various aberrations, that is, spherical aberration, astigmatism, distortion aberration and coma aberration is shown.
In these aberration curve diagrams of FIGS. 5 and 6, the broken line in spherical aberration represents the sine condition, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration curve diagrams according to other examples.

FIG. 7 shows the lens configuration of the longitudinal section of the optical system of the imaging lens according to the third embodiment of the present invention and at the time of focusing on infinity.
That is, as shown in FIG. 7, the optical system of the imaging lens according to Example 3 of the present invention sequentially has a first lens L1, a second lens L2, and an aperture stop AD from the object side to the image surface side. , The third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are arranged, and none of the first lens L1 to the sixth lens L6 constitutes a cemented lens. It is a sheet configuration.
Focusing on the lens group configuration, the first lens L1 to the second lens L2 constitute a first lens group Gr1 having a positive refractive power, and the third lens L3 to the sixth lens L6 have a positive refractive power. A two-lens group Gr2 is configured. That is, the optical system of the imaging lens shown in FIG. 7 has a configuration in which the first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are sequentially arranged from the object side to the image plane side. .

More specifically, the first lens group Gr1 is a negative lens having a biconcave shape in which an aspheric surface is formed on both surfaces sequentially from the object side to the image surface side, and a concave surface having a larger curvature than the image surface side is directed to the object side. A first lens L1 composed of a lens, and a second lens L2 composed of a biconvex positive lens in which a convex surface having a larger curvature than the object side is formed on the image surface side and an aspheric surface is formed on the image surface side. The first lens group Gr1 is configured to exhibit a positive refractive power. An aperture stop AD is disposed between the first lens group Gr1 and the second lens group Gr2.
The second lens group Gr2 has a biconvex shape in which, from the object side to the image surface side, a convex surface formed with an aspheric surface is sequentially directed toward the object side, and a convex surface having a larger curvature than the object side is directed toward the image surface side. A third lens L3 made of a positive lens, a fourth lens L4 made of a negative meniscus negative lens having a negative refractive power that forms an aspherical surface on the object side and has a convex shape on the object side, and an aspherical surface on the object side The fifth lens L5, which is a negative lens having a negative meniscus shape that is concave on the object side with the concave surface formed, and the convex surface that forms an aspheric surface on the image surface side, and a convex shape on the image surface side The sixth lens L6, which is a positive lens having a positive meniscus shape, is arranged so as to exhibit positive refractive power as the second lens group Gr2.

Further, a back insertion glass BG substantially the same as that in the first embodiment (FIG. 1) and the second embodiment (FIG. 4) is disposed behind the first lens group Gr1 and the second lens group Gr2. Is done.
The first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are supported substantially integrally by an appropriate support frame or the like, except for a focusing lens described later, at least when used. That is, for focusing from a state where the shooting distance is infinite to a close object, the two lenses of the fourth lens L4 and the fifth lens L5 in the second lens group Gr2 are used as focusing lenses. Focusing is performed by moving integrally from the object side to the image plane side along the optical axis relative to the lens.
FIG. 7 also shows the surface numbers of the optical surfaces in the optical system of the imaging lens. 7 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, FIG. 1, FIG. 4, FIG. 10, FIG. 13 and FIG. 16 or the like are not necessarily in a common configuration with the embodiments corresponding to them.
In Example 3, the focal length f, the half angle of view ω [degrees], and the open F value F of the entire system are f = 23.49 mm, ω = 31.61 degrees, and F = 2.59 (that is, F2 59), the radius of curvature of the optical surface (paraxial radius of curvature for an aspherical surface) R in each optical element in Example 3, R between adjacent optical surfaces, refractive index Nd, Abbe number νd, and lens The optical properties of the materials and the like are as shown in Table 9 below.

In Table 9, the lens surface with the surface number indicated by adding “*” to the surface number is an aspherical surface. “INF” represents infinity (∞). The same applies to other examples, that is, Example 1, Example 2, and Examples 4 to 6.
That is, in Table 9, the first surface and the second surface, which are optical surfaces on the object side and the image plane side, of the first lens L1 marked with “*”, and the optical surfaces on the image plane side of the second lens L2. A fourth surface, a sixth surface that is the object-side optical surface of the third lens L3, an eighth surface that is the object-side optical surface of the fourth lens L4, and an optical surface that is the object-side optical surface of the fifth lens L5. The tenth surface and the thirteenth surface, which is the optical surface on the image surface side of the sixth lens L6, are aspherical surfaces. The aspherical parameters (aspherical coefficients) in equation [11] are as shown in Table 10 below. In the aspheric parameter, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”. The same applies to the other embodiments.

  In Example 3, since the fourth lens L4 and the fifth lens L5 of the second lens group Gr2 are used as focusing lenses and moved during focusing, the third lens L3 and the second lens L3 of the second lens group Gr2 shown in Table 9 are moved. The variable distance D7 between the fourth lens L4 and the variable distance D11 between the fifth lens L5 and the sixth lens L6 of the second lens group Gr2 changes the imaging magnification and the object distance is infinite (INF ) And an imaging magnification of −1/20 (imaging distance≈500 mm).

  The values corresponding to the conditional expressions [1] to [10] described in the third embodiment are as shown in Table 12 below. In this case as well, as in the case of Example 1 and Example 2, the numerical values of Conditional Expression [2] and Conditional Expression [4] are calculated as imaging magnification β = −1 / 20.

Therefore, the numerical values related to the conditional expressions [1] to [10] described in the third embodiment are within the respective conditional expressions, and satisfy the conditional expressions [1] to [10]. doing.
FIG. 8 shows various aberrations in the d-line and g-line when the imaging lens according to Example 3 is focused on an object at infinity, that is, spherical aberration, astigmatism, distortion aberration, and coma aberration. FIG. 9 is an aberration curve diagram, and FIG. 9 shows the d-line and the g-line when the imaging lens according to Example 3 is focused on an object at an imaging magnification of about −1/20 times (shooting distance≈500 mm). Each aberration curve diagram of various aberrations, that is, spherical aberration, astigmatism, distortion aberration and coma aberration is shown.
In the aberration curve diagrams of FIGS. 8 and 9, the broken line in the spherical aberration represents the sine condition, the solid line in astigmatism represents the sagittal, and the broken line represents the meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration curve diagrams according to other examples.

FIG. 10 is a fourth embodiment of the present invention, and shows a lens configuration of a longitudinal section when the optical system of the imaging lens according to Example 4 is focused at infinity.
That is, as shown in FIG. 10, the optical system of the imaging lens according to Example 4 of the present invention sequentially has a first lens L1, a second lens L2, and an aperture stop AD from the object side to the image surface side. , The third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are arranged, and none of the first lens L1 to the sixth lens L6 constitutes a cemented lens. It is a sheet configuration.
Focusing on the lens group configuration, the first lens L1 to the second lens L2 constitute a first lens group Gr1 having a positive refractive power, and the third lens L3 to the sixth lens L6 have a positive refractive power. A two-lens group Gr2 is configured. That is, the optical system of the imaging lens shown in FIG. 10 has a configuration in which the first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are sequentially arranged from the object side to the image plane side. .

More specifically, the first lens group Gr1 is a negative lens having a biconcave shape in which an aspheric surface is formed on both surfaces sequentially from the object side to the image surface side, and a concave surface having a larger curvature than the image surface side is directed to the object side. A first lens L1 made of a lens and a second lens L2 made of a biconvex positive lens having a convex surface having a curvature larger than the object side on the image side are disposed, and the first lens group Gr1 is positive. It is configured to show refractive power. An aperture stop AD is disposed between the first lens group Gr1 and the second lens group Gr2.
The second lens group Gr2 is a biconvex lens having a convex surface formed of an aspheric surface on the object side and a convex surface having a curvature larger than that of the object side toward the image surface side in order from the object side to the image surface side. A third lens L3 formed of a positive lens having a shape, a fourth lens L4 formed of a negative meniscus negative lens having a negative refractive power having an aspheric surface on both sides and a convex shape on the object side, and an aspheric surface on the object side The fifth lens L5, which is a negative lens having a negative meniscus shape that is concave on the object side with the concave surface formed with a convex surface, and the convex surface that forms an aspheric surface on the image surface side are convex toward the image surface side. A sixth lens L6 made of a positive lens having a positive meniscus shape is arranged so as to exhibit a positive refractive power as the second lens group Gr2.

Further, on the rear side of the first lens group Gr1 and the second lens group Gr2, that is, on the image plane side, substantially the same as Example 1 (FIG. 1), Example 2 (FIG. 4), and Example 3 (FIG. 7). A similar back insertion glass BG is arranged.
The first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are supported substantially integrally by an appropriate support frame or the like, except for a focusing lens described later, at least when used. That is, for focusing from a state where the shooting distance is infinite to a close object, the two lenses of the fourth lens L4 and the fifth lens L5 in the second lens group Gr2 are used as focusing lenses. Focusing is performed by moving integrally from the object side to the image plane side along the optical axis relative to the lens.
In Example 4, the focal length f, the half angle of view ω [degrees], and the open F value F of the entire system are f = 23.50 mm, ω = 31.84 degrees, and F = 2.60 (that is, F2). .60), the radius of curvature of the optical surface (paraxial curvature radius for an aspheric surface) R in each optical element in Example 3, R between adjacent optical surfaces, refractive index Nd, Abbe number νd, and lens The optical characteristics of the materials and the like are as shown in Table 13 below.

In Table 13, the lens surface with the surface number indicated by adding “*” to the surface number is an aspherical surface. “INF” represents infinity (∞). The same applies to other examples, that is, Example 1, Example 2, Example 3, Example 5 to Example 6.
That is, in Table 13, the object-side and image-side optical surfaces of the first lens L1 and the object-side optical surfaces of the third lens L3 are marked with “*”. The sixth surface, the eighth and ninth surfaces that are the object-side and image-side optical surfaces of the fourth lens L4, the tenth surface that is the object-side optical surface of the fifth lens L5, and the sixth lens L6 The thirteenth surfaces, which are optical surfaces on the image plane side, are aspheric surfaces. In the aspheric parameter, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”. The same applies to the other embodiments.

  In Example 4, since the fourth lens L4 and the fifth lens L5 of the second lens group Gr2 are used as focusing lenses and moved during focusing, the third lens L3 and the second lens L3 of the second lens group Gr2 shown in Table 13 are moved. The variable distance D7 between the fourth lens L4 and the variable distance D11 between the fifth lens L5 and the sixth lens L6 of the second lens group Gr2 changes the imaging magnification and the object distance is infinite (INF ) And an imaging magnification of −1/20 (imaging distance≈500 mm).

  The values corresponding to the conditional expressions [1] to [10] described in the fourth embodiment are as shown in Table 16 below. Also in this case, as in the case of the first to third embodiments, the numerical values of the conditional expression [2] and the conditional expression [4] are calculated as the imaging magnification β = −1 / 20.

Therefore, the numerical values related to the conditional expressions [1] to [10] described in the fourth embodiment are within the range of each conditional expression, and satisfy the conditional expressions [1] to [10]. doing.
FIG. 11 shows various aberrations in d-line and g-line in the state where the imaging lens according to Example 4 is focused on an object at infinity, that is, spherical aberration, astigmatism, distortion aberration, and coma aberration. FIG. 12 shows aberration curves, and FIG. 12 shows the d-line and g-line in the state where the imaging lens according to Example 4 is focused on an object at an imaging magnification of about −1/20 times (shooting distance≈500 mm). Each aberration curve diagram of various aberrations, that is, spherical aberration, astigmatism, distortion aberration and coma aberration is shown.
In the aberration curve diagrams of FIGS. 11 and 12, the broken line in spherical aberration represents a sine condition, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration curve diagrams according to other examples.

FIG. 13 is a fifth embodiment of the present invention, and shows a lens configuration of a longitudinal section when the optical system of the imaging lens according to Example 5 is focused at infinity.
That is, as shown in FIG. 13, the optical system of the imaging lens according to Example 5 of the present invention sequentially forms the first lens L1, the second lens L2, and the aperture stop AD from the object side to the image surface side. , The third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are arranged, and none of the first lens L1 to the sixth lens L6 constitutes a cemented lens. It is a sheet configuration.
Focusing on the lens group configuration, the first lens L1 to the second lens L2 constitute a first lens group Gr1 having a positive refractive power, and the third lens L3 to the sixth lens L6 have a positive refractive power. A two-lens group Gr2 is configured. That is, the optical system of the imaging lens shown in FIG. 13 has a configuration in which the first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are sequentially arranged from the object side to the image plane side. .

Specifically, the first lens group Gr1 has a concave surface formed with an aspherical surface on the image surface side, with the concave surface having a larger curvature than the surface on the image surface facing the object side sequentially from the object side to the image surface side. A first lens L1 formed of a negative lens having a biconcave shape facing the surface, and a convex surface having an aspheric surface on the object side and a convex surface having a curvature larger than the object side surface on the image surface side A second lens L2 composed of a positive lens having a shape is arranged, and the first lens group Gr1 is configured to exhibit positive refractive power. An aperture stop AD is disposed between the first lens group Gr1 and the second lens group Gr2.
The second lens group Gr2 is a biconvex lens having a convex surface formed of an aspheric surface on the object side and a convex surface having a curvature larger than that of the object side toward the image surface side in order from the object side to the image surface side. A third lens L3 composed of a positive lens having a shape, and a fourth lens L4 composed of a negative meniscus negative lens having a weak refractive power and having a convex surface on the object side facing a concave surface formed with an aspheric surface on the image surface side. A fifth lens L5 composed of a negative lens having a negative meniscus shape that is concave on the object side and a convex surface that is formed with an aspheric surface on the image side. A sixth lens L6, which is a positive lens having a positive meniscus shape that is convex toward the image surface side, is disposed so that the second lens group Gr2 exhibits a positive refractive power.

Further, Example 1 (FIG. 1), Example 2 (FIG. 4), Example 3 (FIG. 7) and Example are provided behind these first lens group Gr1 and second lens group Gr2, that is, on the image plane side. A back insertion glass BG substantially the same as in Example 4 (FIG. 10) is disposed.
The first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are supported substantially integrally by an appropriate support frame or the like, except for a focusing lens described later, at least when used. That is, for focusing from a state where the shooting distance is infinite to a close object, the two lenses of the fourth lens L4 and the fifth lens L5 in the second lens group Gr2 are used as focusing lenses. Focusing is performed by moving integrally from the object side to the image plane side along the optical axis relative to the lens.
In Example 5, the focal length f, the half angle of view ω [degrees], and the open F value F of the entire system are f = 23.51 mm, ω = 31.54 degrees, and F = 2.58 (that is, F2). .58), the radius of curvature of the optical surface (paraxial curvature radius for an aspheric surface) R in each optical element in Example 5, R between adjacent optical surfaces, refractive index Nd, Abbe number νd, and lens The optical characteristics of the materials and the like are as shown in Table 17 below.

In Table 17, the lens surface with the surface number indicated by adding “*” to the surface number is an aspherical surface. “INF” represents infinity (∞). The same applies to other examples, that is, Example 1, Example 2, Example 3, Example 4, and Example 6.
That is, in Table 17, the second surface which is the optical surface on the image plane side of the first lens L1 marked with “*”, the third surface which is the optical surface on the object side of the second lens L2, and the third lens. A sixth surface that is an optical surface on the object side of L3, a ninth surface that is an optical surface on the image surface side of the fourth lens L4, a tenth surface that is an optical surface on the object side of the fifth lens L5, and a sixth lens The thirteenth surfaces which are optical surfaces on the image plane side of L6 are aspheric surfaces, and the aspheric parameters (aspheric coefficients) in the equation [11] are as shown in Table 18 below. In the aspheric parameter, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”. The same applies to the other embodiments.

  In Example 5, since the fourth lens L4 and the fifth lens L5 of the second lens group Gr2 are used as focusing lenses and moved during focusing, the third lens L3 and the second lens L3 of the second lens group Gr2 shown in Table 17 are moved. The variable distance D7 between the fourth lens L4 and the variable distance D11 between the fifth lens L5 and the sixth lens L6 of the second lens group Gr2 changes the imaging magnification and the object distance is infinite (INF ) And an imaging magnification of −1/20 (imaging distance≈500 mm).

  The values corresponding to the conditional expressions [1] to [10] described in the fifth embodiment are as shown in Table 20 below. Also in this case, as in the case of the first to fourth embodiments, the numerical values of the conditional expressions [2] and [4] are calculated as the imaging magnification β = −1 / 20.

Therefore, the numerical values related to the conditional expressions [1] to [10] described in the fifth embodiment are within the ranges of the conditional expressions, respectively, and satisfy the conditional expressions [1] to [10]. doing.
FIG. 14 shows various aberrations in d-line and g-line when the imaging lens according to Example 5 is focused on an object at infinity, that is, spherical aberration, astigmatism, distortion aberration, and coma aberration. FIG. 15 is an aberration curve diagram, and FIG. 15 shows the d-line and g-line in the state where the imaging lens according to Example 5 is focused on an object at an imaging magnification of about −1/20 times (shooting distance≈500 mm). Each aberration curve diagram of various aberrations, that is, spherical aberration, astigmatism, distortion aberration and coma aberration is shown.
14 and 15 also, the broken line in spherical aberration represents the sine condition, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration curve diagrams according to other examples.

FIG. 16 is a sixth embodiment of the present invention, and shows a longitudinal cross-sectional lens configuration of the imaging lens optical system according to Example 6 when focusing on infinity.
That is, the optical system of the imaging lens according to Example 6 of the present invention, as shown in FIG. 16, sequentially from the object side to the image surface side, the first lens L1, the second lens L2, and the aperture stop AD. , The third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are arranged, and none of the first lens L1 to the sixth lens L6 constitutes a cemented lens. It is a sheet configuration.
Focusing on the lens group configuration, the first lens L1 to the second lens L2 constitute a first lens group Gr1 having a positive refractive power, and the third lens L3 to the sixth lens L6 have a positive refractive power. A two-lens group Gr2 is configured. That is, the optical system of the imaging lens shown in FIG. 16 has a configuration in which the first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are sequentially arranged from the object side to the image plane side. .

Specifically, the first lens group Gr1 has a concave surface formed with an aspherical surface on the image surface side, with the concave surface having a larger curvature than the surface on the image surface facing the object side sequentially from the object side to the image surface side. A first lens L1 formed of a negative lens having a biconcave shape facing the surface, and a convex surface having an aspheric surface on the object side and a convex surface having a curvature larger than the object side surface on the image surface side A second lens L2 composed of a positive lens having a shape is arranged, and the first lens group Gr1 is configured to exhibit positive refractive power. An aperture stop AD is disposed between the first lens group Gr1 and the second lens group Gr2.
The second lens group Gr2 is a biconvex lens having a convex surface formed of an aspheric surface on the object side and a convex surface having a curvature larger than that of the object side toward the image surface side in order from the object side to the image surface side. A third lens L3 formed of a positive lens having a shape, a fourth lens L4 formed of a negative meniscus negative lens having a negative refractive power having an aspheric surface on both sides and a convex shape on the object side, and an aspheric surface on the object side The fifth lens L5, which is a negative lens having a negative meniscus shape that is concave on the object side with the concave surface formed with a convex surface, and the convex surface that forms an aspheric surface on the image surface side are convex toward the image surface side. A sixth lens L6 made of a positive lens having a positive meniscus shape is arranged so as to exhibit a positive refractive power as the second lens group Gr2.

Further, on the rear side of the first lens group Gr1 and the second lens group Gr2, that is, on the image plane side, substantially the same as the first to fifth embodiments (FIGS. 1, 4, 7, 10, and 13). A similar back insertion glass BG is arranged.
The first lens group Gr1, the aperture stop AD, and the second lens group Gr2 are supported substantially integrally by an appropriate support frame or the like, except for a focusing lens described later, at least when used. That is, for focusing from a state where the shooting distance is infinite to a close object, the two lenses of the fourth lens L4 and the fifth lens L5 in the second lens group Gr2 are used as focusing lenses. Focusing is performed by moving integrally from the object side to the image plane side along the optical axis relative to the lens.
In Example 6, the focal length f of the entire system, the half angle of view ω [degrees], and the open F value F are respectively f = 23.51 mm, ω = 32.00 degrees, and F = 2.62 (that is, F2 .62), and the radius of curvature of the optical surface (paraxial radius of curvature for an aspheric surface) R in each optical element in Example 6, R between adjacent optical surfaces, refractive index Nd, Abbe number νd, and lens The optical properties of the materials and the like are as shown in Table 21 below.

In Table 21, the lens surface with the surface number indicated by adding “*” to the surface number is an aspherical surface. “INF” represents infinity (∞). The same applies to other examples, that is, Examples 1 to 5.
That is, in Table 21, the second surface which is the optical surface on the image plane side of the first lens L1 marked with “*”, the third surface which is the optical surface on the object side of the second lens L2, and the third lens. The sixth surface that is the optical surface on the object side of L3, the eighth surface that is the optical surface on the object side of the fourth lens L4, the ninth surface that is the optical surface on the image plane side, and the optical on the object side of the fifth lens L5. The tenth surface, which is a surface, and the thirteenth surface, which is the optical surface on the image surface side of the sixth lens L6, are aspherical surfaces. The aspherical parameters (aspherical coefficients) in equation [11] are It is. In the aspheric parameter, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”. The same applies to the other embodiments.

  In Example 6, since the fourth lens L4 and the fifth lens L5 of the second lens group Gr2 are used as focusing lenses and moved during focusing, the third lens L3 of the second lens group Gr2 and the second lens L3 shown in Table 21 are moved. The variable distance D7 between the fourth lens L4 and the variable distance D11 between the fifth lens L5 and the sixth lens L6 of the second lens group Gr2 changes the imaging magnification and the object distance is infinite (INF ) And imaging magnification-1/20 (imaging distance ≈ 500 mm).

  The values corresponding to the conditional expressions [1] to [10] described in the sixth embodiment are as shown in Table 24 below. Also in this case, as in the case of the first to fifth embodiments, the numerical values of the conditional expressions [2] and [4] are calculated as the imaging magnification β = −1 / 20.

Therefore, the numerical values related to the conditional expressions [1] to [10] described in the sixth embodiment are within the ranges of the conditional expressions, respectively, and satisfy the conditional expressions [1] to [10]. doing.
FIG. 17 shows various aberrations in d-line and g-line in the state where the imaging lens according to Example 6 is focused on an object at infinity, that is, spherical aberration, astigmatism, distortion aberration, and coma aberration. FIG. 18 shows aberration curves, and FIG. 18 shows the d-line and g-line in the state where the imaging lens according to Example 5 is focused on an object at an imaging magnification of about −1/20 times (shooting distance≈500 mm). Each aberration curve diagram of various aberrations, that is, spherical aberration, astigmatism, distortion aberration and coma aberration is shown.
In the aberration curve diagrams of FIGS. 17 and 18, the broken line in spherical aberration represents a sine condition, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration curve diagrams according to other examples.

[Seventh Embodiment]
Next, main parts of some examples of the support structure of the imaging lens according to the seventh embodiment of the present invention will be described with reference to FIGS.
The lens support structure according to the seventh embodiment of the present invention effective in the first to sixth embodiments of the first embodiment of the present invention described above is adjacently and integrally disposed 2. Each lens is formed by integrally processing the lens optical part and the lens peripheral part with the same material, and mutually abuts on the lens peripheral part in an annular line contact or in a ring contact surface contact manner. It is set as the structure to perform. Such two adjacently arranged lenses are the negative lens and the positive lens adjacent to the first lens group or the second lens group in the imaging lenses of the first to sixth embodiments described above. These are two lenses constituting a focusing lens provided integrally.
For example, in FIGS. 19 and 20, the negative lens and the positive lens adjacent to each other included in the first lens group are the same in both the lens optical part and the lens peripheral part constituting the support mechanism part in the vicinity of the lens outer periphery. The structure integrally processed with the material is shown.

FIG. 19 shows a negative lens and a positive lens adjacent to each other included in the first lens group Gr1. For example, in the case of Example 1 and Example 2, the second lens L2 and the third lens L3 are shown. In the case of Example 3 to Example 6, the first lens L1 and the second lens L2. In the configuration of FIG. 19, the adjacent negative lens and positive lens are mutually supported by abutting in a circular line contact with each other at a conical inclined surface portion at the peripheral portion of the lens. With this configuration, it is possible to suppress the occurrence of so-called shift deviation between the lens surfaces of the negative lens and the positive lens adjacent to each other (corresponding to claim 18 ).
FIG. 20 also shows the negative lens and the positive lens adjacent to each other included in the first lens group Gr1, for example, in the case of Example 1 and Example 2, the second lens L2 and the third lens L3. In the case of Example 3 to Example 6, the first lens L1 and the second lens L2. In the configuration of FIG. 20, the adjacent negative lens and positive lens are mutually supported by abutting in a surface contact with each other at a plane portion where the annular belt-shaped optical axes substantially perpendicularly intersect each other at the periphery of the lens. . With this configuration, it is possible to suppress the occurrence of so-called tilt shift between the lens surfaces of the negative lens and the positive lens adjacent to each other (corresponding to claim 19 ).

19 and FIG. 20, not only can shift shift and tilt shift be suppressed, but also the lens optical portion and the lens peripheral portion can be integrally formed with the same material. Further, there is an advantage that it is not necessary to use a separate member such as a lens outer frame that has been conventionally used for the lens, and the number of parts can be reduced.
Further, for example, in FIGS. 21 and 22, two adjacent lenses included in the second lens group and constituting a focusing lens composed of two or more lenses that are moved together for focusing are shown. FIG. 5 also shows a structure in which the lens optical portion and the lens peripheral portion constituting the support mechanism near the lens outer periphery are integrally processed with the same material.
FIG. 21 shows two adjacent lenses included in the second lens group Gr2 and functioning as a focusing lens. For example, in the case of Example 1 and Example 2, the fifth lens L5 and The sixth lens L6 is the fourth lens L4 and the fifth lens L5 in the case of the third to sixth embodiments. In the configuration of FIG. 21, these two adjacent lenses are mutually supported by contacting each other at the peripheral edge portion of the lens at the conical inclined surface portion in an annular line contact. With this configuration, it is possible to suppress the occurrence of a so-called shift shift between the lens surfaces of these two adjacent lenses (corresponding to claim 20 ).

FIG. 22 also shows two adjacent lenses included in the second lens group Gr2 and functioning as a focusing lens. For example, in the case of Example 1 and Example 2, the fifth lens is shown. L5 and the sixth lens L6, and in the case of Example 3 to Example 6, the fourth lens L4 and the fifth lens L5. In the configuration of FIG. 22, these two adjacent lenses are configured to be in contact with each other in a plane contact where the optical axes of the annular belts intersect with each other at the periphery of the lens, and to support each other. With this configuration, it is possible to suppress the occurrence of so-called tilt shift between the lens surfaces of these two adjacent lenses (corresponding to claim 21 ).
The configuration shown in FIGS. 21 and 22 can not only suppress shift deviation and tilt deviation, but also integrally process and form the lens optical portion and the lens peripheral portion with the same material. Further, there is an advantage that it is not necessary to use a separate member such as a lens outer frame that has been conventionally used for the lens, and the number of parts can be reduced.

Furthermore, as shown in FIG. 22 described above, it is preferable to adopt a configuration between adjacent lenses of the focusing lens is moved for focusing interpolate through an annular light-shielding mask AM as a fixed throttle (to claim 22 Corresponding).
In such a configuration, it is possible to suppress the occurrence of harmful ghost flare by shielding stray light in the focusing lens with the light shielding mask AM in accordance with the change in the light path of the focusing lens. In particular, as shown in FIG. 22, in the configuration in which the planar portions formed in the shape of an annular belt are in contact with each other at the peripheral portion in the vicinity of the outer diameter of two adjacent lenses, the contact is made. It is possible to easily sandwich the sheet-shaped light-shielding mask AM in the portion, and it is possible to efficiently suppress harmful stray light in the focusing lens.

[Eighth Embodiment]
Next, according to the eighth aspect of the present invention, an imaging lens such as the first to sixth embodiments according to the first to sixth embodiments of the present invention described above is employed as the imaging optical system. An imaging apparatus according to an embodiment will be described with reference to FIGS.
FIG. 23 schematically shows an external configuration of a digital camera as an imaging apparatus according to the eighth embodiment of the present invention as viewed from the subject side (that is, the front side that is the object side). The perspective view which shows the state by which the imaging lens which consists of the imaging lens comprised according to the 1st-6th embodiment of this invention was collapsed in the body of a digital camera, and (b) is a digital camera It is a perspective view which shows the state which protrudes from the body. FIG. 24 is a perspective view schematically showing an external configuration of the digital camera viewed from the photographer side (that is, the back side). FIG. 25 is a block diagram schematically showing the functional configuration of the digital camera.

Although a digital camera as an imaging device is described here, it is called not only an imaging device mainly for imaging including a video camera and a film camera, but also a mobile phone, a personal data assistant (PDA), and the like. In many cases, an imaging function corresponding to a digital camera or the like is incorporated in various information devices including a portable information terminal device and a portable terminal device called a smartphone that combines these functions. Although such an information device also has a slightly different appearance, it includes substantially the same functions and configurations as a digital camera or the like, and the imaging lens according to the present invention may be employed in such an information device. .
As shown in FIGS. 23 and 24, the digital camera includes an imaging lens 101, a shutter button 102, a zoom button 103, a viewfinder 104, a strobe 105, a liquid crystal monitor 106, an operation button 107, a power switch 108, a memory card slot 109, and communication. A card slot 110 and the like are provided. Furthermore, as shown in FIG. 25, the digital camera also includes a light receiving element 111, a signal processing device 112, an image processing device 113, a central processing unit (CPU) 114, a semiconductor memory 115, a communication card 116, and the like.

The digital camera includes an imaging lens 101 and a light receiving element 111 as an area sensor such as a CMOS (complementary metal oxide semiconductor) imaging device or a CCD (charge coupled device) imaging device, and is an imaging optical system. An optical image of an object to be imaged, that is, a subject is formed by the lens 101, and this optical image is read by the light receiving element 111. As the imaging lens 101, the imaging lens according to the first to sixth embodiments of the present invention described in Examples 1 to 6 is used (corresponding to claim 25 or claim 26 ).
The output of the light receiving element 111 is processed by the signal processing device 112 controlled by the central processing unit 114 and converted into digital image information. The image information digitized by the signal processing device 112 is recorded in a semiconductor memory 115 such as a non-volatile memory after being subjected to predetermined image processing in an image processing device 113 also controlled by the central processing unit 114. In this case, the semiconductor memory 115 may be a memory card loaded in the memory card slot 109 or a semiconductor memory built in the digital camera body. The liquid crystal monitor 106 can display an image being shot, or can display an image recorded in the semiconductor memory 115.

The image recorded in the semiconductor memory 115 can also be transmitted to the outside via a communication card 116 or the like loaded in the communication card slot 110.
When the digital camera is carried, the imaging lens 101 is in the retracted state and buried in the body of the digital camera as shown in FIG. 23A. When the user operates the power switch 108 to turn on the power, As shown in FIG. 23B, the lens barrel is extended and protrudes from the body of the digital camera. Since the imaging lens according to the present invention has a single focal length, it cannot perform an optical scaling function. However, by operating the zoom button 103, the object image cut-out range is changed to simulate the subject image. Zooming of the so-called digital zoom method that changes the zoom ratio can also be performed.
In many cases, focusing is performed by half-pressing the shutter button 102.

When the shutter button 102 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.
When the image recorded in the semiconductor memory 115 is displayed on the liquid crystal monitor 106 or transmitted to the outside via the communication card 116 or the like, the operation button 107 is operated in a predetermined manner. The semiconductor memory 115 and the communication card 116 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 109 and the communication card slot 110, respectively.
When the imaging lens 101 is in the retracted state, the groups of the imaging lenses do not necessarily have to be aligned on the optical axis. For example, if the second lens group Gr2 is retracted from the optical axis when retracted and is stored in parallel with the first lens group Gr1, the digital camera can be made thinner.

Gr1 1st lens group Gr2 2nd lens group L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens AD Aperture stop BG Back insertion glass 101 Imaging lens (Conclusion) Image lens)
102 shutter button 103 zoom button 104 finder 105 strobe 106 liquid crystal monitor 107 operation button 108 power switch 109 memory card slot 110 communication card slot 111 light receiving element (area sensor)
112 signal processing device 113 image processing device 114 central processing unit (CPU)
115 Semiconductor memory 116 Communication card, etc.

Japanese Patent Application Laid-Open No. 2004-295112 (Japanese Patent No. 4616566) JP 2008-76953 A JP 2011-22427 A Japanese Patent Publication No. 1-24284 JP-A-8-338944 Japanese Patent Laid-Open No. 2-101417

Claims (26)

A first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power are sequentially arranged from the object side to the image plane side to form an optical image of the object. In an imaging lens comprising an optical system for imaging,
The first lens group has at least two lenses,
The second lens group has, in order from the object side to the image plane side, a lens having a positive refractive power, a lens having the weakest refractive power in the second lens group, and a negative refractive power. a lens made up of a lens having a positive refractive power, of four lenses,
The entire optical system is composed of seven or less lenses,
By moving the image plane side from the object side at least two lenses in the second lens group as a focusing lens, an imaging characterized by comprising a structure performing the focusing on the close range side from the infinity side lens.   The imaging lens according to claim 1, wherein at least one of the at least two lenses as the focusing lens to be moved for focusing is a negative meniscus lens concave on the object side. During focusing, at least two imaging lens according to claim 1 and claim 2 lenses are synchronized with each other, characterized in that moving integrally with as the focusing lens. The focusing lens according to any one of claims 1 to 3 , wherein during focusing, the lens closest to the object side and the lens closest to the image plane in the second lens group are fixed lenses that are not moved. Image lens. When the focal length of the entire optical system when the shooting distance is infinity is f, and the combined focal length of the focusing lens is ff,
Conditional expression:
[1] 2.1 <| f / ff | <2.7
An imaging lens according to any one of claims 1 to 4, characterized by satisfying the. The focusing lens moving distance in the focusing operation for focusing from an infinite shooting distance to a close object is ΔDf, and the imaging magnification when the close object is focused is β.
Conditional expression:
[2] 8.5 <| ΔDf / β | <12.5
An imaging lens according to any one of claims 1 to 5, characterized by satisfying the. The distance from the most object-side surface of the first lens group to the image plane is L, and the maximum image height is Y ′.
Conditional expression:
[3] 2.2 <L / Y ′ <2.5
An imaging lens according to any one of claims 1 to 6, characterized by satisfying the. The axial chromatic aberration of the g-line with respect to the d-line when the shooting distance is infinite is AX1, the imaging magnification when focusing on a close object is β, and the axial chromatic aberration of the g-line with respect to the d-line when the imaging magnification is β As AX2,
Conditional expression:
[4] 1.0 [mm] <| (AX1-AX2) / β | <1.6 [mm]
The imaging lens according to any one of claims 1 to 7 , wherein the imaging lens is satisfied. The lens closest to the image plane of the first lens group and the lens closest to the object side of the second lens group are biconvex lenses, and the aperture stop is disposed between the two consecutive biconvex lenses,
Let f1p be the focal length of a biconvex lens disposed adjacent to the object side of the aperture stop, and f2p be the focal length of a biconvex lens disposed adjacent to the image plane side of the aperture stop.
Conditional expression:
[5] 0.7 <f1p / f2p <1.1
The imaging lens according to any one of claims 1 to 8 , wherein the imaging lens is satisfied. A positive lens having a convex shape on the image plane side is arranged on the most image plane side of the second lens group,
The focal length of the positive lens closest to the image plane in the second lens group is f2pi, and the focal length of the entire optical system when the shooting distance is infinity is f.
Conditional expression:
[6] 0.7 <f2pi / f <1.0
An imaging lens according to any one of claims 1 to 9, characterized by satisfying the. Before SL closest to the image plane side of the positive lens on the most image surface negative lens and the second lens group side of the second lens group,
The focal length of the positive lens closest to the image plane in the second lens group is f2pi, and the focal length of the negative lens closest to the image plane in the second lens group is f2ni.
Conditional expression:
[7] 1.6 <| f2pi / f2ni | <2.0
An imaging lens according to any one of claims 1 to 10, characterized by satisfying the. The first lens group closer to the object side than the aperture stop is arranged with a lens having a negative refractive power and a lens having a positive refractive power sequentially from the object side to the image plane side.
The focal length of the lens having the positive refractive power of the first lens group is f1p, and the focal length of the lens having the negative refractive power of the first lens group is f1n.
Conditional expression:
[8] 0.7 <| f1p / f1n | <1.1
An imaging lens according to any one of claims 1 to 11, characterized by satisfying the. The maximum effective diameter of the lens having the largest diameter in the first lens group on the object side from the aperture stop is LD1, and the maximum effective diameter of the lens in the second lens group on the image plane side from the aperture stop is the maximum effective diameter. The diameter is LD2,
Conditional expression:
[9] 0.5 <LD1 / LD2 <0.9
An imaging lens according to any one of claims 1 to 12, characterized by satisfying the. Wherein the first lens group, an imaging lens according to any one of claims 1 to 13, characterized in that it comprises at least one sheet constructed lens resin material. The second lens group includes an imaging lens according to any one of claims 1 to 14, characterized in that it comprises at least one lens made of a resin material. 16. The imaging lens according to claim 1, wherein all lenses constituting the entire lens system are made of a resin material. The resin material constituting the constructed lens resin material according to claim 14 to claim 16, characterized in that the two cycloolefin (cycloolefin) based resin materials and polyester (polyester) based resin material The imaging lens according to any one of the above. The first lens group includes a negative lens and a positive lens adjacent to each other, and both the negative lens and the positive lens have the same material for the lens optical portion and the lens peripheral portion constituting the support mechanism near the lens outer periphery. in is one body, according to claim 14, characterized in that a configuration in which mutually supporting the lens peripheral portion annular line contact manner of contact with each other, to any one of claims 16 and claim 17 The imaging lens described. The first lens group includes a negative lens and a positive lens adjacent to each other, and both the negative lens and the positive lens have the same material for the lens optical portion and the lens peripheral portion constituting the support mechanism near the lens outer periphery. in an integral, claim 14, characterized in that a configuration in which mutually supporting the lens peripheral portion at surface contact manner of annular strip in contact with each other, any one of claims 16 and claim 17 1 The imaging lens described in the item. Adjacent each lens of the focusing lens is moved for focusing is an body both the lens periphery portion constituting the supporting mechanism of the lens optic portion and the lens outer periphery is the same material, the lens periphery portion to each other an imaging lens according to any one of claims 15 to claim 17, characterized in that a configuration in which mutually supporting annular line contact manner of contact at. Adjacent each lens of the focusing lens is moved for focusing is an body both the lens periphery portion constituting the supporting mechanism of the lens optic portion and the lens outer periphery is the same material, the lens periphery portion to each other an imaging lens according to any one of claims 15 to claim 17 which circular band-shaped surface contact manner abuts, characterized in that the arrangement for mutual support at. The imaging lens according to any one of claims 14 to 17 , wherein an annular light-shielding mask serving as a fixed stop is interposed between the lenses of the focusing lens. A shutter space for arranging a mechanical shutter between the lenses is provided.
SD is the dimension in the optical axis direction of the shutter space provided between the lenses.
[10] SD> 3.0 [mm]
The imaging lens according to any one of claims 1 to 22 , wherein the imaging lens is satisfied. In seven following lens comprising an imaging lens of the entire system of the optical system,
An aperture stop is arranged between the lenses of the optical system,
Said opening the object side than the diaphragm, have each at least one and a lens having a lens and a negative refractive power having a positive refractive power, and a total of three following lens,
From the object side to the image plane side, the image plane side of the aperture stop is sequentially a lens having a positive refractive power, a lens having the weakest refractive power among the lenses on the image plane side of the aperture stop , A lens having a negative refractive power and a lens having a positive refractive power are arranged and configured.
In focusing, the lens having the weakest refractive power and the lens having a negative refractive power located on the image plane side of the aperture stop are moved from the object side to the image plane side as an infinite point. An imaging lens characterized by a rear focus type optical system that performs a focusing operation from the side to the short distance side. An imaging apparatus comprising the imaging lens according to any one of claims 1 to 24 as an imaging optical system. An information apparatus having an imaging function and using the imaging lens according to any one of claims 1 to 24 as an imaging optical system.

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