JP6759086B2 - Imaging lens system and imaging device equipped with it - Google Patents

Description

The present invention relates to an imaging lens system and an imaging device including the imaging lens system.

When shooting with a telephoto lens or a super-telephoto lens (hereinafter referred to as "telephoto lens"), it is possible to obtain the effect of drawing a distant subject or a small subject in front of the photographer's eyes. Therefore, the telephoto lens is widely used in various scenes such as shooting sports scenes, shooting wild animals such as wild birds, and shooting celestial bodies.

As a telephoto lens used for photographing such a scene, there is a telephoto lens disclosed in Patent Documents 1 to 4.

Japanese Unexamined Patent Publication No. 2009-139543 (First Example) Japanese Unexamined Patent Publication No. 2008-261969 (Third Example) Japanese Unexamined Patent Publication No. 2013-250293 (Third Example) Japanese Unexamined Patent Publication No. 2012-145789 (First Example)

In shooting the above scenes, the superiority or inferiority of the mobility of the imaging device is important. Here, the mobility includes, for example, ease of carrying, stability during handheld shooting, high focus speed, and the like. In order to improve the mobility of the device, it is desirable that the optical system is small and lightweight. In addition, the ability of the optical system to focus on the subject faster is also an important factor that determines the superiority or inferiority of mobility.

In the telephoto lens disclosed in Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 (hereinafter, referred to as "conventional telephoto lens"), a large-diameter negative lens is arranged near the object side. Therefore, the conventional telephoto lens cannot reduce the size and weight of the optical system.

In the telephoto lens, a telephoto type optical system is used. In the telephoto type optical system, a lens group having a positive refractive power is arranged on the object side, and a lens group having a negative refractive power is arranged on the image side. One of the actions in the telephoto type optical system (hereinafter referred to as "telephoto action") is to shorten the total length of the optical system.

In the conventional telephoto lens, focusing is performed by a lens group having a negative refractive power. Focusing should be done at high speed in order to achieve excellent maneuverability. For that purpose, it is desirable to reduce the weight of the lens group for focusing.

However, in a telephoto type optical system, it is difficult to reduce the weight of a lens group having a negative refractive power. That is, in a conventional telephoto lens, it is difficult to reduce the weight of a lens group having a negative refractive power. Therefore, it is difficult to increase the focus speed with a conventional telephoto lens.

Further, in the telephoto lens disclosed in Patent Document 4, the total length of the optical system is shortened by using a diffractive optical element (DOE). However, although the aperture of the portion of the optical system located on the object side is large, the weight of the optical system has not been sufficiently reduced because many lens elements are used in this portion.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an imaging lens system having excellent maneuverability and well-corrected aberrations, and an image pickup apparatus provided with the same. It is a thing.

In order to solve the above-mentioned problems and achieve the object, the imaging lens system of the present invention is used.
From the object side to the image side,
The first lens group with positive refractive power and
A second lens group with negative refractive power,
It consists of a third lens group and
The first lens group is composed of an anterior lens group having a positive refractive power and a posterior lens group in order from the object side with the widest air spacing in the first lens group in between.
The second lens group moves by changing the air spacing on the object side and the image side at the time of focusing.
The third lens group has a positive lens element and has a positive lens element.
The front lens group has a negative lens element and a positive lens element.
Each negative lens element in the front lens group is a negative lens element satisfying the conditional expression ( A-1'''' ).
The posterior lens group has a negative lens element and a positive lens element.
An imaging lens system characterized by satisfying the following conditional expression (1).
DN Lens / φenp ≤ 0.0094 ( A-1'''' )
0.015 ≤ ΔGFGR / f ≤ 0.25 (1)
here,
DN Lens is the thickness of each negative lens element in the front lens group on the optical axis.
Φenp is the maximum diameter of the entrance pupil of the imaging lens system at the longest focal length at the farthest focus.
f is the longest focal length of the entire imaging lens system at the farthest focus.
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
A lens element is a lens having two effective transmission surfaces, an object side surface and an image side surface, and no other effective transmission surface between the two effective transmission surfaces.
Is.

Further, the imaging device of the present invention is
Optical system and
It has an image pickup surface and an image pickup element that converts an image formed on the image pickup surface by an optical system into an electric signal.
The optical system is one of the above-mentioned imaging lens systems.

According to the present invention, it is possible to provide an imaging lens system having excellent maneuverability and satisfactorily corrected aberrations, and an imaging device including the imaging lens system.

It is a lens sectional view of the imaging lens system of Example 1. FIG. It is a lens sectional view of the imaging lens system of Example 2. FIG. It is a lens sectional view of the imaging lens system of Example 3. FIG. It is an aberration diagram of the imaging lens system of Example 1. It is an aberration diagram of the imaging lens system of Example 2. It is an aberration diagram of the imaging lens system of Example 3. It is sectional drawing of the image pickup apparatus. It is a front perspective view of the image pickup apparatus. It is a rear perspective view of the image pickup apparatus. It is a block diagram of the internal circuit of the main part of an image pickup apparatus.

Prior to the description of the examples, the effects of the embodiments according to certain aspects of the present invention will be described. In addition, when concretely explaining the action and effect of this embodiment, a concrete example will be shown and explained. However, as in the case of the examples described later, those exemplified embodiments are only a part of the embodiments included in the present invention, and there are many variations in the embodiments. Therefore, the present invention is not limited to the exemplary embodiments.

The imaging lens system of the present embodiment has a common configuration. In the common configuration, the optical system is composed of a first lens group having a positive refractive force, a second lens group having a negative refractive force, and a third lens group in order from the object side to the image side. One lens group is composed of a front lens group having a positive refractive force and a rear lens group in order from the object side with an air gap in between, and the second lens group is an image of the object side at the time of focusing. The third lens group has a positive lens element, and the front lens group has a negative lens element and a positive lens element, and moves by changing the air spacing of each side.

In order to shorten the total length of the optical system and ensure good imaging performance from the center to the periphery of the image, it is important to ensure optical symmetry in the entire optical system. In the common configuration, the optical system is composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive lens element.

In this case, the arrangement of the refractive powers becomes a positive refractive power, a negative refractive power, and a positive refractive power by the positive lens elements of the first lens group, the second lens group, and the third lens group. That is, the arrangement has a symmetrical refractive power. As described above, by adopting the above-described configuration, it is possible to secure optical symmetry in the common configuration, so that it becomes easy to satisfactorily correct coma, distortion, and chromatic aberration of magnification.

In the first lens group, the front lens group is arranged on the most object side, and the rear lens group is arranged on the image side of the front lens group with a certain wide air gap. The front lens group has a positive refractive power. Therefore, for example, by giving the posterior lens group a negative refractive power, it is possible to correct spherical aberration and chromatic aberration.

In addition, the combination of the positive refractive power and the negative refractive power causes a telephoto action. In the first lens group, the telephoto action can be enhanced by the positive refractive power of the front lens group and the negative refractive power of the rear lens group. As a result, the total length of the optical system can be shortened.

The second lens group moves by changing the air spacing on the object side and the image side at the time of focusing.

The second lens group is located between the first lens group and the third lens group and has a negative refractive power. In the first common configuration, the second lens group is set as the focus lens group, and the second lens group is used for focusing. By doing so, it becomes easy to reduce the weight of the focus lens group and secure good imaging performance around the image at the time of focusing.

The front lens group includes a negative lens element and a positive lens element. By doing so, it is possible to reduce the occurrence of chromatic aberration in the front lens group.

The imaging lens system of the first embodiment has a common configuration, and each negative lens element in the front lens group is a negative lens element satisfying the conditional equation (A-1), and the rear lens group is a negative lens element. It has a negative lens element and a positive lens element, and is characterized by satisfying the following conditional expression (1).
DN Lens / φenp ≤ 0.02 (A-1)
0.015 ≤ ΔGFGR / f ≤ 0.25 (1)
here,
DN Lens is the thickness of each negative lens element in the front lens group on the optical axis.
Φenp is the maximum diameter of the entrance pupil of the imaging lens system at the longest focal length at the farthest focus.
f is the longest focal length of the entire imaging lens system at the farthest focus.
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
A lens element is a lens having two effective transmission surfaces, an object side surface and an image side surface, and no other effective transmission surface between the two effective transmission surfaces.
Is.

In the first lens group, the axial luminous flux is the largest. At a position where the axial luminous flux is large, aberration correction is possible even if the refractive power of the negative lens element is small. Therefore, it is preferable to arrange a negative lens element having a small refractive power in the first lens group. By doing so, the imaging performance can be effectively improved.

The volume of the front lens group is the largest in the optical system. Therefore, in order to reduce the weight of the optical system, it is preferable not to arrange a heavy lens element in the front lens group.

In the imaging optical system of the first embodiment, the front lens group has a negative lens element. The weight of the negative lens element increases as the refractive power increases. Therefore, when arranging the negative lens element in the front lens group, it is preferable to arrange the negative lens element satisfying the conditional expression (A-1).

In the negative lens element satisfying the conditional expression (A-1), since the negative refractive power is small, the weight of the lens element is unlikely to increase. Therefore, it is possible to adopt a configuration in which a negative lens element having a large weight, that is, a negative lens element having a large refractive power is not arranged in the front lens group having the largest volume. As a result, the weight of the optical system can be significantly reduced.

Further, as described above, aberration correction is possible even if the refractive power of the negative lens element is small. Therefore, the imaging performance can be effectively improved.

The posterior lens group has a negative lens element and a positive lens element. Therefore, a telephoto effect can be obtained between the front lens group and the negative lens element of the rear lens group. If the positive refractive power in the front lens group can be increased, the telephoto action can be strengthened. As a result, the total length of the optical system can be further shortened.

By satisfying the conditional expression (1), a sufficient distance between the front lens group and the rear lens group can be secured. In this case, since the front lens group and the rear lens group can be separated from each other, the telephoto action in the first lens group can be strengthened. As a result, the total length of the optical system can be shortened. Further, the weight of the lens located on the image side of the front lens group can be reduced.

If it is less than the lower limit of the conditional expression (1), the telephoto action in the first lens group is weakened, so that it becomes difficult to shorten the total length of the optical system. In order to shorten the total length of the optical system, the telephoto action may be strengthened in the first lens group and the second lens group. However, in this case, the optical symmetry is broken, and it becomes difficult to secure good imaging performance. Further, since the weight of the negative lens in the rear lens group becomes large, it becomes difficult to reduce the weight of the optical system.

If the upper limit of the conditional expression (1) is exceeded, the total length of the first lens group becomes long, so that it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (A-1), it is preferable to satisfy the following conditional expression (A-1'), (A-1'') or (A-1''').
DN Lens / φenp ≤ 0.017 (A-1')
DN Lens / φenp ≤ 0.016 (A-1'')
DN Lens / φenp ≤ 0.015 (A-1''')

Instead of the conditional expression (1), it is preferable to satisfy the following conditional expression (1'), (1 ″) or (1 ′ ″).
0.02 ≤ ΔGFGR / f ≤ 0.2 (1')
0.03 ≤ ΔGFGR / f ≤ 0.17 (1'')
0.04 ≤ ΔGFGR / f ≤ 0.15 (1''')

The imaging lens system of the second embodiment has a common configuration, and each negative lens element in the front lens group is a negative lens element satisfying the conditional equation (A), and the rear lens group is the first. It is composed of a rear lens group and a second rear lens group, and the first rear lens group has a predetermined negative lens element and a positive lens element arranged on the most object side, and is predetermined. The negative lens element satisfies the condition formula (B), and the second rear lens group has a positive lens element.
DN Lens / φenp ≤ 0.025 (A)
0.015 <DNx / φenp (B)
here,
DN Lens is the thickness of each negative lens element in the front lens group on the optical axis.
DNx is the wall thickness of a predetermined negative lens element on the optical axis.
Φenp is the maximum diameter of the entrance pupil of the imaging lens system at the longest focal length at the farthest focus.
A lens element is a lens having two effective transmission surfaces, an object side surface and an image side surface, and no other effective transmission surface between the two effective transmission surfaces.
Is.

The technical significance of the conditional expression (A) is the same as the technical significance of the conditional expression (A-1).

The front lens group is located closest to the object in the first lens group. The front lens group is provided with a positive refractive power, and the first rear lens group is arranged on the image side with an air gap. Then, a negative lens element and a positive lens element are arranged in the first rear lens group.

By doing so, the first lens group has a telephoto type optical system. As a result, the total length of the optical system can be shortened.

The second posterior lens group is arranged on the image side of the first posterior lens group with an air gap. A positive lens element is arranged in the second rear lens group. In this case, the arrangement of the refractive powers in the first lens group becomes a positive refractive power, a negative refractive power, and a positive refractive power. That is, the arrangement has a symmetrical refractive power. As described above, since the optical symmetry is ensured in the first lens group, it is possible to enhance the correction effect of spherical aberration, astigmatism, axial chromatic aberration and chromatic aberration of magnification.

Since the correction effect in the first lens group can be enhanced, it is possible to reduce the occurrence of aberration in the optical system located on the image side of the first lens group. Therefore, even if the total length of the optical system is shortened, it becomes easier to reduce the weight of the optical system located on the image side of the first lens group and to secure the performance at the time of focusing.

As described above, the volume of the front lens group is the largest in the optical system. Therefore, in order to reduce the weight of the optical system, it is preferable not to arrange a heavy lens element in the front lens group.

The negative lens element satisfying the conditional expression (B) is a lens element having a large refractive power, that is, a negative lens element having a large weight. Therefore, it is preferable that the negative lens element satisfying the conditional expression (B) is not included in the front lens group.

In order to prevent the negative lens element satisfying the conditional expression (B) from being included in the front lens group, the front lens group and the rear lens group may be divided into a predetermined negative lens element as a boundary. The predetermined negative lens is a negative lens element located closest to the object side in the posterior lens group among the negative lens elements satisfying the conditional expression (B).

By configuring the front lens group with all the lens elements located closer to the object than the predetermined negative lens element, the heavy lens element is not included in the front lens group. When not only the lens element but also the lens component is located closer to the object than the predetermined negative lens element, the lens component is also included in the front lens group.

A lens element having a value lower than the lower limit of the conditional expression (B) is a lens element having a small refractive power. Therefore, if the negative lens element is below the lower limit of the conditional expression (B), the volume of the lens does not increase even if it is arranged in the front lens group.

Further, since the refractive power is small, even if such a lens element is arranged in the front lens group, the positive refractive power required for the front lens group can be secured without any trouble. Therefore, lenses below the lower limit of the conditional expression (B) may be arranged in the front lens group.

The lens element satisfying the conditional expression (B) is a lens element having a thick wall thickness. If a thick lens element is arranged in the front lens group, the front lens group becomes large. Therefore, it is preferable that the front lens group does not include a negative lens element that satisfies the conditional expression (B).

The lens element below the lower limit of the conditional expression (B) is a lens element having a thin wall thickness. Therefore, if the negative lens element is below the lower limit of the conditional expression (B), the volume of the front lens group does not increase even if it is arranged in the front lens group. Therefore, the lens element below the lower limit of the conditional expression (B) may be arranged in the front lens group.

Instead of the conditional expression (B), it is preferable to satisfy the following conditional expression (B'), (B'') or (B''').
0.016 ≤ DNx / φenp (B')
0.017 ≤ DNx / φenp (B'')
0.02 ≤ DNx / φenp (B''')

The imaging lens system of the third embodiment has a common configuration, and the air spacing is the maximum air spacing between the object side surface of the first lens group and the image side surface of the third lens group. , Any negative lens element in the front lens group is a negative lens element satisfying the conditional equation (C), and the rear lens group has a negative lens element and a positive lens element, and has an axial light beam. An aperture aperture that limits the number of lenses is arranged between the first lens group and the second lens group, and is characterized in that the following condition (1) is satisfied.
DNL / φenp ≤ 0.02 (C)
0.015 ≤ ΔGFGR / f ≤ 0.25 (1)
here,
DNL is the thickness of any negative lens element in the front lens group on the optical axis.
Φenp is the maximum diameter of the entrance pupil of the imaging lens system at the longest focal length at the farthest focus.
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the posterior lens group, and is the maximum value when it changes.
f is the longest focal length of the entire imaging lens system at the farthest focus.
A lens element is a lens having two effective transmission surfaces, an object side surface and an image side surface, and no other effective transmission surface between the two effective transmission surfaces.
Is.

The technical significance of the conditional expression (C) is the same as the technical significance of the conditional expression (A-1).

Instead of the conditional expression (C), it is preferable to satisfy the following conditional expression (C'), (C'') or (C''').
DNL / φenp ≤ 0.017 (C')
DNL / φenp ≤ 0.016 (C'')
DNL / φenp ≤ 0.015 (C''')

In the imaging lens system of the third embodiment, as in the imaging lens system of the first embodiment and the imaging lens system of the second embodiment, the negative lens element included in the front lens group is a thin lens element. It is preferable to have. In the imaging lens system of the third embodiment, one negative lens element having a thin thickness may be arranged in the front lens group.

In the imaging lens system of the third embodiment, as in the imaging lens system of the first embodiment, the posterior lens group includes a negative lens element and a positive lens element. Therefore, the effects described in the imaging lens system of the first embodiment can be obtained.

In the imaging lens system of the third embodiment, an aperture diaphragm that limits the axial luminous flux is arranged between the first lens group and the second lens group.

Since the first lens group has a positive refractive power, a strong astringent action occurs in the first lens group. Therefore, the aperture diaphragm is arranged on the object side of the first lens group, and the second lens group is arranged on the image side of the aperture diaphragm. By doing so, the diameter of the second lens group can be reduced. Further, since the second lens group is a focus lens group, a very small focus lens group can be configured.

The technical significance of the conditional expression (1) is as described above.

In the imaging lens system of the first embodiment and the imaging lens system of the third embodiment, the rear lens group includes a first rear lens group and a second rear lens group with an air gap in between. It is preferable that the first rear lens group has a negative lens element and a positive lens element, and the second rear lens group has a positive lens element.

In the imaging lens system of the first embodiment and the imaging lens system of the third embodiment, the rear lens group includes the first rear lens group and the second, as in the imaging lens system of the second embodiment. It is composed of a rear lens group, the first rear lens group has a negative lens element and a positive lens element, and the second rear lens group has a positive lens element. Therefore, the effects described in the imaging lens system of the second embodiment can be obtained.

The negative lens element of the first rear lens group is preferably a predetermined negative lens element in the imaging lens system of the second embodiment.

In the imaging lens system of the first embodiment to the imaging lens system of the third embodiment (hereinafter, referred to as "imaging lens system of the present embodiment"), the first rear lens group has a negative refractive power. Is preferable.

By doing so, the telephoto action can be further strengthened. As a result, the total length of the optical system can be easily shortened. In addition, it becomes easier to obtain optical symmetry (arrangement of positive refractive power, negative refractive power, and positive refractive power) within the first lens group. Therefore, it is possible to further enhance the correction effect of spherical aberration, astigmatism, axial chromatic aberration, and Magnification chromatic aberration in the first lens group.

In the imaging lens system of the present embodiment, the second rear lens group preferably has a positive refractive power.

By doing so, it becomes easier to obtain optical symmetry (arrangement of positive refractive power, negative refractive power, and positive refractive power) within the first lens group. Therefore, it is possible to further enhance the correction effect of spherical aberration, astigmatism, axial chromatic aberration, and Magnification chromatic aberration in the first lens group.

The imaging lens system of the second embodiment preferably satisfies the following conditional expression (1).
0.015 ≤ ΔGFGR / f ≤ 0.25 (1)
here,
f is the longest focal length of the entire imaging lens system at the farthest focus.
fLens is the focal length of each lens element in the anterior lens group.
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
A lens element is a lens having two refracting surfaces, an object side surface and an image side surface, and no other refracting surface between the two refracting surfaces.
Is.

The technical significance of the conditional expression (1) is as described above.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (2).
0.10 ≤ DG FoGRo / f ≤ 0.5 (2)
here,
DGFoGRo is the distance from the most object-side surface of the front lens group to the most object-side surface of the rear lens group.
f is the longest focal length of the entire imaging lens system at the farthest focus.
Is.

By satisfying the conditional expression (2), it is possible to secure a sufficient distance between the front lens group and the first rear lens group. In this case, since the front lens group and the first rear lens group can be separated from each other, the telephoto action in the first lens group can be strengthened. As a result, the total length of the optical system can be shortened. Further, the weight of the lens located on the image side of the front lens group can be reduced.

If it falls below the lower limit of the conditional expression (2), the telephoto action in the first lens group is weakened, and it becomes difficult to shorten the total length of the optical system. In order to shorten the total length of the optical system, the telephoto action may be strengthened in the first lens group and the second lens group. However, in this case, the optical symmetry is broken, and it becomes difficult to secure good imaging performance. Further, since the weight of the negative lens in the first rear lens group becomes large, it becomes difficult to reduce the weight of the optical system.

If the upper limit of the conditional expression (2) is exceeded, the total length of the first lens group becomes long, so that it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (2), it is preferable to satisfy the following conditional expression (2') or (2 ″).
0.12 ≤ DG FoGRo / f ≤ 0.45 (2')
0.13 ≤ DG FoGRo / f ≤ 0.4 (2'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (3).
45 ≤ νdGFave (3)
here,
νdGFave is the average Abbe number of positive lens elements in the front lens group.
A lens element is a lens having two refracting surfaces, an object side surface and an image side surface, and no other refracting surface between the two refracting surfaces.
Is.

The value of the average Abbe number in the conditional expression (3) can be obtained by averaging the Abbe numbers of the positive lens elements included in the front lens group.

In an imaging lens system, particularly a telephoto lens, in addition to ensuring good imaging performance, miniaturization of the optical system is required. In order to obtain good imaging performance in a telephoto lens, it is mainly necessary to suppress the occurrence of axial chromatic aberration. On the other hand, in order to reduce the size of the optical system, it is necessary to increase the positive refractive power of the lens group located closer to the object side. However, in this way, axial chromatic aberration is likely to occur.

If it is less than the lower limit of the conditional expression (3), the amount of axial chromatic aberration generated becomes large, so that it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (3), it is preferable to satisfy the following conditional expression (3') or (3 ″).
50 ≤ νdGFave (3')
60 ≤ νdGFave (3'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (4).
50 ≤ νdGFmax (4)
here,
νdGFmax is the maximum Abbe number among the Abbe numbers of positive lens elements in the front lens group.
Is.

The technical significance of the conditional expression (4) is the same as the technical significance of the conditional expression (3).

Instead of the conditional expression (4), it is preferable to satisfy the following conditional expression (4'), (4'') or (4''').
60 ≤ νdGFmax (4')
70 ≤ νdGFmax (4'')
80 ≤ νdGFmax (4''')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (5).
0.015 ≤ DGR1GR2 / f ≤ 0.3 (5)
here,
DGR1GR2 is an axial air spacing between the first posterior lens group and the second posterior lens group.
f is the longest focal length of the entire imaging lens system at the farthest focus.
Is.

When the value is below the lower limit of the conditional expression (5), the difference between the ray height in the first posterior lens group and the ray height in the second posterior lens group becomes small. Therefore, it is not possible to enhance the correction effect for each aberration of spherical aberration, astigmatism, axial chromatic aberration, and Magnification chromatic aberration. If the upper limit of the conditional expression (5) is exceeded, it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (5), it is preferable to satisfy the following conditional expression (5'), (5'') or (5''').
0.02 ≤ DGR1GR2 / f ≤ 0.25 (5')
0.025 ≤ DGR1GR2 / f ≤ 0.23 (5 ″)
0.03 ≤ DGR1GR2 / f ≤ 0.2 (5''')

In the imaging lens system of the present embodiment, the front lens group preferably includes a plurality of positive lens elements.

By doing so, even if the refractive power of the front lens group is increased, the positive refractive power can be dispersed among a plurality of lenses. Therefore, the occurrence of spherical aberration can be suppressed to a small extent. Further, since the telephoto action in the first lens group can be strengthened, the total length of the optical system can be easily shortened.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (6).
0.2 ≤ fGF / f ≤ 0.8 (6)
here,
fGF is the focal length of the front lens group,
f is the longest focal length of the entire imaging lens system at the farthest focus.
Is.

When it is less than the lower limit of the conditional expression (6), the amount of axial chromatic aberration and the amount of spherical aberration generated in the front lens group become large. Therefore, good imaging performance cannot be obtained. If the upper limit of the conditional expression (6) is exceeded, it becomes difficult to miniaturize the optical system.

Instead of the conditional expression (6), it is preferable to satisfy the following conditional expression (6') or (6 ″).
0.25 ≤ fGF / f ≤ 0.6 (6')
0.28 ≤ fGF / f ≤ 0.47 (6'')

In the imaging lens system of the present embodiment, it is preferable that the first lens element is arranged on the most object side and the following conditional expression (7) is satisfied.
1.6 ≤ fL1 / fGF ≤ 5.0 (7)
here,
fL1 is the focal length of the first lens element,
fGF is the focal length of the front lens group,
Is.

If it is less than the lower limit of the conditional expression (7), the positive refractive power of the first lens element becomes too large. In this case, the amount of spherical aberration generated in the front lens group becomes large. Therefore, it becomes difficult to reduce the size of the optical system.

If the upper limit of the conditional expression (7) is exceeded, the positive refractive power of the first lens element becomes too small. In this case, the positive refractive force of the front lens group also becomes small. If an attempt is made to secure an appropriate positive refractive power in the front lens group, the load of the refractive power in the lens located on the image side of the first lens element increases. As a result, the amount of spherical aberration generated in the front lens group increases. Therefore, it becomes difficult to reduce the size of the optical system.

Instead of the conditional expression (7), it is preferable to satisfy the following conditional expression (7'), (7 ″) or (7 ′ ″).
1.8 ≤ fL1 / fGF ≤ 4.5 (7')
1.9 ≤ fL1 / fGF ≤ 4.0 (7'')
2.0 ≤ fL1 / fGF ≤ 3.5 (7''')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (8).
−3.0 ≦ fGF / fGR1 ≦ 0.1 (8)
here,
fGF is the focal length of the front lens group,
fGR1 is the focal length of the first posterior lens group,
Is.

If it falls below the lower limit of the conditional expression (8), the spherical aberration becomes overcorrected. Therefore, good imaging performance cannot be obtained. If the upper limit of the conditional expression (8) is exceeded, the negative refractive power of the first rear lens group becomes too small. Therefore, it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (8), it is preferable to satisfy the following conditional expression (8'), (8'') or (8''').
-2.5 ≤ fGF / fGR1 ≤ 0.0 (8')
−2.0 ≦ fGF / fGR1 ≦ 0.2 (8'')
-1.8 ≤ fGF / fGR1 ≤ -0.3 (8''')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (9).
0.06 ≦ | fG2 / f | ≦ 0.25 (9)
here,
fG2 is the focal length of the second lens group,
f is the longest focal length of the entire imaging lens system at the farthest focus.
Is.

In the second lens group, light rays are refracted in a direction away from the optical axis. Below the lower limit of the conditional expression (9), the light beam is refracted in a direction further away from the optical axis. As a result, the lens diameter of the third lens group becomes large. Therefore, it becomes difficult to reduce the size of the optical system.

The second lens group functions as a focus lens group. If the upper limit of the conditional expression (9) is exceeded, the refractive power of the second lens group becomes too small. In this case, the amount of movement of the imaging position with respect to the amount of movement of the second lens group (focus lens group) (hereinafter referred to as "focus sensitivity") becomes smaller, so that the amount of movement of the second lens group during focusing increases. .. Therefore, it becomes difficult to shorten the total length of the optical system. In addition, the telephoto action obtained by the first lens group and the second lens group is also reduced. Therefore, it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (9-3), it is preferable to satisfy the following conditional expression (9') or (9 ″).
0.07 ≤ | fG2 / f | ≤ 0.2 (9')
0.08 ≤ | fG2 / f | ≤ 0.15 (9'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (10).
^{3.0 ≦ | MGG2B 2 × (MGG2} 2 -1) | ≦ 6.5 (10)
here,
MGG2B is the lateral magnification of the first rear lens system,
MGG2 is the lateral magnification of the second lens group,
The horizontal magnification is the horizontal magnification when focusing on an infinite object.
The first rear lens system is a lens system composed of all lenses located on the image side of the second lens group.
Is.

If it is less than the lower limit of the conditional expression (10), the amount of movement of the second lens group at the time of focusing becomes too large. Therefore, it becomes difficult to shorten the total length of the optical system. If the upper limit of the conditional expression (10) is exceeded, it becomes difficult to control the position of the second lens group at the time of focusing. Therefore, accurate focusing cannot be achieved.

Instead of the conditional expression (10), it is preferable to satisfy the following conditional expression (10'), (10 ″), (10 ′ ″) or (10 ″'').
^{3.2 ≦ | MGG2B 2 × (MGG2} 2 -1) | ≦ 6.3 (10 ')
^{3.4 ≦ | MGG2B 2 × (MGG2} 2 -1) | ≦ 6.1 (10 '')
^{3.6 ≦ | MGG2B 2 × (MGG2} 2 -1) | ≦ 6.0 (10 ''')
^{4.0 ≦ | MGG2B 2 × (MGG2} 2 -1) | ≦ 5.6 (10 '''')

In the imaging lens system of the present embodiment, the second lens group is preferably composed of two or less lens elements.

As described above, in the imaging lens system of this embodiment, optical symmetry is ensured. As a result, coma, distortion, and chromatic aberration of magnification are satisfactorily corrected. Therefore, even if the configuration of the second lens group is simplified, high imaging performance can be ensured at the time of focusing.

Therefore, the second lens group is composed of two or less lenses. By doing so, it is possible to reduce the weight of the second lens group, that is, the focus lens group, while maintaining high imaging performance even during focusing.

In the imaging lens system of the present embodiment, the second lens group preferably includes a negative lens element and a positive lens element.

In order to reduce the weight of the second lens group, it is desirable that the second lens group is composed of two or less lens elements. The imaging lens system of the present embodiment has a common configuration. Therefore, the diameter of the second lens group can be reduced.

Even if a positive lens element and a negative lens element are used as the two lens elements, the weight of the second lens group can be reduced. In this case, since the second lens group has a positive lens element and a negative lens element, fluctuations in chromatic aberration during focusing can be further reduced.

In the imaging lens system of the present embodiment, the second lens group preferably includes one negative lens element and one positive lens element.

By doing so, it is possible to reduce the amount of axial chromatic aberration and the amount of chromatic aberration of magnification generated in the second lens group. As a result, stable imaging performance can be ensured during focusing. Further, by forming the second lens group with two lens elements, the weight of the second lens group can be reduced while maintaining high imaging performance.

In the imaging lens system of the present embodiment, it is preferable that the third lens group has a blur correction lens group, and the blur correction lens group moves in a direction perpendicular to the optical axis.

By moving one lens or a plurality of lenses in a direction perpendicular to the optical axis, it is possible to correct the shift of the imaging position caused by camera shake. At this time, if the moving lens (hereinafter referred to as “blurring correction lens”) is small and lightweight, the shift of the imaging position can be quickly corrected.

In the telephoto type optical system, the second lens group and the third lens group are groups having a small diameter. Therefore, by forming the blur correction lens group with the lenses of the third lens group, it is possible to reduce the diameter and weight of the blur correction lens. As a result, the responsiveness of the blur correction lens group can be improved. As a result, the shift of the imaging position caused by camera shake can be corrected at high speed.

In the imaging lens system of the present embodiment, it is preferable that the third lens group has a sub lens group on the object side, and the sub lens group has a refractive power having a code different from that of the blur correction lens group.

By doing so, the shift amount of the imaging position with respect to the shift amount of the blur correction lens group (hereinafter, referred to as “blurring correction sensitivity”) can be increased. That is, the shift amount of the blur correction lens group can be reduced. As a result, the shift of the imaging position caused by camera shake can be corrected at high speed.

In the imaging lens system of the present embodiment, it is preferable that the third lens group has a sub lens group on the image side, and the sub lens group has a refractive power having a code different from that of the blur correction lens group.

By doing so, the blur correction sensitivity can be increased. That is, the shift amount of the blur correction lens group can be reduced. As a result, the shift of the imaging position caused by camera shake can be corrected at high speed.

In the imaging lens system of the present embodiment, the third lens group has an object side sub lens group and an image side sub lens group on the object side and the image side, respectively, and the object side sub lens group and the image side. It is preferable that both the secondary lens groups have a refractive power of a code different from that of the blur correction lens group.

By doing so, the blur correction sensitivity can be increased. That is, the shift amount of the blur correction lens group can be reduced. As a result, the shift of the imaging position caused by camera shake can be corrected at high speed.

In the imaging lens system of the present embodiment, the blur correction lens group includes at least a first correction lens element, a second correction lens element, and a third correction lens element, and the first correction It is preferable that the lens element and the second correction lens element have a refractive power of the same code as the blur correction lens group, and the third correction lens element has a refractive force of a code different from that of the blur correction lens group.

The blur correction lens group moves in the direction perpendicular to the optical axis. This movement mainly causes spherical aberration, astigmatism, and chromatic aberration of magnification to fluctuate. If this amount of fluctuation is large, the imaging performance deteriorates.

Therefore, in the imaging lens system of the present embodiment, the first correction lens element and the second correction lens element are provided with a refractive power having the same code as that of the blur correction lens group. By doing so, the refractive power of the blur correction lens group is dispersed in the first correction lens element and the second correction lens element. As a result, the refractive power of the first correction lens element and the refractive power of the second correction lens element are both reduced. Therefore, the fluctuation amount of spherical aberration and the fluctuation amount of astigmatism can be reduced.

Further, the third correction lens element is provided with a refractive power having a code different from that of the blur correction lens group. By doing so, the amount of fluctuation in chromatic aberration of magnification can be reduced.

In the imaging lens system of the present embodiment, the blur correction lens group preferably has a negative refractive power.

The blur correction lens group moves in the direction perpendicular to the optical axis. Therefore, the blur correction lens group preferably has a small diameter. The blur correction lens group can be miniaturized by forming the lens group located at the position where the light rays are more converged into the blur correction lens group. Then, by setting the refractive power of the blur correction lens group to a negative refractive power, the blur correction lens group can be further miniaturized.

In the imaging lens system of the present embodiment, the third lens group includes an object-side sub-lens group having a positive refractive power, a blur correction lens group having a negative refractive power, and an image-side sub-lens group having a positive refractive power. It is preferable to have a lens group.

As described above, in the imaging lens system of the present embodiment, the first lens group has a positive refractive power and the second lens group has a negative refractive power. Therefore, since the telephoto action can be obtained, the total length of the optical system can be shortened.

Since the first lens group has a positive refractive power, the light rays are converged on the image side of the first lens group. That is, the height of the light beam is low at the position of the second lens group. Therefore, the outer diameter of the second lens group becomes small. Therefore, the second lens group is set as the focus lens group, and the second lens group is used for focusing. By doing so, the outer diameter of the focus lens group can be reduced.

In the focus lens group, the focus sensitivity increases as the refractive power increases. The higher the focus sensitivity, the smaller the amount of movement of the focus lens group during focusing. As described above, the second lens group functions as a focus lens group. Therefore, the refractive power of the second lens group is increased. By doing so, the focus sensitivity can be increased. As a result, the amount of movement of the focus lens group during focusing can be reduced.

The focus unit has a focus lens group and a focus mechanism. By reducing the diameter of the focus lens group and reducing the amount of movement during focusing, the entire focus unit can also be made smaller and lighter.

Further, the light incident on the focus lens group is convergent light. Therefore, even if the refractive power of the focus lens group is increased, the emission of light rays after passing through the focus lens group can be reduced. As a result, the diameter of the entire lens system located on the image side of the second lens group can be reduced while increasing the focus sensitivity.

By arranging the positive lens group on the image side of the second lens group, the focus sensitivity can be increased more easily.

The blur correction lens group moves in the direction perpendicular to the optical axis. It is preferable to minimize the moving range of the blur correction lens group. For this reason, it is desirable that the lens group located at a place where the height of the light beam is low is a blur correction lens group.

As described above, the height of the light beam is lower on the image side than that of the first lens group. Therefore, the blur correction lens group is preferably provided in the second lens group or the third lens group. However, the second lens group functions as a focus lens group. For this reason, it is preferable that the blur correction lens group is arranged in the third lens group.

At this time, the third lens group is composed of an object-side auxiliary lens group having a positive refractive power, a blur correction lens group having a negative refractive power, and an image-side auxiliary lens group having a positive refractive power. ..

With this configuration, lens groups having a positive refractive power are arranged on both sides of the blur correction lens group. Therefore, the blur correction sensitivity can be increased. That is, the shift amount of the blur correction lens group can be reduced. As a result, the shift of the imaging position caused by camera shake can be corrected at high speed.

As described above, the height of the light beam is lower on the image side than that of the first lens group. Therefore, the second lens group may have a blur correction function, and the third lens group may have a focusing function. However, in such a configuration, the fluctuation of coma caused by the blur correction is magnified by the movement of the lens group at the time of focusing. Therefore, it is not preferable to configure it in this way.

When the focus lens group has a negative refractive power, the focus sensitivity can be increased by arranging the positive lens group on the image side of the focus lens group. Further, when the blur correction lens group has a negative refractive power, the blur correction sensitivity can be increased by arranging the positive lens group on the object side of the blur correction lens group.

The object-side sub-lens group is located between the second lens group and the blur correction lens group. The second lens group has a negative refractive power and functions as a focus lens group. Therefore, if the refractive power of the sub-lens group on the object side is set to a positive refractive power, the positive lens group is located on the image side of the focus lens group, so that the focus sensitivity can be increased.

Further, the object-side sub-lens group is located on the object side of the blur correction lens group. Therefore, since the positive lens group is located on the object side of the blur correction lens group, the blur correction sensitivity can be increased. In this way, by setting the refractive power of the object-side auxiliary lens group to a positive refractive power, the focus sensitivity and the blur correction sensitivity can be increased at the same time.

The second lens group and the third lens group are preferably arranged on the image side of the aperture diaphragm. By doing so, the diameter of the focus lens group and the blur correction lens group can be further reduced.

When in focus, the lens group moves along the optical axis. When the lens group moves, the imaging performance tends to deteriorate mainly due to fluctuations in spherical aberration and axial chromatic aberration. In order to reduce the deterioration of imaging performance, it is necessary to reduce the fluctuation of spherical aberration and the fluctuation of axial chromatic aberration. Therefore, it is desirable that the second lens group has at least a positive lens and a negative lens. By doing so, it is possible to prevent deterioration of the imaging performance during focusing.

Fluctuations in spherical aberration and axial chromatic aberration in the second lens group change via the object-side sub-lens group. Therefore, it is desirable that the object-side auxiliary lens group has a positive lens and a negative lens. By doing so, fluctuations in spherical aberration and fluctuations in axial chromatic aberration can be reduced.

During blur correction, the lens group moves in the direction perpendicular to the optical axis. When the lens group moves, the imaging performance tends to deteriorate mainly due to fluctuations in spherical aberration, curvature of field, and chromatic aberration of magnification. In order to reduce the deterioration of imaging performance, it is necessary to reduce fluctuations in spherical aberration, curvature of field, and chromatic aberration of magnification. Therefore, it is desirable that the blur correction lens group has at least one positive lens and two negative lenses. By having two negative lenses, the refractive power of the blur correction lens group can be dispersed among the two negative lenses. As a result, it is possible to prevent deterioration of imaging performance during blur correction.

It is desirable that the second lens group is composed of two lenses, the object-side sub-lens group is composed of two or less lenses, and the blur correction lens group is composed of three lenses. By doing so, it is possible to configure an optical system having high focusing performance and blur correction performance with a small number of lenses.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (13).
1.0 << | MGISB × (MGIS-1) | <4.0 (13)
here,
MGISB is the lateral magnification of the second rear lens system,
MGIS is the horizontal magnification of the blur correction lens group.
The horizontal magnification is the horizontal magnification when focusing on an infinite object.
The second rear lens system is a lens system composed of all lenses located on the image side of the blur correction lens group.
Is.

If it is less than the lower limit of the conditional expression (13), the blur correction effect cannot be sufficiently obtained. When the upper limit of the conditional expression (13) is exceeded, the refractive power of the blur correction lens group becomes large. In this case, fluctuations in spherical aberration, curvature of field, and chromatic aberration of magnification become large. Therefore, it becomes difficult to correct spherical aberration, astigmatism, and chromatic aberration of magnification.

Instead of the conditional expression (13), it is preferable to satisfy the following conditional expression (13') or (13 ″).
1.3 << | MGISB × (MGIS-1) | <3.0 (13')
1.5 << | MGISB × (MGIS-1) | <2.7 (13'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (1A).
0.01 ≤ ΔGFGRmax / f ≤ 0.2 (1A)
here,
f is the longest focal length of the entire imaging lens system at the farthest focus.
ΔGFGRmax is the maximum axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
Is.

By satisfying the conditional expression (1A), a sufficient distance between the front lens group and the first rear lens group can be secured. In this case, since the front lens group and the first rear lens group can be separated from each other, the telephoto action in the first lens group can be strengthened. As a result, the total length of the optical system can be shortened. Further, the weight of the lens located on the image side of the front lens group can be reduced.

If it is less than the lower limit of the conditional expression (1A), the telephoto action in the first lens group is weakened, so that it becomes difficult to shorten the total length of the optical system. In order to shorten the total length of the optical system, the telephoto action may be strengthened in the first lens group and the second lens group. However, in this case, the optical symmetry is broken, and it becomes difficult to secure good imaging performance. Further, since the weight of the negative lens in the first rear lens group becomes large, it becomes difficult to reduce the weight of the optical system.

If the upper limit of the conditional expression (1A) is exceeded, the total length of the first lens group becomes long, so that it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (1A), it is preferable to satisfy the following conditional expression (1A'), (1A''), (1A'''') or (1A'''').
0.015 ≤ ΔGFGRmax / f ≤ 0.18 (1A')
0.02 ≤ ΔGFGRmax / f ≤ 0.17 (1A'')
0.03 ≤ ΔGFGRmax / f ≤ 0.16 (1A''')
0.05 ≤ ΔGFGRmax / f ≤ 0.15 (1A'''')

In the imaging lens system of the present embodiment, the aperture diaphragm is preferably arranged on the object side of the second lens group.

Since the first lens group has a positive refractive power, a strong astringent action occurs in the first lens group. Therefore, the aperture diaphragm is arranged on the object side of the first lens group, and the second lens group is arranged on the image side of the aperture diaphragm. By doing so, the diameter of the second lens group can be reduced. Further, since the second lens group is a focus lens group, a very small focus lens group can be configured.

In the imaging lens system of the present embodiment, the aperture diaphragm is preferably arranged between the first lens group and the second lens group.

Since the first lens group has a positive refractive power, a strong astringent action occurs in the first lens group. Therefore, the aperture diaphragm is arranged on the object side of the first lens group, and the second lens group is arranged on the image side of the aperture diaphragm. By doing so, the diameter of the second lens group can be reduced. Further, since the second lens group is a focus lens group, a very small focus lens group can be configured.

Further, the first lens group has a front lens and a first rear lens group from the object side. The anterior lens has a positive refractive power and the first posterior lens group has a negative refractive power. A second lens group and a third lens group are arranged on the image side of the first lens group. The second lens group has a negative refractive power, and the third lens group has a positive refractive power.

When the aperture diaphragm is arranged between the first lens group and the second lens group, the arrangement of the refractive power becomes symmetrical between the object side and the image side of the aperture diaphragm. Therefore, it is possible to satisfactorily correct off-axis aberrations, mainly chromatic aberration of magnification and distortion.

In the imaging lens system of the present embodiment, the aperture diaphragm is preferably arranged between the first rear lens group and the second lens group.

Further, the first lens group has a front lens and a first rear lens group from the object side. The anterior lens has a positive refractive power and the first posterior lens group has a negative refractive power. A second lens group and a third lens group are arranged on the image side of the first lens group. The second lens group has a negative refractive power, and the third lens group has a positive refractive power.

When the aperture diaphragm is arranged between the first rear lens group and the second lens group, the arrangement of the refractive power becomes symmetrical between the object side and the image side of the aperture diaphragm. Therefore, it is possible to satisfactorily correct off-axis aberrations, mainly chromatic aberration of magnification and distortion.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (14).
0.19 ≤ DGF airmax / DGF ≤ 1.0 (14)
here,
DG Fairmax is the maximum axial air spacing in the front lens group.
DGF is the axial thickness of the front lens group,
Is.

If it falls below the lower limit of the conditional expression (14), the weight of the positive lens in the front lens group increases, which makes it difficult to reduce the weight of the optical system. If the upper limit of the conditional expression (14) is exceeded, it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (14), it is preferable to satisfy the following conditional expression (14') or (14 ″).
0.2 ≤ DGF airmax / DGF ≤ 0.9 (14')
0.25 ≤ DGF airmax / DGF ≤ 0.8 (14'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (15).
0.05 ≤ ΔGFGR / fGF ≤ 0.4 (15)
here,
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
fGF is the focal length of the front lens group,
Is.

If it is less than the lower limit of the conditional expression (15), the astringent action of the luminous flux in the front lens group becomes weak. In this case, the outer diameter of the posterior lens group becomes large. Therefore, it becomes difficult to reduce the size and weight of the first lens group.

When the upper limit of the conditional expression (15) is exceeded, the amount of spherical aberration generated in the front lens group increases. Therefore, it becomes difficult to satisfactorily correct spherical aberration with a lens located on the image side of the front lens group.

Instead of the conditional expression (15), it is preferable to satisfy the following conditional expression (15') or (15 ″).
0.06 ≤ ΔGFGR / fGF ≤ 0.35 (15')
0.08 ≤ ΔGFGR / fGF ≤ 0.33 (15'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (16).
50 ≤ ν dLp1 (16)
here,
νdLp1 is the Abbe number of the positive lens element located closest to the object.
Is.

If it is less than the lower limit of the conditional expression (16), the axial chromatic aberration increases in the first sub-lens group, so that good imaging performance cannot be obtained. Alternatively, in order to obtain good imaging performance, it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (16), it is preferable to satisfy any of the following conditional expressions (16'), (16'') and (16''').
55 ≤ ν dLp1 (16')
62 ≤ ν dLp1 (16'')
65 ≤ ν dLp1 (16''')

In the imaging lens system of the present embodiment, the front lens group is preferably composed of two positive lens elements.

By doing so, it becomes easy to reduce the amount of spherical aberration generated in the front lens group, reduce the weight of the optical system, and shorten the total length of the optical system.

In the imaging lens system of the present embodiment, the first rear lens group preferably has at least two negative lens elements.

A negative lens having a large refractive power is not arranged in the front lens group. Therefore, it is difficult to satisfactorily correct chromatic aberration with the front lens group. Therefore, in the first rear lens group, it is necessary to strengthen the function of correcting the spherical aberration and the axial chromatic aberration remaining in the front lens group. Therefore, by using at least two negative lens elements in the first rear lens group, it is possible to satisfactorily correct both spherical aberration and axial chromatic aberration while shortening the total length of the optical system.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (17).
1.5 ≤ | fG1 / fG2 | ≤ 6.5 (17)
here,
fG1 is the focal length of the first lens group,
fG2 is the focal length of the second lens group,
Is.

When it is less than the lower limit of the conditional expression (17), the amount of spherical aberration generated in the first lens group increases. Therefore, good imaging performance cannot be obtained. If the upper limit of the conditional expression (17) is exceeded, the focus sensitivity is lowered. In this case, the amount of movement of the second lens group during focusing increases. Therefore, the total length of the optical system becomes long.

Instead of the conditional expression (17), it is preferable to satisfy the following conditional expression (17') or (17 ″).
2.0 ≤ | fG1 / fG2 | ≤ 6.0 (17')
2.2 ≤ | fG1 / fG2 | ≤ 5.0 (17'')

In the imaging lens system of the present embodiment, it is preferable that only the second lens group moves in the optical axis direction.

By doing so, the change in the center of gravity of the optical system can be further reduced.

In the imaging lens system of the present embodiment, the third lens group preferably includes a positive lens element and a negative lens element.

By doing so, chromatic aberration correction in the third lens group can be performed better.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (18).
0.08 ≤ ΣdGF / fGF ≤ 0.7 (18)
here,
ΣdGF is the total thickness of the front lens group,
fGF is the focal length of the front lens group,
Is.

Below the lower limit of the conditional expression (18), the number of lens elements having a large aperture increases. Therefore, it becomes difficult to reduce the weight of the optical system. If the upper limit of the conditional expression (18) is exceeded, it becomes difficult to shorten the total length of the optical system.

Instead of the conditional expression (18), it is preferable to satisfy the following conditional expression (18') or (18 ″).
0.1 ≤ ΣdGF / fGF ≤ 0.6 (18')
0.12 ≤ ΣdGF / fGF ≤ 0.5 (18'')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (19).
15 ≤ νdGFnmin ≤ 57 (19)
here,
νdGFnmin is the minimum Abbe number among the Abbe numbers of negative lens elements in the front lens group.
Is.

Below the lower limit of the conditional expression (19), the generation of the secondary spectrum becomes large. Therefore, good imaging performance cannot be obtained. If the upper limit of the conditional expression (19) is exceeded, a sufficient color correction effect cannot be obtained in the front lens group.

Instead of the conditional expression (19), it is preferable to satisfy the following conditional expression (19'), (19'') or (19''').
22 ≤ νdGFnmin ≤ 52 (19')
25 ≤ νdGFnmin ≤ 50 (19'')
30 ≤ νdGFnmin ≤ 45 (19''')

In the imaging lens system of the present embodiment, the negative lens element of the front lens group is preferably a resin lens.

Generally, a transparent resin for optical use has a specific gravity of 1.3 or less. By using a resin lens for the negative lens element in the front lens group, the weight of the optical system can be reduced. Further, by forming the negative lens element with a thermosetting resin or an ultraviolet curable resin, it is possible to produce an optical system at a lower cost.

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (21).
2.2 ≤ | fGFn / fGF | ≤ 6.5 (21)
here,
fGFn is the focal length of any negative lens element in the anterior lens group,
fGF is the focal length of the front lens group,
Is.

If it is less than the lower limit of the conditional expression (21), the refractive power of the negative lens element becomes too large. In this case, the edge of the negative lens element becomes thick. Therefore, it becomes difficult to reduce the weight of the optical system. If it exceeds the upper limit of the conditional expression (21), the effect of correcting axial chromatic aberration cannot be sufficiently obtained. Therefore, good imaging performance cannot be obtained.

In the imaging lens system of the present embodiment, it is preferable that the distance between the front lens group and the first rear lens group and the distance between the first rear lens group and the second rear lens group are always constant. ..

The change in the position of the center of gravity can be reduced, and more stable shooting can be performed.

In the imaging lens system of the present embodiment, the front lens is preferably composed of a lens element located closer to the object than a predetermined negative lens element satisfying the following conditional expression (B').
0.015 ≤ DNx / φenp (B')
DNx is the wall thickness of a predetermined negative lens element on the optical axis.
φenp is the maximum diameter of the entrance pupil of the imaging lens system at the longest focal length at the farthest focus.
Is.

The technical significance of the conditional expression (B') is the same as the technical significance of the conditional expression (B).

In the imaging lens system of the present embodiment, it is preferable that the position of the lens element on the most object side in the first lens group is fixed.

In this way, by fixing the entire length of the optical system in the entire state, the front lens can be fixed. The weight of the front lens group tends to be large. By fixing the front lens, the weight of the front lens group can be reduced, and the change in the center of gravity of the entire system due to the focusing operation can be reduced. Therefore, more stable shooting is possible in all states.

In the imaging lens system of the present embodiment, the lens group located closest to the image side is preferably fixed in all states.

The lens group located closest to the image side is the lens group closest to the imaging surface. Therefore, by fixing the lens group located closest to the image side in all states, it is possible to reduce the generation of dust due to the driving of the lens group, and it is possible to reduce the adhesion of dust to the imaging surface.

In the imaging lens system of the present embodiment, it is preferable that the aperture diaphragm is fixed in position in all states.

By doing so, the position of the aperture stop is stable and the error of the F number can be reduced. In addition, the variation in the incident luminous flux diameter due to the movement of the position of the aperture diaphragm is reduced, and the incident of unnecessary luminous flux can be reduced, so that the occurrence of flare can be reduced.

In the imaging lens system of the present embodiment, it is preferable that the first lens group is fixed in all states.

The weight of the first lens group tends to be large. By fixing the first lens group in all states, the change in the position of the center of gravity of the optical system can be reduced. As a result, more stable shooting becomes possible in all states.

It is preferable that the imaging lens system of the present embodiment has an aspherical surface and satisfies the following conditional expression (22).
0.01 ≤ | ΔZah1 | ≤ 20 (22)
here,
ΔZah1 = 1000 × N × (ΔZasph1 / h1),
h1 is the maximum height of the axially dependent ray on the aspherical surface,
ΔZasph1 is the difference between the reference spherical surface and the aspherical surface, which is measured in the direction horizontal to the optical axis at the maximum height and whose radius is the radius of curvature of the near axis of the aspherical surface and whose surface apex is the aspherical surface.
N is the refractive index of the lens element having an aspherical surface on the d-line.
Is.

The height of the axially dependent light beam passing through the aspherical surface changes depending on the diameter of the aperture diaphragm. Therefore, h1 is the height of the axially dependent light beam on the aspherical surface when the diameter of the aperture diaphragm is maximum. This height is the distance from the intersection of the aspherical surface and the on-axis dependent ray to the optical axis.

If it is less than the lower limit of the conditional expression (22), the effect of correcting spherical aberration cannot be sufficiently obtained. Therefore, it becomes difficult to shorten the total length of the optical system. If the upper limit of the conditional expression (22) is exceeded, the burden of correcting spherical aberration is concentrated on the aspherical surface. Therefore, the deterioration of the imaging performance due to the eccentricity of the aspherical surface becomes large. Therefore, it is not preferable to exceed the upper limit of the conditional expression (22).

Instead of the conditional expression (22), the following conditional expression (22'), (22''), (22''''), (22'''') or (22''''') is satisfied. Is preferable.
0.03 ≤ | ΔZah1 | ≤ 15 (22')
0.1 ≤ | ΔZah1 | ≤ 12 (22'')
0.15 ≤ | ΔZah1 | ≤ 10 (22''')
0.2 ≤ | ΔZah1 | ≤ 8 (22'''')
0.5 ≤ | ΔZah1 | ≤ 7 (22''''')

The imaging lens system of the present embodiment preferably satisfies the following conditional expression (23).
3 ≦ | ΔZah1 | / | ΔZah2 | ≦ 180 (23)
here,
ΔZah1 = 1000 × N × (ΔZasph1 / h1),
ΔZah2 = 1000 × N × (ΔZasph2 / h2),
h1 is the maximum height of the axially dependent ray on the aspherical surface,
h2 is half the maximum height,
ΔZasph1 is the difference between the reference spherical surface and the aspherical surface, which is measured in the direction horizontal to the optical axis at the maximum height and whose radius is the radius of curvature of the near axis of the aspherical surface and whose surface apex is the aspherical surface.
ΔZasph2 is the difference between the reference sphere and the aspherical surface measured in the direction horizontal to the optical axis at half the height of the maximum height.
N is the refractive index of the lens element having an aspherical surface on the d-line.
Is.

If it is less than the lower limit of the conditional expression (23), the bending of the spherical aberration in the middle portion of the vignetting becomes large. In this case, the resolving power is lowered in the region where the spatial frequency is high.

Further, when an image is taken with a large aperture diaphragm, an image in which the difference between the in-focus portion and the out-focus portion is conspicuous can be obtained. Below the lower limit of the conditional expression (23), the non-uniformity of the light intensity in the out-of-focus portion becomes conspicuous. Therefore, the out-of-focus portion, that is, the blurred image becomes dirty. For example, the inhomogeneity of the intensity of the blurred image becomes conspicuous, resulting in an unnatural blurred image such as two-line blurring or emphasizing a certain contour portion. Therefore, it is not preferable that the value falls below the lower limit of the conditional expression (23).

When the upper limit of the conditional expression (23) is exceeded, the bending at the top of the curve mainly showing spherical aberration and the color separation (separation by wavelength of spherical aberration) tend to be large. That is, flare tends to be conspicuous. Therefore, it is not preferable to exceed the upper limit of the conditional expression (23).

Instead of the conditional expression (23), the following conditional expression (23'), (23''), (23'''), (23'''') or (23''''') is satisfied. Is preferable.
3.5 ≤ | ΔZah1 | / | ΔZah2 | ≤ 150 (23')
4 ≦ | ΔZah1 | / | ΔZah2 | ≦ 100 (23'')
4 ≦ | ΔZah1 | / | ΔZah2 | ≦ 50 (23''')
4 ≦ | ΔZah1 | / | ΔZah2 | ≦ 30 (23'''')
4.5 ≤ | ΔZah1 | / | ΔZah2 | ≤10 (23''''')

The imaging lens system of the present embodiment is preferably composed of a front lens group or a lens located closer to the object than a predetermined negative lens satisfying the following conditional expression (c).
0.007 ≤ DNx / LTLmin (c)
here,
DNx is the wall thickness of a predetermined negative lens element on the optical axis.
LTLmin is the minimum total length of the imaging lens system.
Is.

The total length of the imaging lens system is the distance from the surface located closest to the object to the imaging surface.

The lens element satisfying the conditional expression (c) is a lens element having a thick wall thickness. If a thick lens element is arranged in the front lens group, the front lens group becomes large. Therefore, it is preferable that the front lens group does not include a negative lens element that satisfies the conditional expression (c).

The lens element below the lower limit of the conditional expression (c) is a lens element having a thin wall thickness. Therefore, if the negative lens element is below the lower limit of the conditional expression (c), the volume of the front lens group does not increase even if it is arranged in the front lens group. Therefore, the lens element below the lower limit of the conditional expression (c) may be arranged in the front lens group.

Instead of the conditional expression (c), it is preferable to satisfy the following conditional expression (c') or (c'').
0.0065 ≤ DNx / LTLmin (c')
0.006 ≤ DNx / LTLmin (c'')

The image pickup apparatus of the present embodiment includes an optical system and an image pickup element having an image pickup surface and converting an image formed on the image pickup surface by the optical system into an electric signal, and the optical system is the connection of the present embodiment. It is characterized by being an image lens system.

It is possible to provide an image pickup apparatus which is excellent in maneuverability and can obtain a high-quality image.

Hereinafter, examples of the imaging lens system will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

A cross-sectional view of the lens of each embodiment will be described. (A) shows a cross-sectional view of the lens when the infinity object is in focus, and (b) is a cross-sectional view of the lens when the short-distance object is in focus.

The aberration diagram of each embodiment will be described. (A) is spherical aberration (SA) when focusing on an object at infinity, (b) is astigmatism (AS) when focusing on an object at infinity, and (c) is distortion when focusing on an object at infinity. Aberrations (DT) and (d) indicate chromatic aberration of magnification (CC) when focusing on an object at infinity.

Further, (e) is spherical aberration (SA) during short-distance object point focusing, (f) is astigmatism (AS) during short-distance object point focusing, and (g) is short-distance object point focusing. Distortion aberration (DT) and (h) indicate chromatic aberration of magnification (CC) at the time of focusing on a short-distance object.

In the imaging lens system of the first embodiment, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, and the third lens having a positive refractive power are arranged in this order from the object side. It is composed of a group G3. The aperture diaphragm S is arranged between the first lens group G1 and the second lens group G2.

The first lens group G1 includes a biconvex positive lens L1, a positive meniscus lens L2 with a convex surface facing the object side, a negative meniscus lens L3 with a convex surface facing the object side, and a negative meniscus lens L3 with a convex surface facing the object side. L4, a positive meniscus lens L5 with a convex surface facing the object side, a biconvex positive lens L6, a biconcave negative lens L7, a biconvex positive lens L8, and a negative meniscus lens L9 with a convex surface facing the image side. It is composed of.

Here, a meniscus-shaped resin layer, that is, a negative meniscus lens L3 is formed on the image side surface of the positive meniscus lens L2. The negative meniscus lens L4 and the positive meniscus lens L5 are joined. The biconvex positive lens L6 and the biconcave negative lens L7 are joined. The biconvex positive lens L8 and the negative meniscus lens L9 are joined.

The front lens group is composed of a biconvex positive lens L1, a positive meniscus lens L2, and a negative meniscus lens L3. The posterior lens group is composed of a first posterior lens group and a second posterior lens group. The first posterior lens group is composed of a negative meniscus lens L4, a positive meniscus lens L5, a biconvex positive lens L6, and a biconcave negative lens L7. The second rear lens group is composed of a biconvex positive lens L8 and a negative meniscus lens L9.

The second lens group G2 is composed of a biconvex positive lens L10 and a biconcave negative lens L11. Here, the biconvex positive lens L10 and the biconcave negative lens L11 are joined.

The third lens group G3 includes a biconvex positive lens L12, a positive meniscus lens L13 with a convex surface facing the object side, a negative meniscus lens L14 with a convex surface facing the object side, a biconcave negative lens L15, and biconvex positive. It is composed of a lens L16, a biconcave negative lens L17, a biconvex positive lens L18, and a negative meniscus lens L19 with a convex surface facing the image side.

Here, the positive meniscus lens L13 and the negative meniscus lens L14 are joined. The biconvex positive lens L16 and the biconcave negative lens L17 are joined. The biconvex positive lens L18 and the negative meniscus lens L19 are joined.

The object-side sub-lens group is composed of a biconvex positive lens L12. The blur correction lens group is composed of a positive meniscus lens L13, a negative meniscus lens L14, and a biconcave negative lens L15. The image side sub-lens group is composed of a biconvex positive lens L16, a biconcave negative lens L17, a biconvex positive lens L18, and a negative meniscus lens L19.

When focusing from an infinite object to a short-distance object, the second lens group G2 moves to the image side. During blur correction, the blur correction lens group moves in the direction perpendicular to the optical axis.

The aspherical surface is provided on the image side surface of the negative meniscus lens L3.

In the imaging lens system of the second embodiment, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, and the third lens having a positive refractive power are arranged in this order from the object side. It is composed of a group G3. The aperture diaphragm S is arranged between the first lens group G1 and the second lens group G2.

The first lens group G1 includes a positive meniscus lens L1 having a convex surface facing the object side, a positive meniscus lens L2 having a convex surface facing the object side, a negative meniscus lens L3 having a convex surface facing the object side, and a convex surface toward the object side. Negative meniscus lens L4 with facing the object, positive meniscus lens L5 with the convex surface facing the object side, biconvex positive lens L6, biconcave negative lens L7, biconvex positive lens L8, and the convex surface facing the image side. It is composed of a negative meniscus lens L9.

Here, a meniscus-shaped resin layer, that is, a negative meniscus lens L3 is formed on the image side surface of the positive meniscus lens L2. The negative meniscus lens L4 and the positive meniscus lens L5 are joined. The biconvex positive lens L6 and the biconcave negative lens L7 are joined. The biconvex positive lens L8 and the negative meniscus lens L9 are joined.

The front lens group is composed of a positive meniscus lens L1, a positive meniscus lens L2, and a negative meniscus lens L3. The posterior lens group is composed of a first posterior lens group and a second posterior lens group. The first posterior lens group is composed of a negative meniscus lens L4, a positive meniscus lens L5, a biconvex positive lens L6, and a biconcave negative lens L7. The second rear lens group is composed of a biconvex positive lens L8 and a negative meniscus lens L9.

The second lens group G2 is composed of a positive meniscus lens L10 having a convex surface facing the object side and a negative meniscus lens L11 having a convex surface facing the object side. Here, the positive meniscus lens L10 and the negative meniscus lens L11 are joined.

The third lens group G3 includes a biconvex positive lens L12, a biconvex positive lens L13, a biconcave negative lens L14, a biconcave negative lens L15, a biconvex positive lens L16, and a biconvex negative lens L17. It is composed of a convex lens L18 and a negative meniscus lens L19 with a convex surface facing the image side.

Here, the biconvex positive lens L13 and the biconcave negative lens L14 are joined. The biconvex positive lens L16 and the biconcave negative lens L17 are joined. The biconvex positive lens L18 and the negative meniscus lens L19 are joined.

The object-side sub-lens group is composed of a biconvex positive lens L12. The blur correction lens group is composed of a biconvex positive lens L13, a biconcave negative lens L14, and a biconcave negative lens L15. The image side sub-lens group is composed of a biconvex positive lens L16, a biconcave negative lens L17, a biconvex positive lens L18, and a negative meniscus lens L19.

When focusing from an infinite object to a short-distance object, the second lens group G2 moves to the image side. During blur correction, the blur correction lens group moves in the direction perpendicular to the optical axis.

The aspherical surface is provided on the image side surface of the negative meniscus lens L3.

In the imaging lens system of the third embodiment, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, and the third lens having a positive refractive power are arranged in this order from the object side. It is composed of a group G3. The aperture diaphragm S is arranged between the first lens group G1 and the second lens group G2.

The first lens group G1 includes a positive meniscus lens L1 having a convex surface facing the object side, a positive meniscus lens L2 having a convex surface facing the object side, a negative meniscus lens L3 having a convex surface facing the object side, and a convex surface toward the object side. Negative meniscus lens L4 with facing the object, positive meniscus lens L5 with the convex surface facing the object side, biconvex positive lens L6, biconcave negative lens L7, biconvex positive lens L8, and the convex surface facing the image side. It is composed of a negative meniscus lens L9.

Here, a meniscus-shaped resin layer, that is, a negative meniscus lens L3 is formed on the image side surface of the positive meniscus lens L2. The negative meniscus lens L4 and the positive meniscus lens L5 are joined. The biconvex positive lens L6 and the biconcave negative lens L7 are joined. The biconvex positive lens L8 and the negative meniscus lens L9 are joined.

The front lens group is composed of a positive meniscus lens L1, a positive meniscus lens L2, and a negative meniscus lens L3. The posterior lens group is composed of a first posterior lens group and a second posterior lens group. The first posterior lens group is composed of a negative meniscus lens L4, a positive meniscus lens L5, a biconvex positive lens L6, and a biconcave negative lens L7. The second rear lens group is composed of a biconvex positive lens L8 and a negative meniscus lens L9.

The second lens group G2 is composed of a positive meniscus lens L10 having a convex surface facing the object side and a negative meniscus lens L11 having a convex surface facing the object side. Here, the positive meniscus lens L10 and the negative meniscus lens L11 are joined.

The third lens group G3 includes a biconvex positive lens L12, a biconvex positive lens L13, a biconcave negative lens L14, a negative meniscus lens L15 with a convex surface facing the image side, a biconvex positive lens L16, and both concaves. It is composed of a negative lens L17, a biconvex positive lens L18, and a negative meniscus lens L19 with a convex surface facing the image side.

Here, the biconvex positive lens L13 and the biconcave negative lens L14 are joined. The biconvex positive lens L16 and the biconcave negative lens L17 are joined. The biconvex positive lens L18 and the negative meniscus lens L19 are joined.

The object-side sub-lens group is composed of a biconvex positive lens L12. The blur correction lens group is composed of a biconvex positive lens L13, a biconcave negative lens L14, and a negative meniscus lens L15. The image side sub-lens group is composed of a biconvex positive lens L16, a biconcave negative lens L17, a biconvex positive lens L18, and a negative meniscus lens L19.

When focusing from an infinite object to a short-distance object, the second lens group G2 moves to the image side. During blur correction, the blur correction lens group moves in the direction perpendicular to the optical axis.

The aspherical surface is provided on the image side surface of the negative meniscus lens L3.

The numerical data of each of the above examples is shown below. In the surface data, r is the radius of curvature of each lens surface, d is the distance between each lens surface, nd is the refractive index of the d line of each lens, νd is the Abbe number of each lens, and * mark is an aspherical surface.

In various data, OB is the distance to the object, f is the focal length of the entire system, and FNO. Is the F number, ω is the half angle of view, LTL is the total length of the optical system, and BF is the back focus. The back focus represents the distance from the lens surface on the image side to the paraxial image surface in terms of air. The total length is the distance from the lens surface on the most object side to the lens surface on the image side with back focus added. Infinity means when an infinity object is in focus, and close means when a close object is in focus. The unit of OB is m (meter).

The aspherical shape has the following equation when the optical axis direction is z, the direction orthogonal to the optical axis is y, the conical coefficient is k, and the aspherical coefficient is A4, A6, A8, A10, A12, and so on. expressed.
z = (y ² / r) / [1 + {1- (1 + k) (y / r) ² } ^1/2 ]
+ A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰ + A12y ¹² + ...
Further, in the aspherical coefficient, "en" (n is an integer) indicates "10- ⁿ ".
The symbols of these specification values are also common to the numerical data of the examples described later.

Numerical Example 1
Unit mm

Surface data Surface number rd nd ν d
Physical surface ∞ ∞
1 258.546 10.00 1.48749 70.23
2-1406.852 2.00
3 80.992 17.00 1.49700 81.54
4 837.994 0.70 1.60000 41.00
5 * 225.921 53.21
6 124.468 3.20 1.83481 42.73
7 44.039 11.00 1.43875 94.66
8 147.154 0.40
9 53.474 9.80 1.43875 94.66
10 -114.559 2.90 1.77250 49.60
11 115.702 25.05
12 107.147 7.80 1.71736 29.52
13 -77.114 2.00 1.91082 35.25
14 -665.155 3.33
15 (Aperture) ∞ Variable
16 278.186 2.10 1.80810 22.76
17 -100.028 0.80 1.71300 53.87
18 32.155 Variable
19 39.029 5.40 1.43875 94.66
20 -97.053 3.91
21 43.671 2.45 1.92286 20.88
22 158.301 0.90 1.61800 63.40
23 17.805 3.92
24-43.778 0.90 1.69680 55.53
25 84.322 3.31
26 37.705 8.04 1.74951 35.33
27 -35.693 1.80 1.92286 20.88
28 63.424 0.30
29 41.873 8.63 1.74077 27.79
30 -23.209 2.30 1.92286 20.88
31 -60.070 32.98
Image plane ∞

Aspherical data surface 5
k = 0.000
A4 = -7.35194e-09, A6 = -6.59690e-13, A8 = -2.29181e-17

Various data 2ω 3.19
LTL (in air) 270.58
BF (in air) 32.98

Infinity Closest OB ∞ 2.5
f 391.98
FNO. 4.08 3.08
d15 21.25 40.93
d18 23.21 3.53

Focal length of each group
f1 = 189.60 f2 = -54.93 f3 = 146.93

Numerical Example 2
Unit mm

Surface data Surface number rd nd ν d
Physical surface ∞ ∞
1 177.711 10.00 1.48749 70.23
2 793.260 2.00
3 78.980 16.43 1.49700 81.54
4 299.016 0.60 1.59400 37.00
5 * 179.309 50.95
6 97.480 3.20 1.88300 40.76
7 46.776 11.00 1.43875 94.66
8 180.780 0.49
9 58.028 9.80 1.43875 94.66
10 -139.658 2.90 1.77250 49.60
11 94.709 24.89
12 141.605 7.80 1.71736 29.52
13 -56.955 2.00 1.91082 35.25
14 -319.657 6.32
15 (Aperture) ∞ Variable
16 82.322 2.10 1.80810 22.76
17 1055.833 0.80 1.71300 53.87
18 27.027 Variable
19 32.290 5.40 1.43875 94.66
20 -136.369 3.91
21 73.473 2.45 1.92286 20.88
22 -303.723 0.90 1.61800 63.40
23 17.128 3.92
24 -30.056 0.90 1.69680 55.53
25 3912.663 3.31
26 38.071 5.66 1.74951 35.33
27 -35.888 1.80 1.92286 20.88
28 99.292 0.30
29 57.696 8.63 1.69895 30.13
30 -21.800 2.30 1.92286 20.88
31 -41.571 32.97
Image plane ∞

Aspherical data surface 5
k = 0.000
A4 = 2.72668e-09, A6 = -4.53214e-13, A8 = -1.03931e-16

Various data 2ω 3.22
BF (in air) 32.97
LTL (in air) 270.57

Infinity Closest OB ∞ 2.5
f 391.96
FNO. 4.08 3.08
d15 21.38 43.94
d18 25.46 2.89

Focal length of each group
f1 = 196.37 f2 = -61.60 f3 = 139.64

Numerical Example 3
Unit mm

Surface data Surface number rd nd ν d
Physical surface ∞ ∞
1 193.853 10.00 1.48749 70.23
2 855.644 2.00
3 76.895 15.62 1.49700 81.54
4 273.293 0.90 1.74000 33.00
5 * 186.117 50.66
6 83.236 3.20 1.88300 40.76
7 47.296 11.00 1.43875 94.66
8 142.499 0.40
9 63.197 9.80 1.43875 94.66
10 -110.911 2.90 1.77250 49.60
11 93.792 25.14
12 163.855 7.80 1.69895 30.13
13 -53.592 2.00 1.91082 35.25
14 -201.682 6.97
15 (Aperture) ∞ Variable
16 76.604 2.10 1.80810 22.76
17 519.766 0.80 1.71300 53.87
18 26.879 Variable
19 30.230 5.40 1.43875 94.66
20 -148.774 3.91
21 100.226 2.45 1.92286 20.88
22 -149.436 0.90 1.61800 63.40
23 17.521 3.92
24-28.928 0.90 1.69680 55.53
25 -228.512 3.31
26 37.823 5.66 1.74951 35.33
27 -44.858 1.80 1.92286 20.88
28 52.823 0.30
29 44.689 8.63 1.72825 28.46
30 -20.270 2.30 1.92286 20.88
31 -41.181 32.99
Image plane ∞

Aspherical data surface 5
k = 0.000
A4 = 4.73076e-10, A6 = -7.06833e-13, A8 = -1.53205e-16

Various data 2ω 3.21
BF (in air) 32.99
LTL (in air) 270.59

Infinity Closest OB ∞ 2.5
f 391.99
FNO. 4.08 3.08
d15 21.19 43.99
d18 25.64 2.85

Focal length of each group
f1 = 196.47 f2 = -63.68 f3 = 152.04

Next, the values of the conditional expressions in each embodiment are listed below.
Example 1 Example 2 Example 3
(1) ΔGFGR / f 0.136 0.130 0.129
(2) ΔGFFGR1 / f 0.212 0.204 0.202
(1A) ΔGFGR max 0.136 0.130 0.129
(3) νdGFave 75.885 75.885 75.885
(4) νdGFmax 81.540 81.540 81.540
(5) DGR1GR2 / f 0.064 0.064 0.064
(6) fGF / f 0.424 0.451 0.460
(7) fL1 / fGF 2.701 2.641 2.838
(8) fGF / fGR1 -1.058 -0.931 -0.967
(9) | fG2 / f | 0.140 0.157 0.162
(10) | MG G2B ² × (MGG2 ² -1) | 3.838 3.428 3.395
(13) | MGISB × (MGIS-1) | 1.622 1.799 1.799
(14) DGFairmax / DGF 0.067 0.069 0.070
(15) ΔGFGR / fGF 0.320 0.288 0.281
(16) νdLp1 70.230 70.230 70.230
(17) | fG1 / fG2 | 3.452 3.188 3.085
(18) ΣdGF / fGF 0.179 0.164 0.158
(19) νdGFnmin 41.000 37.000 33.000
(21) | fGFn / fGF | 3.103 4.270 4.392
(22) | ΔZah1 | 1.165 0.197 0.224
(23) | ΔZah1 | / | ΔZah2 | 9.051 4.746 142.000

FIG. 7 is a cross-sectional view of a single-lens mirrorless camera as an electronic imaging device. In FIG. 7, the photographing optical system 2 is arranged in the lens barrel of the single-lens mirrorless camera 1. The mount portion 3 allows the photographing optical system 2 to be attached to and detached from the body of the single-lens mirrorless camera 1. As the mount portion 3, a screw type mount, a bayonet type mount, or the like is used. In this example, a bayonet type mount is used. Further, an image sensor surface 4 and a back monitor 5 are arranged on the body of the single-lens mirrorless camera 1. As the image sensor, a small CCD, CMOS, or the like is used.

Then, as the photographing optical system 2 of the single-lens mirrorless camera 1, for example, the imaging lens system shown in Examples 1 to 3 is used.

8 and 9 show a conceptual diagram of the configuration of the image pickup apparatus. FIG. 8 is a front perspective view of the digital camera 40 as an imaging device, and FIG. 9 is a rear perspective view of the digital camera 40. The imaging lens system of this embodiment is used in the photographing optical system 41 of the digital camera 40.

The digital camera 40 of this embodiment includes a photographing optical system 41, a shutter button 45, a liquid crystal display monitor 47, etc. located on an optical path 42 for photographing, and when the shutter button 45 arranged on the upper portion of the digital camera 40 is pressed, a shutter button 45 is pressed. In conjunction with this, imaging is performed through the photographing optical system 41, for example, the imaging lens system of the first embodiment. The object image formed by the photographing optical system 41 is formed on an image sensor (photoelectric conversion surface) provided near the image plane. The object image received by the image sensor is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back surface of the camera by the processing means. Further, the captured electronic image can be recorded in the storage means.

FIG. 10 is a block diagram showing an internal circuit of a main part of the digital camera 40. In the following description, the processing means described above is composed of, for example, a CDS / ADC unit 24, a temporary storage memory 17, an image processing unit 18, and the like, and the storage means is composed of a storage medium unit 19, and the like.

As shown in FIG. 10, the digital camera 40 is connected to the operation unit 12, the control unit 13 connected to the operation unit 12, and the control signal output port of the control unit 13 via buses 14 and 15. It includes an image pickup drive circuit 16, a temporary storage memory 17, an image processing unit 18, a storage medium unit 19, a display unit 20, and a setting information storage memory unit 21.

The temporary storage memory 17, the image processing unit 18, the storage medium unit 19, the display unit 20, and the setting information storage memory unit 21 can mutually input and output data via the bus 22. Further, the CCD 49 and the CDS / ADC unit 24 are connected to the image pickup drive circuit 16.

The operation unit 12 includes various input buttons and switches, and notifies the control unit 13 of event information input from the outside (camera user) via these. The control unit 13 is a central processing unit including, for example, a CPU, and has a built-in program memory (not shown), and controls the entire digital camera 40 according to a program stored in the program memory.

The CCD 49 is an image pickup device that is driven and controlled by an image pickup drive circuit 16 and converts the amount of light for each pixel of an object image formed via the photographing optical system 41 into an electric signal and outputs the light amount to the CDS / ADC unit 24.

The CDS / ADC unit 24 amplifies the electric signal input from the CCD 49 and performs analog / digital conversion, and the video raw data (Bayer data, hereinafter referred to as RAW data) obtained by performing the amplification and digital conversion. Is a circuit that outputs the data to the temporary storage memory 17.

The temporary storage memory 17 is a buffer made of, for example, SDRAM or the like, and is a memory device that temporarily stores RAW data output from the CDS / ADC unit 24. The image processing unit 18 reads out the RAW data stored in the temporary storage memory 17 or the RAW data stored in the storage medium unit 19, and includes distortion correction based on the image quality parameter specified by the control unit 13. It is a circuit that electrically performs various image processing.

The storage medium unit 19 is detachably attached to, for example, a card-type or stick-type recording medium made of a flash memory or the like, and the RAW data or image processing unit 18 transferred from the temporary storage memory 17 to these flash memories. Record and retain image processed image data.

The display unit 20 is composed of a liquid crystal display monitor 47 and the like, and displays captured RAW data, image data, an operation menu, and the like. The setting information storage memory unit 21 includes a ROM unit in which various image quality parameters are stored in advance, and a RAM unit that stores image quality parameters read from the ROM unit by an input operation of the operation unit 12.

It should be noted that the present invention can take various modifications without departing from the spirit of the present invention. Further, the number of shapes shown in each of the above embodiments is not necessarily limited. Further, in each of the above embodiments, the cover glass does not necessarily have to be arranged. Further, a lens not shown in each of the above-described embodiments and having substantially no refractive power may be arranged in or outside each lens group.

Further, the lens may be made of a single material or may be made of a plurality of materials. Examples of the lens made of a plurality of glass materials include the above-mentioned hybrid lens and diffractive optical element in addition to the junction lens. There are, for example, two forms of the diffractive optical element. In the first embodiment, a diffractive surface is formed on the surface of a lens made of a single material. In the second embodiment, another material is provided on the surface of the lens made of a single material, and a diffraction action surface is formed on the surface of the other material.

As described above, the present invention is suitable for an imaging lens system having excellent maneuverability and well-corrected aberrations, and an imaging apparatus having excellent maneuverability and obtaining a high-quality image.

G1 1st lens group G2 2nd lens group G3 3rd lens group S Aperture aperture I Image plane 1 Single-lens mirrorless camera 2 Imaging optical system 3 Lens barrel mount 4 Imaging element surface 5 Back monitor 12 Operation unit 13 Control unit 14 , 15 Bus 16 Imaging drive circuit 17 Temporary storage memory 18 Image processing unit 19 Storage medium unit 20 Display unit 21 Setting information storage memory unit 22 Bus 24 CDS / ADC unit 40 Digital camera 41 Shooting optical system 42 Shooting optical path 45 Shutter button 47 LCD display monitor 49 CCD

Claims (50)

From the object side to the image side,
The first lens group with positive refractive power and
A second lens group with negative refractive power,
It consists of a third lens group and
The first lens group is composed of an anterior lens group having a positive refractive power and a posterior lens group in order from the object side with the widest air spacing in the first lens group in between.
At the time of focusing, the second lens group moves by changing the air spacing between the object side and the image side.
The third lens group has a positive lens element and has a positive lens element.
The front lens group includes a negative lens element and a positive lens element.
Each negative lens element in the front lens group is a negative lens element satisfying the conditional expression ( A-1'''' ).
The posterior lens group includes a negative lens element and a positive lens element.
An imaging lens system characterized by satisfying the following conditional expression (1).
DN Lens / φenp ≤ 0.0094 ( A-1'''' )
0.015 ≤ ΔGFGR / f ≤ 0.25 (1)
here,
DN Lens is the thickness of each negative lens element in the front lens group on the optical axis.
Φenp is the maximum diameter of the entrance pupil of the imaging lens system in the state where it has the longest focal length at the farthest focus.
f is the longest focal length when the entire system of the imaging lens system is in the farthest focus.
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
A lens element is a lens having two effective transmission surfaces, an object side surface and an image side surface, and no other effective transmission surface between the two effective transmission surfaces.
Is. The posterior lens group is composed of a first posterior lens group and a second posterior lens group with the widest air spacing in the posterior lens group in between.
The first rear lens group includes a negative lens element and a positive lens element.
The imaging lens system according to claim 1, wherein the second rear lens group has a positive lens element. The imaging lens system according to claim 2, wherein the first rear lens group has a negative refractive power. The imaging lens system according to claim 2 or 3, wherein the second rear lens group has a positive refractive power. The imaging lens system according to any one of claims 1 to 4, wherein the imaging lens system satisfies the following conditional expression (2).
0.10 ≤ DG FoGRo / f ≤ 0.5 (2)
here,
DGFoGRo is the distance from the most object side surface of the front lens group to the most object side surface of the posterior lens group.
f is the longest focal length when the entire system of the imaging lens system is in the farthest focus.
Is. The imaging lens system according to any one of claims 1 to 5, wherein the imaging lens system satisfies the following conditional expression (3).
45 ≤ νdGFave (3)
here,
νdGFave is the average Abbe number of positive lens elements in the front lens group.
A lens element is a lens having two refracting surfaces, an object side surface and an image side surface, and no other refracting surface between the two refracting surfaces.
Is. The imaging lens system according to any one of claims 1 to 6, wherein the imaging lens system satisfies the following conditional expression (4).
50 ≤ νdGFmax (4)
here,
νdGFmax is the maximum Abbe number among the Abbe numbers of the positive lens elements in the front lens group.
Is. The imaging lens system according to claim 2, wherein the imaging lens system satisfies the following conditional expression (5).
0.015 ≤ DGR1GR2 / f ≤ 0.3 (5)
here,
DGR1GR2 is an axial air gap between the first posterior lens group and the second posterior lens group.
f is the longest focal length when the entire system of the imaging lens system is in the farthest focus.
Is. The imaging lens system according to any one of claims 1 to 8, wherein the imaging lens system satisfies the following conditional expression (6).
0.2 ≤ fGF / f ≤ 0.8 (6)
here,
fGF is the focal length of the anterior lens group,
f is the longest focal length when the entire system of the imaging lens system is in the farthest focus.
Is. The imaging lens system according to any one of claims 1 to 9, wherein the first lens element is arranged on the most object side and satisfies the following conditional expression (7).
1.6 ≤ fL1 / fGF ≤ 5.0 (7)
here,
fL1 is the focal length of the first lens element.
fGF is the focal length of the anterior lens group,
Is. The imaging lens system according to claim 2, wherein the imaging lens system satisfies the following conditional expression (8).
−3.0 ≦ fGF / fGR1 ≦ 0.1 (8)
here,
fGF is the focal length of the anterior lens group,
fGR1 is the focal length of the first posterior lens group.
Is. The imaging lens system according to any one of claims 1 to 11, wherein the imaging lens system satisfies the following conditional expression (9).
0.06 ≦ | fG2 / f | ≦ 0.25 (9)
here,
fG2 is the focal length of the second lens group.
f is the longest focal length when the entire system of the imaging lens system is in the farthest focus.
Is. The imaging lens system according to any one of claims 1 to 12, wherein the imaging lens system satisfies the following conditional expression (10).
3.0 ≦ ｜ MGG2B ² × (MGG2 ² -1) | ≤6.5 (10)
here,
MGG2B is the lateral magnification of the first rear lens system,
MGG2 is the lateral magnification of the second lens group.
The horizontal magnification is the horizontal magnification when focusing on an infinite object.
The first rear lens system is a lens system composed of all lenses located on the image side of the second lens group.
Is. The imaging lens system according to any one of claims 1 to 13, wherein the second lens group is composed of two or less lens elements. The imaging lens system according to any one of claims 1 to 14, wherein the second lens group includes a negative lens element and a positive lens element. The imaging lens system according to any one of claims 1 to 15, wherein the second lens group includes one negative lens element and one positive lens element. The third lens group has a blur correction lens group.
The imaging lens system according to any one of claims 1 to 16, wherein the blur correction lens group moves in a direction perpendicular to the optical axis. The third lens group has an auxiliary lens group on the object side.
The imaging lens system according to claim 17, wherein the sub-lens group has a refractive power having a code different from that of the blur correction lens group. The third lens group has an auxiliary lens group on the image side.
The imaging lens system according to claim 17, wherein the sub-lens group has a refractive power having a code different from that of the blur correction lens group. The third lens group has an object-side sub-lens group and an image-side sub-lens group on the object side and the image side, respectively.
The imaging lens system according to claim 17, wherein both the object-side sub-lens group and the image-side sub-lens group have a refractive power having a code different from that of the blur correction lens group. The blur correction lens group includes at least a first correction lens element, a second correction lens element, and a third correction lens element.
The first correction lens element and the second correction lens element have the same refractive power as the blur correction lens group.
The imaging lens system according to claim 17, wherein the third correction lens element has a refractive power having a code different from that of the blur correction lens group. The imaging lens system according to any one of claims 17 to 21, wherein the blur correction lens group has a negative refractive power. The third lens group is
Object-side auxiliary lens group with positive refractive power,
A group of blur correction lenses with negative refractive power,
The imaging lens system according to claim 1, further comprising an image-side sub-lens group having a positive refractive power. The imaging lens system according to any one of claims 17 to 23, which satisfies the following conditional expression (13).
1.0 << | MGISB × (MGIS-1) | <4.0 (13)
here,
MGISB is the lateral magnification of the second rear lens system,
MGIS is the lateral magnification of the blur correction lens group.
The horizontal magnification is the horizontal magnification when focusing on an infinite object.
The second rear lens system is a lens system composed of all lenses located on the image side of the blur correction lens group.
Is. The imaging lens system according to any one of claims 1 to 24, which satisfies the following conditional expression (1A).
0.01 ≤ ΔGFGRmax / f ≤ 0.2 (1A)
here,
f is the longest focal length when the entire system of the imaging lens system is in the farthest focus.
ΔGFGRmax is the maximum axial air spacing among the axial air spacing from the image side surface in the front lens group to the object side surface in the posterior lens group.
Is. The imaging lens system according to claim 1, wherein the aperture diaphragm is arranged on the object side of the second lens group. The imaging lens system according to any one of claims 1 to 26, wherein the aperture diaphragm is arranged between the first lens group and the second lens group . The imaging lens system according to claim 2, wherein the aperture diaphragm is arranged between the first rear lens group and the second lens group. The imaging lens system according to any one of claims 1 to 28, which satisfies the following conditional expression (14).
0.19 ≤ DGF airmax / DGF ≤ 1.0 (14)
here,
DGFairmax is the maximum axial air spacing in the front lens group.
DGF is the axial thickness of the anterior lens group.
Is. The imaging lens system according to any one of claims 1 to 29, which satisfies the following conditional expression (15).
0.05 ≤ ΔGFGR / fGF ≤ 0.4 (15)
here,
ΔGFGR is the axial air spacing from the image side surface in the front lens group to the object side surface in the rear lens group.
fGF is the focal length of the anterior lens group,
Is. The imaging lens system according to any one of claims 1 to 30, wherein the imaging lens system satisfies the following conditional expression (16).
50 ≤ ν dLp1 (16)
here,
νdLp1 is the Abbe number of the positive lens element located closest to the object.
Is. The imaging lens system according to any one of claims 1 to 31, wherein the number of positive lens elements constituting the front lens group is two. The imaging lens system according to any one of claims 1 to 32, wherein the first rear lens group has at least two negative lens elements. The imaging lens system according to any one of claims 1 to 33, which satisfies the following conditional expression (17).
1.5 ≤ | fG1 / fG2 | ≤ 6.5 (17)
here,
fG1 is the focal length of the first lens group.
fG2 is the focal length of the second lens group.
Is. The imaging lens system according to any one of claims 1 to 34, wherein only the second lens group moves in the optical axis direction. The imaging lens system according to any one of claims 1 to 35, wherein the third lens group includes the positive lens element and the negative lens element. The imaging lens system according to any one of claims 1 to 36, which satisfies the following conditional expression (18).
0.08 ≤ ΣdGF / fGF ≤ 0.7 (18)
here,
ΣdGF is the total thickness of the front lens group,
fGF is the focal length of the anterior lens group,
Is. The imaging lens system according to any one of claims 1 to 37, which satisfies the following conditional expression (19).
15 ≤ νdGFnmin ≤ 57 (19)
here,
νdGFnmin is the minimum Abbe number among the Abbe numbers of the negative lens elements in the front lens group.
Is. The imaging lens system according to any one of claims 1 to 38, wherein the negative lens element of the front lens group is a resin lens. The imaging lens system according to any one of claims 1 to 3, wherein the imaging lens system satisfies the following conditional expression (21).
2.2 ≤ | fGFn / fGF | ≤ 6.5 (21)
here,
fGFn is the focal length of any negative lens element in the anterior lens group.
fGF is the focal length of the anterior lens group,
Is. 2. The second aspect of the present invention is that the distance between the front lens group and the first rear lens group and the distance between the first rear lens group and the second rear lens group are always constant. The imaging lens system described. The imaging lens system according to claim 1, wherein the front lens is composed of a lens element located closer to an object than a predetermined negative lens element satisfying the following conditional expression (B').
0.015 ≤ DNx / φenp (B')
DNx is the wall thickness of the predetermined negative lens element on the optical axis.
φenp is the maximum diameter of the entrance pupil of the imaging lens system in a state where it has the longest focal length at the time of farthest focusing.
Is. The imaging lens system according to any one of claims 1 to 42, wherein the lens element on the most object side in the first lens group has a fixed position. The imaging lens system according to any one of claims 1 to 43, wherein the lens group located closest to the image side is fixed in all states. The imaging lens system according to any one of claims 1 to 44, wherein the aperture diaphragm is fixed in position in all states. The imaging lens system according to any one of claims 1 to 45, wherein the first lens group is fixed in all states. Has an aspherical surface
The imaging lens system according to any one of claims 1 to 46, which satisfies the following conditional expression (22).
0.01 ≤ | ΔZah1 | ≤ 20 (22)
here,
ΔZah1 = 1000 × N × (ΔZasph1 / h1),
h1 is the maximum height of the axially dependent ray on the aspherical surface.
ΔZasph1 is a reference spherical surface and the aspherical surface whose radius is the radius of curvature of the near axis of the aspherical surface and whose surface apex is the surface apex of the aspherical surface, which is measured in a direction horizontal to the optical axis at the maximum height. difference,
N is the refractive index of the lens element having an aspherical surface at line d.
Is. Has an aspherical surface
The imaging lens system according to any one of claims 1 to 47, which satisfies the following conditional expression (23).
3 ≦ | ΔZah1 | / | ΔZah2 | ≦ 100 (23)
here,
ΔZah1 = 1000 × N × (ΔZasph1 / h1),
ΔZah2 = 1000 × N × (ΔZasph2 / h2),
h1 is the maximum height of the axially dependent ray on the aspherical surface.
h2 is half the height of the maximum height,
ΔZasph1 is a reference spherical surface and the aspherical surface whose radius is the radius of curvature of the near axis of the aspherical surface and whose surface apex is the surface apex of the aspherical surface, which is measured in a direction horizontal to the optical axis at the maximum height. difference,
ΔZasph2 is the difference between the reference spherical surface and the aspherical surface measured in the direction horizontal to the optical axis at a height of half the maximum height.
N is the refractive index of the lens element having an aspherical surface at line d.
Is. The method according to any one of claims 1 to 48, wherein the front lens group is composed of a lens located closer to an object than a predetermined negative lens satisfying the following conditional expression (c). Imaging lens system.
0.007 ≤ DNx / LTLmin (c)
here,
DNx is the wall thickness of the predetermined negative lens element on the optical axis.
LTLmin is the minimum total length of the imaging lens system.
Is. Optical system and
It has an image pickup surface and has an image pickup element that converts an image formed on the image pickup surface by the optical system into an electric signal.
An imaging device according to any one of claims 1 to 49, wherein the optical system is an imaging lens system.

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