JP2016161648A - Optical system and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an optical system having a compact size, high performance, and a large diameter that are suitable for a compact imaging system; and an imaging apparatus.SOLUTION: An optical system includes, in order from an object side: a first lens group G1; a second lens group G2 having positive refractive power; and a third lens group G3 having positive refractive power. The first lens group G1 and the third lens group G3 are fixed in an optical axis direction, and by moving the second lens group G2 in the optical axis direction, focusing is performed from an infinite distance object to a finite distance object. The second lens group G2 includes at least one lens having positive refractive power. The optical system satisfies predetermined conditions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical system and an imaging apparatus, and more particularly to an optical system suitable for an imaging apparatus using a solid-state imaging device such as a digital still camera or a digital video camera, and an imaging apparatus including the optical system.

  Conventionally, imaging devices using solid-state imaging devices such as digital still cameras and digital video cameras have become widespread. In particular, with the recent enhancement of performance and size of imaging optical systems, the spread of small imaging systems is rapidly progressing.

  Such a small imaging system is required to have higher performance and smaller size, and in particular, there is a great demand for a large aperture in a single focus optical system. For example, Patent Document 1 discloses a large-aperture single-focus optical system having a small Fno having a close-up performance and a smaller than 2.8.

Japanese Patent Laid-Open No. 7-199066

However, in the optical system described in Patent Document 1, correction of chromatic aberration is insufficient, and it cannot be said that high performance is sufficient.
Therefore, an object of the present invention is to provide a small-sized, high-performance, large-aperture optical system and imaging apparatus suitable for a small-sized imaging system.

  In order to solve the above problems, an optical system according to the present invention includes, in order from the object side, a first lens group, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. The first lens group and the third lens group are fixed in the optical axis direction, and the second lens group is moved in the optical axis direction to perform focusing from an object at infinity to a finite distance object, The second lens group includes at least one lens having a positive refractive power and satisfies the following condition.

0.009 <ΔPgF3 (1)
0 <Cr1r / f (2)

However,
ΔPgF3: C7 (partial dispersion ratio: 0.5393, νd: 60.49) and F2 (partial dispersion ratio: 0.5829, νd: 36.30) of the lens having positive refractive power included in the second lens group. ) Deviation from the reference line of the partial dispersion ratio when the straight line passing through the partial dispersion ratio and the coordinates of νd is used as the reference line. Cr1r: radius of curvature of the surface arranged closest to the image plane in the first lens group f: The focal length of the entire optical system.

  Further, an imaging apparatus of the present invention includes the optical system according to the present invention, and an image sensor that converts an optical image formed by the optical system into an electrical signal on the image plane side of the optical system. It is characterized by.

  According to the present invention, it is possible to provide a small-sized, high-performance, large-diameter optical system and an imaging apparatus suitable for a small-sized imaging system.

It is sectional drawing which shows the lens structural example of the optical system of Example 1 of this invention. FIG. 6 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 1 is focused at infinity. It is sectional drawing which shows the lens structural example of the optical system of Example 2 of this invention. FIG. 7 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 2 is focused at infinity. It is sectional drawing which shows the lens structural example of the optical system of Example 3 of this invention. FIG. 6 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 3 is focused at infinity. It is sectional drawing which shows the lens structural example of the optical system of Example 4 of this invention. FIG. 10 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 4 is focused at infinity. It is sectional drawing which shows the lens structural example of the optical system of Example 5 of this invention. FIG. 7 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 5 is focused at infinity. It is sectional drawing which shows the lens structural example of the optical system of Example 6 of this invention. FIG. 10 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 6 is focused at infinity. It is sectional drawing which shows the lens structural example of the optical system of Example 7 of this invention. FIG. 10 is a spherical aberration diagram, astigmatism diagram, and distortion diagram when the optical system of Example 7 is focused at infinity.

  Hereinafter, embodiments of an optical system and an imaging apparatus according to the present invention will be described.

1. Optical system 1-1. Configuration of Optical System An optical system according to the present invention includes, in order from the object side, a first lens group, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, The first lens group and the third lens group are fixed in the optical axis direction, and the second lens group is moved in the optical axis direction to perform focusing from an object at infinity to an object at a finite distance. The group includes at least one lens having positive refractive power, and satisfies the conditions represented by conditional expressions (1) and (2) described later. First, the configuration of the optical system of the optical system according to the present invention will be described.

  The optical system according to the present invention includes, in order from the object side, a first lens group, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. Since the luminous flux can be condensed by the second lens group and the third lens group to be arranged, the diameter can be increased.

  In the present invention, the first lens group and the third lens group are fixed in the optical axis direction, and the second lens group is moved in the optical axis direction, thereby focusing from an infinite object to a finite distance object. . In order to move only the second lens group, which is a part of the first lens group to the third lens group, constituting the optical system, the focusing group can be reduced in size and weight. The overall size and weight including the lens barrel structure can be reduced. Moreover, the load for moving the focusing group can be reduced, and a quick focusing operation can be performed.

  Hereinafter, the configuration of each lens group will be described.

(1) First lens group Other specific lens configurations of the first lens group are not particularly limited as long as conditional expression (1) described later is satisfied. In the present invention, the refractive power of the first lens group may be positive or negative. In the present invention, the effect of the present invention can be obtained regardless of whether the refractive power of the first lens group is positive or negative. In addition, the matter regarding a conditional expression and a more preferable lens configuration will be described later. The same applies to the other lens groups.

(2) Second lens group The second lens group is a specific lens as long as it includes at least one lens having positive refractive power and satisfying conditional expression (2) described later. The configuration is not particularly limited. The second lens group preferably has at least one lens having negative refractive power in addition to the lens having positive refractive power. By disposing at least one lens having a negative refractive power in the second lens group having a positive refractive power, fluctuations in chromatic aberration associated with the movement of the second lens group during focusing can be suppressed. Excellent imaging performance can be obtained regardless of the distance to the subject.

(3) Third Lens Group The specific configuration of the third lens group is not particularly limited as long as it has a positive refractive power, but it has at least one lens having a negative refractive power. Is preferred. By arranging at least one lens having a negative refractive power in the third lens group having a positive refractive power, it is possible to suppress the occurrence of chromatic aberration in the third lens group and realize a good imaging performance. can do.

  In the third lens group, it is preferable that the surface disposed closest to the image surface side has a convex shape on the image surface side. By making the final surface of the optical system convex to the image surface side, the light beam can be condensed on the final surface, and a large aperture can be realized without increasing the lens diameter of the optical system. Can do.

(4) Anti-Vibration Group In the optical system according to the present invention, the whole or a part of any one of the first lens group to the third lens group described above is moved in the direction perpendicular to the optical axis to capture an image. You may use as a vibration proof group which correct | amends the rotational shake etc. resulting from the vibration of time.

1-2. Conditional Expressions Next, conditions that the optical system according to the present invention should satisfy or conditions that are preferably satisfied will be described.
The optical system according to the present invention satisfies the conditions represented by the following conditional expressions (1) and (2).

0.009 <ΔPgF3 (1)
0 <Cr1r / f (2)

However,
ΔPgF3: C7 (partial dispersion ratio: 0.5393, νd: 60.49) and F2 (partial dispersion ratio: 0.5829, νd: 36.30) of lenses having positive refractive power included in the second lens group Deviation from the reference line of the partial dispersion ratio when a straight line passing through the partial dispersion ratio and the coordinate of νd is used as the reference line. Cr1r: radius of curvature of the surface arranged closest to the image plane in the first lens group f: This is the focal length of the entire optical system.

  Here, when the refractive indexes of glass for g-line (435.8 nm), F-line (486.1 nm), d-line (587.6 nm), and C-line (656.3 nm) are Ng, NF, Nd, and NC, respectively. The Abbe number νd and the partial dispersion ratio PgF can be expressed as follows.

νd = (Nd-1) / (NF-NC)
PgF = (Ng-NF) / (NF-NC)

1-2-1. Conditional expression (1)
In the optical system according to the present invention, the second lens group includes at least one lens having a positive refractive power. The conditional expression (1) is an expression that defines the anomalous dispersion of the lens having the positive refractive power. By including a lens having a positive refractive power that satisfies the conditional expression (1) in the second lens group, it is possible to satisfactorily correct axial chromatic aberration and to suppress fluctuations in chromatic aberration during focusing. it can. For this reason, a small and high-performance optical system can be obtained.

  On the other hand, when the conditional expression (1) is not satisfied, that is, when the anomalous dispersion of the lens having the positive refractive power included in the second lens group is reduced, it is difficult to correct the longitudinal chromatic aberration, which is not preferable. . In addition, the variation in chromatic aberration accompanying the change in the position of the second lens group during focusing increases, which is not preferable.

  In obtaining these effects, it is preferable that the lens having the positive refractive power satisfies the conditional expression (1) ′.

  0.015 <ΔPgF3 (1) ′

1-2-2. Conditional expression (2)
The conditional expression (2) is an expression that defines the radius of curvature of the surface arranged closest to the image plane in the first lens group. When the conditional expression (2) is satisfied, in the first lens group, the surface disposed closest to the image plane is convex on the object side, and the field curvature can be corrected well. For this reason, a small and high-performance optical system can be obtained.

  On the other hand, when the conditional expression (2) is not satisfied, the surface arranged closest to the image plane in the first lens group is a flat surface or a concave shape on the object side, and it becomes difficult to correct the curvature of field. It becomes difficult to reduce the size of the optical system.

  In order to obtain these effects, it is preferable that the surface disposed closest to the image plane in the first lens group satisfies the following conditional expression (2) ′, and satisfies the conditional expression (2) ″ Is more preferable, it is more preferable that the conditional expression (2) ′ ″ is satisfied, and it is most preferable that the conditional expression (2) ″ ″ is satisfied.

0.10 <Cr1r / f <3.00 (2) ′
0.20 <Cr1r / f <1.60 (2) ''
0.25 <Cr1r / f <1.20 (2) ′ ″
0.25 <Cr1r / f <0.80 (2) ''''

1-2-3. Conditional expression (3)
In the optical system according to the present invention, it is preferable that in the first lens group, the lens arranged closest to the object side satisfies the following conditions.

1.80 <Nd1 (3)
However,
Nd1: a refractive index at the d-line of the lens arranged closest to the object side in the first lens group.

  Conditional expression (3) is an expression that defines the refractive index at the d-line of the lens (material) arranged closest to the object side in the first lens group. When the conditional expression (3) is satisfied, the refractive index of the lens disposed closest to the object side in the first lens group becomes an appropriate value, and the field curvature can be corrected well. For this reason, it becomes easier to obtain a compact and high-performance optical system.

  On the other hand, if the numerical value of conditional expression (3) is less than or equal to the lower limit value, the refractive index of the lens arranged closest to the object side in the first lens group is small, and it becomes difficult to correct field curvature. Is not preferable.

  In order to obtain these effects, it is preferable that the lens arranged closest to the object side in the first lens group satisfies the following conditional expression (3) ′, and satisfies the conditional expression (3) ″ Is more preferable, it is more preferable that the conditional expression (3) ′ ″ is satisfied, and it is most preferable that the conditional expression (3) ″ ″ is satisfied.

1.83 <Nd1 (3) ′
1.88 <Nd1 (3) ''
1.89 <Nd1 (3) ′ ″
1.92 <Nd1 (3) ''''

1-2-4. Conditional expression (4)
In the optical system according to the present invention, it is preferable that the surface arranged closest to the object side in the first lens group satisfies the following conditions.

0 <Cr1f / f (4)
However,
Cr1f: radius of curvature of the surface arranged closest to the object side in the first lens group f: a focal length of the entire optical system.

  Conditional expression (4) is an expression that defines the radius of curvature of the surface disposed closest to the object side in the first lens group. When the conditional expression (4) is satisfied, in the first lens group, the surface disposed closest to the object side has a convex shape on the object side, and distortion and field curvature can be corrected well with a small number of lenses. Can do. For this reason, it becomes easier to obtain a compact and high-performance optical system.

  On the other hand, when the conditional expression (4) is not satisfied, that is, when the surface arranged closest to the object side in the first lens group is a flat surface or a concave shape on the object side, distortion aberration and This is not preferable because correction of field curvature is difficult.

  In obtaining these effects, it is preferable that the surface disposed closest to the object side in the first lens group satisfies the following conditional expression (4) ′, and satisfies the following conditional expression (4) ″. More preferably, the conditional expression (4) ″ ″ is further satisfied, and it is most preferable that the conditional expression (4) ″ ″ is satisfied.

0.2 <Cr1f / f <20.0 (4) ′
0.3 <Cr1f / f <10.0 (4) ''
0.4 <Cr1f / f <5.0 (4) '''
0.5 <Cr1f / f <3.0 (4) ''''

1-2-5. Conditional expression (5)
In the optical system according to the present invention, it is preferable that the second lens group satisfies the following conditions.

0.4 <f2 / f <3.0 (5)
However,
f2: focal length of the second lens group.

  Conditional expression (5) defines the ratio of the focal length of the second lens group to the focal length of the entire optical system. When the conditional expression (5) is satisfied, the amount of movement of the second lens group at the time of focusing can be reduced, and the optical system in the optical total length direction can be downsized. Further, when the conditional expression (5) is satisfied, the focal length of the second lens unit, that is, the refractive power is within an appropriate range, and the aberration variation accompanying the position change of the second lens unit during focusing can be suppressed. Therefore, it is possible to realize good imaging performance regardless of the object distance with a smaller number of lenses.

  On the other hand, when the numerical value of the conditional expression (5) exceeds the upper limit value, that is, the focal length of the second lens group is large, that is, the refractive power of the second lens group is small, and the second lens group at the time of focusing. The amount of movement increases. For this reason, the optical total length becomes large, which is not preferable. When the numerical value of conditional expression (5) is less than or equal to the lower limit value, the focal length of the second lens group is small, that is, the refractive power of the second lens group is large, and the position of the second lens group changes during focusing. The accompanying aberration variation is large, and the amount of aberration generated is also large. For this reason, in order to obtain good imaging performance, the number of lenses for aberration correction is required, and the total optical length becomes large, which is not preferable.

  In obtaining these effects, the second lens group preferably satisfies the following conditional expression (5) ′, more preferably satisfies the conditional expression (5) ″, and conditional expression (5) ″. It is more preferable to satisfy ', and it is most preferable to satisfy conditional expression (5)' '' '.

0.5 <f2 / f <2.0 (5) ′
0.5 <f2 / f <1.2 (5) ''
0.5 <f2 / f <1.1 (5) '''
0.5 <f2 / f <1.0 (5) ''''

1-2-6. Conditional expression (6)
In the optical system according to the present invention, it is preferable that the surface arranged closest to the object side in the second lens group satisfies the following conditions.

0 <Cr2f / f (6)
However,
Cr2f: the radius of curvature of the surface arranged closest to the object side in the second lens group.

  Conditional expression (6) defines the ratio of the radius of curvature of the surface closest to the object side of the second lens group to the focal length of the entire optical system. When the conditional expression (6) is satisfied, the most object-side surface of the second lens group has a convex shape on the object side, and it is possible to satisfactorily correct spherical aberration and field curvature. For this reason, it becomes easier to obtain a compact and high-performance optical system.

  On the other hand, when the conditional expression (6) is not satisfied, that is, the surface arranged closest to the object side in the second lens group is a flat surface or a concave shape on the object side, so that spherical aberration and field curvature are reduced with a small number of lenses. This is not preferable because it becomes difficult to correct.

  In order to obtain these effects, it is preferable that the surface disposed closest to the object side in the second lens group satisfies the following conditional expression (6) ′, and satisfies the conditional expression (6) ″. It is more preferable that the conditional expression (6) ′ ″ is satisfied, and it is most preferable that the conditional expression (6) ″ ″ is satisfied.

0.10 <Cr2f / f <3.00 (6) ′
0.20 <Cr2f / f <1.00 (6) ''
0.25 <Cr2f / f <0.80 (6) '''
0.25 <Cr2f / f <0.60 (6) ''''

1-2-7. Conditional expression (7)
In the optical system according to the present invention, it is preferable that the surface disposed closest to the image side in the first lens group and the surface disposed closest to the object side in the second lens group satisfy the following conditions.

0.65 <Cr2f / Cr1r <2.00 (7)
However,
Cr1r: radius of curvature of the surface arranged closest to the image side in the first lens group Cr2f: radius of curvature of the surface arranged closest to the object side in the second lens group.

  Conditional expression (7) is an expression that defines the ratio of the radius of curvature of the surface disposed closest to the object side in the second lens group to the radius of curvature of the surface disposed closest to the image plane in the first lens group. . When the conditional expression (7) is satisfied, the spherical aberration, the coma aberration, and the sagittal flare can be corrected more satisfactorily with a small number of lenses. For this reason, it becomes easier to obtain a compact and high-performance optical system.

  On the other hand, when the conditional expression (7) is not satisfied, it becomes difficult to correct spherical aberration, coma aberration, and sagittal flare with a small number of lenses, and aberration correction is necessary to obtain good imaging performance. This is not preferable because the number of lenses increases, leading to an increase in the size of the optical system.

  In order to obtain these effects, it is preferable that the most object side surface of the object side group and the most image side surface of the object side group satisfy the conditional expression (7) ′, and the conditional expression (7) ′. It is more preferable to satisfy '.

0.65 <Cr2f / Cr1r <1.30 (7) ′
0.70 <Cr2f / Cr1r <1.20 (7) ''

1-2-8. Conditional expression (8)
In the optical system according to the present invention, it is preferable that the second lens group includes at least one lens having a negative refractive power, and the lens having the negative refractive power satisfies the following condition.

0.50 <(R1 + R2) / (R1-R2) <5.00 (8)
However,
R1: radius of curvature of object side surface of lens having negative refractive power included in second lens group R2: radius of curvature of image side surface of lens having negative refractive power included in second lens group is there.

  In the optical system according to the present invention, the second lens group preferably includes a lens having a negative refractive power, and the conditional expression (8) is an expression defining the shape of the lens having the negative refractive power. When the conditional expression (8) is satisfied, the second lens group includes a lens having a negative refractive power with a smaller radius of curvature on the image side surface than on the object side surface. In this case, generation of longitudinal chromatic aberration can be suppressed and spherical aberration can be corrected satisfactorily.

  On the other hand, when the numerical value of conditional expression (8) is less than or equal to the lower limit value, the radius of curvature of the surface on the image plane side becomes too small with respect to the object side surface of the lens having negative refractive power. This is not preferable because the amount of axial chromatic aberration is increased. On the other hand, if the numerical value of conditional expression (8) is equal to or greater than the upper limit value, the radius of curvature of the image side surface of the lens having negative refractive power becomes too large, and correction of spherical aberration becomes insufficient, which is not preferable.

  In obtaining these effects, when the second lens group includes a lens having negative refractive power, it is preferable that the lens having negative refractive power satisfies the conditional expression (8) ′. 8) It is more preferable to satisfy ''.

0.65 <(R1 + R2) / (R1-R2) <3.00 (8) ′
0.78 <(R1 + R2) / (R1-R2) <2.95 (8) ''

1-2-9. Conditional expression (9)
In the optical system according to the present invention, it is preferable that the lens having negative refractive power included in the second lens group satisfies the following condition.

νd2n <45.0 (9)
However,
νd2n: an Abbe number at the d-line of a lens having negative refractive power included in the second lens group.

  Conditional expression (9) is an expression that defines the Abbe number in the d-line of the lens having negative refractive power when the second lens group includes a lens having negative refractive power. When the conditional expression (9) is satisfied, chromatic aberration correction can be performed satisfactorily, and it becomes easier to obtain a compact and high-performance optical system.

  On the other hand, when the conditional expression (9) is not satisfied, the chromatic aberration cannot be sufficiently corrected in the second lens group, and the variation of the chromatic aberration due to the change in the position of the second lens group during focusing is large. The amount generated is also increased. For this reason, in order to obtain good imaging performance, the number of lenses for aberration correction is required, and the total optical length becomes large, which is not preferable.

  In obtaining these effects, when the second lens group includes a lens having negative refractive power, it is preferable that the lens having negative refractive power satisfies the conditional expression (9) ′. 9) It is more preferable to satisfy ''.

νd2n <40.0 (9) ′
νd2n <35.0 (9) ″

1-2-10. Conditional expression (10)
In the optical system according to the present invention, it is preferable that the first lens group satisfies the following conditions.

2.6 <| f1 | / f (10)
However,
f1 is the focal length of the first lens group.

  The conditional expression (10) is an expression defining the ratio of the focal length of the first lens group to the focal length of the entire optical system. In the optical system according to the present invention, as described above, the refractive power of the first lens group may be positive or negative, and in any case, the amount of chromatic aberration generated in the first lens group by satisfying conditional expression (10). Can be reduced. Further, by satisfying conditional expression (10), the convergence effect when the first lens group has a positive refractive power can be within an appropriate range, and the position of the second lens group changes during focusing. Also in this case, fluctuations in the diameter of the light beam incident on the second lens group can be suppressed. For this reason, fluctuations in spherical aberration during focusing can be suppressed, and good imaging performance can be realized with a small number of lenses. In addition, even when the first lens group has a negative refractive power, the diverging action can be within an appropriate range, and an increase in the diameter of the light beam incident on the second lens group can be suppressed. For this reason, it is possible to reduce the size and weight of the second lens group, which is the focusing group, and it is possible to reduce the overall size and weight of the optical system including the barrel structure of the optical system. Further, it becomes easy to perform a quick focusing operation.

  On the other hand, when the numerical value of the conditional expression (10) is less than or equal to the lower limit value, that is, when the focal length of the first lens group becomes small, it becomes difficult to reduce the amount of chromatic aberration generated in the first lens group. Further, since the convergence effect is too strong when the first lens group has a positive refractive power, the variation in spherical aberration accompanying the change in the position of the second lens group during focusing is increased. For these reasons, it becomes difficult to obtain a high-performance optical system with a small number of lenses. In addition, when the first lens unit has negative refractive power, if the numerical value of the conditional expression (10) is less than or equal to the lower limit value, the diverging action in the first lens unit becomes too strong, and therefore the second focusing unit is the second focusing unit. It is necessary to increase the outer diameter of the lens group. In this case, it is difficult to reduce the size of the entire optical system including the lens barrel structure, and it is difficult to perform a quick focusing operation.

  In order to obtain these effects, the first lens group preferably satisfies the conditional expression (10) ′, and more preferably satisfies the conditional expression (10) ″.

3.1 <| f1 | / f (10) ′
3.3 <| f1 | / f (10) ''

1-2-11. Conditional expression (11)
In the optical system according to the present invention, the first lens group preferably includes at least one lens having a positive refractive power, and the lens having the positive refractive power preferably satisfies the following conditions.

  0.009 <ΔPgF1 (11)

However,
ΔPgF1: C7 (partial dispersion ratio: 0.5393, νd: 60.49) and F2 (partial dispersion ratio: 0.5829, νd: 36.30) of the lens having positive refractive power included in the first lens group ) And the deviation from the reference line when the straight line passing through the coordinates of νd is taken as the reference line.

  The conditional expression (11) is an expression that defines anomalous dispersion of a lens having a positive refractive power included in the first lens group. When the first lens group includes a lens having a positive refractive power exhibiting anomalous dispersion satisfying conditional expression (11), it is possible to satisfactorily correct various aberrations of longitudinal chromatic aberration.

  On the other hand, when the conditional expression (11) is not satisfied, if the anomalous dispersion of the lens having the positive refractive power included in the first lens group is reduced, it is difficult to correct the axial chromatic aberration.

  In order to obtain these effects, it is preferable that a lens having positive refractive power in the first lens group satisfies the following conditional expression (11) ′.

  0.015 <ΔPgF1 (11) ′

1-2-12. Conditional expression (12)
When the optical system includes a vibration proof group, the vibration proof group preferably satisfies the following conditions. In this case, fluctuations in aberrations during image stabilization can be suppressed, and high imaging performance can be obtained during image stabilization while keeping the optical system small.

0.1 <| (1-βvc) × βr | <0.8 (12)
However,
An anti-vibration group means a lens group that can move in a direction perpendicular to the optical axis,
βvc: lateral magnification of the image stabilizing group when focusing on infinity βr: composite lateral magnification when focusing on all the lenses located on the image plane side from the image stabilizing group when focusing on infinity.

2. Next, an imaging apparatus according to the present invention will be described. An imaging apparatus according to the present invention includes the optical system according to the present invention, and an imaging element that is provided on the image plane side of the optical system and converts an optical image formed by the optical system into an electrical signal. It is characterized by that. Here, there is no limitation in particular in an image pick-up element etc., Solid-state image pick-up elements, such as a CCD sensor and a CMOS sensor, etc. can be used. The imaging device according to the present invention is suitable for an imaging device using these solid-state imaging devices such as a digital camera and a video camera. Further, the imaging device may be a lens-fixed imaging device in which a lens is fixed to a housing, or may be a lens-exchangeable imaging device such as a single-lens reflex camera or a mirrorless single-lens camera. Of course.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples. The optical system of each example given below is an imaging optical system used for an imaging device (optical device) such as a digital camera, a video camera, or a silver salt film camera. In each lens cross-sectional view, the left side is the object side and the right side is the image plane side in the drawing.

(1) Configuration of Optical System FIG. 1 is a lens cross-sectional view showing the lens configuration of the optical system of Example 1 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1, in order from the object side, includes a lens L1 having a positive refractive power, a cemented lens in which a lens L2 having a positive refractive power and a lens L3 having a negative refractive power are cemented, and a concave surface on the image side. And a lens L4 having negative refractive power directed to

  The second lens group G2 includes, in order from the object side, a lens L5 having a positive refractive power with a convex surface directed toward the object side, a lens L6 having a concave surface with a strong curvature on the image side and a negative refractive power, and a positive It is comprised from the cemented lens which joined the lens L7 which has refractive power.

  The third lens group G3 includes, in order from the object side, a lens L8 having a negative refractive power, an aperture stop S, a lens L9 having a positive refractive power, a lens L10 having a negative refractive power, and an object side. The lens includes a cemented lens obtained by cementing a lens L11 having a negative refractive power with a concave surface and a lens L12 having a positive refractive power, and a lens L13 having a positive refractive power with a convex surface facing the image side.

  In the optical system of Example 1, when focusing from an object at infinity to an object at a short distance, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, the image blur on the image plane IMG is corrected by moving the lens L9 in the third lens group G3 in the direction perpendicular to the optical axis as a vibration-proof group. .

  In FIG. 1, “S” shown in the third lens group G3 is an aperture stop. “CG” shown on the image plane side of the third lens group G3 indicates a low-pass filter, a cover glass, or the like. Further, “IMG” shown on the image plane side of “CG” is an image plane, and specifically indicates an imaging plane of a solid-state imaging device such as a CCD or a CMOS sensor, or a film plane of a silver salt film. Since these symbols and the like are the same in the lens cross-sectional views shown in the following examples, the description thereof will be omitted below.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 1 shows lens data of the optical system. In Table 1 (1-1), “Surface No.” is the order of lens surfaces (surface number) counted from the object side, “r” is the radius of curvature of the lens surface, and “d” is on the optical axis of the lens surface. The interval, “Nd”, designates the refractive index for the d-line (wavelength λ = 587.6 nm), and “νd” designates the Abbe number for the d-line. ΔPgf is a straight line that passes through the partial dispersion ratio of the lens C7 (partial dispersion ratio: 0.5393, νd: 60.49) and F2 (partial dispersion ratio: 0.5829, νd: 36.30) and the coordinates of νd. Is a deviation of the partial dispersion ratio from the reference line, and corresponds to one of the above-described ΔPgF1 to ΔPgF3. Table 1 (1-2) is a variable interval on the optical axis shown in Table 1 (1-1). The unit of length in each table is “mm”, and the unit of angle of view is “°”. Since these items are the same in the following embodiments, the description thereof will be omitted below. Table 8 shows numerical values of the conditional expressions (1) to (12).

  FIG. 2 shows longitudinal aberration diagrams when the optical system is focused on infinity. The longitudinal aberration diagram shows spherical aberration, astigmatism, and distortion aberration in order from the left toward the drawing. In the graph showing spherical aberration, the vertical axis is the ratio to the open F value, the horizontal axis is defocused, the solid line is the d line (wavelength λ = 587.6 nm), the broken line is the C line (wavelength λ = 656.3 nm), one point The chain line represents spherical aberration at the g-line (wavelength λ = 435.8 nm). In the diagram showing astigmatism, the vertical axis represents the image height, the horizontal axis defocused, the solid line represents the astigmatism on the sagittal surface, and the broken line represents the meridional surface. In the diagram showing distortion aberration, the vertical axis represents image height and the horizontal axis represents%, and represents distortion aberration. Since the matters relating to these longitudinal aberration diagrams are the same in the respective longitudinal aberration diagrams shown in the following examples, description thereof will be omitted below.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 84.364
Fno = 1.837
ω = 14.368

(1) Configuration of Optical System FIG. 3 is a lens cross-sectional view showing the lens configuration of the optical system of Example 2 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1 includes, in order from the object side, a cemented lens in which a lens L1 having a positive refractive power, a lens L2 having a positive refractive power and a lens L3 having a negative refractive power are cemented, and an image side. And a lens L4 having a negative refractive power facing the concave surface.

  The second lens group G2 includes, in order from the object side, a lens L5 having a positive refractive power with a convex surface directed toward the object side, a lens L6 having a concave surface with a strong curvature on the image side and a negative refractive power, and a positive It is comprised from the cemented lens which joined the lens L7 which has refractive power.

  The third lens group G3 includes, in order from the object side, a lens L8 having a negative refractive power, an aperture stop S, a lens L9 having a positive refractive power, a lens L10 having a negative refractive power, and an object side. The lens includes a cemented lens obtained by cementing a lens L11 having a negative refractive power with a concave surface and a lens L12 having a positive refractive power, and a lens L13 having a positive refractive power with a convex surface facing the image side.

  In the optical system of Example 2, when focusing from an object at infinity to an object at a short distance, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, the image blur on the image plane IMG is corrected by moving the lens L10 in the third lens group G3 in the direction perpendicular to the optical axis as a vibration-proof group. .

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 2 (2-1) is lens data of the optical system, and Table 2 (2-2) is a variable interval on the optical axis shown in Table 2 (2-1). Table 8 shows numerical values of the conditional expressions (1) to (12). FIG. 4 is a longitudinal aberration diagram of the optical system at the time of focusing on infinity.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 85.383
Fno = 1.835
ω = 14.313

(1) Configuration of Optical System FIG. 5 is a lens cross-sectional view showing the lens configuration of the optical system of Example 3 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1, in order from the object side, includes a lens L1 having a positive refractive power, a cemented lens in which a lens L2 having a positive refractive power and a lens L3 having a negative refractive power are cemented, and a concave surface on the image side. And a lens L4 having negative refractive power directed to

  The second lens group G2 includes, in order from the object side, a lens L5 having a positive refractive power with a convex surface directed toward the object side, a lens L6 having a concave surface with a strong curvature on the image side and a negative refractive power, and a positive It is comprised from the cemented lens which joined the lens L7 which has refractive power.

  The third lens group G3 includes, in order from the object side, a lens L8 having a negative refractive power, an aperture stop S, a lens L9 having a positive refractive power, a lens L10 having a negative refractive power, and an object side. The lens includes a cemented lens obtained by cementing a lens L11 having a negative refractive power with a concave surface and a lens L12 having a positive refractive power, and a lens L13 having a positive refractive power with a convex surface facing the image side.

  In the optical system of the third embodiment, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction at the time of focusing from an object at infinity to an object at a short distance. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, the image blur on the image plane IMG is corrected by moving the lens L9 in the third lens group G3 in the direction perpendicular to the optical axis as a vibration-proof group. .

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 3 (3-1) is lens data of the optical system, and Table 3 (3-2) is a variable interval on the optical axis shown in Table 3 (3-1). Table 8 shows numerical values of the conditional expressions (1) to (12). FIG. 6 is a longitudinal aberration diagram when the optical system is focused on infinity.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 85.959
Fno = 1.838
ω = 14.157

(1) Configuration of Optical System FIG. 7 is a lens cross-sectional view showing the lens configuration of the optical system of Example 4 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1, in order from the object side, includes a lens L1 having a positive refractive power, a cemented lens in which a lens L2 having a positive refractive power and a lens L3 having a negative refractive power are cemented, and a concave surface on the image side. And a lens L4 having negative refractive power directed to

  The second lens group G2 includes, in order from the object side, a lens L5 having a positive refractive power with a convex surface directed toward the object side, a lens L6 having a concave surface with a strong curvature on the image side and a negative refractive power, and a positive It is comprised from the cemented lens which joined the lens L7 which has refractive power.

  The third lens group G3 includes, in order from the object side, a lens L8 having a negative refractive power, an aperture stop, a lens L9 having a positive refractive power, a lens L10 having a negative refractive power, and a concave surface on the object side. A cemented lens obtained by cementing a lens L11 having a negative refractive power and a lens L12 having a positive refractive power, and a lens L13 having a positive refractive power with a convex surface facing the image side.

  In the optical system of the fourth embodiment, when focusing from an object at infinity to an object at a short distance, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, the image blur on the image plane IMG is corrected by moving the lens L9 in the third lens group G3 in the direction perpendicular to the optical axis as a vibration-proof group. .

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 4 (4-1) is lens data of the optical system, and Table 4 (4-2) is a variable interval on the optical axis shown in Table 4 (4-1). Table 8 shows numerical values of the conditional expressions (1) to (12). Further, FIG. 8 is a longitudinal aberration diagram of the optical system when focused on infinity.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 86.875
Fno = 1.836
ω = 13.958

(1) Configuration of Optical System FIG. 9 is a lens cross-sectional view showing the lens configuration of the optical system of Example 5 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1 includes, in order from the object side, a lens L1 having a positive refractive power, a lens L2 having a positive refractive power, and a lens L3 having a negative refractive power with a concave surface facing the image side. Is done.

  The second lens group G2 includes, in order from the object side, a lens L4 having a positive refractive power with a convex surface facing the object side, a lens L5 having a positive refractive power with a convex surface facing the object side, and a strong curvature on the image side. A cemented lens in which a lens L6 having a negative refractive power and a negative refractive power are cemented, an aperture stop S, a biconcave lens L7 having a negative refractive power, and a lens L8 having a positive refractive power; And a lens L9 having a positive refractive power.

  The third lens group G3 includes, in order from the object side, a lens L10 having a negative refractive power and a lens L11 having a positive refractive power.

  In the optical system of the fifth embodiment, when focusing from an object at infinity to an object at a short distance, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, image blur on the image plane IMG is corrected by moving the second lens group G2 as a vibration-proof group in a direction perpendicular to the optical axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 5 (5-1) is lens data of the optical system, and Table 5 (5-2) is a variable interval on the optical axis shown in Table 5 (5-1). Table 8 shows numerical values of the conditional expressions (1) to (12). Further, FIG. 10 is a longitudinal aberration diagram of the optical system when focused on infinity.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 112.109
Fno = 1.445
ω = 10.759

(1) Configuration of Optical System FIG. 11 is a lens cross-sectional view showing the lens configuration of the optical system of Example 6 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1, in order from the object side, includes a lens L1 having a positive refractive power, a cemented lens in which a lens L2 having a positive refractive power and a lens L3 having a negative refractive power are cemented, and a concave surface on the image side. And a lens L4 having negative refractive power directed to

  The second lens group G2 includes, in order from the object side, a lens L5 having a positive refractive power with a convex surface directed toward the object side, a lens L6 having a concave surface with a strong curvature on the image side and a negative refractive power, and a positive It is comprised from the cemented lens which joined the lens L7 which has refractive power.

  The third lens group G3 includes, in order from the object side, a lens L8 having a negative refractive power, an aperture stop S, a lens L9 having a positive refractive power, a lens L10 having a negative refractive power, and an object side. The lens includes a cemented lens obtained by cementing a lens L11 having a negative refractive power with a concave surface and a lens L12 having a positive refractive power, and a lens L13 having a positive refractive power with a convex surface facing the image side.

  In the optical system of Example 6, when focusing from an object at infinity to an object at a short distance, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, the image blur on the image plane IMG is corrected by moving the lens L9 in the third lens group G3 in the direction perpendicular to the optical axis as a vibration-proof group. .

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 6 (6-1) is lens data of the optical system, and Table 6 (6-2) is a variable interval on the optical axis shown in Table 6 (6-1). Table 8 shows numerical values of the conditional expressions (1) to (12). Further, FIG. 12 is a longitudinal aberration diagram of the optical system when focused on infinity.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 82.600
Fno = 1.831
ω = 14.726

(1) Configuration of Optical System FIG. 13 is a lens cross-sectional view showing the lens configuration of the optical system of Example 7 according to the present invention when focusing on infinity. The optical system includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Has been.

  The first lens group G1, in order from the object side, includes a lens L1 having a positive refractive power, a cemented lens in which a lens L2 having a positive refractive power and a lens L3 having a negative refractive power are cemented, and a concave surface on the image side. And a lens L4 having negative refractive power directed to

  The second lens group G2 includes, in order from the object side, a lens L5 having a positive refractive power with a convex surface directed toward the object side, a lens L6 having a concave surface with a strong curvature on the image side and a negative refractive power, and a positive It is comprised from the cemented lens which joined the lens L7 which has refractive power.

  The third lens group G3 includes, in order from the object side, a lens L8 having a negative refractive power, a lens L9 having a positive refractive power, an aperture stop S, a lens L10 having a negative refractive power, and an object side. The lens includes a cemented lens obtained by cementing a lens L11 having a negative refractive power with a concave surface and a lens L12 having a positive refractive power, and a lens L13 having a positive refractive power with a convex surface facing the image side.

  In the optical system of Example 7, when focusing from an object at infinity to an object at a short distance, the second lens group G2 with the first lens group G1 and the third lens group G3 fixed in the optical axis direction. Moves to the image plane IMG side along the optical axis. Further, when vibration occurs during imaging due to camera shake or the like, the image blur on the image plane IMG is corrected by moving the lens L10 in the third lens group G3 in the direction perpendicular to the optical axis as a vibration-proof group. .

(2) Numerical Examples Next, numerical examples to which specific numerical values of the optical system are applied will be described. Table 7 (7-1) is lens data of the optical system, and Table 7 (7-2) is a variable interval on the optical axis shown in Table 7 (7-1). Table 8 shows numerical values of the conditional expressions (1) to (12). Further, FIG. 14 is a longitudinal aberration diagram of the optical system when focused on infinity.

  The focal length (f), F value (Fno), and half angle of view (ω) of the optical system are as follows.

f = 87.499
Fno = 1.831
ω = 13.844

  The optical system according to the present invention is suitable for a small-sized imaging system, and can provide a small-sized, high-performance, large-diameter optical system and imaging apparatus.

Claims (12)

In order from the object side, the first lens group, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
The first lens group and the third lens group are fixed in the optical axis direction, and the second lens group is moved in the optical axis direction to perform focusing from an infinite object to a finite distance object,
The second lens group includes at least one lens having a positive refractive power,
An optical system characterized by satisfying the following conditions.
0.009 <ΔPgF3 (1)
0 <Cr1r / f (2)
However,
ΔPgF3: C7 (partial dispersion ratio: 0.5393, νd: 60.49) and F2 (partial dispersion ratio: 0.5829, νd: 36.30) of the lens having positive refractive power included in the second lens group. ) Deviation from the reference line of the partial dispersion ratio when the straight line passing through the partial dispersion ratio and the coordinates of νd is used as the reference line. Cr1r: radius of curvature of the surface arranged closest to the image plane in the first lens group f: The focal length of the entire optical system. 2. The optical system according to claim 1, wherein a lens disposed closest to the object side in the first lens group satisfies the following condition.
1.80 <Nd1 (3)
However,
Nd1: a refractive index at the d-line of the lens disposed closest to the object side in the first lens group. The optical system according to claim 1, wherein a surface disposed closest to the object side in the first lens group satisfies the following condition.
0 <Cr1f / f (4)
However,
Cr1f: the radius of curvature of the surface arranged closest to the object side in the first lens group. The optical system according to any one of claims 1 to 3, wherein the second lens group satisfies the following condition.
0.4 <f2 / f <3.0 (5)
However,
f2: a focal length of the second lens group. The optical system according to any one of claims 1 to 4, wherein a surface disposed closest to the object side in the second lens group satisfies the following condition.
0 <Cr2f / f (6)
However,
Cr2f: the radius of curvature of the surface arranged closest to the object side in the second lens group. The surface arranged on the most image side in the first lens group and the surface arranged on the most object side in the second lens group satisfy the following conditions. The optical system described in 1.
0.65 <Cr2f / Cr1r <2.00 (7)
However,
Cr1r: radius of curvature of the surface arranged closest to the image side in the first lens group Cr2f: radius of curvature of the surface arranged closest to the object side in the second lens group. The second lens group includes at least one lens having negative refractive power,
The optical system according to claim 1, wherein the lens having the negative refractive power satisfies the following condition.
0.5 <(R1 + R2) / (R1-R2) <5.00 (8)
However,
R1: radius of curvature of the object side surface of the lens having negative refractive power included in the second lens group R2: radius of curvature of the image side surface of the lens having negative refractive power included in the second lens group It is. The optical system according to claim 7, wherein a lens having negative refractive power included in the second lens group satisfies the following condition.
νd2n <45.0 (9)
However,
νd2n: an Abbe number at the d-line of the lens having negative refractive power.   The optical system according to any one of claims 1 to 8, wherein the third lens group includes at least one lens having a negative refractive power. The optical system according to claim 1, wherein the first lens group satisfies the following condition.
2.6 <| f1 | / f (10)
However,
f1 is a focal length of the first lens group. The first lens group includes at least one lens having a positive refractive power,
The optical system according to any one of claims 1 to 10, wherein the lens having the positive refractive power satisfies the following condition.
0.009 <ΔPgF1 (11)
However,
ΔPgF1: C7 (partial dispersion ratio: 0.5393, νd: 60.49) and F2 (partial dispersion ratio: 0.5829, νd: 36.) of the lens having positive refractive power included in the first lens group. 30) The deviation of the partial dispersion ratio from the reference line when a straight line passing through the partial dispersion ratio and the coordinate of νd is used as the reference line.   An optical system according to any one of claims 1 to 11, and an image pickup device that is provided on an image side of the optical system and converts an optical image formed by the optical system into an electrical signal. An image pickup apparatus comprising:

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