JP2016161643A - Imaging lens, optical apparatus having the imaging lens, and method for manufacturing the imaging lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens having sufficient optical performance.SOLUTION: An imaging lens comprises, in order from an object side along an optical axis: a front lens group GF composed of a plurality of lenses; an aperture diaphragm S; and a rear lens group GR composed of a plurality of lenses. The rear lens group includes, in order from the object side along the optical axis: a rear a portion lens group GRa having positive refractive power; and a rear b portion lens group GRb arranged to be spaced from the rear a portion lens group GRa by an air gap. The rear b portion lens group GRb is composed of three or less lenses. At least a portion of the rear a portion lens group GRa moves along the optical axis as a focusing lens group when focusing from an object at infinity to an object at a short distance. The imaging lens satisfies predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photographing lens suitable for a photographic camera, an electronic still camera, a video camera, and the like, an optical apparatus including the photographing lens, and a method for manufacturing the photographing lens.

  Conventionally, a small photographic lens suitable for a photographic camera or a video camera has been proposed (see, for example, Patent Document 1).

JP 2011-081064 A

  However, the conventional small photographic lens has a problem that the optical performance is not sufficient.

In order to solve the above problems, the present invention provides a front lens group composed of a plurality of lenses, an aperture stop, and a rear lens group composed of a plurality of lenses in order from the object side along the optical axis. The rear lens group is arranged in order from the object side along the optical axis, with a rear a partial lens group having a positive refractive power and an air gap from the rear a partial lens group. The rear a partial lens group is composed of three or less lenses, and when focusing from an infinite object to a short distance object, the rear a partial lens group A photographing lens that moves along the optical axis as a focusing lens group and satisfies the following conditional expression is provided.
0.10 <TLf / TL <0.40
3.0 <h1 / hf
However,
TLf: distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group TL: distance on the optical axis from the lens surface closest to the object side to the image plane in the front lens group h1: the above The height from the optical axis of the parallel luminous flux from the object at infinity that determines the open F value that passes through the lens surface closest to the object side of the front lens group hf: the open distance that passes through the lens surface closest to the object side of the focusing lens group Height from the optical axis of the parallel light beam from an infinite object that determines the F value

  The present invention also provides an optical apparatus provided with the above photographing lens.

Further, the present invention provides a photographing lens composed of a front lens group composed of a plurality of lenses, an aperture stop, and a rear lens group composed of a plurality of lenses in order from the object side along the optical axis. The rear lens group is separated from the rear a partial lens group having positive refractive power in order from the object side along the optical axis, and the rear a partial lens group with an air gap. The rear a partial lens group, and the rear a partial lens group is composed of three or less lenses. When focusing from an infinite object to a short distance object, the rear a part Provided is a photographic lens manufacturing method in which a lens group is configured to move along an optical axis as a focusing lens group and is configured to satisfy the following conditional expression.
0.10 <TLf / TL <0.40
3.0 <h1 / hf
However,
TLf: distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group TL: distance on the optical axis from the lens surface closest to the object side to the image plane in the front lens group h1: the above The height from the optical axis of the parallel luminous flux from the object at infinity that determines the open F value that passes through the lens surface closest to the object side of the front lens group hf: the open distance that passes through the lens surface closest to the object side of the focusing lens group Height from the optical axis of the parallel light beam from an infinite object that determines the F value

It is sectional drawing which shows the structure of the imaging lens which concerns on 1st Example. FIG. 4 is a diagram illustrating various aberrations of the photographing lens according to the first example, in which FIG. It is sectional drawing which shows the structure of the photographic lens which concerns on 2nd Example. FIG. 6 is a diagram illustrating various aberrations of the taking lens according to Example 2, wherein (a) shows when an object at infinity is in focus and (b) shows when an object at short distance is in focus. It is sectional drawing which shows the structure of the photographic lens which concerns on 3rd Example. FIG. 6 is a diagram illustrating various aberrations of the photographing lens according to Example 3, wherein (a) shows when an object at infinity is in focus and (b) shows when an object at short distance is in focus. It is sectional drawing of the optical apparatus provided with the imaging lens which concerns on embodiment. It is a figure which shows the outline of the manufacturing method of the imaging lens which concerns on embodiment.

  Hereinafter, a photographic lens, an optical apparatus, and a method for manufacturing the photographic lens according to the embodiment will be described. First, the photographic lens according to the embodiment will be described.

The photographing lens according to the present embodiment includes, in order from the object side along the optical axis, a front lens group including a plurality of lenses, an aperture stop, and a rear lens group including a plurality of lenses. The rear lens group is arranged in order from the object side along the optical axis, a rear a partial lens group having a positive refractive power, and a rear side arranged at an air interval from the rear a partial lens group. b partial lens group, and the rear a partial lens group is composed of three or less lenses. When focusing from an infinite object to a short distance object, the rear a partial lens group is a focusing lens. Move along the optical axis as a group.
With this configuration, the focusing lens group can be driven by a small motor unit while achieving high optical performance.

In addition, the photographic lens according to the present embodiment satisfies the following conditional expression (1) under such a configuration.
(1) 0.10 <TLf / TL <0.40
However,
TLf: distance on the optical axis from the lens surface closest to the object side of the focusing lens group to the image plane TL: distance on the optical axis from the lens surface closest to the object side of the front lens group to the image plane

  Conditional expression (1) is the distance on the optical axis from the lens surface closest to the object side of the focusing lens group to the image plane, and the distance on the optical axis from the lens surface closest to the object side of the front lens group to the image plane. That is, it is a conditional expression for defining an appropriate range of the ratio with the total length of the entire photographing lens system. By satisfying conditional expression (1), astigmatism can be corrected satisfactorily.

  If the corresponding value of conditional expression (1) exceeds the upper limit value, the distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group becomes too large, and the focusing lens group is downsized. If the refractive power of the rear b partial lens unit is increased, correction of astigmatism becomes difficult. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 0.35.

  On the other hand, when the corresponding value of conditional expression (1) is below the lower limit, the distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group becomes too small, and astigmatism at the time of focusing It becomes difficult to correct. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.15.

In addition, the photographic lens according to the present embodiment satisfies the following conditional expression (2) under such a configuration.
(2) 3.0 <h1 / hf
However,
h1: Height from the optical axis of the parallel luminous flux from the infinite object that determines the open F value passing through the lens surface closest to the object side of the front lens group hf: The lens surface closest to the object side of the focusing lens group The height from the optical axis of the parallel light beam from the object at infinity that determines the open F value that passes through.

  Conditional expression (2) indicates that the height from the optical axis of the parallel light beam from the infinite object that determines the open F value passing through the lens surface closest to the object side of the front lens group and the lens closest to the object side of the focusing lens group. It is a conditional expression for prescribing an appropriate range of the ratio of the parallel light flux from the object at infinity that determines the open F value through the surface to the height from the optical axis. When the corresponding value of the conditional expression (2) is below the lower limit value, the refractive power of the focusing lens group becomes relatively weak, and as a result, the spherical aberration generated in the focusing lens group alone becomes insufficiently corrected. It is not preferable. Further, since the refractive power of the lens closest to the object side in the front lens group becomes relatively strong, spherical aberration and coma aberration are greatly generated in the front lens group, which is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 3.1.

  In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 9.0. When the corresponding value of conditional expression (2) is less than 9.0, spherical aberration can be corrected well and high optical performance can be realized.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (3).
(3) 0.01 <| ff / fR |
However,
ff: focal length of the focusing lens group fR: composite focal length in the infinite object focusing state of the entire lens located on the image side of the focusing lens group

  Conditional expression (3) defines an appropriate range of the ratio between the focal length of the focusing lens group and the combined focal length in the infinite object focusing state of the entire lens located on the image side of the focusing lens group. This is a conditional expression. If the corresponding value of conditional expression (3) is below the lower limit value, the combined focal length in the infinite object focusing state of the entire lens located on the image side relative to the focusing lens group becomes too large, and spherical aberration at the time of focusing and Astigmatism correction becomes difficult. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.05.

  In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 1.00. When the corresponding value of conditional expression (3) is less than 1.00, spherical aberration and astigmatism can be corrected well, and high optical performance can be realized.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (4).
(4) | ff / fF + ff / fA | <0.69
However,
ff: focal length of the focusing lens group fF: combined focal length in the infinite object focusing state of the entire lens located on the object side of the focusing lens group fA: from the focusing lens group and the focusing lens group Combined focal length in the infinite object focusing state with the whole lens on the object side

  Conditional expression (4) is the ratio of the focal length of the focusing lens group to the combined focal length in the infinite object focusing state of the entire lens on the object side of the focusing lens group, and the focal point of the focusing lens group. This is a conditional expression that defines the appropriate range of the sum of the distance and the ratio of the combined focal length in the infinite object focusing state between the focusing lens group and the entire lens on the object side of the focusing lens group. is there. When the corresponding value of the conditional expression (4) exceeds the upper limit value, the refractive power of the focusing lens group becomes relatively weak, and as a result, the spherical aberration generated in the focusing lens group alone becomes insufficiently corrected. It is not preferable. Further, since the refractive power of the lens closest to the object side in the front lens group becomes relatively strong, spherical aberration and coma aberration are greatly generated in the front lens group, which is not preferable. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.68.

  In order to further secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.10. When the corresponding value of conditional expression (4) exceeds 0.10, spherical aberration can be corrected well and high optical performance can be realized.

In the photographic lens according to the present embodiment, it is desirable that the front lens group has at least one lens that satisfies the following conditional expression (5).
(5) νdp <35
However,
νdp: Abbe number with respect to d-line of the glass material of the at least one lens in the front lens group

  Conditional expression (5) is a conditional expression for defining the Abbe number with respect to the d-line of the glass material of at least one lens in the front lens group. If the corresponding value of conditional expression (5) exceeds the upper limit value, it will be difficult to correct axial chromatic aberration. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 33. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 32.

  In the photographic lens according to the present embodiment, it is preferable that the at least one lens that satisfies the conditional expression (5) has a positive refractive power. With this configuration, it is possible to satisfactorily correct axial chromatic aberration while shortening the overall length of the photographing lens.

In the photographic lens according to the present embodiment, it is desirable that the front lens group includes at least one lens that satisfies the following conditional expression (6).
(6) 80 <νdh
However,
νdh: Abbe number with respect to d-line of the glass material of the at least one lens in the front lens group

  Conditional expression (6) is a conditional expression for defining the Abbe number with respect to the d-line of the glass material of at least one lens in the front lens group. If the corresponding value of conditional expression (6) is less than the lower limit value, it will be difficult to correct axial chromatic aberration. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (6) to 85. In order to further secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (6) to 90. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit of conditional expression (6) to 95.

  In the photographing lens according to the present embodiment, it is preferable that the plurality of lenses constituting the front lens group is 10 or less. With this configuration, it is possible to reduce the weight of the photographing lens while correcting the curvature of field well.

  In the photographing lens according to the present embodiment, it is preferable that the plurality of lenses constituting the front lens group is six or more. With this configuration, it is possible to satisfactorily correct axial chromatic aberration while shortening the overall length of the photographing lens.

  In addition, the photographing lens according to the present embodiment can shift an image on the image plane by moving a part of the lens groups in the rear lens group so as to include a component in a direction orthogonal to the optical axis. It is desirable to be possible. With this configuration, it is possible to correct the deviation of the optical axis when the camera shakes due to camera shake or the like, and to improve the imaging performance.

In addition, it is desirable that the photographing lens according to the present embodiment satisfies the following conditional expression (7).
(7) TL / f <1.2
However,
TL: Distance on the optical axis from the lens surface closest to the object side of the front lens group to the image plane f: Focal length of the entire photographing lens system

  Conditional expression (7) is a conditional expression for defining the ratio of the distance on the optical axis from the lens surface closest to the object side of the front lens group to the image plane with respect to the focal length of the entire photographing lens system. If the corresponding value of conditional expression (7) exceeds the upper limit value, the amount of peripheral light will decrease, and if the entrance pupil position is moved forward to correct this, it will be difficult to correct distortion. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (7) to 1.1.

  In order to further secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (7) to 0.6. When the corresponding value of conditional expression (7) exceeds 0.6, distortion can be corrected well and high optical performance can be realized.

  The optical apparatus according to the embodiment includes the photographic lens having the above-described configuration. Thereby, an optical apparatus having high optical performance can be realized.

In addition, the method for manufacturing a photographic lens according to the embodiment includes, in order from the object side along the optical axis, a front lens group including a plurality of lenses, an aperture stop, and a rear lens group including a plurality of lenses. And a rear a-group lens group having a positive refractive power in order from the object side along the optical axis, and the rear a-section. Consists of a lens group and a rear b partial lens group arranged at an air interval, and the rear a partial lens group is composed of three or less lenses to focus from an object at infinity to a near object. At this time, the rear a partial lens unit is configured to move along the optical axis as a focusing lens unit, and is configured to satisfy the following conditional expressions (1) and (2). 0.10 <TLf / TL <0.40
(2) 3.0 <h1 / hf
However,
TLf: distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group TL: distance on the optical axis from the lens surface closest to the object side to the image plane in the front lens group h1: the above The height from the optical axis of the parallel luminous flux from the object at infinity that determines the open F value that passes through the lens surface closest to the object side of the front lens group hf: the open distance that passes through the lens surface closest to the object side of the focusing lens group Height from the optical axis of the parallel light beam from an infinite object that determines the F value

  By such a method for manufacturing a photographic lens, a photographic lens having high optical performance can be manufactured.

(Numerical example)
Hereinafter, photographing lenses according to numerical examples of the present embodiment will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the taking lens according to the first embodiment.
As shown in FIG. 1, the photographing lens according to the present embodiment includes a front lens group GF, an aperture stop S, and a rear lens group GR in order from the object side along the optical axis.

  The front lens group GF includes, in order from the object side along the optical axis, a protective glass HG having a very weak refractive power, a biconvex lens L11, a biconvex lens L12, a biconcave lens L13, and a negative meniscus with a convex surface facing the object side. The lens includes a cemented lens of a lens L14 and a positive meniscus lens L15 having a convex surface facing the object side, a positive meniscus lens L16 having a concave surface facing the object side, and a biconcave lens L17.

The rear lens group GR is arranged in order from the object side along the optical axis, the rear a partial lens group GRa having a positive refractive power, and the rear side disposed with an air gap from the rear a partial lens group GRa. b partial lens group GRb.
The rear a partial lens group GRa includes, in order from the object side along the optical axis, a biconvex lens L21 and a negative meniscus lens L22 having a concave surface facing the object side.
The rear group b partial lens group GRb includes, in order from the object side along the optical axis, a cemented lens of a positive meniscus lens L23 having a concave surface facing the object side and a biconcave lens L24, and a negative meniscus lens having a convex surface facing the object side. L25, a positive meniscus lens L26 having a convex surface facing the object side, and a cemented lens of a biconvex lens L27 and a biconcave lens L28.

  A filter FL such as a low-pass filter is disposed on the image plane I side of the rear lens group GR.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  With the configuration described above, the photographing lens according to the present embodiment moves the rear a partial lens group GRa to the object side as the focusing lens group Gf, thereby focusing from an infinite object to a close object. Done. Further, in the rear-group b partial lens group GRb, a cemented lens of a positive meniscus lens L23 having a concave surface facing the object side and a biconcave lens L24, and a negative meniscus lens L25 having a convex surface facing the object side are anti-vibration lens group. As a result, the image on the image plane I is shifted by moving it so as to include a component in a direction orthogonal to the optical axis, and image plane correction when image blurring occurs, that is, image stabilization is performed.

Table 1 below lists values of specifications of the photographing lens according to the present example.
In [Overall Specifications], f is the focal length, FNO is the F number, 2ω is the angle of view (unit is “°”), Y is the maximum image height, TL is the total length of the photographic lens (the number at the time of focusing on an object at infinity). BF represents the back focus (distance on the optical axis between the lens surface closest to the image side and the image plane I). The air conversion TL is a value obtained by measuring the distance on the optical axis from the first surface to the image plane I when focusing on an object at infinity with the optical block such as a filter removed from the optical path, The air conversion BF is a value when the distance on the optical axis from the most image side lens surface in the rear lens group GR to the image plane I is measured in a state where an optical block such as a filter is removed from the optical path. .

  In [Surface Data], the surface number is the order of the optical surfaces counted from the object side, r is the radius of curvature, d is the surface spacing (the space between the nth surface (n is an integer) and the (n + 1) th surface), and nd is The refractive index for d-line (wavelength 587.6 nm) and νd indicate the Abbe number for d-line (wavelength 587.6 nm), respectively. Further, the object plane indicates the object plane, the variable indicates the variable plane spacing, the stop S indicates the aperture stop S, and the image plane indicates the image plane I. The radius of curvature r = ∞ indicates a plane. The description of the refractive index of air nd = 1.00000 is omitted.

  In [variable interval data], f indicates a focal length, β indicates a photographing magnification, and di (i is an integer) indicates a surface interval between the i-th surface and the (i + 1) -th surface. D0 indicates the distance from the object to the lens surface closest to the object.

[Lens Group Data] indicates the start surface number and focal length of each lens group.
[Conditional Expression Corresponding Value] indicates the corresponding value of each conditional expression.

Here, “mm” is generally used as the unit of the focal length f, the radius of curvature r, and other lengths described in Table 1. However, the optical system is not limited to this because an equivalent optical performance can be obtained even when proportionally enlarged or proportionally reduced.
In addition, the code | symbol of Table 1 described above shall be similarly used also in the table | surface of each Example mentioned later.

(Table 1) First Example [Overall Specifications]
f 391.996
FNO 2.880
2ω 6.278
Y 21.60
TL 409.999
Air equivalent TL 409.488
BF 82.573
Air conversion BF 82.062

[Surface data]
Surface number r d nd νd
Object ∞
1) 1200.37040 5.000 1.51680 63.88
2) 1199.78970 1.500
3) 242.43420 15.500 1.43385 95.25
4) -1144.78160 45.000
5) 163.08360 19.000 1.43385 95.25
6) -485.25910 4.000
7) -441.97520 6.000 1.61266 44.46
8) 496.10830 85.000
9) 87.30330 5.400 1.79952 42.22
10) 50.29290 15.500 1.49782 82.57
11) 124.76650 38.108
12) -757.69690 4.000 1.84666 23.80
13) -102.21690 0.002
14) -108.46840 2.500 1.75500 52.33
15) 91.99150 4.980

16) ∞ (Variable) (Aperture)

17) 69.30120 8.500 1.49782 82.57
18) -78.17850 0.600
19) -74.91680 1.900 1.60562 43.71
20) -199.64260 (variable)

21) -20650.78400 4.500 1.88300 40.66
22) -100.03010 3.498 1.51860 69.89
23) 48.86300 3.757
24) 497.87240 3.500 1.65160 58.55
25) 59.08000 4.200
26) 75.55570 4.000 1.81600 46.59
27) 221.65890 0.758
28) 73.34850 4.800 1.74400 44.80
29) -160.31130 1.900 1.84666 23.80
30) 333.76060 6.500

31) ∞ 1.500 1.51680 63.88
32) ∞ 74.573
Image plane ∞

[Variable interval data]
Infinity Close-up shooting distance
forβ 391.996 -0.100
d 0 ∞ 3991.000
d16 28.022 18.987
d20 6.000 15.035

[Lens group data]
Group start face f
GF 1 1487.865
GR 17 150.468

[Conditional expression values]
(1) TLf / TL = 0.318
(2) h1 / hf = 3.423
(3) | ff / fR | = 0.158
(4) | ff / fF + ff / fA | = 0.447
(5) νdp = 23.80
(6) νdh = 95.25
(7) TL / f = 1.046

  2A and 2B are graphs showing various aberrations of the photographing lens according to the first example. FIG. 2A shows the time when an object at infinity is focused, and FIG. 2B shows the time when a short-range object is focused.

  In each aberration diagram, FNO represents an F number, NA represents a numerical aperture, and Y represents an image height. In the figure, d indicates an aberration curve at the d-line (wavelength λ = 587.6 nm), g indicates an aberration curve at the g-line (wavelength λ = 435.8 nm), and those not described are d-line The aberration curve at is shown. The spherical aberration diagram shows the F-number or numerical aperture corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum image height, and the coma diagram shows the value of each image height. . In the aberration diagram showing astigmatism, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In addition, in the various aberration diagrams of the following examples, the same reference numerals as those of the present example are used.

As is apparent from each aberration diagram, the photographic lens according to Example 1 has excellent imaging performance with various aberrations corrected well from the infinite object focusing state to the short distance object focusing state. You can see that

(Second embodiment)
FIG. 3 is a cross-sectional view showing the configuration of the taking lens according to the second embodiment.
As shown in FIG. 3, the photographing lens according to the present embodiment is configured by a front lens group GF, an aperture stop S, and a rear lens group GR in order from the object side along the optical axis.

  The front lens group GF includes, in order from the object side along the optical axis, a protective glass HG having a very weak refractive power, a biconvex lens L11, a biconvex lens L12, a biconcave lens L13, and a negative meniscus with a convex surface facing the object side. The lens includes a cemented lens of a lens L14 and a positive meniscus lens L15 having a convex surface facing the object side, and a cemented lens of a positive meniscus lens L16 having a concave surface facing the object side and a biconcave lens L17.

The rear lens group GR is arranged in order from the object side along the optical axis, the rear a partial lens group GRa having a positive refractive power, and the rear side disposed with an air gap from the rear a partial lens group GRa. b partial lens group GRb.
The rear a partial lens group GRa is composed of a cemented lens of a negative meniscus lens L21 having a convex surface facing the object side and a biconvex lens L22 in order from the object side along the optical axis.
The rear group b partial lens group GRb, in order from the object side along the optical axis, a cemented lens of a biconvex lens L23 and a biconcave lens L24, a biconcave lens L25, a biconvex lens L26, and a negative surface with a concave surface facing the object side. It is composed of a meniscus lens L27 and a biconvex lens L28.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  With the configuration described above, the photographing lens according to the present embodiment moves the rear a partial lens group GRa to the object side as the focusing lens group Gf, thereby focusing from an infinite object to a close object. Done. Further, in the rear group b partial lens group GRb, the cemented lens of the biconvex lens L23 and the biconcave lens L24 and the biconcave lens L25 are moved as a vibration-proof lens group so as to include a component in a direction orthogonal to the optical axis. Thus, the image on the image plane I is shifted to correct the image plane when image blur occurs, that is, to perform image stabilization.

  Table 2 below lists values of specifications of the photographing lens according to the present example.

(Table 2) Second embodiment [Overall specifications]
f 489.998
FNO 4.113
2ω 5.008
Y 21.60
TL 426.000
BF 82.990

[Surface data]
Surface number r d nd νd
Object ∞
1) 1200.37020 5.000 1.51680 63.88
2) 1199.78950 1.000
3) 260.38120 13.453 1.43385 95.25
4) -720.75070 76.693
5) 133.22420 14.689 1.43385 95.25
6) -445.53230 2.178
7) -416.78780 5.200 1.61266 44.46
8) 333.43020 68.917
9) 113.80420 3.500 1.69680 55.52
10) 48.12830 11.000 1.49782 82.57
11) 286.33870 24.362
12) -420.50250 3.900 1.92286 20.88
13) -205.04160 2.500 1.71388 55.48
14) 187.83670 23.418

15) ∞ (Variable) (Aperture)

16) 84.89220 1.800 1.76352 24.16
17) 42.15930 7.500 1.71603 40.65
18) -647.56120 (variable)

19) 191.49780 4.500 1.88476 33.10
20) -108.98170 1.800 1.72293 54.96
21) 48.05870 3.300
22) -160.34260 1.800 1.72916 54.61
23) 235.14740 5.423
24) 683.34780 4.500 1.50524 67.37
25) -62.84020 25.575
26) -56.28090 1.800 1.72916 54.61
27) -164.52330 1.500
28) 121.41330 5.000 1.61266 44.46
29) -468.68370 82.990
Image plane ∞

[Variable interval data]
Infinity Close-up shooting distance
forβ 489.998 -0.100
d 0 ∞ 4638.551
d15 17.009 5.109
d18 4.500 16.401

[Lens group data]
Group start face f
GF 1 639.643
GR 16 939.875

[Conditional expression values]
(1) TLf / TL = 0.360
(2) h1 / hf = 3.152
(3) | ff / fR | = 0.975
(4) | ff / fF + ff / fA | = 0.661
(5) νdp = 23.88
(6) νdh = 95.25
(7) TL / f = 0.869

4A and 4B are graphs showing various aberrations of the photographic lens according to Example 2. FIG. 4A shows the time when an object at infinity is in focus, and FIG. 4B shows the time when a short distance object is focused.
As is clear from each aberration diagram, the photographic lens according to the second example has excellent imaging performance with various aberrations corrected well from the infinite object focusing state to the short distance object focusing state. You can see that

(Third embodiment)
FIG. 5 is a cross-sectional view illustrating a configuration of a photographic lens according to the third example.
As shown in FIG. 5, the photographing lens according to the present embodiment includes a front lens group GF, an aperture stop S, and a rear lens group GR in order from the object side along the optical axis.

  The front lens group GF includes, in order from the object side along the optical axis, a protective glass HG having a very weak refractive power, a biconvex lens L11, a biconvex lens L12, a biconcave lens L13, and a negative meniscus with a convex surface facing the object side. The lens includes a cemented lens of a lens L14 and a biconvex lens L15, a biconcave lens L16, and a cemented lens of a positive meniscus lens L17 having a concave surface facing the object side and a negative meniscus lens L18 having a concave surface facing the object side. .

The rear lens group GR is arranged in order from the object side along the optical axis, the rear a partial lens group GRa having a positive refractive power, and the rear side disposed with an air gap from the rear a partial lens group GRa. b partial lens group GRb.
The rear a partial lens group GRa includes, in order from the object side along the optical axis, a cemented lens of a biconvex lens L21 and a negative meniscus lens L22 having a concave surface facing the object side.
The rear group b partial lens group GRb has, in order from the object side along the optical axis, a cemented lens of a positive meniscus lens L23 having a concave surface facing the object side and a biconcave lens L24, a biconcave lens L25, and a concave surface on the object side. It is composed of a positive meniscus lens L26 directed to, a cemented lens of a biconvex lens L27 and a negative meniscus lens L28 having a concave surface facing the object side.

  A filter FL such as a low-pass filter is disposed on the image plane I side of the rear lens group GR.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed.

  With the configuration described above, the photographing lens according to the present embodiment moves the rear a partial lens group GRa to the object side as the focusing lens group Gf, thereby focusing from an infinite object to a close object. Done. Further, in the rear group b partial lens group GRb, a cemented lens of a positive meniscus lens L23 having a concave surface directed toward the object side and a biconcave lens L24, and a biconcave lens L25 are used as anti-vibration lens groups in a direction orthogonal to the optical axis. The image on the image plane I is shifted by moving the image so as to include the component, and image plane correction when image blurring occurs, that is, image stabilization is performed.

  Table 3 below lists values of specifications of the photographing lens according to the present example.

(Table 3) Third Example [Overall Specifications]
f 587.991
FNO 4.086
2ω 4.156
Y 21.60
TL 494.803
Air equivalent TL 494.292
BF 120.500
Air conversion BF 119.989

[Surface data]
Surface number r d nd νd
Object ∞
1) ∞ 4.583 1.51680 63.88
2) ∞ 0.917
3) 200.00000 17.500 1.43385 95.23
4) -2000.00000 70.000
5) 190.47060 17.500 1.43385 95.23
6) -285.75020 2.000
7) -277.98670 6.000 1.61266 44.46
8) 532.09810 100.000
9) 79.35070 3.500 1.83481 42.73
10) 59.09100 10.500 1.49782 82.57
11) -832.06270 8.761
12) -307.18270 2.000 1.71999 50.27
13) 75.76250 6.500
14) -90.30490 3.500 1.84666 23.80
15) -60.43120 2.000 1.51742 52.20
16) -153.00970 24.539

17) ∞ (Variable) (Aperture)

18) 97.87300 4.500 1.48749 70.31
19) -200.00000 2.000 1.84666 23.80
20) -289.64820 (variable)

21) -606.87630 3.500 1.78472 25.64
22) -78.12600 2.000 1.49782 82.57
23) 79.44260 2.500
24) -101.51470 2.000 1.81600 46.59
25) 144.53630 5.000
26) -315.85810 3.500 1.61266 44.46
27) -113.09750 0.100
28) 212.06620 7.000 1.57957 53.74
29) -46.39380 1.800 1.84666 23.80
30) -70.94450 7.000

31) ∞ 1.500 1.51680 63.88
32) ∞ 112.000
Image plane ∞

[Variable interval data]
Infinity Close-up shooting distance
forβ 587.991 -0.100
d 0 ∞ 5579.522
d17 49.173 39.661
d20 11.431 20.943

[Lens group data]
Group start face f
GF 1 881.338
GR 18 375.436

[Conditional expression values]
(1) TLf / TL = 0.335
(2) h1 / hf = 3.960
(3) | ff / fR | = 0.472
(4) | ff / fF + ff / fA | = 0.624
(5) νdp = 23.80
(6) νdh = 95.23
(7) TL / f = 0.842

6A and 6B are graphs showing various aberrations of the photographic lens according to Example 3. FIG. 6A shows the time when an object at infinity is focused, and FIG. 6B shows the time when a short-range object is focused.
As is clear from each aberration diagram, the photographic lens according to the third example has excellent imaging performance with various aberrations corrected well from the infinite object focusing state to the short distance object focusing state. You can see that

As described above, according to each of the above embodiments, it is possible to realize a photographic lens having a small size and high optical performance. In particular, in an optical system with a long focal length and a bright F-number, an internal focus with a large aperture ratio that can accommodate a wide range of imaging while maintaining excellent optical performance from an infinitely focused object to a close-range object focused state. A photographic lens can be realized.
In addition, each said Example has shown one specific example of this embodiment, and this embodiment is not limited to these. The following contents can be appropriately adopted as long as the optical performance of the photographing lens of the present embodiment is not impaired.

  Although a numerical example of the photographing lens of the present embodiment is shown as having a two-group configuration, it can also be applied to other group configurations such as a third group. Further, a configuration in which a lens or a lens group is added to the most object side or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group refers to a portion having at least one lens separated by an air interval.

  In the photographing lens according to the present embodiment, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to focus on an object at infinity from a short distance object. . The focusing lens group can be applied to autofocus, and is also suitable for driving by an autofocus motor, such as an ultrasonic motor. In particular, it is preferable that at least a part of the rear lens group GR is a focusing lens group.

  Further, in the photographing lens of the present embodiment, the lens group or the partial lens group is moved so as to have a component perpendicular to the optical axis, or is rotated (oscillated) in a direction including the optical axis, and is caused by camera shake. An anti-vibration lens group that corrects image blur may be used. In particular, it is preferable that at least a part of the rear lens group GR is an anti-vibration lens group.

  Further, the lens surface of the lens constituting the photographing lens of the present embodiment may be a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, it is preferable because lens processing and assembly adjustment are easy, and deterioration of optical performance due to errors in lens processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is aspherical, any of aspherical surface by grinding, glass mold aspherical surface in which glass is molded into an aspherical shape, or composite aspherical surface in which resin provided on the glass surface is formed in an aspherical shape Good. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In the photographic lens of this embodiment, the aperture stop is preferably disposed between the front lens GF and the rear lens group GR, but the role of the lens frame is substituted for the aperture stop without providing a member. It is good also as composition to do.

  In addition, an antireflection film having a high transmittance in a wide wavelength range is provided on the lens surface of the lens constituting the photographing lens of the present embodiment in order to reduce flare and ghost and achieve high optical performance with high contrast. You may give it.

Next, a camera equipped with a photographic lens according to this embodiment will be described with reference to FIG.
FIG. 7 is a diagram illustrating a configuration of a camera provided with the photographing lens according to the present embodiment.
As shown in FIG. 7, the camera 1 is a digital single-lens reflex camera provided with the photographing lens according to the first embodiment as the photographing lens 2.
In the digital single-lens reflex camera 1 shown in FIG. 7, light from an object (subject) (not shown) is collected by the photographing lens 2 and imaged on the focusing plate 5 via the quick return mirror 3. The light imaged on the collecting plate 5 is reflected a plurality of times in the pentaprism 7 and guided to the eyepiece lens 9. Thus, the photographer can observe the object (subject) image as an erect image through the eyepiece 9.

  When a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and the light of the object (subject) collected by the photographing lens 2 forms a subject image on the image sensor 11. Thereby, the light from the object is picked up by the image pickup device 11 and stored in a memory (not shown) as an object image. In this way, the photographer can photograph an object with the camera 1.

  Here, the photographing lens according to the first embodiment mounted as the photographing lens 2 on the camera 1 is a small photographing lens having high optical performance. Therefore, this camera 1 is a camera with high optical performance. Note that even if a camera in which the photographing lens according to the second or third embodiment is mounted as the photographing lens 2, the same effect as the camera 1 can be obtained. Moreover, the camera 1 may hold | maintain the photographic lens 2 so that attachment or detachment is possible, and may be shape | molded integrally with the photographic lens 2. FIG. The camera 1 may be a camera that does not have a quick return mirror or the like.

  Next, a method for manufacturing the taking lens according to the present embodiment will be described. FIG. 8 is a diagram showing an outline of a method for manufacturing a photographic lens according to the present embodiment.

The method for manufacturing a photographic lens according to the present embodiment includes, in order from the object side along the optical axis, a front lens group including a plurality of lenses, an aperture stop, and a rear lens group including a plurality of lenses. As shown in FIG. 8, the following steps S1 to S3 are included.
Step S1: A rear lens group is disposed in order from the object side along the optical axis, with a rear a partial lens group having positive refractive power and a rear a partial lens group spaced apart from each other by an air gap. b partial lens group, and the rear a partial lens group is composed of three or less lenses.
Step S2: When focusing from an object at infinity to an object at a short distance, the rear a partial lens unit is configured to move along the optical axis as a focusing lens unit.
Step S3: Configure so as to satisfy the following conditional expressions (1) and (2).
(1) 0.10 <TLf / TL <0.40
(2) 3.0 <h1 / hf
However,
TLf: distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group TL: distance on the optical axis from the lens surface closest to the object side to the image plane in the front lens group h1: the above The height from the optical axis of the parallel luminous flux from the object at infinity that determines the open F value that passes through the lens surface closest to the object side of the front lens group hf: the open distance that passes through the lens surface closest to the object side of the focusing lens group Height from the optical axis of the parallel light beam from an infinite object that determines the F value

  According to the method for manufacturing a photographic lens of this embodiment, a photographic lens having a small size and high optical performance can be manufactured. In particular, in an optical system with a long focal length and a bright F-number, an internal focus with a large aperture ratio that can accommodate a wide range of imaging while maintaining excellent optical performance from an infinitely focused object to a close-range object focused state. A photographic lens can be manufactured.

GF front lens group GR rear lens group GRa rear a partial lens group GRb rear b partial lens group Gf focusing lens group S aperture stop I image plane 1 optical device 2 photographing lens 3 quick return mirror 5 focusing plate 7 penta Prism 9 Eyepiece 11 Image sensor

Claims (12)

In order from the object side along the optical axis, it is composed of a front lens group composed of a plurality of lenses, an aperture stop, and a rear lens group composed of a plurality of lenses.
The rear lens group includes, in order from the object side along the optical axis, a rear a partial lens group having a positive refractive power, and a rear b arranged with an air gap from the rear a partial lens group. Consisting of a partial lens group,
The rear a partial lens group is composed of three or less lenses,
When focusing from an infinite object to a close object, the rear a partial lens group moves along the optical axis as a focusing lens group,
A photographic lens that satisfies the following conditional expression.
0.10 <TLf / TL <0.40
3.0 <h1 / hf
However,
TLf: distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group TL: distance on the optical axis from the lens surface closest to the object side to the image plane in the front lens group h1: the above The height from the optical axis of the parallel luminous flux from the object at infinity that determines the open F value that passes through the lens surface closest to the object side of the front lens group hf: the open distance that passes through the lens surface closest to the object side of the focusing lens group Height from the optical axis of the parallel light beam from an infinite object that determines the F value The photographic lens according to claim 1, wherein the following conditional expression is satisfied.
0.01 <| ff / fR |
However,
ff: focal length of the focusing lens group fR: composite focal length in the infinite object focusing state of the entire lens located on the image side of the focusing lens group The taking lens according to claim 1 or 2, satisfying the following conditional expression.
| Ff / fF + ff / fA | <0.69
However,
ff: focal length of the focusing lens group fF: combined focal length in the infinite object focusing state of the entire lens located on the object side of the focusing lens group fA: from the focusing lens group and the focusing lens group Combined focal length in the infinite object focusing state with the whole lens on the object side The photographing lens according to any one of claims 1 to 3, wherein the front lens group includes at least one lens that satisfies the following conditional expression.
νdp <35
However,
νdp: Abbe number with respect to d-line of the glass material of the at least one lens in the front lens group   The photographing lens according to claim 4, wherein the at least one lens has a positive refractive power. The photographic lens according to claim 1, wherein the front lens group includes at least one lens that satisfies the following conditional expression.
80 <νdh
However,
νdh: Abbe number with respect to d-line of the glass material of the at least one lens in the front lens group   The taking lens according to any one of claims 1 to 6, wherein the plurality of lenses constituting the front lens group is 10 or less.   The photographing lens according to any one of claims 1 to 7, wherein the plurality of lenses constituting the front lens group is six or more.   The image on the image plane can be shifted by moving a part of the lens groups in the rear lens group so as to include a component in a direction orthogonal to the optical axis. The taking lens according to the item. The photographic lens according to claim 1, wherein the following conditional expression is satisfied.
TL / f <1.2
However,
TL: Distance on the optical axis from the lens surface closest to the object side of the front lens group to the image plane f: Focal length of the entire photographing lens system   An optical apparatus having the photographing lens according to any one of claims 1 to 10. A method of manufacturing a photographic lens composed of a front lens group composed of a plurality of lenses, an aperture stop, and a rear lens group composed of a plurality of lenses in order from the object side along the optical axis. ,
The rear lens group is arranged in order from the object side along the optical axis, the rear a partial lens group having a positive refractive power, and the rear side b arranged at an air interval from the rear a partial lens group. Consisting of a partial lens group,
The rear a partial lens group is composed of three or less lenses,
When focusing from an object at infinity to an object at a short distance, the rear a partial lens group is configured to move along the optical axis as a focusing lens group,
A method for manufacturing a photographic lens configured to satisfy the following conditional expression:
0.10 <TLf / TL <0.40
3.0 <h1 / hf
However,
TLf: distance on the optical axis from the lens surface closest to the object side to the image plane in the focusing lens group TL: distance on the optical axis from the lens surface closest to the object side to the image plane in the front lens group h1: the above The height from the optical axis of the parallel luminous flux from the object at infinity that determines the open F value that passes through the lens surface closest to the object side of the front lens group hf: the open distance that passes through the lens surface closest to the object side of the focusing lens group Height from the optical axis of the parallel light beam from an infinite object that determines the F value

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