JP2015152851A - Optical system, imaging device including the optical system, and method for manufacturing optical system - Google Patents

Abstract

An optical system having high optical performance from an infinite object focusing state to a short-distance object focusing state, an imaging apparatus including the optical system, and a method for manufacturing the optical system are provided.
A first lens group, an aperture stop, and a second lens group are arranged in order from the object side along the optical axis, and the first lens group is sequentially arranged from the object side. It includes a partial lens group composed of three or more negative lens components, and by moving the second lens group along the optical axis, focusing from an object at infinity to a near object is performed. An optical system characterized by satisfaction.
1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

Description

  The present invention relates to an optical system suitable for a photographic camera, an electronic still camera, a video camera, and the like, an imaging device including the optical system, and a method for manufacturing the optical system.

  Conventionally, a retrofocus type wide-angle lens has been proposed (see, for example, Patent Document 1).

JP 2011-242520 A

  A conventional retrofocus type wide-angle lens is known to affect distortion, field curvature, downward coma, lateral chromatic aberration, and the like because the front group has a negative refractive power. In addition, it is difficult to correct aberrations when focusing on a short-distance object, and in particular, there is a problem that variations in lateral chromatic aberration and axial chromatic aberration are large.

  The present invention has been made in view of such a situation, and an optical system having high optical performance from an infinite object focusing state to a short-distance object focusing state, an imaging device including the optical system, and an optical system It is an object to provide a manufacturing method.

In order to achieve the above object, an optical system according to the present invention includes, in order from the object side along an optical axis, a first lens group, an aperture stop, and a second lens group, and the first lens group. Includes a partial lens group composed of three or more negative lens components sequentially arranged in order from the object side, and moves the second lens group along the optical axis, so that an object at a short distance from an object at infinity It is characterized by satisfying the following formula condition.
1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

  In addition, an imaging apparatus according to the present invention includes the above optical system.

An optical system manufacturing method according to the present invention is an optical system manufacturing method including a first lens group, an aperture stop, and a second lens group in order from the object side along the optical axis. The first lens group is configured to include a partial lens group composed of three or more negative lens components sequentially arranged from the object side, and the second lens group is moved along the optical axis. It is configured to perform focusing from an infinitely distant object to a close object, and to satisfy the following condition.
1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

  ADVANTAGE OF THE INVENTION According to this invention, the optical system provided with the high optical performance from an infinite object focusing state to a short-distance object focusing state, the imaging device provided with this optical system, and the manufacturing method of an optical system can be provided.

It is sectional drawing which shows the structure of the optical system which concerns on 1st Example. FIG. 5A is a diagram illustrating various aberrations of the optical system according to the first example, where (a) illustrates when an object at infinity is in focus and (b) illustrates when an object at a short distance is in focus. It is sectional drawing which shows the structure of the optical system which concerns on 2nd Example. FIG. 4A is a diagram illustrating various aberrations of the optical system according to Example 2, wherein (a) illustrates when an object at infinity is in focus and (b) illustrates when an object at a short distance is in focus. It is sectional drawing which shows the structure of the optical system which concerns on 3rd Example. FIG. 5A is a diagram illustrating various aberrations of the optical system according to Example 3, wherein (a) illustrates when an object at infinity is in focus and (b) illustrates when an object at a short distance is in focus. It is sectional drawing which shows the structure of the optical system which concerns on 4th Example. FIG. 6A is a diagram illustrating various aberrations of the optical system according to Example 4, wherein (a) shows when an object at infinity is in focus, and (b) shows when an object at close distance is in focus. It is sectional drawing which shows the structure of the optical system which concerns on 5th Example. FIG. 6A is a diagram illustrating various aberrations of the optical system according to Example 5, wherein (a) shows the time when an object at infinity is in focus and (b) shows the time when an object at short distance is in focus. It is sectional drawing which shows the structure of the optical system which concerns on 6th Example. FIG. 11A is a diagram illustrating various aberrations of the optical system according to Example 6, wherein (a) illustrates when an object at infinity is in focus and (b) illustrates when an object at close distance is in focus. It is sectional drawing of the imaging device provided with the optical system which concerns on this invention. It is a figure which shows the outline of the manufacturing method of the optical system which concerns on this invention.

  Hereinafter, an optical system, an imaging device, and an optical system manufacturing method according to the present invention will be described. First, 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 along the optical axis, a first lens group, an aperture stop, and a second lens group, and the first lens group continues in order from the object side. The partial lens group which consists of three or more negative lens components arrange | positioned is included. The lens component refers to a single lens or a cemented lens.

  By disposing a partial lens group composed of three or more negative lens components arranged sequentially in order from the object side in the first lens group, the power of each of these negative lenses can be weakened. As a result, it is possible to suppress distortion, field curvature, downward coma, and lateral chromatic aberration that occur in the first lens group.

  In addition, the optical system according to the present invention performs focusing from an object at infinity to a near object by moving the second lens group along the optical axis in such a configuration.

  By using the entire second lens group behind the aperture stop as the focus lens group, the number of lenses in the focus lens group increases, and good imaging performance can be exhibited. When the number of lenses in the focus lens group increases, the focus speed decreases, and the cost increases due to the increase in the size of the motor and the size of the lens barrel increases. However, the optical system according to the present invention has an aperture in the focus lens group. Since the aperture is not included, the weight can be reduced, and the increase in cost and size can be suppressed.

In addition, the optical system according to the present invention preferably satisfies the following conditional expression (1) under such a configuration.
(1) 1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

  Conditional expression (1) is a conditional expression that defines an appropriate ratio between the focal length of the partial lens group and the focal length of the entire optical system. When the conditional expression (1) is satisfied, the power of the partial lens group becomes appropriate, and in particular, distortion, field curvature, downward coma, and lateral chromatic aberration can be favorably corrected.

  When the corresponding value of the conditional expression (1) exceeds the upper limit value, the power of the partial lens group is decreased, and the lower coma aberration is deteriorated.

  When the corresponding value of the conditional expression (1) is less than the lower limit value, the power of the partial lens group is increased, and distortion and field curvature are deteriorated.

The optical system according to the present invention preferably satisfies the following conditional expression (2).
(2) 0.50 <| f1 / f2 | <5.50
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group

  Conditional expression (2) is a conditional expression that defines an appropriate ratio between the focal length of the first lens group and the focal length of the second lens group. By satisfying conditional expression (2), the power balance of the lens groups arranged before and after the aperture stop becomes appropriate, and in particular, distortion and lateral chromatic aberration can be corrected well.

  If the corresponding value of the conditional expression (2) exceeds the upper limit value, the power of the first lens group becomes small, and field curvature and upper coma aberration deteriorate, which is not preferable.

  If the corresponding value of the conditional expression (2) is less than the lower limit value, the power of the first lens group becomes large, and the lower coma aberration deteriorates. In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (2) to 0.80. In order to further secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (2) to 0.90.

The optical system according to the present invention preferably satisfies the following conditional expression (3).
(3) 0.10 <| fn / f1 | <1.00
However,
fn: focal length of the partial lens group f1: focal length of the first lens group

  Conditional expression (3) is a conditional expression that defines an appropriate ratio between the focal length of the partial lens group and the focal length of the first lens group. By satisfying conditional expression (3), the power of the partial lens group in the first lens group becomes appropriate.

  If the corresponding value of conditional expression (3) exceeds the upper limit value, the power of the partial lens group becomes weaker than the power of the first lens group, and the field curvature is deteriorated. In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (3) to 0.76.

  If the corresponding value of the conditional expression (3) is less than the lower limit value, the power of the partial lens group becomes too strong with respect to the power of the first lens group, which deteriorates the lower coma aberration and distortion aberration. . In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (3) to 0.13.

The optical system according to the present invention preferably satisfies the following conditional expression (4).
(4) 0.10 <| fn / f2 | <1.00
However,
fn: focal length of the partial lens group f2: focal length of the second lens group

  Conditional expression (4) is a conditional expression that defines an appropriate ratio between the focal length of the partial lens group and the focal length of the second lens group. When the conditional expression (4) is satisfied, the power of the partial lens group with respect to the power of the second lens group becomes appropriate.

  If the corresponding value of the conditional expression (4) exceeds the upper limit value, the power of the partial lens group becomes weaker than the power of the second lens group, and the field curvature is deteriorated. In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (3) to 0.80.

  If the corresponding value of the conditional expression (4) is less than the lower limit value, the power of the partial lens group becomes too strong with respect to the power of the second lens group, which deteriorates downward coma and distortion, which is not preferable. . In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (3) to 0.45.

  In the optical system according to the present invention, it is preferable that the second lens group has a positive refractive power. With such a configuration, it is possible to satisfactorily correct distortion, curvature of field, downward coma, and lateral chromatic aberration.

  In the optical system according to the present invention, it is preferable that the first lens group has a positive refractive power. With such a configuration, it is possible to satisfactorily correct distortion, curvature of field, downward coma, and lateral chromatic aberration.

  In the optical system according to the present invention, it is preferable that the first lens group has a negative refractive power. With such a configuration, it is possible to satisfactorily correct distortion and field curvature.

  In the optical system according to the present invention, it is preferable that all of the three or more negative lenses constituting the partial lens group have a negative meniscus shape. By adopting such a configuration, it is possible to satisfactorily correct the distortion aberration, the field curvature, and the downward coma aberration without causing the incident light beam to be bent suddenly.

  In the optical system according to the present invention, the partial lens group includes a negative meniscus shape in which a negative lens closest to the object side and a negative lens adjacent to the image side of the negative lens closest to the object have a convex surface facing the object side. It is preferable that By adopting such a configuration, it is possible to satisfactorily correct the distortion aberration, the field curvature, and the downward coma aberration without causing the incident light beam to be bent suddenly.

  The optical system according to the present invention preferably includes at least one cemented lens in the second lens group. With this configuration, chromatic aberration can be corrected in the second lens group, and chromatic aberration can be corrected well during focusing.

  In the optical system according to the present invention, it is preferable that the partial lens group includes at least one aspheric lens. With such a configuration, it is possible to satisfactorily correct distortion and field curvature.

  Moreover, an imaging apparatus according to the present invention includes the optical system having the above-described configuration. As a result, an imaging device having good optical performance can be realized.

An optical system manufacturing method according to the present invention is an optical system manufacturing method including a first lens group, an aperture stop, and a second lens group in order from the object side along the optical axis. The first lens group is configured to include a partial lens group composed of three or more negative lens components sequentially arranged from the object side, and the second lens group is moved along the optical axis. It is configured to focus from an infinitely distant object to a close object and to satisfy the following conditional expression (1).
(1) 1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

  With such an optical system manufacturing method, a photographic lens having good optical performance can be manufactured.

(Numerical example)
A variable magnification optical system according to numerical examples of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a cross-sectional view illustrating a configuration of an optical system OS1 according to the first example.
As shown in FIG. 1, the optical system OS1 according to the present embodiment has, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refractive power. And a second lens group G2.

  The first lens group G1 has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The lens includes a negative meniscus lens L13, a positive meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The negative meniscus lens L11, the negative meniscus lens L12, and the negative meniscus lens L13 which are sequentially arranged from the object side constitute a partial lens group Gn.

  The second lens group G2 includes a positive meniscus lens L21 having a concave surface facing the object side, a cemented lens of a negative meniscus lens L22 having a concave surface facing the object side and a biconcave lens L23, and a positive meniscus having a concave surface facing the object side. The lens L24 is composed of a biconvex lens L25.

  In the vicinity of the image plane I, a filter group FL including a low-pass filter and an infrared cut filter is disposed.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed. The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and is fixed with respect to the image plane I during focusing from an infinite object focusing state to a short distance object focusing state. It is.

  In the photographing lens OS1 according to the present embodiment, the first lens group G1 is fixed with respect to the image plane I and the second lens group G2 is fixed when focusing from an infinite object focusing state to a short distance object focusing state. It moves toward the object side with respect to the image plane I so that the distance between the aperture stop S and the second lens group G2 decreases.

Table 1 below lists specifications of the photographing lens OS1 according to the first example of the present invention.
In [Surface data] in Table 1, the surface number is the order of the lens surfaces counted from the object side, r is the radius of curvature of the lens surfaces, d is the distance between the lens surfaces, and nd is the d-line (wavelength λ = 587.6 nm). And νd represents the Abbe number for the d-line (wavelength λ = 587.6 nm). The object plane indicates the object plane, (aperture S) indicates the aperture stop S, and the image plane indicates the image plane I. Note that the radius of curvature r = ∞ indicates a plane, and the description of the refractive index of air d = 1.0000 is omitted. When the lens surface is an aspheric surface, the surface number is marked with * and the paraxial radius of curvature is shown in the column of the radius of curvature r.

[Aspherical data] shows the conical coefficient and aspherical coefficient when the shape of the aspherical surface shown in [Surface data] is expressed by the following equation.
X (y) = (y ² / r) / [1+ {1-κ (y ² / r ² )} ^1/2 ] + A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰
Here, the height in the direction perpendicular to the optical axis is y, the amount of displacement in the optical axis direction at height y is X (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the cone coefficient is κ, Let the n-th order aspheric coefficient be An. The secondary aspheric coefficient A2 is 0 (zero), and is not shown. In addition, “E−n” indicates “× 10 ⁻ⁿ ”, for example, “1.234E-05” indicates “1.234 × 10 ⁻⁵ ”.

  In [various data], f is the focal length, FNO is the F number, 2ω is the angle of view (unit is “°”), Y is the image height, TL is the total length of the optical system, and air equivalent BF is the air equivalent back focus. Yes. These values are those when focusing on an object at infinity. Here, the total length TL of the optical system is a distance on the optical axis from the most object side lens surface in the first lens group G1 to the image plane I, and the air conversion BF is the most image side in the second lens group G2. This is a value when the distance on the optical axis from the lens surface to the image plane I is measured in a state where an optical block such as a filter having no refractive power is removed from the optical path.

  In [Variable interval data], di (i is an integer) indicates a surface interval between the i-th surface and the (i + 1) -th surface. Further, β represents the photographing magnification, and d0 represents 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 [Surface Data]
Surface number r d nd νd
Object ∞
1) 18.9303 1.0000 1.516800 63.88
2) 13.0000 1.3000
3) 15.5005 1.0000 1.589130 61.25
* 4) 7.0000 4.0000
5) 16.0384 1.5000 1.589130 61.25
* 6) 7.5000 6.3835
7) 13.0145 1.7977 1.801000 34.92
8) 55.3972 0.1423
9) 72.8570 7.9908 1.517420 52.20
10) −15.6894 0.6000
11) (Aperture S) d11
12) −5.7929 1.0000 1.846660 23.80
13) −6.1003 0.1001
14) −92.3317 2.4538 1.516800 63.88
15) −4.9772 1.0000 1.755200 27.57
16) 151.5394 0.3637
17) −54.6567 1.9341 1.806100 40.97
18) −11.9953 0.1000
19) 86.5428 1.9379 1.772500 49.62
20) −23.5474 d20
21) 0.0000 0.5000 1.516800 63.88
22) 0.0000 1.1100
23) 0.0000 1.5900 1.516800 63.88
24) 0.0000 0.3000
25) 0.0000 0.7000 1.516800 63.88
26) 0.0000 0.7000
Image plane ∞

[Aspherical data]
Surface number: 4
κ = 0.5000
A4 = −1.58688E−04
A6 = -2.16456E-07

Surface number: 6
κ = 0.6570
A4 = 3.17632E−04

[Various data]
f 7.54025
FNO 2.85
2ω 94.66
Y 8.00
TL 51.2997
Air conversion BF 13.6095

[Variable interval data]
Shooting magnification Infinite focus Near focus f or β 7.54 -0.04719
d 0 ∞ 148.7003
d11 2.13619 1.69848
d20 9.65957 10.09728

[Lens group data]
Start surface Focal length
G1 1 16.95374
G2 12 18.03703
Gn 1 -9.28324

[Values for each conditional expression]
(1) (−fn) /f=1.3212
(2) | f1 / f2 | = 0.939994
(3) | fn / f1 | = 0.547563
(4) | fn / f2 | = 0.514677

  FIGS. 2A and 2B are graphs showing various aberrations of the photographic lens OS1 according to the first example. FIG. 2A shows the time when an object at infinity is in focus, and FIG. 2B shows the time when a short distance object is focused.

  In each aberration diagram, FNO represents an F number, A represents a half angle of view (unit: degree), NA represents a numerical aperture, and HO represents an object height. The spherical aberration diagram shows the F-number or numerical aperture value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the half field angle or the maximum object height, and the coma aberration diagram shows each half image. Indicates the value of the corner or each object height. D represents a d-line (λ = 587.6 nm), and g represents a g-line (λ = 435.8 nm). In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, the solid line represents the meridional coma aberration with respect to the d-line and the g-line, and the broken line represents the sagittal coma aberration. In the following examples, the same symbols are used, and the following description is omitted.

From each aberration diagram, it can be seen that the photographic lens OS1 according to Example 1 has excellent optical performance with various aberrations corrected well.

(Second embodiment)
FIG. 3 is a cross-sectional view showing the configuration of the optical system OS2 according to the second embodiment.
As shown in FIG. 3, the optical system OS2 according to the present example has a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refractive power in order from the object side along the optical axis. And a second lens group G2.

  The first lens group G1 has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The lens includes a negative meniscus lens L13, a positive meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The negative meniscus lens L11, the negative meniscus lens L12, and the negative meniscus lens L13 which are sequentially arranged from the object side constitute a partial lens group Gn.

  The second lens group G2 includes a cemented lens formed by a biconvex lens L21 and a biconcave lens L22, a positive meniscus lens L23 having a concave surface directed toward the object side, and a biconvex lens L24.

  In the vicinity of the image plane I, a filter group FL including a low-pass filter and an infrared cut filter is disposed.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed. The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and is fixed with respect to the image plane I during focusing from an infinite object focusing state to a short distance object focusing state. It is.

  In the photographing lens OS2 according to the present embodiment, the first lens group G1 is fixed with respect to the image plane I and the second lens group G2 is fixed when focusing from an infinite object focusing state to a short distance object focusing state. It moves toward the object side with respect to the image plane I so that the distance between the aperture stop S and the second lens group G2 decreases.

  Table 2 below provides specification values of the photographing lens OS2 according to the second example of the present invention.

(Table 2) Second Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 24.0388 1.0000 1.516800 63.88
2) 12.7440 1.3000
3) 14.7179 1.0000 1.592014 67.02
* 4) 7.0000 3.9649
5) 16.6265 1.5000 1.693500 53.20
* 6) 11.0433 10.1270
7) 8.6914 4.0000 1.846660 23.80
8) 7.3873 0.3889
9) 12.5004 1.3898 1.749497 35.28
10) −128.7398 1.3000
11) (Aperture S) d11
12) 105.1593 2.0327 1.563840 60.71
13) −4.8184 2.7809 1.755200 27.57
14) 58.5888 0.4493
15) −54.8621 1.9915 1.772500 49.62
16) −10.9985 0.3694
17) 57.2964 1.9914 1.744000 44.80
18) −25.6110 d18
19) 0.0000 0.5000 1.516800 63.88
20) 0.0000 1.1100
21) 0.0000 1.5900 1.516800 63.88
22) 0.0000 0.3000
23) 0.0000 0.7000 1.516800 63.88
24) 0.0000 0.7000
Image plane ∞

[Aspherical data]
Surface number: 4
κ = 0.0614
A4 = −6.83757E−05
A6 = -3.07496E-07

Surface number: 6
κ = 1.8394
A4 = 1.95678E−04

[Various data]
f 7.54
FNO 2.78
2ω 94.67278
Y 8.00
TL 51.5001
Air equivalent BF 13.6101

[Variable interval data]
Shooting magnification Infinite focus Near focus f or β 7.54 -0.04752
d 0 ∞ 148.4999
d11 1.62413 1.24869
d18 9.66014 10.03558

[Lens group data]
Start surface Focal length
G1 1 33.35300
G2 12 15.64951
Gn 1 -11.29440

[Values for each conditional expression]
(1) (−fn) /f=1.49793
(2) | f1 / f2 | = 2.31249
(3) | fn / f1 | = 0.386632
(4) | fn / f2 | = 0.721709

  FIGS. 4A and 4B are graphs showing various aberrations of the photographic lens OS2 according to the second example. FIG. 4A shows the time when the object at infinity is focused, and FIG. 4B shows the time when the object at short distance is focused.

From the respective aberration diagrams, it can be seen that the photographic lens OS2 according to the second example has excellent optical performance with various aberrations corrected well.

(Third embodiment)
FIG. 5 is a cross-sectional view showing the configuration of the optical system OS3 according to the third embodiment.
As shown in FIG. 5, the optical system OS3 according to the present example has a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refractive power in order from the object side along the optical axis. And a second lens group G2.

  The first lens group G1 has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a convex surface facing the object side. It is composed of a negative meniscus lens L13 and a biconvex lens L14. The negative meniscus lens L11, the negative meniscus lens L12, and the negative meniscus lens L13 which are sequentially arranged from the object side constitute a partial lens group Gn.

  The second lens group G2 includes a positive meniscus lens L21 having a concave surface facing the object side, a cemented lens of a biconcave lens L22 and a biconvex lens L23, a positive meniscus lens L24 having a concave surface facing the object side, and a biconvex lens L25. It is composed of

  In the vicinity of the image plane I, a filter group FL including a low-pass filter and an infrared cut filter is disposed.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed. The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and is fixed with respect to the image plane I during focusing from an infinite object focusing state to a short distance object focusing state. It is.

  In the photographing lens OS3 according to the present embodiment, the first lens group G1 is fixed with respect to the image plane I and the second lens group G2 is fixed when focusing from an infinite object focusing state to a short distance object focusing state. It moves toward the object side with respect to the image plane I so that the distance between the aperture stop S and the second lens group G2 decreases.

  Table 3 below lists specifications of the photographing lens OS3 according to the third example of the present invention.

(Table 3) Third Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 21.7761 1.0000 1.516800 63.88
2) 11.0000 2.6820
3) 17.9067 1.0000 1.589130 61.25
* 4) 7.5000 4.0000
5) 29.5448 1.5000 1.589130 61.25
* 6) 20.1877 9.0387
7) 18.7195 4.0000 1.902650 35.72
8) −61.9477 1.3000
9) (Aperture S) d9
10) -29.2669 1.5901 1.670030 47.14
11) −6.0886 0.2992
12) −5.4890 1.0000 1.755200 27.57
13) 19.9946 2.3009 1.487490 70.32
14) -10.4004 0.1000
15) −31.7574 1.3484 1.883000 40.66
16) -16.6508 0.1000
17) 244.0206 1.4634 1.883000 40.66
18) −32.5731 d18
19) 0.0000 0.5000 1.516800 63.88
20) 0.0000 1.1100
21) 0.0000 1.5900 1.516800 63.88
22) 0.0000 0.3000
23) 0.0000 0.7000 1.516800 63.88
24) 0.0000 0.7000
Image plane ∞

[Aspherical data]
Surface number: 4
κ = 0.5000
A4 = -2.76311E-04
A6 = -1.93208E-06

Surface number: 6
κ = −8.8510
A4 = 5.23452E−04

[Various data]
f 7.54
FNO 2.82
2ω 94.71436
Y 8.00
TL 50.99864
Air equivalent BF 13.6086

[Variable interval data]
Shooting magnification Infinite focus Near focus f or β 7.54 -0.04716
d 0 ∞ 149.0014
d11 3.71737 3.31023
d18 9.65864 10.06577

[Lens group data]
Start surface Focal length
G1 1 20.51903
G2 12 17.98484
Gn 1 -12.05156

[Values for each conditional expression]
(1) (−fn) /f=1.59839
(2) | f1 / f2 | = 1.140907
(3) | fn / f1 | = 0.587336
(4) | fn / f2 | = 0.6070095

  FIGS. 6A and 6B are graphs showing various aberrations of the photographic lens OS3 according to the third example. FIG. 6A shows the time when an object at infinity is in focus, and FIG.

From each aberration diagram, it can be seen that the photographic lens OS3 according to the third example has excellent optical performance with various aberrations corrected well.

(Fourth embodiment)
FIG. 7 is a cross-sectional view showing a configuration of an optical system OS4 according to the fourth example.
As shown in FIG. 7, the optical system OS4 according to the present embodiment has a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refractive power in order from the object side along the optical axis. And a second lens group G2.

  The first lens group G1 has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a concave surface facing the object side. It is composed of a negative meniscus lens L13, a positive meniscus lens L14 having a convex surface facing the object side, and a positive meniscus lens L15 having a convex surface facing the object side. The negative meniscus lens L11, the negative meniscus lens L12, and the negative meniscus lens L13 which are sequentially arranged from the object side constitute a partial lens group Gn.

  The second lens group G2 includes a cemented lens of a biconcave lens L21 and a biconvex lens L22, and a biconvex lens L23.

  In the vicinity of the image plane I, a filter group FL including a low-pass filter and an infrared cut filter is disposed.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed. The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and is fixed with respect to the image plane I during focusing from an infinite object focusing state to a short distance object focusing state. It is.

  In the imaging lens OS4 according to the present embodiment, the first lens group G1 is fixed with respect to the image plane I and the second lens group G2 is fixed when focusing from the infinite object focusing state to the short distance object focusing state. It moves toward the object side with respect to the image plane I so that the distance between the aperture stop S and the second lens group G2 decreases.

  Table 4 below provides specification values of the photographing lens OS4 according to the fourth example of the present invention.

(Table 4) Fourth Example [Surface Data]
Surface number r d nd νd
Object ∞
1) 46.0000 1.0000 1.589130 61.22
* 2) 7.6947 3.0000
3) 16.2934 1.0000 1.589130 61.25
* 4) 14.8246 5.7647
5) −15.6280 1.9516 1.804000 46.60
6) -17.4538 1.3000
7) 15.8055 3.0087 1.788000 47.35
8) 3420.8217 4.1771
9) 32.1592 1.2453 1.804400 39.61
10) 104.4016 2.0000
11) (Aperture S) d11
12) −10.9303 2.8061 1.846660 23.80
13) 21.5013 1.7211 1.713000 53.96
* 14) −32.2406 0.1000
15) 37.5616 2.8699 1.816000 46.59
16) −11.9037 d16
17) 0.0000 0.5000 1.516800 63.88
18) 0.0000 1.1100
19) 0.0000 1.5900 1.516800 63.88
20) 0.0000 0.3000
21) 0.0000 0.7000 1.516800 63.88
22) 0.0000 0.7000
Image plane ∞

[Aspherical data]
Surface number: 2
κ = 0.3686
A4 = -1.25276E-04
A6 = −8.40333E−07
A8 = 1.30522E-11

Surface number: 4
κ = −4.9032
A4 = 3.77016E−04
A6 = −9.18775E−07
A8 = 1.54066E−08

Surface number: 14
κ = 1.0398
A4 = 2.44618E−04
A6 = 1.61786E−06
A8 = -1.50124E-08

[Various data]
f 9.14
FNO 1.86
2ω 83.84306
Y 8.00
TL 50.0000
Air conversion BF 14.3054

[Variable interval data]
Magnification at infinity Focus Near focus f or β 9.14 -0.05706
d 0 ∞ 149.9999
d11 2.80000 2.14035
d18 10.35546 11.01511

[Lens group data]
Start surface Focal length
G1 1 19.20410
G2 12 18.28705
Gn 1 -14.49990

[Values for each conditional expression]
(1) (−fn) /f=1.58642
(2) | f1 / f2 | = 1.050148
(3) | fn / f1 | = 0.755042
(4) | fn / f2 | = 0.792905

  FIGS. 8A and 8B are graphs showing various aberrations of the photographic lens OS4 according to the fourth example. FIG. 8A shows the time when an object at infinity is focused, and FIG. 8B shows the time when an object at short distance is focused.

From each aberration diagram, it can be seen that the photographic lens OS4 according to Example 4 has various aberrations corrected well and has excellent optical performance.

(5th Example)
FIG. 9 is a cross-sectional view showing a configuration of an optical system OS5 according to the fifth example.
As shown in FIG. 9, the optical system OS5 according to the present example has a first lens group G1 having a negative refractive power, an aperture stop S, and a positive refractive power in order from the object side along the optical axis. And a second lens group G2.

  The first lens group G1 has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a convex surface facing the object side. It is composed of a negative meniscus lens L13, a negative meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The negative meniscus lens L11, the negative meniscus lens L12, the negative meniscus lens L13, and the negative meniscus lens L14, which are sequentially arranged from the object side, constitute a partial lens group Gn.

  The second lens group G2 includes a positive meniscus lens L21 having a concave surface facing the object side, a cemented lens of a positive meniscus lens L22 having a concave surface facing the object side and a biconcave lens L23, and a positive meniscus having a concave surface facing the object side. The lens L24 is composed of a biconvex lens L25.

  In the vicinity of the image plane I, a filter group FL including a low-pass filter and an infrared cut filter is disposed.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed. The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and is fixed with respect to the image plane I during focusing from an infinite object focusing state to a short distance object focusing state. It is.

  In the imaging lens OS5 according to the present embodiment, the first lens group G1 is fixed with respect to the image plane I and the second lens group G2 is fixed when focusing from an infinite object focusing state to a short distance object focusing state. It moves toward the object side with respect to the image plane I so that the distance between the aperture stop S and the second lens group G2 decreases.

  Table 5 below gives specifications of the taking lens OS5 according to the fifth example of the present invention.

(Table 5) Fifth Example [Surface data]
Surface number r d nd νd
Object ∞
1) 19.9930 1.0000 1.516799 63.88
2) 12.4862 1.3000
3) 14.2352 1.0000 1.592013 67.02
* 4) 7.0910 4.0000
5) 12.1000 1.0000 1.693499 53.20
* 6) 11.4000 1.1645
7) 8.8092 1.5334 1.589130 61.22
8) 6.0681 5.8267
9) 33.2997 7.5000 1.741697 29.56
10) −35.5172 0.6000
11) (Aperture S) d11
12) −35.3279 1.2407 1.816000 46.59
13) −12.3037 1.7183
14) −107.4093 2.0708 1.564700 63.62
15) -6.8021 1.0000 1.755201 27.58
16) 31.8807 0.4902
17) −103.6435 1.6491 1.789749 47.57
18) -15.3196 0.1000
19) 30.7276 1.8788 1.654924 54.37
20) −33.8797 d20
21) 0.0000 0.5000 1.516800 63.88
22) 0.0000 1.1100
23) 0.0000 1.5900 1.516800 63.88
24) 0.0000 0.3000
25) 0.0000 0.7000 1.516800 63.88
26) 0.0000 0.7000
Image plane ∞

[Aspherical data]
Surface number: 4
κ = −0.0132
A4 = -7.80211E-06
A6 = −8.09721E−07

Surface number: 6
κ = 2.2258
A4 = 1.72308E−04

[Various data]
f 7.54
FNO 2.84
2ω 95.97872
Y 8.00
TL 51.5000
Air conversion BF 13.6100

[Variable interval data]
Shooting magnification Infinity focus Near focus f or β 7.54 -0.04777
d 0 ∞ 149.9999
d11 1.86748 1.50317
d20 9.65998 10.02429

[Lens group data]
Start surface Focal length
G1 1 -79.55442
G2 12 14.68103
Gn 1 -10.51779

[Values for each conditional expression]
(1) (−fn) /f=1.39492
(2) | f1 / f2 | = 5.41886
(3) | fn / f1 | = 0.13221
(4) | fn / f2 | = 0.16442

  FIGS. 10A and 10B are graphs showing various aberrations of the taking lens OS5 according to the fifth example. FIG. 10A shows the time when an object at infinity is in focus, and FIG.

From each aberration diagram, it can be seen that the photographic lens OS5 according to Example 5 has various optical aberrations corrected and has excellent optical performance.

(Sixth embodiment)
FIG. 11 is a cross-sectional view illustrating a configuration of an optical system OS6 according to the sixth example.
As shown in FIG. 11, the optical system OS6 according to the present example has a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refractive power in order from the object side along the optical axis. And a second lens group G2.

  The first lens group G1 has, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The lens includes a negative meniscus lens L13, a cemented negative lens L134 of a positive meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The negative meniscus lens L11, the negative meniscus lens L12, and the cemented negative lens L134 which are sequentially arranged from the object side constitute a partial lens group Gn.

  The second lens group G2 includes a positive meniscus lens L21 having a concave surface facing the object side, a cemented lens of a biconcave lens L22 and a biconvex lens L23, a positive meniscus lens L24 having a concave surface facing the object side, and a biconvex lens L25. It is composed of

  In the vicinity of the image plane I, a filter group FL including a low-pass filter and an infrared cut filter is disposed.

  On the image plane I, an image sensor (not shown) made up of a CCD, a CMOS, or the like is disposed. The aperture stop S is disposed between the first lens group G1 and the second lens group G2, and is fixed with respect to the image plane I during focusing from an infinite object focusing state to a short distance object focusing state. It is.

  In the photographing lens OS6 according to the present embodiment, the first lens group G1 is fixed with respect to the image plane I and the second lens group G2 is fixed when focusing from an infinite object focusing state to a short distance object focusing state. It moves toward the object side with respect to the image plane I so that the distance between the aperture stop S and the second lens group G2 decreases.

  Table 6 below provides specification values of the photographing lens OS6 according to the sixth example of the present invention.

(Table 6) Sixth Example [Surface data]
Surface number r d nd νd
Object ∞
1) 24.8381 1.0000 1.516800 63.88
2) 11.0000 1.4330
3) 12.4616 1.0000 1.589130 61.25
* 4) 7.1000 4.0000
5) 23.3169 1.4749 1.617720 49.81
6) 10.3012 1.9802 1.806100 40.73
* 7) 11.3674 8.7502
8) 14.1965 4.5000 1.749500 35.25
9) −50.4832 1.4000
10) (Aperture S) d10
11) -27.1912 1.8504 1.622990 58.12
12) −6.2027 0.4666
13) -5.3691 1.0000 1.755200 27.57
14) 30.4370 2.3960 1.516800 63.88
15) −10.2686 0.1000
16) −50.9881 1.5543 1.795000 45.31
17) −18.6000 0.1000
18) 70.9553 1.7346 1.744000 44.80
19) −37.1801 d19
20) 0.0000 0.5000 1.516800 63.88
21) 0.0000 1.1100
22) 0.0000 1.5900 1.516800 63.88
23) 0.0000 0.3000
24) 0.0000 0.7000 1.516800 63.88
25) 0.0000 0.7000
Image plane ∞

[Aspherical data]
Surface number: 4
κ = 0.3573
A4 = -9.54944E-05
A6 = −1.11506E−06

Surface number: 7
κ = −2.8492
A4 = 5.47237E−04

[Various data]
f 7.54
FNO 2.87
2ω 94.6813
Y 8.00
TL 52.5000
Air conversion BF 13.6100

[Variable interval data]
Shooting magnification Infinity focusing Near focus f or β 7.54 -0.04762
d 0 ∞ 147.5000
d10 3.20000 2.79264
d19 9.65999 10.06735

[Lens group data]
Start surface Focal length
G1 1 21.18033
G2 12 17.87158
Gn 1 -230.78443

[Values for each conditional expression]
(1) (−fn) /f=1.39257
(2) | f1 / f2 | = 1.1.8514
(3) | fn / f1 | = 0.495743
(4) | fn / f2 | = 0.587525

  12A and 12B are graphs showing various aberrations of the photographic lens OS6 according to the sixth example. FIG. 12A shows the time when an object at infinity is in focus, and FIG. 12B shows the time when a short distance object is focused.

  From each aberration diagram, it can be seen that the taking lens OS6 according to Example 6 has various aberrations corrected well and has excellent optical performance.

  As described above, according to each of the above embodiments, an optical system having high optical performance can be realized. The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  Although a two-group configuration is shown as a numerical example of the optical system of the present invention, the present invention is not limited to this, and an optical system of another group configuration (for example, three groups) can be configured. Specifically, a configuration in which a lens or a lens group is added to the most object side of the optical system of the present invention, or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group indicates a portion having at least one lens separated by an air interval.

  In the optical system of the present invention, the focus lens group can be applied to autofocus, and is also suitable for driving by an autofocus motor such as an ultrasonic motor.

  Further, in the optical system of the present invention, the blur detection system for detecting the blur of the lens system due to camera shake or the like is combined with the driving means, and one lens group or a partial lens group has a component in a direction perpendicular to the optical axis. It is possible to function as an anti-vibration photographic lens that corrects image blur caused by camera shake by moving the lens so as to hold it or by rotating (swinging) it in the in-plane direction including the optical axis.

  The lens surface of the lens constituting the optical system of the present invention 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 facilitated, 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 aspheric, any of aspherical surfaces by grinding, a glass mold aspherical surface formed by molding glass into an aspherical surface, or a composite aspherical surface formed by forming resin on the glass surface into an aspherical surface An aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In addition, the aperture stop S of the optical system of the present invention is preferably disposed between the first lens group G1 and the second lens group G2, but instead of providing a member as an aperture stop, its role is replaced by a lens frame. You may do it.

  Further, an antireflection film having a high transmittance in a wide wavelength range may be provided on the lens surface of the lens constituting the optical system of the present invention. Thereby, flare and ghost can be reduced and high contrast optical performance can be achieved.

  Next, an imaging apparatus provided with the optical system according to the present invention will be described.

  FIG. 13 is a diagram showing a configuration of a camera provided with the optical system according to the present invention. As shown in FIG. 13, the camera 1 is a so-called mirrorless camera of an interchangeable lens provided with the optical system OS <b> 1 according to the first embodiment as the photographing lens 2. In the camera 1, light from an object (not shown) (not shown) is collected by the photographing lens 2 and forms a subject image on the imaging surface of the imaging unit 3 via an optical low-pass filter (not shown). Then, the subject image is photoelectrically converted by the photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed on the electronic viewfinder 4 provided in the camera 1. Thus, the photographer can observe the subject through the electronic viewfinder 4.

  When a release button (not shown) is pressed by the photographer, an image photoelectrically converted by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1.

  Here, the optical system OS1 according to the first embodiment mounted as the photographing lens 2 on the camera 1 is an optical system having high optical performance with little aberration variation from the infinite object focusing state to the short distance object focusing state. It is. Therefore, the camera 1 having high optical performance can be realized.

  Note that even if a camera in which any one of OS2 to OS6 according to the second to sixth embodiments is mounted as the photographing lens 2, the same effect as the camera 1 can be obtained. In this embodiment, an example of a mirrorless camera has been described. However, the photographic lens according to each of the above embodiments is mounted on a single-lens reflex camera that has a quick return mirror in the camera body and observes a subject with a finder optical system. Even in this case, the same effect as the camera 1 can be obtained.

  Next, a method for manufacturing an optical system according to the present invention will be described. FIG. 14 is a diagram showing an outline of a method for manufacturing an optical system according to the present invention.

The optical system manufacturing method according to the present invention is a method of manufacturing an optical system having a first lens group, an aperture stop, and a second lens group in order from the object side along the optical axis. As shown, the following steps S1 to S3 are included.
Step S1: The first lens group is configured to include a partial lens group composed of three or more negative lens components that are sequentially arranged from the object side.
Step S2: The second lens group is moved along the optical axis to perform focusing from an object at infinity to an object at a short distance.
Step S3: Configure so as to satisfy the following conditional expression (1).
(1) 1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

  According to the method for manufacturing a variable magnification optical system of the present invention, it is possible to manufacture a photographic lens having good optical performance and focusing performance from an infinitely focused object state to a short-distance object focused state.

OS Optical system G1 First lens group G2 Second lens group Gn Partial lens group S Aperture stop I Image plane 1 Camera 2 Shooting lens 3 Shooting unit 4 Electronic viewfinder

Claims (13)

In order from the object side along the optical axis, the first lens group, an aperture stop, and a second lens group,
The first lens group includes a partial lens group composed of three or more negative lens components arranged sequentially in order from the object side,
By moving the second lens group along the optical axis, focusing from an infinite object to a close object,
An optical system characterized by satisfying the following formula.
1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system The optical system according to claim 1, wherein a condition of the following formula is satisfied.
0.50 <| f1 / f2 | <5.50
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group The optical system according to claim 1, wherein a condition of the following formula is satisfied.
0.10 <| fn / f1 | <1.00
However,
fn: focal length of the partial lens group f1: focal length of the first lens group The optical system according to any one of claims 1 to 3, wherein a condition of the following formula is satisfied.
0.10 <| fn / f2 | <1.00
However,
fn: focal length of the partial lens group f2: focal length of the second lens group   The optical system according to any one of claims 1 to 4, wherein the second lens group has a positive refractive power.   The optical system according to any one of claims 1 to 5, wherein the first lens group has a positive refractive power.   The optical system according to claim 1, wherein the first lens group has negative refractive power.   8. The optical system according to claim 1, wherein all of the three or more negative lenses constituting the partial lens group have a negative meniscus shape. 9.   2. The partial lens group according to claim 1, wherein the negative lens closest to the object side and the negative lens adjacent to the image side of the negative lens closest to the object have a negative meniscus shape with a convex surface facing the object side. The optical system according to any one of 1 to 8.   The optical system according to any one of claims 1 to 9, wherein the second lens group includes at least one cemented lens.   The optical system according to claim 1, wherein the partial lens group includes at least one aspheric lens.   An imaging apparatus comprising the optical system according to any one of claims 1 to 11. A method of manufacturing an optical system having a first lens group, an aperture stop, and a second lens group in order from the object side along the optical axis,
The first lens group is configured to include a partial lens group including three or more negative lens components sequentially arranged from the object side.
By moving the second lens group along the optical axis, it is configured to focus from an object at infinity to a near object,
A method for manufacturing an optical system, characterized by satisfying the following formula.
1.13 <(− fn) / f <1.65
However,
fn: focal length of the partial lens group f: focal length of the optical system

Images