WO2012169154A1 - Lens assembly and camera - Google Patents

Abstract

Provided is a lens assembly and a camera comprising the lens assembly, said lens assembly being formed from a plurality of lens groups which are positioned in order from the object side to the image side. The intervals between the lens groups are mutually changed, with at least either zoom or focus being possible. The lens groups are respectively configured of at least one lens element. The lens group which is positioned closest to the image side is configured of one lens element. In at least one lens surface of the lens element which configures the lens group which is positioned closest to the image side, the following condition is satisfied: R < 0.2, where R is an energy reflection rate (expressed as a percentage) with respect to a line (d).

Description

Lens system and camera

The technology disclosed here relates to a lens system and a camera.

Conventionally, various lens systems used for cameras and the like have been proposed. In the lens system, it is important to reduce ghosts and flares.

Patent Document 1 discloses a photographing lens in which ghost and flare are further reduced. Patent Document 1 discloses an antireflection film whose reflectance is suppressed to 0.2% or less.

JP 2009-139416 A

However, a film that lowers the reflectivity, such as the antireflection film disclosed in Patent Document 1, is difficult to mold and the cost of film formation is high. For this reason, when such a film is formed on a large number of surfaces of the lens constituting the lens system, the manufacturing cost of the lens system increases.

On the other hand, if the surface that is the main cause of ghost generation can be identified, the generation of ghost can be suppressed at low cost by forming a film with low reflectance on the surface. However, it is still unclear what causes ghosts for what lens system.

The technique disclosed herein aims to suppress the generation of ghosts at a low cost in a lens system that satisfies specific conditions.

(I) One of the above objects is achieved by the following lens system. The lens system is
Consists of a plurality of lens groups arranged in order from the object side to the image side,
The at least one of zooming and focusing can be performed by changing a distance between the lens groups.
Each of the lens groups is composed of at least one lens element,
The lens group arranged on the most image side of the lens group is composed of one lens element,
On at least one lens surface of the lens elements constituting the lens group disposed on the most image side, the following condition (1):
R <0.2 (1)
(here,
R: Energy reflectance for d-line (%)
Is)
Is satisfied.

One of the above objects is achieved by the following camera. The camera
It consists of a plurality of lens groups arranged in order from the object side to the image side,
The at least one of zooming and focusing can be performed by changing a distance between the lens groups.
Each of the lens groups is composed of at least one lens element,
The lens group arranged on the most image side of the lens group is composed of one lens element,
On at least one lens surface of the lens elements constituting the lens group disposed on the most image side, the following condition (1):
R <0.2 (1)
(here,
R: Energy reflectance for d-line (%)
Is)
A lens system characterized by satisfying
An image sensor that receives an optical image formed by the lens system and converts it into an electrical image signal.

(II) One of the above objects is achieved by the following lens system. The lens system is
Consists of a plurality of lens groups arranged in order from the object side to the image side,
The at least one of zooming and focusing can be performed by changing a distance between the lens groups.
Each of the lens groups is composed of at least one lens element,
The lens group arranged on the most image side of the lens group is composed of one lens element,
The energy reflectance with respect to d-line of at least one lens surface of the lens elements constituting the lens group disposed on the most image side is the reflectance with respect to d-line of all lens surfaces of the lens elements included in the lens system. Characterized by the lowest.

One of the above objects is achieved by the following camera. The camera
Consists of a plurality of lens groups arranged in order from the object side to the image side,
The at least one of zooming and focusing can be performed by changing a distance between the lens groups.
Each of the lens groups is composed of at least one lens element,
The lens group arranged on the most image side of the lens group is composed of one lens element,
The energy reflectance with respect to d-line of at least one lens surface of the lens elements constituting the lens group disposed on the most image side is the reflectance with respect to d-line of all lens surfaces of the lens elements included in the lens system. A lens system characterized by the lowest,
An image sensor that receives an optical image formed by the lens system and converts it into an electrical image signal.

According to the technology disclosed herein, it is possible to suppress the generation of ghosts at a low cost in a lens system that satisfies specific conditions.

FIG. 1 is a lens arrangement diagram illustrating an infinitely focused state of the zoom lens system according to Embodiment 1 (Numerical Example 1). FIG. 2 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 1 when the zoom lens system is in focus at infinity. FIG. 3 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 1 in the close object in-focus state. 4 is a lateral aberration diagram in a basic state where image blur correction is not performed and in an image blur correction state at the telephoto end of the zoom lens system according to Numerical Example 1. FIG. FIG. 5 is a lens arrangement diagram of the inner focus lens according to Embodiment 2 (Numerical Example 2) in an infinitely focused state. FIG. 6 is a longitudinal aberration diagram of the inner focus lens according to Numerical Example 2 in a focused state at infinity. FIG. 7 is a lens layout diagram illustrating an infinitely focused state of the zoom lens system according to Embodiment 3 (Numerical Example 3). FIG. 8 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 3 when the zoom lens system is in focus at infinity. FIG. 9 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 3 in the close object in-focus state. FIG. 10 is a lateral aberration diagram in a basic state where image blur correction is not performed and in an image blur correction state at the telephoto end of a zoom lens system according to Numerical Example 3. FIG. 11 is a schematic configuration diagram of a camera system according to the fourth embodiment. FIG. 12 is a schematic configuration diagram of a camera according to the fifth embodiment.

<Embodiment 1>
FIG. 1 is a lens arrangement diagram of the zoom lens system according to Embodiment 1, and represents the zoom lens system in an infinite focus state.

1A shows a lens configuration at the wide-angle end (shortest focal length state: focal length f _W ), and FIG. 1B shows an intermediate position (intermediate focal length state: focal length f _M = √ (f _W * f). The lens configuration of _T )) and (c) show the lens configuration at the telephoto end (longest focal length state: focal length f _T ). Further, in FIG. 1, the broken line arrows provided between FIGS. 1A and 1B are obtained by connecting the positions of the lens groups in the wide-angle end, the intermediate position, and the telephoto end in order from the top. Straight line. The wide-angle end and the intermediate position, and the intermediate position and the telephoto end are simply connected by a straight line, which is different from the actual movement of each lens group.

Further, in FIG. 1, an arrow attached to the lens group represents focusing from an infinitely focused state to a close object focused state. That is, FIG. 1 shows a direction in which a later-described fourth lens group G4 moves during focusing from the infinite focus state to the close object focus state. In FIG. 1, since the reference numerals of the respective lens groups are shown in FIG. 1A, for the sake of convenience, an arrow indicating focusing is attached below the reference numerals of the respective lens groups. However, in each zooming state, The direction in which each lens group moves during focusing will be described in detail later.

The zoom lens system according to Embodiment 1 includes, in order from the object side to the image side, a first lens group G1 having a positive power, a second lens group G2 having a negative power, and a first lens group having a positive power. A third lens group G3; a fourth lens group G4 having negative power; a fifth lens group G5 having negative power; and a sixth lens group G6 having positive power. In the zoom lens system according to Embodiment 1, during zooming, the distance between the lens groups, that is, the distance between the first lens group G1 and the second lens group G2, the second lens group G2 and the third lens group G3, The distance between the third lens group G3 and the fourth lens group G4, the distance between the fourth lens group G4 and the fifth lens group G5, and the distance between the fifth lens group G5 and the sixth lens group G6. Also, the second lens group G2, the fourth lens group G4, and the fifth lens group G5 move in the direction along the optical axis so as to change. In the zoom lens system according to Embodiment 1, by making these lens groups have a desired power arrangement, the entire lens system can be reduced in size while maintaining high optical performance.

In FIG. 1, an asterisk * attached to a specific surface indicates that the surface is aspherical. In FIG. 1, a symbol (+) and a symbol (−) attached to a symbol of each lens group correspond to a power symbol of each lens group. In each figure, the straight line described on the rightmost side represents the position of the image plane S.

As shown in FIG. 1, the first lens group G1 includes, in order from the object side to the image side, a biconvex first lens element L1 and a negative meniscus second lens element L2 with a convex surface facing the object side. And a positive meniscus third lens element L3 having a convex surface facing the object side. Among these, the second lens element L2 and the third lens element L3 are cemented.

The second lens group G2 includes, in order from the object side to the image side, a negative meniscus fourth lens element L4 with a convex surface facing the object side, and a positive meniscus fifth lens element L5 with a convex surface facing the object side. And a biconcave sixth lens element L6. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented.

The third lens group G3 includes, in order from the object side to the image side, a biconvex seventh lens element L7, a negative meniscus eighth lens element L8 with a convex surface facing the object side, and a convex surface facing the object side. It comprises a positive meniscus ninth lens element L9 directed, a biconvex tenth lens element L10, and a negative meniscus eleventh lens element L11 with a convex surface facing the image side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented, and the tenth lens element L10 and the eleventh lens element L11 are cemented. The seventh lens element L7 has two aspheric surfaces, and the tenth lens element L10 has an aspheric object side surface. Further, an aperture stop A is provided between the seventh lens element L7 and the eighth lens element L8.

The fourth lens group G4 comprises solely a negative meniscus twelfth lens element L12 with the convex surface facing the object side.

The fifth lens group G5 comprises solely a bi-concave thirteenth lens element L13.

The sixth lens group G6 comprises solely a biconvex fourteenth lens element L14.

In the zoom lens system according to Embodiment 1, the tenth lens element L10 and the eleventh lens element L11 in the third lens group G3 are arranged on the optical axis to optically correct image blur, which will be described later. This corresponds to an image blur correction lens group that moves in the vertical direction.

In the zoom lens system according to Embodiment 1, during zooming from the wide-angle end to the telephoto end during imaging, the second lens group G2 monotonously moves toward the image side, and the fourth lens group G4 moves toward the image side. The fifth lens group G5 moves to the object side substantially monotonously, and the first lens group G1, the third lens group G3, and the sixth lens group G6 move relative to the image plane S. Is fixed. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 and the distance between the fifth lens group G5 and the sixth lens group G6 increase, and the second lens group G2 and the third lens group G3 And the fourth lens group G4 and the fifth lens group G5 are decreased, and the distance between the third lens group G3 and the fourth lens group G4 is changed. The group G4 and the fifth lens group G5 move along the optical axis.

Furthermore, in the zoom lens system according to Embodiment 1, the fourth lens group G4 moves toward the image side along the optical axis in any zooming state when focusing from the infinitely focused state to the close object focused state. Moving.

ここで、
Ｚ：光軸からの高さがｈの非球面上の点から、非球面頂点の接平面までの距離、
ｈ：光軸からの高さ、
ｒ：頂点曲率半径、
κ：円錐定数、
Ａｎ：ｎ次の非球面係数
である。 Next, Numerical Example 1 in which the zoom lens system according to Embodiment 1 is specifically implemented will be described. In Numerical Example 1, the units of length in the table are all “mm”, and the units of angle of view are all “°”. In Numerical Example 1, r is a radius of curvature, d is a surface interval, nd is a refractive index with respect to the d line, and νd is an Abbe number with respect to the d line. In Numerical Example 1, the surface marked with * is an aspheric surface, and the aspheric surface shape is defined by the following equation (AC).

here,
Z: distance from a point on the aspheric surface having a height h from the optical axis to the tangent plane of the aspheric vertex,
h: height from the optical axis,
r: vertex radius of curvature,
κ: conic constant,
An: n-order aspherical coefficient.

FIG. 2 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 1 in a focused state at infinity.

FIG. 3 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 1 in the close object in-focus state. The object distance in Numerical Example 1 is 1887 mm.

In each longitudinal aberration diagram, (a) shows the aberration at the wide angle end, (b) shows the intermediate position, and (c) shows the aberration at the telephoto end. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left side. In the spherical aberration diagram, the vertical axis represents the F number (indicated by F in the figure), the solid line is the d line (wavelength: 587.6 nm, d-line), and the short broken line is the F line (wavelength: 486.1 nm, F -Line) and the long broken line are the characteristics of the C-line (wavelength: 656.3 nm, C-line). In the astigmatism diagram, the vertical axis represents the image height (indicated by H in the figure), the solid line represents the sagittal plane (indicated by s), and the broken line represents the meridional plane (indicated by m in the figure). is there. In the distortion diagram, the vertical axis represents the image height (indicated by H in the figure).

4 is a lateral aberration diagram in a basic state where image blur correction is not performed and in an image blur correction state at the telephoto end of the zoom lens system according to Numerical Example 1. FIG.

In the lateral aberration diagram, the upper three aberration diagrams show the basic state in which image blur correction is not performed at the telephoto end, and the lower three aberration diagrams show the image blur correction lens group moved by a predetermined amount in a direction perpendicular to the optical axis. Each corresponds to the image blur correction state at the telephoto end. Of the lateral aberration diagrams in the basic state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the lateral aberration at the image point of -70% of the maximum image height. Respectively. Of each lateral aberration diagram in the image blur correction state, the upper stage is the lateral aberration at the image point of 70% of the maximum image height, the middle stage is the lateral aberration at the axial image point, and the lower stage is at the image point of -70% of the maximum image height. Each corresponds to lateral aberration. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line ( C-line) characteristics. In each lateral aberration diagram, the meridional plane is a plane including the optical axis of the first lens group G1 and the optical axis of the third lens group G3.

In the zoom lens system of Numerical Example 1, the moving amount in the direction perpendicular to the optical axis of the image blur correction lens group in the image blur correction state at the telephoto end is 0.300 mm.

When the shooting distance is ∞ and the zoom lens system is tilted by a predetermined angle at the telephoto end, the image decentering amount is the image when the image blur correction lens group translates by the above values in the direction perpendicular to the optical axis. Equal to eccentricity.

As is apparent from the lateral aberration diagram, it is understood that the symmetry of the lateral aberration at the axial image point is good. In addition, when the lateral aberration at the + 70% image point and the lateral aberration at the −70% image point are compared in the basic state, the curvature is small and the inclinations of the aberration curves are almost equal. It can be seen that the aberration is small. This means that sufficient imaging performance is obtained even in the image blur correction state. When the image blur correction angle of the zoom lens system is the same, the amount of parallel movement required for image blur correction decreases as the focal length of the entire zoom lens system decreases. Therefore, at any zoom position, it is possible to perform sufficient image blur correction without deteriorating the imaging characteristics with respect to the image blur correction angle up to a predetermined angle.

(Numerical example 1)
The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. Table 1 shows surface data of the zoom lens system of Numerical Example 1, Table 2 shows aspheric data, Table 3 shows various data in the infinite focus state, and Table 4 shows various data in the close object in focus state. Shown in

Table 1 (surface data)

Surface number r d nd vd Effective radius
Object ∞
1 52.40790 4.16040 1.48749 70.4 15.284
2 -409.46720 0.15000 14.986
3 38.20510 1.00000 1.85026 32.3 14.051
4 25.19230 5.00000 1.49700 81.6 13.459
5 129.07560 Variable 13.129
6 3610.88200 0.80000 1.80610 33.3 8.154
7 13.09000 2.75540 1.94595 18.0 7.378
8 25.71900 1.82700 6.973
9 -42.76750 0.70000 1.80420 46.5 6.914
10 86.12560 Variable 6.866
11 * 17.89940 4.44090 1.73077 40.5 8.919
12 * -551.13770 1.50000 8.705
13 (Aperture) ∞ 1.84 180 8.312
14 47.14250 0.80000 1.90366 31.3 7.712
15 12.32910 3.27170 1.48749 70.4 7.201
16 33.57730 1.60000 7.077
17 * 21.15520 4.77640 1.58913 61.3 7.251
18 -20.47470 0.70000 1.76182 26.6 7.095
19 -32.11930 Variable 7.096
20 41.83650 0.70000 1.77250 49.6 6.404
21 15.88470 Variable 6.160
22 -25.74280 0.80000 1.80420 46.5 7.366
23 157.00800 Variable 7.787
24 48.74570 3.86270 1.84666 23.8 10.768
25 -62.66020 (BF) 10.901
Image plane ∞

Table 2 (Aspheric data)

11th surface K = 0.00000E + 00, A4 = -1.40838E-05, A6 = -3.36993E-08, A8 = -7.27662E-10
A10 = -1.68262E-11
12th surface K = 0.00000E + 00, A4 = 5.37846E-06, A6 = 6.25748E-08, A8 = -3.61395E-09
A10 = 3.00574E-12
17th surface K = 0.00000E + 00, A4 = -2.54955E-05, A6 = 1.56273E-07, A8 = -6.17885E-09
A10 = 5.91994E-11

Table 3 (Various data in focus at infinity)

Zoom ratio 4.12019
Wide angle Medium telephoto Focal length 41.1999 83.6183 169.7513
F number 4.12035 4.94425 5.76854
Angle of view 15.0728 7.2789 3.5687
Image height 10.8150 10.8150 10.8150
Total lens length 113.00 113.00 113.00
BF 15.05 15.05 15.05
d5 1.2806 16.2389 29.2395
d10 29.1045 14.1462 1.1455
d19 2.6014 6.5190 2.6000
d21 22.7760 16.2979 15.5666
d23 1.5000 4.0605 8.7109

Zoom lens group data Group Start surface Focal length 1 1 65.47364
2 6 -18.35878
3 11 21.26021
4 20 -33.54315
5 22 -27.44782
6 24 32.90549

Table 4 (Various data in the state of focusing on a close object)

Zoom ratio 3.66941
Wide angle Medium telephoto Object distance 1887.0000 1887.0000 1887.0000
Focal length 40.6198 79.4226 149.0505
F number 4.13170 4.96652 5.89019
Angle of view 15.0401 7.2497 3.4904
Image height 10.8150 10.8150 10.8150
Total lens length 113.00 113.00 113.00
BF 15.05 15.05 15.05
d5 1.2806 16.2389 29.2395
d10 29.1045 14.1462 1.1455
d19 2.7907 7.4215 5.9664
d21 22.5867 15.3954 12.2002
d23 1.5000 4.0605 8.7109

Zoom lens group data Group Start surface Focal length 1 1 65.47364
2 6 -18.35878
3 11 21.26021
4 20 -33.54315
5 22 -27.44782
6 24 32.90549

<Embodiment 2>
FIG. 5 is a lens arrangement diagram of the inner focus lens according to Embodiment 2 in an infinitely focused state.

The inner focus lens according to Embodiment 2 includes, in order from the object side to the image side, a first lens group G1 having a positive power, a second lens group G2 having a negative power, and a third lens having a positive power. It consists of a lens group G3.

The first lens group G1 includes, in order from the object side to the image side, a positive meniscus first lens element L1 having a convex surface facing the object side, and a negative meniscus second lens having a concave surface with a strong curvature on the image side. A cemented lens element of an element L2, an aperture stop A, a biconcave third lens element L3 having a concave surface with a strong curvature on the object side, and a biconvex fourth lens element L4, and an image side surface is aspheric. It is composed of a biconvex fifth lens element L5.

The second lens group G2 is composed of only a biconcave sixth lens element L6 having aspherical surfaces on both sides and a concave surface with a strong curvature on the image side. By moving the second lens group G2 to the image side along the optical axis, focusing from the infinity object side to the near object side is performed.

The third lens group G3 includes only a biconvex seventh lens element L7.

Hereinafter, Numerical Example 2 in which the inner focus lens according to Embodiment 2 is specifically implemented will be described. In Numerical Example 2, the units of length in the table are all “mm”, and the units of angle of view are all “°”. In Numerical Example 2, “surface number” is the i-th surface counted from the object side, “r” is the paraxial radius of curvature of the i-th surface from the object side, and “d” is the i-th surface. Is the refractive index with respect to the d-line of the glass material having the i-th surface on the object side, and “vd” is the d-line of the glass material having the i-th surface on the object side. The Abbe numbers for are respectively shown. “Variable” indicates that the shaft upper surface interval is a variable interval. Further, the surface with “*” after the surface number i is an aspherical surface, and the aspherical shape is defined by the formula (AC).

FIG. 6 is a longitudinal aberration diagram of the inner focus lens according to Numerical Example 2 in a focused state at infinity. Each longitudinal aberration diagram shows spherical aberration, astigmatism, and distortion aberration in order from the left side. In the spherical aberration diagram, the vertical axis represents the ratio to the open F number, the horizontal axis represents defocus, the solid line is d-line, the long broken line is C line (C-line), and the short broken line is F line ( F-line) represents spherical aberration. In the astigmatism diagram, the vertical axis is the image height, the horizontal axis is the focus, the solid line is the sagittal image plane (indicated by s), and the broken line is the astigmatism of the meridional image plane (indicated by m in the figure). Represent. In the distortion diagram, the vertical axis represents the image height, and the distortion is expressed in%.

(Numerical example 2)
The inner focus lens of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. Table 5 shows lens data of the inner focus lens of Numerical Example 2.

Table 5 (Lens data)

Surface data Surface number r d nd vd Effective radius
Object ∞
1 18.74540 4.20230 1.88300 40.8 10.699
2 68.34600 0.58830 9.850
3 39.42090 1.20000 1.51198 54.6 8.840
4 10.02710 5.97820 7.316
5 (Aperture) ∞ 5.64000 6.953
6 -11.03380 1.00000 1.80518 25.5 7.078
7 34.67830 6.54960 1.88300 40.8 8.805
8 -17.84130 0.10000 9.665
9 37.38830 4.20550 1.80139 45.4 10.100
10 * -32.91630 Variable 10.092
11 * -126.83080 1.00000 1.68893 31.2 9.000
12 * 27.17400 Variable 9.092
13 114.19150 3.92620 1.83480 42.7 10.974
14 -33.79120 (BF) 11.194
Image plane ∞

Aspheric data 10th surface K = 0.00000E + 00, A4 = 2.11487E-05, A6 = -4.74672E-08, A8 = 2.19448E-10
A10 = -5.03837E-13, A12 = 0.00000E + 00
11th surface K = 0.00000E + 00, A4 = 3.62979E-05, A6 = -4.48579E-07, A8 = 2.76766E-09
A10 = -7.32635E-12, A12 = 2.28019E-15
12th surface K = 0.00000E + 00, A4 = 4.29240E-05, A6 = -4.05961E-07, A8 = 2.90164E-09
A10 = -1.27839E-11, A12 = 3.16035E-14

Various data Focal length 25.6692
F number 1.44319
Angle of View 22.9335
Statue height 10.8150
Total lens length 60.5607
BF 18.03332

Interval data d0 ∞ 938 238
d10 1.9100 2.5773 4.5173
d12 6.2273 5.5599 3.6200

Single lens data Lens Start surface Focal length 1 1 28.1345
2 3 -26.6341
3 6 -10.2953
4 7 14.1701
5 9 22.4406
6 11 -32.3981
7 13 31.6167

Lens group data Group Start surface Focal length Lens composition length Front principal point position Rear principal point position 1 1 23.59025 29.46390 28.45049 28.34207
2 11 -32.39815 1.00000 0.48633 0.89580
3 13 31.61672 3.92620 1.67140 3.43160

Lens group magnification Group Start surface ∞ 1000 300
1 1 0.00000 -0.02502 -0.09714
2 11 2.62843 2.61210 2.56276
3 13 0.41398 0.41324 0.41140

<Embodiment 3>
FIG. 7 is a lens arrangement diagram of the zoom lens system according to Embodiment 3, and represents the zoom lens system in the infinitely focused state.

7A shows a lens configuration at the wide angle end (shortest focal length state: focal length f _W ), and FIG. 7B shows an intermediate position (intermediate focal length state: focal length f _M = √ (f _W * f). The lens configuration of _T )) and (c) show the lens configuration at the telephoto end (longest focal length state: focal length f _T ). In FIG. 7, the broken line arrows provided between FIGS. 7A and 7B are obtained by connecting the positions of the lens groups in the wide-angle end, intermediate position, and telephoto end states in order from the top. Straight line. The wide-angle end and the intermediate position, and the intermediate position and the telephoto end are simply connected by a straight line, which is different from the actual movement of each lens group.

Further, in FIG. 7, an arrow attached to the lens group represents focusing from an infinitely focused state to a close object focused state. That is, FIG. 7 shows a direction in which a third lens group G3, which will be described later, moves during focusing from the infinite focus state to the close object focus state. In FIG. 7, since the reference numerals of the respective lens groups are described in FIG. 7A, for convenience, an arrow indicating focusing is attached below the reference numerals of the respective lens groups. In each zooming state, The direction in which each lens group moves during focusing will be described in detail later.

The zoom lens system according to Embodiment 3 includes, in order from the object side to the image side, a first lens group G1 having negative power, a second lens group G2 having positive power, and a first lens group having negative power. 3 lens group G3 and 4th lens group G4 which has positive power are provided. In the zoom lens system according to Embodiment 3, during zooming, the distance between the lens groups, that is, the distance between the first lens group G1 and the second lens group G2, the second lens group G2 and the third lens group G3, The first lens group G1, the second lens group G2, and the third lens group G3 are in a direction along the optical axis so that the distance between the third lens group G3 and the fourth lens group G4 changes. Move to each. In the zoom lens system according to Embodiment 3, these lens groups are arranged in a desired power arrangement, so that the entire lens system can be reduced in size while maintaining high optical performance.

In FIG. 7, an asterisk * attached to a specific surface indicates that the surface is aspherical. In FIG. 7, a symbol (+) and a symbol (−) attached to a symbol of each lens group correspond to a power symbol of each lens group. In each figure, the straight line described on the rightmost side represents the position of the image plane S.

As shown in FIG. 7, the first lens group G1 includes, in order from the object side to the image side, a negative meniscus first lens element L1 having a convex surface facing the object side, and a negative meniscus having a convex surface facing the image side. It comprises a second lens element L2 having a shape and a third lens element L3 having a positive meniscus shape with a convex surface facing the object side. Among these, the first lens element L1 has an aspheric image side surface, and the second lens element L2 has both aspheric surfaces.

The second lens group G2 includes, in order from the object side to the image side, a biconvex fourth lens element L4, a negative meniscus fifth lens element L5 with a convex surface facing the object side, and a biconvex second lens element L5. 6 lens elements L6 and a biconvex seventh lens element L7. Among these, the fifth lens element L5 and the sixth lens element L6 are cemented. The fourth lens element L4 has two aspheric surfaces. Furthermore, an aperture stop A is provided between the fourth lens element L4 and the fifth lens element L5.

The third lens group G3 comprises solely a negative meniscus eighth lens element L8 with the convex surface facing the object side. The eighth lens element L8 has two aspheric surfaces.

The fourth lens group G4 comprises solely a biconvex ninth lens element L9. The ninth lens element L9 has two aspheric surfaces.

In the zoom lens system according to Embodiment 3, the seventh lens element L7 in the second lens group G2 moves in the direction perpendicular to the optical axis to optically correct image blur, which will be described later. This corresponds to the image blur correction lens group.

In the zoom lens system according to Embodiment 3, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 moves along a locus convex toward the image side, and the second lens group G2 Is monotonously moved to the object side, the third lens group G3 is monotonously slightly moved to the object side, and the fourth lens group G4 is fixed with respect to the image plane S. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the fourth lens. The first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis so that the distance from the group G4 changes.

Further, in the zoom lens system according to Embodiment 3, the third lens group G3 moves toward the image side along the optical axis in any zooming state during focusing from the infinitely focused state to the close object focused state. Moving.

Next, Numerical Example 3 in which the zoom lens system according to Embodiment 3 is specifically implemented will be described. In Numerical Example 3, the unit of length in the table is “mm”, and the unit of angle of view is “°”. In Numerical Example 3, r is a radius of curvature, d is a surface interval, nd is a refractive index with respect to the d line, and νd is an Abbe number with respect to the d line. In Numerical Example 3, the surface marked with * is an aspherical surface, and the aspherical shape is defined by the formula (AC).

FIG. 8 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 3 when the zoom lens system is in focus at infinity.

FIG. 9 is a longitudinal aberration diagram of the zoom lens system according to Numerical Example 3 in the close object in-focus state. In addition, the object distance in Numerical Example 3 is 300 mm.

In each longitudinal aberration diagram, (a) shows the aberration at the wide angle end, (b) shows the intermediate position, and (c) shows the aberration at the telephoto end. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left side. In the spherical aberration diagram, the vertical axis represents the F number (indicated by F in the figure), the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line (C- line). In the astigmatism diagram, the vertical axis represents the image height (indicated by H in the figure), the solid line represents the sagittal plane (indicated by s), and the broken line represents the meridional plane (indicated by m in the figure). is there. In the distortion diagram, the vertical axis represents the image height (indicated by H in the figure).

FIG. 10 is a lateral aberration diagram in a basic state where image blur correction is not performed and in an image blur correction state at the telephoto end of the zoom lens system according to Numerical Example 3.

In the lateral aberration diagram, the upper three aberration diagrams show the basic state in which image blur correction is not performed at the telephoto end, and the lower three aberration diagrams show the image blur correction lens group moved by a predetermined amount in a direction perpendicular to the optical axis. Each corresponds to the image blur correction state at the telephoto end. Of the lateral aberration diagrams in the basic state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the lateral aberration at the image point of -70% of the maximum image height. Respectively. Of each lateral aberration diagram in the image blur correction state, the upper stage is the lateral aberration at the image point of 70% of the maximum image height, the middle stage is the lateral aberration at the axial image point, and the lower stage is at the image point of -70% of the maximum image height. Each corresponds to lateral aberration. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line ( C-line) characteristics. In each lateral aberration diagram, the meridional plane is a plane including the optical axis of the first lens group G1 and the optical axis of the second lens group G2.

In the zoom lens system of Numerical Example 3, the amount of movement of the image blur correction lens group in the image blur correction state at the telephoto end in the direction perpendicular to the optical axis is 0.187 mm.

When the shooting distance is ∞ and the zoom lens system is tilted by 0.3 ° at the telephoto end, the image decentering amount is the value when the image blur correction lens group translates by the above values in the direction perpendicular to the optical axis. Equal to image eccentricity.

As is apparent from the lateral aberration diagram, it is understood that the symmetry of the lateral aberration at the axial image point is good. In addition, when the lateral aberration at the + 70% image point and the lateral aberration at the −70% image point are compared in the basic state, the curvature is small and the inclinations of the aberration curves are almost equal. It can be seen that the aberration is small. This means that sufficient imaging performance is obtained even in the image blur correction state. When the image blur correction angle of the zoom lens system is the same, the amount of parallel movement required for image blur correction decreases as the focal length of the entire zoom lens system decreases. Therefore, at any zoom position, it is possible to perform sufficient image blur correction without deteriorating the imaging characteristics for an image blur correction angle up to 0.3 °.

(Numerical Example 3)
The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. Table 6 shows surface data of the zoom lens system of Numerical Example 3, Table 7 shows aspheric data, Table 8 shows various data in the infinite focus state, and Table 9 shows various data in the close object in focus state. Shown in

Table 6 (surface data)

Surface number r d nd vd Effective radius
Object ∞
1 16.42280 0.80000 1.85400 40.4 8.030
2 * 8.69880 5.35360 6.761
3 * -16.24340 0.50000 1.58700 59.6 6.363
4 * -1000.00000 0.20000 6.236
5 21.90190 1.25200 1.94595 18.0 6.114
6 40.03200 Variable 6.004
7 * 11.89960 2.02150 1.77200 50.0 4.892
8 * -1000.00000 1.00000 4.833
9 (Aperture) ∞ 2.00000 4.526
10 25.47380 0.58990 1.90366 31.3 4.448
11 7.34840 2.70950 1.49700 81.6 4.301
12 -33.68110 1.50000 4.382
13 33.63990 1.20000 1.58144 40.9 4.653
14 -86.34380 Variable 4.636
15 * 89.01190 0.40000 1.77200 50.0 4.227
16 * 10.64130 Variable 4.311
17 * 43.32750 3.19620 1.77200 50.0 9.416
18 * -62.33520 (BF) 9.654
Image plane ∞

Table 7 (Aspherical data)

2nd surface K = 0.00000E + 00, A4 = -3.04224E-05, A6 = -3.39736E-07, A8 = 0.00000E + 00
A10 = 0.00000E + 00
3rd surface K = 0.00000E + 00, A4 = 8.94998E-05, A6 = -1.77785E-06, A8 = 3.92646E-08
A10 = -3.91376E-10
4th surface K = 0.00000E + 00, A4 = 7.11423E-05, A6 = -1.79171E-06, A8 = 2.82400E-08
A10 = -2.93586E-10
7th surface K = 0.00000E + 00, A4 = -4.57043E-05, A6 = -8.52737E-08, A8 = 3.62974E-09
A10 = -1.40385E-09
8th surface K = 0.00000E + 00, A4 = 4.15779E-05, A6 = -2.33061E-07, A8 = -3.98850E-09
A10 = -1.29915E-09
15th surface K = 0.00000E + 00, A4 = 1.00000E-04, A6 = -1.10837E-05, A8 = 2.79906E-07
A10 = -2.65808E-09
16th surface K = 0.00000E + 00, A4 = 1.21515E-04, A6 = -1.15513E-05, A8 = 1.97566E-07
A10 = -9.89769E-10
17th surface K = 0.00000E + 00, A4 = 7.90705E-05, A6 = -1.03130E-06, A8 = 1.21938E-08
A10 = -8.96221E-11
18th surface K = 0.00000E + 00, A4 = 5.73840E-05, A6 = -1.13324E-06, A8 = 1.43220E-08
A10 = -1.00247E-10

Table 8 (Various data in focus at infinity)

Zoom ratio 2.79708
Wide angle Medium telephoto Focal length 14.4901 24.2333 40.5299
F number 3.64071 5.30497 5.82465
Angle of view 40.7465 24.2568 14.8037
Image height 10.8150 10.8150 10.8150
Total lens length 62.5692 57.3716 60.2745
BF 14.1990 14.1990 14.1990
d6 17.0129 6.6327 0.6000
d14 2.1442 6.6384 13.4790
d16 6.4901 7.1788 9.2741

Zoom lens group data Start surface Focal length 1 1 -15.88153
2 7 13.59210
3 15 -15.69064
4 17 33.55220

Table 9 (Various data in the proximity object in-focus state)

Wide angle Medium telephoto Object distance 300.0000 300.0000 300.0000
BF 14.1990 14.1990 14.1990
d6 17.0129 6.6327 0.6000
d14 2.3848 7.3054 15.2480
d16 6.2496 6.5118 7.5052

<Inhibition of ghosting>
Each of the lens systems according to Embodiments 1 to 3 includes a plurality of lens groups arranged in order from the object side to the image side, and changes the mutual distance between the lens groups to perform at least zooming and focusing. Each of the lens groups is composed of at least one lens element. Among the lens groups, the lens group disposed on the most image side (hereinafter also referred to as the most image side lens group) is composed of one lens element.

As in the lens systems according to Embodiments 1 to 3, the most image-side lens unit is composed of one lens element, so that the thickness in the optical axis direction can be minimized, and the lens system can be downsized. Can be realized.

In such a lens system, the main cause of ghosting has been clarified. Specifically, it was found that unnecessary reflected light generated from a member such as an image sensor or a protective glass of the image sensor is reflected again by the most image side lens group, and this reflected light is easily guided to the image sensor. .

Here, as in the lens systems according to Embodiments 1 to 3, if an appropriate power is given to the most image side lens unit, the aberration of the lens system is improved. However, when the most image side lens unit is composed of one lens element, it is necessary to give a strong power to the lens element. In such a case, the influence of the ghost due to the reflection at the most image side lens group is further increased.

Further, when the most image side lens unit is composed of one lens element, the effective radius of the most image side lens unit tends to increase. In such a case, the influence of the ghost due to the reflection at the most image side lens group is further increased.

From these, simulation was performed using the lens systems according to Embodiments 1 to 3 (Numerical Examples 1 to 3). In any of the lens systems of Numerical Examples 1 to 3, the most image side lens unit is composed of one lens element. The simulation results are shown in Table 10 below.

Table 10 (Simulation results)

The “evaluation targets” are as follows.
L14R1: Object side surface R1 of the fourteenth lens element L14 constituting the most image side lens unit.
L13R2: Image side surface R2 of the thirteenth lens element L13
L7R1: Object side surface R1 of the seventh lens element L7 constituting the most image side lens unit
L2R2: Image side surface R2 of the second lens element L2
L9R1: Object side surface R1 of the ninth lens element L9 constituting the most image side lens unit
L2R2: Image side surface R2 of the second lens element L2

In addition, when the lens system to be analyzed is in the wide-angle end and light having a predetermined angle with respect to the optical axis is incident on the lens system, the “ghost intensity” The intensity of the light that is further reflected by the lens surface and incident on the image sensor is quantified.

In the lens system of Numerical Example 1 shown in FIG. 1, a simulation was performed in which 5.0 ° light with respect to the optical axis was incident on the lens system. As a result, the “ghost intensity” generated by the L14R1 reflecting again the unnecessary reflected light from the image sensor is that the lens surface of the lens element other than the fourteenth lens element L14, for example, L13R2, is the unnecessary reflected light from the image sensor. Was about 19.8 times higher than the “ghost intensity” caused by re-reflection.

In the lens system of Numerical Example 2 shown in FIG. 5, a simulation was performed in which 7.5 ° light with respect to the optical axis was incident on the lens system. As a result, the “ghost intensity” generated by the L7R1 reflecting the unnecessary reflected light from the image sensor again is an unnecessary reflected light from the lens surface of the lens elements other than the seventh lens element L7, for example, the L2R2. Was about 3.8 times higher than the “ghost intensity” caused by re-reflection.

In the lens system of Numerical Example 3 shown in FIG. 7, a simulation was performed in which 7.5 ° light with respect to the optical axis was incident on the lens system. As a result, the “ghost intensity” generated by the L9R1 reflecting the unnecessary reflected light from the image sensor again is that the lens surface of the lens element other than the ninth lens element L9, for example L2R2, is the unnecessary reflected light from the image sensor. Was about 8.8 times higher than the “ghost intensity” produced by reflecting the light again.

From these simulation results, in the lens system in which the most image side lens group is composed of one lens element, it is found that the main cause of ghost is reflection by the lens elements constituting the most image side lens group. It was done.

Therefore, in the lens systems according to Embodiments 1 to 3, for example, an antireflection film is formed so that the energy reflectance is relatively low on at least one lens surface of the lens elements constituting the most image side lens group. Has been. Specifically, the following condition (1) is satisfied on at least one lens surface of the lens elements constituting the most image side lens group.
R <0.2 (1)
here,
R: Energy reflectance for d-line (%)
It is.

An antireflection film exhibiting such energy reflectivity can be realized by the technique described in Patent Document 1 and the like, but the antireflection film is difficult to mold and the cost of film formation is high. However, in the lens systems according to Embodiments 1 to 3, the lens surface that is the main cause of the ghost is specified, and the antireflection film is formed on the lens surface. For example, even if an inexpensive antireflection film is formed on other lens surfaces, the occurrence of ghost can be suppressed. That is, in the lens systems according to Embodiments 1 to 3, ghosting can be suppressed at a low cost.

In addition, the energy reflectivity for d-line of at least one lens surface of the lens elements constituting the most image side lens group is the lowest among the reflectivities for d-line of all lens surfaces of the lens elements included in the lens system. . Therefore, for example, even if an expensive antireflection film is formed on the lens surface that is a main cause of ghosting, the ghosting can be suppressed at low cost by forming an inexpensive antireflection film on the other lens surface. be able to.

The effect is more prominent when the following condition (1) ′ is satisfied on at least one lens surface of the lens elements constituting the most image side lens group.
R <0.1 (1) '

The effect is more remarkable when the lens system satisfies the following condition (2).
0.5 <D _eff / H _max <1.4 (2)
here,
D _eff : Effective radius on the object side of the lens elements constituting the most image side lens group,
H _max : The maximum image height of the lens system.

The effect is more remarkable when the lens system satisfies at least one of the following conditions (2) ′ and (2) ″.
0.8 <D _eff / H _max (2) ′
D _eff / H _max <1.1 (2) ''

The effect is more prominent when the lens system satisfies the following condition (3).
f _b / H _max <3.5 (3)
here,
f _b : focal length of the most image side lens unit,
H _max : The maximum image height of the lens system.

The effect is more remarkable when the lens system satisfies the following condition (3) ′.
f _b / H _max <3.2 (3) ′

Table 11 below shows the corresponding values for each condition in the lens system of each numerical example.

Table 11 (corresponding values of conditions)

<Embodiment 4>
FIG. 11 is a schematic configuration diagram of a camera system according to the fourth embodiment.

The camera system 100 according to the fourth embodiment includes a camera body 101 and an interchangeable lens device 201 that is detachably connected to the camera body 101.

The camera body 101 receives an optical image formed by the lens system 202 of the interchangeable lens device 201 and converts it into an electrical image signal, and a display for displaying the image signal converted by the image sensor 102. Part 103 and camera mount part 104. On the other hand, the interchangeable lens device 201 is connected to the lens system 202 according to any of Embodiments 1 to 3, the lens barrel 203 (an example of a holding unit) that holds the lens system 202, and the camera mount unit 104 of the camera body. And a lens mount unit 204 (an example of a mount). The camera mount unit 104 and the lens mount unit 204 electrically connect not only a physical connection but also a controller (not shown) in the camera body 101 and a controller (not shown) in the interchangeable lens device 201. It also functions as an interface that enables mutual signal exchange. In FIG. 11, the configuration illustrated as the lens system 202 is an example, and the lens system according to any embodiment may be used.

In the fourth embodiment, since the lens system 202 according to any one of the first to third embodiments is used, the interchangeable lens device 201 having excellent imaging performance and suppressing the occurrence of ghost can be realized at low cost. . In addition, it is possible to suppress the occurrence of ghost in the entire camera system 100 according to Embodiment 4 at a low cost.

In the technology disclosed here, the camera system is a concept included in the camera.

<Embodiment 5>
FIG. 12 is a schematic configuration diagram of a camera according to the fifth embodiment.

The camera 300 according to the fifth embodiment includes a camera main body 301 and a lens barrel 403 fixed to the camera main body 301.

The camera body 301 receives an optical image formed by the lens system 402 of the lens barrel 403 and converts it into an electrical image signal, and a display for displaying the image signal converted by the image sensor 302 Part 303. On the other hand, the lens barrel 403 holds the lens system 402 according to any of Embodiments 1 to 3 by its holding unit. In FIG. 12, the configuration illustrated as the lens system 402 is an example, and the lens system of any embodiment may be used.

In the fifth embodiment, since the lens system 402 according to any one of the first to third embodiments is used, it is possible to realize the lens barrel 403 that has excellent imaging performance and suppresses the generation of ghosts at low cost. . In addition, it is possible to suppress the occurrence of ghost in the entire camera 300 according to Embodiment 5 at a low cost.

The lens system disclosed herein can be applied to a digital still camera, a digital video camera, a camera of a portable information terminal such as a smartphone, a surveillance camera in a surveillance system, a web camera, an in-vehicle camera, and the like. It is suitable for a photographing optical system that requires high image quality, such as a digital video camera system.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group L1 1st lens element L2 2nd lens element L3 3rd lens element L4 4th lens element L5 5th lens element L6 6th lens element L7 7th lens element L8 8th lens element L9 9th lens element L10 10th lens element L11 11th lens element L12 12th lens element L13 13th lens element L14 14th lens element A Aperture stop S Image surface 100 Camera system 101, 301 Camera body 102, 302 Image sensor 103, 303 Display unit 104 Camera mount unit 201 Interchangeable lens device 202, 402 Lens system 203, 403 Lens barrel 204 Lens mount unit 300 Camera

Claims (5)

It consists of a plurality of lens groups arranged in order from the object side to the image side,
The at least one of zooming and focusing can be performed by changing a distance between the lens groups.
Each of the lens groups is composed of at least one lens element,
The lens group arranged on the most image side of the lens group is composed of one lens element,
The lens system characterized in that the following condition (1) is satisfied on at least one lens surface of a lens element constituting the lens group disposed on the most image side:
R <0.2 (1)
here,
R: Energy reflectance for d-line (%)
It is. It consists of a plurality of lens groups arranged in order from the object side to the image side,
The at least one of zooming and focusing can be performed by changing a distance between the lens groups.
Each of the lens groups is composed of at least one lens element,
The lens group arranged on the most image side of the lens group is composed of one lens element,
The energy reflectance with respect to d-line of at least one lens surface of the lens elements constituting the lens group disposed on the most image side is the reflectance with respect to d-line of all lens surfaces of the lens elements included in the lens system. Lens system characterized by the lowest. The lens system according to claim 1 or 2, wherein the following condition (2) is satisfied:
0.5 <D _eff / H _max <1.4 (2)
here,
D _eff : Effective radius on the object side of the lens element constituting the lens group arranged on the most image side,
H _max : The maximum image height of the lens system. The lens system according to claim 1 or 2, which satisfies the following condition (3):
f _b / H _max <3.5 (3)
here,
f _b : the focal length of the lens unit disposed on the most image side,
H _max : The maximum image height of the lens system. The lens system according to claim 1 or 2,
A camera comprising: an imaging device that receives an optical image formed by the lens system and converts the optical image into an electrical image signal.

Images