JP2014089352A - Inner focus lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact inner focus lens which offers superior imaging performance, has a focal length that allows the lens to be used as a standard lens, and can be used for shooting videos.SOLUTION: The inner focus lens comprises a first lens group Gwhich includes an aperture stop S and has positive refractive power, a second lens group Ghaving negative refractive power, and a third lens group Ghaving positive refractive power arranged in order from the object side. The inner focus lens adjusts focus by moving the second lens group Galong the optical axis. The third lens group Gincludes a positive lens Lwhich functions as an anti-vibration group. A compact inner focus lens which offers superior imaging performance and can be used as a standard lens even for shooting videos can be realized by satisfying predetermined conditions.

Description

  The present invention relates to a small, high-performance inner focus lens capable of moving image shooting.

  Many inner focus lenses that can be used in photographic cameras and video cameras have been proposed (see, for example, Patent Documents 1 and 2).

  Each of the inner focus lenses described in Patent Documents 1 and 2 has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. The third lens group is disposed, and focusing is performed by moving the second lens group.

Japanese Patent No. 3950571 Japanese Patent No. 3445554

  However, the inner focus type lenses described in Patent Documents 1 and 2 are both assumed to be telephoto lenses. Conventional lenses of this type, including the inner focus lens described in each of the above-mentioned patent documents, can be used as a standard lens having a focal length of about 50 mm in terms of a 35 mm camera, and can shoot good moving images. There was nothing wrong.

  In recent years, there has been a strong demand for downsizing of the image pickup apparatus, and therefore, a small lens is desired for the lens mounted on the image pickup apparatus. However, the inner focus lens described in Patent Document 2 cannot be said to be downsized in the entire optical system, and is not suitable for a small imaging device.

  The present invention eliminates the problems caused by the prior art described above, and has a focal length that can be used as a standard lens. The object is to provide a lens. In addition, it is an object of the present invention to provide an inner focus type lens having a small and high imaging performance, having a vibration-proof group with a small movement amount for image blur correction.

In order to solve the above-described problems and achieve the object, an inner focus lens according to the present invention includes a first lens group including an aperture stop and having a positive refractive power, which is arranged in order from the object side, and negative refraction. A second lens group having a power and a third lens group having a positive refractive power, the optical axis directions of the first lens group and the third lens group are fixed, and the second lens group is irradiated with light. The focusing is performed by moving along the axis, and the following conditional expression is satisfied.
(1) 50 ≦ 1 / (tan (α1) / LS1 / f) ≦ 250
Where α1 is the principal ray incident angle of the maximum field angle ray incident on the most object side surface of the second lens group in the infinite object focusing state, and LS1 is the aperture stop and the second lens in the infinite object focusing state. The distance from the group, f indicates the focal length of the entire optical system.

  According to the present invention, it is possible to provide an inner focus type lens having a focal length that can be used as a standard lens and capable of capturing a good moving image and having a small size and high imaging performance.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(2) 0.50 ≦ f1 / f ≦ 0.80
Here, f1 represents the focal length of the first lens group.

  According to the present invention, it is possible to provide an inner focus lens that is small in size and has higher imaging performance.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(3) 1.00 ≦ FI × f1 / f ≦ 1.40
However, FI indicates the F number of the entire optical system in the infinite object focusing state.

  According to the present invention, it is possible to provide an inner focus lens having a small size, a large aperture, and high imaging performance.

Furthermore, the inner focus lens according to the present invention is the lens according to any one of the above-mentioned inventions, wherein the third lens group is moved in a direction substantially perpendicular to the optical axis to cause image blurring when the optical system vibrates. It includes an anti-vibration group that performs correction, and satisfies the following conditional expression.
(4) 1.33 ≦ | 1 / (((1-βvr) × βr) | ≦ 4.00
However, βvr represents the imaging magnification of the image stabilizing group, and βr represents the combined image forming magnification of the entire lens disposed on the image side from the image stabilizing group.

  According to the present invention, it is possible to provide an inner focus type lens having a small and high imaging performance, which has a vibration-proof group with a small movement amount for image blur correction.

Furthermore, the inner focus type lens according to the present invention is characterized in that, in any one of the above inventions, the following conditional expression is satisfied.
(5) −3.00 ≦ r1 / f ≦ 0.00
Here, r1 represents the radius of curvature of the most object side surface of the entire optical system.

  According to the present invention, it is possible to provide an inner focus lens that is small in size and has extremely high imaging performance.

  According to the present invention, it is possible to provide an inner focus lens that has a focal length that can be used as a standard lens, that can perform good moving image shooting, and that is small and has high imaging performance. Play. In addition, there is an effect that it is possible to provide a small inner focus type lens having a high image forming performance and having a vibration proof group with a small movement amount for image blur correction.

1 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 1. FIG. FIG. 6 is a longitudinal aberration diagram with respect to e line of the inner focus lens according to Example 1; FIG. 6 is a lateral aberration diagram with respect to e line in the state of focusing on an object at infinity of the inner focus lens according to Example 1; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to Example 2. FIG. 6 is a longitudinal aberration diagram with respect to e line of the inner focus lens according to Example 2; FIG. 12 is a lateral aberration diagram with respect to e line in the state of focusing on an object at infinity of the inner focus lens according to Example 2; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 3; FIG. 10 is a longitudinal aberration diagram with respect to e line of the inner focus lens according to Example 3; FIG. 10 is a lateral aberration diagram with respect to e line in the state of focusing on an object at infinity of the inner focus lens according to Example 3;

  Hereinafter, a preferred embodiment of an inner focus type lens according to the present invention will be described in detail.

  An inner focus type lens according to the present invention includes a first lens group including an aperture stop and having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power, which are arranged in order from the object side. And a third lens group. In this inner focus type lens, the optical axis directions of the first lens group and the third lens group are fixed, and focusing is performed by moving the second lens group along the optical axis.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an inner focus type lens having a focal length that can be used as a standard lens and capable of taking a good moving image and having a small size and high imaging performance. Therefore, in order to achieve such an object, various conditions as shown below are set in addition to the above characteristics.

First, in the zoom lens according to the present invention, the principal ray incident angle of the maximum field angle ray incident on the most object side surface of the second lens group in the infinite object focusing state is α1, and the aperture stop in the infinite object focusing state is When the distance from the second lens group is LS1 and the focal length of the entire optical system is f, it is preferable that the following conditional expression is satisfied.
(1) 50 ≦ 1 / (tan (α1) / LS1 / f) ≦ 250

  Conditional expression (1) represents a condition for realizing an inner focus lens capable of performing good moving image shooting while having a focal length that can be used as a standard lens. By satisfying conditional expression (1), the incident angle of the light beam to the second lens group that is the focus group is limited, and the image height of the second lens group when it moves on the optical axis (during focusing) It becomes possible to suppress fluctuations and to perform good moving image shooting.

  If the lower limit of conditional expression (1) is not reached, the entire length of the optical system is extended, and it is difficult to reduce the size of the optical system. On the other hand, if the upper limit in conditional expression (1) is exceeded, the variation in image height due to focusing increases, making it difficult to perform good moving image shooting.

In addition, the said conditional expression (1) can anticipate a more preferable effect, if the range shown next is satisfied.
(1a) 80 ≦ 1 / (tan (α1) / LS1 / f) ≦ 200
By satisfying the range defined by the conditional expression (1a), the imaging performance can be further improved while sufficiently miniaturizing the optical system.

Furthermore, when the conditional expression (1a) satisfies the following range, a further preferable effect can be expected.
(1b) 100 ≦ 1 / (tan (α1) / LS1 / f) ≦ 180
By satisfying the range defined by the conditional expression (1b), the imaging performance can be further improved while sufficiently reducing the size of the optical system.

Furthermore, in the inner focus type lens according to the present invention, it is preferable that the following conditional expression is satisfied, where f1 is the focal length of the first lens unit and f is the focal length of the entire optical system.
(2) 0.50 ≦ f1 / f ≦ 0.80

  Conditional expression (2) represents a condition for ensuring good imaging performance while reducing the size of the inner focus lens.

  If the lower limit of conditional expression (2) is not reached, the focal length of the first lens group becomes short, and the spherical aberration becomes excessive on the under side. In addition, the paraxial imaging magnification after the second lens group is increased, the rear lens diameter is enlarged, and the radial direction of the optical system is increased. On the other hand, if the upper limit of conditional expression (2) is exceeded, the focal length of the first lens group becomes long and the entire length of the optical system is extended.

In addition, the said conditional expression (2) can anticipate a more preferable effect, if the range shown next is satisfied.
(2a) 0.55 ≦ f1 / f ≦ 0.79
By satisfying the range defined by this conditional expression (2a), the imaging performance can be further improved while sufficiently reducing the size of the optical system.

Furthermore, if the said conditional expression (2a) satisfies the range shown next, the further preferable effect can be anticipated.
(2b) 0.65 ≦ f1 / f ≦ 0.78
By satisfying the range defined by the conditional expression (2b), the imaging performance can be further improved while sufficiently reducing the size of the optical system.

Further, in the inner focus type lens according to the present invention, the F number of the entire optical system in the infinite object focusing state is FI, the focal length of the first lens group is f1, and the focal length of the entire optical system is f. It is preferable that the following conditional expression is satisfied.
(3) 1.00 ≦ FI × f1 / f ≦ 1.40

  Conditional expression (3) represents a condition for realizing an inner focus lens having a small size, a large aperture, and high imaging performance. By satisfying conditional expression (3), it is possible to realize an inner focus lens that is bright and has excellent imaging performance while shortening the total length of the optical system.

  If the lower limit of conditional expression (3) is not reached, the focal length of the first lens group becomes short and the F-number becomes small, which is advantageous for realizing a bright lens, but distortion is prominent. It is not preferable. On the other hand, if the upper limit in conditional expression (3) is exceeded, the back focus of the optical system becomes long, and the downsizing of the optical system is hindered. In addition, it becomes difficult to widen the angle of the optical system.

In addition, if the said conditional expression (3) satisfies the range shown next, a more preferable effect can be anticipated.
(3a) 1.10 ≦ FI × f1 / f ≦ 1.39
By satisfying the range defined by the conditional expression (3a), the imaging performance can be further improved while sufficiently miniaturizing the optical system.

Furthermore, if the said conditional expression (3a) satisfies the range shown next, the further preferable effect can be anticipated.
(3b) 1.20 ≦ FI × f1 / f ≦ 1.38
By satisfying the range defined by the conditional expression (3b), it is possible to further improve the imaging performance while sufficiently reducing the size of the optical system.

Furthermore, in the inner focus type lens according to the present invention, a part of the lenses constituting the third lens group has a function as an anti-vibration group. The anti-vibration group performs correction of image blur caused when the optical system vibrates due to camera shake or the like by moving (eccentric) in a direction substantially perpendicular to the optical axis. In the inner focus type lens of the present invention, when the imaging magnification of the image stabilizing group is βvr, and the combined image forming magnification of the entire lens arranged on the image side from the image stabilizing group is βr, the following conditional expression is satisfied. It is preferable to satisfy.
(4) 1.33 ≦ | 1 / (((1-βvr) × βr) | ≦ 4.00

  When it is intended to reduce the size of an optical system provided with an image stabilization group for correcting image blur, it becomes a problem to suppress the amount of movement of the image stabilization group in a direction substantially perpendicular to the optical axis. Therefore, conditional expression (4) is defined in the present invention. Conditional expression (4) indicates a condition for appropriately setting the amount of movement of the image stabilizing group at the time of image blur correction to achieve a reduction in the radial direction of the optical system and a reduction in the total length of the optical system. Is.

  If the lower limit of conditional expression (4) is not reached, the combined imaging magnification of the entire lens arranged on the image side from the image stabilization group becomes large, so that the back focus of the optical system becomes long and the optical system becomes smaller. Be inhibited. On the other hand, if the upper limit in conditional expression (4) is exceeded, the amount of movement of the image stabilization group at the time of image stabilization correction increases, and the radial direction of the optical system increases.

In addition, if the said conditional expression (4) satisfies the range shown next, a more preferable effect can be anticipated.
(4a) 1.40 ≦ | 1 / ((1-βvr) × βr) | ≦ 3.00
By satisfying the range defined by the conditional expression (4a), it is possible to further suppress the movement amount of the image stabilizing group at the time of image stabilization and further reduce the size of the optical system.

Furthermore, when the conditional expression (4a) satisfies the following range, a further preferable effect can be expected.
(4b) 1.69 ≦ | 1 / ((1-βvr) × βr) | ≦ 2.00
By satisfying the range defined by the conditional expression (4b), it is possible to further reduce the amount of movement of the image stabilizing group at the time of image stabilization and further reduce the size of the optical system.

Further, in the inner focus type lens according to the present invention, it is preferable that the following conditional expression is satisfied, where r1 is the radius of curvature of the most object side surface of the entire optical system, and f is the focal length of the entire optical system.
(5) −3.00 ≦ r1 / f ≦ 0.00

  Conditional expression (5) shows conditions for maintaining good imaging performance while reducing the size of the entire optical system. When an inner focus type lens having a focal length that can be used as a standard lens is to be realized, it is indispensable to sufficiently correct aberrations, particularly distortion aberrations, that become prominent due to widening the angle of view. Therefore, by satisfying conditional expression (5), it becomes possible to dispose a lens having a concave surface facing the object side on the most object side of the optical system without hindering downsizing of the optical system, and distortion aberration. Can be corrected sufficiently.

  If the lower limit of conditional expression (5) is not reached, the image plane fluctuation during focusing becomes large, which is not preferable. On the other hand, if the upper limit of conditional expression (5) is exceeded, the radial direction of the optical system enlarges as the entrance pupil diameter increases, which is not preferable.

In addition, the said conditional expression (5) can anticipate a more preferable effect, if the range shown next is satisfied.
(5a) -1.50 ≦ r1 / f ≦ −0.35
By satisfying the range defined by the conditional expression (5a), the imaging performance can be further improved while sufficiently reducing the size of the optical system.

Furthermore, when the conditional expression (5a) satisfies the following range, a further preferable effect can be expected.
(5b) −1.00 ≦ r1 / f ≦ −0.70
By satisfying the range defined by the conditional expression (5b), it is possible to further improve the imaging performance while sufficiently reducing the size of the optical system.

  As described above, according to the present invention, it is possible to realize an inner focus type lens having a focal length that can be used as a standard lens, and having a small size and high imaging performance. In particular, by satisfying the above conditional expression, it becomes an inner focus type lens having a small size, a large aperture, and an excellent imaging performance, which is optimal for moving image shooting. In addition, it is possible to realize a small-sized inner focus type lens having a high image forming performance and having a vibration proof group with a small movement amount for image blur correction.

  Embodiments of an inner focus lens according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the following examples.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the first embodiment. The inner focus type lens includes a first lens group G ₁₁ having a positive refractive power, a second lens group G ₁₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _13, is formed is disposed. Note that a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the image plane IMG.

The first lens group G ₁₁ includes, in order from the object side, a negative lens L _111, a positive lens L _112, a positive lens L _113, and the aperture stop S for defining a predetermined diameter, is formed are disposed. The negative lens L ₁₁₁ and the positive lens L ₁₁₂ are cemented. Furthermore, the object side surface of the positive lens L ₁₁₃ is a composite aspherical surface is formed. Optical axis direction of the first lens group G ₁₁ is fixed.

The second lens group G ₁₂ includes, is composed of a negative lens L _121. The second lens group G ₁₂ includes, by moving toward the image plane IMG side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₁₃ is constituted in order from the object side, a positive lens L _131, a positive lens L _132, a negative lens L _133, a positive lens L _134, is the arrangement. The positive lens L ₁₃₂ and the negative lens L ₁₃₃ are cemented. An aspheric surface is formed on both surfaces of the positive lens _L134 . Optical axis direction of the third lens group G ₁₃ is fixed.

The positive lens L ₁₃₁ has a function as an anti-vibration group. That is, by moving (decentering) the positive lens L ₁₃₁ in a direction substantially perpendicular to the optical axis, image blur that occurs during vibration of the optical system due to camera shake is corrected.

  Various numerical data related to the inner focus lens according to Example 1 will be described below.

(Lens data)
r ₁ = -28.141
d ₁ = 2.386 nd ₁ = 1.762 νd ₁ = 26.609
r ₂ = 28.141
d ₂ = 4.990 nd ₂ = 1.835 νd ₂ = 42.722
r ₃ = -45.876
d ₃ = 0.300
r ₄ = 27.040 (aspherical surface)
d ₄ = 0.200 nd ₃ = 1.540 νd ₃ = 41.200
r ₅ = 29.618
d ₅ = 4.230 nd ₄ = 1.911 νd ₄ = 35.250
r ₆ = -103.468
d ₆ = 2.572
r ₇ = ∞ (aperture stop)
d ₇ = D (7) (variable)
r ₈ = 204.507
d ₈ = 0.950 nd ₅ = 1.497 νd ₅ = 81.608
r ₉ = 13.699
d ₉ = D (9) (variable)
r ₁₀ = 45.273
d ₁₀ = 1.839 nd ₆ = 1.911 νd ₆ = 35.250
r ₁₁ = 89.356
d ₁₁ = 1.697
r ₁₂ = 233.694
d ₁₂ = 4.949 nd ₇ = 1.911 νd ₇ = 35.250
r ₁₃ = -12.000
d ₁₃ = 1.273 nd ₈ = 1.762 νd ₈ = 26.609
r ₁₄ = 26.307
d ₁₄ = 0.826
r ₁₅ = 28.017 (aspherical surface)
d ₁₅ = 2.995 nd ₉ = 1.851 νd ₉ = 40.105
r ₁₆ = 217.238 (aspherical surface)
d ₁₆ = fB
r ₁₇ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Fourth surface)
k = 0,
A = -1.759 × 10 ⁻⁵ , B = −2.541 × 10 ⁻⁸ ,
C = 2.140 × 10 ^-11 , D = 0
(15th page)
k = 0,
A = 4.393 × 10 ⁻⁵ , B = -5.539 × 10 ⁻⁸ ,
C = 1.026 × 10 ^-9 , D = -4.000 × 10 ^-13
(16th page)
k = 0,
A = 6.097 × 10 ^-5 , B = -6.809 × 10 ^-8 ,
C = 1.937 × 10 ^-9 , D = -2.882 × 10 ^-12

(Numeric data for each in-focus state)
Infinity Nearest object distance ∞ 300
D (7) 1.799 4.719
D (9) 8.353 5.434
fB (back focus) 18.140 18.140
f (focal length of the entire optical system) 34.914 33.351

FI (F number of the entire optical system in the state of focusing on an object at infinity) = 1.861
2ω (angle of view) = 44.664
[alpha] 1 (principal ray incident angle of the maximum angle rays incident on the most object side surface of the infinite object focusing the second lens group G ₁₂ in the state) = 24.099
LS1 (distance between the aperture stop S and the second lens group G ₁₂ in the infinite object in-focus state) = 1.799
f1 (the focal length of the first lens group G ₁₁₎ = 24.533
βvr (imaging magnification of positive lens L ₁₃₁ (anti-vibration group)) = 0.300
βr (combined imaging magnification of the entire lens disposed on the image side from the positive lens L ₁₃₁ (anti-vibration group)) = 0.803
r1 (curvature radius of the most object side surface of the entire optical system) = − 28.141
Y (image height) = 14.20

(Numerical values related to conditional expression (1))
1 / (tan (α1) / LS1 / f) = 140.438

(Numerical value related to conditional expression (2))
f1 / f = 0.703

(Numerical values related to conditional expression (3))
FI × f1 / f = 1.307

(Numerical values related to conditional expression (4))
| 1 / ((1-βvr) × βr) | = 1.799

(Numerical values related to conditional expression (5))
r1 / f = -0.806

  FIG. 2 is a longitudinal aberration diagram of the inner focus lens according to Example 1 with respect to the e line (λ = 546.07 nm). S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 3 is a lateral aberration diagram with respect to e line (λ = 546.07 nm) of the inner focus lens according to Example 1 in the state of focusing on an object at infinity. In the figure, (a) is a lateral aberration curve from 0 mm to 14.20 mm in real image height (Y ′) at the time of non-shake correction, and (b) is a light beam through the positive lens L ₁₃₁ (anti-shake group) at the time of shake correction. Actual aberration (Y ') from 0mm to + 14.20mm lateral aberration curve when moving the imaging position vertically upward with respect to the axis and corresponding to the angle of view +0.3 degree, (c) is anti-shake correction When the positive lens L ₁₃₁ (anti-vibration group) is moved vertically downward with respect to the optical axis and the imaging position is moved by an angle of view equivalent to −0.3 degrees, the real image height (Y ′) from 0 mm to − 14 shows a transverse aberration curve of 20 mm.

FIG. 4 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the second embodiment. The inner focus type lens includes a first lens group G ₂₁ having a positive refractive power, a second lens group G ₂₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _23, is formed are disposed. Note that a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the image plane IMG.

The first lens group G ₂₁ includes, in order from the object side, a negative lens L ₂₁₁ , a positive lens L ₂₁₂ , a positive lens L _213, and an aperture stop S that defines a predetermined aperture. The negative lens L ₂₁₁ and the positive lens L ₂₁₂ are cemented. A composite aspherical surface is formed on the object side surface of the positive lens _L213 . Optical axis direction of the The first lens group G ₂₁ includes, is fixed.

The second lens group G ₂₂ includes, is composed of a negative lens L _221. The second lens group G ₂₂ includes, by moving toward the image plane IMG side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₂₃ is constituted in order from the object side, a positive lens L _231, a positive lens L _232, a negative lens L _233, a positive lens L _234, is the arrangement. The positive lens L ₂₃₂ and the negative lens L ₂₃₃ are cemented. In addition, aspherical surfaces are formed on both surfaces of the positive lens _L234 . Optical axis direction of the third lens group G ₂₃ is fixed.

Further, the positive lens L ₂₃₁ has a function as an anti-vibration group. That is, by moving the positive lens L ₂₃₁ in a direction substantially perpendicular to the optical axis (eccentricity), image blur that occurs during vibration of the optical system due to camera shake is corrected.

  Various numerical data related to the inner focus lens according to Example 2 will be described below.

(Lens data)
r ₁ = -26.314
d ₁ = 1.262 nd ₁ = 1.830 νd ₁ = 22.754
r ₂ = 26.314
d ₂ = 5.409 nd ₂ = 1.837 νd ₂ = 30.168
r ₃ = -37.888
d ₃ = 0.300
r ₄ = 24.589 (aspherical surface)
d ₄ = 0.200 nd ₃ = 1.540 νd ₃ = 41.200
r ₅ = 27.288
d ₅ = 4.595 nd ₄ = 1.911 νd ₄ = 35.250
r ₆ = -87.084
d ₆ = 2.455
r ₇ = ∞ (aperture stop)
d ₇ = D (7) (variable)
r ₈ = 187.659
d ₈ = 0.950 nd ₅ = 1.556 νd ₅ = 43.923
r ₉ = 13.032
d ₉ = D (9) (variable)
r ₁₀ = 47.786
d ₁₀ = 1.871 nd ₆ = 1.854 νd ₆ = 36.932
r ₁₁ = 107.173
d ₁₁ = 1.733
r ₁₂ = 613.381
d ₁₂ = 4.873 nd ₇ = 1.913 νd ₇ = 31.278
r ₁₃ = -12.000
d ₁₃ = 1.200 nd ₈ = 1.725 νd ₈ = 26.145
r ₁₄ = 26.236
d ₁₄ = 0.076
r ₁₅ = 24.888 (aspherical surface)
d ₁₅ = 2.949 nd ₉ = 1.646 νd ₉ = 48.887
r ₁₆ = 503.193 (aspherical surface)
d ₁₆ = fB
r ₁₇ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Fourth surface)
k = 0,
A = -2.034 × 10 ^-5 , B = -3.619 × 10 ^-8 ,
C = 4.597 × 10 ^-11 , D = 0
(15th page)
k = 0,
A = 4.393 × 10 ⁻⁵ , B = -5.539 × 10 ⁻⁸ ,
C = 1.026 × 10 ^-9 , D = -4.000 × 10 ^-13
(16th surface)
k = 0,
A = 6.973 × 10 ⁻⁵ , B = -1.670 × 10 ⁻⁷ ,
C = 3.651 × 10 ^-9 , D = -1.121 × 10 ^-11

(Numeric data for each in-focus state)
Infinity Nearest object distance ∞ 300
D (7) 1.802 4.184
D (9) 7.949 5.566
fB (Back focus) 19.877 19.877
f (focal length of the entire optical system) 36.047 34.140

FI (F number of the entire optical system in the state of focusing on an object at infinity) = 1.896
2ω (angle of view) = 43.198
[alpha] 1 (principal ray incident angle of the maximum angle rays incident on the most object side surface of the second lens group G ₂₂ in the infinite object in-focus state) = 23.329
LS1 (distance between the aperture stop S and the second lens group G ₂₂ in the infinite object in-focus state) = 1.802
f1 (the focal length of the first lens group G ₂₁₎ = 22.757
βvr (imaging magnification of positive lens L ₂₃₁ (anti-vibration group)) = 0.292
βr (combined imaging magnification of the entire lens disposed on the image side from the positive lens L ₂₃₁ (anti-vibration group)) = 0.835
r1 (curvature radius of the most object side surface of the entire optical system) = − 26.314
Y (image height) = 14.20

(Numerical values related to conditional expression (1))
1 / (tan (α1) / LS1 / f) = 150.596

(Numerical value related to conditional expression (2))
f1 / f = 0.631

(Numerical values related to conditional expression (3))
FI × f1 / f = 1.197

(Numerical values related to conditional expression (4))
| 1 / ((1-βvr) × βr) | = 1.682

(Numerical values related to conditional expression (5))
r1 / f = -0.730

  FIG. 5 is a longitudinal aberration diagram of the inner focus lens according to Example 2 with respect to the e line (λ = 546.07 nm). S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 6 is a lateral aberration diagram with respect to the e line (λ = 546.07 nm) of the inner focus lens according to Example 2 when the object at infinity is in focus. In the figure, (a) is a lateral aberration curve from 0 mm to 14.20 mm in real image height (Y ′) at the time of non-shake correction, and (b) is a light beam through the positive lens L ₂₃₁ (anti-shake group) at the time of shake correction. Actual aberration (Y ') from 0mm to + 14.20mm lateral aberration curve when moving the imaging position vertically upward with respect to the axis and corresponding to the angle of view +0.3 degree, (c) is anti-shake correction When the positive lens L ₂₃₁ (anti-vibration group) is moved vertically downward with respect to the optical axis and the image forming position is moved by an angle of view equivalent to −0.3 degrees, the real image height (Y ′) from 0 mm to − 14 shows a transverse aberration curve of 20 mm.

FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the third embodiment. The inner focus type lens includes a first lens group G ₃₁ having a positive refractive power, a second lens group G ₃₂ having a negative refractive power, and a third lens having a positive refractive power in order from an object side (not shown). a lens group G _33, is formed are disposed. Note that a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the image plane IMG.

The first lens group G ₃₁ includes a negative lens L ₃₁₁ , a positive lens L ₃₁₂ , a positive lens L _313, and an aperture stop S that defines a predetermined aperture in order from the object side. The negative lens L ₃₁₁ and the positive lens L ₃₁₂ are cemented. A composite aspherical surface is formed on the object side surface of the positive lens _L313 . The optical axis direction of the first lens group G ₃₁ is fixed.

The second lens group G ₃₂ is constituted by a negative lens L _321. Aspherical surfaces are formed on both surfaces of the negative lens _L321 . The second lens group G ₃₂ is, by moving toward the image plane IMG side from the object side along the optical axis to perform focusing from infinity in-focus state to a closest distance object in-focus state.

The third lens group G ₃₃ is constituted in order from the object side, a positive lens L _331, a positive lens L _332, a negative lens L _333, a positive lens L _334, is the arrangement. The positive lens L ₃₃₂ and the negative lens L ₃₃₃ are cemented. Further, aspherical surfaces are formed on both surfaces of the positive lens _L334 . Optical axis direction of the third lens group G ₃₃ is fixed.

Further, the positive lens L ₃₃₁ has a function as an anti-vibration group. That is, by moving the positive lens L ₃₃₁ in the direction substantially perpendicular to the optical axis (eccentricity), correction of image blur that occurs when the optical system vibrates due to camera shake or the like is performed.

  Various numerical data relating to the inner focus lens according to Example 3 will be described below.

(Lens data)
r ₁ = -33.286
d ₁ = 2.834 nd ₁ = 1.812 νd ₁ = 23.211
r ₂ = 33.286
d ₂ = 4.623 nd ₂ = 1.901 νd ₂ = 35.513
r ₃ = -47.213
d ₃ = 0.300
r ₄ = 27.249 (aspherical surface)
d ₄ = 0.200 nd ₃ = 1.540 νd ₃ = 41.200
r ₅ = 28.556
d ₅ = 3.879 nd ₄ = 1.911 νd ₄ = 35.250
r ₆ = -325.526
d ₆ = 2.939
r ₇ = ∞ (aperture stop)
d ₇ = D (7) (variable)
r ₈ = -108.362 (aspherical surface)
d ₈ = 0.950 nd ₅ = 1.497 νd ₅ = 81.608
r ₉ = 17.353 (aspherical surface)
d ₉ = D (9) (variable)
r ₁₀ = 45.043
d ₁₀ = 2.003 nd ₆ = 1.911 νd ₆ = 35.250
r ₁₁ = 154.371
d ₁₁ = 1.840
r ₁₂ = -225.775
d ₁₂ = 4.709 nd ₇ = 1.911 νd ₇ = 35.250
r ₁₃ = -12.000
d ₁₃ = 1.300 nd ₈ = 1.736 νd ₈ = 25.696
r ₁₄ = 28.856
d ₁₄ = 0.170
r ₁₅ = 23.228 (aspherical surface)
d ₁₅ = 2.760 nd ₉ = 1.911 νd ₉ = 35.250
r ₁₆ = 76.237 (aspherical surface)
d ₁₆ = fB
r ₁₇ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Fourth surface)
k = 0,
A = -1.050 × 10 ^-5 , B = -3.116 × 10 ^-8 ,
C = 4.797 × 10 ^-11 , D = 0
(8th page)
k = 0,
A = 6.358 x 10 ^-5 , B = 2.211 x 10 ^-7 ,
C = 1.666 × 10 ⁻⁸ , D = 1.281 × 10 ⁻¹⁰
(9th page)
k = 0,
A = 5.240 × 10 ⁻⁵ , B = 1.649 × 10 ⁻⁶ ,
C = -5.151 × 10 ⁻⁸ , D = 4.195 × 10 ⁻¹⁰
(15th page)
k = 0,
A = 4.393 × 10 ⁻⁵ , B = -5.539 × 10 ⁻⁸ ,
C = 1.026 × 10 ^-9 , D = -4.000 × 10 ^-13
(16th surface)
k = 0,
A = 7.509 × 10 ^-5 , B = -3.858 × 10 ^-8 ,
C = 1.924 × 10 ⁻⁹ , D = −4.077 × 10 ⁻¹²

(Numeric data for each in-focus state)
Infinity Nearest object distance ∞ 300
D (7) 1.783 5.105
D (9) 8.556 5.234
fB (back focus) 18.654 18.654
f (focal length of the entire optical system) 34.434 33.321

FI (F number of the entire optical system in an infinite object focused state) = 1.801
2ω (angle of view) = 45.230
[alpha] 1 (principal ray incident angle of the maximum angle rays incident on the most object side surface of the second lens group G ₃₂ in the infinite object in-focus state) = 25.174
LS1 (distance between the aperture stop S and the second lens group G ₃₂ in the infinite object in-focus state) = 1.783
f1 (the focal length of the first lens group G ₃₁₎ = 26.385
βvr (imaging magnification of positive lens L ₃₃₁ (anti-vibration group)) = 0.401
βr (combined imaging magnification of the entire lens arranged on the image side from the positive lens L ₃₃₁ (anti-vibration group)) = 0.868
r1 (curvature radius of the most object side surface of the entire optical system) = − 33.286
Y (image height) = 14.20

(Numerical values related to conditional expression (1))
1 / (tan (α1) / LS1 / f) = 130.598

(Numerical value related to conditional expression (2))
f1 / f = 0.766

(Numerical values related to conditional expression (3))
FI × f1 / f = 1.380

(Numerical values related to conditional expression (4))
| 1 / ((1-βvr) × βr) | = 1.923

(Numerical values related to conditional expression (5))
r1 / f = -0.967

  FIG. 8 is a longitudinal aberration diagram of the inner focus lens according to Example 3 with respect to the e line (λ = 546.07 nm). S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 9 is a lateral aberration diagram with respect to e line (λ = 546.07 nm) of the inner focus lens according to Example 3 when the object at infinity is in focus. In this figure, (a) is a lateral aberration curve from 0 mm to 14.20 mm in real image height (Y ′) at the time of non-shake correction, and (b) is a light beam through the positive lens L ₃₃₁ (anti-shake group) at the time of shake correction. Actual aberration (Y ') from 0mm to + 14.20mm lateral aberration curve when moving the imaging position vertically upward with respect to the axis and corresponding to the angle of view +0.3 degree, (c) is anti-shake correction When the positive lens L ₃₃₁ (anti-vibration group) is moved vertically downward with respect to the optical axis and the imaging position is moved by an angle of view equivalent to −0.3 degrees, the real image height (Y ′) from 0 mm to − 14 shows a transverse aberration curve of 20 mm.

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the curvature radii of the respective lenses and diaphragm surfaces, and d ₁ , d ₂ ,. thickness or their surface separations, nd _1, nd _2, the refractive index with respect to ... the d-line of each lens _{(λ = 587.56nm), νd 1} , νd 2, ···· are each lens d The Abbe number for the line (λ = 587.56 nm) is shown. The unit of length is all “mm”, and the unit of angle is “°”.

  In addition, each of the above aspheric shapes has a depth of the aspheric surface Z, a curvature c (1 / r), a height from the optical axis h, a cone coefficient k, 4th order, 6th order, 8th order, 10th order. When the following aspheric coefficients are A, B, C, and D, respectively, and the traveling direction of light is positive, the following aspheric coefficients are expressed by the following equations.

  In each of the above-described embodiments, an example of an inner focus type lens having a focal length of about 50 mm in terms of a 35 mm camera and having an optical image stabilization function and having a high imaging performance with a large aperture is shown. According to this inner focus lens, it is possible to shoot a good moving image.

  The inner focus type lens shown in each of the above embodiments can achieve high imaging performance while reducing the size of the entire optical system while reducing the weight of the focus group by configuring the focus group as a single lens. . Further, it is possible to obtain a high imaging performance while reducing the weight of the image stabilization group by configuring the image stabilization group with a single lens and suppressing the movement amount of the image stabilization group during image blur correction.

  In addition, the inner focus type lens shown in each of the above-described embodiments uses an aspherical lens or a cemented lens as appropriate, so that various aberrations are favorably corrected and the imaging performance is improved.

  As described above, the inner focus type lens according to the present invention is useful for small-sized imaging devices such as a photographic camera and a video camera, and exhibits an excellent effect particularly when used for the purpose of moving image shooting.

G ₁₁ , G ₂₁ , G ₃₁ 1st lens group G ₁₂ , G ₂₂ , G ₃₂ 2nd lens group G ₁₃ , G ₂₃ , G ₃₃ 3rd lens group L ₁₁₁ , L ₁₂₁ , L ₁₃₃ , L ₂₁₁ , L ₂₂₁ , L ₂₃₃ , L ₃₁₁ , L ₃₂₁ , L ₃₃₃ negative lens L ₁₁₂ , L ₁₁₃ , L ₁₃₁ , L ₁₃₂ , L ₁₃₄ , L ₂₁₂ , L ₂₁₃ , L ₂₃₁ , L ₂₃₂ , L ₂₃₄ , L ₃₁₂ , L ₃₁₃ , _L331 , _L332 , _L334 positive lens IMG Image surface S Aperture stop

Claims (5)

A first lens group including an aperture stop and having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged in order from the object side; ,
The optical axis directions of the first lens group and the third lens group are fixed, and the second lens group is moved along the optical axis to perform focusing,
An inner focus type lens satisfying the following conditional expression:
(1) 50 ≦ 1 / (tan (α1) / LS1 / f) ≦ 250
Where α1 is the principal ray incident angle of the maximum field angle ray incident on the most object side surface of the second lens group in the infinite object focusing state, and LS1 is the aperture stop and the second lens in the infinite object focusing state. The distance from the group, f indicates the focal length of the entire optical system. The inner focus type lens according to claim 1, wherein the following conditional expression is satisfied.
(2) 0.50 ≦ f1 / f ≦ 0.80
Here, f1 represents the focal length of the first lens group. The inner focus lens according to claim 1, wherein the following conditional expression is satisfied.
(3) 1.00 ≦ FI × f1 / f ≦ 1.40
However, FI indicates the F number of the entire optical system in the infinite object focusing state. The third lens group includes an anti-vibration group that corrects image blur caused when the optical system vibrates by moving in a direction substantially perpendicular to the optical axis.
The inner focus type lens according to claim 1, wherein the following conditional expression is satisfied.
(4) 1.33 ≦ | 1 / (((1-βvr) × βr) | ≦ 4.00
However, βvr represents the imaging magnification of the image stabilizing group, and βr represents the combined image forming magnification of the entire lens disposed on the image side from the image stabilizing group. 5. The inner focus lens according to claim 1, wherein the following conditional expression is satisfied.
(5) −3.00 ≦ r1 / f ≦ 0.00
Here, r1 represents the radius of curvature of the most object side surface of the entire optical system.

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