JP6216246B2 - Inner focus lens - Google Patents

Description

  The present invention relates to a small and lightweight inner focus lens.

  Conventionally, lenses for single-lens reflex cameras in particular have adopted a configuration that facilitates ensuring back focus by arranging a positive lens group behind the optical system in order to ensure a long flange back with respect to the focal length. There were a lot of things. However, in recent years, there has been an increase in cases where it is not necessary to ensure a long flange back due to the progress of miniaturization of camera bodies and the spread of digital cameras. Therefore, an inner focus lens with a relatively short back focus has been proposed so that it can be mounted on a small camera (see, for example, Patent Documents 1 and 2).

  The inner focus type lens disclosed in Patent Document 1 includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. Is arranged to perform focusing by moving the second lens group, and has a wide-angle focal length in terms of a 35 mm film camera.

  The inner focus type lens disclosed in Patent Document 2 includes, from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. It is arranged and performs focusing by moving the second lens group, and has a standard focal length in terms of a 35 mm film camera.

Japanese Patent No. 3579627 JP 2012-189637 A

  Since digital cameras can also shoot moving images, high-speed autofocus processing that supports moving image shooting is desired. In autofocus, first, a part of lens groups (focus group) are vibrated at high speed in the optical axis direction (wobbling) to create a non-focus state → a focus state → a non-focus state. Then, a signal component in a specific frequency band in a partial image region is detected from the output signal of the image sensor, the optimum position of the focus group that is in focus is obtained, and the focus group is moved to the optimum position. In particular, in moving image shooting, it is required to continuously repeat these series of operations at a high speed.

  The inner focus type lens disclosed in Patent Document 1 is heavy because the focus group is composed of positive lenses, and is slow in driving, so that it cannot perform quick autofocus and is not suitable for moving image shooting. There's a problem.

  Also, during moving image shooting, the orientation of the camera is changed in accordance with the movement of the subject, and the photographer often needs to move, so image blurring is likely to occur. For this reason, it is preferable that the photographic lens is provided with an image stabilization function. However, the inner focus lens disclosed in Patent Document 1 does not have an image stabilization function. From this point, the inner focus type lens disclosed in Patent Document 1 can be said to be a photographing lens that is not suitable for moving image photographing.

  Since the inner focus type lens disclosed in Patent Document 2 employs a negative lens for the focus group, the focus group is reduced in weight and also has an anti-vibration correction function. It is a photographic lens that can also be used for video shooting. However, since it is not intended for widening the angle, considerations such as field curvature, distortion correction, and securing of the amount of peripheral light necessary for widening the angle are not taken into consideration.

  Conventionally, in an imaging sensor that receives an optical image and converts it into an electrical image signal, there is a limitation for efficiently capturing incident light with an on-chip microlens or the like. It has been desired to ensure the telecentricity of the incident light beam to the image sensor by increasing it to a certain value or more.

  However, recent imaging sensors have improved aperture ratios and advances in design flexibility of on-chip microlenses, and there are fewer restrictions on the exit pupil required on the photographic lens side. Due to recent advances and improvements in software and camera systems, distortion aberration is large to some extent, and it has become possible to correct even conspicuous ones by image processing.

  For this reason, in conventional photographic lenses, a positive lens is placed behind the optical system to ensure telecentricity. However, in recent years, this has become unnecessary, and a negative lens is placed behind the optical system to capture images. Even if the light beam is obliquely incident on the sensor, peripheral light reduction (shading) due to a pupil mismatch with the on-chip microlens has become inconspicuous. In addition, since the negative lens can be arranged behind the optical system, it is possible to expect a reduction in the diameter of the optical system.

  On the other hand, in the inner focus type lenses disclosed in Patent Documents 1 and 2, since the positive lens is disposed behind the optical system, the aperture size of the optical system is not sufficiently reduced.

  An object of the present invention is to provide a small, wide-angle inner focus type lens having high imaging performance, which is provided with a small and light focus group and an anti-vibration group, in order to eliminate the above-described problems caused by the prior art. And It is another object of the present invention to provide an inner focus lens suitable for moving image shooting.

In order to solve the above-described problems and achieve the object, an inner focus type lens according to the present invention includes a first lens group having a positive refractive power and a first lens group having a negative refractive power arranged in order from the object side. 2 lens group and a third lens group having a positive refractive power. By moving the second lens group along the optical axis, the infinite object focusing state from the infinite object focusing state An inner focus type lens that performs focusing up to the first lens group, a negative meniscus lens is disposed closest to the object side of the first lens group, the second lens group includes a single lens component, and the first lens group Alternatively, the third lens group includes an image stabilization lens including a single lens component that performs image stabilization by moving in a direction perpendicular to the optical axis, and satisfies the following conditional expression:
(1) 0.34 ≦ f1 / f ≦ 1.48
Here, f1 represents the focal length of the first lens group in the infinite object focusing state, and f represents the focal length of the entire optical system in the infinite object focusing state.

  According to the present invention, it is possible to provide a small and wide-angle inner focus type lens having a high image forming performance, which is provided with a small and light focus group and an image stabilization group.

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) 0.82 ≦ f3 / f ≦ 3.81
However, f3 shows the focal distance of the said 3rd lens group in an infinite object focusing state.

  According to the present invention, it is possible to reduce the size of the entire optical system and further improve the 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) 0.10 ≦ | βr × (1-βv) | ≦ 1.36
Where βr is the combined lateral magnification of the entire lens located on the image plane side of the image stabilization lens, and βv is the lateral magnification of the image stabilization lens.

  According to the present invention, it is possible to provide a smaller inner focus lens having an image stabilization function.

  Furthermore, the inner focus type lens according to the present invention is characterized in that, in the above-mentioned invention, a negative meniscus lens having a convex surface facing the image surface side is disposed on the most image surface side of the third lens group. To do.

  According to the present invention, it is possible to promote the downsizing of the aperture on the rear side (image plane side) of the optical system and improve the imaging performance.

  Furthermore, the inner focus lens according to the present invention is characterized in that, in the above invention, the image stabilization lens is disposed adjacent to the second lens group.

  According to the present invention, the image stabilization lens can be reduced in size and weight.

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.
(4) 0.16 ≦ L1s / L ≦ 0.60
Here, L1s is the axial distance from the most object side surface of the first lens group to the aperture stop, and L is the total length of the optical system.

  According to the present invention, it is possible to reduce the diameter of the optical system while maintaining high imaging performance. In addition, it is possible to realize an inner focus lens suitable for moving image shooting by suppressing a change in shooting magnification due to wobbling.

  According to the present invention, there is an effect that it is possible to provide a small and wide-angle inner focus type lens having a high imaging performance, which includes a small and light focus group and a vibration isolation group. In addition, it is possible to provide an inner focus lens suitable for moving image shooting.

1 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 1. FIG. FIG. 5 is a diagram illustrating all aberrations 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. 10 is a diagram illustrating all aberrations 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. 9 is a diagram illustrating all aberrations of the inner focus lens according to Example 3; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of an inner focus lens according to Example 4; FIG. 10 is a diagram illustrating all aberrations of the inner focus lens according to Example 4;

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

  The inner focus type lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the object side. And a lens group.

  In the inner focus type lens according to the present invention, focusing is performed from the infinitely focused object state to the closest object focused state by moving the second lens group along the optical axis. Thus, by performing the focusing by moving the second lens group, there is no change in the overall length of the optical system, and the dustproof and soundproof performance is enhanced.

  In particular, it is preferable that the second lens group which is a focus group is composed of a single lens component. By using the second lens group as a single lens component, the focus group can be reduced in size and weight, enabling high-speed focusing, which is effective for moving image shooting. Also, by reducing the size and weight of the focus group, the load on the driving means that controls the focus group is reduced, which contributes to power saving.

  The single lens component includes a single polished lens, an aspheric lens, a composite aspheric lens, and a cemented lens, and does not include, for example, two positive and negative lenses that have an air layer and are not bonded to each other.

  In the inner focus type lens according to the present invention, a negative meniscus lens is disposed closest to the object side of the first lens group. By doing so, it is possible to reduce the diameter of the first lens unit, and it is also effective for correcting off-axis aberrations, particularly distortion aberration, which is a problem in widening the angle.

  Further, in the inner focus type lens according to the present invention, the image stabilization lens comprising a single lens component that performs image stabilization correction by moving in the direction perpendicular to the optical axis in the first lens group or the third lens group. It has. Since the image stabilization lens is a single lens component, it is possible to reduce the weight of the image stabilization lens, increase the stop position accuracy of the image stabilization lens at the time of image stabilization, and realize good image stabilization. .

  Furthermore, in the present invention, in order to realize a small and wide-angle inner focus lens having a high imaging performance and having a small and light focus group and an anti-vibration group, in addition to the above-described features, Conditions are set.

First, in the inner focus type lens according to the present invention, when the focal length of the first lens group in the infinite object focusing state is f1, and the focal length of the entire optical system in the infinite object focusing state is f, It is preferable to satisfy the following conditional expression.
(1) 0.34 ≦ f1 / f ≦ 1.48

  Conditional expression (1) shows conditions for reducing the size of the optical system and improving the imaging performance. If the lower limit of conditional expression (1) is not reached, the focal length of the first lens group becomes short, the spherical aberration becomes excessive on the under side, and the paraxial imaging magnification of the subsequent lens group becomes large. , The rear lens diameter increases, leading to an increase in the size of the optical system. On the other hand, if the upper limit in conditional expression (1) is exceeded, the focal length of the first lens group becomes long, the total length of the optical system increases, and it becomes difficult to reduce the size of the optical system.

In addition, the said conditional expression (1) can anticipate a more preferable effect, if the range shown next is satisfied.
(1a) 0.46 ≦ f1 / f ≦ 1.27
By satisfying the range defined by the conditional expression (1a), it is possible to realize an inner focus type lens that is small in size and has superior imaging performance.

Furthermore, when the conditional expression (1a) satisfies the following range, a smaller and higher performance inner focus lens can be realized.
(1b) 0.57 ≦ f1 / f ≦ 1.06

Furthermore, in the inner focus type lens according to the present invention, when the focal length of the third lens group in the infinite object focusing state is f3 and the focal length of the entire optical system in the infinite object focusing state is f, It is preferable to satisfy the following conditional expression.
(2) 0.82 ≦ f3 / f ≦ 3.81

  Conditional expression (2) is an expression that prescribes the ratio of the focal length of the third lens group and the focal length of the entire optical system in an infinitely focused object state. By satisfying conditional expression (2), the refractive power of the third lens group becomes appropriate, and the overall length of the optical system can be shortened, and a bright optical system having good imaging performance can be realized.

  If the lower limit of conditional expression (2) is not reached, the refractive power of the third lens group becomes strong, so that it becomes difficult to correct coma and distortion, and good imaging performance cannot be maintained. On the other hand, if the upper limit of conditional expression (2) is exceeded, the refractive power of the third lens group becomes weak. In this case, the F number in the entire optical system tends to increase, and a bright optical system cannot be obtained. In order to realize a bright optical system in this state, it is necessary to widen the aperture stop. However, since the occurrence of various aberrations becomes significant when the aperture stop is greatly opened, the number of lenses required for aberration correction increases in order to realize an optical system with good imaging performance. In particular, it is necessary to increase the number of lenses constituting the first lens group. If the number of lenses constituting the optical system increases, it is difficult to reduce the size and weight of the optical system, which is not preferable.

In addition, the said conditional expression (2) can anticipate a more preferable effect, if the range shown next is satisfied.
(2a) 1.10 ≦ f3 / f ≦ 3.26
By satisfying the range defined by the conditional expression (2a), it is possible to realize an inner focus lens that is small in size and has superior imaging performance.

Furthermore, when the conditional expression (2a) satisfies the following range, a smaller and higher performance inner focus lens can be realized.
(2b) 1.37 ≦ f3 / f ≦ 2.72

Further, in the inner focus type lens according to the present invention, when the combined lateral magnification of the entire lens positioned on the image plane side with respect to the image stabilization lens is βr and the lateral magnification of the image stabilization lens is βv, the following conditional expression Is preferably satisfied.
(3) 0.10 ≦ | βr × (1-βv) | ≦ 1.36

  Conditional expression (3) shows conditions for realizing a small inner focus lens with an image stabilization function. If the lower limit of conditional expression (3) is not reached, the combined imaging magnification of the entire lens disposed on the image plane side from the lens group including the image stabilization lens increases, so that the back focus of the optical system becomes longer. The total length of the optical system increases. On the other hand, if the upper limit in conditional expression (3) is exceeded, the amount of movement of the image stabilization lens during image stabilization increases, and the aperture of the optical system increases. In any case, it is not preferable because miniaturization of the optical system is hindered.

In addition, if the said conditional expression (3) satisfies the range shown next, a more preferable effect can be anticipated.
(3a) 0.13 ≦ | βr × (1-βv) | ≦ 1.17
By satisfying the range defined by the conditional expression (3a), a smaller inner focus lens with an image stabilization function can be realized.

Furthermore, when the conditional expression (3a) satisfies the following range, it is possible to realize a further compact inner focus lens with an image stabilization function.
(3b) 0.16 ≦ | βr × (1-βv) | ≦ 0.97

  Furthermore, in the inner focus type lens according to the present invention, a negative meniscus lens having a convex surface facing the image plane side may be disposed closest to the image plane side of the third lens group.

  By doing so, in addition to suppressing the enlargement of the lens aperture on the image plane side, which is a problem in downsizing the optical system of the short flange back used for mirrorless single-lens cameras, etc., the field curvature and distortion are improved. It can be corrected.

  Also, by directing the convex surface to the image surface side, unlike the case of directing the concave surface to the image surface side, the reflected light on the image sensor surface is reflected by the image surface side surface of the negative meniscus lens and multiple reflections between these surfaces By repeating the above, it is possible to prevent multiple reflected light from being re-imaged on the image sensor surface. For this reason, it is advantageous in suppressing ghosts and the like, and an inner focus lens having good imaging performance can be realized.

  Furthermore, in the inner focus type lens according to the present invention, it is preferable that the image stabilization lens is disposed adjacent to the second lens group.

  In order to improve the image stabilization capability, it is necessary to improve the stop position accuracy of the image stabilization lens at the time of image stabilization. For this purpose, the weight reduction of the image stabilization lens is required. In order to reduce the weight of the image stabilization lens, it is effective to reduce the diameter of the image stabilization lens.

  Therefore, in the inner focus type lens according to the present invention having the positive / negative / positive three-group configuration, the image stabilization lens is disposed adjacent to the second lens group which is the negative lens group having the smallest light beam diameter in the optical system. Further, it is possible to reduce the diameter of the image stabilization lens. In this way, in addition to configuring the image stabilization lens with a single lens component, the size of the image stabilization lens can be reduced by reducing the aperture. Further, by reducing the size and weight of the image stabilization lens, the load on the driving means that controls the image stabilization lens is reduced, which contributes to power saving.

Furthermore, in the inner focus type lens according to the present invention, it is preferable that the following conditional expression is satisfied, where L1s is the axial distance from the most object side surface of the first lens unit to the aperture stop, and L is the total length of the optical system. .
(4) 0.16 ≦ L1s / L ≦ 0.60

  Conditional expression (4) represents a condition for realizing a reduction in the diameter of the optical system while maintaining high imaging performance. By satisfying conditional expression (4), it is possible to define an appropriate position of the aperture stop with respect to the entire length of the optical system, and to realize downsizing of the optical system. Further, by satisfying conditional expression (4), the second lens group as the focus group can be disposed behind (image plane side) with respect to the aperture stop, and a change in photographing magnification due to wobbling can be suppressed. Can do.

  If the lower limit of conditional expression (4) is not reached, the aperture stop becomes too close to the object side and the lens aperture on the image plane side is enlarged, and off-axis aberrations, mainly distortion, in the rear group become prominent. Therefore, it is not preferable. On the other hand, if the upper limit of conditional expression (4) is exceeded, the aperture stop gets too close to the image plane side, leading to an increase in the effective diameter of the front lens, which is not preferable for downsizing the optical system.

In addition, if the said conditional expression (4) satisfies the range shown next, a more preferable effect can be anticipated.
(4a) 0.21 ≦ L1s / L ≦ 0.52
By satisfying the range defined by the conditional expression (4a), it is possible to further reduce the aperture of the optical system while maintaining high imaging performance.

Furthermore, when the conditional expression (4a) satisfies the following range, it is possible to further reduce the aperture of the optical system.
(4b) 0.26 ≦ L1s / L ≦ 0.43

  As described above, according to the present invention, it is possible to provide a small, wide-angle inner focus lens having high imaging performance, which includes a small and light focus group and an anti-vibration group. In particular, by satisfying the above conditional expressions, it is possible to realize an inner focus type lens that is suitable for moving image shooting and has a smaller size and high imaging performance.

  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. FIG. 1 shows an infinite object focusing state. 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.

The first lens group G ₁₁ includes, in order from the object side, a negative meniscus lens L ₁₁₁ , an aperture stop S that defines a predetermined aperture, a positive lens L _112, and a negative lens L _113. The The negative meniscus lens L ₁₁₁ is disposed with the convex surface facing the object side. The both surfaces of the positive lens L _112, aspheric surface is formed. The negative lens L ₁₁₃ has a function as an image stabilization lens, and performs image stabilization correction by moving in a direction perpendicular to the optical axis.

The second lens group G ₁₂ includes, is composed of a negative lens L _121. On both surfaces of the negative lens L _121, aspheric surface is formed. 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 negative meniscus lens L _132, is the arrangement. The negative meniscus lens L ₁₃₂ is arranged with the convex surface facing the image plane IMG side. On both surfaces of the negative meniscus lens L _132, aspheric surface is formed.

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

(Lens data)
r ₁ = 113.2282
d ₁ = 1.2000 nd ₁ = 1.48749 νd ₁ = 70.44
r ₂ = 17.4489
d ₂ = 30.8462
r ₃ = ∞ (aperture stop)
d ₃ = 1.5000
r ₄ = 21.5581 (aspherical surface)
d ₄ = 6.0374 nd ₂ = 1.82080 νd ₂ = 42.71
r ₅ = -37.5027 (aspherical surface)
d ₅ = 0.5000
r ₆ = -124.0286
d ₆ = 0.7000 nd ₃ = 1.84666 νd ₃ = 23.78
r ₇ = 51.8966
d ₇ = D (7) (variable)
r ₈ = 660.0942 (aspherical surface)
d ₈ = 1.000 nd ₄ = 1.68893 νd ₄ = 31.16
r ₉ = 27.1042 (aspherical surface)
d ₉ = D (9) (variable)
r ₁₀ = 35.4279
d ₁₀ = 5.3771 nd ₅ = 1.49700 νd ₅ = 81.61
r ₁₁ = -23.5064
d ₁₁ = 11.0398
r ₁₂ = -24.2416 (aspherical surface)
d ₁₂ = 1.2000 nd ₆ = 1.68893 νd ₆ = 31.16
r ₁₃ = -71.3343 (Aspherical surface)
d ₁₃ = Bf

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Fourth surface)
k = 0,
A ₄ = −6.22999 × 10 ⁻⁶ , A ₆ = −8.29140 × 10 ⁻⁹ ,
A ₈ = 6.14663 × 10 ^-11 , A ₁₀ = 1.45011 × 10 ^-13
(5th page)
k = 0,
A ₄ = 2.38586 × 10 ^-5 , A ₆ = -1.56222 × 10 ^-8 ,
A ₈ = 1.10314 × 10 ^-10 , A ₁₀ = -2.66652 × 10 ^-13
(8th page)
k = 0,
A ₄ = 3.39396 × 10 ⁻⁵ , A ₆ = −2.16547 × 10 ⁻⁷ ,
A ₈ = 9.74072 × 10 ^-10 , A ₁₀ = -3.49597 × 10 ^-12
(9th page)
k = 0,
A ₄ = 4.92320 × 10 ⁻⁵ , A ₆ = -1.80536 × 10 ⁻⁷ ,
A ₈ = 1.03819 × 10 ⁻⁹ , A ₁₀ = −3.116605 × 10 ⁻¹²
(Twelfth surface)
k = 0,
A ₄ = -5.34457 × 10 ^-5 , A ₆ = 2.71957 × 10 ^-7 ,
A ₈ = -1.21898 × 10 ⁻⁹ , A ₁₀ = 2.80044 × 10 ⁻¹³
(13th page)
k = 0,
A ₄ = -2.95059 × 10 ⁻⁵ , A ₆ = 2.76801 × 10 ⁻⁷ ,
A ₈ = -1.14673 × 10 ^-9 , A ₁₀ = 1.58937 × 10 ^-12

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 165mm)
D (7) 1.5024 4.6450
D (9) 6.5972 3.4546
f (focal length of the entire optical system) 24.2505 23.6710
Fno. (F number) 2.0600 2.1925
ω (half angle of view) 42.9614 40.9431
Bf (Back focus) 17.5000 17.5000

(Numerical values related to conditional expression (1))
f1 (the focal length of the first lens group G ₁₁ in the infinite object in-focus state) = 23.2809
f1 / f = 0.96

(Numerical value related to conditional expression (2))
f3 (the focal length of the third lens group G ₁₃ in the infinite object in-focus state) = 42.9234
f3 / f = 1.77

(Numerical values related to conditional expression (3))
βr (combined lateral magnification of the entire lens located on the image plane side from the image stabilization lens (negative lens L ₁₁₃ )) = 1.0412
βv (lateral magnification of image stabilization lens (negative lens L ₁₁₃ )) = 1.8479
| Βr × (1−βv) | = 0.88

(Numerical values related to conditional expression (4))
L1s (axial distance from the most object side surface to the aperture stop S in the first lens group G ₁₁₎ = 32.0462
L (total length of optical system) = 85.0001
L1s / L = 0.38

  FIG. 2 is a diagram illustrating various aberrations of the inner focus lens according to Example 1. In the figure, the curve represents the aberration of the wavelength corresponding to the e-line (λ = 546.074 nm). Further, 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 cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the second embodiment. FIG. 3 shows an infinite object focusing state. 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.

The first lens group G ₂₁ includes, in order from the object side, a negative meniscus lens L ₂₁₁ , an aperture stop S that defines a predetermined aperture, a positive lens L _212, and a positive lens L _213. The The negative meniscus lens _L211 is disposed with the convex surface facing the object side. Aspherical surfaces are formed on both surfaces of the positive lens _L212 . The positive lens L ₂₁₃ has a function as an image stabilization lens, and performs image stabilization correction by moving in the direction perpendicular to the optical axis.

The second lens group G ₂₂ includes, is composed of a negative lens L _221. An aspheric surface is formed on both surfaces of the 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 negative meniscus lens L _232, is the arrangement. The negative meniscus lens L ₂₃₂ is arranged with the convex surface facing the image plane IMG side. On both surfaces of the negative meniscus lens L _232, aspheric surface is formed.

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

(Lens data)
r ₁ = 50.7966
d ₁ = 1.2000 nd ₁ = 1.65844 νd ₁ = 50.85
r ₂ = 16.4740
d ₂ = 28.9459
r ₃ = ∞ (aperture stop)
d ₃ = 1.5000
r ₄ = 25.9067 (aspherical surface)
d ₄ = 6.3217 nd ₂ = 1.82080 νd ₂ = 42.71
r ₅ = -53.0773 (aspherical surface)
d ₅ = 1.6170
r ₆ = 60.7371
d ₆ = 1.7262 nd ₃ = 1.83481 νd ₃ = 42.72
r ₇ = 87.3487
d ₇ = D (7) (variable)
r ₈ = 108.5200 (aspherical surface)
d ₈ = 1.0000 nd ₄ = 1.82115 νd ₄ = 24.06
r ₉ = 16.1465 (aspherical surface)
d ₉ = D (9) (variable)
r ₁₀ = 35.3691
d ₁₀ = 5.9722 nd ₅ = 1.49700 νd ₅ = 81.61
r ₁₁ = -21.3423
d ₁₁ = 11.3254
r ₁₂ = -14.6475 (aspherical surface)
d ₁₂ = 1.2000 nd ₆ = 1.68893 νd ₆ = 31.16
r ₁₃ = -22.5821 (aspherical surface)
d ₁₃ = Bf

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Fourth surface)
k = 0,
A ₄ = -1.19735 × 10 ⁻⁵ , A ₆ = 1.30026 × 10 ⁻⁸ ,
A ₈ = -1.46375 × 10 ⁻¹² , A ₁₀ = 1.12146 × 10 ⁻¹²
(5th page)
k = 0,
A ₄ = 8.80828 × 10 ⁻⁶ , A ₆ = −2.81490 × 10 ⁻⁸ ,
A ₈ = 3.74731 × 10 ^-10 , A ₁₀ = 7.37631 × 10 ^-14
(8th page)
k = 0,
A ₄ = -2.84488 × 10 ^-5 , A ₆ = -1.38681 × 10 ^-7 ,
A ₈ = 2.17840 × 10 ⁻⁹ , A ₁₀ = −9.94443 × 10 ⁻¹²
(9th page)
k = 0,
A ₄ = -2.96055 × 10 ^-5 , A ₆ = -1.89514 × 10 ^-7 ,
A ₈ = 1.95330 × 10 ^-9 , A ₁₀ = -1.16569 × 10 ^-11
(Twelfth surface)
k = 0,
A ₄ = 3.05501 × 10 ^-4 , A ₆ = -1.98913 × 10 ^-6 ,
A ₈ = 8.91545 × 10 ^-9 , A ₁₀ = -1.40504 × 10 ^-11
(13th page)
k = 0,
A ₄ = 2.76920 × 10 ^-4 , A ₆ = -1.85115 × 10 ^-6 ,
A ₈ = 7.58787 × 10 ^-9 , A ₁₀ = -1.34483 × 10 ^-11

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 165mm)
D (7) 1.2067 2.5556
D (9) 5.4849 4.1360
f (focal length of the entire optical system) 24.2496 23.3660
Fno. (F number) 2.0600 2.1468
ω (half angle of view) 42.7201 41.2990
Bf (Back focus) 17.5000 17.5000

(Numerical values related to conditional expression (1))
f1 (the focal length of the first lens group G ₂₁ in the infinite object in-focus state) = 15.5197
f1 / f = 0.64

(Numerical value related to conditional expression (2))
f3 (the focal length of the third lens group G ₂₃ in the infinite object in-focus state) = 37.1019
f3 / f = 1.53

(Numerical values related to conditional expression (3))
βr (the combined lateral magnification of the entire lens located on the image plane side from the image stabilization lens (positive lens L ₂₁₃ )) = 1.5677
.beta.v (lateral magnification of the shake correction lens (positive lens L ₂₁₃₎₎ = 0.8843
| Βr × (1−βv) | = 0.18

(Numerical values related to conditional expression (4))
L1s (axial distance from the most object side surface of the first lens group G ₂₁ to the aperture stop S) = 30.1459
L (total length of optical system) = 85.0
L1s / L = 0.35

  FIG. 4 is a diagram illustrating various aberrations of the inner focus lens according to Example 2. In the figure, the curve represents the aberration of the wavelength corresponding to the e-line (λ = 546.074 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the third embodiment. FIG. 5 shows an infinite object focusing state. 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.

The first lens group G ₃₁ includes a negative meniscus lens L ₃₁₁ , an aperture stop S that defines a predetermined aperture, and a positive lens L _{312 in} order from the object side. The negative meniscus lens L ₃₁₁ is arranged with the convex surface facing the object side. Aspherical surfaces are formed on both surfaces of the positive lens L ₃₁₂ .

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 includes, in order from the object side, a negative lens L _331, a positive lens L _332, a negative meniscus lens L _333, is formed are disposed. Aspherical surfaces are formed on both surfaces of the negative lens _L331 . The negative lens L ₃₃₁ has a function as an image stabilization lens, and performs image stabilization correction by moving in a direction perpendicular to the optical axis. The negative meniscus lens _L333 is arranged with the convex surface facing the image plane IMG side. An aspheric surface is formed on both surfaces of the negative meniscus lens _L333 .

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

(Lens data)
r ₁ = 59.9809
d ₁ = 1.2000 nd ₁ = 1.62041 νd ₁ = 60.34
r ₂ = 16.7464
d ₂ = 23.3740
r ₃ = ∞ (aperture stop)
d ₃ = 7.2000
r ₄ = 23.4500 (aspherical surface)
d ₄ = 5.7158 nd ₂ = 1.82080 νd ₂ = 42.71
r ₅ = -53.3571 (aspherical surface)
d ₅ = D (5) (variable)
r ₆ = 69.2565 (aspherical surface)
d ₆ = 0.7000 nd ₃ = 1.82115 νd ₃ = 24.06
r ₇ = 18.5013 (aspherical surface)
d ₇ = D (7) (variable)
r ₈ = 33.2931 (aspherical surface)
d ₈ = 1.000 nd ₄ = 1.68893 νd ₄ = 31.16
r ₉ = 26.3278 (aspherical surface)
d ₉ = 1.5000
r ₁₀ = 36.1037
d ₁₀ = 6.0682 nd ₅ = 1.49700 νd ₅ = 81.61
r ₁₁ = -20.6114
d ₁₁ = 11.1149
r ₁₂ = -21.5561 (aspherical surface)
d ₁₂ = 1.2000 nd ₆ = 1.68893 νd ₆ = 31.16
r ₁₃ = -68.3787 (aspherical surface)
d ₁₃ = Bf

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Fourth surface)
k = 0,
A ₄ = -1.66004 × 10 ⁻⁵ , A ₆ = −5.43170 × 10 ⁻⁸ ,
A ₈ = 2.00939 × 10 ^-10 , A ₁₀ = -4.95458 × 10 ^-13
(5th page)
k = 0,
A ₄ = -1.91576 × 10 ⁻⁶ , A ₆ = 5.81292 × 10 ⁻⁸ ,
A ₈ = -3.75639 × 10 ⁻¹⁰ , A ₁₀ = 6.81515 × 10 ⁻¹³
(Sixth surface)
k = 0,
A ₄ = 3.38272 × 10 ⁻⁶ , A ₆ = −2.776388 × 10 ⁻⁸ ,
A ₈ = -1.13900 × 10 ^-9 , A ₁₀ = 9.00318 × 10 ^-13
(Seventh side)
k = 0,
A ₄ = 2.39738 × 10 ⁻⁵ , A ₆ = −1.08643 × 10 ⁻⁷ ,
A ₈ = -7.56657 × 10 ^-10 , A ₁₀ = -4.37423 × 10 ^-12
(8th page)
k = 0,
A ₄ = -8.15146 × 10 ^-6 , A ₆ = -1.81322 × 10 ^-7 ,
A ₈ = 2.19877 × 10 ⁻⁹ , A ₁₀ = −7.48481 × 10 ⁻¹²
(9th page)
k = 0,
A ₄ = -1.20490 × 10 ⁻⁵ , A ₆ = −2.01960 × 10 ⁻⁷ ,
A ₈ = 2.14883 × 10 ⁻⁹ , A ₁₀ = −6.888228 × 10 ⁻¹²
(Twelfth surface)
k = 0,
A ₄ = -5.35091 × 10 ⁻⁵ , A ₆ = 2.40846 × 10 ⁻⁷ ,
A ₈ = -1.22462 × 10 ^-9 , A ₁₀ = 2.2011 × 10 ^-12
(13th page)
k = 0,
A ₄ = -3.96839 × 10 ⁻⁵ , A ₆ = 2.38572 × 10 ⁻⁷ ,
A ₈ = -9.426 × 10 ^-10 , A ₁₀ = 1.69354 × 10 ^-12

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 215mm)
D (5) 1.5064 2.5986
D (7) 6.9207 5.8284
f (focal length of the entire optical system) 24.2465 23.4634
Fno. (F number) 2.0733 2.1222
ω (half angle of view) 43.3199 42.9121
Bf (Back focus) 17.5000 17.5000

(Numerical values related to conditional expression (1))
f1 (the focal length of the first lens group G ₃₁ in the infinite object in-focus state) = 15.7602
f1 / f = 0.65

(Numerical value related to conditional expression (2))
f3 (focal length of the third lens group G ₃₃ in the infinite object focusing state) = 54.5546
f3 / f = 2.25

(Numerical values related to conditional expression (3))
βr (combined lateral magnification of the entire lens positioned on the image plane side from the image stabilization lens (negative lens L ₃₃₁ )) = 0.1132
βv (lateral magnification of image stabilization lens (negative lens L ₃₃₁ )) = 2.6018
| Βr × (1−βv) | = 0.18

(Numerical values related to conditional expression (4))
L1s (axial distance from the most object side surface to the aperture stop S in the first lens group G ₃₁₎ = 24.5740
L (total length of optical system) = 85.0
L1s / L = 0.29

  FIG. 6 is a diagram illustrating various aberrations of the inner focus lens according to Example 3. In the figure, the curve represents the aberration of the wavelength corresponding to the e-line (λ = 546.074 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the inner focus lens according to the fourth example. FIG. 7 shows an infinite object focusing state. The inner focus type lens includes a first lens group G ₄₁ having a positive refractive power, a second lens group G ₄₂ 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 _43, is formed are disposed.

The first lens group G ₄₁ defines, in order from the object side, a negative meniscus lens L ₄₁₁ , a positive lens L ₄₁₂ , a negative lens L ₄₁₃ , a negative lens L ₄₁₄ , a positive lens L _415, and a predetermined aperture. An aperture stop S and a positive lens L ₄₁₆ are arranged. The negative meniscus lens L ₄₁₁ is disposed with the convex surface facing the object side. The positive lens L ₄₁₂ and the negative lens L ₄₁₃ are cemented. The negative lens L ₄₁₄ and the positive lens L ₄₁₅ are cemented. Aspherical surfaces are formed on both surfaces of the positive lens L ₄₁₆ .

The second lens group _G42 includes a negative lens _L421 . An aspheric surface is formed on both surfaces of the negative lens _L421 . The second lens group G ₄₂ 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 ₄₃ is constituted in order from the object side, a positive lens L _431, a positive lens L _432, a negative meniscus lens L _433, is the arrangement. The positive lens L ₄₃₁ has a function as an image stabilization lens, and performs image stabilization correction by moving in the direction perpendicular to the optical axis. Aspherical surfaces are formed on both surfaces of the positive lens _L432 . The negative meniscus lens L ₄₃₃ is arranged with the convex surface facing the image plane IMG side. Aspherical surfaces are formed on both surfaces of the negative meniscus lens _L433 .

  Various numerical data relating to the inner focus lens according to Example 4 will be described below.

(Lens data)
r ₁ = 31.5654
d ₁ = 1.4000 nd ₁ = 1.59349 νd ₁ = 67.00
r ₂ = 16.6857
d ₂ = 6.7441
r ₃ = 30.6835
d ₃ = 4.9298 nd ₂ = 1.92286 νd ₂ = 20.88
r ₄ = 196.4467
d ₄ = 1.5000 nd ₃ = 1.49700 νd ₃ = 81.61
r ₅ = 12.0646
d ₅ = 8.5002
r ₆ = -39.4077
d ₆ = 0.9500 nd ₄ = 1.84666 νd ₄ = 23.78
r ₇ = 18.3311
d ₇ = 5.2475 nd ₅ = 1.83481 νd ₅ = 42.72
r ₈ = -37.1613
d ₈ = 5.3995
r ₉ = ∞ (aperture stop)
d ₉ = 1.3000
r ₁₀ = 33.7647 (aspherical surface)
d ₁₀ = 7.2414 nd ₆ = 1.61881 νd ₆ = 63.86
r ₁₁ = -20.5786 (aspherical surface)
d ₁₁ = D (11) (variable)
r ₁₂ = 101.3252 (aspherical surface)
d ₁₂ = 0.7000 nd ₇ = 1.58313 νd ₇ = 59.46
r ₁₃ = 19.7653 (aspherical surface)
d ₁₃ = D (13) (variable)
r ₁₄ = 60.8684
d ₁₄ = 2.0222 nd ₈ = 1.49700 νd ₈ = 81.61
r ₁₅ = 1468.5933
d ₁₅ = 1.5500
r ₁₆ = 185.2329 (aspherical surface)
d ₁₆ = 3.8000 nd ₉ = 1.49710 νd ₉ = 81.56
r ₁₇ = -42.9547 (aspherical surface)
d ₁₇ = 10.3904
r ₁₈ = -17.3765 (aspherical surface)
d ₁₈ = 1.2000 nd ₁₀ = 1.62263 νd ₁₀ = 58.16
r ₁₉ = -21.4062 (aspherical surface)
d ₁₉ = Bf

Conical coefficient (k) and aspheric coefficient (A ₄ , A ₆ , A ₈ , A ₁₀ )
(Tenth aspect)
k = 0,
A ₄ = -2.12096 × 10 ^-5 , A ₆ = -2.32683 × 10 ^-8 ,
A ₈ = 7.54664 × 10 ^-11 , A ₁₀ = 0
(11th page)
k = 0,
A ₄ = 1.66117 × 10 ⁻⁵ , A ₆ = −3.999193 × 10 ⁻⁸ ,
A ₈ = 1.28760 × 10 ^-10 , A ₁₀ = 0
(Twelfth surface)
k = 0,
A ₄ = -2.20256 × 10 ^-6 , A ₆ = -1.17681 × 10 ^-7 ,
A ₈ = 3.58823 × 10 ^-10 , A ₁₀ = -3.78077 × 10 ^-13
(13th page)
k = 0,
A ₄ = 4.82922 × 10 ⁻⁶ , A ₆ = −1.20093 × 10 ⁻⁷ ,
A ₈ = 1.06466 × 10 ^-10 , A ₁₀ = -5.93216 × 10 ^-13
(16th surface)
k = 0,
A ₄ = 5.93514 × 10 ^-5 , A ₆ = -1.01507 × 10 ^-8 ,
A ₈ = -5.11953 × 10 ^-11 , A ₁₀ = 5.332827 × 10 ^-13
(Seventeenth surface)
k = 0,
A ₄ = 3.95560 × 10 ⁻⁵ , A ₆ = −7.004346 × 10 ⁻⁸ ,
A ₈ = -1.18331 × 10 ⁻¹⁰ , A ₁₀ = 3.11147 × 10 ⁻¹³
(18th page)
k = 0,
A ₄ = 0.000197062, A ₆ = -1.48374 × 10 ⁻⁶ ,
A ₈ = 4.30243 × 10 ⁻⁹ , A ₁₀ = −9.11363 × 10 ⁻¹²
(19th page)
k = 0,
A ₄ = 0.000202908, A ₆ = -1.23492 × 10 ⁻⁶ ,
A ₈ = 3.23871 × 10 ⁻⁹ , A ₁₀ = −2.16836 × 10 ⁻¹²

(Numeric data for each in-focus state)
Infinite distance Closest distance (object distance 110.5mm)
D (11) 1.4993 4.6395
D (13) 8.1256 4.9855
f (focal length of the entire optical system) 24.2502 23.1966
Fno. (F number) 2.0600 2.0600
ω (half angle of view) 41.9023 39.5710
Bf (Back focus) 17.0000 17.0000

(Numerical values related to conditional expression (1))
f1 (the focal length of the first lens group G ₄₁ in the infinite object in-focus state) = 18.4302
f1 / f = 0.76

(Numerical value for conditional expression (2))
f3 (the focal length of the third lens group G ₄₃ in the infinite object in-focus state) = 59.8980
f3 / f = 2.47

(Numerical value for conditional expression (3))
βr (the combined lateral magnification of the entire lens positioned on the image plane side from the image stabilization lens (positive lens L ₄₃₁ )) = 0.7147
βv (lateral magnification of image stabilization lens (positive lens L ₄₃₁ )) = 0.6447
| Βr × (1−βv) | = 0.25

(Numerical values related to conditional expression (4))
L1s (axial distance from the most object side surface to the aperture stop S in the first lens group G ₄₁₎ = 34.6711
L (total length of optical system) = 89.5
L1s / L = 0.39

  FIG. 8 is a diagram illustrating various aberrations of the inner focus lens according to Example 4. In the figure, the curve represents the aberration of the wavelength corresponding to the e-line (λ = 546.074 nm). Further, S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

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 ₄ , A ₆ , A ₈ , and A ₁₀ , respectively, and the light traveling direction is positive, the following aspheric coefficients are expressed by the following equations.

  In each of the above embodiments, an example of an inner focus type lens having a focal length of 25 mm in terms of a 35 mm film camera is shown. The inner focus type lens in each of the above-described embodiments can achieve high-speed autofocus processing and image stabilization that are indispensable for video shooting by reducing the size and weight of the focus group and image stabilization group. Become. In particular, by satisfying the above conditional expressions, it is possible to realize a small, wide-angle, and high-focusing inner focusing lens suitable for moving image shooting.

  As described above, the inner focus type lens according to the present invention is useful for a small-sized imaging device such as a photographic camera or a video camera, and is particularly suitable for an imaging device for moving image shooting.

G ₁₁ , G ₂₁ , G ₃₁ , G ₄₁ first lens group G ₁₂ , G ₂₂ , G ₃₂ , G ₄₂ second lens group G ₁₃ , G ₂₃ , G ₃₃ , G ₄₃ third lens group L ₁₁₁ , L ₁₃₂ , L ₂₁₁ , L ₂₃₂ , L ₃₁₁ , L ₃₃₃ , L ₄₁₁ , L ₄₃₃ Negative meniscus lenses L ₁₁₂ , L ₁₃₁ , L ₂₁₂ , L ₂₁₃ , L ₂₃₁ , L ₃₁₂ , L ₃₃₂ , L ₄₁₂ , L ₄₁₅ , L _416, L _431, L ₄₃₂ positive lens _{L 113, L 121, L 221} , L 321, L 331, L 413, L 414, L 421 negative lens S aperture stop IMG image plane

Claims (5)

The first lens group 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, and the second lens group. An inner focus type lens that performs focusing from an infinite object focusing state to a closest object focusing state by moving a lens group along an optical axis,
A negative meniscus lens is disposed on the most object side of the first lens group,
The second lens group is composed of a single lens component,
The first lens group or the third lens group includes an image stabilization lens composed of a single lens component that performs image stabilization correction by moving in a direction perpendicular to the optical axis.
A negative meniscus lens having a convex surface facing the image surface side is disposed on the most image surface side of the third lens group,
An inner focus type lens satisfying the following conditional expression:
(1) 0.34 ≦ f1 / f ≦ 1.48
Here, f1 represents the focal length of the first lens group in the infinite object focusing state, and f represents the focal length of the entire optical system in the infinite object focusing state. The inner focus type lens according to claim 1, wherein the following conditional expression is satisfied.
(2) 0.82 ≦ f3 / f ≦ 3.81
However, f3 shows the focal distance of the said 3rd lens group in an infinite object focusing state. The inner focus lens according to claim 1, wherein the following conditional expression is satisfied.
(3) 0.10 ≦ | βr × (1-βv) | ≦ 1.36
Where βr is the combined lateral magnification of the entire lens located on the image plane side of the image stabilization lens, and βv is the lateral magnification of the image stabilization lens. The inner focus lens according to claim 1, wherein the image stabilization lens is disposed adjacent to the second lens group. 5. The inner focus lens according to claim 1, wherein the following conditional expression is satisfied.
(4) 0.16 ≦ L1s / L ≦ 0.60
  Here, L1s is the axial distance from the most object side surface of the first lens group to the aperture stop, and L is the total length of the optical system.

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