JP2014041224A - Macro lens having vibration compensation mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain an appropriate vibration-proof sensitivity from infinity to a macro area and besides, to obtain excellent performances both at a reference time and in vibration-proofing.SOLUTION: There is provided a macro lens which comprises, from an object side: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive or negative refractive power. The fourth lens group is located nearest to an image side and comprises, in order from an object side, a 4a-th lens group having a negative refractive power and a 4b-th lens group having a positive refractive power, the 4b-th lens group is moved in a direction substantially perpendicular to an optical axis so as to correct an optical performance during vibration. Upon focusing from infinity to a finite distance, at least the second lens group and the third lens group move independently. The macro lens satisfies the following conditional expression: 0.15<|f4a/f|<0.450. 6<|f4a/f4b|≤1.0 where f4a represents a focal length of the 4a-th lens group, f4b represents a focal length of the 4b-th lens group, and f represents a focal length of an entire system.

Description

  The present invention relates to an interchangeable lens suitable for a photographic camera, a video camera, an electronic still camera, etc., and is capable of taking a close-up shot at a shooting magnification of the same magnification and capable of optically compensating for image blur due to camera shake. Related to lenses.

  2. Description of the Related Art Conventionally, in a photographic camera, there is a macro lens as a photographic lens for short-distance shooting. The macro lens is designed so that high optical performance can be obtained during close-up shooting from infinity to the same magnification.

  In general, as the photographing magnification increases, the variation in aberration accompanying focusing increases, making it difficult to correct well. In view of this, floating is employed in which a plurality of lens groups are independently moved during focusing to a short distance to correct aberration variations.

  However, the conventional floating focus method in which the first lens group is extended toward the object side has problems that rapid focusing is difficult and the distance (working distance) from the subject is shortened.

  Therefore, an inner focus type macro lens in which the first lens group does not move during focusing to a short distance has been proposed.

  Furthermore, there has been proposed a macro lens in which image blur is corrected in a vibration-proof state by moving a part of the optical system in a direction substantially perpendicular to the optical axis.

JP 2003-329919 A JP 2000-214380 A

  In macro shooting with a high shooting magnification, it is common to shoot with narrowing down to ensure a depth of field. However, this results in a slow shutter and camera shake during shooting is a problem.

  Further, at the time of macro photography, the influence of camera shake on the photographed image increases as the photographing magnification increases. For this reason, the anti-vibration lens group requires appropriate decentration sensitivity in order to compensate for image blur in the macro imaging region.

  In order to avoid an increase in the size of the anti-vibration group driving portion, it is desirable that the anti-vibration lens group be as small and light as possible.

  In view of the above problems, the present invention is an inner focus type that does not change in overall length, optically compensates for image blur due to camera shake, and has a good performance in both a non-eccentric reference state and an anti-vibration state. The purpose is to provide.

In order to achieve the above object, a photographic lens according to claim 1 of the present invention comprises:
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive or negative refractive power The fourth lens group closest to the image side is composed of a 4a lens group having a negative refractive power and a 4b lens group having a positive refractive power in order from the object side. The optical performance during vibration is corrected by moving in a direction substantially perpendicular to the axis, and at the time of focusing from infinity to a finite distance, at least the second lens group and the third lens group move independently,
The following conditional expression is satisfied.

0.15 <| f4a / f | <0.45
0.6 <| f4a / f4b | ≦ 1.0
In the equation, f4a represents the focal length of the 4a lens group, f4b represents the focal length of the 4b lens group, and f represents the focal length of the entire system.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  As described above, according to the present invention, in the inner focus type telephoto macro lens, compensation of image blur during vibration is optically performed, and from the infinity to the equal magnification region, a reference state that is an eccentric state, an eccentricity Good optical performance can be obtained in any vibration-proof state.

(A) Lens cross-sectional view of Numerical Example 1 of the present invention in an infinite state, (B) Lens cross-sectional view of Numerical Example 1 of the present invention in a magnification of −0.5 times, and (C) of the present invention. Lens sectional view of Numerical Example 1 at a magnification of -1.0 times (A) Aberration diagram in infinity state of Numerical Example 1 of the present invention, (B) Aberration diagram in magnification -0.5 times state of Numerical Example 1 of the present invention, (C) Numerical implementation of the present invention. Aberration diagram of Example 1 at magnification -1.0x (A) Aberration diagram in the state of infinity when the optical axis is inclined by 0.3 ° in Numerical Example 1 of the present invention, (B) Optical axis is 0.3 ° in Numerical Example 1 of the present invention. Aberration diagram in a tilted state at a magnification of −0.5 ×, (C) Aberration diagram in a numerical embodiment of the present invention at a magnification of −1.0 × in a state in which the optical axis is tilted by 0.3 ° (A) Lens cross-sectional view of Numerical Example 2 of the present invention in an infinite state, (B) Lens cross-sectional view of Numerical Example 2 of the present invention in a magnification of −0.5 times, and (C) of the present invention. Lens sectional view of Numerical Example 2 at a magnification of -1.0 times (A) Aberration diagram of Numerical Example 2 of the present invention in an infinite state, (B) Aberration diagram of Numerical Example 2 of the present invention at a magnification of −0.5 times, (C) Numerical implementation of the present invention. Aberration diagram of Example 2 at magnification -1.0x (A) Aberration diagram in the state of infinity when the optical axis is tilted by 0.3 ° in Numerical Example 2 of the present invention, (B) In the Numerical Example 2 of the present invention, the optical axis is 0.3 °. Aberration diagram in the state of magnification -0.5 times when tilted, (C) Aberration diagram in the state of magnification -1.0 times when the optical axis is tilted by 0.3 ° in Numerical Example 2 of the present invention (A) Lens cross-sectional view of Numerical Example 3 of the present invention in an infinite state, (B) Lens cross-sectional view of Numerical Example 3 of the present invention in a magnification of −0.5 times, and (C) of the present invention. Lens sectional view of Numerical Example 3 at a magnification of -1.0 times (A) Aberration diagram of Numerical Example 3 of the present invention in an infinite state, (B) Aberration diagram of Numerical Example 3 of the present invention at a magnification of −0.5 times, (C) Numerical implementation of the present invention. Aberration diagram of Example 3 at magnification -1.0 times (A) Aberration diagram in the state of infinity when the optical axis is tilted by 0.3 ° in Numerical Example 3 of the present invention, (B) In the Numerical Example 3 of the present invention, the optical axis is 0.3 °. Aberration diagram in a tilted state at a magnification of −0.5 ×, (C) Aberration diagram in a numerical embodiment 3 of the present invention at a magnification of −1.0 × in a state in which the optical axis is tilted by 0.3 °

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Numerical Example 1]
Table 1 (a) and Table 1 (b) are numerical values of Numerical Example 1 of the present invention. In the numerical values, r is the radius of curvature, d is the surface spacing, nd is the refractive index of the d-line, and νd is the Abbe number.

  FIG. 1A is a lens cross-sectional view in the infinity state according to Numerical Example 1 of the present invention. FIG. 1B is a lens cross-sectional view in a state where the photographing magnification is 0.5 times and FIG. 1C is a state in which the photographing magnification is 1.0 times.

  In FIG. 1A, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 has a positive refractive power. This is a 4b lens group.

  During focusing to a short distance, the first lens group is fixed, the second lens group moves to the image side, and the third lens group moves to the object side. By fixing the first lens group, it is possible to realize a lens having a good overall operability with a constant overall length. Independent of the movement of the second lens group to the image side, the third lens group is moved to the object side to increase the magnification at close distance to the same magnification, and at the same time, aberrations due to focusing to the short distance The fluctuation can be corrected well.

  In the L4 lens group, L4a is a 4a lens group having negative refractive power, and L4b is a 4b lens group having positive refractive power. The 4a lens group includes a cemented lens composed of a lens having negative refractive power and a lens having positive refractive power from the object side, and a single lens having negative refractive power, and is substantially perpendicular to the optical axis. Image blurring during vibration is corrected by moving in the direction. SP is a stop, SP2 is a sub stop, and IP is an image plane.

In order to obtain higher optical performance in the macro lens of the present invention, it is necessary to satisfy the following conditional expression.
0.15 <| f4a / f | <0.45 (1)
0.6 <| f4a / f4b | ≦ 1.0 (2)
Conditional expression (1) is a conditional expression relating to the focal length of the 4a lens group having the image stabilization function, and is a condition for obtaining an appropriate lens refractive power for performing image stabilization with the telephoto macro lens.

  In general, a condition necessary for reducing the eccentric field curvature in the vibration-proof state is expressed by the following equation.

(Source: Yoshiya Matsui Third-order aberration theory of optical system with eccentricity Japan Opto-Mechatronics Association 1989)
In the equation, Pp is the Petzval sum of the anti-vibration lens group, Pq is the Petzval sum of the rear group of the anti-vibration lens group, αp is the angle of light incident on the anti-vibration lens group, and α′p is emitted from the anti-vibration lens group. Represents the angle of the ray.

From equation (A), in order to make the field curvature in the eccentric state zero, for example, in this conditional expression:
・ Α′p = 0, that is, the light beam emitted from the image stabilization group is parallel to the optical axis (afocal) ・ The combined Petzval sum of the image stabilization group 5a and the lens group 5b needs to be 0 become.

  In addition, in the macro area where the shooting magnification is high, in addition to the blurring in the rotation direction around the fulcrum on the optical axis, which is the cause of camera shake at a long distance, the contribution of blurring that occurs substantially parallel to the optical axis growing.

  In order to correct the above two different types of camera shake, an appropriate refractive power is required for the anti-vibration lens group.

  If the refractive power of the 4a lens group is so weak that the upper limit of conditional expression (1) is exceeded, image blurring during vibration at the low shutter speed will not be sufficiently corrected, and it will be difficult to maintain good anti-shake performance. . Conversely, if the refractive power of the third lens group is so strong that the lower limit of conditional expression (1) is exceeded, it becomes difficult to correct various aberrations during focusing.

In the telephoto macro lens, satisfying the conditional expression (1) in order to obtain appropriate sensitivity at the time of image stabilization increases the negative refractive power of the image stabilization lens group.
α′p> 0
It becomes. Conditional expression (2) is a conditional expression relating to the ratio of refractive powers of the 4a lens group and 4b lens group having an anti-vibration function. In the above-mentioned expression (A), the conditional expression (1) is satisfied and This is a conditional expression for maintaining good conditions and ensuring good performance in both the reference state and the vibration-proof state. If the ratio of the refractive powers of the two lens groups is so small that the upper limit of conditional expression (2) is exceeded, correction of various aberrations in the reference state becomes difficult. If the ratio of the refractive powers of the two lens groups is so large that the lower limit of conditional expression (2) is exceeded, the direction deviates from the aforementioned condition for reducing the decentered field curvature, and it becomes difficult to correct the vibration-proof aberration.

In order to obtain higher optical performance in the macro lens of the present invention, it is further necessary to satisfy the following conditional expression.
−1.0 <β2∞ / β2mod <1.0 (3)
1.0 <| β3∞ / β3mod | <20 (4)
Conditional expressions (3) and (4) are conditions relating to magnification sharing in the telephoto macro lens. By moving the second lens group to the image side by focusing, the photographing magnification is increased. By moving the third lens group toward the object side, it is possible to reduce fluctuations in various aberrations at the focus. As a result, it is possible to obtain a good performance in the entire focus area by floating while securing an equal magnification in the entire system.

  Conditional expression (3) is a conditional expression related to the photographing magnification of the second lens group, and is a condition for obtaining a high photographing magnification in the telephoto macro lens. If the change in magnification due to the focus of the second lens group is so small that the upper limit of conditional expression (3) is exceeded, it will be difficult to obtain the same magnification. If the refractive power of the second lens group is so strong that the lower limit of conditional expression (3) is exceeded, it becomes difficult to correct variations in various aberrations due to focusing.

Desirably, the range of conditional expression (3) is
−0.1 <β2∞ / β2mod <0.8
As a result, good performance can be obtained.

  Conditional expression (4) is a conditional expression for the photographing magnification of the third lens group, and is a condition for obtaining a high photographing magnification in the telephoto macro lens. If the refractive power of the third lens unit is so weak that the upper limit of conditional expression (3) is exceeded, the amount of extension for obtaining the floating effect increases, leading to an increase in the size of the entire system. When the lower limit of conditional expression (3) is exceeded, correction of aberrations due to floating becomes difficult.

Desirably, the range of conditional expression (3) is
1.2 <| β3∞ / β3mod | <5.0
As a result, good performance can be obtained.

  FIG. 2A is an aberration diagram in the infinite state according to Example 1 of the present invention. FIG. 2B is an aberration diagram for Example 1 with a photographing magnification of 0.5. FIG. 2C is an aberration diagram in Example 1 according to the present invention when the photographing magnification is 1.0. Both have good aberrations.

FIG. 3A is an aberration diagram in Example 1 according to the present invention when the lens is tilted 0.3 ° from the optical axis at infinity. FIG. 3B is an aberration diagram in Example 1 of the present invention when the photographing magnification is 0.5 times and the optical axis is inclined by 0.3 °. FIG. 3C is an aberration diagram in the first embodiment of the present invention when the photographing magnification is 1.0 and the lens is inclined 0.3 ° from the optical axis. Good aberrations when decentered.
[Numerical Example 2]
Table 2 (a) and Table 2 (b) are numerical values of Numerical Example 2 of the present invention. In the numerical values, r is the radius of curvature, d is the surface spacing, nd is the refractive index of the d-line, and νd is the Abbe number.

  FIG. 4A is a lens cross-sectional view in the infinity state according to Numerical Example 2 of the present invention. FIG. 4B is a lens cross-sectional view at a shooting magnification of 0.5 times. FIG. 4C is a lens cross-sectional view at a photographing magnification of 1.0.

  In FIG. 4A, L1 is a first lens unit having a positive refractive power, L2 is a second lens unit having a negative refractive power, L3 includes a stop, a third lens group having a positive refractive power, and L4 is a positive lens unit. This is a fourth lens unit having a refractive power of. During focusing to a short distance, the first lens group is fixed, the second lens group moves to the image side, and the third lens group moves to the object side. By fixing the first lens group, it is possible to realize a lens having a good overall operability with a constant overall length. Independent of the movement of the second lens group to the image side, the third lens group is moved to the object side to increase the magnification at close distance to the same magnification, and at the same time, aberrations due to focusing to the short distance The fluctuation can be corrected well.

In the L4 lens group, L4a is a 4a lens group having negative refractive power, and L4b is a 4b lens group having positive refractive power. The 4a lens group is a cemented lens of a lens having a negative refractive power and a lens having a positive refractive power, and is moved in a direction substantially perpendicular to the optical axis to correct image blur during vibration. . SP is a stop, SP2 is a sub stop, and IP is an image plane.
In the macro lens of the present invention, the conditional expressions and their meanings necessary for obtaining higher performance are the same as those in the numerical example 1.

FIG. 5A is an aberration diagram in Example 2 of the present invention in the state of infinity. FIG. 5B is an aberration diagram for Example 2 of the present invention when the photographing magnification is 0.5 times. FIG. 5C is an aberration diagram for Example 2 of the present invention when the photographing magnification is 1.0.
Both have good aberrations.

FIG. 6A is an aberration diagram in Example 2 according to the present invention when the lens is tilted 0.3 ° from the optical axis at infinity. FIG. 6B is an aberration diagram in Example 2 of the present invention when the photographing magnification is 0.5 times and the optical axis is inclined by 0.3 °. FIG. 6C is an aberration diagram in Example 2 of the present invention when the photographing magnification is 1.0 and the lens is inclined by 0.3 ° from the optical axis. Good aberrations when decentered.
[Numerical Example 3]
Table 3 (a) and Table 3 (b) are numerical values of Numerical Example 3 of the present invention. In the numerical values, r is the radius of curvature, d is the surface spacing, nd is the refractive index of the d-line, and νd is the Abbe number.

  FIG. 7A is a lens cross-sectional view in the infinity state according to Numerical Example 3 of the present invention. FIG. 7B is a lens cross-sectional view in the same magnification state at a photographing magnification of 0.5 times. FIG. 7C is a lens cross-sectional view in the same magnification state at a photographing magnification of 1.0.

  In FIG. 7A, L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, L3 includes a stop, a third lens group having a positive refractive power, and L4 is negative. This is a fourth lens unit having a refractive power of.

  During focusing to a short distance, the first lens group is fixed, the second lens group is moved to the image side, the third lens group is fixed, and the fourth lens group is moved to the object side. By fixing the first lens group, it is possible to realize a lens having a good overall operability with a constant overall length. Independent of the movement of the second lens group to the image side, the third lens group is moved to the object side to increase the magnification at close distance to the same magnification, and at the same time, aberrations due to focusing to the short distance The fluctuation can be corrected well.

  In the L4 lens group, L4a is a 4a lens group having negative refractive power, and L4b is a 4b lens group having positive refractive power. The 4a lens group is a cemented lens of a lens having a negative refractive power and a lens having a positive refractive power, and is moved in a direction substantially perpendicular to the optical axis to correct image blur during vibration. . SP is a stop, SP2 is a sub stop, and IP is an image plane.

  In the macro lens of the present invention, the conditional expressions and their meanings necessary for obtaining higher performance are the same as those in the numerical example 1.

  FIG. 8A is an aberration diagram in Example 3 of the present invention in the infinity state. FIG. 8B is an aberration diagram for Example 3 of the present invention when the photographing magnification is 0.5 times. FIG. 8C is an aberration diagram for Example 3 of the present invention when the imaging magnification is 1.0.

  Both have good aberrations.

  FIG. 9A is an aberration diagram in Example 3 of the present invention when the lens is tilted 0.3 ° from the optical axis at infinity. FIG. 9B is an aberration diagram in Example 3 according to the present invention when the photographing magnification is 0.5 times and the optical axis is inclined by 0.3 °. FIG. 9C is an aberration diagram in Example 3 according to the present invention when the photographing magnification is 1.0 and the lens is inclined by 0.3 ° from the optical axis. Good aberrations when decentered.

In general, with a macro lens, Fno is
(1-β) ・ Fno
It will change according to the equation. By changing the sub-aperture SP2 in accordance with the change of the on-axis light beam, it is possible to reduce the diameter of the aperture and cut an unnecessary light beam.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5a 4a lens group L5b 4b lens group SP Aperture SP2 Sub-aperture IP Image surface Y Image height solid line d-line M Meridional image surface S Sagittal Image plane

Claims (4)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive or negative refractive power Consists of
The fourth lens group closest to the image side includes a 4a lens group having negative refractive power and a 4b lens group having positive refractive power in order from the object side, and the previous 4b lens group is perpendicular to the optical axis. To correct the optical performance during vibration,
At the time of focusing from infinity to a finite distance, at least the second lens group and the third lens group move independently,

A macro lens characterized by satisfying the following conditional expression:
0.15 <| f4a / f | <0.45
0.6 <| f4a / f4b | ≦ 1.0

f4a: focal length of the 4a lens group, f4b: focal length of the 4b lens group, f: focal length of the entire system   The macro lens according to claim 1, wherein the fourth lens group includes at least one lens having a positive refractive power and one lens having a negative refractive power. The macro lens according to claim 1, wherein the following conditional expression is satisfied.
−1.0 <β2∞ / β2mod <1.0
β2∞: photographing magnification at infinity of the second lens group β2mod: photographing magnification at the same magnification as the second lens group The macro lens according to claim 1, wherein the following conditional expression is satisfied.
1.0 <| β3∞ / β3mod | <20
β3∞: photographing magnification at infinity of the third lens group β3mod: photographing magnification at the same magnification as that of the third lens group