JP5378880B2 - Inner focus type macro lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner focus type macro lens where, on focusing, the swift performance of the driving of lens groups is achievable, and photographing magnification is large than 0.45 times in absolute value, and which has a half angle of view satisfying about 20 degrees, in which various aberrations are satisfactorily rectified, and which can have a vibration-proof function as well. <P>SOLUTION: The inner focus type macro lens is composed, in the order from the object side, of a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power; and a fourth lens group having negative refractive power, and, when focusing is performed from an infinity object to a short-distance object, the first lens group and the fourth lens group are fixed to the image plane, when the second lens group move to the image plane side, simultaneously, the third lens group is moved to the object side, part or the whole of any lens group is moved almost to the vertical direction to an optical axis, an image can be moved almost in the direction vertical to the optical axis, and prescribed conditional expression is satisfied. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to an inner focus type macro lens, in particular, a digital still camera that can shoot from an object at infinity to an object at a close distance, and can have an image stabilization function for correcting image blur due to camera shake, The present invention relates to an inner focus type macro lens such as an interchangeable lens suitable for a silver salt camera and a video camera.

Conventionally, a macro lens using an inner focus is known (see, for example, Patent Documents 1 to 5).

JP 2005-292345 A

JP 2006-171432 A

JP 2006-106112 A

JP 2008-257200 A

JP 2009-063715 A

In the inventions described in Patent Document 1 and Patent Document 2, the number of lens groups that move during focusing is as large as three, and it is not easy to increase the focusing driving speed.

In the invention described in Patent Document 3, there are only two lens groups that move during focusing, but the half field angle of about 20 degrees, which is the object of the present invention, cannot be obtained.

In the invention described in Patent Document 4, there are only two lens groups that move during focusing, and a half field angle of about 20 degrees, which is the object of the present invention, is obtained. However, a lens group having an anti-vibration function is clearly disclosed. It has not been.

In the invention described in Patent Document 5, there are only two lens groups that move during focusing, and a half field angle of about 20 degrees, which is the object of the present invention, is obtained, but the distance from the image plane to the image stabilizing lens group is small. Since it is short, it is difficult to dispose electrical parts and mechanical parts for controlling the anti-vibration lens group.

According to the present invention, the lens group can be driven quickly during focusing, the photographing magnification can be made larger than 0.45 times in absolute value, it has a half angle of view of about 20 degrees, and various aberrations. Provided is an inner focus type macro lens capable of having a vibration-proof function for satisfactorily correcting the above.

In order to solve the above-described problems, an inner focus type macro lens of the present invention includes, 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 refraction. The third lens group having power and the fourth lens group having negative refracting power are capable of making the photographing magnification at the shortest photographing distance at least an absolute value larger than 0.45 times, and infinite When focusing from a distant object to a close object, the first lens group and the fourth lens group are fixed with respect to the image plane, and at the same time the second lens group moves to the image plane side, the third lens group Are moved to the object side, and the first lens group includes, in order from the object side, a 1a lens group having a positive refractive power, a 1b lens group having a negative refractive power, and a first lens group having a positive refractive power. 1c lens group and 1b By moving in a direction substantially perpendicular to lens group with respect to the optical axis, it is possible to move in the vertical direction of the image with respect to the optical axis, internal focusing, characterized by satisfying the following condition A macro lens was used.
(1) 0.0 <f3 / f1 <0.45
(2) -1.5 <f1b / f1c <-0.6
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group
f1b: Focal length of the 1b lens group
f1c: Focal length of the first c lens group

In the inner focus type macro lens of the present invention, it is preferable that the first lens group includes at least one lens using an aspheric surface.

The present invention satisfies the above conditions, so that the lens group can be driven quickly during focusing, the photographing magnification can be made larger than 0.45 times in absolute value, and a half angle of view of about 20 degrees can be obtained. It is possible to obtain an inner focus type macro lens that has an anti-vibration function that favorably corrects various aberrations.

It is a lens block diagram of the macro lens which concerns on Example 1 of this invention. It is various aberrations in the infinity photographing state of the macro lens concerning Example 1 of the present invention. These are various aberrations at the photographing magnification | β | = 1.0 of the macro lens according to Example 1 of the present invention. FIG. 5A is a lateral aberration diagram of the macro lens according to Example 1 of the present invention at infinity shooting state, and a lateral aberration diagram at the time of image stabilization in which the image stabilization lens unit is moved by +0.45 mm in a direction perpendicular to the optical axis (A FIG. 6B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. FIG. 6 is a lateral aberration diagram at the photographing magnification | β | = 1.0 of the macro lens according to Example 1 of the present invention, and the image stabilization lens group is moved by +0.45 mm in a direction perpendicular to the optical axis. FIG. 4A is a lateral aberration diagram (A), and FIG. 4B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. It is a lens block diagram of the macro lens which concerns on Example 2 of this invention. It is various aberrations in the infinity photographing state of the macro lens concerning Example 2 of the present invention. These are various aberrations at the shooting magnification | β | = 1.0 of the macro lens according to Example 2 of the present invention. Lateral aberration diagram of the macro lens according to Example 2 of the present invention in an infinite state photographing state, and lateral aberration diagram at the time of image stabilization in which the image stabilization lens unit is moved +0.45 mm in a direction perpendicular to the optical axis (A FIG. 6B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. FIG. 10 is a lateral aberration diagram at the photographing magnification | β | = 1.0 of the macro lens according to Example 2 of the present invention, and the image stabilization lens group is moved by +0.45 mm in a direction perpendicular to the optical axis. FIG. 4A is a lateral aberration diagram (A), and FIG. 4B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. It is a lens block diagram of the macro lens which concerns on Example 3 of this invention. It is various aberrations in the infinity photographing state of the macro lens concerning Example 3 of the present invention. These are various aberrations at the photographic magnification | β | = 1.0 of the macro lens according to Example 3 of the present invention. Lateral aberration diagram of the macro lens according to Example 3 of the present invention in an infinite photographing state, and lateral aberration diagram at the time of image stabilization in which the image stabilization lens unit is moved +0.45 mm in a direction perpendicular to the optical axis (A FIG. 6B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. FIG. 6 is a lateral aberration diagram at the imaging magnification | β | = 1.0 of the macro lens according to Example 3 of the present invention, and the image stabilization lens group is moved by +0.45 mm in a direction perpendicular to the optical axis. FIG. 4A is a lateral aberration diagram (A), and FIG. 4B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. It is a lens block diagram of the macro lens which concerns on Example 4 of this invention. It is various aberrations in the infinity photographing state of the macro lens concerning Example 4 of the present invention. These are various aberrations at the photographing magnification | β | = 0.5 of the macro lens according to Example 4 of the present invention. Lateral aberration diagram of the macro lens according to Example 4 of the present invention in the state of photographing at infinity, Lateral aberration diagram at the time of image stabilization when the image stabilization lens unit is moved +0.45 mm in a direction perpendicular to the optical axis (A FIG. 6B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. FIG. 5 is a lateral aberration diagram at the photographing magnification | β | = 0.5 of the macro lens according to Example 4 of the present invention, and the image stabilization lens group is moved by +0.45 mm in a direction perpendicular to the optical axis. FIG. 4A is a lateral aberration diagram (A), and FIG. 4B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. It is a lens block diagram of the macro lens which concerns on Example 5 of this invention. FIG. 11 shows various aberrations of the macro lens according to Example 5 of the present invention in an infinite photographing state. These are various aberrations at the photographing magnification | β | = 0.5 of the macro lens according to Example 5 of the present invention. Lateral aberration diagram of the macro lens according to Example 5 of the present invention in the shooting state at infinity, Lateral aberration diagram at the time of image stabilization when the image stabilization lens unit is moved +0.45 mm in a direction perpendicular to the optical axis (A FIG. 6B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. FIG. 10 is a lateral aberration diagram at the photographing magnification | β | = 0.5 of the macro lens according to Example 5 of the present invention, and the image stabilization lens group is moved by +0.45 mm in a direction perpendicular to the optical axis. FIG. 4A is a lateral aberration diagram (A), and FIG. 4B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. It is a lens block diagram of the macro lens which concerns on Example 6 of this invention. It is various aberrations in the infinity photographing state of the macro lens concerning Example 6 of the present invention. These are various aberrations at the photographing magnification | β | = 0.5 of the macro lens according to Example 6 of the present invention. Lateral aberration diagram of the macro lens according to Example 6 of the present invention in the shooting state at infinity, Lateral aberration diagram at the time of image stabilization when the image stabilization lens unit is moved +0.45 mm in a direction perpendicular to the optical axis (A FIG. 6B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis. FIG. 10 is a lateral aberration diagram at the photographing magnification | β | = 0.5 of the macro lens according to Example 6 of the present invention; the image stabilization lens group is moved by +0.45 mm in a direction perpendicular to the optical axis; FIG. 4A is a lateral aberration diagram (A), and FIG. 4B is a lateral aberration diagram (B) at the time of image stabilization in which the image stabilization lens group is moved by −0.45 mm in a direction perpendicular to the optical axis.

Embodiments according to the inner focus type macro lens of the present invention will be described below in detail with reference to the drawings.

The inner focus type macro lens of the present invention includes, 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 negative lens group. And a fourth lens group having a refractive power of 5.

In the present invention, the shooting magnification at the shortest shooting distance can be made larger than at least 0.45 times in absolute value. The first lens group and the fourth lens group are fixed with respect to the image plane, and the third lens group moves toward the object side at the same time as the second lens group moves toward the image plane. It is possible to focus quickly by reducing the number of lens groups that sometimes move. In addition, it is possible to mount an anti-vibration function that moves part or all of any lens group in a direction substantially perpendicular to the optical axis and moves the image in a direction substantially perpendicular to the optical axis.

The inner focus type macro lens of the present invention satisfies the following conditional expression.
(1) 0.0 <f3 / f1 <0.45
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group

Conditional expression (1) defines the ratio of the focal lengths of the first lens group and the third lens group.

If f1 becomes small and exceeds the upper limit of conditional expression (1), a lens having a small radius of curvature in the first lens group must be made a smaller radius of curvature, and it is difficult to suppress spherical aberration of the first lens group. It becomes. At the same time, the Petzval sum increases on the negative side, making it difficult to correct astigmatism and field curvature. Further, if f3 is increased, the amount of movement of the focus is increased and the entire lens is increased in size.

When f1 becomes extremely large and approaches the lower limit of the expression (1), if the maximum photographing magnification | β | = about 0.5, good aberration correction can be performed with the subsequent lens groups. In order to increase the maximum photographing magnification | β | while maintaining the aberration correction in a good state, it is desirable to increase the amount of movement of the third lens group without decreasing f3, but the entire lens system becomes large. . Therefore, it is possible to reduce the amount of movement of the second lens group by increasing the refractive power of the second lens group and avoid an increase in the size of the entire lens system, but by increasing the refractive power of the second lens group, In particular, the spherical aberration coefficient and the coma aberration coefficient in the second lens group become large. Therefore, when the maximum photographing magnification is increased to near | β | = 1.0, the lower limit of conditional expression (1) may be about 0.1 in order to perform good aberration correction in the entire lens system. desirable. In addition, when f3 becomes smaller and approaches the lower limit value of the conditional expression (1), the radius of curvature of the third lens group becomes small, and correction of spherical aberration becomes particularly difficult.

The inner focus type macro lens in the present invention can have an anti-vibration function. Regarding the anti-vibration lens group, the first lens group includes, in order from the object side, a 1a lens group having a positive refractive power, a 1b lens group having a negative refractive power, and a first c having a positive refractive power. The first b lens group is moved in a direction substantially perpendicular to the optical axis, thereby moving the image in the direction perpendicular to the optical axis, and functions as an anti-vibration lens group.

When the inner focus type macro lens of the present invention has an anti-vibration function, it is desirable to satisfy the following conditional expression.
(2) -1.5 <f1b / f1c <-0.6
However,
f1b: focal length of the 1b lens group f1c: focal length of the 1c lens group

Conditional expression (2) defines the ratio between the focal length of the 1b lens group, which is the anti-vibration lens group, and the focal length of the first c lens group disposed thereafter.

When the lower limit value of conditional expression (2) is exceeded, an anti-vibration coefficient, which will be described later, decreases, and the amount of movement of the anti-vibration lens group in a direction substantially perpendicular to the optical axis during anti-vibration increases. The mechanical parts around the group become larger. When the upper limit value of conditional expression (2) is exceeded, the refractive power of the anti-vibration lens group becomes large, so that decentration coma aberration that occurs particularly during image stabilization tends to occur, and aberration correction of the entire lens system during image stabilization occurs. It becomes difficult.

Further, in the inner focus type macro lens of the present invention, it is desirable to use one or more aspheric surfaces for the first lens group. In particular, by using an aspherical surface for the 1b lens group, it becomes easy to correct off-axis aberrations during image stabilization, and it becomes easy to correct decentration coma.

By using one or more aspheric surfaces for the first lens group, in particular, coma, astigmatism, and distortion are corrected, the number of lenses in the first lens group that increases the lens diameter is reduced, and the entire lens system Can be miniaturized.

Further, by using an aspherical surface for the second lens group, it becomes easy to correct both the on-axis aberration and the off-axis aberration of the second lens group. In particular, it is possible to correct aberrations of the entire lens system by suppressing coma during focusing.

Further, by using an aspheric surface for the third lens group, it becomes easy to correct astigmatism during focusing. For this reason, even when the third lens group and subsequent lens groups are fixed with respect to the image plane, it is easy to correct field curvature during focusing.

At the time of image stabilization, the amount of movement of the image stabilization lens group in a direction substantially perpendicular to the optical axis direction is obtained from the image stabilization coefficient. The image stabilization coefficient is a ratio of the amount of movement of the image stabilization lens group to the amount of image displacement, and more specifically, all the lenses between the image stabilization lens group and the image plane (including the image stabilization lens group). And the lateral magnification of all the lenses between the lens group after the image stabilizing lens group and the image plane (not including the image stabilizing lens group).

Hereinafter, Numerical Example 1 to Numerical Example 6 of the present invention will be described.

In each numerical example, f in the overall specifications represents the focal length, Fno represents the F number, and Y represents the maximum image height from the optical axis. In the lens specifications, the first column number is the surface number of the lens surface from the object side, the second column R is the radius of curvature of the lens surface, the third column D is the lens surface interval, and the fourth column nd is the d line. The refractive index with respect to (wavelength λ = 587.56 mm), the fifth column νd represents the Abbe number with respect to the d-line. Also, “diaphragm” in the second column represents the diaphragm surface, and B. F. Represents the back focus. The variable lens surface interval represents each corresponding value with a variable interval. In the drawing, d-line, g-line, and C-line are aberrations with respect to respective wavelengths, ΔS indicates a sagittal image plane, and ΔM indicates a meridional image plane.

In all the values of the following specifications, “mm” is used as the focal length f, the radius of curvature R, the lens surface interval D, and other length units unless otherwise specified. Since the same optical performance can be obtained in proportional expansion and proportional reduction, the unit of length is not limited to “mm”.

なお、ｚは、レンズ面の頂点を基準として光軸からの高さｙの位置における光軸方向への変位量、Ｋは、円錐係数、Ａ４、Ａ６、Ａ８、Ａ１０、Ａ１２は非球面係数、ｒは基準球面の曲率半径（近軸曲率半径）を示す。なお、「Ｅ−ｎ」は「×１０＾（−ｎ）」を示し、例えば、「１．２３４Ｅ−４」は「１．２３４×１０＾（−４）」を示す。防振時の横収差を示した図面において、防振レンズ群を光軸方向に対して略垂直方向に移動させる移動量は０．４５ｍｍである。 As aspherical data, the aspherical coefficient and the conical coefficient in the case where the surface number and the shape of the aspherical surface are expressed by the following equations are shown.

Here, z is the amount of displacement in the optical axis direction at the position of the height y from the optical axis with reference to the apex of the lens surface, K is a conical coefficient, A4, A6, A8, A10, and A12 are aspheric coefficients, r indicates the radius of curvature of the reference spherical surface (paraxial radius of curvature). “E-n” indicates “× 10 ^ (− n)”, and for example, “1.234E-4” indicates “1.234 × 10 ^ (− 4)”. In the drawing showing the lateral aberration during image stabilization, the amount of movement for moving the image stabilization lens group in a direction substantially perpendicular to the optical axis direction is 0.45 mm.

(Numerical example 1)

(Numerical example 2)

(Numerical Example 3)

(Numerical example 4)

(Numerical example 5)

(Numerical example 6)

S aperture stop I image plane Gr1 first lens group Gr1a 1a lens group Gr1b 1b lens group Gr1c 1c lens group Gr2 second lens group Gr3 third lens group Gr4 fourth lens group CC line (wavelength λ = 656. 3nm)
dd line (wavelength λ = 587.6 nm)
g g line (wavelength λ = 435.8 nm)
Y Image height ΔS Sagittal image plane ΔM Medianal image plane

Claims (2)

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 having a negative refractive power Composed of groups,
The shooting magnification at the shortest shooting distance can be at least 0.45 times in absolute value,
When focusing from an object at infinity to a short distance object, the first lens group and the fourth lens group are fixed with respect to the image plane, and at the same time the second lens group moves to the image plane side, the third lens The group is moved to the object side,
The first lens group includes, in order from the object side, a 1a lens group having a positive refractive power, a 1b lens group having a negative refractive power, and a first c lens group having a positive refractive power. ,
By moving the first lens group in a direction substantially perpendicular to the optical axis, it is possible to move the image in a direction perpendicular to the optical axis,
An inner focus type macro lens that satisfies the following conditional expression.
(1) 0.0 <f3 / f1 <0.45
(2) -1.5 <f1b / f1c <-0.6
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group
f1b: Focal length of the 1b lens group
f1c: Focal length of the first c lens group The inner focus type macro lens according to claim 1,
The inner focus type macro lens according to claim 1, wherein the first lens group includes at least one lens using an aspheric surface.

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