JP2665878B2 - Internal focusing zoom lens with tele macro function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of the internal focusing zoom lens, a positive as a whole first lens group having a refractive power or a portion of the first lens group as a whole, especially constituting an afocal By extending the lens group largely in the optical axis direction, extremely high-magnification tele-macro photography is enabled, and by providing an aperture stop that satisfies predetermined conditions at the subsequent stage of the lens group extended for this tele-macro photography, The present invention relates to an in-focus zoom lens that prevents deterioration in image quality due to a large extension of a first lens group.

[0002]

2. Description of the Related Art An internal focus zoom lens in which a master lens is disposed at the subsequent stage of an afocal system, particularly an internal focus zoom lens in which a lens group having a positive refractive power as a whole is disposed in the first group of the afocal system In this case, it is conventionally known that a high magnification tele macro photographing is possible by extending the first lens unit largely in the optical axis direction. However, in general, the image quality is greatly reduced with the large extension of the first lens unit. Resulting in. In order to perform high-magnification telemacro shooting, a conversion lens and an extender in addition to the original zoom lens system are generally known.

[0003]

However, in the case of using a conversion lens or an extender as described above, there is a problem that another lens system must be prepared in addition to the original zoom lens.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and has an internal focus zoom lens capable of performing high-magnification telemacro photographing without adding another lens system. It is intended to provide.

In summary, the internal focusing zoom lens according to the present invention has a preferred mode in which: an afocal lens group and a master lens group are sequentially arranged from the object side, and the afocal lens group performs a zooming operation. Assuming that the internal focusing zoom lens performs focusing by the master lens group, the afocal lens group includes a first lens group having a positive combined refractive power and a negative combined refractive power sequentially from the object side. to be moved in the optical axis direction have a
A second lens group that performs zooming and a negative combined refractive power
Moving in the direction of the optical axis
A third lens group for performing correction and a fourth lens group having a positive combined refracting power: for close-up photography on the telephoto side, the entire first lens group or the first lens group on the subject side. Partially extended in the optical axis direction: A lens group extended in the optical axis direction during close-up photographing on the telephoto side of the afocal lens group is defined as a front afocal group, and the other in the afocal lens group When the lens group of a is defined as a group after afocal: when the conditions defined in Equations 1 and 2 are satisfied and close-up shooting is performed on the telephoto side,
At least one or more apertures face the optical axis of the front afocal group and the rear afocal group extended in the optical axis direction for close-up photography on the telephoto side, and at least one of the apertures Is characterized in that it functions as an aperture stop satisfying the condition defined in Expression 3.

[0006]

| F1 + f2-D | <0.1FW

[0007]

X (fM / f1)> 2.4FW

[0008]

[Equation 3] 8 <EFNO <32

However, in Equations 1 to 3, fM, f
1, f2, D, FW, X and EFNO are defined as follows. fM: focal length of the master lens group. f1: focal length of the afocal front group. f2: focal length of the post-afocal group in a state set as a whole on the telephoto side. D: The distance between the rear principal point of the front group before the afocal group and the front principal point of the rear group after the afocal group in a state set as a whole on the telephoto side. FW: the focal length of the entire lens system in the state set as a whole on the wide angle side. X: The extension amount of the front afocal group in the optical axis direction during close-up shooting on the telephoto side. EFNO: Effective F value of the entire lens system when performing close-up photography on the telephoto side.

The internal focusing zoom lens according to the present invention is preferably arranged as follows: an afocal lens group and a master lens group are sequentially arranged from the object side, and the afocal lens group performs a zooming operation. of the master lens group
Assuming an internally focused zoom lens that corrects the focus movement accompanying focusing and zooming by moving in the direction of the optical axis : the afocal lens group is sequentially shifted from the object side to have a positive combined refractive power. a first lens group, a zooming action by moving have a negative composite refractive power in the optical axis direction
And a third lens group having a positive combined refracting power. For close-up photography on the telephoto side, the entire first lens group or a part of the first lens group on the subject side is photographed. Without extending out in the optical axis direction: the lens group extended in the optical axis direction during close-up photographing on the telephoto side of the afocal lens group is defined as a front afocal group,
When the other lens group in the afocal lens group is defined as a post-afocal group: when the conditions defined in the above equations 1 and 2 are satisfied and close-up shooting is performed on the telephoto side,
At least one or more apertures face the optical axis of the front afocal group and the rear afocal group extended in the optical axis direction for close-up photography on the telephoto side, and at least one of the apertures Is an internal focusing zoom lens having a tele macro function that functions as an aperture stop that satisfies the condition defined by the above equation (3).

[0011]

The internal focusing zoom lens according to the present invention basically has a master lens disposed after the afocal system and a lens group having a positive combined refractive power disposed in the first group of the afocal system. Is performed as a whole or by partially moving a part of the first lens group in the optical axis direction, thereby performing high-magnification telemacro shooting. The above conditions are provided in order to prevent the image quality from deteriorating due to high-magnification tele macro photography. Among the above-mentioned conditions, the condition defined by the expression 1 is used to enable tele macro photography by extending the afocal front group in the optical axis direction, and to configure an afocal system without extending the afocal front group. Condition. The condition defined in Equation 2 is a condition that defines the amount of extension of the front group before afocal in tele macro photography. By satisfying this condition, it is possible to perform close-up close-up photography or enlarged close-up photography. If the value falls below the lower limit of the condition defined by the equation (2), it becomes difficult to perform close-up close-up photography. Further, the condition defined in Expression 3 is a condition for removing various aberrations that increase with the advance of the afocal group and maintaining the image quality. If the upper limit is exceeded, it is theoretically impossible to maintain image quality due to the wave nature of light. If the lower limit is exceeded, the influence of aberration on image quality degradation increases.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIGS. 1 and 2 are optical axis sectional views showing a first embodiment of the present invention in principle. A first lens group 1 having a positive combined refractive power and a negative combined refractive power are sequentially arranged from the object side. A second lens group 2 having a negative refractive power and a third lens group 2 having a negative combined refractive power.
A lens group 3 and a fourth lens group 4 having a positive combined refractive power
And a fifth lens group 5 having a positive combined refractive power.
The first to fourth lens groups 1 to 4 constitute an afocal system, and the fifth lens group 5 constitutes a master lens for focus adjustment. The movement of the second lens group 2 in the afocal system in the optical axis direction performs a magnification change operation, and the movement of the third lens group 3 in the optical axis direction corrects the focal movement accompanying the magnification change. When performing tele macro photography, as shown in FIG. 2, the first lens group 1 is entirely extended in the optical axis direction. That is, in the first embodiment, the first lens group 1 as a whole corresponds to the front afocal group in the claims, and the second lens group 2 to the fourth lens group 4 correspond to the rear afocal group. And the first group, which is the group before the afocal
At least one aperture stop A1, A2 is provided between the first lens group 1 and the second lens group 2 in order to suppress various aberrations that increase with the extension of the lens groups. still,
The apertures A1 and A2 may be retracted outside the optical path by an arbitrary method.

Next, Table 1 shows a specific configuration example of the first embodiment, and FIGS. 3 and 4 show specific optical axis sectional views. FIG. 3 shows an intermediate focal length, and FIG. 4 shows a tele macro state. In the table, ri is i sequentially from the object side.
The radius of curvature of each curved surface, Ti is the distance between the top surfaces of the axes from the i-th curved surface to the next curved surface sequentially from the object side, and Ndi is the refraction of the glass from the i-th curved surface to the next curved surface sequentially from the object side. The rate and νdi indicate the Abbe number of the glass from the i-th curved surface to the next curved surface in order from the object side, and ri is indicated as the sign of the surface corresponding to FIGS.

[0014]

[Table 1]

FIGS. 5 to 8 show aberration diagrams of the first embodiment shown in Table 1. FIG. 5 is an aberration diagram at the wide-angle end with a focal length of 1, FIG. 6 is an aberration diagram at a standard position with a focal length of 2.12, and FIG. 7 is an aberration diagram at a tele-end with a focal length of 7.45. 8 is an aberration diagram in a tele-macro state with a photographing magnification of −1.0, and the aberration diagrams in FIGS. 5 to 8 show spherical aberration, astigmatism, and distortion in order from left to right. Shown,
d indicates a d-line, DS indicates a sagittal direction, DT indicates a meridional direction, and SC indicates a sine condition. As shown in these aberration diagrams, according to the first embodiment shown in Table 1, practically good aberration characteristics can be obtained while performing tele-macro photographing with a photographing magnification of -1.0. .

FIGS. 9 and 10 are sectional views of an optical axis showing a second embodiment of the present invention in principle. The first lens group 11a and the first lens group 11a having a positive combined refractive power are sequentially arranged from the object side. 1
1b, a second lens group 12 having a negative combined refractive power,
A first lens group 11a having a third lens group 13 having a negative combined refractive power, a fourth lens group 14 having a positive combined refractive power, and a fifth lens group 15 having a positive combined refractive power;
And 11b to the fourth lens group 14 constitute an afocal system, and the fifth lens group 15 constitutes a master lens for focus adjustment. The zooming action is performed by moving the second lens group 12 in the afocal system in the direction of the optical axis, and the focus movement accompanying the zooming is corrected by moving the third lens group 13 in the direction of the optical axis. When performing tele macro photography, as shown in FIG. 10, the object side lens group 11a of the first lens groups 11a and 11b is extended in the optical axis direction. That is, in the second embodiment, the first lens groups 11a and 11a
The object side lens group 11a in 1b corresponds to the front afocal group in the claims, and the rear lens group 11b to the fourth lens group 14 in the first lens groups 11a and 11b correspond to the rear afocal group. . And afocal front group 11a
In order to suppress various types of aberrations that increase as the lens is extended, at least one or more aperture stops A1 and A2 are provided between the front afocal group 11a and the lens group 11b. still,
The apertures A1 and A2 may be retracted outside the optical path by an arbitrary method.

Next, Table 2 shows a specific configuration example of the second embodiment, and FIGS. 11 and 12 show specific optical axis sectional views. FIG. 11 shows an intermediate focal length, and FIG. 12 shows a tele macro state. In the table, ri is the radius of curvature of each i-th curved surface from the object side, Ti is the distance between the top surfaces of the axes from the i-th curved surface to the next curved surface from the object side, Nd
i is the refractive index of the glass from the i-th curved surface to the next curved surface sequentially from the object side, and νdi is the Abbe number of the glass from the i-th curved surface to the next curved surface sequentially from the object side. It is shown as the reference numeral of the surface corresponding to FIGS.

[0018]

[Table 2]

The aberration diagrams of the second embodiment shown in Table 2 are shown in FIGS. FIG. 13 is an aberration diagram at the wide-angle end when the focal length is 1, and FIG.
3 is an aberration diagram at a standard position, and FIG. 15 is a diagram showing a focal length of 8.2.
FIG. 16 is an aberration diagram at the telephoto end of FIG.
13 to 16 show aberration diagrams in the tele macro state of FIG.
Aberration diagrams of spherical aberration, astigmatism,
Indicates distortion, d is d-line, DS is sagittal direction, DT
Indicates a meridional direction, and SC indicates a sign condition. As shown in these aberration diagrams, according to the second embodiment shown in Table 2, it is possible to obtain practically good aberration characteristics while performing tele-macro photographing with a photographing magnification of -1.1. .

Next, FIGS. 17 and 18 are sectional views along the optical axis showing the principle of the third embodiment of the present invention. The first lens group 21 having a positive combined refracting power is sequentially arranged from the object side. , A second lens group 22 having a negative combined refractive power, a third lens group 23 having a positive combined refractive power, and a fourth lens group 24 having a positive combined refractive power. An afocal system is constituted by the lens groups 21 to the third lens group 23, and the fourth lens group 24 constitutes a master lens. The movement of the second lens group 22 in the afocal system in the direction of the optical axis performs a zooming operation, and the movement of the master lens 24 in the direction of the optical axis corrects and shifts the focal point movement accompanying the zooming. FIG. 18 when performing tele macro photography
As shown in (1), the first lens group 21 is entirely extended in the optical axis direction. That is, in the third embodiment, the first lens group 21 as a whole corresponds to a front afocal group in the claims, and the second to third lens groups 22 to 23 correspond to a rear afocal group. At least one aperture stop A1 or A2 is provided between the first lens group 21 and the second lens group 22 in order to suppress various aberrations that increase with the extension of the first lens group 21. The apertures A1 and A2 may be retracted by any method from outside the optical path.

Next, Table 3 shows a specific configuration example of the third embodiment, and FIGS. 19 and 20 show specific optical axis sectional views. FIG. 19 shows the intermediate focal length, and FIG. 20 shows the tele macro state. In the table, ri is the radius of curvature of each i-th curved surface from the object side, Ti is the distance between the top surfaces of the axes from the i-th curved surface to the next curved surface from the object side, Nd
i is the refractive index of the glass from the i-th curved surface to the next curved surface sequentially from the object side, and νdi is the Abbe number of the glass from the i-th curved surface to the next curved surface sequentially from the object side. This is shown as the reference numeral of the surface corresponding to FIGS. 19 and 20.

[0022]

[Table 3]

FIGS. 21 to 24 show aberration diagrams of the second embodiment shown in Table 3. FIG. 21 is an aberration diagram at the wide-angle end where the focal length is 1, and FIG. 22 is a focal length of 3.9.
23 shows an aberration diagram at a standard position, and FIG. 23 shows a focal length of 7.68.
FIG. 24 shows an aberration diagram at the telephoto end of FIG.
FIGS. 21 to 24 show aberration diagrams in the tele macro state.
Aberration diagrams of spherical aberration, astigmatism,
Indicates distortion, d is d-line, DS is sagittal direction, DT
Indicates a meridional direction, and SC indicates a sign condition. As shown in these aberration diagrams, according to the third embodiment shown in Table 3, it is possible to obtain practically good aberration characteristics while performing tele-macro photographing with a photographing magnification of −1.05. .

[0024]

As shown in the above-described embodiments and the aberration diagrams thereof, according to the present invention, it is possible to realize tele-macro photographing with a photographing magnification of 1 × or more, and to obtain a practically satisfactory photographing magnification. Aberration characteristics can be obtained, and no separate lens system such as an extender and a conversion lens is required in addition to the original lens system for the tele macro photographing.

[Brief description of the drawings]

FIG. 1 is an optical axis sectional view showing a first embodiment of the present invention in principle.

FIG. 2 is an optical axis sectional view showing a tele macro state of the first embodiment in principle.

FIG. 3 is an optical axis cross-sectional view at a standard focus position in a specific example of the first embodiment.

FIG. 4 is an optical axis cross-sectional view of the embodiment shown in FIG. 3 in a tele macro state.

FIG. 5 is an aberration diagram at the wide end of the first embodiment.

FIG. 6 is an aberration diagram at a standard focus position in the first embodiment.

FIG. 7 is an aberration diagram at the telephoto end of the first embodiment.

FIG. 8 is an aberration diagram in a tele macro state of the first embodiment.

FIG. 9 is an optical axis sectional view showing the principle of the second embodiment of the present invention.

FIG. 10 is an optical axis sectional view showing a tele macro state of the second embodiment in principle.

FIG. 11 is an optical axis cross-sectional view at a standard focus position in a specific example of the second embodiment.

FIG. 12 is an optical axis cross-sectional view of the embodiment shown in FIG. 11 in a tele macro state.

FIG. 13 is an aberration diagram at a wide end in the second embodiment.

FIG. 14 is an aberration diagram at a standard focus position in the second embodiment.

FIG. 15 is an aberration diagram at a telephoto end in the second embodiment.

FIG. 16 is an aberration diagram in a tele macro state of the second embodiment.

FIG. 17 is an optical axis sectional view showing a third embodiment of the present invention in principle.

FIG. 18 is an optical axis sectional view showing a tele macro state of the third embodiment in principle.

FIG. 19 is an optical axis cross-sectional view at a standard focus position in a specific example of the third embodiment.

FIG. 20 is an optical axis cross-sectional view of the embodiment shown in FIG. 19 in a tele macro state.

FIG. 21 is an aberration diagram at a wide end of the third embodiment.

FIG. 22 is an aberration diagram at a standard focus position in the third embodiment.

FIG. 23 is an aberration diagram at a telephoto end in the third embodiment.

FIG. 24 is an aberration diagram in a tele macro state of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st lens group 2 2nd lens group 3 3rd lens group 4 4th lens group 5 5th lens group

Claims (2)

(57) [Claims] 1. An internal focusing zoom lens in which an afocal lens group and a master lens group are sequentially arranged from an object side, a zooming operation is performed by the afocal lens group, and focusing is performed by the master lens group. the afocal lens group sequentially from the object side, a first lens group having a positive composite refractive power, a second performing zooming action by moving into a closed to the optical axis direction negative composite refractive power
A lens group, moving the negative composite refractive power Yes to the optical axis direction
A third lens group for correcting the focus shift due to zooming by, constituted by a fourth lens group having a positive composite refractive power, when close-up photography on the telephoto side, the whole of the first lens group or A part of the first lens group on the object side is extended in the optical axis direction, and a lens group extended in the optical axis direction during close-up photographing on the telephoto side in the afocal lens group is defined as a front afocal group. When the other lens groups in the afocal lens group are defined as the post-afocal group, the conditions 1 and 2 are satisfied and the close-up photographing is performed on the telephoto side.
Occasionally, at least one or more apertures face the optical axis of the front afocal group and the rear afocal group extended in the optical axis direction for close-up photography on the telephoto side, and at least One is an internal focusing zoom lens with a tele macro function that functions as an aperture stop that satisfies Condition 3. Condition 1: | f1 + f2-D | <0.1 FW Condition 2: X (fM / f1)> 2.4 FW Condition 3: 8 <EFNO <32 where fM: focal length of the master lens group. f1: focal length of the afocal front group. f2: focal length of the post-afocal group in a state set as a whole on the telephoto side. D: The distance between the rear principal point of the front group before the afocal and the front principal point of the rear group after the afocal group in the state set as a whole on the telephoto side. FW: the focal length of the entire lens system in the state set as a wide-angle side as a whole. X: The amount of extension of the front group in the optical axis direction during close-up shooting on the telephoto side. EFNO: Effective F value of the entire lens system when performing close-up photography on the telephoto side. 2. An afocal lens group and a master lens group are sequentially arranged from the object side, and a magnification change operation is performed by the afocal lens group .
In the internal focusing zoom lens which corrects the focal point shift accompanying the focusing and the magnification change by the movement of the zoom lens, the afocal lens group is sequentially arranged from the object side to a first lens group having a positive combined refractive power and a negative lens group. have a synthetic refractive power
A second lens group that performs a zooming action by moving in the optical axis direction, and a third lens group that has a positive combined refracting power; Alternatively, a part of the first lens group on the object side is extended in the optical axis direction, and a lens group extended in the optical axis direction during close-up photographing on the telephoto side in the afocal lens group is defined as a front afocal group. When the other lens group in the afocal lens group is defined as the post-afocal group, conditions 1 and 2 are satisfied, and close-up photographing on the telephoto side is performed.
Occasionally, at least one or more apertures face the optical axis of the front afocal group and the rear afocal group extended in the optical axis direction for close-up photography on the telephoto side, and at least One is an internal focusing zoom lens with a tele macro function that functions as an aperture stop that satisfies Condition 3. Condition 1: | f1 + f2-D | <0.1 FW Condition 2: X (fM / f1)> 2.4 FW Condition 3: 8 <EFNO <32 where fM: focal length of the master lens group. f1: focal length of the afocal front group. f2: focal length of the post-afocal group in a state set as a whole on the telephoto side. D: The distance between the rear principal point of the front group before the afocal and the front principal point of the rear group after the afocal group in the state set as a whole on the telephoto side. FW: the focal length of the entire lens system in the state set as a wide-angle side as a whole. X: The amount of extension of the front group in the optical axis direction during close-up shooting on the telephoto side. EFNO: Effective F value of the entire lens system when performing close-up photography on the telephoto side.