JPH07151966A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide a zoom lens which executes focusing by allowing a part of lens groups of a first group of a 4-group zoom lens to float and has high optical performance. CONSTITUTION:This zoom lens has, successively from an object side, a first group L1 having a positive refracting power, a second group L2 having a negative refracting power for variable power, a third group L3 having a positive or negative refracting power for correcting a fluctuation in image plane according to variable power, an aperture diaphragm SP and a fourth group L4 having a stationary imaging action during the variable power. The first group L1 has three lens groups; an A-th group LA having a negative refracting power, a B1-th LB1 having a positive refracting power and a B2-th group LB2 having a positive refracting power. Focusing from an infinite object side to a short distance object is executed by moving the B1-th group LB1 and the B2-th group LB2 to the object side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens suitable for a television camera, a video camera, a photographic camera, etc., and in particular, it uses a so-called inner focus type for focusing with a part of the first lens group. The present invention relates to a zoom lens having an F number of 1.7 at a wide angle end with a short object distance, a large aperture of about 13 to 44 and a high zoom ratio.

[0002]

2. Description of the Related Art Conventionally, with the miniaturization of television cameras, zoom lenses for television cameras and the like have been required to have a compact overall lens system with a large aperture ratio and a high zoom ratio.

In a zoom lens system in which focusing (focusing) is performed by a lens unit located closer to the object side than the zooming lens unit, zooming (magnification) and focusing can be performed independently, so that the mechanism for movement is simplified. The advantage of this is that focusing does not occur due to zooming, and focusing can be performed with a constant amount of extension for a constant object distance regardless of the zoom position.

Among such zoom lenses, a first group (focusing lens group) having a positive refractive power for focusing and a second group (magnifying lens group having a negative refractive power for zooming) are arranged in order from the object side. ), A third group (correction lens group) having a positive or negative refractive power for correcting an image surface that varies with zooming, an aperture stop, and a fourth group (relay) having a positive refractive power for image formation. In a so-called four-group zoom lens composed of four lens groups (lens groups), a so-called inner focus type in which a part of the lens groups in the first group is moved for focusing is disclosed in, for example, Japanese Patent Publication No. Sho 59.
It is proposed in Japanese Patent No. 4686.

In the same publication, the first group is referred to as an eleventh lens having a negative refractive power.
Group consisting of three lens groups, a positive refractive power twelfth lens group and a positive refractive power thirteenth lens group, and moving the twelfth lens group toward the image plane side for focusing from an object at infinity to an object at a close range. I am doing it.

Further, JP-A-52-109952, JP-A-55-57815 and JP-A-55-11711.
9, Japanese Patent Publication No. 61-53696, Japanese Patent Publication No. 52
In the -41068 publication, etc., in a 4-group zoom lens, the first group is divided into a plurality of lens groups, and the lens group closest to the object side is fixed during focusing, and a part of the lens group on the image plane side behind that is fixed. Is the inner focusing that moves during focusing.

Further, in Japanese Unexamined Patent Publication No. 52-128153, the first lens unit is divided into two lens units, and the distance between the two lens units is increased when focusing from an object at infinity to an object at a finite distance. We are moving and focusing.

Generally, in an inner focus type zoom lens, the effective diameter of the first lens group is smaller than that of a zoom lens in which the entire first lens group is moved to perform focusing, which facilitates downsizing of the entire lens system and close-up photography. In particular, it is easy to perform extremely close-up photography, and since the relatively small and lightweight lens group is moved to perform the operation, the driving force of the lens group is small and quick focusing can be performed.

[0009]

The zoom lens has a large aperture ratio (for example, F number of 1.7 to 3.3), a high zoom ratio (for example, zoom ratio of 13 to 44), and a total zoom range. In order to obtain high optical performance over the entire focus range, it is necessary to appropriately set the refractive power (power) of each lens group, the lens configuration, and the achromatic share.

Generally, in order to obtain high optical performance with little aberration variation over the entire zoom range and the entire focus range, for example, the power of each lens group is reduced to reduce the aberration amount generated in each lens group, or each lens group is reduced. It becomes necessary to increase the degree of freedom in aberration correction by increasing the number of lenses in the group. Therefore, when trying to achieve a zoom lens with a large aperture ratio and a high zoom ratio, the air space between each lens group will inevitably increase, the number of lenses will increase, and so on.
There is a problem that the entire lens system becomes heavy and large.

In recent broadcast zoom lenses, there is a demand for wider angles and higher zoom ratios, and further improvements in short-distance performance and M.D. O. Shortening the D (shortest shooting distance) is becoming an important factor in terms of specifications and image effects.

However, in the zoom lens for broadcasting, variations in various aberrations due to focusing, particularly variations in spherical aberration, axial chromatic aberration, astigmatism, etc. are remarkable, and it is very difficult to maintain good optical performance. The aberration variation at this time is generally as the focal length becomes larger, the F number becomes smaller, and the aperture ratio becomes larger. O. The shorter D was, the larger the tendency was.

Regarding the above-mentioned focusing method, Japanese Patent Laid-Open Nos. 52-109952 and 55-5 are available.
In the zoom lenses disclosed in Japanese Patent No. 7815 and Japanese Patent Laid-Open No. 55-117119, the number of constituent lenses of the first group is large in terms of aberration correction, so that the entire lens system becomes large, complicated, and heavy.

In the zoom lens disclosed in Japanese Patent Publication No. 61-53696, the first lens group has a relatively simple structure.
The air gap between the first lens group and the variable power lens group at the time of focusing at infinity is wide, and the focus lens group of negative refractive power moves toward the image plane side at the time of focusing at a short distance, so that it is off-axis on the wide angle side. The height of the light beam becomes high in the first group, and the lens system becomes large.

In the first-group extension type zoom lens, the first group has a relatively simple structure and is suitable for downsizing, but in particular, fluctuations in spherical aberration and axial chromatic aberration due to focusing become large. For example, as the focus becomes closer, spherical aberration falls to under, and axial chromatic aberration also becomes under.

The mechanism of aberration variation at this time will be described below.

FIG. 18 shows the first lens unit as the eleventh lens unit (concave lens unit) L11 having negative refractive power and the twelfth lens unit (convex lens unit) L12 having positive refractive power.
It is explanatory drawing of the thin-walled paraxial system when it comprised. FIG. 19 is a lens cross-sectional view of a typical first group L1 in a 4-group zoom lens.

In FIG. 18, the solid line indicates the position when the object at infinity is in focus, and the dotted line indicates the position of M.I. O. This is the position at D. The 11th group and the 1st group of paraxial rays at infinity focus shown by the solid line
The incident heights to the second group are ha and hb, the tilt angles between the 11th and 12th groups are α, and M. O. The incident heights of paraxial rays on the first and second groups at D are ha ′, hb ′, and 11th, respectively.
If the tilt angle between the group and the twelfth group is α ', then α'<α, and therefore hb-ha <hb'-ha '.

In the third-order aberration theory, the third-order aberration coefficient L of axial chromatic aberration is proportional to the square of the paraxial ray height h, and the third-order aberration coefficient I of spherical aberration is the fourth axis of the paraxial ray height h. Proportional. In this focusing method, the M.D. O. At the time of D, the coefficient L becomes larger in the plus direction, so the axial chromatic aberration becomes under, and the coefficient I also becomes larger in the plus direction, so that the spherical aberration also changes to under.

In the zoom lens of Japanese Patent Publication No. 52-41068, as shown in FIG. 21, the first group is divided into two lens groups, of which the 11th group L11 on the object side has a weak negative refractive power of substantially no power. And is fixed during focusing, and focusing is performed by moving the twelfth lens unit L12 having a positive refractive power on the image side.

FIG. 20 shows this as a thin-walled paraxial system for the 11th and 12th groups. As shown in FIG. 20, the twelfth group is shown as the movement of its principal point.

The solid lines are paraxial rays when an object at infinity is focused, and the incident heights on the 11th group and the 12th group at this time are hf, hm and M. O. First paraxial ray at D
Assuming that the incident heights on the first group and the twelfth group are hf 'and hm' respectively, hb-ha <hm-hf hb'-ha'.apprxeq.hm'-compared with FIG. 18 (first group feeding method). hf '.

Therefore, according to the zoom lens of the above publication, the M.M. O. D
It is possible to reduce the amount of change in the third-order spherical aberration coefficient I and the axial chromatic aberration coefficient L until time. Therefore, spherical aberration due to focusing,
It is possible to reduce the fluctuation of the axial chromatic aberration. However, the variation is still unsatisfactory, and further improvement is desired.

In the zoom lens disclosed in Japanese Unexamined Patent Publication No. 52-128153, the first lens unit is divided into two lens units, both of which are moved during focusing, and the distance between the two lens units becomes closer to the near focus. By increasing the size, the peripheral performance is mainly improved. However, according to the example, the spherical aberration is also under-corrected at the time of focusing at a short distance, and the central performance is deteriorated.

The present invention adopts an inner focus system in which a part of the first lens group for focusing, which constitutes a four-group zoom lens, is moved along the optical axis to perform focusing, while increasing the aperture and increasing the zoom ratio. By adjusting the lens configuration of each lens group appropriately, the variation of various aberrations such as spherical aberration and chromatic aberration due to zooming and focusing is reduced, and high optical power is achieved over the entire zoom range and the entire focus range. It is an object of the present invention to provide a zoom lens having a wide-angle end F number of about 1.7, a large aperture ratio of about 13 to 44 and a high zoom ratio, which has a high performance.

[0026]

The zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power for zooming, and an image plane accompanying zooming. A zoom lens having a third lens unit having a positive or negative refractive power for correcting fluctuations, and a fourth lens unit having an image forming action fixed during zooming,
The group has three lens groups, a negative refractive power A group, a positive refractive power B1 group, and a positive refractive power B2 group, and focuses on an object at infinity to a short-distance object. In addition, the first group B1 and the second group B2 are moved to the object side by different amounts of movement.

Others In the present invention, the first group B1 and the second group B2
When the moving amounts of the group are MB1 and MB2, respectively, the condition of MB2 / MB1 <1 (1) is satisfied, and the refracting power and F number of the entire system at the telephoto end are each φT. , FNT, where the refracting power and F number of the first group are φ1 and FN1, respectively, 1.05 <FN1 (2) where FN1 = (1 / φ1) / {(1 / φT) / FN
It is characterized in that the condition T} is satisfied.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2, 3 and 4 are lens cross-sectional views at the wide-angle end of Numerical Embodiments 1, 2, 3 and 4 of the present invention, respectively. FIG. 17 is an explanatory diagram of the paraxial refractive power arrangement of the first group of the zoom lens of the present invention.

In the figure, L1 is a focus group (front lens group) having a positive refractive power as the first group, and includes a fixed negative refractive power A group LA and a positive refractive power focusing group LA. B1 group LB1 and the second B group L for focusing with a positive refractive power
B2 and.

Focusing from an object at infinity to an object at a close distance is performed by moving the B1st group LB1 and the B2nd group LB2 independently to the object side by different amounts. L2 is a variator of negative refractive power for zooming as the second group,
By monotonically moving to the image plane side on the optical axis, the magnification is changed from the wide-angle end (wide) to the telephoto end (tele).

In the second lens unit L2, the image-forming magnification is changed within a region including the same magnification (-1) during the magnification change.

L3 is a compensator for positive or negative refracting power as the third lens unit, which corrects the image plane variation due to zooming, and has a convex locus on the object side in the case of negative refracting power. To move. In the case of positive refracting power, it moves monotonically to the object side.
SP is a stop, and L4 is a relay group having a positive refractive power as the fourth group. P is a color separation prism, an optical filter, or the like, and is shown as a glass block in FIG.

Generally, in the so-called front lens focus system in which focusing is performed on the entire first lens unit closest to the object side in a four-unit zoom lens, the amount of extension of the first lens unit is constant for the same object distance at each focal length. Therefore, it has a feature that the lens barrel structure is simple.

However, the first group has a positive refractive power,
In a zoom lens including a wide angle of view, when focusing on an object at a close range at the wide-angle end, the first group moves toward the object side, so that the effective diameter of the first group increases to secure an off-axis light beam. Further, since the first group, which is relatively heavy, is moved, the driving torque increases, and quick focusing becomes difficult.

Therefore, in the present invention, in the zoom lens having the above-described structure, focusing from an object at infinity to an object at a close range is performed by moving the B1 group LB1 and the B2 group LB2 to the object side by different amounts. By adopting the inner focus method that uses floating, the movable parts are lightened and good optical performance is obtained.

That is, in the present invention, light rays pass by using a floating that expands or contracts an arbitrary air space in the lens group that moves when the object distance changes and the object is focused. Aberration variation is corrected well by changing the angle and height.

In particular, when focusing from an object at infinity to an object at the shortest distance, the moving amounts of the B1 and B2 groups are respectively set to M.
B1, MB2, the refractive power and F number of the entire system at the telephoto end are φT and FNT respectively, and the refractive power and F number of the first group are φ1 and FN1, respectively, the above conditional expression (1),
Each element is set so as to satisfy the condition (2), so that variation in aberration is reduced over the entire focus range and high optical performance is obtained.

Next, in the zoom lens of the present invention,
An optical action when focusing is performed using the B1st group LB1 and the B2nd group LB2 of the group L1 will be described with reference to FIG.

The first lens unit L1 is, in order from the object side, a fixed A lens unit LA for focusing, and a B lens unit for moving during focusing.
First group LB1, second group LB2 that moves during focusing
Are arranged. The paraxial ray at an object at infinity is shown by a solid line, and the positions on the optical axis of the B1 group and the B2 group at this time are represented by b.
1, b2, the interval is t, and the paraxial ray heights are Ha, H
It is shown as b1 and Hb2. On the other hand, a paraxial ray at a certain finite distance object is shown by a dotted line, and the positions on the optical axis of the B1 group and the B2 group at this time are b1 'and b2', and the interval is T
(When t <T), the respective paraxial ray heights are set to Ha ′, Hb.
It is shown as 1 ', Hb2'.

The position on the optical axis when the distance t between the first group B1 and the second group B2, which are arranged in the same positional relationship as the case of an infinite object with respect to the same finite object, is maintained (when t = T). , No. B
For the first group, the position b1 ″ is closer to the image surface than the position b1 ′, and for the second group B2, the position b2 ″ is closer to the object side than the position b2 ′. The paraxial ray heights at the respective positions are now Ha ″ and Hb.
1 ″ and Hb2 ″.

In the present invention, the A-th group and the B1-th group at the time of an object at infinity
By separating the distance from the group, the difference between Hb1-Ha and, for example, Hb1'-Ha 'when the object is at a finite distance is reduced, and fluctuations in spherical aberration and axial chromatic aberration are reduced to some extent.

Next, focusing on the changes in the paraxial ray heights of the B1 and B2 groups when t <T and when t = T, Hb1 '> Hb1 "Hb2'<Hb2".

Therefore, as described above, the change in the third-order aberration coefficient of spherical aberration and axial chromatic aberration is t = T when t <T.
From the time of, the B1 group and the B2 group are (a) B1 group: the third-order aberration coefficient I of spherical aberration changes in the positive direction, and the third-order aberration coefficient L of axial chromatic aberration also changes in the positive direction. Aberration changes to under and axial chromatic aberration also changes to under. (B) Group B2: The third-order aberration coefficient I of spherical aberration changes in the negative direction, and the third-order aberration coefficient L of axial chromatic aberration also changes in the negative direction. Therefore, spherical aberration changes to over and axial chromatic aberration changes to over. To do. The action occurs.

In the present invention, the aberration change due to the movement of the B1 and B2 groups is skillfully utilized to suppress the aberration variation due to focusing.

M. O. At an object distance near D, the distance between the A group and the B1 group is narrowed because the B1 group moves toward the object side, and the difference Hb1 ′ between Hb1 ′ and Ha ′ when t <T.
-Ha 'and the difference Hb between Hb1 "and Ha" at t = T
1 ″ -Ha ″ is substantially equal and Hb1′−Ha′≈Hb1 ″ −Ha ″.

Therefore, the total sum of the spherical aberration and the axial chromatic aberration generated in the A-th group and the B1-th group becomes substantially equal, but when t <T, the aberration generation in the B2-th group occurs due to the action of (b) above. It is possible to reduce the amount of M. O. D
It corrects under spherical aberration and under axial chromatic aberration at nearby object distances.

On the other hand, when the object distance is small in the vicinity of the infinitely distant object and the distance between the A group and the B1 group is relatively large, both the above (a) and (b) actions are performed. Aberration correction can be used. For example, when the aberration variation due to focusing from an object at infinity to an object at a finite distance is over spherical aberration and under axial chromatic aberration, the effects of the spherical aberration and axial chromatic aberration due to (a) and (b) above are reduced. By taking advantage of the difference, spherical aberration is corrected to the under side and axial chromatic aberration is corrected to the over side.

According to the present invention, when focusing on a change in the object distance, by moving the B1 group and the B2 group so that their relative positional relationship changes, mainly fluctuations in spherical aberration and axial chromatic aberration are caused. Is corrected well. At this time B
The moving directions of the first group and the second group B2 are M. O. D
When focusing on an object, the object side is moved monotonically so as to satisfy the conditional expression (1), thereby preventing an increase in the total lens length of the first group and suppressing the complication of the moving mechanism. .

When MB2 / MB1 <1, t in the above description is satisfied.
<Corresponding to T, and when MB2 / MB1 = 1 corresponds to t = T. When MB2 / MB1> 1, the moving amount of the B2 group becomes larger than the moving amount of the B1 group, so that it becomes necessary to additionally set an interval between the B1 group and the B2 group at the time of an object at infinity. The overall length and size of the first lens group increase.

Further, the zoom lens of the present invention uses a bright lens system which satisfies the conditional expression (2) for the first lens unit.
It has a zoom ratio of about 3 to 44 times and realizes a large aperture ratio in the entire zoom range.

In the present invention, high optical performance is obtained by setting each element as described above, but in order to obtain high optical performance over the entire object distance and the entire zoom range, the following various conditions are required. Is good to satisfy.

The group A includes a negative first lens A1 and a positive first lens A1.
It has two independent lenses, the refractive power of the A-th group is φA, the sum of the ratio of the refractive power φAi of the Ai-th lens and the Abbe number νAi of the material is ΣA = φAi / νAi, The group has at least one positive B1,1 lens, the refractive power of the B1 group is φB1, the sum of the ratio of the refractive power φB1, i of the B1,1 lens and the Abbe number νB1, i of the material is Σ
B1 = φB1, i / νB1, i, the second B2 group has a positive meniscus B2,1 lens having a convex surface directed toward the object side, and the refractive powers of the B2 group are φB2, B2, The ratio of the refractive power of one lens to φB2,1 and the Abbe number of material νB2,1 is ΣB2
= ΦB2,1 / νB2,1 −0.30 <φA / φ1 <−0.0095 (3) −0.02 <ΣA / φ1 <−0.009 (4) −1.22 <ΣA / (ΣB1 + ΣB2) <− 0.77 (5) 0.23 <φB2 / φB1 <0.95 ・ ・ ・ ( 6) 0.23 <ΣφB2 / ΣφB1 <1.40 (7) is satisfied.

In the zoom lens of the present invention, the height of the axial ray passing through the first lens unit is highest at the telephoto end. And the second
Since the aberrations generated in the first lens group are magnified by the magnifications after the lens group, the spherical aberration and the axial chromatic aberration at the telephoto end largely depend on the amount of aberrations generated in the first lens group. In particular, the zoom lens for broadcasting is required to have high specifications and high performance, and it is necessary to increase the focal length at the telephoto end and increase the aperture ratio.

Therefore, it becomes difficult to correct various aberrations such as spherical aberration and chromatic aberration due to zooming and focusing. On the other hand, if the power of each lens is reduced by design or the number of lenses is increased to cope with the problem, the entire lens system becomes large, and the weight and the manufacturing cost increase.

Therefore, of the first group, the fixed group A is composed of two lenses, a negative first lens A1 and a positive second lens A2, which have at least a negative refractive power surface and are separated by a relatively small air space. There is. By providing this air space, the degree of freedom in design is increased, variations in various aberrations are reduced, and various aberrations can be easily controlled in a well-balanced manner. Furthermore, by pushing out the rear principal point of the first lens group, the entire lens system The miniaturization of

Both the B1 group for focusing and the B2 group for focusing are constructed to have at least one positive lens to reduce the amount of various aberrations and at the same time cancel out the residual aberration in the A group. In particular, the second lens group B2 includes a positive meniscus second lens B1 having a convex surface directed toward the object side, which reduces the amount of spherical aberration generated by itself and at the same time corrects distortion and astigmatism well. There is. still,
It is preferable to provide a concave lens in the B1 group or the B2 group because various aberrations can be easily corrected.

Next, the technical meaning of the conditional expressions (3) to (7) will be described.

Conditional expression (3) limits the power of the A-th group in the first group. When the value goes below the lower limit of conditional expression (3), the power becomes large, so that high-order aberrations such as spherical aberration and coma are likely to occur, and in order to correct the residual higher-order aberrations, the moving lens groups B1 and B2 need to be corrected. It is necessary to increase the power and decrease the radius of curvature, and as a result, it becomes difficult to correct aberration fluctuations due to zooming and focusing. Further, when the value exceeds the upper limit, the power becomes almost no power, so that the difference in paraxial ray height between the A-group and the B1-group at the time of an object at infinity becomes small, and fluctuations in spherical aberration and axial chromatic aberration due to focusing are reduced. It becomes difficult to correct it well.

Conditional expression (4) defines the achromatic condition of the A-th group as the first condition.
It is standardized by the power of the group. Conditional expression (5) is defined by the first group A, which is fixed, and the first group B1, which is moved during focusing.
This is defined as the shared value of the achromatic condition when divided into two lens groups, that is, the first lens group and the second lens group B2. Conditional expression (4),
(5) is for keeping the variation of the axial chromatic aberration due to focusing in good balance.

The achromatization conditions for the first group A, the second group B1 and the second group B2 are preferably Σa≈Σb1 + Σb2≈0. However, the focus moving group is usually a convex lens in consideration of the size of the first group. Since this is the only configuration, the achromatic condition of the focus moving group is always a positive value. In order to cancel this, conditional expression (4) has a slightly negative value. In conditional expressions (4) and (5), if the lower limit value is exceeded, overcorrection occurs, and over-axial chromatic aberration remains over the entire focus range, and if it exceeds the upper limit value, undercorrection occurs, and under-axial chromatic aberration remains. Resulting in.

The conditional expressions (6) and (7) relate to the floating, and each of the B1 group and the B2 group that moves during focusing.
It specifies the power sharing and achromatic sharing of the group.

If the lower limit of conditional expression (6) is exceeded, the power of the second lens group B2 becomes relatively weak.
Is lost, and it becomes difficult to satisfactorily correct fluctuations in spherical aberration and axial chromatic aberration due to focusing. When the value exceeds the upper limit, the power of the B1 group becomes relatively weaker this time, so that the effect of the above (a) is lost, and it is difficult to satisfactorily correct the fluctuations of the spherical aberration and the axial chromatic aberration due to focusing. That is, the amount of focus movement of the first lens group B1 increases, and the total lens length or lens system of the first lens group increases, which is not good.

If the lower limit of conditional expression (7) is exceeded, the amount of change in axial chromatic aberration to under will increase due to the action of (a), and the amount of change to over will decrease in the action of (b). Therefore, the amount of change in the axial chromatic aberration to under is increased as a whole, which is not good. On the other hand, if the upper limit is exceeded, the amount of change in the axial chromatic aberration to the contrary increases, which is not good.

As described above, in the present invention, the first group is set to 1
It is divided into one fixed group A and two lens groups that move during focusing, and the lens groups are divided so that aberration fluctuations due to focusing can be suppressed, the amount of movement is limited, lens arrangement, power sharing, and achromatism. By stipulating the sharing, mainly the fluctuations of spherical aberration and axial chromatic aberration are corrected well.

Numerical Examples 1 to 1 of the present invention shown in FIGS.
The lens configuration of No. 4 will be described.

FIG. 1 is a lens cross-sectional view at the wide-angle end according to Numerical Embodiment 1 of the present invention, in which the object distance is infinity and 3.0.
Aberration diagrams at the telephoto end when m and 0.9 m (MOD) are shown in FIGS.

In this embodiment, the zoom ratio is 13 times, and R
1 to R8 are a first group having a positive refractive power. Of these, R1
R4 is a group A having a fixed negative refractive power during focusing and zooming, R5 and R6 are a group B1 having positive refractive power, R7,
R8 is the second lens group B2 having a positive refractive power.

Since R9 to R15 are for zooming, they move monotonically toward the image side from the wide-angle end to the telephoto end, and the lateral magnification -1 on the way.
It is the second group of negative refracting power that passes double. R16-R1
Numeral 8 is a third lens unit for compensating for image plane variation due to zooming, which moves convexly toward the object side from the wide-angle end to the telephoto end. R19 (S
P) is an aperture. R20 to R37 are a fourth group having an image forming action, and R38 and R39 are glass blocks P equivalent to a color separation prism, a trimming filter and the like.

In this embodiment, the F number of the first group is FN1 = (1 / φ) 1 / {1 / φT) /
When defined as FNT}, FN1 = 1.33. On the other hand, in the first group, in order to correct spherical aberration and axial chromatic aberration, the A group is composed of one positive and one negative lens, and
Each of the group B and the group B2 is composed of one positive lens to share the aberration correction.

Regarding the floating of the present invention, the relationship between the moving amount MB1 of the B1st group and the moving amount MB2 of the B2th group from the infinitely distant object to a certain finite object is given by MB2 = 0.60564MB1 + 0.01174MB1 ^2. The parameters at 3.0 m and 0.9 m are shown in Table 1. At this time, the maximum value of MB2 / MB1 is 0.606 near infinity, and the minimum value is M.M. O. It is 0.455 of D.

In this embodiment, M. O. By making the rate of change of the relative movement amount of the B2 group with respect to the B1 group as D becomes smaller, the effect of the above (B) is effectively used to correct the fluctuations of the spherical aberration and the axial chromatic aberration. is doing.

Further, by increasing the difference in Abbe number between the positive lens and the negative lens in the group A to be about 70, it is advantageous to correct the chromatic aberration in the first group. The first group B1 is made up of one positive lens having a large Abbe number, and the second group B2 is made up of one positive lens having a high refractive index, which is advantageous for correction of chromatic aberration, spherical aberration, etc., while supplementing the degree of freedom of aberration correction. ΦB2 / φB1 = 0.929, ΣB2 / Σ in terms of power sharing and achromatic sharing
B1 = 1.365.

As shown in the aberration charts of FIGS. 5 to 7, spherical aberration and axial chromatic aberration are particularly well corrected.

FIG. 2 is a lens cross-sectional view at the wide-angle end according to Numerical Embodiment 2 of the present invention, in which the object distance is infinity and 3.0.
Aberration diagrams at the telephoto end at m and 0.8 m (MOD) are shown in FIGS.

In the present embodiment, although the lens configuration is substantially the same as in Numerical Embodiment 1, a high zoom ratio of 14 times and a large F-number at the telephoto end of 1.9 and a large M.E. O.
D is very short at 0.8m. FN in the first group
1 = 1.07, which is very bright, and in order to correct spherical aberration and axial chromatic aberration, the group A is composed of one positive lens and one negative lens, and the group B1 is composed of two positive lenses and two group B2. Is composed of one positive lens to share the correction of aberrations.

Regarding the floating of the present invention, the relationship between the moving amount MB1 of the B1st group and the moving amount MB2 of the B2th group from the object at infinity to a certain finite object is MB2 = 0.40263MB1-0.02753MB1 ² . The parameters at 3.0 m and 0.8 m are shown in Table 2. At this time, the maximum value of MB2 / MB1 is M.M. O. D is 0.712, and the minimum value is 0.403 near infinity.

Therefore, in this embodiment, M. O. The change rate of the relative movement amount of the B2 group with respect to the B1 group becomes large as the distance becomes D. Thereby, M. O. D
On the side, the increase in the lens system of the first lens unit due to the large movement amount MB1 of the first lens unit B1 is suppressed within an allowable range, and at the same time, the effect of the above (B) is effectively used, mainly in the entire focus region. The fluctuation of the axial chromatic aberration of is corrected.

Further, the F number, M. O. In order to make it compact with respect to D, the group A is made to have a strong divergence system and the rear principal point of the first group is pushed out. Therefore, the B1 group is composed of two positive lenses and the B2 group is composed of one positive lens to increase the degree of freedom of aberration correction. At this time, φA / φ1 =
−0.298, ΣA / φ1 = −0.0184, ΣA /
(ΣB1 + ΣB2) = − 1.214.

As shown in the aberration diagrams of FIGS. 8 to 10, not only the axial chromatic aberration is well corrected, but the M.M. O. Despite D, the spherical aberration is well corrected.

FIG. 3 is a lens cross-sectional view at the wide-angle end according to Numerical Embodiment 3 of the present invention, in which the object distance is infinity and 10.0.
Aberration diagrams at the telephoto end at m and 2.0 m (M.O.D.) are shown in FIGS.

In this embodiment, the zoom ratio is 44 times, and R
1 to R10 are the first group having a positive refractive power. Of these, R1
˜R4 are fixed and have a negative refractive power during the focusing and zooming, and R5 to R8 are the positive B1 group, R9 and R10.
Is a positive group B2.

Since R11 to R17 are for zooming, they move monotonously toward the image plane from the wide-angle end to the telephoto end, and the lateral magnification −
It is the second group of negative refracting power that passes 1 times. R18-R
Reference numeral 27 denotes a third lens unit having a positive refracting power which compensates for the image plane variation as well as the zooming action, moves monotonically to the object side, and passes lateral magnification -1 × on the way. R28 (SP) is a diaphragm. R29 ~
R44 is a fourth group having an image forming action, and R45 and R46 are glass blocks P equivalent to a color separation prism, a trimming filter and the like.

In this embodiment, the focal length at the wide angle end is 9.0 m.
Despite being widened to m, the focal length at the telephoto end is 396.0 mm with a very high zoom ratio of 44 times. On the other hand, in order to correct the spherical aberration and the axial chromatic aberration in the first group, the group A is composed of one positive lens and one negative lens,
The B1 group is composed of two positive lenses and the B2 group is composed of one positive lens to share the aberration correction.

Regarding the floating of the present invention, the relationship between the movement amount MB1 of the B1st group and the movement amount MB2 of the B2th group from the object at infinity to a certain finite object is MB2 = 0.0250MB1-0.05181MB1 ² . Table 3 shows the parameters at 10.0 m and 2.0 m. At this time, the maximum value of MB2 / MB1 is M.M. O. D is 0.995, and the minimum value is 0.025 near infinity.

Therefore, in this embodiment, M. O. The change rate of the relative movement amount of the B2 group with respect to the B1 group becomes large as the distance becomes D. Especially at 10.0 m, M
B2 / MB1 = 0.277, which is a small value, and M.M. O. D
At (2.0 m), Y / X = 0.995, which is a large value. This is for the following reason.

MB2 / MB1 = 0.27 of 10.0 m
About 1. From the infinite object peculiar to a long focal length zoom lens.
The changes in spherical aberration and axial chromatic aberration in the vicinity of 0 m are overcorrected and undercorrected, respectively, by boldly correcting the effects of both (a) and (b).

M. O. MB / MB of D (2.0m)
1 = 0.995 In order to suppress the increase in the lens diameter of the first group due to the widening of the angle within the allowable range, M.I. O. The movement amount MB1 of the B1st lens unit is regulated on the D side.

Generally, the larger the zoom ratio and the longer the focal length at the telephoto end, the more difficult it becomes to correct spherical aberration and axial chromatic aberration. Therefore, in the present embodiment, the first group includes one positive lens and one negative lens for the A group, two positive lenses for the B1 side, and the B2 side.
The group is composed of five positive lenses in total, and all the positive lenses have Abbe numbers of 90 or more. At this time, φB2 / φB1 = 0.239, Σ in terms of power sharing and achromaticity.
B2 / ΣB1 = 0.237.

As shown in the aberration diagrams of FIGS. 11 to 13, the spherical aberration is well corrected, and the axial chromatic aberration is M.I. O. D
Although it is slightly undercorrected, it is corrected well overall.

FIG. 4 is a lens cross-sectional view at the wide-angle end according to Numerical Embodiment 4 of the present invention, in which the object distance is infinity and 10.0.
Aberration diagrams at the telephoto end at m and 2.5 m (M.O.D.) are shown in FIGS.

In this embodiment, the zoom ratio is 44 times and the configuration is substantially the same as that of the numerical embodiment 3, but the focal length at the telephoto end is 440.0.
Despite shifting to the telephoto side by mm, the F number at the telephoto end became brighter at 3.0. On the other hand, in order to correct spherical aberration and axial chromatic aberration in the first group,
The A group is composed of one positive and one negative lens, the B1 group is composed of two positive lenses, and the B2 group is composed of one positive lens to share the aberration correction.

Regarding the floating of the present invention, the relationship between the movement amount MB1 of the B1st group and the movement amount MB2 of the B2th group from the object at infinity to a certain finite object is MB2 = 0.15360MB1-0.02364MB1 ² . Table 4 shows the parameters at 10.0 m and 2.5 m. At this time, the maximum value of MB2 / MB1 is M.M. O. D is 0.598, and the minimum value is 0.1536 near infinity.

Therefore, in this embodiment, M. O. The change rate of the relative movement amount of the B2 group with respect to the B1 group becomes large as the distance becomes D. MB at 10.0 m
The small value of 2 / MB1 = 0.287 is set for the same reason as the numerical example 3. M. O. D (2.5m)
MB2 / MB1 = 0.598, which is smaller than the numerical value of Example 3, is because the focal length at the wide-angle end is 10.0 mm.
Since the shift to the telephoto side mitigated the increase in the lens diameter of the first lens group, the effect of the above (a) was effectively utilized.

Correction of spherical aberration and axial chromatic aberration becomes difficult even if the F number becomes small. Therefore, in this embodiment, the first group includes one positive lens and one negative lens, each of the B1 group includes two positive lenses, and the second lens group includes one positive lens, for a total of five lenses.
The positive lenses of the A group and the B1 group all have Abbe numbers of 90 or more, and the positive lenses of the B2 group have a higher refractive index than other positive lenses. And at this time, φA
/Φ1=−0.00987, ΣA / φ1 = −0.009
06, ΣA / (ΣB1 + ΣB2) = − 0.794.

As shown in the aberration diagrams of FIGS. 14 to 16, both spherical aberration and axial chromatic aberration are well corrected as a whole.

In each of the above embodiments, the relational expressions of floating MB1 and MB2 are used up to the quadratic term of MB1, but it is not necessary to pay attention to this and higher order terms may be used. According to the method, it is possible to increase the degree of freedom in correcting aberration variation.

[0097]

[Table 1] Next, numerical examples of the present invention will be shown. R in numerical examples
i is the radius of curvature of the i-th lens surface in order from the object side, D
i is the i-th lens thickness from the object side and the air gap, Ni
And νi are the refractive index and Abbe number of the glass with respect to the i-th lens d-line in order from the object side. In the numerical examples, the last two lens surfaces are glass blocks such as face plates and filters.

Table 5 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples. (Numerical Example 1) F = 9.5 to 123.5 FNO = 1: 1.7 to 2.1 2 ω = 60.1 ° to 5.10 ° R 1 = 2416.35 D 1 = 2.50 N 1 = 1.81265 ν 1 = 25.4 R 2 = 132.40 D 2 = 2.30 R 3 = 184.73 D 3 = 12.65 N 2 = 1.43496 ν 2 = 95.1 R 4 = -156.08 D 4 = 13.84 R 5 = 98.12 D 5 = 11.61 N 3 = 1.49845 ν 3 = 81.6 R 6 = -307.33 D 6 = 0.50 R 7 = 61.69 D 7 = 6.19 N 4 = 1.69979 ν 4 = 55.5 R 8 = 129.64 D 8 = Variable R 9 = 599.24 D 9 = 1.00 N 5 = 1. 88 814 ν 5 = 40.8 R10 = 24.10 D10 = 3.67 R11 = -120.24 D11 = 0.80 N 6 = 1.82017 ν 6 = 46.6 R12 = 123.78 D12 = 3.51 R13 = -22.87 D13 = 0.80 N 7 = 1.77621 ν 7 = 49.6 R14 = 39.63 D14 = 4.62 N 8 = 1.85501 ν 8 = 23.9 R15 = -42.35 D15 = Variable R16 = -32.80 D16 = 0.90 N 9 = 1.82017 ν 9 = 46.6 R17 = 48.63 D17 = 3.32 N10 = 1.85501 ν10 = 23.9 R18 = -300.67 D18 = Variable R19 = (Aperture) D19 = 1.91 R20 = 12579.43 D20 = 5.10 N11 = 1.70559 ν11 = 41.2 R21 = -34.16 D21 = 0.10 R22 = 118.95 D22 = 6.39 N12 = 1.51678 ν12 = 54.7 R23 = -29.86 D23 = 1.40 N13 = 1.83945 ν13 = 42.7 R24 = -128.11 D24 = 0.10 R25 = 52.29 D25 = 8.51 N14 = 1.52032 ν14 = 59.0 R26 = -27.92 D26 = 1.50 N15 = 1.82017 ν15 = 4 6.6 R27 = 811.08 D27 = 20.04 R28 = -546.10 D28 = 6.51 N16 = 1.51825 ν16 = 64.2 R29 = -37.49 D29 = 0.15 R30 = 191.65 D30 = 1.50 N17 = 1.83932 ν17 = 37.2 R31 = 31.05 D31 = 6.80 N18 = 1.48915 ν18 = 70.2 R32 = -246.48 D32 = 0.15 R33 = 215.34 D33 = 6.68 N19 = 1.51825 ν19 = 64.2 R34 = -34.23 D34 = 1.40 N20 = 1.83932 ν20 = 37.2 R35 = -86.47 D35 = 0.15 R36 = 53.33 D36 = 5.40 N21 = 1.48915 ν21 = 70.2 R37 = -95.33 D37 = 3.40 R38 = ∞ D38 = 50.00 N22 = 1.51825 ν22 = 64.2 R39 = ∞

[0099]

[Table 2] (Numerical Example 2) F = 9.5 to 133.0 FNO = 1: 1.9 2 ω = 60.1 ° to 4.74 ° R 1 = -232.61 D 1 = 2.50 N 1 = 1.81264 ν 1 = 25.4 R 2 = 234.08 D 2 = 8.73 R 3 = -553.00 D 3 = 8.31 N 2 = 1.43496 ν 2 = 95.1 R 4 = -126.13 D 4 = 12.02 R 5 = 244.28 D 5 = 12.39 N 3 = 1.49845 ν 3 = 81.6 R 6 = -147.31 D 6 = 0.15 R 7 = 86.20 D 7 = 11.67 N 4 = 1.49845 ν 4 = 81.6 R 8 = 2257.02 D 8 = 0.50 R 9 = 56.58 D 9 = 6.28 N 5 = 1.69979 ν 5 = 55.5 R10 = 78.22 D10 = variable R11 = 80.39 D11 = 1.00 N 6 = 1.82017 ν 6 = 46.6 R12 = 18.69 D12 = 4.14 R13 = -238.72 D13 = 0.80 N 7 = 1.80811 ν 7 = 46.6 R14 = 145.49 D14 = 3.87 R15 = -20.40 D15 = 0.80 N 8 = 1.77621 ν 8 = 49.6 R16 = 31.76 D16 = 4.59 N 9 = 1.85501 ν 9 = 23.9 R17 = -47.21 D17 = variable R18 = -28.33 D18 = 0.90 N10 = 1.77621 ν10 = 49.6 R19 = 35.47 D19 = 4.05 N11 = 1.81265 ν11 = 25.4 R20 =- 443.14 D20 = Variable R21 = (Aperture) D21 = 1.83 R22 = 255.00 D22 = 5.26 N12 = 1.67000 ν12 = 48.3 R23 = -32.99 D23 = 0.10 R24 = 74.08 D24 = 6.99 N13 = 1.51678 ν13 = 54.7 R25 = -25.63 D25 = 1.40 N14 = 1.82017 ν14 = 46.6 R26 = -321.97 D26 = 0.10 R27 = 50.07 D27 = 7.25 N15 = 1 .58482 ν15 = 40.8 R28 = -29.92 D28 = 1.50 N16 = 1.82017 ν16 = 46.6 R29 = 133.07 D29 = 14.60 R30 = 296.81 D30 = 6.78 N17 = 1.51825 ν17 = 64.2 R31 = -34.60 D31 = 0.15 R32 = -198.34 D32 = 1.50 N18 = 1.83932 ν18 = 37.2 R33 = 32.91 D33 = 6.67 N19 = 1.48915 ν19 = 70.2 R34 = -107.26 D34 = 0.15 R35 = 72.63 D35 = 8.42 N20 = 1.51825 ν20 = 64.2 R36 = -26.85 D36 = 1.40 N21 = 1.83932 ν21 = 37.2 R37 = -101.49 D37 = 0.15 R38 = 69.95 D38 = 6.28 N22 = 1.48915 ν22 = 70.2 R39 = -56.30 D39 = 3.40 R40 = ∞ D40 = 55.50 N23 = 1.51825 ν23 = 64.2 R41 = ∞

[0100]

[Table 3] (Numerical Example 3) F = 9.0 to 396.0 FNO = 1: 1.75 to 3.3 2 ω = 62.9 ° to 1.59 ° R 1 = -2535.35 D 1 = 5.50 N 1 = 1.62409 ν 1 = 36.3 R 2 = 220.34 D 2 = 1.60 R 3 = 234.37 D 3 = 21.48 N 2 = 1.43496 ν 2 = 95.1 R 4 = -557.29 D 4 = 20.21 R 5 = 311.46 D 5 = 15.02 N 3 = 1.43496 ν 3 = 95.1 R 6 = -615.77 D 6 = 0.30 R 7 = 160.85 D 7 = 15.22 N 4 = 1.43496 ν 4 = 95.1 R 8 = 2398.75 D 8 = 1.00 R 9 = 129.19 D 9 = 6.55 N 5 = 1.43985 ν 5 = 95.0 R10 = 187.50 D10 = variable R11 = -2292.00 D11 = 2.00 N 6 = 1.82017 ν 6 = 46.6 R12 = 42.43 D12 = 6.91 R13 = -89.57 D13 = 1.80 N 7 = 1.77621 ν 7 = 49.6 R14 = 79.59 D14 = 3.72 R15 = -91.85 D15 = 1.80 N 8 = 1.77621 ν 8 = 49.6 R16 = 46.03 D16 = 6.98 N 9 = 1.93306 ν 9 = 21.3 R17 = -251.80 D17 = variable R18 = 202.24 D18 = 8.74 N10 = 1.49845 ν10 = 81.6 R19 = -121.69 D19 = 0.30 R20 = 120.71 D20 = 2.50 N11 = 1.85501 ν11 = 23.9 R21 = 66.74 D21 = 11.92 N12 = 1.48915 ν12 = 70.2 R22 = -163.36 D22 = 0.20 R23 = 121.25 D23 = 10.94 N13 = 1.62032 ν13 = 63.4 R24 = -96.60 D24 = 2.50 N14 = 1.85501 ν14 = 23.9 R25 = -261.20 D25 = 0.20 R26 = 90.48 D26 = 7.52 N15 = 1.48915 ν15 = 70 .2 R27 = 510.88 D27 = Variable R28 = (Aperture) D28 = 2.64 R29 = -71.36 D29 = 1.80 N16 = 1.79013 ν16 = 44.2 R30 = 19.17 D30 = 5.77 N17 = 1.81265 ν17 = 25.4 R31 = 74.85 D31 = 6.00 R32 =- 29.47 D32 = 1.60 N18 = 1.73234 ν18 = 54.7 R33 = 32.71 D33 = 8.82 N19 = 1.59911 ν19 = 39.2 R34 = -28.80 D34 = 24.00 R35 = -153.14 D35 = 6.44 N20 = 1.48915 ν20 = 70.2 R36 = -30.96 D36 = 0.20 R37 = -54.49 D37 = 2.20 N21 = 1.79013 ν21 = 44.2 R38 = 41.22 D38 = 7.72 N22 = 1.50349 ν22 = 56.4 R39 = -48.56 D39 = 1.10 R40 = 173.49 D40 = 7.17 N23 = 1.55099 ν23 = 45.8 R41 = -27.83 D41 = 2.20 N24 = 1.81265 ν24 = 25.4 R42 = -94.90 D42 = 0.20 R43 = 63.75 D43 = 5.89 N25 = 1.51977 ν25 = 52.4 R44 = -62.21 D44 = 5.00 R45 = ∞ D45 = 50.00 N26 = 1.51825 ν23 = 64.2 R46 = ∞

[0101]

[Table 4] (Numerical Example 4) F = 10.0 to 440.0 FNO = 1: 1.75 to 3.0 2 ω = 57.6 ° to 1.43 ° R 1 = 335.04 D 1 = 5.50 N 1 = 1.74618 ν 1 = 28.3 R 2 = 176.61 D 2 = 2.05 R 3 = 176.88 D 3 = 15.75 N 2 = 1.43496 ν 2 = 95.1 R 4 = 803.17 D 4 = 20.11 R 5 = 390.22 D 5 = 11.32 N 3 = 1.43496 ν 3 = 95.1 R 6 = -1444.28 D 6 = 0.30 R 7 = 193.35 D 7 = 16.61 N 4 = 1.43496 ν 4 = 95.1 R 8 = -3277.13 D 8 = 1.00 R 9 = 137.02 D 9 = 10.70 N 5 = 1.49845 ν 5 = 81.6 R10 = 265.11 D10 = variable R11 = 20035.88 D11 = 2.00 N 6 = 1.82017 ν 6 = 46.6 R12 = 49.31 D12 = 5.33 R13 = -151.12 D13 = 1.80 N 7 = 1.77621 ν 7 = 49.6 R14 = 60.83 D14 = 5.04 R15 = -70.46 D15 = 1.80 N 8 = 1.77621 ν 8 = 49.6 R16 = 48.83 D16 = 6.55 N 9 = 1.93306 ν 9 = 21.3 R17 = -375.68 D17 = variable R18 = 282.65 D18 = 8.70 N10 = 1.49845 ν10 = 81.6 R19 = -100.57 D19 = 0.30 R20 = 157.49 D20 = 2.50 N11 = 1.81265 ν11 = 25.4 R21 = 83.03 D21 = 11.25 N12 = 1.48915 ν12 = 70.2 R22 = -152.19 D22 = 0.20 R23 = 139.97 D23 = 10.57 N13 = 1.62032 ν13 = 63.4 R24 = -97.64 D24 = 2.50 N14 = 1.85501 ν14 = 23.9 R25 =- 253.50 D25 = 0.20 R26 = 91.15 D26 = 7.16 N15 = 1.48915 ν15 = 7 0.2 R27 = 500.08 D27 = Variable R28 = (Aperture) D28 = 4.07 R29 = -55.87 D29 = 1.80 N16 = 1.79013 ν16 = 44.2 R30 = 25.90 D30 = 5.48 N17 = 1.81265 ν17 = 25.4 R31 = 132.84 D31 = 6.10 R32 = -30.14 D32 = 1.60 N18 = 1.73234 ν18 = 54.7 R33 = 32.18 D33 = 10.57 N19 = 1.59911 ν19 = 39.2 R34 = -27.39 D34 = 24.00 R35 = -262.03 D35 = 6.95 N20 = 1.48915 ν20 = 70.2 R36 = -31.46 D36 = 0.20 R37 = -53.85 D37 = 2.20 N21 = 1.79013 ν21 = 44.2 R38 = 41.01 D38 = 7.81 N22 = 1.50349 ν22 = 56.4 R39 = -52.46 D39 = 1.10 R40 = 128.36 D40 = 7.29 N23 = 1.55099 ν23 = 45.8 R41 = -28.99 D41 = 2.20 N24 = 1.81265 ν24 = 25.4 R42 = -121.65 D42 = 0.20 R43 = 73.01 D43 = 5.52 N25 = 1.51977 ν25 = 52.4 R44 = -66.47 D44 = 5.00 R45 = ∞ D45 = 50.00 N26 = 1.51825 ν23 = 64.2 R46 = ∞

[0102]

[Table 5]

[0103]

As described above, according to the present invention, the inner focus method is adopted in which a part of the first lens group for focusing which constitutes the four-group zoom lens is moved along the optical axis for focusing. Meanwhile, when increasing the aperture and increasing the zoom ratio, by appropriately setting the lens configuration of each lens group, it is possible to reduce the fluctuations of various aberrations such as spherical aberration and chromatic aberration due to zooming and focusing, and to reduce the total change. It is possible to achieve a zoom lens having a large aperture ratio and a high zoom ratio of about 1.7 at the wide angle end and a zoom ratio of about 13 to 44, which has high optical performance over the zoom range and the entire focus range.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view at a wide-angle end according to Numerical Example 1 of the present invention.

FIG. 2 is a lens cross-sectional view at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 3 is a lens cross-sectional view at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 4 is a lens cross-sectional view at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 5 is an aberration diagram of an object at infinity at the telephoto end according to Numerical Example 1 of the present invention.

FIG. 6 is an aberration diagram at 3 m in Numerical Example 1 of the present invention.

FIG. 7 is an aberration diagram of Numerical example 1 of the present invention at 0.9 m.

FIG. 8 is an aberration diagram of a numerical example 2 of the present invention when an object at infinity is located at the telephoto end.

FIG. 9 is an aberration diagram of Numerical example 2 of the present invention at 3 m.

FIG. 10 is an aberration diagram of Numerical example 2 of the present invention at 0.8 m.

FIG. 11 is an aberration diagram of an object at infinity at the telephoto end according to Numerical Example 3 of the present invention.

FIG. 12 is an aberration diagram at 10 m in Numerical Example 3 of the present invention.

FIG. 13 is an aberration diagram of Numerical example 3 of the present invention at 2 m.

FIG. 14 is an aberration diagram of an infinite object at the telephoto end according to Numerical Example 4 of the present invention.

FIG. 15 is an aberration diagram of Numerical example 4 of the present invention at 10 m.

FIG. 16 is an aberration diagram of Numerical example 4 of the present invention at 2.5 m.

FIG. 17 is an explanatory diagram of the paraxial refractive power arrangement of the first group of the zoom lens of the present invention.

FIG. 18 is an explanatory diagram of a paraxial refractive power arrangement of the first group of the conventional four-group zoom lens.

FIG. 19 is a lens sectional view of a first group of a conventional four-group zoom lens.

FIG. 20 is an explanatory diagram of a paraxial refractive power arrangement of the first group of the conventional four-group zoom lens.

FIG. 21 is a lens cross-sectional view of a first group of a conventional four-group zoom lens.

[Explanation of symbols]

 L1 1st group L2 2nd group L3 3rd group L4 4th group LA 4th group LA 1st group LB1 1st group 1st group LB2 2nd group 2nd SP SP diaphragm P glass block e e line g g line S sagittal image surface M meridional image surface

Claims (4)

[Claims] 1. A first group of positive refracting powers, a second group of negative refracting powers for zooming, and a positive or negative refracting powers for correcting image plane fluctuations associated with zooming in order from the object side. In a zoom lens having a third lens unit and a fourth lens unit having a fixed image-forming action during zooming, the first lens unit has a negative refractive power group A and a positive refractive power group B.
It has three lens groups, a first lens group and a second lens group B2 having a positive refracting power, and moves the first lens group B1 and the second lens group B2 with different amounts of movement at the time of focusing from an object at infinity to a near object. A zoom lens characterized by being moved to. 2. The zoom lens according to claim 1, wherein the condition that MB2 / MB1 <1 is satisfied, where MB1 and MB2 are the movement amounts of the B1 and B2 groups, respectively. 3. When the refractive power and F number of the entire system at the telephoto end are φT and FNT, and the refractive power and F number of the first group are φ1 and FN1, respectively, 1.05 <FN1 where FN1 = (1 / φ1) / {(1 / φT) / FN
The zoom lens according to claim 1, wherein the condition T} is satisfied. 4. The group A includes at least two independent lenses, a negative A1 lens and a positive A2 lens,
The refractive power of the A-th group is φA, and the refractive power of the Ai-th lens is φAi.
And the Abbe number νAi of the material are summed up ΣA = φAi / ν
Ai, and said group B1 is at least one positive group B
It has a 1,1 lens and the refracting power of the B1 group is φB1,
1, i Lens refractive power φB1, i and material Abbe number νB1, i
The total sum of the ratios is ΣB1 = φB1, i / νB1, i, and the B2 group is a meniscus-shaped positive B-side lens with a convex surface facing the object side.
It has a 2,1 lens and the refractive power of the B2 group is φB2,
Refractive power of 2,1 lens φB2,1 and Abbe number of material νB2,1
When the ratio of ΣB2 = φB2,1 / νB2,1 is set, −0.30 <φA / φ1 <−0.0095 −0.02 <ΣA / φ1 <−0.009 −1.22 <ΣA / ( The zoom lens according to claim 1, wherein a condition of ΣB1 + ΣB2) <− 0.77 0.23 <φB2 / φB1 <0.95 0.23 <ΣφB2 / ΣφB1 <1.40 is satisfied.