JPH0829688A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain the rear focus zoom lens which has high optical performance over the entire power variation range by providing two lens groups on the whole and properly setting the movement conditions, refracting power, etc., of the respective lens groups as to power variation and focusing. CONSTITUTION:The zoom lens which has plural lens groups in order from the object side, has a group L1 having positive composite refracting power at the wide-angle end and a group L2 having negative refracting power, and varies in power by varying the gap between the groups L1 and L2; and the group L2 has two lens groups that are a group L21 with negative refracting power and a group L22 with negative refracting power, and the zoom lens is put in focus by varying the gap between the groups L21 and L22.

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 lens shutter camera, a video camera, etc., and particularly adopts a so-called rear focus in which focusing is performed by a lens group other than the first lens group on the object side, and the whole lens system. Is small,
Moreover, the present invention relates to a zoom lens having a variable power ratio of about 2.5 to 3.5, which has high optical performance over the entire object distance.

[0002]

2. Description of the Related Art Recently, in a lens shutter camera, a video camera, etc., a compact zoom lens having a short total lens length has been demanded as the camera becomes smaller. In particular, lens shutter cameras are becoming smaller and smaller due to the development of peripheral technologies such as zoom driving electric circuits. There is.

As one means for achieving these objects, there is known a so-called rear focus type zoom lens in which a lens unit other than the first lens unit on the object side is moved for focusing.

Generally, in a rear focus type zoom lens, the effective diameter of the first lens group is smaller than that of a zoom lens in which the first lens group is moved to perform focusing, which facilitates downsizing of the entire lens system and close-up photography. In particular, since extremely close-up photography is facilitated and the relatively small and lightweight lens group is moved, the driving force of the lens group is small, and quick focusing is possible.

A zoom lens for a single-lens reflex camera or a VTR using such a rear focus type is disclosed in, for example, Japanese Patent Laid-Open No.
It is proposed in JP-A-3-66523, JP-A-64-68709, and JP-A-58-179810. Further, in Japanese Patent Application Laid-Open No. 1-204013, a zoom lens in which a second lens group or a third lens group is focused in a three-group zoom lens including three lens groups having positive, positive, and negative refractive powers in order from the object side. Is proposed.

Further, JP-A-62-24213, JP-A-63-247316 and JP-A-4-433.
In the publication No. 11, the first group having positive refracting power in order from the object side,
It has four lens groups, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, and the second lens group is moved to perform zooming. We have proposed a zoom lens that moves the lens group to focus and focus on the image plane due to zooming.

[0007]

Generally, in a rear 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 for focusing. It becomes easier and close-up photography becomes easier. Furthermore, since the relatively small and lightweight lens group is moved, the driving force of the lens group can be small,
It has features such as quick focusing.

On the other hand, however, the aberration variation at the time of focusing becomes large, and it becomes very difficult to obtain high optical performance over the entire object distance from an object at infinity to a near object.

Particularly, in a zoom lens having a wide angle of view and a high zoom ratio, it becomes very difficult to obtain high optical performance over the entire zoom range and over the entire object distance.

The present invention adopts a rear focus system,
By appropriately moving each lens group along with zooming and arranging paraxial refractive power, etc., over the entire zoom range from the wide-angle end to the telephoto end,
Another object of the present invention is to provide a zoom lens having a wide angle of view and a high zoom ratio, which has good optical performance over the entire object distance from an infinite object to a close object.

[0011]

A zoom lens according to the present invention comprises a plurality of lens groups in order from the object side, and has a positive refractive power L1 group and a negative refractive power L2 group at the wide-angle end. In the zoom lens which performs zooming by changing the distance between the L1 group and the L2 group, the L2 group includes two lens groups, an L21 group having a negative refractive power and an L22 group having a negative refractive power, L2
It is characterized in that the distance between the first lens group and the L22 lens group is changed to perform focusing.

[0012]

1 to 5 are numerical examples 1 to 5 of the present invention.
2 is a lens cross-sectional view at the wide-angle end of FIG. 6 to 38 are various aberration diagrams of Numerical Examples 1 to 5 of the present invention. FIG. 39 is an explanatory diagram of the paraxial refractive power arrangement in the focus of the zoom lens according to the present invention.

In the figure, L1 is a plurality of lens groups (L1i, i
= 1 to 5), and the combined refractive power is a positive refractive power L1 group,
L2 is an L2 group having a negative combined refractive power. The L2 group has two lens groups, an L21 group having a negative refractive power and an L22 group having a negative refractive power. SP is an aperture and IP is an image plane. The arrows indicate the method of moving each lens group when performing zooming from the wide-angle side to the telephoto side. That is, zooming is performed by changing the distance between the lens groups in the L1 group and the distance between the L1 group and the L2 group.

In this embodiment, as shown in FIGS. 39A and 39B, focusing is performed by changing the distance between the L21 group and the L22 group. Specifically, as shown in FIG. 39 (B), the L22 group is fixed and the L21 group is moved to the image side, and as shown in FIG. 39 (A), the L21 group and L22 group are moved.
A method of moving both groups to the image plane side while changing the distance between the two groups is used.

Generally, in a zoom lens such as a photographic camera or a video camera, the exit pupil is located closer to the object side than the image plane (film surface). Therefore, compared with the L21 group, L2
The effective diameter of the second group becomes larger. Focal length f of L2 group
L2 represents the focal lengths of the L21 group and the L22 group by fL21,
Let fL22 and e be the principal point spacing between the L21 group and the L22 group.

[0016]

[Equation 1] Becomes

Therefore, in this embodiment, when focusing, L2
Move it so that the distance between the first group and the L22 group becomes smaller,
The negative refracting power of the L2 group is weakened so that the moving amount of the focusing lens groups L21 and L22 becomes smaller than that in the case of performing the L2 group alone. As a result, the total lens length is shortened and the driving torque during focusing is reduced. In particular, during focusing, the L22 group is fixed and the lens outer diameter is smaller than that of the L22 group.
The method of moving the group to the image plane side is characterized in that the focus moving torque is reduced and the focus mechanism is simplified.

In this embodiment, by adopting such a zoom type and focus type lens configuration, a zoom ratio of 2.5 to 3.5 is achieved while achieving a wide angle of view at the wide angle end and a reduction of the total lens length. Aberration variation due to the degree of magnification and zooming is corrected well, and high optical performance is obtained over the entire zoom range and over the entire object distance.

In the present invention, in order to correct aberration variation and obtain high optical performance over the entire range of zooming and over the entire object distance, or to properly configure the lens barrel structure, It is better to satisfy at least one of the conditions.

(1-1) The focal lengths of the L1 group and the entire system at the wide-angle end are fL1W and fW, respectively, and the L21 group and the L21 group are L, respectively.
When the focal lengths of the two groups are fL21 and fL2 and the lateral magnification of the L2 group at the wide-angle end is βL2W, 0.5 <| fL2 / fW | <0.95 (1) 0. 25 <fL2 / fL21 <0.9 (2) 1.2 <βL2W <1.85 (3) 0.5 <fL1W / fW <0.95 (4) To satisfy the following condition.

Conditional expression (1) is the negative refractive power L including the focal length and the focus lens group at the wide-angle end of the entire lens system.
With respect to the ratio of the refracting powers of the two groups, it is intended to effectively obtain a predetermined zoom ratio while shortening the overall lens length. If the upper limit of conditional expression (1) is exceeded, the negative refractive power of the L2 group becomes too weak, and the amount of movement of each lens group including the L2 group becomes large in order to obtain a constant zoom ratio. The total length of the lens system increases.

On the other hand, if the lower limit of conditional expression (1) is exceeded,
Since the negative refracting power of the L2 group becomes too strong, the entire lens system becomes a strong telephoto type, and it becomes difficult to obtain a positive back focus, and at the same time a lot of off-axis aberrations occur, which It becomes difficult to correct it well.

Conditional expression (2) relates to the ratio of the refractive powers of the negative refractive power L21 group, which is the focus lens group, and the negative refractive power L2 group including the negative refractive power L2 group. This is a condition for reducing the size of the lens system while suppressing it.

When the negative refracting power of the L21 lens unit, which is the focus lens unit, is weakened beyond the upper limit of conditional expression (2), the focus movement amount of the L21 lens unit during focusing becomes large. Therefore, the other L2 in the L2 group
In order to prevent interference with the second group, the air space between the L21 group and the L22 group must be widened in advance, resulting in an increase in the size of the lens system.

If the lower limit of conditional expression (2) is exceeded, the refractive power of the L21 lens unit, which is the focus lens unit, becomes too strong, and the aberration variation of the off-axis aberration during focusing becomes large. However, since the lens has a large divergence in the L21 group, the lens outer diameter of the L22 group becomes large, which is not good.

Conditional expression (3) relates to the lateral magnification at the wide-angle end of the L2 group, and is mainly for shortening the total lens length and maintaining a good balance of optical performance. Now, the focal length at the wide-angle end is fW, and the focal length at the wide-angle end of the L1 group is fL.
Assuming 1 W, the focal length fW is given by the following equation: fW = fL1W.βL2W (b)

Therefore, the upper limit of conditional expression (3) is exceeded and L2 is exceeded.
As the lateral magnification of the group becomes large, the positive refracting power of the L1 group must be made strong in widening the angle, as understood from the expression (b), so that a large spherical aberration is generated under and this is caused. It becomes difficult to correct with the L2 group.

When the lateral magnification of the L2 unit becomes smaller than the lower limit value of the conditional expression (3), the paraxial back focus βfW at the wide angle end of the lens system is given by the following expression βfW = fL2 (1-βL2W) As is guided, it becomes difficult to keep the back focus positive, and at the same time, the lens outer diameter of the L2 group becomes large in order to keep a constant peripheral light amount ratio, which is not good.

Conditional expression (4) relates to the ratio of the combined focal length of the L1 group having a plurality of lens units at the wide-angle end to the focal length of the entire lens system, and mainly makes good aberration correction while reducing the size of the entire lens system. It is for the purpose of

If the upper limit of conditional expression (4) is exceeded, the refracting power of the L1 group becomes too weak, and it is necessary to widen the air distance between the L1 group and the L2 group in advance in order to obtain a constant focal length at the wide angle end. Therefore, it is not good because the entire lens system becomes large.

If the lower limit of conditional expression (4) is exceeded, L1
Since the positive refracting power of the group becomes too strong and the action of the telephoto type of the entire lens system becomes strong, it becomes difficult to keep the back focus positive, and at the same time the spherical aberration is strongly under-produced. Becomes difficult to correct in the L2 group.

In the present invention, the upper limit and the lower limit of the conditional expressions (1) to (4) are set as follows in order to perform better correction of various aberrations while reducing the size of the entire lens system. Is good.

0.6 <| fL2 / fW | <0.8 (1a) 0.35 <fL2 / fL21 <0.7 (2a) 1.3 <βL2W <1.6 ···· (3a) 0.6 <fL1W / fW <0.8 ··· (4a) (1-2) The L21 group is a negative lens whose concave surface faces the image plane side. And the L22 group has a negative lens with a concave surface facing the object side. By providing a negative lens having such a shape in the two lens units of the L2 group, a good balance is achieved between spherical aberration and various off-axis aberrations over the entire object distance, and a high-performance optical system is achieved.

(1-3) Introducing at least one positive lens element into the L2 group is preferable for good chromatic aberration correction in the entire zoom range. Further, in this case, it is desirable that the Abbe number ν _P of the material of the positive lens to be introduced be ν _P <35 in order to correct chromatic aberration.

(1-4) Introducing an aspherical surface into each lens group is preferable for aberration correction.

(1-5) Two or more lens groups may be moved integrally during zooming. This is preferable because the lens barrel structure is simplified.

(1-6) It is preferable to move the aperture stop SP independently during zooming or integrally with other lens groups.
According to this, it is possible to dispose the diaphragm near the position of the entrance pupil that moves with zooming, and it is possible to prevent the aberration change of the image plane curvature when the diaphragm is small.

Next, the features of the lens configuration of each embodiment will be described. In Numerical Embodiment 1 of FIG. 1, the L1 group having positive refracting power in order from the object side is the L11 group having positive refracting power composed of a single positive lens having a convex surface facing the object side, and both lens surfaces have a single concave surface L12 group of negative refractive power consisting of a negative lens, a positive lens having a convex surface directed to the object side, a positive lens having both convex lens surfaces, and a meniscus negative lens having a convex surface directed to the image side.
L13 with positive refractive power as a whole with two lenses cemented together
L14 group having a negative refracting power composed of a group, an aperture stop SP, and a single meniscus negative lens having a convex surface directed toward the image side, and a positive refracting power composed of a single positive lens having a convex surface directed toward the image side. L1
It has five lens groups of five groups.

The L2 group having a negative refracting power has a negative refracting power as a whole in which a negative lens having both concave lens surfaces and a meniscus positive lens having a convex surface facing the object side are cemented together.
It has two lens groups of a negative refractive power L22 group consisting of a single negative lens having a concave surface facing the object side.

Upon zooming from the wide-angle end to the telephoto end, L1
The distance between the first group and the L12 group, the distance between the L13 group and the L14 group, and the distance between the L14 group and the L15 group increase,
Each lens group is moved as indicated by an arrow so that the distance between the second lens group and the L13 lens group and the distance between the L1 lens group and the L2 lens group are reduced. Focusing is performed with the L21 group.

In Numerical Embodiment 2 of FIG. 2, the L1 group having positive refracting power in order from the object side is the L11 group having positive refracting power composed of a single positive lens having a convex surface facing the object side, and both lens surfaces are concave surfaces. Negative refractive power L12 group consisting of a single negative lens, a positive lens having a convex surface directed toward the object side and a positive lens having convex lens surfaces on both sides,
Then, L13 having a positive refracting power as a whole, which is obtained by cementing three meniscus negative lenses whose convex surface faces the image surface side, is cemented.
L14 group having a negative refracting power composed of a group, an aperture stop SP, and a single meniscus negative lens having a convex surface directed toward the image side, and a positive refracting power composed of a single positive lens having a convex surface directed toward the image side. L1
It has five lens groups of five groups.

The L2 lens unit having a negative refracting power is a L21 lens unit having a negative refracting power composed of a single negative lens having concave lens surfaces, and a meniscus positive lens having a convex surface facing the object side and an object side. It has two lens units of the L22 unit having a negative refracting power, which is composed of a negative lens having a concave surface facing to.

Upon zooming from the wide-angle end to the telephoto end, L1
The distance between the first group and the L12 group, the distance between the L13 group and the L14 group, and the distance between the L14 group and the L15 group increase,
Each lens group is moved as indicated by an arrow so that the distance between the second lens group and the L13 lens group and the distance between the L1 lens group and the L2 lens group are reduced. Focusing is performed with the L21 group.

In Numerical Embodiment 3 of FIG. 3, the L1 group having positive refracting power in order from the object side has a negative refracting power L11 composed of a negative lens having both concave lens surfaces and a positive lens having a convex surface facing the object side.
L12 having a positive refractive power as a whole by cementing three lenses, a group, a positive lens having a convex surface directed to the object side, a positive lens having both convex lens surfaces, and a meniscus negative lens having a convex surface directed to the image side. L13 having a negative refracting power, which includes a group, an aperture stop SP, and a single meniscus negative lens having a convex surface directed toward the image plane side.
The lens unit has four lens units, the L14 unit having a positive refractive power, which is composed of a single positive lens having a convex surface directed toward the image plane side.

The L2 lens unit having a negative refracting power has a negative refracting power L21 unit composed of a single negative lens having concave lens surfaces, and the meniscus-shaped positive lens having a convex surface facing the object side and both lens surfaces. 2 of the L22 group of negative refracting power composed of a negative lens having a concave surface
It has two lens groups.

Upon zooming from the wide-angle end to the telephoto end, L1
The distance between the second group and the L13 group, the distance between the L13 group and the L14 group increases, the distance between the L11 group and the L12 group, the L1 group and the L2 group
Each lens group is moved as indicated by an arrow so that the distance between the lens group and the lens group is reduced. Focusing is performed with the L21 group.

Numerical embodiment 4 of FIG. 4 is a cemented lens in which a positive lens having a positive refractive power in order from the object side is a positive lens having a convex surface facing the image side and a negative lens having a concave surface on both surfaces.
Then, the L11 lens unit having a negative refractive power and composed of a positive lens having a convex surface directed toward the object side, a meniscus negative lens having a convex surface directed toward the object side, a positive lens having convex lens surfaces on both sides, and a convex surface directed toward the image surface side. The L12 lens unit having a positive refracting power as a whole in which three meniscus-shaped negative lenses are cemented, an aperture stop SP,
A meniscus negative lens having a convex surface directed toward the image side, a cemented lens in which a negative lens having a concave surface on both lens surfaces and a positive lens having a convex surface on both lens surfaces are cemented together, and has a positive refractive power L13.
It has three lens groups of groups.

The L2 group having a negative refractive power is composed of a single negative lens having concave surfaces on both sides, and the L21 group having a negative refractive power, and a meniscus-shaped positive lens having a convex surface facing the object side and an object side. It has two lens units of the L22 unit having a negative refracting power and composed of a negative lens having a concave surface.

Upon zooming from the wide-angle end to the telephoto end, L1
The lens groups are moved as indicated by the arrows so that the distance between the second lens group and the L13 lens group increases, the distance between the L11 lens group and the L12 lens group decreases, and the distance between the L1 lens group and the L2 lens group decreases. Focusing is performed with the L21 group.

In Numerical Embodiment 5 of FIG. 5, in order from the object side, the L1 lens unit having a positive refractive power is composed of a meniscus negative lens having a convex surface directed toward the object side and a positive lens having a convex surface directed toward the object side. L11 group of power, stop SP, a cemented lens in which a negative lens having a concave surface facing the object side and a positive lens are cemented, a meniscus-shaped negative lens having a convex surface facing the object side, and a positive lens having convex lens surfaces on both sides. It has two lens groups of L12 group having a positive refracting power, which is composed of a cemented lens in which is cemented.

The negative refractive power L2 group is a negative refractive power L21 group in which a positive meniscus lens having a convex surface facing the image side and a negative lens having concave lens surfaces are cemented together.
It has two lens groups of a negative refractive power L22 group consisting of a single negative lens whose both lens surfaces are concave.

Upon zooming from the wide-angle end to the telephoto end, L1
The respective lens groups are moved as indicated by arrows so that the distance between the first lens group and the L12 lens group increases and the distance between the L1 lens group and the L2 lens group decreases. Focusing is performed with the L21 group.

Next, numerical examples of the present invention will be shown. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air gap from the object side, and Ni and νi are respectively from the object side of the i-th lens. The refractive index of glass and the Abbe number.

Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples.

The aspherical shape has an X axis in the optical axis direction, an H axis in the direction perpendicular to the optical axis, a positive light traveling direction, and R as a paraxial radius of curvature,
When K, A, B, C, D and E are aspherical coefficients,

[0056]

[Equation 2] It is expressed by Also, "e-0X" is "10 ^-X "
Means (Numerical Example 1) F = 28.86 to 101.39 FNO = 4.33 to 9.06 2ω = 73.7 to 24.1 R 1 = 53.81 D 1 = 2.40 N 1 = 1.84665 ν 1 = 23.8 R 2 = 1346.34 D 2 = variable R 3 = -48.28 D 3 = 1.20 N 2 = 1.67790 ν 2 = 54.9 R 4 = 20.69 D 4 = Variable R 5 = 14.96 D 5 = 1.80 N 3 = 1.80609 ν 3 = 41.0 R 6 = 17.17 D 6 = 3.30 N 4 = 1.58913 ν 4 = 61.2 R 7 = -20.02 D 7 = 1.00 N 5 = 1.84665 ν 5 = 23.8 R 8 = -48.60 D 8 = Variable R 9 = Aperture D 9 = 2.00 R10 = -20.16 D10 = 1.20 N 6 = 1.80518 ν 6 = 25.4 R11 = -63.02 D11 = Variable R12 = 283.18 D12 = 4.90 N 7 = 1.73077 ν 7 = 40.6 R13 = -14.50 D13 = Variable R14 = -86.38 D14 = 1.20 N 8 = 1.77249 ν 8 = 49.6 R15 = 69.98 D15 = 2.20 N 9 = 1.69894 ν 9 = 30.1 R16 = 86.43 D16 = 6.74 R17 = -27.85 D17 = 1.50 N10 = 1.74319 ν10 = 49.3 R18 = -4518.62

[0057]

[Table 1] Four aspherical coefficients: K = 2.482e-01 A = 0 B = -1.870e-05 C = -4.346e-08
D = -2.257e-10 E = 0 10 side: K = 4.04329 A = 0 B = -6.210e-05 C = -2.925e-07
D = -8.844e-09 E = 0 13 side: K = -2.81235 A = 0 B = -8.961e-05 C = 2.350e-07
D = -6.170e-10 E = 0 (Numerical example 2) F = 28.87 to 100.96 FNO = 4.33 to 9.06 2ω = 73.7 to 24.2 R 1 = 53.62 D 1 = 2.40 N 1 = 1.84665 ν 1 = 23.8 R 2 = 2359.07 D 2 = Variable R 3 = -47.19 D 3 = 1.20 N 2 = 1.67790 ν 2 = 54.9 R 4 = 20.14 D 4 = Variable R 5 = 15.03 D 5 = 1.80 N 3 = 1.80609 ν 3 = 41.0 R 6 = 17.51 D 6 = 3.30 N 4 = 1.58913 ν 4 = 61.2 R 7 = -18.42 D 7 = 1.00 N 5 = 1.84665 ν 5 = 23.8 R 8 = -37.77 D 8 = Variable R 9 = Aperture D 9 = 2.00 R10 = -19.59 D10 = 1.20 N 6 = 1.80518 ν 6 = 25.4 R11 = -103.12 D11 = variable R12 = 158.88 D12 = 4.90 N 7 = 1.73077 ν 7 = 40.6 R13 = -14.29 D13 = variable R14 = -74.61 D14 = 1.20 N 8 = 1.77249 ν 8 = 49.6 R15 = 48.59 D15 = 2.93 R16 = 62.86 D16 = 2.50 N 9 = 1.69894 ν 9 = 30.1 R17 = 155.09 D17 = 4.03 R18 = -30.71 D18 = 1.50 N10 = 1.74319 ν10 = 49.3 R19 = -2469.17

[0058]

[Table 2] Four aspherical coefficients: K = 2.354e-01 A = 0 B = -1.566e-05 C = -5.423e-08
D = -1.294e-10 E = 0 10 side: K = 3.68674 A = 0 B = -6.371e-05 C = -3.434e-07
D = -1.145e-08 E = 0 13 side: K = -2.86420 A = 0 B = -9.380e-05 C = 2.964e-07
D = -8.088e-10 E = 0 (Numerical example 3) F = 28.84 to 102.90 FNO = 4.33 to 9.06 2ω = 73.8 to 23.8 R 1 = -74.16 D 1 = 1.10 N 1 = 1.77249 ν 1 = 49.6 R 2 = 20.25 D 2 = 1.12 R 3 = 26.77 D 3 = 2.20 N 2 = 1.84665 ν 2 = 23.8 R 4 = 62.61 D 4 = Variable R 5 = 14.84 D 5 = 1.80 N 3 = 1.80609 ν 3 = 41.0 R 6 = 17.26 D 6 = 4.10 N 4 = 1.58913 ν 4 = 61.2 R 7 = -19.94 D 7 = 1.00 N 5 = 1.84665 ν 5 = 23.8 R 8 = -39.89 D 8 = Variable R 9 = Aperture D 9 = 2.00 R10 = -19.68 D10 = 1.20 N 6 = 1.80518 ν 6 = 25.4 R11 = -75.03 D11 = Variable R12 = -5905.34 D12 = 4.30 N 7 = 1.73077 ν 7 = 40.6 R13 = -15.04 D13 = Variable R14 = -55.39 D14 = 1.20 N 8 = 1.77249 ν 8 = 49.6 R15 = 39.93 D15 = 2.29 R16 = 37.23 D16 = 3.00 N 9 = 1.69894 ν 9 = 30.1 R17 = 152.45 D17 = 3.00 R18 = -41.23 D18 = 1.50 N10 = 1.77249 ν10 = 49.6 R19 = 91.48

[0059]

[Table 3] One aspherical surface: K = -1.350e-01 A = 0 B = -3.125e-06 C = -2.570e-08
D = -3.970e-11 E = 0 10 side: K = 3.77316 A = 0 B = -8.280e-05 C = -4.129e-07
D = -1.164e-08 E = 0 13 side: K = -2.97836 A = 0 B = -1.000e-04 C = 2.620e-07
D = -1.139e-09 E = 0 (Numerical example 4) F = 29.18 to 88.82 FNO = 3.75 to 9.00 2ω = 73.1 to 27.4 R 1 = -205.07 D 1 = 2.80 N 1 = 1.51633 ν 1 = 64.2 R 2 = -42.00 D 2 = 1.20 N 2 = 1.80400 ν 2 = 46.6 R 3 = 16.58 D 3 = 2.34 R 4 = 20.25 D 4 = 4.20 N 3 = 1.84665 ν 3 = 23.8 R 5 = 200.06 D 5 = variable R 6 = 17.29 D 6 = 0.90 N 4 = 1.84665 ν 4 = 23.8 R 7 = 11.68 D 7 = 5.20 N 5 = 1.48749 ν 5 = 70.2 R 8 = -20.58 D 8 = 0.90 N 6 = 1.84665 ν 6 = 23.8 R 9 =- 29.72 D 9 = Variable R10 = Aperture D10 = 2.00 R11 = -24.06 D11 = 2.00 N 7 = 1.80518 ν 7 = 25.4 R12 = -35.93 D12 = 0.73 R13 = -22.89 D13 = 1.30 N 8 = 1.65159 ν 8 = 58.5 R14 = 73.08 D14 = 4.00 N 9 = 1.77249 ν 9 = 49.6 R15 = -13.31 D15 = Variable R16 = -66.06 D16 = 1.20 N10 = 1.77249 ν10 = 49.6 R17 = 50.01 D17 = 2.26 R18 = 41.36 D18 = 2.90 N11 = 1.69894 ν11 = 30.1 R19 = 221.99 D19 = 5.02 R20 = -23.64 D20 = 1.50 N12 = 1.77249 ν12 = 49.6 R21 = -173.10

[0060]

[Table 4] Aspheric surface coefficient 3rd surface: K = 2.216e-01 A = 0 B = -1.254e-05 C = 2.253e-08
D = -5.639e-10 E = 0 11 side: K = 6.26902 A = 0 B = -6.294e-05 C = -3.412e-07
D = -9.389e-09 E = 0 15 side: K = -2.72205 A = 0 B = -1.510e-04 C = 1.387e-07
D = -3.214e-09 E = 0 (Numerical example 5) F = 39.67 to 101.24 FNO = 4.00 to 7.80 2ω = 57.2 to 24.1 R 1 = 48.56 D 1 = 1.20 N 1 = 1.84665 ν 1 = 23.9 R 2 = 35.12 D 2 = 0.30 R 3 = 24.35 D 3 = 2.80 N 2 = 1.48749 ν 2 = 70.2 R 4 = 166.60 D 4 = Variable R 5 = Aperture D 5 = 2.00 R 6 = -17.23 D 6 = 1.20 N 3 = 1.48749 ν 3 = 70.2 R 7 = -168.98 D 7 = 8.49 N 4 = 1.80517 ν 4 = 25.4 R 8 = -33.56 D 8 = 4.74 R 9 = 36.00 D 9 = 1.10 N 5 = 1.84665 ν 5 = 23.9 R10 = 17.05 D10 = 5.30 N 6 = 1.58312 ν 6 = 59.4 R11 = -30.35 D11 = Variable R12 = -49.04 D12 = 3.40 N 7 = 1.69894 ν 7 = 30.1 R13 = -25.21 D13 = 1.10 N 8 = 1.58913 ν 8 = 61.2 R14 = 85.79 D14 = 8.00 R15 = -65.34 D15 = 1.50 N 9 = 1.63853 ν 9 = 55.4 R16 = 169.94

[0061]

[Table 5] Aspherical surface coefficient 11 surfaces: K = -3.015e-02 A = 0 B = 8.045e-06 C = -1.134e-
07 D = 1.843e-09 E = -1.305e-11

[0062]

[Table 6]

[0063]

As described above, according to the present invention, the rear focus system is adopted, and the movement of each lens unit and the paraxial refracting power arrangement are appropriately performed in accordance with the magnification change, and from the wide angle end to the telephoto end. It is possible to achieve a zoom lens with a wide field angle and a high zoom ratio, which has good optical performance over the entire zoom range and over the entire object distance from an object at infinity to a close object.

[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 a lens cross-sectional view at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 6 is an aberration diagram at the wide-angle end for an object at infinity according to Numerical Example 1 of the present invention.

FIG. 7 is an intermediate aberration diagram for an object at infinity according to Numerical Example 1 of the present invention.

FIG. 8 is an aberration diagram at a telephoto end when an object at infinity according to Numerical Example 1 of the present invention is used.

FIG. 9 is an aberration diagram at the wide-angle end at 800 from the image plane of Numerical Example 1 of the present invention.

FIG. 10 is an intermediate aberration diagram of the numerical value example 1 of the present invention at 800 from the image plane.

FIG. 11 is an aberration diagram at the telephoto end at 800 from the image plane of Numerical Example 1 of the present invention.

FIG. 12 is an aberration diagram at the wide-angle end for an object at infinity according to Numerical Example 2 of the present invention.

FIG. 13 is an intermediate aberration diagram for an object at infinity according to Numerical Example 2 of the present invention.

FIG. 14 is an aberration diagram at the telephoto end for an object at infinity according to Numerical Example 2 of the present invention.

FIG. 15 is an aberration diagram at the wide-angle end when the image plane is 800 from Numerical Example 2 of the present invention.

FIG. 16 is an intermediate aberration diagram of Numerical example 2 of the present invention when the image plane is 800.

FIG. 17 is an aberration diagram at a telephoto end when the image plane is 800 from Numerical Example 2 of the present invention.

FIG. 18 is an aberration diagram at the wide-angle end when the moving amount of the L21 group and the L22 group when the image surface is 800 in Numerical Example 2 of the present invention, and is 1: 0.5.

FIG. 19 is an intermediate aberration diagram when the moving amount of the L21 group and the L22 group when the image plane is 800 in Numerical Example 2 of the present invention is 1: 0.5.

20 is an aberration diagram at the telephoto end when the moving amount of the L21 group and the L22 group when the image plane is 800 in Numerical Example 2 of the present invention, and is 1: 0.5. FIG.

FIG. 21 is an aberration diagram at the wide-angle end for an object at infinity according to Numerical Example 3 of the present invention.

FIG. 22 is an intermediate aberration diagram of an object at infinity according to Numerical Example 3 of the present invention.

FIG. 23 is an aberration diagram at the telephoto end for an infinitely distant object according to Numerical Example 3 of the present invention.

FIG. 24 is an aberration diagram at the wide-angle end at 800 from the image plane of Numerical Example 3 of the present invention.

FIG. 25 is an intermediate aberration diagram at 800 from the image plane of Numerical Example 3 of the present invention.

FIG. 26 is an aberration diagram at the telephoto end when the image plane is 800 from Numerical Example 3 of the present invention.

FIG. 27 is an aberration diagram at a wide-angle end when an object at infinity according to Numerical Example 4 of the present invention.

FIG. 28 is an intermediate aberration diagram of an infinitely distant object according to Numerical Example 4 of the present invention.

FIG. 29 is an aberration diagram at the telephoto end for an infinitely distant object according to Numerical Example 4 of the present invention.

FIG. 30 is an aberration diagram at the wide-angle end at 800 from the image plane of Numerical Example 4 of the present invention.

FIG. 31 is an intermediate aberration diagram of Numerical example 4 of the present invention when the image plane is 800.

32 is an aberration diagram at the telephoto end when the image plane is 800 from Numerical Example 4 of the present invention. FIG.

FIG. 33 is an aberration diagram at the wide-angle end for an object at infinity according to Numerical Example 5 of the present invention.

FIG. 34 is an intermediate aberration diagram of an infinitely distant object according to Numerical Example 5 of the present invention.

FIG. 35 is an aberration diagram at the telephoto end for an infinitely distant object according to Numerical Example 5 of the present invention.

FIG. 36 is an aberration diagram at the wide-angle end at 800 from the image plane of Numerical Example 5 of the present invention.

FIG. 37 is an intermediate aberration diagram of Numerical example 5 of the present invention when the image plane is 800.

FIG. 38 is an aberration diagram at the telephoto end when the image plane is 800 from Numerical Example 5 of the present invention.

FIG. 39 is an explanatory view of the paraxial refractive power arrangement of the present invention.

[Explanation of symbols]

 L1 L1 group L2 L2 group SP diaphragm IP image plane d d line g g line S. C Sine condition ΔS Sagittal image plane ΔM Meridional image plane

Claims (5)

[Claims] 1. A plurality of lens groups are arranged in order from the object side,
In a zoom lens including a L1 group having a positive combined refractive power and an L2 group having a negative combined refractive power at the wide-angle end, and varying the distance between the L1 group and the L2 group, the L2 group has a negative refractive power. A zoom lens comprising two lens groups, an L21 group having a power and an L22 group having a negative refractive power, and performing focusing by changing a distance between the L21 group and the L22 group. 2. The zoom lens according to claim 1, wherein the distance between the plurality of lens groups of the L1 group is changed upon zooming. 3. The zoom lens according to claim 1, wherein the L21 unit is moved for focusing. 4. The focal lengths of the L1 group and the entire system at the wide-angle end are fL1W and fW, the focal lengths of the L21 group and the L2 group are fL21 and fL2, respectively, and the L2 at the wide-angle end is L2.
When the lateral magnification of the group is βL2W, 0.5 <| fL2 / fW | <0.95 0.25 <fL2 / fL21 <0.9 1.2 <βL2W <1.85 0.5 <fL1W / fW The zoom lens according to claim 1, wherein the condition <0.95 is satisfied. 5. The L21 group has a negative lens having a concave surface facing the image side, and the L22 group has a negative lens having a concave surface facing the object side. Zoom lens.