JPH07261079A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide a telephoto type zoom lens which consists of six lens groups with specific refractive powers and has a high power variable ratio of 4. CONSTITUTION:The zoom lens consists of the six lens groups which are a 1st group L1 with positive refractive power, a 2nd group L2 with negative refractive power, a 3rd group L3 with positive refractive power, a 4th group L4 with negative refractive power, a 5th group L5 with positive refractive power, and a 6th group L6 with negative refractive power, and when the power is varied from the wide-angle end to the telephoto end, the air interval between an (i)th group and an (i+1)th group at the wide-angle end and telephoto end is properly varied and the ratio of the focal length of the 4th group and the focal length of the whole system at the telephoto end is properly set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephoto type zoom lens suitable for a 35 mm camera, a video camera, an electronic still camera and the like, and in particular, it has six lens groups as a whole, of which a predetermined lens group can be moved. The present invention relates to a zoom lens which has a variable power ratio of about 4 and has a high variable power ratio and high optical performance over the entire variable power range, and which is intended to reduce the size of the entire lens system.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having a high zoom ratio and high optical performance has been required for a photographic camera, a video camera and the like. Various telephoto-type multi-group zoom lenses have been proposed in which three or more lens groups are moved to perform zooming.

For example, a three-group zoom lens including three lens groups having positive, negative and positive refractive powers in order from the object side,
Four lens groups with positive, negative, positive and positive refracting power, or a four-group zoom lens consisting of four lens groups with positive, negative, negative and positive refracting power, positive, negative, positive, negative and positive refracting A multi-group zoom lens in which zooming is performed by moving a plurality of lens groups in a five-group zoom lens composed of five lens groups of power or five lens groups of positive, negative, positive, positive and negative refractive powers. Various proposals have been made.

In these three-group zoom lens, four-group zoom lens, and five-group zoom lens, a plurality of lens groups are moved to perform zooming, thereby reducing the size of the entire lens system while maintaining a predetermined zoom ratio. Is getting

Further, the applicant of the present invention has disclosed in Japanese Patent Laid-Open No. 4-186212 a high zoom ratio of about 10 consisting of six lens groups having positive, negative, positive, negative, positive and negative refracting powers in order from the object side. It proposes a 6-group zoom lens with a ratio.

[0006]

Generally, in a zoom lens, it is desired that the entire lens system be made compact and at the same time have a high magnification (high magnification). To increase the zoom lens magnification, increase the number of lens groups that contribute to zooming,
Further, the refractive power of each lens group may be strengthened to strengthen the zooming effect, or the amount of movement of the lens groups contributing to zooming may be increased.

However, in the former case, it becomes necessary to increase the number of lens components in order to satisfactorily correct the variation of various aberrations due to zooming, which makes it difficult to make the entire lens system compact. Problems arise.

In the latter case, more space must be secured for moving the lens unit due to zooming, and the total length of the lens becomes longer. Especially when the moving form of the lens unit is complicated, the moving lens It becomes difficult to support the lens barrel of the group, and it becomes difficult to make the entire lens system compact.

According to the present invention, a zoom lens as a whole is composed of six lens groups having a predetermined refractive power, and the refractive power of each lens group and the moving conditions of each lens group for zooming are appropriately set. By doing so, an object of the present invention is to provide a telephoto type zoom lens having a variable power ratio of about 4 which has high optical performance over the entire variable power range while reducing the number of lenses and shortening the total lens length.

[0010]

A zoom lens according to the present invention comprises, in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a negative refractive power. It has six lens groups, a fourth lens group of power, a fifth lens group of positive refractive power, and a sixth lens group of negative refractive power, and when zooming from the wide-angle end to the telephoto end,
When the air distances at the wide-angle end and the telephoto end of the i-th group and the (i + 1) th group are DiW and DiT, respectively, D1W <D1T D2W> D2T D3W <D3T D4W> D4T D5W> D5T is satisfied. When the focal lengths of the fourth lens group and the entire system at the telephoto end are f4 and fT, respectively, 0.3 <| f4 / fT | <10.0 ... -It is characterized by satisfying the condition (1).

[0011]

1 to 3 are cross-sectional views of lenses according to Numerical Examples 1 to 3 of the present invention. 4 to 12 are aberration diagrams of Numerical Examples 1 to 3 of the present invention. In the lens cross-sectional views, (A) shows the wide-angle end, (B) shows the middle, and (C) shows the telephoto end.

In the figure, L1 is a first group having a positive refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, and L4.
Is the fourth group of negative refractive power, L5 is the fifth group of positive refractive power, L
6 is a sixth lens unit having a negative refractive power, SP is a diaphragm, and IP is an image plane. The arrows indicate the movement loci of the respective lens groups during zooming from the wide-angle end to the telephoto end.

In the present embodiment, a predetermined lens group is moved so as to satisfy the above-mentioned condition upon zooming from the wide-angle end to the telephoto end.

That is, the distance between the first group and the second group increases, and the second group
The distance between the third and fourth groups decreases, the distance between the third and fourth groups increases, the distance between the fourth and fifth groups decreases, and the distance between the fifth and sixth groups decreases. Then, the predetermined lens group is moved. Then, by setting the optical characteristics of the fourth lens unit so as to satisfy the above-mentioned conditional expression (1), the variable magnification effect can be shared among the lens groups in a well-balanced manner, and the total lens length can be shortened while achieving high variable magnification. Makes it easy. The aperture SP is the third
It is moved together with the group.

In the zoom lens of the present invention, the first group and the second group are arranged close to each other at the wide-angle end so that the combined refractive power becomes negative. Further, the third group and the fourth group are arranged close to each other. The refracting power of the combined lens unit after the third lens unit is set to be positive, so that the entire lens system is of a retrofocus type.

At the telephoto end, the second group and the third group are arranged close to each other so that the combined refractive power becomes negative. Further, the fourth group, the fifth group, and the sixth group are arranged close to each other so that the combined refractive power is negative or weak positive, and a diaphragm is arranged near the third group.

With such a lens configuration, while the refractive power arrangement is of a substantially retrofocus type at the wide-angle end, the sixth lens group disposed closest to the image plane is a negative lens group, so that asymmetry such as coma aberration occurs. Corrects sexual aberration well. At the same time, at the telephoto end, while using a telephoto type refractive power arrangement with a compact lens configuration,
Corrects various aberrations well.

Further, by specifying the refracting power of the fourth lens unit as in the conditional expression (1), the fluctuations of various aberrations due to zooming are reduced. Conditional expression (1) defines the ratio of the focal length of the fourth lens unit to the focal length of the entire system at the telephoto end, and mainly has a refractive power arrangement for favorably correcting variations in various aberrations during zooming. Is giving.

When the absolute value of the focal length of the fourth lens unit becomes smaller than the focal length of the entire system at the telephoto end beyond the lower limit of conditional expression (1), the absolute value of the focal length of the sixth lens unit is changed to a relative value. In this case, the symmetry of the refracting power arrangement becomes worse especially at the wide-angle end, and it becomes difficult to correct asymmetrical aberrations such as coma. On the contrary, when the absolute value of the focal length of the fourth lens unit exceeds the upper limit of conditional expression (1) and becomes larger than the focal length of the entire system at the telephoto end, the variation of spherical aberration due to zooming mainly performed in the fourth lens unit. Is difficult to correct.

In the zoom lens of the present invention, the zooming from the wide-angle end to the telephoto end is performed by changing the spacing defined as described above during zooming of the six lens groups having the above-mentioned signs of refractive power. Further, by making the refractive power arrangement satisfying the conditional expression (1), various aberrations are corrected particularly well, and high optical performance is obtained over the entire zoom range.

Further, in the present invention, in order to obtain less aberration variation over the entire zoom range and high optical performance over the entire screen, when the focal length of the i-th group is fi, 0.1 <| f2 / fT | <0.18 (2) 0.12 <| f6 / fT | <0.3 (3) It is preferable to satisfy the condition. Conditional expression (2) relates to the ratio between the focal length of the second lens unit having negative refractive power and the focal length of the entire system at the telephoto end, and conditional expression (3) is the focal length of the sixth lens unit having negative refractive power. And the focal length of the entire system at the telephoto end.

The conditional expressions (2) and (3) achieve the object of the present invention by defining the focal lengths of the negative lens groups arranged in the entire system together with the aforementioned conditional expression (1). This shows the refractive power arrangement of a zoom lens that can be used.

If the absolute value of the focal length of the second lens unit becomes smaller than the lower limit of conditional expression (2), it becomes difficult to correct coma and astigmatism mainly at the telephoto end. On the other hand, if the absolute value of the focal length of the second lens unit exceeds the upper limit and becomes large, the amount of movement of the first lens unit must be increased for zooming, which is not preferable because the total lens length becomes longer.

When the absolute value of the focal length of the sixth lens unit becomes smaller than the lower limit of conditional expression (3), the pincushion distortion aberration mainly at the telephoto end becomes strong. Further, if the absolute value of the focal length of the sixth lens unit exceeds the upper limit and becomes large, the total lens length generally becomes long, which is not preferable.

The adverse effects caused when the focal lengths of the respective lens groups deviate from the ranges of the conditional expressions (2) and (3) have been briefly described above. However, in reality, the above-mentioned factors are involved in a complicated manner.
While satisfying the conditional expressions (2) and (3) after satisfying the conditional expression (1), the zoom lens is compact and the various aberrations are well corrected while maintaining a sufficient zoom ratio of about 4 times. It will be easier to do.

In the present invention, at least one of the second lens group and the fourth lens group may be fixed during zooming,
According to this, it is possible to achieve simplification of the lens barrel structure at the time of zooming despite the six-group configuration (Numerical Example 1,
In No. 2, the second group and the fourth group are fixed, and in Numerical Example 3, the second group is fixed).

Further, in the present invention, the fourth lens unit is constituted by a single meniscus negative lens whose convex surface faces the image side so that the refractive power of the fourth lens unit satisfies the conditional expression (1). There is. As a result, the variation of the spherical aberration mainly due to the magnification change is well corrected.

In addition, in the present invention, the third lens group is composed of a positive lens and a cemented lens of a positive lens and a negative lens, and the fifth lens group is a cemented lens of a positive lens and a negative lens. A two-group three-lens configuration of a positive lens, or a two-group two-lens configuration of a positive lens and a negative lens, and a sixth lens group consisting of a negative lens and a cemented lens of a positive lens and a negative lens,
Or, it is composed of a cemented lens composed of a negative lens and a positive lens, composed of two elements in one group, or a composition composed of two elements composed of a negative lens and a positive lens, composed of two elements. It has gained.

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 in the i-th lens. The refractive index of glass and the Abbe number. In addition, the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples is shown in (Table-1).
Shown in.

Numerical Example 1 Focal length 76.51 to 292.00 f-number 4.00 to 5.86 R 1 = 103.34 D 1 = 2.8 N 1 = 1.80518 ν 1 = 25.4 R 2 = 65.53 D 2 = 6.6 N 2 = 1.51633 ν 2 = 64.2 R 3 = 1941.34 D 3 = 0.2 R 4 = 212.98 D 4 = 4.2 N 3 = 1.48749 ν 3 = 70.2 R 5 = -305.81 D 5 = Variable R 6 = -115.87 D 6 = 1.5 N 4 = 1.77250 ν 4 = 49.6 R 7 = 131.18 D 7 = 2.8 R 8 = -57.65 D 8 = 1.5 N 5 = 1.60311 ν 5 = 60.7 R 9 = 60.38 D 9 = 3.4 N 6 = 1.84666 ν 6 = 23.8 R10 = 313.25 D10 = variable R11 = 366.28 D11 = 3.4 N 7 = 1.48749 ν 7 = 70.2 R12 = -89.07 D12 = 0.2 R13 = 50.08 D13 = 5.2 N 8 = 1.60311 ν 8 = 60.7 R14 = -90.47 D14 = 1.5 N 9 = 1.83400 ν 9 = 37.2 R15 = -5450.60 D15 = 2.0 R16 = (Aperture) D16 = Variable R17 = -85.14 D17 = 2.5 N10 = 1.51633 ν10 = 64.2 R18 = -114.60 D18 = Variable R19 = 124.60 D19 = 4.4 N11 = 1.60311 ν11 = 60.7 R20 = -38.67 D20 = 1.5 N12 = 1.80518 ν12 = 25.4 R21 = -181.93 D21 = 0.2 R22 = 56.62 D22 = 3.4 N13 = 1.51633 ν13 = 64.2 R23 = -206.31 D23 = variable R24 = -51.93 D24 = 1.5 N14 = 1.77250 ν14 = 49.6 R25 = 71.28 D25 = 1.4 R26 = 641.53 D26 = 4.0 N15 = 1.8 0518 ν15 = 25.4 R27 = -38.69 D27 = 1.5 N16 = 1.69680 ν16 = 55.5 R28 = -907.33

[0031]

[Table 1] <Numerical Example 2> Focal length 76.53 to 291.99 f-number 4.05 to 5.78 R 1 = 117.46 D 1 = 2.8 N 1 = 1.80518 ν 1 = 25.4 R 2 = 70.46 D 2 = 6.1 N 2 = 1.51633 ν 2 = 64.2 R 3 = 896.98 D 3 = 0.2 R 4 = 110.38 D 4 = 5.4 N 3 = 1.48749 ν 3 = 70.2 R 5 = -444.29 D 5 = Variable R 6 = -103.08 D 6 = 1.5 N 4 = 1.77250 ν 4 = 49.6 R 7 = 79.32 D 7 = 2.8 R 8 = -70.54 D 8 = 1.5 N 5 = 1.60311 ν 5 = 60.7 R 9 = 43.52 D 9 = 3.6 N 6 = 1.84666 ν 6 = 23.8 R10 = 188.82 D10 = variable R11 = 70.72 D11 = 4.1 N 7 = 1.60311 ν 7 = 60.7 R12 = -95.89 D12 = 0.2 R13 = 69.47 D13 = 4.6 N 8 = 1.60311 ν 8 = 60.7 R14 = -58.59 D14 = 1.5 N 9 = 1.83400 ν 9 = 37.2 R15 = 275.47 D15 = 2.0 R16 = (Aperture) D16 = Variable R17 = -56.86 D17 = 2.5 N10 = 1.51633 ν10 = 64.2 R18 = -84.28 D18 = Variable R19 = 137.95 D19 = 5.4 N11 = 1.60311 ν11 = 60.7 R20 = -33.51 D20 = 1.5 N12 = 1.76182 ν12 = 26.5 R21 = -91.67 D21 = 0.2 R22 = 66.61 D22 = 3.3 N13 = 1.60311 ν13 = 60.7 R23 = -2072.51 D23 = variable R24 = -67.27 D24 = 1.5 N14 = 1.77250 ν14 = 49.6 R25 = 29.73 D25 = 4.0 N15 = 1.80518 ν15 = 25.4 R26 = 92.37

[0032]

[Table 2] <Numerical Example 3> Focal length 75.99 to 291.99 f-number 4.05 to 5.75 R 1 = 94.35 D 1 = 2.8 N 1 = 1.80518 ν 1 = 25.4 R 2 = 61.27 D 2 = 7.3 N 2 = 1.51633 ν 2 = 64.2 R 3 = -757.11 D 3 = 0.2 R 4 = 313.60 D 4 = 3.6 N 3 = 1.48749 ν 3 = 70.2 R 5 = -481.24 D 5 = Variable R 6 = -114.27 D 6 = 1.5 N 4 = 1.77250 ν 4 = 49.6 R 7 = 146.02 D 7 = 2.5 R 8 = -71.58 D 8 = 1.5 N 5 = 1.60311 ν 5 = 60.7 R 9 = 41.03 D 9 = 3.3 N 6 = 1.84666 ν 6 = 23.8 R10 = 109.42 D10 = variable R11 = 127.60 D11 = 3.6 N 7 = 1.48749 ν 7 = 70.2 R12 = -84.87 D12 = 0.2 R13 = 42.12 D13 = 5.3 N 8 = 1.51633 ν 8 = 64.2 R14 = -76.46 D14 = 1.5 N 9 = 1.83400 ν 9 = 37.2 R15 = 1363.46 D15 = 2.0 R16 = (Aperture) D16 = Variable R17 = -65.36 D17 = 2.5 N10 = 1.51633 ν10 = 64.2 R18 = -78.94 D18 = Variable R19 = 76.31 D19 = 4.1 N11 = 1.69680 ν11 = 55.5 R20 = -43.97 D20 = 1.7 R21 = -38.11 D21 = 1.5 N12 = 1.84666 ν12 = 23.8 R22 = -111.62 D22 = Variable R23 = -58.91 D23 = 1.5 N13 = 1.77250 ν13 = 49.6 R24 = 35.27 D24 = 3.0 R25 = 44.47 D25 = 3.7 N14 = 1.74077 ν14 = 27.8 R26 = -473.11

[0033]

[Table 3]

[0034]

As described above, according to the present invention, the zoom lens is composed of six lens groups each having a predetermined refractive power as a whole, and each lens group is used for performing the refractive power and zooming of each lens group. By properly setting the movement conditions of
Magnification ratio 4 with high optical performance over the entire zoom range while reducing the number of lenses and shortening the total lens length
It is possible to achieve a telephoto zoom lens of a degree.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of Numerical Example 1 of the present invention.

FIG. 2 is a lens cross-sectional view of Numerical Example 2 of the present invention.

FIG. 3 is a lens cross-sectional view of Numerical Example 3 of the present invention.

FIG. 4 is an aberration diagram at a wide-angle end according to Numerical Example 1 of the present invention.

FIG. 5 is an intermediate aberration diagram of Numerical example 1 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end according to Numerical Example 1 of the present invention.

FIG. 7 is an aberration diagram at the wide-angle end according to Numerical Example 2 of the present invention.

FIG. 8 is an intermediate aberration diagram of Numerical example 2 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 10 is an aberration diagram at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 11 is an intermediate aberration diagram of Numerical Example 3 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end according to Numerical Example 3 of the present invention.

[Explanation of symbols]

 L1 1st group L2 2nd group L3 3rd group L4 4th group L5 5th group L6 6th group SP Aperture IP image plane d d line g g line ΔS sagittal image plane ΔM meridional image plane

Claims (4)

[Claims] 1. A first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, a fourth group having a negative refractive power, and a fourth group having a positive refractive power in order from the object side. It has six lens groups, a fifth lens group and a sixth lens group having negative refractive power, and at the time of zooming from the wide-angle end to the telephoto end, at the wide-angle end and the telephoto end of the i-th group and the (i + 1) th group, , D1T <D1T D2W> D2T D3W <D3T D4W> D4T D5W> D5T, the predetermined lens groups are moved so as to satisfy the following conditions: A zoom lens characterized by satisfying a condition of 0.3 <| f4 / fT | <10.0, where f4 and fT are focal lengths of the entire system at the end. 2. When the focal length of the i-th group is fi, the following condition is satisfied: 0.1 <| f2 / fT | <0.18 0.12 <| f6 / fT | <0.3 The zoom lens according to claim 1, wherein 3. The zoom lens according to claim 1, wherein at least one of the second lens group and the fourth lens group is fixed during zooming. 4. The zoom lens according to claim 1, wherein the fourth lens group is composed of a meniscus negative lens having a convex surface facing the image plane side.