JPH08313809A - Zoom lens - Google Patents

Abstract

PURPOSE: To provide a zoos lens having high optical performance over a whole variable power range by comprising five lens groups as a whole and properly setting refractive powers of the respective lens groups and moving conditions accompanied by power variation, etc. CONSTITUTION: This zoom lens has, in order from the object side, five lens groups of a first group L1 of positive refractive power, a second group L2 of negative refractive power, a third group L3 of positive refractive power, a fourth group L4 of positive refractive power and a fifth group L5 of negative refractive power, at the time of varying the power from the wide-angle end to the telescopic end, the respective lens groups are moved so that an interval between the first group L1 and the second group L2 is increased, an interval between the second group L2 and the third group L3 is decreased and an interval between the third group L3 and the fourht group L4 is decreased and the image forming magnification β2W at the wide-angle end of the second group L2 for an object at infinity 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 zoom lens, and in particular, has a shooting angle of view at the wide-angle end of about 82 degrees and an F number of 3.6.
A zoom lens with a high zoom ratio and a wide angle of view, which is suitable for a photographic camera, a video camera, an electronic still camera, etc., which has good optical performance over the entire zoom range of up to about 5.8 and a zoom ratio of about 4. It is about.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having a high zoom ratio, a wide angle of view, a high contrast and a high optical performance over the entire zoom range has been required for a photographing system such as a photographic camera or a video camera. ing.

In Japanese Laid-Open Patent Publication No. 3-83005, there are five lens groups having positive, negative, positive, positive, and negative refracting powers in order from the object side. The photographing angle of view at the wide-angle end is about 75 degrees, and the magnification is changed. A zoom lens with a ratio of about 10 has been proposed.

In Japanese Patent Laid-Open No. 4-70708, there are five lens groups of positive, negative, positive, positive, and negative refracting powers in order from the object side, and the photographing angle of view at the wide-angle end is about 75 degrees and the magnification is varied. A zoom lens with a ratio of about 7 has been proposed.

[0005]

Generally, in a 5-group zoom lens including five lens groups of positive, negative, positive, positive, and negative refracting powers in order from the object side, the photographing field angle at the wide-angle end is 80 degrees. In order to maintain a high optical performance over the entire zoom range while achieving a wide angle of view and a high zoom ratio of about 4, an optical ratio of each lens group that constitutes the lens system is obtained. It is important to properly set the various constants.

For example, in the above-mentioned 5 group zoom lens,
If the moving conditions of each lens unit associated with zooming, the refracting power of each lens unit, and the zooming ratio and magnification of the second lens unit that performs zooming are not set appropriately, the occurrence of various aberrations will increase and good image quality will be obtained. It becomes difficult to get the video of.

According to the present invention, in a 5-group zoom lens, a wide-angle lens is mainly set by appropriately setting the moving condition of each lens group associated with zooming, the refractive power of each lens group, and the image-forming magnification of the second group. It is an object of the present invention to provide a zoom lens having a high optical performance over the entire zooming range with a shooting angle of view of about 82 degrees and a zooming ratio of about 4.

[0008]

The zoom lens of the present invention comprises (1-1) a first group having a positive refractive power, a second group having a negative refractive power, and a third group having a positive refractive power in order from the object side. Group, fourth with positive refractive power
Group, and 5 lens groups of the 5th group of negative refractive power, each lens group at the time of the magnification change from the wide-angle end to the telephoto end,
The distance between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is decreased, and the distance between the third lens group and the fourth lens group is decreased. When the imaging magnification at the wide-angle end of the second lens unit in the object is β2W, the condition is 0.17 <| β2W | <0.255 (1).

[0009]

1 to 3 are lens cross-sectional views at the wide-angle end in Numerical Embodiments 1 to 3 of the present invention. In the figure, L1 is the first group of positive refractive power, L2 is the second group of negative refractive power, L3 is the third group of positive refractive power, L4 is the fourth group of positive refractive power, and L5 is negative. The fifth lens unit SP having a refracting power of 1 is a stop, and is provided in front of the third lens unit.

In this embodiment, at the time of zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases and the distance between the second lens group and the third lens group decreases as indicated by the arrows. , The distance between the third group and the fourth group is decreased, and the distance between the fourth group and the fifth group is increased. The diaphragm SP is moved integrally with the third lens group.

Particularly in this embodiment, the first to fourth groups are all moved to the object side, and the fifth group is moved to have a convex locus on the object side.

In the present embodiment, as described above, the refractive power of each lens group is measured, and each lens group is moved during zooming so that each zoom lens can effectively share the zooming. Then, the aberration is satisfactorily corrected over the entire zoom range, especially at the zoom position of the intermediate focal length.

Then, the imaging magnification β2W at the wide-angle end of the second lens unit is set so as to satisfy the conditional expression (1), and the aberration of the zoom lens is favorably corrected while the lens length is shortened. ing. If the lower limit of conditional expression (1) is exceeded, the focal length of the first lens unit will become long and the total lens length will increase. On the other hand, when the value exceeds the upper limit, the focal length of the first lens unit becomes short, and the total lens length is shortened, but the aberration variation due to zooming becomes large, and it becomes difficult to widen the angle of view at the wide angle end.

The zoom lens according to the present invention can be achieved by satisfying the above-mentioned various conditions. However, it is possible to satisfactorily correct aberration fluctuations when achieving a wider angle of view and a higher zoom ratio, and to obtain high optical performance. It is preferable to satisfy at least one of the following conditions in order to obtain

(2-1) When the focal length of the i-th group is fi, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, respectively 1.8 <| f5 | / f4 <4. (2) 5.8 <f1 / | f2 | <8.5 (3) 1.5 <| f5 | / fW <3 (4) 0.4 <| f5 | / fT <0 .............. (5) It is to satisfy the following condition.

Conditional expression (2) defines the ratio of the focal length of the fifth lens unit to the focal length of the fourth lens unit. If the focal length of the fifth lens unit becomes too short beyond the lower limit value,
Various aberrations occurring in the lens group become large, and it is necessary to increase the number of lenses to correct this, which is not preferable. If the focal length of the fifth lens unit becomes too long beyond the upper limit, it will be advantageous for aberration correction, but it will be difficult to achieve a wide angle of view and a compact overall lens length.

Conditional expression (3) defines the ratio of the focal length of the first lens unit to the focal length of the second lens unit, mainly reduces the lens outer diameter of the third lens unit at the telephoto end, and facilitates high zooming. To achieve. If the positive refracting power of the first lens group becomes too strong beyond the lower limit of conditional expression (3), aberrations on the telephoto side, particularly spherical aberration, generated in the first lens group will become large, and this will be caused by other lens groups. It becomes difficult to correct in a good balance. When the upper limit is exceeded and the positive refractive power of the first lens unit becomes weak, it is difficult to make the entire lens length compact.

Conditional expressions (4) and (5) define the ratio of the focal length of the fifth lens unit to the focal length of the entire system at the wide-angle end and the telephoto end, respectively. This is for achieving higher performance. When the negative refractive power of the fifth lens unit becomes strong beyond the lower limit of conditional expression (4) or (5), various aberrations generated in this fifth lens unit become large, and the number of lenses is increased to correct this. Is necessary and not preferable.

If the negative refracting power of the fifth lens unit becomes too weak beyond the upper limits of the conditional expressions (4) and (5), it will be advantageous for aberration correction, but a wide angle of view and a compact overall lens length. Becomes difficult.

(2-2) In the first group, a cemented lens in which a negative meniscus lens having a convex surface on the object side and a positive lens having convex lens surfaces on both sides are cemented together, and the convex surface is directed to the object side The second lens unit has a meniscus-shaped positive lens, and the second group has a meniscus-shaped negative lens having a convex surface directed toward the object side, a negative lens having both concave lens surfaces, and a positive lens having both convex lens surfaces.
And both lens surfaces have a concave negative lens.

Thus, while the negative refracting power of the second lens unit is strengthened to properly correct the aberration variation due to zooming when securing the zoom ratio of about 4, a wide field angle of the photographing field angle at the wide-angle end is obtained. Has been achieved. Further, the effective diameter of the first lens group is reduced, and the overall lens system is efficiently downsized.

(2-3) The third group has at least two positive lenses whose both lens surfaces are convex surfaces, and negative lenses whose both lens surfaces are concave surfaces.

By constructing the third group having a relatively strong positive refractive power with such a lens shape, mainly various aberrations such as spherical aberration are favorably corrected.

(2-4) The fourth group has at least two positive lenses and at least one negative lens.

In the zoom lens according to the present invention, since the positive refractive power of the fourth lens unit is relatively strong, various aberrations are satisfactorily corrected by using at least three lenses in this way.

In the present embodiment, more preferably, the fourth
The group consists of three lenses: a positive lens whose both lens surfaces are convex, a positive lens whose convex surface faces the image side, and a meniscus negative lens whose convex surface faces the image side, or both lens groups Consists of four lenses: a positive lens with a convex surface, a negative meniscus lens with a convex surface facing the object side, a positive lens with convex surfaces on both lens surfaces, and a negative meniscus lens with a convex surface facing the image side. good.

(2-5) The fifth group is constituted by a negative meniscus lens having a convex surface facing the image plane side.

As a result, the size of the entire lens system can be reduced, and aberration fluctuations due to zooming can be corrected well. Further, the fifth lens unit is moved to have a convex locus on the object side in accordance with zooming, so that the fifth lens unit has a flare cutting role.

(2-6) When the second group is moved on the optical axis for focusing, and the imaging magnification of the second group is β2T when focusing on an object at infinity at the telephoto end. β2T | <1 (6) The condition is satisfied.

Generally, when the focusable short distance is shortened by the method of focusing with the first lens group, the effective diameter of the first lens group is increased in order to secure the light quantity in the peripheral portion of the screen.

Therefore, in the present embodiment, focusing is performed by the second lens unit to prevent the effective diameter of the first lens unit from increasing and at the same time shorten the shortest focusable distance. Further, each element is set so as to satisfy the conditional expression (6), and thereby focusing is effectively performed.

In particular, by satisfying the condition of the conditional expression (6), the magnification of the second lens unit at the time of zooming from the wide-angle end to the telephoto end does not sandwich an equal magnification. Focusing in the second lens unit is possible by always moving the second lens unit in the same direction.

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

[0034]

[Equation 1] It is expressed by the formula. "E-x" is "e-10 ^-X "
Is represented.

Numerical Example 1 f = 24.9 to 101.8 fno = 1: 3.6 to 5.8 2 ω = 82.1 ° to 24.0 ° R 1 = 149.78 D 1 = 2.00 N 1 = 1.84666 ν 1 = 23.8 R 2 = 55.24 D 2 = 6.80 N 2 = 1.65160 ν 2 = 58.5 R 3 = 1471.66 D 3 = 0.15 R 4 = 40.99 D 4 = 5.00 N 3 = 1.71300 ν 3 = 53.8 R 5 = 99.84 D 5 = Variable R 6 = 37.86 D 6 = 1.20 N 4 = 1.80610 ν 4 = 41.0 R 7 = 10.64 D 7 = 6.00 R 8 = -42.37 D 8 = 1.10 N 5 = 1.80400 ν 5 = 46.6 R 9 = 35.56 D 9 = 0.15 R10 = 26.74 D10 = 3.60 N 6 = 1.84666 ν 6 = 23.9 R11 = -32.66 D11 = 0.60 R12 = -23.83 D12 = 1.10 N 7 = 1.83481 ν 7 = 42.7 R13 = 226.52 D13 = Variable R14 = (Aperture) D14 = 1.00 R15 = 29.51 D15 = 3.30 N 8 = 1.48749 ν 8 = 70.2 R16 = -44.13 D16 = 0.20 R17 = 18.88 D17 = 4.60 N 9 = 1.51742 ν 9 = 52.4 R18 = -27.40 D18 = 0.80 R19 = -24.02 D19 = 1.20 N10 = 1.88300 ν10 = 40.8 R20 = 68.97 D20 = Variable R21 = 86.68 D21 = 3.30 N11 = 1.48749 ν11 = 70.2 R22 = -24.10 D22 = 0.15 R23 = 1729.42 D23 = 3.00 N12 = 1.48749 ν12 = 70.2 R24 = -23.14 D24 = 0.60 R25 = -28.76 D25 = 1.00 N13 = 1.80518 ν13 = 25.4 R26 = -53.05 D26 = Variable R27 = -17.61 D27 = 1.20 N14 = 1.8 5026 ν14 = 32.3 R28 = -29.33 \ Focal length 24.87 45.88 101.79 Variable distance \ D 5 1.30 14.85 28.79 D13 14.46 8.68 0.99 D20 5.49 3.89 1.45 D26 3.00 5.12 21.06 Aspheric surface coefficient R26 surface A = 0 B = 2.643 e-05 C = 1.005 e-07 D = 3.465 e-10 E = 4.401 e-12 <Numerical Example 2> f = 24.8 to 101.8 fno = 1: 3.6 to 5.8 2 ω = 82.2 ° to 24.0 ° R 1 = 147.49 D 1 = 2.00 N 1 = 1.84666 ν 1 = 23.8 R 2 = 52.12 D 2 = 6.80 N 2 = 1.65160 ν 2 = 58.5 R 3 = 1034.32 D 3 = 0.15 R 4 = 40.62 D 4 = 5.00 N 3 = 1.71300 ν 3 = 53.8 R 5 = 118.22 D 5 = Variable R 6 = 45.45 D 6 = 1.20 N 4 = 1.80610 ν 4 = 41.0 R 7 = 10.77 D 7 = 5.20 R 8 = -40.92 D 8 = 1.10 N 5 = 1.80400 ν 5 = 46.6 R 9 = 29.39 D 9 = 0.15 R10 = 25.07 D10 = 3.60 N 6 = 1.84666 ν 6 = 23.9 R11 = -26.83 D11 = 0.70 R12 = -21.10 D12 = 1.10 N 7 = 1.83481 ν 7 = 42.7 R13 = 172.42 D13 = Variable R14 = (Aperture ) D14 = 1.00 R15 = 32.97 D15 = 3.00 N 8 = 1.48749 ν 8 = 70.2 R16 = -43.61 D16 = 0.20 R17 = 21.91 D17 = 4.40 N 9 = 1.51742 ν 9 = 52.4 R18 = -28.46 D18 = 0.80 R19 = -24.88 D19 = 1.20 N10 = 1.88300 ν10 = 40.8 R20 = 85.98 D20 = variable R21 = 26. 68 D21 = 4.00 N11 = 1.48749 ν11 = 70.2 R22 = -29.48 D22 = 0.15 R23 = 29.58 D23 = 1.00 N12 = 1.85026 ν12 = 32.3 R24 = 22.12 D24 = 1.60 R25 = 84.16 D25 = 3.00 N13 = 1.48749 ν13 = 70.2 R26 =- 29.98 D26 = 0.20 R27 = -32.68 D27 = 1.00 N14 = 1.80518 ν14 = 25.4 R28 = -46.81 D28 = Variable R29 = -17.97 D29 = 1.20 N15 = 1.85026 ν15 = 32.3 R30 = -29.67 \ Focal length 24.81 45.79 101.80 Variable distance \ D 5 1.30 14.26 27.57 D13 12.08 7.27 0.96 D20 6.11 4.16 0.98 D28 3.00 4.97 20.73 Aspherical surface R28 surface A = 0 B = 2.643 e-05 C = 1.005 e-07 D = 3.465 e-10 E = 4.401 e-12 〈 Numerical Example 3> f = 24.8 to 101.8 fno = 1: 3.6 to 5.8 2ω = 82.2 ° to 24.0 ° R 1 = 129.42 D 1 = 2.00 N 1 = 1.84666 ν 1 = 23.8 R 2 = 49.39 D 2 = 6.80 N 2 = 1.65160 ν 2 = 58.5 R 3 = 468.47 D 3 = 0.15 R 4 = 39.45 D 4 = 5.00 N 3 = 1.71300 ν 3 = 53.8 R 5 = 120.44 D 5 = variable R 6 = 44.95 D 6 = 1.20 N 4 = 1.80610 ν 4 = 41.0 R 7 = 10.79 D 7 = 5.20 R 8 = -43.17 D 8 = 1.10 N 5 = 1.80400 ν 5 = 46.6 R 9 = 27.59 D 9 = 0.15 R10 = 22.79 D10 = 3.80 N 6 = 1.84666 ν 6 = 23.9 R11 = -28.13 D11 = 0.80 R12 = -21.13 D12 = 1.10 N 7 = 1.83481 ν 7 = 42.7 R13 = 70.60 D13 = Variable R14 = (Aperture) D14 = 1.00 R15 = 36.35 D15 = 2.50 N 8 = 1.48749 ν 8 = 70.2 R16 = -92.48 D16 = 0.12 R17 = 36.35 D17 = 2.50 N 9 = 1.48749 ν 9 = 70.2 R18 = -204.31 D18 = 0.15 R19 = 26.31 D19 = 3.50 N10 = 1.53172 ν10 = 48.9 R20 = -33.00 D20 = 0.80 R21 = -29.16 D21 = 1.20 N11 = 1.88300 ν11 = 40.8 R22 = 50.19 D22 = Variable R23 = 23.33 D23 = 4.80 N12 = 1.48749 ν12 = 70.2 R24 = -31.13 D24 = 0.15 R25 = 30.66 D25 = 1.00 N13 = 1.83400 ν13 = 37.2 R26 = 23.05 D26 = 1.20 R27 = 58.96 D27 = 3.70 N14 = 1.48749 ν14 = 70.2 R28 = -34.82 D28 = 1.00 N15 = 1.80518 ν15 = 25.4 R29 = -53.91 D29 = variable R30 = -18.89 D30 = 1.20 N16 = 1.85026 ν16 = 32.3 R31 = -31.42 \ focal length 24.82 46.41 101.79 variable interval \ D 5 1.30 14.25 26.95 D13 10.30 6.11 0.99 D22 6.81 4.52 0.97 D29 3.00 5.50 22.21 Aspheric surface R28 surface A = 0 B = 2.786 e-05 C = 1.346 e-07 D = -1.351 e-10 E = 5.462 e-12

[0036]

[Table 1]

[0037]

As described above, according to the present invention, in the five-group zoom lens, the moving condition of each lens group, the refractive power of each lens group, and the image-forming magnification of the second group are mainly caused by zooming. It is possible to achieve a zoom lens having a high optical performance over the entire zoom range with a shooting angle of view at the wide-angle end of about 82 degrees and a zoom ratio of about 4 by appropriately setting the above.

[Brief description of drawings]

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

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

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

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

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

FIG. 6 is an aberration diagram at the wide-angle end according to Numerical Example 2 of the present invention.

FIG. 7 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 8 is an aberration diagram at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 9 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 SP Aperture stop d d line g g line S.L. C Sine condition S Sagittal image plane M Meridional image plane

Claims (7)

[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 positive refractive power, and a negative refractive power in order from the object side. 5 lens groups of the fifth lens group, the distance between the first lens group and the second lens group is increased during zooming from the wide-angle end to the telephoto end, and the second lens group and the third lens group are increased.
When the distance between the groups is decreased and the distance between the third group and the fourth group is decreased, the imaging magnification at the wide-angle end of the second group of an object at infinity is β2W. A zoom lens characterized by satisfying a condition of <| β2W | <0.255. 2. When the focal length of the i-th group is fi and the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, respectively 1.8 <| f5 | / f4 <4 5.8 <f1 / The zoom lens according to claim 1, wherein a condition of | f2 | <8.5 1.5 <| f5 | / fW <3 0.4 <| f5 | / fT <0.7 is satisfied. 3. A cemented lens in which a meniscus negative lens having a convex surface directed toward the object side and a positive lens having a convex surface on both lens surfaces are cemented together, and a meniscus-shaped lens having a convex surface directed toward the object side. The second lens unit has a positive lens, and the second lens unit has a meniscus negative lens having a convex surface directed toward the object side, a negative lens having both concave lens surfaces, a positive lens having both convex lens surfaces, and a negative lens having both concave lens surfaces. The zoom lens according to claim 1, further comprising a lens. 4. The zoom lens according to claim 1, wherein the third lens group has at least two positive lenses each having a convex surface on both lens surfaces and a negative lens each having a concave surface on both lens surfaces. 5. The zoom lens according to claim 1, wherein the fourth group includes at least two positive lenses and at least one negative lens. 6. The zoom lens according to claim 1, wherein the fifth lens unit is composed of one negative meniscus lens having a convex surface facing the image plane side. 7. When the second group is moved on the optical axis for focusing, and the imaging magnification of the second group when focusing on an object at infinity at the telephoto end is β2T | β2T | < The zoom lens according to claim 1, wherein the condition 1 is satisfied.