JP3175484B2 - Zoom lens - Google Patents

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 photographic camera, a video camera and an SV camera for 35 mm film, and more particularly to a zoom lens comprising a plurality of lens groups, for example, three lens groups as a whole. A zoom lens having a wide angle of view and a high zoom ratio, which can easily obtain high optical performance while reducing the size of the entire lens system by appropriately setting the lens configuration of each lens group of these three groups. It is about.

[0002]

2. Description of the Related Art Conventionally, a so-called negative lead type zoom lens in which a lens group having a negative refractive power precedes a zoom type is relatively easy to widen the angle of view.
It is often used for a zoom lens having an angle of 0 ° or more.

For example, Japanese Patent Laid-Open Publication No. Sho 59-16248 has two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power. Has been proposed.

In Japanese Patent Application Laid-Open Nos. Hei 2-72316 and Hei 3-233422, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a negative lens having a negative refractive power are sequentially arranged from the object side. A three-group zoom lens having a wide angle of view, which has three lens groups and performs zooming by moving each lens group, has been proposed.

In Japanese Patent Application Laid-Open No. 2-72316, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power are sequentially arranged from the object side.
There has been proposed a four-unit zoom lens which includes a third unit having a positive refractive power and a fourth unit having a negative refractive power, and performs zooming by moving each lens unit.

On the other hand, as a zoom type, there are two lens units, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, in order from the object side. Zoom lenses are often used in small cameras such as lens shutter cameras because it is easy to reduce the size of the entire lens system. In the two-unit zoom lens, since the zooming operation is performed by only one lens group (second group), the zoom ratio is 1.6 to
Many are about twice. Forcibly increasing the zoom ratio in the two-unit zoom lens increases the size of the lens system and makes it difficult to maintain high optical performance.

In the two-unit zoom lens, the first unit is 2
Divided into two positive refractive power lens groups.
A three-unit zoom lens, which includes three lens units having positive and negative refractive powers and aims at high zooming, is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-73907.
JP, JP-A-3-282409, JP-A-4-3
No. 7810, Japanese Patent Application Laid-Open No. 4-76511 and the like.

When an attempt is made to achieve a wide-angle zoom lens system having a half angle of view of 35 ° or more with these three-unit zoom lenses, for example, the position of the entrance pupil at the time of zooming becomes large, and aberrations at the time of high zooming are achieved. It becomes difficult to suppress the fluctuation.

[0009]

Generally, a negative lead type zoom lens is relatively easy to widen the angle of view. However, it is necessary to appropriately set the refractive power arrangement and the lens configuration of each lens group in order to achieve a wide angle of view of 70 ° or more and a good optical performance over the entire screen.
If the refractive power arrangement or the lens configuration of each lens group is inappropriate, even if the number of lenses is increased, the aberration variation accompanying zooming becomes large, and it becomes difficult to obtain high optical performance over the entire zoom range.

For example, Japanese Patent Application Laid-Open No. 3-233422 proposes a zoom lens having a wide angle of view composed of three lens units having negative, positive and negative refractive powers. However, the zoom lens proposed in the publication has an overall optical length of about 66 mm at the wide-angle end, and it is difficult to say that the overall lens length is short. It is difficult to perform aberration correction.

The present invention provides a zoom lens having a plurality of lens groups, for example, a zoom lens divided into three groups as a whole, by appropriately setting the lens configuration of each lens group, thereby achieving a wide angle of view and a wide angle of view. It is an object of the present invention to provide a zoom lens having high optical performance over the entire zooming range in which the entire lens system is miniaturized while satisfactorily correcting various aberrations that become a problem during high zooming.

[0012]

The zoom lens system according to the present invention comprises, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. A zoom lens having a lens group and performing zooming by changing a lens interval between the lens groups, wherein the second group includes four lenses of a 2a group, a 2b group, a 2c group, and a 2d group The zoom lens has a lens group, and performs zooming by changing the air spacing of each of the four lens groups in the second group. The combined focal lengths of the second group at the wide-angle end and the telephoto end are respectively f2w, f2T, Assuming that the focal length of the third lens unit is f3 and the focal length of the entire system at the wide-angle end is fw, f2w <f2T (1) 0.9 ≦ | fw / f3 | ≦ 2.2 (1) (2) 1.0 ≦ fw / f2w ≦ 1.8 (3) The following condition must be satisfied.

[0013]

1 to 4 are schematic views showing paraxial refractive power arrangements of Embodiments 1 to 4 of the zoom lens according to the present invention. 5 to 8 show numerical examples 1 to 4 of the zoom lens according to the present invention, which will be described later.
3 is a lens cross-sectional view at the wide-angle end of FIG. 1 to 4, (A) shows the wide-angle end and (B) shows the telephoto end. FIG. 9-
11 is an aberration diagram at a wide angle end, a middle position, and a telephoto end of Numerical Example 1 of the present invention. FIGS. 12 to 14 are aberration diagrams at a wide angle end, a middle position, and a telephoto end of Numerical Example 2 of the present invention. FIG. 17 is an aberration diagram at a wide angle end, a middle position, and a telephoto end of Numerical Example 3 of the present invention.
8 to 20 are aberration diagrams at the wide-angle end, a middle position, and a telephoto end in Numerical Embodiment 4 of the present invention.

In the figure, L1 is a first group having a negative refractive power, L2 is a second group having a positive refractive power, L3 is a third group having a negative refractive power, SP
Is an aperture stop, and IP is an image plane.

In the zoom lens according to the present invention, the second group is composed of a plurality of lens groups. In each of the embodiments shown in FIGS. 1 to 4, for the sake of convenience, the entire lens is divided into three groups: a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens unit having a negative refractive power. . And basically, the first group L1 and the second group L
Each lens unit is moved as indicated by an arrow so as to change the distance from the wide-angle end to the telephoto end so that the distance between the second lens unit and the distance between the second lens unit L2 and the third lens unit changes.

The second lens unit L2 comprises four lens units, ie, a second lens unit L2a, a second lens unit L2b, a second lens unit L2c, and a second lens unit L2d, for zooming from the wide-angle end to the telephoto end. Each of these lens groups is moved to the object side. In this embodiment, the second-a group L2a and the second-b group L2
b constitutes a second lens unit F having a positive combined refractive power, and the second lens unit L2c and the second lens unit L2d having a positive combined refractive power constitute the second R lens unit.
Make up a group.

Further, according to the present invention, when constituted by such a plurality of lens units, the above-mentioned conditional expressions (1) to (3) are satisfied. In particular, by setting the focal lengths at the wide-angle end and the telephoto end of the second lens unit so as to satisfy the conditional expression (1), aberration fluctuations in achieving a wide angle of view and a high zoom ratio can be satisfactorily corrected. High optical performance over a double range. If conditional expression (1) is not satisfied, it becomes difficult to efficiently perform zooming. Conditional expression (2) relates to the refractive power of the third lens unit L3. If the refractive power of the third lens unit L3 becomes too strong beyond the upper limit value of the conditional expression (2), the aberration of the third lens unit L3 is limited in order to obtain a positive back focus amount at the wide angle end. Is difficult to satisfactorily correct. If the refractive power of the third unit L3 is too weak below the lower limit,
During zooming, the zooming effect of the third lens unit L3 is weakened. As a result, the amount of movement of each lens unit must be increased in order to secure a constant zooming ratio. As a result, the overall length of the lens increases. Not good because it comes. In the present invention, in order to achieve better optical performance, it is desirable that the conditional expression (2) has the following range. 1.0 ≦ | fw / f3 | ≦ 1.8 (2a) Conditional expression (3) relates to the refractive power of the second lens unit L2. If the refractive power of the second unit L2 is too strong beyond the upper limit of the conditional expression (3), the effect of the telephoto type by the second unit and the third unit becomes too strong, and it is difficult to secure the back focus. Become. If the refractive power of the second lens unit L2 is too weak below the lower limit value of the conditional expression (3), the refractive power of the negative lens unit will be weakened in order to obtain a constant focal length at the wide-angle end. It is not good because the total lens length increases. If conditional expression (3) desirably satisfies the following range, it is possible to achieve a further extremely compact and high optical performance. 1.1 ≦ fw / f2w ≦ 1.5 (3a)

Next, the features of the lens configuration of the zoom lens according to the present invention will be described.

At the wide-angle end, the zoom lens of the present invention has
A first lens unit L1 having a negative refractive power, a second lens unit L2 having a combined refractive power of a positive refractive power at a certain distance, and a third lens unit L3 having a negative refractive power at a certain distance from the object side are arranged. are doing. By taking such a symmetrical optical arrangement of negative, positive and negative refractive powers at the wide-angle end, the refractive power of the second lens unit L2 can be increased, thereby achieving a wide angle of view and miniaturization. In this case, various aberrations can be satisfactorily corrected.

The first negative lens unit L1 and the second negative lens unit L2 having a positive combined refractive power are arranged at a certain distance from each other to form a retrofocus type, thereby providing a wide angle of view. In this case, it is easy to secure the back focus, which is a problem in the case of switching. The second lens unit L2 includes a second lens unit L2a having a positive or negative refractive power, a second lens unit L2b having a positive or negative refractive power, a second lens unit L2c having a negative refractive power, and a positive refractive power. And a second lens unit L2d having the following configuration.

For zooming from the wide-angle end to the telephoto end, the second
The distance between the a-group L2a and the second-b group L2b decreases,
Each lens group is moved to the object side such that the distance between the second lens group L2b and the second lens group L2c increases, and the distance between the second lens group L2c and the second lens group L2d increases. At this time, each lens group is moved to the object side so that the combined refractive power of the second group becomes weaker at the telephoto end than at the wide-angle end. The second lens unit is configured as described above, and the first lens unit having a negative refractive power as a whole of the lens system.
With a lens arrangement having a group, a second group having a positive refractive power, a second R group having a positive refractive power, and a third group having a negative refractive power, a wide angle of view and a high zoom ratio can be achieved. Aberration fluctuation is corrected well, and high optical performance is obtained over the entire zoom range.

In the present invention, a small zoom lens having a wide angle of view and a high zoom ratio is obtained by setting each element as described above. More preferably, at least one of the following conditions is satisfied. It is better to satisfy.

[0023]

[0024]

[0025]

[0026]

[0027]

(1-b) Assuming that the focal lengths of the second and fourth lens groups at the wide-angle end are f2Fw and f2Rw, respectively, and the focal length of the entire system at the wide-angle end is fw, 0.5 ≦ fw / f2Fw ≦ 1.7 (4) 0.5 ≦ fw / f2Rw ≦ 1.5 (5) The following condition must be satisfied.

If the refractive power of the second F group or the second R group becomes too strong beyond the upper limits of the conditional expressions (4) and (5), it becomes difficult to secure the back focus at the wide-angle end. If the refractive power of the second F group or the second R group is too weak below the lower limit, the refractive power of the negative lens group must be weakened in order to obtain a predetermined focal length at the wide-angle end. And it becomes difficult to achieve miniaturization.

In order to obtain a zoom lens with good back-focus and good optical performance even though it is more compact, conditional expressions (4) and (5) preferably have the following ranges.

0.6 ≦ fw / f2Fw ≦ 1.2 (4a) 0.6 ≦ fw / f2Rw ≦ 1.3 (5a) (1-c) When the air intervals at the wide angle end and the telephoto end of the 2c group and the 2d group are DW _cd and DT _cd , respectively, the following condition is satisfied: DW _cd <DT _cd ...

Now, a combined refraction of a two-unit zoom lens, which includes two lens units, a first unit (refractive power φ1) and a second unit (refractive power φ2), and changes the distance between both lens units to perform zooming. The force φ12 is as follows: φ12 = φ1 + φ2-e × φ1 × φ2 (a), where e is the distance between the principal points of both lens groups.

Conditional expression (6) relates to the distance between the lens units 2c and 2d at the wide-angle end and the telephoto end. As can be seen from the equation (a), it can be said that it is originally better to reduce the distance between the second lens unit having a negative refractive power and the second lens unit having a positive refractive power during telephoto. However, if such a lens group arrangement is adopted, the lens form becomes totally asymmetric at the telephoto end, which is disadvantageous for performing good aberration correction. Therefore, in order to maintain good various aberration characteristics over the entire zoom range, it is necessary to increase the number of lens components, which results in an increase in the size of the lens system. Therefore, in the present invention, the conditional expression (6) is set to facilitate high zooming and to favorably correct various aberrations.

(1-d) When the lateral magnifications of the second lens unit at the wide-angle end and the telephoto end are respectively βW _2c and βT _2c , | 1 / βW _2c | <1.0 (1.0) 7) | 1 / βT _2c | <1.0 (8) The following condition must be satisfied.

The conditional expressions (7) and (8) are for obtaining an optical system which is small and has good correction of various aberrations with a small number of lenses. The position of the lens exit pupil from the final lens surface moves toward the object side from the telephoto end because the back focus becomes larger at the telephoto end than at the wide-angle end. In order to balance the on-axis aberration and the off-axis aberration, it is effective to adjust the incident height of the on-axis light beam and the off-axis light beam incident on the lens group apart from the pupil position by changing the lens group interval. In particular, it is desired that the above-mentioned light beam has a somewhat higher incident height off-axis than on-axis. Therefore, at the telephoto end, the second lens unit and the second lens unit
The distance between the lens groups of the group must be larger than the wide-angle end due to the positional relationship between the exit pupils.

However, this is disadvantageous for telephoto as described in relation to the equation (a) (the magnification reduction effect is large). Therefore, it is preferable to take a value in a range where the lateral magnification of the second lens unit does not become a reduction system so as to satisfy the conditional expressions (7) and (8). As a result, even if the distance between the lens units 2c and 2d becomes larger at the telephoto end than at the wide-angle end, a large reduction effect does not occur, and the balance between on-axis aberrations and off-axis aberrations is maintained well throughout the zoom range. .

(1-e) When the lateral magnification of the second lens unit at the wide angle end is β2w, the following condition is satisfied: -0.6 <β2w <-0.1 (9) It is.

Conditional expression (9) relates to the lateral magnification of the second lens unit at the wide-angle end. When the value exceeds the upper limit of conditional expression (9), it becomes difficult to obtain a back focus at the wide-angle end, and as a result, the lens diameter of the third unit increases. On the other hand, if the lower limit value is exceeded, the refractive power of the other lens units exceeds the limit in order to obtain a fixed focal length, which is not good because many aberrations occur.

In particular, in order to achieve both correction of various aberrations and miniaturization, it is desirable that the conditional expression (9) has the following range.

−0.5 <β2w <−0.15 (9a) (1-f) An aperture is arranged between the second F lens unit and the second R lens unit, and is moved together with zooming. That is.

Thus, the position of the entrance pupil is appropriately arranged, and variation in aberration due to zooming is suppressed. In the present invention, the aperture may be in the L2 group. Instead of moving the stop together with the second lens unit for zooming, it may be moved integrally with another lens unit.

(1-g) In at least one lens surface having a positive refractive power as the distance from the optical axis of the second R group increases, the refractive power of the lens surface decreases or the lens surface having a negative refractive power: It is preferable to apply an aspherical surface having a shape that enhances the refractive power. According to this, the optical performance of the entire screen can be further improved.

In the zoom lens according to the present invention, any lens group whose lateral magnification does not become equal during zooming can be used. When the first lens unit has a relatively high refractive power to some extent, focusing by this first lens unit can make the focusing amount at an arbitrary object distance in the entire zoom range constant, so that it is preferable to simplify the mechanism. At the wide-angle end, when the back focus is sufficient, the final lens group has a negative refractive power, and the refractive power is strong to some extent, a focusing method of moving the final lens group to the image plane side is preferable.

At this time, it is expected that the outer diameter of the first lens group can be reduced. Alternatively, a method of simultaneously moving two or more lens groups in the first lens group to the last lens group may be used. When the focus group includes a diaphragm, it is preferable to move the focus group while the diaphragm is fixed on the optical axis because a driving torque for moving the diaphragm mechanism during focusing can be reduced.

In the present invention, the second group is divided into four lens groups of positive, positive, positive, and positive refractive power in order from the object side.
Four lens groups with negative, negative, negative, and positive refractive power, positive,
Four lens groups with negative, negative, and negative refractive power, positive, positive,
It may be composed of four lens units having negative and negative refractive power.

Next, numerical examples of the present invention will be described. 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 spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass. In the numerical examples, the last two lens surfaces are glass blocks such as a face plate and a filter.

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

The aspheric surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When K, A, B, C, and D are aspheric coefficients, respectively,

[0049]

(Equation 1) It is represented by the following equation.

"E-0x" means "10 ^-x ". (Numerical Example 1) F = 28.17 to 90.19 FNO = 3.64 to 9.00 2ω = 75.0 ° to 27.0 ° R 1 = 690.43 D 1 = 1.30 N 1 = 1.49699 ν 1 = 81.6 R 2 = 26.19 D 2 = variable R 3 = 20.65 D 3 = 2.30 N 2 = 1.77249 ν 2 = 49.6 R 4 = 23.31 D 4 = Variable R 5 = 14.34 D 5 = 2.50 N 3 = 1.61800 ν 3 = 63.4 R 6 = 68.41 D 6 = Variable R 7 = Aperture D 7 = 0.99 R 8 = -25.73 D 8 = 2.80 N 4 = 1.84665 ν 4 = 23.8 R 9 = -161.40 D 9 = Variable R10 = 1328.46 D10 = 4.50 N 5 = 1.77249 ν 5 = 49.6 R11 = -16.85 D11 = Variable R12 = -14.43 D12 = 1.80 N 6 = 1.60970 ν 6 = 57.8 R13 = -102.98

[0051]

[Table 1] Aspherical surface 2 surface: K = -5.789e-02 A = 0 B = 6.189e-06 C = -8.330e-09 D = 6.659e-11 5 surface: K = 2.190e-01 A = 0 B = 1.507 e-06 C = 3.397e-07 D = -8.543e-09 8 face: K = 1.323e + 01 A = 0 B = 2.082e-05 C = -8.274e-07 D = 8.719e-08 11 face: K = -2.612e + 00 A = 0 B = -4.988e-05 C = -1.792e-08 D = -1.183e-10 12 faces: K = -2.825e-01 A = 0 B = 3.173e-05 C = -1.666e-07 D = 3.858e-10 (Numerical Example 2) F = 28.84 to 90.01 FNO = 3.46 to 9.00 2ω = 73.8 ° to 27.0 ° R 1 = -65.83 D 1 = 1.30 N 1 = 1.49699 ν 1 = 81.6 R 2 = 249.68 D 2 = Variable R 3 = -691.61 D 3 = 1.60 N 2 = 1.49699 ν 2 = 81.6 R 4 = 54.33 D 4 = Variable R 5 = 13.16 D 5 = 2.50 N 3 = 1.51633 ν 3 = 64.2 R 6 = -993.17 D 6 = Variable R 7 = Aperture D 7 = 1.00 R 8 = -19.61 D 8 = 2.50 N 4 = 1.80518 ν 4 = 25.4 R 9 = -78.22 D 9 = Variable R10 = -2685.70 D10 = 4.00 N 5 = 1.77249 ν 5 = 49.6 R11 = -15.54 D11 = Variable R12 = -14.51 D12 = 1.80 N 6 = 1.63999 ν 6 = 60.1 R13 = -137.90

[0052]

[Table 2] Aspherical surface coefficient 2 surface: K = 3.345e + 02 A = 0 B = -6.074e-06 C = -1.144e-08 D = -1.574e-11 4 surface: K = 1.789e + 01 A = 0 B = -7.283e-06 C = -4.857e-08 D = -8.630e-11 5th surface: K = 1.336e-01 A = 0 B = 0 C = 1.090e-07 D = -2.087e-09 8th surface: K = 6.635e + 00 A = 0 B = -2.746e-06 C = -3.565e-08 D = 3.803e-08 11: K = -9.879e-01 A = 0 B = -3.036e-05 C = -2.304e-08 D = -1.023e-09 12: K = -2.850e-01 A = 0 B = 7.882e-06 C = -6.264e-08 D = -4.413e-11 (Numerical example 3) F = 28.32 ~ 90.13 FNO = 3.61 ~ 9.00 2ω = 74.8 ° ~ 27.0 ° R 1 = 102.60 D 1 = 1.60 N 1 = 1.49699 ν 1 = 81.6 R 2 = 31.00 D 2 = Variable R 3 = 220.75 D 3 = 1.60 N 2 = 1.48749 ν 2 = 70.2 R 4 = 46.13 D 4 = Variable R 5 = 11.73 D 5 = 2.80 N 3 = 1.51633 ν 3 = 64.2 R 6 = 127.74 D 6 = Variable R 7 = Aperture D 7 = 1.35 R 8 = -19.05 D 8 = 2.80 N 4 = 1.80518 ν 4 = 25.4 R 9 = -73.28 D 9 = Variable R10 = 956.98 D10 = 4.50 N 5 = 1.77249 ν 5 = 49.6 R11 = -16.14 D11 = Variable R12 = -15.53 D12 = 1.80 N 6 = 1.63999 ν 6 = 60.1 R13 = -196.08

[0053]

[Table 3] Aspheric surface coefficient 2 surface: K = 5.012e-01 A = 0 B = -5.015e-07 C = 2.129e-08 D = 9.775e-13 4 surface: K = 1.090e + 00 A = 0 B = -1.301 e-06 C = -2.099e-08 D = -3.339e-10 5 faces: K = 6.031e-03 A = 0 B = -1.005e-05 C = 1.109e-07 D = -2.227e-09 8 Surface: K = 6.733e + 00 A = 0 B = 4.456e-06 C = 2.597e-07 D = 3.168e-08 Surface 11: K = -1.150e + 00 A = 0 B = -2.883e-05 C = -3.543e-08 D = 3.957e-10 12 faces: K = -2.731e-01 A = 0 B = 1.062e-05 C = -1.954e-08 D = 2.997e-11 (Numerical example 4) F = 30.00 to 94.65 FNO = 3.27 to 10.00 2ω = 71.6 ° to 25.8 ° R 1 = 68.48 D 1 = 1.60 N 1 = 1.53171 ν 1 = 48.9 R 2 = 26.02 D 2 = Variable R 3 = 22.41 D 3 = 3.50 N 2 = 1.60300 ν 2 = 65.5 R 4 = -166.95 D 4 = Variable R 5 = 35.84 D 5 = 2.50 N 3 = 1.51822 ν 3 = 59.0 R 6 = 23.94 D 6 = Variable R 7 = Aperture D 7 = 3.90 R 8 = -35.74 D 8 = 2.00 N 4 = 1.76182 ν 4 = 26.5 R 9 = -77.77 D 9 = Variable R10 = 58.70 D10 = 4.50 N 5 = 1.72915 ν 5 = 54.7 R11 = -21.35 D11 = Variable R12 = -18.13 D12 = 1.80 N 6 = 1.69679 ν 6 = 55.5 R13 = 155.55

[0054]

[Table 4] Aspheric surface coefficient 2 surface: K = -2.125e + 00 A = 0 B = 2.249e-05 C = 2.949e-08 D = 6.979e-10 3 surface: K = 8.158e-01 A = 0 B = -8.155 e-06 C = 3.714e-09 D = 6.233e-10 5 faces: K = -4.506e + 00 A = 0 B = -3.222e-06 C = 2.563e-07 D = -1.031e-08 8 faces : K = 3.452e + 01 A = 0 B = 1.358e-04 C = 1.630e-07 D = 7.988e-08 10 faces: K = -1.605e + 01 A = 0 B = -1.283e-06 C = -3.407e-07 D = 2.543e-10 11: K = -7.763e + 00 A = 0 B = -4.113e-05 C = -1.022e-08 D = -1.826e-09 12: K = -1.626e + 00 A = 0 B = 4.315e-05 C = -3.382e-07 D = 6.583e-10

[0055]

[Table 5]

[0056]

According to the present invention, as described above, in a zoom lens having a plurality of lens groups, for example, in a zoom lens divided into three groups as a whole, the lens configuration of each lens group is appropriately set. Achieved a zoom lens that has high optical performance over the entire zoom range by miniaturizing the entire lens system while satisfactorily correcting various aberrations that are a problem during wide angle of view and high zoom ratio. can do.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a paraxial refractive power arrangement according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a paraxial refractive power arrangement according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of a paraxial refractive power arrangement according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a lens at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 6 is a sectional view of a lens at a wide-angle end according to a second numerical embodiment of the present invention.

FIG. 7 is a sectional view of a lens at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 8 is a sectional view of a lens at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 9 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 10 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 11 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

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

FIG. 13 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 14 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 15 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 16 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 17 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 18 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 19 is an intermediate aberration diagram of the numerical example 4 of the present invention.

FIG. 20 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L2a Second lens unit L2b Second lens unit L2c Second lens unit L2d Second lens unit L3 Third lens unit SP Aperture IP Image plane dd line gg line S. C Sine condition ΔS Sagittal image plane ΔM Meridional image plane

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (11)

(57) [Claims] 1. A lens group comprising: a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. A zoom lens that changes magnification by changing an interval, wherein the second group includes four lens groups of a 2a group, a 2b group, a 2c group, and a 2d group. The air spacing of each of the four lens groups in the group is changed, and the combined focal lengths of the second group at the wide-angle end and the telephoto end are respectively f2w and f2T, and the focal length of the third group
Assuming that the separation is f3 and the focal length of the whole system at the wide-angle end is fw , the condition of f2w <f2T 0.9 ≦ | fw / f3 | ≦ 2.2 1.0 ≦ fw / f2w ≦ 1.8 is satisfied. A zoom lens characterized in that: 2. At the wide-angle end, the second lens unit is moved to the second lens unit.
The combined refractive power of the second lens unit composed of the lens unit and the second lens unit is composed of a second lens unit having a positive refractive power, and the composite refractive power of the second lens unit of the negative refractive power and the second lens unit having a positive refractive power is composed of the second positive lens unit. The zoom lens according to claim 1, wherein: 3. When the focal lengths of the second F group and the second R group at the wide angle end are f2Fw and f2Rw, respectively, and the focal length of the entire system at the wide angle end is fw, 0.5 ≦ fw / f2Fw ≦ 1.7. 3. The zoom lens according to claim 2, wherein the following condition is satisfied: 0.5 ≦ fw / f2Rw ≦ 1.5. Wherein said first 2c group and each DW _cd air space at the wide-angle end and telephoto end of the 2d group, when the DT _cd, claims, characterized by satisfying the DW _cd <DT _cd condition: 2 zoom lens. 5. The second lens unit has a positive refractive power and the second lens unit has a positive refractive power.
3. The zoom lens according to claim 2, wherein the group has a positive refractive power. 6. The second lens unit has a positive refractive power, and the second lens unit has a positive refractive power.
3. The zoom lens according to claim 2, wherein the group has a negative refractive power. 7. The second lens unit has a negative refractive power, and the second lens unit has a negative refractive power.
3. The zoom lens according to claim 2, wherein the group has a positive refractive power. 8. When the lateral magnifications of the second lens unit at the wide-angle end and the telephoto end are respectively βW _2c and βT _2c , | 1 / βW _2c | <1.0 | 1 / βT _2c | <1.0 The zoom lens according to claim 3, wherein the following condition is satisfied. 9. The lateral magnification of the second lens unit at the wide angle end is β
2. The zoom lens according to claim 1, wherein a condition of −0.6 <β2w <−0.1 is satisfied when 2 w is set. 10. The zoom lens according to claim 2, wherein a stop is disposed between the second F group and the second R group, and the zoom lens is moved together with zooming. 11. When zooming from the wide-angle end to the telephoto end,
2. The zoom lens according to claim 1, wherein all of the first lens unit, the four lens units of the second unit, and the third unit are moved to the object side. 3.