JPH11160621A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens having a high variable power ratio and a large diameter ratio and constituted of a small number of lenses by arranging 1st to 3rd lens groups adjacently in a wide angle end state, providing strong negative refractive power by combining and extending space between the 3rd lens group and the 4th lens group so that the arrangement of the refractive power of an entire lens system is made an inverted telephoto type and arranging an aperture diaphragm near the center of the entire system. SOLUTION: A 5th lens group G5 is constituted of a positive lens part group including at least one positive lens component and having positive refractive power as a whole, and a negative lens part group consisting of a negative lens component and a positive lens component arranged on the image side of the negative lens component through a distance and having negative refractive power as a whole in order from an object side. Then, a conditional expression; 0.15<(r1+r2)/(r1-r2)<1.2 is satisfied. r1 means the radius of curvature of the lens surface on the object side of the positive lens component included in the negative lens part group and r2 means the radius of curvature of the lens surface on the image side of the positive lens component included in the negative lens part group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zoom lens, and more particularly to a zoom lens having a high zoom ratio and a large aperture ratio.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No.
A positive / negative / positive / positive four-group type lens as disclosed in Japanese Patent Publication No. 2 (JP-A) No. 2 is known. This positive / negative positive / positive four-group type lens
A zoom lens having a focal length range including a lens position state in which a focal length is 50 mm with a 35 mm film is generally used, and is suitable for a standard zoom lens.

Japanese Patent Laid-Open Publication No. Hei 6-34885 discloses a positive, negative, negative, positive and positive five-group type lens. By arranging two negative lens groups on the image side of the first lens group, a high zoom ratio can be obtained. Has been realized. Further, Japanese Unexamined Patent Publication No.
The publication discloses high zoom ratio by introducing an aspherical surface into the second lens group of the positive / negative / positive / positive four-group type lens.

[0004]

However, when the above-mentioned conventional type of zoom lens is used, the zoom ratio is 4
With a photographic zoom lens exceeding 2x, the F at the telephoto end
Since the number is about 5.6, it is difficult to realize a high zoom ratio and a large aperture ratio at the same time. In particular, in the case of increasing the aperture using the above-described conventional zoom lens type, it is necessary to favorably perform aberration correction for each lens group. Therefore, it is desirable to increase the number of lenses constituting each lens group. . Therefore, the number of lenses increases, the weight of the entire zoom lens barrel increases, and the size of the zoom lens barrel increases.

The present invention has been made in view of the above problems, and has as its object to provide a zoom lens having a high zoom ratio, a large aperture ratio, and a small number of lenses.

[0006]

In order to achieve the above object, the present invention provides, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a negative refractive power. Has a third lens group G3, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power. When the lens position state changes from the wide-angle end state to the telephoto end state, The first
The distance between the lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G2 and the fourth lens group G4 increase. At least the second lens group G2 moves to the image side so that the distance between the first lens group G4 and the fifth lens group G5 decreases, and the first lens group G2 moves toward the image side.
At least one of the lens group G1 and the fourth lens group G4 moves, and the aperture stop moves to the first lens group G.
1 and the fifth lens group G5. The fifth lens group G5 includes, in order from the object side, at least one positive lens component and a positive lens subgroup having a positive refractive power as a whole, and a negative lens. Component and a positive lens component disposed on the image side of the negative lens component with an air space therebetween, and is composed of a negative lens subgroup having a negative refractive power as a whole, and the following conditional expression (1): 0.15 < (R1 + r2) / (r1-r2) <1.2 (1)

Here, r1 is the radius of curvature of the lens surface on the object side of the positive lens component included in the negative lens sub-group,
r2 represents the radius of curvature of the lens surface on the image side of the positive lens component included in the negative lens subgroup.

As described above, the zoom lens according to the present invention comprises, in order from the object side, the first lens G1 having a positive refractive power.
Group, a second lens group G2 having a negative refractive power, a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power,
From the wide-angle end state (the lens position state with the shortest focal length) to the telephoto end state (the lens position state with the longest focal length)
When the lens position changes to the first lens group G1
The distance between the second lens group G2 and the second lens group G2 increases.
The distance between the second and third lens groups G3 increases, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 changes. To
At least the second lens group G2 moves to the image side,
By moving at least one of the lens group G1 and the fourth lens group G4, it is possible to achieve both a high zoom ratio and a large aperture.

Next, the arrangement of the aperture stop will be described.
In general, an off-axis light beam passes away from the optical axis in a lens group far from the aperture stop, so that it is easy to correct on-axis aberration and off-axis aberration independently, and is suitable for correction of off-axis aberration. Further, when the height of the off-axis light beam passing through each lens group changes greatly when the lens position changes, it is possible to satisfactorily correct the fluctuation of off-axis aberration generated according to the change of the lens position. Therefore, by disposing the aperture stop near the center of the optical system and setting the zoom trajectory of the plurality of lens groups to greatly change the distance from the aperture stop when the lens position changes, the lens position can be changed. It is known that fluctuations in off-axis aberrations caused by the change can be satisfactorily corrected. Also in the zoom lens of the present invention, the high aperture ratio and the high performance can be achieved by disposing the aperture stop between the first lens unit and the fifth lens unit, more preferably near the center of the entire optical system. ing.

Here, the function of each lens group constituting the zoom lens according to the present invention in correcting aberration will be described.

In the wide-angle end state, the first to third lens units G1 to G3
The lens unit G3 is disposed adjacent to the lens unit G3 and has a strong negative refracting power in combination. By increasing the distance between the third lens unit G3 and the fourth lens unit G4, the refractive power arrangement of the entire lens system can be changed to an inverse telephoto type. As a sufficient back focus.

In particular, when covering an angle of view exceeding 70 degrees, it is important to satisfactorily correct the fluctuation of coma due to the angle of view. In the zoom lens of the present invention, in the wide-angle end state, the distance between the lens groups is appropriately set so that off-axis light beams passing through the second lens group G2 to the third lens group G3 and the fifth lens group G5 are separated from the optical axis. Accordingly, the second lens group 2 to the third lens group G3 satisfactorily correct the coma aberration of the lower light beam, and the fifth lens group G5 satisfactorily correct the coma aberration of the upper light beam. In particular, as described later, the focal lengths of the second lens group G2 and the third lens group G3 are appropriately set, and the first lens group G1 and the second lens group G2 are arranged so as to be adjacent to each other. It is desirable that the off-axis light beam passing through the lens group G1 is not too far from the optical axis.

When the lens position changes from the wide-angle end state to the telephoto end state, at least the second lens group G2 is moved toward the image side so as to increase the distance between the first lens group G1 and the second lens group G2. By moving it, the first
The convergence action of the lens group G1 is strengthened, and the overall length of the lens is shortened.

When the lens position changes from the wide-angle end state to the telephoto end state, the distance between the second lens group G2 and the third lens group G3 is increased so that the distance between the second lens group G2 and the third lens group G3 is increased.
By moving the third lens group G3 to the image side and narrowing the distance between the third lens group G3 and the aperture stop, the lateral magnification of the second lens group G2 and the third lens group G3 is increased. High zoom ratio is realized. Also, the second lens group G2
And the off-axis light beam passing through the third lens group G3 is made closer to the optical axis, and the fluctuation of off-axis aberrations due to the change in the lens position is satisfactorily corrected.

In addition, when the lens position changes from the wide-angle end state to the telephoto end state, the distance between the fourth lens group G4 and the fifth lens group G5 is narrowed, so that the off-axis light flux is reduced in the wide-angle end state. After passing through the fifth lens group G5 away from the optical axis,
As approaching the telephoto end, the off-axis light flux approaches the optical axis,
Variations in off-axis aberrations that occur when the lens position changes are satisfactorily corrected.

In order to increase the diameter of the lens,
It is important to satisfactorily correct the axial aberration generated in each lens group.

In the zoom lens of the present invention, the third lens group G3 and the fourth lens group G4 mainly correct the axial aberration. The third lens group G3 and the fourth lens group G4 are located near the center of the optical system, and since the aperture stop is preferably located relatively near, the off-axis light beam tends to pass near the optical axis. Less occurrence of external aberration. Therefore, by properly correcting the axial aberration generated by the third lens group G3 and the fourth lens group G4, it is possible to satisfactorily correct the fluctuation of the axial aberration generated due to the change in the lens position state, and to achieve a large aperture. Can be achieved.

As described above, the zoom lens of the present invention clarifies the function of each lens unit on aberration correction and satisfactorily corrects aberrations generated in each lens unit, thereby achieving high zoom ratio and large zoom ratio. Achieving both calibers.

Further, since the interchangeable lens for a single-lens reflex (SLR) camera has a fixed mount diameter of the lens barrel, the lens diameter of the lens disposed closest to the image is limited. Generally, the lens group arranged closest to the image side has a positive refractive power,
In addition, when the aperture stop is arranged on the object side of the lens group, if the back focus is short, the diameter of the lens arranged closest to the image side of the lens system tends to increase. Therefore,
For example, as in the lens system disclosed in JP-A-6-34885, a negative lens is often arranged closest to the image side.

In the zoom lens of the present invention, the fifth lens group G5 includes at least one positive lens, a positive lens subgroup having a positive refractive power, a negative lens, and a positive lens disposed on the image side thereof. A negative lens sub-group is formed so that an off-axis light beam passing through a lens disposed closest to the image side is made closer to the optical axis. For this reason, in the present invention, the fifth lens group G5 has the above-described configuration, thereby enabling good imaging performance and miniaturization with a small number of lens components.

The conditional expression (1) satisfies the fifth lens group G5.
It defines the shape of the positive lens disposed closest to the object in the middle positive lens part group. If the upper limit of conditional expression (1) is exceeded, a large amount of outward coma will occur in the wide-angle end state. Conversely, when the value goes below the lower limit of conditional expression (1), a large amount of inward coma occurs in the wide-angle end state.

In the zoom lens of the present invention, it is preferable that only the third lens group G3 is movable at the time of focusing.

In a zoom lens, it is common to perform focusing at a short distance by moving one lens group. The following three methods (A), (B) or (C), (A) FF (front) Group focus) method (B) IF (inner focus) method (C) RF (rear focus) method

In the case of (A) front-group focusing, the amount of focusing movement of the first lens group necessary for focusing on a predetermined subject is almost constant regardless of the lens position. Easy to do.

Here, in recent years, as the autofocus function has become popular, the speed of the autofocus function has been increased. To speed up the autofocus function, it is important that the work amount (= weight × movement amount) of the focus group is small. However, in the case of (A), the lens diameter is very large and is not suitable for autofocus.

On the other hand, in the case of the inner focus of (B) and the rear focus of (C), a lens group having a small lens diameter can be selected as a focusing group, which is suitable for speeding up the autofocus function. Therefore, in the zoom lens of the present invention, it is desirable to employ an IF system or an RF system suitable for the autofocus function.

In particular, in the present invention, the third
It is desirable that the lens group G3 be a focusing group. In the present invention, since the third lens group G3 and the fourth lens group G4 are located near the center of the optical system, an off-axis light beam passes near the optical axis, so that less off-axis aberrations occur. For this reason, the third lens group G3 and the fourth lens group G4 mainly perform correction of axial aberration. Therefore, even if the third lens group G3 or the fourth lens group G4 moves in the optical axis direction, there is little change in the correction state of the off-axis aberration. For this reason, when the third lens group G3 is a focusing group, variation in off-axis aberrations generated at the time of short-distance focusing is small, which is suitable for high performance. In particular, in the present invention, since the axial light flux is diverged by the third lens group G3 and enters the fourth lens group G4, the third lens group G3 has a smaller lens diameter, and
It is desirable that the lens group G3 be a focusing group.

Further, in the zoom lens of the present invention, the role of each lens unit in correcting aberrations is clarified, and the third lens unit G3
And the fourth lens group G4 mainly correct the axial aberration,
It is desirable to dispose an aperture stop between the third lens group G3 and the fourth lens group G4.

Conventionally, there have been known a case where the aperture stop is constant irrespective of the lens position and a case where the aperture stop moves integrally with another lens group. In the zoom lens of the present invention, it is desirable that the aperture stop be at a fixed position regardless of the lens position in order to simplify the lens barrel structure. It is desirable that the aperture stop move integrally with the fourth lens unit.

In the zoom lens according to the present invention, it is preferable that the following conditional expression (2) is satisfied: 0.75 <| fb | / f5 <1.50 (2)

Here, fb represents the focal length of the negative lens unit, and f5 represents the focal length of the fifth lens unit G5.

Conditional expression (2) defines an appropriate focal length of the negative lens subunit of the fifth lens unit G5. This is a necessary condition for achieving a balance between miniaturization and high performance.
If the upper limit of conditional expression (2) is exceeded, it is not possible to reduce the total lens length in the telephoto end state. Conversely, when the value goes below the lower limit of conditional expression (2), the off-axis light flux passing through the fifth lens group in the wide-angle end state approaches the optical axis, and the coma due to the angle of view cannot be corrected well.

In the zoom lens according to the present invention, it is desirable that the following conditional expression (3) is satisfied: 0.2 <(f4-f5) / (f4 + f5) <0.2 (3)

Here, f4 represents the focal length of the fourth lens group G4, and f5 represents the focal length of the fifth lens group G5.

Conditional expression (3) indicates that the fourth lens unit G4 and the fifth lens unit G4
An appropriate ratio of the focal length to the lens group G5 is defined.
When the value exceeds the upper limit of the conditional expression (3), the off-axis light beam passing through the fifth lens group in the wide-angle end state approaches the optical axis, and it becomes impossible to satisfactorily correct the fluctuation of the coma aberration due to the change in the angle of view. Conversely, when the value goes below the lower limit of conditional expression (3), the negative spherical aberration that occurs in the fourth lens unit increases, and the fluctuation of the axial aberration that occurs according to the change in the lens position state increases.

In the zoom lens according to the present invention, it is preferable that the following conditional expression (4) is satisfied: 2.5 <f1 / | f2 | <3.5 (4).

Here, f1 represents the focal length of the first lens group G1, and f2 represents the focal length of the second lens group G2.

Conditional expression (4) satisfies the first lens group G1 and the second lens group G1.
This defines an appropriate ratio of the focal length to the lens group G2.
This is a necessary condition for downsizing the lens system. If the upper limit of conditional expression (4) is exceeded, the overall length of the lens in the telephoto end state will increase. Conversely, when the value goes below the lower limit of conditional expression (4), the off-axis light beam passing through the first lens group is separated from the optical axis, and the lens diameter becomes large.

In the zoom lens according to the present invention, it is desirable that the following conditional expression (5) is satisfied: -0.5 <(f2-f3) / (f2 + f3) <0 (5)

Here, f2 represents the focal length of the second lens group G2, and f3 represents the focal length of the third lens group G3.

Conditional expression (5) indicates that the second lens group G2 and the third
This defines an appropriate range of the focal length of the lens group G3.
Conditional expression (5) is a condition necessary for achieving both high zooming and high performance of the lens. If the upper limit value of conditional expression (5) is exceeded, the positive spherical aberration generated in the third lens group G3 cannot be satisfactorily corrected. Conversely, if the lower limit value of conditional expression (5) is not reached, the off-axis light flux passing through the second lens group in the wide-angle end state approaches the optical axis, and the fluctuation of coma caused by the change in the angle of view is favorably reduced. Cannot correct.

In the zoom lens according to the present invention, it is desirable that the following conditional expression (6) is satisfied: ft / | f12t | <0.6 (6).

Here, ft represents the focal length of the entire lens system at the telephoto end, and f12t represents the combined focal length of the first lens group G1 and the second lens group G2 at the telephoto end.

Conditional expression (6) is a conditional expression for defining the lateral magnification of the third lens group G3 at the telephoto end. Conditional expression (6)
When the third lens group G3 is a focusing group,
It defines the conditions necessary to reduce the amount of lens movement. If the upper limit of conditional expression (6) is exceeded, the lateral magnification of the third lens group G3 will be large, so that the amount of movement when focusing on a short distance will be extremely large.

[0045]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a refractive power distribution of a variable power optical system according to each embodiment of the zoom lens of the present invention. In order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, and a positive lens group. The fifth lens unit G5 has a refractive power. Then, upon zooming from the wide-angle end state to the telephoto end state, the air gap between the first lens group G1 and the second lens group G2 increases, and the air gap between the second lens group G2 and the third lens group G3 becomes larger. The air gap between the third lens group G3 and the fourth lens group G4 decreases, and the fourth lens group G4 and the fifth lens group G5 increase.
At least the second lens group G2 and the third lens group G3 move to the image side, and the fifth lens group G5 moves to the object side so that the air gap between the second lens group G2 and the third lens group G3 moves.

(First Embodiment) FIG. 2 is a diagram showing a lens configuration of a zoom lens according to a first embodiment of the present invention.
In order from the object side, the first lens group G1 is
Meniscus negative lens L11 with the convex surface facing the object side
A positive lens L12 having a convex surface facing the object side, a meniscus positive lens L13 having a convex surface facing the object side, and the second lens group G2 includes a negative lens L21 having a concave surface facing the image side; A cemented negative lens L22 composed of a biconcave lens having a concave surface facing the object side and a positive lens having a convex surface facing the object side
The third lens group G3 is composed of a cemented negative lens L3 composed of a biconcave lens having a concave surface facing the object side and a positive lens having a convex surface facing the object side. The fourth lens group G4 has a biconvex shape. The fifth lens group G5 includes a positive lens L41, a cemented positive lens L42 including a biconvex lens, and a negative lens having a concave surface facing the object side, and the fifth lens group G5 includes a biconvex positive lens L51,
It comprises a biconvex positive lens L52, a negative lens L53 with the concave surface facing the image side, and a biconvex positive lens L54. The aperture stop S is disposed between the third lens group G3 and the fourth lens group G4, and the fourth lens increases while the stop diameter increases in accordance with a change in the lens position from the wide-angle end state to the telephoto end state. Move with the group. In addition, the third lens group G3 moves to the object side when focusing on a short distance.

Table 1 shows the specification values of the zoom lens according to the first embodiment. In the table, f is the focal length, FNO
Represents the F number, and 2ω represents the angle of view. The surface number is the number of the surface counted from the object side, r is the radius of curvature, d is the surface interval, n is the refractive index for the d-line (λ = 587.6 nm), and ν is the Abbe number. Note that a curvature radius r of 0 indicates a plane.

The aspheric surface is represented by the following equation.

[0049]

(Equation 1)

Here, y represents the height from the optical axis, x represents the amount of sag, c represents the curvature, κ represents the conic constant, and C4, C6,...

In the following description, the same reference numerals, aspherical expressions, and the like are used in the specification values of all the embodiments.

[0052]

Table 1 f 28.80 to 70.00 to 140.00 to 194.00 FNO 2.90 to 2.90 to 2.90 to 2.90 2ω 76.19 to 33.30 to 17.03 to 12 .34 ° Aperture diameter 25.02 to 31.46 to 35.32 to 35.98 Surface number Curvature radius Surface spacing Refractive index Abbe number rd n ν 1 132.3062 1.500 1.84666 23.83 2 79.2121 1.000 1.0 3 78.3091 11.200 1.60309 65.42 4- 532.8922 0.100 1.0 5 73.5167 4.300 1.65160 58.44 6 126.0337 (D6) 1.0 7 193.2957 1.200 1.77250 49.61 8 30.4799 7.950 1.0 9 -225.6733 0.900 1.77250 49.61 10 58.5416 3.900 1.84666 23.83 11 0.0000 (D11) 1.0 12 -44.9319 1.000 1.62280 56.93 1352.8818 3.250 23.83 14 227.8615 (D14) 1.0 15 0.0000 0.700 1.0 16 88.1418 3.300 1.59319 67.87 17 -578.8843 0.100 1.0 18 49.4409 8.650 1.49782.82.52 19 -52.6791 1.000 1.83500 42.97 20 1988.2645 (D20) 1.0 21 406.5779 4.000 1.69680 45.48 22 -92.0325 0.100 23 67.9050 13.000 1.65160 58.44 24 -50.3510 0.100 1.0 25 -76.7669 7.000 1.83400 37.35 26 43.6883 7.000 1.0 27 930.6501 4.650 1.62041 60.35 28 -56.3613 (Bf) 1.0 The seventh surface and the twenty-first surface are aspherical surfaces, and each coefficient is as follows. (Seventh surface) κ = 7.3794 C4 = + 3.885273 × 10^-7 C6 = −1.17922 × 10^-9 C8 = + 2.51899 × 10^-12 C10 = -1.731515 × 10^-15 (Surface 21) κ = 11.000 C4 = −4.222179 × 10^-6 C6 = −7.52773 × 10^-Ten C8 = −5.36928 × 10^-13 C10 = -2.80474 × 10^-15 (Variable interval table) f 28.8000 70.0000 140.0007 194.0017 D5 1.5000 27.0469 48.7470 52.2784 D11 7.5535 10.8417 11.4417 12.0417 D14 44.9410 18.4841 7.5263 1.7500 D21 21.9616 8.7679 3.8265 1.7958 Bf 50.2372 76.9262 89.3996 91.2335 Focusing distance from infinity focusing The amount of movement Δ3 of the third lens group up to the state (imaging magnification −1/30), and the movement toward the object side is positive. f 28.8000 70.0000 140.0000 194.0000 Δ3 1.7981 1.4367 1.8116 2.2466 (Values corresponding to the conditional expressions) f1 = 1119.234 f2 = -42.0547 f3 = −74.6172 f4 = 85.9153 f5 = 70.2833 fb = −66.0953 f12t = -423.364 (1) (r1 + r2) / (r1-r2) = 0.886 (2) | fb | /f5=0.940 (3) (f4-f5) / (f4 + f5) = 0.100 ( 4) f1 / | f2 | = 2.852 (5) (f2-f3) / (f2 + f3) =-0.279 (6) ft / | f12t | = 0.458

FIGS. 3 to 10 show various aberrations of the zoom lens according to the first embodiment of the present invention. 3 to 6 show various aberration diagrams in the infinity in-focus state, and FIGS.
Numeral 0 indicates various aberration diagrams in the short-distance in-focus state. FIGS. 3 and 7, FIGS. 4 and 8, FIGS. 5 and 9, FIGS. 6 and 10 show the wide-angle end state (f = 2
8.8), the first intermediate focal length state (f = 70.0), the second intermediate focal length state (f = 140.0), and various aberration diagrams in the telephoto end state (f = 194.0). I have.

In each of the aberration diagrams of FIGS. 3 to 10, the solid line in the spherical aberration diagram is the spherical aberration, the dotted line is the sine condition, y is the image height, and the solid line in the astigmatism diagram is the sagittal image plane.
The broken lines represent the meridional image planes, respectively. d indicates an aberration with respect to the d line (λ = 587.56 nm). The coma diagram shows the image height y = 0, 5.4, 10.8, 1
The coma aberration at 5.1, 11.6 is shown, A indicates the angle of view, and H indicates the object height. Hereinafter, the same reference numerals are used in the aberration diagrams of all the embodiments.

As is clear from the aberration diagrams, this embodiment has excellent aberrations corrected for various aberrations and excellent imaging performance.

(Second Embodiment) FIG. 11 is a diagram showing the structure of a zoom lens according to a second embodiment of the present invention. In order from the object side, the first lens group G1 includes, in order from the object side, a meniscus-shaped negative lens L having a convex surface facing the object side.
11, a positive lens L12 having a convex surface facing the object side, a meniscus-shaped positive lens L13 having a convex surface facing the object side, and the second lens group G2 includes a negative lens L21 having a concave surface facing the image side. The third lens unit G3 includes a biconcave lens having a concave surface facing the object side and a cemented negative lens L22 composed of a positive lens having a convex surface facing the object side. The third lens group G3 has a biconcave lens having a concave surface facing the object side and a convex surface facing the object side. The fourth lens group G4 is composed of a biconvex positive lens L41, and a cemented positive lens L42 composed of a biconvex lens and a negative lens having a concave surface facing the object side. The fifth lens group G5 includes a biconvex positive lens L51, a biconvex positive lens L52, and a negative lens L having a concave surface facing the image side.
53 and a biconvex positive lens L54. Further, the aperture stop S has a third lens group G3 and a fourth lens group G4.
And moves integrally with the fourth lens group while increasing the aperture diameter according to a change in the lens position state from the wide-angle end state to the telephoto end state. In addition, the third lens group G3 moves to the object side when focusing on a short distance.

Table 2 below shows data values of the zoom lens according to the second embodiment of the present invention.

[0058]

F 28.80 to 70.00 to 140.00 to 194.00 FNO 2.90 to 2.90 to 2.90 to 2.90 2ω 76.27 to 33.30 to 17.03 to 12 .34 ° Aperture diameter 24.98 to 31.28 to 35.18 to 35.86 Surface number Curvature radius Surface spacing Refractive index Abbe number rd nu 1 117.1024 1.500 1.92286 20.88 2 80.6231 1.000 1.0 3 80.2776 10.580 1.60300 65.42 4- 717.9301 0.100 1.0 5 76.6585 4.400 1.65160 58.44 6 131.1840 (D6) 1.0 7 188.4345 1.200 1.80420 46.51 8 30.4799 7.920 1.0 9 -249.2295 0.900 1.77250 49.61 10 53.8578 3.940 1.84666 23.83 11 0.0000 (D11) 1.0 12 -44.0313 1.000 1.62280 56.93 1351.8050 3.280 23.83 14 221.8299 (D14) 1.0 15 0.0000 0.700 1.0 16 77.7674 3.450 1.59319 67.87 17 -1048.4714 0.100 1.0 18 53.4900 8.330 1.49782.82.52 19 -51.9829 1.000 1.83500 42.97 20 0.0000 (D20) 1.0 21 303.6197 3.000 1.75500 52.32 22 -98.6602 3.600 1.0 2 3 133.3430 13.000 1.60 300 65.47 24 -44.7587 0.100 1.0 25 -117.7427 7.000 1.80610 33.27 26 46.8016 6.470 1.0 27 349.8673 3.560 1.80420 46.51 28 -96.9906 (Bf) 1.0 The seventh surface and the twenty-first surface are aspherical surfaces, and each coefficient is as follows. (Seventh surface) κ = −0.2776 C4 = + 5.03090 × 10^-7 C6 = -9.02122 * 10^-Ten C8 = + 1.848410 × 10^-12 C10 = −1.26710 × 10^-15 (21st surface) κ = 1.4967 C4 = −4.776220 × 10^-6 C6 = −7.554770 × 10^-Ten C8 = -1.39350 × 10^-12 C10 = −5.68570 × 10^-16 (Variable interval table) f 28.8002 70.0004 140.0008 194.0009 D5 1.5000 27.0603 48.2785 56.6649 D11 8.2306 10.6283 11.2283 11.8283 D14 43.4664 18.2124 7.4043 1.7500 D21 21.1458 8.5565 3.6850 1.7000 Bf 50.8695 77.2317 90.0235 91.9270 Focusing distance to infinity focusing The movement amount Δ3 of the third lens group up to the state (imaging magnification −1 / 30 ×), and the movement toward the object side is positive. F 28.8002 70.0004 140.0008 194.0009 Δ3 1.7158 1.4068 1.7659 2.1887 (Values corresponding to conditional expressions) f1 = 118.8613 f2 = -41.5933 f3 = −72.9824 f4 = 86.3188 f5 = 69.5681 fb = −86.0682 f12t = −424.898 (1) (r1 + r2) / (r1−r2) = 0.566 (2) | fb | /f5=1.237 (3) (f4-f5) / (f4 + f5) = 0.107 (4) f1 / | f 2 | = 2.856 (5) (f2-f3) / (f2 + f3) =-0.274 (6) ft / | f12t | = 0.457

FIGS. 12 to 19 show various aberrations of the zoom lens according to the second embodiment of the present invention. 12 to 15 show various aberration diagrams in the infinity in-focus state.
19 to 19 show various aberration diagrams in the short-distance in-focus state. 12 and 16, FIGS. 13 and 17, FIGS. 14 and 18, and FIGS. 15 and 19 show the wide-angle end state (f = 28.8) and the first intermediate focal length state (f = 70, respectively). .0), the second intermediate focal length state (f = 14
0.0) and various aberration diagrams in the telephoto end state (f = 194.0).

As is clear from the aberration diagrams, this embodiment has excellent aberrations corrected for various aberrations and excellent imaging performance.

(Third Embodiment) FIG. 20 is a view showing a lens configuration of a zoom lens according to a third embodiment of the present invention. In order from the object side, the first lens group G1 includes, in order from the object side, a meniscus-shaped negative lens L having a convex surface facing the object side.
11, a positive lens L12 having a convex surface facing the object side, a meniscus-shaped positive lens L13 having a convex surface facing the object side, and the second lens group G2 includes a negative lens L21 having a concave surface facing the image side. The third lens unit G3 includes a biconcave lens having a concave surface facing the object side and a cemented negative lens L22 composed of a positive lens having a convex surface facing the object side. The third lens group G3 has a biconcave lens having a concave surface facing the object side and a convex surface facing the object side. The fourth lens group G4 is composed of a biconvex positive lens L41, and a cemented positive lens L42 composed of a biconvex lens and a negative lens having a concave surface facing the object side. The fifth lens group G5 includes a positive lens L51 having a biconvex shape,
It is composed of a biconvex positive lens L52, a negative lens L53 with a concave surface facing the image side, and a biconvex positive lens L54. Further, the aperture stop S is disposed between the third lens group G3 and the fourth lens group G4, and the fourth lens increases while the stop diameter increases according to a change in the lens position from the wide-angle end state to the telephoto end state. Move with the group. In addition, the third lens group moves to the object side when focusing on a short distance.

Table 3 below summarizes data values of the zoom lens according to the third embodiment of the present invention.

[0063]

F 28.80 to 70.00 to 140.00 to 194.00 FNO 2.90 to 2.90 to 2.90 to 2.90 2ω 76.25 to 33.30 to 17.03 to 12 .34 ° Aperture diameter 25.62 to 32.20 to 26.52 to 32.20 Surface number Curvature radius Surface spacing Refractive index Abbe number rd n ν 1 115.8022 1.500 1.92286 20.88 2 79.4173 1.000 1.0 3 79.0424 10.730 1.60300 65.42 4- 701.5145 0.100 1.0 5 76.7245 4.330 1.65160 58.44 6 127.3222 (D6) 1.0 7 182.6349 1.200 1.80420 46.51 8 30.2450 8.060 1.0 9 -219.8733 0.900 1.77250 49.61 10 46.8071 4.360 1.84666 23.83 11 0.0000 (D11) 1.0 12 -42.8771 1.000 1.62280 56.93 135586 23.83 14 268.8082 (D14) 1.0 15 0.0000 0.700 1.0 16 94.9355 3.940 1.49782 82.52 17 -208.7690 0.100 1.0 18 50.5793 9.220 1.49782.82.52 19 -55.6780 1.000 1.83400 37.35 20 3712.9134 (D20) 1.0 21 240.6326 7.850 1.74330 49.23 22 -93.7463 4.410 1.0 23 118.8725 9.580 1.48749 70.45 24 -42.3887 0.100 1.0 25 -158.9909 7.000 1.83400 37.35 26 46.9155 4.300 1.0 27 269.8997 3.500 1.80420 46.51 28 -113.1850 (Bf) 1.0 The 7th and 21st surfaces are aspherical, and each coefficient is It is on the street. (Seventh surface) κ = −4.29293 C4 = + 5.7342 × 10 ⁻⁷ C6 = −9.28161 × 10 ⁻¹⁰ C8 = + 1.88381 × 10 ⁻¹² C10 = −1.29468 × 10 ⁻¹⁵ ( Surface 21) κ = 8.7601 C4 = −4.885424 × 10 ⁻⁶ C6 = −1.26065 × 10 ⁻⁹ C8 = −2.95632 × 10 ⁻¹³ C10 = −2.77484 × 10 ⁻¹⁵ Variable interval table) f 28.7999 69.9997 139.9991 193.9984 D5 1.5000 27.1463 48.4908 56.9003 D11 8.2407 10.0787 10.6787 11.2787 D14 43.0788 17.8880 7.2001 1.7500 D21 22.6609 8.8857 3.7274 1.7000 Bf 52.6277 80.2031 94.4433 97.4598 (focusing distance) The movement amount of the third lens group up to (photographing magnification -1 / 30x) is Δ3, and the movement to the object side is positive. F 28.7999 69.9997 139.9991 193.9984 Δ3 1.6616 1.3566 1.6640 2.0157 F1 = 120.2915 f2 = -41.0605 f3 = -73.0708 f4 = 84.8082 f5 = 72.6558 fb = -84.7356 f12t = -374.623 (1) (r1 + r2) / (r1- (r2) = 0.409 (2) | fb | /f5=1.166 (3) (f4-f5) / (f4 + f5) = 0.077 (4) f1 / | f2 | = 2.930 (5) ( f2−f3) / (f2 + f3) = − 0.280 (6) ft / | f12t | = 0.518

FIGS. 21 to 28 show various aberration diagrams of the zoom lens according to the third embodiment of the present invention. FIGS. 21 to 24 show various aberration diagrams in the infinity in-focus state.
28 show various aberration diagrams in the short-distance in-focus state. 21 and 25, FIGS. 22 and 26, FIGS. 23 and 27, and FIGS. 24 and 28 show the wide-angle end state (f = 28.8) and the first intermediate focal length state (f = 70. 0), the second intermediate focal length state (f = 14
0.0) and various aberration diagrams in the telephoto end state (f = 194.0).

As is clear from the aberration diagrams, the present embodiment has excellent aberrations corrected for various aberrations and excellent imaging performance.

In the zoom lens according to the embodiment of the present invention, an aperture ratio having an F-number of about 2.8 is realized. For example, the zoom ratio is reduced to achieve a larger aperture ratio, or the F-number is increased. And it is easy to achieve a higher zoom ratio.

In the zoom lens of the present invention,
According to another aspect, when taking a photograph, in order to prevent a failure due to image blur caused by hand shake or the like that is likely to occur with a high zoom lens, a blur detection system for detecting blur and a drive unit are used. Can be combined into a system. As a result, the blur is detected by the blur detection system, and the eccentric lens group is decentered by the driving means to shift the image so as to correct the detected blur. Here, it is desirable to decenter all or a part of one lens group among the lens groups constituting the lens system as an eccentric lens group. As a result, image blur can be corrected, and a vibration-proof optical system can be provided.

It is needless to say that the variable power optical system according to the present invention can be applied not only to a zoom lens but also to a varifocal zoom lens in which the focal length state does not exist continuously.

[0069]

As described above, according to the zoom lens of the present invention, the aperture ratio is approximately 2.8, and the angle of view in the wide-angle end state covers a wide angle of view exceeding 75 degrees. In addition, a zoom lens having a zoom ratio of about 7 can be achieved.

Also, by appropriately using an aspherical surface,
At the same time, the lens diameter has been reduced and the overall length of the lens at the telephoto end has been shortened.However, the use of an aspherical surface allows for a higher zoom ratio and a larger aperture, or a smaller lens system. Needless to say, it can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement of refractive power of a zoom lens according to the present invention.

FIG. 2 is a diagram illustrating a configuration of a zoom lens according to a first example of the present invention.

FIG. 3 is a diagram illustrating various aberrations in a wide-angle end state when the zoom lens according to the first example of the present invention is in an infinity in-focus state.

FIG. 4 is a diagram illustrating various aberrations in a first intermediate focal length state when the zoom lens according to the first example of the present invention is in an infinity in-focus state;

FIG. 5 is a diagram illustrating various aberrations in a second intermediate focal length state when the zoom lens according to the first example of the present invention is in an infinity in-focus state.

FIG. 6 is a diagram illustrating various aberrations at the telephoto end when the zoom lens according to the first example of the present invention is in an infinity in-focus state.

FIG. 7 is a diagram illustrating various aberrations in a wide-angle end state when the zoom lens according to the first example of the present invention is in a short-distance in-focus state;

FIG. 8 is a diagram illustrating various aberrations in a first intermediate focal length state when the zoom lens according to the first example of the present invention is in a short-distance in-focus state;

FIG. 9 is a diagram illustrating various aberrations in a second intermediate focal length state when the zoom lens according to the first example of the present invention is in a short-distance in-focus state;

FIG. 10 is a diagram illustrating various aberrations at a telephoto end state when the zoom lens according to the first example of the present invention is in a short-distance in-focus state.

FIG. 11 is a diagram illustrating a configuration of a zoom lens according to a second example of the present invention.

FIG. 12 is a diagram illustrating various aberrations in a wide-angle end state when the zoom lens according to Example 2 of the present invention is in an infinity in-focus state.

FIG. 13 is a diagram illustrating various aberrations in a first intermediate focal length state when the zoom lens according to Example 2 of the present invention is in an infinity in-focus state.

FIG. 14 is a diagram illustrating various aberrations in a second intermediate focal length state when the zoom lens according to Example 2 of the present invention is in an infinity in-focus state.

FIG. 15 is a diagram illustrating various aberrations at the telephoto end when the zoom lens according to Example 2 of the present invention is in an infinity in-focus condition.

FIG. 16 is a diagram illustrating various aberrations in a wide-angle end state when the zoom lens according to the second example of the present invention is in a short-distance in-focus state.

FIG. 17 is a diagram illustrating various aberrations in a first intermediate focal length state when the zoom lens according to the second example of the present invention is in a short-distance in-focus state;

FIG. 18 is a diagram illustrating various aberrations in a second intermediate focal length state when the zoom lens according to the second example of the present invention is in a short-distance in-focus state.

FIG. 19 is a diagram illustrating various aberrations at the telephoto end when the zoom lens according to the second example of the present invention is in a short-distance focusing state.

FIG. 20 is a diagram showing a configuration of a zoom lens according to a third example of the present invention.

FIG. 21 is a diagram illustrating various aberrations in a wide-angle end state when the zoom lens according to Example 3 of the present invention is in an infinity in-focus state.

FIG. 22 is a diagram illustrating various aberrations in a first intermediate focal length state when the zoom lens according to Example 3 of the present invention is in an infinity in-focus state.

FIG. 23 is a diagram illustrating various aberrations in a second intermediate focal length state when the zoom lens according to Example 3 of the present invention is in an infinity in-focus state.

FIG. 24 is a diagram showing various aberrations at the telephoto end when the zoom lens according to Example 3 of the present invention is in an infinity in-focus condition.

FIG. 25 is a diagram illustrating various aberrations in a wide-angle end state when the zoom lens according to Example 3 of the present invention is in a short-distance in-focus state.

FIG. 26 is a diagram illustrating various aberrations in a first intermediate focal length state when the zoom lens according to Example 3 of the present invention is in a short-distance in-focus state;

FIG. 27 is a diagram illustrating various aberrations in a second intermediate focal length state when the zoom lens according to Example 3 of the present invention is in a short-distance in-focus state;

FIG. 28 is a diagram illustrating various aberrations at a telephoto end when the zoom lens according to Example 3 of the present invention is in a short-distance in-focus state.

[Explanation of symbols]

 G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group S Aperture

Claims (11)

[Claims] 1. A first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a negative refractive power, and a fourth lens having a positive refractive power are arranged in order from the object side. Group G4,
A fifth lens group G5 having a positive refractive power, wherein when the lens position state changes from the wide-angle end state to the telephoto end state, the first lens group G1 and the second lens group G2
, The distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G2 and the fourth lens group G4 decreases, and the distance between the fourth lens group G2 and the fourth lens group G4 decreases. At least the second lens group G2 moves to the image side so that the distance between the lens group G4 and the fifth lens group G5 decreases, and at least one of the first lens group G1 and the fourth lens group G4 is moved. One of them moves, and an aperture stop is disposed between the first lens group G1 and the fifth lens group G5. The fifth lens group G5 includes at least one positive lens component in order from the object side. It is composed of a positive lens part group having a positive refractive power as a whole, a negative lens part group composed of a negative lens component and a positive lens component disposed at an image distance from the image side of the negative lens component, and having a total negative refractive power. Included in the negative lens subgroup When the radius of curvature of the lens surface on the object side of the positive lens component is r1, and the radius of curvature of the lens surface on the image side of the positive lens component included in the negative lens subgroup is r2, 0.15 <(r1 + r2) / A zoom lens characterized by satisfying the following condition: (r1-r2) <1.2. 2. The zoom lens according to claim 1, wherein one lens group disposed closer to the image side than said first lens group G1 is movable during focusing. 3. The zoom lens according to claim 2, wherein only the third lens group G3 is movable during focusing. 4. The zoom lens according to claim 3, wherein said aperture stop is provided between said third lens group G3 and said fourth lens group G4. 5. The zoom lens according to claim 1, wherein the aperture stop is provided between the third lens group G3 and the fourth lens group G4. 6. The zoom lens according to claim 5, wherein the position of the aperture stop is constant irrespective of a change in a lens position state. 7. The zoom lens according to claim 5, wherein the aperture stop moves integrally with the fourth lens group G4 according to a change in a lens position state. 8. A condition of 0.75 <| fb | / f5 <1.50 (2) where fb is a focal length of the negative lens subunit and f5 is a focal length of the fifth lens unit G5. 8. The zoom lens according to claim 3, wherein the zoom lens is satisfied. 9. The focal length of the fourth lens group G4 is f
4. The condition of -0.2 <(f4-f5) / (f4 + f5) <0.2 (3) is satisfied, where f5 is the focal length of the fifth lens group G5. The zoom lens according to 1. 10. The focal length of the first lens group G1 is f
10. The condition of 2.5 <f1 / | f2 | <3.5 (4) is satisfied, where f2 is the focal length of the second lens group G2. Zoom lens. 11. The focal length of the second lens group G2 is f
2. The condition of -0.5 <(f2-f3) / (f2 + f3) <0 (5) is satisfied, where f3 is the focal length of the third lens group G3. Zoom lens.