JPH07306363A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide a zoom lens capable of decreasing the amount of work at the time of focusing and having a small number of lens components, excellent image forming performance and a high variable power ratio. CONSTITUTION:This zoom lens is provided, in order from the object side, with a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having-negative refractive power. Focusing is performed by moving the fourth group G4 to the object side for a long distance object to a short distance object so as to satisfy the conditions: 0.15 <f3/f1<0.7, 0.1<(d2w-d2t)/(d1t-d1w)<0.85. In the relations, f1, f3 are focal distances of the lens groups G1, G2, d1w, d2w are air gaps between the lens groups G1 and G2, between G2 and G3 at the wide-angle end and d1t, d2t are air gaps along the optical axis between the lens groups G1 and G2, between G2 and G3 at the telescopic end.

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 more particularly to a zoom lens suitable for a lens shutter type camera.

[0002]

2. Description of the Related Art Among lens shutter type cameras, cameras equipped with a zoom lens are becoming mainstream. Particularly in recent years, various zoom types have been proposed in which a high zoom ratio is achieved by using a so-called multi-group zoom lens configured by three or more movable lens groups due to the progress of lens barrel technology and the like.

First, it has three or more movable lens groups,
The general theory of so-called multi-group zoom lenses will be described. In a zoom lens having a multi-group configuration, the degree of freedom in selecting a zooming trajectory of each lens group during zooming from the wide-angle end to the telephoto end increases, so that the degree of freedom in aberration correction increases. In addition, since the number of lens groups responsible for zooming increases, it is easy to equalize the zooming load of each lens group, and it is possible to achieve high performance while achieving high zooming. Conventionally, there has been a problem that the lens barrel structure is complicated due to the increase of movable parts,
Recent advances in lens barrel technology have overcome this problem to some extent.

Conventionally, in a zoom lens having no restriction on back focus, a negative lens group is arranged closest to the image side in order to shorten the overall lens length and the size of each lens, and from the wide-angle end. Zooming was effectively performed by increasing the change in the back focus upon zooming to the telephoto end. Further, by arranging the positive lens group on the most object side of the lens system, the total lens length is shortened. From the above, as a multi-group zoom lens that is capable of achieving a high zoom ratio and is suitable for downsizing, a positive / negative 3 group zoom lens, a positive / negative positive / negative 4 group zoom lens, and the like can be mentioned. Suggestions have been made.

The positive / negative three-group zoom lens comprises, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power. When zooming from the end to the telephoto end, the air gap between the first lens group and the second lens group increases, and the air gap between the second lens group and the third lens group decreases. Has been done.

On the other hand, the positive, negative, positive and negative four-group zoom lens comprises, in order from the object side, a first lens group having a positive refracting power, a second lens group having a negative refracting power, a third lens group having a positive refracting power, and a negative refracting power. And a fourth lens group of optical power, the air gap between the first lens group and the second lens group increases during zooming from the wide-angle end to the telephoto end, and the second lens group and the third lens group increase. The air gap between the lens unit and the third lens unit is reduced, and the air gap between the third lens unit and the fourth lens unit is reduced.

Next, focusing in a multi-group zoom lens will be described. Generally, what is required of a lens group that moves along the optical axis when focusing a zoom lens on an object, that is, a focusing group, is that the amount of movement is small and the weight thereof is small. This is because a smaller amount of movement of the focusing unit is advantageous for downsizing the entire lens system, and a smaller weight of the focusing unit is advantageous for simplifying the mechanism for driving the focusing unit.

Conventionally, when focusing a long-distance object to a short-distance object in a multi-group zoom lens, (A) first group extension method (B) IF (inner focus) method (C) RF (rear There are three methods, the focus method, and various proposals have been made for these methods.

[0009]

However, in the conventional positive / negative three-group zoom lens, the ratio of the third lens group to the zooming is large relative to the zooming of the entire lens system. As a result, in the case of achieving a high zoom ratio, there is a disadvantage that the fluctuation of the off-axis aberration generated in the third lens group during zooming becomes large.

Further, in the conventional positive / negative / negative / four-group zoom lens, the total lens length at the telephoto end can be shortened as compared with the conventional positive / negative / three-group zoom lens, and it is also suitable for high zooming. However, since the combined refractive power of the first lens group and the second lens group is negatively small, the diverging action is weak, sufficient back focus cannot be obtained at the wide angle end, and the rear lens effective diameter becomes large. was there. As described above, with the conventional multi-group zoom lens, it has been extremely difficult to obtain excellent image forming performance with a small number of constituent lenses while achieving a wide angle, high zoom ratio, and size reduction.

In a multi-group zoom lens such as a conventional positive / negative three-group zoom lens or a conventional positive / negative positive / negative four-group zoom lens which has no restriction on back focus, the positive lens group is arranged closest to the object in the lens system. There is. However, in order to satisfactorily correct the positive distortion that occurs at the wide-angle end, the refractive power of the positive lens unit closest to the object is set to be positively weak. Therefore, when focusing is performed using the (1) first group extension method, the amount of movement of the first lens group, which is the focusing group, becomes excessive.

Further, in the case of focusing using the rear focus method of (C), since the back focus at the wide-angle end is small, it becomes impossible to focus on a short-distance object. further,
When focusing is performed by using the inner focus method of (B), the second lens group is divided into a front group and a rear group, as in a positive / negative three-group zoom lens disclosed in Japanese Patent Laid-Open No. 4-338910. Focusing is performed by the front group of the second lens unit on the object side. However, since the front lens group of the second lens group, which is a focusing lens group, has a weak refractive power, the moving amount of the focusing lens group at the time of short-distance focusing becomes excessive.

As described above, in the conventional focusing method for a multi-group zoom lens, the work amount at the time of focusing,
That is, there is a disadvantage that the weight of the focusing group × the moving amount is large. The present invention has been made in view of the above-described problems, and provides a zoom lens that reduces the workload during focusing, has a small number of constituent lenses, has excellent imaging performance, and is capable of high zooming. The purpose is to do.

[0014]

In order to solve the above problems, in the present invention, a first lens group G1 having a positive refractive power and a second lens group having a negative refractive power are arranged in order from the object side. G2 and the third lens group G3 having a positive refractive power
And a fourth lens group G4 having a positive refractive power and a fifth lens group G5 having a negative refractive power, and at least the first lens group G1 at the time of zooming from the wide-angle end to the telephoto end.
And the fifth lens group G5 moves to the object side, the air gap between the first lens group G1 and the second lens group G2 increases, and the third lens group G3 and the fourth lens group G4.
In the zoom lens, the air distance between the fourth lens group G4 and the fifth lens group G5 decreases, and the fourth lens group G4 is changed from a long-distance object to a short-distance object. To the side to perform focusing, the focal length of the first lens group G1 is set to f1, the focal length of the third lens group G3 is set to f3, and the first lens group G1 and the second lens group at the wide angle end are set. An air space between the first lens group G1 and the second lens group G2 at the telephoto end is d1t, and an air space between the first lens group G1 and the second lens group G2 at the telephoto end is d1t. An air gap along the optical axis between the second lens group G2 and the third lens group G3 is set to d2w, and an optical axis between the second lens group G2 and the third lens group G3 at the telephoto end. Air spacing along the line is d2t When, to provide 0.15 <f3 / f1 <0.7 0.1 <(d2w-d2t) / (d1t-d1w) <zoom lens satisfies the 0.85 condition.

According to a preferred embodiment of the present invention, when the image forming magnification of the fourth lens group G4 at the wide-angle end is β4w and the image forming magnification of the fourth lens group G4 at the telephoto end is β4t, it is 0. The condition of 8 <β4t / β4w <2.5 is satisfied. When the back focus at the wide-angle end is Bfw, the back focus at the telephoto end is Bft, the focal length of the entire lens system at the wide-angle end is fw, and the focal length of the entire lens system at the telephoto end is ft, 0. It is preferable that the condition of 4 <(Bft−Bfw) / (ft−fw) <0.8 is satisfied.

[0016]

The zoom lens according to the present invention comprises a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power.
A fourth lens group G4 having a positive refractive power and a fifth lens group G5 having a negative refractive power are provided, and at least the first lens group G1 and the fifth lens group G5 are used at the time of zooming from the wide-angle end to the telephoto end. The lens group G5 moves toward the object side, the air distance between the first lens group G1 and the second lens group G2 increases, and the air distance between the third lens group G3 and the fourth lens group G4 increases. However, the air distance between the fourth lens group G4 and the fifth lens group G5 decreases, and the fourth lens group G4 is moved toward the object side from a long-distance object to a short-distance object to perform focusing. Has been adopted. In this way, it is possible to achieve a zoom lens capable of achieving a high zoom ratio while having a small size with a small number of constituent lenses.

The aperture stop is preferably arranged near the center of the lens system (from the surface closest to the object to the surface closest to the image). In particular, the second lens group G2 and the third lens group G3
Between the third lens group G3 and the fourth lens group G4,
Alternatively, it is preferable to dispose an aperture stop between the fourth lens group G4 and the fifth lens group G5. The features of the zoom lens of the present invention will be described below.

As described above, in a zoom lens used in a lens shutter type camera (a zoom lens having no limitation on back focus), a negative lens group may be arranged closest to the image side in order to shorten the total lens length. It is valid. Therefore, also in the present invention, the fifth lens group G5 arranged closest to the image side has a negative refractive power. Further, in order to achieve a wide angle, the back focus at the wide angle end is made small to some extent, and the height of the off-axis light flux passing through the fifth lens group G5 is separated from the optical axis to reduce the coma aberration caused by the change in the angle of view. It facilitates correction of fluctuations. However, if the back focus at the wide-angle end is made too short, the height of the off-axis light flux passing through the fifth lens group G5 becomes too far from the optical axis, and the lens diameter becomes large. Should be an appropriate value.

Then, by increasing the change of the back focus at the time of zooming from the wide-angle end to the telephoto end, the change of the height of the off-axis light flux passing through the fifth lens group G5 is increased, and at the time of zooming. The fluctuation of the coma aberration of is well corrected.
Also, by shortening the total lens length at the wide-angle end rather than at the telephoto end (shortening the total lens length at the wide-angle end),
At the wide-angle end, the height of the off-axis light flux that passes through the first lens group G1 is brought closer to the optical axis to reduce the lens diameter of the first lens group G1.

In the present invention, in order to achieve both high zooming and high performance, the ratio of the fifth lens group G5 arranged closest to the image plane to carry out zooming is reduced, The lens group G1 to the fourth lens group G4 bear the zooming action. In particular, in the present invention, the image forming magnification of the second lens group G2 is largely changed, and the second lens group G2 plays a large amount of zooming action.

At the wide-angle end, the first lens group G1 and the second lens group G2 are brought as close as possible to each other to make the combined refractive power of the first lens group G1 and the second lens group G2 a strong negative refractive power.
By arranging this at a position away from the image plane, a sufficient back focus is obtained. In addition, the third of the positive refractive power
A strong positive refracting power is obtained by bringing the lens group G3 and the fourth lens group G4 close to each other. On the contrary, at the telephoto end,
The first lens group G1 is moved by moving the lens group G1 to the object side.
By widening the distance between the second lens group G2 and the second lens group G2, the converging action is strengthened and the total lens length is shortened. Further, the third lens group G3 having a positive refracting power is moved to the object side to narrow the gap between the third lens group G3 and the second lens group G2, thereby further reducing the total lens length.

In the present invention, the combined refractive power of the first lens group G1 and the second lens group G2 is always negative during zooming,
During zooming from the wide-angle end to the telephoto end, the air gap between the first lens group G1 and the second lens group G2 increases. For this reason,
The second lens group G2 is used for multiplication so that the imaging magnification increases negatively, and when the magnification is changed from the wide-angle end to the telephoto end, the combined refractive power of the first lens group G1 and the second lens group G2. Becomes smaller negatively. Also, the second lens group G at the wide-angle end
When the imaging magnification of 2 is β2w, by setting -1 <β2w <0, a sufficient back focus can be obtained at the wide-angle end. Further, since the height of the off-axis light flux passing through the first lens group G1 becomes closer to the optical axis, the lens diameter (front lens effective diameter) of the first lens group G1 can be reduced.

Next, the conditions for focusing by the fourth lens group G4 will be described. When the position of the subject moves from a long distance to a short distance, the fourth lens group G4 is moved so that the image positions of the first lens group G1 to the fourth lens group G4 are constant with respect to the fifth lens group G5. If so, focusing can be performed. At this time, the fourth lens group G
The conditions for reducing the movement amount Δ of No. 4 will be described using a thin lens system.

First, as shown in FIG. 2, the fourth lens group G
When the position of the object point with respect to 4 moves by δ, if the imaging magnification of the fourth lens group G4 is β4, the fourth lens group G4
The movement amount Δ of is given by the following mathematical expression (a). Δ = [β4 ² / (β4 ² -1)] · δ (a) In the equation (a), if k = β4 ² / (β4 ² -1), the value of k depends on the value of β4 ^2. It is expressed by the following equations (b) and (c). 1 ≦ k (β4 ² > 1) (b) 0> k (β4 ² <1) (c)

Therefore, in order to reduce the movement amount Δ of the fourth lens group 4, in the case of (b), k is brought close to 1.
That is, it is necessary to bring 1 / β4 close to 0, and in the case of (c), k is made close to 0, that is, β
It is necessary to bring 4 closer to 0. In the present invention, by making β4 close to 0, the movement amount Δ of the fourth lens group G4 during focusing is reduced.

At this time, in the present invention, β4 is set as close to 0 as possible as described above, so that the combined refractive power of the first lens group G1 to the third lens group G3 is set to 0 as much as possible.
It is desirable to approach. That is, the third lens group G
When the usage magnification of 3 is β3, it is desirable to bring 1 / β3 close to 0. As described above, when focusing is performed by the fourth lens group G4, it is required to set the image forming magnifications of the third lens group G3 and the fourth lens group G4 to appropriate values.

Each conditional expression of the present invention will be described below. The zoom lens of the present invention satisfies the following conditional expressions (1) and (2). 0.15 <f3 / f1 <0.7 (1) 0.1 <(d2w-d2t) / (d1t-d1w) <0.85 (2) where, f1: focal length of the first lens group G1 f3 : Focal length of second lens group G3 d1w: First lens group G1 and second lens group G2 at wide-angle end
On-axis air distance d1t: first lens group G1 and second lens group G2 at the telephoto end
On-axis air distance d2w: second lens group G2 and third lens group G3 at the wide-angle end
On-axis air distance d2t: second lens group G2 and third lens group G3 at the telephoto end
On-axis air distance from

Conditional expression (1) defines the ratio between the focal length of the first lens group G1 and the focal length of the third lens group G3, and is a balance between widening the angle and shortening the total lens length at the telephoto end. Is a conditional expression for When the value exceeds the upper limit of conditional expression (1), the converging action of the first lens group G1 is strengthened, and the total lens length at the telephoto end can be shortened.
However, at the wide-angle end, the height of the off-axis light flux passing through the first lens group G1 is too far from the optical axis, the lens diameter of the first lens group G1 becomes large, and positive distortion can be suppressed. It will be difficult.

On the other hand, when the value goes below the lower limit of conditional expression (1), the converging action of the first lens group G1 is weakened, so that the total lens length at the telephoto end becomes large. Further, the converging action of the third lens group G3 is strengthened, the height of the off-axis light flux passing through the third lens group G3 does not change much during zooming, and the incident angle tends to increase. As a result, if an attempt is made to construct a zoom lens with a small number of lenses, it becomes impossible to correct the fluctuation of off-axis aberration that occurs in the third lens group G3 during zooming.

Conditional expression (2) is expressed by the amount of change in the axial air gap between the first lens group G1 and the second lens group G2 upon zooming and the axis between the second lens group G2 and the third lens group G3. It defines the ratio to the change amount of the upper air space. If the upper limit of conditional expression (2) is exceeded, the amount of change in the axial air gap between the second lens group G2 and the third lens group G3 during zooming becomes large, so the first lens group G1 through the first lens group G1 at the wide-angle end. The height of the off-axis light flux passing through each lens group of the third lens group G3 is too far from the optical axis, and it becomes impossible to suppress the variation of coma aberration depending on the angle of view.

On the contrary, if the lower limit value of the conditional expression (2) is not reached, the second lens group G2 and the third lens group G3 will be used during zooming.
Since the amount of change in the axial air distance between and becomes too small, sufficient back focus cannot be obtained at the wide-angle end,
The lens diameter of the fifth lens group G5 becomes large. Further, the amount of change in the axial air distance between the first lens group G1 and the second lens group G2 during zooming becomes large, and the height of the off-axis light flux passing through the first lens group G1 at the telephoto end is the optical axis. Further away, the positive distortion cannot be suppressed.

In the present invention, in order to further reduce the total lens length at the telephoto end, it is desirable to set the upper limit of conditional expression (1) to 0.65. Further, in order to further increase the zoom ratio, it is desirable to set the lower limit of conditional expression (1) to 0.2 or the upper limit of conditional expression (2) to 0.75.

In order to further improve the performance, it is desirable to satisfy the following conditional expression (3). 0.8 <β4t / β4w <2.5 (3) where β4w: Imaging magnification of the fourth lens group G4 at the wide-angle end β4t: Imaging magnification of the fourth lens group G4 at the telephoto end

Conditional expression (3) is a condition for satisfactorily correcting fluctuations of various aberrations that occur when focusing is performed by moving the fourth lens group G4 from a long-distance object to a short-distance object. . If the upper limit of conditional expression (3) is exceeded,
The change in the imaging magnification of the fourth lens group G4 during zooming becomes large. That is, the object point position with respect to the fourth lens group G4 changes significantly during zooming. Therefore, variations in various aberrations occur with changes in the position of the object point, and particularly variations in axial aberration at the telephoto end increase. Further, the movement amount of the fourth lens group G4 at the telephoto end becomes too large.

If the lower limit of conditional expression (3) is not reached, the fourth
The imaging magnification of the lens group G4 does not change much during zooming. That is, the ratio of the first lens group G1 to the fourth lens group G4 responsible for zooming to the zooming of the entire lens system decreases. As a result, the ratio of the fifth lens group G5 responsible for zooming increases too much, and the fifth lens group G5 does during zooming.
The fluctuation of the off-axis aberration that occurs in 1 cannot be suppressed well. In order to suppress the axial aberration associated with focusing at the telephoto end, it is desirable to set the upper limit of conditional expression (3) to 1.8.

To further increase the zoom ratio, it is desirable to satisfy the following conditional expression (4). 0.4 <(Bft−Bfw) / (ft−fw) <0.8 (4) where Bfw: back focus at wide-angle end Bft: back focus at telephoto end fw: focal length of entire lens system at wide-angle end ft: focal length of the entire lens system at the telephoto end

Conditional expression (4) defines the ratio of the amount of change in the back focus to the amount of change in the focal length of the entire lens system during zooming, and defines the ratio responsible for zooming in the fifth lens group G5. To do. If the upper limit of conditional expression (4) is exceeded, the ratio of the fifth lens group G5 responsible for zooming to the zooming of the entire lens system becomes too large, and the off-axis that occurs in the fifth lens group G5 during zooming. It becomes difficult to suppress variation in aberration.

On the contrary, when the value goes below the lower limit of the conditional expression (4), the ratio of the zooming of the fifth lens group G5 to the zooming of the entire lens system becomes small, and the first to fourth lenses G1 to G4. The ratio of zooming in the group G4 becomes too large.
Therefore, it is not possible to simplify the lens system,
It goes against the purpose of the present invention. In order to further increase the zoom ratio, it is preferable to set the upper limit of conditional expression (4) to 0.7.

[0039]

FIG. 1 shows the basic structure of a zoom lens according to each embodiment of the present invention, the state of movement of each lens group during zooming from the wide-angle end to the telephoto end, and the object from a long-distance object to a short-distance object. FIG. 11 is a diagram showing a state of movement of a fourth lens unit G4 in focusing with respect to. As shown in FIG. 1, in each embodiment, the zoom lens according to the present invention includes, in order from the object side, the 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 positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens having a negative refractive power. Group G
And 5 at the time of zooming from the wide-angle end to the telephoto end, at least the first lens group G1 and the fifth lens group G
5 moves to the object side, and the first lens group G1 and the second lens group G1
The air distance between the lens group G2 increases, the air distance between the third lens group G3 and the fourth lens group G4 increases, and the air distance between the fourth lens group G4 and the fifth lens group G5 increases. Decrease. It should be noted that when focusing from a long-distance object to a short-distance object, the fourth lens group G4 is moved to the object side.

Each embodiment of the present invention will be described below with reference to the accompanying drawings. Example 1 FIG. 3 is a diagram showing the configuration of a zoom lens according to Example 1 of the present invention. The illustrated zoom lens is a first lens including, in order from the object side, a cemented lens L11 including a biconcave lens and a biconvex lens, and a biconvex lens L12.
Lens group G1, biconcave lens L21, biconvex lens L22
And a second lens group G2 including a biconcave lens L23,
A third lens group G3 composed of a biconvex lens L3, a fourth lens group G4 composed of a positive lens component L4 cemented with a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a positive meniscus having a concave surface facing the object side. It includes a lens L51, a negative meniscus lens L52 having a concave surface facing the object side, and a fifth lens group G5 including a negative meniscus lens L53 having a concave surface facing the object side.

FIG. 3 shows the positional relationship of each lens group at the wide-angle end, and when the magnification is changed to the telephoto end, it moves on the optical axis along the zoom orbit shown by the arrow in FIG. The aperture stop S is arranged between the third lens group G3 and the fourth lens group G4, and moves integrally with the fourth lens group G4 during zooming from the wide-angle end to the telephoto end. Table 1 below lists values of specifications of the first embodiment of the present invention. In Table (1),
f is the focal length, FN is the F number, 2ω is the angle of view,
Bf represents the back focus, and R represents the shooting distance. Further, the refractive index and the Abbe number are d-line (λ = 58
7.6 nm).

[0042]

[Table 1] f = 38.80 to 75.68 to 121.80mm FN = 4.3 to 6.9 to 9.0 2ω = 59.2 to 31.4 to 19.8 ° Surface number Curvature radius Surface spacing Abbe number Refractive index 1 -136.6894 1.50 33.89 1.80384 2 39.0402 3.51 60.69 1.56384 3- 80.2574 0.13 4 42.4571 3.01 57.03 1.62280 5 -147.2072 (d5 = variable) 6 -32.7823 1.26 49.45 1.77279 7 28.5446 1.00 8 18.8958 2.76 25.80 1.78472 9 -251.4186 1.00 10 -26.8968 1.26 45.37 1.79668 11 129.1609 (d11 = variable) 12 360.3996 1. 1.53996 13 -20.5975 (d13 = variable) 14 ∞ 1.51 (aperture) 15 21.9826 3.27 59.60 1.53996 16 -13.3086 1.26 25.35 1.80518 17 -36.5419 (d17 = variable) 18 -71.7851 2.89 25.35 1.80518 19 -20.7264 0.38 20 -37.6538 1.26 45.35 1.84042 21 -504.2084 4.40 22 -12.4513 1.51 49.45 1.77279 23 -53.6689 (Bf) (Variable spacing during zoom) f 38.8006 75.6784 121.8082 d5 2.1349 10.3930 17.1158 d11 4.7612 3.5057 1.2558 d13 3.1959 4.4513 6.7013 d17 15.1723 6.4633 2.5116 Bf 9.4854 33.6355 54.86 -Of the 4th lens group at 1/40 times Focusing moving amount) f 38.8006 75.6784 121.8082 R 1621.2778 3113.3359 4977.7728 Moving amount 0.5229 0.3701 0.3292 (The sign of the moving amount Δ is the subject direction is positive) (Condition corresponding value) f1 = 68.3664 f3 = 37.76848 d1w = 2. 1349 d1t = 17.1158 d2w = 4.7612 d2t = 1.2558 β4w = 0.15099 β4t = 0.20497 Bfw = 9.4854 Bft = 54.8653 fw = 38.80 ft = 121.80 (1) f3 /F1=0.552 (2) (d2w-d2t) / (d1t-d1w) = 0.234 (3) β4t / β4w = 1.358 (4) (Bft-Bfw) / (ft-fw) = 0 .547

4 to 9 are graphs showing various aberrations of the first embodiment, which are graphs showing various aberrations at the wide-angle end (shortest focal length state) at infinity and in the intermediate focal length state, respectively. Various aberration diagrams in the in-focus state, various aberration diagrams in the infinity in-focus state at the telephoto end (longest focal length state), various aberration diagrams in the short-distance in-focus state at the wide-angle end (shooting magnification-1 / 40 times), FIG. 9 is a diagram showing various aberrations in a short-distance focus state (shooting magnification −1 / 40 ×) in the intermediate focal length state, and various aberration diagrams in a short-distance focus state (shooting magnification −1 / 40 ×) at the telephoto end. . In each aberration diagram, FN is the F number and H is
Indicates the height of incident light, Y indicates the image height, and A indicates the incident angle of the chief ray. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected from the long-distance object to the short-distance object in each focal length state.

Example 2 FIG. 10 is a diagram showing the structure of a zoom lens according to Example 2 of the present invention. The zoom lens shown in the figure is, in order from the object side, a cemented lens L11 and a biconvex lens L12 that are a biconcave lens and a biconvex lens.
A second lens group G2 including a biconcave lens L21, a biconvex lens L22, and a biconcave lens L23, a third lens group G3 including a positive meniscus lens L3 having a concave surface facing the object side, and A fourth lens group G4 composed of a positive lens component L4 cemented with a convex lens and a negative meniscus lens having a concave surface facing the object side, a positive meniscus lens L51 having a concave surface facing the object side, and a negative meniscus lens having a concave surface facing the object side. L52 and a fifth lens group G5 including a negative meniscus lens L53 having a concave surface facing the object side.

FIG. 10 shows the positional relationship between the lens groups at the wide-angle end, which moves along the optical axis along the zoom orbit indicated by the arrow in FIG. 1 during zooming to the telephoto end. Further, the aperture stop S is arranged between the fourth lens group G4 and the fifth lens group G5, and is used for zooming from the wide-angle end to the telephoto end at the fourth position.
It moves integrally with the lens group G4. Table 2 below lists values of specifications of the second embodiment of the present invention. In Table (2), f is the focal length, FN is the F number, 2ω is the angle of view, Bf is the back focus, and R is the shooting distance.
Further, the refractive index and the Abbe number are d-line (λ = 5, respectively).
87.6 nm).

[0046]

[Table 2] f = 38.80 to 75.57 to 121.82 mm FN = 4.2 to 6.4 to 9.1 2 ω = 59.2 to 31.4 to 19.8 ° Surface number Curvature radius Surface spacing Abbe number Refractive index 1 -100.5729 1.50 33.89 1.80384 2 42.6868 3.51 60.69 1.56384 3- 71.3582 0.13 4 39.2139 3.01 57.03 1.62280 5 -183.9500 (d5 = variable) 6 -31.2574 1.26 46.54 1.80411 7 26.1122 1.00 8 18.5106 2.76 25.80 1.78472 9 -85.1359 1.00 10 -21.4109 1.26 46.80 1.76684 11 301.5949 (d11 = variable) 12 -2139.4562 1.88 69.98 1.51860 13 -17.7170 (d13 = variable) 14 23.2348 3.27 59.60 1.53996 15 -12.1777 1.26 25.35 1.80518 16 -32.5065 0.63 17 ∞ (d17 = variable) (aperture) 18 -64.1787 2.89 25.35 1.80518 19 -18.9047 0.68 20 -25.1436 1.26 45.35 1.84042 21 -120.8813 4.10 22 -12.9063 1.51 49.45 1.77279 23 -53.5807 (Bf) (Variable spacing during zoom) f 38.8004 75.5681 121.8183 d5 2.1349 12.3788 17.2777 d11 3.5163 2.1298 1.0047 d13 4.0186 5.4051 6.5302 d17 14.2797 6.1305 1.8837 Bf 9.4962 31.2449 56. 4th lens group at 1 / 40x magnification Focusing movement amount) f 38.8004 75.5681 121.8183 R 1553.4629 3015.8638 4861.5888 Movement amount 0.5077 0.3860 0.3021 (The sign of the movement amount Δ is positive in the direction of the subject) (Condition corresponding value) f1 = 69.0790 f3 = 34.4379 d1w = 2. 1349 d1t = 17.2777 d2w = 3.5163 d2t = 1.0047 β4w = 0.23882 β4t = 0.13842 Bfw = 9.4962 Bft = 56.5986 fw = 38.80 ft = 121.82 (1) f3 /F1=0.499 (2) (d2w-d2t) / (d1t-d1w) = 0.166 (3) β4t / β4w = 1.302 (4) (Bft-Bfw) / (ft-fw) = 0 .567

11 to 16 are graphs showing various aberrations of the second embodiment, that is, graphs showing various aberrations at the wide-angle end (shortest focal length state) in the infinity state and in the intermediate focal length state. Various aberration diagrams in the in-focus state, various aberration diagrams in the infinity in-focus state at the telephoto end (longest focal length state), various aberration diagrams in the short-distance in-focus state at the wide-angle end (shooting magnification-1 / 40 times), FIG. 9 is a diagram showing various aberrations in a short-distance focus state (shooting magnification −1 / 40 ×) in the intermediate focal length state, and various aberration diagrams in a short-distance focus state (shooting magnification −1 / 40 ×) at the telephoto end. . In each aberration diagram, FN is the F number,
H indicates the height of the incident light, Y indicates the image height, and A indicates the incident angle of the chief ray. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected from the long-distance object to the short-distance object in each focal length state.

Example 3 FIG. 17 is a diagram showing the structure of a zoom lens according to Example 3 of the present invention. The zoom lens shown in the figure is, in order from the object side, a cemented lens L11 and a biconvex lens L12 that are a biconcave lens and a biconvex lens.
A second lens group G2 including a biconcave lens L21, a biconvex lens L22 and a biconcave lens L23, and a third lens group G3 including a biconvex lens L3.
And a fourth lens unit G composed of a cemented positive lens component L4 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side.
4 and a positive meniscus lens L5 having a concave surface facing the object side
1. The fifth lens unit G5 includes a negative meniscus lens L52 having a concave surface facing the object side and a negative meniscus lens L53 having a concave surface facing the object side.

FIG. 17 shows the positional relationship between the lens groups at the wide-angle end, which moves along the optical axis along the zoom orbit shown by the arrow in FIG. 1 during zooming to the telephoto end. Further, the aperture stop S is arranged between the fourth lens group G4 and the fifth lens group G5, and is used for zooming from the wide-angle end to the telephoto end at the fourth position.
It moves integrally with the lens group G4. Table 3 below lists values of specifications of the third embodiment of the present invention. In Table (3), f is the focal length, FN is the F number, 2ω is the angle of view, Bf is the back focus, and R is the shooting distance.
Further, the refractive index and the Abbe number are d-line (λ = 5, respectively).
87.6 nm).

[0050]

[Table 3] f = 38.80 to 77.87 to 134.38 mm FN = 3.9 to 6.5 to 9.5 2 ω = 60.6 to 31.0 to 18.2 ° Surface number Curvature radius Surface spacing Abbe number Refractive index 1 -118.8494 1.50 33.89 1.80384 2 43.4496 3.51 60.69 1.56384 3- 123.1496 0.13 4 39.7137 3.01 57.03 1.62280 5 -151.1848 (d5 = variable) 6 -31.3246 1.26 46.54 1.80411 7 29.6582 0.88 8 20.5366 2.89 25.80 1.78472 9 -121.1359 1.00 10 -25.3972 1.26 46.80 1.76684 11 530.2191 (d11 = variable) 12 158.0 7 1.58913 13 -23.4619 (d13 = variable) 14 25.8414 3.27 59.60 1.53996 15 -13.2417 1.26 25.35 1.80518 16 -39.2875 0.63 17 ∞ (d17 = variable) (aperture) 18 -58.5051 2.89 25.35 1.80518 19 -19.5210 0.13 20 -28.8382 1.26 45.35 1.84042 21 -181.9438 4.65 22 -13.0533 1.51 49.45 1.77279 23 -41.2762 (Bf) (Variable spacing during zoom) f 38.8004 75.5681 121.8183 d5 2.1349 11.0232 17.2356 d11 4.3380 2.7166 1.0047 d13 4.0186 5.6400 7.3506 d17 14.9595 6.2751 1.8837 Bf 9.5605 36.4211 68.9655 -4th lens group at 1/40 times Focusing moving amount) f 38.8004 75.5681 121.8183 R 1553.4629 3015.8638 4861.5888 Moving amount 0.5077 0.3860 0.3021 (The sign of the moving amount Δ is the subject direction is positive) (Conditional value) f1 = 62.0761 f3 = 27.7205 d1w = 2. 1349 d1t = 17.2356 d2w = 4.3380 d2t = 1.0047 β4w = 0.2495 β4t = 0.2220 Bfw = 9.5605 Bft = 68.9655 fw = 38.80 ft = 134.38 (1) f3 /F1=0.447 (2) (d2w-d2t) / (d1t-d1w) = 0.221 (3) β4t / β4w = 1.124 (4) (Bft-Bfw) / (ft-fw) = 0 .622

18 to 23 are graphs showing various aberrations of the third embodiment, that is, graphs showing various aberrations at the wide-angle end (shortest focal length state) at infinity and infinity at intermediate focal length. Various aberration diagrams in the in-focus state, various aberration diagrams in the infinity in-focus state at the telephoto end (longest focal length state), various aberration diagrams in the short-distance in-focus state at the wide-angle end (shooting magnification-1 / 40 times), FIG. 9 is a diagram showing various aberrations in a short-distance focus state (shooting magnification −1 / 40 ×) in the intermediate focal length state, and various aberration diagrams in a short-distance focus state (shooting magnification −1 / 40 ×) at the telephoto end. . In each aberration diagram, FN is the F number,
H indicates the height of the incident light, Y indicates the image height, and A indicates the incident angle of the chief ray. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected from the long-distance object to the short-distance object in each focal length state.

Example 4 FIG. 24 is a diagram showing the structure of a zoom lens according to Example 4 of the present invention. The illustrated zoom lens includes, in order from the object side, a first lens group G1 including a cemented lens L1 including a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a biconcave lens L21,
A second lens group G2 including a positive meniscus lens L22 having a convex surface facing the object side and a negative meniscus lens L23 having a concave surface facing the object side, a biconvex lens L31, and a cemented lens L32 including a biconvex lens and a biconcave lens. A third lens group G3, a fourth lens group G4 composed of a cemented positive lens component L4 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, a cemented lens L51 of a positive lens and a negative lens, and an object The fifth lens group G5 is composed of a negative meniscus lens L52 having a concave surface facing toward the side.

FIG. 24 shows the positional relationship between the lens groups at the wide-angle end, which moves on the optical axis along the zoom orbit shown by the arrow in FIG. 1 during zooming to the telephoto end. Further, the aperture stop S is arranged between the third lens group G3 and the fourth lens group G4, and is used for zooming from the wide-angle end to the telephoto end at the fourth position.
It moves integrally with the lens group G4. Note that the third lens group G3 and the fifth lens group G5 move integrally during zooming. Table (4) below lists values of specifications of the fourth embodiment of the present invention. In Table (4), f is the focal length, FN
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and R represents the shooting distance. Furthermore, the refractive index and the Abbe number show values for the d-line (λ = 587.6 nm), respectively.

[0054]

[Table 4] f = 38.80 to 75.33 to 146.85 mm FN = 3.9 to 6.1 to 9.7 2 ω = 60.4 to 31.0 to 16.4 ° Surface number Curvature radius Surface spacing Abbe number Refractive index 1 120.2315 1.38 23.01 1.86074 2 43.7628 4.40 69.98 1.51860 3 -53.8968 (d3 = variable) 4 -40.1762 1.26 52.30 1.74809 5 20.8189 0.88 6 21.3856 2.76 25.50 1.80458 7 1851.4159 1.60 8 -21.7157 1.26 45.37 1.79668 9 -52.5487 (d9 = variable) 10 27.3726 1.88 60.14 1.62041 11 -52.4243 0.13 12 30.8175 2.51 60. 13 -30.7809 1.26 40.90 1.79631 14 125.5814 (d14 = variable) 15 ∞ 1.88 (aperture) 16 38.5145 2.51 60.23 1.51835 17 -15.3596 1.26 25.35 1.80518 18 -40.1933 (d18 = variable) 19 109.9525 2.89 25.80 1.78472 20 -24.7439 1.26 45.37 1.79668 21 617.7218 4.63 22 -12.9093 1.51 45.37 1.77279 23 -57.6176 (Bf) (Variable spacing during zoom) f 38.7990 75.3280 146.8528 d3 2.2273 7.6100 14.7855 d9 9.7152 4.4285 1.2558 d14 3.7674 7.3613 10.3543 d18 7.6555 4.0613 1.0687 Bf 14.8873 34.1176 67.8124 4th lens at 40 times Focusing movement amount of the lens group) f 38.7990 75.3280 146.8528 R 1614.6686 3093.6601 5986.8050 Movement amount 0.5983 0.5097 0.3958 (The sign of the movement amount Δ is positive in the direction of the subject) (Conditional value) f1 = 111.9170 f3 = 25.1163 d1w = 2.227 d1t = 14.7855 d2w = 9.7152 d2t = 1.258 β4w = 0.6088 β4t = 0.5740 Bfw = 14.8873 Bft = 67.8124 fw = 38.7990 ft = 146.528 ( 1) f3 / f1 = 0.224 (2) (d2w-d2t) / (d1t-d1w) = 0.674 (3) β4t / β4w = 0.943 (4) (Bft-Bfw) / (ft-fw) ) = 0.490

24 to 30 are graphs showing various aberrations of the fourth embodiment, that is, graphs showing various aberrations at the wide-angle end (shortest focal length state) at infinity and infinity at intermediate focal length. Various aberration diagrams in the in-focus state, various aberration diagrams in the infinity in-focus state at the telephoto end (longest focal length state), various aberration diagrams in the short-distance in-focus state at the wide-angle end (shooting magnification-1 / 40 times), FIG. 9 is a diagram showing various aberrations in a short-distance focus state (shooting magnification −1 / 40 ×) in the intermediate focal length state, and various aberration diagrams in a short-distance focus state (shooting magnification −1 / 40 ×) at the telephoto end. . In each aberration diagram, FN is the F number,
H indicates the height of the incident light, Y indicates the image height, and A indicates the incident angle of the chief ray. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in the present embodiment, it is understood that various aberrations are satisfactorily corrected from the long-distance object to the short-distance object in each focal length state.

In the present invention, by introducing at least one aspherical surface, it is possible to obtain higher-performance imaging performance and to simplify the structure. Further, by appropriately moving (decentering) one lens group or a plurality of lens groups in a direction substantially orthogonal to the optical axis,
It is also possible to obtain the so-called anti-vibration effect by correcting the fluctuation of the image position due to camera shake or the like. Furthermore, in the above-described embodiment, an example in which only the fourth lens group G4 moves during focusing is shown, but by moving the fourth lens group G4 and the other lens groups by different amounts of movement, the subject is at a long distance. It is also possible to obtain a better imaging performance over a short distance from.

[0057]

As described above, according to the present invention, it is possible to realize a zoom lens which has a reduced amount of work during focusing, is configured with a small number of lenses, has excellent imaging performance, and is capable of high zooming. be able to.

[Brief description of drawings]

FIG. 1 is a view showing a basic configuration of a zoom lens according to each embodiment of the present invention, a state of movement of each lens unit during zooming from a wide-angle end to a telephoto end, and focusing in a long-distance object to a short-distance object. It is a figure which shows the mode of movement of the 4th lens group G4.

FIG. 2 is a diagram illustrating a focusing method of the present invention.

FIG. 3 is a diagram showing a configuration of a zoom lens according to Example 1 of the present invention.

FIG. 4 is a diagram of various types of aberration in the first embodiment at a wide-angle end and at an infinity in-focus state.

FIG. 5 is a diagram of various types of aberration in the in-focus state at the intermediate focal length state of Example 1;

FIG. 6 is a diagram of various types of aberration in the first embodiment at the telephoto end in the in-focus state at infinity.

FIG. 7 is a diagram of various types of aberration in a short-distance focused state at the wide-angle end according to the first exemplary embodiment.

FIG. 8 is a diagram of various types of aberration in a short-distance focused state in the intermediate focal length state of Example 1.

FIG. 9 is a diagram of various types of aberration in a close-range in-focus state at the telephoto end according to the first exemplary embodiment.

FIG. 10 is a diagram showing a configuration of a zoom lens according to Example 2 of the present invention.

FIG. 11 is a diagram of various types of aberration in a second embodiment at a wide-angle end when focused on an object at infinity;

FIG. 12 is a diagram of various types of aberration in Example 2 in the in-focus state at the intermediate focal length state;

FIG. 13 is a diagram of various types of aberration in Example 2 at the telephoto end in the in-focus state at infinity.

FIG. 14 is a diagram of various types of aberration in a short-distance focus state at the wide-angle end according to the second exemplary embodiment.

FIG. 15 is a diagram of various types of aberration in a short-distance focusing state in the intermediate focal length state of Example 2.

FIG. 16 is a diagram of various types of aberration in a short-distance focus state at the telephoto end according to the second exemplary embodiment.

FIG. 17 is a diagram showing a configuration of a zoom lens according to Example 3 of the present invention.

FIG. 18 is a diagram of various types of aberration in Example 3 at the wide-angle end when focused on an object at infinity;

FIG. 19 is a diagram of various types of aberration in an in-focus state of infinity in the intermediate focal length state of Example 3;

FIG. 20 is a diagram of various types of aberration in the infinity in-focus state at the telephoto end according to the third example.

FIG. 21 is a diagram of various types of aberration in a short-distance focused state at the wide-angle end according to the third example.

FIG. 22 is a diagram of various types of aberration in a short distance in-focus state in the intermediate focal length state of Example 3.

FIG. 23 is a diagram of various types of aberration in a close-range in-focus state at the telephoto end according to the third example.

FIG. 24 is a diagram showing a configuration of a zoom lens according to Example 4 of the present invention.

FIG. 25 is a diagram of various types of aberration in Example 4 at the wide-angle end when focused on an object at infinity;

FIG. 26 is a diagram of various types of aberration in an infinity in-focus state in the intermediate focal length state of Example 4.

FIG. 27 is a diagram of various types of aberration in the fourth embodiment at the telephoto end and in the in-focus state at infinity.

FIG. 28 is a diagram of various types of aberration in a short-distance focusing state at the wide-angle end according to the fourth example.

FIG. 29 is a diagram of various types of aberration in a short distance in-focus state in the intermediate focal length state of Example 4.

FIG. 30 is a diagram of various types of aberration in a short-distance-focused state at the telephoto end according to the fourth example.

[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 stop

Claims (3)

[Claims] 1. A first lens group G1 having a positive refractive power and a second lens group G having a negative refractive power in order from the object side.
2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power, from the wide-angle end to the telephoto end. At the time of zooming, at least the first lens group G1 and the fifth lens group G5 move to the object side, and the first lens group G1 and the second lens group G2
The air gap between the third lens group G3 and the fourth lens group G4 increases, and the air gap between the fourth lens group G4 and the fifth lens group G5 decreases. In the lens, the fourth lens group G from a long-distance object to a short-distance object
4 is moved to the object side for focusing, and the focal length of the first lens group G1 is set to f1.
The focal length of the lens group G3 is f3, the air gap along the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end is d1w, and the first lens group G1 at the telephoto end. And an air gap between the second lens group G2 and the second lens group G2 along the optical axis is d1t, and an air gap along the optical axis between the second lens group G2 and the third lens group G3 at the wide-angle end is set. When d2w is set and the air gap along the optical axis between the second lens group G2 and the third lens group G3 at the telephoto end is set to d2t, 0.15 <f3 / f1 <0.7 0.1 A zoom lens characterized by satisfying a condition of <(d2w-d2t) / (d1t-d1w) <0.85. 2. When the image forming magnification of the fourth lens group G4 at the wide angle end is β4w and the image forming magnification of the fourth lens group G4 at the telephoto end is β4t, 0.8 <β4t / β4w <2 The zoom lens according to claim 1, wherein the zoom lens satisfies the condition (5). 3. The back focus at the wide-angle end is set to Bf.
When w, the back focus at the telephoto end is Bft, the focal length of the entire lens system at the wide-angle end is fw, and the focal length of the entire lens system at the telephoto end is ft, 0.4 <(Bft−Bfw) / The zoom lens according to claim 1, wherein the condition (ft-fw) <0.8 is satisfied.