JP3414499B2 - Zoom lens - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens,
In particular, the angle of view at the wide-angle end includes at least about 73 °,
The angle of view at the telephoto end is about 35 ° or less, and the aperture ratio is 1:
The present invention relates to a zoom lens having a large aperture ratio of about 2.8.

[0002]

2. Description of the Related Art Conventionally, many so-called large-aperture wide-angle zoom lenses have been proposed as a negative group preceding type in which the first lens group has a negative refractive power. For example, JP-A-63-241511, JP-A-5-134184 and the like are disclosed. Both of them are negative-group-leading 4-group zoom lenses, and the first lens group has a function of correcting the image plane position. Therefore, when the rear lens group moves substantially linearly for zooming, the first lens group moves as a quadratic function and has an inflection point in relation to the zoom ratio. Therefore, the change in the entire length of the lens system due to the arrangement of the refractive power is large. In addition, the problem of performance due to the widening of the angle and the increase in the aperture ratio is generally solved by using an aspherical surface. Further, focusing is performed by moving the first lens group, which has a relatively large refractive power, toward the object side, as in the conventional case. Therefore, the aberration variation due to focusing caused by the refractive power arrangement remains a problem, and it is difficult to correct spherical aberration in the telephoto range.

[0003]

The present applicant proposes an optical system in which the total length does not change during zooming in Japanese Patent Laid-Open No. 19169/1993, with the intention of solving the above-mentioned problems. 1 proposal is disclosed in JP-A-6-5120.
I went to No. 3.

However, the problem with the large-diameter wide-angle zoom lens has not been solved, and the focusing proposed above has a problem that the finite object distance is limited.

The present invention has been made in view of the above problems of the prior art, and an object thereof is that the angle of view at the wide-angle end includes at least about 73 ° and the angle of view at the telephoto end is 35 °.
By providing a zoom lens having a large aperture ratio of about 1: 2.8 or less and a stable aperture performance from infinity to a close-up distance, it is possible to obtain a stable imaging performance. is there.

[0006]

A zoom lens according to the present invention which achieves the above object has a first negative refractive power in order from the object side.
It is composed of a lens group, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power, from the wide angle end to the telephoto end. Zooming is performed by fixing the first lens group and the fifth lens group, and moving the second lens group to the fourth lens group toward the object side while changing the relative distances respectively, and from the object at infinity to the object at finite distance. Focusing on the first lens group is divided into a front lens group (G ₁₁ ) having negative refractive power, a middle lens group (G ₁₂ ) having positive refractive power, and a rear lens group (G ₁₃ ) having negative refractive power, and the rear lens group (G ₁₃ ) G ₁₃ ) is fixed, the front group (G ₁₁ ) and the middle group (G ₁₂ ) are moved to the object side, respectively, and the following conditions are satisfied. . 0.5 <| φ ₁₁ / φ ₁₂ | <3.0 (3) 1 <ΔG ₁₁ / ΔG ₁₂ <1.8 (4) where φ ₁₁ is in front of the first lens group The refractive power of the group (G ₁₁ ), φ ₁₂ is the refractive power of the middle group (G ₁₂ ) in the first lens group, Δ
G ₁₁ is the amount of focusing movement to the shortest shooting distance of the front lens unit (G ₁₁ ) in the first lens unit, ΔG ₁₂ is the amount of focusing movement to the shortest shooting distance of the middle lens unit (G ₁₂ ) in the first lens unit The reference position of the focusing movement amount is the infinite object position, and a negative sign is taken when moving to the object side.

Another zoom lens according to the present invention comprises, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power.
It is composed of a lens group, a third lens group having a negative refracting power, a fourth lens group having a positive refracting power, and a fifth lens group having a positive refracting power, and zooming from the wide-angle end to the telephoto end is performed with the first lens group. Focusing from an object at infinity to an object at finite distance is performed by moving the second lens group to the fourth lens group toward the object side while changing the relative spacing, while fixing the fifth lens group. Is divided into a front group (G ₁₁ ) having a negative refractive power, a middle group (G ₁₂ ) having a positive refractive power, and a rear group (G ₁₃ ) having a negative refractive power, and the rear group (G ₁₃ ) is fixed, performed by moving the axial distance to each object side is variable of the front group (G ₁₁₎ and Chugun (G _12), said front group (G ₁₁₎ is
It is characterized in that at least two negative lens components are formed and the following conditions are satisfied. _{0.2 <| φ 1W / φ W} | <0.95 ··· (1) 0.1 <φ 234W / φ W <1.2 ··· (2) However, φ _1W, φ _234W wide-angle end In the above, the refracting power of the first lens group, the combined refracting power from the second lens group to the fourth lens group, and φ _W are the refracting powers at the wide-angle end of the entire system. Still another zoom lens according to the present invention, in order from the object side,
A first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, and a fifth lens group having positive refractive power, Zooming from the wide-angle end to the telephoto end is performed by fixing the first lens group and the fifth lens group and moving the second lens group to the fourth lens group toward the object side while changing the relative intervals, respectively. Focusing from a distant object to a finite object is performed by dividing the first lens group into a front group (G ₁₁ ) having negative refractive power, a middle group (G ₁₂ ) having positive refractive power, and a rear group (G ₁₃ ) having negative refractive power. Then, in the state where the rear group (G ₁₃ ) is fixed, the axial distance between the front group (G ₁₁ ) and the middle group (G ₁₂ ) is made variable, and each is moved toward the object side. It is characterized by satisfying the conditions. _{0.2 <| φ 1W / φ W} | <0.95 ··· (1) 0.1 <φ 234W / φ W <1.2 ··· (2) 1 <ΔG 11 / ΔG 12 <1. 8 (4) where φ _1W and φ _234W are the refracting power of the first lens group at the wide-angle end, the combined refracting power from the second lens group to the fourth lens group, and φ _W is the wide angle of the entire system. The refractive power at the edge, ΔG ₁₁
Is the amount of focusing movement to the shortest shooting distance of the front group (G ₁₁ ) in the first lens group, ΔG ₁₂ is the amount of focusing movement to the shortest shooting distance of the middle group (G ₁₂ ) in the first lens group, It is assumed that the reference position of the amount of focusing movement is the infinite object position, and a negative sign is taken when moving to the object side.

[0008]

In the present invention, the reason why the above structure is adopted and the function thereof will be described. As the large-diameter wide-angle zoom lens, there are the negative group leading type and the positive group leading type zoom lenses as described above, but for widening the angle, the former of the reverse telephoto type has been proposed in many cases. The reason for this is that in the latter case, the first lens group having a positive refracting power, which takes into account even focusing, becomes large. On the other hand, in the negative group preceding type, since the refractive power of the first lens group becomes large, if this is used as the focusing lens group, the movement amount can be suppressed.

However, since the light beam incident on the second lens group is divergent, spherical aberration and coma aberration tend to be significantly changed in the telephoto range. Therefore, it is considered that this type has a difficulty in increasing the aperture ratio. In addition, it has the characteristic that the overall lens length becomes considerably large at the wide-angle end where the overall length becomes short when the zoom ratio is increased. As a solution to this, the use of an aspherical surface is generally used, but the problem of aberration variation due to focusing cannot be solved.

Therefore, the present invention proposes the following lens structure in consideration of operability and in order to maintain stable image forming performance even in short-distance shooting. That is, in order from the object side, the first lens group having negative refractive power and the second lens group having positive refractive power
The third lens group having a negative refractive power, the fourth lens group having a positive refractive power, and the fifth lens group having a positive refractive power are used. Zooming from the wide-angle end to the telephoto end is performed from the first lens group. Focusing from an object at infinity to an object at finite distance is performed by moving at least three lens groups in the fifth lens group, and the first lens group has a negative refractive power front group (G ₁₁ ).
And the middle group (G ₁₂ ) of positive refracting power and the rear group (G ₁₃ ) of negative refracting power, and the front group (G ₁₁ ) and the middle group (G ₁₂ ) each move toward the object side. Is a zoom lens.

One feature of the zoom lens of the present invention is that the first lens group as a fixed lens group has a strong divergent refractive power. Further, when the second lens group having a positive refractive power, which is a movable lens group, is moved substantially linearly, the third lens group having a negative refractive power is caused to function for image plane position correction, so that the fourth lens group having a positive refractive power is corrected. Is a movement that is almost linear. In addition, a fixed fifth lens group, which has a function of raising the image plane, is placed behind. FIG. 1 shows this movement locus. In the figure,
The first to fifth lens groups are indicated by G1 to G5, respectively. The front lens group, the middle lens group, and the rear lens group of the first lens group G1 are denoted by G ₁₁ , G ₁₂ , and G ₁₃ , respectively.

In the wide-angle range, the first lens unit having a negative refractive power has a large distance on the optical axis from the aperture stop and a large incident angle of the off-axis chief ray, so that the distortion aberration developed as a function of the angle of view is large. A difficulty is likely to occur between the correction of coma and the coma. Therefore, adoption of an aspherical surface is desired. In addition, it is necessary to correct spherical aberration, which is overcorrected in the telephoto range, in the second lens group.

Further, the movement of the third lens unit during zooming has a small effect of increasing the magnification, but on the other hand, it is effective for correcting the curvature of field. Further, the fourth lens group has a multiplying effect at the time of zooming. Further, since the fixed fifth lens group has a positive refracting power, it is possible to prevent the refracting powers of the first to fourth lens groups from increasing at the same time as increasing the refracting powers of the respective lens groups. Then it becomes advantageous. Further, in order to satisfactorily correct aberrations, it is desirable to satisfy the following conditional expression.

0.2 <| φ _1W / φ _W | <0.95 ・ ・ ・ (1) 0.1 <φ _234W / φ _W <1.2 ・ ・ ・ (2) However, φ _1W , φ _234W Is the refracting power of the first lens group at the wide-angle end, the combined refracting power from the second lens group to the fourth lens group, and φ _W is the refracting power at the wide-angle end of the entire system.

Conditional expression (1) represents the refracting power of the first lens unit having a divergent action, and is a condition necessary for widening the angle of view. When the upper limit of 0.95 is exceeded, it is effective in reducing the total length of the lens system, but it becomes difficult to correct off-axis aberrations such as field curvature, chromatic aberration of magnification, and distortion. On the other hand, when the lower limit of 0.2 is exceeded, it is advantageous in terms of aberration correction in the first lens group, but there is a tendency for the total length of the lens system and the outer diameter to increase.
Not desirable.

Conditional expression (2) defines the combined refracting power from the second lens group to the fourth lens group having a positive refracting power as a whole. If the upper limit of 1.2 is exceeded, the thick lens component of each lens group will be made large, and it will not be possible to secure a sufficient moving space during zooming due to the advantage in terms of aberration correction, and the scaling factor will be reduced. It is not desirable because it will be necessary.
Further, the off-axis light flux passing position of the fifth lens group is likely to be high, which causes a restriction in the mechanical structure and the camera mirror prohibited area,
The result is undesired. When the lower limit of 0.1 is exceeded,
This leads to the generation of higher-order aberrations, which increases sensitivity to manufacturing errors such as coma and spherical aberration, which is not desirable.

Further, as described above, in the zoom lens of the negative group preceding type, the fluctuation of the spherical aberration during focusing on the telephoto side rather than the wide angle side is remarkably remarkable, and a countermeasure against this is desired. In the present invention, the focusing lens group is the first
Although the lens group is the same as the conventional one, in order to focus from an object at infinity to an object at finite distance, the first lens group is formed of a front lens group (G ₁₁ ) of negative refracting power and a positive refracting power. It is divided into a group (G ₁₂ ) and a rear group (G ₁₃ ) of negative refracting power, and a front group (G ₁₂ )
₁₁ ) and each of the middle group (G ₁₂ ) move toward the object side to realize focusing from an object at infinity to an object at finite distance.

The front lens group (G ₁₁ ) in the first lens group is composed of at least two negative lens components, and the incident off-axis light beam is made gentle to the middle lens group (G ₁₂ ) to reduce the sagittal coma aberration. Suppress the occurrence of. Furthermore, by changing the axial distance between the front lens group (G ₁₁ ) and the middle lens group (G ₁₂ ) during focusing, fluctuations in off-axis aberrations can be easily suppressed. The rear group (G ₁₃ ) of negative refracting power is a field flattener lens used for field curvature correction, and the axial distance from the middle group (G ₁₂ ) is made variable to obtain a stronger effect. It is possible. This idea is common to the idea of floating wide-angle lenses.

In consideration of the degree of aberration variation during aberration correction and focusing, it is desirable to satisfy the following conditional expression. 0.5 <| φ ₁₁ / φ ₁₂ | <3.0 (3) where φ ₁₁ is the refracting power of the front group (G ₁₁ ) in the first lens group, and φ ₁₂ is the first lens group. It is the refractive power of the middle group (G ₁₂ ).

When the upper limit of 3.0 of the conditional expression (3) is exceeded, the diverging action of the front lens group (G ₁₁ ) becomes too strong and the negative lens component must be increased, which causes an increase in field curvature and the like. It is disadvantageous in terms of performance. On the other hand, when the lower limit of 0.5 is exceeded, it is advantageous in terms of aberration correction, but the passing position of the off-axis light beam becomes high, and the lens system becomes large.

The focusing movement amount ratio at the shortest shooting distance between the front lens group (G ₁₁ ) and the middle lens group (G ₁₂ ) in the first lens group should have the following relationship, regardless of changes in the focal lengths. Is desirable.

1 <ΔG ₁₁ / ΔG ₁₂ <1.8 (4) where ΔG ₁₁ is the focusing movement amount to the shortest shooting distance of the front lens group (G ₁₁ ) in the first lens group, and ΔG ₁₂ is It is the focusing movement amount up to the shortest shooting distance of the middle group (G ₁₂ ) in the first lens group, and the reference position of the focusing movement amount is the object position at infinity, and a negative sign is taken when moving to the object side. .

Conditional expression (4) means the relationship of the amount of movement at the time of focusing on an object at a finite distance, and when only the first lens group is moved, aberration fluctuation due to focusing is remarkable,
Only the arrangement of the rear group (G ₁₃ ) has an effect on the fluctuation of the image plane, but it is still not practically sufficient, and the moving speed of the middle group (G ₁₂ ) is delayed from the moving speed of the front group (G ₁₁ ). This makes it possible to suppress aberration fluctuations. Therefore, outside the upper limit of 1.8, the fluctuation of aberration due to focusing in the first lens group becomes large on the contrary, which causes a problem in performance in the lens configuration of the present invention. Also,
When the lower limit of 1 is exceeded, interference between lens components may occur,
In addition, the effect of correcting aberration variation is significantly reduced, which is not desirable.

Next, based on Example 1 which will be described later, the situation of aberration variation will be viewed with a third-order aberration coefficient. Here, Table-1 and Table-2 show the third-order spherical aberration coefficient SA3, third-order coma-aberration coefficient CM3, and third-order astigmatism coefficient AS3 at infinite distance objects at the wide-angle end and the telephoto end and at a close range (1 m or less). .
The sign of the aberration coefficient corresponds to the actual aberration. Further, the focal length to be normalized is the same at the wide-angle end and the telephoto end.

[0025]

[0026]

According to each aberration coefficient at the wide-angle end, although the spherical aberration, astigmatism, and coma aberration change in opposite directions, the aberrations occurring in the lens groups other than the focusing lens group are similar to those of an infinite object. Since the objects at a finite distance do not differ greatly, the amount of aberration generated in the focusing portion contributes to the performance of the entire system. Therefore, as shown in Tables 1 and 2, the front group (G ₁₁ ), the middle group (G ₁₂ ), the rear group (G ₁₃ ).
It can be seen that the correction has been made. At the telephoto end, it can be seen that the spherical aberration fluctuates particularly, but the overcorrected spherical aberration generated in the divergent front group (G ₁₁ ) causes the undercorrected spherical aberration in the middle group (G ₁₂ ). It can be seen that it cancels and compensates. Since the amount generated by the rear group (G ₁₃ ) hardly changes between an object at infinity and an object at finite distance, it can be seen that the effect of the middle group (G ₁₂ ) is extremely important in terms of correcting spherical aberration. .

[0028]

EXAMPLES The zoom lenses of Examples 1 to 3 of the present invention will be described below. Numerical data of each example will be described later, but FIGS. 2 to 4 show lens cross-sectional views of the wide-angle end (a) and the telephoto end (b) of the infinitely distant objects of Examples 1 to 3, respectively.

In the first embodiment, the angle of view from 73.54 ° to 35.
It is a wide-angle large-aperture-ratio zoom lens with an aperture ratio of 54 ° of 1: 2.85. The divergent first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side and a biconcave lens, and the front group G1 thereof.
_The intermediate group G ₁₂ includes a positive meniscus lens having a convex surface directed toward the object side. The rear group G ₁₃ of the field flattener lens is a negative meniscus lens having a convex surface directed toward the object side.

As already mentioned, the front group G ₁₁ and the middle group G ₁₂
The variable spacing makes it possible to correct sagittal coma aberration, which is difficult to correct, and at the same time, it also leads to improvement of two-line blurring, which is a problem in zoom lenses. Further, in correcting the field curvature that represents the flatness of the off-axis image surface, the distance between the middle group G ₁₂ and the rear group G ₁₃ is made variable to solve the aberration variation due to focusing. Second lens unit G having positive refractive power
The refracting power of 2 and the lens configuration play a large role in correcting spherical aberration, and are important because they are related to the aperture ratio limitation on the telephoto side. The lens configuration includes a cemented lens and has a minimum of two positive lens components. In this embodiment, a positive meniscus lens having a convex surface on the object side, a negative meniscus lens having a convex surface on the object side, a cemented lens of a positive meniscus lens having a convex surface on the object side, and a biconvex lens are used. There is.

Further, the third lens group G3 having negative refracting power includes at least one cemented lens of a positive lens and a negative lens so that the variation of chromatic aberration does not become large during the field curvature correction during zooming. I have to. In this embodiment, it is a cemented lens of a positive meniscus lens having a convex surface facing the image side and a biconcave lens, and an aperture is integrally arranged on the object side.

The fourth lens group G4 having a positive refracting power has a cemented lens of a positive lens and a negative lens and one positive lens component, and acts as a relay lens. In this embodiment, a positive meniscus lens having a convex surface facing the image side, a biconvex lens,
It is composed of a cemented lens of a negative meniscus lens with a convex surface facing the image side.

The fifth lens group G5 is a positive lens component, and has an important function of correcting the tilt of the image plane remaining in the first lens group G1 to the fourth lens group G4. By disposing this lens group, it is possible to prevent the refractive power of each lens group from the first lens group G1 to the fourth lens group G4 from becoming unnecessarily large. In this embodiment, it is a cemented lens of a biconvex lens and a negative meniscus lens having a convex surface facing the image side.

The aspherical surface is the first lens group of the first lens group G1.
It is used for the three surfaces of the back surface of the lens component, the front surface of the final lens component of the second lens group G2, and the front surface of the first lens component of the fourth lens group G4. The aspherical surface used for the back surface has a great effect on the correction of the distortion aberration, and by correcting this, the deterioration of the coma aberration is less likely to occur. The aspherical surface used in the second lens group G2 is intended to correct axial spherical aberration in the telephoto range. The aspherical surface used in the fourth lens group G4 is used to effectively correct off-axis coma.

Aberration diagrams of Example 1 are shown in FIGS.
FIG. 5 is an aberration diagram for an object at infinity at the wide-angle end, and FIG. 6 is an aberration diagram for an object at finite distance at the wide-angle end at 0.67 m from the apex of the first lens surface. The aberration diagram shows spherical aberration, astigmatism, lateral chromatic aberration, and distortion. same as below. As can be seen from FIGS. 5 and 6, it is clear that the aberration variation due to focusing is very small. Further, FIG. 7 shows an aberration diagram for an object at infinity at an intermediate focal length, and FIG. 8 shows an aberration diagram for an object at finite distance at an intermediate focal length at 0.89 m. Further, FIG. 9 shows an aberration diagram of an object at infinity at the telephoto end, and FIG. 10 shows an aberration diagram of a finite object at the telephoto end at 0.98 m. It is shown that the aberration variation during focusing is suppressed to be small in all cases.

In the state of FIG. 6, the front group G ₁₁ and the middle group G _11
12 distance (d ₄₎ is increased from 1.945 at infinity object to 2.631, the spacing of the middle group G ₁₂ and the rear group G ₁₃ (d
₆ ) is from 0.500 to 3.710 for an object at infinity
Increase to. In the state of FIG. 8, the distance (d ₄ ) between the front group G ₁₁ and the middle group G ₁₂ is from 1.945 to 2.
The distance (d ₆ ) between the middle group G ₁₂ and the rear group G ₁₃ increases from 0.500 at an object at infinity to 4.303. In the state of FIG. 10, the distance (d ₄ ) between the front group G ₁₁ and the middle group G ₁₂ is from 1.945 to 2.0 at the time of an object at infinity.
96, and the distance (d ₆ ) between the middle group G ₁₂ and the rear group G ₁₃ increases from 0.500 at an object at infinity to 3.889.

The second embodiment is a wide-angle, large-aperture-ratio zoom lens having an aperture ratio of 1: 2.85 with a field angle of 73.58 ° to 35.59 °. As compared with Example 1, the fifth lens group G5
Is composed of one positive lens component.

The first lens group G1 is a negative meniscus lens having a convex surface directed toward the object side and a biconcave lens, and its front group G ₁₁ is composed of:
Middle group G _{12 with} a positive meniscus lens with the convex surface facing the object side
With a negative meniscus lens with a convex surface facing the object side.
₁₃ are composed respectively. The second lens group G2 includes a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, a cemented lens of a positive meniscus lens having a convex surface facing the object side, and a biconvex lens. is doing.

The third lens group G3 is composed of a cemented lens of a positive meniscus lens having a convex surface facing the image side and a biconcave lens, and an aperture is integrally arranged on the object side. The fourth lens group G4 includes a positive meniscus lens having a convex surface directed toward the image side, and a cemented lens including a biconvex lens and a biconcave lens. The fifth lens group G5 includes the biconvex lens 1
It consists of one sheet. The aspherical surface is the first lens of the first lens group G1.
It is used for the three surfaces of the back surface of the lens component, the front surface of the final lens component of the second lens group G2, and the back surface of the final lens component of the fourth lens group G4.

Aberration diagrams of Example 2 are shown in FIGS. FIG. 11 shows aberrations at an object at infinity at the wide-angle end, FIG. 12 shows aberrations at an object at finite distance at the wide-angle end at 0.67 m from the apex of the first lens surface, and FIG. 13 shows aberration diagrams at an object at infinity at an intermediate focal length. FIG. 14 shows an aberration diagram at 0.89 m for a finite object at the intermediate focal length, FIG. 15 shows an aberration diagram for an infinite object at the telephoto end, and FIG.
The aberration diagram at 98 m is shown in FIG.

In the state of FIG. 12, the distance (d ₄ ) between the front group G ₁₁ and the middle group G ₁₂ is 2.812 when an object is at infinity.
The distance (d ₆ ) between the middle group G ₁₂ and the rear group G ₁₃ increases from 0.500 to 5.2 at an object at infinity.
Increase to 76. In the state of FIG. 14, the front group G ₁₁ and the middle group G
₁₂ distance (d ₄₎ is increased from 2.812 at infinity object to 2.949, the spacing of the middle group G ₁₂ and the rear group G ₁₃ (d
₆ ) is from 0.500 to 4.440 for an infinite object
Increase to. In the state of FIG. 16, the distance between the front group G ₁₁ and Chugun G ₁₂ (d ₄₎ is infinity increased from 2.812 at the object at the time of 2.964, the distance between the middle lens group G ₁₂ rear group G ₁₃ ( d ₆ ) is from 0.500 to 3.9 when the object is at infinity.
Increase to 88.

In the third embodiment, the angle of view is from 73.45 ° to 35.
It is a wide-angle large-aperture-ratio zoom lens with an aperture ratio of 54 ° of 1: 2.85. This example has the effect that the outer diameter of the first lens group G1 can be made extremely small. Also,
In this embodiment, a part of the fourth lens group G4 is an air lens.

The first lens group G1 is composed of two negative meniscus lenses having a convex surface facing the object side, the front group G ₁₁ thereof, and a positive meniscus lens having a convex surface facing the object side is the middle group G ₁₂ ; The negative meniscus lens having the convex surface facing toward each other constitutes the rear group G ₁₃ . The second lens group G2 includes a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, a cemented lens of a positive meniscus lens having a convex surface facing the object side, and a biconvex lens. is doing.

The third lens group G3 is composed of a cemented lens of a positive meniscus lens having a convex surface facing the image side and a biconcave lens, and an aperture is integrally arranged on the object side. The fourth lens group G4 includes a biconvex lens, a positive meniscus lens having a convex surface directed toward the image side, and a negative meniscus lens having a convex surface directed toward the image side. In addition, the fifth lens group G5
Consists of one biconvex lens. The aspherical surface is the back surface of the first lens component of the first lens group G1, the second lens group G2.
Are used for the three surfaces of the front surface of the final lens component of and the back surface of the final lens component of the fourth lens group G4.

Aberration diagrams of the third embodiment are shown in FIGS. FIG. 17 shows aberrations of an object at infinity at the wide-angle end, FIG. 18 shows aberrations of a finite object at the wide-angle end at 0.66 m from the apex of the first lens surface, and FIGS. 20 shows an aberration diagram at 0.88 m for a finite object at the intermediate focal length, FIG. 21 shows an aberration diagram for an infinite object at the telephoto end, and FIG.
The aberration diagram at 97 m is shown in FIG.

In the state shown in FIG. 18, the distance (d ₄ ) between the front group G ₁₁ and the middle group G ₁₂ is 2.266 when an object at infinity is used.
From 3.043 to 3.095, the distance (d ₆ ) between the middle group G ₁₂ and the rear group G ₁₃ is changed from 0.543 to 5.5 at an object at infinity.
42. In the state of FIG. 20, the front group G ₁₁ and the middle group G
₁₂ distance (d ₄₎ is increased from 2.266 at infinity object to 2.578, the spacing of the middle group G ₁₂ and the rear group G ₁₃ (d
₆ ) is from 0.543 to 6.053 for an object at infinity
Increase to. In the state of FIG. 22, the distance between the front group G ₁₁ and Chugun G ₁₂ (d ₄₎ is infinity increased from 2.266 at the object at the time of 2.624, the distance between the middle lens group G ₁₂ rear group G ₁₃ ( d ₆ ) is 0.543 to 5.1 for an infinitely distant object.
Increase to 60.

The numerical data of each example are shown below.
Symbols are other than the above, f is the focal length of the entire system, F _NO is the F number, 2ω is the angle of view, r ₁ , r ₂ ... Is the radius of curvature of each lens surface, and d ₁ , d ₂ ... Is between each lens surface. Interval, n _d1 , n _d2 ...
Is the d-line refractive index of each lens, and ν _d1 , ν _d2 ... Is the Abbe number of each lens. The aspherical shape is expressed by the following equation, where x is the traveling direction of light on the optical axis and y is the direction orthogonal to the optical axis. ^{x = (y 2 / r)} / [1+ {1- (y / r) 2} 1/2]
＋ A ₄ y ⁴ ＋ A ₆ y ⁶ ＋ A ₈ y ⁸ ＋ A ₁₀ y ¹⁰ However, r is the paraxial radius of curvature, and A ₄ , A ₆ , A ₈ , and A ₁₀ are the 4th, 6th, 8th, and 10th orders, respectively. It is an aspherical coefficient.

Example 1 f = 28.950 ~ 52.001 ~ 67.501 F _NO = 2.85 ~ 2.85 ~ 2.85 2ω = 73.4 ° ~ 45.2 ° ~ 35.4 ° r ₁ = 118.8694 d ₁ = 1.7000 n _d1 = 1.60342 ν _d1 = 38.01 r ₂ = 24.8027 (aspherical surface) d ₂ = 11.5689 r ₃ = -96.2164 d ₃ = 1.7000 n _d2 = 1.49782 ν _d2 = 66.83 r ₄ = 147.6071 d ₄ = 1.9451 r ₅ = 57.7091 d ₅ = 4.3718 n _d3 = 1.80518 ν _d3 = 25.43 r ₆ = 253.0803 d ₆ = 0.5000 r ₇ = 84.6626 d ₇ = 1.7000 n _d4 = 1.49700 ν _d4 = 81.61 r ₈ = 46.9601 d ₈ = (variable) r ₉ = 45.5868 d ₉ = 4.4110 n _d5 = 1.80610 ν _d5 = 40.95 r ₁₀ = 140.6935 d ₁₀ = 0.1000 r ₁₁ = 65.6584 d ₁₁ = 1.7000 n _d6 = 1.80518 ν _d6 = 25.43 r ₁₂ = 23.2774 d ₁₂ = 8.1471 n _d7 = 1.69680 ν _d7 = 55.52 r ₁₃ = 162.1932 d ₁₃ = 0.1000 r ₁₄ = 54.7604 (aspherical surface) d ₁₄ = 4.6107 n _d8 = 1.81554 ν _d8 = 44.36 r ₁₅ = -706.7788 d ₁₅ = (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 2.5400 r ₁₇ = -101.2008 d ₁₇ = 5.1588 n _d9 = 1.78470 ν _d9 = 26.22 r _{1 8} = -17.6567 d ₁₈ = 1.7000 n _d10 = 1.79952 ν _d10 = 42.24 r ₁₉ = 44.0678 d ₁₉ = (Variable) r ₂₀ = -56.6426 (aspherical) d ₂₀ = 5.8584 n _d11 = 1.80100 ν _d11 = 34.97 r ₂₁ = -34.3019 d ₂₁ = 0.1000 r ₂₂ = 99.3499 d ₂₂ = 8.8319 n _d12 = 1.56873 ν _d12 = 63.16 r ₂₃ = -22.1708 d ₂₃ = 0.5000 n _d13 = 1.80518 ν _d13 = 25.43 r ₂₄ = -150.1097 d ₂₄ = (variable) _{r 25 = 263.2085 d 25 = 5.5248} n d14 = 1.77250 ν d14 = 49.66 r 26 = -72.7759 d 26 = 1.7000 n d15 = 1.80518 ν d15 = 25.43 r 27 = -81.9754 Aspheric coefficient 2nd surface A ₄ = -0.40787 × 10 ^-5 A ₆ = -0.69357 × 10 ^-8 A ₈ = 0.80237 × 10 ^-11 A ₁₀ = -0.36456 × 10 ^-13 14th surface A ₄ = -0.89659 × 10 ^-6 A ₆ = -0.44 490 × 10 ^-9 A ₈ = 0.27638 × 10 ^-11 A ₁₀ = -0.23523 × 10 ^-14 20th surface A ₄ = 0.13481 × 10 ^-5 A ₆ = -0.14582 × 10 ^-7 A ₈ = 0.11878 × 10 ^-9 A ₁₀ = -0.26708 × 10 ^-12
.

Example 2 f = 28.930 ~ 52.000 ~ 67.400 F _NO = 2.85 ~ 2.86 ~ 2.85 2ω = 73.6 ° ~ 45.2 ° ~ 35.6 ° r ₁ = 147.0443 d ₁ = 1.7000 n _d1 = 1.60562 ν _d1 = 43.72 r ₂ = 25.6888 (aspherical surface) d ₂ = 10.9702 r ₃ = -102.0030 d ₃ = 1.7000 n _d2 = 1.51454 ν _d2 = 54.69 r ₄ = 130.8939 d ₄ = 2.8119 r ₅ = 60.1551 d ₅ = 4.5829 n _d3 = 1.80518 ν _d3 = 25.43 r ₆ = 392.2320 d ₆ = 0.5000 r ₇ = 111.5955 d ₇ = 1.7000 n _d4 = 1.50048 ν _d4 = 65.99 r ₈ = 50.3553 d ₈ = (variable) r ₉ = 47.3815 d ₉ = 4.4051 n _d5 = 1.79952 ν _d5 = 42.24 r ₁₀ = 158.6478 d ₁₀ = 2.4675 r ₁₁ = 77.8646 d ₁₁ = 1.7000 n _d6 = 1.80518 ν _d6 = 25.43 r ₁₂ = 24.5247 d ₁₂ = 8.2319 n _d7 = 1.69680 ν _d7 = 55.52 r ₁₃ = 271.7259 d ₁₃ = 0.1000 r ₁₄ = 54.9531 (aspherical surface) d ₁₄ = 4.7526 n _d8 = 1.81554 ν _d8 = 44.36 r ₁₅ = -744.5762 d ₁₅ = (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 2.5400 r ₁₇ = -102.4460 d ₁₇ = 5.1580 n _d9 = 1.78472 ν _d9 = 25.71 r ₁₈ = -18.4708 d ₁₈ = 1.7000 n _d10 = 1.80440 ν _d10 = 39.58 r ₁₉ = 54.8323 d ₁₉ = (variable) r ₂₀ = -49.2201 d ₂₀ = 4.6200 n _d11 = 1.83481 ν _d11 = 42.72 r ₂₁ = -33.7462 d _{21 = 0.1000 r 22 = 67.7196 d 22} = 7.1886 n d12 = 1.56873 ν d12 = 63.16 r 23 = -28.7406 d 23 = 0.5000 n d13 = 1.74000 ν d13 = 28.29 r 24 = 251.1481 ( aspherical) d ₂₄ = (variable) r ₂₅ = 147.6334 d ₂₅ = 5.6225 n _d14 = 1.61700 ν _d14 = 62.79 r ₂₆ = -83.6457 Aspheric coefficient 2nd surface A ₄ = -0.34861 × 10 ^-5 A ₆ = -0.52512 × 10 ^-8 A ₈ = 0.38616 × 10 ^-11 A ₁₀ = -0.23053 × 10 ^-13 14th surface A ₄ = -0.57723 × 10 ^-6 A ₆ = -0.89606 x 10 ^-9 A ₈ = 0.38110 x 10 ^-11 A ₁₀ = -0.43244 x 10 ^-14 24th surface A ₄ = 0.23759 x 10 ^-5 A ₆ = 0.23187 x 10 ^-8 A ₈ = -0.61246 × 10 ^-11 A ₁₀ = 0.75478 × 10 ^-14
.

Example 3 f = 28.950 ~ 51.999 ~ 67.399 F _NO = 2.85 ~ 2.86 ~ 2.85 2ω = 73.4 ° ~ 45.2 ° ~ 35.6 ° r ₁ = 145.5081 d ₁ = 1.7000 n _d1 = 1.61700 ν _d1 = 62.80 r ₂ = 25.9863 (aspherical surface) d ₂ = 9.0598 r ₃ = 2588.2205 d ₃ = 1.7000 n _d2 = 1.49700 ν _d2 = 81.61 r ₄ = 67.4698 d ₄ = 2.2659 r ₅ = 45.7230 d ₅ = 5.0194 n _d3 = 1.80610 ν _d3 = 33.27 r ₆ = 160.2035 d ₆ = 0.5427 r ₇ = 119.9935 d ₇ = 1.7000 n _d4 = 1.58215 ν _d4 = 42.09 r ₈ = 43.1309 d ₈ = (variable) r ₉ = 42.3538 d ₉ = 4.3924 n _d5 = 1.83481 ν _d5 = 42.72 r ₁₀ = 106.6088 d ₁₀ = 0.1000 r ₁₁ = 68.7133 d ₁₁ = 1.7000 n _d6 = 1.84666 ν _d6 = 23.88 r ₁₂ = 26.8981 d ₁₂ = 6.6749 n _d7 = 1.69680 ν _d7 = 55.53 r ₁₃ = 133.9447 d ₁₃ = 0.1000 r ₁₄ = 41.9880 (aspherical surface) d ₁₄ = 5.3467 n _d8 = 1.81554 ν _d8 = 44.36 r ₁₅ = -7498.9818 d ₁₅ = (variable) r ₁₆ = ∞ (aperture) d ₁₆ = 2.5400 r ₁₇ = -60.0377 d ₁₇ = 3.5236 n _d9 = 1.84666 ν _d9 = 23.88 r ₁₈ = -23.3751 d ₁₈ = 1.7000 n _d10 = 1.80400 ν _d10 = 46.58 r ₁₉ = 46.3105 d ₁₉ = (Variable) r ₂₀ = 72.4846 d ₂₀ = 4.6200 n _d11 = 1.69680 ν _d11 = 55.53 r ₂₁ = -30.7488 d ₂₁ = 0.1000 r ₂₂ = -58.8016 d ₂₂ = 3.4860 n _d12 = 1.61117 ν _d12 = 55.92 r ₂₃ = -30.7002 d ₂₃ = 0.5000 r ₂₄ = -26.1241 d ₂₄ = 1.7000 n _d13 = 1.84666 ν _d13 = 23.88 r ₂₅ = -145.4460 ( Aspherical surface) d ₂₅ = (variable) r ₂₆ = 172.0449 d ₂₆ = 4.5171 n _d14 = 1.83481 ν _d14 = 42.72 r ₂₇ = -131.1502 Aspheric coefficient 2nd surface A ₄ = -0.37627 × 10 ^-5 A ₆ = -0.46229 × 10 ^-8 A ₈ = -0.64026 × 10 ^-12 A ₁₀ = -0.16 800 × 10 ^-13 14th surface A ₄ = -0.83267 × 10 ^-6 A ₆ = -0.25 105 × 10 ^-8 A ₈ = 0.41376 × 10 ^-11 A ₁₀ = 0.73187 × 10 ^-14 25th surface A ₄ = 0.38463 × 10 ^-5 A ₆ = 0.65925 × 10 ^-8 A ₈ = -0.22350 x 10 ^-10 A ₁₀ = 0.19856 x 10 ^-13
.

Next, the values of the conditional expressions (4) in the above Examples 1 to 3 are shown in Tables 3 and 4 below.

[0052]

[0053]

As is apparent from the above description, with the above-described structure of the present invention, in the wide-angle, large-aperture-ratio zoom lens, stable focusing can be achieved, including focusing from infinity to a close-up distance, which has been difficult in the past. It was possible to obtain imaging performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a locus of movement of each group during zooming of a zoom lens of the present invention.

FIG. 2 is a lens cross-sectional view of a wide-angle end (a) and a telephoto end (b) of an object at infinity according to Example 1 of the zoom lens of the present invention.

FIG. 3 is a lens cross-sectional view similar to FIG. 2 of Example 2.

FIG. 4 is a lens cross-sectional view similar to FIG. 2 of Example 3.

FIG. 5 is an aberration diagram of an object at infinity at the wide-angle end according to Example 1.

FIG. 6 is an aberration diagram of an object at finite distance at the wide-angle end of Example 1.

FIG. 7 is an aberration diagram for an object at infinity with an intermediate focal length in Example 1.

FIG. 8 is an aberration diagram of an object at finite distance with an intermediate focal length of Example 1.

FIG. 9 is an aberration diagram of an object at infinity at the telephoto end according to Example 1.

FIG. 10 is an aberration diagram of a finite object at the telephoto end according to Example 1.

FIG. 11 is an aberration diagram of an object at infinity at the wide-angle end according to Example 2.

FIG. 12 is an aberration diagram of an object at finite distance at the wide-angle end according to Example 2.

FIG. 13 is an aberration diagram of an object at infinity with an intermediate focal length in Example 2.

FIG. 14 is an aberration diagram of an object at finite distance with an intermediate focal length of Example 2.

FIG. 15 is an aberration diagram of an object at infinity at the telephoto end according to Example 2.

FIG. 16 is an aberration diagram of a finite object at the telephoto end according to Example 2.

FIG. 17 is an aberration diagram of an object at infinity at the wide-angle end according to Example 3.

FIG. 18 is an aberration diagram of an object at finite distance at the wide-angle end according to Example 3.

FIG. 19 is an aberration diagram of an object at infinity with an intermediate focal length in Example 3.

FIG. 20 is an aberration diagram of an object at finite distance with an intermediate focal length in Example 3.

FIG. 21 is an aberration diagram of an object at infinity at the telephoto end according to Example 3.

FIG. 22 is an aberration diagram of a finite object at the telephoto end according to Example 3.

[Explanation of symbols]

G1 ... middle lens group of the first lens group G2 ... the second lens group G3 ... third lens group G4 ... fourth lens group G5 ... front group G ₁₂ ... the first lens group in the fifth lens group G ₁₁ ... the first lens group G ₁₃ ... rear group of the first lens group

Claims (5)

(57) [Claims] 1. A first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, a fourth lens group having a positive refracting power, and a positive refracting power in order from the object side. The fifth lens group of power is used, and for zooming from the wide-angle end to the telephoto end, the first lens group and the fifth lens group are fixed, and the second lens group is fixed.
While changing the relative distance from the lens group to the fourth lens group,
Performed by moving Luo object side, infinity focusing from an object to a finite distance object is a first lens group having negative refracting power of the front group (G ₁₁₎ and the positive refractive power middle lens group and (G ₁₂₎ negative divided into groups (G ₁₃₎ after the power, while fixing the rear group (G _13), it is performed by moving Chugun the (G ₁₂₎ respectively on the object side to the front group (G ₁₁₎ And a zoom lens characterized by satisfying the following conditions. 0.5 <| φ ₁₁ / φ ₁₂ | <3.0 (3) 1 <ΔG ₁₁ / ΔG ₁₂ <1.8 (4) where φ ₁₁ is in front of the first lens group The refractive power of the group (G ₁₁ ), φ ₁₂ is the refractive power of the middle group (G ₁₂ ) in the first lens group, Δ
G ₁₁ is the amount of focusing movement to the shortest shooting distance of the front lens unit (G ₁₁ ) in the first lens unit, ΔG ₁₂ is the amount of focusing movement to the shortest shooting distance of the middle lens unit (G ₁₂ ) in the first lens unit The reference position of the focusing movement amount is the infinite object position, and a negative sign is taken when moving to the object side. 2. A first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, a fourth lens group having a positive refracting power, and a positive refracting power in order from the object side. The fifth lens group of power is used, and for zooming from the wide-angle end to the telephoto end, the first lens group and the fifth lens group are fixed, and the second lens group is fixed.
While changing the relative distance from the lens group to the fourth lens group,
Performed by moving Luo object side, infinity focusing from an object to a finite distance object is a first lens group having negative refracting power of the front group (G ₁₁₎ and the positive refractive power middle lens group and (G ₁₂₎ negative divided into groups (G ₁₃₎ after the power, while fixing the rear group (G _13), axial distance of the front group (G ₁₁₎ and Chugun (G ₁₂₎
Was carried out by moving each object side is made variable, before
The front group (G ₁₁ ) has at least two negative lens components.
Form, and the zoom lens satisfies the following condition. _{0.2 <| φ 1W / φ W} | <0.95 ··· (1) 0.1 <φ 234W / φ W <1.2 ··· (2) However, φ _1W, φ _234W wide-angle end In the above, the refracting power of the first lens group, the combined refracting power from the second lens group to the fourth lens group, and φ _W are the refracting powers at the wide-angle end of the entire system. 3. The zoom lens according to claim 2, wherein the following condition is satisfied. 0.5 <| φ ₁₁ / φ ₁₂ | <3.0 (3) where φ ₁₁ is the refracting power of the front group (G ₁₁ ) in the first lens group, and φ ₁₂ is the first lens group. It is the refractive power of the middle group (G ₁₂ ). 4. The method of claim 2 or 3, wherein the zoom lens satisfies the following condition. 1 <ΔG ₁₁ / ΔG ₁₂ <1.8 (4) where ΔG ₁₁ is the focusing movement amount to the shortest shooting distance of the front lens group (G ₁₁ ) in the first lens group, and ΔG ₁₂ is the first lens It is the focusing movement amount up to the shortest shooting distance of the middle group (G ₁₂ ) in the group, and the reference position of the focusing movement amount is the object position at infinity, and a negative sign is taken when moving to the object side. 5. A first lens having negative refractive power in order from the object side.
Group, second lens group having positive refractive power, third lens having negative refractive power
Group, fourth lens group having positive refracting power, and fifth lens group having positive refracting power
Zoom from the wide-angle end to the telephoto end
Fixes the first lens group and the fifth lens group, and the second lens
While changing the relative distance from the lens group to the fourth lens group,
From the object at infinity
Focusing on an object at finite distance causes the first lens group to bend.
Folding power front group (G ₁₁ ) and positive refractive power middle group (G ₁₂ ) and negative refraction
Divided into groups after the force (G _13), the rear group of (G ₁₃₎ fixed
The axial distance between the front group (G ₁₁ ) and the middle group (G ₁₂ )
By moving each object side.
A zoom lens characterized by satisfying the following conditions . _{0.2 <| φ 1W / φ W} | <0.95 ··· (1) 0.1 <φ 234W / φ W <1.2 ··· (2) 1 <ΔG 11 / ΔG 12 <1. 8 (4) However, φ _1W and φ _234W are the first lenses at the wide-angle end, respectively.
Refractive power of the group, composition from the second lens group to the fourth lens group
Refractive power, φ _W, is the refractive power at the wide-angle end of the entire system, and ΔG ₁₁
Up to the shortest shooting distance of the front lens group (G ₁₁ ) in the first lens group
Focusing movement amount, ΔG ₁₂ is the middle group in the first lens group
Focusing movement amount to the shortest shooting distance of (G ₁₂ )
Yes, the reference position for focusing movement is set to the infinity object position.
And take a negative sign when moving to the object side.
It