JPH07151974A - Zoom lens - Google Patents

Abstract

PURPOSE:To provide a zoom lens having a wide angle of view and high variable power ratio while miniaturizing the size over the entire part of the lens by constituting the zoom lens of three lens groups as a whole and forming an adequate aspherical lens at a prescribed lens face. CONSTITUTION:This zoom lens has, successively from an object side, three lens groups; a first group having a negative refracting power, a second group having a positive refracting power and a third group having a negative refracting power. Variable magnification is executed by changing the spacings between the respective lens groups. The zoom lens is so constituted with the object side as to satisfy Hiw>¦(Hbiw¦, Hit>¦Hbit¦ when the incident angles of axial rays on the i-th face at the wide angle end and telephoto end in the case of an infinite object are respectively defined as Hiw(Hiw>0), Hit(Hit>0) and the incident angles of the off-axial main rays of the max. angle of view on the i-th face at the wide angle end and telephoto end as Hbiw, Hbit, respectively. The aspherical face of the shape to intensify the negative refracting power increasingly from the lens center toward the lens periphery is formed on the lens face Ra of the negative refracting power of which the concave face is directed to the object side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens suitable for a 35 mm film photographic camera, a video camera, an SV camera and the like, and in particular, it comprises a plurality of lens groups, for example, a total of three lens groups. By appropriately setting the lens configuration of each lens group of these three groups and providing an aspherical surface of an appropriate shape on a predetermined lens surface, it is possible to easily obtain high optical performance while downsizing the entire lens system. The present invention relates to a zoom lens having a wide angle of view and a high zoom ratio.

[0002]

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

For example, Japanese Laid-Open Patent Publication No. 59-16248 has two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and the zooming is performed by changing the distance between the two lens groups. The so-called short zoom lens is proposed.

Further, in JP-A-2-73216 and JP-A-3-233422, a first group having a negative refractive power, a second group having a positive refractive power, and a second group having a negative refractive power are sequentially arranged from the object side. It proposes a three-group zoom lens having a wide angle of view, which has three lens groups of three groups, and each lens group is moved for zooming.

Further, in Japanese Patent Application Laid-Open No. 2-73216, a first group having a negative refractive power and a second group having a positive refractive power are arranged in order from the object side.
It proposes a four-group zoom lens composed of a third group having a positive refractive power and a fourth group having a negative refractive power, in which each lens group is moved to perform zooming.

On the other hand, as a zoom type, it has two lens groups, a first lens group having a positive refractive power and a second lens group having a negative refractive power in order from the object side. Zoom lenses are often used in small cameras such as lens shutter cameras because it is easy to downsize the entire lens system. The zoom ratio of the two-group zoom lens is 1.6 to 1.6 because only one lens group (second group) performs zooming.
Many are about twice as many. If the zoom ratio of the two-group zoom lens is forcibly increased, the size of the lens system becomes large and it becomes difficult to maintain high optical performance.

In the second group zoom lens, the first group is
Divided into two positive refractive power lens groups, positive overall,
A three-group zoom lens composed of three lens groups having positive and negative refracting power and aiming for high zooming is disclosed in, for example, Japanese Patent Laid-Open No. 3-73907.
Japanese Patent Laid-Open No. 3-282409, Japanese Patent Laid-Open No. 4-3
It is proposed in Japanese Patent No. 7810, Japanese Patent Laid-Open No. 4-76511, and the like.

When an attempt is made to achieve a wide-angle zoom lens system having a half field angle of 35 ° or more with these three-group zoom lenses, the position of the entrance pupil at the time of zooming becomes large, and aberrations at the time of achieving high zooming become large. It becomes difficult to control fluctuations.

[0009]

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

Further, in a zoom lens having a wide angle of view and a high zoom ratio, it is very effective to use an aspherical surface in order to achieve downsizing and high performance of the entire lens system. However, what kind of lens surface should be introduced at this time is very important, and the aberration correction effect of the aspherical surface greatly differs depending on this. Effective aberration correction becomes difficult unless an aspherical surface is introduced into the appropriate lens surface.

For example, the above-mentioned JP-A-3-282409, JP-A-4-37810, and JP-A-4-7651.
According to Japanese Patent Laid-Open No. 1-58, an aspherical surface is introduced into the positive lens in the second lens group so that the positive refracting power becomes weaker as the distance from the optical axis increases. In both cases, the aspherical introduction surface is arranged with a certain distance from the stop on the optical axis, and the variation of aberrations is made by utilizing the fact that the axial ray height or off-axis ray height on the aspherical introduction surface differs due to zooming. Is being corrected. However, if widening the angle and further increasing the magnification,
For example, variations in spherical aberration and off-axis aberrations accompanying this increase, and it becomes difficult to simultaneously correct by this aspherical surface.

In US Pat. No. 5,095,536, in a three-group zoom lens consisting of three lens groups having positive, positive and negative refracting powers, a concave surface is provided on the object side near the stop in the second lens group having positive refracting power. Introducing an aspherical surface on the lens surface with a negative refraction effect. However, if an attempt is made to achieve a wide angle of view and a high zoom ratio in this zoom lens, the amount of movement of each lens group increases and the front lens diameter of the first group also increases, so that the lens system becomes large, and It becomes difficult to satisfactorily correct the aberration variation generated by increasing the refracting power of the lens group with the aspherical surface.

In Japanese Laid-Open Patent Publication No. 3-249614, a wide lens group composed of four lens groups having positive, positive, and negative refractive powers, or four lens groups having positive, negative, positive, and negative refractive powers. Although a zoom lens with a wide angle of view and a high zoom ratio is shown, the number of constituent lenses is large and the effect of the aspherical surface is not sufficiently exerted.

Further, in Japanese Patent Laid-Open No. 3-73907, it is composed of three lens groups having positive, positive and negative refracting powers.
An aspherical surface is introduced into the positive lens near the stop in the second lens unit having at least positive refractive power so that the positive refractive power weakens as the distance from the optical axis increases. This achieves a zoom lens with a wide angle of view, but the number of lenses in the second lens group is large, and the aspherical surface in the same lens group does not effectively contribute to size reduction.

Further, in Japanese Patent Laid-Open No. 3-233422, it is composed of three lens groups having negative, positive and negative refracting powers, and a plurality of aspherical surfaces are introduced in the third lens group. However, the total optical length is about 66 m at the wide-angle end.
It is difficult to say that the total lens length is short, and it is difficult to perform good aberration correction over the entire zooming range when the wide angle is further increased.

According to the present invention, in a zoom lens having a plurality of lens groups, for example, in a zoom lens divided into three groups as a whole, an aspherical surface is applied to a lens surface of an appropriate lens group to obtain a wide angle of view. It is an object of the present invention to provide a zoom lens having high optical performance over the entire zoom range in which various aberrations that become a problem at the time of zooming and high zooming are favorably corrected and the overall lens system is downsized.

[0017]

The zoom lens according to the present invention comprises three lenses, in order from the object side, a first group having a negative refractive power, a second group having a positive refractive power, and a third group having a negative refractive power. The zoom lens has a group, and the distance between each lens group is changed to perform zooming. When an object at infinity is used, the incident heights of the axial ray on the i-th surface at the wide-angle end and the telephoto end are respectively Hiw (Hiw> 0), Hit (Hit> 0),
Letting Hbiw and Hbit be the incident heights of the off-axis chief ray with the maximum angle of view at the wide-angle end and the telephoto end, respectively, Hiw> | Hbiw | ... (1) Hit> | Hbit | ··························································· (2) It is characterized by having an aspherical surface.

[0018]

1 to 5 are schematic views showing the paraxial refractive power arrangements of Examples 1 to 5 of the zoom lens of the present invention. 6 to 10 are numerical examples 1 to be described later of the zoom lens of the present invention.
5 is a lens cross-sectional view at the wide-angle end of FIG. 1 to 5, (A) shows the wide-angle end and (B) shows the telephoto end. Figure 11
To FIG. 13 are aberration diagrams of the numerical example 1 of the present invention at the wide-angle end, the middle, and the telephoto end, and FIGS. 14 to 16 are aberration diagrams of the wide-angle end, the middle, and the telephoto end of the numerical example 2 of the present invention. 19 is an aberration diagram at the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 3 of the present invention, and FIGS.
23 to 25 are aberration diagrams at the telephoto end, and FIGS. 23 to 25 are aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Example 5 of the present invention.

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

The zoom lens according to the present invention comprises a plurality of lens groups. In each of the embodiments shown in FIGS. 1 to 5, the plurality of lens groups are used for convenience as a whole with the first lens unit L1 having a negative refracting power and the lens unit having a positive refracting power. It is divided into three groups, a second group L2 and a third group having negative refractive power. Then, basically, each lens group is moved as indicated by an arrow so that the distance between the first lens unit L1 and the second lens unit L2 and the lens unit distance between the second lens unit L2 and the third lens unit are changed so as to change from the wide angle end to the telephoto end. We are scaling to the edge.

Further, in the case of being constituted by such a plurality of lens groups, a wide angle of view and high zooming can be achieved by providing an aspherical surface of a predetermined shape on the lens surface which satisfies the above-mentioned conditional expressions (1) and (2). Aberration fluctuations at the time of improvement are satisfactorily corrected, and high optical performance is obtained over the entire zoom range.

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

At the wide-angle end, the zoom lens of the present invention is
From the object side, the first lens unit L1 having negative refracting power and the second lens unit L1 having positive refracting power with a certain distance from each other.
2. The third lens unit L3 having a negative refractive power is arranged with a certain distance. By taking such a symmetrical optical arrangement of negative, positive, and negative refracting powers at the wide-angle end, it is possible to strengthen the refracting power of the second lens unit L2, thereby achieving a wide angle of view and downsizing. When this is done, it is possible to favorably correct various aberrations.

Further, the first lens unit L1 having a negative composite refractive power and the second lens unit L2 having a positive composite refractive power are arranged with a certain distance therebetween to form a retrofocus type. This makes it easy to secure the back focus, which is a problem when widening the angle of view. The second lens unit L2 is composed of a second lens unit L2a having a positive refractive power, a second lens unit L2b having a negative refractive power, and a second lens unit L2c having a positive refractive power from the object side. Are arranged so that they are close to each other, and the second group L
The various aberrations generated in 2 are effectively corrected.

In general, in order to achieve downsizing and high zooming of a lens system, it is necessary to strengthen the refractive power of each lens group and reduce the number of constituent lenses of each lens group as much as possible. As this size reduction and higher zooming are promoted, it becomes difficult to correct negative spherical aberration by the positive lens group. In the present invention, in order to correct spherical aberration at this time, the off-axis chief ray height becomes smaller in absolute value with respect to the on-axis ray height at the wide-angle end and the telephoto end, and the negative refracting power with the concave surface facing the object side. Introducing an aspherical surface into the lens surface of.

That is, by introducing an aspherical surface having a shape that strengthens the negative refracting power action with increasing distance from the optical axis into the lens surface that simultaneously satisfies the conditional expressions (1) and (2), a spherical surface mainly in the negative direction is introduced. Aberration is corrected in the positive direction.

In addition to this, by providing an aspherical surface of a predetermined shape on the lens surface in a range that satisfies the conditional expressions (1) and (2), the variation of astigmatism is not greatly affected in the entire variable power range. Instead, spherical aberration and coma are well corrected. If this conditional expression is not satisfied, it becomes difficult to effectively correct the on-axis aberration without affecting the off-axis aberration in the entire zoom range. Further, it is desirable to introduce an aspherical surface having the above-mentioned shape into the concave lens surface on the object side of the negative lens because it can have a stronger spherical aberration correcting action.

FIGS. 26 (A) and 26 (B) are explanatory views showing incident states of the axial ray and the off-axis ray on the lens surface satisfying the conditional expressions (1) and (2) at the wide-angle end and the telephoto end. Is.

Further, when an aspherical surface is applied to the lens surface satisfying the conditional expressions (1) and (2), it is applied to the negative lens in the second group L2b of the second group L2 having a positive refractive power as a whole. This is preferable because the fluctuation of the spherical aberration can be effectively corrected without much influence on the fluctuation of the off-axis aberration during zooming.

As described above, according to the present invention, at least one aspherical surface is introduced into the lens surface having the negative refraction action with the concave surface facing the object side, which satisfies the above-mentioned conditional expression. Aberrations are well-balanced and high zoom ratio and wide angle of view are achieved.

In the zoom lens according to the present invention, focusing is performed by an arbitrary lens group in which the lateral magnification of the focus group does not become equal during zooming. First group L
When one lens group in 1 has a certain degree of strong refractive power, focusing by this lens group can make the focusing amount constant at an arbitrary object distance throughout the zoom range, so that simplification of the mechanism can be expected.

At the wide-angle end, when the back focus is sufficient, the final lens unit has a negative refracting power, and the refracting power is strong to some extent, the final lens unit may be moved to the image plane side. At this time, it is expected that the outer diameter of the lens of the first lens group will be reduced. Also, two or more lens groups in the first lens group to the last lens group may be moved simultaneously. When the focus group includes a diaphragm, it is preferable to move the focus group while keeping the diaphragm fixed on the optical axis because the driving torque for moving the diaphragm mechanism during focusing can be reduced.

Next, the features of each zoom lens shown in FIGS. 1 to 5 will be described.

FIG. 1 shows a paraxial refractive power arrangement diagram of Numerical Embodiment 1 of the present invention. In FIG. 1, the first lens unit L1 is a lens unit (L1 lens unit) having a negative refractive power from the object side.
The second lens unit L2 includes a second lens unit L2a having a positive refractive power (L2a lens) and a second lens subunit L2b having a negative refractive power (L2b) from the object side.
Lens group) and a second lens group (L2c group) having a positive refractive power, and the third lens group is composed of one lens group (L3 group) having a negative refractive power.

By reducing the group spacing between the L1 group and the L2a group from the wide-angle end to the telephoto end, as will be understood from the equation (9) described later, the combined refractive powers of the L1 group and the L2a group are different from each other. The focal length becomes small (composite focal length is long), and as a result, by the multiplication effect of the L2a group and the L3 group, it becomes possible to efficiently perform telephoto, and it is effective for high zooming. Also, L
By increasing the group interval between the 2b group and the L2c group,
The off-axis ray passes through a position away from the optical axis of the L2c group, and the axial aberration and the off-axis aberration are well balanced.

FIG. 2 shows a paraxial refractive power arrangement of Numerical Embodiment 2 of the present invention. In FIG. 2, the first lens unit L1 is composed of two lens units, a first lens unit (L1a) having a positive refractive power and a first lens group 1b (L1b) having a negative refractive power from the object side, and the second lens unit L2 is an object. The second group a (L2
a), a second lens group (L2b) having a negative refractive power, and a second lens group (L2c) having a positive refractive power.
The group is composed of one lens group (L3 group) having a negative refractive power.

At the wide-angle end, the L1 group and the L2 group are arranged with a certain distance, and as a result, L1 group and L2 group are arranged.
The group and the L2 group have a retrofocus type form. This facilitates ensuring a back focus, which is a problem when widening the angle. Further, by reducing the distance between the L1a, L2a group and the L2c, L3 group from the wide-angle end to the telephoto end, the composite refractive power with each other becomes smaller as understood from the expression (9) ( (The combined focal length is long), and as a result, the zooming effect of the L2b group and the L3 group makes it possible to efficiently perform a telephoto operation and facilitate a high zoom ratio. By reducing the group distance between the L1a and L1b groups at the wide-angle end, the negative distortion aberration occurring in the L1b group when the angle of view is widened is favorably corrected.

FIG. 3 shows a paraxial refractive power arrangement diagram of Numerical Embodiment 3 of the present invention. In FIG. 3, the first lens unit L1 is composed of two lens units, a first lens unit (L1a) having a positive refractive power and a first lens group 1b (L1b) having a negative refractive power from the object side, and the second lens unit L2 is an object. The second group a (L2
a), a second lens unit L2b having a negative refractive power, and a second lens unit L2c having a positive refractive power (L2c), and the third lens unit L3 having a negative refractive power. It is composed of groups.

However, the L2b group and the L2c group move integrally during zooming, and in FIG.
It is represented as a 2 bc group. Here, at the telephoto end rather than at the wide-angle end, the group distance between the L1a group and the L1 group is increased, and the group distance between the L1b group and the L2a group is decreased to correct negative distortion at the wide-angle end and at the telephoto end. By configuring the above, the total lens length is shortened.

FIG. 4 shows a paraxial refractive power arrangement diagram of Numerical Embodiment 4 of the present invention. In FIG. 4, the first group L1 is composed of one lens group (L1) having a negative refractive power from the object side, and the second group L2 is a second lens group having a positive refractive power from the object side.
One lens having a negative refractive power, which is composed of three lens groups, a group (L2a), a second group b having a negative refractive power (L2b), and a second group c having a positive refractive power (L2c). Group L3
It is composed of groups.

However, the second group L2b and the second group C2c move together during zooming, and are shown as a group L2bc having a positive combined focal length in FIG. From the wide-angle end to the telephoto end, the distance between the L1 group and the L2a group, and L2
The group distance between the group (L2bc group) and the L3 group is made small so that the lens system during zooming maintains a symmetric type as a whole so that good optical performance is easily obtained, and the total lens length at the wide-angle end is made small. is doing.

FIG. 5 shows a paraxial refractive power arrangement diagram of Numerical Embodiment 5 of the present invention. In FIG. 5, the first lens unit L1 is a single lens unit (L1) having a negative refractive power from the object side.
The second lens unit L2 includes a second lens unit L2a having a positive refractive power, a second lens unit L2b having a negative refractive power, and a second lens unit L2b having a negative refractive power from the object side.
It is composed of three lens groups of the second c group (L2c) having a positive refractive power, and the third group is composed of one lens group L3 group having a negative refractive power.

However, the L2b group and the L2c group move integrally during zooming, and are shown as the L2bc group having a positive combined focal length in FIG. From the wide-angle end to the telephoto end, the distance between the L1 group and the L2 group and the L2 group and the L3 group is reduced, and at the same time, each group moves toward the object side so that the lens system during zooming maintains a symmetrical shape as a whole. Zooming is effectively performed while making it easy to obtain good optical performance.

The zoom lens which is the object of the present invention can be achieved by satisfying the above-mentioned various conditions. However, while further downsizing the entire lens system, a wide angle of view, high zoom ratio and high optical performance are achieved. To obtain, it is good to satisfy the following conditions.

(1-1) The focal length of the third lens unit is f3,
When the focal length of the entire system at the wide-angle end is Fw, the condition of 0.7 ≦ | Fw / f3 | ≦ 2.5 (3) is satisfied.

Conditional expression (3) relates to the negative refracting power of the third lens unit L3. If the refracting power of the third lens unit L3 is increased beyond the upper limit, the back focus becomes too short at the wide-angle end. However, it is not good because the outer diameter of the third lens unit L3 is increased in order to secure a constant amount of peripheral light. If the lower limit is exceeded and the refractive power of the third lens unit L3 becomes weak, the zooming effect of the third lens unit becomes weak during zooming. As a result, in order to ensure a constant zoom ratio, each lens unit must move. The amount must be increased, which results in an increase in the total lens length, which is not good.

(1-2) It is preferable to arrange the diaphragm in the second lens group. Then, it is preferable that the diaphragm is moved integrally with the other lens groups when the magnification is changed or independently. The diaphragm may be arranged in the air space between the first lens unit L1 and the second lens unit L2 in addition to the second lens unit L2. According to this, from the viewpoint of downsizing of the lens diameter and balance in aberration correction. Good to see.

(1-3) In the present invention, in order to perform even better aberration correction, it is preferable to introduce an aspherical surface in addition to the lens surfaces that satisfy the above conditional expressions (1) and (2). For example, if at least one aspherical surface is introduced into at least one negative lens of the third lens unit L3, it becomes possible to mainly correct better the fluctuation of the off-axis aberration. In addition, the second group L
If an aspherical surface is introduced into lens surface 2 other than the aspherical surface described above, off-axis aberration correction can be favorably performed. For example, it is preferable to introduce an aspherical surface having a shape in which the positive refracting power is weakened as the distance from the optical axis is increased, to the lens surface having the convex surface facing the increasing surface in the L2c group. Further, if an aspherical surface is introduced into the first lens unit L1, mainly distortion can be easily corrected.

(1-4) When the focal lengths at the wide-angle end of the first group and the second group are f1 and f2, respectively, 0.2 ≦ | Fw / f1 | ≦ 1.0 · (4) 1.0 ≦ Fw / f2 ≦ 2.5 (5) The condition is satisfied.

If the upper limit of conditional expression (4) is exceeded, the negative refracting power of the first lens unit L1 at the wide-angle end becomes too strong, and the action of the retrofocus system becomes too strong. In addition, spherical aberration is strongly generated in the first lens unit L1 and it is difficult to correct this with another lens unit. On the other hand, if the lower limit is exceeded, it becomes difficult to secure a predetermined amount of back focus.

Conditional expression (5) relates to the positive refractive power of the second lens unit L2. If the upper limit of conditional expression (5) is exceeded, the refractive power of the second lens unit L2 becomes too strong, and the second lens unit L2. As a result, the telephoto type action of the third lens unit L3 becomes too strong, and it becomes difficult to secure a predetermined amount of back focus. On the other hand, if the lower limit of conditional expression (5) is exceeded, the refracting power of the second lens unit L2 will become weak, and the refracting power of the negative lens unit will be weakened in order to obtain a fixed focal length at the wide-angle end. It is not good because the total length will increase.

(1-5) When the imaging magnification at the wide-angle end of the third lens unit is β3w, 0.1 ≦ f3 × (1−β3w) /Fw≦0.5 ... (6) To satisfy the following condition.

Conditional expression (6) relates to a condition for properly setting the back focus at the wide-angle end. If the upper limit of conditional expression (6) is exceeded, the back focus becomes unnecessarily long at the wide-angle end, making it difficult to achieve miniaturization of the entire lens system. On the other hand, when the value goes below the lower limit, it becomes difficult to secure a predetermined amount of back focus at the wide-angle end, resulting in an increase in the lens diameter of the third lens unit L3, which is not preferable.

(1-6) When the lateral magnification of the third lens unit at the wide-angle end is β3w, by satisfying the condition of 1.1 <β3w <1.8 (7) is there.

Conditional expression (7) relates to the lateral magnification of the third lens unit L3. When the lateral magnification of the third lens unit L3 becomes too large beyond the upper limit value, the back focus becomes long, but the power of the lens unit before that becomes too strong and aberration correction becomes difficult. If the lateral magnification of the third lens unit L3 becomes too small below the lower limit, it becomes difficult to downsize the entire lens system.

(1-7) When the lateral magnification of the second lens unit at the wide-angle end is β2w (β2w <0), 0.1 <| β2w | <0.6 (8) To satisfy the condition.

Here, two adjacent lens groups (kth
The formula showing the combined refractive power φkj in the (group, j-th group) is as follows.

Φkj = φk + φj−φk * φj * e (9) where φk: refractive power of the kth lens group φj: refractive power of the jth lens group e: kth lens group Principal point spacing between the j-th lens group Since the second lens unit L2 and the third lens unit L3 have mutually opposite refracting powers, the air distance is made smaller at the telephoto end than at the wide-angle end, as can be seen from equation (9). As a result, the combined refractive power can be reduced.

Conditional expression (8) is the second lens unit L2 at the wide-angle end.
The lateral magnification of the above is regulated by referring to the equation (9). If the upper limit of conditional expression (8) is exceeded, the back focus becomes difficult at the wide-angle end, resulting in an increase in the lens diameter of the third lens unit L3. or,
When the value goes below the lower limit, the refracting power of the other lens units exceeds the limit and becomes strong in order to obtain a constant focal length, which causes many aberrations, which is not good.

Next, numerical examples of the present invention will be shown. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air gap from the object side, and Ni and νi are respectively from the object side of the i-th lens. The refractive index of glass and the Abbe number.

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

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

[0063]

[Equation 1] It is expressed by (Numerical Example 1) F = 28.84 to 101.45 FNO = 3.5 to 92 ω = 73.8 ° to 24.1 ° R 1 = -129.95 D 1 = 1.30 N 1 = 1.48749 ν 1 = 70.2 R 2 = 29.51 D 2 = 1.99 R 3 = 29.12 D 3 = 2.20 N 2 = 1.84666 ν 2 = 23.8 R 4 = 39.39 D 4 = Variable R 5 = 14.00 D 5 = 1.10 N 3 = 1.84666 ν 3 = 23.8 R 6 = 11.92 D 6 = 3.00 N 4 = 1.48749 ν 4 = 70.2 R 7 = -234.68 D 7 = Variable R 8 = ∞ (Aperture) D 8 = 2.50 R 9 = -19.70 D 9 = 1.50 N 5 = 1.69320 ν 5 = 33.7 R10 = -21.42 D10 = 2.00 N 6 = 1.84666 ν 6 = 23.8 R11 = -62.22 D11 = variable R12 = 25202.75 D12 = 4.10 N 7 = 1.77250 ν 7 = 49.6 R13 = -15.62 D13 = variable R14 = -18.26 D14 = 1.50 N 8 = 1.69680 ν 8 = 55.5 R15 = 73.66 D15 = 2.30 N 9 = 1.84666 ν 9 = 23.8 R16 = 218.48 Aspheric surface coefficient 9 faces K = 5.081 A = 0 B = 2.434 × 10 ^-6 C = 6.462 × 10 ^-7 D = 0 E = 0 13 faces K = -2.521 A = 0 B = -5.677 × 10 ^-5 C = 1.319 × 10 ^-7 D = 0 E = 0 14 faces K = 4.719 × 10 ^-1 A = 0 B = 2.780 × 10 ^-5 C = 8.034 × 10 ^-8 D = 0 E = 0

[0064]

[Table 1] (Numerical Example 2) F = 28.83 to 102.38 FNO = 3.71 to 10.00 2 ω = 73.8 ° to 23.9 ° R 1 = 519.61 D 1 = 1.60 N 1 = 1.80518 ν 1 = 25.4 R 2 = -351.51 D 2 = variable R 3 = -112.82 D 3 = 1.30 N 2 = 1.49699 ν 2 = 81.6 R 4 = 28.78 D 4 = variable R 5 = 13.78 D 5 = 2.50 N 3 = 1.49699 ν 3 = 81.6 R 6 = 2684.81 D 6 = variable R 7 = ∞ (Aperture) D 7 = 1.00 R 8 = -35.81 D 8 = 2.80 N 4 = 1.84665 ν 4 = 23.8 R 9 = 1454.82 D 9 = Variable R10 = -317.50 D10 = 4.50 N 5 = 1.77249 ν 5 = 49.6 R11 = -16.39 D11 = Variable R12 = -15.81 D12 = 1.80 N 6 = 1.63999 ν 6 = 60.1 R13 = -425.93 Aspheric coefficient 8 faces K = -2.282 × 10 ⁺¹ A = 0 B = -1.474 × 10 ^-4 C = ^{1.145 × 10 -8 D = -5.666 ×} 10 -9 E = 0 11 surface ^{K = -2.726 × 10 -2 A =} 0 B = 6.307 × 10 -6 C = 3.236 × 10 -8 D = -5.515 × 10 - ¹¹ E = 0 12 sides K = -1.579 × 10 ^-1 A = 0 B = 1.052 × 10 ^-5 C = 3.60 4 × 10 ^-8 D = -9.831 × 10 ^-11 E = 0

[0065]

[Table 2] (Numerical Example 3) F = 28.85 to 101.00 FNO = 3.30 to 9.00 2 ω = 73.7 ° to 24.2 ° R 1 = 424.11 D 1 = 2.40 N 1 = 1.51633 ν 1 = 64.2 R 2 = -60.06 D 2 = variable R 3 = -38.54 D 3 = 1.20 N 2 = 1.80400 ν 2 = 46.6 R 4 = 19.56 D 4 = 1.35 R 5 = 21.49 D 5 = 2.90 N 3 = 1.84665 ν 3 = 23.8 R 6 = 176.01 D 6 = variable R 7 = 15.65 D 7 = 0.90 N 4 = 1.84665 ν 4 = 23.8 R 8 = 11.27 D 8 = 4.50 N 5 = 1.48749 ν 5 = 70.2 R 9 = -21.44 D 9 = 0.90 N 6 = 1.84665 ν 6 = 23.8 R10 = -29.88 D10 = Variable R11 = ∞ (Aperture) D11 = 3.00 R12 = -24.67 D12 = 2.55 N 7 = 1.80518 ν 7 = 25.4 R13 = -47.29 D13 = 0.50 R14 = -36.54 D14 = 1.00 N 8 = 1.65159 ν 8 = 58.5 R15 = 155.75 D15 = 5.80 N 9 = 1.77249 ν 9 = 49.6 R16 = -14.23 D16 = variable R17 = -28.76 D17 = 2.30 N10 = 1.84665 ν10 = 23.8 R18 = -20.20 D18 = 0.30 R19 = -25.76 D19 = 1.30 N11 = 1.69679 ν11 = 55.5 R20 = -80.69 D20 = 3.51 R21 = -18.83 D21 = 1.50 N12 = 1.77249 ν12 = 49.6 R22 = 431.90 Aspherical surface 12 faces K = 4.963 A = 0 B = -6.074 × 10 ^-5 C = -3.607 × 10 ^-7 D = 3.331 × 10 ^-9 E = 0 16 faces K = -2.664 A = 0 B = -1.127 × 10 ^-4 C = 1.634 × 10 ^-7 D = -1.376 × 10 ^-9 E = 0

[0066]

[Table 3] (Numerical Example 4) F = 28.86 to 101.58 FNO = 3.06 to 9.00 2 ω = 73.7 ° to 24.1 ° R 1 = 101.89 D 1 = 2.85 N 1 = 1.51633 ν 1 = 64.2 R 2 = -61.28 D 2 = 0.84 R 3 = -39.42 D 3 = 1.20 N 2 = 1.80400 ν 2 = 46.6 R 4 = 17.90 D 4 = 1.07 R 5 = 19.60 D 5 = 3.35 N 3 = 1.84665 ν 3 = 23.8 R 6 = 95.82 D 6 = variable R 7 = 16.21 D 7 = 0.90 N 4 = 1.84665 ν 4 = 23.8 R 8 = 11.92 D 8 = 4.80 N 5 = 1.48749 ν 5 = 70.2 R 9 = -19.85 D 9 = 0.90 N 6 = 1.84665 ν 6 = 23.8 R10 = -27.78 D10 = Variable R11 = ∞ (Aperture) D11 = 3.50 R12 = -26.05 D12 = 2.42 N 7 = 1.80518 ν 7 = 25.4 R13 = -45.55 D13 = 0.56 R14 = -34.59 D14 = 1.00 N 8 = 1.65159 ν 8 = 58.5 R15 = 310.25 D15 = 5.80 N 9 = 1.77249 ν 9 = 49.6 R16 = -13.79 D16 = variable R17 = -28.83 D17 = 2.30 N10 = 1.84665 ν10 = 23.8 R18 = -20.42 D18 = 0.24 R19 = -25.56 D19 = 1.30 N11 = 1.69679 ν11 = 55.5 R20 = -131.56 D20 = 3.53 R21 = -20.55 D21 = 1.50 N12 = 1.77249 ν12 = 49.6 R22 = 204.29 Aspherical coefficient 12 surfaces K = 6.017 A = 0 B = -6.890 × 10 ^-5 C = -6.114 × 10 ^-7 D = -4.934 × 10 ^-9 E = 0 16 faces K = -2.445 A = 0 B = -1.158 × 10 ^-4 C = 1.246 × 10 ^-7 D = -1.894 × 10 ^-9 E = 0

[0067]

[Table 4] (Numerical Example 5) F = 29.47 to 80.02 FNO = 3.80 to 8.79 2 ω = 72.6 ° to 30.3 ° R 1 = 104.99 D 1 = 2.85 N 1 = 1.51633 ν 1 = 64.2 R 2 = -79.20 D 2 = 0.84 R 3 = -58.17 D 3 = 1.20 N 2 = 1.88299 ν 2 = 40.8 R 4 = 18.99 D 4 = 1.07 R 5 = 19.98 D 5 = 3.35 N 3 = 1.80518 ν 3 = 25.4 R 6 = 81.43 D 6 = variable R 7 = 14.33 D 7 = 0.90 N 4 = 1.84665 ν 4 = 23.8 R 8 = 15.71 D 8 = 4.80 N 5 = 1.48749 ν 5 = 70.2 R 9 = -16.46 D 9 = 0.90 N 6 = 1.84665 ν 6 = 23.8 R10 = -25.87 D10 = 2.36 R11 = ∞ (Aperture) D11 = 2.70 R12 = -26.70 D12 = 2.42 N 7 = 1.80518 ν 7 = 25.4 R13 = 65.44 D13 = 1.00 R14 = -59.75 D14 = 1.00 N 8 = 1.65159 ν 8 = 58.5 R15 = 27.74 D15 = 5.80 N 9 = 1.80 400 ν 9 = 46.6 R16 = -14.65 D16 = Variable R17 = -25.00 D17 = 2.49 N10 = 1.84665 ν10 = 23.8 R18 = -17.35 D18 = 0.40 R19 = -23.62 D19 = 1.30 N11 = 1.69679 ν11 = 55.5 R20 = -62.18 D20 = 4.00 R21 = -16.00 D21 = 1.99 N12 = 1.77249 ν12 = 49.6 R22 = -170.60 Aspheric coefficient 12 faces K = -6.839 × 10 ^-1 A = 0 B = -1.773 × 10 ^-4 C = 2.030 × 10 ^-7 D = -4.48 ⁸ × 10 ^-8 E = 0 16 faces K = -2.383 A = 0 B = -1.044 × 10 ^-4 C = 1.158 × 10 ^-7 D = -1.694 × 10 ^-9 E = 0

[0068]

[Table 5]

[0069]

As described above, according to the present invention, in the zoom lens having a plurality of lens groups, for example, in the zoom lens divided into three lens groups as a whole, the aspherical surface of the lens group is appropriate. The zoom lens has a high optical performance over the entire zoom range, which is suitable for wide angle of view and various aberrations that become a problem at high zooming, and the size of the entire lens system is reduced. Can be achieved.

[Brief description of drawings]

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

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

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

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

FIG. 5 is an explanatory diagram of a paraxial refractive power arrangement according to Example 5 of the present invention.

FIG. 6 is a lens cross-sectional view at a wide-angle end according to Numerical Example 1 of the present invention.

FIG. 7 is a lens cross-sectional view at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 8 is a lens cross-sectional view at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 9 is a lens cross-sectional view at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 10 is a lens cross-sectional view at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 11 is an aberration diagram at the wide-angle end according to Numerical Example 1 of the present invention.

FIG. 12 is an intermediate aberration diagram of Numerical example 1 of the present invention.

FIG. 13 is an aberration diagram at a telephoto end according to Numerical Example 1 of the present invention.

FIG. 14 is an aberration diagram at the wide-angle end according to Numerical Example 2 of the present invention.

FIG. 15 is an intermediate aberration diagram of Numerical example 2 of the present invention.

FIG. 16 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 17 is an aberration diagram at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 18 is an intermediate aberration diagram of Numerical example 3 of the present invention.

FIG. 19 is an aberration diagram at a telephoto end according to Numerical Example 3 of the present invention.

FIG. 20 is an aberration diagram at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 21 is an intermediate aberration diagram of Numerical Example 4 of the present invention.

FIG. 22 is an aberration diagram at a telephoto end according to Numerical Example 4 of the present invention.

FIG. 23 is an aberration diagram at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 24 is an intermediate aberration diagram of Numerical Example 5 of the present invention.

FIG. 25 is an aberration diagram at a telephoto end according to Numerical Example 5 of the present invention.

FIG. 26 is an explanatory diagram of an aspherical surface according to the zoom lens of the present invention.

[Explanation of symbols]

 L1 1st group L1a 1a group L1b 1b group L2 2nd group L2a 2a group L2b 2b group L2c 2c group L3 3rd group SP aperture IP image surface d d line g g line S. C Sine condition ΔS Sagittal image plane ΔM Meridional image plane

Claims (8)

[Claims] 1. A three-lens group having, in order from the object side, a negative refractive power first group, a positive refractive power second group, and a negative refractive power third group, and the distance between each lens group is changed. When the object is at infinity, the incident heights of the axial ray on the i-th surface at the wide-angle end and the telephoto end are Hiw (Hiw> 0) and Hit (Hii, respectively.
t> 0), and when the incident heights of the off-axis chief ray with the maximum angle of view to the i-th surface at the wide-angle end and the telephoto end are Hbiw and Hbit, respectively, Hiw> | Hbiw | Hit> | Hbit | is satisfied. A zoom lens having a negative refractive power lens surface Ra having a concave surface facing the object side, and an aspherical surface having a shape in which the negative refractive power increases from the lens center to the lens periphery. 2. The second lens group has, in order from the object side, a second lens group having a positive refractive power, a second lens group having a negative refractive power, and a second lens group having a positive refractive power. The zoom lens according to claim 1. 3. When the focal length of the third lens unit is f3 and the focal length of the entire system at the wide angle end is Fw, the condition of 0.7 ≦ | Fw / f3 | ≦ 2.5 is satisfied. The zoom lens according to claim 2. 4. When the focal lengths at the wide-angle end of the first lens unit and the second lens unit are f1 and f2, respectively, 0.2 ≦ | Fw / f1 | ≦ 1.0 1.0 ≦ Fw / f2 ≦ 2 The zoom lens according to claim 3, wherein the condition (5) is satisfied. 5. When the imaging magnification at the wide-angle end of the third lens unit is β3w, the condition of 0.1 ≦ f3 × (1−β3w) /Fw≦0.5 is satisfied. Item 4 zoom lens. 6. The zoom lens according to claim 2, wherein the lens surface Ra is included in the second group b. 7. The zoom lens according to claim 2, wherein the lens surface Ra is included in the negative lens of the second group b. 8. The zoom lens according to claim 1, wherein the lens surface Ra is included in a single negative lens.