JPH10260353A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high power variation rate and relatively small size although the field angle at the wide-angle end is increased by making the focal length of the whole zoom lens meet specific requirements. SOLUTION: This lens has a 1st lens group G1 with positive refracting power, a 2nd lens group G2 which moves along the optical axis for power variation and has negative refracting power, and a 3rd lens group G3 which has positive refracting power. Further, the lens is equipped with a 4th lens group G4 and 6th lens groups G6 which has positive refracting power and a 5th lens group G5 which has negative refracting power. Variation in image point position due to the power variation is corrected by the movement of at least one lens group among the 3rd lens group G3 to the 6th lens group G6 along the optical axis. Here, 0.05<Fw/F3<1.0 and 0.05<Fw/F4<1.0 hold, where F3 is the focal length of the 3rd lens group G3, F4 is the focal length of the 4th lens group G4, and the Fw is the focal length of the whole zoom lens system at the wide-angle 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 camcorder (home handy video camera) using a solid-state image sensor, a small micro camera, and the like.

[0002]

2. Description of the Related Art A small zoom lens having a high zoom ratio and high optical performance from a wide angle range to a telephoto range has long been required for a photographic camera, a video camera and the like. Further, further expansion to a wide-angle region and close-up photography with higher magnification are also required. For this reason, many types of multi-group zoom lenses have been proposed. For example, JP-A-5-21
JP-A-5967 and JP-A-8-5913 propose a five-group zoom lens having positive, negative, positive, negative, and positive refractive power arrangements. Japanese Patent Application Laid-Open No. 58-186715 proposes a six-unit zoom lens having a positive, negative, positive, negative, and positive refractive power arrangement.

[0003]

SUMMARY OF THE INVENTION
With the zoom lenses disclosed in Japanese Patent Application Laid-Open No. 5-215967 and Japanese Patent Application Laid-Open No. H8-5913, it is difficult to say that the correction of distortion at the wide-angle end is sufficient, and the amount of peripheral light is not sufficient. In particular, the distortion at the wide-angle end largely occurs on the negative side, and if this is to be corrected, the distortion at the intermediate magnification state or at the telephoto end will increase on the positive side.

In the zoom lens disclosed in Japanese Patent Application Laid-Open No. H5-215967, focusing is performed by the fifth lens group, so that a prism, a mirror, and the like are provided after the last lens group (fifth lens group). The back focus was short when inserting an optical element or the like or attaching to an existing camera. Furthermore, since the movable range (lens group interval) of the focusing lens group (the lens group that moves for focusing) is not sufficient, it has been difficult to perform extremely close-up photographing over the entire angle of view range of the zoom lens.

Also, in the zoom lens disclosed in Japanese Patent Application Laid-Open No. Hei 8-5913, a rear focus for focusing on a short-distance object by moving a fourth lens group having a negative refractive power to the image side along the optical axis. The method is adopted. However, since the movable range of the focusing lens group (the fourth lens group) is limited by the front and rear lens groups, it is difficult to perform high-power close-up shooting. In addition, the fourth lens group, which is the focusing lens group, moves along a curved locus having a convex shape on the image side during zooming, so that it is even more difficult to perform extremely close-up shooting at an intermediate magnification state during zooming. .

In the zoom lens disclosed in Japanese Patent Application Laid-Open No. 58-186715, zooming is performed by moving a fourth lens unit having a positive refractive power and a fifth lens unit having a negative refractive power together. I do. Since the composite lens group of the fourth lens group and the fifth lens group has a weak positive combined refractive power, this apparently six-unit zoom lens actually has five groups having positive, negative, positive, positive, and positive refractive power arrangements. It can be said that the zoom lens has a configuration. That is, the fourth lens group is not a six-group configuration for increasing the zoom ratio from the wide-angle end to the telephoto end, but is a split lens group for floating focus.

The present invention has been made in view of the above-mentioned problems, and has a high zoom ratio and a relatively small size despite the wide angle of view at the wide-angle end. It is an object to provide an achieved zoom lens.

[0008]

In order to solve the above-mentioned problems, a zoom lens according to the present invention includes, in order from an object side, a first lens group G1 having a positive refractive power, and a first lens group G1 having an optical axis for zooming. A second lens group G2 having a moving negative refractive power, a third lens group G3 having a positive refractive power moving on the optical axis for zooming, a fourth lens group G4 having a positive refractive power, A fifth lens group G5 having a refractive power; and a sixth lens group G6 having a positive refractive power. The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens. A novel zooming method is adopted in which at least one lens group of the group G6 moves on the optical axis to correct the fluctuation of the image point position due to zooming. In the present invention, the third lens group G3
When the focal length of the fourth lens group G4 is F4 and the focal length of the entire zoom lens system at the wide angle end is Fw, 0.05 <Fw / F3 <1.0 0.05 The condition of <Fw / F4 <1.0 is satisfied.

According to a preferred aspect of the present invention, the combined focal length of the third lens group G3 and the fourth lens group G4 at the wide angle end is F34W, and the third focal length at the telephoto end is F34W.
Assuming that the combined focal length of the lens group G3 and the fourth lens group G4 is F34T, the following condition is satisfied: 0.4 <F34W / F34T <1.0.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, by adopting a new zooming method, it is possible to secure a relatively small zoom lens having a wide angle of view at the wide-angle end and a high zooming ratio. I have. In general, as the angle of view on the wide-angle side is widened in this type of zoom lens, negative distortion, higher-order astigmatism, and field curvature increase, making it difficult to correct. Therefore, it is important to increase the zoom ratio from the wide-angle end to the telephoto end while widening the angle of view at the wide-angle end. Also, if a zoom lens with small distortion is realized over the entire zoom range, the range of application as an optical system for an image input camera is expanded.

In the zoom lens system according to the present invention, when zooming from the wide-angle end to the telephoto end, it is preferable that the second lens group G2 moves so as to reduce the air gap with the third lens group G3. It is preferable that the group G3 moves so as to increase the air gap with the fourth lens group G4. Then, in order to suppress fluctuation of various aberrations (particularly spherical aberration) due to zooming, it is preferable that the third lens group G3 moves along a curved locus having a convex shape facing the image side. In the zoom lens of the present invention, by increasing the number of constituent lens groups responsible for zooming as compared with the conventional zoom lens, the air space (lens group space) in the zoom lens is effectively used, and the degree of freedom for aberration correction is increased. Is secured. With this configuration, it is possible to not only reduce the overall length of the lens and the diameter of the front lens, but also suppress variations in various aberrations such as distortion.

Hereinafter, the conditional expression of the present invention will be described.
In the present invention, the following conditional expressions (1) and (2) are satisfied. 0.05 <Fw / F3 <1.0 (1) 0.05 <Fw / F4 <1.0 (2) where: F3: focal length of the third lens group G3 F4: focal point of the fourth lens group G4 Distance Fw: focal length of entire zoom lens system at wide-angle end

Conditional expressions (1) and (2) regulate the appropriate refractive power distribution of the third lens unit G3 and the fourth lens unit G4, respectively. Exceeding the upper limits of these conditional expressions is advantageous for miniaturization because the amount of movement of each lens unit upon zooming is small, but is advantageous in that various aberrations (particularly spherical aberration) due to zooming increase. Not preferred. On the other hand, if the lower limits of these conditional expressions are exceeded, the amount of movement of each lens unit accompanying zooming becomes large, making it difficult to reduce the overall length of the lens. Further, since the amount of movement of the lens unit responsible for zooming becomes large, it becomes difficult to expand the zooming range due to interference with the adjacent lens unit. Furthermore, the first
Since the incident light beam to the lens group G1 is largely separated from the optical axis, the diameter of the front lens increases in order to secure the light amount. Further, the Petzval sum also becomes large on the negative side, and it becomes difficult to satisfactorily correct the curvature of field, which is not preferable.

In the present invention, upon zooming, it is preferable that a light ray incident on the fourth lens group G4 is substantially parallel to the optical axis. In this case, since the incident height of the light beam incident on the fourth lens group G4 does not change significantly during zooming, it is easy to reduce the fluctuation of various aberrations (particularly, spherical aberration and coma aberration). Therefore, it is possible to use the fourth lens group G4 as a lens group for performing image blur correction by moving vertically to the optical axis, that is, a correction lens group for image stabilization. In the correction lens group for image stabilization, it is necessary to reduce the size and weight in order to perform effective image stabilization control with a small amount of movement in a direction perpendicular to the optical axis. Therefore, as shown in each embodiment, it is preferable that the fourth lens group G4 be formed of a single lens having a positive refractive power.

In the present invention, the third lens group in the conventional five-group zoom lens having positive, negative, positive, negative, and positive refractive power arrangements is replaced by a third lens group G3 having both positive refractive powers in accordance with an appropriate refractive power distribution. It is divided into four lens groups G4. With this configuration, the burden on each lens group in correcting aberrations is reduced, and it becomes easy to suppress variations in various aberrations due to zooming. Furthermore, since the number of lens groups increases the degree of freedom in using the lens group spacing, it is possible to achieve a high zoom ratio of a compact, high-performance zoom lens.

In the present invention, it is preferable to satisfy the following conditional expression (3). 0.4 <F34W / F34T <1.0 (3) where, F34W: the composite focal length of the third lens group G3 and the fourth lens group G4 at the wide angle end F34T: the third lens group G3 and the third lens group at the telephoto end Synthetic focal length with 4-lens group G4

Conditional expression (3) indicates that the third lens group G3 and the fourth
This is an expression that defines the optimum zooming efficiency with the lens group G4,
It is also an equation relating to the air spacing between these lens groups. When the value goes below the lower limit of conditional expression (3), the amount of movement of the third lens group G3 that moves for zooming becomes large, and the second lens group G2 and the third lens group G3 interfere at the telephoto end, It becomes difficult to expand the zoom range to the telephoto side.

On the other hand, exceeding the upper limit of conditional expression (3) indicates that the combined focal length of the third lens group G3 and the fourth lens group G4 is longer at the wide angle end than at the telephoto side. This means that the efficiency of zoom lens zooming becomes very poor. Therefore, when the value exceeds the upper limit of the conditional expression (3), the magnification does not increase with zooming toward the telephoto side, and it becomes difficult to efficiently expand the zooming range toward the telephoto side. As a result, the fourth lens group G4
Is reduced, and the amount of movement of the second lens group G2 is increased. At the telephoto end, the second lens group G2 and the third lens group G3 interfere with each other, so that it becomes difficult to expand the zoom range to the telephoto side. Further, a change in magnification accompanying zooming of the second lens group G2, the third lens group G3, and the fourth lens group G4 becomes unnecessarily large, and it becomes difficult to suppress variations in various aberrations.

In the present invention, it is preferable to satisfy the following conditional expression (4). 0.8 <| Fw / F2 | <1.5 (4) where, F2: focal length of the second lens group G2

Conditional expression (4) defines an appropriate refractive power distribution of the second lens group G2. When the value goes below the lower limit of conditional expression (4), the amount of movement of the second lens group G2 during zooming increases, and it is possible to secure an interval between the first lens group G1 and the second lens group G2 at the wide angle end. Since it becomes difficult, it is disadvantageous to extend the zoom range to the wide-angle side. Also, at the telephoto end, the second lens group G2 and the third lens group G3 interfere with each other, making it difficult to expand the zoom range to the telephoto side. on the other hand,
When the value exceeds the upper limit of conditional expression (4), the Petzval sum of the entire zoom lens system becomes large on the negative side, so that it is difficult to correct the field curvature. Further, it becomes difficult to correct distortion in the second lens group G2.

In the present invention, it is preferable to satisfy the following conditional expression (5). 0.18 <| F2 / F1 | <0.3 (5) where, F1: focal length of the first lens group G1

Conditional expression (5) is an expression for defining conditions that enable the front lens diameter to be reduced and the zoom lens to have a high zoom ratio. If the upper limit of conditional expression (5) is exceeded, the amount of movement of the second lens group G2 due to zooming increases, and the first lens group G
Since it becomes difficult to secure an interval between the first lens group G2 and the second lens group G2, it is disadvantageous to widen the variable power range to the wide angle side.
On the other hand, when the value goes below the lower limit value of the conditional expression (5), the beam height of the off-axis incident light beam is largely separated from the optical axis, so that the diameter of the front lens becomes large. As a result, it becomes difficult to increase the wide-angle end to a wider angle of view while achieving downsizing of the entire zoom lens system. Also,
The Petzval sum becomes large on the negative side, and it becomes difficult to correct the field curvature, which is not preferable.

In the present invention, it is preferable to satisfy the following conditional expression (6). 1.3 <| F6 / F5 | <2.0 (6) Here, F5: focal length of the fifth lens group G5 F6: focal length of the sixth lens group G6

Conditional expression (6) defines the ratio between the focal length of the sixth lens group G6 and the focal length of the fifth lens group G5, and relates to an appropriate back focus. If the lower limit value of the conditional expression (6) is not reached, it becomes difficult to secure a sufficient back focus, which is not preferable. On the other hand, when the value exceeds the upper limit of conditional expression (6), it is easy to secure a long back focus, but since the Petzval sum increases to the negative side, it becomes difficult to satisfactorily correct the field curvature. . Further, too long back focus is not preferable because it leads to enlargement of the entire zoom lens system.

In the present invention, it is preferable to satisfy the following conditional expression (7). 2.0 <Bf / Fw <4.0 (7) where, Bf: back focus of the zoom lens

Conditional expression (7) is a conditional expression relating to an appropriate length of the back focus. If the lower limit of conditional expression (7) is exceeded, the back focus becomes too short, and it becomes difficult to insert a prism, a mirror, an optical element, or the like after the last lens group of the zoom lens, or to attach it to an existing camera. . On the other hand, when the value exceeds the upper limit value of the conditional expression (7), the back focus becomes too long, which leads to an increase in the size of the entire zoom lens system.

In the zoom lens of the present invention, focusing is performed by moving at least one of the third lens group G3 to the sixth lens group G6 along the optical axis.
It is preferable to employ a so-called rear focus method (including an inner focus method). In the rear focus method, the effective diameter of the first lens group is small and the moving amount at the time of focusing is small as compared with the front focus method in which the first lens group is a focusing lens group. . In addition, in order to simplify a driving mechanism for moving the lens units, it is preferable that focusing and correction of a change in the image plane position due to zooming be performed simultaneously by one lens unit.

In the present invention, the third lens group G
In the case where 3 is a focusing lens unit, the paraxial lateral magnification of the third lens unit G3 is set over conditional expression (8) over the entire zoom range.
When the fourth lens group G4 is a focusing lens group, the paraxial lateral magnification of the fourth lens group G4 satisfies conditional expression (9) over the entire zoom range, and the fifth lens group G5 is a focusing lens group. Is satisfied, the paraxial lateral magnification of the fifth lens group G5 satisfies conditional expression (10) over the entire zoom range, and the sixth lens group G
When the focusing lens unit 6 is used, it is preferable that the paraxial lateral magnification of the sixth lens unit G6 satisfies the conditional expression (11) over the entire zoom range.

The ^{_{β 3 2 ≠ 1 (8)}} β 4 2 ≠ 1 (9) β 5 2 ≠ 1 (10) β 6 2 ≠ 1 (11) where, beta _3: paraxial lateral of the third lens group G3 Magnification β ₄ : Paraxial lateral magnification of fourth lens group G4 β ₅ : Paraxial lateral magnification of fifth lens group G5 β ₆ : Paraxial lateral magnification of sixth lens group G6 This is the paraxial lateral magnification of focusing lens group. This is because, when the square of the magnification becomes 1, that is, when the magnification becomes equal, there may be an area where focusing cannot be performed monotonously.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a refractive power arrangement of a zoom lens according to each embodiment of the present invention. As shown in FIG. 1, in each embodiment, the zoom lens of the present invention includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. Third lens group G3 having power and fourth lens group G having positive refractive power
4, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a positive refractive power.

In each embodiment, at the time of zooming, the second lens group G2, the third lens group G3 and the fifth lens group G5 move on the optical axis, and the first lens group G1, the fourth lens group G4 and the Six lens groups G6 are fixed along the optical axis. Specifically, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 moves so as to reduce the air gap with the third lens group G3, and the third lens group G3 moves to the fourth lens group G4. The fifth lens group G5 moves so that the air gap with the sixth lens group G6 decreases after the air gap with the sixth lens group G6 decreases. The movement of the fifth lens group G5 on the optical axis corrects the fluctuation of the image point position due to zooming. In each embodiment, focusing on a short-distance object is performed by moving the fifth lens group G5 to the image side.

[First Embodiment] FIG. 2 is a diagram showing a lens configuration of a zoom lens according to a first embodiment of the present invention.
In the zoom lens of FIG. 2, the first lens group G1 includes, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. It is configured.
The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side. ing.

The third lens group G3 is composed of, in order from the object side, a biconvex lens, and a cemented lens of the biconvex lens and a negative meniscus lens having a concave surface facing the object side. The fourth lens group G4 is composed of a biconvex lens. Further, the fifth lens group G5 includes, in order from the object side, a cemented lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens. The sixth lens group G6 includes, in order from the object side, a biconvex lens, and a cemented lens formed by a biconvex lens and a negative meniscus lens having a concave surface facing the object side.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), β represents the magnification, and FNO
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and d0 represents the object distance (axial distance between the object and the lens surface closest to the object). In Table (1), the surface numbers indicate the order of the lens surfaces from the object side, r indicates the radius of curvature of the lens surfaces, d indicates the distance between the lens surfaces, and ν and n indicate the d-line (λ = 587.56 nm). ) Are shown for Abbe number and refractive index, respectively. In Table (1) (values corresponding to the conditional expressions), β _iw and β _it indicate the paraxial lateral magnification of the i-th lens unit at the wide-angle end and the telephoto end.

[0035]

[Table 1]

FIGS. 3 to 5 show various aberration diagrams of the first embodiment. That is, FIG. 3 shows the state at the wide angle end (minimum magnification state: pos.
FIGS. 4A and 4B show various aberration diagrams.
s.2), and FIG. 5 is an aberration diagram at the telephoto end (maximum magnification: pos.3). In each aberration diagram, NA is the numerical aperture, Y is the image height, and d is the d-line (λ =
587.56 nm) and g is the g-line (λ = 435.83 n).
m). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. 3 to 5, it can be seen that in the first embodiment, various aberrations are favorably corrected in each magnification state from the wide-angle end to the telephoto end, and excellent imaging performance is secured.

[Second Embodiment] FIG. 6 is a diagram showing a lens configuration of a zoom lens according to a second embodiment of the present invention.
In the zoom lens of FIG. 6, the first lens group G1 includes, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. It is configured.
The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side. ing.

The third lens group G3 is composed of, in order from the object side, a biconvex lens, and a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 includes a positive meniscus lens having a convex surface facing the object side. Further, the fifth lens group G5 includes, in order from the object side, a cemented lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens.
The sixth lens group G6 is composed of, in order from the object side, a biconvex lens, and a cemented lens of the biconvex lens and a negative meniscus lens having a concave surface facing the object side.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), β represents the magnification, and FNO
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and d0 represents the object distance (axial distance between the object and the lens surface closest to the object). In Table (2), the surface number indicates the order of the lens surface from the object side, r indicates the radius of curvature of the lens surface, d indicates the distance between the lens surfaces, and ν and n indicate the d-line (λ = 587.56 nm). ) Are shown for Abbe number and refractive index, respectively. In Table (2) (values corresponding to the conditional expressions), β _iw and β _it indicate the paraxial lateral magnification of the i-th lens unit at the wide-angle end and the telephoto end.

[0040]

[Table 2]

FIGS. 7 to 9 show various aberration diagrams of the second embodiment. 7 shows various aberrations at the wide-angle end (pos. 1), FIG. 8 shows various aberrations at the intermediate magnification state (pos. 2), and FIG. 9 shows various aberrations at the telephoto end (pos. 3). FIG. In each aberration diagram, NA indicates a numerical aperture, Y indicates an image height, d indicates a d-line (λ = 587.56 nm), and g indicates a g-line (λ = 435.83 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 7 to 9, it can be seen that in the second embodiment, various aberrations are satisfactorily corrected in each magnification state from the wide-angle end to the telephoto end, and excellent imaging performance is secured.

[Third Embodiment] FIG. 10 is a diagram showing a lens configuration of a zoom lens according to a third embodiment of the present invention. In the zoom lens of FIG. 10, the first lens group G1
Comprises, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens,
And a cemented lens of a biconcave lens and a biconvex lens.

Further, the third lens group G3 comprises, in order from the object side, a biconvex lens, and a cemented lens formed by a biconvex lens and a negative meniscus lens having a concave surface facing the object side. The fourth lens group G4 is composed of a biconvex lens. Further, the fifth lens group G5 includes, in order from the object side, a cemented lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens. The sixth lens group G6 includes, in order from the object side, a biconvex lens, and a cemented lens formed by a biconvex lens and a negative meniscus lens having a concave surface facing the object side.

Table 3 below summarizes data values of the third embodiment of the present invention. In Table (3), β represents the magnification, and FNO
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and d0 represents the object distance (axial distance between the object and the lens surface closest to the object). In Table (3), the surface number indicates the order of the lens surface from the object side, r indicates the radius of curvature of the lens surface, d indicates the distance between the lens surfaces, and ν and n indicate the d-line (λ = 587.56 nm). ) Are shown for Abbe number and refractive index, respectively. Further, in Table 3 (values corresponding to the conditional expressions), β _iw and β _it indicate the paraxial lateral magnification of the i-th lens unit at the wide-angle end and the telephoto end.

[0045]

[Table 3]

FIGS. 11 to 13 show various aberration diagrams of the third embodiment. That is, FIG. 11 is a diagram showing various aberrations at the wide-angle end (pos. 1), FIG. 12 is a diagram showing various aberrations at the intermediate magnification state (pos. 2), and FIG. 13 is a diagram showing various aberrations at the telephoto end (pos. 3). FIG. In each aberration diagram, NA is the numerical aperture, Y is the image height, and d is the d line (λ = 587.56 nm).
And g represents a g-line (λ = 435.83 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 11 to 13, it can be seen that in the third embodiment, various aberrations are favorably corrected in each magnification state from the wide-angle end to the telephoto end, and excellent imaging performance is secured.

[Fourth Embodiment] FIG. 14 is a diagram showing a lens configuration of a zoom lens according to a fourth embodiment of the present invention. In the zoom lens of FIG. 14, the first lens group G1
Comprises, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens having a substantially planar convex surface facing the object side;
It is composed of a biconcave lens, and a cemented lens of a biconcave lens and a positive meniscus lens with the convex surface facing the object side.

Further, the third lens group G3 is composed of, in order from the object side, a biconvex lens, and a cemented lens of the biconvex lens and a negative meniscus lens having a concave surface facing the object side. The fourth lens group G4 is composed of a biconvex lens. Further, the fifth lens group G5 includes, in order from the object side, a cemented lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens. The sixth lens group G6 includes, in order from the object side, a biconvex lens, and a cemented lens formed by a biconvex lens and a negative meniscus lens having a concave surface facing the object side.

Table 4 below summarizes the data values of the fourth embodiment of the present invention. In Table (4), β represents the magnification, and FNO
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and d0 represents the object distance (axial distance between the object and the lens surface closest to the object). In Table (4), the surface number indicates the order of the lens surface from the object side, r indicates the radius of curvature of the lens surface, d indicates the distance between the lens surfaces, and ν and n indicate the d-line (λ = 587.56 nm). ) Are shown for Abbe number and refractive index, respectively. Further, in (Values for Conditional Expressions) in Table (4), β _iw and β _it indicate the paraxial lateral magnification of the i-th lens unit at the wide-angle end and the telephoto end.

[0050]

[Table 4]

FIGS. 15 to 17 are graphs showing various aberrations of the fourth embodiment. 15 shows various aberrations at the wide-angle end (pos. 1), FIG. 16 shows various aberrations at the intermediate magnification state (pos. 2), and FIG. 17 shows various aberrations at the telephoto end (pos. 3). FIG. In each aberration diagram, NA is the numerical aperture, Y is the image height, and d is the d line (λ = 587.56 nm).
And g represents a g-line (λ = 435.83 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 15 to 17, it can be seen that in the fourth embodiment, various aberrations are favorably corrected in each magnification state from the wide-angle end to the telephoto end, and excellent imaging performance is secured.

[Fifth Embodiment] FIG. 18 is a diagram showing a lens configuration of a zoom lens according to a fifth embodiment of the present invention. In the zoom lens of FIG. 18, the first lens group G1
Comprises, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens,
And a cemented lens of a biconcave lens and a positive meniscus lens with the convex surface facing the object side.

The third lens group G3 is composed of, in order from the object side, a biconvex lens and a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 is composed of a biconvex lens. Further, the fifth lens group G5 includes, in order from the object side, a cemented lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens. The sixth lens group G6 is composed of, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side.

Table 5 below summarizes the data values of the fifth embodiment of the present invention. In Table (5), β represents the magnification, and FNO
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and d0 represents the object distance (axial distance between the object and the lens surface closest to the object). In Table (5), the surface number indicates the order of the lens surface from the object side, r indicates the radius of curvature of the lens surface, d indicates the distance between the lens surfaces, and ν and n indicate the d-line (λ = 587.56 nm). ) Are shown for Abbe number and refractive index, respectively. Further, in (values corresponding to conditional expressions) in Table (5), β _iw and β _it indicate the paraxial lateral magnification of the i-th lens unit at the wide-angle end and the telephoto end.

[0055]

[Table 5]

FIGS. 19 to 21 show various aberration diagrams of the fifth embodiment. 19 shows various aberrations at the wide-angle end (pos. 1), FIG. 20 shows various aberrations at the intermediate magnification state (pos. 2), and FIG. 21 shows various aberrations at the telephoto end (pos. 3). FIG. In each aberration diagram, NA is the numerical aperture, Y is the image height, and d is the d line (λ = 587.56 nm).
And g represents a g-line (λ = 435.83 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. 19 to 21, it can be seen that in the fifth embodiment, various aberrations are favorably corrected in each magnification state from the wide-angle end to the telephoto end, and excellent imaging performance is secured.

[Sixth Embodiment] FIG. 22 is a diagram showing a lens configuration of a zoom lens according to a sixth embodiment of the present invention. In the zoom lens of FIG. 22, the first lens group G1
Comprises, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens,
And a cemented lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens.

Further, the third lens group G3 is composed of, in order from the object side, a biconvex lens, and a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The fourth lens group G4 includes a positive meniscus lens having a convex surface facing the object side. Further, the fifth lens group G5 includes, in order from the object side, a cemented lens of a biconcave lens, a positive meniscus lens having a convex surface facing the object side, and a biconcave lens.
The sixth lens group G6 is composed of, in order from the object side, a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a biconvex lens.

Table 6 below summarizes the data values of the sixth embodiment of the present invention. In Table (6), β represents the magnification, and FNO
Represents the F number, 2ω represents the angle of view, Bf represents the back focus, and d0 represents the object distance (axial distance between the object and the lens surface closest to the object). In Table (6), the surface numbers indicate the order of the lens surfaces from the object side, r indicates the radius of curvature of the lens surfaces, d indicates the distance between the lens surfaces, and ν and n indicate the d-line (λ = 587.56 nm). ) Are shown for Abbe number and refractive index, respectively. In Table (6) (values corresponding to the conditional expressions), β _iw and β _it indicate the paraxial lateral magnification of the i-th lens unit at the wide-angle end and the telephoto end.

[0060]

[Table 6]

FIGS. 23 to 25 show various aberration diagrams of the sixth embodiment. 23 shows various aberrations at the wide-angle end (pos. 1), FIG. 24 shows various aberrations at the intermediate magnification state (pos. 2), and FIG. 25 shows various aberrations at the telephoto end (pos. 3). FIG. In each aberration diagram, NA is the numerical aperture, Y is the image height, and d is the d line (λ = 587.56 nm).
And g represents a g-line (λ = 435.83 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 23 to 25, in the sixth embodiment, it is understood that various aberrations are favorably corrected in each magnification state from the wide-angle end to the telephoto end, and excellent imaging performance is secured.

Although each of the above embodiments is a finite distance zoom lens, the first lens group G1 may be moved to the image side along the optical axis to form an infinity zoom lens. It is possible. In this case, if there is no air gap necessary for the first lens group G1 to move to the image side, the magnification is slightly changed from the wide-angle end to the telephoto side to widen the air gap with the second lens group G2, thereby achieving infinity. It becomes possible to use a distant zoom lens.

In each of the above embodiments, focusing on a short-distance object is realized by moving the fifth lens unit G5 having a negative refracting power to the image side.
By moving at least one of the third lens group G3 to the sixth lens group G6, it is possible to focus on a short-distance object. For example, in order to achieve focusing on a short-distance object with at least one of the third lens group G3, the fourth lens group G4, and the sixth lens group G6 having a positive refractive power, this lens group is required. Should be moved to the object side. The number of lens groups that move in the optical axis direction for focusing is not limited to one. In each of the above-described embodiments, the movement of the fifth lens group G5 corrects the change in the image point position caused by zooming. Instead, the third lens group G3, the fourth lens group G4, This may be performed by moving at least one lens group of the sixth lens group G6 in the optical axis direction.

[0064]

As described above, according to the present invention, it is possible to provide a small zoom lens having a high zoom ratio and high optical performance and capable of high-power close-up photography. Thus, it is possible to optimally use the zoom lens of the present invention according to various purposes. Specifically, the zoom lens of the present invention can be applied to digital still cameras, industrial cameras, micro cameras, video cameras, and the like.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram illustrating various aberrations of the first example at the wide-angle end (pos. 1).

FIG. 4 is a diagram illustrating various aberrations of the first embodiment in an intermediate magnification state (pos. 2).

FIG. 5 is a diagram of various types of aberration at the telephoto end (pos. 3) of the first example.

FIG. 6 is a diagram illustrating a lens configuration of a zoom lens according to a second example of the present invention.

FIG. 7 is a diagram showing various aberrations of the second embodiment at the wide-angle end (pos. 1).

FIG. 8 is a diagram illustrating various aberrations of the second embodiment in an intermediate magnification state (pos. 2).

FIG. 9 is a diagram of various types of aberration at the telephoto end (pos. 3) of the second embodiment.

FIG. 10 is a diagram illustrating a lens configuration of a zoom lens according to a third example of the present invention.

FIG. 11 is a diagram illustrating various aberrations of the third embodiment at a wide-angle end (pos. 1).

FIG. 12 is a diagram illustrating various aberrations of the third embodiment in an intermediate magnification state (pos. 2).

FIG. 13 is a diagram of various types of aberration at the telephoto end (pos. 3) of the third example.

FIG. 14 is a diagram showing a lens configuration of a zoom lens according to Example 4 of the present invention.

FIG. 15 is a diagram illustrating various aberrations of the fourth example at the wide-angle end (pos. 1).

FIG. 16 is a diagram illustrating various aberrations of the fourth embodiment in an intermediate magnification state (pos. 2).

FIG. 17 is a diagram showing various aberrations at the telephoto end (pos. 3) of the fourth embodiment;

FIG. 18 is a diagram illustrating a lens configuration of a zoom lens according to a fifth embodiment of the present invention.

FIG. 19 is a diagram illustrating various aberrations of the fifth embodiment at a wide-angle end (pos. 1).

FIG. 20 is a diagram illustrating various aberrations of the fifth embodiment in an intermediate magnification state (pos. 2).

FIG. 21 is a diagram of various types of aberration at the telephoto end (pos. 3) in the fifth example.

FIG. 22 is a diagram illustrating a lens configuration of a zoom lens according to Example 6 of the present invention.

FIG. 23 is a diagram showing various aberrations at the wide-angle end (pos. 1) in the sixth example;

FIG. 24 is a diagram illustrating various aberrations of the sixth embodiment in an intermediate magnification state (pos. 2);

FIG. 25 is a diagram of various types of aberration at the telephoto end (pos. 3) in the sixth example.

[Explanation of symbols]

 G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group

Claims (7)

[Claims] 1. A first lens having a positive refractive power in order from an object side.
A lens group G1, a second lens group G2 having a negative refractive power moving on the optical axis for zooming, and a third lens group G3 having a positive refractive power moving on the optical axis for zooming. A fourth lens group G4 having a positive refractive power and a fourth lens group G4 having a negative refractive power.
A lens group G5 and a sixth lens group G6 having a positive refractive power, and at least one of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. The movement of one lens group on the optical axis corrects the change of the image point position due to zooming. The focal length of the third lens group G3 is F3,
When the focal length of the lens group G4 is F4 and the focal length of the entire zoom lens system at the wide-angle end is Fw, the following condition is satisfied: 0.05 <Fw / F3 <1.0 0.05 <Fw / F4 <1.0 A zoom lens characterized by satisfying the following. 2. A combined focal length of the third lens group G3 and the fourth lens group G4 at a wide angle end is F34W,
4. The lens system according to claim 1, wherein when a combined focal length of said third lens group G3 and said fourth lens group G4 at the telephoto end is F34T, a condition of 0.4 <F34W / F34T <1.0 is satisfied. 2. The zoom lens according to 1. 3. The focal length of the second lens group G2 is set to F2.
And the focal length of the entire zoom lens system at the wide-angle end is F
The zoom lens according to claim 1, wherein when w is satisfied, the following condition is satisfied: 0.8 <| Fw / F2 | <1.5. 4. The focal length of the first lens group G1 is set to F1.
4. The lens system according to claim 1, wherein a condition of 0.18 <| F2 / F1 | <0.3 is satisfied, where F2 is a focal length of the second lens group G2. A zoom lens according to claim 1. 5. The focal length of said fifth lens group G5 is F5
5. The lens system according to claim 1, wherein a condition of 1.3 <| F6 / F5 | <2.0 is satisfied, where F6 is a focal length of the sixth lens group G6. A zoom lens according to claim 1. 6. The focal length of the entire zoom lens system at the wide-angle end is Fw, and the back focus of the zoom lens is Bf.
6. The zoom lens according to claim 1, wherein the following condition is satisfied: 2.0 <Bf / Fw <4.0. 7. When at least one of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 moves on the optical axis, The zoom lens according to claim 1, wherein focusing is performed on an object.