JPH08327902A - Zoom lens - Google Patents

Abstract

PURPOSE: To provide a zoom lens which has high performance and high variable power and meets a wide range of purposes of utilization. CONSTITUTION: This zoom lens has, successively from an object side, a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power, a fourth lens group G4 having negative refracting power and a fifth lens group G5 having positive refracting power. The zoom lens described above includes a zoom arrangement in which the magnification born by the second lens group G2, the magnification born by the third lens group G3 and the magnification born by the fourth lens group G4 nearly simultaneously attain equal magnification within the zoom region.

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 high variable power zoom lens.

[0002]

2. Description of the Related Art Conventionally, a finite optical system has been widely used in various electronic image devices which require photographing and projection by an optical system in inputting and outputting an image. Specifically, a finite optical system is used for a lens system for a digital still camera, a close-up photographing optical system, an enlargement / enlargement optical system, a reduction optical system, a projection lens for a liquid crystal video projector, and the like.

Of the finite optical systems, the finite system single focus lens is poor in versatility, and a dedicated optical system is used depending on the purpose. On the other hand, the finite zoom lens has higher versatility than the single focus lens, but the number of types of lenses is small. Finite system zoom lenses are often used in 35 mm still camera lens systems, 16 mm cine lens systems, and TV lens systems. In particular, as a compact and high-quality image input optical system for electronic image devices, low magnification (1/50 × to 1/3)
There has been a demand for an imaging zoom lens with a wide angle of view of about 0 ×).

[0004]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 3-7168
Japanese Patent No. 6 discloses a zoom lens having a low magnification and a wide angle of view. However, it is difficult to achieve a high zoom ratio in the zoom system (zooming system) of the zoom lens disclosed in this publication.
The zoom trajectory of each lens group is also complicated. Further, this zoom lens is an optical system for a measurement projector and strongly demands telecentricity. Further, since the effective F number is as dark as about F / 3.5 to F / 6.5, it is insufficient for photographing a dark subject with a black design depending on the illumination condition. In contrast, a bright, wide-angle, high-magnification, high-performance optical system has long been desired.

Optical systems used in electronic image equipment and the like include
Specifications corresponding to an extremely large number of purposes are required, and dedicated optical systems are provided according to various purposes. That is, in the conventional zoom lens, it is necessary to design a dedicated optical system according to the target number, which is very inefficient and uneconomical.

Further, as an optical system that can be used for an image pickup system requiring high resolution, chromatic aberration of magnification is well corrected, it is bright, has high performance, and high zooming is possible, and its conjugate length is short. There has been a demand for a zoom lens which has a wide angle of view and has little distortion and its variation during zooming. Further, in order to reduce shading, there has been a demand for a zoom lens that can secure a sufficient amount of peripheral light around the screen.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a zoom lens having a high performance, a high zoom ratio, and a wide range of purposes.

[0008]

In order to solve the above-mentioned problems, in the present invention, a first lens group G1 having a positive refractive power and a second lens group having a negative refractive power are arranged in this order from the object side. G2 and the third lens group G3 having a positive refractive power
And a fourth lens group G4 having a negative refracting power and a fifth lens group G5 having a positive refracting power, the second lens group G2 in the zoom region.
There is provided a zoom lens characterized in that it includes a zoom arrangement in which the magnification carried by the third lens group G3, the magnification carried by the third lens group G3, and the magnification carried by the fourth lens group G4 are substantially equal to each other.

[0009]

The zoom lens of the present invention comprises, in order from the object side, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, and the third lens having a positive refractive power. A group G3 and a fourth lens group G4 having a negative refractive power,
And a fifth lens group G5 having a positive refractive power.
Then, within the zoom region, the second lens group G2
Of the third lens group G3 and the magnification of the fourth lens group G4 are substantially equal to each other (-1).
×) is included.

Generally, in a zoom lens having a zooming unit composed of two or more lens groups, each zoom lens is arranged in a specific zoom arrangement lower than the lens arrangement (simultaneous same-magnification arrangement) that simultaneously satisfies the same magnification. The magnification of the lens group always satisfies the following conditional expressions (a) and (b). | Βi | <1 (a) | ... βi-1 βi βi + 1 ... | <1 (b) where βi is the lateral magnification of the i-th lens group i from the object side.

Further, in a specific zoom arrangement higher than the simultaneous equal-magnification arrangement, the magnifications of the respective lens groups always satisfy the following conditional expressions (c) and (d). | Βi |> 1 (c) | ... βi-1 βi βi + 1 ... |> 1 (d) From the above, in order to perform zooming efficiently in the zoom lens, the zooming unit is configured. It is optimal that the magnifications of the respective lens groups to be simultaneously become the same magnification (simultaneous same-magnification arrangement).

Further, when the zoom unit (variable-magnification unit) has a two-group configuration, among the solutions (zoom equation solution or zoom solution) satisfying the zoom equation, the variator group has the same magnification (βi = -1).
When the compensator group is also the same size (β j = -1), the two movement curves (solution curves of the zoom orbits) of the compensator group proliferate in the arrangement of the same size (β j = -1), It is possible to change trajectories. The zoom arrangement that positively uses this transfer of orbits and also makes the magnification of other lens groups the same at the same time, and the magnification of each lens group constituting the zoom unit (variable magnification unit) is the same magnification at the same time. It is essential to have a zoom arrangement such that the stable existence of zoom equation solutions and high zooming in the entire zoom range. As a result, it is possible to select a zoom power arrangement with very good zooming efficiency, and it is possible to achieve an optical system with a large zoom ratio (zooming ratio). Furthermore, a zoom trajectory (zoom equation solution) that can be reliably adopted can be realized.

However, when such a simultaneous equal-magnification arrangement is not adopted, examination of a solution of a zoom equation having a multi-group variable magnification lens group becomes complicated. Furthermore, since a solution curve in which zoom trajectories do not exist continuously is obtained, it is very difficult to continuously increase the zoom ratio. As a method of reducing distortion, a lens configuration having high symmetry with respect to the lens shape and the aperture stop having the refractive power arrangement can be considered. However,
With a zoom lens in which each lens unit moves along the optical axis with zooming, it is not possible to maintain symmetry with respect to the aperture stop over the entire zooming region (zoom region).

Therefore, in order to obtain an optical system in which distortion and its variation are small even during zooming, the refractive power distribution of each lens group has a certain symmetry with respect to the aperture stop as in the basic configuration of the present invention. The configuration that you have is essential. When analyzing the occurrence of distortion, it is desirable to consider the entire zoom lens by dividing it into three parts. That is, the lens group including the aperture stop is the middle group, the lens group on the object side of the middle group is the front group, and the lens group on the image side of the middle group is the rear group. In this case, in each of the front group and the rear group, a refractive power configuration and a lens configuration capable of correcting distortion to a considerable extent are required. The distortion aberration components that cannot be corrected by the front group and the rear group, and the distortion aberration components that cannot be canceled by the front group and the rear group are divided so that the middle group corrects them.

By adopting such a lens configuration, it is possible to reduce fluctuations in distortion even in a lens group that moves with zooming (magnification).
On the other hand, in order to reduce distortion very much, it is indispensable to make the internal refractive power distribution of the front group and the rear group positive, negative or negative, or positive to make the lens configuration and refractive power distribution capable of canceling aberrations. is there.

When a desired zoom ratio is obtained by forming a zoom unit with two or more lens groups,
It is possible to perform zooming by reducing the amount of movement of the lens group. As a result, the incident height of the chief ray at the wide-angle end can be made small, which is very effective for downsizing the lens diameter on the object side. As will be described later, each embodiment of the present invention shows an example in which the variable power portion is composed of three lens groups. However, even if the variable power section is composed of four lens groups, five lens groups or more lens groups while maintaining the symmetry with respect to the aperture stop, the variable power section may have the same-magnification arrangement. If so, a high-magnification zoom lens can be easily realized.

Usually, when the position of the pupil is brought as close as possible to the surface of the lens end, the arrangement of the refractive power of the lens group is such that the lens group of negative refractive power precedes the surface side of the lens end.
On the other hand, when the position of the pupil is moved as far away as possible from the surface of the lens end, the lens group having a positive refractive power precedes the lens group having a positive refractive power. By adopting such a refractive power distribution, a telecentric optical system on the image side, a telecentric optical system on the object side, or an optical system close to this can be realized. However, the zoom lens of the present invention does not need to be a telecentric optical system.
The position of the aperture stop is determined by the second lens group G2 and the third lens group G.
3 or the third lens group G3 and the fourth lens group G
It may be any position between 4 and 4. The aperture stop may be spatially moved in association with zooming (magnification), or the aperture stop may be fixed during magnification change.

Further, in the present invention, it is desirable that the following conditional expression (1) is satisfied in order to secure compactness and a large aperture ratio of the optical system. 0.3 <φ / f3 <0.8 (1) where φ: maximum effective diameter of the object side surface of the third lens group G3 at the wide-angle end f3: focal length of the third lens group G3

Conditional expression (1) is defined by the maximum effective diameter of the object side surface of the third lens group G3 at the wide-angle end and the third lens group G3.
It defines an appropriate range for the ratio to the focal length of.
If the upper limit of conditional expression (1) is exceeded, the optical system becomes unnecessarily bright, the size of the optical system becomes large, and the number of lenses increases significantly, which is not preferable. Further, the refracting power of the third lens group G3 becomes too strong, which makes it difficult to correct various aberrations including spherical aberration, which is not preferable.

On the contrary, if the lower limit of conditional expression (1) is exceeded,
The refractive power of the third lens group G3 becomes too weak, and the amount of movement of the lens group during zooming increases. As a result, interference with adjacent lens groups occurs, which makes it difficult to secure a sufficient zoom ratio, which is inconvenient. In addition, it becomes a dark optical system, and it is not desirable because the frequency of illumination is increased when photographing a dark subject. However, this does not apply to lighting. If only the brightness of the optical system is considered, the resolution may be darkened to the limit of diffraction. In this case, the lower limit of conditional expression (1) may be set to 0 and the upper limit may be set to 0.35. In the dark optical system, it is possible to easily further reduce the number of lenses in the second lens group G2 and the third lens group G3.

FIG. 1 is a diagram showing the basic structure of a zoom lens according to the present invention and the movement trajectory of each lens group due to zooming. In FIG. 1, fi is the focal length of the i-th lens group,
βw is the combined shooting magnification of the entire zoom lens system at the wide-angle end, βt is the combined shooting magnification of the entire zoom lens system at the telephoto end, and βc is the combined shooting magnification of the entire zoom lens system in the simultaneous equal-magnification arrangement. There is. Also, βwi
Is the magnification of the i-th lens group at the wide-angle end, βti is the magnification of the i-th lens group at the telephoto end, and βci is the magnification of the i-th lens group in the simultaneous equal magnification arrangement state.

In each zoom arrangement, the relationships shown in the following equations (e) to (m) are established. β = β1 β2 β3 β4 β5 (e) βz = β2 β3 β4 (f) βw = βw1 βw2 βw3 βw4 βw5 (g) βc = -βc1 βc5 (h) βt = βt1βt2 βt3βt4βt5 (i) | βw2β3β4 | 3w4βw4 (K) | βt2 βt3βt4 |> 1 (m) where β: Magnification of the entire zoom lens system in an arbitrary zoom arrangement βz: Magnification of the zooming section in an arbitrary zoom arrangement

It is desirable that the magnifications of the respective lens units of the variable power portion be within the range defined by the following conditional expressions (2) to (4) while having the simultaneous magnification arrangement. -1.4 <β2 <-0.4 (2) -1.5 <β3 <-0.5 (3) -1.5 <β4 <-0.6 (4)

When the upper limit of conditional expression (2) is exceeded, the incident height of the chief ray at the outermost periphery of the screen passing through the surface closest to the object (first lens surface) is significantly separated from the optical axis. As a result, the lens diameter is increased and the first lens group G
This is not preferable because the first lens group G2 and the first lens group G2 interfere with each other.
Further, at the wide-angle end, it becomes difficult to correct the outer coma aberration of the lower light flux of the principal ray. Conversely, if the lower limit of conditional expression (2) is exceeded, the second lens group G2 and the third lens group G2
It interferes with 3 and is not preferable.

If the upper limit of conditional expression (3) is exceeded, the incident height of the chief ray at the outermost periphery of the screen that passes through the surface closest to the object side will be significantly separated from the optical axis. As a result, the lens diameter is increased, and the second lens group G2 and the third lens group G are used.
It interferes with 3 and is not preferable. Conversely, conditional expression (3)
Below the lower limit of, it becomes difficult to correct spherical aberration at the telephoto end, and the third lens group G3 and the fourth lens group G4 interfere with each other, which is not preferable.

If the upper limit of conditional expression (4) is exceeded, the incident height of the chief ray at the outermost periphery of the screen that passes through the surface closest to the object side will be significantly separated from the optical axis. As a result, the lens diameter is increased, and the third lens group G3 and the fourth lens group G are used.
It interferes with 4 and is not preferable. Conversely, conditional expression (4)
When the value is below the lower limit of, it becomes difficult to correct the outer coma aberration of the upper light flux of the principal ray, and the fourth lens group G4 and the fifth lens group G5 interfere with each other, which is not preferable.

However, in the present invention, the second lens group G2
The lens arrangement in which the third lens group G3 and the fourth lens group G4 simultaneously satisfy equal magnification, that is, the simultaneous equal magnification arrangement is not only a lens arrangement that requires mathematical strictness, but also substantially equal magnification. The lens arrangement is also included. That is, a magnification error range that causes a focus error such as a rounding error, a manufacturing tolerance, and the like, which is about the depth of focus on the imaging surface, and an error range due to adjustment are recognized. Thus, in the present invention,
A zoom arrangement in which the magnification is approximately the same magnification within the allowable range is also included in the simultaneous magnification. Then, even if a region where no zoom solution exists near the simultaneous equal-magnification arrangement occurs, it is considered that there is no practical problem as long as the zoom region that causes the focus jump on the image plane is small.

As a guide for a desirable allowable range, at least one of the magnifications βc2, βc3 and βc4 of the second lens group G2 to the fourth lens group G4 is equal to (-1).
In the case of x), if the combined magnification βci carried by the other lens units constituting the variable power portion is within the range of the following conditional expression (5), the simultaneous equal magnification arrangement is allowed. 0.9 <| βci | <1.1 (5)

If the upper limit of conditional expression (5) is exceeded, the area where no zoom solution exists from the telephoto end increases, and the area in which focus is fixed due to zooming becomes unfavorable. vice versa,
When the value goes below the lower limit of conditional expression (5), the area where no zoom solution exists from the wide-angle end increases, and the area in which the focus is fixed due to zooming is unfavorable. If these areas without zoom solutions expand, the areas where continuous variable magnification cannot be achieved increase, and the practicality is significantly reduced, which is not preferable.

Further, in the present invention, it is desirable that the following conditional expression (6) is satisfied. 0.05 <β1 / β5 <0.5 (6) Conditional expression (6) defines an appropriate range for the ratio between the magnification β1 of the first lens group G1 and the magnification β5 of the fifth lens group G5. ing. The conditional expression (6) is an effective expression only in the case of the optical system for finite distance.

If the upper limit of conditional expression (6) is exceeded, the back focus becomes short and the working distance (working distance) to the object point becomes short. As a result, a desired magnification cannot be secured as a finite system, which is not preferable. On the other hand, when the value goes below the lower limit of conditional expression (6), the working distance to the object point becomes unnecessarily long, the back focus becomes long, and the optical system becomes large, which is not preferable. However, this does not mean that focusing on an object at infinity is impossible in general photography.

Further, in the present invention, it is desirable that the following conditional expression (7) is satisfied. 0.7 <f2 / f4 <1.3 (7) Conditional expression (7) defines an appropriate range for the ratio between the focal length of the second lens group G2 and the focal length of the fourth lens group G4. .

When the value exceeds the upper limit of the conditional expression (7), the moving amount of the second lens group G2 increases and interferes with other lens groups to reduce the zooming efficiency, so that a zoom lens having a high zooming ratio is obtained. Not good for Further, the refracting power of the fourth lens group G4 becomes too strong, the load on the fifth lens group G5 increases, and it becomes difficult to correct the coma aberration of the upper light flux of the chief ray, which is not preferable. On the other hand, when the value goes below the lower limit of the conditional expression (7), the refractive power of the second lens group G2 becomes strong and the telephoto end can be widened, so that the magnification can be increased. However, at the wide-angle end, the incident height of the chief ray at the outermost periphery of the screen that passes through the surface closest to the object side is significantly separated from the optical axis, and the lens diameter is increased, which is not preferable. Further, it becomes difficult to correct various aberrations such as spherical aberration and coma.

The second lens group G2 and the third lens group G
As the allowable range of the lens arrangement (simultaneous same-magnification arrangement) in which the third and fourth lens groups G4 simultaneously satisfy the same magnification, it is possible to introduce a guide different from the above-mentioned conditional expression (5). That is, as another target of the allowable range, at least one of the magnifications βc2, βc3, and βc4 carried by the second lens group G2 to the fourth lens group G4 is equal magnification (-1 ×).
At this time, if the composite magnification | βc2βc3βc4 | that the variable-magnification unit has is within the range of the following conditional expression (8), the simultaneous equal-magnification arrangement is permitted. 0.95 <| βc2βc3βc4 | <1.05 (8)

If the upper limit of conditional expression (8) is exceeded, the area where no zoom solution exists from the telephoto end increases, and the area in which focus is fixed due to zooming is unfavorable. vice versa,
When the value goes below the lower limit of conditional expression (8), the area where no zoom solution exists from the wide-angle end increases, and the area where the focus is fixed due to zooming becomes narrow, which is not preferable. If these areas without zoom solutions expand, continuous variable magnification cannot be achieved. However, for discontinuous use purposes, if only the wide-angle region and the telephoto region are adopted and the intermediate focal length region is unnecessary, the upper limit value and the lower limit value of the conditional expression (8) inevitably change. Then, in such a case, it is obvious that the practicability does not decrease even if the region where the zoom solution does not exist expands.

[0036]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The zoom lens according to each embodiment 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 first lens group G2 having a positive refractive power. It includes a third lens group G3, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power. In the zoom area, a zoom arrangement is included in which the magnification of the second lens group G2, the magnification of the third lens group G3, and the magnification of the fourth lens group G4 are simultaneously equal.

In each embodiment, it is possible to focus by moving the first lens group G1 toward the object side, and it is possible to change the photographing distance, the area of magnification change, and the like. The second lens group G2 is a compensator group, the third lens group G3 is a main lead group, and the fourth lens group G4 is a sub lead group. That is, the second lens group G2 to the fourth lens group G4 form a variable power unit that moves along the optical axis to perform variable power. The fifth lens group G5 is a lens group fixed with respect to the image plane, and is a main lens group that determines the length of the back focus and the exit pupil position. In each embodiment, an aperture stop is provided immediately on the object side of the third lens group G3.

Example 1 FIG. 2 is a diagram showing a lens configuration of a zoom lens according to Example 1 of the present invention. In the zoom lens of FIG. 2, on the object side of the first lens group G1,
A filter composed of parallel plane plates is provided. The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side, and a strong curvature on the object side. It consists of a positive meniscus lens with its convex surface facing. The second lens group G2 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, a biconcave lens, and a cemented positive lens including a biconvex lens and a biconcave lens.

The third lens group G3 comprises a cemented positive lens composed of a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens. The fourth lens group G4 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, and a cemented negative lens including a biconcave lens and a biconvex lens. The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens.

The zoom lens of the first embodiment has a zoom ratio of 6 times and a lens construction of 17 elements in 12 groups. The feature of this embodiment is the lens arrangement of the second lens group G2 and the lens arrangement of the fifth lens group G5. The lens arrangement of this embodiment is a typical lens arrangement of the present invention.

The following table (1) lists the values of specifications of the first embodiment of the present invention. In Table (1), f is the focal length and F is
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0042]

[Table 1] (Variable spacing during zooming) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.120 D0 692.838 692.838 692.838 692.838 692.838 692.838 d7 0.545 10.032 12.459 16.773 18.670 19.511 d14 47.610 31.222 26.297 16.196 11.070 8.131 d19 2.874 11.638 10.864 10.29 d. 8.669 7.995 6.433 5.956 4.374 Bf 37.387 37.387 37.387 37.387 37.387 37.387 (Condition value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -19.300 βw2 = -0.5691 βc2 = -1.0000 βf2 = -1.2914 33.073 βw3 = -0.6344 βc3 = -1.0000 βt3 = -1.2436 f4 = -21.096 βw4 = -0.8366 βc4 = -1.0000 βt4 = -1.1285 f5 = 24.210 βw5 = -0.7191 βc5 = -0.7191 βt5 = -0.7191 fw = 14.850 βw =- 0.0200 βc = -0.0662 βt = -0.1200 ft = 101.114 φ = 15.7 (1) φ / f3 = 0.47471 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 0.91487

3 and 4 show the d line (λ = 587.6).
nm) and the first for the g-line (λ = 435.8 nm)
FIG. 7 is a diagram of various types of aberration of the example. 3 shows various aberration diagrams at the wide-angle end (shortest focal length state), and FIG. 4 shows various aberration diagrams at the telephoto end (longest focal length state). In each aberration diagram, H is the height of the incident light and FN is F.
Number, Y is the image height, D is the d-line (λ = 587.6n
m), and G indicates the g-line (λ = 435.8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, in this example,
It can be seen that various aberrations are satisfactorily corrected in each focal length state.

Example 2 FIG. 5 is a diagram showing a lens configuration of a zoom lens according to Example 2 of the present invention. In the zoom lens of FIG. 5, on the object side of the first lens group G1,
A filter composed of parallel plane plates is provided. The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side, and a strong curvature on the object side. It consists of a positive meniscus lens with its convex surface facing. The second lens group G2 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, a biconcave lens, and a cemented positive lens including a biconvex lens and a biconcave lens.

The third lens group G3 includes a cemented positive lens including a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens. The fourth lens group G4 includes a cemented negative lens including a positive meniscus lens having a concave surface with a weak curvature facing the object side and a biconcave lens, and a negative meniscus lens having a concave surface having a strong curvature facing the object side.

The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens. Consists of. The zoom lens of the second example has a zoom ratio of 6 and a lens configuration of 17 elements in 12 groups. The lens arrangement of this embodiment is also a typical lens arrangement of the present invention.

The following table (2) lists the values of specifications of the second embodiment of the present invention. In Table (2), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0048]

[Table 2] (Variable spacing during zooming) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.120 D0 692.785 692.785 692.785 692.785 692.785 692.785 d7 0.538 10.025 12.452 16.767 18.663 19.340 d14 47.815 31.427 26.502 16.401 11.276 8.671 d19 2.022 10.785 12.9558 21.306 2 10.332 9.657 8.095 7.618 5.718 Bf 37.405 37.405 37.405 37.405 37.405 37.405 (Value corresponding to the condition) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -19.300 βw2 = -0.5691 βc2 = -1.0000 βt2 = -1.2774 33.073 βw3 = -0.6344 βc3 = -1.0000 βt3 = -1.2406 f4 = -21.096 βw4 = -0.8366 βc4 = -1.0000 βt4 = -1.1436 f5 = 24.210 βw5 = -0.7191 βc5 = -0.7191 βt5 = -0.7191 fw = 14.850 βw =- 0.0200 βc = -0.0662 βt = -0.1200 ft = 100.361 φ = 15.8 (1) φ / f3 = 0.47773 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 0.91487

FIGS. 6 and 7 show d line (λ = 587.6).
nm) and the second for the g-line (λ = 435.8 nm)
FIG. 7 is a diagram of various types of aberration of the example. 6 is a diagram showing various aberrations at the wide-angle end, and FIG. 7 is a diagram showing various aberrations at the telephoto end. In each aberration diagram, H is the height of incident light, FN is the F number, Y is the image height, and D is the d-line (λ =
587.6 nm) and G is the g-line (λ = 435.8 nm)
Are shown respectively. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Third Embodiment] FIG. 8 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. 8, on the object side of the first lens group G1,
A filter composed of parallel plane plates is provided. The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side, and a strong curvature on the object side. It consists of a positive meniscus lens with its convex surface facing. The second lens group G2 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, a biconcave lens, and a cemented positive lens including a biconvex lens and a biconcave lens.

The third lens group G3 includes a cemented positive lens including a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens. The fourth lens group G4 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, and a cemented negative lens including a biconcave lens and a biconvex lens. The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a biconvex lens,
And a biconvex lens and a negative meniscus lens having a concave surface with a strong curvature facing the object side, which is a positive lens. Third
The zoom lens of the embodiment has a zoom ratio of 5 times, and has 12 groups 1
It has a seven-lens configuration.

Table (3) below lists values of specifications of the third embodiment of the present invention. In Table (3), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0053]

[Table 3] (Variable interval in zooming) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.100 D0 692.653 692.653 692.653 692.653 692.653 692.653 d7 0.668 4.082 10.156 12.582 16.897 18.794 d14 47.038 41.533 30.650 25.725 15.624 10.498 d19 2.969 5.625 11.733 14.906 22.254 25.959 d. (10327) 33.073 βw3 = -0.6344 βc3 = -1.0000 βt3 = -1.1725 f4 = -21.096 βw4 = -0.8366 βc4 = -1.0000 βt4 = -1.0535 f5 = 24.210 βw5 = -0.7191 βc5 = -0.7191 βt5 = -0.7191 fw = 14.850 βw =- 0.0200 βc = -0.0662 βt = -0.1000 ft = 84.638 φ = 15.7 (1) φ / f3 = 0.47471 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 0.91487

FIGS. 9 and 10 show d line (λ = 587.
6 nm) and g-line (λ = 435.8 nm) for various aberrations of the third example. 9 shows various aberration diagrams at the wide-angle end, and FIG. 10 shows various aberration diagrams at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is the d-line (λ
= 587.6 nm), G is the g-line (λ = 435.8n)
m) are shown respectively. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Fourth Embodiment] FIG. 11 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. 11, a filter formed of a plane parallel plate is provided on the object side of the first lens group G1.
The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side.
And a positive meniscus lens having a convex surface with a strong curvature facing the object side. The second lens group G2 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, a biconcave lens, and a cemented positive lens including a biconvex lens and a biconcave lens.

The third lens group G3 is composed of a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a positive meniscus lens having a convex surface having a strong curvature facing the object side. The fourth lens group G4 includes a cemented negative lens including a positive meniscus lens having a concave surface with a weak curvature facing the object side and a biconcave lens, and a biconcave lens.

The fifth lens group G5 is a cemented positive lens, a biconvex lens, and a biconvex lens, in which a positive meniscus lens having a concave surface with a weak curvature facing the object side and a negative meniscus lens with a concave surface having a strong curvature facing the object side are cemented together. Consists of. The zoom lens of the fourth embodiment has a zoom ratio of 5 and a lens configuration of 17 elements in 12 groups. The characteristics of this embodiment are the lens shape of the third lens group G3 (positive meniscus lens) and the lens shape of the fifth lens group G5 (bonded positive lens).

The following table (4) lists the values of specifications of the fourth embodiment of the present invention. In Table (4), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0059]

[Table 4] (Variable spacing during zooming) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.100 D0 692.544 692.544 692.544 692.544 692.544 692.544 d7 0.184 3.597 9.671 12.098 16.413 18.310 d14 47.862 42.357 31.474 26.549 16.449 11.323 d19 0.965 3.621 23.729 12.901 12.901 11.157 9.858 9.184 7.621 7.145 Bf 38.789 38.789 38.789 38.789 38.789 38.789 (Condition corresponding value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -19.300 βw2 = -0.5691 βc2 = -1.0000 βt2 = -1.2226 33.073 βw3 = -0.6344 βc3 = -1.0000 βt3 = -1.1725 f4 = -21.096 βw4 = -0.8366 βc4 = -1.0000 βt4 = -1.0535 f5 = 24.210 βw5 = -0.7191 βc5 = -0.7191 βt5 = -0.7191 fw = 14.850 βw =- 0.0200 βc = -0.0662 βt = -0.1000 ft = 84.638 φ = 16.0 (1) φ / f3 = 0.48378 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 0.91487

12 and 13 show d line (λ = 58).
(7.6 nm) and g-line (λ = 435.8 nm) are graphs showing various aberrations of the fourth example. FIG. 12 is a diagram showing various aberrations at the wide-angle end, and FIG. 13 is a diagram showing various aberrations at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is d.
Line (λ = 587.6 nm) and G is the g line (λ = 435.
8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Fifth Embodiment] FIG. 14 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. 14, a filter formed of a plane parallel plate is provided on the object side of the first lens group G1.
The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side.
And a positive meniscus lens having a convex surface with a strong curvature facing the object side. The second lens group G2 includes a negative meniscus lens having a convex surface with a weak curvature facing the object side, a biconcave lens, and a cemented positive lens including a biconvex lens and a biconcave lens.

The third lens group G3 is composed of a cemented positive lens including a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens. The fourth lens group G4 includes a biconcave lens, a cemented negative lens including a biconvex lens and a biconcave lens, and a negative meniscus lens having a concave surface having a strong curvature facing the object side. The fifth lens group G5 includes
A positive meniscus lens with a concave surface with a weak curvature facing the object side,
It consists of a positive lens cemented with a biconvex lens and a negative meniscus lens having a concave surface with a strong curvature facing the object side, and a biconvex lens. The zoom lens of the fifth embodiment has a zoom ratio of 5 and a lens configuration of 18 elements in 13 groups. The feature of this embodiment is the lens arrangement of the fourth lens group G4.

Table (5) below shows values of specifications of the fifth embodiment of the present invention. In Table (5), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0064]

[Table 5] (Variable spacing during zooming) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.100 D0 692.863 692.863 692.863 692.863 692.863 692.863 d7 0.603 4.016 10.090 12.517 16.832 18.729 d14 47.458 41.953 31.070 26.145 16.044 10.918 d19 2.702 5.358 25.465 14.638 2 8.474 7.175 6.501 4.939 4.462 Bf 37.651 37.651 37.651 37.651 37.651 37.651 (Condition value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -19.300 βw2 = -0.5691 βc2 = -1.0000 βt2 = -1.2226 33.073 βw3 = -0.6344 βc3 = -1.0000 βt3 = -1.1725 f4 = -21.096 βw4 = -0.8366 βc4 = -1.0000 βt4 = -1.0535 f5 = 24.210 βw5 = -0.7191 βc5 = -0.7191 βt5 = -0.7191 fw = 14.850 βw =- 0.0200 βc = -0.0662 βt = -0.1000 ft = 84.638 φ = 15.7 (1) φ / f3 = 0.47471 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 0.91487

15 and 16 show d line (λ = 58).
(7.6 nm) and g-line (λ = 435.8 nm) are various aberration diagrams of the fifth example. FIG. 15 shows various aberration diagrams at the wide-angle end, and FIG. 16 shows various aberration diagrams at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is d.
Line (λ = 587.6 nm) and G is the g line (λ = 435.
8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Sixth Embodiment] FIG. 17 is a view showing the lens arrangement of a zoom lens according to the sixth embodiment of the present invention.
In the zoom lens of FIG. 17, a filter formed of a plane parallel plate is provided on the object side of the first lens group G1.
The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side.
And a positive meniscus lens having a convex surface with a strong curvature facing the object side. The second lens group G2 includes a negative meniscus lens having a convex surface having a weak curvature facing the object side, a negative meniscus lens having a convex surface having a weak curvature facing the object side, and a positive meniscus lens having a concave surface having a weak curvature facing the object side. It consists of a cemented negative lens with a negative meniscus lens with a concave surface with a strong curvature facing the object side.

The third lens group G3 is composed of a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a positive meniscus lens having a convex surface having a strong curvature facing the object side. The fourth lens group G4 includes a negative meniscus lens having a convex surface having a strong curvature facing the object side, and a cemented negative lens including a biconcave lens and a biconvex lens. The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens.

The zoom lens of the sixth embodiment has a zoom ratio of 7 and has a lens configuration of 17 elements in 12 groups. The characteristics of this embodiment are the lens arrangement and lens shape of the second lens group G2, and the lens shape of the third lens group G3. With such a configuration, the fluctuation of the coma aberration of the lower light flux of the principal ray due to the magnification change is corrected.

The following table (6) lists the values of specifications of the sixth embodiment of the present invention. In Table (6), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0070]

[Table 6] (Variable spacing during zooming) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.140 D0 692.818 692.818 692.818 692.818 692.818 692.818 d7 1.684 10.229 12.436 16.185 17.644 18.985 d14 42.613 26.781 22.046 12.660 8.447 3.292 d19 3.059 12.604 15.4071 23.871 27.27 2771. 11.147 10.299 8.046 6.728 3.468 Bf 35.931 35.931 35.931 35.931 35.931 35.931 (Condition value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -20.000 βw2 = -0.6071 βc2 = -1.0000 βt2 = -1.2786 33.073 βw3 = -0.6453 βc3 = -1.0000 βt3 = -1.3041 f4 = -20.000 βw4 = -0.7709 βc4 = -1.0000 βt4 = -1.2678 f5 = 24.133 βw5 = -0.7192 βc5 = -0.7192 βt5 = -0.7192 fw = 14.909 βw =- 0.0200 βc = -0.0662 βt = -0.1400 ft = 116.246 φ = 15.5 (1) φ / f3 = 0.46866 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 1.00000

18 and 19 show d line (λ = 58).
(7.6 nm) and g-line (λ = 435.8 nm) are various aberration diagrams of the sixth example. 18 is a diagram showing various aberrations at the wide-angle end, and FIG. 19 is a diagram showing various aberrations at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is d.
Line (λ = 587.6 nm) and G is the g line (λ = 435.
8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Seventh Embodiment] FIG. 20 is a diagram showing a lens structure of a zoom lens according to a seventh embodiment of the present invention.
In the zoom lens of FIG. 20, a filter formed of a plane parallel plate is provided on the object side of the first lens group G1.
The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side.
And a positive meniscus lens having a convex surface with a strong curvature facing the object side. The second lens group G2 includes a negative meniscus lens having a convex surface having a weak curvature facing the object side, a negative meniscus lens having a convex surface having a weak curvature facing the object side, and a positive meniscus lens having a concave surface having a weak curvature facing the object side. It consists of a cemented negative lens with a negative meniscus lens with a concave surface with a strong curvature facing the object side.

The third lens group G3 is composed of a biconvex lens and a positive meniscus lens having a convex surface having a strong curvature facing the object side. The fourth lens group G4 includes a cemented negative lens including a positive meniscus lens having a concave surface with a weak curvature facing the object side and a biconcave lens, and a negative meniscus lens having a concave surface having a strong curvature facing the object side. The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens.

The zoom lens of the seventh embodiment has a zoom ratio of 6 times and a lens structure of 16 elements in 12 groups. The feature of this embodiment is that the number of lenses of the third lens group G3 is two and no cemented lens is used, and the second lens group G3.
2 lens arrangement and lens shape. With such a configuration, similarly to the sixth embodiment, the variation due to the magnification change of the coma aberration of the lower light flux of the principal ray is corrected.

The following table (7) lists the values of specifications of the seventh embodiment of the present invention. In Table (7), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0076]

[Table 7] (Variable spacing during zooming) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.120 D0 692.911 692.911 692.911 692.911 692.911 692.911 d7 0.145 8.699 11.213 15.277 17.166 16.554 d14 44.065 28.621 23.645 13.841 9.125 5.833 d18 1.803 11.359 14.489 22.197 25.852 30.002 d. 11.589 10.921 8.953 8.124 5.878 Bf 36.693 36.693 36.693 36.693 36.693 36.693 (Value corresponding to condition) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -20.000 βw2 = -0.5862 βc2 = -1.0000 βt2 = -1.1971 33.073 βw3 = -0.6385 βc3 = -1.0000 βt3 = -1.2351 f4 = -20.000 βw4 = -0.8068 βc4 = -1.0000 βt4 = -1.2257 f5 = 24.133 βw5 = -0.7192 βc5 = -0.7192 βt5 = -0.7192 fw = 14.838 βw =- 0.0200 βc = -0.0662 βt = -0.1200 ft = 99.572 φ = 16.0 (1) φ / f3 = 0.48378 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 1.00000

21 and 22 show d line (λ = 58).
(7.6 nm) and g-line (λ = 435.8 nm) are graphs showing various aberrations of the seventh example. 21 shows various aberration diagrams at the wide-angle end, and FIG. 22 shows various aberration diagrams at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is d.
Line (λ = 587.6 nm) and G is the g line (λ = 435.
8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Embodiment 8] FIG. 23 is a diagram showing a lens structure of a zoom lens according to an eighth embodiment of the present invention.
In the zoom lens of FIG. 23, a filter formed of a plane parallel plate is provided on the object side of the first lens group G1.
The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side.
And a positive meniscus lens having a convex surface with a strong curvature facing the object side.

The second lens group G2 includes a negative meniscus lens having a convex surface having a weak curvature facing the object side, a negative meniscus lens having a convex surface having a weak curvature facing the object side, and a cemented negative lens including a biconcave lens and a biconvex lens. Consists of. The third lens group G3 includes a cemented positive lens including a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens.

The fourth lens group G4 is composed of a cemented negative lens composed of a positive meniscus lens having a concave surface with a weak curvature facing the object side and a biconcave lens, and a biconcave lens. The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a cemented positive lens having a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a biconvex lens. The zoom lens of Example 8 has a zoom ratio of 6 and a lens configuration of 17 elements in 12 groups. The feature of this embodiment is the lens arrangement and the lens shape of the second lens group G2.

The following table (8) lists the values of specifications of the eighth embodiment of the present invention. In Table (8), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0082]

[Table 8] (Variable interval in zooming) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.120 D0 694.019 694.019 694.019 694.019 694.019 694.019 d7 0.572 8.493 10.861 14.926 16.419 15.353 d14 40.529 25.362 20.494 10.802 6.550 3.828 d19 1.185 11.260 14.510 22.121 26.166 30.807 d. 12.266 11.516 9.531 8.244 5.391 Bf 36.950 36.950 36.950 36.950 36.950 36.950 (corresponding value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -20.000 βw2 = -0.6071 βc2 = -1.0000 βt2 = -1.1654 33.073 βw3 = -0.6453 βc3 = -1.0000 βt3 = -1.2380 f4 = -20.000 βw4 = -0.7709 βc4 = -1.0000 βt4 = -1.2560 f5 = 24.133 βw5 = -0.7192 βc5 = -0.7192 βt5 = -0.7192 fw = 14.909 βw =- 0.0200 βc = -0.0662 βt = -0.1200 ft = 98.091 φ = 15.7 (1) φ / f3 = 0.47471 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 1.00000

24 and 25 show d line (λ = 58).
(7.6 nm) and g-line (λ = 435.8 nm) are various aberration diagrams of the eighth example. Then, FIG. 24 shows various aberration diagrams at the wide-angle end, and FIG. 25 shows various aberration diagrams at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is d.
Line (λ = 587.6 nm) and G is the g line (λ = 435.
8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

[Embodiment 9] FIG. 26 is a diagram showing a lens structure of a zoom lens according to a ninth embodiment of the present invention.
In the zoom lens of FIG. 26, a filter formed of a plane parallel plate is provided on the object side of the first lens group G1.
The first lens group G1 is a positive lens cemented with a negative meniscus lens having a convex surface having a weak curvature facing the object side and a positive meniscus lens having a convex surface having a strong curvature facing the object side.
And a positive meniscus lens having a convex surface with a strong curvature facing the object side.

The second lens group G2 includes a negative meniscus lens having a convex surface having a weak curvature facing the object side, a negative meniscus lens having a convex surface having a weak curvature facing the object side, and a cemented negative lens including a biconcave lens and a biconvex lens. Consists of. The third lens group G3 includes a cemented positive lens including a biconvex lens and a negative meniscus lens having a concave surface having a strong curvature facing the object side, and a positive meniscus lens having a convex surface having a weak curvature facing the object side.

The fourth lens group G4 is composed of a cemented negative lens including a biconvex lens and a biconcave lens, and a negative meniscus lens having a concave surface having a strong curvature facing the object side. The fifth lens group G5 includes a positive meniscus lens having a concave surface with a weak curvature facing the object side, a cemented positive lens of a biconcave lens and a biconvex lens, a biconvex lens, and a biconvex lens.

The zoom lens of the ninth embodiment has a zoom ratio of 6 times and a lens construction of 17 elements in 12 groups. The feature of this embodiment is that the lens arrangement of the second lens group G2, the lens shape of the third lens group G3 (biconvex lens), and the number of lenses of the fifth lens group G5 are one more than in the other embodiments. is there. By arranging the negative lens component in the fifth lens group G5 as close to the object side as possible, it is possible to secure a long back focus. Further, with such a lens arrangement and lens shape, fluctuations due to the magnification variation of the coma aberration of the upper light flux and the lower light flux of the chief ray are corrected.

The following table (9) lists the values of specifications of the ninth embodiment of the present invention. In Table (9), f is the focal length, F
N is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and D0 is the object point distance. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number respectively indicate values for the d-line (λ = 587.6 nm).

[0089]

[Table 9] (Variable spacing in zoom) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.120 D0 693.451 693.451 693.451 693.451 693.451 693.451 d7 1.089 9.500 11.611 15.771 16.638 14.870 d14 41.250 25.551 20.929 10.971 7.716 4.549 d19 1.129 10.793 14.258 21.807 26.386 30.750 d. 9.219 8.264 6.512 4.322 1.893 Bf 39.720 39.720 39.720 39.720 39.720 39.720 (Condition corresponding value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -20.000 βw2 = -0.6071 βc2 = -1.0000 βt2 = -1.1654 33.073 βw3 = -0.6453 βc3 = -1.0000 βt3 = -1.2380 f4 = -20.000 βw4 = -0.7709 βc4 = -1.0000 βt4 = -1.2560 f5 = 24.133 βw5 = -0.7192 βc5 = -0.7192 βt5 = -0.7192 fw = 14.909 βw =- 0.0200 βc = -0.0662 βt = -0.1200 ft = 98.091 φ = 16.0 (1) φ / f3 = 0.48378 (6) β1 / β5 = 0.1281 (7) f2 / f4 = 1.00000

27 and 28 show d line (λ = 58).
(7.6 nm) and g-line (λ = 435.8 nm) are graphs showing various aberrations of the ninth example. Then, FIG. 27 shows various aberration diagrams at the wide-angle end, and FIG. 28 shows various aberration diagrams at the telephoto end. In each aberration diagram, H is the height of the incident light, FN is the F number, Y is the image height, and D is d.
Line (λ = 587.6 nm) and G is the g line (λ = 435.
8 nm). Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. As is clear from each aberration diagram, it is understood that various aberrations are satisfactorily corrected in each focal length state in the present embodiment.

As described above, in each embodiment, the effective F value at the wide-angle end is about F / 2.0, which is very bright, and the peripheral light quantity is sufficiently secured. Further, in each of the above-described embodiments, particularly at the wide-angle end, the distortion aberration is almost completely corrected, and the decrease in the illuminance ratio depends on cos ⁴ θ, so it is necessary to suppress the vignetting. As is clear from the aberration diagrams, a sufficient amount of peripheral light is secured in each example.
Since the amount of peripheral light is large, in order to suppress the occurrence of coma aberration variation due to zooming, in particular as a measure against coma aberration of the lower light flux of the principal ray, the lens arrangement and lens shape of the second lens group G2, and the third lens group G2 Consideration has been given to the lens shape of the lens group G3. On the other hand, the lens arrangement and lens shape of the fifth lens group G5 have been devised as a countermeasure against the coma of the upper light flux of the chief ray.

By increasing the number of cemented lenses in the lens arrangement of the fourth lens group G4, it is possible to secure a sufficient degree of freedom to simultaneously correct axial chromatic aberration and lateral chromatic aberration at the wide-angle end. Is possible. In this case, it is possible to reduce the achromatic load of the second lens group G2. Furthermore, in each of the above-described embodiments, the lens system is composed of five lens groups.
However, it is also easy to divide the third lens group G3 into two lens groups to form a lens system having a six-group structure as a whole. Similarly, it is easy to divide the third lens group G3 into three lens groups so as to secure the degree of freedom in increasing the aperture and to make a lens system having a seven-group structure as a whole.

Needless to say, when it is unnecessary to widen the angle of the optical system or when the dark optical system serves its purpose sufficiently, it is possible to reduce the number of constituent lenses as compared with the above embodiments. In particular, it is much easier to increase the zoom ratio by enlarging the zoom area to the telephoto end side than to expand to the wide-angle end. Further, shortening the conjugate length and increasing the photographing magnification can be easily realized by the present invention because it is not necessary to widen the angle. As one method for realizing this, the first lens group G1 can be extended to the object side. Further, although the above-mentioned embodiment is limited to the finite system, it can be sufficiently applied to the infinite photographing system.

Furthermore, in each of the above-mentioned embodiments, the effective F value is very bright at about F / 2.0 at the wide-angle end, and the peripheral light quantity is sufficiently secured. And despite the bright optics,
The effective diameter of the most object-side surface is kept small, and the optical system is compact. Despite this optical system,
As a reason why it is possible to satisfactorily correct various aberrations and realize a high-performance optical system, the efficient zoom type of the present invention,
That is, the magnification of each lens group, the distribution of the refractive power of each lens group, and the skillful selection of the zoom orbit can be mentioned.

[0095]

As described above, according to the present invention, it is possible to realize a high-resolution, high-performance, finite-system, high-variation-magnification zoom lens, and an optical system suitable for a wide range of purposes can be easily provided. It is possible to provide. In particular, it is possible to realize a compact zoom lens which is bright, has a short conjugate length, and has a wide angle of view. Further, it is possible to realize a zoom lens in which distortion and its variation during zooming are very small. Furthermore, since the shading of the image pickup system is reduced, it is possible to realize a zoom lens that can secure a sufficient amount of peripheral light around the screen.

By realizing an optical system which simultaneously satisfies these characteristics according to the present invention, the versatility of the optical system is significantly increased. The size, conjugate length, and working distance of the captured image or projected image can be easily set by moving and focusing the focusing lens group, and can be used in an optimal arrangement according to various purposes of use. . Specifically, the zoom lens of the present invention can be used for a document lens system, a digital still camera lens system, a close-up shooting optical system, a magnifying / enlarging optical system, a liquid crystal video projector projection lens, and the like. .

[Brief description of drawings]

FIG. 1 is a diagram showing a basic structure of a zoom lens according to the present invention and a movement trajectory of each lens unit due to zooming.

FIG. 2 is a diagram showing a lens configuration of a zoom lens according to Example 1 of the present invention.

FIG. 3 is a diagram of various types of aberration at the wide-angle end of Example 1.

FIG. 4 is a diagram of various types of aberration at the telephoto end of the first example.

FIG. 5 is a diagram showing a lens configuration of a zoom lens according to Example 2 of the present invention.

FIG. 6 is a diagram of various types of aberration at the wide-angle end of Example 2.

FIG. 7 is a diagram of various types of aberration at the telephoto end of the second example.

FIG. 8 is a diagram showing a lens configuration of a zoom lens according to Example 3 of the present invention.

FIG. 9 is a diagram of various types of aberration at the wide-angle end of Example 3;

FIG. 10 is a diagram of various types of aberration at the telephoto end of the third example.

FIG. 11 is a diagram showing a lens configuration of a zoom lens according to Example 4 of the present invention.

FIG. 12 is a diagram of various types of aberration at the wide angle end of Example 4;

FIG. 13 is a diagram of various types of aberration at the telephoto end of the fourth example.

FIG. 14 is a diagram showing a lens configuration of a zoom lens according to Example 5 of the present invention.

FIG. 15 is a diagram of various types of aberration at the wide-angle end of Example 5;

FIG. 16 is a diagram of various types of aberration at the telephoto end of Example 5;

FIG. 17 is a diagram showing a lens configuration of a zoom lens according to Example 6 of the present invention.

FIG. 18 is a diagram of various types of aberration at the wide-angle end of Example 6;

FIG. 19 is a diagram of various types of aberration at the telephoto end of the sixth example.

FIG. 20 is a diagram showing a lens configuration of a zoom lens according to Example 7 of the present invention.

FIG. 21 is a diagram of various types of aberration at the wide-angle end of Example 7.

FIG. 22 is a diagram of various types of aberration at the telephoto end of the seventh example.

FIG. 23 is a diagram showing a lens configuration of a zoom lens according to Example 8 of the present invention.

FIG. 24 is a diagram of various types of aberration at the wide angle end of Example 8;

FIG. 25 is a diagram of various types of aberration at the telephoto end of the eighth example.

FIG. 26 is a diagram showing a lens configuration of a zoom lens according to Example 9 of the present invention.

FIG. 27 is a diagram of various types of aberration at the wide angle end of Example 9;

FIG. 28 is a diagram of various types of aberration at the telephoto end of the ninth example.

[Explanation of symbols]

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

Claims (8)

[Claims] 1. A first lens group G1 having a positive refractive power and a second lens group G having a negative refractive power in order from the object side.
2, a third lens group G3 having a positive refracting power, a fourth lens group G4 having a negative refracting power, and a fifth lens group G5 having a positive refracting power. And a zoom arrangement in which the magnification of the second lens group G2, the magnification of the third lens group G3, and the magnification of the fourth lens group G4 are substantially equal to each other. Zoom lens to do. 2. The second lens group G2 to the fourth lens group G2 is located on the telephoto side of the zoom arrangement, which is substantially the same magnification.
The zoom lens according to claim 1, wherein the lens group G4 simultaneously carries a magnification higher than the same magnification. 3. The second lens group G2 to the fourth lens group G2 on the substantially wide-angle side relative to the zoom arrangement that provides substantially the same magnification.
The zoom lens according to claim 1, wherein the lens group G4 simultaneously bears a magnification lower than the same magnification. 4. The maximum effective diameter of the object side surface of the third lens group G3 at the wide-angle end is φ, and the third lens group G
The zoom lens according to any one of claims 1 to 3, wherein the condition of 0.3 <φ / f3 <0.8 is satisfied, where f3 is the focal length of No. 3. 5. The magnification of the second lens group G2 is β2.
When the magnification of the third lens group G3 is β3 and the magnification of the fourth lens group G4 is β4, -1.4 <β2 <-0.4-1.5 <β3 <-0 The zoom lens according to claim 1, wherein a condition of 0.5-1.5 <β4 <-0.6 is satisfied. 6. In a predetermined zoom arrangement, when at least any one of the magnifications of the second lens group G2 to the fourth lens group G4 is a unity magnification, the other lens groups constituting the variable power unit are The zoom lens according to claim 1, wherein the combined magnification βci to be satisfied satisfies a condition of 0.9 <| βci | <1.1. 7. The magnification of the first lens group G1 is β1
The zoom lens according to claim 1, wherein when the magnification of the fifth lens group G5 is β5, the condition of 0.05 <β1 / β5 <0.5 is satisfied. 8. The focal length of the second lens group G2 is f2
The zoom lens according to claim 1, wherein, when the focal length of the fourth lens group G4 is f4, the condition of 0.7 <f2 / f4 <1.3 is satisfied.