JPH08327905A - Zoom lens - Google Patents

Abstract

PURPOSE: To obtain a zoom lens which has high performance and high variable power and meets a wide range of purposes of utilization by satisfying specific conditions relating to focal lengths. 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 the 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 simultaneously attain equal magnification within the zoom region. The zoom lens is so formed as to satisfy the conditions -0.9<(1/f1+1/f2)fw<0, -0.5<(1/f4+1/f5)fw<0.2 when the focal length of the first lens group G1 is defined as fl, the focal length of the second lens group G2 as f2, the focal length of the fourth lens group G4 as f4, the focal length of the fifth lens group G5 as f5 and the focal length over the entire part of the zoom lens at the wide angle lens as fw.

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. In addition, as an optical system that can be used for imaging systems that require high resolution, chromatic aberration of magnification is well corrected, it is bright, has high performance, and high zooming is possible, the conjugate length is short, and the angle of view is wide. Therefore, there has been a demand for a zoom lens that has little distortion and its variation even 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 high performance, high zoom ratio, and suitable for a wide range of purposes.

[0007]

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.
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, and the focal length of the first lens group G1 is f
1 and the focal length of the second lens group G2 is f2,
When the focal length of the fourth lens group G4 is f4,
When the focal length of the lens group G5 is f4 and the focal length of the entire zoom lens system at the wide-angle end is fw, -0.9 <(1 / f1 + 1 / f2) fw <0 -0.5 <(1 / Provided is a zoom lens which satisfies the condition of f4 + 1 / f5) fw <0.2.

According to a preferred embodiment of the present invention, when the maximum effective diameter of the object side surface of the third lens group G3 at the wide-angle end is φ and the focal length of the third lens group G3 is f3, The condition of 3 <φ / f3 <0.8 is satisfied.

[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).

When the zoom unit (variable-magnification unit) is composed of two groups, among the solutions satisfying the zoom equation (zoom equation solution or zoom solution), the variator group has the same magnification (βi =-
In 1), the compensator group is also the same size (βj = -1)
In the case of, the two movement curves of the compensator group (the solution curve of the zoom trajectory) proliferate in the arrangement of equal size (β j = -1),
Orbits can be transferred to each other. 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 the distortion very much, the inner refractive power distribution of the front group should be positive (1 / f1) and negative (1 / f2) sequentially from the object side, and the inner refractive power distribution of the rear group should be the object side. It is indispensable to have a lens configuration and refractive power distribution capable of canceling aberrations by sequentially making the values negative (1 / f4) and positive (1 / f5). This becomes clear by examining the contribution of each lens group in the third-order aberration.

The internal refractive power distribution of the front group is negative (1 / f1) and positive (1 / f2) in order from the object side, and the internal refractive power distribution of the rear group is positive (1 / f4) in order from the object side. Also, even if it is negative (1 / f5), it is possible to have a lens configuration suitable for correcting distortion.

In the present invention, the following conditional expressions (1) and (2) are satisfied. -0.9 <(1 / f1 + 1 / f2) fw <0 (1) -0.5 <(1 / f4 + 1 / f5) fw <0.2 (2) where f1: the first lens group G1 F2: Focal length of second lens group G2 f4: Focal length of fourth lens group G4 f5: Focal length of fifth lens group G5 fw: Focal length of entire zoom lens system at wide-angle end

Conditional expression (1) defines the distribution of refractive power at the wide-angle end of each lens unit forming the front unit. If the upper limit of conditional expression (1) is exceeded, the refracting power of the front group becomes too weak, which is not suitable for widening the angle of view. Further, the balance of the symmetry of the refractive power of the entire system is lost, and the burden of correcting the distortion aberration on the shape of the lens increases, which is not preferable. On the other hand, if the value goes below the lower limit of conditional expression (1), the refracting power of the front group becomes too strong in the negative direction, the symmetry of the refracting power is further broken, and the burden of correcting distortion is increased, which is not preferable. .

Conditional expression (2) defines the distribution of refractive power at the wide-angle end of each lens unit forming the rear lens group. If the upper limit of conditional expression (2) is exceeded, the refractive power of the rear group will weaken,
The refractive power becomes excessive in the positive direction. As a result, the balance of the symmetry of the refracting power of the entire system is lost, and the burden of correcting the distortion on the lens shape increases, which is not preferable. On the other hand, if the value goes below the lower limit of conditional expression (2), the refracting power of the rear group becomes too strong in the negative direction, the symmetry of the refracting power is further broken, and the burden of correcting distortion is increased, which is not preferable. .

Further, 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.

Generally, when the position of the pupil is brought as close as possible to the surface of the lens end, the refractive power arrangement 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 order to secure compactness and a large aperture ratio of the optical system, it is desirable that the following conditional expression (3) is satisfied. 0.3 <φ / f3 <0.8 (3) 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 (3) 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.
When the value exceeds the upper limit of conditional expression (3), the optical system becomes unnecessarily bright, the size of the optical system is increased, and the number of lenses is extremely increased, 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 (3) 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 (3) 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 unit 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 expressions (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 (4) to (6) while having the simultaneous magnification arrangement. -1.4 <β2 <-0.4 (4) -1.5 <β3 <-0.5 (5) -1.5 <β4 <-0.6 (6)

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 (first lens surface) will be 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 (4) 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 (5) 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 (5)
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 (6) 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 (6)
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 carried by 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 (7), the simultaneous equal-magnification arrangement is allowed. 0.9 <| βci | <1.1 (7)

If the upper limit of conditional expression (7) 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,
If the value goes below the lower limit of conditional expression (7), the area where no zoom solution exists from the wide-angle end increases, and the area in which focus is fixed due to zooming becomes narrow, which is not preferable. 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 (8) is satisfied. 0.7 <f2 / f4 <1.3 (8) Conditional expression (8) 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 (8), the moving amount of the second lens group G2 increases and interferes with other lens groups to reduce the zooming efficiency, so that a high zooming lens 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 contrary, when the value goes below the lower limit of the conditional expression (8), 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.

Further, in the present invention, it is desirable that the following conditional expression (9) is satisfied. 0.05 <β1 / β5 <0.5 (9) Conditional expression (9) 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.

If the upper limit of conditional expression (9) 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 (9), 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.

Further, in the present invention, it is desirable that the following conditional expression (10) is satisfied. -0.9 <fw / f12 <-0.1 (10) where, f12: composite focal length of front group

Conditional expression (10) defines the refractive power distribution of the front lens group (first lens group G1 and second lens group G2) at the wide-angle end. If the upper limit of conditional expression (10) is exceeded, the refracting power of the front group becomes too weak, making it difficult to widen the angle, and it becomes impossible to realize a system having a short conjugate length. Further, the balance of the symmetry of the refracting power of the entire system is lost, and the load of correcting the distortion aberration with respect to the shape of the lens increases, which is not preferable. Conversely, when the value goes below the lower limit of conditional expression (10), the refracting power of the front unit becomes too strong in the negative direction. As a result, the symmetry of the refracting power is further broken, the load of correcting the distortion aberration increases, it becomes difficult to correct various aberrations, and it becomes difficult to secure the peripheral light amount, which is not preferable.

Further, in the present invention, it is desirable that the following conditional expression (11) is satisfied. 0.1 <fw / f45 <0.8 (11) where f45: composite focal length of rear group

Conditional expression (11) defines the distribution of the refractive power of the rear group (the fourth lens group G4 and the fifth lens group G5) at the wide-angle end. If the upper limit of conditional expression (11) is exceeded, the refractive power of the rear group becomes too strong, making it difficult to correct various aberrations, and the refractive power of the front group becomes weak, making it difficult to widen the angle. In addition, the strong positive refracting power of the rear group destroys the symmetry of the refracting power of the entire system, increasing the load of distortion aberration correction on the lens shape, which is not preferable. On the other hand, if the lower limit of conditional expression (11) is exceeded, the refractive power of the rear group will weaken,
The refractive power of the front group also becomes weak. As a result, the dependency of aberration correction on only the middle group increases, and it becomes difficult to correct various aberrations, which is inconvenient.

Further, in the present invention, it is desirable that the following conditional expression (12) is satisfied. -1.4 <ft / f12 <-0.3 (12) Conditional expression (12) defines the refractive power distribution of the front group at the telephoto end.

If the upper limit of conditional expression (12) is exceeded, the refracting power of the front group becomes too weak, and the contribution to the refracting power of the entire system decreases, so that it is not possible to effectively arrange the refracting power. On the other hand, when the value goes below the lower limit of conditional expression (12), the refracting power of the front unit becomes too strong in the negative direction, and it becomes more difficult to achieve a telephoto state. Further, the symmetry between the refractive power of the front lens group and the refractive power of the rear lens group is remarkably broken, and the load of correcting various aberrations as well as the correction of distortion aberration is increased, which is not preferable.

Further, in the present invention, it is desirable that the following conditional expression (13) is satisfied. 0.7 <ft / f45 <3.0 (13) Conditional expression (13) defines the refractive power distribution of the rear group at the telephoto end.

If the upper limit of conditional expression (13) is exceeded, the refracting power of the rear group will become too strong, making zooming to the telephoto side difficult and inefficient. Furthermore, in the rear group, axial chromatic aberration,
It is not preferable because it becomes difficult to correct various aberrations such as off-axis chromatic aberration and distortion. On the other hand, when the value goes below the lower limit of conditional expression (13), the refracting power of the rear group becomes weak, and zooming to the telephoto end is possible. However, this is inconvenient because the magnification of each lens group becomes high and it becomes difficult to correct various aberrations.

[0046]

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 region of variable magnification, 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 having a weak curvature on the object side, a negative meniscus lens having a convex surface having a weak curvature on the object side, and a biconcave lens and a positive convex surface having a strong curvature on the object side. It consists of a negative lens cemented with a meniscus lens.

The third lens group G3 is composed of a positive lens cemented with 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
It comprises a cemented negative lens composed of a biconvex lens and a biconcave lens, and a cemented negative lens composed of a biconcave lens and a positive meniscus lens having a convex 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 including a biconcave lens and a biconvex lens, a biconvex lens, and a biconvex lens.

The zoom lens of the first embodiment has a zoom ratio of 5 and a lens configuration of 19 elements in 13 groups. The feature of this embodiment is the lens arrangement of the second lens group G2 and the lens arrangement of the fourth lens group G4. With such a 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.

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).

[0052]

[Table 1] (Variable spacing during zooming) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.120 D0 693.200 693.200 693.200 693.200 693.200 693.200 d7 0.588 4.399 10.075 12.850 16.868 19.223 d14 44.655 38.761 28.267 22.912 13.146 5.828 d19 0.671 2.996 9.435 12.284 19.912 27. 7.583 5.961 5.692 3.811 1.037 Bf 40.278 40.278 40.278 40.278 40.278 40.278 (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 = -1.2495 33.073 βw3 = -0.6344 βc3 = -1.0000 βt3 = -1.2367 f4 = -21.096 βw4 = -0.8366 βc4 = -1.0000 βt4 = -1.1728 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 = 99.643 φ = 15.9 (1) (1 / f1 + 1 / f2) fw = -0.517037 (2) (1 / f4 + 1 / f5) fw = -0.090542 (3) φ / f3 = 0.48075 (8) f2 / f4 = 0.91487 (9) β1 / β5 = 0.1281 (1 0) fw / f12 = -0.37263 (11) fw / f45 = 0.46574 (12) ft / f12 = -0.86504 (13) ft / f45 = 1.80079

3 and 4 show 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 cemented positive lens having a biconcave lens and a biconvex lens, and a biconcave lens.

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 having a weak curvature facing the object side, a positive meniscus lens having a concave surface having a weak curvature facing the object side, and a negative meniscus lens having a concave surface having a strong curvature facing the object side. It consists of a cemented positive lens and a biconvex lens.

The zoom lens of the second embodiment has a zoom ratio of 5 and a lens structure of 16 elements in 12 groups. The features of this embodiment are that the third lens group G3 has two lenses and no cemented lens is used, and the lens shape and lens arrangement of the second lens group G2. With this configuration, the fluctuation of the coma aberration of the lower light beam of the chief ray due to the magnification change is corrected.

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).

[0058]

[Table 2] (Variable spacing in zoom) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.100 D0 691.628 691.628 691.628 691.628 691.628 691.628 d7 0.543 3.956 10.030 12.457 16.772 18.669 d14 48.147 42.642 31.759 26.834 16.733 11.607 d18 1.839 4.495 10.602 13.775 21.123 24.828 d23. 11.741 10.442 9.768 8.206 7.729 Bf 37.421 37.421 37.421 37.421 37.421 37.421 (Conformance 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 = 16.1 (1) (1 / f1 + 1 / f2) fw = -0.517037 (2) (1 / f4 + 1 / f5) fw = -0.090542 (3) φ / f3 = 0.48680 (8) f2 / f4 = 0.91487 (9) β1 / β5 = 0.1281 (10) fw / f12 = -0.37263 (11) fw / f45 = 0.46574 (12) ft / f12 = -0.77281 (13) ft / f45 = 1.89613

6 and 7 show the 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 negative lens including a biconvex lens and a biconcave lens.

The third lens group G3 is composed of 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 cemented negative lens including a biconvex lens and a biconcave lens, and a negative meniscus lens having a concave surface with 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 third example has a zoom ratio of 5 and a lens configuration of 18 elements in 13 groups.

The following table (3) lists the 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).

[0063]

[Table 3] (Variable interval in zooming) β -0.020 -0.025 -0.040 -0.060 -0.080 -0.100 D0 692.474 692.474 692.474 692.474 692.474 692.474 d7 0.433 3.790 9.062 13.681 15.915 17.290 d14 46.886 41.511 31.854 22.718 16.937 13.015 d19 1.025 3.588 10.024 15.348 20.107. 6.476 4.424 3.618 2.405 0.971 Bf 37.435 37.435 37.435 37.435 37.435 37.435 (Condition value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -19.000 βw2 = -0.5650 βc2 = -1.0000 βt2 = -1.1329 f3 32.000 βw3 = -0.6279 βc3 = -1.0000 βt3 = -1.1475 f4 = -21.001 βw4 = -0.8301 βc4 = -1.0000 βt4 = -1.1326 f5 = 22.500 βw5 = -0.7375 βc5 = -0.7375 βt5 = -0.7375 fw = 14.861 βw =- 0.0200 βc = -0.0679 βt = -0.1000 ft = 80.593 φ = 15.8 (1) (1 / f1 + 1 / f2) fw = -0.529787 (2) (1 / f4 + 1 / f5) fw = -0.047144 (3) φ / f3 = 0.49375 (8) f2 / f4 = 0.90472 (9) β1 / β5 = 0.1249 ( 10) fw / f12 = -0.37010 (11) fw / f45 = 0.45912 (12) ft / f12 = -0.81841 (13) ft / f45 = 1.40642

FIGS. 9 and 10 show the 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.

[Embodiment 4] 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 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 composed of a biconvex lens and a biconcave lens, and a cemented negative lens composed of a biconcave lens and a positive meniscus lens having a convex 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 fourth embodiment has a zoom ratio of 6 times,
This is a lens configuration of 18 elements in 13 groups. The feature of this embodiment is the lens shape of the third lens group G3 and the lens shape of the fifth lens group G5 (bonding positive lens).

Table (4) below shows 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).

[0068]

[Table 4] (Variable spacing during zooming) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.120 D0 692.709 692.709 692.709 692.709 692.709 692.709 d7 0.217 4.092 9.879 12.473 16.532 19.500 d14 48.036 42.185 31.772 26.755 17.278 9.038 d19 0.682 2.862 8.939 11.827 19.067 d. 6.492 5.041 4.576 2.752 1.171 Bf 40.455 40.455 40.455 40.455 40.455 40.455 (Condition value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -19.000 βw2 = -0.5536 βc2 = -1.0000 βt2 = -1.2633 f3 32.000 βw3 = -0.6175 βc3 = -1.0000 βt3 = -1.2161 f4 = -20.000 βw4 = -0.8248 βc4 = -1.0000 βt4 = -1.1011 f5 = 23.500 βw5 = -0.7704 βc5 = -0.7704 βt5 = -0.7704 fw = 14.822 βw =- 0.0200 βc = -0.0709 βt = -0.1200 ft = 112.444 φ = 15.8 (1) (1 / f1 + 1 / f2) fw = -0.528189 (2) (1 / f4 + 1 / f5) fw = -0.110377 (3) φ / f3 = 0.49375 (8) f2 / f4 = 0.950 (9) β1 / β5 = 0.1195 (10 fw / f12 = -0.40414 (11) fw / f45 = 0.44167 (12) ft / f12 = -0.85417 (13) ft / f45 = 1.79082

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.

[Embodiment 5] FIG. 14 is a diagram showing a lens structure 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 includes a cemented positive lens including a negative meniscus lens having a convex surface having a weak curvature facing the object side and a biconvex lens, and a positive meniscus lens having a convex surface having 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 biconcave lens, and a positive meniscus lens having a convex surface having a strong curvature facing the object side and a negative meniscus lens having a convex surface having a weak curvature facing the object side. Consisting of a positive lens laminated with a meniscus lens.

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

The zoom lens of the fifth embodiment has a zoom ratio of 6 times and is composed of 19 lenses in 13 groups. The feature of this embodiment is that the refractive power of the first lens group G1 is weakened, the refractive power of the second lens group G2 and the refractive power of the fourth lens group G4 are strengthened, and the second lens group is used. G
2 lens arrangement.

The following table (5) lists the 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).

[0074]

[Table 5] (Variable interval in zooming) β -0.020 -0.025 -0.040 -0.060 -0.080 -0.120 D0 794.086 794.086 794.086 794.086 794.086 794.086 d7 3.405 6.650 12.496 16.845 19.123 22.237 d14 48.650 43.570 33.589 25.257 19.988 12.034 d19 2.489 4.837 10.131 14.25 19.016 24.911 24. 5.796 4.638 3.773 2.726 1.671 Bf 49.449 49.449 49.449 49.449 49.449 49.449 (Condition corresponding value) f1 = 60.000 βw1 = -0.0811 βc1 = -0.0811 βt1 = -0.0811 f2 = -17.500 βw2 = -0.5205 βc2 = -1.0000 βf2 = -1.120 30.000 βw3 = -0.5853 βc3 = -1.0000 βt3 = -1.1433 f4 = -17.000 βw4 = -0.7772 βc4 = -1.0000 βt4 = -1.0501 f5 = 25.000 βw5 = -1.0417 βc5 = -1.0417 βt5 = -1.0417 fw = 16.978 βw =- 0.0200 βc = -0.0845 βt = -0.1200 ft = 112.443 φ = 15.7 (1) (1 / f1 + 1 / f2) fw = -0.687205 (2) (1 / f4 + 1 / f5) fw = -0.319586 (3) φ / f3 = 0.52333 (8) f2 / f4 = 1.02941 (9) β1 / β5 = 0.07785 (10) fw / f12 = -0.46494 (11) fw / f45 = 0.43093 (12) ft / f12 = -1.06252 (13) ft / f45 = 1.62675

FIGS. 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 diagram showing a lens structure of a zoom lens according to a 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 cemented negative lens including a biconcave lens and a biconvex 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 biconvex lens and a biconcave lens, and a negative meniscus lens having a concave surface with 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 sixth embodiment has a zoom ratio of 5 and has a lens configuration of 18 elements in 13 groups. The feature of this embodiment is that the first lens group G1 has a strong refractive power, the second lens group G2 has a strong refractive power, and the fourth lens group G4 has a strong refractive power. G
5 lens arrangement and lens shape.

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).

[0080]

[Table 6] (Variable spacing during zooming) β -0.020 -0.025 -0.040 -0.060 -0.080 -0.100 D0 594.080 594.080 594.080 594.080 594.080 594.080 d7 0.041 3.593 7.501 10.782 12.805 14.345 d14 44.537 39.255 31.084 23.798 18.589 14.117 d19 0.686 2.130 8.2308 13.384 17.246 20. 6.292 4.389 3.307 2.631 2.501 Bf 40.473 40.473 40.473 40.473 40.473 40.473 (Condition corresponding value) f1 = 45.000 βw1 = -0.0811 βc1 = -0.0811 βt1 = -0.0811 f2 = -14.000 βw2 = -0.5489 βc2 = -1.0000 βf2 = -1.2497 30.000 βw3 = -0.6475 βc3 = -1.0000 βt3 = -1.1663 f4 = -19.000 βw4 = -0.8417 βc4 = -1.0000 βt4 = -1.0262 f5 = 23.500 βw5 = -0.8246 βc5 = -0.8246 βt5 = -0.8246 fw = 12.734 βw =- 0.0200 βc = -0.0669 βt = -0.1000 ft = 72.682 φ = 15.4 (1) (1 / f1 + 1 / f2) fw = -0.626594 (2) (1 / f4 + 1 / f5) fw = -0.128338 (3) φ / f3 = 0.51333 (8) f2 / f4 = 0.73684 (9) β1 / β5 = 0.09835 ( 10) fw / f12 = -0.44180 (11) fw / f45 = 0.35672 (12) ft / f12 = -0.87146 (13) ft / f45 = 1.46543

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 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 cemented lens including a biconcave lens and a positive meniscus lens having a convex surface having a strong curvature facing the object side. Consist of a negative 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 of a biconcave lens and a biconvex lens, a biconvex lens, and a biconvex lens.

The zoom lens of the seventh embodiment has a zoom ratio of 6 times and a lens configuration of 19 elements in 13 groups. The features of this embodiment are proper refracting power of the second lens group G2, lens arrangement and lens shape, and proper refracting power distribution of the fourth lens group G4.

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).

[0086]

[Table 7] (Variable interval in zoom) β -0.020 -0.025 -0.040 -0.050 -0.080 -0.120 D0 693.295 693.295 693.295 693.295 693.295 693.295 d7 0.244 3.118 8.655 10.766 14.717 17.070 d14 43.831 38.671 28.133 23.510 13.925 6.660 d19 1.598 4.685 11.262 14.727 22.432 30.152 d25 10.295 9.495 7.919 6.964 4.894 2.086 Bf 39.671 39.671 39.671 39.671 39.671 39.671 (conditional value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -20.000 βw2 = -0.6071 βc2 = -1.0000 βt2 = -1.2409 33.073 βw3 = -0.6453 βc3 = -1.0000 βt3 = -1.2361 f4 = -20.000 βw4 = -0.7709 βc4 = -1.0000 βt4 = -1.1813 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 = 101.848 φ = 15.87 (1) (1 / f1 + 1 / f2) fw = -0.492055 (2) (1 / f4 + 1 / f5) fw = -0.008563 (3) φ / f3 = 0.479847 (8) f2 / f4 = 1.00000 (9) β1 / β5 = 0.1281 (10) fw / f12 = -0.34874 (11) fw / f45 = 0.56028 (12) ft / f12 = -0.92608 (13) ft / f45 = 2.09534

21 and 22 show the 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 concave surface having a weak curvature surface facing the object side. It consists of a cemented negative lens consisting of a meniscus lens and a negative meniscus lens having a concave surface with a strong curvature facing the object side. 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 strong curvature facing the object side.

The fourth lens group G4 is composed of a cemented negative lens having a positive meniscus lens having a concave surface having 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 eighth embodiment has a zoom ratio of 7 and a lens construction of 17 elements in 12 groups. The features of this embodiment are the proper distribution of the refractive power of the second lens group G2 and the lens arrangement and lens shape of the fifth lens group G5, as in the seventh embodiment.

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).

[0093]

[Table 8] (Variable spacing in zoom) β -0.020 -0.040 -0.050 -0.080 -0.100 -0.140 D0 694.036 694.036 694.036 694.036 694.036 694.036 d7 0.235 7.933 10.283 14.558 16.083 15.969 d14 42.624 27.726 22.926 12.940 8.645 5.358 d19 1.781 12.032 15.291 22.745 26.762 35.491 35. 11.458 10.649 8.906 7.659 2.331 Bf 36.917 36.917 36.917 36.917 36.917 36.917 (Condition value) f1 = 58.837 βw1 = -0.0921 βc1 = -0.0921 βt1 = -0.0921 f2 = -20.000 βw2 = -0.6071 βc2 = -1.0000 βt2 = -1.1621 33.073 βw3 = -0.6453 βc3 = -1.0000 βt3 = -1.3184 f4 = -20.000 βw4 = -0.7709 βc4 = -1.0000 βt4 = -1.3796 f5 = 24.133 βw5 = -0.7191 βc5 = -0.7191 βt5 = -0.7191 fw = 14.909 βw =- 0.0200 βc = -0.0662 βt = -0.1400 ft = 108.958 φ = 15.9 (1) (1 / f1 + 1 / f2) fw = -0.492055 (2) (1 / f4 + 1 / f5) fw = -0.008563 (3) φ / f3 = 0.48075 (8) f2 / f4 = 1.00000 (9) β1 / β5 = 0.1281 (10) fw / f12 = -0.34874 (11) fw / f45 = 0.56028 (12) ft / f12 = -1.009185 (13) ft / f45 = 1.34560

24 and 25, the 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.

As described above, in each embodiment, the first lens group G1, the second lens group G2, and the fourth lens group G4.
The refractive power of has changed greatly. However, with the zoom lens according to the present invention, distortion and other various aberrations can be satisfactorily corrected even with such a change in refractive power, and sufficient imaging performance can be ensured. Further, in each of the embodiments, the effective F value at the wide-angle end is very bright at about F / 2.0, and the peripheral light quantity is sufficiently secured.

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 for simultaneously correcting 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 objective is sufficiently achieved by the dark optical system, 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. Furthermore, although each of the above-mentioned embodiments is only a finite system,
It can also be used for infinite shooting systems.

Further, in each of the above-described 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.

[0099]

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.

[Explanation of symbols]

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

Claims (10)

[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. The focal length of G1 is f1 and the second
The focal length of the lens group G2 is f2, the focal length of the fourth lens group G4 is f4, the focal length of the fifth lens group G5 is f4, and the focal length of the entire zoom lens system at the wide-angle end is fw. At this time, the zoom lens is characterized by satisfying the condition of -0.9 <(1 / f1 + 1 / f2) fw <0 -0.5 <(1 / f4 + 1 / f5) fw <0.2. 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 any one of claims 1 to 4, wherein the 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 any one of claims 1 to 5, wherein the combined magnification βci to be satisfied satisfies the condition of 0.9 <| βci | <1.1. 7. The focal length of the second lens group G2 is f2
7. When the focal length of the fourth lens group G4 is f4, the condition of 0.7 <f2 / f4 <1.3 is satisfied. Zoom lens. 8. The magnification of the first lens group G1 is β1
8. When the magnification of the fifth lens group G5 is β5, the condition of 0.05 <β1 / β5 <0.5 is satisfied, and the condition is satisfied. Zoom lens. 9. A combined focal length of the first lens group G1 and the second lens group G2 is f12, a combined focal length of the fourth lens group G4 and the fifth lens group G5 is f45, and a wide angle The focal length of the entire zoom lens system at the edge is fw
The following condition is satisfied: -0.9 <fw / f12 <-0.1 0.1 <fw / f45 <0.8. Zoom lens. 10. A composite focal length of the first lens group G1 and the second lens group G2 is f12, and a composite focal length of the fourth lens group G4 and the fifth lens group G5 is f45.
And the focal length of the entire zoom lens system at the telephoto end is f
10. When t is satisfied, the condition of -1.4 <ft / f12 <-0.3 0.7 <ft / f45 <3.0 is satisfied, according to any one of claims 1 to 9. The described zoom lens.