JPH1039216A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens having high performance and a high variable power ratio and suitable for wide use purpose. SOLUTION: This zoom lens is provided with, in order from the object side, five lens groups G1-G5 of positive, negative, positive, negative and positive lenses and at the time of varying power, the second lens group G2 to the fourth lens group G4 are moved along the optical axis. In a variable power area and out of the variable power area, the magnifications of three lens groups of the second lens group G2 to the fourth lens group G4 do not almost simultaneously become unmagnified. the magnification of any one lens group among the second lens group G2 to the fourth lens group G4 does not become unmagnified and the magnifications of the remaining two lens groups do not almost simultaneously become unmagnified.

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-magnification zoom lens.

[0002]

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

[0003] Among the finite optical systems, the finite system single focus lens is poor in versatility, and a dedicated optical system is used for each purpose. On the other hand, a finite zoom lens has higher versatility than a single focus lens, but has few types of lenses. A finite zoom lens is often used for a 35 mm still camera lens system, a 16 mm cine lens system, and a TV lens system. In particular, as a small and high-quality image input optical system of an electronic image device, a low magnification (1/50 × to 1/3) is used.
(About 0x) and a wide-angle imaging zoom lens have been demanded.

[0004]

[Problems to be Solved by the Invention]
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses a zoom lens having a low magnification and a wide angle of view. However, the zoom method (magnification method) of the zoom lens disclosed in this publication is difficult to achieve high magnification, and the zoom trajectory of each lens group is also complicated. Further, this zoom lens is an optical system for a measuring projector, and strongly demands telecentricity. Furthermore, the effective F number is F
/3.5 to F / 6.5, which is insufficient for capturing a dark subject with a black pattern depending on the lighting conditions. On the other hand, a bright, wide-angle, high-magnification, high-performance optical system has long been demanded.

[0005] Optical systems used in electronic image equipment and the like include:
Specifications are required for very many purposes, and dedicated optical systems are provided for various purposes. That is, in the conventional zoom lens, it is necessary to design a dedicated optical system according to the number of objectives, 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, bright, high performance, high zoom ratio is possible, short conjugate length, wide angle of view Therefore, there has been a demand for a zoom lens which has little distortion and its fluctuation even during zooming. Further, in order to reduce shading, there has been a demand for a zoom lens capable of securing a sufficient peripheral light amount around a screen.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a zoom lens having high performance, high magnification, and suitable for a wide range of applications.

[0007]

According to the present invention, a first lens group G1 having a positive refractive power and a second lens group G1 having a negative refractive power are sequentially arranged from the object side. G2 and a 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 to the fourth lens group during zooming. G4 moves along the optical axis, and the magnifications of the three lens units of the second lens group G2 to the fourth lens group G4 become almost the same at the same time inside and outside the zooming area. In the variable power range, any one of the second lens group G2 to the fourth lens group G4 does not have the same magnification, and the remaining two lens groups have the same magnification. Provided is a zoom lens characterized in that the magnification does not become equal at almost the same time.

According to a preferred aspect of the present invention, the magnification carried by the second lens group G2 does not become the same magnification within the variable magnification area, and the magnification carried by the third lens group G3 and the fourth lens The magnification of the group G4 does not become almost equal at the same time. Alternatively, in the variable magnification area, the magnification carried by the fourth lens group G4 does not become the same magnification, and the magnification carried by the second lens group G2 and the third lens group G3
Are not almost equal at the same time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A zoom lens according to the present invention comprises, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. 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. Then, upon zooming, the second lens group G2
In addition, the fourth lens group G4 moves along the optical axis. Also,
Inside the zooming area and outside the zooming area, the second lens group G
The magnifications of the three lens units of the second to fourth lens units G4 do not become almost equal at almost the same time. Further, in the variable power region, the magnification of any one of the second lens group G2 to the fourth lens group G4 is the same magnification (−1 ×).
, And the magnifications of the remaining two lens groups do not become almost equal at the same time. As described above, in the basic configuration of the present invention, the three lens units, the second lens unit G2 to the fourth lens unit G4, constitute a zooming unit that moves in the optical axis direction during zooming.

FIGS. 1 to 4 are views showing the basic configuration of a zoom lens according to the present invention and the arrangement of zoom trajectories of each lens group by zooming. In the intermediate focal length state of FIGS. 1 and 2, the fourth lens group G, which is a lead variator group,
4 is the same size (-1 ×). In the intermediate focal length state shown in FIGS. 3 and 4, the second lens group G2, which is a lead variator group, has an equal magnification (−1 ×). 1 to 4, fi is the focal length of the i-th lens unit,
βw indicates the combined photographing magnification of the entire zoom lens system at the wide-angle end, βt indicates the combined photographing magnification of the entire zoom lens system at the telephoto end, and βc indicates the combined photographing magnification of the entire zoom lens system at the intermediate focal length state. . Also, βwi
Represents the magnification of the i-th lens unit at the wide-angle end, βti represents the magnification of the i-th lens unit at the telephoto end, and βci represents the magnification of the i-th lens unit in the intermediate focal length state.

In each zoom arrangement, the following equations (a) to (h) hold. β = β1 β2 β3 β4 β5 (a) βz = β2 β3 β4 (b) βw = βw1βw2βw3βw4βw5 (c) βc = βc1βc2βc3βc4βc5 (d) βt = βt1βt2βt3βt4βt3 (w) βc βt2βt3βt4 (h)

Here, β: combined photographing magnification of the entire zoom lens system in an arbitrary zoom arrangement βi: lateral magnification carried by the i-th lens group βz: magnification of the magnification unit in an arbitrary zoom arrangement βzw: magnification at the wide-angle end Part magnification βzc: Magnification of the magnification part at the intermediate focal length state βzt: Magnification of the magnification part at the telephoto end

In general, in a zoom lens having a variable power unit composed of two or more lens units, the sign of the power (refractive power) of each lens unit of the variable power unit and the magnification of each lens unit of the variable power unit. Attention should be paid to a lens arrangement that satisfies the same magnification (± 1), 0 and ± ∞. In the present invention, 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 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, and a zoom solution is analyzed by paying particular attention to the magnification of each lens group of the variable power unit. I do. According to the present invention, in a zoom lens having a zooming unit composed of three or more lens groups, the magnifications of the zooming lens groups inside and outside the zooming area are almost the same (1 ×).
Avoiding the zoom arrangement. Such a configuration of the present invention complicates the analysis of the zoom solution, but creates a new degree of freedom in the arrangement of the refractive power of the optical system, the size of the optical system, and the like.

When performing zooming with three or more lens units, it is better to avoid a configuration in which each zooming lens unit individually becomes the same magnification (-1 ×) in the zoom area (magnification area). desirable. In a zoom system in which three lens groups are moved to perform zooming, if a configuration is adopted in which each zooming lens group is individually equal in magnification (-1 ×), zoom solutions may not exist continuously. The nature becomes high. In this case, by stopping the movement of any one of the three zoom lens groups, a continuous zoom solution can be obtained as a partially moved two-unit zoom lens, but the processing is complicated. There is not efficient. In addition, since the zooming unit changes from the third-group movement to the second-group movement, the structure of the aberration fluctuation also greatly changes, and it becomes difficult to correct the aberration with a bright optical system.

More specifically, referring to FIG. 1, in the present invention, at the time of zooming from the wide-angle end to the telephoto end, the magnification of each lens unit of the zooming unit increases. In particular, the magnification β3 of the third lens group G3 and the fourth magnification
The magnification β4 carried by the lens group G4 is a low magnification of less than or equal to 1 at the wide-angle end, but gradually increases with zooming to the telephoto end, becomes individually equal to each other, and eventually reaches the maximum magnification at the telephoto end. Becomes On the other hand, the second lens group G2
Does not become the same magnification within the variable magnification area, and always keeps a low magnification equal to or less than the same magnification. In this way, the second lens group G2 moves in the optical axis direction as a variable power lens group, but does not largely perform variable power, and is dedicated to the role of a compensator group. By setting such a lens arrangement, a continuous zoom solution can be stably obtained. In the present invention, the size of a practical optical system and good optical performance can be ensured.
In this specification, the expressions “high magnification” and “low magnification” are expressions based on the magnitude of the absolute value of the magnification.

In the present invention, since the lens units of the zooming unit do not have a zoom arrangement in which the magnification becomes almost the same at the same time, the frequency of defocusing on the image plane such as rounding errors and manufacturing tolerances is small. Further, in the present invention, the zoom solution is stable against the magnification error and the adjustment error. Further, with the zoom method of the present invention, it is possible to avoid sudden jumps in focus on the image plane. In order to ensure a large zoom ratio (magnification ratio), it is inevitable to adopt a configuration in which the magnification of each lens group of the magnification unit is the same. However,
When the zoom ratio is small, it is not necessary to positively incorporate a zoom arrangement in which the magnification of each lens unit is equal to the zoom ratio into the zoom region. One means is to avoid near the place where the magnification of the variable power lens group other than the compensator group is the same magnification (βj = −1). The present invention focuses on the magnification and refractive power distribution of the variable magnification unit composed of multiple groups, and obtains a suitable zoom solution curve such that a continuous zoom trajectory exists.

As a method of reducing distortion, a lens configuration having high symmetry with respect to an aperture stop having a lens shape and a refractive power arrangement can be considered. However, in a zoom lens in which each lens group moves along the optical axis with zooming,
It is not possible to maintain symmetry with respect to the aperture stop over the entire zooming area (zoom area). Therefore, in order to obtain an optical system with little distortion and its fluctuation even during zooming, a configuration in which the refractive power distribution of each lens group has a certain degree of symmetry with respect to the aperture stop as in the basic configuration of the present invention. It is essential.

When analyzing the state of 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 defined as the middle group, the lens group on the object side of the middle group is defined as the front group, and the lens group on the image side of the middle group is defined as the rear group. In this case, inside each of the front group and the rear group, a refractive power configuration and a lens configuration that can correct distortion to a considerable extent are required. For the distortion components that could not be corrected in the front group and the rear group, and the distortion components that could not be canceled in the front group and the rear group, the middle group is assigned to correct the roles. By adopting such a lens configuration, the fluctuation of distortion can be reduced even in a lens group that moves with zooming (magnification change). On the other hand, to minimize distortion, aberrations can be canceled by setting the internal refractive power distribution of the front group to positive and negative in order from the object side, and the internal refractive power distribution of the rear group to negative and positive in order from the object side. A proper lens configuration and refractive power distribution are indispensable.

Further, when a desired zoom ratio is obtained by forming a zooming unit with three or more lens units, the amount of movement of each lens unit is reduced as compared with the zooming unit having a two-unit configuration, and zooming is performed. It is possible to do. As a result, the incident height of the principal ray at the wide-angle end can be reduced, which is very effective in reducing the lens diameter on the object side. As will be described later, in each embodiment of the present invention, the zooming unit is composed of three lens groups. However, while maintaining symmetry, four, five or more lens groups are used. By configuring the zooming unit, extension to a high zooming 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 lens unit having a negative refractive power precedes the refractive power arrangement of the lens units. On the other hand, when the position of the pupil is as far as possible from the surface of the lens end, the lens unit having a positive refractive power precedes the refractive power arrangement of the lens units. When such a refractive power distribution is employed, an image-side telecentric optical system, an object-side telecentric optical system, or an optical system close thereto can be realized. However, the present invention does not need to be a telecentric optical system. Therefore, the aperture stop may be positioned at any position from the distance between the second lens group G2 and the third lens group G3 to the distance between the fourth lens group G4 and the fifth lens group G5. Also, the aperture stop may move spatially in conjunction with zooming, or may be fixed along the optical axis during zooming. In the configuration of the optical system of the present invention, a negative pupil magnification can be easily realized, and the position of the exit pupil can be located further behind (image side) than the image plane.

In the present invention, in the zooming area, the magnifications of the two lens groups of the second lens group G2 to the fourth lens group G4 constituting the zooming unit do not become almost equal at the same time. As a result, especially for a high-magnification zoom lens having a zoom ratio of 4 to 5 or more, the zoom solution tends to be discontinuous during zooming. For this reason, by adopting a configuration in which the magnification of the compensator group does not become equal in the zooming area, high zooming is possible and a stable zoom solution having a continuous orbit is secured. be able to. In the present invention, since the lens units in the zooming unit do not have a zoom arrangement in which the magnification becomes almost the same, the frequency of defocusing of the image plane due to rounding errors, manufacturing tolerances, and the like is small. Further, a new degree of freedom can be secured for the refractive power arrangement of the optical system and the size of the optical system.

In the present invention, the magnification of the third lens group G3 and the fourth lens group G4
And the magnification carried by the second lens group G2 should not be substantially equal. This indicates that in order to ensure a continuous zoom solution having a high zoom ratio, the magnification of the second lens group G2, which is a compensator group, is classified based on the unity magnification. When the compensator is configured, two solutions of the zoom equation are obtained as solutions of the quadratic equation. At this time, the magnification carried by the second lens group G2, which is a compensator group, is always lower than the same magnification as shown in FIG. 1, or higher than the same magnification as shown in FIG. There is a need. If the magnification of the second lens group G2 is not classified based on the same magnification, it is necessary to obtain a continuous solution by another measure.

In the present invention, the second compensator group
In the above-described configuration in which the magnification carried by the lens group G2 is classified at the same magnification, the following conditional expressions (1) and (2) may be satisfied, or conditional expressions (3) and (4) may be satisfied. desirable. 0.3 ≦ | βw2 | <1.0 (1) 0.3 ≦ | βt2 | <1.0 (2) 1.0 <| βw2 | ≦ 2.5 (3) 1.0 <| βt2 | ≦ 2.5 (4) Here, βw2: magnification carried by the second lens group G2 at the wide-angle end βt2: magnification carried by the second lens group G2 at the telephoto end

The conditional expressions (1) and (2) correspond to the zoom trajectory arrangement in FIG. 1, and define appropriate ranges for the magnification at the wide-angle end and the magnification at the telephoto end of the second lens group G2. . Also, conditional expressions (3) and (4)
Corresponds to the zoom trajectory arrangement in FIG. 2 and defines appropriate ranges for the magnification at the wide-angle end and the magnification at the telephoto end of the second lens group G2. In FIG. 1, if the magnitude of the magnification βt2 of the second lens group G2 at the telephoto end exceeds the upper limit, that is, if it exceeds the upper limit in the conditional expression (2), there is no continuous solution, which is not preferable. Also, as the magnitude of the magnification βw2 of the second lens group G2 at the wide angle end approaches the upper limit, the zooming efficiency decreases, which is not preferable. Further, if the magnitude of the magnification βw2 of the second lens group G2 at the wide-angle end exceeds the upper limit, that is, if it exceeds the upper limit in the conditional expression (1), it is not preferable because there is no continuous solution.

If the magnitude of the magnification βt2 of the second lens group G2 at the telephoto end is below the lower limit, that is, below the lower limit in the conditional expression (2), the zooming efficiency is undesirably reduced. If the magnitude of the magnification βw2 of the second lens group G2 at the wide-angle end exceeds the lower limit, that is, falls below the lower limit in conditional expression (1), the first lens group G
The off-axis light flux passing through 1 is not preferable because it significantly separates from the optical axis and causes an increase in the size of the optical system.

On the other hand, if the magnitude of the magnification βt2 of the second lens group G2 at the telephoto end in FIG. 2 exceeds the upper limit, ie, exceeds the upper limit in the conditional expression (4), the load on the second lens group G2 increases. It is not preferable because it becomes too much. Further, the magnifications of the variable power lens units subsequent to the second lens unit G2 also increase rapidly, making it difficult to correct various aberrations, and undesirably causing interference between the lens units. If the magnitude of the magnification βw2 of the second lens group G2 at the wide-angle end exceeds the upper limit, that is, if it exceeds the upper limit in the conditional expression (3), the zooming efficiency is significantly reduced, which is not preferable.

On the other hand, as the magnitude of the magnification βt2 of the second lens group G2 at the telephoto end approaches the lower limit, the zooming efficiency decreases. If the magnitude of the magnification βt2 of the second lens group G2 at the telephoto end is below the lower limit, that is, below the lower limit in the conditional expression (4), it is not preferable because there is no continuous solution. If the magnitude of the magnification βw2 of the second lens group G2 at the wide-angle end is below the lower limit, that is, below the lower limit in the conditional expression (3), a continuous solution does not exist, which is not preferable.

It is possible to adjust the magnification range of the variable magnification unit by adjusting the magnification of the fixed lens group by changing the magnification range of the variable magnification unit. However, since the shooting distance and the back focus greatly change, and the specifications change, the adjustment of the magnification range of the zoom unit is naturally limited. If conditional expressions (1) and (2) or conditional expressions (3) and (4) are satisfied, a zoom solution can be stably obtained in the variable power region from the wide-angle end to the telephoto end. Conversely, if conditional expressions (1) and (2) or conditional expressions (3) and (4) are not satisfied, a region where no zoom solution exists is likely to occur, and the analysis of a continuous solution within the variable magnification region is complicated. Become. For this reason, when the variable power unit is composed of two or more lens units, it is necessary to perform a work such as partially fixing a specific variable power lens unit, and the variable power efficiency is reduced. Further, the cam shape becomes complicated, and it becomes difficult to obtain a smooth zoom cam trajectory.

In the present invention, the magnification carried by the third lens group G3 in the variable magnification area is determined by the following conditional expression (5). ) Should be satisfied. 0.3 ≦ | βw3 | <| β3 | <| βt3 | ≦ 2.5 (5) where β3: magnification of the third lens group G3 in an arbitrary zoom arrangement βw3: third lens group G3 at the wide-angle end Βt3: Magnification of the third lens group G3 at the telephoto end

Conditional expression (5) satisfies the third condition in the variable power range.
This defines an appropriate range of magnification that the lens group G3 carries. Exceeding the upper limit of conditional expression (5) is not preferable because the second lens group G2 and the third lens group G3 interfere at the telephoto end. In order to eliminate this interference, it is necessary to excessively increase the refractive power of the second lens group G2.
As a result, it becomes difficult to correct astigmatism and coma, which is not preferable. On the other hand, when the value goes below the lower limit of conditional expression (5), the third lens group G3 and the fourth lens group G4 interfere with each other at the wide angle end, which is not preferable.

In the present invention, the magnification carried by the fourth lens group G4 in the variable magnification area is determined by the following conditional expression (6) in the above-described configuration in which the magnification carried by the second lens group G2 is classified at the same magnification. ) Should be satisfied. 0.3 ≦ | βw4 | <| β4 | <| βt4 | ≦ 2.5 (6) where β4 is the magnification of the fourth lens group G4 in an arbitrary zoom arrangement. Βw4 is the fourth lens group G4 at the wide-angle end. Βt4: Magnification of the fourth lens group G4 at the telephoto end

Conditional expression (6) satisfies the fourth condition in the variable power range.
An appropriate range of the magnification that the lens group G4 carries is defined. Exceeding the upper limit of conditional expression (6) is not preferred because the fourth lens group G4 and the fifth lens group G5 interfere at the telephoto end. In order to eliminate this interference, it is necessary to make the refractive power of the fourth lens group G4 excessively strong.
As a result, it becomes difficult to correct spherical aberration and coma, which is not preferable. Conversely, when the value goes below the lower limit of conditional expression (6), the third lens group G3 and the fourth lens group G4 interfere with each other at the wide angle end, which is not preferable.

On the other hand, in the present invention, the magnification carried by the second lens group G2 and the third lens group G3
It is desirable that the magnifications of the fourth lens group G4 do not become equal to each other at almost the same time. This indicates that the magnification of the fourth lens group G4, which is a compensator group, is classified based on the unity magnification in order to reliably secure a continuous zoom solution having a high zoom ratio. Are obtained as solutions of quadratic equations. At this time, the magnification carried by the fourth lens group G4, which is the compensator group, is always lower than the same magnification as shown in FIG. 4, or higher than the same magnification as shown in FIG. There is a need. When the magnification of the fourth lens group G4 is not classified based on the same magnification, it is necessary to obtain a continuous solution by another measure.

In the present invention, the fourth compensator group
In the above-described configuration in which the magnification carried by the lens group G4 is classified at the same magnification, the following conditional expressions (7) and (8) may be satisfied, or conditional expressions (9) and (10) may be satisfied. desirable. 0.3 ≦ | βw4 | <1.0 (7) 0.3 ≦ | βt4 | <1.0 (8) 1.0 <| βw4 | ≦ 3.2 (9) 1.0 <| βt4 | ≦ 3.2 (10) where, βw4: magnification of the fourth lens group G4 at the wide-angle end βt4: magnification of the fourth lens group G4 at the telephoto end

Conditional expressions (7) and (8) correspond to the zoom trajectory arrangement in FIG. 4, and define appropriate ranges for the magnification at the wide-angle end and the magnification at the telephoto end of the fourth lens unit G4. . Also, conditional expressions (9) and (10)
Corresponds to the zoom trajectory arrangement in FIG. 3 and defines appropriate ranges for the magnification at the wide-angle end and the magnification at the telephoto end of the fourth lens group G4. In FIG. 4, if the magnitude of the magnification βt4 of the fourth lens group G4 at the telephoto end exceeds the upper limit, that is, if the magnitude exceeds the upper limit in the conditional expression (8), it is not preferable because there is no continuous solution. Also, as the magnitude of the magnification βw4 of the fourth lens group G4 at the wide angle end approaches the upper limit, the zooming efficiency decreases, which is not preferable. Further, if the magnitude of the magnification βw4 of the fourth lens group G4 at the wide-angle end exceeds the upper limit, that is, exceeds the upper limit in the conditional expression (7), it is not preferable because there is no continuous solution.

If the magnitude of the magnification βt4 of the fourth lens unit G4 at the telephoto end exceeds the lower limit, that is, if it falls below the lower limit in the conditional expression (8), the zooming efficiency is undesirably reduced. If the magnitude of the magnification βw4 of the fourth lens group G4 at the wide angle end exceeds the lower limit, that is, falls below the lower limit in the conditional expression (7), the first lens group G4.
The off-axis light flux passing through 1 is not preferable because it significantly separates from the optical axis and causes an increase in the size of the optical system.

On the other hand, in FIG. 3, when the magnitude of the magnification βt4 of the fourth lens group G4 at the telephoto end exceeds the upper limit, ie, exceeds the upper limit in the conditional expression (10), the load on the fourth lens group G4 increases. It is not preferable because it becomes too much. Further, the magnification of each lens unit in the zooming unit also increases rapidly, making it difficult to correct various aberrations, and interference between the lens units occurs, which is not preferable. The magnification β of the fourth lens group G4 at the wide angle end
If the value of w4 exceeds the upper limit, that is, if the value exceeds the upper limit in the conditional expression (9), the zooming efficiency is significantly reduced, which is not preferable.

On the other hand, as the magnitude of the magnification βt4 of the fourth lens group G4 at the telephoto end approaches the lower limit, the zooming efficiency decreases. If the magnitude of the magnification βt4 of the fourth lens group G4 at the telephoto end exceeds the lower limit, that is, the conditional expression (1)
If the value falls below the lower limit in 0), there is no continuous solution, which is not preferable. If the magnitude of the magnification βw4 of the fourth lens group G4 at the wide-angle end is below the lower limit, that is, below the lower limit in the conditional expression (9), a continuous solution does not exist, which is also not preferable.

The magnification range of the variable magnification unit can be adjusted by adjusting the magnification of the fixed lens group. However, when the magnification of the zoom unit changes, the shooting distance and the back focus change greatly, and the specifications change. Therefore, the adjustment of the magnification range of the zoom unit is naturally limited. Conditional expressions (7) and (8) or conditional expressions (9) and (10)
Is satisfied, a zoom solution can be stably obtained in the variable power range from the wide-angle end to the telephoto end. Conversely, conditional expressions (7) and (8) or conditional expressions (9) and (1)
If 0) is not satisfied, a region where no zoom solution exists is likely to occur, and the analysis of the continuous solution in the variable magnification region becomes complicated. For this reason, when the variable power unit is composed of two or more lens units, it is necessary to perform a work such as partially fixing a specific variable power lens unit, and the variable power efficiency is reduced. Further, the cam shape becomes complicated, and it becomes difficult to obtain a smooth zoom cam trajectory.

In the present invention, the magnification carried by the second lens group G2 in the variable magnification area is determined by the following conditional expression (11) in the above-described configuration in which the magnification carried by the fourth lens group G4 is classified with the same magnification. ) Should be satisfied. 0.2 ≦ | βw2 | <| β2 | <| βt2 | ≦ 2.5 (11) where β2: magnification of the second lens group G2 in an arbitrary zoom arrangement βw2: second lens group G2 at the wide-angle end Βt2: Magnification of the second lens group G2 at the telephoto end

Conditional expression (11) satisfies the second condition in the variable power range.
An appropriate range of the magnification that the lens group G2 carries is defined. Exceeding the upper limit of conditional expression (11) is not preferable because the second lens group G2 and the third lens group G3 interfere at the telephoto end. In order to eliminate this interference, it is necessary to excessively increase the refractive power of the second lens group G2.
As a result, it becomes difficult to correct astigmatism and coma, which is not preferable. When falling below the lower limit of conditional expression (11),
It is not preferable because the first lens group G1 and the second lens group G2 interfere at the wide angle end.

Further, according to the present invention, in the above-described configuration in which the magnification carried by the fourth lens group G4 is classified at the same magnification, the magnification carried by the third lens group G3 in the variable magnification area is represented by the following conditional expression (12). ) Should be satisfied. 0.2 ≦ | βw3 | <| β3 | <| βt3 | ≦ 2.5 (12) where β3: magnification of the third lens group G3 in an arbitrary zoom arrangement βw3: third lens group G3 at the wide-angle end Βt3: Magnification of the third lens group G3 at the telephoto end

Conditional expression (12) is satisfied in the zooming region.
This defines an appropriate range of magnification that the lens group G3 carries. Exceeding the upper limit of conditional expression (12) is not preferable because the second lens group G2 and the third lens group G3 interfere at the telephoto end. In order to eliminate this interference, it is necessary to make the refractive power of the fourth lens group G4 excessively strong.
As a result, it becomes difficult to correct spherical aberration and coma, which is not preferable. When the value goes below the lower limit of conditional expression (12),
It is not preferable because the third lens group G3 and the fourth lens group G4 interfere at the wide angle end.

In the present invention, if the diameter of the aperture stop is kept constant at the time of zooming, the F value changes greatly. Therefore, it is necessary to increase the aperture diameter with zooming to the telephoto side. Also,
To ensure the compactness of the optical system and the large aperture ratio,
It is necessary to control the relationship between the maximum effective diameter of the surface closest to the object side of the third lens group G3 and the refractive power of the third lens group G3 over the entire zooming region. That is, in the present invention, it is desirable that the following conditional expression (13) is satisfied. 0.3 <φ / f3 <0.8 (13) where φ: maximum effective diameter of the surface closest to the object side of the third lens group G3 f3: focal length of the third lens group G3

If the value exceeds the upper limit of conditional expression (13), the optical system becomes unnecessarily bright and the size of the optical system becomes large.
It is not preferable because the number of constituent lenses is extremely increased. Further, the refractive power of the third lens group G3 becomes too strong, and it becomes difficult to correct various aberrations including the spherical aberration, which is not preferable. On the other hand, when the value goes below the lower limit value of conditional expression (13), the refractive power of the third lens unit G3 becomes too weak, and the amount of zoom movement of the third lens unit G3 increases. as a result,
Interference between the third lens group G3 and an adjacent lens group occurs,
It is not preferable because it becomes difficult to secure a sufficient zoom ratio. In addition, when the value is below the lower limit value, a dark optical system is formed, which is not desirable because illumination is required more frequently when photographing a dark subject. Note that this does not apply to illuminating a dark subject. When focusing only on the brightness of the optical system, it may be as dark as the limit of the resolving power due to diffraction.
It may be set to <0.35. Further, in the dark optical system, the number of constituent lenses in the second lens group G2, the third lens group G3, and the fourth lens group G4 can be further easily reduced.

In the present invention, the following conditional expression (1) is satisfied.
It is desirable to satisfy 4). 0.1 <| f2 / f1 | <0.7 (14) where, f1: focal length of the first lens group G1 f2: focal length of the second lens group G2

If the upper limit of conditional expression (14) is exceeded, the refracting power of the second lens group G2 becomes excessively weak, and
The zoom movement amount of No. 2 increases. Further, the distance between the first lens group G1 and the second lens group G2 becomes too small, and the lens groups interfere with each other. As a result, the zooming efficiency decreases, which is not preferable for obtaining a high zooming zoom lens. In addition, the refractive power of the first lens group G1 becomes too strong, and the load on the angle of view increases, which makes it difficult to correct coma aberration below the principal ray, which is not preferable. On the other hand, when the value goes below the lower limit of conditional expression (14), the refractive power of the second lens unit G2 becomes strong,
Since the angle of view at the wide-angle end can be widened, high magnification can be achieved. However, the refracting power of the second lens group G2 becomes too strong, and at the wide-angle end, the incident height of the principal ray at the outermost periphery of the screen passing through the most object side surface of the optical system is significantly separated from the optical axis, and the lens diameter becomes large. It is not preferable because it leads to chemical conversion. Further, it is not preferable because it becomes difficult to correct various aberrations such as astigmatism and coma.

In the present invention, the following conditional expression (1) is satisfied.
It is desirable to satisfy 5). 0.3 <| f4 / f3 | <1.1 (15) where, f3: focal length of the third lens group G3 f4: focal length of the fourth lens group G4

When the value exceeds the upper limit of conditional expression (15), the refractive power of the third lens unit G3 becomes too strong, and it becomes difficult to correct various aberrations such as spherical aberration and coma on the telephoto side. Further, since the focal length of the fourth lens group G4 becomes negatively long,
On the telephoto side, the third lens group G3 and the fourth lens group G4 interfere with each other, and the zooming efficiency is reduced. Therefore, it is not preferable to obtain a high zooming zoom lens. On the other hand, when the value goes below the lower limit of conditional expression (15), the refracting power of the fourth lens unit G4 becomes too strong, and the load on the fifth lens unit G5 increases. It is not preferable because it becomes difficult. Also, the refractive power of the third lens group G3 becomes too weak,
The movement amount of the lens group G3 increases. As a result, it is necessary to ensure a sufficient distance between the third lens group G3 and the adjacent lens group, so that the optical system becomes longer and larger. Furthermore, it is preferable to increase the zoom ratio, because at the wide-angle end, the incident height of the principal ray at the outermost periphery of the screen passing through the most object side surface of the optical system is significantly separated from the optical axis, and the lens diameter becomes large. Absent.

In the present invention, the following conditional expression (1) is satisfied.
It is desirable to satisfy 6). 0.05 <β1 / β5 <0.5 (16) Conditional expression (16) defines the focusing range that changes with the focusing movement of the first lens group G1, and also defines the length of the back focus. . This condition greatly affects the specifications of the photographing optical system.

When the value exceeds the upper limit of conditional expression (16), the back focus becomes short, and the 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 (16), the working distance becomes unnecessarily long, the back focus becomes long, and the size of the optical system becomes large. Further, the first lens group G1 and the second lens group G2
Interference is likely to occur, and the distribution of refractive power is unreasonable, making it difficult to correct various aberrations such as coma. However, this does not apply if the wide-angle end is not so widened at the wide-angle end. In this case, the lower limit of conditional expression (16) can be set to 0.

[0052]

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 second lens group G2 having a positive refractive power. The zoom lens 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. Upon zooming, the second lens group G
The second to fourth lens groups G4 move along the optical axis. Then, inside and outside the zooming area, the magnifications of the three lens groups of the second lens group G2 to the fourth lens group G4 do not become almost equal at the same time. Further, in the variable power range, the second lens group G2 to the fourth lens group G
The magnification carried by any one of the lens groups 4 does not become the same magnification, and the magnifications carried by the remaining two lens groups do not become the same magnification almost simultaneously.

In each embodiment, it is possible to focus by extending the first lens group G1 toward the object side, and it is possible to change the photographing distance, the magnification range, 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 constitute a zoom unit that moves along the optical axis to perform zooming. The fifth lens group G5 is a lens group fixed to the image plane, and is a main lens group that determines the length of the back focus and the position of the exit pupil. The magnification of the second lens group G2 does not change much between the wide-angle end and the telephoto end. On the other hand, the magnification carried by the third lens group G3 and the magnification carried by the fourth lens group G4 greatly change in the variable power region via the same magnification.
However, the third lens group G3 and the fourth lens group G4 do not have the same magnification at almost the same time, and the magnification is independently changed according to the zoom trajectory passing through the same magnification.

[First Embodiment] FIG. 5 is a diagram showing a lens configuration of a zoom lens according to a first embodiment of the present invention.
In the zoom lens of FIG. 5, 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, in order from the object side, a positive meniscus lens in which a negative meniscus lens having a convex surface facing the object side and a biconvex lens are bonded, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a cemented positive lens of a biconvex lens and a biconcave lens.

The third lens group G3 is composed of, in order from the object side, a cemented positive lens of a biconvex lens, a negative meniscus lens having a concave surface facing the object side, and a biconvex lens. The fourth lens group G4 includes, in order from the object side, a cemented negative lens composed of a biconvex lens and a biconcave lens, and a negative meniscus lens having a concave surface facing the object side. Fifth lens group G5
Comprises, in order from the object side, a positive meniscus lens having a concave surface facing the object side, a cemented positive lens of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, and a biconvex lens. Note that the second lens group G2 and the third lens group G3
An aperture stop S is arranged between the two. FIG. 5 shows a lens arrangement at the wide-angle end. When the magnification is changed to the telephoto end, the second lens group G2 to the fourth lens group G4 move along a predetermined zoom trajectory.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), f is the focal length,
FN represents the F number, 2ω represents the angle of view, Bf represents the back focus, β represents the shooting magnification, and d0 represents the object distance. Further, the surface number indicates the order of the lens surface from the object side along the direction in which the light beam travels, and the refractive index and Abbe number indicate values for the d-line (λ = 587.6 nm).

[0057]

Table 1 f = 16.1 to 80.1 FN = 1.84 to 3.63 β = −0.02 to −0.1 2ω = 37.4 ° to 8.4 ° Surface number Curvature radius Surface spacing Abbe number Refractive index 1 ∞ 2.000 64.1 1.51680 2 ∞ 2.000 3 80.876 2.000 25.3 1.80518 4 46.000 7.500 60.1 1.62041 5 -537.395 0.200 6 43.439 4.300 60.0 1.64000 7 66.249 (d7 = variable) 8 79.980 1.600 55.6 1.69680 9 21.578 6.500 10 -95.951 1.600 55.6 1.69680 11 42.999 0.300 12 35.133 5.400 25.3 1.80518 13 -70.000 1.500 60.0 1.64000 14 41.749 (d14 = variable) 15 54.697 9.000 82.5 1.49782 16 -24.000 1.800 25.3 1.80518 17 -50.209 0.298 18 74.993 5.800 82.5 1.49782 19 -55.428 (d19 = variable ) 20 341.761 4.000 25.3 1.80518 21 -19.600 1.400 42.0 1.66755 22 32.000 4.500 23 -14.566 1.400 54.0 1.61720 24 -259.562 (d24 = variable) 25 -113.283 5.000 52.3 1.74810 26 -28.663 0.200 27 59.011 8.000 82.5 1.49782 28 -28.000 1.700 25.3 1.80518 29 -65.960 0.200 30 41.133 4.500 82.5 1.49782 31 -780.344 Bf (Variable in scaling) (Interval) β -0.020 -0.030 -0.060 -0.080 -0.100 d0 742.599 742.599 742.599 742.599 742.599 d7 1.542 6.053 10.062 6.531 3.615 d14 48.845 38.388 18.524 14.207 11.637 d19 2.442 10.468 29.050 40.686 49.875 d24 16.162 14.081 11.356 7.567 38.49438 3838. F1 = 80.000 βw1 = -0.1200 βm1 = -0.1200 βt1 = -0.1200 f2 = -25.000 βw2 = -0.4936 βm2 = -0.5934 βt2 = -0.5147 f3 = 38.000 βw3 = -0.6121 βm3 = -1.1098 βt3 = -1.4958 f4 = -19.000 βw4 = -0.6727 βm4 = -0.9260 βt4 = -1.3199 f5 = 25.000 βw5 = -0.8200 βm5 = -0.8200 βt5 = -0.8200 βw = -0.0200 βm = -0.0600 βt = -0.1000 φ = 24.7 fw = 16.062 ft = 80.097 (13) φ / f3 = 0.658 (14) | f2 / f1 | = 0.313 (15) | f4 / f3 | = 0.500 (16) β1 / β5 = 0.146

FIGS. 6 to 8 are graphs showing various aberrations of the first embodiment. FIG. 6 is a diagram showing various aberrations at the wide-angle end (shortest focal length state), and FIG. 7 is an intermediate focal length state (photographing magnification β
= −0.06), and FIG. 8 shows various aberration diagrams at the telephoto end (the longest focal length state). In each aberration diagram, H is the height of 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). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment,
It can be seen that various aberrations are favorably corrected in each focal length state.

[Second Embodiment] FIG. 9 is a diagram showing a lens configuration of a zoom lens according to a second embodiment of the present invention.
In the zoom lens of FIG. 9, 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, in order from the object side, a positive meniscus lens in which a negative meniscus lens having a convex surface facing the object side and a biconvex lens are bonded, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a cemented positive lens of a biconvex lens and a biconcave lens.

The third lens group G3 comprises, in order from the object side, a positive lens cemented with a biconvex lens surface and a negative meniscus lens having a concave surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. The fourth lens group G4 includes, in order from the object side, a cemented negative lens having a concave surface facing the object side and a biconcave lens, and a cemented lens having a biconcave lens and a positive meniscus lens having a convex surface facing the object side. Consists of a negative lens. The fifth lens group G5 includes, in order from the object, a positive meniscus lens having a concave surface facing the object side, a positive meniscus lens having a concave surface facing the object side, and a negative meniscus lens having a concave surface facing the object side. , And a biconvex lens. An aperture stop S is arranged between the second lens group G2 and the third lens group G3. FIG. 9 shows the lens arrangement at the wide-angle end.
The lens group G4 moves along a predetermined zoom trajectory.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), f is the focal length,
FN represents the F number, 2ω represents the angle of view, Bf represents the back focus, β represents the shooting magnification, and d0 represents the object distance. Further, the surface number indicates the order of the lens surface from the object side along the direction in which the light beam travels, and the refractive index and Abbe number indicate values for the d-line (λ = 587.6 nm).

[0062]

F = 14.0-68.3 FN = 2.0-6.1 β = −0.02-−0.1 2ω = 42.6 ° -9.2 ° Surface number Curvature radius Surface spacing Abbe number Refractive index 1 ∞ 2.000 64.1 1.51680 2 ∞ 2.000 3 490.252 1.800 25.3 1.80518 4 37.000 11.000 48.0 1.71700 5 -201.108 0.200 6 38.398 5.000 45.0 1.74400 7 87.536 (d7 = variable) 8 49.475 1.400 52.3 1.74810 9 18.907 6.000 10 -115.105 1.250 45.0 1.74400 11 44.571 0.200 12 37.627 5.700 25.3 1.80518 13 -40.000 1.200 49.5 1.77279 14 46.819 (d14 = variable) 15 90.341 3.100 82.5 1.49782 16 -18.000 1.100 25.3 1.80518 17 -25.913 0.200 18 26.432 2.400 82.5 1.49782 19 47.904 (d19 = variable) 20 -142.693 2.700 25.3 1.80518 21 -14.000 1.100 67.9 1.59319 22 81.996 2.700 23 -13.959 1.000 37.9 1.72342 24 25.000 2.200 35.2 1.74950 25 180.752 (d25 = variable) 26 -66.411 4.000 49.5 1.74443 27 -20.407 0.200 28 -182.595 6.000 82.5 1.49782 29 -16.648 1.100 25.3 1.80518 30 -42.733 0.200 31 28.835 5.000 82.5 1.49782 32 -185.212 Bf (Variable interval at zooming) β -0.020 -0.030 -0.060 -0.080 -0.100 d0 643.945 643.945 643.945 643.945 643.945 d7 2.622 8.400 10.099 5.850 2.369 d14 51.532 40.282 23.524 19.116 16.705 d19 1.644 8.211 26.896 39.294 49.002 d24 14.179 13.084 9.457 5.717. 38.544 38.544 38.544 (Values for conditions) f1 = 70.000 βw1 = -0.1200 βm1 = -0.1200 βt1 = -0.1200 f2 = -22.000 βw2 = -0.4936 βm2 = -0.5932 βt2 = -0.4908 f3 = 35.000 βw3 = -0.6121 βm3 = -1.1159 βt3 = -1.5698 f4 = -19.000 βw4 = -0.6727 βm4 = -0.9212 βt4 = -1.3189 f5 = 24.000 βw5 = -0.8200 βm5 = -0.8200 βt5 = -0.8200 βw = -0.0200 βm = -0.0600 βt = -0.1000 φ = 15.2 fw = 14.022 ft = 68.340 (13) φ / f3 = 0.434 (14) | f2 / f1 | = 0.314 (15) | f4 / f3 | = 0.543 (16) β1 / β5 = 0.146

FIGS. 10 to 12 show various aberration diagrams of the second embodiment. 10 shows various aberration diagrams at the wide-angle end (shortest focal length state), FIG. 11 shows various aberration diagrams at an intermediate focal length state (photographing magnification β = −0.06), and FIG.
Reference numeral 2 denotes various aberration diagrams at the telephoto end (the longest focal length state). 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) and G is the g-line (λ = 435.8 n).
m). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected in each focal length state.

As described above, 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 amount is sufficiently secured. The aperture diameter changes with the magnification. In each embodiment, especially at the wide-angle end, the distortion is almost completely corrected, and the decrease in the illuminance ratio is cos ⁴ θ
It is necessary to suppress bignetting. Therefore, as is clear from the aberration diagrams, in each embodiment, a sufficient peripheral light amount is secured. Since there is a large amount of peripheral light, the lens arrangement of the second lens group G2, the second lens group G2, The lens shape of the lens group G2 and the lens shape of the third lens group G3 are devised.

On the other hand, as a countermeasure against the coma aberration above the principal ray, the lens arrangement of the fifth lens group G5 and the fifth
Consideration is given to the lens shape of the lens group G5. By increasing the number of cemented lenses in the lens arrangement of the fourth lens group G4, in the second embodiment, sufficient freedom to simultaneously correct axial chromatic aberration and chromatic aberration of magnification at the wide-angle end is sufficiently ensured. It is possible to do. At this time, it is possible to reduce the load for achromatizing the second lens group G2. In the second embodiment, the third
The magnification of the lens group G3 and the magnification of the fourth lens group G4 are separately equal to each other, and have values exceeding the same magnification at the telephoto end, thereby achieving higher magnification. Also, since the aperture diameter is kept constant during zooming, the F-number changes greatly at the telephoto end.

In each of the above embodiments, a lens system is constituted by five lens groups. However, it is also easy to divide the third lens group G3 into two lens groups to form a six-unit lens system as a whole. Similarly, the third lens group G3 is divided into three lens groups to secure a degree of freedom in increasing the aperture, and it is easy to form a lens system having a total of seven groups. It is needless to say that the number of constituent lenses can be reduced as compared with the above-described embodiments when widening of the angle is unnecessary or when a dark optical system can sufficiently fulfill the purpose. In particular, it is much easier to further enlarge the variable power region toward the telephoto side to increase the variable power ratio than to expand to the wide angle end.
Furthermore, in the present invention, shortening the conjugate length and increasing the photographing magnification can be easily realized because it is not necessary to widen the angle. One way to achieve this is as follows:
The lens group G1 can be extended to the object side. Also,
Even in an optical system in which the combined magnification range and the conjugate length are significantly different, the magnification and focal length of the first lens group G1 and the fourth
The present invention can be easily coped with by changing the magnification and the focal length of the lens group G4. Furthermore, by using an aspheric surface for each specific lens group,
High performance, large diameter, and high zoom ratio can be realized.

Further, as described above, in each of the embodiments, the effective F value at the wide-angle end is very bright, about F / 2.0, and the peripheral light amount is sufficiently secured. Further, despite the fact that the optical system is very bright, the effective diameter of the surface closest to the object side of the optical system is kept small, so that the optical system is compact. This is considered to be due to the fact that the fourth lens group G4 also employs a configuration that contributes to zooming. In addition, it is possible to satisfactorily correct various aberrations and realize an optical system having good optical performance. In particular, it is possible to realize an optical system with good optical performance by using an arbitrary magnification range with respect to the magnification carried by each lens group and by appropriately distributing the refractive power of each lens group. In addition to the above two embodiments, the function of the second lens group G2 can be assigned to another lens group by appropriately selecting the magnification that each lens group bears, so that the movement of the third lens group or more lens groups can be performed. It is also possible to find other zoom solutions in which the scaling unit of the group movement configuration does not include a simultaneous unity arrangement.

Tables (3) to (8) show specific examples of the zoom method according to each of the zoom trajectory arrangements shown in FIGS. In each table, β is the photographing magnification, R is the photographing distance, D0 is the distance between the object and the principal point of the first lens group G1,
D1 is the distance between the principal points between the first lens group G1 and the second lens group G2, D2 is the distance between the principal points between the second lens group G2 and the third lens group G3, and D3 is the distance between the third lens group G3 and the fourth lens group. Lens group G
4, the distance between the principal point of the fourth lens group G4 and the fifth lens group G5, and the distance D5 between the principal point of the fifth lens group G5 and the image plane, respectively. Βi is the magnification of the i-th lens group Gi, and fi is the i-th lens group G
i is the focal length of the lens HP, and HP is the aperture stop S of the third lens group G3.
Is the height of incidence of the principal ray at the principal point of the first lens group G1 when is in close contact.

The zoom methods shown in the following tables (3) and (4) correspond to the zoom trajectory arrangement shown in FIG. Table (3)
And (4), the third lens group G3
Is a main lead group, the fourth lens group G4 is a sub lead group, and the second lens group G2 is a compensator group.
In the zoom method shown in Table (3), the magnification of the second lens group G2, which is a compensator group, is used at a low magnification equal to or less than the same magnification. On the other hand, in the zoom method shown in Table (4), the magnification of the fourth lens group G4 is used at a high magnification equal to or higher than the same magnification.

[0070]

[Table 3] D0 = 746.6667 f1 f2 f3 f4 f5 80.0000 -25.0000 38.0000 -19.0000 25.0000 D1 D2 D3 D4 D5 β R 14.2731 63.0583 13.8688 23.7062 45.5000 -0.0200 907.0731 18.9974 52.4649 21.7411 21.7300 45.000 35.0 20.0251 28.1978 51.3736 15.3099 45.5000 -0.0800 907.0731 17.1376 25.5849 60.5398 11.6441 45.5000 -0.1000 907.0731 9.6156 22.8382 74.4026 8.0500 45.5000 -0.1200 907.0731 β1 β2 β3 β4 β5 βHP -0.1200 -0.4968 -0.608 -0.0200 -0.1 -0.0200 -0.1 0.7147 -0.7781 -0.8200 -0.0300 -14.7276 -0.1200 -0.6074 -1.0931 -0.9184 -0.8200 -0.0600 -7.9481 -0.1200 -0.5609 -1.3005 -1.1146 -0.8200 -0.0800 -4.8742 -0.1200 -0.5267 -1.4755 -1.3076 -0.8200 -0.1000- 3.2860 -0.1200 -0.4547 -1.7920 -1.4967 -0.8200 -0.1200 -1.7418

[0071]

Table 4 D0 = 1080.0000 f1 f2 f3 f4 f5 80.0000 -25.0000 30.0000 -19.0000 25.0000 D1 D2 D3 D4 D5 β R 11.7403 32.6947 16.2460 26.5522 40.0000 -0.0200 1207.2333 14.1839 28.8137 19.6513 24.5844 407.20000 10.0 21.0966 17.8347 30.7788 17.5231 40.0000 -0.0500 1207.2333 25.1829 11.3448 39.1302 11.5755 40.0000 -0.0800 1207.2333 26.9877 8.4782 43.4039 8.3634 40.0000 -0.1000 1207.2333 β1 β2 β3 β4 β5 β HP -0.0800 -0.5034 -0.7448 -1.1113 -0.6000 -0.0800 -295 0.8097 -1.2149 -0.6000 -0.0250 -8.2479 -0.0800 -0.5896 -0.9706 -1.4563 -0.6000 -0.0400 -5.9894 -0.0800 -0.6203 -1.0585 -1.5865 -0.6000 -0.0500 -5.0506 -0.0800 -0.6903 -1.2711 -1.8995 -0.6000 -0.0800- 3.3966 -0.0800 -0.7265 -1.3863 -2.0686 -0.6000 -0.1000 -2.7619

The zoom methods shown in the following tables (5) and (6) correspond to the zoom trajectory arrangement shown in FIG. Table (5)
And (6), the third lens group G3
Is a main lead group, the fourth lens group G4 is a sub lead group, and the second lens group G2 is a compensator group.
In the zoom method shown in Table (5), the magnification of the second lens group G2, which is a compensator group, is used at a high magnification equal to or higher than the same magnification. On the other hand, in the zoom method shown in Table (6), the magnification of the fixed lens group is higher than the magnification of the fixed lens group shown in Table (5).

[0073]

Table 5 D0 = 1050.0000 f1 f2 f3 f4 f5 50.0000 -20.0000 40.0000 -19.0000 20.0000 D1 D2 D3 D4 D5 β R 21.5740 43.1685 24.4934 35.4879 28.0000 -0.0200 1202.7237 16.9360 28.4042 53.5967 25.7400 28.0000 28.0000 20.0581 13.9680 70.5679 20.1297 28.0000 -0.0800 1202.7237 21.0652 9.1547 76.2772 18.2266 28.0000 -0.1000 1202.7237 21.8392 5.1243 81.1616 16.5985 28.0000 -0.1200 1202.7237 β1 β2 β3 β4 β5 β HP -0.0500 -1.8305 -0.6691 -0.8164 -0.4000 -0.0200 -1.280 1.1729 -1.3270 -0.4000 -0.0400 -8.2686 -0.0500 -1.4483 -1.3797 -1.5013 -0.4000 -0.0600 -5.5258 -0.0500 -1.6075 -1.5316 -1.6247 -0.4000 -0.0800 -4.0144 -0.0500 -1.7490 -1.6573 -1.7249 -0.4000 -0.1000- 2.9895 -0.0500 -1.8760 -1.7664 -1.8106 -0.4000 -0.1200 -2.2345

[0074]

[Table 6] D0 = 764.2857 f1 f2 f3 f4 f5 50.0000 -20.0000 40.0000 -19.0000 20.0000 D1 D2 D3 D4 D5 β R 21.1321 40.2945 30.9671 23.3300 30.0000 -0.0400 910.0094 17.6619 31.5882 49.2318 10.0 358.000 10.0 19.4572 21.0406 62.3604 12.8656 30.0000 -0.1000 910.0094 21.3759 12.4922 72.3048 9.5508 30.0000 -0.1500 910.0094 22.6366 6.2125 79.8332 7.0413 30.0000 -0.2000 910.0094 β1 β2 β3 β4 β5 β HP -0.0700 -1.6171 -0.7599 -0.9300 -0.5000 -0.0400 -1.742 -0.0700 1.0857 -1.2504 -0.5000 -0.0600 -8.1347 -0.0700 -1.3276 -1.2420 -1.3862 -0.5000 -0.0800 -5.9938 -0.0700 -1.4242 -1.3548 -1.4808 -0.5000 -0.1000 -4.8083 -0.0700 -1.6496 -1.5696 -1.6552 -0.5000 -0.1500- 3.0531 -0.0700 -1.8411 -1.7366 -1.7873 -0.5000 -0.2000 -2.0174

The zoom method shown in the following Table (7) corresponds to the zoom trajectory arrangement shown in FIG. In the zoom method shown in Table (7), the third lens group G3 is a main lead group, the second lens group G2 is a sub lead group, and the fourth lens group G4 is a compensator group. The magnification of the fourth lens group G4, which is a compensator group, is used at a high magnification equal to or higher than the same magnification.

[0076]

[Table 7] D0 = 660.0000 f1 f2 f3 f4 f5 60.0000 -13.0000 25.0000 -16.0000 25.0000 D1 D2 D3 D4 D5 β R 11.5944 70.4162 11.9673 8.3151 42.4999 -0.0200 804.7928 17.1812 61.5429 43.0999 -1. 29.1195 42.5822 17.5013 13.0899 42.4999 -0.0500 804.7928 34.6433 33.8091 21.1596 12.6809 42.4999 -0.0800 804.7928 36.9354 30.1687 22.8876 12.3012 42.4999 -0.1000 804.7928 38.7528 27.2821 24.1817 12.0762 42.4999 -0.1200 4804.29 12.804.24 12.79 24.79. β3 β4 β5 β HP -0.1000 -0.3140 -0.4000 -2.2750 -0.7000 -0.0200 -14.2898 -0.1000 -0.3629 -0.4607 -2.1358 -0.7000 -0.0250 -16.1243 -0.1000 -0.4803 -0.5969 -1.9932 -0.7000 -0.0400 -16.6495 -0.1000- 0.5444 -0.6639 -1.9765 -0.7000 -0.0500 -15.9677 -0.1000 -0.7082 -0.8060 -2.0021 -0.7000 -0.0800 -13.7809 -0.1000 -0.80 92 -0.8714 -2.0258 -0.7000 -0.1000 -12.6686 -0.1000 -0.9125 -0.9210 -2.0399 -0.7000 -0.1200 -11.8189 -0.1000 -1.0253 -0.9571 -2.0382 -0.7000 -0.1400 -11.1888 -0.1000 -1.3572 -0.9800 -1.9334 -0.7000- 0.1800 -10.6443

The zoom method shown in the following Table (8) corresponds to the zoom trajectory arrangement shown in FIG. In the zoom method shown in Table (8), the third lens group G3 is a main lead group, the second lens group G2 is a sub lead group, and the fourth lens group G4 is a compensator group. The magnification of the fourth lens group G4, which is a compensator group, is used at a low magnification equal to or less than the same magnification. The third lens group G3 serving as the main lead group
Can be exchanged with the role of the second lens group G2 serving as the sub-lead group.

[0078]

[Table 8] D0 = 550.0000 f1 f2 f3 f4 f5 50.0000 -13.0000 25.0000 -16.0000 20.0000 D1 D2 D3 D4 D5 βR 11.4077 43.9897 8.6691 15.6002 35.0000 -0.0200 664.6667 16.6903 35.5997 9.2852 18.092503.60000 -20.0 28.6727 16.5689 11.3036 23.1215 35.0000 -0.0500 664.6667 32.9917 9.7092 14.0901 22.8757 35.0000 -0.0800 664.6667 34.2503 7.7103 15.9506 21.7555 35.0000 -0.1000 664.6667 β1 β2 β3 β4 β5 β HP -0.1000 -0.4249 -0.6664 -0.9417 -0.7500 -0.0200-17.5 0.8257 -0.7860 -0.7500 -0.0250 -20.0327 -0.1000 -0.7956 -1.2693 -0.5281 -0.7500 -0.0400 -21.8228 -0.1000 -0.9754 -1.4493 -0.4716 -0.7500 -0.0500 -20.7705 -0.1000 -1.4431 -1.5179 -0.4869 -0.7500 -0.0800- 16.1110 -0.1000 -1.6775 -1.4271 -0.5569 -0.7500 -0.1000 -13.5133

[0079]

As described above, according to the present invention, it is possible to realize a high-resolution, high-performance, finite high-magnification zoom lens, and an optical system suitable for a wide range of applications can be easily realized. It is possible to provide. In particular, a compact zoom lens that is bright, has a short conjugate length, and has a wide angle of view can be realized. Further, it is possible to realize a zoom lens in which distortion and its fluctuation during zooming are very small. Further, it is possible to realize a zoom lens capable of securing a sufficient peripheral light amount around the screen in order to reduce shading of the imaging system.

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

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic configuration of a zoom lens according to the present invention and a movement trajectory of each lens group due to zooming.

FIG. 2 is a diagram illustrating a basic configuration of a zoom lens according to the present invention and a movement trajectory of each lens group due to zooming.

FIG. 3 is a diagram illustrating a basic configuration of a zoom lens according to the present invention and a movement trajectory of each lens group due to zooming.

FIG. 4 is a diagram showing a basic configuration of a zoom lens according to the present invention and a movement trajectory of each lens group due to zooming.

FIG. 5 is a diagram illustrating a lens configuration of a zoom lens according to a first example of the present invention.

FIG. 6 is a diagram illustrating various aberrations of the first example at the wide-angle end.

FIG. 7 is a diagram illustrating various aberrations of the first example in an intermediate focal length state.

FIG. 8 is a diagram illustrating various aberrations of the first example at a telephoto end.

FIG. 9 is a diagram illustrating a lens configuration of a zoom lens according to a second example of the present invention.

FIG. 10 is a diagram illustrating various aberrations of the second example at the wide-angle end.

FIG. 11 is a diagram illustrating various aberrations of the second embodiment in an intermediate focal length state.

FIG. 12 is a diagram illustrating various aberrations of the second example at a telephoto end.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group G5 fifth lens group S aperture stop

Claims (15)

[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 refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power. At this time, the second lens group G2 to the fourth lens group G4 move along the optical axis, and the third lens group G2 to the fourth lens group G4 are moved in and out of the variable power region. The magnifications carried by the two lens groups do not become the same magnification almost at the same time, and the magnification carried by any one of the second lens group G2 to the fourth lens group G4 is the same magnification within the variable magnification area. The zoom lens is characterized in that the remaining two lens groups do not have the same magnification almost simultaneously. 2. In the variable magnification area, the magnification of the second lens group G2 does not become equal, and the magnification of the third lens group G3 and the magnification of the fourth lens group G4 are different. 2. The zoom lens according to claim 1, wherein the magnification is not substantially equal. 3. When the magnification of the second lens group G2 at the wide angle end is βw2 and the magnification of the second lens group G2 at the telephoto end is βt2, 0.3 ≦ | βw2 | <1.0 3. The zoom lens according to claim 2, wherein a condition of 0.3 ≦ | βt2 | <1.0 is satisfied. 4. When the magnification of the second lens group G2 at the wide angle end is βw2 and the magnification of the second lens group G2 at the telephoto end is βt2, 1.0 <| βw2 | ≦ 2.5 The zoom lens according to claim 2, wherein a condition of 1.0 <| βt2 | ≦ 2.5 is satisfied. 5. The third lens group G within a variable power range.
Where β3 is β3, the magnification of the third lens group G3 at the wide-angle end is βw3, and the magnification of the third lens group G3 at the telephoto end is βt3, 0.3 ≦ | βw3 | <0.3 The zoom lens according to claim 2, wherein a condition of | β3 | <| βt3 | ≦ 2.5 is satisfied. 6. The fourth lens group G within a variable power range.
4 is β4, the magnification of the fourth lens group G4 at the wide angle end is βw4, and the magnification of the fourth lens group G4 at the telephoto end is βt4, 0.3 ≦ | βw4 | < The zoom lens according to claim 2, wherein a condition of | β4 | <| βt4 | ≦ 2.5 is satisfied. 7. The magnification carried by the fourth lens group G4 does not become the same magnification within the variable magnification area, and the magnification carried by the second lens group G2 and the magnification carried by the third lens group G3 are not equal. 2. The zoom lens according to claim 1, wherein the magnification is not substantially equal. 8. When the magnification of the fourth lens group G4 at the wide angle end is βw4 and the magnification of the fourth lens group G4 at the telephoto end is βt4, 0.3 ≦ | βw4 | <1.0 The zoom lens according to claim 7, wherein a condition of 0.3 ≦ | βt4 | <1.0 is satisfied. 9. When the magnification of the fourth lens group G4 at the wide angle end is βw4 and the magnification of the fourth lens group G4 at the telephoto end is βt4, 1.0 <| βw4 | ≦ 3.2. The zoom lens according to claim 7, wherein a condition of 1.0 <| βt4 | ≦ 3.2 is satisfied. 10. The magnification carried by the second lens group G2 in the variable magnification area is β2, the magnification carried by the second lens group G2 at the wide-angle end is βw2, and the magnification carried by the second lens group G2 at the telephoto end. 8. The zoom lens according to claim 7, wherein when a magnification is βt2, a condition of 0.2 ≦ | βw2 | <| β2 | <| βt2 | ≦ 2.5 is satisfied. 11. The magnification carried by the third lens group G3 in the variable power range is β3, the magnification carried by the third lens group G3 at the wide angle end is βw3, and the magnification carried by the third lens group G3 at the telephoto end. 8. The zoom lens according to claim 7, wherein when a magnification is βt3, a condition of 0.2 ≦ | βw3 | <| β3 | <| βt3 | ≦ 2.5 is satisfied. 12. When the maximum effective diameter of the surface closest to the object side of the third lens group G3 is φ and the focal length of the third lens group G3 is f3, 0.3 <φ / f3 <0. The zoom lens according to any one of claims 1 to 11, wherein the zoom lens satisfies the following condition (8). 13. The focal length of the first lens group G1 is f
13. When the focal length of the second lens group G2 is f2, the condition of 0.1 <| f2 / f1 | <0.7 is satisfied. The zoom lens according to the item. 14. The focal length of the third lens group G3 is f
14. When the focal length of the fourth lens group G4 is f4, the following condition is satisfied: 0.3 <| f4 / f3 | <1.1. The zoom lens according to the item. 15. The magnification of the first lens group G1 is β
15. When the magnification of the fifth lens group G5 is β5, the condition of 0.05 <β1 / β5 <0.5 is satisfied. The zoom lens described.