JP3060118B2 - High-magnification zoom lens with minimal short-range aberration fluctuation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-magnification zoom lens, and more particularly to a high-magnification zoom lens which has a small aberration variation even when focusing on a short distance and shortens a minimum photographing distance.

[0002]

2. Description of the Related Art In recent years, a fully automatic camera equipped with a zoom lens having a high magnification has been gaining momentum in commercialization as a new concept camera. Among them, when the zoom ratio exceeds about 3, it is difficult to realize with a two-unit zoom lens having a simple configuration, and thus a new lens type has been devised.

Under such circumstances, the present applicant has developed a high-magnification three-group zoom lens developed from a unique four-group zoom lens (Japanese Patent Application Laid-Open No. 63-43115).
Japanese Patent Laid-Open No. Hei 1-204001 proposes a focusing method proposed in Japanese Patent No.
No. 3 proposed.

This focusing method is an indispensable technique for realizing the above-described zoom lens because the amount of focusing movement to a short distance can be reduced and the variation in aberration is relatively small.

The conventional focusing of a zoom lens is generally performed by moving the first lens unit, and many focusing methods have been proposed as a parallax solution which does not take into account aberration fluctuations. ing.

[0006]

On the other hand, there is a demand for a further reduction in the close distance, and in the above-described invention of the present applicant, fluctuations in aberrations near the telephoto end where the focusing movement amount becomes large are suppressed, and high performance is achieved. To do so, new technologies are needed.

The present invention has been made in view of such a situation, and an object thereof is to provide a first lens unit having a positive refractive power and a second lens having a positive refractive power in order from the object side proposed by the present applicant. A three-unit zoom lens composed of a lens unit and a third lens unit having a negative refractive power, and a first lens having a positive refractive power in order from the object side.
At the time of short-distance focusing, a four-unit zoom lens including a lens unit, a second lens unit having a positive or negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power is targeted. An object of the present invention is to provide a zoom lens that stabilizes the optical performance of the zoom lens and obtains satisfactory performance from infinity to close range.

[0008]

A high-magnification zoom lens according to the present invention, which achieves the above object and has a small variation in near-field aberration, comprises:
In order from the object side, the first lens unit includes a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power.
Zooming from the wide-angle end to the telephoto end is performed by moving each lens unit toward the object side, and the following conditions (2), (3), and
It is characterized by satisfying (4). 0.4 <φ ₁ / φ _W <1.25 (2) 1.1 <φ ₁₂ / φ _W <3.0 (3) 2.85 <β _3T / β _3W <4. 0 (4) where φ ₁ is the refractive power of the first lens group, φ _W is the refractive power of the entire system at the wide-angle end, and φ ₁₂ is the first and second lens groups at the wide-angle end. , Β _3W is the paraxial lateral magnification of the third lens unit at the wide-angle end, and β _3T is the paraxial lateral magnification of the third lens unit at the telephoto end.

[0009]

[0010]

As described above, a number of focusing methods have been conventionally proposed. In practice, however, suppression of aberration fluctuation is extremely important, and driving methods and control means relating to the focusing lens group are also important. Have meaning.

The present invention mainly focuses on suppressing fluctuations in spherical aberration and astigmatism due to focusing near the telephoto end. It is for shortening. That is, as a method of realizing this, the concept of floating is introduced by a so-called in-focus method, the degree of aberration fluctuation is reduced with a simple lens configuration, and the performance is intended to be stabilized.

As described above, the method of moving the first lens group is generally used for focusing in a zoom lens. However, in recent years, an auto-focus method has been adopted. It is possible to solve it. Therefore, it is technically possible to determine a power arrangement in which the focal position falls within a substantially constant depth of focus and mechanically realize the focal position correction, and it may be considered that the degree of freedom in optical design is also increased. .

Under such circumstances, the present invention comprises, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. A method of focusing on a short distance without aberration variation was studied for the zoom lens of the three groups. A four-unit zoom lens having a basic configuration of the optical system, wherein the second lens unit includes a negative front unit and a positive rear unit;
It was also confirmed that the focusing method could be applied to a similar optical system in which the front group of the second lens group had a positive refractive power.

As shown in FIG. 1, the basic focusing method is as follows: a first lens unit having positive refractive power (power is φ ₁ ), a second lens unit having positive refractive power (power is φ ₂ ), and a negative lens unit. In a three-unit zoom lens system including a third lens unit having a refractive power (the power is φ ₃ ), the second lens unit is moved to the object side to focus on a short-distance object point. According to this method, the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group change, and the effect of compensating for the fluctuation of aberration can be used. .

On the other hand, when the close distance is further shortened, the focal length of the focusing lens at a specific focal length is constant, but in general, the amount of focusing movement remarkably increases on the long focal length side. Therefore, it is necessary to further reduce the variation in aberrations.

In focusing, the idea of correcting the field curvature while slightly changing the lens unit interval employed in a wide-angle lens or the like can be easily conceived. It is not desirable to have a cam independently in the movement of the lens and in the movement of the focusing from the viewpoint of the mechanism and also from the viewpoint of manufacturing error integration.

Therefore, according to the present invention, as shown in FIG. 2, in a three-group zoom lens having the same power arrangement as in FIG.
At the most image plane side of the second group that forms the focusing lens group,
A lens component L _F (power is φ _LF ) having a relatively small power is provided and fixed during focusing.
By moving the remaining lens units (the power is φ _2F ) to the object side, an effect of floating is obtained.

The following Table 1 shows the aberration coefficient of each lens group with respect to an object point at infinity at the telephoto end in the later-described fourth embodiment in which the zoom ratio is not so large, and is used as a reference value.
In Table 1, SA3, SA5, and SA7 are third-, fifth-, and seventh-order spherical aberration coefficients, respectively.
MA5 is the third-order and fifth-order coma aberration coefficients, respectively.
AST3 and AST5 are third-order and fifth-order astigmatism coefficients, respectively, and DIS3 and DIS5 are third-order and fifth-order astigmatism coefficients, respectively.
This is the next distortion aberration coefficient (the same applies hereinafter).

Table 1 Object point at infinity (∞) Lens group SA3 SA5 SA7 CMA3 CMA5 1 -0.08670 -0.00974 -0.00132 0.12667 0.02527 2 -0.02523 0.04735 0.02241 -0.05921 0.00013 3 0.11403 -0.03713 -0.02335 -0.06568 -0.03619 Total 0.00210 0.00048 -0.00226 0.00179 -0.01078 Lens group AST3 AST5 DIS3 DIS5 1 -0.03661 -0.00235 0.05643 0.00245 2 0.05276 0.00227 -0.07744 -0.00097 3 -0.01668 -0.00010 0.04883 0.00071 Total -0.00053 -0.00018 0.02782 0.00219.

Next, Table 2 shows aberration coefficients of the optical system of the present invention shown in FIG. 2 at a short distance (-0.5 m) when a conventional focusing method is used. Indicates an aberration coefficient at a short distance (−0.5 m) in the focusing method according to the present invention. Here, the higher-order aberration coefficients are also shown so that the two coefficients can be compared strictly at the aberration level. The state of the object point at infinity and the performance change at a short distance can be evaluated from the sum of the intrinsic coefficients of each group and the image plane in these tables.

Table 2 Short-range object point (-0.5 m) Conventional focusing method Lens group SA3 SA5 SA7 CMA3 CMA5 1 -0.05798 -0.00507 -0.00055 0.05811 0.01023 2 -0.04258 0.04639 0.02411 -0.00529 0.01410 3 0.08671 -0.02459 -0.01352- 0.04602 -0.03094 Sum -0.01385 0.01674 0.01004 0.00680 -0.00661 Lens group AST3 AST5 DIS3 DIS5 1 -0.01779 -0.00093 0.03657 0.00110 2 0.03422 0.00135 -0.06202 -0.00039 3 -0.01551 -0.00001 0.04547 0.00035 Sum 0.00092 0.00041 0.02003 0.00107.

Table 3 Short-range object point (-0.5 m) Focusing method of the present invention Lens group SA3 SA5 SA7 CMA3 CMA5 1 -0.05872 -0.00517 -0.00056 0.06027 0.01063 2 -0.05737 0.04083 0.02244 0.00358 0.01954 3 0.08715 -0.02486 -0.01334 -0.04637 -0.03083 Total -0.02894 0.01080 0.00854 0.01747 -0.00067 Lens group AST3 AST5 DIS3 DIS5 1 -0.01822 -0.00096 0.03716 0.00114 2 0.03399 0.00139 -0.06226 -0.00041 3 -0.01553 -0.00004 0.04553 0.00037 Total 0.00024 0.00039 0.02043 0.00110.

From these tables, it is clear that the focusing method of the present invention is effective in suppressing remarkable fluctuations of high-order aberrations including spherical aberration on the telephoto side. The difference in the aberration correction state is particularly remarkable in spherical aberration. In Table 2, the higher order (SA5, 7) is larger than the third order, and the overall balance is broken. On the other hand, in Table-3, such a situation does not occur, and the balance is good. The aberration diagrams are as shown in FIGS. 3A and 3B, respectively. In A of the figure, the lens is tilted to the + side due to the influence of the higher order, and the balance with other aberrations is not good.

At this time, it is desirable that the power φ _LF of the lens component L _F of the second lens unit disposed closest to the image plane be used in the following range.

Φ _LF / φ _W <1.5 (1) where φ _W is the refractive power (power) at the wide-angle end of the entire system.
It is.

[0026] Outside the conditional expression (1), the power of the lens component L _F increases, occurs must be composed of a plurality of number of lenses. As a result, the overall length of the lens system is undesirably increased. In order to configure the focusing lens unit without increasing the power of the entire focusing lens unit, if the value of the expression (1) can be appropriately selected, it will be extremely advantageous in terms of the whole aberration correction. Since the lens component L _F is fixed during focusing, it can be easily realized if the lens holding frame is configured to be held separately from the focusing unit as illustrated in a lens barrel cross section in FIG. Here, the configuration and operation of FIG. 4 will be briefly described.

Each lens 14 of the first group includes the lens holding frame 1
It is fixed to. Each lens 15 except for the lens component L _F of the second group is fixed to the lens holding frame 4. Further, each lens 16 of the third group is similarly fixed to the lens holding frame 7. The lens component L _F of the second group is fixed to the lens holding frame A. The lens holding frame 1 is fixed to the moving frame 10. The pins 3 are mounted on the moving frame 10, the pins 6 are mounted on the lens holding frame A, and the pins 9 are mounted on the lens holding frame 7, respectively. The fixed frame 11 is provided with a long hole in the optical axis direction, and each of the pins 3, 6, 9 is slidable in the axial direction therein. A cam ring (zoom ring) 12 is provided with a cam groove for zooming. By rotating the cam ring 12 around an axis, the pins 3, 6, and 9 move, and the respective groups are accordingly moved. Zooming is performed by moving along a zoom locus.

A focusing rod 13 is attached to the lens holding frame A, and the focusing rod 13 is fitted into a hole provided in the lens holding frame 4. The lens holding frame 4 is pressed against the lens holding frame A by a spring 17 wound around the focusing rod 13, and both move together during zooming.

[0029] When focusing is focusing member (not shown) is moved by the focus motor, the lens holding frame 4 press to the left, only the lens holding frame 4 in the focusing rod 13 independently of the lens component L _F And the focusing is performed. Since the spring 17 is provided, if the pressing is stopped, the lens holding frame 4 naturally returns to the right, so that the first lens group having positive refractive power and the positive refractive power can be freely moved back and forth in order from the object side. Alternatively, even in a four-unit zoom lens including a second lens unit having a negative refracting power, a third lens unit having a positive refracting power, and a fourth lens unit having a negative refracting power, the influence on the image plane due to the change in the lens unit interval is as follows.
Basically have optical properties similar to the above zoom lens, it is applicable the same way with respect to the lens component L _F similar lens component.

To show this, first, FIG. 5 shows a first lens unit having positive refractive power (having a power of φ ₁ ) and a second lens unit having negative refractive power.
A four-unit zoom lens consisting of a lens group (power is φ ₂ ), a third lens group with positive refractive power (power is φ ₁ ), and a fourth lens group with negative refractive power (power is φ ₄ ), FIG.
A first lens unit having a positive refractive power (power is φ ₁ ), a second lens unit having a positive refractive power (power is φ ₂ ), a third lens unit having a positive refractive power (power is φ ₁ ), and negative refraction. 9 shows a power arrangement of a four-unit zoom lens including a fourth lens unit of power (power is φ ₄ ). In focusing, a lens component L _F (power is φ _LF ) having a relatively low power is provided on the image plane side of the third lens unit that forms the focusing lens unit, and is fixed during focusing. By moving the remaining lens unit and the second unit together, a floating effect is obtained in the same manner.

In order to show this, a second embodiment of a high-magnification zoom lens having a magnification ratio of 4.63, which will be described later, has a table showing aberration coefficients similar to those in Tables 1 to 3 above.
Tables 4 to 6 are shown.

Table 4 Object point at infinity (∞) Lens group SA3 SA5 SA7 CMA3 CMA5 1 -0.04682 -0.00671 -0.00112 0.04417 0.01216 2 0.24511 0.04398 0.00840 -0.09794 -0.02170 3 -0.25298 -0.01759 0.00057 0.10612 0.02488 4 0.05368 -0.01927- 0.00739 -0.04908 -0.01836 Total -0.00101 0.00040 0.00046 0.00327 -0.00303 Lens group AST3 AST5 DIS3 DIS5 1 -0.01074 -0.00012 0.02040 0.00018 2 0.01932 0.00035 -0.01654 -0.00016 3 0.00084 0.00005 -0.01358 0.00001 4 -0.00940 -0.00012 0.01614 -0.00003 Total Sum 0.00000 0.00016 0.00643 -0.00001.

Table 5 Short-range object point (-0.5 m) Conventional focusing method Lens group SA3 SA5 SA7 CMA3 CMA5 1 -0.03080 -0.00323 -0.00039 0.01211 0.00400 2 0.22231 0.04147 0.00851 -0.06510 -0.01445 3 -0.23046 -0.01451 0.00078 0.09470 0.02065 4 0.03604 -0.01075 -0.00342 -0.03104 -0.01387 Total -0.00291 0.01297 0.00548 0.01067 -0.00368 Lens group AST3 AST5 DIS3 DIS5 1 -0.00358 -0.00002 0.01217 0.00009 2 0.01239 0.00018 -0.01157 -0.00010 3 -0.00167 0.00000 -0.01034 0.00005 4 -0.00882 -0.00014 0.01415 -0.00007 Total -0.00168 0.00002 0.00440 -0.00003.

Table 6 Short-range object point (-0.5 m) Focusing method of the present invention Lens group SA3 SA5 SA7 CMA3 CMA5 1 -0.03159 -0.00336 -0.00041 0.01392 0.00440 2 0.22281 0.04140 0.00846 -0.06560 -0.01453 3 -0.24356 -0.01785 0.00011 0.10232 0.02389 4 0.03658 -0.01094 -0.00332 -0.03169 -0.01381 Total -0.01577 0.00925 0.00484 0.01894 -0.00005 Lens group AST3 AST5 DIS3 DIS5 1 -0.00375 -0.00002 0.01245 0.00009 2 0.01251 0.00018 -0.01170 -0.00010 3 -0.00194 0.00001 -0.01045 0.00004 4 -0.00883 -0.00014 0.01423 -0.00007 Total -0.00201 0.00003 0.00454 -0.00003.

These tables clearly show the effects of the focusing method of the present invention. In particular, fluctuations in high-order spherical aberration can be suppressed. That is, in Tables 5 and 6,
Since the zoom lens has a higher zoom ratio as compared with the cases of Tables 1 to 3, the difference due to the focusing method becomes clearer.
In Table-5, the higher-order spherical aberration is very large, and when shown in an aberration diagram, as shown in FIG. 7A, the aberration curve largely falls rightward. In Table-6, the balance is as a whole, and this also appears in the aberration diagram shown in FIG. 7B.

In this case, the second lens group and the third lens group basically move integrally during focusing, and the zoom cam mechanisms of the second and third groups are independently extended toward the object side so that they can be moved closer to the object side. It will focus on a distance object point. Therefore, the second to third groups can be realized by another mechanism that integrates only focusing. In addition, a fixed lens component L _F having the action of a field flattener
Is fixed to a specific position during focusing and does not move during focusing. On the other hand, during zooming, it moves as a part of the third lens group together with the remaining constituent lens components of the third lens group. The conditional expression (1) is also applied to the four-unit zoom lens.

On the other hand, on the aberration correction surface, the lens component L
Because of the effect of correcting the image plane of flatness _F, the curvature of field before the lens component L _F is not limited to a particular focal position even aberration balance that occurs somewhat large,
With this lens component L _F, it is possible to obtain image plane flatness, and the burden on aberration correction can be reduced.
This point is a great merit, and has a significant meaning in that it improves the performance of zoom lenses, which previously had good performance at distant object points and markedly deteriorated performance at near object points. I have. In particular, optical systems for applications other than single-lens reflex cameras tended to be compromised in terms of optical performance, but according to the present invention, by making significant improvements in design and providing a margin in performance, products It is possible to provide a satisfactory image quality at the time of conversion.

It is desirable that the zoom lens to which the focusing method of the present invention is applied satisfies the following paraxial conditional expression.

For the three-group zoom lens, 0.4 <φ ₁ / φ _W <1.25 (2) 1.1 <φ ₁₂ / φ _W <3.0 (3) 85 <β _3T / β _3W <4.0 (4) where φ ₁ is the refracting power φ _W of the first lens group, and the refracting power φ ₁₂ of the whole system at the wide-angle end is The combined refractive power β _3W of the first and second lens groups is the paraxial lateral magnification β _3T of the third lens group at the wide angle end, and the paraxial lateral magnification of the third lens group at the telephoto end.

For the four-unit zoom lens, φ _{12 in} the above equation (3) can be considered as a similar relation by expressing it in the following relation.

Φ ₂ = φ ₂ + φ ₃ −e ′ ₂₃ φ ₂ φ ₃ φ ₁₂ = φ ₁ + φ ₂ −e ′ ₁₂ φ ₁ φ ₂ Here, φ ₂ and φ ₃ are each a four-group zoom lens for convenience. , The power of the second and third units, e ′ ₂₃ is the distance between them, and φ ₂ is the combined power of the second and third units. Further, e ′ ₁₂ is the distance between the first lens group and the group synthesized as described above.

However, in the four-unit zoom lens, it should be noted that the lens unit interval between the second and third units corresponding to the second unit of the three-unit zoom lens is variable. From this relationship, the four-unit zoom lens can be configured to have a shorter overall lens system at the telephoto end.

The above equation (2) defines the power of the first lens group. This value can be particularly increased when the zoom ratio is small. Further, under such conditions, the first lens group can be constituted by a single lens made of a special low dispersion glass material. When the lower limit of conditional expression (2) is exceeded,
Difficulty remains in the chromatic aberration of magnification on the wide-angle side. Also,
If the upper limit is exceeded, the amount of movement of the first lens unit at the time of zooming will increase, which undesirably increases the overall length of the lens system at the telephoto end. Also, there is a restriction on the design of the optical system that simplifies the lens frame configuration by making the moving amounts of the first lens unit and the third lens unit at the time of zooming the same.

According to the above equation (3), the first lens group and the second lens group
It defines the combined power of the lens groups and relates to the overall length of the lens system at the wide-angle end that determines the size of the camera. The reduction of the overall length of this type of optical system largely depends on the size of the second lens group. After the power of the first lens group is determined within the range of the equation (2), the second lens is determined by the equation (3). The power of the group and the principal point spacing between the first and second lens groups are determined. If the lower limit of conditional expression (3) is exceeded, it will be difficult to correct the aberration, and the number of constituent lenses and the use of new materials will be inevitable for the purpose of miniaturization. If the value exceeds the upper limit that is advantageous for aberration correction, the moving amount at the time of zooming and the entire length of the lens system increase, deviating from the gist of the present invention in which the size is reduced.

The above equation (4) is equivalent to the third lens group (fourth group zoom lens in the fourth group zoom lens) characteristic of the optical system to which the present invention is applied.
This is an expression in which the magnification load at the time of zooming of the lens unit is limited as a ratio of values at the telephoto end and the wide-angle end. If the value is much lower than the lower limit, it is more suitable to use a zoom system having a simpler configuration than the zoom lens type of the present invention (however, when the ultra wide angle is set to the wide angle end, this is not necessarily the case. Absent.). In addition, if the upper limit is exceeded, it is considered that the manufacturing error sensitivity is at a level exceeding the machining accuracy due to the mechanism configuration, the aperture ratio is reduced, and the result is given as a result of considering the practicality as a lens system. It is a limitation.

[0046]

Next, first to sixth embodiments of the present invention will be described. The lens data of each embodiment will be described later. The first embodiment is an optical system having a focal length of 39 mm to 148 mm, and belongs to a considerably high-magnification zoom lens in this class. Therefore, if not only aberration fluctuations at the time of zooming but also aberration fluctuations at the time of focusing are not kept small, it leads to unsatisfactory performance even if it is commercialized,
It will not be accepted in the market. As shown in the sectional views of the lens at the wide-angle end and the telephoto end in FIG. 8, the zoom lens is a three-unit zoom lens including lens units I to III, and the lens component L _F located closest to the image plane in the second lens unit is are arranged for the purpose of suppressing variation in aberrations during focusing, by moving the lens component L _F other lens components in the second lens group II at the time of focusing, it is possible to focus to a close object point. The focal length f _LF of the lens component L _F at this time
Is f _LF ≒ ∞, that is, this lens component L _F is an almost powerless lens component. FIG. 14 shows the spherical aberration, astigmatism, lateral chromatic aberration, and distortion at the object point at infinity and at a short distance of -2.0 m at the wide angle end, the intermediate focal length, and the telephoto end, respectively.

Returning to the first embodiment, the total length of the lens system (the distance from the first surface to the film surface) at the wide-angle end is less than about 82 mm, and the spherical aberration at the telephoto end slightly decreases at a short distance. However, although it is large in the orbicular zone, the variation in astigmatism is similar to this, so that the optical performance is stable and good.

In the third lens group, an aspherical surface made of resin is used, which has a great effect in correcting the field curvature. If an aspheric surface is used in the second lens group,
It is clear that an effect can be obtained in correcting spherical aberration.

The second embodiment has a focal length of 38 mm to 176 mm.
This is a four-unit zoom lens optical system composed of lens groups I to IV having a length of 1 mm, and the zoom ratio is slightly increased to reduce the aperture ratio at the telephoto end. The configuration of the lens system is almost the same as in the first embodiment. FIG. 9 shows a lens cross-sectional view, and FIG. 15 shows aberration diagrams similar to FIG. 14 corresponding to an object point at infinity and an object point at a short distance of -2.0 m. Focusing is performed by the method shown in FIG. F _LF at this time = −199
8.96. As is clear from the aberration diagram, aberration fluctuation is suppressed to a small value. In particular, the balance is good at a short distance at the telephoto end, which is effective for high-magnification photography.

The third embodiment has a focal length of 38.0 mm to
This is a four-group zoom lens optical system including 150 mm lens groups I to IV, and is intended for a zoom lens having high performance and versatility within a range satisfying normal photographing. FIG.
0 shows a lens sectional view, and FIG. 16 shows an aberration diagram. The configuration of the lens system is almost the same as in the above-described embodiment. From the aberration diagram,
It can be seen that the optical performance is stable and at a practical level, regardless of the focal length in any focal range. The feature of this embodiment is that the aperture ratio at the telephoto end is large.

In the fourth embodiment, the focal length is 36.2 mm
This is a three-unit zoom lens optical system including lens units I to III having a diameter of up to 131 mm. By reducing the zoom ratio, stable performance can be obtained in the zoom range. FIG. 11 is a lens cross-sectional view, and FIG. 17 is an aberration diagram. At this time, the lens component L
The focal length of _F is f _LF = −545.76.

In the fifth embodiment, the focal length is 29.2 mm
It is a four-unit zoom lens optical system consisting of lens units I to IV of up to 54 mm, has a wide angle of view at the wide-angle end, and may have difficulty in correcting chromatic aberration of magnification at this focal length.
In the present embodiment, the configuration shown in FIG. 12 is employed to improve the performance by effectively utilizing the aspherical surface. This example is also a four-unit zoom lens, and employs aspheric surfaces on the seventh surface (in the second lens group II) and the eighteenth surface (in the fourth lens group IV).
At this time, f _LF = 77.294, which is higher in power than the previous embodiments, and also performs a correcting action at each focal position on the aberration correcting surface. As shown in the aberration diagram in FIG. 18, it can be seen that the aberration balance at each focal length and the short distance is good, and the aberration fluctuation is extremely small.

The sixth embodiment has a focal length of 36 mm to 13 mm.
This is an example in which a 1.5 mm optical system is constituted by a four-group zoom lens including lens groups I to IV, and the amount of change in the distance between the second lens group II and the third lens group III during zooming is small. Since this point contributes to the aberration correction surface, it can be inferred that the three-unit zoom lens can be easily configured, and basically, the same effect can be obtained. Here, FIG.
3 shows a sectional view of the lens, and FIG. 19 shows an aberration diagram.

The following shows lens data of each embodiment.
In the following, the symbols are the above, f is the focal length of the entire system, F _NO is the F number, ω is the half angle of view, f _B is the back focus, r ₁ , r _2, ... d ₁ ,
d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, ν _d1, ν _d2 ... is the Abbe number of each lens, also aspherical shape, light When the axial direction is x and the direction orthogonal to the optical axis is y, it is expressed by the following equation.

X = (y ² / r) / [1+ {1-P (y ² / r ² )}
_{^{1/2] + A 4 y 4 +}} A 6 y 6 + A 8 y 8 + A 10 y 10 where, r is the paraxial radius of curvature, P is a conical _{coefficient, A 4, A 6, A} 8
Is an aspheric coefficient.

First Embodiment f = 39.0 to 80.9 to 148.5 F _NO = 4.58 to 6.20 to 8.68 ω = 28.9 to 14.9 to 8.3 ° f _B = 9.68 to 40.53 to 91.44 r ₁ = -316.3761 d ₁ = 1.3400 nd ₁ = _{1.83400 ν d1 = 37.16 r 2 =} 37.7799 d 2 = 0.8432 r 3 = 55.0945 d 3 = 3.1600 n d2 = 1.61405 ν d2 = 54.95 r 4 = -586.4745 d 4 = 0.1847 r 5 = 29.8948 d 5 = 4.9000 n d3 = 1.53996 _{ν d3 = 59.57 r 6 = -115.6637} d 6 = ( _{variable) r 7 = -37.4745 d 7 =} 1.1800 n d4 = 1.78590 ν d4 = 44.18 r 8 = 21.1223 d 8 = 0.9701 r 9 = 36.2884 d 9 = 2.6500 n d5 = 1.78472 ν _d5 = 25.71 r ₁₀ = -45.5730 d ₁₀ = 2.3180 r ₁₁ = -22.6975 d ₁₁ = 1.3000 nd ₆ = 1.63854 ν _d6 = 55.38 r ₁₂ = -27.7381 d ₁₂ = 4.0650 r ₁₃ = ∞. (Aperture) d _{13 = 4.0859 r 14 = -182.3473 d} 14 = 2.0800 n d7 = 1.68893 ν d7 = 31.08 r 15 = -194.6074 d 15 = 0.4088 r 16 = 100.1782 d 16 = 2.3800 n d8 = 1.54739 ν d8 = 53.55 r 17 = -36.4417 d ₁₇ = 1.3474 r ₁₈ = 112.2452 d ₁₈ = 1.2900 _nd9 = 1.78 _{472 ν d9 = 25.71 r 19 =} 19.0879 d 19 = 4.2650 n d10 = 1.58313 ν d10 = 59.36 r 20 = -28.1382 d 20 = 1.6500 r 21 = -20.0777 d 21 = 1.7100 n d11 = 1.72600 ν d11 = 53.56 r 22 = -20.7925 d ₂₂ = _{(variable) r 23 = -42.0853 d 23 =} 3.1200 n d12 = 1.84666 ν d12 = 23.78 r 24 = -22.8307 d 24 = 2.3287 r 25 = -18.1063 ( aspherical) d ₂₅ = 0.8600 n _d13 = _{1.51742 ν d13 = 52.41 r 26 =} -18.2961 d 26 = 1.5000 n d14 = 1.77250 ν d14 = 49.66 r 27 = 89.0676 Aspherical coefficient 25 surface _{P = 1 A 4 = 0.15094 ×} 10 -4 A 6 = 0.36466 × 10 -7 A 8 = -0.40180 × 10 -10 A 10 = 0.56431 × 10 -12.

[0057] The second embodiment _{f = 38.0~ 82.8~ 176.0 F NO =} 4.62~ 7.53~ 11.15 ω = 29.6~ 14.6~ 6.9 ° f B = 6.18~ 38.03~106.05 r 1 = -8204.4298 d 1 = 1.4500 n d1 = _{1.83400 ν d1 = 37.16 r 2 =} 32.1497 d 2 = 0.8500 r 3 = 47.5851 d 3 = 3.2000 n d2 = 1.61405 ν d2 = 54.95 r 4 = -1942.9777 d 4 = 0.2150 r 5 = 26.3265 d 5 = 5.0000 n d3 = 1.53996 _{ν d3 = 59.57 r 6 = -200.2508} d 6 = ( _{variable) r 7 = -39.1402 d 7 =} 1.3000 n d4 = 1.78590 ν d4 = 44.18 r 8 = 20.1050 d 8 = 0.6478 r 9 = 33.8748 d 9 = 2.6500 n d5 = 1.78472 ν _d5 = 25.68 r ₁₀ = -38.3830 d ₁₀ = 1.2259 r ₁₁ = -29.0561 d ₁₁ = 1.3000 nd ₆ = 1.61405 ν _d6 = 54.95 r ₁₂ = -36.4855 d ₁₂ = (variable) r ₁₃ = ∞. _{) d 13 = 4.0000 r 14 =} -92.6144 d 14 = 2.1000 n d7 = 1.68893 ν d7 = 31.08 r 15 = -322.7288 d 15 = 0.3250 r 16 = 88.7094 d 16 = 2.2000 n d8 = 1.54739 ν d8 = 53.55 r 17 = _{-33.9960 d 17 = 0.5862 r 18 =} 209.5506 d 18 = 1.3000 n d9 = 1. _{78472 ν d9 = 25.71 r 19 =} 21.0222 d 19 = 4.0000 n d10 = 1.58913 ν d10 = 60.97 r 20 = -25.0062 d 20 = 1.0000 r 21 = -19.2691 d 21 = 1.7000 n d11 = 1.74100 ν d11 = 52.68 r 22 = -20.2562 d ₂₂ = _{(variable) r 23 = -36.6191 d 23 =} 3.1500 n d12 = 1.84666 ν d12 = 23.78 r 24 = -21.2860 d 24 = 2.7816 r 25 = -16.1349 ( aspherical) d ₂₅ = 0.1000 n _d13 = 1.51742 v _d13 = 52.41 r ₂₆ = -16.8308 d ₂₆ = 1.5000 n _d14 = 1.777250 v _d14 = 49.66 r ₂₇ = 177.70101 Aspherical coefficient 25 surface _{P = 1 A 4 = 0.25779 ×} 10 -4 A 6 = 0.78006 × 10 -7 A 8 = -0.15033 × 10 -9 A 10 = 0.17915 × 10 -11.

[0058] Third embodiment _{f = 38.0~ 81.5~ 150.0 F NO =} 4.62~ 6.24~ 8.81 ω = 29.6~ 14.9~ 8.2 ° f B = 9.46~ 41.78~ 93.55 r 1 = -531.9150 d 1 = 1.4500 n d1 = _{1.83400 ν d1 = 37.16 r 2 =} 36.7581 d 2 = 0.8500 r 3 = 54.0975 d 3 = 3.2000 n d2 = 1.61405 ν d2 = 54.95 r 4 = -710.7728 d 4 = 0.2150 r 5 = 28.8796 d 5 = 5.0000 n d3 = 1.53996 _{ν d3 = 59.57 r 6 = -126.5198} d 6 = ( _{variable) r 7 = -35.3558 d 7 =} 1.3000 n d4 = 1.78590 ν d4 = 44.18 r 8 = 20.9761 d 8 = 1.0031 r 9 = 40.6555 d 9 = 2.6500 n d5 = 1.78472 ν _d5 = 25.71 r ₁₀ = -41.9853 d ₁₀ = 2.2155 r ₁₁ = -23.5923 d ₁₁ = 1.3000 nd ₆ = 1.63854 ν _d6 = 55.38 r ₁₂ = -27.9570 d ₁₂ = (variable) r ₁₃ = ∞. _{) d 13 = 4.0000 r 14 =} -167.5276 d 14 = 2.1000 n d7 = 1.68893 ν d7 = 31.08 r 15 = -192.1174 d 15 = 0.3250 r 16 = 144.5763 d 16 = 2.2000 n d8 = 1.54739 ν d8 = 53.55 r 17 = _{-35.1160 d 17 = 1.3859 r 18 =} 99.6476 d 18 = 1.3000 n d9 = 1.7 _{8472 ν d9 = 25.71 r 19 =} 19.5849 d 19 = 4.0000 n d10 = 1.58313 ν d10 = 59.36 r 20 = -26.8188 d 20 = 1.0000 r 21 = -20.3106 d 21 = 1.7000 n d11 = 1.74100 ν d11 = 52.68 r 22 = -20.9455 d ₂₂ = _{(variable) r 23 = -39.8644 d 23 =} 3.1500 n d12 = 1.84666 ν d12 = 23.78 r 24 = -22.9355 d 24 = 2.3185 r 25 = -18.8212 ( aspherical) d ₂₅ = 0.8500 n _d13 = _{1.51742 ν d13 = 52.41 r 26 =} -19.0277 d 26 = 1.5000 n d14 = 1.77250 ν d14 = 49.66 r 27 = 85.3632 Aspherical surface 25th surface P = 1 A ₄ = 0.12231 × 10 ⁻⁴ A ₆ = 0.29324 × 10 ⁻⁷ A ₈ = −0.91602 × 10 ⁻¹⁰ A ₁₀ = 0.62671 × 10 ⁻¹² .

[0059] Fourth Embodiment _{f = 36.2~ 68.0~ 131.0 F NO =} 3.60~ 5.65~ 7.42 ω = 30.8~ 17.6~ 9.4 ° f B = 9.78~ 32.68~ 81.23 r 1 = -86.8576 d 1 = 0.9500 n d1 = _{1.83400 ν d1 = 37.16 r 2 =} 41.4110 d 2 = 0.9080 r 3 = 51.8432 d 3 = 3.2800 n d2 = 1.65844 ν d2 = 50.86 r 4 = -137.6627 d 4 = 0.1200 r 5 = 33.2481 d 5 = 4.5600 n d3 = 1.51823 _{ν d3 = 58.96 r 6 = -86.0513} d 6 = ( _{variable) r 7 = -56.6012 d 7 =} 0.5000 n d4 = 1.78590 ν d4 = 44.18 r 8 = 19.1893 d 8 = 0.8890 r 9 = 36.0325 d 9 = 2.7900 n d5 = 1.78470 ν _d5 = 26.22 r ₁₀ = -47.5157 d ₁₀ = 3.2380 r ₁₁ = -21.0043 d ₁₁ = 1.3300 nd ₆ = 1.65830 ν _d6 = 53.44 r ₁₂ = -26.9041 d ₁₂ = 4.5520 r ₁₃ = ∞. _{13 = 4.1200 r 14 = -110.2549 d} 14 = 2.1300 n d7 = 1.68893 ν d7 = 31.08 r 15 = -69.7784 d 15 = 0.5940 r 16 = 139.7565 d 16 = 2.9700 n d8 = 1.54739 ν d8 = 53.55 r 17 = -32.6632 d ₁₇ = 1.2060 r ₁₈ = 161.2610 d ₁₈ = 1.1100 _nd9 = 1.7847 _{2 ν d9 = 25.71 r 19 =} 18.7929 d 19 = 5.1500 n d10 = 1.58313 ν d10 = 59.36 r 20 = -28.0029 d 20 = 0.7190 r 21 = -20.9845 d 21 = 1.6700 n d11 = 1.74100 ν d11 = 52.68 r 22 = -21.8084 d ₂₂ = _{(variable) r 23 = -49.7366 d 23 =} 3.0300 n d12 = 1.84666 ν d12 = 23.78 r 24 = -24.4370 d 24 = 2.7250 r 25 = -17.5797 ( aspherical) d ₂₅ = 0.6500 n _d13 = _{1.52492 ν d13 = 51.77 r 26 =} -18.2786 d 26 = 1.0000 n d14 = 1.77250 ν d14 = 49.66 r 27 = 71.7600 Aspherical coefficient 25 surface _{P = 1 A 4 = 0.21637 ×} 10 -4 A 6 = 0.49594 × 10 -7 A 8 = -0.10228 × 10 -11 A 10 = 0.56359 × 10 -12.

[0060] Fifth Embodiment _{f = 29.2~ 37.0~ 54.0 F NO =} 4.60~ 5.11~ 6.30 ω = 36.5~ 30.3~ 21.8 ° f B = 5.02~ 11.53~ 27.41 r 1 = -26.4534 d 1 = 1.0000 n d1 = _{1.83400 ν d1 = 37.16 r 2 =} -881.8774 d 2 = 0.4200 r 3 = -278.5753 d 3 = 3.6189 n d2 = 1.69680 ν d2 = 56.49 r 4 = -24.7811 d 4 = 0.5000 r 5 = 27.8321 d 5 = 1.6197 n d3 _{= 1.69680 ν d3 = 56.49 r 6} = 67.7204 d 6 = ( variable) r ₇ = -54.9522 _{(aspherical) d 7 = 3.0703 n d4 =} 1.78800 ν d4 = 47.38 r 8 = 9.9882 d 8 = 4.4827 n d5 = 1.83400 ν _{d5 = 37.16 r 9 = -111.8670 d} 9 = ( variable) r ₁₀ = ∞. _{(stop) d 10 = 4.1130 r 11 =} -530.8542 d 11 = 3.8073 n d6 = 1.61405 ν d6 = 54.95 r 12 = -8.8197 d 12 _{= 0.5000 n d7 = 1.84666 ν d7} = 23.88 r 13 = -17.3752 d 13 = 0.5000 r 14 = -42.6880 d 14 = 1.1971 n d8 = 1.64000 ν d8 = 60.09 r 15 = -23.1652 d 15 = ( variable) r ₁₆ = -23.7219 d ₁₆ = 2.3041 n _d9 = 1.84666 ν _d9 = 23.88 r ₁₇ = -15.7393 d ₁₇ = 2.3156 r ₁₈ = -14.1806 _{(aspherical) d 18 = 0.5000 n d10 =} 1.64000 ν d10 = 60.09 r 19 = -87.5074 d 19 = 2.0761 r 20 = -27.9339 d 20 = 0.5500 n d11 = 1.60311 ν d11 = 60.70 r 21 = 334.4222 Aspherical surface 7th surface P = 1 A ₄ = -0.24960 × 10 ^-4 A ₆ = 0.97359 × 10 ^-7 A ₈ = -0.34211 × 10 ^-8 A ₁₀ = 0.24291 × 10 ^-10 18th surface P = 1 A ₄ = 0.76581 x 10 ^-5 A ₆ = -0.54028 x 10 ^-7 A ₈ = 0.14985 x 10 ^-8 A ₁₀ = -0.73315 x 10 ^-11 .

[0061] Sixth Embodiment _{f = 36.0~ 68.8~ 131.5 F NO =} 4.62~ 5.80~ 7.50 ω = 30.9~ 17.5~ 9.3 ° f B = 9.78~ 34.28~ 83.34 r 1 = -179.8187 d 1 = 1.0919 n d1 = _{1.83400 ν d1 = 37.16 r 2 =} 38.4651 d 2 = 0.8788 r 3 = 49.9828 d 3 = 3.1628 n d2 = 1.61720 ν d2 = 54.04 r 4 = -279.9562 d 4 = 0.1998 r 5 = 30.1522 d 5 = 4.7290 n d3 = 1.51823 _{ν d3 = 58.96 r 6 = -112.6403} d 6 = ( _{variable) r 7 = -42.9353 d 7 =} 0.7101 n d4 = 1.78590 ν d4 = 44.18 r 8 = 19.2434 d 8 = 1.0696 r 9 = 38.2064 d 9 = 2.7010 n d5 = 1.78472 ν _d5 = 25.71 r ₁₀ = -44.0457 d ₁₀ = 2.6789 r ₁₁ = -21.2365 d ₁₁ = 1.2931 nd ₆ = 1.63854 ν _d6 = 55.38 r ₁₂ = -27.2568 d ₁₂ = (variable) r ₁₃ = ∞. _{) d 13 = 4.0108 r 14 =} -402.5078 d 14 = 2.1024 n d7 = 1.68893 ν d7 = 31.08 r 15 = -97.7116 d 15 = 0.3479 r 16 = 107.4156 d 16 = 2.6354 n d8 = 1.54739 ν d8 = 53.55 r 17 = _{-33.2395 d 17 = 1.5238 r 18 =} 193.3836 d 18 = 1.2076 n d9 = 1.784 _{72 ν d9 = 25.71 r 19 =} 18.0304 d 19 = 4.6310 n d10 = 1.58313 ν d10 = 59.36 r 20 = -27.2813 d 20 = 0.9453 r 21 = -19.4411 d 21 = 1.6868 n d11 = 1.74100 ν d11 = 52.68 r 22 = -20.1265 d ₂₂ = _{(variable) r 23 = -47.2575 d 23 =} 3.0383 n d12 = 1.84666 ν d12 = 23.78 r 24 = -23.6858 d 24 = 2.4178 r 25 = -17.7464 ( aspherical) d ₂₅ = 0.7957 n _d13 = _{1.50137 ν d13 = 56.40 r 26 =} -18.0796 d 26 = 0.6371 n d14 = 1.77250 ν d14 = 49.66 r 27 = 74.5122 Aspheric coefficient 25th surface P = 1 A ₄ = 0.19070 × 10 ⁻⁴ A ₆ = 0.49353 × 10 ⁻⁷ A ₈ = −0.16021 × 10 ⁻¹⁰ A ₁₀ = 0.58494 × 10 ⁻¹² .

[0062] above, the entire system power phi _W of the sixth embodiment from the first embodiment, the lens component L refractive power _F phi _LF, and the parameters corresponding the conditional formulas (1) to (4) The values are shown in Table 7 below.

[0063]

[0064]

As described above, according to the high-magnification zoom lens of the present invention having a small variation in near-field aberration, the focusing unit of the conventional high-magnification zoom lens proposed by the present applicant is fixed to the focusing unit during focusing. By arranging the lens components, it is possible to easily realize an optical system having extremely stable performance up to a short distance. As a result, the performance of a zoom lens for a photographic camera, which is said to be weak at short distances, can be improved, and a new market can be developed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a power arrangement of a three-unit zoom lens for describing a basic focusing method based on a premise of the present invention.

FIG. 2 is a diagram showing a power arrangement when a focusing method according to the present invention is applied to a three-unit zoom lens.

FIG. 3 is an aberration diagram at a short distance when a conventional focusing method is applied to a three-unit zoom lens and when a focusing method according to the present invention is provided.

FIG. 4 is a diagram showing a case where the focusing method according to the present invention is adopted.
FIG. 3 is a cross-sectional view illustrating an example of a lens barrel structure of a group zoom lens.

FIG. 5 is a diagram showing a power arrangement when the focusing method according to the present invention is applied to a four-unit zoom lens in which the second lens group is negative.

FIG. 6 is a diagram showing a power arrangement in a case where the focusing method according to the present invention is applied to a four-unit zoom lens in which the second lens group is positive.

FIG. 7 is an aberration diagram at a short distance when a conventional focusing method is applied to a four-unit zoom lens and when a focusing method according to the present invention is provided.

FIG. 8 is a lens cross-sectional view at a wide angle end and a telephoto end of the first embodiment.

FIG. 9 is a sectional view of a lens at a wide angle end and a telephoto end according to a second embodiment.

FIG. 10 is a sectional view of a lens at a wide angle end and a telephoto end according to a third embodiment.

FIG. 11 is a sectional view of a lens at a wide angle end and a telephoto end according to a fourth embodiment.

FIG. 12 is a sectional view of a lens at a wide angle end and a telephoto end according to a fifth embodiment.

FIG. 13 is a sectional view of a lens at a wide angle end and a telephoto end according to a sixth embodiment.

FIG. 14 is an aberration diagram of the first example.

FIG. 15 is an aberration diagram of the second example.

FIG. 16 is an aberration diagram of the third example.

FIG. 17 is an aberration diagram of the fourth example.

FIG. 18 is an aberration diagram of the fifth embodiment.

FIG. 19 is an aberration diagram of the sixth example.

[Explanation of symbols]

L _F : lens component fixed during focusing in the focusing group I: first lens group II ... second lens group III ... third lens group IV ... fourth lens group

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-153511 (JP, A) JP-A-2-73211 (JP, A) JP-A-2-287507 (JP, A) JP-A-2- 207210 (JP, A) JP-A-58-178317 (JP, A) JP-A-2-244110 (JP, A) JP-A-63-205629 (JP, A) JP-A-63-89813 (JP, A) JP-A-61-258217 (JP, A) JP-A-3-17609 (JP, A) JP-A-54-29659 (JP, A) Japanese utility model application Sho 62-76313 (JP, U) (58) (Int.Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (1)

(57) [Claims] 1. A first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power are arranged in order from the object side. A high-magnification zoom lens with little short-range aberration fluctuation, characterized by satisfying the following conditions (2), (3), and (4) by moving each lens group to the object side. 0.4 <φ ₁ / φ _W <1.25 (2) 1.1 <φ ₁₂ / φ _W <3.0 (3) 2.85 <β _3T / β _3W <4. 0 (4) where φ ₁ is the refractive power of the first lens group, φ _W is the refractive power of the entire system at the wide-angle end, and φ ₁₂ is the first and second lens groups at the wide-angle end. Β _3W is the paraxial lateral magnification of the third lens unit at the wide-angle end, and β _3T is the paraxial lateral magnification of the third lens unit at the telephoto end.