JP2025119019A - Variable magnification optical system and optical equipment - Google Patents

Abstract

A negative-lead variable magnification optical system, an optical device, and a method for manufacturing a variable magnification optical system that has a wide angle of view, high resolution, and sufficiently suppresses aberration fluctuations during focusing are provided.
[Solution] The spacing between adjacent lens groups changes during zooming, and the first lens group includes, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a negative meniscus lens L2 with a convex surface facing the object side, and a negative lens L3, and has at least one positive lens, and at least one focusing lens group that moves in the optical axis direction during focusing is located closer to the image than the second lens group, and the first focusing lens group that is located closest to the object side among the focusing lens groups satisfies the following conditional expressions: 1.50<|mP1w| or -0.95<mP1w<0.95, 94.0°<2ωw<140.0°, where mP1w is the magnification of the first focusing lens group at the wide-angle end, and ωw is the half angle of view (unit: degrees) of the entire variable magnification optical system at the wide-angle end.
[Selected Figure] Figure 1

Description

The present invention relates to a variable magnification optical system suitable for photographic optical systems such as digital cameras, film cameras, and video cameras, an optical device, and a method for manufacturing a variable magnification optical system.

Many negative-lead type wide-angle variable magnification optical systems have been proposed (see Patent Document 1), but there have been few proposals for variable magnification optical systems that sufficiently suppress aberration fluctuations during focusing in the ultra-wide-angle range.
There is also a growing demand for wider angles of view, and in recent years, with the shift to digital cameras, there has been a demand for higher optical performance.

JP 2016-75741 A

A variable magnification optical system according to a first embodiment includes, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group, and the spacing between adjacent lens groups changes during magnification variation; the first lens group includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a negative meniscus lens L2 having a convex surface facing the object side, and a negative lens L3, and includes at least one positive lens;
At least one focusing lens group that moves in the optical axis direction during focusing is located closer to the image than the second lens group, and a first focusing lens group that is located closest to the object among the focusing lens groups satisfies the following conditional expression:
1.50 < |mP1w| or -0.95 < mP1w < 0.95
100.0° < 2ωw < 140.0°
-3.00 < (L2r2+L2r1)/(L2r2-L2r1) < -1.50
Bfw/fw < 1.38
3.00 < (L2r1+L1r2)/(L2r1-L1r2) < 20.00
however,
mP1w: magnification of the first focusing lens group at the wide-angle end,
ωw: half angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees),
L2r1: the radius of curvature of the object side surface of the negative meniscus lens L2,
L2r2: radius of curvature of the image side surface of the negative meniscus lens L2,
Bfw: back focus at the wide-angle end,
fw: focal length at the wide-angle end ,
L1r2: the radius of curvature of the image side surface of the negative meniscus lens L1.

Furthermore, the optical device according to the second embodiment is equipped with the variable magnification optical system.

Furthermore, a manufacturing method for a variable magnification optical system according to a third aspect is a manufacturing method for a variable magnification optical system having, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group, and a fourth lens group G4, wherein the lens groups are arranged so that the spacing between adjacent lens groups changes during magnification variation, and the first lens group is arranged, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a negative meniscus lens L2 with a convex surface facing the object side, and a negative lens L3, and is arranged so as to have at least one positive lens, and is arranged so as to have at least one focusing lens group that moves in the optical axis direction during focusing, closer to the image side than the second lens group, and the first focusing lens group that is arranged closest to the object side is arranged so as to satisfy the following conditional expression:
1.50 < |mP1w| or -0.95 < mP1w < 0.95
94.0° < 2ωw < 140.0°
however,
mP1w: magnification of the first focusing lens group at the wide-angle end,
ωw: half angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees).

1A and 1B are a cross-sectional view of a variable magnification optical system according to Example 1 in an infinity focused state and a movement locus during magnification variation. 5A to 5C are diagrams illustrating various aberrations at the wide-angle end in the infinity-focused state of the variable-magnification optical system according to Example 1. 5A to 5C are diagrams illustrating various aberrations at the telephoto end in the infinity-focused state of the variable magnification optical system according to Example 1. 10A and 10B are diagrams illustrating various aberrations at the wide-angle end in a close-distance focused state (β=−0.025) of the variable magnification optical system according to Example 1. 10A to 10C are diagrams showing various aberrations at the telephoto end in a close-up focus state (β=−0.025) of the variable magnification optical system according to Example 1. 10A and 10B are cross-sectional views of a variable magnification optical system according to Example 2 in an infinity focused state and a movement locus during magnification variation. 10A to 10C are diagrams illustrating various aberrations at the wide-angle end in the infinity-focused state of the variable magnification optical system according to Example 2. 10A to 10C are diagrams illustrating various aberrations at the telephoto end in the infinity focused state of the variable magnification optical system according to Example 2. 10A and 10B are diagrams illustrating various aberrations at the wide-angle end in a close-distance focused state (β=−0.025) of the variable magnification optical system according to Example 2. 10A and 10B are diagrams illustrating various aberrations at the telephoto end in a close-up focus state (β=−0.025) of the variable magnification optical system according to Example 2. 10A and 10B are cross-sectional views of a variable magnification optical system according to Example 3 in an infinity focused state and a movement locus during magnification variation. 10A to 10C are diagrams illustrating various aberrations at the wide-angle end in the infinity-focused state of the variable magnification optical system according to Example 3. 10A to 10C are diagrams illustrating various aberrations at the telephoto end in the infinity-focused state of the variable magnification optical system according to Example 3. 10A and 10B are diagrams illustrating various aberrations at the wide-angle end in a close-distance focused state (β=−0.025) of the variable magnification optical system according to Example 3. 10A and 10B are diagrams illustrating various aberrations at the telephoto end in a close-up focus state (β=−0.025) of the variable magnification optical system according to Example 3. 10A and 10B are cross-sectional views of a variable magnification optical system according to Example 4 in an infinity focused state and a movement locus during magnification variation. 10A to 10C are diagrams illustrating various aberrations at the wide-angle end in the infinity-focused state of the variable magnification optical system according to Example 4. 10A to 10C are diagrams illustrating various aberrations at the telephoto end in the infinity-focused state of the variable magnification optical system according to Example 4. 10A and 10B are diagrams illustrating various aberrations at the wide-angle end in a close-distance focused state (β=−0.025) of the variable magnification optical system according to Example 4. 10A and 10B are diagrams illustrating various aberrations at the telephoto end in a close-up focus state (β=−0.025) of the variable magnification optical system according to Example 4. 10A and 10B are cross-sectional views of a variable magnification optical system according to Example 5 in an infinity focused state and a movement locus during magnification variation. 10A to 10C are diagrams illustrating various aberrations at the wide-angle end in the infinity-focused state of the variable magnification optical system according to Example 5. 10A to 10C are diagrams illustrating various aberrations at the telephoto end in the infinity-focused state of the variable magnification optical system according to Example 5. 10A and 10B are diagrams illustrating various aberrations at the wide-angle end in a close-distance focused state (β=−0.025) of the variable magnification optical system according to Example 5. 10A to 10C are diagrams showing various aberrations at the telephoto end in a close-up focus state (β=−0.025) of the variable magnification optical system according to Example 5. FIG. 1 is a diagram illustrating an example of the configuration of a camera equipped with the variable magnification optical system. 3A to 3C are diagrams illustrating an example of a manufacturing method for the variable magnification optical system.

The following describes the variable magnification optical system, optical device, and method for manufacturing the variable magnification optical system according to this embodiment.

As shown in Figures 1, 6, 11, 16, and 21, the variable magnification optical system according to this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3, and a fourth lens group G4. Furthermore, this variable magnification optical system can achieve good aberration correction during magnification by changing the spacing between adjacent lens groups during magnification.

Furthermore, the first lens group G1 is composed of, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a negative meniscus lens L2 with a convex surface facing the object side, and a negative lens L3, which allows for a wide angle of view and excellent aberration correction. This is particularly effective for distortion and field curvature.

In addition, the inclusion of at least one positive lens in the first lens group G1 enables even better aberration correction.

Furthermore, there is at least one focusing lens group located closer to the image than the second lens group G2, which moves in the optical axis direction during focusing, and the first focusing lens group, which is located closest to the object among the focusing lens groups, satisfies the following conditional expressions (1) and (2), thereby sufficiently suppressing aberration fluctuations during focusing.
1.50 < |mP1w| or -0.95 < mP1w < 0.95 (1)
94.0° < 2ωw < 140.0° (2)
however,
mP1w: magnification of the first focusing lens group at the wide-angle end,
ωw: half angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees).

Conditional expression (1) defines the numerical range of the lateral magnification of the first focusing lens group in the wide-angle end state of the variable magnification optical system. Conditional expression (1) is made up of the following conditional expressions (1a) and (1b), and conditional expression (1) is satisfied by satisfying either conditional expression (1a) or (1b).
1.50 < |mP1w| (1a)
-0.95 < mP1w < 0.95 (1b)
Conditions (1a) and (1b) will now be described.
Conditional expression (1a) defines the absolute value of the lateral magnification of the first focusing lens group in the wide-angle end state of the variable-magnification optical system. If this value is greater than the lower limit of conditional expression (1a), the amount of movement of the first focusing lens group can be reduced, thereby reducing the aberration fluctuations that occur with the movement. If the value is less than the lower limit of conditional expression (1a), the aberration fluctuations that occur with the movement of the first focusing lens group become large.
To ensure the effect of conditional formula (1a), the lower limit of conditional formula (1a) is preferably set to 1.80, and more preferably set to 2.00, 2.20, 2.50, 2.80, 3.00, 3.50, 4.00, or 4.30.
Furthermore, conditional expression (1b) defines the value of the lateral magnification of the first focusing lens group in the wide-angle end state of the variable magnification optical system, and if this value is within the numerical range defined by conditional expression (1b), it is possible to reduce aberration fluctuations that occur as the first focusing lens group moves.
To ensure the effect of conditional formula (1b), it is preferable to set the lower limit of conditional formula (1b) to −0.90, and more preferably to −0.85, −0.80, −0.75, −0.70, −0.65, −0.60, or −0.50. To ensure the effect of conditional formula (1b), it is preferable to set the upper limit of conditional formula (1b) to 0.90, and more preferably to 0.88, 0.85, 0.83, 0.80, 0.79, 0.78, or 0.77.

Furthermore, conditional expression (2) defines the total angle of view 2ωw (unit: degrees) of the variable magnification optical system in the wide-angle end state. By satisfying the numerical range of conditional expression (2), a variable magnification optical system with a wide angle of view and little aberration fluctuation during focusing can be achieved. If the upper limit of conditional expression (2) is exceeded, the angle of view becomes too large and it becomes impossible to correct aberration fluctuation during focusing. Furthermore, if the lower limit of conditional expression (2) is not satisfied, it becomes impossible to achieve a sufficient angle of view.
To ensure the effect of conditional expression (2), the lower limit of conditional expression (2) is preferably set to 90.0, and more preferably to 100.0, 110.0, 115.0, 120.0, or 121.0. To ensure the effect of conditional expression (2), the upper limit of conditional expression (2) is preferably set to 139.0, and more preferably to 138.0, 137.5, or 137.0.

By satisfying these conditional expressions (1) and (2), it is possible to reduce aberration fluctuations during focusing in an ultra-wide-angle variable magnification optical system.

Furthermore, in the variable magnification optical system according to this embodiment, it is desirable that the first lens group G1 has a total of five or more lenses.

By having a total of five or more lenses in the first lens group G1, it is possible to sufficiently suppress aberration fluctuations, particularly distortion and curvature of field, during focusing in the ultra-wide-angle range.

It is also desirable that the variable magnification optical system according to this embodiment satisfy the following conditional expression (3).
0.05 < (-f1)/f2 < 1.50 (3)
however,
f1: focal length of the first lens group G1,
f2: the focal length of the second lens group G2.

Conditional expression (3) defines an appropriate power balance between the focal length of the first lens group G1 and the focal length of the second lens group G2. Being within the range of conditional expression (3) is preferable because it results in an optical system of appropriate size with little curvature of field and little distortion. Exceeding the upper limit of conditional expression (3) results in the focal length of the first lens group G1 becoming long relative to the focal length of the second lens group G2, making the entire variable magnification optical system large.
To ensure the effect of conditional expression (3), the upper limit of conditional expression (3) is preferably set to 1.40, and more preferably set to 1.20, 1.00, 0.90, 0.85, 0.80, 0.75, or 0.70.
If the lower limit of conditional expression (3) is not reached, the focal length of the first lens group G1 becomes shorter relative to the focal length of the second lens group G2, and as a result, the relative power of the first lens group G1 becomes too strong, making it difficult to correct aberrations, and in particular, having a significant effect on field curvature.
To ensure the effect of conditional expression (3), the lower limit of conditional expression (3) is preferably set to 0.10, and more preferably set to 0.15, 0.18, 0.20, 0.22, 0.25, 0.27, or 0.29.

It is also desirable that the variable magnification optical system according to this embodiment satisfy the following conditional expression (4).
0.50 < (-f1)/fw < 5.30 (4)

Conditional expression (4) defines an appropriate power balance between the focal length of the first lens group G1 in the wide-angle end state and the focal length of the entire system. Being within the range of conditional expression (4) is preferable because it minimizes the occurrence of curvature of field and distortion throughout the entire zoom range, resulting in a variable-magnification optical system of appropriate size. Exceeding the upper limit of conditional expression (4) results in the focal length of the first lens group G1 becoming large relative to the focal length of the entire system, making the entire optical system larger.
To ensure the effect of conditional expression (4), it is preferable to set the upper limit of conditional expression (4) to 5.00, and more preferably to set it to 4.50, 4.00, 3.50, 3.30, 3.00, 2.80, 2.50, 2.30, or 2.20.
If the lower limit of conditional expression (4) is not reached, the focal length of the first lens group G1 becomes short relative to the focal length of the entire system, and as a result, the relative power of the first lens group G1 becomes too strong, making it difficult to correct aberrations, and in particular, having a significant effect on field curvature.
To ensure the effect of conditional expression (4), the lower limit of conditional expression (4) is preferably set to 0.60, and more preferably set to 0.80, 1.00, 1.20, 1.40, 1.50, 1.60, or 1.65.

It is also desirable that the variable magnification optical system according to this embodiment satisfy the following conditional expression (5).
-5.00 <(L2r2+L2r1)/(L2r2-L2r1)< -0.50 (5)
however,
L2r1: the radius of curvature of the object side surface of the negative meniscus lens L2,
L2r2: the radius of curvature of the image side surface of the negative meniscus lens L2.

Conditional expression (5) defines the appropriate range of the shape factor of the negative meniscus lens L2, and if conditional expression (5) is satisfied, a variable magnification optical system can be achieved in which fluctuations in spherical aberration and coma aberration during magnification are well corrected (suppressed).
If the lower limit of this condition is not met, coma and astigmatism will worsen, and the curvature will become too sharp, making processing difficult, which is not desirable.
To further ensure the effect of conditional expression (5), it is preferable to set the lower limit of conditional expression (5) to −4.50, and more preferably to −4.30, −4.00, −3.80, −3.50, −3.30, −3.00, −2.80, −2.60, or further preferably to −2.50.
If the upper limit of conditional expression (5) is exceeded, coma and astigmatism will also worsen, which is not preferable.
To ensure the effect of conditional expression (5), it is preferable to set the upper limit of conditional expression (5) to −0.60, and more preferably to −0.80, −1.00, −1.20, −1.40, −1.50, −1.60, −1.70, or further preferably to −1.80.

It is also desirable that the variable magnification optical system according to this embodiment satisfy the following conditional expression (6).
1.00 <(L2r1+L1r2)/(L2r1-L1r2)< 20.00 (6)
however,
L1r2: radius of curvature of the image side surface of the negative meniscus lens L1,
L2r1: the radius of curvature of the object side surface of the negative meniscus lens L2.

Conditional expression (6) defines the appropriate range of the shape factor of the air lens when the air gap between the negative meniscus lens L1 and the negative meniscus lens L2 in the first lens group G1 is considered to be an air lens. If conditional expression (6) is satisfied, it is possible to achieve a variable magnification optical system in which fluctuations in spherical aberration and coma aberration during magnification are well corrected (suppressed).
If the lower limit of this condition is not met, coma and astigmatism will worsen, which is not desirable.
To ensure the effect of conditional expression (6), the lower limit of conditional expression (6) is preferably set to 2.00, and more preferably set to 3.00, 4.00, 4.50, 5.00, 5.50, 6.00, 6.20, or 6.40.
If the upper limit of conditional expression (6) is exceeded, coma and astigmatism will also worsen, which is not preferable.
To ensure the effect of conditional expression (6), it is preferable to set the upper limit of conditional expression (6) to 19.00, and more preferably to 18.00, 16.00, 14.00, 13.50, 13.00, 12.00, 11.00, or 10.00.

It is also desirable that the variable magnification optical system according to this embodiment satisfy the following conditional expression (7).
1.00 < f2/fw < 22.50 (7)
however,
f2: the focal length of the second lens group G2,
fw: focal length at the wide-angle end.

Conditional expression (7) defines an appropriate power balance between the focal length of the second lens group G2 in the wide-angle end state and the focal length of the entire system. By satisfying conditional expression (7), the variable magnification optical system according to this embodiment can achieve both a compact overall lens system and excellent correction of field curvature and distortion throughout the entire focusing range. Exceeding the upper limit of conditional expression (7) increases the focal length of the second lens group G2 relative to the focal length of the entire system, resulting in a larger overall optical system. To ensure the effect of conditional expression (7), it is preferable to set the upper limit of conditional expression (7) to 20.00, and more preferably to 18.00, 15.00, 13.00, 10.00, 9.00, 8.00, 7.50, 7.00, 6.50, or even 6.00.
If the lower limit of conditional expression (7) is not reached, the focal length of the second lens group G2 becomes short relative to the focal length of the entire system, and the relative power of the second lens group G2 becomes too strong, making it difficult to correct aberrations, and in particular, having a large effect on field curvature.
To ensure the effect of conditional expression (7), the lower limit of conditional expression (7) is preferably set to 1.30, and more preferably set to 1.50, 1.80, 2.00, 2.30, 2.50, 2.75, 3.00, or 3.10.

It is also desirable that the variable magnification optical system according to this embodiment satisfy the following conditional expression (8).
Bfw/fw < 2.00 (8)
however,
Bfw: back focus at the wide-angle end,
fw: focal length at the wide-angle end.

Here, conditional expression (8) defines the relationship between the back focus in the wide-angle end state and the focal length of the entire system.
By satisfying conditional expression (8), it is possible to suppress the occurrence of various aberrations and achieve an appropriate back focal length. If the upper limit of conditional expression (8) is exceeded, the back focal length at the wide-angle end state becomes long, resulting in an increase in the size of the entire variable-magnification optical system. In addition, the positional relationship between the first lens group G1 and the rear group becomes inappropriate, resulting in an increase in the amount of field curvature and astigmatism.
To ensure the effect of conditional expression (1), the upper limit of conditional expression (1) is preferably set to 1.90, and more preferably set to 1.80, 1.75, 1.70, 1.68, 1.60, 1.55, 1.50, 1.45, 1.40, or 1.38.

Furthermore, in the variable magnification optical system according to this embodiment, it is desirable that the positive lens be cemented with the negative lens L3.

By cementing the positive lens with the negative lens L3, various aberrations that occur within the first lens group G1, particularly lower coma and lateral chromatic aberration, can be effectively corrected.

Furthermore, in the variable magnification optical system according to this embodiment, it is desirable that the first lens group G1 has at least one aspherical lens.

By including at least one aspherical lens in the first lens group G1, the number of lenses in the first lens group G1 can be reduced, making it smaller and lighter while correcting various aberrations, particularly spherical aberration, to achieve good optical performance.

Furthermore, the variable magnification optical system according to this embodiment has a first focusing lens group and a second focusing lens group whose distance from each other changes and which move in the optical axis direction during focusing, and it is desirable that the following conditional expression (9) be satisfied:
0.50 <|fF1/fF2|< 1.50 (9)
however,
fF1: focal length of the first focusing lens group,
fF2: the focal length of the second focusing lens group.

Conditional expression (9) defines an appropriate power balance between the first and second focusing lens groups, which move independently. By satisfying conditional expression (9), the variable magnification optical system according to this embodiment can suppress changes in image magnification that accompany focusing, and can provide a variable magnification optical system with extremely good optical performance throughout the entire focusing range.
If the upper limit of conditional expression (9) is exceeded, the refractive power of the second focusing lens group becomes excessive relative to that of the first focusing lens group, making it difficult to suppress aberration fluctuations accompanying focusing over the entire zoom range.
To ensure the effect of conditional expression (9), the upper limit of conditional expression (9) is preferably set to 1.48, and more preferably set to 1.46, 1.45, 1.44, 1.43, 1.42, 1.41, or 1.40.
If the lower limit of conditional expression (9) is not reached, the refractive power of the first focusing lens group becomes excessive relative to that of the second focusing lens group, making it difficult to suppress aberration fluctuations associated with focusing over the entire zoom range.
To ensure the effect of conditional expression (9), the lower limit of conditional expression (9) is preferably set to 0.55, and more preferably set to 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, or 0.93.

Furthermore, the variable magnification optical system according to this embodiment has a first focusing lens group and a second focusing lens group whose distance from each other changes and which move in the optical axis direction during focusing, and it is desirable that the following conditional expression (10) be satisfied:
0.50 <-(fF1/fF2) < 1.50 (10)
however,
fF1: focal length of the first focusing lens group,
fF2: the focal length of the second focusing lens group.

Conditional expression (10) defines an appropriate power balance between the first and second focusing lens groups, each of which has a focal length with an opposite sign and moves independently. By satisfying conditional expression (10), the variable magnification optical system according to this embodiment can further suppress changes in image magnification that occur during focusing, thereby providing a variable magnification optical system with even better optical performance throughout the entire focusing range.
If the upper limit of conditional expression (10) is exceeded, the refractive power of the second focusing lens group becomes excessive relative to that of the first focusing lens group, making it difficult to suppress aberration fluctuations accompanying focusing over the entire zoom range.
To ensure the effect of conditional expression (10), it is preferable to set the upper limit of conditional expression (10) to 1.48, and more preferably to set it to 1.46, 1.45, 1.44, 1.43, 1.42, 1.41, or 1.40.
If the lower limit of conditional expression (10) is not reached, the refractive power of the first focusing lens group becomes excessive relative to that of the second focusing lens group, making it difficult to suppress aberration fluctuations accompanying focusing over the entire zoom range.
To ensure the effect of conditional expression (10), the lower limit of conditional expression (10) is preferably set to 0.55, and more preferably set to 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, or 0.93.

The optical device according to this embodiment is equipped with the variable magnification optical system described above.

Here, we will explain an example of a camera (optical device) equipped with the variable magnification optical system OL of this embodiment. Figure 26 is a diagram showing an example of the configuration of a camera 1 equipped with a zoom lens OL.

As shown in FIG. 26, the camera 1 is a so-called mirrorless camera with interchangeable lenses, which is provided with a variable magnification optical system OL as a photographing lens 2.
In camera 1, light from an object (subject) (not shown) is collected by photographing lens 2 and passes through an OLPF (optical low pass filter) (not shown) to form a subject image on the imaging surface of imaging unit 3. The subject image is then photoelectrically converted by a photoelectric conversion element provided in imaging unit 3 to generate an image of the subject. This image is displayed on EVF (electronic viewfinder) 4 provided in camera 1. This allows the photographer to observe the subject through EVF 4. Furthermore, when the photographer presses a release button (not shown), the image of the subject generated by imaging unit 3 is stored in memory (not shown). In this manner, the photographer can photograph the subject using camera 1.

The variable magnification optical system OL mounted on the camera 1 as the photographic lens 2 has a characteristic lens configuration that, as will be seen from the examples described below, provides a negative-lead variable magnification optical system with a wide angle of view, high resolution, and sufficient suppression of aberration fluctuations during focusing. Therefore, camera 1 can be used to realize an optical device with a negative-lead variable magnification optical system with a wide angle of view, high resolution, and sufficient suppression of aberration fluctuations during focusing.

Note that while a mirrorless camera has been described as an example of camera 1, the optical device of this embodiment is not limited to this. For example, the same effects as camera 1 can be achieved even if the above-described zoom lens OL is installed in a single-lens reflex camera that has a quick-return mirror in the camera body and observes the subject through a viewfinder optical system.

The manufacturing method of a variable magnification optical system according to this embodiment is a manufacturing method of a variable magnification optical system having, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3, and a fourth lens group G4, wherein the lens groups are arranged so that the spacing between adjacent lens groups changes during magnification variation, and the first lens group G1 is arranged, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a negative meniscus lens L2 having a convex surface facing the object side, and a negative lens L3, and is arranged so as to have at least one positive lens, and is arranged so as to have at least one focusing lens group that moves in the optical axis direction during focusing, closer to the image side than the second lens group G2, and the first focusing lens group that is arranged closest to the object side among the focusing lens groups is arranged so as to satisfy the following conditional expressions (1) and (2):
1.50 < |mP1w| or -0.95 < mP1w < 0.95 (1)
94.0° < 2ωw < 140.0° (2)
however,
mP1w: magnification of the first focusing lens group at the wide-angle end,
ωw: half angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees).

Below, an outline of a manufacturing method for a variable magnification optical system OL according to an embodiment will be described with reference to FIG. 27. First, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3, and a fourth lens group G4 are arranged (S1). Next, the lenses are arranged so that the spacing between adjacent lens groups changes during magnification (S2). The first lens group G1 then includes, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object side, a negative meniscus lens L2 with a convex surface facing the object side, and a negative lens L3, and is arranged so as to have at least one positive lens (S3). Furthermore, at least one focusing lens group that moves in the optical axis direction during focusing is arranged closer to the image than the second lens group G2, and the first focusing lens group, which is arranged closest to the object side, is arranged so as to satisfy a predetermined conditional expression (S4).

The above-described optical system manufacturing method makes it possible to manufacture a negative-lead variable magnification optical system that has a wide angle of view, high resolution, and sufficiently suppresses aberration fluctuations during focusing.

Note that the conditions and configurations described above each provide the aforementioned effects, and are not limited to those that satisfy all of the conditions and configurations. The aforementioned effects can be obtained by satisfying any one of the conditions or configurations, or a combination of any one of the conditions or configurations.

In addition, the contents described below can be adopted as appropriate as long as they do not impair optical performance.

In this specification, a lens group refers to a section having at least one lens separated by an air gap that changes when changing magnification or focusing.

The focusing lens group can also be used for autofocusing, and is suitable for driving motors (such as ultrasonic motors) for autofocusing.

Also, a lens group or partial lens group may be moved so as to have a displacement component perpendicular to the optical axis, or rotated (oscillated) in a plane including the optical axis, to create an anti-vibration lens group that corrects image blur caused by camera shake.

The lens surface may be spherical, flat, or aspherical. A spherical or flat lens surface is preferable because it facilitates lens processing and assembly adjustment and prevents degradation of optical performance due to errors in processing and assembly adjustment. It is also preferable because there is little degradation of imaging performance even when the image plane is misaligned. If the lens surface is aspherical, the aspherical surface may be any of the following aspherical surfaces: a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which resin is molded into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

The aperture stop S is preferably located inside or outside the lens group, but it is also possible to use the lens frame to fulfill that role without providing a component serving as an aperture stop.

In addition, each lens surface may be coated with an anti-reflection coating with high transmittance over a wide wavelength range to reduce flare and ghosting and achieve high-contrast optical performance.

The above configuration makes it possible to provide a bright variable magnification optical system OL with good optical performance, and an imaging device equipped with this variable magnification optical system OL.

Each example of this embodiment will be described below with reference to the drawings. Tables 1 to 5 are tables showing the specifications for Examples 1 to 5. Examples 1 and 3 are reference examples of this application.

The cross-sectional view of the optical system shown in FIG. 1 is a cross-sectional view of the optical system of Example 1 when focusing at infinity, with the wide-angle end state shown at the top of the page and the telephoto end state shown at the bottom, and the movement trajectories of each lens group (first lens group G1 and second lens group G2) when changing magnification from the wide-angle end state to the telephoto end state shown between the two.
1 are denoted in order from the object side (left side of the page) as L11, L12, L13, .... The negative meniscus lens L1, negative meniscus lens L2, and negative lens L3 described in this specification correspond to L11, L12, and L13 in FIG. 1, respectively.
In FIG. 1, the focusing lens group is indicated by F along with its movement locus during focusing.
2 and 3 are aberration diagrams of Example 1 in the wide-angle end state (FIG. 2) and the telephoto end state (FIG. 3) when focusing at infinity, and it can be seen that aberrations are well corrected. Also, FIGS. 4 and 5 are aberration diagrams of Example 1 in the wide-angle end state (FIG. 4) and the telephoto end state (FIG. 5) when focusing at close distances. It can be seen that aberrations are well corrected, just like at other focal lengths. Here, FNO denotes the F-number, Y denotes the image height, and d and g denote the aberration curves for the d-line and g-line, respectively. Regarding astigmatism, the solid line denotes the sagittal image plane, and the dotted line denotes the meridional image plane.

Note that the reference symbols in Figure 1 for the first embodiment are used independently for each embodiment to avoid complicating the explanation due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are used with drawings relating to other embodiments, they do not necessarily represent common configurations with those other embodiments. However, L11, L12, L13, G1, and G2 in the drawings relating to the other embodiments correspond to the negative meniscus lens L1, negative meniscus lens L2, negative lens L3, first lens group G1, and second lens group G2 described in this specification, respectively, as in Figure 1 for the first embodiment.

In each example, the C-line (wavelength 656.3 nm), d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and g-line (wavelength 435.8 nm) are selected as the targets for calculating aberration characteristics.

In the table (Basic specifications), f is the focal length of the entire variable magnification optical system OL, ω is the half angle of view (maximum angle of incidence in degrees), Y is the image height, and FNO is the F-number.

In the (Surface Data) table, the surface number indicates the order of the optical surface from the object side along the direction of light ray travel, r indicates the radius of curvature of each optical surface, d indicates the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane), nd indicates the refractive index of the optical element material relative to the d-line, and νd indicates the Abbe number based on the d-line of the optical element material. Furthermore, (Object Surface) indicates the object surface, (Variable) indicates the variable surface spacing, the "∞" in the radius of curvature indicates a flat surface or aperture, (Aperture) indicates the aperture stop S, the image plane is the image plane I, and BF indicates the back focus (the distance from the final lens surface on the optical axis to the paraxial image plane). Even if BF is not marked as (Variable), it may still be variable. The refractive index of air, "1.000000," is omitted.

In the (aspheric surface data) table, the aspheric surface is expressed by the following formula (a), where y is the height perpendicular to the optical axis, S(y) is the distance along the optical axis from the tangent plane to the vertex of each aspheric surface at height y (amount of sag), r is the radius of curvature of the reference spherical surface (paraxial radius of curvature), κ is the conic constant, and An is the aspheric coefficient of order n (n = 4, 6, 8, 10, 12, 14). Note that in the following examples, "E-n" stands for "×10-n." For example, "-4.54914E-06" stands for "-4.54914×10-6".

S(y)=(y2/r)/{1+(1-κ×y2/r2)1/2}
+A4×y4+A6×y6+A8×y8+A10×y10+A12×y12+A14×y14 (a)

In each example, the second-order aspherical coefficient A2 is 0. In addition, in the tables for each example, aspherical surfaces are marked with an * to the right of the surface number.

In the table (lens group focal length), the first surface indicates the surface number of each group closest to the object, the last surface indicates the surface number of each group closest to the image, and the group focal length indicates the focal length of each group.

In the table, (Variable Distance Data) shows the variable distance di for each of the infinity focusing state, the intermediate distance focusing state, and the close distance focusing state. Here, di indicates the variable distance between the i-th surface and the (i+1)-th surface. Note that d0 indicates the distance on the optical axis from the object to the vertex of the lens surface closest to the object.

The (conditional expression) in the table indicates the values corresponding to the above conditional expressions (1) to (10).

In the following, all specifications, such as focal length f, radius of curvature r, surface spacing d, and other lengths, are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as optical systems can achieve the same optical performance whether proportionally enlarged or reduced. Furthermore, units are not limited to "mm" and other appropriate units can be used.

The explanation of the table up to this point is common to all examples, so it will not be repeated below.

(First Example)
FIG. 1 is a cross-sectional view of a variable magnification optical system according to a first example in a state where the optical system is focused at infinity.
The optical system according to this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power.

The first lens group G1 is composed of, in order from the object side, a negative lens L11 having a meniscus lens shape with its convex surface facing the object side, a negative lens L12 having a meniscus lens shape with its convex surface facing the object side, a negative lens L13 having a meniscus lens shape with its convex surface facing the object side, a biconcave negative lens L14, and a positive lens L15 having a meniscus lens shape with its convex surface facing the object side. The second lens group G2 is composed of a cemented positive lens formed by cementing together a meniscus-shaped negative lens L21 with a convex surface facing the object side and a biconvex positive lens L22, a meniscus-shaped positive lens L23 with a convex surface facing the object side, a biconcave negative lens L24, a biconvex positive lens L25, a cemented positive lens formed by cementing together a meniscus-shaped negative lens L26 with a convex surface facing the object side and a meniscus-shaped positive lens L27 with a convex surface facing the object side, a cemented positive lens formed by cementing together a biconvex positive lens L28 and a meniscus-shaped negative lens L29 with a concave surface facing the object side, and a cemented negative lens formed by cementing together a meniscus-shaped positive lens L210 with a concave surface facing the object side and a meniscus-shaped negative lens L211 with a concave surface facing the object side. An aperture stop S is located between the biconvex positive lens L22 and the positive lens L23 in the second lens group G2.

In the variable magnification optical system of Example 1, when changing magnification from the wide-angle end state to the telephoto end state, the first lens group G1 moves toward the image, and the second lens group G2 moves toward the object, so that the air gap between the first lens group G1 and the second lens group G2 decreases. The aperture stop S moves together with the second lens group G2 when changing magnification.

In this optical system, focusing from infinity to a close object point is performed by moving a cemented positive lens, which is made by cementing a negative lens L21 and a biconvex positive lens L22, toward the image side along the optical axis.

This optical system forms an image on an image plane I for photography. The optical system and the image plane I of the optical system are shown in FIG.
Table 1 below shows the values of each parameter in the first embodiment.

(First Example)
FIG. 1 is a cross-sectional view of the optical system according to the first embodiment in a state where the optical system is focused at infinity.
The optical system of this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

The first lens group G1 is composed of, in order from the object side, a meniscus-shaped negative lens L11 with a convex surface facing the object side, a meniscus-shaped negative lens L12 with a convex surface facing the object side, a meniscus-shaped negative lens L13 with a convex surface facing the object side, a meniscus-shaped negative lens L14 with a convex surface facing the object side, a biconcave negative lens L15, and a biconvex positive lens L16. The second lens group G2 is composed of a cemented positive lens formed by cementing a meniscus-shaped negative lens L21 with a convex surface facing the object side and a biconvex positive lens L22, a cemented negative lens formed by cementing a biconvex positive lens L23 and a biconcave negative lens L24, a cemented negative lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a biconvex positive lens L27. The third lens group G3 is composed of a meniscus-shaped negative lens L31 with a convex surface facing the object side. The fourth lens group G4 is composed of a cemented positive lens formed by cementing together a meniscus-shaped negative lens L41 with its convex surface facing the object side and a biconvex lens L42. The fifth lens group G5 is composed of a cemented positive lens formed by cementing together a biconvex positive lens L51 and a meniscus-shaped negative lens L52 with its concave surface facing the object side, and a cemented negative lens formed by cementing together a meniscus-shaped positive lens L53 with its concave surface facing the object side and a biconcave negative lens L54. An aperture stop S is disposed between the biconvex positive lens L22 and the biconvex positive lens L23 in the second lens group G2.

In the variable magnification optical system of Example 1, when changing magnification from the wide-angle end state to the telephoto end state, the first lens group G1 moves toward the image, and the second lens group G2 to the fifth lens group G5 move toward the object, so that the air space between the first lens group G1 and the second lens group G2 decreases, the air space between the second lens group G2 and the third lens group G3 decreases, the air space between the third lens group G3 and the fourth lens group G4 increases, and the air space between the fourth lens group G4 and the fifth lens group G5 decreases. The aperture stop S moves together with the second lens group G2 when changing magnification.

In this optical system, focusing from infinity to a close object point is performed by moving the negative lens L31 and the cemented lens made of the negative lens L41 and the positive lens L42 toward the object along the optical axis.

This optical system forms an image on an image plane I for photography. Figure 1 shows the optical system and the image plane I of the optical system.
Table 1 below shows the values of each parameter in the first embodiment.

(Table 1) First Example (basic specifications)
Wide-angle end Telephoto end
f 12.3 23.3
2ω 123.1 86.2
Y 21.6 21.6
FNO 2.8

(surface data)
Surface number rd nd νd
0 (object surface) ∞ (variable)
1 57.1521 4.2550 1.804000 46.57
2 34.6210 9.1692
3 43.2490 3.3685 1.693500 53.20
4* 17.2849 13.7538
5 79.3002 2.6594 1.743200 49.26
6* 36.6533 7.5796
7 95.2465 1.9502 1.693500 53.20
8* 33.5324 6.6258
9 -90.7147 1.7729 1.456000 91.37
10 67.9931 0.1000
11 50.2253 7.0916 1.902650 35.72
12 -142.8147 (variable)
13 0.0000 0.0000
14 35.9099 2.0000 1.834807 42.72
15 20.0037 4.2875 1.623740 47.05
16 -724.9654 1.5000
17 (Aperture) ∞ 1.0000
18 0.0000 0.0000
19 43.4184 3.7326 1.497820 82.57
20 -42.0220 1.0344 1.846660 23.78
21 106.0127 2.1021
22 0.0000 0.0000
23 46.5845 5.1719 1.846660 23.80
24 -41.5898 1.0000 1.790630 44.98
25 26.0416 0.1000
26 25.4204 4.5008 1.497820 82.57
27 -66.0121 (variable)
28* 157.9235 1.5000 1.806040 40.74
29 30.2603 (variable)
30 23.3556 1.0000 1.902650 35.72
31 19.4772 7.0538 1.497820 82.57
32 -38.5746 (variable)
33 210.6651 9.0757 1.497820 82.57
34 -15.6607 0.9629 1.804000 46.60
35 -22.0349 0.1000
36* -120.1278 3.7610 1.497820 82.57
37 -22.5756 0.9629 1.772500 49.62
38 67.4557 BF
Image plane ∞

(aspheric data)
4th side κ = -0.6087
A4=-7.03133E-06, A6=-2.03872E-08, A8=6.61264E-11, A10=-2.43283E-13
A12=0.33893E-15, A14=-0.19378E-18
6th side κ = -5.6445
A4=3.37992E-05, A6=9.98365E-09, A8=-8.09901E-11, A10=5.51009E-13
A12=-0.10852E-14, A14=0.87353E-18
8th side κ = 0.3922
A4=-1.20245E-05, A6=-1.28688E-08, A8=1.33746E-10, A10=-7.49348E-13
A12=0.19014E-14, A14=-0.19785E-17
28th surface κ = 0.0000
A4=-7.93664E-06, A6=-2.65637E-10, A8=-3.74111E-11, A10=0.00000E+00
36th surface κ = 0.0000
A4=-1.85161E-05, A6=-6.22793E-08, A8=3.11065E-10, A10=-1.83103E-12

(lens group focal length)
Lens group First surface Last surface Group focal length First lens group 1 13 -24.00
Second lens group: 14 27 42.60
Third lens group 28 29 -46.69
4th lens group 30 32 33.54
5th lens group 33 38 -137.98
First focusing lens group 28 29 -46.69
Second focusing lens group 30 32 33.54

(variable interval data)
Wide Angle Intermediate 1 Intermediate 2 Telephoto Wide Angle Intermediate 1 Intermediate 2 Telephoto
f 12.300 13.900 17.928 23.300
β ― ― ― ― -0.025 -0.025 -0.025 -0.025
d0 ∞ ∞ ∞ ∞ 456.955 521.662 683.254 901.265
d12 34.826 26.524 12.280 1.000 34.826 26.524 12.280 1.000
d27 5.743 5.226 4.646 4.206 4.842 4.417 4.049 3.732
d29 1.500 1.704 2.149 2.436 1.710 1.873 2.193 2.368
d32 2.366 2.362 2.081 1.500 3.057 3.002 2.636 2.041
d38 20.285 23.054 29.882 39.073 20.285 23.054 29.882 39.073

(Conditional Expression)
(1) |mP1w| = 12.95
(2) 2ωw = 123.1
(3) (-f1)/f2 = 0.56
(4) (-f1)/fw = 1.95
(5) (L2r2+L2r1)/(L2r2-L2r1) = -2.33
(6) (L2r1+L1r2)/(L2r1-L1r2) = 9.03
(7) f2/fw = 3.46
(8) Bfw/fw = 1.65
(9) |fF1/fF2| = 1.39
(10) - (fF1/fF2) = 1.39

2 and 3 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system according to Example 1 when focused on infinity, and it can be seen that various aberrations are well corrected.
Furthermore, Figures 4 and 5 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system of Example 1 when focusing on a close distance (β = -0.025), and it can be seen that, as with the other focal lengths, various aberrations are well corrected, resulting in excellent imaging performance.

(Second Example)
FIG. 6 is a cross-sectional view of the optical system according to the second example in a state where the optical system is focused at infinity.
The optical system of this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power.

The first lens group G1 is composed of, from the object side, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a negative meniscus lens L13 with a convex surface facing the object side, a negative meniscus lens L14 with a convex surface facing the object side, a biconcave negative lens L15, and a positive meniscus lens L16 with a convex surface facing the object side. The second lens group G2 is composed of a biconvex positive lens L21, a positive meniscus lens L22 with a concave surface facing the object side, and a cemented negative lens formed by cementing a biconvex positive lens L23 and a biconcave negative lens L24. The third lens group G3 is composed of a cemented negative lens formed by cementing a biconvex positive lens G31 and a biconcave negative lens G32. The fourth lens group G4 is composed of a meniscus-shaped positive lens L41 with a convex surface facing the object side and a meniscus-shaped positive lens L42 with a convex surface facing the object side. The fifth lens group G5 is composed of a cemented positive lens formed by cementing a meniscus-shaped negative lens L51 with a convex surface facing the object side and a biconvex positive lens L52. The sixth lens group G6 is composed of a cemented positive lens formed by cementing a biconvex positive lens L61 and a meniscus-shaped negative lens L62 with a concave surface facing the object side. The seventh lens group G7 is composed of a cemented negative lens formed by cementing a meniscus-shaped positive lens L71 with a concave surface facing the object side and a meniscus-shaped negative lens L72 with a concave surface facing the object side. The aperture stop S is located on the object side of the biconvex positive lens G31 in the third lens group G3.

In the variable magnification optical system of Example 2, when zooming from the wide-angle end state to the telephoto end state, the first lens group G1 moves toward the image, and the second to seventh lens groups G2 to G7 move toward the object, so that the air space between the first lens group G1 and the second lens group G2 decreases, the air space between the second lens group G2 and the third lens group G3 increases, the air space between the third lens group G3 and the fourth lens group G4 increases, the air space between the fourth lens group G4 and the fifth lens group G5 decreases, the air space between the fifth lens group G5 and the sixth lens group G6 increases, and the air space between the sixth lens group G6 and the seventh lens group G7 decreases. The aperture stop S moves along with the third lens group G3 during zooming.

In this optical system, focusing from infinity to a close object point is performed by moving the cemented lens of negative lens L51 and positive lens L52, and the cemented lens of positive lens L61 and negative lens L62, respectively, toward the object along the optical axis.

This optical system forms an image on an image plane I for photography. The optical system and the image plane I of the optical system are shown in FIG.
Table 2 below shows the values of the various parameters in the second embodiment.

(Table 2) Second Example (basic specifications)
Wide-angle end Telephoto end
f 12.3 21.5
2ω 126.6 91.8
Y 21.6 21.6
FNO 2.8

(surface data)
Surface number rd nd νd
0 (object surface) ∞ (variable)
1 57.0032 2.5859 1.804000 46.57
2 39.1556 10.3437
3 48.8259 2.5859 1.693500 53.20
4* 19.0966 15.5155
5 90.1666 2.0687 1.743200 49.26
6* 41.3824 9.6242
7 96.5570 2.0687 1.497820 82.57
8* 30.6401 8.3594
9 -120.6719 1.5516 1.456000 91.37
10 40.3419 0.1000
11 39.8853 7.5283 1.902650 35.72
12 893.5053 (variable)
13 58.7977 5.0000 1.677980 54.89
14 -90.2943 2.4928
15 0.0000 5.2166
16 -30.7660 2.3994 1.618000 63.34
17 -29.4427 0.1000
18 67.8365 5.5624 1.497820 82.57
19 -27.4980 1.0344 1.846660 23.78
20 318.7015 (variable)
21 (aperture) ∞ 1.5516
22 53.5300 5.1719 1.846660 23.80
23 -38.3786 1.0000 1.790630 44.98
24 28.2781 (variable)
25 24.5667 3.4280 1.497820 82.57
26 43.8414 0.1000
27 24.5667 3.5616 1.497820 82.57
28 43.8414 (variable)
29 34.8771 1.0344 1.902650 35.72
30 22.7984 5.2844 1.497820 82.57
31 -190.8229 (variable)
32 51.5752 9.3952 1.497820 82.57
33 -18.4971 1.0344 1.804000 46.60
34 -46.7053 (variable)
35* -139.0242 7.8545 1.497820 82.57
36 -17.5000 1.0344 1.772500 49.62
37 -82.4256 BF
Image plane ∞

(aspheric data)
4th side κ = -0.652
A4=-7.70873E-06, A6=-7.02346E-09, A8=1.12414E-11, A10=-5.60027E-14
A12=0.85100E-16, A14=-0.43362E-19
6th side κ = -5.794
A4=3.14615E-05, A6=-4.78832E-09, A8=5.01882E-11, A10=-7.85428E-14
A12=0.36476E-17, A14=-0.21719E-19
8th side κ = -1.464
A4=-7.66203E-06, A6=4.17937E-09, A8=4.21806E-11, A10=-1.10845E-13
A12=0.10952E-15, A14=0.47422E-19
35th surface κ = 0.0000
A4=-1.04475E-05, A6=-2.24487E-08, A8=1.83415E-10, A10=-6.80286E-13

(lens group focal length)
Lens group First surface Last surface Group focal length First lens group 1 12 -20.87
Second lens group 13 21 69.46
Third lens group 22 24 -108.22
4th lens group 25 28 53.48
5th lens group 29 31 92.01
6th lens group 32 34 96.78
7th lens group 35 37 -100.84
First focusing lens group 29 31 92.01
Second focusing lens group 32 34 96.78

(variable interval data)
Wide Angle Intermediate 1 Intermediate 2 Telephoto Wide Angle Intermediate 1 Intermediate 2 Telephoto
f 12.3 13.9 17.9 21.5
β ― ― ― ― -0.025 -0.025 -0.025 -0.025
d0 0.000 0.000 0.000 0.000 458.975 523.611 685.301 830.920
d12 28.536 21.017 8.206 1.000 28.536 21.017 8.206 1.000
d20 0.812 1.869 2.591 2.887 0.812 1.869 2.591 2.887
d24 0.500 0.627 0.680 0.500 0.500 0.627 0.680 0.500
d28 6.099 4.571 2.791 1.863 5.625 4.261 2.692 1.846
d31 1.930 2.677 3.479 3.798 2.318 2.747 3.151 3.328
d34 1.650 1.420 1.490 1.696 1.735 1.660 1.917 2.184
d37 15.204 18.215 25.075 31.020 15.204 18.215 25.075 31.020

(Conditional Expression)
(1) |mP1w| = 0.55
(2) 2ωw = 126.6
(3) (-f1)/f2 = 0.30
(4) (-f1)/fw = 1.70
(5) (L2r2+L2r1)/(L2r2-L2r1) = -2.28
(6) (L2r1+L1r2)/(L2r1-L1r2) = 9.10
(7) f2/fw = 5.65
(8) Bfw/fw = 1.24
(9) |fF1/fF2| = 0.95
(10) -(fF1/fF2) = -0.95

7 and 8 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system according to Example 2 when focused on infinity, and it can be seen that various aberrations are well corrected.
Furthermore, Figures 9 and 10 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system of Example 2 when focusing on close distances (β = -0.025), and it can be seen that, as with the other focal lengths, various aberrations are well corrected, resulting in excellent imaging performance.

(Third Example)
FIG. 11 is a cross-sectional view of the optical system according to the third example in a state where the optical system is focused at infinity.
The optical system of this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power.

The first lens group G1 is composed of, from the object side, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a negative meniscus lens L13 with a convex surface facing the object side, a negative meniscus lens L14 with a convex surface facing the object side, a biconcave negative lens L15, and a biconvex positive lens L16. The second lens group G2 is composed of a cemented positive lens formed by cementing a negative meniscus lens L21 with a convex surface facing the object side and a positive meniscus lens L22 with a convex surface facing the object side, a cemented negative lens formed by cementing a biconvex positive lens L23 and a biconcave negative lens L24, a cemented negative lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a biconvex positive lens L27. The third lens group G3 is composed of a negative meniscus lens L31 with its convex surface facing the object side. The fourth lens group G4 is composed of a cemented positive lens formed by cementing a negative meniscus lens L41 with its convex surface facing the object side and a biconvex positive lens L42. The fifth lens group G5 is composed of a cemented positive lens formed by cementing a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object side. The sixth lens group G6 is composed of a cemented negative lens formed by cementing a positive meniscus lens L61 with its concave surface facing the object side and a biconcave negative lens L62. An aperture stop S is disposed between the positive lens L22 and the biconvex positive lens L23 in the second lens group G2.

In the variable magnification optical system of Example 3, when changing magnification from the wide-angle end state to the telephoto end state, the first lens group G1 moves toward the image direction, and the second lens group G2 to the sixth lens group G6 move toward the object direction, so that the air space between the first lens group G1 and the second lens group G2 decreases, the air space between the second lens group G2 and the third lens group G3 decreases, the air space between the third lens group G3 and the fourth lens group G4 increases, the air space between the fourth lens group G4 and the fifth lens group G5 increases, and the air space between the fifth lens group G5 and the sixth lens group G6 increases. The aperture stop S moves along with the second lens group G2 when changing magnification.

In this optical system, focusing from infinity to a close object point is performed by moving the cemented lens made of a positive lens L51 and a negative lens L52 toward the object along the optical axis, and by moving the cemented lens made of a positive lens L61 and a negative lens L62 toward the image along the optical axis.

This optical system forms an image on an image plane I for photography. Figure 11 shows the optical system and the image plane I of the optical system.
Table 3 below shows the values of the various parameters in the third embodiment.

(Table 3) Third Example (basic specifications)
Wide-angle end Telephoto end
f 12.3 23.3
2ω 123.2 86.0
Y 21.6 21.6
FNO 2.8

(surface data)
Surface number rd nd νd
0 (object surface) ∞ (variable)
1 62.0763 4.8000 1.804000 46.57
2 38.4678 10.3437
3 47.8724 3.8000 1.693500 53.20
4* 19.4726 15.5155
5 82.0452 3.0000 1.743200 49.26
6* 38.4338 8.7288
7 123.8482 2.2000 1.693500 53.20
8* 33.6111 6.8270
9 -198.0094 2.0000 1.456000 91.37
10 53.4287 0.2192
11 47.3351 8.0000 1.902650 35.72
12 -198.9493 (variable)
13 0.0000 0.0000
14 37.3813 2.0000 1.834807 42.72
15 22.1025 4.1269 1.623740 47.05
16 599.3338 1.5000
17 (Aperture) ∞ 1.0000
18 0.0000 0.0000
19 38.8499 7.6378 1.497820 82.57
20 -41.4457 1.0344 1.846660 23.78
21 107.2371 0.6305
22 0.0000 0.0000
23 47.7312 5.1719 1.846660 23.80
24 -41.9875 1.0000 1.790630 44.98
25 21.5469 0.0000
26 20.9806 5.0543 1.497820 82.57
27 -89.8971 (variable)
28* 86.2409 1.5000 1.806040 40.74
29 30.9693 (variable)
30 23.3392 1.0000 1.902650 35.72
31 20.2744 9.6416 1.497820 82.57
32 -83.3188 (variable)
33 45.4381 10.4151 1.497820 82.57
34 -18.9092 1.5359 1.804000 46.60
35 -28.5746 (variable)
36* -150.2493 4.4214 1.497820 82.57
37 -24.0507 1.5359 1.772500 49.62
38 59.6072 BF
Image plane ∞

(aspheric data)
4th side κ = -0.6285
A4=-3.74219E-06, A6=-6.54892E-09, A8=2.69809E-11, A10=-8.66382E-14
A12=0.86066E-16, A14=-0.31372E-19
6th side κ = -3.8972
A4=2.00509E-05, A6=9.67128E-09, A8=-3.84214E-11, A10=2.17016E-13
A12=-0.26944E-15, A14=0.67240E-19
8th side κ = 0.3692
A4=-8.94380E-06, A6=-1.21320E-08, A8=5.36893E-11, A10=-2.27166E-13
A12=0.45637E-15, A14=-0.35728E-18
28th surface κ = 0.0000
A4=-1.72849E-06, A6=1.02202E-08, A8=-6.85068E-11, A10=0.00000E+00
36th surface κ = 0.0000
A4=-2.31259E-05, A6=-5.14283E-08, A8=1.88788E-10, A10=-1.03526E-12

(lens group focal length)
Lens group First surface Last surface Group focal length First lens group 1 13 -25.49
Second lens group: 14 27 49.67
Third lens group 28 29 -60.68
4th lens group 30 32 41.27
5th lens group: 33 35 45.28
6th lens group 36 38 -35.59
First focusing lens group 33 35 45.28
Second focusing lens group 36 38 -35.59

(variable interval data)
Wide Angle Intermediate 1 Intermediate 2 Telephoto Wide Angle Intermediate 1 Intermediate 2 Telephoto
f 12.3 13.9 17.9 23.3
β ― ― ― ― -0.025 -0.025 -0.025 -0.025
d0 0.000 0.000 0.000 0.000 456.955 521.662 683.254 901.265
d12 37.942 28.742 13.300 1.000 37.942 28.742 13.300 1.000
d27 3.291 2.838 2.559 2.389 3.291 2.838 2.559 2.389
d29 2.317 3.494 3.713 3.462 2.317 3.494 3.713 3.462
d32 2.197 2.218 2.408 2.063 2.088 2.111 2.304 1.965
d35 0.102 0.104 0.138 0.244 0.320 0.318 0.346 0.440
d38 17.704 20.236 25.959 33.842 17.595 20.129 25.855 33.744

(Conditional Expression)
(1) |mP1w| = 0.59
(2) 2ωw = 123.2
(3) (-f1)/f2 = 0.51
(4) (-f1)/fw = 2.07
(5) (L2r2+L2r1)/(L2r2-L2r1) = -2.37
(6) (L2r1+L1r2)/(L2r1-L1r2) = 9.18
(7) f2/fw = 4.04
(8) Bfw/fw = 1.44
(9) |fF1/fF2| = 1.27
(10) - (fF1/fF2) = 1.27

12 and 13 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system according to Example 3 when focused on infinity, and it can be seen that various aberrations are well corrected.
Furthermore, Figures 14 and 15 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system of Example 3 when focusing on close distances (β = -0.025), and it can be seen that, as with the other focal lengths, various aberrations are well corrected, resulting in excellent imaging performance.

(Fourth Example)
FIG. 16 is a cross-sectional view of the optical system according to the fourth example in a state where the optical system is focused at infinity.
The optical system of this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power.

The first lens group G1 is composed of, from the object side, a meniscus-shaped negative lens L11 with its convex surface facing the object side, a meniscus-shaped negative lens L12 with its convex surface facing the object side, a meniscus-shaped negative lens L13 with its convex surface facing the object side, a meniscus-shaped negative lens L14 with its convex surface facing the object side, a biconcave negative lens L15, and a biconvex positive lens L16. The second lens group G2 is composed of a biconvex positive lens L21, a meniscus-shaped positive lens L22 with its concave surface facing the object side, and a cemented negative lens formed by cementing a biconvex positive lens L23 and a biconcave negative lens L24. The third lens group G3 is composed of a biconvex positive lens L31 and a cemented negative lens formed by cementing a biconcave negative lens. The fourth lens group G4 is composed of a meniscus-shaped positive lens L41 with a convex surface facing the object side and a meniscus-shaped positive lens L42 with a convex surface facing the object side. The fifth lens group G5 is composed of a cemented positive lens formed by cementing a meniscus-shaped negative lens L51 with a convex surface facing the object side and a biconvex positive lens. The sixth lens group G6 is composed of a cemented positive lens formed by cementing a biconvex positive lens L61 and a meniscus-shaped negative lens L62 with a concave surface facing the object side. The seventh lens group G7 is composed of a cemented negative lens formed by cementing a meniscus-shaped positive lens L71 with a concave surface facing the object side and a meniscus-shaped negative lens L72 with a concave surface facing the object side. An aperture stop S is located on the object side of the positive-convex lens L31 in the third lens group G3.

In the variable magnification optical system of Example 4, when zooming from the wide-angle end state to the telephoto end state, the first lens group G1 moves toward the image, and the second to seventh lens groups G2 to G7 move toward the object, so that the air space between the first lens group G1 and the second lens group G2 decreases, the air space between the second lens group G2 and the third lens group G3 increases, the air space between the third lens group G3 and the fourth lens group G4 increases, the air space between the fourth lens group G4 and the fifth lens group G5 decreases, the air space between the fifth lens group G5 and the sixth lens group G6 increases, and the air space between the sixth lens group G6 and the seventh lens group G7 decreases. The aperture stop S moves along with the third lens group G3 during zooming.

In this optical system, focusing from infinity to a close object point is performed by moving the cemented lens made of a positive lens L61 and a negative lens L62 toward the object along the optical axis, and by moving the cemented lens made of a positive lens L71 and a negative lens L72 toward the image along the optical axis.

This optical system forms an image on an image plane I for photography. Figure 16 shows the optical system and the image plane I of the optical system.
Table 4 below shows the values of each parameter in the fourth embodiment.

(Table 4) Fourth Example (basic specifications)
Wide-angle end Telephoto end
f 12.3 21.5
2ω 126.5 92.6
Y 21.6 21.6
FNO 2.8

(surface data)
Surface number rd nd νd
0 (object surface) ∞ (variable)
1 56.1975 2.5859 1.804000 46.57
2 39.1377 10.3437
3 47.8632 2.5859 1.693500 53.20
4* 17.4938 15.5155
5 61.8393 2.0687 1.743200 49.26
6* 47.7705 9.8148
7 339.3515 2.0687 1.497820 82.57
8* 32.0223 8.4787
9 -88.7656 1.5516 1.456000 91.37
10 47.6490 0.1000
11 43.1843 7.2480 1.902650 35.72
12 -2125.6418 (variable)
13 55.9225 5.0000 1.677980 54.89
14 -87.2998 1.2716
15 0.0000 3.3100
16 -29.9347 2.8260 1.618000 63.34
17 -29.3752 2.1651
18 77.1268 5.8033 1.497820 82.57
19 -27.6160 1.0344 1.846660 23.78
20 297.6160 (variable)
21 (aperture) ∞ 1.5518
22 46.7649 5.1719 1.846660 23.80
23 -45.4165 1.0000 1.790630 44.98
24 24.5158 (variable)
25 22.2938 3.8856 1.497820 82.57
26 38.5625 0.7300
27 22.2938 3.9520 1.497820 82.57
28 38.5625 (variable)
29 33.3413 1.0344 1.902650 35.72
30 23.9938 3.7363 1.497820 82.57
31 -305.0131 (variable)
32 45.2142 8.8846 1.497820 82.57
33 -17.3584 1.0344 1.804000 46.60
34 -52.6512 (variable)
35* -149.2963 7.1718 1.497820 82.57
36 -17.5000 1.0344 1.772500 49.62
37 -68.7952 BF
Image plane ∞

(aspheric data)
4th side κ = -0.7521
A4=-5.23127E-06, A6=-2.86027E-10, A8=1.19543E-11, A10=-6.30066E-14
A12=0.74715E-16, A14=-0.32320E-19
6th side κ = -4.6145
A4=2.37756E-05, A6=-1.02131E-08, A8=7.10569E-11, A10=-1.16780E-13
A12=0.10088E-15, A14=-0.22119E-19
8th side κ = 1.0192
A4=-1.58123E-05, A6=7.87279E-09, A8=-3.05529E-11, A10=1.09571E-13
A12=0.20893E-15, A14=0.47685E-19
35th surface κ = 0.0000
A4=-1.13706E-05, A6=-1.63012E-08, A8=1.35751E-10, A10=-7.80491E-13

(lens group focal length)
Lens group First surface Last surface Group focal length First lens group 1 12 -21.43
Second lens group 13 21 71.62
Third lens group 22 24 -90.98
4th lens group 25 28 49.92
5th lens group 29 31 83.23
6th lens group 32 34 113.06
7th lens group 35 37 -129.09
First focusing lens group 32 34 113.06
Second focusing lens group 35 37 -129.09

(variable interval data)
Wide Angle Intermediate 1 Intermediate 2 Telephoto Wide Angle Intermediate 1 Intermediate 2 Telephoto

f 12.3 13.9 17.9 21.5
β ― ― ― ― -0.025 -0.025 -0.025 -0.025
d0 0.000 0.000 0.000 0.000 458.975 523.611 685.301 830.920
d12 29.032 21.295 8.322 1.000 29.032 21.295 8.322 1.000
d20 1.910 2.843 3.604 3.983 1.910 2.843 3.604 3.983
d24 0.513 0.552 0.598 0.500 0.513 0.552 0.598 0.500
d28 4.414 3.503 2.266 1.500 4.414 3.503 2.266 1.500
d31 2.873 3.062 3.522 3.866 2.596 2.712 3.110 3.437
d34 2.220 2.182 1.724 1.279 2.984 2.883 2.383 1.929
d37 15.395 18.324 25.787 32.470 14.908 17.973 25.540 32.249

(Conditional Expression)
(1) |mP1w| = 0.76
(2) 2ωw = 126.5
(3) (-f1)/f2 = 0.30
(4) (-f1)/fw = 1.74
(5) (L2r2+L2r1)/(L2r2-L2r1) = -2.15
(6) (L2r1+L1r2)/(L2r1-L1r2) = 9.97
(7) f2/fw = 5.82
(8) Bfw/fw = 1.25
(9) |fF1/fF2| = 0.88
(10) - (fF1/fF2) = 0.88

17 and 18 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system according to Example 4 when focused on infinity, and it can be seen that various aberrations are well corrected.
19 and 20 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system of Example 4 when focusing on a close distance (β=−0.025), and it can be seen that, as with the other focal lengths, various aberrations are well corrected, resulting in excellent imaging performance.

(Fifth Example)
FIG. 21 is a cross-sectional view of the optical system according to Example 5 in a state where the optical system is focused at infinity.
The optical system of this embodiment is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power.

The first lens group G1 is composed of, from the object side, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a negative meniscus lens L13 with a convex surface facing the object side, a negative meniscus lens L14 with a convex surface facing the object side, a biconcave negative lens L15, and a positive meniscus lens L16 with a convex surface facing the object side. The second lens group G2 is composed of a biconvex positive lens L21, a positive meniscus lens L22 with a concave surface facing the object side, and a cemented negative lens formed by cementing a biconvex positive lens L23 and a biconcave negative lens L24. The third lens group G3 is composed of a cemented negative lens formed by cementing a biconvex positive lens L31 and a biconcave negative lens. The fourth lens group G4 is composed of a meniscus-shaped positive lens L41 with a convex surface facing the object side and a meniscus-shaped positive lens L42 with a convex surface facing the object side. The fifth lens group G5 is composed of a cemented positive lens formed by cementing a meniscus-shaped negative lens L51 with a convex surface facing the object side and a biconvex positive lens. The sixth lens group G6 is composed of a cemented positive lens formed by cementing a biconvex positive lens L61 and a meniscus-shaped negative lens L62 with a concave surface facing the object side. The seventh lens group G7 is composed of a cemented negative lens formed by cementing a meniscus-shaped positive lens L71 with a concave surface facing the object side and a meniscus-shaped negative lens L72 with a concave surface facing the object side. An aperture stop S is located on the object side of the positive lens L31 in the third lens group G3.

In the variable magnification optical system of Example 5, when zooming from the wide-angle end state to the telephoto end state, the first lens group G1 moves toward the image, and the second to seventh lens groups G2 to G7 move toward the object, so that the air space between the first lens group G1 and the second lens group G2 decreases, the air space between the second lens group G2 and the third lens group G3 increases, the air space between the third lens group G3 and the fourth lens group G4 increases, the air space between the fourth lens group G4 and the fifth lens group G5 decreases, the air space between the fifth lens group G5 and the sixth lens group G6 increases, and the air space between the sixth lens group G6 and the seventh lens group G7 decreases. The aperture stop S moves along with the third lens group G3 during zooming.

In this optical system, focusing from infinity to a close object point is performed by moving the cemented lens made up of a positive lens L61 and a negative lens L62 toward the object along the optical axis.

This optical system forms an image on an image plane I for photography. Figure 21 shows the optical system and the image plane I of the optical system.
Table 5 below shows the values of each parameter in the fifth embodiment.

(Table 5) Fifth Example (basic specifications)
Wide-angle end Telephoto end
f 12.3 21.5
2ω 126.5 91.7
Y 21.6 21.6
FNO 2.8

(surface data)
Surface number rd nd νd
0 (object surface) ∞ (variable)
1 57.0463 2.5859 1.804000 46.57
2 39.1707 10.3437
3 48.8779 2.5859 1.693500 53.20
4* 18.8953 15.5155
5 89.6883 2.0687 1.743200 49.26
6* 42.5144 10.0206
7 116.1498 2.0687 1.497820 82.57
8* 31.2733 7.9254
9 -140.7179 1.5516 1.456000 91.37
10 39.8197 0.1000
11 39.3289 7.6120 1.902650 35.72
12 796.6359 (variable)
13 57.0385 5.0000 1.677980 54.89
14 -89.6290 2.3366
15 0.0000 5.0605
16 -29.4308 2.3996 1.618000 63.34
17 -28.3356 0.1000
18 77.0106 5.3623 1.497820 82.57
19 -26.7202 1.0344 1.846660 23.78
20 404.7546 (variable)
21 (aperture) ∞ 1.5518
22 58.2996 5.1719 1.846660 23.80
23 -36.2445 1.0000 1.790630 44.98
24 28.5693 (variable)
25 24.6417 3.4612 1.497820 82.57
26 45.5916 0.1000
27 24.6417 3.6087 1.497820 82.57
28 45.5916 (variable)
29 35.4346 1.0344 1.902650 35.72
30 24.3236 4.6376 1.497820 82.57
31 -1192.8465 (variable)
32 45.2835 9.6972 1.497820 82.57
33 -18.6662 1.0344 1.804000 46.60
34 -47.9210 (variable)
35* -523.8408 8.2637 1.497820 82.57
36 -17.5000 1.0344 1.772500 49.62
37 -104.3835 BF
Image plane ∞

(aspheric data)
4th side κ = 0.3414
A4=-8.00292E-06, A6=-7.70275E-09, A8=1.17451E-11, A10=-5.58935E-14
A12=0.86393E-16, A14=-0.44779E-19
6th side κ = -4.3366
A4=3.09247E-05, A6=-5.15554E-10, A8=4.49113E-11, A10=-8.34686E-14
A12=0.10410E-16, A14=-0.21719E-19
8th side κ = -0.6249
A4=-8.19052E-06, A6=4.90989E-09, A8=4.75791E-11, A10=-1.30056E-13
A12=0.13181E-15, A14=0.47422E-19
35th surface κ = 1.0000
A4=-1.22858E-05, A6=-2.24066E-08, A8=1.68819E-10, A10=-6.54827E-13

(lens group focal length)
Lens group First surface Last surface Group focal length First lens group 1 12 -21.07
Second lens group: 13 21 71.10
Third lens group 22 24 -97.13
4th lens group: 25 28 51.55
5th lens group 29 31 105.70
6th lens group 32 34 87.86
7th lens group 35 37 -108.50
First focusing lens group 32 34 87.86

(variable interval data)
Wide Angle Intermediate 1 Intermediate 2 Telephoto Wide Angle Intermediate 1 Intermediate 2 Telephoto

f 12.3 13.9 17.9 21.5
β ― ― ― ― -0.025 -0.025 -0.025 -0.025
d0 0.000 0.000 0.000 0.000 458.603 523.043 684.155 829.142
d12 28.651 20.951 8.126 1.000 28.651 20.951 8.126 1.000
d20 0.500 1.594 2.330 2.582 0.500 1.594 2.330 2.582
d24 0.500 0.684 0.709 0.500 0.500 0.684 0.709 0.500
d28 5.449 4.167 2.465 1.500 5.449 4.167 2.465 1.500
d31 3.147 3.382 3.914 4.210 2.703 2.933 3.452 3.740
d34 1.553 1.532 1.615 1.724 1.998 1.981 2.077 2.193
d37 15.251 18.292 25.234 31.250 15.251 18.292 25.234 31.250

(Conditional Expression)
(1) |mP1w| = 0.70
(2) 2ωw = 126.5
(3) (-f1)/f2 = 0.30
(4) (-f1)/fw = 1.71
(5) (L2r2+L2r1)/(L2r2-L2r1) = -2.26
(6) (L2r1+L1r2)/(L2r1-L1r2) = 9.07
(7) f2/fw = 5.78
(8) Bfw/fw = 1.24

22 and 23 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system according to Example 5 when focused on infinity, and it can be seen that various aberrations are well corrected.
Furthermore, Figures 24 and 25 are diagrams showing various aberrations in the wide-angle end state and the telephoto end state, respectively, of the optical system of Example 5 when focusing on close distances (β = -0.025), and it can be seen that, as with the other focal lengths, various aberrations are well corrected, resulting in excellent imaging performance.

OL Variable magnification optical system G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group G7 Seventh lens group F Focusing lens group S Aperture stop I Image plane

Claims (10)

The optical system has, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group,
When changing magnification, the spacing between adjacent lens groups changes,
the first lens group includes, in order from the object side, a negative meniscus lens L1 having a convex surface facing the object side, a negative meniscus lens L2 having a convex surface facing the object side, and a negative lens L3, and has at least one positive lens;
At least one focusing lens group that moves in the optical axis direction during focusing is located closer to the image side than the second lens group, and a first focusing lens group that is located closest to the object side among the focusing lens groups is
A variable magnification optical system that satisfies the following condition:
1.50 < |mP1w| or -0.95 < mP1w < 0.95
100.0° < 2ωw < 140.0°
-3.00 < (L2r2+L2r1)/(L2r2-L2r1) < -1.50
Bfw/fw < 1.38
3.00 < (L2r1+L1r2)/(L2r1-L1r2) < 20.00
however,
mP1w: magnification of the first focusing lens group at the wide-angle end,
ωw: half angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees),
L2r1: the radius of curvature of the object side surface of the negative meniscus lens L2,
L2r2: radius of curvature of the image side surface of the negative meniscus lens L2,
Bfw: back focus at the wide-angle end,
fw: focal length at the wide-angle end ,
L1r2: the radius of curvature of the image side surface of the negative meniscus lens L1. The variable magnification optical system according to claim 1, wherein the first lens group has five or more lenses. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied:
0.05 < (-f1)/f2 < 1.50
however,
f1: focal length of the first lens group,
f2: the focal length of the second lens group. 4. The variable magnification optical system according to claim 1, wherein the following condition is satisfied:
0.50 < (-f1)/fw < 5.30
however,
f1: focal length of the first lens group,
fw: focal length at the wide-angle end. 5. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.0<f< 1.0 <f<1.0;
1.00 < f2/fw < 22.50
however,
f2: the focal length of the second lens group,
fw: focal length at the wide-angle end. 6. The variable magnification optical system according to claim 1 , wherein the positive lens is cemented to the negative lens L3. 7. The variable magnification optical system according to claim 1, wherein the first lens group has at least one aspherical lens. The lens system has a first focusing lens group and a second focusing lens group whose distance from each other changes and which move in the optical axis direction during focusing,
8. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.0<f< 1.0 <f<1.0;
0.50 < | fF1/fF2 | < 1.50
however,
fF1: focal length of the first focusing lens group,
fF2: the focal length of the second focusing lens group. The lens system has a first focusing lens group and a second focusing lens group whose mutual distance changes and whose movement is in the optical axis direction during focusing,
9. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.0 < 1.0 <1.0.
0.50 < -(fF1/fF2) < 1.50
however,
fF1: focal length of the first focusing lens group,
fF2: the focal length of the second focusing lens group. An optical device equipped with the variable magnification optical system according to any one of claims 1 to 9 .