Variable magnification optical system and optical instrument

Abstract

A wide-angle lens with high resolution and well-suppressed aberration fluctuations during focusing, featuring a negative-leaning type aperture. To provide a magnification optical system, an optical instrument, and a method for manufacturing a variable magnification optical system. [Solution] The system has 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, in order from the object side, and when magnification is changed, the spacing between adjacent lens groups changes. The first lens group has, in order from the object side, a negative meniscus lens L1 with a convex surface facing the object, a negative meniscus lens L2 with a convex surface facing the object, and a negative lens L3, and has at least one positive lens. There is at least one focusing lens group that moves in the optical axis direction when focusing, located on the image side of the second lens group, and the first focusing lens group, which is located closest to the object, satisfies a specific condition.

Description

Technical Field

[0001] The present invention relates to a zoom optical system suitable for a photographing optical system such as a digital camera, a film camera, and a video camera, an optical device, and a method for manufacturing the zoom optical system.

Background Art

[0002] Conventionally, many negative-leading wide-angle zoom optical systems have been proposed (Patent Document 1). However, there are still few proposals for a zoom optical system in which aberration fluctuations at the time of focusing are sufficiently suppressed in the ultra-wide-angle region. In addition, there has been a demand for a wider angle of view. Furthermore, in recent years, with the digitalization of cameras, higher optical performance has been required.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The zoom optical system according to the first aspect includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, in order from the object side, 、 a third lens group, and a fourth lens group. During zooming, the interval 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. On the image side of the second lens group, it has at least one focusing lens group that moves in the optical axis direction during focusing. The first focusing lens group arranged closest to the object side among the focusing lens groups satisfies the following conditional expressions. 1.50 < |mP1w| or -0.95 < mP1w < 0.95 100.0° < 2ωw < 140.0° 0.05 < (-f1) / f2 < 0.75 -3. 8 0 < (L2r2+L2r1) / (L2r2-L2r1) < -1. 6 0 5.50 < (L2r1+L1r2) / (L2r1-L1r2) < 20.00 however, mP1w: Magnification at the wide-angle end of the first focusing lens group, ωw: Half-angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees) f1: Focal length of the first lens group, f2: Focal length of the second lens group, L1r2: Radius of curvature of the image side of the negative meniscus lens L1, L2r1: Radius of curvature of the object side surface of the negative meniscus lens L2, L2r2: Radius of curvature of the image surface of the negative meniscus lens L2. 。

[0005] Furthermore, the optical device relating to the second embodiment is equipped with the variable magnification optical system.

[0006] Furthermore, the manufacturing method for a variable magnification optical system according to the third embodiment 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 such that the spacing between adjacent lens groups changes when magnification occurs, the first lens group is arranged in order from the object side, with a negative meniscus lens L1, a negative meniscus lens L2, and a negative lens L3 facing the object side, and having at least one positive lens, and is arranged on the image side of the second lens group to have at least one focusing lens group that moves in the optical axis direction when focusing, and the first focusing lens group, which is located closest to the object among the focusing lens groups, is arranged to satisfy the following conditional expression. 1.50 < |mP1w| or -0.95 < mP1w < 0.95 94.0° < 2ωw < 140.0° however, mP1w: Magnification at the wide-angle end of the first focusing lens group, ωw: Half angle of the entire zoom optical system at the wide-angle end (unit: degree).

Brief Description of Drawings

[0007] [Figure 1] It is an optical system cross-sectional view in the infinity focus state of the zoom optical system according to Example 1 and the movement locus during zooming. [Figure 2] It is a diagram of various aberrations at the wide-angle end in the infinity focus state of the zoom optical system according to Example 1. [Figure 3] It is a diagram of various aberrations at the telephoto end in the infinity focus state of the zoom optical system according to Example 1. [Figure 4] It is a diagram of various aberrations at the wide-angle end in the close-focus state (β = -0.025) of the zoom optical system according to Example 1. [Figure 5] It is a diagram of various aberrations at the telephoto end in the close-focus state (β = -0.025) of the zoom optical system according to Example 1. [Figure 6] It is an optical system cross-sectional view in the infinity focus state of the zoom optical system according to Example 2 and the movement locus during zooming. [Figure 7] It is a diagram of various aberrations at the wide-angle end in the infinity focus state of the zoom optical system according to Example 2. [Figure 8] It is a diagram of various aberrations at the telephoto end in the infinity focus state of the zoom optical system according to Example 2. [Figure 9] It is a diagram of various aberrations at the wide-angle end in the close-focus state (β = -0.025) of the zoom optical system according to Example 2. [Figure 10] It is a diagram of various aberrations at the telephoto end in the close-focus state (β = -0.025) of the zoom optical system according to Example 2. [Figure 11] It is an optical system cross-sectional view in the infinity focus state of the zoom optical system according to Example 3 and the movement locus during zooming. [Figure 12] It is a diagram of various aberrations at the wide-angle end in the infinity focus state of the zoom optical system according to Example 3. [Figure 13] It is a diagram of various aberrations at the telephoto end in the infinity focus state of the zoom optical system according to Example 3. [Figure 14]It is a diagram of various aberrations at the wide-angle end in the close-focus state (β = -0.025) of the zoom optical system according to Example 3. [Figure 15] It is a diagram of various aberrations at the telephoto end in the close-focus state (β = -0.025) of the zoom optical system according to Example 3. [Figure 16] It is a cross-sectional view of the optical system and the movement locus during zooming in the infinity-focus state of the zoom optical system according to Example 4. [Figure 17] It is a diagram of various aberrations at the wide-angle end in the infinity-focus state of the zoom optical system according to Example 4. [Figure 18] It is a diagram of various aberrations at the telephoto end in the infinity-focus state of the zoom optical system according to Example 4. [Figure 19] It is a diagram of various aberrations at the wide-angle end in the close-focus state (β = -0.025) of the zoom optical system according to Example 4. [Figure 20] It is a diagram of various aberrations at the telephoto end in the close-focus state (β = -0.025) of the zoom optical system according to Example 4. [Figure 21] It is a cross-sectional view of the optical system and the movement locus during zooming in the infinity-focus state of the zoom optical system according to Example 5. [Figure 22] It is a diagram of various aberrations at the wide-angle end in the infinity-focus state of the zoom optical system according to Example 5. [Figure 23] It is a diagram of various aberrations at the telephoto end in the infinity-focus state of the zoom optical system according to Example 5. [Figure 24] It is a diagram of various aberrations at the wide-angle end in the close-focus state (β = -0.025) of the zoom optical system according to Example 5. [Figure 25] It is a diagram of various aberrations at the telephoto end in the close-focus state (β = -0.025) of the zoom optical system according to Example 5. [Figure 26] It is a diagram showing an example of the configuration of a camera equipped with the above zoom optical system. [Figure 27] It is a diagram showing an outline of an example of the manufacturing method of the above zoom optical system.

Embodiments for Carrying Out the Invention

[0008] The following describes the magnification optical system, optical instrument, and method for manufacturing the magnification optical system according to this embodiment.

[0009] As shown in Figures 1, 6, 11, 16, and 21, the variable magnification optical system according to this embodiment is configured to have, 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.

[0010] Furthermore, the first lens group G1 is configured with a negative meniscus lens L1, a negative meniscus lens L2, and a negative lens L3, all facing the object, in that order from the object side. This configuration allows for wide-angle viewing and excellent aberration correction. It is particularly effective against distortion and field curvature.

[0011] Furthermore, the inclusion of at least one positive lens element in the first lens group G1 enables even better aberration correction.

[0012] Furthermore, on the image side of the second lens group G2, there is at least one focusing lens group that moves in the optical axis direction when focusing, and the first focusing lens group, which is positioned closest to the object among the focusing lens groups, satisfies the following conditions (1) and (2) to sufficiently suppress aberration fluctuations during focusing. 1.50 < |mP1w| or -0.95 < mP1w < 0.95 (1) 94.0° < 2ωw < 140.0° (2) however, mP1w: Magnification at the wide-angle end of the first focusing lens group, ωw: Half-angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees).

[0013] Condition (1) defines the numerical range of the lateral magnification of the first focusing lens group at the wide-angle end of the variable magnification optical system. Condition (1) consists of the following conditions (1a) and (1b), and condition (1) is satisfied if either condition (1a) or (1b) is satisfied. 1.50 < |mP1w| (1a) -0.95 < mP1w < 0.95 (1b) The following explains the conditions (1a) and (1b). Conditional equation (1a) specifies the magnitude of the absolute value of the lateral magnification of the first focusing lens group at the wide-angle end of the variable magnification optical system. If this value is greater than the lower limit of conditional equation (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 it falls below the lower limit of conditional equation (1a), the aberration fluctuations that occur with the movement of the first focusing lens group will become larger. To ensure the effectiveness of condition (1a), it is preferable to set the lower limit of condition (1a) to 1.80, and more preferably to 2.00, 2.20, 2.50, 2.80, 3.00, 3.50, 4.00, and even more preferably to 4.30. Furthermore, condition (1b) is the value of the lateral magnification of the first focusing lens group at the wide-angle end of the variable magnification optical system. If this value is within the numerical range defined by condition (1b), the aberration fluctuations that occur as the first focusing lens group moves can be reduced. To make the effect of condition (1b) more certain, it is preferable to set the lower limit of condition (1b) to -0.90, and more preferably to -0.85, -0.80, -0.75, -0.70, -0.65, -0.60, and even more preferably to -0.50. Also, to make the effect of condition (1b) more certain, it is preferable to set the upper limit of condition (1b) to 0.90, and more preferably to 0.88, 0.85, 0.83, 0.80, 0.79, 0.78, and even more preferably to 0.77.

[0014] Furthermore, condition (2) specifies the total angle of view 2ωw (in degrees) of the variable magnification optical system at the wide-angle end. By satisfying the numerical range of condition (2), a wide-angle variable magnification optical system with minimal aberration variation at focus can be achieved. If the value exceeds the upper limit of condition (2), the angle of view becomes too large, making it impossible to correct the aberration variation at focus. Conversely, if the value falls below the lower limit of condition (2), a sufficient angle of view cannot be achieved. To make the effect of condition (2) more certain, it is preferable to set the lower limit of condition (2) to 90.0, and more preferably to 100.0, 110.0, 115.0, 120.0, and even more preferably to 121.0. Also, to make the effect of condition (2) more certain, it is preferable to set the upper limit of condition (2) to 139.0, and more preferably to 138.0, 137.5, and even more preferably to 137.0.

[0015] By satisfying these conditions (1) and (2), it is possible to reduce aberration variations during focusing in a wide-angle variable magnification optical system.

[0016] 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.

[0017] The first lens group G1 has five or more lenses in total, which allows for sufficient suppression of aberration variations during focusing in the ultra-wide-angle range, particularly distortion and field curvature.

[0018] Furthermore, it is desirable that the variable magnification optical system according to this embodiment satisfies the following condition (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.

[0019] Conditional equation (3) defines the appropriate power balance between the focal length of the first lens group G1 and the focal length of the second lens group G2. Within the range of conditional equation (3), an optical system of a moderate size is obtained, which is preferable because it minimizes the occurrence of field curvature and distortion. If the upper limit of conditional equation (3) is exceeded, the focal length of the first lens group G1 becomes relatively larger than that of the second lens group G2, and the entire variable magnification optical system becomes larger. To make the effect of condition (3) more reliable, it is preferable to set the upper limit of condition (3) to 1.40, and more preferably to 1.20, 1.00, 0.90, 0.85, 0.80, 0.75, and even more preferably to 0.70. If the value falls below the lower limit of condition (3), the focal length of the first lens group G1 becomes relatively smaller than that of the second lens group G2. As a result, the relative power of the first lens group G1 becomes too strong, making aberration correction difficult. The effect on field curvature is particularly significant. To ensure the effectiveness of condition (3), it is preferable to set the lower limit of condition (3) to 0.10, and more preferably to 0.15, 0.18, 0.20, 0.22, 0.25, 0.27, and even more preferably to 0.29.

[0020] Furthermore, it is desirable that the variable magnification optical system according to this embodiment satisfies the following condition (4). 0.50 < (-f1) / fw < 5.30 (4)

[0021] Conditional equation (4) defines an appropriate power balance between the focal length of the first lens group G1 and the overall focal length of the system at the wide-angle end. Within the range of conditional equation (4), the occurrence of field curvature and distortion is small throughout the entire magnification range, and a magnification optical system of a suitable size is obtained, which is preferable. If the upper limit of conditional equation (4) is exceeded, the focal length of the first lens group G1 becomes relatively large relative to the overall focal length of the system, and the entire optical system becomes larger. To make the effect of conditional expression (4) more reliable, it is preferable to set the upper limit of conditional expression (4) to 5.00, and more preferably to 4.50, 4.00, 3.50, 3.30, 3.00, 2.80, 2.50, 2.30, and even more preferably to 2.20. If the value falls below the lower limit of condition (4), the focal length of the first lens group G1 becomes relatively small compared to the overall focal length of the system. As a result, the relative power of the first lens group G1 becomes too strong, making aberration correction difficult. The effect on field curvature is particularly significant. To ensure the effectiveness of conditional equation (4), it is preferable to set the lower limit of conditional equation (4) to 0.60, and more preferably to 0.80, 1.00, 1.20, 1.40, 1.50, 1.60, and even more preferably to 1.65.

[0022] Furthermore, it is desirable that the variable magnification optical system according to this embodiment satisfies the following condition (5). -5.00 <(L2r2+L2r1) / (L2r2-L2r1)< -0.50 (5) however, L2r1: Radius of curvature of the object side surface of the negative meniscus lens L2, L2r2: The radius of curvature of the image surface of the negative meniscus lens L2.

[0023] Conditional equation (5) defines the appropriate range for the shape factor of the negative meniscus lens L2. When conditional equation (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 formula is exceeded, coma aberration and astigmatism worsen, and the curvature becomes too sharp, making processing difficult, which is undesirable. To ensure the effectiveness of condition (5), it is preferable to set the lower limit of condition (5) to -4.50, and more preferably -4.30, -4.00, -3.80, -3.50, -3.30, -3.00, -2.80, -2.60, and even more preferably -2.50. If the upper limit of condition (5) is exceeded, coma aberration and astigmatism will worsen, which is undesirable. To make the effect of condition (5) more reliable, it is preferable to set the upper limit of condition (5) to -0.60, and more preferably to -0.80, -1.00, -1.20, -1.40, -1.50, -1.60, -1.70, and even more preferably to -1.80.

[0024] Furthermore, it is desirable that the variable magnification optical system according to this embodiment satisfies the following condition (6). 1.00 <(L2r1+L1r2) / (L2r1-L1r2)< 20.00 (6) however, L1r2: Radius of curvature of the image side of the negative meniscus lens L1, L2r1: The radius of curvature of the object side surface of the negative meniscus lens L2.

[0025] Conditional equation (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 as an air lens. When conditional equation (6) 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 formula is exceeded, coma aberration and astigmatism worsen, which is undesirable. To ensure the effectiveness of conditional equation (6), it is preferable to set the lower limit of conditional equation (6) to 2.00, and more preferably to 3.00, 4.00, 4.50, 5.00, 5.50, 6.00, 6.20, and even more preferably to 6.40. If the upper limit of condition (6) is exceeded, coma aberration and astigmatism will worsen, which is undesirable. To make the effect of conditional expression (6) more reliable, 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, and even more preferably to 10.00.

[0026] Furthermore, it is desirable that the variable magnification optical system according to this embodiment satisfies the following condition (7). 1.00 < f2 / fw < 22.50 (7) however, f2: Focal length of the second lens group G2, fw: Focal length at the wide-angle end.

[0027] Conditional equation (7) defines an appropriate power balance between the focal length of the second lens group G2 and the focal length of the entire system at the wide-angle end. By satisfying conditional equation (7), the variable magnification optical system according to this embodiment can achieve both miniaturization of the entire lens and good correction of field curvature and distortion aberrations across the entire focusing region. If the upper limit of conditional equation (7) is exceeded, the focal length of the second lens group G2 becomes larger relative to the focal length of the entire system, and the entire optical system becomes larger. To make the effect of conditional equation (7) more reliable, it is preferable to set the upper limit of conditional equation (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, and even more preferably to 6.00. If the value falls below the lower limit of condition (7), the focal length of the second lens group G2 becomes relatively small compared to the overall focal length of the system. This results in the relative power of the second lens group G2 becoming too strong, making aberration correction difficult. The effect on field curvature, in particular, becomes significant. To ensure the effectiveness of condition (7), it is preferable to set the lower limit of condition (7) to 1.30, and more preferably to 1.50, 1.80, 2.00, 2.30, 2.50, 2.75, 3.00, and even more preferably to 3.10.

[0028] Furthermore, it is desirable that the variable magnification optical system according to this embodiment satisfies the following condition (8). Bfw / fw < 2.00 (8) however, Bfw: Back focus at the wide-angle end, fw: Focal length at the wide-angle end.

[0029] Here, condition (8) defines the relationship between the back focus and the overall focal length at the wide-angle end. By satisfying condition (8), the occurrence of various aberrations can be suppressed, resulting in a back focus of an appropriate length. If the upper limit of condition (8) is exceeded, the back focus at the wide-angle end becomes longer, resulting in an increase in the overall size of the variable magnification optical system. In addition, the arrangement relationship between the first lens group G1 and the rear group becomes inappropriate, increasing the amount of field curvature and astigmatism. Conditional expression ( 8 To make the effect of ) more certain, the conditional expression ( 8 The upper limit of ) is preferably 1.90, and more preferably 1.80, 1.75, 1.70, 1.68, 1.60, 1.55, 1.50, 1.45, 1.40, and even more preferably 1.38.

[0030] Furthermore, in the variable magnification optical system according to this embodiment, it is desirable that the positive lens is joined to the negative lens L3.

[0031] By joining the positive lens with the negative lens L3, various aberrations occurring within the first lens group G1, particularly lower coma aberration and lateral chromatic aberration, can be effectively corrected.

[0032] 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.

[0033] By including at least one aspherical lens in the first lens group G1, the number of lens elements within the first lens group G1 can be reduced, resulting in a smaller and lighter design while correcting various aberrations, particularly spherical aberration, to obtain good optical performance.

[0034] Furthermore, the variable magnification optical system according to this embodiment has a first focusing lens group and a second focusing lens group whose spacing changes and which move in the direction of the optical axis when focusing, and it is desirable that the following condition equation (9) is 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.

[0035] Conditional equation (9) defines an appropriate power balance between the first focusing lens group and the second focusing lens group, which move independently. By satisfying conditional equation (9), the variable magnification optical system according to this embodiment can suppress changes in image magnification associated with focusing, and a variable magnification optical system with extremely good optical performance across the entire focusing region can be obtained. If the upper limit of condition (9) is exceeded, the refractive power of the second focusing lens group becomes excessive compared to the first focusing lens group, making it difficult to suppress aberration fluctuations associated with focusing across the entire magnification range. To ensure the effectiveness of conditional expression (9), it is preferable to set the upper limit of conditional expression (9) to 1.48, and more preferably to 1.46, 1.45, 1.44, 1.43, 1.42, 1.41, and even more preferably to 1.40. If the value falls below the lower limit of condition (9), the refractive power of the first focusing lens group becomes excessive compared to the second focusing lens group, making it difficult to suppress aberration fluctuations associated with focusing across the entire magnification range. To ensure the effectiveness of condition (9), it is preferable to set the lower limit of condition (9) to 0.55, and more preferably to 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and even more preferably to 0.93.

[0036] 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 direction of the optical axis when focusing, and it is desirable that the following conditional equation (10) is 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.

[0037] Conditional equation (10) defines an appropriate power balance between the first focusing lens group and the second focusing lens group, whose focal lengths move independently with opposite signs. By satisfying conditional equation (10), the variable magnification optical system according to this embodiment can further suppress the change in image magnification associated with focusing, and a variable magnification optical system with extremely good optical performance across the entire focusing region can be obtained. If the upper limit of condition (10) is exceeded, the refractive power of the second focusing lens group becomes excessive compared to the first focusing lens group, making it difficult to suppress aberration fluctuations associated with focusing across the entire magnification range. To make the effect of conditional expression (10) more reliable, it is preferable to set the upper limit of conditional expression (10) to 1.48, and more preferably to 1.46, 1.45, 1.44, 1.43, 1.42, 1.41, and even more preferably to 1.40. If the value falls below the lower limit of condition (10), the refractive power of the first focusing lens group becomes excessive compared to the second focusing lens group, making it difficult to suppress aberration fluctuations associated with focusing across the entire magnification range. To ensure the effectiveness of condition (10), it is preferable to set the lower limit of condition (10) to 0.55, and more preferably to 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and even more preferably to 0.93.

[0038] The optical device according to this embodiment is equipped with the variable magnification optical system described above.

[0039] Here, an example of a camera (optical device) equipped with the variable magnification optical system OL of this embodiment will be described. Figure 26 is a diagram showing an example of the configuration of camera 1 equipped with a zoom lens OL.

[0040] As shown in Figure 26, camera 1 is a so-called mirrorless camera with interchangeable lenses, equipped with a variable magnification optical system OL as the photographic lens 2. In camera 1, light from an object (subject) not shown is focused by the photographic lens 2 and, via an OLPF (Optical low pass filter) not shown, forms an image of the subject on the imaging surface of the imaging unit 3. Then, the subject image is photoelectrically converted by a photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed in the EVF (Electronic viewfinder) 4 provided in camera 1. This allows the photographer to observe the subject through the EVF 4. Furthermore, when the photographer presses the release button not shown, the image of the subject generated by the imaging unit 3 is stored in memory not shown. In this way, the photographer can take a photograph of the subject with camera 1.

[0041] The variable magnification optical system OL mounted as the photographic lens 2 in camera 1, as can be seen from the embodiments described later, has a negative-leading variable magnification optical system with a wide field of view, high resolution, and sufficiently suppressed aberration fluctuations during focusing, thanks to its characteristic lens configuration. Therefore, camera 1 makes it possible to realize an optical device with a negative-leading variable magnification optical system that has a wide field of view, high resolution, and sufficiently suppressed aberration fluctuations during focusing.

[0042] Although a mirrorless camera was described as an example of camera 1, the optical equipment in this embodiment is not limited to this. For example, even if a single-lens reflex type camera, which has a quick-return mirror in the camera body and observes the subject through a viewfinder optical system, is equipped with the above-mentioned zoom lens OL, the same effect as camera 1 can be achieved.

[0043] The method for manufacturing a variable magnification optical system according to this embodiment is a method for manufacturing a variable magnification optical system having, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3, and a fourth lens group G4, wherein the lenses are arranged such that the spacing between adjacent lens groups changes when magnification occurs, the first lens group G1 is arranged in order from the object side, with a negative meniscus lens L1 facing the object side, a negative meniscus lens L2 facing the object side, and a negative lens L3, and has at least one positive lens, and is arranged to have at least one focusing lens group that moves in the optical axis direction when focusing, on the image side of the second lens group G2, and the first focusing lens group which is located closest to the object among the focusing lens groups is arranged to satisfy the following conditions (1) and (2). 1.50 < |mP1w| or -0.95 < mP1w < 0.95 (1) 94.0° < 2ωw < 140.0° (2) however, mP1w: Magnification at the wide-angle end of the first focusing lens group, ωw: Half-angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees).

[0044] The following outline of the manufacturing method of the variable magnification optical system OL according to the embodiment will be described with reference to Figure 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, they are arranged so that the spacing between adjacent lens groups changes when magnification occurs (S2). The first lens group G1 is arranged in order from the object side, with a negative meniscus lens L1 facing the object side, a negative meniscus lens L2 facing the object side, and a negative lens L3, and is arranged to have at least one positive lens (S3). Furthermore, at least one focusing lens group that moves in the optical axis direction when focusing is located is arranged on the image side of the second lens group G2, and the first focusing lens group located closest to the object is arranged to satisfy a predetermined condition (S4).

[0045] According to the optical system manufacturing method described above, it is possible to manufacture a negative-leading variable magnification optical system that has a wide field of view, high resolution, and sufficiently suppresses aberration fluctuations during focusing.

[0046] Furthermore, the conditions and configurations described above each produce the effects mentioned above, and it is not limited to those that satisfy all of them. It is possible to obtain the effects described above by satisfying any one of the conditions or configurations, or any combination of any of the conditions or configurations.

[0047] Furthermore, the following points can be adopted as appropriate, provided they do not impair optical performance.

[0048] In this specification, a lens group refers to a portion having at least one lens, separated by an air gap that changes during magnification or focusing.

[0049] Furthermore, the focusing lens group can also be applied to autofocus and is suitable for motor drive (such as an ultrasonic motor) for autofocus.

[0050] Alternatively, a lens group or partial lens group may be moved to have a displacement component perpendicular to the optical axis, or rotated (oscillated) in an in-plane direction including the optical axis, to correct image blur caused by camera shake.

[0051] Furthermore, the lens surface may be formed as a sphere, a plane, or an aspherical surface. A spherical or plane lens surface is preferable because it facilitates lens processing and assembly adjustment, and prevents deterioration of optical performance due to processing and assembly adjustment errors. It is also preferable because even if the image plane is misaligned, the deterioration of image quality is minimal. If the lens surface is aspherical, it may be an aspherical surface formed by grinding, a glass molded aspherical surface formed from glass using a mold, or a composite aspherical surface formed by forming resin in an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, and the lens may be a refractive index distribution lens (GRIN lens) or a plastic lens.

[0052] The aperture diaphragm S is preferably located inside or outside the lens group, but its function may be substituted by the lens frame without providing a separate aperture diaphragm component.

[0053] Furthermore, each lens surface may be coated with an anti-reflective coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high contrast optical performance.

[0054] With the above configuration, it is possible to provide a bright variable magnification optical system OL with good optical performance and an imaging device having this variable magnification optical system OL.

[0055] The following describes each embodiment according to this invention with reference to the drawings. Tables 1 to 5 are shown below, which are tables of specifications for the first to fifth embodiments. Here, the first and third embodiments are reference examples of this application.

[0056] The cross-sectional view of the optical system shown in Figure 1 is a cross-sectional view of the optical system of Example 1 when in focus at infinity. The wide-angle end state is shown at the top of the page, and the telephoto end state is shown at the bottom of the page. Between the two, the movement trajectories of each lens group (first lens group G1 and second lens group G2) during the change in magnification from the wide-angle end state to the telephoto end state are shown. In Figure 1, the lenses are labeled L11, L12, L13, ... from the object side (left side of the paper) in order. Here, the negative meniscus lens L1, negative meniscus lens L2, and negative lens L3 described herein correspond to L11, L12, and L13 in Figure 1, respectively. Furthermore, in Figure 1, the focusing lens group is indicated as F along with its movement trajectory during focusing. Furthermore, Figures 2 and 3 show the aberration diagrams for the wide-angle end (Figure 2) and telephoto end (Figure 3) of Example 1 when focused at infinity, demonstrating good aberration correction. Figures 4 and 5 show the aberration diagrams for the wide-angle end (Figure 4) and telephoto end (Figure 5) of Example 1 when focused at close range. Similar to other focal lengths, good aberration correction is evident. Note that FNO represents the F-number, Y represents the image height, and d and g represent the d-line and g-line aberration curves, respectively. In the astigmatism diagram, the solid line represents the sagittal image plane, and the dotted line represents the meridional image plane.

[0057] Note that the reference numerals in Figure 1 relating to 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 numerals. Therefore, even if the same reference numerals are used in the drawings relating to other embodiments, they do not necessarily have the same configuration as those in other embodiments. However, L11, L12, L13, G1, and G2 in the drawings relating to 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 herein, respectively, as in Figure 1 relating to the first embodiment.

[0058] In each embodiment, 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) were selected as the parameters for calculating aberration characteristics.

[0059] In the table, under (Basic Specifications), f represents the focal length of the entire variable magnification optical system OL, ω represents the half-angle of view (in degrees, maximum angle of incidence), Y represents the image height, and FNO represents the F-number.

[0060] In the table, under (surface data), the surface number indicates the order of the optical surfaces from the object side along the direction of light propagation, r is the radius of curvature of each optical surface, d is the interplanar spacing, which is the distance along the optical axis from each optical surface to the next optical surface (or image plane), nd is the refractive index of the optical material with respect to the d line, and νd is the Abbe number of the optical material with respect to the d line. Also, (object surface) indicates the object surface, (variable) indicates a variable interplanar spacing, "∞" for the radius of curvature indicates a plane or aperture, (aperture) indicates the aperture diaphragm S, image plane is the image plane I, and BF is the back focus (distance from the final lens surface to the paraxial image plane on the optical axis). BF includes cases where it is variable even if it is not indicated as (variable). The refractive index of air "1.000000" is omitted.

[0061] In the table, under (Aspherical Data), an aspherical surface is expressed by the following equation (a), where y is the height perpendicular to the optical axis, S(y) is the distance along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface (sag), r is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the cone constant, and An is the nth-order (n=4,6,8,10,12,14) aspherical coefficient. In the following examples, "En" represents "×10-n". For example, "-4.54914E-06" represents "-4.54914×10-6".

[0062] S(y)=(y2 / r) / {1+(1-κ×y2 / r2)1 / 2} +A4×y4+A6×y6+A8×y8+A10×y10+A12×y12+A14×y14 (a)

[0063] In each example, the second-order aspheric coefficient A2 is 0. Also, in the table for each example, aspheric surfaces are marked with an asterisk (*) to the right of the surface number.

[0064] In the table, under (Lens Group Focal Length), the starting plane is the number of the face closest to the object in each group, the ending plane is the number of the face closest to the image in each group, and the group focal length is the focal length of each group.

[0065] The (Variable Interval Data) in the table shows the variable interval di for the infinity focus state, intermediate distance focus state, and close distance focus state, respectively. Here, di represents the variable interval between the i-th plane and the (i+1)-th plane. Note that d0 represents the distance along the optical axis from the object to the vertex of the lens surface closest to the object.

[0066] The (conditional expression) in the table shows the value corresponding to the above conditional expressions (1) to (10).

[0067] In all specifications listed below, the focal length f, radius of curvature r, interplanar spacing d, and other lengths are generally expressed in "mm" unless otherwise specified. However, since optical systems can achieve equivalent optical performance even when proportionally enlarged or reduced, this is not the only unit used. Furthermore, the unit is not limited to "mm" and other appropriate units can be used.

[0068] The explanations in the table above are common to all examples, and will not be explained further below.

[0069] (First embodiment) Figure 1 is a cross-sectional view of the variable magnification optical system according to the first embodiment in the state of infinity focus. 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.

[0070] The first lens group G1 consists of, in order from the object side, a negative lens L11 with a meniscus shape with its convex surface facing the object, a negative lens L12 with a meniscus shape with its convex surface facing the object, a negative lens L13 with a meniscus shape with its convex surface facing the object, a biconcave negative lens L14, and a positive lens L15 with a meniscus shape with its convex surface facing the object. Furthermore, the second lens group G2 consists of a bonded positive lens formed by joining a negative lens L21 with a meniscus shape facing the object and a biconvex positive lens L22, a positive lens L23 with a meniscus shape facing the object and a convex surface facing the object, a biconcave negative lens L24, a biconvex positive lens L25, a bonded positive lens formed by joining a negative lens L26 with a meniscus shape facing the object and a positive lens L27 with a meniscus shape facing the object and a convex surface facing the object, a bonded positive lens formed by joining a biconvex positive lens L28 and a negative lens L29 with a meniscus shape facing the object and a concave surface facing the object, and a bonded negative lens formed by joining a positive lens L210 with a meniscus shape facing the object and a negative lens L211 with a meniscus shape facing the object and a concave surface facing the object. In addition, the aperture diaphragm S is positioned between the biconvex positive lens L22 and the positive lens L23 within the second lens group G2.

[0071] In the variable magnification optical system according to this first embodiment, when magnification is changed from the wide-angle end to the telephoto end, the first lens group G1 moves in the image direction and the second lens group G2 moves in the object direction so that the air gap between the first lens group G1 and the second lens group G2 decreases. The aperture diaphragm S moves together with the second lens group G2 during magnification.

[0072] In this optical system, focusing from infinity to the nearest object point is achieved by moving a cemented positive lens, which is formed by joining a negative lens L21 and a biconvex positive lens L22, towards the image side along the optical axis.

[0073] This optical system forms an image on the image plane I, enabling imaging. Figure 1 illustrates the optical system and its image plane I. Table 1 below shows the values ​​of each parameter in the first embodiment.

[0074] (First embodiment) Figure 1 is a cross-sectional view of the optical system according to the first embodiment in the state of infinity focus. 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, 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.

[0075] The first lens group G1 consists of, in order from the object side, a negative lens L11 with a meniscus shape with its convex surface facing the object, a negative lens L12 with a meniscus shape with its convex surface facing the object, a negative lens L13 with a meniscus shape with its convex surface facing the object, a negative lens L14 with a meniscus shape with its convex surface facing the object, a biconcave negative lens L15, and a biconvex positive lens L16. The second lens group G2 consists of a bonded positive lens formed by joining a negative lens L21 with a meniscus shape with its convex surface facing the object and a biconvex positive lens L22, a bonded negative lens formed by joining a biconvex positive lens L23 and a biconcave negative lens L24, a bonded negative lens formed by joining a biconvex positive lens L25 and a biconcave negative lens L26, and a biconvex positive lens L27. The third lens group G3 consists of a negative lens L31 with a meniscus shape with its convex surface facing the object. Furthermore, the fourth lens group G4 is composed of a bonded positive lens formed by joining a negative lens L41, which has a meniscus lens shape with its convex surface facing the object, and a biconvex lens L42. G5 consists of a bonded positive lens formed by joining a biconvex positive lens L51 and a meniscus-shaped negative lens L52 with its concave surface facing the object, and a bonded negative lens formed by joining a meniscus-shaped positive lens L53 with its concave surface facing the object and a biconcave negative lens L54. The aperture diaphragm S is positioned between the biconvex positive lenses L22 and L23 in the second lens group G2.

[0076] In the variable magnification optical system according to this first embodiment, when magnification changes from the wide-angle end to the telephoto end, the first lens group G1 moves in the image direction, and the second to fifth lens groups G5 move in the object direction, such that the air gap between the first lens group G1 and the second lens group G2 decreases, the air gap between the second lens group G2 and the third lens group G3 decreases, the air gap between the third lens group G3 and the fourth lens group G4 increases, and the air gap between the fourth lens group G4 and the fifth lens group G5 decreases. The aperture diaphragm S moves together with the second lens group G2 during magnification.

[0077] In this optical system, focusing from infinity to the nearest object point is achieved by moving the negative lens L31 and the cemented lens formed by the negative lens L41 and the positive lens L42 toward the object along the optical axis.

[0078] This optical system forms an image on the image plane I, enabling imaging. Figure 1 illustrates the optical system and its image plane I. Table 1 below shows the values ​​of each parameter in the first embodiment.

[0079] (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) Face 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 surface) Page 4 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 Page 6 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 Page 8 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 Page 28 κ = 0.0000 A4=-7.93664E-06, A6=-2.65637E-10, A8=-3.74111E-11, A10=0.00000E+00 Page 36 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, starting plane, ending plane, group focal length Lens group 1 13 -24.00 Second lens group 14 27 42.60 Third lens group 28 29 -46.69 Lens group 4: 30 32 33.54 Fifth 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

[0080] Figures 2 and 3 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the first embodiment when focused at infinity, respectively, and it can be seen that the aberrations are well corrected. Furthermore, Figures 4 and 5 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the first embodiment when focusing at close range (β = -0.025), respectively. It can be seen that, as with other focal lengths, the aberrations are well corrected and the image-forming performance is excellent.

[0081] (Second example) Figure 6 is a cross-sectional view of the optical system according to the second embodiment in the state of infinity focus. 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, 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.

[0082] The first lens group G1 consists of, in order from the object side, a negative lens L11 with a meniscus shape with its convex surface facing the object, a negative lens L12 with a meniscus shape with its convex surface facing the object, a negative lens L13 with a meniscus shape with its convex surface facing the object, a negative lens L14 with a meniscus shape with its convex surface facing the object, a biconcave negative lens L15, and a positive lens L16 with a meniscus shape with its convex surface facing the object. The second lens group G2 consists of a biconvex positive lens L21, a positive lens L22 with a meniscus shape with its concave surface facing the object, and a bonded negative lens formed by joining a biconvex positive lens L23 and a biconcave negative lens L24. The third lens group G3 consists of a bonded negative lens formed by joining a biconvex positive lens G31 and a biconcave negative lens G32. Furthermore, the fourth lens group G4 consists of a positive lens L41 with a meniscus shape facing the object and a positive lens L42 with a meniscus shape facing the object. The fifth lens group G5 consists of a cemented positive lens formed by joining a negative lens L51 with a meniscus shape facing the object and a biconvex positive lens L52. The sixth lens group G6 consists of a cemented positive lens formed by joining a biconvex positive lens L61 and a negative lens L62 with a meniscus shape facing the object and a concave surface. The seventh lens group G7 consists of a cemented negative lens formed by joining a positive lens L71 with a meniscus shape facing the object and a negative lens L72 with a meniscus shape facing the object and a concave surface. The aperture diaphragm S is located on the object side of the biconvex positive lens G31 in the third lens group G3.

[0083] In the variable magnification optical system according to this second embodiment, when magnification changes from the wide-angle end to the telephoto end, the first lens group G1 moves in the image direction, and the second lens group G2 to the seventh lens group G7 move in the object direction, such that the air gap between the first lens group G1 and the second lens group G2 decreases, the air gap between the second lens group G2 and the third lens group G3 increases, the air gap between the third lens group G3 and the fourth lens group G4 increases, the air gap between the fourth lens group G4 and the fifth lens group G5 decreases, the air gap between the fifth lens group G5 and the sixth lens group G6 increases, and the air gap between the sixth lens group G6 and the seventh lens group G7 decreases.

[0084] In this optical system, focusing from infinity to the nearest object point is achieved by moving the cemented lens formed by the negative lens L51 and the positive lens L52, and the cemented lens formed by the positive lens L61 and the negative lens L62, towards the object along the optical axis.

[0085] This optical system forms an image on the image plane I, enabling imaging. Figure 6 illustrates the optical system and its image plane I. Table 2 below shows the values ​​of each parameter in the second embodiment.

[0086] (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) Face 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 ∞ (Aspherical data) Side 4 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 Side 6 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 Side 8 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 Page 35 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, starting plane, ending plane, group focal length Lens group 1 12 -20.87 Second lens group 13 21 69.46 Third lens group 22 24 -108.22 Fourth lens group: 25 28 53.48 Fifth lens group 29 31 92.01 Lens group 6 32 34 96.78 Lens group 7 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

[0087] Figures 7 and 8 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the second embodiment when focused at infinity, respectively, and it can be seen that the aberrations are well corrected. Furthermore, Figures 9 and 10 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the second embodiment when focusing at close range (β = -0.025), respectively. It can be seen that, as with other focal lengths, the aberrations are well corrected and the image-forming performance is excellent.

[0088] (Third embodiment) Figure 11 is a cross-sectional view of the optical system according to the third embodiment in the state of infinity focus. 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, 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.

[0089] The first lens group G1 consists of, in order from the object side, a negative lens L11 with a meniscus shape with its convex surface facing the object, a negative lens L12 with a meniscus shape with its convex surface facing the object, a negative lens L13 with a meniscus shape with its convex surface facing the object, a negative lens L14 with a meniscus shape with its convex surface facing the object, a biconcave negative lens L15, and a biconvex positive lens L16. The second lens group G2 consists of a bonded positive lens formed by joining a negative lens L21 with a meniscus shape with its convex surface facing the object and a positive lens L22 with a meniscus shape with its convex surface facing the object, a bonded negative lens formed by joining a biconvex positive lens L23 and a biconcave negative lens L24, a bonded negative lens formed by joining a biconvex positive lens L25 and a biconcave negative lens L26, and a biconvex positive lens L27. The third lens group G3 consists of a negative lens L31 with a meniscus shape with its convex surface facing the object. Furthermore, the fourth lens group G4 is composed of a cemented positive lens formed by joining a negative lens L41 with a meniscus shape and a biconvex positive lens L42, with the convex surface facing the object side. The fifth lens group G5 is composed of a cemented positive lens formed by joining a biconvex positive lens L51 and a negative lens L52 with a meniscus shape and a concave surface facing the object side. The sixth lens group G6 is composed of a cemented negative lens formed by joining a positive lens L61 with a meniscus shape and a biconcave negative lens L62, with the concave surface facing the object side. The aperture diaphragm S is positioned between the positive lens L22 and the biconvex positive lens L23 in the second lens group G2.

[0090] In the variable magnification optical system according to this third embodiment, when magnification changes from the wide-angle end to the telephoto end, the first lens group G1 moves in the image direction, and the second to sixth lens groups G6 move in the object direction, such that the air gap between the first lens group G1 and the second lens group G2 decreases, the air gap between the second lens group G2 and the third lens group G3 decreases, the air gap between the third lens group G3 and the fourth lens group G4 increases, the air gap between the fourth lens group G4 and the fifth lens group G5 increases, and the air gap between the fifth lens group G5 and the sixth lens group G6 increases. The aperture diaphragm S moves together with the second lens group G2 during magnification.

[0091] In this optical system, focusing from infinity to the nearest object point is achieved by moving the cemented lens of positive lens L51 and negative lens L52 toward the object along the optical axis, and simultaneously moving the cemented lens of positive lens L61 and negative lens L62 toward the image along the optical axis.

[0092] This optical system forms an image on the image plane I, enabling imaging. Figure 11 illustrates the optical system and its image plane I. Table 3 below shows the values ​​of each parameter in the third embodiment.

[0093] (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) Face 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 ∞ (Aspherical data) Side 4 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 Side 6 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 Side 8 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 Page 28 κ = 0.0000 A4=-1.72849E-06, A6=1.02202E-08, A8=-6.85068E-11, A10=0.00000E+00 Page 36 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, starting plane, ending plane, group focal length Lens group 1 13 -25.49 Second lens group 14 27 49.67 Third lens group 28 29 -60.68 Fourth lens group: 30 32 41.27 Fifth lens group: 33 35 45.28 Lens group 6 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

[0094] Figures 12 and 13 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the third embodiment when focused at infinity, respectively, and it can be seen that the aberrations are well corrected. Furthermore, Figures 14 and 15 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the third embodiment when focusing at close range (β = -0.025), respectively. It can be seen that, as with other focal lengths, the aberrations are well corrected and the image-forming performance is excellent.

[0095] (Fourth embodiment) Figure 16 is a cross-sectional view of the optical system according to the fourth embodiment in the state of infinity focus. 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, 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.

[0096] The first lens group G1 consists of, in order from the object side, a negative lens L11 with a meniscus shape with its convex surface facing the object, a negative lens L12 with a meniscus shape with its convex surface facing the object, a negative lens L13 with a meniscus shape with its convex surface facing the object, a negative lens L14 with a meniscus shape with its convex surface facing the object, a biconcave negative lens L15, and a biconvex positive lens L16. The second lens group G2 consists of a biconvex positive lens L21, a positive lens L22 with a meniscus shape with its concave surface facing the object, and a bonded negative lens formed by joining a biconvex positive lens L23 and a biconcave negative lens L24. The third lens group G3 consists of a bonded negative lens formed by joining a biconvex positive lens L31 and a biconcave negative lens. The fourth lens group G4 consists of a positive lens L41 with a meniscus shape facing the object and a positive lens L42 with a meniscus shape facing the object. The fifth lens group G5 consists of a negative lens L51 with a meniscus shape facing the object and a bonded positive lens formed by joining a biconvex positive lens. The sixth lens group G6 consists of a bonded positive lens formed by joining a biconvex positive lens L61 and a negative lens L62 with a meniscus shape facing the object and a concave lens. The seventh lens group G7 consists of a bonded negative lens formed by joining a positive lens L71 with a meniscus shape facing the object and a negative lens L72 with a meniscus shape facing the object and a concave lens. The aperture diaphragm S is located on the object side of the positive-convex lens L31 in the third lens group G3.

[0097] In this fourth embodiment of the variable magnification optical system, when magnification changes from the wide-angle end to the telephoto end, the first lens group G1 moves in the image direction, and the second lens group G2 to the seventh lens group G7 move in the object direction, such that the air gap between the first lens group G1 and the second lens group G2 decreases, the air gap between the second lens group G2 and the third lens group G3 increases, the air gap between the third lens group G3 and the fourth lens group G4 increases, the air gap between the fourth lens group G4 and the fifth lens group G5 decreases, the air gap between the fifth lens group G5 and the sixth lens group G6 increases, and the air gap between the sixth lens group G6 and the seventh lens group G7 decreases.

[0098] In this optical system, focusing from infinity to the nearest object point is achieved by moving the cemented lens of positive lens L61 and negative lens L62 toward the object along the optical axis, and simultaneously moving the cemented lens of positive lens L71 and negative lens L72 toward the image along the optical axis.

[0099] This optical system forms an image on the image plane I, enabling imaging. Figure 16 illustrates the optical system and its image plane I. Table 4 below shows the values ​​of each parameter in the fourth embodiment.

[0100] (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) Face 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 ∞ (Aspherical data) Side 4 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 Side 6 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 Side 8 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 Page 35 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, starting plane, ending plane, group focal length Lens group 1 12 -21.43 Second lens group 13 21 71.62 Third lens group 22 24 -90.98 Fourth lens group: 25 28 49.92 Fifth lens group: 29 31 83.23 Lens group 6: 32 34 113.06 Lens group 7 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 formula) (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

[0101] Figures 17 and 18 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the fourth embodiment when focused at infinity, respectively, and it can be seen that the aberrations are well corrected. Furthermore, Figures 19 and 20 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the fourth embodiment when focusing at close range (β = -0.025), respectively. It can be seen that, as with other focal lengths, the aberrations are well corrected and the image-forming performance is excellent.

[0102] (Fifth example) Figure 21 is a cross-sectional view of the optical system according to the fifth embodiment in the state of infinity focus. 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, 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.

[0103] The first lens group G1 consists of, in order from the object side, a negative lens L11 with a meniscus shape with its convex surface facing the object, a negative lens L12 with a meniscus shape with its convex surface facing the object, a negative lens L13 with a meniscus shape with its convex surface facing the object, a negative lens L14 with a meniscus shape with its convex surface facing the object, a biconcave negative lens L15, and a positive lens L16 with a meniscus shape with its convex surface facing the object. The second lens group G2 consists of a biconvex positive lens L21, a positive lens L22 with a meniscus shape with its concave surface facing the object, and a bonded negative lens formed by joining a biconvex positive lens L23 and a biconcave negative lens L24. The third lens group G3 consists of a bonded negative lens formed by joining a biconvex positive lens L31 and a biconcave negative lens. The fourth lens group G4 consists of a positive lens L41 with a meniscus shape facing the object and a positive lens L42 with a meniscus shape facing the object. The fifth lens group G5 consists of a negative lens L51 with a meniscus shape facing the object and a bonded positive lens formed by joining a biconvex positive lens. The sixth lens group G6 consists of a bonded positive lens formed by joining a biconvex positive lens L61 and a negative lens L62 with a meniscus shape facing the object and a concave lens. The seventh lens group G7 consists of a bonded negative lens formed by joining a positive lens L71 with a meniscus shape facing the object and a negative lens L72 with a meniscus shape facing the object and a concave lens. The aperture diaphragm S is located on the object side of the positive lens L31 in the third lens group G3.

[0104] In the variable magnification optical system according to this fifth embodiment, when magnification changes from the wide-angle end to the telephoto end, the first lens group G1 moves in the image direction, and the second lens group G2 to the seventh lens group G7 move in the object direction, such that the air gap between the first lens group G1 and the second lens group G2 decreases, the air gap between the second lens group G2 and the third lens group G3 increases, the air gap between the third lens group G3 and the fourth lens group G4 increases, the air gap between the fourth lens group G4 and the fifth lens group G5 decreases, the air gap between the fifth lens group G5 and the sixth lens group G6 increases, and the air gap between the sixth lens group G6 and the seventh lens group G7 decreases.

[0105] In this optical system, focusing from infinity to the nearest object point is achieved by moving the cemented lens, consisting of the positive lens L61 and the negative lens L62, toward the object along the optical axis.

[0106] This optical system forms an image on the image plane I, enabling imaging. Figure 21 illustrates the optical system and its image plane I. Table 5 below shows the values ​​of each parameter in the fifth embodiment.

[0107] (Table 5) Example 5 (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) Face 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 二十 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 ∞ (Aspherical data) The fourth surface 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 Side 6 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 Side 8 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 Page 35 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, starting plane, ending plane, group focal length Lens group 1 12 -21.07 Second lens group 13 21 71.10 Third lens group 22 24 -97.13 Fourth lens group: 25 28 51.55 Fifth lens group 29 31 105.70 Lens group 6: 32 34 87.86 Lens group 7 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 (New York) (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) = (7) f2 / fw = 5.78 (8) Bfw / fw = 1.24

[0108] Figures 22 and 23 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the fifth embodiment when it is focused at infinity, and it can be seen that the aberrations are well corrected. Furthermore, Figures 24 and 25 show the aberration diagrams for the wide-angle and telephoto ends of the optical system according to the fifth embodiment when focusing at close range (β = -0.025), respectively. It can be seen that, as with other focal lengths, the aberrations are well corrected and the image-forming performance is excellent. [Explanation of symbols]

[0109] OL variable magnification optical system G1 First Lens Group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group G7 7th lens group F Focusing Lens Group S Aperture diaphragm I image plane

Claims

[Claim 1] It has, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group, and a fourth lens group. When magnification is changed, the spacing between adjacent lens groups changes. The first lens group is arranged in order from the object side, with a negative meniscus lens L1 facing the object side, a negative meniscus lens L2 facing the object side, and a negative lens L3, and has at least one positive lens. The second lens group has at least one focusing lens group that moves in the optical axis direction when focusing, and the first focusing lens group, which is positioned closest to the object, A variable magnification optical system that satisfies the following conditions. 1.50 < |mP1w| or -0.95 < mP1w < 0.95 100.0° < 2ωw < 140.0° 0.05 < (-f1) / f2 < 0.75 -3.80 < (L2r2+L2r1) / (L2r2-L2r1) < -1.60 5.50 < (L2r1+L1r2) / (L2r1-L1r2) < 20.00 however, mP1w: Magnification at the wide-angle end of the first focusing lens group, ωw: Half-angle of view of the entire variable magnification optical system at the wide-angle end (unit: degrees) f1: Focal length of the first lens group, f2: Focal length of the second lens group, L1r2: Radius of curvature of the image surface of the negative meniscus lens L1, L2r1: Radius of curvature of the object side surface of the negative meniscus lens L2, L2r2: The radius of curvature of the image surface of the negative meniscus lens L2.

Images