JP2017156429A - Optical system, optical apparatus, and method for manufacturing optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system that is bright and has good optical performance, an optical apparatus and a method for manufacturing an optical system.SOLUTION: The optical system comprises, in order from an object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3. The first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, and a biconcave negative lens L12 having a concave surface facing the object side. In the optical system, a lens surface on an image side of a lens closest to the image side is a concave surface facing the image side. Upon focusing, an interval between the first lens group G1 and the second lens group G2 varies, and an interval between the second lens group G2 and the third lens group G3 varies, satisfying a condition defined by a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical system, an optical apparatus, and a method for manufacturing the optical system.

  Conventionally, a variable magnification optical system suitable for a photographic camera, an electronic still camera, a video camera, and the like has been proposed (see, for example, Patent Document 1). However, Patent Document 1 has a problem that further improvement in optical performance is desired.

Japanese Patent Laid-Open No. 11-211978

The optical system according to the first aspect of the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group. The first lens group includes, in order from the object side, a first lens that is a negative meniscus lens having a convex surface facing the object side, and a second lens having a concave surface facing the object side. The lens surface on the image side of the lens is a concave surface facing the image side, and the distance between the first lens group and the second lens group changes during focusing and the distance between the second lens group and the third lens group. Changes to satisfy the condition of the following equation.
0.50 <ff / f <20.00
However,
ff: Focal length of the lens group that moves during focusing f: Focal length of the entire system

The method for manufacturing an optical system according to the first aspect of the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens. A first lens that is a negative meniscus lens having a convex surface facing the object side in order from the object side, and a first lens group having a concave surface facing the object side. Two lenses are arranged, and the lens whose concave surface is directed to the image side is located closest to the image side, and the distance between the first lens group and the second lens group changes at the time of focusing. The second lens group and the third lens group are arranged so that the distance between them changes, and the second lens group and the third lens group are arranged so as to satisfy the condition of the following expression.
0.50 <ff / f <20.00
However,
ff: Focal length of the lens group that moves during focusing f: Focal length of the entire system

It is sectional drawing which shows the lens structure of the optical system which concerns on 1st Example, Comprising: (a) shows an infinite focus state, (b) shows a close-up focus state. FIG. 5A is a diagram illustrating various aberrations of the optical system according to Example 1, where (a) shows an infinitely focused state and (b) shows a very close focused state. It is sectional drawing which shows the lens structure of the optical system which concerns on 2nd Example, Comprising: (a) shows an infinite focus state, (b) shows a close-up focus state. FIG. 5A is a diagram illustrating various aberrations of the optical system according to Example 2, wherein (a) shows an infinitely focused state, and (b) shows a close-up focused state. It is sectional drawing which shows the lens structure of the optical system which concerns on 3rd Example, Comprising: (a) shows an infinite focus state, (b) shows a close-up focus state. FIG. 5A is a diagram illustrating various aberrations of the optical system according to Example 3, wherein (a) illustrates an infinite focus state and (b) illustrates a close focus state. It is sectional drawing which shows the lens structure of the optical system which concerns on 4th Example, (a) shows an infinite focus state, (b) shows a close-up focus state. FIG. 7A is a diagram illustrating various aberrations of the optical system according to Example 4, wherein (a) shows an infinitely focused state, and (b) shows a close-up focused state. It is sectional drawing which shows the lens structure of the optical system which concerns on 5th Example, Comprising: (a) shows an infinite focus state, (b) shows a close-up focus state. FIG. 9A is a diagram illustrating various aberrations of the optical system according to Example 5, wherein (a) shows an infinitely focused state, and (b) shows a close-up focused state. It is sectional drawing which shows the lens structure of the optical system which concerns on 6th Example, Comprising: (a) shows an infinite focus state, (b) shows a close-up focus state. FIG. 9A is a diagram illustrating various aberrations of the optical system according to Example 6, wherein (a) shows an infinitely focused state, and (b) shows a close-up focused state. It is sectional drawing of the camera carrying the said optical system. It is a flowchart for demonstrating the manufacturing method of the said optical system.

  Hereinafter, preferred embodiments will be described with reference to the drawings. As shown in FIG. 1, the optical system OL according to this embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G2. And a lens group G3. In this optical system OL, the first lens group G1 includes, in order from the object side, a first lens that is a negative meniscus lens having a convex surface facing the object side (for example, the negative meniscus lens L11 in FIG. 1), and the object side. And a second lens (for example, a biconcave negative lens L12 in FIG. 1) having a concave surface. The image-side lens surface of the most image-side lens is configured by a concave surface facing the image side (for example, the image-side lens surface (24th surface) of the positive meniscus lens L32 in FIG. 1). Further, the optical system OL is configured such that the distance between the first lens group G1 and the second lens group G2 changes and the distance between the second lens group G2 and the third lens group G3 changes during focusing. Has been. With this configuration, a bright optical system can be realized, and excellent optical performance can be obtained from the infinitely focused state to the closest focused state.

  Moreover, it is desirable that the optical system OL according to the present embodiment satisfies the following conditional expression (1).

0.50 <ff / f <20.00 (1)
However,
ff: Focal length of the lens group that moves during focusing f: Focal length of the entire system

  Conditional expression (1) defines the focal length of a lens group that moves during focusing with respect to the focal length of the entire system (hereinafter referred to as “focusing lens group”). The focal length of the focusing lens group is the combined focal length of these lens groups when focusing on infinity when focusing is performed with a plurality of lens groups. Exceeding the upper limit of conditional expression (1) is not preferable because the refractive power of the focusing lens group becomes weak and spherical aberration deteriorates. In order to secure the effect of conditional expression (1), it is desirable to set the upper limit value of conditional expression (1) to 15.00. In order to further secure the effect of conditional expression (1), it is desirable to set the upper limit of conditional expression (1) to 10.00. On the other hand, if the lower limit value of conditional expression (1) is not reached, the refractive power of the focusing lens group becomes strong, and the optical performance, particularly coma aberration, at the time of closest focusing is deteriorated. In order to secure the effect of conditional expression (1), it is desirable to set the lower limit value of conditional expression (1) to 0.60. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.70. In order to further secure the effect of the conditional expression (1), it is desirable to set the lower limit value of the conditional expression (1) to 0.80.

  The optical system OL according to the present embodiment preferably has an aperture stop S, and the image-side lens surface facing the aperture stop S has an aspherical shape. By comprising in this way, spherical aberration can be correct | amended favorably. The aperture stop S is preferably disposed in the second lens group G2. Note that “in the second lens group G2” means that the lens is disposed between the most object side lens and the most image side lens of the second lens group G2.

  In the optical system OL according to the present embodiment, it is desirable that the first lens group G1 is fixed with respect to the image plane during zooming. With this configuration, it is possible to reduce the fluctuation of the field curvature during focusing. In addition, the optical system OL can be reduced in size.

  In the optical system OL according to the present embodiment, it is desirable that the third lens group G3 is fixed with respect to the image plane during zooming. Such a configuration is advantageous for correction of coma aberration.

  In the optical system OL according to this embodiment, it is desirable that the third lens group G3 has a negative refractive power. That is, the optical system OL is constituted by the first lens group G1 having negative refractive power, the second lens group G2 having positive refractive power, and the third lens group G3 having negative refractive power. This is advantageous for correcting coma.

  Further, the optical system OL according to the present embodiment is configured such that the second lens group G2 moves along the optical axis at the time of zooming, that is, the second lens group G2 is used as a focusing lens group. desirable. With this configuration, the spherical aberration fluctuation at the time of focusing becomes small, and it is advantageous for the axial chromatic aberration and the lateral chromatic aberration fluctuation.

  In addition, it is desirable that the optical system OL according to the present embodiment satisfies the following conditional expression (2).

0.01 <1 / re <0.04 (2)
However,
re: the radius of curvature of the image-side lens surface of the most image-side lens

  Conditional expression (2) defines the curvature of the image-side lens surface of the most image-side lens of the optical system OL. Exceeding the upper limit of conditional expression (2) is not preferable because the curvature of the lens surface closest to the image becomes strong and adversely affects coma aberration. In order to secure the effect of conditional expression (2), it is desirable to set the upper limit of conditional expression (2) to 0.03. On the other hand, if the lower limit of conditional expression (2) is not reached, this lens surface will stand up (curvature becomes loose) and adversely affects spherical aberration and the like, which is not preferable. In order to secure the effect of the conditional expression (2), it is desirable that the lower limit value of the conditional expression (2) is 0.02.

  In addition, it is desirable that the optical system OL according to the present embodiment satisfies the following conditional expression (3).

−0.6 <(r2 + r3) / (r2−r3) <− 0.3 (3)
However,
r2: radius of curvature of the image side lens surface of the first lens r3: radius of curvature of the object side lens surface of the second lens

  Conditional expression (3) defines the shape of the first air lens from the object side (the air distance between the first lens and the second lens in the first lens group G1) in the optical system OL. If the upper limit value of conditional expression (3) is exceeded, the negative refractive power of the air lens becomes weak, which adversely affects various aberrations. In particular, it is not preferable because correction of distortion and curvature of field becomes difficult. In order to secure the effect of the conditional expression (3), it is desirable to set the upper limit value of the conditional expression (3) to −0.4. If the lower limit of conditional expression (3) is not reached, the negative refractive power of the air lens becomes strong, which adversely affects various aberrations. In particular, it is not preferable because correction of distortion and curvature of field becomes difficult. In order to secure the effect of conditional expression (3), it is desirable to set the lower limit value of conditional expression (3) to −0.5.

  Moreover, it is desirable that the optical system OL according to the present embodiment satisfies the following conditional expression (4).

Fno <1.50 (4)
However,
Fno: F number

  Conditional expression (4) defines the F number of the optical system OL. When this conditional expression (4) is satisfied, a bright optical system can be obtained. In order to secure the effect of conditional expression (4), it is desirable to set the upper limit of conditional expression (4) to 1.40. In order to further secure the effect of conditional expression (4), it is desirable to set the upper limit of conditional expression (4) to 1.30. In order to further secure the effect of conditional expression (4), it is desirable to set the upper limit of conditional expression (4) to 1.25.

  Note that the conditions and configurations described above each exhibit the above-described effects, and are not limited to satisfying all the conditions and configurations. The above-described effects can be obtained even if the combination of the above conditions or configurations is satisfied.

  Next, a camera that is an optical apparatus including the optical system OL according to the present embodiment will be described with reference to FIG. This camera 1 is a so-called mirrorless camera of an interchangeable lens provided with an optical system OL according to the present embodiment as a photographing lens 2. In the camera 1, light from an object (subject) (not shown) is collected by the photographing lens 2 and is on the imaging surface of the imaging unit 3 via an OLPF (Optical low pass filter) (not shown). A subject image is formed on the screen. Then, the subject image is photoelectrically converted by the photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed on an EVF (Electronic view finder) 4 provided in the camera 1. Thus, the photographer can observe the subject via the EVF 4.

  Further, when a release button (not shown) is pressed by the photographer, an image photoelectrically converted by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1. In this embodiment, an example of a mirrorless camera has been described. However, an optical system OL according to this embodiment is mounted on a single-lens reflex camera that has a quick return mirror in the camera body and observes a subject using a finder optical system. Even in this case, the same effect as the camera 1 can be obtained.

  Hereinafter, an outline of a method for manufacturing the optical system OL according to the present embodiment will be described with reference to FIG. First, each lens is arranged to prepare a first lens group G1, a second lens group G2, and a third lens group G3 (step S100). Then, as the first lens group G1, a first lens that is a negative meniscus lens having a convex surface facing the object side and a second lens having a concave surface facing the object side are arranged in order from the object side (step S200). The lens having the concave surface with the image-side lens surface facing the image side is disposed closest to the image side (step S300). Further, at the time of focusing, the distance between the first lens group G1 and the second lens group G2 is changed, and the distance between the second lens group G2 and the third lens group G3 is changed (Step S400). Furthermore, it arrange | positions so that the conditions by predetermined | prescribed conditional expression (For example, conditional expression (1) mentioned above) may be satisfied (step S500).

  Specifically, in the present embodiment, for example, as shown in FIG. 1, in order from the object side, a negative meniscus lens L11 having a convex surface directed toward the object side, a biconcave negative lens L12, and a biconvex positive lens L13 are provided. A cemented positive lens is arranged to form the first lens group G1, and a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, a biconvex positive lens L23, and a biconcave negative lens L24 are cemented. A cemented lens including a negative lens, an aperture stop S, a negative lens L25 having a biconcave shape with an aspheric lens surface on the object side, and a positive meniscus lens L27 having a convex surface facing the object side. A negative lens and a positive lens L28 having a biconvex lens shape in which the image side lens surface is formed in an aspherical shape are arranged to form the second lens group G2, and a negative meniscus lens L3 having a convex surface facing the object side. And a convex surface on the object side (a concave surface facing the image side) and the third lens group G3 disposed a positive meniscus lens L32. The lens groups prepared in this way are arranged according to the above-described procedure to manufacture the optical system OL.

  The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  In the present embodiment, the optical system OL having the three-group configuration is shown, but the above-described configuration conditions and the like can be applied to other group configurations such as the fourth group, the fifth group, and the like. Further, a configuration in which a lens or a lens group is added closest to the object side, or a configuration in which a lens or a lens group is added closest to the image plane side may be used. Specifically, a configuration in which a lens group whose position relative to the image plane is fixed at the time of zooming or focusing is added to the most image plane side. The lens group refers to a portion having at least one lens separated by an air interval that changes at the time of zooming or focusing. The lens component refers to a single lens or a cemented lens in which a plurality of lenses are cemented.

  Alternatively, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. In this case, the focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor). In particular, the second lens group G2 is preferably a focusing lens group, and the other lenses are preferably fixed in position relative to the image plane during focusing. Considering the load applied to the motor, it is preferable that the focusing lens group is composed of a single lens.

  In addition, the lens group or partial lens group is moved so as to have a displacement component perpendicular to the optical axis, or rotated (swinged) in the in-plane direction including the optical axis to correct image blur caused by camera shake. An anti-vibration lens group may be used. In particular, it is preferable that at least a part of the second lens group G2 or at least a part of the third lens group G3 (excluding the lens component closest to the image side of the third lens group G3) is the anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Any aspherical surface may be used. The lens surface may 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 disposed in the second lens group G2. However, the role of the aperture stop may be substituted by a lens frame without providing a member as an aperture stop.

  Further, each lens surface may be provided with an antireflection film having high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

  With the configuration as described above, it is possible to provide a bright optical system OL having good optical performance, an optical apparatus having the optical system OL, and a method for manufacturing the optical system OL.

  Hereinafter, each example of the present application will be described with reference to the drawings. 1, 3, 5, 7, 9, and 11 are cross-sectional views illustrating the configuration and refractive power distribution of the optical system OL (OL1 to OL6) according to each example. Further, in the lower part of the sectional views of these optical systems OL1 to OL6, the moving direction along the optical axis of the lens group that moves when focusing from the infinite focus state to the close focus state is indicated by an arrow. ing.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), r is the radius of curvature of the reference sphere (paraxial radius of curvature), K is the conic constant, and An is the nth-order aspherical coefficient, it is expressed by the following equation (a). . In the following examples, “E−n” indicates “× 10 ⁻ⁿ ”.

S (y) = (y ² / r) / {1+ (1−K × y ² / r ² ) ^1/2 }
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰ (a)

  In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the right side of the surface number.

[First embodiment]
FIG. 1 is a diagram illustrating a configuration of an optical system OL1 according to the first example. The optical system OL1 includes, 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 having a negative refractive power, It is composed of

  In the optical system OL1, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface directed toward the object side, and a cemented positive lens in which a biconcave negative lens L12 and a biconvex positive lens L13 are cemented. It consists of The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, and a cemented negative lens in which a biconvex positive lens L23 and a biconcave negative lens L24 are cemented. A negative lens L25 having a biconcave shape in which the object-side lens surface is formed in an aspherical shape, a cemented negative lens in which a biconcave negative lens L26 and a positive meniscus lens L27 having a convex surface facing the object are cemented, and both It is composed of a convex positive lens L28. The third lens group G3 includes, in order from the object side, a negative lens L31 having a meniscus lens shape with a convex surface facing the object side, the lens surface on the image side formed in an aspheric shape, and a convex surface facing the object side. It consists of a positive meniscus lens L32 (with the concave surface facing the image side). The aperture stop S is an image side of a cemented negative lens in which the biconvex positive lens L23 and the biconcave negative lens L24 in the second lens group G2 are cemented (between the biconcave negative lens L24 and the aspherical negative lens L25). Is arranged. A filter group FL is disposed between the optical system OL1 and the image plane I.

  In the optical system OL1, focusing from infinity to the closest object point is performed by moving the second lens group G2 to the object side.

  Table 1 below shows values of specifications of the optical system OL1. In Table 1, f shown in the overall specifications is the focal length of the entire system, FNO is the F number, ω is the half field angle [°], Y is the maximum image height, TL is the full length, and BF is the back focus value. Represents. Here, the total length TL indicates the distance on the optical axis from the most object side lens surface (first surface) to the image plane I at the time of infinite focusing. Further, the back focus BF indicates the distance on the optical axis from the lens surface closest to the image plane to the image plane I at the time of focusing on infinity and the air equivalent length thereof. In the lens data, the first column m indicates the order (surface number) of the lens surfaces from the object side along the traveling direction of the light beam, the second column r indicates the curvature radius of each lens surface, and the third column. d is the distance on the optical axis from each optical surface to the next optical surface (surface interval). The fourth column nd and the fifth column νd are the refractive index and Abbe number for the d-line (λ = 587.6 nm). Is shown. Further, the radius of curvature of 0.00000 indicates a plane, and the refractive index of air of 1.0000 is omitted. The lens group focal length indicates the number of the starting surface and the focal length of each of the first to third lens groups G1 to G3.

  Here, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or proportional. Since the same optical performance can be obtained even if the image is reduced, the present invention is not limited to this. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1) First Example [Overall Specifications]
f = 36.00
FNo = 1.27
ω = 31.0
Y = 20.94
TL = 159.500
BF = 21.673
BF (Air equivalent length) = 20.991

[Lens data]
m r d nd νd
Object ∞
1 219.89650 2.500 1.58913 61.2
2 36.65680 30.287
3 -80.31177 2.200 1.49782 82.6
4 107.63024 11.655 1.85026 32.4
5 -266.99457 D5
6 66.74362 15.450 1.43700 95.1
7 -88.13127 0.200
8 53.89207 5.408 1.80400 46.6
9 124.87901 0.040
10 40.75122 10.000 1.80400 46.6
11 -177.14586 2.469 1.78472 25.6
12 28.55427 6.000
13 0.00000 5.500 Aperture stop S
14 * -300.20287 2.500 1.58913 61.2
15 770.69740 1.500
16 -92.49917 1.500 1.62004 36.4
17 26.27027 5.786 1.49782 82.6
18 115.96610 2.617
19 77.41625 8.770 1.80400 46.6
20 -40.30267 D20
21 56.86132 2.945 1.49710 81.6
22 * 32.88058 3.000
23 50.78860 5.000 1.80400 46.6
24 60.00000 17.673
25 0.00000 2.000 1.51680 63.9
26 0.00000 2.000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -80.62
Second lens group 6 53.00
Third lens group 21 -301.07

  In this optical system OL1, the 14th surface and the 22nd surface are formed in an aspherical shape. The following Table 2 shows aspheric data, that is, the values of the conic constant K and the aspheric constants A4 to A10.

(Table 2)
[Aspherical data]
Surface K A4 A6 A8 A10
14 -4.90000e + 01 -1.43121e-05 -5.65379e-09 -1.13282e-11 3.45438e-14
22 1.87050e + 00 -1.72052e-06 -4.28818e-09 2.47112e-12 -1.11278e-14

  In the optical system OL1, the axial air distance D5 between the first lens group G1 and the second lens group G2 and the axial air distance D20 between the second lens group G2 and the third lens group G3 are as described above. However, it changes upon focusing. Table 3 below shows the variable intervals in the infinitely focused object state and the close-up focused state. D0 represents the distance from the most object-side surface (first surface) of the optical system OL1 to the object, and β represents the magnification (the same applies to the following examples).

(Table 3)
[Variable interval data]
Infinity Closest D0 ∞ 140.50
β − -0.2438
f 36.00 −
D5 12.000 0.930
D20 0.500 11.570

  Table 4 below shows values corresponding to the conditional expressions in the optical system OL1. In Table 4, f is the focal length of the entire system, ff is the focal length of the focusing lens group, re is the radius of curvature of the most image side lens surface, and r2 is the image side lens surface of the first lens. The radius of curvature, r3 represents the radius of curvature of the object-side lens surface of the second lens, and Fno represents the FM number. The description of the reference numerals is the same in the following embodiments. In the first example, the negative meniscus lens L11 corresponds to the first lens, and the biconcave negative lens L12 corresponds to the second lens. The second lens group G2 corresponds to the focusing lens group.

(Table 4)
[Conditional expression values]
(1) ff / f = 1.47
(2) 1 / re = 0.02
(3) (r2 + r3) / (r2-r3) = − 0.37
(4) Fno = 1.27

  Thus, this optical system OL1 satisfies all the conditional expressions (1) to (4).

  FIG. 2 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, a lateral chromatic aberration diagram, and a lateral aberration diagram of the optical system OL1 in an infinitely focused state and a close-up focused state. In each aberration diagram, FNO represents an F number, NA represents a numerical aperture, Y represents an image height, and H0 represents an object height. The spherical aberration diagram shows the F-number or numerical aperture value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum image height or object height, and the lateral aberration diagram shows each image height or The value of each object height is shown. D represents the d-line (λ = 587.6 nm), and g represents the g-line (λ = 435.8 nm). In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. Further, the distortion diagram shows the value of the d-line. Also, the same reference numerals as in this example are used in the aberration diagrams of the examples shown below. From these respective aberration diagrams, it can be seen that in the optical system OL1, various aberrations are satisfactorily corrected from the infinite object focusing state to the closest focusing state.

[Second Embodiment]
FIG. 3 is a diagram illustrating a configuration of the optical system OL2 according to the second example. The optical system OL2 includes, 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 having a negative refractive power, It is composed of

  In the optical system OL2, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface directed toward the object side, and a cemented positive lens in which a biconcave negative lens L12 and a biconvex positive lens L13 are cemented. It consists of The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, and a cemented negative lens in which a biconvex positive lens L23 and a biconcave negative lens L24 are cemented. A negative lens L25 having a biconcave shape in which the object-side lens surface is formed in an aspherical shape, a cemented negative lens in which a biconcave negative lens L26 and a positive meniscus lens L27 having a convex surface facing the object are cemented, and both It is composed of a convex positive lens L28. The third lens group G3 includes, in order from the object side, a negative lens L31 having a meniscus lens shape with a convex surface facing the object side, the lens surface on the image side formed in an aspheric shape, and a convex surface facing the object side. It consists of a positive meniscus lens L32 (with the concave surface facing the image side). The aperture stop S is an image side of a cemented negative lens in which the biconvex positive lens L23 and the biconcave negative lens L24 in the second lens group G2 are cemented (between the biconcave negative lens L24 and the aspherical negative lens L25). Is arranged. A filter group FL is disposed between the optical system OL2 and the image plane I.

  In the optical system OL2, focusing from infinity to the closest object point is performed by moving the second lens group G2 to the object side.

  Table 5 below lists values of specifications of the optical system OL2.

(Table 5) Second Example [Overall Specifications]
f = 36.00
FNo = 1.25
ω = 31.8
Y = 21.64
TL = 159.500
BF = 22.298
BF (air equivalent length) = 21.617

[Lens data]
m r d nd νd
Object ∞
1 246.05022 2.500 1.58913 61.2
2 36.66899 29.381
3 -88.05876 2.292 1.49782 82.6
4 99.30956 12.694 1.85026 32.4
5 -315.07398 D5
6 67.04505 15.024 1.43700 95.1
7 -85.05554 0.200
8 51.92997 5.292 1.80400 46.6
9 109.80341 0.076
10 40.84094 10.000 1.80400 46.6
11 -180.43368 2.275 1.78472 25.6
12 28.59592 6.014
13 0.00000 5.500 Aperture stop S
14 * -248.39060 2.500 1.58913 61.2
15 620.45949 1.500
16 -94.42498 1.500 1.62004 36.4
17 26.26690 5.950 1.49782 82.6
18 125.00265 2.281
19 77.69599 8.826 1.80400 46.6
20 -39.67814 D20
21 57.20705 2.899 1.49710 81.6
22 * 32.37479 3.000
23 49.86745 5.000 1.80 400 46.6
24 60.00000 18.298
25 0.00000 2.000 1.51680 63.9
26 0.00000 2.000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -81.49
Second lens group 6 52.84
Third lens group 21 -301.65

  In the optical system OL2, the 14th surface and the 22nd surface are formed in an aspherical shape. Table 6 below shows the aspheric data, that is, the values of the conic constant K and the aspheric constants A4 to A10.

(Table 6)
[Aspherical data]
Surface K A4 A6 A8 A10
14 -5.09240e + 00 -1.44908e-05 -5.86467e-09 -9.70725e-12 3.11615e-14
22 1.74910e + 00 -1.53739e-06 -3.80710e-09 1.72799e-12 -6.57323e-15

  In the optical system OL2, the axial air distance D5 between the first lens group G1 and the second lens group G2 and the axial air distance D20 between the second lens group G2 and the third lens group G3 are as described above. However, it changes upon focusing. Table 7 below shows variable intervals in an infinitely focused object state and a close-in focused state.

(Table 7)
[Variable interval data]
Infinity Closest D0 ∞ 140.50
β − -0.2436
f 36.00 −
D5 12.000 1.118
D20 0.500 11.382

  Table 8 below shows values corresponding to the conditional expressions in the optical system OL2. In the second embodiment, the negative meniscus lens L11 corresponds to the first lens, and the biconcave negative lens L12 corresponds to the second lens. The second lens group G2 corresponds to the focusing lens group.

(Table 8)
[Conditional expression values]
(1) ff / f = 1.47
(2) 1 / re = 0.02
(3) (r2 + r3) / (r2-r3) = − 0.41
(4) Fno = 1.25

  Thus, the optical system OL2 satisfies all the conditional expressions (1) to (4).

  FIG. 4 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, a lateral chromatic aberration diagram, and a lateral aberration diagram of the optical system OL2 in an infinitely focused state and a close-up focused state. From these aberration diagrams, it can be seen that in the optical system OL2, various aberrations are satisfactorily corrected from the infinite object focusing state to the closest focusing state.

[Third embodiment]
FIG. 5 is a diagram illustrating a configuration of the optical system OL3 according to the third example. The optical system OL3 includes, 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 having a negative refractive power, It is composed of

  In the optical system OL3, in order from the object side, the first lens group G1 includes a negative meniscus lens L11 having a convex surface facing the object side, a biconcave negative lens L12, and a positive meniscus lens L13 having a convex surface facing the object side. It is composed of a cemented negative lens. The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, and a cemented positive lens in which a biconvex positive lens L23 and a biconcave negative lens L24 are cemented. A positive lens L25 having a biconvex lens shape in which the lens surface on the object side is formed in an aspheric shape, a cemented negative lens in which a biconcave negative lens L26 and a positive meniscus lens L27 having a convex surface facing the object side are cemented, and both It is composed of a convex positive lens L28. The third lens group G3 includes, in order from the object side, a negative lens L31 having a meniscus lens shape with a convex surface facing the object side, the lens surface on the image side formed in an aspheric shape, and a convex surface facing the object side. It consists of a positive meniscus lens L32 (with the concave surface facing the image side). The aperture stop S is an image side of a cemented positive lens in which the biconvex positive lens L23 and the biconcave negative lens L24 in the second lens group G2 are cemented (between the biconcave negative lens L24 and the aspherical positive lens L25). Is arranged. A filter group FL is disposed between the optical system OL3 and the image plane I.

  In the optical system OL3, focusing from infinity to the closest object point is performed by moving the second lens group G2 to the object side.

  Table 9 below lists values of specifications of the optical system OL3.

(Table 9) Third Example [Overall Specifications]
f = 36.00
FNo = 1.26
ω = 31.0
Y = 20.94
TL = 159.500
BF = 24.982
BF (air equivalent length) = 24.300

[Lens data]
m r d nd νd
Object ∞
1 56.34034 3.000 1.58913 61.2
2 29.51320 30.470
3 -80.37066 2.200 1.49782 82.6
4 53.53185 22.517 1.85026 32.4
5 105.06163 D5
6 101.38502 12.057 1.43700 95.1
7 -50.69927 0.200
8 48.33234 4.415 1.80 400 46.6
9 78.64722 0.000
10 36.84443 10.000 1.80 400 46.6
11 -455.49991 1.800 1.78472 25.6
12 33.41670 6.000
13 0.00000 4.700 Aperture stop S
14 * 86.31951 3.000 1.58913 61.2
15 -330.60152 1.500
16 -69.41237 1.500 1.62004 36.4
17 29.37490 3.355 1.49782 82.6
18 45.67496 1.600
19 47.14 360 7.652 1.80 400 46.6
20 -44.02788 D20
21 322.20199 1.600 1.49710 81.6
22 * 28.00000 3.000
23 43.29099 3.500 1.80 400 46.6
24 60.00000 20.982
25 0.00000 2.000 1.51680 63.9
26 0.00000 2.000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -50.84
Second lens group 6 39.00
Third lens group 21 -93.61

  In this optical system OL3, the 14th surface and the 22nd surface are formed in an aspherical shape. Table 10 below shows the aspheric data, that is, the values of the conic constant K and the aspheric constants A4 to A10.

(Table 10)
[Aspherical data]
Surface K A4 A6 A8 A10
14 -3.79400e-01 -1.01346e-05 -8.44430e-09 -1.58206e-11 2.71537e-14
22 1.72830e + 00 -1.06092e-06 -6.82637e-09 -1.83223e-11 1.00110e-14

  In the optical system OL3, the axial air distance D5 between the first lens group G1 and the second lens group G2 and the axial air distance D20 between the second lens group G2 and the third lens group G3 are as described above. However, it changes upon focusing. Table 11 below shows variable intervals in an infinitely focused object state and a close-in focused state.

(Table 11)
[Variable interval data]
Infinity Closest D0 ∞ 140.50
β − −0.2411
f 36.00 −
D5 9.954 1.095
D20 0.500 9.359

  Table 12 below shows values corresponding to the conditional expressions in the optical system OL3. In the third example, the negative meniscus lens L11 corresponds to the first lens, and the biconcave negative lens L12 corresponds to the second lens. The second lens group G2 corresponds to the focusing lens group.

(Table 12)
[Conditional expression values]
(1) ff / f = 1.08
(2) 1 / re = 0.02
(3) (r2 + r3) / (r2-r3) = − 0.46
(4) Fno = 1.26

  Thus, this optical system OL3 satisfies all the conditional expressions (1) to (4).

  FIG. 6 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, a chromatic aberration diagram, and a lateral aberration diagram of the optical system OL3 in the infinitely focused state and the close-up focused state. From these respective aberration diagrams, it can be seen that in the optical system OL3, various aberrations are satisfactorily corrected from the infinite object focusing state to the closest focusing state.

[Fourth embodiment]
FIG. 7 is a diagram illustrating a configuration of an optical system OL4 according to the fourth example. The optical system OL4 includes, 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 having a negative refractive power, It is composed of

  In the optical system OL4, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, a biconcave negative lens L12, and a positive meniscus lens L13 having a convex surface facing the object side. It is composed of a cemented negative lens. The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, and a cemented positive lens in which a biconvex positive lens L23 and a biconcave negative lens L24 are cemented. A negative lens L25 having a meniscus lens shape with a concave surface facing the object side, the object-side lens surface being formed in an aspheric shape, a cemented negative lens in which a biconcave negative lens L26 and a biconvex positive lens L27 are cemented, and biconvex The lens includes a positive lens L28 and a biconvex positive lens L29. The third lens group G3 includes a negative lens L31 having a biconcave lens shape in which an object-side lens surface and an image-side lens surface are formed in an aspheric shape. The aperture stop S is an image side of a cemented positive lens in which the biconvex positive lens L23 and the biconcave negative lens L24 in the second lens group G2 are cemented (between the biconcave negative lens L24 and the aspheric negative lens L25). Is arranged. A filter group FL is disposed between the optical system OL4 and the image plane I.

  In the optical system OL4, focusing from infinity to the closest object point is performed by moving the second lens group G2 to the object side.

  Table 13 below lists values of specifications of the optical system OL4.

(Table 13) Fourth Example [Overall Specifications]
f = 35.98
FNo = 1.27
ω = 31.8
Y = 21.64
TL = 163.947
BF = 24.606
BF (air equivalent length) = 23.924

[Lens data]
m r d nd νd
Object ∞
1 216.86600 1.152 1.58913 61.2
2 35.11157 15.690
3 -125.44233 1.176 1.49782 82.6
4 45.20690 4.381 1.83400 37.2
5 59.40289 D5
6 63.75781 9.160 1.43385 95.2
7 -648.64355 10.892
8 53.15512 9.759 1.80 400 46.6
9 2111.54700 10.028
10 62.88393 13.074 1.77250 49.6
11 -46.26170 1.803 1.79504 28.7
12 103.52264 6.003
13 0.00000 6.001 Aperture stop S
14 * -138.20036 2.515 1.58913 61.2
15 -3613.69650 3.274
16 -43.04113 1.500 1.60342 38.0
17 35.24270 11.340 1.49782 82.6
18 -40.21062 0.495
19 102.31995 9.383 1.49782 82.6
20 -48.33420 1.144
21 84.51525 7.893 1.80 400 46.6
22 -92.66154 D22
23 * -171.56086 1.410 1.49710 81.6
24 * 27.97393 20.606
25 0.00000 2.000 1.51680 63.9
26 0.00000 2.000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -36.59
Second lens group 6 138.34
Third lens group 23 -48.27

  In this optical system OL4, the 14th surface, the 23rd surface and the 24th surface are formed in an aspherical shape. Table 14 below shows the aspheric data, that is, the values of the conic constant K and the aspheric constants A4 to A10.

(Table 14)
[Aspherical data]
Surface K A4 A6 A8 A10
14 2.54314e + 01 -1.41995e-05 -4.97141e-09 -1.06303e-11 4.20381e-14
23 -5.45042e + 01 -4.90431e-06 1.58151e-08 -3.00219e-11 2.33168e-14
24 4.00700e-01 1.24797e-06 2.04323e-08 -2.36678e-11 4.57415e-14

  In the optical system OL4, the axial air distance D5 between the first lens group G1 and the second lens group G2 and the axial air distance D20 between the second lens group G2 and the third lens group G3 are as described above. However, it changes upon focusing. Table 15 below shows the variable intervals in the infinitely focused object state and the closest focused state.

(Table 15)
[Variable interval data]
Infinity Closest D0 ∞ 136.05
β − −0.2128
f 35.98 −
D5 8.111 1.785
D22 3.158 9.483

  Table 16 below shows values corresponding to the conditional expressions in the optical system OL4. In the fourth example, the negative meniscus lens L11 corresponds to the first lens, and the biconcave negative lens L12 corresponds to the second lens. The second lens group G2 corresponds to the focusing lens group.

(Table 16)
[Conditional expression values]
(1) ff / f = 3.84
(2) 1 / re = 0.04
(3) (r2 + r3) / (r2-r3) = − 0.56
(4) Fno = 1.27

  Thus, this optical system OL4 satisfies all the conditional expressions (1) to (4).

  FIG. 8 shows a spherical aberration diagram, an astigmatism diagram, a distortion aberration diagram, a lateral chromatic aberration diagram, and a lateral aberration diagram of the optical system OL4 in the infinitely focused state and the closest focused state. From these aberration diagrams, it can be seen that in the optical system OL4, various aberrations are satisfactorily corrected from the infinite object focusing state to the closest focusing state.

[Fifth embodiment]
FIG. 9 is a diagram illustrating a configuration of an optical system OL5 according to the fifth example. The optical system OL5 includes, 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 having a positive refractive power, It is composed of

  In the optical system OL5, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface directed toward the object side, and a cemented positive lens in which a biconcave negative lens L12 and a biconvex positive lens L13 are cemented. It consists of The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, a positive meniscus lens L23 having a convex surface facing the object side, and a convex surface facing the object side. A cemented negative lens in which the negative meniscus lens L24 is cemented, a biconcave negative lens L25 in which the object-side lens surface is formed in an aspherical shape, and a cemented lens in which the biconcave negative lens L26 and the biconvex positive lens L27 are cemented. The lens includes a negative lens and a biconvex positive lens L28. The third lens group G3 includes, in order from the object side, a negative lens L31 having a meniscus lens shape with a convex surface facing the object side, the lens surface on the image side formed in an aspheric shape, and a convex surface facing the object side. The positive meniscus lens L32 is used. The aperture stop S is disposed on the image side (between the negative meniscus lens L24 and the aspheric negative lens L25) of the cemented negative lens in which the positive meniscus lens L23 and the negative meniscus lens L24 in the second lens group G2 are cemented. ing. A filter group FL is disposed between the optical system OL5 and the image plane I.

  In the optical system OL5, focusing from infinity to the closest object point is performed by moving the second lens group G2 to the object side.

  Table 17 below provides values of specifications of the optical system OL5.

(Table 17) Fifth Example [Overall Specifications]
f = 36.00
FNo = 1.19
ω = 31.0
Y = 20.94
TL = 166.000
BF = 16.500
BF (air equivalent length) = 15.819

[Lens data]
m r d nd νd
Object ∞
1 226.77416 2.500 1.58913 61.2
2 42.56008 24.089
3 -99.20602 3.000 1.49782 82.6
4 179.50875 23.995 1.85026 32.4
5 -178.38716 D5
6 54.76646 14.389 1.43700 95.1
7 -127.19541 0.100
8 45.69050 4.785 1.80 400 46.6
9 72.53249 0.200
10 32.89215 8.503 1.80400 46.6
11 596.69382 2.619 1.78472 25.6
12 21.89256 7.575
13 0.00000 4.489 Aperture stop S
14 * -784.67328 2.500 1.58913 61.2
15 115.72650 3.693
16 -41.72563 2.000 1.62004 36.4
17 71.83778 4.815 1.49782 82.6
18 -100.00000 0.200
19 122.20408 8.077 1.80400 46.6
20 -39.42496 D20
21 42.11001 6.940 1.49710 81.6
22 * 33.71561 3.688
23 56.46265 5.000 1.80 400 46.6
24 80.37069 12.500
25 0.00000 2.000 1.51680 63.9
26 0.00000 2.000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length First lens group 1 -127.24
Second lens group 6 58.67
Third lens group 21 450.00

  In this optical system OL5, the 14th surface and the 22nd surface are formed in an aspherical shape. Table 18 below shows the aspheric data, that is, the values of the conical constant K and the aspheric constants A4 to A10.

(Table 18)
[Aspherical data]
Surface K A4 A6 A8 A10
14 1.10000e + 01 -1.30087e-05 -9.53891e-09 -3.89996e-11 6.10828e-14
22 1.93340e + 00 -1.43816e-06 -3.97575e-09 -9.29548e-13 -7.64725e-15

  In the optical system OL5, the axial air distance D5 between the first lens group G1 and the second lens group G2 and the axial air distance D20 between the second lens group G2 and the third lens group G3 are as described above. However, it changes upon focusing. Table 19 below shows the variable intervals in the infinitely focused object state and the closest focused state.

(Table 19)
[Variable interval data]
Infinity Closest D0 ∞ 134.00
β − −0.2566
f 36.00 −
D5 16.143 1.800
D20 0.200 14.543

  Table 20 below shows values corresponding to the conditional expressions in the optical system OL5. In the fifth example, the negative meniscus lens L11 corresponds to the first lens, and the biconcave negative lens L12 corresponds to the second lens. The second lens group G2 corresponds to the focusing lens group.

(Table 20)
[Conditional expression values]
(1) ff / f = 1.63
(2) 1 / re = 0.01
(3) (r2 + r3) / (r2-r3) =-0.40
(4) Fno = 1.19

  Thus, this optical system OL5 satisfies all the conditional expressions (1) to (4).

  FIG. 10 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, a chromatic aberration diagram, and a lateral aberration diagram of the optical system OL5 in the infinitely focused state and the close-up focused state. From these respective aberration diagrams, it can be seen that in the optical system OL5, various aberrations are satisfactorily corrected from the infinite object focusing state to the closest focusing state.

[Sixth embodiment]
FIG. 11 is a diagram illustrating a configuration of an optical system OL6 according to the sixth example. The optical system OL6 includes, 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 having a negative refractive power, It is composed of

  In the optical system OL6, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a convex surface directed toward the object side, a biconcave negative lens L12, and a biconvex positive lens L13. The second lens group G2 includes, in order from the object side, a biconvex positive lens L21, a positive meniscus lens L22 having a convex surface facing the object side, and a cemented positive lens in which a biconvex positive lens L23 and a biconcave negative lens L24 are cemented. A negative lens L25 having a biconcave lens shape having an aspheric lens surface on the object side, a negative meniscus lens L26 having a convex surface facing the object side, and a positive meniscus lens L27 having a convex surface facing the object side. The lens includes a negative lens and a biconvex positive lens L28. The third lens group G3 includes, in order from the object side, a negative lens L31 having a meniscus lens shape with a convex surface facing the object side, the lens surface on the image side formed in an aspheric shape, and a convex surface facing the object side. The negative meniscus lens L32. The aperture stop S is located on the image side (between the biconcave negative lens L24 and the aspheric negative lens L25) of the cemented positive lens in which the biconvex positive lens L23 and the biconcave negative L24 in the second lens group G2 are cemented. Has been placed. A filter group FL is disposed between the optical system OL6 and the image plane I.

  In the optical system OL6, focusing from infinity to the closest object point is performed by moving the second lens group G2 to the object side.

  Table 21 below provides values of specifications of the optical system OL6.

(Table 21) Sixth Example [Overall specifications]
f = 35.97
FNo = 1.26
ω = 31.0
Y = 21.14
TL = 163.808
BF = 25.103
BF (air equivalent length) = 24.422

[Lens data]
m r d nd νd
Object ∞
1 227.65237 1.805 1.58913 61.2
2 35.11588 18.920
3 -73.99938 2.201 1.49782 82.6
4 118.34909 4.756
5 162.85190 4.797 1.85026 32.4
6 -1978.57950 D6
7 66.32474 14.757 1.43700 95.1
8 -120.19105 8.963
9 64.08024 7.209 1.80 400 46.6
10 425.17412 9.324
11 57.89484 10.469 1.80 400 46.6
12 -59.86202 2.199 1.78472 25.6
13 56.67080 4.075
14 0.00000 2.872 Aperture stop S
15 * -278.52828 2.500 1.58913 61.2
16 192.66799 1.098
17 905.99129 2.000 1.62004 36.4
18 23.92094 5.794 1.49782 82.6
19 70.90966 4.545
20 71.05101 8.313 1.80 400 46.6
21 -41.80902 D21
22 51.83072 1.999 1.49710 81.6
23 * 36.76981 2.686
24 58.71193 4.008 1.80 400 46.6
25 39.15432 22.103
26 0.00000 2.000 1.51680 63.9
27 0.00000 1.000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 -50.02
Second lens group 7 57.06
Third lens group 22 -98.76

  In this optical system OL6, the 15th surface and the 23rd surface are formed in an aspherical shape. Table 22 below shows the aspheric data, that is, the values of the conic constant K and the aspheric constants A4 to A10.

(Table 22)
[Aspherical data]
Surface K A4 A6 A8 A10
15 -7.63800e-01 -1.28105e-05 -5.41102e-09 3.98672e-12 4.03529e-15
23 1.04030e + 00 4.43461e-06 8.54853e-10 1.14308e-11 1.98808e-14

  In the optical system OL6, the axial air distance D6 between the first lens group G1 and the second lens group G2 and the axial air distance D21 between the second lens group G2 and the third lens group G3 are as described above. However, it changes upon focusing. Table 23 below shows variable intervals in an infinitely focused object state and a close-in focused state.

(Table 23)
[Variable interval data]
Infinity Closest D0 ∞ 136.19
β − −0.2521
f 35.97 −
D6 12.412 1.124
D21 1.001 12.288

  Table 24 below shows values corresponding to the conditional expressions in the optical system OL6. In the sixth example, the negative meniscus lens L11 corresponds to the first lens, and the biconcave negative lens L12 corresponds to the second lens. The second lens group G2 corresponds to the focusing lens group.

(Table 24)
[Conditional expression values]
(1) ff / f = 1.59
(2) 1 / re = 0.03
(3) (r2 + r3) / (r2-r3) = − 0.36
(4) Fno = 1.26

  Thus, this optical system OL6 satisfies all the conditional expressions (1) to (4).

  FIG. 12 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, a lateral chromatic aberration diagram, and a lateral aberration diagram of the optical system OL6 in an infinitely focused state and a close-up focused state. From these respective aberration diagrams, it can be seen that in the optical system OL6, various aberrations are satisfactorily corrected from the infinite object focusing state to the closest focusing state.

OL (OL1 to OL6) optical system G1 first lens group
G2 Second lens group (focusing lens group) G3 Third lens group S Aperture stop 1 Camera (optical equipment)

Claims (12)

From the object side,
A first lens group having negative refractive power;
A second lens group having a positive refractive power;
A third lens group,
The first lens group is in order from the object side.
A first lens that is a negative meniscus lens having a convex surface facing the object side;
A second lens having a concave surface facing the object side,
The image side lens surface of the most image side lens is a concave surface facing the image side,
At the time of focusing, the distance between the first lens group and the second lens group changes, and the distance between the second lens group and the third lens group changes,
An optical system characterized by satisfying the following formula.
0.50 <ff / f <20.00
However,
ff: Focal length of the lens group that moves during focusing f: Focal length of the entire system Having an aperture stop,
The optical system according to claim 1, wherein an image-side lens surface facing the aperture stop has an aspherical shape.   The optical system according to claim 2, wherein the aperture stop is disposed in the second lens group.   The optical system according to any one of claims 1 to 3, wherein the first lens group is fixed with respect to an image plane during zooming.   The optical system according to any one of claims 1 to 4, wherein the third lens group is fixed with respect to the image plane during zooming.   The optical system according to claim 1, wherein the third lens group has a negative refractive power.   The optical system according to claim 1, wherein the second lens group moves along an optical axis during zooming. The optical system according to claim 1, wherein a condition of the following formula is satisfied.
0.01 <1 / re <0.04
However,
re: radius of curvature of the image-side lens surface of the most image-side lens The optical system according to claim 1, wherein the condition of the following formula is satisfied.
−0.6 <(r2 + r3) / (r2−r3) <− 0.3
However,
r2: radius of curvature of the image side lens surface of the first lens r3: radius of curvature of the object side lens surface of the second lens The optical system according to claim 1, wherein the condition of the following formula is satisfied.
Fno <1.50
However,
Fno: F number   An optical apparatus comprising the optical system according to claim 1. In order from the object side, a manufacturing method of an optical system having a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group,
As the first lens group, in order from the object side, a first lens that is a negative meniscus lens having a convex surface facing the object side, and a second lens having a concave surface facing the object side are arranged,
On the most image side, a lens whose concave surface faces the image side is arranged on the image side,
At the time of focusing, the distance between the first lens group and the second lens group is changed, and the distance between the second lens group and the third lens group is changed,
A method of manufacturing an optical system, wherein the optical system is arranged so as to satisfy the condition of the following formula.
0.50 <ff / f <20.00
However,
ff: Focal length of the lens group that moves during focusing f: Focal length of the entire system