JP6331673B2 - Optical system, optical device - Google Patents

Description

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

  Conventionally, an 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).

JP 2011-81064 A

  However, the conventional optical system as described above has a problem that it is difficult to maintain high optical performance while reducing the weight and suppressing aberration fluctuation at the time of focusing.

  Therefore, the present invention has been made in view of the above problems, and provides an optical system, an optical device, and a method for manufacturing the optical system that are light in weight, suppress aberration fluctuations during focusing, and have excellent optical performance. For the purpose.

In order to solve the above problems, the present invention
In order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power are substantially three lens groups. Consists of
The first lens group includes, in order from the object side, a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power,
When focusing from an infinite object to a close object, the second lens group moves along the optical axis, and the interval between adjacent lens groups changes,
An optical system characterized by satisfying the following conditional expression is provided.
0.380 <f1 / f <0.526
0.800 <β23 <0.960
0.80 <fL1 / f <1.50
However,
f1: Focal length of the first lens group f: Focal length of the optical system β23: Composite lateral magnification of the second lens and the third lens when an object at infinity is in focus
fL1: Focal length of the first lens
The present invention also provides
In order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power are substantially three lens groups. Consists of
The first lens group includes, in order from the object side, a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power,
When focusing from an infinite object to a close object, the second lens group moves along the optical axis, and the interval between adjacent lens groups changes,
An optical system characterized by satisfying the following conditional expression is provided.
0.450 <f1 / f <0.526
0.600 <β23 <0.960
8.00 <| fL23 | / f
However,
f1: Focal length of the first lens group
f: Focal length of the optical system
β23: combined lateral magnification of the second lens and the third lens when focusing on an object at infinity
fL23: Composite focal length of the second lens and the third lens

The present invention also provides
An optical apparatus comprising the optical system is provided.

  According to the present invention, it is possible to provide an optical system, an optical device, and an optical system manufacturing method that achieve weight reduction, suppress aberration fluctuations during focusing, and have excellent optical performance.

FIG. 1 is a cross-sectional view showing the lens arrangement when focusing on an object at infinity in the optical system according to the first example of the present application. FIGS. 2A and 2B are graphs showing various aberrations when the optical system according to Example 1 of the present application is focused on an object at infinity and focused on a short distance object, respectively. FIG. 3 is a cross-sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the second example of the present application. FIGS. 4A and 4B are graphs showing various aberrations when the optical system according to Example 2 of the present application is focused on an object at infinity and focused on a short distance object, respectively. FIG. 5 is a diagram illustrating a configuration of a camera including the optical system of the present application. FIG. 6 is a diagram showing an outline of the manufacturing method of the optical system of the present application.

Hereinafter, the optical system, the optical device, and the method for manufacturing the optical system of the present application will be described.
The optical system of the present application includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, The first lens group includes a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power in order from the object side. At the time of focusing from an object to a short distance object, the second lens group moves along the optical axis and satisfies the following conditional expressions (1) and (2).
(1) 0.380 <f1 / f <0.526
(2) 0.600 <β23 <0.960
However,
f1: Focal length of the first lens group f: Focal length of the optical system β23: Composite lateral magnification of the second lens and the third lens when an object at infinity is in focus

  Conditional expression (1) defines an appropriate range of the ratio between the focal length of the first lens group and the focal length of the entire optical system of the present application. By satisfying conditional expression (1), the optical system of the present application can suppress weight variation and suppress aberration fluctuations when focusing on a short-distance object while preventing an increase in total length.

  If the corresponding value of the conditional expression (1) of the optical system of the present application exceeds the upper limit value, the refractive power of the first lens group decreases, and the total length of the optical system of the present application increases, which is not preferable. A configuration in which at least a part of the third lens group moves so as to include a component in a direction perpendicular to the optical axis in order to correct image blur caused by camera shake or the like in the optical system of the present application, that is, to prevent vibration; In this case, the refractive power of the third lens group becomes large, and the optical performance at the time of image stabilization is deteriorated. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (1) to 0.523.

  On the other hand, when the corresponding value of the conditional expression (1) of the optical system of the present application is below the lower limit value, the refractive power of the first lens group becomes large, and the fluctuations of the reference aberration and the chromatic aberration at the time of focusing on a short distance object become large. This is not preferable. Further, the refractive power of each of the first to third lenses in the first lens group increases, and the weight of the lens increases. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (1) to 0.450.

  Conditional expression (2) defines an appropriate range of the combined lateral magnification of the second lens and the third lens when an object at infinity is in focus. The optical system of the present application can satisfactorily correct spherical aberration, coma, field curvature, and chromatic aberration by satisfying conditional expression (2).

  When the corresponding value of the conditional expression (2) of the optical system of the present application exceeds the upper limit value, the declination angle between the zonal ray of the axial ray incident on the second lens and the optical axis is the ray after the third lens exits. It becomes smaller than the declination made by the optical axis and becomes a divergent ray. For this reason, the refractive power of the second lens and the third lens is increased, the fluctuation of the deflection angle of the light ray follows a convergent, divergent, and convergent path, and a reference aberration such as spherical aberration, coma aberration, curvature of field, etc. Since it will deteriorate, it is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (2) to 0.950.

  On the other hand, when the corresponding value of the conditional expression (2) of the optical system of the present application is lower than the lower limit value, the declination angle between the zonal ray of the axial ray incident on the second lens and the optical axis is The light beam is converged to be larger than the declination angle formed by the optical axis. Accordingly, the combined focal length is positive, the refractive power is reduced, and the ability to correct chromatic aberration is reduced. Therefore, the first lens must be arranged on the object side as much as possible. As a result, the diameter and weight of the first lens are increased. In order to secure the effect of the present application, it is more preferable to set the lower limit value of conditional expression (2) to 0.700. In order to secure the effect of the present application, it is more preferable to set the lower limit value of conditional expression (2) to 0.800.

  With the above configuration, it is possible to realize an optical system that achieves weight reduction, suppresses fluctuations in aberrations during focusing, and has excellent optical performance.

Moreover, it is desirable that the optical system of the present application satisfies the following conditional expression (3).
(3) 1.00 <| fL23 | / f
However,
fL23: Composite focal length of the second lens and the third lens f: Focal length of the optical system

  Conditional expression (3) defines an appropriate range of the ratio between the absolute value of the combined focal length of the second lens and the third lens and the focal length of the entire optical system of the present application. The optical system of the present application can satisfactorily correct spherical aberration, coma aberration, field curvature, and chromatic aberration by satisfying conditional expression (3).

  When the corresponding value of the conditional expression (3) of the optical system of the present application is below the lower limit value, the absolute value of the combined focal length of the second lens and the third lens becomes small, and standards for spherical aberration, coma aberration, field curvature, etc. Since aberrations are deteriorated, it is not preferable. Further, when “fL23” is a negative value and the corresponding value of the conditional expression (3) is lower than the lower limit value, the chromatic aberration is a combined negative lens component, which is overcorrected and the chromatic aberration of the positive lens component is reduced. It is necessary to supplement from other lenses. Further, when “fL23” is a positive value and the corresponding value of the conditional expression (3) is lower than the lower limit value, the chromatic aberration is as a combined positive lens component and is overcorrected, and the chromatic aberration of the negative lens component is reduced. It is necessary to supplement from other lenses. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (3) to 4.00. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (3) to 8.00. In order to further secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (3) to “<10000.00”.

Moreover, it is desirable that the optical system of the present application satisfies the following conditional expression (4).
(4) 0.70 <fL1 / f <1.50
However,
fL1: Focal length of the first lens f: Focal length of the optical system

  Conditional expression (4) defines an appropriate range of the ratio between the focal length of the first lens and the focal length of the entire optical system of the present application. By satisfying conditional expression (4), the optical system of the present application can satisfactorily correct various aberrations while preventing an increase in the overall length, and suppress a decrease in optical performance during focusing.

  When the corresponding value of the conditional expression (4) of the optical system of the present application exceeds the upper limit value, the refractive power of the second lens and the third lens following the first lens is increased, and the combined refractive power becomes negative refractive power. Since optical performance will fall, it is not preferable. In addition, the entire length of the optical system of the present application is not preferable. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) to 1.30. In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) to 1.10.

  On the other hand, if the corresponding value of conditional expression (4) of the optical system of the present application is below the lower limit, the first lens that is most effective for correcting chromatic aberration cannot be used effectively, and chromatic aberration is corrected by a lens other than the first lens. This is not preferable. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (4) to 0.80. In order to further secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (4) to 0.90.

In the optical system of the present application, the first lens group has one positive lens and one negative lens closer to the image side than the third lens, and is composed of a total of 5 or 6 lenses. desirable.
In the optical system of the present application, the second lens and the third lens in the first lens group may be bonded to form a cemented lens. Further, air may be interposed between the second lens and the third lens without bonding them.
Further, it is desirable that the optical system of the present application is configured to move so that at least a part of the third lens group includes a component in a direction orthogonal to the optical axis as a vibration-proof lens group.

In the optical system of the present application, the first lens group may have a protective filter glass on the most object side. In this case, the protective filter glass is a lens having substantially no refractive power, and preferably has a focal length of 500 mm or more. In particular, the optical system of the present application preferably has a negative meniscus shape in which the protective filter glass has a convex surface facing the object side. With this configuration, the ghost can be cut well.
The optical system of the present application is preferably used for a photographing lens having a focal length in terms of 35 mm of 380 to 420 mm, but this is not restrictive.

  The optical apparatus according to the present application includes the optical system having the above-described configuration. Thereby, it is possible to realize an optical device having an optical performance that is light in weight, suppresses aberration fluctuations during focusing, and has excellent optical performance.

The optical system manufacturing method of the present application includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. The first lens group has a first lens having a positive refractive power, a second lens having a positive refractive power, and a negative refractive power in order from the object side. The second lens group is moved along the optical axis at the time of focusing from an object at infinity to a near object, and the following conditional expressions (1) and (2) It is characterized by satisfying. As a result, it is possible to manufacture an optical system having an optical performance that is light in weight, suppresses aberration fluctuations during focusing, and has excellent optical performance.
(1) 0.380 <f1 / f <0.526
(2) 0.600 <β23 <0.960
However,
f1: Focal length of the first lens group f: Focal length of the optical system β23: Composite lateral magnification of the second lens and the third lens when an object at infinity is in focus

Hereinafter, optical systems according to numerical examples of the present application will be described with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a cross-sectional view showing the lens arrangement when focusing on an object at infinity in the optical system according to the first example of the present application.
The optical system according to this example 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 having a positive refractive power. And G3. An aperture stop S is provided near the object side of the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, a biconvex positive lens L12, a biconcave negative lens L13, and a positive meniscus lens L14 having a convex surface facing the object side. And a negative meniscus lens L15 having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a cemented lens of a biconvex positive lens L21 and a biconcave negative lens L22.

  The third lens group G3 includes, in order from the object side, a cemented lens of a biconvex positive lens L31 and a negative meniscus lens L32 having a convex surface facing the image side, a biconvex positive lens L33, and a biconcave negative lens. The lens includes a cemented lens with the lens L34, a biconcave negative lens L35, a biconvex positive lens L36, and a cemented lens with a biconvex positive lens L37 and a biconcave negative lens L38.

  Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object. At this time, the position of the aperture stop S is fixed.

Table 1 below lists values of specifications of the optical system according to the present example.
In Table 1, f represents the focal length, and Bf represents the back focus (distance on the optical axis between the filter FL and the image plane I).
In [Surface data], the surface number is the order of the optical surfaces counted from the object side, r is the radius of curvature, d is the surface interval (the interval between the nth surface (n is an integer) and the n + 1th surface), and nd is The refractive index for d-line (wavelength 587.6 nm) and νd indicate the Abbe number for d-line (wavelength 587.6 nm), respectively. Further, the object plane indicates the object plane, the variable indicates the variable plane spacing, the stop S indicates the aperture stop S, and the image plane indicates the image plane I. The radius of curvature r = ∞ indicates a plane. Further, the description of the refractive index nd of air = 1.000000 is omitted.

In [various data], FNO is the F number, 2ω is the angle of view (unit is “°”), Y is the image height, TL is the total length of the optical system according to the present embodiment (light from the first surface to the image surface I). (Distance on the axis), dn indicates a variable distance between the nth surface and the (n + 1) th surface, respectively. D0 represents the distance from the object to the first surface.
[Lens Group Data] indicates the start surface and focal length of each lens group.
[Conditional Expression Corresponding Value] indicates the corresponding value of each conditional expression of the optical system according to the present example.

Here, the focal length f, the radius of curvature r, and other length units listed in Table 1 are generally “mm”. However, the optical system is not limited to this because an equivalent optical performance can be obtained even when proportionally enlarged or proportionally reduced.
It should be noted that the symbols in Table 1 described above are similarly used in the table of the second embodiment described later.

(Table 1) First Example
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 302.14500 16.85 1.487490 70.23
2 -439.42600 22.74
3 133.92100 23.10 1.433852 95.25
4 -348.06 100 0.13
5 -339.36700 4.30 1.654115 39.68
6 236.14600 29.16
7 86.12631 15.28 1.433852 95.25
8 453.19705 1.00
9 64.22992 6.00 1.487490 70.23
10 49.79096 Variable

11 34715.64768 6.72 1.808095 22.76
12 -144.21954 2.60 1.806100 40.73
13 113.05265 Variable

14 (Aperture S) ∞ 2.04

15 189.75235 8.07 1.772499 49.60
16 -52.45473 2.05 1.805181 25.42
17 -187.07175 7.19493
18 99.24296 4.48 1.846660 23.78
19 -66.09200 1.71 1.729157 54.68
20 52.13050 4.41
21 -85.48867 1.63 1.834807 42.71
22 98.25325 3.16912
23 239.50429 4.56 1.772499 49.60
24 -101.28666 10.16
25 57.14434 8.29 1.654115 39.68
26 -80.45881 1.91 1.808095 22.76
27 128.05547 5.29

28 ∞ 2.20 1.516330 61.14
29 ∞ Bf

Image plane ∞

[Various data]
f 392.03583
FNO 2.90849
2ω 6.31
Y 21.63
TL 371.860
Bf 64.31159

When focusing on an object at infinity When focusing on a near object d0 ∞ 11833.2398
d10 27.542 31.61252
d13 84.94299 80.87247

[Lens group data]
Group start surface f
1 1 204.000
2 11 -141.000
3 15 384.031

[Conditional expression values]
(1) f1 / f = 0.520
(2) β23 = 0.943
(3) | fL23 | /f=259.629
(4) fL1 / f = 0.944

FIGS. 2A and 2B are graphs showing various aberrations when the optical system according to Example 1 of the present application is focused on an object at infinity and focused on a short distance object, respectively.
In each aberration diagram, FNO is the F number, NA is the numerical aperture, Y is the image height, A is the half field angle (unit is “°”), and H0 is the object height (unit is “mm”). d represents the d-line (wavelength 587.6 nm), g represents the g-line (wavelength 435.8 nm), F represents the F-line (wavelength 486.1 nm), and C represents the C-line (wavelength 656.3 nm) aberration. In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the aberration diagrams of the second embodiment described later, the same reference numerals as in this embodiment are used.
From each aberration diagram, it can be seen that the optical system according to the present example has excellent imaging performance by properly correcting various aberrations when focusing on an object at infinity and focusing on a short distance object.

(Second embodiment)
FIG. 3 is a cross-sectional view showing the lens arrangement at the time of focusing on an object at infinity of the optical system according to the second example of the present application.
The optical system according to this example 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 having a positive refractive power. And G3. An aperture stop S is provided near the object side of the third lens group G3, and a filter FL is provided between the third lens group G3 and the image plane I.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, a biconvex positive lens L12, a biconcave negative lens L13, and a negative meniscus lens L14 having a convex surface facing the object side. And a positive meniscus lens L15 having a convex surface facing the object side.

  The second lens group G2 includes, in order from the object side, a biconcave negative lens L21, and a cemented lens of a positive meniscus lens L22 having a convex surface facing the image side and a biconcave negative lens L23.

  The third lens group G3 includes, in order from the object side, a biconvex positive lens L31, a negative meniscus lens L32 having a convex surface directed toward the image side, a biconvex positive lens L33, and a biconcave negative lens L34. And a biconvex positive lens L35.

Under the above configuration, in the optical system according to the present embodiment, the second lens group G2 is moved to the image side along the optical axis, thereby focusing from an object at infinity to a near object. At this time, the position of the aperture stop S is fixed.
Table 2 below lists values of specifications of the optical system according to the present example.

(Table 2) Second Example
[Surface data]
Surface number r d nd νd
Object ∞ ∞

1 209.14115 17.50 1.433843 95.27
2 -1073.44852 44.90
3 174.31781 18.00 1.433843 95.27
4 -405.00000 3.07
5 -363.67644 6.00 1.612660 44.46
6 360.68580 92.00
7 64.20083 4.00 1.794997 45.32
8 44.77971 16.00 1.497820 82.54
9 1030.28230 Variable

10 -701.18723 2.50 1.772499 49.68
11 90.06629 3.35
12 -272.30521 3.50 1.846679 23.83
13 -76.50824 2.40 1.518229 58.84
14 65.07236 Variable

15 (Aperture S) ∞ 1.50

16 8886.02258 6.00 1.487490 70.44
17 -57.39587 1.20
18 -67.18402 1.90 1.846679 23.83
19 -142.88620 2.00
20 4533.20909 3.50 1.846679 23.83
21 -297.57132 1.90 1.593190 67.94
22 174.48827 2.00
23 130.81019 3.50 1.772499 49.68
24 -385.74895 3.00
25 ∞ 1.50 1.516800 63.88
26 ∞ Bf

Image plane ∞

[Various data]
f 385.4708
FNO 2.84547
2ω 6.42
Y 21.63
TL 392.979
Bf 95.07718

When focusing on an object at infinity When focusing on a near object d0 ∞ 11705.085
d9 18.50291 21.34351
d14 38.17937 35.33878

[Lens group data]
Group start surface f
1 1 175.073
2 10 -59.179
3 16 135.150

[Conditional expression values]
(1) f1 / f = 0.454
(2) β23 = 0.872
(3) | fL23 | /f=8.712
(4) fL1 / f = 1.051

FIGS. 4A and 4B are graphs showing various aberrations when the optical system according to Example 2 of the present application is focused on an object at infinity and focused on a short distance object, respectively.
From each aberration diagram, it can be seen that the optical system according to the present example has excellent imaging performance by properly correcting various aberrations when focusing on an object at infinity and focusing on a short distance object.

  According to each of the above embodiments, it is possible to realize an optical system that achieves weight reduction, suppresses aberration fluctuations during focusing, and has excellent optical performance. In addition, each said Example has shown one specific example of this invention, and this invention is not limited to these. The following contents can be appropriately adopted as long as the optical performance of the optical system of the present application is not impaired.

  Although a three-group configuration is shown as a numerical example of the optical system of the present application, the present application is not limited to this, and an optical system of another group configuration (for example, the fourth group or the fifth group) can also be configured. Specifically, a configuration in which a lens or a lens group is added to the most object side or the most image side of the optical system of the present application may be used.

  Further, the optical system of the present application uses a part of a lens group, an entire lens group, or a plurality of lens groups as a focusing lens group in order to perform focusing from an object at infinity to a near object in the optical axis direction. It is good also as a structure moved to. In particular, it is preferable that at least a part of the second lens group is a focusing lens group. Such a focusing lens group can be applied to autofocus, and is also suitable for driving by an autofocus motor such as an ultrasonic motor.

  Further, in the optical system of the present application, either the entire lens group or a part thereof is moved as an anti-vibration lens group so as to include a component in a direction perpendicular to the optical axis, or an in-plane direction including the optical axis It can also be set as the structure which carries out anti-vibration by carrying out rotational movement (oscillation) to (F). In particular, in the optical system of the present application, it is preferable that at least a part of the third lens group is an anti-vibration lens group.

  The lens surface of the lens constituting the optical system of the present application may be a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, it is preferable because lens processing and assembly adjustment are easy, and deterioration of optical performance due to errors in lens 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 aspherical, any of aspherical surface by grinding, glass mold aspherical surface in which glass is molded into an aspherical shape, or composite aspherical surface in which resin provided on the glass surface is formed in an aspherical shape Good. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In the optical system of the present application, the aperture stop is preferably arranged in the vicinity of the object side of the third lens group, and the role may be substituted by a lens frame without providing a member as the aperture stop.

  Further, an antireflection film having a high transmittance in a wide wavelength range may be applied to the lens surface of the lens constituting the optical system of the present application. Thereby, flare and ghost can be reduced, and high optical performance with high contrast can be achieved.

Next, a camera equipped with the optical system of the present application will be described with reference to FIG.
FIG. 5 is a diagram illustrating a configuration of a camera including the optical system of the present application.
The camera 1 is a lens-interchangeable digital single-lens reflex camera provided with the optical system according to the first embodiment as the photographing lens 2.
In the present camera 1, light from an object (not shown) that is a subject is collected by the photographing lens 2 and imaged on the focusing screen 4 via the quick return mirror 3. The light imaged on the focusing screen 4 is reflected in the pentaprism 5 a plurality of times and guided to the eyepiece lens 6. Thus, the photographer can observe the subject image as an erect image through the eyepiece 6.

  When the release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light from the subject (not shown) reaches the image sensor 7. Thereby, the light from the subject is picked up by the image pickup device 7 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1.

  Here, as described above, the optical system according to the first example mounted on the camera 1 as the photographing lens 2 is light in weight, suppresses aberration fluctuation at the time of focusing, and has excellent optical performance. ing. That is, this camera 1 can suppress aberration fluctuations during focusing, and can realize high performance and light weight. Even if the camera having the optical system according to the second embodiment mounted as the taking lens 2 is configured, the same effect as the camera 1 can be obtained. Further, even when the optical system according to each of the above embodiments is mounted on a camera having a configuration that does not include the quick return mirror 3, the same effect as the camera 1 can be obtained.

Finally, the outline of the manufacturing method of the optical system of this application is demonstrated based on FIG.
FIG. 6 is a diagram showing an outline of the manufacturing method of the optical system of the present application.
The optical system manufacturing method shown in FIG. 6 includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power. A manufacturing method of an optical system having a lens group, which includes the following steps S1 to S3.

  Step S1: First to third lens groups are prepared, and the first lens group includes, in order from the object side, a first lens having a positive refractive power, a second lens having a positive refractive power, and negative refraction. A third lens having power. Then, each lens group is arranged in the lens barrel in order from the object side.

  Step S2: A known moving mechanism is provided on the lens barrel so that the second lens group moves along the optical axis when focusing from an object at infinity to an object at a short distance.

Step S3: The optical system is made to satisfy the following conditional expressions (1) and (2).
(1) 0.380 <f1 / f <0.526
(2) 0.600 <β23 <0.960
However,
f1: focal length of the first lens group f: focal length of the optical system β23: combined lateral magnification of the second lens and the third lens when an object at infinity is in focus

  According to such an optical system manufacturing method of the present application, it is possible to reduce the weight, suppress aberration fluctuations during focusing, and manufacture an optical system having excellent optical performance.

G1 First lens group G2 Second lens group G3 Third lens group FL Filter S Aperture stop I Image surface

Claims (5)

In order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power are substantially three lens groups. Consists of
The first lens group includes, in order from the object side, a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power,
When focusing from an infinite object to a close object, the second lens group moves along the optical axis, and the interval between adjacent lens groups changes,
An optical system satisfying the following conditional expression:
0.380 <f1 / f <0.526
0.800 <β23 <0.960
0.80 <fL1 / f <1.50
However,
f1: Focal length of the first lens group f: Focal length of the optical system β23: Composite lateral magnification of the second lens and the third lens when an object at infinity is in focus
fL1: Focal length of the first lens In order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, and the third lens group having a positive refractive power are substantially three lens groups. Consists of
The first lens group includes, in order from the object side, a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power,
When focusing from an infinite object to a close object, the second lens group moves along the optical axis, and the interval between adjacent lens groups changes,
An optical system satisfying the following conditional expression:
0.450 <f1 / f <0.526
0.600 <β23 <0.960
8.00 <| fL23 | / f
However,
f1: Focal length of the first lens group f: Focal length of the optical system β23: Composite lateral magnification of the second lens and the third lens when an object at infinity is in focus
fL23: Composite focal length of the second lens and the third lens The optical system according to claim 1, wherein the following conditional expression is satisfied.
1.00 <| fL23 | / f
However,
fL23: Composite focal length of the second lens and the third lens f: Focal length of the optical system The optical system according to claim 2 , wherein the following conditional expression is satisfied.
0.70 <fL1 / f <1.50
However,
fL1: Focal length of the first lens f: Focal length of the optical system An optical apparatus comprising the optical system according to any one of claims 1 to 4 .

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