WO2022215380A1

WO2022215380A1 - Optical system, optical device, and method for manufacturing optical system

Info

Publication number: WO2022215380A1
Application number: PCT/JP2022/007509
Authority: WO
Inventors: 壮基原田
Original assignee: 株式会社ニコン
Priority date: 2021-04-09
Filing date: 2022-02-24
Publication date: 2022-10-13
Also published as: CN116964503A; JPWO2022215380A1

Abstract

Provided are an optical system having a short optical total length, an optical device, and a method for manufacturing the optical system. An optical system OL comprises, in order from the object side, a front group GA, an aperture stop S, and a back group GB having positive refractive power, and satisfies the condition of the following expression. 0.100 < LA/LB < 0.400 where LA is the distance on an optical axis from a lens surface closest to the object side to a lens surface closest to the image side in the front group GA when focusing at infinity, and LB is the distance on the optical axis from a lens surface closest to the object side to a lens surface closest to the image side in the back group GB when focusing at infinity.

Description

Optical system, optical equipment, and method for manufacturing optical system

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

In recent years, there has been a demand for an optical system with a short overall optical length (see Patent Document 1, for example). However, Patent Literature 1 requires further improvement in optical performance.

JP 2013-195587 A

An optical system according to a first aspect of the present invention has, in order from the object side, a front group, a diaphragm, and a rear group having positive refractive power, and satisfies the following formula.
0.100 < LA/LB < 0.400
however,
LA: Distance on the optical axis from the most object-side lens surface of the front group to the most image-side lens surface when focusing at infinity LB: The distance from the most object-side lens surface of the rear group when focusing at infinity Distance on the optical axis to the lens surface on the image side

Further, in the method for manufacturing an optical system according to the first aspect of the present invention, the front group, the diaphragm, and the rear group having positive refractive power are arranged in order from the object side so as to satisfy the following formula. Deploy.
0.100 < LA/LB < 0.400
however,
LA: Distance on the optical axis from the most object-side lens surface of the front group to the most image-side lens surface when focusing at infinity LB: The distance from the most object-side lens surface of the rear group when focusing at infinity Distance on the optical axis to the lens surface on the image side

FIG. 3 is a cross-sectional view showing the lens configuration of the optical system according to the first example when focusing on infinity. 4A and 4B are various aberration diagrams of the optical system according to the first embodiment, in which (a) shows when focusing at infinity, and (b) shows when focusing at a short distance. FIG. 11 is a cross-sectional view showing the lens configuration of the optical system according to the second embodiment when focusing on infinity. 4A and 4B are various aberration diagrams of the optical system according to the second embodiment, in which (a) shows when focusing at infinity, and (b) shows when focusing at a short distance. FIG. 11 is a cross-sectional view showing the lens configuration of the optical system according to the third embodiment when focusing on infinity. 3A and 3B are various aberration diagrams of the optical system according to the third embodiment, in which (a) shows when focusing at infinity and (b) shows when focusing at a short distance; FIG. 12 is a cross-sectional view showing the lens configuration of the optical system according to the fourth embodiment when focusing on infinity. 4A and 4B are various aberration diagrams of the optical system according to the fourth embodiment, in which (a) shows when focusing at infinity, and (b) shows when focusing at a short distance. FIG. 12 is a cross-sectional view showing the lens configuration of the optical system according to the fifth embodiment when focusing on infinity. 10A and 10B are various aberration diagrams of the optical system according to the fifth embodiment, in which (a) shows when focusing at infinity, and (b) shows when focusing at a short distance. It is a cross-sectional view of a camera equipped with the optical system. 4 is a flow chart for explaining a method of manufacturing the optical system;

A preferred embodiment will be described below 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 front group GA, a diaphragm S, and a rear group GB having positive refractive power. . With this configuration, the total optical length of the optical system OL can be shortened while suppressing various aberrations.

The optical system OL according to this embodiment preferably satisfies the following conditional expression (1).

0.100 < LA/LB < 0.400 (1)
however,
LA: Distance on the optical axis from the most object side lens surface of the front group GA to the most image side lens surface when focusing on infinity LB: The most object side lens surface of the rear group GB when focusing on infinity to the lens surface closest to the image side on the optical axis

Conditional expression (1) is the length of the rear group GB of the optical system OL (the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the rear group GB) in the optical system OL when focusing on infinity. It defines the ratio of the length of the front group GA (distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side of the front group GA) to the length of the front group GA. By satisfying this conditional expression (1), the length of the rear group GB becomes longer than the length of the front group GA. Good field curvature and astigmatism correction can be realized in the system OL. In order to ensure the effect of conditional expression (1), it is more desirable to set the upper limit of conditional expression (1) to 0.350, more preferably 0.320. In order to ensure the effect of conditional expression (1), it is more desirable to set the lower limit of conditional expression (1) to 0.130, more preferably 0.150.

Further, it is desirable that the optical system OL according to this embodiment satisfy the following conditional expression (2).

0.070<LAS/LAB<0.300 (2)
however,
LAS: Distance on the optical axis from the most object side lens surface of the front group GA to the stop S when focusing on infinity LAB: Distance from the most object side lens surface of the front group GA to the rear group GB when focusing on infinity distance on the optical axis to the lens surface closest to the image side of

Conditional expression (2) is the length of the optical system OL when focusing on infinity (distance on the optical axis from the most object-side lens surface of the front group GA to the most image-side lens surface of the rear group GB) It defines the ratio of the length of the front group GA to the stop S (distance on the optical axis from the lens surface of the front group GA closest to the object side to the stop S) to the . By satisfying the conditional expression (2), the optical system closer to the object side than the stop S becomes shorter than the length of the optical system OL, so that the entrance pupil of the optical system OL approaches the object side. Field curvature, astigmatism, and distortion can be corrected. In order to ensure the effect of conditional expression (2), it is more desirable to set the upper limit of conditional expression (2) to 0.280, more preferably 0.260. In order to ensure the effect of conditional expression (2), it is more desirable to set the lower limit of conditional expression (2) to 0.100, more preferably 0.130.

In addition, in the optical system OL according to this embodiment, it is desirable that the rear group GB have a negative lens NR that satisfies conditional expression (3) shown below.

0.000 < LNRL/LB < 0.500 (3)
however,
LB: Distance on the optical axis from the most object-side lens surface of the rear group GB to the most image-side lens surface when focusing at infinity LNRL: From the image-side lens surface of the negative lens NR when focusing at infinity Distance on the optical axis to the lens surface closest to the image side in the rear group GB

Conditional expression (3) defines the ratio of the length (distance on the optical axis) from the image-side lens surface of the negative lens NR to the most image-side lens surface of the rear group GB with respect to the length of the rear group GB. It is. By satisfying conditional expression (3), the negative lens NR is arranged on the image side of the rear group GB, i.e., near the image plane I. The total optical length of the optical system OL can be shortened while satisfactorily suppressing aberrations. In order to ensure the effect of conditional expression (3), it is more desirable to set the upper limit of conditional expression (3) to 0.450, more preferably 0.400, 0.360, and 0.320. In order to ensure the effect of conditional expression (3), it is more desirable to set the lower limit of conditional expression (3) to 0.070, more preferably 0.150.

Also, the negative lens NR preferably satisfies the following conditional expression (4).

0.800<R2NR/Bfa<3.000 (4)
however,
R2NR: Curvature radius of the image-side lens surface of the negative lens NR Bfa: Back focus of the optical system OL during focusing at infinity (air conversion length)

Conditional expression (4) defines the ratio of the radius of curvature of the image-side lens surface of the negative lens NR to the back focus of the optical system OL. If the negative lens NR that satisfies the conditional expression (3) and is arranged near the image plane I satisfies the conditional expression (4), it is possible to realize good correction of curvature of field, astigmatism, and distortion. . In order to ensure the effect of conditional expression (4), it is more desirable to set the upper limit of conditional expression (4) to 2.700, more preferably 2.400. In order to ensure the effect of conditional expression (4), it is more desirable to set the lower limit of conditional expression (4) to 0.850, more preferably 0.900.

In addition, in the optical system OL according to this embodiment, it is desirable that the rear group GB have a negative lens NF that satisfies conditional expression (5) shown below.

0.600 < LNFL/LB ≤ 1.000 (5)
however,
LB: Distance on the optical axis from the most object side lens surface of the rear group GB to the most image side lens surface when focusing at infinity LNFL: From the object side lens surface of the negative lens NF when focusing at infinity Distance on the optical axis to the lens surface closest to the image side in the rear group GB

Conditional expression (5) defines the ratio of the length (distance on the optical axis) from the object-side lens surface of the negative lens NF to the most image-side lens surface of the rear group GB with respect to the length of the rear group GB. It is. By satisfying the conditional expression (5), the negative lens NF is arranged on the object side of the rear group GB, that is, near the stop S, and various aberrations such as spherical aberration, axial chromatic aberration, and curvature of field are provided. can be satisfactorily suppressed, and the total optical length of the optical system OL can be shortened. In order to ensure the effect of conditional expression (5), it is more desirable to set the lower limit of conditional expression (5) to 0.700, more preferably 0.800.

Also, the negative lens NF preferably satisfies the following conditional expression (6).

-3.000 < R1NF/Bfa < -0.500 (6)
however,
R1NF: Curvature radius of the object-side lens surface of the negative lens NF Bfa: Back focus of the optical system OL during focusing at infinity (air conversion length)

Conditional expression (6) defines the ratio of the radius of curvature of the object-side lens surface of the negative lens NF to the back focus of the optical system OL. By satisfying the conditional expression (5) and the negative lens NF arranged near the diaphragm S and satisfying the conditional expression (6), it is possible to realize good correction of spherical aberration, curvature of field, and longitudinal chromatic aberration. In order to ensure the effect of conditional expression (6), it is more desirable to set the upper limit of conditional expression (6) to -0.600, more preferably -0.700. In order to ensure the effect of conditional expression (6), it is more desirable to set the lower limit of conditional expression (6) to -2.500, more preferably -2.000.

In the following description, when there are a plurality of negative lenses satisfying conditional expressions (3) and (4) in the rear group GB, the negative lens having the highest refractive power among these negative lenses is the negative lens NR. and When the rear group GB includes a plurality of negative lenses that satisfy the conditional expressions (5) and (6), the negative lens having the highest refractive power among the negative lenses is the negative lens NF.

In the optical system OL according to this embodiment, it is desirable that the negative lens NR and the negative lens NF satisfy conditional expression (7) shown below.

-0.800<(R1NF+R2NR)/(R1NF-R2NR)<0.800 (7)
however,
R1NF: radius of curvature of the object-side lens surface of the negative lens NF R2NR: radius of curvature of the image-side lens surface of the negative lens NR

Conditional expression (7) defines the shape factor from the object-side lens surface of the negative lens NF to the image-side lens surface of the negative lens NR. Satisfying conditional expression (7) means that the absolute values of the radii of curvature of the object-side lens surface of the negative lens NF and the image-side lens surface of the negative lens NR are close to each other. By satisfying conditional expression (7), the symmetry of the negative lens included in the rear group GB is enhanced, resulting in a balance of spherical aberration, curvature of field, axial chromatic aberration, astigmatism, distortion, and the like. good correction can be realized. In order to ensure the effect of conditional expression (7), it is more desirable to set the upper limit of conditional expression (7) to 0.600, more preferably 0.400 and 0.200. In order to ensure the effect of conditional expression (7), it is more desirable to set the lower limit of conditional expression (7) to -0.600, more preferably -0.400 and -0.200.

Also, in the optical system OL according to this embodiment, it is desirable that the negative lens NR and the negative lens NF satisfy conditional expression (8) shown below.

0.200 < fNF/fNR < 1.200 (8)
however,
fNF: focal length of negative lens NF fNR: focal length of negative lens NR

Conditional expression (8) defines the ratio of the focal length of the negative lens NF to the focal length of the negative lens NR. By satisfying the conditional expression (8), the refractive power of the negative lens NF and the refractive power of the negative lens NR are close to each other. As a result, well-balanced correction of curvature of field, astigmatism, distortion, and the like can be realized. In order to ensure the effect of conditional expression (8), it is more desirable to set the upper limit of conditional expression (8) to 1.000, more preferably 0.900 and 0.800. In order to ensure the effect of conditional expression (8), it is more desirable to set the lower limit of conditional expression (8) to 0.300, more preferably 0.400.

Also, in the optical system OL according to this embodiment, the rear group GB preferably has at least two positive lenses between the negative lens NF and the negative lens NR. By configuring in this way, it is possible to easily perform good aberration correction. In particular, spherical aberration, axial chromatic aberration, curvature of field, astigmatism, etc. can be satisfactorily corrected.

In the optical system OL according to this embodiment, the front group GA has at least one negative lens N1, and the rear group GB has at least one negative lens NL on the image side of the negative lens NR. , it is desirable to satisfy the following conditional expression (9).

0.300<fN1/fNL<1.200 (9)
however,
fN1: focal length of negative lens N1 fNL: focal length of negative lens NL

Conditional expression (9) defines the ratio of the focal length of the negative lens N1 included in the front group GA to the focal length of the negative lens NL included in the rear group GB. Negative lenses that satisfy the conditional expression (9), that is, negative lenses N1 and NL having similar refractive powers are placed on the object side of the negative lens NF and the image side of the negative lens NR, and the negative lenses NF and NR are sandwiched. In the optical system as a whole, the symmetry of the negative lens becomes high, and as a result, it is possible to achieve well-balanced correction of curvature of field, astigmatism, distortion, and the like. In order to ensure the effect of conditional expression (9), it is more desirable to set the upper limit of conditional expression (9) to 1.100, more preferably 1.000 and 0.900. In order to ensure the effect of conditional expression (9), it is more desirable to set the lower limit of conditional expression (9) to 0.330, more preferably 0.360.

Further, in the optical system OL according to the present embodiment, the rear group GB has an aspherical lens in which at least one of the object-side lens surface and the image-side lens surface is formed with an aspherical surface. It is desirable to satisfy (10).

0.100<LASI/LAB<0.600 (10)
however,
LASI: Distance on the optical axis from the aspherical surface located closest to the image side in the rear group GB to the image plane when focused at infinity LAB: Lens closest to the object side in the front group GA when focused at infinity distance on the optical axis from the surface to the lens surface of the rear group GB closest to the image side

Conditional expression (10) defines the ratio of the length (distance on the optical axis) from the aspherical surface arranged closest to the image side to the image plane with respect to the length of the optical system OL. By satisfying the conditional expression (10), the aspherical surface located closest to the image side in the rear group GB is located near the image plane I, so that curvature of field, astigmatism, and distortion can be reduced satisfactorily. can be corrected. In order to ensure the effect of conditional expression (10), it is more desirable to set the upper limit of conditional expression (10) to 0.550, more preferably 0.500. In order to ensure the effect of conditional expression (10), it is more desirable to set the lower limit of conditional expression (10) to 0.200, more preferably 0.300.

Further, in the optical system OL according to the present embodiment, the rear group GB has an aspherical lens in which at least one of the object-side lens surface and the image-side lens surface is formed with an aspherical surface. It is desirable to satisfy (11).

0.000≦LASL/LAB<0.150 (11)
however,
LASL: Distance on the optical axis from the most image-side aspherical surface in the rear group GB to the most image-side lens surface of the rear group GB when focused on infinity LAB: Front when focused on infinity Distance on the optical axis from the most object side lens surface of the rear group GB to the most image side lens surface of the rear group GB

Conditional expression (11) defines the ratio of the length (distance on the optical axis) from the aspherical surface arranged closest to the image side to the surface of the rear group GB closest to the image side with respect to the length of the optical system OL. is. By satisfying the conditional expression (11), the aspherical surface located closest to the image side in the rear group GB is located near the image plane I, so that curvature of field, astigmatism, and distortion can be reduced satisfactorily. can be corrected. In order to ensure the effect of conditional expression (11), it is more desirable to set the upper limit of conditional expression (11) to 0.120, more preferably 0.100. In order to ensure the effect of conditional expression (11), it is more desirable to set the lower limit of conditional expression (11) to 0.007.

Further, it is desirable that the optical system OL according to this embodiment satisfy the following conditional expression (12).

0.800<fB/f<1.600 (12)
however,
fB: focal length of the rear group GB when focusing on infinity f: focal length of the entire optical system OL when focusing on infinity

Conditional expression (12) defines the ratio of the focal length of the rear group GB to the focal length of the entire system. By satisfying conditional expression (12), the total optical length of the optical system OL can be shortened while various aberrations such as spherical aberration, coma, curvature of field, and astigmatism are satisfactorily suppressed. In order to ensure the effect of conditional expression (12), it is more desirable to set the upper limit of conditional expression (12) to 1.500, more preferably 1.400. In order to ensure the effect of conditional expression (12), it is more desirable to set the lower limit of conditional expression (12) to 0.900, more preferably 0.950.

In addition, the conditions and configurations described above exhibit the effects described above, and are not limited to those that satisfy all the conditions and configurations. It is possible to obtain the above-described effects even if the conditions or combinations of the above conditions are satisfied.

Next, a camera, which is an optical device equipped with the optical system OL according to this embodiment, will be described with reference to FIG. This camera 1 is a lens interchangeable so-called mirrorless camera that includes an optical system OL according to the present embodiment as a photographing lens 2 . In this camera 1, light from an unillustrated object (subject) is condensed by a photographing lens 2 and passes through an unillustrated OLPF (Optical low pass filter) on the imaging surface of the imaging unit 3. to form an image of the subject. Then, a subject image is photoelectrically converted by a photoelectric conversion element provided in the imaging unit 3 to generate an image of the subject. This image is displayed on an EVF (Electronic view finder) 4 provided in the camera 1 . This allows the photographer to observe the subject through the EVF4.

Also, 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 manner, the photographer can photograph the subject with the camera 1. FIG. In this embodiment, an example of a mirrorless camera has been described, but the optical system OL according to this embodiment is installed in a single-lens reflex camera that has a quick return mirror in the camera body and observes the subject through the finder optical system. Even in this case, the same effect as the camera 1 can be obtained.

The outline of the method for manufacturing the optical system OL according to this embodiment will be described below with reference to FIG.

First, each lens is arranged to prepare the front group GA, the diaphragm S, and the rear group GB of the optical system OL (step S100). Then, the front group GA, the diaphragm S, and the rear group GB are arranged so as to satisfy the conditions of a predetermined conditional expression (for example, conditional expression (1) described above) (step S200).

With the configuration as described above, it is possible to provide an optical system OL with a short overall optical length in which various aberrations are satisfactorily suppressed, an optical device having this optical system OL, and a method for manufacturing the optical system OL.

Each embodiment of the present application will be described below based on the drawings. 1, 3, 5, 7 and 9 are sectional views showing the configuration and refractive power distribution of the optical system OL (OL1 to OL5) according to each embodiment.

In each embodiment, the aspherical surface has a height y in the direction perpendicular to the optical axis, and the distance along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface (amount of sag) 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 n-th order aspherical surface coefficient. . In the following examples, "en" indicates "×10 ^-n ".

S(y)=(y ² /r)/{1+(1−K×y ² /r ² ) ^1/2 }
+A4×y4+A6× ^y6 +A8× ^y8 +A10× ^y10 +A12× ^y12 ⁽ a)

Also, in each embodiment, the second-order aspheric coefficient A2 is zero.

In addition, each of the following examples shows one specific example of the present invention, and the present invention is not limited to these.

[First embodiment]
FIG. 1 is a diagram showing the configuration of an optical system OL1 according to the first example. This optical system OL1 is composed of, in order from the object side, a front group GA, an aperture stop S, and a rear group GB having positive refractive power. The front group GA is composed of a first lens group G1 having negative refractive power, and the rear group GB is composed of, in order from the object side, a second lens group G2 having positive refractive power and a negative refractive power. and a third lens group G3.

The first lens group G1 is composed of, 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 biconvex positive lens L13. The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side, a cemented negative lens in which a biconcave negative lens L22 and a biconvex positive lens L23 are cemented together, and a biconvex positive lens L24. , a cemented positive lens in which a biconvex positive lens L25 and a biconcave negative lens L26 are cemented; It is composed of a shaped aspherical positive lens L27. The third lens group G3 is composed of a biconcave negative lens L31. An optical filter FL is arranged between the rear group GB and the image plane I.

In this optical system OL1, the negative meniscus lens L11 is the negative lens N1, the biconcave negative lens L22 is the negative lens NF, the biconcave negative lens L26 is the negative lens NR, and the biconcave negative lens L31 is the negative lens NL. is.

Also, in this optical system OL1, focusing from infinity to a short distance object is performed by moving the second lens group G2 toward the object.

Table 1 below lists the values of the specifications of the optical system OL1. In the overall specifications of Table 1, f is the focal length of the entire optical system OL1, FNO is the F number, ω is the half angle of view [°], Y is the maximum image height, TL is the total length, and BF is the back Represents the focus value. Here, the total length TL indicates the distance (actual distance) on the optical axis from the lens surface (first surface) closest to the object side to the image plane I at infinity focus. The back focus BF indicates the distance (actual distance and air conversion length) on the optical axis from the lens surface (21st surface) closest to the image plane to the image plane I when focusing on infinity. In addition, the first column m in the lens data indicates the order (surface number) of the lens surfaces from the object side along the direction in which light rays travel, the second column r indicates the radius of curvature of each lens surface, and the third column d is the distance (surface distance) on the optical axis from each optical surface to the next optical surface, and the fourth column nd and fifth column νd are the refractive index and Abbe number for the d-line (λ = 587.6 nm). is shown. A radius of curvature of 0.00000 indicates a plane, and the refractive index of air of 1.00000 is omitted. The lens group focal length indicates the surface number of the starting surface of each lens group and the focal length.

Here, the focal length f, radius of curvature r, surface spacing d, and other lengths listed in all the specifications below are generally expressed in units of "mm". The same optical performance can be obtained even if the size is reduced, so the size is not limited to this. Further, the explanation of these symbols and the explanation of the specification table are the same in the following embodiments.

(Table 1) First embodiment [overall specifications]
f 18.66
FNO 1.88
ω [°] 39.7
Y 14.50
TL 50.948
BF 14.138
BF (air conversion length) 13.593

[Lens data]
m r d nd νd
object ∞
1 30.88470 0.800 1.51680 63.9
2 10.13359 3.253
3 -19.53734 0.800 1.51680 63.9
4 61.77677 0.200
5 28.44452 1.786 1.88300 40.7
6 -44.24172 2.161
7 0.00000 D7 Aperture diaphragm S
8 25.03904 1.406 1.67790 55.4
9 71.55004 2.029
10 -17.74480 0.800 1.73800 32.3
11 17.70671 4.036 1.72916 54.6
12 -57.28104 0.200
13 44.58187 4.546 1.77250 49.6
14 -26.47919 0.200
15 24.68842 4.741 1.77250 49.6
16 -41.92740 0.800 1.73800 32.3
17 28.22236 3.986
18* -340.64532 1.217 1.53113 55.8
19* -28.19344 D19
20 -49.63870 0.800 1.51680 63.9
21 102.44757 11.540
22 0.00000 1.600 1.51680 64.1
23 0.00000 0.998
Image plane ∞

[Lens group focal length]
Lens group Starting surface Focal length 1st lens group G1 1 -76.08
Second lens group G2 8 17.43
3rd lens group G3 20 -64.58

In this optical system OL1, the 18th and 19th lens surfaces are formed in an aspherical shape. Table 2 below shows the surface number m and the data of the aspherical surface, that is, the values of the conic constant K and the aspherical constants A4 to A12.

(Table 2)
[Aspheric data]
18th surface K=1.00000e+00
A4 = -1.34226e-04 A6 = 4.64940e-06 A8 = -3.86730e-08
A10 = 0.00000e+00 A12 = 0.00000e+00
19th surface K=1.00000e+00
A4 = -2.70832e-06 A6 = 5.26276e-06 A8 = -3.87365e-08
A10 = 0.00000e+00 A12 = 0.00000e+00

In this optical system OL1, the axial air gap D7 between the first lens group G1 and the second lens group G2 and the axial air gap D19 between the second lens group G2 and the third lens group G3 are Change. Table 3 below shows the variable spacing for infinity focus and short distance focus. D0 indicates the distance on the optical axis from the object to the most object-side lens surface (first surface) of optical system OL1, β indicates magnification, and f indicates the focal length of the entire system. The description of these symbols is the same in the subsequent embodiments.

(Table 3)
Infinity Close D0 ∞ 188.54
β - -0.1000
f 18.66 -
D7 1.878 0.541
D19 1.170 2.508

FIG. 2 shows spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, magnification chromatic aberration diagrams, and coma aberration diagrams of this optical system OL1 when focusing on infinity and when focusing on a short distance. In each aberration diagram, FNO indicates F number, NA indicates numerical aperture, and Y indicates image height. The spherical aberration diagram shows the F-number or numerical aperture corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum image height, and the coma aberration diagram shows the value of each image height. . d indicates the d-line (λ=587.6 nm) and g indicates the g-line (λ=435.8 nm). In the astigmatism diagrams, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Further, in the aberration diagrams of each example shown below, the same reference numerals as in this example are used. From these aberration diagrams, it can be seen that the various aberrations of the optical system OL1 are well corrected.

[Second embodiment]
FIG. 3 is a diagram showing the configuration of the optical system OL2 according to the second embodiment. This optical system OL2 is composed of, in order from the object side, a front group GA, an aperture stop S, and a rear group GB having positive refractive power. The front group GA is composed of a first lens group G1 having positive refractive power, and the rear group GB is composed of, in order from the object side, a second lens group G2 having positive refractive power and a negative refractive power. and a third lens group G3.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 with a convex surface facing the object side, and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a cemented negative lens formed by cementing a biconcave negative lens L21 and a biconvex positive lens L22, a biconvex positive lens L23, and a positive meniscus lens L24 having a convex surface facing the object side. and a negative meniscus lens L25 with a convex surface facing the object side, and a positive meniscus shape with a concave surface facing the object side, the lens surface on the object side and the lens surface on the image side being aspheric. It is composed of a shaped aspherical positive lens L26. The third lens group G3 is composed of a biconcave negative lens L31. An optical filter FL is arranged between the rear group GB and the image plane I.

In this optical system OL2, the negative meniscus lens L11 is the negative lens N1, the biconcave negative lens L21 is the negative lens NF, the negative meniscus lens L25 is the negative lens NR, and the biconcave negative lens L31 is the negative lens NL. be.

Also, in this optical system OL2, focusing from infinity to a short distance object is performed by moving the second lens group G2 toward the object.

Table 4 below lists the values of the specifications of the optical system OL2. Although the third surface of the lens data is a virtual surface, it is not shown in the cross-sectional view of FIG.

(Table 4) Second embodiment [overall specifications]
f24.21
FNO 1.76
ω [°] 30.5
Y 14.50
TL 50.004
BF 14.096
BF (air conversion length) 13.551

[Lens data]
m r d nd νd
object ∞
1 26.24690 0.800 1.60311 60.7
2 12.59482 1.700
3 0.00000 0.400
4 15.67302 1.691 1.80400 46.6
5 30.29814 1.833
6 0.00000 D6 Aperture diaphragm S
7 -12.84018 0.800 1.73800 32.3
8 75.53056 4.818 1.75500 52.3
9 -16.73420 0.200
10 36.79732 4.800 1.72916 54.6
11 -47.51982 0.200
12 18.21772 3.700 1.72916 54.6
13 41.67744 2.081 1.67300 38.1
14 14.30567 3.803
15* -60.75531 1.465 1.53110 55.9
16* -21.32052 D16
17 -58.67999 0.800 1.75520 27.6
18 120.38649 11.496
19 0.00000 1.600 1.51680 64.1
20 0.00000 1.000
Image plane ∞

[Lens group focal length]
Lens group Starting surface Focal length 1st lens group G1 1 474.50
Second lens group G2 7 19.56
Third lens group G3 17 -52.14

In this optical system OL2, the 15th and 16th lens surfaces are aspherical. Table 5 below shows the surface number m and the data of the aspherical surface, that is, the values of the conic constant K and the aspherical constants A4 to A12.

(Table 5)
[Aspheric data]
15th surface K=1.00000e+00
A4 = -4.27043e-05 A6 = 3.35775e-07 A8 = 1.40921e-08
A10 = 0.00000e+00 A12 = 0.00000e+00
16th surface K=1.00000e+00
A4 = 5.80487e-05 A6 = 4.09696e-07 A8 = 1.64474e-08
A10 = 0.00000e+00 A12 = 0.00000e+00

In this optical system OL2, the axial air gap D6 between the first lens group G1 and the second lens group G2 and the axial air gap D16 between the second lens group G2 and the third lens group G3 are Change. Table 5 below shows the variable spacing for infinity focus and short distance focus.

(Table 6)
Infinity Short distance D0 ∞ 243.98
β - -0.1000
f 24.21 -
D6 5.818 4.309
D16 1.000 2.509

FIG. 4 shows spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, magnification chromatic aberration diagrams, and coma aberration diagrams of this optical system OL2 when focusing on infinity and when focusing on a short distance. From these aberration diagrams, it can be seen that the various aberrations of the optical system OL2 are well corrected.

[Third embodiment]
FIG. 5 is a diagram showing the configuration of the optical system OL3 according to the third example. This optical system OL3 is composed of, in order from the object side, a front group GA, an aperture stop S, and a rear group GB having positive refractive power. The front group GA is composed of a first lens group G1 having positive refractive power, and the rear group GB is composed of, in order from the object side, a second lens group G2 having positive refractive power and a negative refractive power. and a third lens group G3.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 with a convex surface facing the object side, and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a cemented negative lens L23 which is a cemented negative meniscus lens L21 having a concave surface facing the object side and a positive meniscus lens L22 having a convex surface facing the object side, and a biconvex positive lens L23. , a positive meniscus lens L24 with a convex surface facing the object side, a negative meniscus lens L25 with a convex surface facing the object side, and a positive meniscus shape with a concave surface facing the object side, the lens surface on the object side and the lens surface on the image side. It is composed of an aspherical positive lens L26 having an aspherical lens surface. The third lens group G3 is composed of a biconcave aspherical negative lens L31 having an object-side lens surface and an image-side lens surface formed in an aspherical shape. An optical filter FL is arranged between the rear group GB and the image plane I.

In this optical system OL3, the negative meniscus lens L11 is the negative lens N1, the negative meniscus lens L21 is the negative lens NF, the negative meniscus lens L25 is the negative lens NR, and the aspheric negative lens L31 is the negative lens NL. .

Also, in this optical system OL3, focusing from infinity to a short distance object is performed by moving the second lens group G2 toward the object.

Table 7 below lists the values of the specifications of the optical system OL3. Although the third surface of the lens data is a virtual surface, it is not shown in the sectional view of FIG.

(Table 7) Third embodiment [overall specifications]
f23.99
FNO 1.74
ω [°] 30.1
Y 14.50
TL 49.992
BF 12.990
BF (air conversion length) 12.445

[Lens data]
m r d nd νd
object ∞
1 25.94000 0.800 1.60311 60.7
2 14.70210 2.017
3 0.00000 0.780
4 19.62856 1.510 1.80400 46.6
5 40.55492 1.609
6 0.00000 D6 Aperture diaphragm S
7 -11.09774 0.800 1.73800 32.3
8 -71.62023 4.000 1.75500 52.3
9 -15.17987 0.000
10 2312.74590 3.823 1.72916 54.6
11 -26.33558 0.200
12 18.26036 5.535 1.72916 54.6
13 137.30289 0.200
14 49.24547 1.572 1.76182 26.6
15 16.62297 4.616
16* -12.37612 0.919 1.53113 55.8
17* -11.35573 D17
18* -128.13552 0.800 1.64000 60.2
19* 104.42083 10.390
20 0.00000 1.600 1.51680 64.1
21 0.00000 1.000
Image plane ∞

[Lens group focal length]
Lens group Starting surface Focal length 1st lens group G1 1 198.61
Second lens group G2 7 22.16
3rd lens group G3 18 -89.78

In this optical system OL3, the 16th, 17th, 18th and 19th lens surfaces are formed in an aspherical shape. Table 8 below shows the surface number m and the data of the aspherical surface, that is, the values of the conic constant K and the aspherical constants A4 to A12.

(Table 8)
[Aspheric data]
16th surface K=1.00000e+00
A4 = 3.18413e-04 A6 = 1.91924e-06 A8 = -8.92961e-09
A10 = 0.00000e+00 A12 = 0.00000e+00
17th surface K=1.00000e+00
A4 = 4.58812e-04 A6 = 7.66215e-07 A8 = 3.67698e-09
A10 = 0.00000e+00 A12 = 0.00000e+00
18th surface K=1.00000e+00
A4 = -5.32694e-07 A6 = -8.50693e-07 A8 = 4.38809e-09
A10 = 0.00000e+00 A12 = 0.00000e+00
19th surface K=1.00000e+00
A4 = -3.35211e-05 A6 = 2.16253e-07 A8 = 0.00000e+00
A10 = 0.00000e+00 A12 = 0.00000e+00

In this optical system OL3, the axial air gap D6 between the first lens group G1 and the second lens group G2 and the axial air gap D17 between the second lens group G2 and the third lens group G3 are Change. Table 9 below shows the variable spacing for infinity focus and short distance focus.

(Table 9)
Infinity Short distance D0 ∞ 242.49
β - -0.1000
f23.99 -
D6 6.793 4.946
D17 1.028 2.875

FIG. 6 shows spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, lateral chromatic aberration diagrams, and coma aberration diagrams of this optical system OL3 when focusing on infinity and when focusing on a short distance. From these aberration diagrams, it can be seen that the various aberrations of the optical system OL3 are well corrected.

[Fourth embodiment]
FIG. 7 is a diagram showing the configuration of the optical system OL4 according to the fourth example. This optical system OL4 is composed of, in order from the object side, a front group GA, an aperture stop S, and a rear group GB having positive refractive power. The front group GA is composed of a first lens group G1 having positive refractive power, and the rear group GB is composed of, in order from the object side, a second lens group G2 having positive refractive power and a negative refractive power. and a third lens group G3.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, and a biconvex positive lens L12. The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 with a concave surface facing the object side, a positive meniscus lens L22 with a concave surface facing the object side, and a biconvex lens surface facing the object side. and a cemented aspherical positive lens L23 having an aspherical image-side lens surface, and a positive meniscus lens L24 having a convex surface facing the object side and a negative meniscus lens L25 having a convex surface facing the object side. It consists of a negative lens. The third lens group G3 is composed of an aspherical negative lens L31 in which a resin layer provided on the object-side lens surface of the biconcave negative lens is formed into an aspherical shape. An optical filter FL is arranged between the rear group GB and the image plane I.

In this optical system OL4, the negative meniscus lens L11 is the negative lens N1, the negative meniscus lens L21 is the negative lens NF, the negative meniscus lens L25 is the negative lens NR, and the aspheric negative lens L31 is the negative lens NL. .

Also, in this optical system OL4, focusing from infinity to a short distance object is performed by moving the second lens group G2 toward the object.

Table 10 below lists the values of the specifications of the optical system OL4. Although the 3rd and 11th surfaces of the lens data are virtual surfaces, they are not shown in the cross-sectional view of FIG.

(Table 10) Fourth embodiment [overall specifications]
f24.64
FNO 1.75
ω [°] 30.3
Y 14.50
TL 50.000
BF 13.012
BF (air conversion length) 12.467

[Lens data]
m r d nd νd
object ∞
1 95.72479 0.800 1.69680 55.5
2 30.29508 3.511
3 0.00000 -0.700
4 26.01082 1.945 1.77250 49.6
5 -349.67569 1.000
6 0.00000 D6 Aperture diaphragm S
7 -10.06582 0.800 1.72825 28.4
8 -42.33130 0.901
9 -35.35053 5.000 1.77250 49.6
10 -13.06203 -0.500
11 0.00000 0.600
12* 34.65982 4.800 1.69350 53.3
13* -52.08174 0.200
14 30.12605 2.885 1.77250 49.6
15 101.41586 2.700 1.78472 25.6
16 23.50659 D16
17* -212.49838 0.100 1.56093 36.6
18 -125.18463 1.100 1.51680 63.9
19 54.07182 10.412
20 0.00000 1.600 1.51680 63.9
21 0.00000 1.000
Image plane ∞

[Lens group focal length]
Lens group Starting surface Focal length 1st lens group G1 1 57.07
Second lens group G2 7 25.23
Third lens group G3 17 -84.30

In this optical system OL4, the 12th, 13th and 17th lens surfaces are formed in an aspherical shape. Table 11 below shows the surface number m and the data of the aspherical surface, that is, the values of the conic constant K and the aspherical constants A4 to A12.

(Table 11)
[Aspheric data]
12th surface K=1.00000e+00
A4 = 2.63231e-05 A6 = -2.91715e-08 A8 = 1.91541e-10
A10 = 0.00000e+00 A12 = 0.00000e+00
13th surface K=1.00000e+00
A4 = 5.30867e-05 A6 = -5.02435e-08 A8 = 0.00000e+00
A10 = 0.00000e+00 A12 = 0.00000e+00
17th surface K=1.00000e+00
A4 = 6.34469e-06 A6 = -2.28171e-07 A8 = 1.47869e-10
A10=-6.83855e-12 A12= 0.00000e+00

In this optical system OL4, the axial air gap D6 between the first lens group G1 and the second lens group G2 and the axial air gap D16 between the second lens group G2 and the third lens group G3 are Change. Table 12 below shows the variable spacing for infinity focus and short distance focus.

(Table 12)
Infinity Close D0 ∞ 162.24
β - -0.1500
f24.64 -
D6 7.809 4.719
D16 4.037 7.127

FIG. 8 shows spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, lateral chromatic aberration diagrams, and coma aberration diagrams of this optical system OL4 when focusing on infinity and when focusing on a short distance. From these aberration diagrams, it can be seen that the various aberrations of the optical system OL4 are well corrected.

[Fifth embodiment]
FIG. 9 is a diagram showing the configuration of an optical system OL5 according to the fifth embodiment. This optical system OL5 is composed of, in order from the object side, a front group GA, an aperture stop S, and a rear group GB having positive refractive power. The front group GA is composed of a first lens group G1 having positive refractive power, and the rear group GB is composed of a second lens group G2 having positive refractive power.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 with a convex surface facing the object side, and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 with a concave surface facing the object side, a positive meniscus lens L22 with a concave surface facing the object side, and a biconvex lens surface facing the object side. and an aspherical positive lens L23 having an aspherical lens surface on the image side, and a cemented positive lens in which a positive meniscus lens L24 having a convex surface facing the object side and a negative meniscus lens L25 having a convex surface facing the object side are cemented together. , and an aspherical negative lens L26 in which a resin layer provided on the object-side lens surface of the biconcave negative lens is formed into an aspherical shape. An optical filter FL is arranged between the rear group GB and the image plane I.

In this optical system OL5, the negative meniscus lens L11 is the negative lens N1, the negative meniscus lens L21 is the negative lens NF, the negative meniscus lens L25 is the negative lens NR, and the aspheric negative lens L26 is the negative lens NL. .

Also, in this optical system OL5, focusing from infinity to a short distance object is performed by moving the second lens group G2 toward the object.

Table 13 below lists the values of the specifications of the optical system OL5. Although the 3rd and 11th surfaces of the lens data are virtual surfaces, they are not shown in the sectional view of FIG.

(Table 13) Fifth embodiment [overall specifications]
f24.28
FNO 1.74
ω [°] 30.0
Y 14.50
TL 50.000
BF 13.413
BF (air conversion length) 12.868

[Lens data]
m r d nd νd
object ∞
1 50.00000 0.800 1.69680 55.5
2 17.24209 2.151
3 0.00000 -0.700
4 19.58974 2.153 1.77250 49.6
5 205.71020 1.601
6 0.00000 D6 Aperture diaphragm S
7 -10.35061 0.800 1.72825 28.4
8 -32.62394 0.335
9 -40.55777 5.000 1.77250 49.6
10 -13.65162 -0.800
11 0.00000 0.900
12* 32.69590 4.800 1.69350 53.3
13* -281.19271 0.259
14 21.08477 3.700 1.77250 49.6
15 152.39896 2.700 1.78472 25.6
16 22.00000 3.177
17* 280.88096 0.100 1.56093 36.6
18 -134.95915 1.100 1.51680 64.1
19 40.00000 D19
20 0.00000 1.600 1.51680 64.1
21 0.00000 1.000
Image plane ∞

[Lens group focal length]
Lens group Starting surface Focal length 1st lens group G1 1 93.85
Second lens group G2 7 28.46

In this optical system OL5, the 12th, 13th and 17th lens surfaces are formed in an aspherical shape. Table 14 below shows the surface number m and the data of the aspherical surface, that is, the values of the conic constant K and the aspherical constants A4 to A12.

(Table 14)
[Aspheric data]
12th surface K=1.00000e+00
A4 = 2.55005e-05 A6 = 2.68082e-07 A8 = -4.15521e-09
A10 = 1.91843e-11 A12 = -7.32920e-14
13th surface K=1.00000e+00
A4 = 2.69977e-05 A6 = 2.93612e-07 A8 = -3.82736e-09
A10 = 0.00000e+00 A12 = 0.00000e+00
17th surface K=1.00000e+00
A4 = -8.70020e-05 A6 = -1.11329e-08 A8 = -4.28635e-09
A10=-1.69867e-11 A12= 0.00000e+00

In this optical system OL5, an axial air space D6 between the first lens group G1 and the second lens group G2 and an axial air space D19 between the second lens group G2 and the filter group FL change upon focusing. . Table 15 below shows the variable spacing for infinity focus and short distance focus.

(Table 15)
Infinity Close D0 ∞ 168.61
β - -0.1500
f24.28 -
D6 8.511 4.746
D19 10.813 14.578

FIG. 10 shows spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, magnification chromatic aberration diagrams, and coma aberration diagrams of this optical system OL5 when focusing on infinity and when focusing on a short distance. From these aberration diagrams, it can be seen that the various aberrations of the optical system OL5 are well corrected.

[Value corresponding to conditional expression]
Table 16 below shows the corresponding values of conditional expressions (1) to (12) in the first to fifth embodiments.

(Table 16)
(1) LA/LB
(2) LAS/LAB
(3) LNRL/LB
(4) R2NR/Bfa
(5) LNFL/LB
(6) R1NF/Bfa
(7) (R1NF+R2NR)/(R1NF-R2NR)
(8) fNF/fNR
(9) fN1/fNL
(10) LASI/LAB
(11) LASL/LAB
(12) fB/f

1st embodiment 2nd embodiment 3rd embodiment 4th embodiment 5th embodiment f 18.663 24.208 23.987 24.645 24.278
fB 19.882 25.239 26.058 33.313 28.463
fNR -22.746 -33.387 -33.640 -39.597 -33.066
fNF -11.895 -14.814 -17.895 -18.325 -21.138
fN1 -29.572 -41.054 -57.817 -63.929 -38.152
fNL -64.585 -52.138 -89.777 -84.301 -94.584
LA 6.839 4.591 5.107 5.556 4.404
LB 25.931 23.667 23.493 22.623 22.071
LAB 36.809 35.903 37.002 36.988 36.587
LAS 9.000 6.424 6.716 6.556 6.005
LASI 15.563 15.351 12.445 13.667 14.068
LASL 1.970 1.800 0.000 1.200 1.200
Bfa 13.593 13.551 12.445 12.467 12.868
LNRL 7.173 7.068 7.363 5.237 4.377
R2NR 28.222 14.306 16.623 23.507 22.000
LNFL 22.496 23.667 23.493 22.623 22.071
R1NF -17.745 -12.840 -11.098 -10.066 -10.351

(1) 0.264 0.194 0.217 0.246 0.200
(2) 0.245 0.179 0.182 0.177 0.164
(3) 0.277 0.299 0.313 0.231 0.198
(4) 2.076 1.056 1.336 1.886 1.710
(5) 0.868 1.000 1.000 1.000 1.000
(6) -1.305 -0.948 -0.892 -0.807 -0.804
(7) -0.228 -0.054 -0.199 -0.400 -0.360
(8) 0.523 0.444 0.532 0.463 0.639
(9) 0.458 0.787 0.644 0.758 0.403
(10) 0.423 0.428 0.336 0.369 0.385
(11) 0.054 0.050 0.000 0.032 0.033
(12) 1.065 1.043 1.086 1.352 1.172

In addition, the contents described below can be appropriately adopted within a range that does not impair the optical performance.

In this embodiment, an optical system OL having a two-group or three-group configuration is shown, but the above configuration conditions and the like are also applicable to other group configurations such as a four-group configuration and a five-group configuration. Also, a configuration in which a lens or lens group is added closest to the object side, or a configuration in which a lens or lens group is added closest to the image side may be used. Specifically, a configuration is conceivable in which a lens group, which is positioned closest to the image side and has a fixed position with respect to the image plane during zooming or focusing, is added. Also, a lens group refers to a portion having at least one lens separated by an air gap that changes during zooming or focusing. A lens component refers to a single lens or a cemented lens in which a plurality of lenses are cemented together.

Also, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to serve as a focusing group for focusing from an object at infinity to an object at a short distance. In this case, the focusing group can also be applied to autofocus, and is suitable for driving a motor (such as an ultrasonic motor) for autofocus. In particular, it is preferable to use the second lens group G2 as the focusing group and fix the positions of the other lenses with respect to the image plane when focusing. may Considering the load on the motor, it is preferable that the focusing group consist of a single lens.

In addition, the lens group or partial lens group is moved so as to have a displacement component in the direction perpendicular to the optical axis, or rotated (oscillated) in the in-plane direction including the optical axis to correct image blur caused by camera shake. It is good also as a vibration-proof group which carries out. In particular, it is preferable to use at least part of the first lens group G1 or the second lens group G2 as a vibration reduction group.

Also, the lens surface may be formed as a spherical surface, a flat surface, or an aspherical surface. If the lens surface is spherical or flat, it is preferable because it facilitates lens processing and assembly adjustment and prevents deterioration of optical performance due to errors in processing and assembly adjustment. Also, even if the image plane is deviated, there is little deterioration in rendering performance, which is preferable. If the lens surface is aspherical, the aspherical surface can be ground aspherical, glass-molded aspherical, which is formed into an aspherical shape from glass, or composite aspherical, which is formed into an aspherical shape from resin on the surface of glass. Any aspheric surface may be used. Further, 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 arranged between the first lens group G1 and the second lens group G2, but a lens frame may be used instead of providing a member as the aperture stop. .

In addition, each lens surface may be coated with an antireflection film that has high transmittance over a wide wavelength range in order to reduce flare and ghost and achieve high contrast and high optical performance.

1 camera (optical device) OS (OS1 to OS5) optical system GA front group GB rear group S diaphragm (aperture diaphragm)

Claims

From the object side,
front group;
Aperture and
a rear group having positive refractive power,
An optical system that satisfies the following conditions.
0.100 < LA/LB < 0.400
however,
LA: Distance on the optical axis from the most object-side lens surface of the front group to the most image-side lens surface when focusing on infinity LB: The most object-side lens surface of the rear group when focusing on infinity to the lens surface closest to the image side on the optical axis
2. The optical system according to claim 1, wherein the following condition is satisfied.
0.070<LAS/LAB<0.300
however,
LAS: Distance on the optical axis from the most object-side lens surface of the front group to the stop when focusing on infinity LAB: Distance from the most object-side lens surface of the front group to the rear group when focusing on infinity distance on the optical axis to the lens surface closest to the image side of
3. The optical system according to claim 1, wherein said rear group has a negative lens NR satisfying the following condition.
0.000 < LNRL/LB < 0.400
0.800<R2NR/Bfa<3.000
however,
LB: distance on the optical axis from the most object-side lens surface of the rear group to the most image-side lens surface when focusing on infinity LNRL: the image-side lens surface of the negative lens NR when focusing on infinity to the lens surface of the rear group closest to the image side R2NR: the radius of curvature of the image side lens surface of the negative lens NR Bfa: the back focus of the optical system when focusing on infinity (air conversion long)
The optical system according to any one of claims 1 to 3, wherein the rear group has a negative lens NF that satisfies the following condition.
0.600 < LNFL/LB < 1.000
0.500 < (-R1NF)/Bfa < 3.000
however,
LB: distance on the optical axis from the most object-side lens surface of the rear group to the most image-side lens surface when focusing on infinity LNFL: the object-side lens surface of the negative lens NF when focusing on infinity to the lens surface of the rear group closest to the image side R1NF: Radius of curvature of the object-side lens surface of the negative lens NF Bfa: Back focus of the optical system when focusing on infinity (converted to air long)
The rear group is
a negative lens NR which is a negative lens having the largest refractive power among negative lenses satisfying the following condition;
a negative lens NF which is a negative lens having the largest refractive power among the negative lenses satisfying the conditions of the following formula;
The optical system according to any one of claims 1 to 4.
0.000 < LNRL/LB < 0.400
0.800<R2NR/Bfa<3.000
0.600 < LNFL/LB < 1.000
0.500 < (-R1NF)/Bfa < 3.000
however,
LB: distance on the optical axis from the most object-side lens surface of the rear group to the most image-side lens surface when focusing on infinity LNRL: the image-side lens surface of the negative lens NR when focusing on infinity to the most image-side lens surface of the rear group R2NR: radius of curvature of the image-side lens surface of the negative lens NR LNFL: object-side lens of the negative lens NF during focusing at infinity R1NF: Radius of curvature of the object-side lens surface of the negative lens NF Bfa: Back focus of the optical system when focusing on infinity (air conversion length)
6. The optical system according to claim 5, which satisfies the following condition.
-0.800<(R1NF+R2NR)/(R1NF-R2NR)<0.800
however,
R1NF: radius of curvature of the object-side lens surface of the negative lens NF R2NR: radius of curvature of the image-side lens surface of the negative lens NR
7. The optical system according to claim 5, which satisfies the following condition.
0.200 < fNF/fNR < 1.200
however,
fNF: focal length of the negative lens NF fNR: focal length of the negative lens NR
The optical system according to any one of claims 5 to 7, wherein the rear group has at least two positive lenses between the negative lens NF and the negative lens NR.
The front group has at least one negative lens N1,
The rear group has at least one negative lens NL on the image side of the negative lens NR,
9. The optical system according to any one of claims 5 to 8, which satisfies the following formula.
0.300 < fN1/fNL < 1.200
however,
fN1: focal length of the negative lens N1 fNL: focal length of the negative lens NL
The rear group has an aspherical lens,
10. The optical system according to any one of claims 1 to 9, which satisfies the following conditions.
0.100 < LASI/LAB < 0.600
however,
LASI: Distance on the optical axis from the aspherical surface located closest to the image side in the rear group to the image plane when focused on infinity LAB: Lens closest to the object side in the front group when focused on infinity distance on the optical axis from the surface to the lens surface of the rear group closest to the image side
The rear group has an aspherical lens,
11. The optical system according to any one of claims 1 to 10, which satisfies the following formula.
0.000 < LASL/LAB < 0.150
however,
LASL: The distance on the optical axis from the aspherical surface located closest to the image side in the rear group to the lens surface closest to the image side in the rear group when focusing on infinity LAB: Said when focusing on infinity Distance on the optical axis from the lens surface of the front group closest to the object side to the lens surface of the rear group closest to the image side
12. The optical system according to any one of claims 1 to 11, which satisfies the following formula.
0.800 < fB/f < 1.600
however,
fB: focal length of the rear group when focused on infinity f: focal length of the entire system when focused on infinity
An optical instrument comprising the optical system according to any one of claims 1 to 12.
From the object side,
front group;
Aperture and
A method of manufacturing an optical system in which a rear group having a positive refractive power and a rear group are arranged so as to satisfy the following condition.
0.100 < LA/LB < 0.400
however,
LA: Distance on the optical axis from the most object-side lens surface of the front group to the most image-side lens surface when focusing on infinity LB: The most object-side lens surface of the rear group when focusing on infinity to the lens surface closest to the image side on the optical axis