CN116964503A

CN116964503A - Optical system, optical device, and method for manufacturing optical system

Info

Publication number: CN116964503A
Application number: CN202280017700.4A
Authority: CN
Inventors: 原田壮基
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 2021-04-09
Filing date: 2022-02-24
Publication date: 2023-10-27
Also published as: JPWO2022215380A1; WO2022215380A1

Abstract

The application provides an optical system with short optical full length, an optical device and a method for manufacturing the optical system. The optical system (OL) is provided with a front Group (GA), an aperture diaphragm (S) and a rear Group (GB) with positive focal power in order from the object side, and the optical system (OL) satisfies the following conditions: 0.100< LA/LB <0.400 where LA: distance on optical axis from lens surface closest to object side of front Group (GA) to lens surface closest to image side of front Group (GA) at the time of infinity focusing, LB: and a distance on an optical axis from a lens surface of the rear Group (GB) closest to the object side to a lens surface of the rear Group (GB) closest to the image side during infinity focusing.

Description

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

Technical Field

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

Background

In recent years, an optical system having a short optical length has been demanded (for example, refer to patent document 1). However, patent document 1 is required to further improve optical performance.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2013-195587

Disclosure of Invention

An optical system according to a first aspect of the present application includes, in order from an object side, a front group, an aperture, and a rear group having positive optical power, and satisfies the following condition:

0.100<LA/LB<0.400

wherein,,

LA: the distance on the optical axis from the lens surface closest to the object side of the front group to the lens surface closest to the image side of the front group at the time of infinity focusing,

LB: distance on the optical axis from the lens surface on the object side of the rear group to the lens surface on the image side of the rear group at the time of infinity focusing.

In the method for manufacturing an optical system according to the first aspect of the present application, the front group, the diaphragm, and the rear group having positive optical power are disposed in order from the object side so as to satisfy the following conditions:

0.100<LA/LB<0.400

wherein,,

Drawings

Fig. 1 is a sectional view showing a lens structure at the time of infinity focusing of the optical system of embodiment 1.

Fig. 2 is an aberration diagram of the optical system of embodiment 1, (a) shows an infinity focusing time, and (b) shows a close-range focusing time.

Fig. 3 is a sectional view showing a lens structure at the time of infinity focusing of the optical system of embodiment 2.

Fig. 4 is an aberration diagram of the optical system of embodiment 2, (a) shows an infinity focusing time, and (b) shows a close-range focusing time.

Fig. 5 is a sectional view showing a lens structure at the time of infinity focusing of the optical system of embodiment 3.

Fig. 6 is an aberration diagram of the optical system of embodiment 3, (a) shows an infinity focusing time, and (b) shows a close-range focusing time.

Fig. 7 is a sectional view showing a lens structure at the time of infinity focusing of the optical system of embodiment 4.

Fig. 8 is an aberration diagram of the optical system of embodiment 4, (a) shows an infinity focusing time, and (b) shows a close-range focusing time.

Fig. 9 is a sectional view showing a lens structure at the time of infinity focusing of the optical system of embodiment 5.

Fig. 10 is an aberration diagram of the optical system of embodiment 5, (a) shows an infinity focusing time, and (b) shows a close-range focusing time.

Fig. 11 is a cross-sectional view of a camera in which the optical system is mounted.

Fig. 12 is a flowchart for explaining a method of manufacturing the optical system.

Detailed Description

Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. As shown in fig. 1, the optical system OL of the present embodiment is configured to include, in order from the object side, a front group GA, an aperture S, and a rear group GB having positive optical power. With this configuration, each aberration can be favorably suppressed, and the total optical length of the optical system OL can be shortened.

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

0.100 < LA/LB < 0.400 (1)

Wherein,,

LA: distance on optical axis from most object side lens surface of front group GA to most image side lens surface of front group GA at the time of infinity focusing

LB: distance on optical axis from most object side lens surface of rear group GB to most image side lens surface of rear group GB at the time of infinity focusing

The condition (1) specifies a ratio of the length of the front group GA (the distance on the optical axis from the lens surface closest to the object side of the front group GA to the lens surface closest to the image side of the front group GA) to the length of the rear group GB of the optical system OL (the distance on the optical axis from the lens surface closest to the object side of the rear group GB to the lens surface closest to the image side of the rear group GB) in the optical system OL at the time of infinity focusing. By satisfying the conditional expression (1), the length of the rear group GB becomes longer than the length of the front group GA, that is, the length of the optical system on the image side of the aperture S becomes longer, and thus, good correction of image surface curvature and astigmatism can be achieved in the optical system OL having a full length or a short length. In order to reliably obtain the effect of the conditional expression (1), the upper limit value of the conditional expression (1) is more preferably 0.350, and still more preferably 0.320. In order to reliably obtain the effect of the conditional expression (1), the lower limit value of the conditional expression (1) is more preferably 0.130, and still more preferably 0.150.

The optical system OL of the present embodiment preferably satisfies the following conditional expression (2).

0.070 < LAS/LAB < 0.300 (2)

Wherein,,

LAS: distance on optical axis from most object side lens surface of front group GA to aperture S at the time of infinity focusing

LAB (LAB): distance on optical axis from most object side lens surface of front group GA to most image side lens surface of rear group GB at the time of infinity focusing

The condition (2) specifies the ratio of the length of the front group GA up to the diaphragm S (the distance on the optical axis from the most object side lens surface of the front group GA to the diaphragm S) at the time of infinity focusing to the length of the optical system OL (the 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). By satisfying the conditional expression (2), the optical system on the object side of the aperture S is shortened with respect to the length of the optical system OL, and therefore the entrance pupil of the optical system OL is brought closer to the object side, and excellent correction of image surface curvature, astigmatism, and distortion can be achieved. In order to reliably obtain the effect of the conditional expression (2), the upper limit value of the conditional expression (2) is more preferably 0.280, and still more preferably 0.260. In order to reliably obtain the effect of the conditional expression (2), the lower limit value of the conditional expression (2) is more preferably 0.100, and still more preferably 0.130.

In the optical system OL of the present embodiment, the rear group GB preferably has a negative lens NR satisfying the following conditional expression (3).

0.000<LNRL/LB<0.500 (3)

Wherein,,

LNRL: distance on optical axis from image side lens surface of negative lens NR to most image side lens surface of rear group GB at the time of infinity focusing

The conditional expression (3) specifies the ratio of the length (distance on the optical axis) from the image side lens surface of the negative lens NR to the lens surface on the most image side of the rear group GB to the length of the rear group GB. By satisfying the conditional expression (3), the negative lens NR is disposed near the image plane I, which is the image side of the rear group GB, and thus, various aberrations such as image plane bending, astigmatism, and distortion can be favorably suppressed, and the optical overall length of the optical system OL can be shortened. In order to reliably obtain the effect of the conditional expression (3), the upper limit value of the conditional expression (3) is more preferably set to 0.450, and further preferably set to 0.400, 0.360, and 0.320. In order to reliably obtain the effect of the conditional expression (3), the lower limit value of the conditional expression (3) is more preferably 0.070, and still more preferably 0.150.

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

0.800<R2NR/Bfa<3.000 (4)

Wherein,,

r2NR: radius of curvature of image side lens surface of negative lens NR

Bfa: back focal length (air conversion length) of optical system OL at the time of infinity focusing

The condition (4) specifies the ratio of the radius of curvature of the image side lens surface of the negative lens NR to the back focal length of the optical system OL. The negative lens NR disposed near the image plane I satisfying the conditional expression (3) satisfies the conditional expression (4), and thus can achieve good correction of image plane curvature, astigmatism, and distortion. In order to reliably obtain the effect of the conditional expression (4), the upper limit value of the conditional expression (4) is more preferably 2.700, and still more preferably 2.400. In order to reliably obtain the effect of the conditional expression (4), the lower limit value of the conditional expression (4) is more preferably 0.850, and still more preferably 0.900.

In the optical system OL of the present embodiment, the rear group GB preferably has a negative lens NF satisfying the following conditional expression (5).

0.600 < LNFL/LB ≤ 1.000 (5)

Wherein,,

LNFL: distance on optical axis from object side lens surface of negative lens NF to most image side lens surface of rear group GB at the time of infinity focusing

The condition (5) specifies the ratio of the length (distance on the optical axis) from the object-side lens surface of the negative lens NF to the lens surface on the most image side of the rear group GB to the length of the rear group GB. By satisfying the conditional expression (5), the negative lens NF is disposed on the object side of the rear group GB, that is, in the vicinity of the aperture S, and therefore, it is possible to satisfactorily suppress various aberrations such as spherical aberration, axial chromatic aberration, and image surface curvature, and to shorten the optical overall length of the optical system OL. In order to reliably obtain the effect of the conditional expression (5), the lower limit value of the conditional expression (5) is more preferably 0.700, and still more preferably 0.800.

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

-3.000 < R1NF/Bfa < -0.500 (6)

Wherein,,

r1NF: radius of curvature of object-side lens surface of negative lens NF

The condition (6) specifies the ratio of the radius of curvature of the object-side lens surface of the negative lens NF to the back focal length of the optical system OL. The negative lens NF disposed near the diaphragm S satisfying the conditional expression (5) satisfies the conditional expression (6), and thus can achieve good correction of spherical aberration, image surface curvature, and axial chromatic aberration. In order to reliably obtain the effect of the conditional expression (6), the upper limit value of the conditional expression (6) is more preferably-0.600, and further-0.700. In order to reliably obtain the effect of the conditional expression (6), it is more preferable that the lower limit value of the conditional expression (6) is-2.500, and further-2.000.

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

In the optical system OL of the present embodiment, the negative lens NR and the negative lens NF preferably satisfy the following conditional expression (7).

-0.800<(R1NF+R2NR)/(R1NF-R2NR)<0.800 (7)

Wherein,,

r1NF: radius of curvature of object-side lens surface of negative lens NF

R2NR: radius of curvature of image side lens surface of negative lens NR

Conditional expression (7) specifies a shape factor from the object-side lens surface of the negative lens NF to the image-side lens surface of the negative lens NR. The satisfaction of conditional expression (7) indicates 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. By satisfying the conditional expression (7), the symmetry of the negative lens included in the rear group GB becomes high, and as a result, excellent correction of the balance of spherical aberration, image surface curvature, axial chromatic aberration, astigmatism, distortion, and the like can be achieved. In order to reliably obtain the effect of the conditional expression (7), the upper limit value of the conditional expression (7) is more preferably set to 0.600, and further more preferably set to 0.400 or 0.200. In order to reliably obtain the effect of the conditional expression (7), it is more preferable that the lower limit value of the conditional expression (7) is-0.600, and further-0.400 and-0.200.

In the optical system OL of the present embodiment, the negative lens NR and the negative lens NF preferably satisfy the following conditional expression (8).

0.200<fNF/fNR<1.200 (8)

Wherein,,

fNF: focal length of negative lens NF

fNR: focal length of negative lens NR

Conditional expression (8) specifies 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 power of the negative lens NF and the power of the negative lens NR become close to each other, and therefore, the symmetry of the power of the negative lens becomes high as the rear group GB, and as a result, excellent correction of balance of image surface curvature, astigmatism, distortion, and the like can be achieved. In order to reliably obtain the effect of the conditional expression (8), the upper limit value of the conditional expression (8) is more preferably set to 1.000, and further preferably set to 0.900 or 0.800. In order to reliably obtain the effect of the conditional expression (8), the lower limit value of the conditional expression (8) is more preferably 0.300, and still more preferably 0.400.

In the optical system OL of the present embodiment, it is preferable that the rear group GB has at least two positive lenses between the negative lens NF and the negative lens NR. With the above configuration, it is possible to easily perform good aberration correction. In particular, spherical aberration, axial chromatic aberration, image surface curvature, astigmatism, and the like can be corrected satisfactorily.

In the optical system OL of the present embodiment, it is preferable that 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, and the optical system OL satisfies the following conditional expression (9).

0.300<fN1/fNL<1.200 (9)

Wherein,,

fN1: focal length of negative lens N1

fNL: focal length of negative lens NL

The conditional expression (9) specifies 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. By disposing negative lenses satisfying the conditional expression (9), that is, negative lenses N1 and NL having close optical powers, on the object side of the negative lens NF and the image side of the negative lens NR, and sandwiching the negative lenses NF and NR, the symmetry of the negative lenses becomes high even in the whole optical system, and as a result, it is possible to realize more excellent correction of balance of image surface curvature, astigmatism, distortion, and the like. In order to reliably obtain the effect of the conditional expression (9), the upper limit value of the conditional expression (9) is more preferably 1.100, and further more preferably 1.000 or 0.900. In order to reliably obtain the effect of the conditional expression (9), the lower limit value of the conditional expression (9) is more preferably 0.330, and still more preferably 0.360.

In the optical system OL of the present embodiment, it is preferable that the rear group GB has an aspherical lens in which an aspherical surface is formed on at least one of the object side lens surface and the image side lens surface, and satisfies the following conditional expression (10).

0.100 < LASI/LAB < 0.600 (10)

Wherein,,

LASI: distance on optical axis from aspherical surface disposed on most image side to image surface in rear group GB at the time of infinity focusing

The conditional expression (10) specifies the ratio of the length (distance on the optical axis) from the aspherical surface disposed on the most image side to the image plane to the length of the optical system OL. By satisfying the conditional expression (10), the aspherical surface disposed on the most image side in the rear group GB is located in the vicinity of the image plane I, and thus the curvature of the image plane, astigmatism, and distortion can be corrected satisfactorily. In order to reliably obtain the effect of the conditional expression (10), the upper limit value of the conditional expression (10) is more preferably 0.550, and still more preferably 0.500. In order to reliably obtain the effect of the conditional expression (10), the lower limit value of the conditional expression (10) is more preferably 0.200, and still more preferably 0.300.

In the optical system OL of the present embodiment, it is preferable that the rear group GB has an aspherical lens in which an aspherical surface is formed on at least one of the object side lens surface and the image side lens surface, and satisfies the following conditional expression (11).

0.000 ≤ LASL/LAB < 0.150 (11)

Wherein,,

LASL: distance on optical axis from aspherical surface disposed on most image side in rear group GB to lens surface on most image side in rear group GB at the time of infinity focusing

The conditional expression (11) specifies the ratio of the length (distance on the optical axis) from the aspherical surface disposed on the most image side to the most image side surface of the rear group GB to the length of the optical system OL. By satisfying the conditional expression (11), the aspherical surface disposed on the most image side in the rear group GB is located in the vicinity of the image plane I, and thus the curvature of the image plane, astigmatism, and distortion can be corrected satisfactorily. In order to reliably obtain the effect of the conditional expression (11), the upper limit value of the conditional expression (11) is more preferably 0.120, and still more preferably 0.100. In order to reliably obtain the effect of the conditional expression (11), the lower limit value of the conditional expression (11) is more preferably set to 0.007.

The optical system OL of the present embodiment preferably satisfies the following conditional expression (12).

0.800 < fB/f < 1.600 (12)

Wherein,,

fB: focal length of rear group GB at infinity focusing

f: focal length of the entire system of the optical system OL at the time of infinity focusing

Conditional expression (12) specifies the ratio of the focal length of the rear group GB to the focal length of the entire system. By satisfying the conditional expression (12), it is possible to satisfactorily suppress various aberrations such as spherical aberration, coma, curvature of field, and astigmatism, and to shorten the optical overall length of the optical system OL. In order to reliably obtain the effect of the conditional expression (12), the upper limit value of the conditional expression (12) is more preferably 1.500, and further more preferably 1.400. In order to reliably obtain the effect of the conditional expression (12), the lower limit value of the conditional expression (12) is more preferably 0.900, and still more preferably 0.950.

The conditions and structures described above are not limited to a system satisfying all the conditions and structures, and a system satisfying any one of the conditions and structures, or a combination of any of the conditions and structures can be used to achieve the above effects.

Next, a camera as an optical device including the optical system OL of the present embodiment will be described with reference to fig. 11. The camera 1 is a so-called mirror-less camera having an optical system OL according to the present embodiment as a lens interchangeable with the photographing lens 2. In the camera 1, light from an object (subject) not shown is condensed by the photographing lens 2, and a subject image is formed on an image pickup surface of the image pickup section 3 by an OLPF (Optical low pass filter: optical low-pass filter) not shown. The object image is photoelectrically converted by a photoelectric conversion element provided in the image pickup unit 3 to generate an image of the object. The image is displayed on an EVF (Electronic view finder: electronic viewfinder) 4 provided to the camera 1. Thereby, the photographer can observe the subject through the EVF 4.

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. Thus, the photographer can take an image of the subject by the own camera 1. In the present embodiment, although an example of a mirror-less camera has been described, the same effects as those of the camera 1 described above can be obtained even when the optical system OL of the present embodiment is mounted in a single-lens-type camera in which a camera body has a quick return mirror and a subject is observed through a viewfinder optical system.

Hereinafter, a method for manufacturing the optical system OL according to the present embodiment will be described in brief with reference to fig. 12.

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

With the above configuration, an optical system OL having a short optical length and each aberration being well suppressed, an optical device having the optical system OL, and a method of manufacturing the optical system OL can be provided.

[ example ]

Hereinafter, embodiments of the present application will be described with reference to the drawings. Fig. 1, 3, 5, 7, and 9 are cross-sectional views showing the configuration and power distribution of the optical systems OL (OL 1 to OL 5) of each embodiment.

In each embodiment, when the height in the direction perpendicular to the optical axis is set to y, the distance (concave amount) along the optical axis from the tangential plane at the vertex of each aspherical surface to each aspherical surface at the height y is set to S (y), the radius of curvature (paraxial radius of curvature) of the reference spherical surface is set to r, the conic constant is set to K, and the n-th order aspherical coefficient is set to An, the aspherical surface is represented by the following expression (a). In the examples hereinafter, "e-n" means ". Times.10 ^-n ”。

S(y)＝(y ² /r)/{1+(1-K×y ² /r ² ) ^1/2 }

+A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y ¹⁰ +A12×y ¹² (a)

In addition, in each embodiment, the secondary aspherical coefficient A2 is 0.

The following examples illustrate specific examples of the present application, but the present application is not limited thereto.

[ example 1 ]

Fig. 1 is a diagram showing the structure of an optical system OL1 of embodiment 1. The 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 optical power. The front group GA is constituted by a1 st lens group G1 having negative optical power, and the rear group GB is constituted by a2 nd lens group G2 having positive optical power and a 3 rd lens group G3 having negative optical power in order from the object side.

The 1 st lens group G1 is composed of a negative meniscus lens L11, a biconcave negative lens L12, and a biconvex positive lens L13, the convex surface of which faces the object side, in order from the object side. The 2 nd lens group G2 is composed of, 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 is cemented with a biconvex positive lens L23, a biconvex positive lens L24, a cemented positive lens in which a biconvex positive lens L25 is cemented with a biconcave negative lens L26, and an aspherical positive lens L27 having a positive meniscus shape having a concave surface facing the object side and having an object side lens surface and an image side lens surface. In addition, the 3 rd lens group G3 is constituted by a biconcave negative lens L31. An optical filter FL is disposed between the rear group GB and the image plane I.

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

In the optical system OL1, focusing from infinity to a close-distance object is performed by moving the 2 nd lens group G2 in the object direction.

Table 1 below shows values of parameters of the optical system OL 1. In the overall parameters of table 1, F represents the focal length of the entire optical system OL1, FNO represents the F value, ω represents the half angle of view [ °, Y represents the maximum image height, TL represents the full length, and BF represents the value of the back focal length. Here, the full length TL represents the distance (actual distance) on the optical axis from the lens surface (1 st surface) closest to the object side to the image surface I at the time of infinity focusing. The back focal length BF represents the distance (actual distance and air conversion length) on the optical axis from the lens surface (21 st surface) closest to the image surface I at the time of infinity focusing. In the lens data, column 1 m indicates the order (plane number) of the lens surfaces from the object side along the direction in which the light beam travels, column 2 r indicates the radius of curvature of each lens surface, column 3 d indicates the distance (plane interval) on the optical axis from each optical surface to the next optical surface, and columns 4 nd and 5 vd indicate the refractive index and abbe number for d-line (λ=587.6 nm). The radius of curvature 0.00000 represents a plane, and the refractive index of air is 1.00000. The lens group focal length represents the surface number and focal length of the initial surface of each lens group.

Here, although "mm" is generally used for the focal length f, the radius of curvature r, the surface interval d, and other length units described in all the following parameter values, the same optical performance can be obtained even when the optical system is scaled up or scaled down, and therefore, the present application is not limited thereto. The description of these reference numerals and the description of the parameter table are the same in the following examples.

(Table 1) example 1

[ overall parameters ]

[ lens data ]

[ focal Length of lens group ]

In the optical system OL1, each of the lens surfaces of the 18 th and 19 th surfaces is formed into an aspherical shape. Table 2 below shows the data of the surface number m and the aspherical surface, that is, the values of the conic constant K and the respective aspherical constants A4 to a 12.

(Table 2)

Aspherical data

18 th face k=1.00000e+00

A4＝-1.34226e-04A6＝4.64940e-06A8＝-3.86730e-08

A10＝0.00000e+00A12＝0.00000e+00

19 th face k=1.00000e+00

A4＝-2.70832e-06A6＝5.26276e-06A8＝-3.87365e-08

A10＝0.00000e+00A12＝0.00000e+00

In the optical system OL1, an on-axis air space D7 between the 1 st lens group G1 and the 2 nd lens group G2 and an on-axis air space D19 between the 2 nd lens group G2 and the 3 rd lens group G3 change when focusing is performed. Table 3 below shows the variable intervals at the time of infinity focusing and at the time of close-range focusing. D0 represents the distance on the optical axis from the object to the most object side lens surface (surface 1) of the optical system OL1, β represents the magnification, and f represents the focal length of the entire system. These reference numerals are also the same in the following embodiments.

(Table 3)

Fig. 2 shows spherical aberration diagrams, astigmatism diagrams, distortion diagrams, chromatic aberration diagrams, and coma diagrams of the optical system OL1 at the time of infinity focusing and at the time of close focusing. In each aberration diagram, FNO denotes an F value, NA denotes a numerical aperture, and Y denotes an image height. The spherical aberration diagram shows the value of the F value or numerical aperture corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum value of the image height, and the coma diagram shows the value of each image height. d represents d-line (λ=587.6 nm), g represents g-line (λ=435.8 nm). In the astigmatism diagrams, a solid line represents a sagittal image surface, and a broken line represents a meridional image surface. Note that, in aberration diagrams of the respective embodiments shown below, the same symbols as those of the present embodiment are also used. As is clear from these aberration diagrams, the optical system OL1 satisfactorily corrects the aberrations.

[ example 2 ]

Fig. 3 is a diagram showing the structure of an optical system OL2 of embodiment 2. The 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 optical power. The front group GA is constituted by a1 st lens group G1 having positive optical power, and the rear group GB is constituted by a2 nd lens group G2 having positive optical power and a 3 rd lens group G3 having negative optical power in order from the object side.

The 1 st lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 with its convex surface facing the object side, and a positive meniscus lens L12 with its convex surface facing the object side. The 2 nd lens group G2 is composed of, in order from the object side, a cemented negative lens in which a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a biconvex positive lens L23, a cemented negative 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, and an aspherical positive lens L26 in which a concave surface facing the object side and an object side lens surface and an image side lens surface are formed in aspherical shapes. In addition, the 3 rd lens group G3 is constituted by a biconcave negative lens L31. An optical filter FL is disposed between the rear group GB and the image plane I.

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

In the optical system OL2, focusing from infinity to a close-distance object is performed by moving the 2 nd lens group G2 in the object direction.

Table 4 below shows values of parameters of the optical system OL 2. The 3 rd surface of the lens data is a virtual surface, and is not shown in the cross-sectional view of fig. 3.

(Table 4) example 2

[ overall parameters ]

[ lens data ]

[ focal Length of lens group ]

In the optical system OL2, each of the lens surfaces of the 15 th and 16 th surfaces is formed into an aspherical shape. Table 5 below shows the data of the surface number m and the aspherical surface, that is, the values of the conic constant K and the aspherical constants A4 to a 12.

(Table 5)

Aspherical data

15 th face k=1.00000e+00

A4＝-4.27043e-05A6＝3.35775e-07A8＝1.40921e-08

A10＝0.00000e+00A12＝0.00000e+00

16 th face k=1.00000e+00

A4＝5.80487e-05A6＝4.09696e-07A8＝1.64474e-08

A10＝0.00000e+00A12＝0.00000e+00

In the optical system OL2, the on-axis air space D6 between the 1 st lens group G1 and the 2 nd lens group G2 and the on-axis air space D16 between the 2 nd lens group G2 and the 3 rd lens group G3 change when focusing is performed. Table 5 below shows the variable intervals at the time of infinity focusing and at the time of close-range focusing.

(Table 6)

Fig. 4 shows spherical aberration diagrams, astigmatism diagrams, distortion diagrams, chromatic aberration diagrams, and coma diagrams of the optical system OL2 at the time of infinity focusing and at the time of close focusing. As is clear from these aberration diagrams, the optical system OL2 satisfactorily corrects the aberrations.

[ example 3 ]

Fig. 5 is a diagram showing the structure of an optical system OL3 of embodiment 3. The 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 optical power. The front group GA is constituted by a1 st lens group G1 having positive optical power, and the rear group GB is constituted by a2 nd lens group G2 having positive optical power and a 3 rd lens group G3 having negative optical power in order from the object side.

The 1 st lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 with its convex surface facing the object side, and a positive meniscus lens L12 with its convex surface facing the object side. The 2 nd lens group G2 is composed of, in order from the object side, a joined negative lens in which a negative meniscus lens L21 having a concave surface facing the object side is joined to a positive meniscus lens L22 having a convex surface facing the object side, a biconvex positive lens L23, a positive meniscus lens L24 having a convex surface facing the object side, a negative meniscus lens L25 having a convex surface facing the object side, and a positive meniscus lens L25 having a concave surface facing the object side, and an aspherical positive lens L26 having an aspherical surface. The 3 rd lens group G3 is composed of an aspherical negative lens L31 having a biconcave shape, with an object-side lens surface and an image-side lens surface formed in an aspherical shape. An optical filter FL is disposed between the rear group GB and the image plane I.

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

In the optical system OL3, focusing from infinity to a close-distance object is performed by moving the 2 nd lens group G2 in the object direction.

Table 7 below shows values of parameters of the optical system OL 3. The 3 rd surface of the lens data is a virtual surface, and is not shown in the cross-sectional view of fig. 5.

(Table 7) example 3

[ overall parameters ]

[ lens data ]

/>

[ focal Length of lens group ]

In the optical system OL3, each lens surface of the 16 th, 17 th, 18 th, and 19 th surfaces is formed into an aspherical shape. Table 8 below shows the data of the surface number m and the aspherical surface, that is, the values of the conic constant K and the respective aspherical constants A4 to a 12.

(Table 8)

Aspherical data

16 th face k=1.00000e+00

A4＝3.18413e-04A6＝1.91924e-06A8＝-8.92961e-09

A10＝0.00000e+00A12＝0.00000e+00

17 th face k=1.00000e+00

A4＝4.58812e-04A6＝7.66215e-07A8＝3.67698e-09

A10＝0.00000e+00A12＝0.00000e+00

18 th face k=1.00000e+00

A4＝-5.32694e-07A6＝-8.50693e-07A8＝4.38809e-09

A10＝0.00000e+00A12＝0.00000e+00

19 th face k=1.00000e+00

A4＝-3.35211e-05A6＝2.16253e-07A8＝0.00000e+00

A10＝0.00000e+00A12＝0.00000e+00

In the optical system OL3, the on-axis air space D6 between the 1 st lens group G1 and the 2 nd lens group G2 and the on-axis air space D17 between the 2 nd lens group G2 and the 3 rd lens group G3 change when focusing is performed. Table 9 below shows the variable intervals at the time of infinity focusing and at the time of close-range focusing.

(Table 9)

/>

Fig. 6 shows spherical aberration diagrams, astigmatism diagrams, distortion diagrams, chromatic aberration diagrams, and coma diagrams of the optical system OL3 at the time of infinity focusing and at the time of close focusing. As is clear from these aberration diagrams, the optical system OL3 satisfactorily corrects the aberrations.

[ example 4 ]

Fig. 7 is a diagram showing the structure of an optical system OL4 of embodiment 4. The 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 optical power. The front group GA is constituted by a1 st lens group G1 having positive optical power, and the rear group GB is constituted by a2 nd lens group G2 having positive optical power and a 3 rd lens group G3 having negative optical power in order from the object side.

The 1 st lens group G1 is composed of a negative meniscus lens L11 and a biconvex positive lens L12, the convex surface of which faces the object side, in order from the object side. The 2 nd lens group G2 is composed of, in order from the object side, a negative meniscus lens L21 having a concave surface facing the object side, a positive meniscus lens L22 having a concave surface facing the object side, an aspherical positive lens L23 having a biconvex shape and having an object side lens surface and an image side lens surface, and a cemented negative lens for cemented between 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. The 3 rd lens group G3 is composed of an aspherical negative lens L31 in which a resin layer provided on an object side lens surface of the biconcave negative lens is formed in an aspherical shape. An optical filter FL is disposed between the rear group GB and the image plane I.

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

In the optical system OL4, focusing from infinity to a close-distance object is performed by moving the 2 nd lens group G2 in the object direction.

Table 10 below shows values of parameters of the optical system OL 4. The 3 rd and 11 th surfaces of the lens data are virtual surfaces, and are not shown in the cross-sectional view of fig. 7.

(Table 10) example 4

[ overall parameters ]

[ lens data ]

/>

[ focal Length of lens group ]

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

(Table 11)

Aspherical data

12 th face k=1.00000e+00

A4＝2.63231e-05A6＝-2.91715e-08A8＝1.91541e-10

A10＝0.00000e+00A12＝0.00000e+00

13 th face k=1.00000e+00

A4＝5.30867e-05A6＝-5.02435e-08A8＝0.00000e+00

A10＝0.00000e+00A12＝0.00000e+00

17 th face k=1.00000e+00

A4＝6.34469e-06A6＝-2.28171e-07A8＝1.47869e-10

A10＝-6.83855e-12A12＝0.00000e+00

In the optical system OL4, the on-axis air space D6 between the 1 st lens group G1 and the 2 nd lens group G2 and the on-axis air space D16 between the 2 nd lens group G2 and the 3 rd lens group G3 change when focusing is performed. Table 12 below shows the variable intervals at the time of infinity focusing and at the time of close-range focusing.

(Table 12)

Fig. 8 shows spherical aberration diagrams, astigmatism diagrams, distortion diagrams, chromatic aberration diagrams, and coma diagrams of the optical system OL4 at the time of infinity focusing and at the time of close focusing. As is clear from these aberration diagrams, the optical system OL4 satisfactorily corrects the aberrations.

[ example 5 ]

Fig. 9 is a diagram showing the structure of an optical system OL5 of embodiment 5. The 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 optical power. In addition, the front group GA is constituted by the 1 st lens group G1 having positive optical power, and the rear group GB is constituted by the 2 nd lens group G2 having positive optical power.

The 1 st lens group G1 is composed of, in order from the object side, a negative meniscus lens L11 with its convex surface facing the object side, and a positive meniscus lens L12 with its convex surface facing the object side. The 2 nd lens group G2 is composed of, in order from the object side, a negative meniscus lens L21 having a concave surface facing the object side, a positive meniscus lens L22 having a concave surface facing the object side, an aspherical positive lens L23 having a biconvex shape and having an object side lens surface and an image side lens surface, a positive lens for joining 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, and an aspherical negative lens L26 having a resin layer provided on the object side lens surface of the biconcave negative lens formed in an aspherical shape. An optical filter FL is disposed between the rear group GB and the image plane I.

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

In the optical system OL5, focusing from infinity to a close-distance object is performed by moving the 2 nd lens group G2 in the object direction.

Table 13 below shows values of parameters of the optical system OL 5. The 3 rd and 11 th surfaces of the lens data are virtual surfaces, and are not shown in the cross-sectional view of fig. 9.

(Table 13) example 5

[ overall parameters ]

[ lens data ]

/>

[ focal Length of lens group ]

Lens group initial focal length

1 st lens group G1.93.85

Group 2 lens G2 7.28.46

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

(Table 14)

Aspherical data

12 th face k=1.00000e+00

A4＝2.55005e-05 A6＝2.68082e-07 A8＝-4.15521e-09

A10＝1.91843e-11 A12＝-7.32920e-14

13 th face k=1.00000e+00

A4＝2.69977e-05 A6＝2.93612e-07 A8＝-3.82736e-09

A10＝0.00000e+00 A12＝0.00000e+00

17 th face 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 the optical system OL5, the on-axis air space D6 between the 1 st lens group G1 and the 2 nd lens group G2 and the on-axis air space D19 between the 2 nd lens group G2 and the filter group FL are changed when focusing is performed. Table 15 below shows the variable intervals at the time of infinity focusing and at the time of close-range focusing.

(Table 15)

Fig. 10 shows spherical aberration diagrams, astigmatism diagrams, distortion diagrams, chromatic aberration diagrams, and coma diagrams of the optical system OL5 at the time of infinity focusing and at the time of close focusing. As is clear from these aberration diagrams, the optical system OL5 satisfactorily corrects the aberrations.

[ Condition-based correspondence value ]

Table 16 below shows the corresponding values of conditional expressions (1) to (12) of examples 1 to 5.

(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

/>

The following can be suitably employed within a range that does not deteriorate the optical performance. In the present embodiment, the optical system OL having a 2-group or 3-group configuration is shown, but the above configuration conditions and the like can be applied to other group configurations such as 4 groups and 5 groups. The lens or lens group may be added to the most object side or the lens or lens group may be added to the most image side. Specifically, it is conceivable to add a lens group whose position with respect to the image plane is fixed at the time of zooming or focusing at the most image side. The lens group means a portion having at least one lens separated by an air space that changes when changing magnification or when focusing. The lens component is a single lens or a bonded lens in which a plurality of lenses are bonded.

In addition, a single lens group or a plurality of lens groups, or a part of lens groups may be used as a focusing group that moves in the optical axis direction to focus from an infinitely distant object to a close object. In this case, the focusing group can be applied to automatic focusing, and also to motor driving (of an ultrasonic motor or the like) for automatic focusing. In particular, although the 2 nd lens group G2 is preferably a focusing group and the position of the other lens with respect to the image plane is fixed at the time of focusing, the entire optical system OL may be moved in the optical axis direction to perform focusing. When considering the load applied to the motor, the focus group is preferably constituted by a single lens.

In addition, the lens group or a part of the lens group may be set as an anti-shake group that moves so as to have a displacement component in a direction orthogonal to the optical axis or rotationally moves (swings) in an in-plane direction including the optical axis, thereby correcting an image shake caused by hand shake. In particular, at least a part of the 1 st lens group G1 or the 2 nd lens group G2 is preferably an anti-shake group.

The lens surface may be formed of a spherical surface or a planar surface, or may be formed of an aspherical surface. In the case where the lens surface is a spherical surface or a planar surface, lens processing and assembly adjustment are easy, and deterioration of optical performance due to errors in processing and assembly adjustment can be prevented, which is preferable. In addition, the image plane is preferably shifted because deterioration of the drawing performance is small. In the case where the lens surface is an aspherical surface, the aspherical surface may be any one of an aspherical surface obtained by polishing, a glass-molded aspherical surface obtained by molding glass into an aspherical shape with a mold, and a compound aspherical surface obtained by molding a resin into an aspherical shape on the surface of glass. The lens surface may be a diffraction surface, or a refractive index distribution lens (GRIN lens) or a plastic lens may be used as the lens.

Although the aperture stop S is preferably disposed between the 1 st lens group G1 and the 2 nd lens group G2, it is also possible to replace the function by a frame of the lens without providing a member as an aperture stop.

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

Description of the reference numerals

1 Camera (optical device) OS (OS 1 to OS 5) optical system

GA front group GB back group S aperture (aperture diaphragm)

Claims

1. An optical system, wherein,

a front group, an aperture and a rear group with positive focal power are arranged in order from the object side,

the optical system satisfies the following condition:

0.100<LA/LB<0.400

wherein,,

LA: a distance on an optical axis from a lens surface of the front group closest to the object side to a lens surface of the front group closest to the image side at the time of infinity focusing,

LB: and a distance on an optical axis from a lens surface of the rear group closest to the object side to a lens surface of the rear group closest to the image side at the time of infinity focusing.

2. The optical system according to claim 1, wherein,

the optical system satisfies the following condition:

0.070<LAS/LAB<0.300

wherein,,

LAS: a distance on an optical axis from a lens surface of the front group closest to the object side to the diaphragm at the time of infinity focusing,

LAB (LAB): and a distance on an optical axis from a lens surface of the front group closest to the object side to a lens surface of the rear group closest to the image side at the time of infinity focusing.

3. The optical system according to claim 1 or 2, wherein,

the rear group has a negative lens NR satisfying the following condition:

0.000<LNRL/LB<0.400

0.800<R2NR/Bfa<3.000

wherein,,

LB: a distance on an optical axis from a lens surface of the rear group closest to the object side to a lens surface of the rear group closest to the image side at the time of infinity focusing,

LNRL: a distance on an optical axis from an image side lens surface of the negative lens NR to a lens surface of the rear group closest to the image side at the time of infinity focusing,

r2NR: the radius of curvature of the image side lens surface of the negative lens NR,

bfa: back focal length (air conversion length) of the optical system at the time of infinity focusing.

4. An optical system according to any one of claims 1 to 3, wherein,

the rear group has a negative lens NF satisfying the following formula:

0.600<LNFL/LB<1.000

0.500<(-R1NF)/Bfa<3.000

wherein,,

LNFL: an optical axis distance from an object side lens surface of the negative lens NF to a lens surface of the rear group closest to the image side at the time of infinity focusing,

r1NF: the radius of curvature of the object side lens surface of the negative lens NF,

5. The optical system according to any one of claims 1 to 4, wherein,

the rear group has:

a negative lens NR that is a negative lens having the largest optical power among negative lenses satisfying the following expression; and

Negative lens NF, which is the negative lens having the largest optical power among negative lenses satisfying the following expression:

0.000<LNRL/LB<0.400

0.800<R2NR/Bfa<3.000

0.600<LNFL/LB<1.000

0.500<(-R1NF)/Bfa<3.000

wherein,,

6. The optical system according to claim 5, wherein,

the optical system satisfies the following condition:

-0.800<(R1NF+R2NR)/(R1NF-R2NR)<0.800

wherein,,

r2NR: the negative lens NR has a radius of curvature of an image side lens surface.

7. An optical system according to claim 5 or 6, wherein,

the optical system satisfies the following condition:

0.200<fNF/fNR<1.200

wherein,,

fNF: the focal length of the negative lens NF,

fNR: the focal length of the negative lens NR.

8. 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.

9. The optical system according to any one of claims 5 to 8, wherein,

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,

the optical system satisfies the following condition:

0.300<fN1/fNL<1.200

wherein,,

fN1: the focal length of the negative lens N1,

fNL: the focal length of the negative lens NL.

10. The optical system according to any one of claims 1 to 9, wherein,

the rear group has an aspherical lens,

the optical system satisfies the following condition:

0.100<LASI/LAB<0.600

wherein,,

LASI: at the time of infinity focusing, the distance on the optical axis from the aspherical surface disposed closest to the image side in the rear group to the image plane,

11. The optical system according to any one of claims 1 to 10, wherein,

the rear group has an aspherical lens,

the optical system satisfies the following condition:

0.000<LASL/LAB<0.150

wherein,,

LASL: a distance on an optical axis from an aspherical surface disposed on the most image side in the rear group to a lens surface on the most image side in the rear group at the time of infinity focusing,

12. The optical system according to any one of claims 1 to 11, wherein,

the optical system satisfies the following condition:

0.800<fB/f<1.600

wherein,,

fB: focal length of the rear group at infinity focusing,

f: focal length of the entire system at infinity focusing.

13. An optical device comprising the optical system according to any one of claims 1 to 12.

14. A method of manufacturing an optical system, comprising,

the front group, the diaphragm, and the rear group having positive optical power are arranged in order from the object side so as to satisfy the following conditions:

0.100<LA/LB<0.400

wherein,,