JP2022176367A - Optical system and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system which offers a good optical performance, and an optical device having the same.

SOLUTION: An optical system OL substantially consists of two lens groups comprising, in order from an object side, a front group GF having a first negative meniscus lens L11, a second negative meniscus lens L12, and a third negative meniscus lens L13 and having negative refractive power, and a rear group GR with positive refractive power disposed on an image-plane side of the front group GF. The front group GF has a focusing lens group Gfo provided on the most image plane-side and configured to move along an optical axis direction when focusing. The first negative meniscus lens L11, the second negative meniscus lens L12, and the third negative meniscus lens L13 are stationary relative to the image plane while focusing and the rear group GR is also stationary relative to the image plane while focusing. The optical system is configured to satisfy conditions represented by given conditional expressions.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to optical systems and optical instruments.

2. Description of the Related Art Conventionally, an optical system that achieves a small size and a wide angle of view by using an aspherical lens has been proposed (see, for example, Patent Document 1). However, Patent Document 1 has a problem that further improvement in optical performance is demanded.

International Publication No. 2016/056310

An optical system according to a first aspect of the present invention is a front group having negative refractive power, which includes, in order from the object side, a first negative meniscus lens, a second negative meniscus lens, and a third negative meniscus lens. and a rear group having a positive refractive power disposed closer to the image plane than the front group, and the front group is located closest to the image plane side and is located on the optical axis during focusing. said first negative meniscus lens, said second negative meniscus lens and said third negative meniscus lens are fixed with respect to an image plane during focusing, said rear group is fixed with respect to the image plane during focusing and satisfies the following equation.
80° < 2ω < 180°
1.20<(-fF)/f<2.50
0.65<(-fF)/fR<0.85
0.85<(-fn123)/f<1.50
however,
2ω: total angle of view of the optical system f: focal length of the entire optical system in infinity focused state fF: focal length of the front group in infinity focused state fR: focal length of the rear group fn123: A combined focal length of the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens

Further, an optical system according to a second aspect of the present invention has a negative refractive power including, in order from the object side, a first negative meniscus lens, a second negative meniscus lens, and a third negative meniscus lens. It consists essentially of two lens groups, a front group and a rear group having a positive refractive power arranged closer to the image plane than the front group, and the front group is located closest to the image plane side, and is used for focusing. a focusing lens group that moves in an optical axis direction, wherein the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed with respect to an image plane during focusing; The rear group is fixed with respect to the image plane during focusing and satisfies the following condition.
80° < 2ω < 180°
0.65<(-fF)/fR<0.85
2.80<(-fn)/f<10.50
0.85<(-fn123)/f<1.50
however,
2ω: total angle of view of the optical system fF: focal length of the front group in an infinity focused state fR: focal length of the rear group f: focal length of the entire optical system in an infinity focused state fn: Focal length of the first negative meniscus lens fn123: combined focal length of the first negative meniscus lens, the second negative meniscus lens and the third negative meniscus lens

Further, an optical system according to a third aspect of the present invention has a negative refractive power having, in order from the object side, a first negative meniscus lens, a second negative meniscus lens, and a third negative meniscus lens. It consists essentially of two lens groups, a front group and a rear group having a positive refractive power arranged closer to the image plane than the front group, and the front group is located closest to the image plane side, and is used for focusing. a focusing lens group that moves in an optical axis direction, wherein the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed with respect to an image plane during focusing; The rear group is fixed with respect to the image plane during focusing and satisfies the following condition.
80° < 2ω < 180°
2.80<(-fn)/f<10.50
1.00 < fn/fF < 10.00
0.65<(-fF)/fR<0.85
0.85<(-fn123)/f<1.50
however,
2ω: total angle of view of the optical system f: focal length of the entire optical system in the infinity focused state fn: focal length of the first negative meniscus lens fF: focus of the front group in the infinity focused state Distance fR: Focal length of the rear group fn123: Combined focal length of the first negative meniscus lens, the second negative meniscus lens and the third negative meniscus lens

Further, an optical system according to a fourth aspect of the present invention comprises, in order from the object side, substantially two groups: a front group having negative refractive power, an aperture stop, and a rear group having positive refractive power. The front group has a focusing lens group that moves in the optical axis direction during focusing, and the front group has a positive lens component arranged adjacent to the object side of the focusing lens group. and the front group has a first negative meniscus lens closest to the object side and satisfies the following condition.
80° < 2ω < 180°
0.75<(-fF)/fR<0.95
1.20<(-fF)/f≤2.172
3.20<(-fn)/f<12.00
however,
2ω: total angle of view of the optical system fF: focal length of the front group in an infinity focused state fR: focal length of the rear group f: focal length of the entire optical system in an infinity focused state fn: Focal length of the first negative meniscus lens

FIG. 2 is a cross-sectional view showing the lens configuration of the optical system according to the first example in an infinity focused state; 4A and 4B are various aberration diagrams in the infinity focused state of the optical system according to the first example. FIG. 11 is a cross-sectional view showing the lens configuration of the optical system according to the second example in an infinity focused state; It is an aberration diagram in the infinity focus state of the optical system which concerns on 2nd Example. FIG. 12 is a cross-sectional view showing the lens configuration of the optical system according to the third embodiment in an infinity focused state; FIG. 10 is a diagram of various aberrations in the infinity focused state of the optical system according to the third example; 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;

Preferred embodiments are described below with reference to the drawings. As shown in FIG. 1, the optical system OL according to the first embodiment includes, in order from the most object side, a first negative meniscus lens L11, a second negative meniscus lens L12, a third negative meniscus lens L13, and a rear group GR arranged closer to the image plane than the front group GF. With this configuration, it is possible to realize an optical system that suppresses the occurrence of curvature of field and distortion, has small fluctuations in aberration due to focusing, and has a large back focal length relative to the focal length.

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

80° < 2ω < 180° (1)
however,
2ω: full angle of view of optical system OL

Conditional expression (1) defines the total angle of view of the optical system OL. By satisfying the conditional expression (1), it is possible to obtain good optical performance over the entire image circle while being compact and lightweight. If the lower limit of conditional expression (1) is not reached, it becomes difficult to correct spherical aberration and axial chromatic aberration, which is not preferable. In order to ensure the effect of conditional expression (1), it is more desirable to set the lower limit of conditional expression (1) to 85°, more preferably 90°, 95°, and 100°. Further, in order to ensure the effect of conditional expression (1), it is more desirable to set the upper limit of conditional expression (1) to 175°, more preferably 170°, 165°, 160°, and 150°.

In the optical system OL according to the first embodiment, the front group GF desirably has a focusing lens group Gfo that moves in the optical axis direction during focusing, closest to the image plane side. By configuring in this way, it is possible to suppress aberration fluctuation accompanying focusing.

Further, in the optical system OL according to the first embodiment, it is desirable that the focusing lens group Gfo moves along the optical axis toward the object side when focusing from infinity to a short distance object. With this configuration, it is possible to suppress variations in curvature of field and distortion accompanying focusing.

In the optical system OL according to the first embodiment, the front group GF includes a positive lens component (for example, the biconvex positive lens L16 in FIG. 1) arranged adjacent to the object side of the focusing lens group Gfo. It is desirable to have

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

0.05<(-fn123)/fp<1.00 (2)
however,
fn123: the combined focal length of the first negative meniscus lens L11, the second negative meniscus lens L12 and the third negative meniscus lens L13 fp: the positive lens component arranged adjacent to the object side of the focusing lens group Gfo of the front group GF focal length of

Conditional expression (2) is defined by three lens elements arranged closest to the object side of the focusing lens group Gfo of the front group GF with respect to the focal length of the positive lens component arranged adjacent to the object side of the focusing lens group Gfo of the front group GF. It specifies the synthetic focal length of a negative meniscus lens. Satisfying conditional expression (2) makes it possible to achieve compactness, satisfactorily correct spherical aberration, axial chromatic aberration, chromatic aberration of magnification, and the like, while suppressing aberration fluctuations due to focusing. If the lower limit of conditional expression (2) is not reached, it is difficult to correct chromatic aberration of magnification, curvature of field, and distortion, which is not preferable. In order to ensure the effect of conditional expression (2), the lower limit of conditional expression (2) should be set to 0.10, and further to 0.15, 0.20, 0.25, and 0.28. is more desirable. If the upper limit of conditional expression (2) is exceeded, it is difficult to suppress aberration fluctuations due to focusing, which is not preferable. In order to ensure the effect of the conditional expression (2), the upper limit of the conditional expression (2) is set to 0.90, 0.85, 0.80, 0.75, 0.70, 0.90, 0.85, 0.80, 0.75, 0.70, 0.90. More preferably 65, 0.60, 0.55, 0.50, 0.45 and 0.42.

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

0.50<(-fn123)/f<1.50 (3)
however,
f: focal length of the entire optical system OL in the infinity focused state fn123: combined focal length of the first negative meniscus lens L11, the second negative meniscus lens L12, and the third negative meniscus lens L13

Conditional expression (3) defines the combined focal length of the three negative meniscus lenses arranged closest to the object side in the first lens group G1 with respect to the focal length of the entire optical system OL in the infinity focused state. It is stipulated. By satisfying the conditional expression (3), it is possible to obtain a compact optical system in which various aberrations are satisfactorily corrected while ensuring a long back focus with respect to the focal length. If the lower limit of conditional expression (3) is not reached, it becomes difficult to correct lateral chromatic aberration, which is not preferable. In order to ensure the effect of conditional expression (3), the lower limit of conditional expression (3) is set to 0.55, and further to 0.60, 0.65, 0.70, 0.75, 0.55, 0.60, 0.65, 0.70, 0.75, 0.55 80, 0.85, 0.90, 0.95 and 1.00 are more desirable. If the upper limit of conditional expression (3) is exceeded, the size of the optical system will increase. In order to ensure the effect of conditional expression (3), the upper limit of conditional expression (3) is set to 1.45, and further 1.40, 1.35, 1.30, 1.25, 1.45, 1.30, 1.25, 1.45, 1.40, 1.35, 1.30, 1.25, 1.45. 20 and 1.15 are more desirable.

Moreover, in the optical system OL according to the first embodiment, it is desirable that the front group GF has negative refractive power and the rear group GR has positive refractive power. With this configuration, aberrations can be satisfactorily corrected, and favorable optical performance can be ensured.

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

0.20<(-fF)/fR<2.00 (4)
however,
fF: focal length of the front group GF when in focus at infinity fR: focal length of the rear group GR

Conditional expression (4) defines the focal length of the front group GF in the infinity focused state with respect to the focal length of the rear group GR. By satisfying the conditional expression (4), it is possible to obtain a compact optical system in which various aberrations are satisfactorily corrected while ensuring a sufficient back focus for the focal length. If the lower limit of conditional expression (4) is not reached, the size of the rear group GR increases, and if the size is forcibly reduced, it becomes difficult to correct spherical aberration, coma, and chromatic aberration of magnification, which is not preferable. In order to ensure the effect of conditional expression (4), the lower limit of conditional expression (4) is set to 0.25, 0.30, 0.35, 0.40, 0.45, 0.25, 0.30, 0.35, 0.40, 0.45, 0.25. 50, 0.55, 0.60, 0.65, 0.70 and 0.75 are more desirable. If the upper limit of conditional expression (4) is exceeded, the size of the front group GF becomes large in order to secure a sufficient back focus, and if the size is forcibly reduced, correction of curvature of field and distortion becomes difficult, which is not preferable. . In order to ensure the effect of conditional expression (4), the upper limit of conditional expression (3) is set to 1.90, further 1.80, 1.70, 1.60, 1.50, 1.90 40, 1.30, 1.20, 1.10, 1.00, 0.95, 0.90 and 0.85 are more desirable.

Further, the optical system OL according to the second embodiment has, in order from the object side, a front group GF having negative refractive power, an aperture stop S, and a rear group GR having positive refractive power. , the front group GF has a focusing lens group Gfo that moves in the optical axis direction during focusing. With this configuration, it is possible to realize an optical system that suppresses the occurrence of curvature of field and distortion, has small fluctuations in aberration due to focusing, and has a large back focal length relative to the focal length.

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

Conditional expression (1) defines the total angle of view of the optical system OL. By satisfying the conditional expression (1), it is possible to obtain good optical performance over the entire image circle while being compact and lightweight. If the lower limit of conditional expression (1) is not reached, it becomes difficult to correct spherical aberration and axial chromatic aberration, which is not preferable. In order to ensure the effect of conditional expression (1), it is more desirable to set the lower limit of conditional expression (1) to 85°, more preferably 90°, 95°, and 100°. Further, in order to ensure the effect of conditional expression (1), it is more desirable to set the upper limit of conditional expression (1) to 175°, more preferably 170°, 165°, 160°, and 150°.

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

0.20<(-fF)/fR<2.00 (4)
however,
fF: focal length of the front group GF when in focus at infinity fR: focal length of the rear group GR

Conditional expression (4) defines the focal length of the front group GF in the infinity focused state with respect to the focal length of the rear group GR. By satisfying the conditional expression (4), it is possible to obtain a compact optical system in which various aberrations are satisfactorily corrected while ensuring a sufficient back focus for the focal length. If the lower limit of conditional expression (4) is not reached, the size of the rear group GR increases, and if the size is forcibly reduced, it becomes difficult to correct spherical aberration, coma, and chromatic aberration of magnification, which is not preferable. In order to ensure the effect of conditional expression (4), the lower limit of conditional expression (4) is set to 0.25, 0.30, 0.35, 0.40, 0.45, 0.25, 0.30, 0.35, 0.40, 0.45, 0.25. 50, 0.55, 0.60, 0.65, 0.70 and 0.75 are more desirable. If the upper limit of conditional expression (4) is exceeded, the size of the front group GF becomes large in order to secure a sufficient back focus, and if the size is forcibly reduced, correction of curvature of field and distortion becomes difficult, which is not preferable. . In order to ensure the effect of conditional expression (4), the upper limit of conditional expression (3) is set to 1.90, further 1.80, 1.70, 1.60, 1.50, 1.90 40, 1.30, 1.20, 1.10, 1.00, 0.95, 0.90 and 0.85 are more desirable.

Further, in the optical system OL according to the second embodiment, it is desirable that the focusing lens group Gfo moves along the optical axis toward the object side when focusing from infinity to a short distance object. With this configuration, fluctuations in spherical aberration and longitudinal chromatic aberration due to focusing can be suppressed.

Further, in the optical system OL according to the second embodiment, the front group GF has, in order from the most object side, a first negative lens L11, a second negative lens L12, and a third negative lens L13. is desirable. With this configuration, it is possible to satisfactorily correct curvature of field and distortion.

In the optical system OL according to the second embodiment, the front group GF has at least one positive lens component (for example, the biconvex positive lens L16 in FIG. 1) on the object side of the focusing lens group Gfo. is desirable. With such a configuration, spherical aberration, longitudinal chromatic aberration, and lateral chromatic aberration can be satisfactorily corrected.

Further, it is desirable that the optical system OL according to the first and second embodiments satisfy the following conditional expression (5).

1.00 < bfa/f (5)
however,
f: focal length of the entire optical system OL in the infinity focused state bfa: air-converted back focus of the optical system OL

Conditional expression (5) defines the air-converted back focus of the optical system OL with respect to the focal length of the entire optical system OL in the infinity focused state. The back focus bfa indicates the distance (air conversion length) on the optical axis from the lens surface closest to the image plane side of the optical system OL to the image plane I when focusing on infinity. By satisfying conditional expression (5), it is possible to obtain a long back focus suitable for a single-lens reflex camera having a mirror box while ensuring a wide angle of view. If the lower limit of conditional expression (5) is not reached, the focal length must be increased in order to secure the back focus, and a wide angle of view cannot be secured, which is not preferable. In order to ensure the effect of conditional expression (5), the lower limit of conditional expression (5) is set to 1, 30, 1.50, 1.80, 2.00, 2.10, 2. 20, 2.30 is more desirable.

In the optical system OL according to the first and second embodiments, the front group GF desirably has a negative meniscus lens (for example, the negative meniscus lens L11 in FIG. 1) closest to the object side. With this configuration, various aberrations, particularly curvature of field and distortion can be corrected satisfactorily.

Moreover, it is desirable that the optical system OL according to the first and second embodiments satisfy the following conditional expression (6).

2.00<(-fn)/f<12.00 (6)
however,
f: focal length of the entire optical system OL in the infinity focused state fn: focal length of the negative meniscus lens closest to the object side in the front group GF

Conditional expression (6) defines the focal length of the negative meniscus lens closest to the object side in the front group GF with respect to the focal length of the entire optical system OL in the infinity focused state. By satisfying the conditional expression (6), it is possible to obtain an optical system which has a sufficient amount of peripheral light in spite of its small size and which satisfactorily corrects curvature of field and distortion. If the lower limit of conditional expression (6) is not reached, correction of distortion becomes difficult, which is not preferable. In order to ensure the effect of conditional expression (6), the lower limit of conditional expression (6) is set to 2.30, further 2.50, 2.80, 3.00, 3.10, 3.00, 3.00, 3.10, 3.00, 2.50, 2.80, 3.00, 3.10, and 3.00. 20 and 3.30 are more desirable. Further, if the upper limit of conditional expression (6) is exceeded, correction of curvature of field becomes difficult, which is not preferable. In addition, in order to ensure the effect of conditional expression (6), the upper limit of conditional expression (6) is set to 11.00, and further to 10.50, 10.00, 9.50, 9.00, 8. 90, 8.80 and 8.70 are more desirable.

Further, it is desirable that the optical system OL according to the first and second embodiments satisfy conditional expression (7) shown below.

1.00 < fn/fF < 10.00 (7)
however,
fF: focal length of the front group GF when in focus at infinity fn: focal length of the negative meniscus lens closest to the object in the front group GF

Conditional expression (7) defines the focal length of the negative meniscus lens closest to the object side of the front group GF with respect to the focal length of the front group GF in the infinity focused state. By satisfying the conditional expression (7), it is possible to obtain an optical system which has a sufficient amount of peripheral light in spite of its small size and which satisfactorily corrects curvature of field and distortion. If the lower limit of conditional expression (7) is not reached, it becomes difficult to correct distortion. In addition, it becomes difficult to correct the chromatic aberration of magnification. In order to ensure the effect of conditional expression (7), the lower limit of conditional expression (7) is set to 1.10, and further 1.20, 1.30, 1.40, 1.45, 1.20, 1.30, 1.40, 1.45, 1.10. 50 and 1.55 are more desirable. Further, when the upper limit of conditional expression (7) is exceeded, it becomes difficult to correct field curvature and secure the amount of peripheral light. In addition, in order to ensure the effect of conditional expression (7), the upper limit of conditional expression (7) is set to 9.00, and further 8.00, 7.50, 7.00, 6.50, 6.00, 7.00, 6.50, 6.00, 7.00, 6.50, 6.00, 8.00, 7.50, 7.00, 6.50, 6.00 00 and 5.50 are more desirable.

Moreover, it is desirable that the optical system OL according to the first and second embodiments satisfy the following conditional expression (8).

1.00<(-fF)/f<5.00 (8)
however,
f: focal length of the entire optical system OL in the infinity focused state fF: focal length of the front group GF in the infinity focused state

Conditional expression (8) defines the focal length of the front group GF in the infinity focused state with respect to the focal length of the entire optical system OL in the infinity focused state. By satisfying the conditional expression (8), it is possible to obtain an optical system which is compact and lightweight, secures a sufficient back focus for a single-lens reflex camera equipped with a mirror box, and satisfactorily corrects various aberrations. can be done. If the lower limit of conditional expression (8) is not reached, the size of the rear group GR increases, and if the size is forcibly reduced, it becomes difficult to correct spherical aberration, coma, and chromatic aberration of magnification, which is not preferable. In order to ensure the effect of conditional expression (8), the lower limit of conditional expression (8) is set to 1.10, and further 1.20, 1.30, 1.35, 1.40, 1.20, 1.30, 1.35, 1.40, 1.10. 45, 1.50 and 1.55 are more desirable. Further, if the upper limit of conditional expression (8) is exceeded, the size of the front group GF becomes large in order to secure a sufficient back focus. . In order to ensure the effect of conditional expression (8), the upper limit of conditional expression (8) is set to 4.50, and further to 4.00, 3.50, 3.00, 2.80, 2. 50, 2.40, 2.30 and 2.20 are more desirable.

Further, in the optical system OL according to the first and second embodiments, the front group GF has a positive lens component arranged adjacent to the object side of the focusing lens group Gfo under the following conditions: It is desirable to satisfy equation (9).

1.00<fp/f<5.00 (9)
however,
f: focal length of the entire optical system OL in the infinity focused state fp: focal length of the positive lens component arranged adjacent to the object side of the focusing lens group Gfo of the front group GF

Conditional expression (9) is the focal length of the positive lens component arranged adjacent to the object side of the focusing lens group Gfo of the front group GF with respect to the focal length of the entire optical system OL in the infinity focused state. It defines the distance. By satisfying the conditional expression (9), various aberrations, especially curvature of field and spherical aberration can be satisfactorily corrected. If the lower limit of conditional expression (9) is not reached, correction of spherical aberration becomes difficult, which is not preferable. In order to ensure the effect of conditional expression (9), the lower limit of conditional expression (9) is set to 1.30, and further 1.50, 1.80, 2.00, 2.30, 2.00, 2.00, 2.30, 2.00, 1.50, 1.80, 2.00, 2.30, 2.30 40, 2.50, 2.60 and 2.70 are more desirable. On the other hand, if the upper limit of conditional expression (9) is exceeded, aberration fluctuations accompanying focusing become large, which is not preferable. In addition, in order to ensure the effect of conditional expression (9), the upper limit of conditional expression (9) is set to 4.80, and further to 4.50, 4.30, 4.00, 3.90, 3.00, 4.50, 4.30, 4.00, 3.90, 3.00, and 3.00. 80, 3.70 and 3.60 are more desirable.

Further, in the optical system OL according to the first and second embodiments, it is desirable that the focusing lens group Gfo is a cemented lens in which a negative lens and a positive lens are cemented together. By using a cemented lens in which a positive lens and a negative lens are cemented together as the focusing lens group Gfo, it is possible to suppress aberration fluctuations accompanying focusing, especially axial fluctuations.

In the optical system OL according to the first and second embodiments, the front group GF includes a cemented lens in which a positive lens and a negative lens are cemented together (for example, a biconvex positive lens L14 and a biconcave negative lens L14 in FIG. 1). It is desirable to have cemented lens CL1) cemented with lens L15. With this configuration, various aberrations, especially lateral chromatic aberration, can be suppressed.

In the optical system OL according to the first and second embodiments, the first lens group G1 includes, from the side closest to the object, a first negative lens L11, a second negative lens L12, a third negative lens L13, a positive lens By having L14 and the fourth negative lens L15, it is possible to satisfactorily correct field curvature, distortion, and lateral chromatic aberration.

Here, it is desirable that the positive lens L14 and the fourth negative lens L15 be a cemented lens. With this configuration, various aberrations, especially lateral chromatic aberration, can be suppressed.

Also, the first negative lens L11 is preferably a negative meniscus lens with a convex surface facing the object side. With this configuration, various aberrations, particularly curvature of field and distortion can be corrected satisfactorily.

Also, the second negative lens L12 is preferably a negative meniscus lens with a convex surface facing the object side. With this configuration, various aberrations, particularly curvature of field and distortion can be corrected satisfactorily.

Also, the third negative lens L13 is preferably a negative meniscus lens with a convex surface facing the object side. With this configuration, various aberrations, particularly curvature of field and distortion can be corrected satisfactorily.

In the optical system OL according to the first and second embodiments, it is desirable that the focusing lens group Gfo moves along the optical axis toward the object side when focusing from infinity to a short distance object. With this configuration, fluctuations in spherical aberration and longitudinal chromatic aberration due to focusing can be suppressed.

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.

FIG. 7 shows a schematic cross-sectional view of a single-lens reflex camera 1 (hereinafter simply referred to as a camera) as an imaging device equipped with the optical system OL described above. In this camera 1, light from an unillustrated object (subject) is condensed by a photographing lens 2 (optical system OL) and formed into an image on a focusing screen 4 via a quick return mirror 3. FIG. The light imaged on the reticle 4 is reflected multiple times in the pentaprism 5 and guided to the eyepiece 6 . This allows the photographer to observe the object (subject) image as an erect image through the eyepiece lens 6 .

Also, when a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light from an object (subject) (not shown) condensed by the taking lens 2 is transferred to the image sensor 7. A subject image is formed on the top. As a result, light from an object (subject) is imaged by the imaging element 7 and recorded in a memory (not shown) as an object (subject) image. In this way, the photographer can photograph an object (subject) with the camera 1 . The camera 1 shown in FIG. 7 may detachably hold the photographing lens 2 or may be molded integrally with the photographing lens 2 . The camera 1 may be a so-called single-lens reflex camera, a compact camera without a quick return mirror or the like, or a mirrorless single-lens reflex camera.

Taking the optical system OL according to the second embodiment as an example, the outline of the method for manufacturing the optical system OL according to the present embodiment will be described below with reference to FIG. First, each lens is arranged to prepare the front group GF, the aperture diaphragm S and the rear group GR of the optical system OL (step S100). Further, a focusing lens group Gfo that moves in the optical axis direction during focusing is arranged in the front group GF (step S200). Then, each lens group and the aperture stop S are arranged so as to satisfy the condition of a predetermined conditional expression (for example, conditional expression (1) described above) (step S300).

Specifically, in this embodiment, for example, as shown in FIG. 1, the optical system OL includes, in order from the object side, a meniscus-shaped first negative lens L11 with a convex surface facing the object side, a second meniscus-shaped negative lens L12, a third meniscus-shaped negative lens L13 with a convex surface facing the object side, a cemented lens CL1 in which a biconvex positive lens L14 and a biconcave negative lens L15 are cemented together, and a biconvex positive lens L16. , and a cemented lens in which a meniscus-shaped negative lens L21 having a convex surface facing the object side and a meniscus-shaped positive lens L22 having a convex surface facing the object side are cemented to form a front group GF, and a biconvex positive lens L31. and a biconcave negative lens L32, a meniscus positive lens L33 with a convex surface facing the object side, and a meniscus negative lens L34 with a convex surface facing the object side cemented with a biconvex positive lens L35. A cemented lens, a cemented lens in which a negative meniscus lens L36 having a convex surface facing the object side and a biconvex positive lens L37 are cemented together, and a negative meniscus lens L38 having a convex surface facing the image plane side are arranged. Let the group be GR. A cemented lens obtained by cementing a negative lens L21 having a convex surface facing the object side and a positive lens L22 having a convex surface facing the object side in the front group GF is referred to as a focusing lens group Gfo. Then, the optical system OL is manufactured by arranging the lens groups and the aperture stop S prepared in this way according to the procedure described above.

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

Each embodiment of the present application will be described below with reference to the drawings. 1, 3, and 5 are sectional views showing the configuration and refractive power distribution of the optical system OL (OL1 to OL3) 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 (a)

In each embodiment, the second-order aspheric coefficient A2 is zero. In addition, in the tables of each example, an asterisk (*) is attached to the right side of the surface number of an aspherical surface.

[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 GF having negative refractive power and a rear group GR having positive refractive power. The front group GF is composed of, in order from the object side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power.

The first lens group G1 includes, in order from the object side, a meniscus-shaped first negative lens (or first negative meniscus lens) L11 with a convex surface facing the object side, and a meniscus-shaped second negative lens with a convex surface facing the object side. (or second negative meniscus lens) L12, a third negative meniscus lens (or third negative meniscus lens) L13 having a convex surface facing the object side, and a cemented joint of a biconvex positive lens L14 and a biconcave negative lens L15. It is composed of a lens CL1 and a biconvex positive lens L16.

The second lens group G2 is composed of a cemented lens in which a meniscus-shaped negative lens L21 having a convex surface facing the object side and a meniscus-shaped positive lens L22 having a convex surface facing the object side are cemented in order from the object side. .

The rear group GR (hereinafter referred to as the "third lens group G3") comprises, in order from the object side, a cemented lens in which a biconvex positive lens L31 and a biconcave negative lens L32 are cemented together. A positive lens L33, a cemented lens in which a meniscus-shaped negative lens L34 having a convex surface facing the object side and a biconvex positive lens L35 are cemented together, a meniscus-shaped negative lens L36 having a convex surface facing the object side, and a biconvex positive lens L37. and a negative meniscus lens L38 with a convex surface facing the image plane side.

In the optical system OL1, an aperture stop S is arranged between the second lens group G2 and the third lens group G3 (between the front group GF and the rear group GR). A filter FL is arranged between the third lens group G3 and the image plane I in the optical system OL1.

In this optical system OL1, focusing from an infinite object to a close object is performed by fixing the first lens group G1 and the third lens group G3 with respect to the image plane I, and the second lens group G2. This is done by moving the focusing lens group Gfo along the optical axis from the image plane side to the object side.

Table 1 below lists the values of the specifications of the optical system OL1. In this Table 1, f shown in the overall specifications is the focal length of the entire system in the infinity focused state, FNO is the F number, ω is the half angle of view [°], Y is the maximum image height, and TL is the total length. represents a value. Here, the total length TL indicates the distance on the optical axis from the lens surface closest to the object (the first surface in FIG. 1) to the image plane I when in focus at 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 νd and the fifth column nd are the Abbe number and refractive index 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. Further, the lens group focal length indicates the surface number and focal length of the starting surface of each of the front group GF, the first lens group G1, the second lens group G2 and the third lens group G3 (the focal length of the front group GF The distance is the value when the lens is in focus at infinity).

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 = 14.36
FNO = 2.88
ω [°] = 56.4
Y = 21.60
TL = 159.9

[Lens data]
m r d νd nd
Object plane ∞ D0
1 47.0219 2.5000 59.95 1.631835
2 26.9000 8.6766
3* 37.7100 2.5000 82.57 1.497820
4* 13.9470 16.4215
5 125.3586 2.3000 52.67 1.741000
6* 28.0288 7.9769
7 384.3276 6.4852 31.85 1.826164
8 -32.1222 3.0000 81.47 1.487469
9 32.0024 10.9635
10 84.4517 9.4797 91.37 1.456000
11 -25.7140 D1
12 152.3955 1.2000 33.60 1.862086
13 13.3320 4.3737 30.37 1.899345
14 40.8063 D2
15 0.0000 0.0500 Aperture diaphragm S
16 21.4627 5.6551 53.56 1.507742
17 -29.7782 1.0000 25.46 2.000690
18 39.2894 0.1000
19 24.3575 2.3131 23.94 1.768502
20 98.6099 0.1000
21 17.1858 1.0000 31.10 1.897498
22 12.1955 5.3161 70.32 1.487490
23 -53.4117 0.1592
24 2408.9184 1.0000 32.26 1.737999
25 11.7446 5.2963 26.87 1.659398
26 -45.7195 0.3474
27 -68.6279 1.2000 47.25 1.773870
28* -986.9537 38.0908
29 0.0000 2.0000 64.13 1.516800
30 0.0000 BF
Image plane ∞

[Lens group focal length]
Lens group starting surface focal length front group GF 1 -26.6303
1st lens group G1 1 127.4216
Second lens group G2 12 -76.3989
Third lens group G3 16 33.6830

In this optical system OL1, the 3rd, 4th, 6th and 28th surfaces are aspherical. Table 2 below shows the data of the aspherical surface, namely the values of the conic constant K and the respective aspherical constants A4-A10.

(Table 2)
[Aspheric data]
Surface K A4 A6 A8 A10
3 1.0000 -2.84128E-06 1.77032E-08 -1.78479E-11 1.20562E-14
4 0.1703 -1.57086E-06 8.88007E-09 9.96821E-11 -7.62152E-14
6 1.0000 2.01863E-05 1.95042E-08 2.45909E-11 -2.94950E-14
28 1.0000 3.93832E-05 5.20934E-08 8.66287E-10 -5.91381E-12

In this optical system OL1, the axial distance D0 from the most object side surface (first surface) of the optical system OL1 to the object, the axial distance D1 between the first lens group G1 and the second lens group G2, the second lens An axial distance D2 between the group G2 and the aperture diaphragm S (the third lens group G3) and an axial distance BF between the filter FL and the image plane I change upon focusing. Table 3 below shows the variable spacing for infinity focus and near object focus. Note that β indicates a photographing magnification.

(Table 3)
[Variable interval data]
Infinity Short distance f 14.35999 －
β - -0.03330
D0 ∞ 392.93110
D1 18.06566 16.30623
D2 2.42023 4.15465
BF 0.00000 -0.00603

Table 4 below shows values corresponding to each conditional expression in this optical system OL1. In Table 4, 2ω is the total angle of view of the optical system OL1, f is the focal length of the entire optical system OL1 in the infinity focused state, and fF is the focal length of the front group GF in the infinity focused state. , fR is the focal length of the third lens group G3 which is the rear group GR, fp is the focal length of the positive lens component arranged adjacent to the object side of the focusing lens group Gfo of the front group GF, and fn123 is the focal length of the third lens group G3. bfa is the back focus of the optical system OL1 converted to air; Each represents the focal length of the lens. The description of these symbols is the same for the following embodiments. In this first embodiment, fp is the focal length of the biconvex positive lens L16, and fn is the focal length of the first negative meniscus lens L11.

(Table 4)
fp = 44.4254
fn123=-14.9537
bfa = 39.4093
fn=-104.5181

(1) 2ω=112.8
(2) (-fn123)/fp=0.337
(3) (-fn123)/f = 1.041
(4) (-fF)/fR = 0.791
(5) bfa/f = 2.744
(6) (-fn)/f = 7.278
(7) fn/fF = 3.925
(8) (-fF)/f = 1.854
(9) fp/f = 3.094

Thus, the optical system OL1 satisfies all of the above conditional expressions (1) to (9).

FIG. 2 shows a spherical aberration diagram, an astigmatism diagram, a distortion aberration diagram, a lateral chromatic aberration diagram, and a coma aberration diagram when the optical system OL1 is in focus at infinity. In each aberration diagram, FNO indicates F number and Y indicates image height. The spherical aberration diagram shows the F-number value 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, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. In the coma aberration diagrams, the solid line indicates the meridional coma, and the dashed lines indicate the Y direction (meridional) and Z direction (sagittal) of the skew ray. 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 GF having negative refractive power and a rear group GR having positive refractive power. The front group GF is composed of, in order from the object side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power.

The first lens group G1 includes, in order from the object side, a meniscus-shaped first negative lens (or first negative meniscus lens) L11 with a convex surface facing the object side, and a meniscus-shaped second negative lens with a convex surface facing the object side. (or second negative meniscus lens) L12, a third negative meniscus lens (or third negative meniscus lens) L13 having a convex surface facing the object side, and a cemented joint of a biconvex positive lens L14 and a biconcave negative lens L15. It is composed of a lens CL1 and a biconvex positive lens L16.

The second lens group G2 is composed of a cemented lens in which a meniscus-shaped negative lens L21 having a convex surface facing the object side and a meniscus-shaped positive lens L22 having a convex surface facing the object side are cemented in order from the object side. .

The rear group GR (hereinafter referred to as the "third lens group G3") comprises, in order from the object side, a cemented lens in which a biconvex positive lens L31 and a biconcave negative lens L32 are cemented together. A positive lens L33, a cemented lens in which a meniscus-shaped negative lens L34 having a convex surface facing the object side and a biconvex positive lens L35 are cemented together, a meniscus-shaped negative lens L36 having a convex surface facing the object side, and a biconvex positive lens L37. and a double concave negative lens L38.

In the optical system OL2, an aperture stop S is arranged between the second lens group G2 and the third lens group G3 (between the front group GF and the rear group GR). A filter FL is arranged between the third lens group G3 and the image plane I in the optical system OL2.

In this optical system OL2, focusing from an infinite object to a close object is performed by fixing the first lens group G1 and the third lens group G3 with respect to the image plane I, and the second lens group G2. This is done by moving the focusing lens group Gfo along the optical axis from the image plane side to the object side.

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

(Table 5) Second embodiment [overall specifications]
f = 12.36
FNO = 2.88
ω [°] = 61.2
Y = 21.60
TL = 165.6

[Lens data]
m r d νd nd
Object plane ∞ D0
1* 123.6764 3.0000 43.81 1.837208
2 26.9000 10.8592
3* 34.1255 2.5000 87.13 1.468099
4* 17.5865 13.7281
5 72.2114 2.3000 40.66 1.883000
6* 28.0288 9.3790
7 209.6969 9.2128 26.90 1.755328
8 -29.5048 2.5559 84.24 1.477461
9 31.8373 8.9410
10 60.9536 12.1981 91.37 1.456000
11-28.3539 D1
12 297.1761 1.0226 30.08 1.806044
13 12.2150 5.9179 28.04 1.813749
14 51.2545 D2
15 0.0000 0.0500 Aperture diaphragm S
16 22.5323 4.6551 56.39 1.500845
17 -33.5240 1.0000 25.38 1.994547
18 37.3510 0.1000
19 25.0529 2.1694 25.77 1.720823
20 90.6318 0.1000
21 17.7582 1.0000 33.75 1.865872
22 12.8125 5.0030 70.32 1.487490
23 -54.9085 0.9159
24 326.9572 1.0000 32.26 1.737999
25 11.6430 5.2310 26.87 1.659398
26 -50.9878 0.0500
27 -96.5889 1.1078 47.25 1.773870
28* 4697.2424 38.0937
29 0.0000 2.0000 64.13 1.516800
30 0.0000 BF
Image plane ∞

[Lens group focal length]
Lens group starting surface focal length front group GF 1 -26.8417
First lens group G1 1 89.3772
Second lens group G2 12 -81.0572
Third lens group G3 16 34.7892

In this optical system OL2, the first, third, fourth, sixth and twenty-eighth surfaces are aspherical. Table 6 below shows the data of the aspherical surface, namely the values of the conic constant K and the respective aspherical constants A4-A10.

(Table 6)
[Aspheric data]
Surface K A4 A6 A8 A10
1 2.9452 8.50155E-06 -6.55314E-09 2.83916E-12 -4.23824E-16
3 1.0000 -1.17482E-05 2.74323E-08 -1.86417E-11 -1.88477E-15
4 0.5619 -4.26615E-06 7.98631E-08 -2.70962E-10 1.56850E-13
6 1.0000 1.13709E-05 1.60615E-09 1.49741E-10 -3.77636E-13
28 1.0000 3.40787E-05 4.23370E-08 7.46077E-10 -4.31808E-12

In this optical system OL2, an axial distance D0 from the most object-side surface (first surface) of the optical system OL1 to the object, an axial distance D1 between the first lens group G1 and the second lens group G2, a second lens An axial distance D2 between the group G2 and the aperture diaphragm S (the third lens group G3) and an axial distance BF between the filter FL and the image plane I change upon focusing. Table 7 below shows the variable spacing for infinity focus and near object focus. Note that β indicates a photographing magnification.

(Table 7)
[Variable interval data]
Infinity Short distance f 12.36000 －
β - -0.02500
D0 ∞ 460.73750
D1 19.32015 17.66124
D2 2.21228 3.87119
BF 0.00000 -0.01285

Table 8 below shows values corresponding to each conditional expression in this optical system OL2. In this second embodiment, fp is the focal length of the biconvex positive lens L16, and fn is the focal length of the first negative meniscus lens L11.

(Table 8)
fp = 44.3349
fn123=-13.1306
bfa = 39.4122
fn=-41.6500

(1) 2ω=122.4
(2) (-fn123)/fp=0.296
(3) (-fn123)/f = 1.062
(4) (-fF)/fR = 0.772
(5) bfa/f = 3.189
(6) (-fn)/f = 3.370
(7) fn/fF = 1.552
(8) (-fF)/f = 2.172
(9) fp/f = 3.587

Thus, the optical system OL2 satisfies all of the above conditional expressions (1) to (9).

FIG. 4 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, a lateral chromatic aberration diagram, and a coma aberration diagram when the optical system OL2 is in focus at infinity. From these aberration diagrams, it can be seen that the optical system OL2 is well corrected for various aberrations.

[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 GF having negative refractive power and a rear group GR having positive refractive power. The front group GF is composed of, in order from the object side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power.

The first lens group G1 includes, in order from the object side, a meniscus-shaped first negative lens (or first negative meniscus lens) L11 with a convex surface facing the object side, and a meniscus-shaped second negative lens with a convex surface facing the object side. (or second negative meniscus lens) L12, a third negative meniscus lens (or third negative meniscus lens) L13 having a convex surface facing the object side, and a cemented joint of a biconvex positive lens L14 and a biconcave negative lens L15. It is composed of a lens CL1 and a biconvex positive lens L16.

The second lens group G2 is composed of a cemented lens in which a meniscus-shaped negative lens L21 having a convex surface facing the object side and a meniscus-shaped positive lens L22 having a convex surface facing the object side are cemented in order from the object side. .

The rear group GR (hereinafter referred to as the "third lens group G3") comprises, in order from the object side, a cemented lens in which a biconvex positive lens L31 and a biconcave negative lens L32 are cemented together. A positive lens L33, a cemented lens in which a meniscus-shaped negative lens L34 with a convex surface facing the object side is cemented with a biconvex positive lens L35, a cemented lens in which a biconcave negative lens L36 and a biconvex positive lens L37 are cemented, and It is composed of a biconcave negative lens L38.

Further, in the optical system OL3, an aperture stop S is arranged between the second lens group G2 and the third lens group G3. A filter FL is arranged between the third lens group G3 and the image plane I in the optical system OL3.

In the optical system OL3, focusing from an infinite object to a close object is performed by fixing the first lens group G1 and the third lens group G3 with respect to the image plane I, and the second lens group G2. This is done by moving the focusing lens group Gfo along the optical axis from the image plane side to the object side.

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

(Table 9) Third embodiment [overall specifications]
f = 16.48
FNO = 2.88
ω [°] = 52.8
Y = 21.60
TL = 160.0

[Lens data]
m r d νd nd
Object plane ∞ D0
1 39.6142 5.0000 52.34 1.755000
2 27.3858 8.5477
3* 33.2055 2.5000 82.57 1.497820
4* 13.1996 15.9987
5 83.3700 2.3000 52.67 1.741000
6* 28.0288 7.4882
7 903.1304 8.3689 30.08 1.911918
8 -41.4440 3.0000 80.65 1.490638
9 33.5455 10.7750
10 84.0718 10.1279 91.37 1.456000
11-26.2853 D1
12 446.9940 1.2000 33.67 1.861126
13 15.7892 4.2607 29.37 1.922788
14 44.2919 D2
15 0.0000 0.0500 Aperture diaphragm S
16 22.0269 4.2536 53.81 1.507088
17 -35.1767 1.0000 25.32 1.989791
18 41.4549 0.1000
19 28.1065 2.5043 22.74 1.808090
20 464.3428 0.1000
21 17.9194 1.0000 30.30 1.908654
22 12.7733 5.3094 70.32 1.487490
23 -52.2422 1.5697
24 -75.1921 1.0000 32.26 1.737999
25 12.5296 5.1199 26.87 1.659398
26 -75.7013 0.1000
27 -2698.6076 1.2000 47.25 1.773870
28* 598.3062 38.3669
29 0.0000 2.0000 64.13 1.516800
30 0.0000 BF
Image plane ∞

[Lens group focal length]
Lens group starting surface focal length front group GF 1 -26.3599
First lens group G1 1 132.8313
Second lens group G2 12 -67.9699
Third lens group G3 16 32.6991

In this optical system OL3, the 3rd, 4th, 6th and 28th surfaces are aspherical. Table 10 below shows the data of the aspheric surface, namely the values of the conic constant K and each of the aspheric constants A4-A10.

(Table 10)
[Aspheric data]
Surface K A4 A6 A8 A10
3 1.0000 -6.10454E-06 1.37878E-08 -1.88319E-11 1.07993E-14
4 0.3686 -4.34076E-06 -1.36341E-08 1.07882E-10 -2.38693E-13
6 1.0000 1.36143E-05 2.57728E-08 -9.18517E-12 2.04898E-13
28 1.0000 3.36113E-05 3.50988E-08 5.15560E-10 -3.38548E-12

In this optical system OL3, the axial distance D0 from the most object side surface (first surface) of the optical system OL1 to the object, the axial distance D1 between the first lens group G1 and the second lens group G2, the second lens An axial distance D2 between the group G2 and the aperture stop S (the third lens group G3) and an axial distance BF between the filter FL and the image plane I change upon focusing. Table 11 below shows the variable spacing for infinity focus and near object focus. Note that β indicates a photographing magnification.

(Table 11)
[Variable interval data]
Infinity Short distance f 16.48000 －
β - -0.03300
D0 ∞ 450.56370
D1 14.28467 12.81127
D2 2.47799 3.95140
BF 0.00000 -0.00671

Table 12 below shows values corresponding to each conditional expression in this optical system OL3. In the third embodiment, fp is the focal length of the biconvex positive lens L16, and fn is the focal length of the first negative meniscus lens L11.

(Table 8)
fp = 45.2130
fn123=-17.9914
bfa = 39.6855
fn=-142.5868

(1) 2ω=105.6
(2) (-fn123)/fp=0.398
(3) (-fn123)/f = 1.092
(4) (-fF)/fR = 0.806
(5) bfa/f = 2.408
(6) (-fn)/f = 8.652
(7) fn/fF = 5.409
(8) (-fF)/f = 1.600
(9) fp/f = 2.744

Thus, the optical system OL3 satisfies all of the above conditional expressions (1) to (9).

FIG. 6 shows a spherical aberration diagram, an astigmatism diagram, a distortion aberration diagram, a lateral chromatic aberration diagram, and a coma aberration diagram when the optical system OL3 is in focus at infinity. From these aberration diagrams, it can be seen that the optical system OL3 is well corrected for various aberrations.

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

In this embodiment, the optical system OL having a three-group configuration is shown, but the above configuration conditions and the like can also be applied to other group configurations such as four groups and five groups. 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 plane side may be used. Specifically, a configuration is conceivable in which a lens group whose position with respect to the image plane is fixed during zooming or focusing is added to the side closest to the image plane. 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 form a focusing lens group that performs focusing from an object at infinity to an object at a short distance. In this case, the focusing lens group can also be applied to autofocus and is suitable for driving a motor (such as an ultrasonic motor) for autofocus. In particular, as described above, it is preferable to use the second lens group GR as the focusing lens group Gfo, and to fix the positions of the other lenses with respect to the image plane during focusing. Considering the load on the motor, the focusing lens group preferably consists 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. An anti-vibration lens group may also be used. In particular, it is preferable to use at least part of the third lens group G3 as a vibration reduction lens group.

Also, the lens surface may be spherical, planar, or aspherical. 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 in the vicinity of or inside the third lens group G3, but a lens frame may be used instead of providing a member as the aperture stop.

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

1 Camera (optical equipment) OL (OL1 to OL3) Optical system GF Front group G1 First lens group G2 Second lens group (Gfo focusing lens group) S Aperture diaphragm G3 Third lens group (GR rear group)
L11 first negative meniscus lens, first negative lens L12 second negative meniscus lens, second negative lens L13 third negative meniscus lens, third negative lens L16 biconvex positive lens (positive lens component)

Claims (13)

In order from the object side,
a first negative meniscus lens;
a second negative meniscus lens;
a front group having negative refractive power, comprising a third negative meniscus lens;
Consists of substantially two lens groups, a rear group having positive refractive power disposed closer to the image plane than the front group,
The front group has a focusing lens group closest to the image plane side that moves in the optical axis direction during focusing,
wherein the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed with respect to an image plane during focusing;
The rear group is fixed with respect to the image plane during focusing,
An optical system that satisfies the following conditions.
80° < 2ω < 180°
1.20<(-fF)/f<2.50
0.65<(-fF)/fR<0.85
0.85<(-fn123)/f<1.50
however,
2ω: total angle of view of the optical system f: focal length of the entire optical system in infinity focused state fF: focal length of the front group in infinity focused state fR: focal length of the rear group fn123: A combined focal length of the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens In order from the object side,
a first negative meniscus lens;
a second negative meniscus lens;
a front group having negative refractive power, comprising a third negative meniscus lens;
Consists of substantially two lens groups, a rear group having positive refractive power disposed closer to the image plane than the front group,
The front group has a focusing lens group closest to the image plane side that moves in the optical axis direction during focusing,
wherein the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed with respect to an image plane during focusing;
The rear group is fixed with respect to the image plane during focusing,
An optical system that satisfies the following conditions.
80° < 2ω < 180°
0.65<(-fF)/fR<0.85
2.80<(-fn)/f<10.50
0.85<(-fn123)/f<1.50
however,
2ω: total angle of view of the optical system fF: focal length of the front group in an infinity focused state fR: focal length of the rear group f: focal length of the entire optical system in an infinity focused state fn: Focal length of the first negative meniscus lens fn123: combined focal length of the first negative meniscus lens, the second negative meniscus lens and the third negative meniscus lens In order from the object side,
a first negative meniscus lens;
a second negative meniscus lens;
a front group having negative refractive power, comprising a third negative meniscus lens;
Consists of substantially two lens groups, a rear group having positive refractive power disposed closer to the image plane than the front group,
The front group has a focusing lens group closest to the image plane side that moves in the optical axis direction during focusing,
wherein the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed with respect to an image plane during focusing;
The rear group is fixed with respect to the image plane during focusing,
An optical system that satisfies the following conditions.
80° < 2ω < 180°
2.80<(-fn)/f<10.50
1.00 < fn/fF < 10.00
0.65<(-fF)/fR<0.85
0.85<(-fn123)/f<1.50
however,
2ω: total angle of view of the optical system f: focal length of the entire optical system in the infinity focused state fn: focal length of the first negative meniscus lens fF: focus of the front group in the infinity focused state Distance fR: Focal length of the rear group fn123: Combined focal length of the first negative meniscus lens, the second negative meniscus lens and the third negative meniscus lens From the object side,
a front group having negative refractive power;
aperture diaphragm and
consists of substantially two lens groups with a rear group having positive refractive power,
The front group has a focusing lens group that moves in the optical axis direction during focusing,
the front group has a positive lens component positioned adjacent to the object side of the focusing lens group;
The front group has a first negative meniscus lens closest to the object side,
An optical system that satisfies the following conditions.
80° < 2ω < 180°
0.75<(-fF)/fR<0.95
1.20<(-fF)/f≤2.172
3.20<(-fn)/f<12.00
however,
2ω: total angle of view of the optical system fF: focal length of the front group in an infinity focused state fR: focal length of the rear group f: focal length of the entire optical system in an infinity focused state fn: Focal length of the first negative meniscus lens 4. The optical system according to claim 2, which satisfies the following condition.
1.00 < (-fF)/f < 5.00
however,
f: focal length of the entire optical system in the infinity focused state fF: focal length of the front group in the infinity focused state the front group has a positive lens component positioned adjacent to the object side of the focusing lens group;
The optical system according to any one of claims 1 to 3 and 5, which satisfies the following formula.
0.05 < (-fn123)/fp < 1.00
however,
fn123: combined focal length of the first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens fp: the focal length of the positive lens component 2. The optical system according to claim 1, wherein the following condition is satisfied.
2.00 < (-fn)/f < 12.00
however,
f: focal length of the entire optical system in an infinity focused state fn: focal length of the first negative meniscus lens The front group is
In order from the object side,
a first negative lens;
a second negative lens;
5. The optical system according to claim 4, comprising a third negative lens. 5. The optical system according to any one of claims 1, 2, and 4, which satisfies the following formula.
1.00 < fn/fF < 10.00
however,
fF: focal length of the front group in an infinity focused state fn: focal length of the first negative meniscus lens The optical system according to any one of claims 1 to 9, wherein the focusing lens group moves along the optical axis toward the object side when focusing from infinity to a short distance object. 11. The optical system according to any one of claims 1 to 10, which satisfies the following formula.
1.00 < bfa/f
however,
f: focal length of the entire optical system in the infinity focused state bfa: air-converted back focus of the optical system the front group has a positive lens component positioned adjacent to the object side of the focusing lens group;
12. The optical system according to any one of claims 1 to 11, which satisfies the following formula.
1.00 < fp/f < 5.00
however,
f: focal length of the entire optical system in the infinity focused state fp: focal length of the positive lens component An optical instrument comprising the optical system according to any one of claims 1 to 12.

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