JP7414107B2 - Optical system and optical equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to optical systems and optical instruments.

Conventionally, an optical system that is compact and achieves a wide angle of view using an aspherical lens has been proposed (see, for example, Patent Document 1). However, Patent Document 1 has a problem in that further improvement in optical performance is desired.

International Publication No. 2016/056310

The optical system according to the first aspect of the present invention includes a front group having negative refractive power and including, 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, which is disposed closer to the image plane than the front group, and the front group includes a focusing lens group that moves in the optical axis direction upon focusing, located closest to the image plane. The first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed to the image plane during focusing, and the rear group is fixed to the image plane during focusing. , the front group has a positive lens component disposed adjacent to the object side of the focusing lens group, and when focusing from infinity to a close object, the focusing lens group It moves toward the object along the optical axis and satisfies the following condition.
80° < 2ω < 180°
1.20 < (-fF)/f < 2.50
0.65 < (-fF)/fR < 0.85
0.85 < (-fn123)/f < 1.50
3.10 < (-fn)/f < 12.00
however,
2ω: Full angle of view of the optical system f: Focal length of the entire optical system in the infinity focus state fF: Focal length of the front group in the infinity focus state fR: Focal length of the rear group fn123: Synthetic focal length of the first negative meniscus lens, second negative meniscus lens, and third negative meniscus lens fn: focal length of the first negative meniscus lens

Further, the optical system according to the 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 of a front group and a rear group having positive refractive power, which is disposed closer to the image plane than the front group, and the front group is a focusing lens that moves in the optical axis direction when focusing, which is closest to the image plane. The first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed to the image plane during focusing, and the rear group is fixed to the image plane during focusing. The front group is fixed with respect to the image plane, and has a positive lens component disposed adjacent to the object side of the focusing lens group, and when focusing from infinity to a short distance object, the focusing lens The group moves toward the object along the optical axis 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: Full angle of view of the optical system fF: Focal length of the front group in the infinity focus state fR: Focal length of the rear group f: Focal length of the entire optical system in the infinity focus 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, the optical system according to the third 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 of a front group and a rear group having positive refractive power, which is disposed closer to the image plane than the front group, and the front group is a focusing lens that moves in the optical axis direction when focusing, which is closest to the image plane. The first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed to the image plane during focusing, and the rear group is fixed to the image plane during focusing. The front group is fixed with respect to the image plane, and has a positive lens component disposed adjacent to the object side of the focusing lens group, and when focusing from infinity to a short distance object, the focusing lens The group moves toward the object along the optical axis 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 focus state fn: Focal length of the first negative meniscus lens fF: Focus of the front group in the infinity focus 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 includes , in order from the object side, a front group having negative refractive power, an aperture stop, and a rear group having positive refractive power, and the front group is , a focusing lens group that moves in the optical axis direction upon focusing, the front group having a positive lens component disposed adjacent to the object side of the focusing lens group, the front group: The focusing lens group includes, in order from the object side, a first negative meniscus lens, a second negative lens, and a third negative lens, and when focusing from infinity to a short distance object, the focusing lens group is arranged along the optical axis. and moves to the object side, satisfying the condition of the following equation.
80° < 2ω < 180°
0.75 < (-fF)/fR < 0.95
1.20 < (-fF)/f ≦ 2.172
3.20 < (-fn)/f < 12.00
however,
2ω: Full angle of view of the optical system fF: Focal length of the front group in the infinity focus state fR: Focal length of the rear group f: Focal length of the entire optical system in the infinity focus 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 a focused state at infinity. FIG. 4 is a diagram of various aberrations of the optical system according to the first example in an infinity focused state. FIG. 7 is a cross-sectional view showing a lens configuration of an optical system according to a second example in a focused state at infinity. FIG. 7 is a diagram of various aberrations of the optical system according to the second example in the infinity focused state. FIG. 7 is a cross-sectional view showing a lens configuration of an optical system according to a third example in a focused state at infinity. FIG. 7 is a diagram of various aberrations of the optical system according to the third example in a focused state at infinity. FIG. 2 is a cross-sectional view of a camera equipped with the above optical system. It is a flowchart for explaining the manufacturing method of the above-mentioned optical system.

Hereinafter, preferred embodiments will be described with reference to the drawings. As shown in FIG. 1, the optical system OL according to the first embodiment includes, in order from the object side, a first negative meniscus lens L11, a second negative meniscus lens L12, and a third negative meniscus lens L13. The front group GF has a front group GF, and the rear group GR is 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 field curvature and distortion, has small fluctuations in aberration due to focusing, and has a long back focus relative to the focal length.

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

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

Conditional expression (1) defines the entire angle of view of the optical system OL. By satisfying conditional expression (1), it is possible to obtain good optical performance over the entire image circle while being small and lightweight. If the lower limit of conditional expression (1) is exceeded, it is not preferable because it becomes difficult to correct spherical aberration and longitudinal chromatic aberration. In addition, in order to ensure the effect of conditional expression (1), it is more desirable that the lower limit of conditional expression (1) be 85 degrees, and more preferably 90 degrees, 95 degrees, and 100 degrees. 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°, and more preferably to 170°, 165°, 160°, and 150°.

Furthermore, in the optical system OL according to the first embodiment, it is desirable that the front group GF has a focusing lens group Gfo that moves in the optical axis direction upon focusing, located closest to the image plane. With this configuration, it is possible to suppress aberration fluctuations caused by focusing.

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

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

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

0.05 < (-fn123)/fp < 1.00 (2)
however,
fn123: composite focal length of the first negative meniscus lens L11, second negative meniscus lens L12, and third negative meniscus lens L13 fp: 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 based on the focal length of the positive lens component placed adjacent to the object side of the focusing lens group Gfo of the front group GF, and the focal length of the three lenses placed closest to the object side of the front group GF. This defines the composite focal length of a negative meniscus lens. By satisfying conditional expression (2), size reduction can be achieved, spherical aberration, longitudinal chromatic aberration, lateral chromatic aberration, etc. can be favorably corrected, and aberration fluctuations associated with focusing can be suppressed. If the lower limit of conditional expression (2) is not reached, it is not preferable because it is difficult to correct lateral chromatic aberration, curvature of field, and distortion. In addition, 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. Moreover, if the upper limit of conditional expression (2) is exceeded, it is not preferable because it is difficult to suppress aberration fluctuations due to focusing. In order to ensure the effect of conditional expression (2), the upper limit of conditional expression (2) is set to 0.90, and further to 0.85, 0.80, 0.75, 0.70, 0. It is more desirable to set it to 65, 0.60, 0.55, 0.50, 0.45, and 0.42.

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

0.50 < (-fn123)/f < 1.50 (3)
however,
f: Focal length of the entire optical system OL in the infinity focus 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) expresses the combined focal length of the three negative meniscus lenses arranged closest to the object side of 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 conditional expression (3), it is possible to obtain an optical system that is compact and in which various aberrations are well corrected while ensuring a long back focus relative 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, further 0.60, 0.65, 0.70, 0.75, 0. It is more desirable to set it to 80, 0.85, 0.90, 0.95, and 1.00. Moreover, if the upper limit of conditional expression (3) is exceeded, the optical system becomes large, and if it is made too small, it becomes difficult to correct curvature of field and distortion, which is not preferable. In order to ensure the effect of conditional expression (3), the upper limit of conditional expression (3) is set to 1.45, and further to 1.40, 1.35, 1.30, 1.25, 1. 20, more preferably 1.15.

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

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

0.20 < (-fF)/fR < 2.00 (4)
however,
fF: Focal length of front group GF in infinity focus state fR: Focal length of rear group GR

Conditional expression (4) defines the focal length of the front group GF in the infinity focus state with respect to the focal length of the rear group GR. By satisfying conditional expression (4), it is possible to obtain a compact optical system in which various aberrations are well corrected while ensuring sufficient back focus for the focal length. If the lower limit of conditional expression (4) is not reached, the rear group GR becomes large, and if an attempt is made to forcefully reduce the size, it becomes difficult to correct spherical aberration, coma aberration, and lateral chromatic aberration, 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, further 0.30, 0.35, 0.40, 0.45, 0. More preferably, it is 50, 0.55, 0.60, 0.65, 0.70, and 0.75. Furthermore, if the upper limit of conditional expression (4) is exceeded, the front group GF will become larger in order to ensure sufficient back focus, and if you try to forcefully reduce the size, it will become difficult to correct field curvature and distortion, which is not desirable. . In order to ensure the effect of conditional expression (4), the upper limit of conditional expression (3) is set to 1.90, and further to 1.80, 1.70, 1.60, 1.50, 1. 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 includes, in order from the object side, a front group GF having a negative refractive power, an aperture stop S, and a rear group GR having a positive refractive power. , the front group GF includes a focusing lens group Gfo that moves in the optical axis direction upon focusing. With this configuration, it is possible to realize an optical system that suppresses the occurrence of field curvature and distortion, has small fluctuations in aberration due to focusing, and has a long back focus relative to the focal length.

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

Conditional expression (1) defines the entire angle of view of the optical system OL. By satisfying conditional expression (1), it is possible to obtain good optical performance over the entire image circle while being small and lightweight. If the lower limit of conditional expression (1) is exceeded, it is not preferable because it becomes difficult to correct spherical aberration and longitudinal chromatic aberration. In addition, in order to ensure the effect of conditional expression (1), it is more desirable that the lower limit of conditional expression (1) be 85 degrees, and more preferably 90 degrees, 95 degrees, and 100 degrees. 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°, and more preferably to 170°, 165°, 160°, and 150°.

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

0.20 < (-fF)/fR < 2.00 (4)
however,
fF: Focal length of front group GF in infinity focus state fR: Focal length of rear group GR

Conditional expression (4) defines the focal length of the front group GF in the infinity focus state with respect to the focal length of the rear group GR. By satisfying conditional expression (4), it is possible to obtain a compact optical system in which various aberrations are well corrected while ensuring sufficient back focus for the focal length. If the lower limit of conditional expression (4) is not reached, the rear group GR becomes large, and if an attempt is made to forcefully reduce the size, it becomes difficult to correct spherical aberration, coma aberration, and lateral chromatic aberration, 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, further 0.30, 0.35, 0.40, 0.45, 0. More preferably, it is 50, 0.55, 0.60, 0.65, 0.70, and 0.75. Furthermore, if the upper limit of conditional expression (4) is exceeded, the front group GF will become larger in order to ensure sufficient back focus, and if you try to forcefully reduce the size, it will become difficult to correct field curvature and distortion, which is not desirable. . In order to ensure the effect of conditional expression (4), the upper limit of conditional expression (3) is set to 1.90, and further to 1.80, 1.70, 1.60, 1.50, 1. 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 toward the object side along the optical axis when focusing from infinity to a close 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 includes, 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, field curvature and distortion can be favorably corrected.

In the optical system OL according to the second embodiment, the front group GF includes 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. This is desirable. With this configuration, spherical aberration, longitudinal chromatic aberration, and lateral chromatic aberration can be favorably corrected.

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

1.00 < bfa/f (5)
however,
f: Focal length of the entire optical system OL in the infinity focus state bfa: Air-equivalent back focus of the optical system OL

Conditional expression (5) defines the air-equivalent back focus of the optical system OL with respect to the focal length of the entire optical system OL in the infinity focus state. Note that the back focus bfa indicates the distance on the optical axis (air equivalent length) from the lens surface of the optical system OL closest to the image plane to the image plane I when focusing at infinity. By satisfying conditional expression (5), it is possible to obtain a long back focus suitable for a single-lens reflex camera equipped with 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 to ensure back focus, and a wide angle of view cannot be ensured, which is undesirable. In order to ensure the effect of conditional expression (5), the lower limit of conditional expression (5) is set to 1, 30, further 1.50, 1.80, 2.00, 2.10, 2. It is more desirable to set it to 20, 2.30.

Furthermore, in the optical systems OL according to the first and second embodiments, it is desirable that the front group GF 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 field curvature and distortion, can be corrected well.

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

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 in the front group GF

Conditional expression (6) defines the focal length of the negative meniscus lens closest to the object in the front group GF with respect to the focal length of the entire optical system OL in the infinity focused state. By satisfying conditional expression (6), it is possible to obtain an optical system that is small but has a sufficient amount of peripheral light and that satisfactorily corrects field curvature and distortion aberration. 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. It is more desirable to set it to 20, 3.30. Moreover, if the upper limit of conditional expression (6) is exceeded, it becomes difficult to correct the curvature of field, which is not preferable. Note that 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. More preferably, it is 90, 8.80, or 8.70.

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 in the infinity focus state 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 in the front group GF with respect to the focal length of the front group GF in the infinity focused state. By satisfying conditional expression (7), it is possible to obtain an optical system that is small but has a sufficient amount of peripheral light and that satisfactorily corrects field curvature and distortion aberration. Below the lower limit of conditional expression (7), it becomes difficult to correct distortion. Furthermore, it becomes difficult to correct lateral chromatic aberration. In order to ensure the effect of conditional expression (7), the lower limit of conditional expression (7) is set to 1.10, further 1.20, 1.30, 1.40, 1.45, 1. 50, more preferably 1.55. Moreover, when the upper limit of conditional expression (7) is exceeded, it becomes difficult to correct the curvature of field and secure the amount of peripheral light. In order to ensure the effect of conditional expression (7), the upper limit of conditional expression (7) is set to 9.00, and furthermore to 8.00, 7.50, 7.00, 6.50, 6. It is more desirable to set it to 00, 5.50.

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

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

Conditional expression (8) defines the focal length of the front group GF in the infinity focus state with respect to the focal length of the entire optical system OL in the infinity focus state. By satisfying conditional expression (8), it is possible to obtain an optical system that is small and lightweight, yet has sufficient back focus for a single-lens reflex camera equipped with a mirror box, and has various aberrations well corrected. Can be done. If the lower limit of conditional expression (8) is not reached, the rear group GR becomes large, and if an attempt is made to forcefully reduce the size, it becomes difficult to correct spherical aberration, coma aberration, and lateral chromatic aberration, 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, further 1.20, 1.30, 1.35, 1.40, 1. It is more desirable to set it to 45, 1.50, and 1.55. Furthermore, if the upper limit of conditional expression (8) is exceeded, the front group GF will become larger in order to ensure sufficient back focus, and if you try to forcefully reduce the size, it will become difficult to correct field curvature and distortion, which is not desirable. . In addition, 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. More preferably, it is 50, 2.40, 2.30, or 2.20.

Further, in the optical system OL according to the first and second embodiments, the front group GF has a positive lens component disposed adjacent to the object side of the focusing lens group Gfo, and the conditions shown below are satisfied. It is desirable that equation (9) be satisfied.

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 disposed adjacent to the object side of the focusing lens group Gfo of the front group GF

Conditional expression (9) expresses the focal length of the positive lens component disposed 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. This specifies the distance. By satisfying conditional expression (9), various aberrations, especially field curvature and spherical aberration, can be favorably corrected. If the lower limit of conditional expression (9) is not reached, it becomes difficult to correct spherical aberration, 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, further 1.50, 1.80, 2.00, 2.30, 2. It is more desirable to set it to 40, 2.50, 2.60, and 2.70. Moreover, if the upper limit of conditional expression (9) is exceeded, aberration fluctuations accompanying focusing become large, which is not preferable. 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. More preferably, it is 80, 3.70, or 3.60.

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. By forming the focusing lens group Gfo as a cemented lens consisting of a positive lens and a negative lens, it is possible to suppress aberration fluctuations associated with focusing, especially axial fluctuations.

In the optical system OL according to the first and second embodiments, the front group GF is a cemented lens in which a positive lens and a negative lens are cemented (for example, a double convex positive lens L14 and a double concave negative lens in FIG. 1). It is desirable to have a cemented lens CL1) which is cemented with a 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 object side, a first negative lens L11, a second negative lens L12, a third negative lens L13, and a positive lens. By having L14 and the fourth negative lens L15, field curvature, distortion, and chromatic aberration of magnification can be favorably corrected.

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

Further, 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 field curvature and distortion, can be corrected well.

Further, 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 field curvature and distortion, can be corrected well.

Moreover, it is desirable that the third negative lens L13 is a negative meniscus lens with a convex surface facing the object side. With this configuration, various aberrations, particularly field curvature and distortion, can be corrected well.

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

Note that the conditions and configurations explained above each exhibit the effects described above, and are not limited to those that satisfy all conditions and configurations. It is possible to obtain the above-mentioned effects even if the above conditions or combinations of configurations 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 including the optical system OL described above. In this camera 1, light from an object (subject) (not shown) is focused by a photographing lens 2 (optical system OL), and is imaged on a focus plate 4 via a quick return mirror 3. The light focused on the focus plate 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.

Furthermore, when the photographer presses a release button (not shown), the quick return mirror 3 retreats out of the optical path, and the light from an object (subject) (not shown) focused by the photographic lens 2 is transferred to the image sensor 7. Form an image of the subject on top. Thereby, light from the object (subject) is imaged by the image sensor 7 and recorded as an object (subject) image in a memory (not shown). In this way, the photographer can photograph an object (subject) using the camera 1. Note that the camera 1 shown in FIG. 7 may be one that detachably holds the photographic lens 2, or may be molded integrally with the photographic lens 2. Further, the camera 1 may be a so-called single-lens reflex camera, a compact camera without a quick return mirror, or a mirrorless single-lens reflex camera.

Hereinafter, using the optical system OL according to the second embodiment as an example, a method for manufacturing the optical system OL according to the present embodiment will be outlined with reference to FIG. 8. First, the front group GF, aperture stop S, and rear group GR of the optical system OL are prepared by arranging each lens (step S100). Furthermore, a focusing lens group Gfo that moves in the optical axis direction upon 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 a predetermined conditional expression (for example, the above-mentioned conditional expression (1)) (step S300).

Specifically, in this embodiment, as shown in FIG. 1, for example, 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 that is a combination of a biconvex positive lens L14 and a biconcave negative lens L15, and a biconvex positive lens L16. , and a cemented lens consisting of a meniscus-shaped negative lens L21 with a convex surface facing the object side and a meniscus-shaped positive lens L22 with a convex surface facing the object side is arranged to form the front group GF, and a biconvex positive lens L31 and a biconcave negative lens L32, a meniscus-shaped positive lens L33 with a convex surface facing the object side, a meniscus-shaped negative lens L34 with a convex surface facing the object side, and a biconvex positive lens L35. After arranging a cemented lens, a cemented lens made by cementing a meniscus-shaped negative lens L36 with a convex surface facing the object side and a double-convex positive lens L37, and a meniscus-shaped negative lens L38 with a convex surface facing the image side. Group GR. Note that a cemented lens obtained by cementing a negative lens L21 having a convex surface facing the object side of the front group GF and a positive lens L22 having a convex surface facing the object side is referred to as a focusing lens group Gfo. Then, the optical system OL is manufactured by arranging each lens group and aperture stop S prepared in this manner in accordance with the above-described procedure.

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

Hereinafter, each embodiment of the present application will be described based on the drawings. Note that FIG. 1, FIG. 3, and FIG. 5 are cross-sectional views showing the configuration and refractive power distribution of the optical system OL (OL1 to OL3) according to each embodiment.

In each example, the height of the aspherical surface in the direction perpendicular to the optical axis is y, and the distance along the optical axis from the tangent plane of the vertex of each aspherical surface to each aspherical surface at the height y (sag amount) is S(y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic constant is K, and the nth-order aspheric coefficient is An, it is expressed by the following formula (a). . In addition, in the following examples, "E-n" indicates "×10 ^-n ".

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

In each example, the second-order aspherical coefficient A2 is 0. In addition, in the tables of each example, aspherical surfaces are marked with * on the right side of the surface number.

[First example]
FIG. 1 is a diagram showing the configuration of an optical system OL1 according to the first embodiment. This optical system OL1 is composed of, in order from the object side, a front group GF having a negative refractive power and a rear group GR having a positive refractive power. Further, the front group GF is composed of, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a 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 second meniscus-shaped negative lens with a convex surface facing the object side. (or second negative meniscus lens) L12, third meniscus-shaped negative lens with a convex surface facing the object side (or third negative meniscus lens) L13, cemented double-convex positive lens L14 and double-concave 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, in order from the object side, a meniscus-shaped negative lens L21 with a convex surface facing the object side and a meniscus-shaped positive lens L22 with a convex surface facing the object side are cemented together. .

The rear group GR (hereinafter referred to as "third lens group G3") includes, in order from the object side, a cemented lens made of a double-convex positive lens L31 and a double-concave negative lens L32, and a meniscus-shaped lens with a convex surface facing the object side. A positive lens L33, a cemented lens made by cementing a meniscus-shaped negative lens L34 with a convex surface facing the object side and a biconvex positive lens L35, a meniscus-shaped negative lens L36 with a convex surface facing the object side, and a biconvex positive lens L37. and a meniscus-shaped negative lens L38 with a convex surface facing the image plane side.

Furthermore, 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). Further, in the optical system OL1, a filter FL is arranged between the third lens group G3 and the image plane I.

In addition, in this optical system OL1, focusing from an object at infinity to an object at a short distance is achieved by fixing the first lens group G1 and the third lens group G3 with respect to the image plane I, and focusing with the second lens group G2. This is performed 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 Table 1, f shown in the overall specifications is the focal length of the entire system when focused at infinity, 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 side (the first surface in FIG. 1) to the image surface I at the time of infinite focusing. 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 the light ray travels, and the second column r indicates the radius of curvature of each lens surface. d is the distance on the optical axis from each optical surface to the next optical surface (surface spacing), 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). It shows. Also, the radius of curvature of 0.00000 indicates a plane, and the refractive index of air of 1.00000 is omitted. In addition, the lens group focal length indicates the surface number and focal length of the starting surface of each of the front group GF, first lens group G1, second lens group G2, and third lens group G3 (the focal length of the front group GF Distance is the value when focused at infinity).

Here, "mm" is generally used for the focal length f, radius of curvature r, surface spacing d, and other length units listed in all the specification values below, but the optical system Since the same optical performance can be obtained even if the size is reduced, the present invention is not limited to this. Further, the explanations of these symbols and the specifications 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 surface ∞ 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 stop 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 0.0000BF
Image plane ∞

[Lens group focal length]
Lens group Starting plane Focal length Front group GF 1 -26.6303
1st lens group G1 1 127.4216
2nd lens group G2 12 -76.3989
3rd lens group G3 16 33.6830

In this optical system OL1, the third surface, the fourth surface, the sixth surface, and the twenty-eighth surface are formed into an aspherical shape. Table 2 below shows aspherical data, ie, the conic constant K and the values of each aspherical constant A4 to 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, an axial distance D0 from the surface closest to the object (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, and a second lens The axial distance D2 between the group G2 and the aperture stop S (third lens group G3) and the axial distance BF between the filter FL and the image plane I change upon focusing. Table 3 below shows the variable intervals in the infinity focus state and the near object focus state. Note that β indicates the imaging magnification.

(Table 3)
[Variable interval data]
Infinity Near 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 focus state, and fF is the focal length of the front group GF in the infinity focus 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 disposed 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 which is the rear group GR. The composite focal length of the first negative meniscus lens L11, the second negative meniscus lens L12, and the third negative meniscus lens L13, bfa is the air-equivalent back focus of the optical system OL1, and fn is the negative meniscus of the front group GF that is closest to the object side. Each represents the focal length of the lens. The explanation of these symbols is the same in the following embodiments. In this first example, 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

In this way, 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 magnification chromatic aberration diagram, and a coma aberration diagram of this optical system OL1 in the infinity focused state. In each aberration diagram, FNO indicates the F number and Y indicates the image height. Note that the spherical aberration diagram shows the value of the F number corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram each show the maximum value of the 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), respectively. In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, the solid line indicates the meridional coma, and the broken line indicates the Y direction (meridional) and Z direction (sagittal) of the skew ray, respectively. Further, in the aberration diagrams of each example shown below, the same symbols as in this example are used. From these aberration diagrams, it can be seen that various aberrations are well corrected in the optical system OL1.

[Second example]
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 a negative refractive power and a rear group GR having a positive refractive power. Further, the front group GF is composed of, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a 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 second meniscus-shaped negative lens with a convex surface facing the object side. (or second negative meniscus lens) L12, third meniscus-shaped negative lens with a convex surface facing the object side (or third negative meniscus lens) L13, cemented double-convex positive lens L14 and double-concave 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, in order from the object side, a meniscus-shaped negative lens L21 with a convex surface facing the object side and a meniscus-shaped positive lens L22 with a convex surface facing the object side are cemented together. .

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

Further, 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). Further, in the optical system OL2, a filter FL is arranged between the third lens group G3 and the image plane I.

In addition, in this optical system OL2, focusing from an object at infinity to an object at a short distance is performed by fixing the first lens group G1 and the third lens group G3 with respect to the image plane I, and focusing the focus from an object at infinity to a short distance object using the second lens group G2. This is performed 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 surface ∞ 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 stop 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 0.0000BF
Image plane ∞

[Lens group focal length]
Lens group Starting plane Focal length Front group GF 1 -26.8417
1st lens group G1 1 89.3772
2nd lens group G2 12 -81.0572
3rd lens group G3 16 34.7892

In this optical system OL2, the first surface, the third surface, the fourth surface, the sixth surface, and the 28th surface are formed into an aspherical shape. Table 6 below shows aspherical data, ie, the conic constant K and the values of each aspherical constant A4 to 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 surface closest to the object (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, and a second lens The axial distance D2 between the group G2 and the aperture stop S (third lens group G3) and the axial distance BF between the filter FL and the image plane I change upon focusing. Table 7 below shows the variable intervals in the infinity focus state and the near object focus state. Note that β indicates the imaging magnification.

(Table 7)
[Variable interval data]
Infinity Near 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 example, 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

In this way, 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 aberration diagram, a magnification chromatic aberration diagram, and a coma aberration diagram of this optical system OL2 in the infinity focused state. From these aberration diagrams, it can be seen that various aberrations are well corrected in the optical system OL2.

[Third example]
FIG. 5 is a diagram showing the configuration of the optical system OL3 according to the third embodiment. This optical system OL3 is composed of, in order from the object side, a front group GF having a negative refractive power and a rear group GR having a positive refractive power. Further, the front group GF is composed of, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a 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 second meniscus-shaped negative lens with a convex surface facing the object side. (or a second negative meniscus lens) L12, a third meniscus-shaped negative lens with a convex surface facing the object side (or a third negative meniscus lens) L13, a cemented double-convex positive lens L14 and a double-concave 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, in order from the object side, a meniscus-shaped negative lens L21 with a convex surface facing the object side and a meniscus-shaped positive lens L22 with a convex surface facing the object side are cemented together. .

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

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

In addition, in this optical system OL3, focusing from an object at infinity to an object at a short distance is performed by fixing the first lens group G1 and the third lens group G3 with respect to the image plane I, and focusing with the second lens group G2. This is performed 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 surface ∞ 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 stop 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 0.0000BF
Image plane ∞

[Lens group focal length]
Lens group Starting plane Focal length Front group GF 1 -26.3599
1st lens group G1 1 132.8313
2nd lens group G2 12 -67.9699
Third lens group G3 16 32.6991

In this optical system OL3, the third surface, the fourth surface, the sixth surface, and the twenty-eighth surface are formed into an aspherical shape. Table 10 below shows aspherical data, ie, the conic constant K and the values of each aspherical constant A4 to 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, an axial distance D0 from the surface closest to the object (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, and a second lens The axial distance D2 between the group G2 and the aperture stop S (third lens group G3) and the axial distance BF between the filter FL and the image plane I change upon focusing. Table 11 below shows variable intervals in the infinity focus state and the near object focus state. Note that β indicates the imaging magnification.

(Table 11)
[Variable interval data]
Infinity Near 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 this 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

In this way, 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 magnification chromatic aberration diagram, and a coma aberration diagram of this optical system OL3 in the infinity focused state. From these aberration diagrams, it can be seen that various aberrations are well corrected in the optical system OL3.

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

In this embodiment, an optical system OL having a three-group configuration is shown, but the above configuration conditions are also applicable to other group configurations such as a four-group, a five-group, etc. Alternatively, 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 may be considered in which a lens group whose position with respect to the image plane is fixed during zooming or focusing is added to the closest to the image plane. Further, the lens group refers to a portion having at least one lens separated by an air gap that changes during zooming or focusing. Further, the lens component refers to a single lens or a cemented lens in which a plurality of lenses are cemented together.

Alternatively, a focusing lens group may be used to focus from an object at infinity to an object at a short distance by moving a single lens group, a plurality of lens groups, or a partial lens group in the optical axis direction. In this case, the focusing lens group can also be applied to autofocus, and is also suitable for driving a motor (such as an ultrasonic motor) for autofocus. In particular, as described above, it is preferable that the second lens group GR is the focusing lens group Gfo, and that the other lenses are fixed in position with respect to the image plane during focusing. Considering the load on the motor, it is preferable that the focusing lens group is composed of a single lens.

In addition, image blur caused by camera shake can be corrected by moving the lens group or partial lens group so that it has a displacement component perpendicular to the optical axis, or rotating (swinging) it in a plane that includes the optical axis. It may also be used as an anti-vibration lens group. In particular, it is preferable that at least a portion of the third lens group G3 be an anti-vibration lens group.

Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspherical surface. It is preferable that the lens surface is spherical or flat because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment can be prevented. Further, even if the image plane shifts, there is little deterioration in depiction performance, which is preferable. When the lens surface is aspherical, the aspherical surface can be an aspherical surface made by grinding, a glass molded aspherical surface made by molding glass into an aspherical shape, or a composite aspherical surface made by molding resin into an aspherical shape on the glass surface. Any aspherical 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.

Although it is preferable that the aperture stop S be disposed near or inside the third lens group G3, the role may be replaced by a lens frame without providing an aperture stop member.

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

1 Camera (optical equipment) OL (OL1 to OL3) Optical system GF Front group G1 1st lens group G2 2nd lens group (Gfo Focusing lens group) S Aperture diaphragm G3 3rd 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 (10)

Starting from the object side,
a first negative meniscus lens;
a second negative meniscus lens;
a third negative meniscus lens; a front group having negative refractive power;
and a rear group having positive refractive power, which is disposed closer to the image plane than the front group,
The front group has a focusing lens group closest to the image plane that moves in the optical axis direction during focusing,
The first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed relative to the image plane during focusing,
The rear group is fixed with respect to the image plane during focusing,
The front group has a positive lens component disposed adjacent to the object side of the focusing lens group,
When focusing from infinity to a close object, the focusing lens group moves toward the object along the optical axis,
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
3.10 < (-fn)/f < 12.00
however,
2ω: Full angle of view of the optical system f: Focal length of the entire optical system in the infinity focus state fF: Focal length of the front group in the infinity focus state fR: Focal length of the rear group fn123: Synthetic focal length of the first negative meniscus lens, second negative meniscus lens, and third negative meniscus lens fn: focal length of the first negative meniscus lens Starting from the object side,
a first negative meniscus lens;
a second negative meniscus lens;
a third negative meniscus lens; a front group having negative refractive power;
and a rear group having positive refractive power, which is disposed closer to the image plane than the front group,
The front group has a focusing lens group closest to the image plane that moves in the optical axis direction during focusing,
The first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed relative to the image plane during focusing,
The rear group is fixed with respect to the image plane during focusing,
The front group has a positive lens component disposed adjacent to the object side of the focusing lens group,
When focusing from infinity to a close object, the focusing lens group moves toward the object along the optical axis,
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: Full angle of view of the optical system fF: Focal length of the front group in the infinity focus state fR: Focal length of the rear group f: Focal length of the entire optical system in the infinity focus 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 Starting from the object side,
a first negative meniscus lens;
a second negative meniscus lens;
a third negative meniscus lens; a front group having negative refractive power;
and a rear group having positive refractive power, which is disposed closer to the image plane than the front group,
The front group has a focusing lens group closest to the image plane that moves in the optical axis direction during focusing,
The first negative meniscus lens, the second negative meniscus lens, and the third negative meniscus lens are fixed relative to the image plane during focusing,
The rear group is fixed with respect to the image plane during focusing,
The front group has a positive lens component disposed adjacent to the object side of the focusing lens group,
When focusing from infinity to a close object, the focusing lens group moves toward the object along the optical axis,
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 focus state fn: Focal length of the first negative meniscus lens fF: Focus of the front group in the infinity focus 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 Starting from the object side,
a front group having negative refractive power;
an aperture diaphragm,
Consisting of a rear group with positive refractive power,
The front group includes a focusing lens group that moves in the optical axis direction during focusing,
The front group has a positive lens component disposed adjacent to the object side of the focusing lens group,
The front group includes, in order from the object side, a first negative meniscus lens, a second negative lens, and a third negative lens,
When focusing from infinity to a close object, the focusing lens group moves toward the object along the optical axis,
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: Full angle of view of the optical system fF: Focal length of the front group in the infinity focus state fR: Focal length of the rear group f: Focal length of the entire optical system in the infinity focus state fn: Focal length of the first negative meniscus lens The optical system according to claim 2 or 3, which satisfies the following condition.
1.00 < (-fF)/f < 5.00
however,
f: Focal length of the entire optical system in the infinity focus state fF: Focal length of the front group in the infinity focus state The optical system according to claim 1, which satisfies the following condition.
0.05 < (-fn123)/fp < 1.00
however,
fn123: composite focal length of the first negative meniscus lens, second negative meniscus lens, and third negative meniscus lens fp: focal length of the positive lens component The optical system according to any one of claims 1, 2, and 4, which satisfies the following condition.
1.00 < fn/fF < 10.00
however,
fF: Focal length of the front group in the infinity focused state fn: Focal length of the first negative meniscus lens The optical system according to any one of claims 1 to 7, which satisfies the following condition.
1.00 < bfa/f
however,
f: Focal length of the entire optical system in the infinity focus state bfa: Air-equivalent back focus of the optical system The front group has a positive lens component disposed adjacent to the object side of the focusing lens group,
The optical system according to any one of claims 1 to 8, which satisfies the following condition.
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 device comprising the optical system according to any one of claims 1 to 9 .