JP7171017B2 - Imaging optical system - Google Patents

Description

The present invention relates to a compact imaging optical system used in imaging devices such as digital cameras and video cameras.

In recent years, imaging devices such as digital still cameras and video cameras have become widespread. Among them, interchangeable lens type digital still cameras have a mirror between the image forming optical system and the image sensor to guide light rays to the viewfinder optical system. is removed and the distance between the imaging optical system and the imaging device is shortened.

Among them, a compact image pickup device using a large image pickup element is in widespread use. A downsizing of the imaging optical system is required for the downsizing of the imaging device. By increasing the size of the image pickup device, it is possible to shoot with a shallow depth of field and a large amount of blurring of the background even with a lens having a large f-number. As the distance between the background and the subject increases, the blurring amount of the background increases.

In addition, the image sensors widely used in imaging devices generally have the characteristic of being less sensitive to light with a large angle of incidence on the image sensor. . Therefore, it is necessary to suppress the decrease in sensitivity by suppressing the angle of incidence on the imaging device, that is, the angle of emergence of light rays from the imaging optical system.

In view of the above, there is a demand for an imaging optical system that is compact, capable of photographing at a short photographing distance, and that suppresses the ray exit angle.

Patent documents related to the above are disclosed in Patent Documents 1 to 5, for example.

JP 2013-195587 A WO2013/099211 JP 2015-041012 A JP-A-06-222260 JP-A-09-236746

In Patent Documents 1 and 2, the lens used for focusing is large with respect to the peripheral image height. Therefore, an actuator for moving the focus lens becomes large. This is not preferable because it is difficult to reduce the size of an imaging device having a large imaging element.

Japanese Patent Application Laid-Open No. 2002-200002 uses one lens for focusing, and is not preferable because longitudinal chromatic aberration increases when the photographing distance is shortened.

In Patent Documents 4 and 5, miniaturization is achieved by shortening the image circle corresponding to a large-sized imaging device and the overall optical length. However, it is not suitable for general imaging devices because of its large ray exit angle.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides an imaging optical system that is compact, allows a focus lens to be made lightweight, enables shooting at a short shooting distance, and suppresses the light exit angle. intended to

A first invention for solving the above-mentioned problem is composed of a group G1, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power, and is configured to focus at infinity. During focusing from an object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is widened. , wherein the second lens group G2 moves toward the object side, and the following conditional expression is satisfied.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
(5) 2.0<LT/(Ymax)<3.10
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: Focal length LT of the first lens group G1: The first lens group G1 in the infinity focused state distance from the surface closest to the object side to the image plane of
Ymax: Maximum image height

The second invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an infinity object to a short distance object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the second lens group G2 and the third lens group An imaging optical system characterized by having a configuration in which the distance from G3 is widened and the second lens group G2 is moved toward the object side, and which satisfies the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
(8) 0.30<|f3/f|<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: focal length f3 of the first lens group G1: focal length of the third lens group G3

The third invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an infinity object to a short distance object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the second lens group G2 and the third lens group An imaging optical system characterized by having a configuration in which the distance from G3 is widened and the second lens group G2 is moved toward the object side, and which satisfies the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
(10) 1.60<|EXP/Ymax|<3.50
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: Focal length EXP of the first lens group G1: From the exit pupil position to the image plane when in focus at infinity distance to
Ymax: Maximum image height

A fourth aspect of the invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an infinity object to a short distance object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the second lens group G2 and the third lens group An imaging optical system characterized by having a configuration in which the distance from G3 is widened and the second lens group G2 is moved toward the object side, and which satisfies the following conditional expression.
(1) 1.40<f/f12<2.80
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9′) 0.67≦((D1_2)*K2)/f<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity LT: the first lens when focused on infinity Surface distance from the surface closest to the object side of the group G1 to the image plane
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f1 of the second lens group G2 at : focal length D1_2 of the first lens group G1: the most image-side surface of the first lens group G1 and the most object of the second lens group G2 in an infinite focus state Spacing of side faces

A fifth aspect of the invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. consists of
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9) 0.50<((D1_2)*K2)/f<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index LT for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: the distance from the most object-side surface of the first lens group G1 to the image plane in the infinity focused state Surface spacing
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f1 of the second lens group G2 at : focal length D1_2 of the first lens group G1: the most image-side surface of the first lens group G1 and the most object of the second lens group G2 in an infinite focus state Spacing of side faces

The sixth invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an infinity object to a short distance object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the second lens group G2 and the third lens group An imaging optical system characterized by having a configuration in which the distance from G3 is widened and the second lens group G2 is moved toward the object side, and which satisfies the following conditional expression.
(1) 1.40<f/f12<2.80
(3) 1.80<G3nd
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9) 0.50<((D1_2)*K2)/f<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3nd: the focal length of the positive lens in the third lens group G3 Refractive index LT for the largest d-line (wavelength λ=587.56): Surface distance from the most object-side surface of the first lens group G1 to the image plane when in focus at infinity
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f1 of the second lens group G2 at : focal length D1_2 of the first lens group G1: the most image-side surface of the first lens group G1 and the most object of the second lens group G2 in an infinite focus state Spacing of side faces

The seventh invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. consists of
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9) 0.50<((D1_2)*K2)/f<1.40
(10′) 2.14<|EXP/Ymax|<3.50
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity LT: the first lens when focused on infinity Surface distance from the surface closest to the object side of the group G1 to the image plane
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f1 of the second lens group G2 at : focal length D1_2 of the first lens group G1: the most image-side surface of the first lens group G1 and the most object of the second lens group G2 in an infinite focus state Surface distance EXP of the side surface: Distance from the exit pupil position to the image plane when in focus at infinity

The eighth invention is composed of, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an infinity object to a short distance object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the second lens group G2 and the third lens group An imaging optical system characterized by having a configuration in which the distance from G3 is widened and the second lens group G2 is moved toward the object side, and which satisfies the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(5) 2.0<LT/(Ymax)<3.10
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index LT for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: the distance from the most object-side surface of the first lens group G1 to the image plane in the infinity focused state Spacing
Ymax: Maximum image height

A ninth aspect of the invention comprises, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. The first lens group G1 is fixed with respect to the image plane, and the third lens group G3 is fixed with respect to the image plane when focusing from an infinite object to a short distance object. , wherein the second lens group G2 moves toward the object side, and the following conditional expression is satisfied.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) LT: infinity Surface distance from the most object side surface of the first lens group G1 to the image plane in the in-focus state
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused lateral magnification f1 of the second lens group G2 in the state: focal length of the first lens group G1

A tenth invention is an imaging optical system according to the second invention, characterized by satisfying the following conditions.
(2) 0.020<G3ΔPgFmax<0.300
G3ΔPgFmax: the largest value of ΔPgF among the positive lenses in the third lens group G3 ΔPgF=PgF−0.64833+0.00180νd: g, abnormal partial dispersion between F lines PgF=(ng−nF)/(nF) -nC): g, partial dispersion ratio between F lines ng: refractive index for g line (wavelength λ = 435.84 nm) nF: refractive index for F line (wavelength λ = 486.13 nm) nC: C line (wavelength λ = 656.27 nm): refractive index for the largest d-line (wavelength λ = 587.56) among the positive lenses in the third lens group G3

An eleventh invention is an imaging optical system according to any one of the second invention, the fourth invention, and the fifth invention, which satisfies the following conditions.
(3) 1.80<G3nd
G3nd: Refractive index for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3

A twelfth invention is an imaging optical system according to any one of the second to sixth inventions, characterized by satisfying the following conditions.
(4) 0.60<f1/f<6.50
f: focal length of the entire system when in focus at infinity f1: focal length of the first lens group G1

A thirteenth invention is an imaging optical system according to any one of the first invention, the third invention, the seventh invention, and the eighth invention, which satisfies the following conditions.
(6) 2.00<K2<5.00
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused Lateral magnification f of the second lens group G2 in the state: focal length f12 of the entire system in the infinity focused state: combined focus f1 of the first lens group G1 and the second lens group G2 in the infinity focused state: Focal length of the first lens group G1

A fourteenth invention is an imaging optical system according to any one of the first to ninth inventions, wherein the following conditions are satisfied.
(7) 0.30<f2/f<0.95
f2: focal length of the second lens group G2 f: focal length of the entire system when in focus at infinity

A fifteenth invention is an imaging optical system according to any one of the first to tenth inventions, wherein the following conditions are satisfied.
(8) 0.30<|f3/f|<1.40
f3: focal length of the third lens group G3 f: focal length of the entire system when in focus at infinity

A sixteenth invention is an imaging optical system according to any one of the first invention, the third invention, the fourth invention, the seventh invention to the eleventh invention, wherein the following conditions are satisfied: system.
(9) 0.50<((D1_2)*K2)/f<1.40
D1_2: Surface distance between the surface closest to the image side of the first lens group G1 and the surface closest to the object side of the second lens group G2 in the infinity focused state K2: Distance of the second lens group G2 in the infinity focused state Focus sensitivity K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused Lateral magnification f of the second lens group G2 in the state: focal length f1 of the entire system in the infinity focused state: focal length f12 of the first lens group G1: the first lens group G1 in the infinity focused state Composite focal length of the second lens group G2

In a seventeenth aspect of the invention, the first lens group G1 is fixed with respect to the image plane and the third lens group G3 is fixed with respect to the image plane when focusing from an infinity object to a short distance object. The imaging optical system according to any one of the first to third inventions and the fifth to twelfth inventions, characterized in that it has a configuration as follows.

An eighteenth invention is characterized in that the aperture stop S is adjacent to the image side of the first lens group G1 and is fixed in the optical axis direction during focusing. An imaging optical system according to any one of the above.

A nineteenth invention is an imaging optical system according to any one of the first to fourteenth inventions, wherein the following conditional expression is satisfied.
(10) 1.60<|EXP/Ymax|<3.50
EXP: Distance from the exit pupil position to the image plane when in focus at infinity
Ymax: Maximum image height

A twentieth invention is characterized in that the first lens group G1 consists of a positive lens L1 and a negative lens L2 in order from the object side, and has a positive refractive power as a whole. An imaging optical system according to any one of the above.

A twenty -first invention is characterized in that the second lens group G2 consists of a negative lens L3, a positive lens L4, and a positive lens L5 in order from the object side, and has a positive refractive power as a whole. 16. An imaging optical system according to any one of the 16 inventions.

A twenty -second invention is characterized in that the third lens group G3 consists of a negative lens L6, a negative lens L7 and a positive lens L8 in order from the object side, and has negative refractive power as a whole. 17. An imaging optical system according to any one of 17 inventions.

The present invention makes it possible to provide an image-forming optical system that is compact, has a lightweight focus lens, is capable of photographing at a short photographing distance, and has a suppressed ray exit angle.

FIG. 2 is a lens configuration diagram when focusing on infinity according to Example 1 of the present invention; FIG. 4 is a longitudinal aberration diagram when focusing on infinity according to Example 1 of the present invention; FIG. 4 is a lateral aberration diagram during focusing at infinity according to Example 1 of the present invention; 4 is a longitudinal aberration diagram at a shooting distance of 240 mm according to Example 1 of the present invention; FIG. 4 is a lateral aberration diagram at a shooting distance of 240 mm according to Example 1 of the present invention; FIG. FIG. 10 is a lens configuration diagram when focusing on infinity according to Example 2 of the present invention; FIG. 10 is a longitudinal aberration diagram when focusing on infinity according to Example 2 of the present invention; FIG. 10 is a lateral aberration diagram when focusing on infinity according to Example 2 of the present invention; FIG. 10 is a longitudinal aberration diagram at a shooting distance of 240 mm according to Example 2 of the present invention; FIG. 10 is a lateral aberration diagram at a shooting distance of 240 mm according to Example 2 of the present invention; It is a lens configuration diagram at the time of infinity focusing according to Example 3 of the present invention. FIG. 10 is a longitudinal aberration diagram during focusing at infinity according to Example 3 of the present invention; FIG. 11 is a lateral aberration diagram at the time of focusing at infinity according to Example 3 of the present invention; FIG. 10 is a longitudinal aberration diagram at a shooting distance of 200 mm according to Example 3 of the present invention; It is a lateral aberration diagram at a shooting distance of 200 mm according to Example 3 of the present invention. FIG. 11 is a lens configuration diagram when focusing on infinity according to Example 4 of the present invention; FIG. 11 is a longitudinal aberration diagram during focusing at infinity according to Example 4 of the present invention; FIG. 11 is a lateral aberration diagram during focusing at infinity according to Example 4 of the present invention; FIG. 11 is a longitudinal aberration diagram at a shooting distance of 220 mm according to Example 4 of the present invention; FIG. 10 is a lateral aberration diagram at a shooting distance of 220 mm according to Example 4 of the present invention; FIG. 11 is a lens configuration diagram when focusing on infinity according to Example 5 of the present invention; FIG. 11 is a longitudinal aberration diagram during focusing at infinity according to Example 5 of the present invention; FIG. 11 is a lateral aberration diagram at the time of focusing on infinity according to Example 5 of the present invention; FIG. 10 is a longitudinal aberration diagram at a shooting distance of 210 mm according to Example 5 of the present invention; FIG. 11 is a lateral aberration diagram at a shooting distance of 210 mm according to Example 5 of the present invention; FIG. 11 is a lens configuration diagram when focusing on infinity according to Example 6 of the present invention; FIG. 12 is a longitudinal aberration diagram during focusing at infinity according to Example 6 of the present invention; FIG. 11 is a lateral aberration diagram during focusing at infinity according to Example 6 of the present invention; FIG. 10 is a longitudinal aberration diagram at a shooting distance of 260 mm according to Example 6 of the present invention; FIG. 11 is a lateral aberration diagram at a shooting distance of 260 mm according to Example 6 of the present invention; FIG. 11 is a lens configuration diagram when focusing on infinity according to Example 7 of the present invention; FIG. 12 is a longitudinal aberration diagram during focusing at infinity according to Example 7 of the present invention; FIG. 11 is a lateral aberration diagram at the time of focusing on infinity according to Example 7 of the present invention; FIG. 11 is a longitudinal aberration diagram at a shooting distance of 260 mm according to Example 7 of the present invention; FIG. 11 is a lateral aberration diagram at a shooting distance of 260 mm according to Example 7 of the present invention; FIG. 12 is a lens configuration diagram when focusing on infinity according to Example 8 of the present invention; FIG. 12 is a longitudinal aberration diagram when focusing on infinity according to Example 8 of the present invention; FIG. 12 is a lateral aberration diagram during focusing at infinity according to Example 8 of the present invention; FIG. 12 is a longitudinal aberration diagram at a shooting distance of 290 mm according to Example 8 of the present invention; FIG. 12 is a lateral aberration diagram at a shooting distance of 290 mm according to Example 8 of the present invention; FIG. 20 is a lens configuration diagram when focusing on infinity according to Example 9 of the present invention; FIG. 12 is a longitudinal aberration diagram at the time of focusing at infinity according to Example 9 of the present invention; FIG. 12 is a lateral aberration diagram at the time of focusing at infinity according to Example 9 of the present invention; FIG. 12 is a longitudinal aberration diagram at a shooting distance of 240 mm according to Example 9 of the present invention; FIG. 12 is a lateral aberration diagram at a shooting distance of 240 mm according to Example 9 of the present invention; FIG. 12 is a longitudinal aberration diagram at a shooting distance of 150 mm according to Example 9 of the present invention; FIG. 20 is a lateral aberration diagram at a shooting distance of 150 mm according to Example 9 of the present invention; FIG. 20 is a lens configuration diagram when focusing on infinity according to Example 10 of the present invention; FIG. 20 is a longitudinal aberration diagram when focusing on infinity according to Example 10 of the present invention; FIG. 20 is a lateral aberration diagram at the time of focusing at infinity according to Example 10 of the present invention; FIG. 12 is a longitudinal aberration diagram at a shooting distance of 290 mm according to Example 10 of the present invention; FIG. 11 is a lateral aberration diagram at a shooting distance of 290 mm according to Example 10 of the present invention;

It consists of, in order from the object side, a first lens group G1 with positive refractive power, an aperture stop S, a second lens group G2 with positive refractive power, and a third lens group G3 with negative refractive power. During focusing from an object to a close object, the distance between the first lens group G1 and the lens group G2 is reduced, the distance between the second lens group G2 and the third lens group G3 is increased, and the distance between the second lens group G2 and the third lens group G3 is increased. The second lens group G2 is configured to move toward the object side.

By using the first lens group G1 having a positive refractive power, it is possible to reduce the diameter of the light beam passing through the lens on the image side in order to reduce the size of the entire system.

By arranging the aperture stop S between the first lens group G1 and the second lens group G2, the exit pupil position can be brought closer to the object side, and the light exit angle can be reduced.

By using the second lens group G2 having a positive refractive power and satisfying the conditions described later, it is possible to correct aberrations during focusing and reduce the size of the entire lens system.

By using the third lens group G3 having negative refractive power and satisfying the conditions described later, it is possible to achieve a balance between enlarging the image circle, miniaturizing the entire lens system, and correcting aberrations.

Further, according to the present invention, the distance between the second lens group G2 and the third lens group G3 is widened when focusing from an object at infinity to an object at a short distance, thereby reducing the amount of lens movement. can be done.

It is configured to satisfy the following conditional expressions.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: Focal length of the first lens group G1

The distance between the second lens group G2 and the third lens group G3 is widened when focusing from an infinity object to a close object. A small amount of focus can be used. Therefore, it is possible to reduce the size of the entire system and to photograph at a short photographing distance. Combined with conditional expression (2), it is possible to satisfactorily correct lateral chromatic aberration.

Conditional expression (1) defines the lateral magnification of the third lens group G3 as a favorable condition for balancing the enlargement of the image circle, the miniaturization of the entire lens system, and the correction of aberrations.

If the lateral magnification of the third lens group G3 exceeds the upper limit of conditional expression (1), the residual aberration of the combined system of the first lens group G1 and the second lens group G2 will increase, which is not preferable. If the lateral magnification of the third lens group G3 becomes smaller than the lower limit of conditional expression (1), the image circle becomes smaller and the amount of movement of the lens during focusing becomes larger, making it difficult to reduce the size of the entire lens system. Become. Reducing only the amount of movement of the lens during focusing is not preferable because the photographing distance becomes longer.

By setting the lower limit to 1.55 and the upper limit to 2.50 for conditional expression (1), the above effects can be more reliably achieved.

Conditional expression (2) defines the anomalous partial dispersion of the medium used for the positive lens of the third lens group G3 as a preferable condition for correcting lateral chromatic aberration.

Of the light beams passing through the third lens group G3 of the present invention, the axial light beam passes near the center of the third lens group G3, and the off-axis light beam passes near the periphery of the third lens group G3. The closer the lens in the third lens group G3 is to the image plane, the greater the divergence between the passage points of the axial light flux and the off-axis light flux. Therefore, it is possible to separately correct the chromatic aberration of magnification due to the off-axis light flux depending on the conditions of the medium.

If the upper limit of conditional expression (2) is exceeded and the abnormal partial dispersion increases, the chromatic aberration of the g-line becomes too large, making it difficult to correct the chromatic aberration of magnification. If the lower limit of conditional expression (2) is exceeded and the abnormal partial dispersion becomes small, the chromatic aberration of the g-line becomes excessively large, making it difficult to correct the chromatic aberration of magnification.

By setting the lower limit to 0.025 and the upper limit to 0.100 for conditional expression (2), the above effect can be more reliably achieved.

Conditional expression (3) defines the refractive index of the positive lens in the third lens group G3 as a preferable condition for correcting astigmatism.

If the lower limit of conditional expression (3) is exceeded and G3nd becomes small, the radius of curvature must be made small in order to obtain the refractive power of G3, which is undesirable because astigmatism will increase.

By setting the lower limit of conditional expression (3) to 1.90, the above effect can be more reliably obtained.

Conditional expression (4) defines the ratio of the focal lengths of the first lens group G1 and the entire system as preferable conditions for downsizing the entire lens system and correcting aberrations.

When the upper limit of conditional expression (4) is exceeded and the refractive power of the first lens group G1 becomes small, it becomes difficult to reduce the size of the entire lens system. If the lower limit of conditional expression (4) is exceeded and the refractive power of the first lens group G1 increases, the balance of aberration correction with the second lens group G2 will be lost, which is not preferable.

By setting the lower limit to 0.95 and the upper limit to 4.50 for conditional expression (4), the above effects can be more reliably achieved.

Further, the present invention is constructed so as to satisfy the following conditional expressions.
(5) 2.00<LT/(Ymax)<3.10
LT: Surface distance from the surface closest to the object side of the first lens group G1 to the image plane when in focus at infinity
Ymax: Maximum image height

Conditional expression (5) prescribes the relationship between the length of the entire lens system and the maximum image height as a preferable condition for balancing the compactness of the entire lens system and correction of aberrations.

If the upper limit of conditional expression (5) is exceeded, it exceeds 1.5 times the image circle, and it cannot be said that the size is reduced with respect to the image circle, and the object of the present invention cannot be achieved. If the lower limit of conditional expression (5) is exceeded, the size of the entire lens system becomes small and the refractive power of each group increases, resulting in an increase in the amount of aberration produced, making it difficult to perform good aberration correction.

By setting the lower limit to 2.45 and the upper limit to 3.05 for conditional expression (5), the above effect can be more reliably achieved.

Further, the present invention is constructed so as to satisfy the following conditional expressions.
(6) 2.00<K2<5.00
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused lateral magnification of the second lens group G2 in the state f: focal length of the entire system in the infinity focused state f12: infinity focused

Conditional expression (6) prescribes the focus sensitivity of the second lens group as a favorable condition for the balance between downsizing of the entire lens system and correction of aberrations.

If the upper limit of conditional expression (6) is exceeded and the refracting power of each group increases, the amount of aberrations generated increases, making it difficult to correct aberrations satisfactorily. In addition, as the focus sensitivity increases, it becomes difficult to satisfy the drive accuracy required for focusing. When the lower limit of conditional expression (6) is exceeded and the amount of movement of the second lens group G2 increases, it becomes difficult to reduce the size of the entire lens system.

By setting the lower limit to 2.30 and the upper limit to 4.80 for conditional expression (6), the above effects can be more reliably achieved.

Further, the present invention is constructed so as to satisfy the following conditional expressions.
(7) 0.30<f2/f<0.95
f2: focal length of the second lens group G2
f: focal length of the entire system when in focus at infinity

Conditional expression (7) defines the ratio of the focal lengths of the second lens group G2 and the entire system as a preferable condition for making the entire lens system compact and capable of photographing at a short shooting distance, and for correcting aberrations. is.

When the upper limit of conditional expression (7) is exceeded and the refractive power of the second lens group G2 becomes small, the focus sensitivity becomes small, making it difficult to achieve both miniaturization of the entire lens system and photography at a short shooting distance. If the lower limit of conditional expression (7) is exceeded and the refractive power of the second lens group G2 increases, aberration fluctuations during focusing will increase, and the balance of aberration correction with the second lens group G2 will be lost, which is not preferable.

By setting the lower limit to 0.35 and the upper limit to 0.70 for conditional expression (7), the above effects can be more reliably achieved.

Further, the present invention is constructed so as to satisfy the following conditional expressions.
(8) 0.30<|f3/f|<1.40
f3: focal length of the third lens group G3 f: focal length of the entire system when in focus at infinity

Conditional expression (8) defines the ratio of the focal lengths of the third lens group G3 and the entire system as preferable conditions for enlarging the image circle, miniaturizing the entire lens system, and correcting aberrations.

If the upper limit of conditional expression (8) is exceeded and the refracting power of the third lens group G3 becomes small, the lateral magnification becomes small. Exceeding the lower limit of conditional expression (8) is not preferable because the aberrations generated in the first lens group G1 and the second lens group G2 are remarkably magnified and the balance of aberration correction is lost.

By setting the lower limit to 0.45 and the upper limit to 1.30 for conditional expression (8), the above effects can be more reliably obtained.

Further, the present invention is constructed so as to satisfy the following conditional expressions.
(9) 0.50<((D1_2)*K2)/f<1.40
D1_2: Surface distance between the most image side surface of the first lens group G1 and the most object side surface of the second lens group G2 in the infinity focused state K2: Distance of the second lens group G2 in the infinity focused state Focus sensitivity K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused Lateral magnification f of the second lens group G2 in the state: focal length f1 of the entire system in the infinity focused state: focal length f12 of the first lens group G1: the first lens group G1 in the infinity focused state Composite focal length of the second lens group G2

Conditional expression (9) satisfies a favorable balance between downsizing of the entire lens system, enabling shooting at a short shooting distance, and aberration correction. It defines the sensitivity relationship.

If the upper limit of conditional expression (9) is exceeded and the distance between the first lens G1 and the second lens group G2 increases, it becomes difficult to reduce the size of the entire lens system. If the lower limit of conditional expression (9) is exceeded and the distance between the first lens group G1 and the second lens group G2 becomes small, it interferes with the first lens group G1 and the aperture diaphragm S in the in-focus state at a short shooting distance. Therefore, it becomes impossible to shoot at a short shooting distance, which is not preferable.

By setting the lower limit to 0.60 and the upper limit to 1.25 for conditional expression (9), the above effect can be more reliably achieved.

Further, according to the present invention, the first lens group G1 is fixed with respect to the image plane and the third lens group G3 is fixed with respect to the image plane during focusing from an infinity object to a close object. It is configured.

By fixing the first lens group G1 related to the appearance structure with respect to the image plane, the weight of the lens group that moves during focusing can be reduced. Therefore, the focus actuator can be made smaller, and the size of the product can be reduced.

By fixing the third lens group G3, which is the largest lens group in the entire system, with respect to the image plane, the amount of movement of the lens during focusing can be reduced, and the weight of the focus group can be reduced. Therefore, it is possible to reduce the size of the entire system and to shoot at a short shooting distance.

Focus sensitivity can be increased by fixing the third lens group G3, which has a large lateral magnification, during focusing. Therefore, the amount of movement of the focus group for focusing on a short-distance object becomes small, and photography at a short photography distance becomes possible.

In addition, the present invention employs a configuration in which the first lens group G1 is fixed with respect to the image plane and the third lens group G3 is fixed with respect to the image plane when focusing from an infinity object to a short distance object. Take.

The effect is as described above, and by adopting this configuration, it is possible to efficiently adopt a focusing method with a small amount of movement of the lens during focusing, making the entire lens system compact and shooting at a short shooting distance. can make it possible.

In the present invention, the aperture diaphragm S is adjacent to the image side of the first lens group G1 and is fixed in the optical axis direction during focusing.

The aperture diaphragm S is adjacent to the image side of the first lens group G1 and is fixed in the optical axis direction during focusing, so that the weight of the mechanism that moves during focusing can be reduced. Therefore, the focus actuator can be made smaller, and the size of the product can be reduced. In order to reduce the size of the entire lens system, it is desirable to dispose the diaphragm mechanism on the image side of the first lens group G1 in order to use it for adjusting the amount of light.

Further, the present invention is constructed so as to satisfy the following conditional expressions.
(10) 1.60<|EXP/Ymax|<3.50
EXP: Distance from the exit pupil position to the image plane when in focus at infinity
Ymax: Maximum image height

Conditional expression (10) defines the ratio of the exit pupil position to the maximum image height as a preferable condition for the ray exit angle reaching the edge of the image circle.

When the upper limit of conditional expression (10) is exceeded and EXP increases, the length of the entire lens system and the diameter of the lens arranged on the image side are increased, making it difficult to reduce the size of the entire lens system. When the lower limit of conditional expression (10) is exceeded and the EXP becomes small, the ray exit angle reaches a steep angle with respect to the image plane. When an image sensor used in a digital still camera or the like is used, the sensitivity at the edge of the image circle is lowered, and the amount of peripheral light is remarkably lowered, which is not preferable.

By restricting the lower limit to 1.80 and the upper limit to 2.80 for conditional expression (10), the above effect can be more reliably achieved.

In the present invention, the first lens group G1 consists of a positive lens L1 and a negative lens L2 in order from the object side, and has a positive refractive power as a whole.

The first lens group G1 is composed of a positive lens L1 and a negative lens L2 in order from the object side, and has a positive refractive power as a whole. As a result, the positive lens L1 can reduce the luminous flux, contributing to the miniaturization of the entire lens system. do. Aberration correction with the second lens group G2 can be balanced by softening the ray angle of the axial marginal ray with respect to the optical axis by the subsequent negative lens L2. At this time, it is desirable not to cement the positive lens L1 and the negative lens L2 in order to increase the number of surfaces used for aberration correction. L2 is preferably a concave meniscus lens with a convex surface facing the object side. In order to reduce the size of the entire lens system, it is desirable to dispose the aperture mechanism used for adjusting the amount of light, etc., on the image side of the first lens group G1.

It is more desirable to use an aspherical surface for the first lens group G1. This makes it possible to appropriately correct spherical aberration and coma. The most effective way to correct aberrations is to use aspherical surfaces on both sides of the positive lens L1.

In the present invention, the second lens group G2 consists of a negative lens L3, a positive lens L4, and a positive lens L5 in order from the object side, and has a positive refractive power as a whole.

The second lens group G2 is composed of a negative lens L3, a positive lens L4, and a positive lens L5 in order from the object side, and has a positive refractive power as a whole. , the manufacturing error sensitivity can be reduced. One negative lens is required in the second lens group for aberration balance with the first lens group G1, but the negative lens L3, which is thicker at the periphery, is placed at a position where the light beam diameter is small. Become. In order to move the exit pupil position toward the object side, it is desirable to dispose the negative lens L3 closer to the object side. In order to correct the chromatic aberration of the negative lens L3, it is desirable to place the positive lens L4 adjacent to the positive lens L4, and furthermore, to reduce the manufacturing error sensitivity between the adjacent positive lens L4, the negative lens L3 and the positive lens L4 can be cemented. desirable. Further, by arranging the positive lens L5 on the image plane side, the optical system becomes symmetrical with the first lens group G1, and the aberration correction can be balanced. At this time, the cemented lens, that is, the cemented lens composed of the negative lens L3 and the positive lens L4 is a meniscus lens with a concave surface facing the object side in order to reduce the manufacturing error sensitivity between the positive lens L5 adjacent to the image plane side. A shape is desirable.

As described above, the second lens group G2 has the effect of correcting aberrations and reducing the sensitivity to manufacturing errors, thereby making it possible to increase the focus sensitivity.

The positive lens L5 tends to have a large lens diameter because off-axis rays pass through a position away from the optical axis. Therefore, it is desirable to use a material with a low specific gravity.

Further, it is more desirable to use an aspherical surface for the second lens group G2. This makes it possible to appropriately correct spherical aberration and astigmatism during focusing. The most effective way to correct aberrations is to use aspherical surfaces on both sides of the positive lens L5.

In the present invention, the third lens group G3 consists of a negative lens L6, a negative lens L7, and a positive lens L8 in order from the object side, and has a negative refractive power as a whole.

The third lens group G3 consists of a negative lens L6, a negative lens L7, and a positive lens L8 in order from the object side, and has a negative refractive power as a whole. can be done. By setting the lens diameter of the negative lens L6 to be the same as that of the positive lens L5, the marginal ray on the upper side of the off-axis light beam becomes substantially parallel to the optical axis, thereby reducing the manufacturing error sensitivity with the second lens group G2 and during focusing. It is possible to achieve both reduction of aberration fluctuations. In addition, it is desirable that the lens be a concave meniscus lens with a convex surface facing the object side in order to have a strong negative refractive power for expanding the image circle and to reduce aberration fluctuations during focusing. The negative lens L7 is used for correcting astigmatism, is arranged at a position close to the image plane where the axial ray height is low, and is desirably a concave meniscus lens with a concave surface facing the object side. It is desirable to use a medium with a high refractive index, high dispersion, and high anomalous partial dispersion for the positive lens L8. Since it is used for correction of off-axis chromatic aberration of magnification, correction of astigmatism, and correction of distortion, it is desirable that it be close to the image plane.

Next, a description will be given of the lens construction of an embodiment of the imaging optical system of the present invention.
In the following description, lens configurations are described in order from the object side to the image side.

In [Surface data], the surface number is the number of the lens surface or aperture stop counted from the object side, r is the radius of curvature of each lens surface, d is the distance between each lens surface, and nd is for the d-line (wavelength 587.56 nm). The refractive index, vd is the Abbe number for the d-line, PgF is the partial dispersion ratio between the g-line and the F-line, and the effective diameter is the lens effective diameter.

An asterisk (*) attached to the surface number indicates that the lens surface shape is aspheric. Also, BF represents back focus.

The (diaphragm) attached to the surface number indicates that the aperture diaphragm is located at that position. ∞ (infinity) is entered for the radius of curvature for a plane or aperture stop.

[Aspheric surface data] shows the value of each coefficient that gives the aspheric shape of the lens surface marked with * in [Surface data]. The shape of the aspheric surface is represented by the following formula. In the following formula, y is the displacement from the optical axis in the direction orthogonal to the optical axis, z is the displacement (sag amount) in the optical axis direction from the intersection of the aspherical surface and the optical axis, r is the radius of curvature of the reference spherical surface, K represents the conic coefficient. 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th and 20th aspheric coefficients are represented by A4, A6, A8, A10, A12, A14, A16, A18 and A20, respectively.

[Various data] shows values such as the focal length at the time of focusing at infinity.

[Variable interval data] shows the variable interval and BF values in each photographing distance state.

[Lens group data] shows the lens surface number closest to the object side constituting each lens group and the combined focal length of the entire lens group.

In addition, in the values of all the specifications below, unless otherwise specified, millimeters (mm) are used for the focal length f, radius of curvature r, distance between lens surfaces d, and other lengths. The system is not limited to this because the same optical performance can be obtained in both proportional enlargement and proportional reduction.

FIG. 1 is a lens configuration diagram of an imaging optical system according to Example 1 of the present invention when focusing on infinity.

In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having a convex surface facing the object side and having aspherical surfaces on both sides, and a negative meniscus lens L2 having a convex surface facing the object side. The diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens L5 having aspherical surfaces on both sides. The third lens group G3 having negative refractive power consists of a negative meniscus lens L6 with a convex surface facing the object side, a negative meniscus lens L7 with a concave surface facing the object side, and a biconvex lens L8. When focusing from a distant object to a close object, the first lens group G1, the aperture diaphragm S and the third lens group G3 are fixed with respect to the image plane, and the second lens group G2 moves toward the object side. .

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 1 are shown below.
Numerical example 1
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 23.3681 3.7585 1.77250 49.50 0.5519 20.01
2* 144.1153 0.3080 18.30
3 45.1236 0.8000 1.51742 52.15 0.5589 16.74
4 16.3472 4.6499 14.58
5 (Aperture) ∞ (d5) 12.90
6 -12.2130 0.8000 1.69895 30.05 0.6028 12.85
7 55.6607 4.2213 1.87070 40.73 0.5682 14.54
8 -18.8353 0.1500 15.60
9* 37.4761 4.7493 1.58913 61.25 0.5373 17.90
10* -23.9712 (d10) 18.50
11 109.6497 0.9857 1.67300 38.26 0.5757 18.97
12 21.1832 8.7012 19.20
13 -19.7354 0.8000 1.75211 25.05 0.6191 21.87
14 -29.9543 0.1500 23.66
15 95.8651 2.5968 1.98612 16.48 0.6656 28.20
16 -580.7065 16.3216 28.72
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric data]
1 side 2 sides
K 0.7548 0.0000
A4 -1.0943E-05 -2.3116E-06
A6-9.0526E-08 1.4773E-07
A8 3.3856E-09 -4.0502E-09
A10 -6.8374E-11 7.7863E-11
A12 7.5676E-13 -9.6225E-13
A14 -4.8496E-15 6.3690E-15
A16 1.5425E-17 -2.0898E-17
A18 -1.8709E-20 2.6920E-20
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -2.3178 -2.6500
A4 -2.4796E-06 -4.7357E-06
A6 -9.6746E-09 1.5970E-08
A8 -5.6804E-10 3.7484E-10
A10 3.7440E-11 -1.2512E-11
A12 -7.5858E-13 2.6612E-13
A14 7.5576E-15 -3.0274E-15
A16 -3.5787E-17 1.8357E-17
A18 6.4474E-20 -4.2619E-20
A20 0.0000E+00 0.0000E+00

[Various data]
INF 240
Focal length 43.93 36.81
F number 2.90 3.02
Full angle of view 2ω 51.10 49.90
Image height Y 21.63 21.63
Total lens length 63.57 63.57

[Variable interval data]
INF 240
d0 ∞ 172.6297
d5 8.3114 4.8314
d10 1.7666 5.2466
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 98.79
G26 22.68
G3 11 -39.36
G12 1 24.39
G23 6 54.90

FIG. 6 is a lens configuration diagram of the imaging optical system according to Example 2 of the present invention when focusing on infinity.
The first lens group G1 having positive refractive power, in order from the object side, comprises a positive meniscus lens L1 with a convex surface facing the object side, and a negative meniscus lens L1 with an aspheric surface on the object side and a convex surface on the object side. It consists of a cemented lens L2 composed of a lens made of resin or the like and a negative meniscus lens having a convex surface facing the object side. The lens group G2 is composed of a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens L5 having aspherical surfaces on both sides. The third lens group G3 having negative refractive power has a convex surface facing the object side. It consists of a negative meniscus lens L6, a negative meniscus lens L7 having a concave surface facing the object side, and a biconvex lens L8. and the third lens group G3 are fixed with respect to the image plane, and the second lens group G2 moves toward the object side.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 2 are shown below.
Numerical example 2
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1 25.0272 3.6286 1.77250 49.62 0.5503 19.60
2 148.6155 0.1500 17.88
3* 44.5784 0.1188 1.51840 52.10 0.5538 16.79
4 35.9682 0.8000 1.51742 52.15 0.5589 16.45
5 18.3624 3.6611 14.90
6 (Aperture) ∞ (d6) 13.28
7 -11.8564 0.8000 1.69895 30.05 0.6028 13.05
8 74.0878 4.2582 1.87070 40.73 0.5682 14.70
9 -17.7220 0.1500 15.70
10* 43.7832 4.3575 1.58913 61.25 0.5373 18.00
11* -26.0653 (d11) 18.57
12 100.0000 0.8000 1.64769 33.84 0.5923 19.27
13 22.6971 9.6164 19.38
14 -20.0973 0.8000 1.67270 32.17 0.5962 22.62
15 -33.0792 0.1500 24.58
16 120.8436 2.5285 1.98612 16.48 0.6656 28.58
17 -317.4586 16.1672 29.10
18 ∞ 2.5000 1.51633 64.14 0.5353
19∞ (BF)
Image plane ∞

[Aspheric data]
3 sides 10 sides 11 sides
K -0.5947 -4.1801 -2.6057
A4 -3.1404E-06 3.2870E-07 -3.7190E-06
A6 -1.9502E-07 -1.7897E-08 1.2815E-08
A8 8.0064E-09 -4.0774E-09 -1.3261E-09
A10 -1.4668E-10 1.6733E-10 1.5502E-11
A12 1.2804E-12 -3.0256E-12 2.6614E-13
A14 -4.1538E-15 2.8060E-14 -7.3721E-15
A16 0.0000E+00 -1.3039E-16 5.6089E-17
A18 0.0000E+00 2.4152E-19 -1.3703E-19
A20 0.0000E+00 0.0000E+00 0.0000E+00

[Various data]
INF 240
Focal length 44.27 37.14
F number 2.90 3.00
Full angle of view 2ω 50.75 49.99
Image height Y 21.63 21.63
Overall lens length 63.57 63.57

[Variable interval data]
INF 240
d0 ∞ 174.9301
d6 9.4838 5.6659
d11 1.6000 5.4179
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 89.60
G2 7 24.41
G3 12 -43.26
G12 1 25.50
G23 7 58.75

FIG. 11 is a lens configuration diagram of the imaging optical system according to Example 3 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having aspherical surfaces on both sides and having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side. , the aperture diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens having aspherical surfaces on both sides. A third lens group G3 having a negative refractive power is composed of a negative meniscus lens L6 having a convex surface facing the object side, a negative meniscus lens L7 having a concave surface facing the object side, and a concave surface facing the object side. The first lens group G1, the aperture diaphragm S, and the third lens group G3 are fixed with respect to the image plane when focusing from an infinity object to a short distance object. The second lens group G2 moves to the object side.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 3 are shown below.
Numerical example 3
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 40.0578 1.9199 1.72903 54.04 0.5446 17.97
2* 1035.9646 0.1500 17.19
3 35.3446 0.8000 1.51823 58.96 0.5441 15.51
4 21.8772 3.9211 14.20
5 (Aperture) ∞ (d5) 11.81
6 -11.9037 0.8000 1.69895 30.05 0.6028 12.14
7 33.6044 4.8000 1.87070 40.73 0.5682 14.18
8 -18.2410 0.1500 15.40
9* 38.2460 4.6535 1.58913 61.25 0.5373 17.60
10* -23.7324 (d10) 18.30
11 36.1340 0.8000 1.51742 52.15 0.5589 19.30
12 17.4730 6.9149 19.08
13 -18.7936 0.8000 1.64769 33.84 0.5923 19.93
14 -52.5631 0.1500 22.15
15 -160.7300 1.9252 1.92286 20.88 0.6388 23.30
16 -65.0696 15.3702 24.11
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric data]
1 side 2 sides
K 2.2440 0.0000
A4 -4.7931E-06 3.5362E-06
A6 -1.1561E-06 -1.2927E-06
A8 3.9457E-08 5.9642E-08
A10 -5.1536E-10 -1.1713E-09
A12 -3.6010E-14 8.3976E-12
A14 7.2185E-14 4.6761E-14
A16 -7.2860E-16 -1.0681E-15
A18 2.3716E-18 4.6152E-18
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -3.5035 -2.7645
A4 -5.9110E-06 -6.8076E-06
A6 -2.5290E-09 1.9360E-08
A8 3.4621E-10 3.2163E-10
A10 4.9236E-13 1.3592E-12
A12 0.0000E+00 1.9007E-15
A14 0.0000E+00 0.0000E+00
A16 0.0000E+00 0.0000E+00
A18 0.0000E+00 0.0000E+00
A20 0.0000E+00 0.0000E+00

[Various data]
INF 200
Focal length 37.01 31.09
F number 2.90 3.02
Full angle of view 2ω 59.14 58.03
Image height Y 21.63 21.63
Overall lens length 57.27 57.27

[Variable interval data]
INF 200
d0 ∞ 142.7325
d5 8.0119 4.7646
d10 1.6000 4.8473
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 110.04
G2 6 21.04
G3 11 -34.64
G12 1 21.48
G23 6 45.56

FIG. 16 is a lens configuration diagram of the imaging optical system according to Example 4 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having aspherical surfaces on both sides and having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side. , the aperture diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens having aspherical surfaces on both sides. A third lens group G3 having a negative refractive power includes a negative meniscus lens L6 having a convex surface facing the object side, a negative meniscus lens L7 having a concave surface facing the object side, and a concave surface facing the object side. The first lens group G1, the aperture stop S, and the third lens group G3 are fixed with respect to the image plane when focusing from an infinity object to a short distance object. The second lens group G2 moves to the object side.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 4 are shown below.
Numerical example 4
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 27.9565 2.1228 1.85135 40.10 0.5694 20.03
2* 68.1371 0.1500 19.12
3 19.1686 0.8000 1.55298 55.07 0.5447 16.74
4 13.0798 5.4212 15.00
5 (Aperture) ∞ (d5) 12.38
6 -12.8045 0.8000 1.69895 30.05 0.6028 12.61
7 26.7275 4.8000 1.87070 40.73 0.5682 14.71
8 -20.8226 0.1500 15.80
9* 42.5418 4.5045 1.58913 61.25 0.5373 17.90
10 -24.4535 (d10) 18.54
11 34.5567 1.4070 1.67300 38.26 0.5757 19.43
12 18.8436 10.2837 19.10
13 -17.0132 0.8000 1.75211 25.05 0.6191 21.82
14 -32.5270 0.1500 24.42
15 -626.8220 2.9061 1.98612 16.48 0.6656 27.60
16 -60.7974 14.8183 28.43
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric data]
1 side 2 sides
K 1.4127 0.0000
A4 -1.6186E-05 -1.0510E-05
A6 -9.2237E-08 1.9241E-08
A8 1.9145E-09 2.9174E-09
A10 2.2312E-11 -2.4662E-11
A12 -6.4984E-13 -2.1752E-13
A14 3.6410E-15 2.6677E-15
A16 0.0000E+00 0.0000E+00
A18 0.0000E+00 0.0000E+00
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -4.3611 -2.2863
A4 -4.9661E-06 -7.4309E-06
A6 5.1598E-09 2.2351E-08
A8 -3.8894E-10 -1.5640E-10
A10 4.9734E-12 2.4462E-12
A12 0.0000E+00 1.5323E-14
A14 0.0000E+00 0.0000E+00
A16 0.0000E+00 0.0000E+00
A18 0.0000E+00 0.0000E+00
A20 0.0000E+00 0.0000E+00

[Various data]
INF 220
Focal length 40.00 34.53
F number 2.90 3.08
Full angle of view 2ω 55.84 53.58
Image height Y 21.63 21.63
Total lens length 63.57 63.57

[Variable interval data]
INF 220
d0 ∞ 156.4295
d5 8.3569 4.4610
d10 1.6000 5.4959
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 154.41
G26 23.51
G3 11 -48.02
G12 1 24.61
G23 6 43.75

FIG. 21 is a lens configuration diagram of the imaging optical system according to Example 5 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having aspherical surfaces on both sides and having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side. , the aperture diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens having aspherical surfaces on both sides. The third lens group G3 having negative refractive power consists of a negative meniscus lens L6 with a convex surface facing the object side, a negative meniscus lens L7 with a concave surface facing the object side, and a biconvex lens L8. , the first lens group G1, the aperture stop S and the third lens group G3 are fixed with respect to the image plane, and the second lens group G2 is directed toward the object side when focusing from an infinite object to a short distance object. Moving.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 5 are shown below.
Numerical example 5
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 21.0823 3.4782 1.76802 49.24 0.5515 21.16
2* 99.2280 0.1608 20.07
3 47.5622 0.8000 1.51742 52.15 0.5589 18.94
4 19.4504 4.4894 16.80
5 (Aperture) ∞ (d5) 14.80
6 -15.0441 0.8000 1.69895 30.05 0.6028 14.30
7 21.1179 4.7971 1.87070 40.73 0.5682 15.72
8 -26.2651 0.1870 16.20
9* 45.2265 4.2577 1.58913 61.25 0.5373 17.80
10* -27.0031 (d10) 18.39
11 1450.3022 1.3351 1.67300 38.26 0.5757 19.13
12 25.6487 8.1008 19.40
13 -17.7190 0.8004 1.75211 25.05 0.6191 21.66
14 -51.2250 0.1502 25.06
15 1000.0000 4.3333 1.98612 16.48 0.6656 28.40
16 -42.8968 14.0137 29.54
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric Data]
1 side 2 sides
K 0.6876 12.9030
A4 -1.3213E-05 -9.8307E-07
A6 3.2013E-07 1.2898E-07
A8 -1.8639E-08 -8.8793E-09
A10 5.2041E-10 3.1773E-10
A12 -8.2976E-12 -6.4386E-12
A14 7.5237E-14 7.2797E-14
A16 -3.6261E-16 -4.3185E-16
A18 7.1284E-19 1.0386E-18
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -2.4143 -4.0616
A4 -5.0885E-06 -6.7662E-06
A6 -1.4701E-08 3.9183E-08
A8 -1.9852E-09 2.3073E-08
A10 9.1678E-11 -1.2237E-09
A12 -1.1699E-12 2.9740E-11
A14 2.3893E-15 -3.7929E-13
A16 5.7896E-17 2.4731E-15
A18 -3.1362E-19 -6.4997E-18
A20 0.0000E+00 0.0000E+00

[Various data]
INF 210
Focal length 50.72 34.65
F number 2.90 2.98
Full angle of view 2ω 44.98 44.39
Image height Y 21.63 21.63
Total lens length 64.52 64.52

[Variable interval data]
INF 210
d0 ∞ 144.4762
d5 10.6925 5.0552
d10 1.6281 7.2654
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 65.48
G26 26.88
G3 11 -38.63
G12 1 27.64
G23 6 107.03

FIG. 26 is a lens configuration diagram of the imaging optical system according to Example 6 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having aspherical surfaces on both sides and having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side. , the aperture diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens having aspherical surfaces on both sides. L5, and the third lens group G3 having negative refractive power is composed of a negative meniscus lens L6 with a convex surface facing the object side, a negative meniscus lens L7 with a concave surface facing the object side, and a biconvex lens L8, When focusing from an infinity object to a close object, the first lens group G1, the aperture diaphragm S and the third lens group G3 are fixed with respect to the image plane, and the second lens group G2 moves toward the object side. do.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 6 are shown below.
Numerical example 6
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 21.0987 3.3398 1.77250 49.50 0.5519 19.88
2* 54.6445 0.7934 18.16
3 29.1842 0.8000 1.48749 70.44 0.5306 16.60
4 17.2858 3.6525 15.68
5 (Aperture) ∞ (d5) 15.00
6 -13.4041 0.8000 1.69895 30.05 0.6028 14.41
7 30.1667 4.7697 1.87070 40.73 0.5682 16.18
8 -20.0313 0.1500 16.80
9* 26.9679 4.4763 1.58913 61.25 0.5373 17.80
10* -37.7416 (d10) 18.16
11 138.9423 0.8000 1.95375 32.32 0.5901 18.22
12 22.4583 10.0862 18.00
13 -16.4066 0.8000 1.70154 41.15 0.5769 21.66
14 -29.7489 0.1500 24.39
15 178.9531 3.4842 1.98612 16.48 0.6656 29.30
16 -81.0895 15.1006 30.05
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric data]
1 side 2 sides
K 2.1022 10.6169
A4 -1.5287E-05 7.0189E-06
A6 -2.1976E-07 1.8322E-07
A8 -4.4936E-10 -1.5319E-08
A10 2.1212E-10 7.5207E-10
A12 -6.3286E-12 -1.7441E-11
A14 8.8011E-14 2.2713E-13
A16 -6.0800E-16 -1.5745E-15
A18 1.7022E-18 4.6288E-18
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -2.1665 -4.9007
A4 5.0447E-06 4.5712E-06
A6 -1.3519E-08 1.2052E-08
A8 2.6215E-09 3.3008E-09
A10 -7.1467E-11 -8.7446E-11
A12 7.7627E-13 9.2023E-13
A14 -3.2966E-15 -3.7697E-15
A16 0.0000E+00 0.0000E+00
A18 0.0000E+00 0.0000E+00
A20 0.0000E+00 0.0000E+00

[Various data]
INF 260
Focal length 51.30 40.89
F number 2.90 2.94
Full angle of view 2ω 44.52 44.28
Image height Y 21.63 21.63
Total lens length 64.57 64.57

[Variable interval data]
INF 260
d0 ∞ 195.4280
d5 9.2671 6.2340
d10 1.6000 4.6331
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 73.81
G2 6 22.28
G3 11 -29.05
G12 1 23.90
G23 6 102.38

FIG. 31 is a lens configuration diagram of the imaging optical system according to Example 7 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having aspherical surfaces on both sides and having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side. , the aperture diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens having aspherical surfaces on both sides. The third lens group G3 having a negative refractive power is composed of a negative meniscus lens L6 having a convex surface facing the object side, a negative meniscus lens L7 having a concave surface facing the object side, and a biconvex lens L8. Thus, when focusing from an infinite object to a close object, the first lens group G1, the aperture diaphragm S and the third lens group G3 are fixed with respect to the image plane, and the second lens group G2 is on the object side. move to

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 7 are shown below.
Numerical example 7
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 20.6620 3.1514 1.85135 40.10 0.5694 19.63
2* 47.5814 0.4460 17.95
3 23.7152 0.8000 1.67300 38.26 0.5757 16.60
4 15.8076 3.7525 15.65
5 (Aperture) ∞ (d5) 15.03
6 -13.7424 0.8000 1.69895 30.05 0.6028 14.56
7 33.2777 4.8000 1.87070 40.73 0.5682 16.30
8 -19.2935 0.1895 17.00
9* 23.9858 4.5111 1.58913 61.25 0.5373 17.50
10* -45.1305 (d10) 17.74
11 141.4802 0.8000 1.95375 32.32 0.5901 17.66
12 21.0998 10.5351 17.50
13 -17.0176 0.8000 1.83400 37.35 0.5789 21.74
14 -28.6516 0.1500 24.22
15 208.3778 3.5796 1.98612 16.48 0.6656 29.20
16 -72.4839 14.9309 30.01
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric data]
1 side 2 sides
K 2.0719 11.2100
A4 -1.8102E-05 2.1864E-06
A6 -2.5741E-07 -6.4336E-08
A8 5.6331E-10 -2.6344E-09
A10 1.5449E-10 3.4042E-10
A12 -4.5910E-12 -8.8147E-12
A14 6.3669E-14 1.1928E-13
A16 -4.4851E-16 -8.4905E-16
A18 1.3183E-18 2.6669E-18
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -1.8995 -5.1449
A4 8.2067E-06 8.1730E-06
A6-1.1855E-08 7.2803E-09
A8 2.6173E-09 2.4921E-09
A10 -7.3732E-11 -7.1060E-11
A12 8.0300E-13 7.6064E-13
A14 -3.4811E-15 -3.2809E-15
A16 0.0000E+00 0.0000E+00
A18 0.0000E+00 0.0000E+00
A20 0.0000E+00 0.0000E+00

[Various data]
INF 260
Focal length 51.21 40.91
F number 2.90 2.95
Full angle of view 2ω 44.59 44.29
Image height Y 21.63 21.63
Total lens length 64.39 64.39

[Variable interval data]
INF 260
d0 ∞ 195.6050
d5 9.0455 6.3188
d10 1.6000 4.3267
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 79.67
G2 6 21.04
G3 11 -27.24
G12 1 22.82
G23 6 93.77

FIG. 36 is a lens configuration diagram of the imaging optical system according to Example 8 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having aspherical surfaces on both sides and having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side. , the aperture diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a double-sided aspherical surface. A third lens group G3 having a negative refractive power, consisting of a convex lens L5, comprises a negative meniscus lens L6 having a convex surface facing the object side, a negative meniscus lens L7 having a concave surface facing the object side, and a biconvex lens L8. Thus, when focusing from an infinite object to a close object, the first lens group G1, the aperture diaphragm S and the third lens group G3 are fixed with respect to the image plane, and the second lens group G2 is on the object side. Move to

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 8 are shown below.
Numerical example 8
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 19.2943 4.3849 1.77250 49.50 0.5519 21.91
2* 83.4557 0.4474 20.13
3 37.3406 0.8000 1.64769 33.84 0.5923 18.60
4 17.8608 3.9704 17.25
5 (Aperture) ∞ (d5) 16.38
6 -17.4689 0.8000 1.67270 32.17 0.5962 15.46
7 18.5228 4.7563 1.87070 40.73 0.5682 16.88
8 -37.3036 0.1500 17.20
9* 61.4797 3.6234 1.58913 61.25 0.5373 17.10
10* -27.3796 (d10) 17.71
11 108.5223 0.8000 1.88300 40.81 0.5654 18.75
12 28.8108 8.2602 18.80
13 -17.3629 0.8000 1.83400 37.35 0.5789 21.12
14 -33.0352 0.1500 23.51
15 159.5584 2.9136 1.98612 16.48 0.6656 27.52
16 -112.0386 15.6000 28.23
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric data]
1 side 2 sides
K 1.2865 3.6433
A4 -2.2596E-05 4.5240E-06
A6 -9.5381E-08 4.9414E-08
A8-9.9329E-10 1.1435E-09
A10 6.9611E-11 -2.6295E-11
A12 -1.8807E-12 1.4369E-13
A14 2.3787E-14 4.2434E-15
A16 -1.4812E-16 -6.1675E-17
A18 3.6682E-19 2.5658E-19
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -12.4781 -3.2159
A4 -6.8969E-06 -4.7966E-06
A6 -2.7438E-08 2.8670E-08
A8 -1.6769E-09 2.9749E-09
A10 1.8763E-11 -1.0572E-10
A12 8.9135E-14 1.3762E-12
A14 -1.0850E-15 -5.7279E-15
A16 0.0000E+00 0.0000E+00
A18 0.0000E+00 0.0000E+00
A20 0.0000E+00 0.0000E+00

[Various data]
INF 290
Focal length 58.00 44.21
F number 2.90 2.95
Full angle of view 2ω 39.82 39.34
Image height Y 21.63 21.63
Total lens length 64.57 64.57

[Variable interval data]
INF 290
d0 ∞ 225.4298
d5 11.0138 5.9218
d10 1.6000 6.6920
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 63.49
G26 32.00
G3 11 -33.78
G12 1 31.29
G23 6 440.27

FIG. 41 is a lens configuration diagram of the imaging optical system according to Example 9 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having a convex surface facing the object side and having aspherical surfaces on both sides, and a negative meniscus lens L2 having a convex surface facing the object side. The diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens L5 having aspherical surfaces on both sides. The third lens group G3 having negative refractive power consists of a negative meniscus lens L6 with a convex surface facing the object side, a negative meniscus lens L7 with a concave surface facing the object side, and a biconvex lens L8. When focusing from a distant object to a close object, the third lens group G3 is fixed with respect to the image plane, and the first lens group G1, the aperture diaphragm S, and the second lens group G2 are integrated to the object side. As it moves, the second lens group moves further toward the object side.

The power for integrally moving the first lens group G1, the aperture diaphragm S, and the second lens group G2 may be an actuator with a large torque, or a mechanical extension mechanism that does not depend on an actuator, which is exclusively used for close-up photography. Although a lens system may be used, it is desirable to use a compact actuator for driving the second lens group G2 so as to enable minute driving in the optical axis direction. At this time, by moving the second lens group G2 toward the object side, it becomes possible to focus on an object at a closer distance.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 9 are shown below.
Numerical example 9
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 23.3681 3.7585 1.77250 49.50 0.5519 20.01
2* 144.1153 0.3080 18.30
3 45.1236 0.8000 1.51742 52.15 0.5589 16.74
4 16.3472 4.6499 14.58
5 (Aperture) ∞ (d5) 12.90
6 -12.2130 0.8000 1.69895 30.05 0.6028 12.85
7 55.6607 4.2213 1.87070 40.73 0.5682 14.54
8 -18.8353 0.1500 15.60
9* 37.4761 4.7493 1.58913 61.25 0.5373 17.90
10* -23.9712 (d10) 18.50
11 109.6497 0.9857 1.67300 38.26 0.5757 18.97
12 21.1832 8.7012 19.20
13 -19.7354 0.8000 1.75211 25.05 0.6191 21.87
14 -29.9543 0.1500 23.66
15 95.8651 2.5968 1.98612 16.48 0.6656 28.20
16 -580.7065 16.3216 28.72
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞



[Aspheric data]
1 side 2 sides
K 0.7548 0.0000
A4 -1.0943E-05 -2.3116E-06
A6-9.0526E-08 1.4773E-07
A8 3.3856E-09 -4.0502E-09
A10 -6.8374E-11 7.7863E-11
A12 7.5676E-13 -9.6225E-13
A14 -4.8496E-15 6.3690E-15
A16 1.5425E-17 -2.0898E-17
A18 -1.8709E-20 2.6920E-20
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -2.3178 -2.6500
A4 -2.4796E-06 -4.7357E-06
A6 -9.6746E-09 1.5970E-08
A8 -5.6804E-10 3.7484E-10
A10 3.7440E-11 -1.2512E-11
A12 -7.5858E-13 2.6612E-13
A14 7.5576E-15 -3.0274E-15
A16 -3.5787E-17 1.8357E-17
A18 6.4474E-20 -4.2619E-20
A20 0.0000E+00 0.0000E+00

[Various data]
INF 240 150
Focal length 43.93 37.82 32.28
F number 2.90 3.07 3.26
Full angle of view 2ω 51.10 48.96 46.43
Image height Y 21.63 21.63 21.63
Overall lens length 63.57 67.10 67.10

[Variable interval data]
INF 240 150
d0 ∞ 168.8040 85.1913
d5 8.3114 8.3114 4.8314
d10 1.7666 5.2940 8.7740
BF 2.0000 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 98.79
G26 22.68
G3 11 -39.36
G12 1 24.39
G23 6 54.90

FIG. 46 is a lens configuration diagram of the imaging optical system according to Example 10 of the present invention when focusing on infinity.
In order from the object side, the first lens group G1 having positive refractive power is composed of a positive meniscus lens L1 having a convex surface facing the object side and having aspherical surfaces on both sides, and a negative meniscus lens L2 having a convex surface facing the object side. The diaphragm S is adjacent to the image side of the first lens group G1, and the second lens group G2 having positive refractive power includes a cemented lens composed of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens L5 having aspherical surfaces on both sides. The third lens group G3 having negative refractive power consists of a negative meniscus lens L6 with a convex surface facing the object side, a negative meniscus lens L7 with a concave surface facing the object side, and a biconvex lens L8, During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. expands, and the first lens group G1, the aperture stop S, the second lens group G2, and the third lens group G3 move separately toward the object side.

By reducing the distance between the first lens group G1 and the second lens group G2, an increase in the total optical length can be suppressed, and by increasing the distance between the second lens group G2 and the third lens group G3, astigmatism can be corrected appropriately. As a result, the curvature of field can be effectively corrected.

Although an actuator with a large torque may be used as the power for moving each lens group, a small actuator may be used for driving the second lens group G2 so as to enable minute driving in the direction of the optical axis. desirable.

A filter F, which is a plane-parallel plate, is arranged between the third lens group G3 and the image plane. The position of the filter F on the optical axis does not affect aberrations anywhere between the third lens group G3 and the image plane.

Next, the specification values of the imaging optical system according to Example 10 are shown below.
Numerical Example 10
Unit: mm
[Surface data]
Surface number rd nd vd PgF Effective diameter Object surface ∞ (d0)
1* 23.3681 3.7585 1.77250 49.50 0.5519 20.01
2* 144.1153 0.3080 18.30
3 45.1236 0.8000 1.51742 52.15 0.5589 16.74
4 16.3472 4.6499 14.58
5 (Aperture) ∞ (d5) 12.90
6 -12.2130 0.8000 1.69895 30.05 0.6028 12.85
7 55.6607 4.2213 1.87070 40.73 0.5682 14.54
8 -18.8353 0.1500 15.60
9* 37.4761 4.7493 1.58913 61.25 0.5373 17.90
10* -23.9712 (d10) 18.50
11 109.6497 0.9857 1.67300 38.26 0.5757 18.97
12 21.1832 8.7012 19.20
13 -19.7354 0.8000 1.75211 25.05 0.6191 21.87
14 -29.9543 0.1500 23.66
15 95.8651 2.5968 1.98612 16.48 0.6656 28.20
16 -580.7065 (d16) 28.72
17∞ 2.5000 1.51633 64.14 0.5353
18∞ (BF)
Image plane ∞

[Aspheric Data]
1 side 2 sides
K 0.7548 0.0000
A4 -1.0943E-05 -2.3116E-06
A6-9.0526E-08 1.4773E-07
A8 3.3856E-09 -4.0502E-09
A10 -6.8374E-11 7.7863E-11
A12 7.5676E-13 -9.6225E-13
A14 -4.8496E-15 6.3690E-15
A16 1.5425E-17 -2.0898E-17
A18 -1.8709E-20 2.6920E-20
A20 0.0000E+00 0.0000E+00

9 sides 10 sides
K -2.3178 -2.6500
A4 -2.4796E-06 -4.7357E-06
A6 -9.6746E-09 1.5970E-08
A8 -5.6804E-10 3.7484E-10
A10 3.7440E-11 -1.2512E-11
A12 -7.5858E-13 2.6612E-13
A14 7.5576E-15 -3.0274E-15
A16 -3.5787E-17 1.8357E-17
A18 6.4474E-20 -4.2619E-20
A20 0.0000E+00 0.0000E+00

[Various data]
INF 240
Focal length 43.93 38.38
F number 2.90 3.18
Full angle of view 2ω 51.10 48.07
Image height Y 21.63 21.63
Total lens length 63.57 66.23

[Variable interval data]
INF 240
d0 ∞ 169.9704
d5 8.3114 4.8314
d10 1.7666 4.2180
d16 16.3216 20.0097
BF 2.0000 2.0000

[Lens group data]
Group Starting surface Focal length
G1 1 98.79
G26 22.68
G3 11 -39.36
G12 1 24.39
G23 6 54.90

The values corresponding to the conditional expressions corresponding to the above embodiments are shown above.
Conditional expression/Example EX1 EX2 EX3 EX4 EX5
1.40<f/f12<2.80 1.80 1.74 1.72 1.63 1.84
0.020<G3ΔPgFmax<0.300 0.047 0.047 0.028 0.047 0.047
1.80<G3nd 1.99 1.99 1.92 1.99 1.99
0.60<f1/f<6.50 2.25 2.02 2.97 3.86 1.29
2.00<LT/(Ymax)<3.10 2.94 2.94 2.65 2.94 2.98
2.00<K2<5.00 3.05 2.77 2.85 2.57 2.77
0.30<f2/f<0.95 0.52 0.55 0.57 0.59 0.53
0.30<|f3/f|<1.40 0.90 0.98 0.94 1.20 0.76
0.50<((D1_2)*K2)/f<1.40 0.90 0.82 0.92 0.89 0.83
1.60<EXP/Ymax<3.50 2.43 2.55 2.14 2.49 2.51

Conditional expression/Example EX6 EX7 EX8 EX9 EX10
1.40<f/f12<2.80 2.15 2.24 1.85 1.80 1.80
0.020<G3ΔPgFmax<0.300 0.047 0.047 0.047 0.047 0.047
1.80<G3nd 1.99 1.99 1.99 1.99 1.99
0.60<f1/f<6.50 1.44 1.56 1.09 2.25 2.25
2.00<LT/(Ymax)<3.10 2.99 2.98 2.99 2.94 2.94
2.00<K2<5.00 4.12 4.62 2.60 3.05 3.05
0.30<f2/f<0.95 0.43 0.41 0.55 0.52 0.52
0.30<|f3/f|<1.40 0.57 0.53 0.58 0.90 0.90
0.50<((D1_2)*K2)/f<1.40 1.04 1.16 0.67 0.90 0.90
1.60<EXP/Ymax<3.50 2.40 2.40 2.19 2.43 2.43

G1 1st lens group G2 2nd lens group G3 3rd lens group I Image plane F Filter S Aperture stop

Claims (22)

Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
(5) 2.0<LT/(Ymax)<3.10
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: Focal length LT of the first lens group G1: The first lens group G1 in the infinity focused state distance from the surface closest to the object side to the image plane of
Ymax: Maximum image height Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
(8) 0.30<|f3/f|<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: focal length f3 of the first lens group G1: focal length of the third lens group G3 Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(4) 0.60<f1/f<6.50
(10) 1.60<|EXP/Ymax|<3.50
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index f1 for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: Focal length EXP of the first lens group G1: From the exit pupil position to the image plane when in focus at infinity distance to
Ymax: Maximum image height Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
When focusing from an infinite object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9′) 0.67≦((D1_2)*K2)/f<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity LT: the first lens when focused on infinity Surface distance from the surface closest to the object side of the group G1 to the image plane
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused lateral magnification f1 of the second lens group G2 in the state: focal length D1_2 of the first lens group G1: the surface of the first lens group G1 closest to the image side and the surface of the second lens group G2 closest to the image in the infinite focus state Surface spacing on the object side Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9) 0.50<((D1_2)*K2)/f<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index LT for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: the distance from the most object-side surface of the first lens group G1 to the image plane in the infinity focused state Spacing
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f1 of the second lens group G2 at : focal length D1_2 of the first lens group G1: the most image-side surface of the first lens group G1 and the most object of the second lens group G2 in an infinite focus state Spacing of side faces Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(3) 1.80<G3nd
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9) 0.50<((D1_2)*K2)/f<1.40
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3nd: the focal length of the positive lens in the third lens group G3 Refractive index LT for the largest d-line (wavelength λ=587.56): Surface distance from the most object-side surface of the first lens group G1 to the image plane when in focus at infinity
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused lateral magnification f1 of the second lens group G2 in the state: focal length D1_2 of the first lens group G1: the surface of the first lens group G1 closest to the image side and the surface of the second lens group G2 closest to the image in the infinite focus state Spacing of the surface on the object side Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
(9) 0.50<((D1_2)*K2)/f<1.40
(10′) 2.14<|EXP/Ymax|<3.50
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity LT: the first lens when focused on infinity Surface distance from the surface closest to the object side of the group G1 to the image plane
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f1 of the second lens group G2 at : focal length D1_2 of the first lens group G1: the most image-side surface of the first lens group G1 and the most object of the second lens group G2 in an infinite focus state Surface distance EXP of the side surface: Distance from the exit pupil position to the image plane when in focus at infinity Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
When focusing from an infinite object to a close object, the distance between the first lens group G1 and the second lens group G2 is reduced, and the distance between the second lens group G2 and the third lens group G3 is reduced. spreads and the second lens group G2 moves toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(3) 1.80<G3nd
(5) 2.0<LT/(Ymax)<3.10
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) G3nd: the above Refractive index LT for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3: the distance from the most object-side surface of the first lens group G1 to the image plane in the infinity focused state Spacing
Ymax: Maximum image height Consists of, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power,
During focusing from an infinity object to a close object, the first lens group G1 is fixed with respect to the image plane, the third lens group G3 is fixed with respect to the image plane, and the second lens group G3 is fixed with respect to the image plane. The lens group G2 is configured to move toward the object side,
An imaging optical system characterized by satisfying the following conditional expression.
(1) 1.40<f/f12<2.80
(2) 0.020<G3ΔPgFmax<0.300
(5) 2.0<LT/(Ymax)<3.10
(6) 2.00<K2<5.00
f: the focal length of the entire system when focused on infinity f12: the combined focal length of the first lens group G1 and the second lens group G2 when focused on infinity G3ΔPgFmax: the focal length of the positive lens in the third lens group G3 Among them, the largest ΔPgF value ΔPgF = PgF - 0.64833 + 0.00180νd: g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial dispersion between F lines Ratio ng: refractive index for g-line (wavelength λ = 435.84 nm) nF: refractive index for F-line (wavelength λ = 486.13 nm) nC: refractive index for C-line (wavelength λ = 656.27 nm) LT: infinity Surface distance from the most object side surface of the first lens group G1 to the image plane in the in-focus state
Ymax: Maximum image height
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state lateral magnification f1 of the second lens group G2 at: focal length of the first lens group G1 8. An imaging optical system according to claim 4, wherein the following conditions are satisfied.
(2) 0.020<G3ΔPgFmax<0.300
G3ΔPgFmax: the largest value of ΔPgF among the positive lenses in the third lens group G3 ΔPgF=PgF−0.64833+0.00180νd: g, abnormal partial dispersion between F lines PgF=(ng−nF)/(nF) -nC): g, partial dispersion ratio between F lines ng: refractive index for g line (wavelength λ = 435.84 nm) nF: refractive index for F line (wavelength λ = 486.13 nm) nC: C line (wavelength λ = 656.27 nm): refractive index for the largest d-line (wavelength λ = 587.56) among the positive lenses in the third lens group G3 11. An imaging optical system according to any one of claims 4, 5, 7, 9 and 10, wherein the following conditions are satisfied.
(3) 1.80<G3nd
G3nd: Refractive index for the largest d-line (wavelength λ=587.56) among the positive lenses in the third lens group G3 12. The imaging optical system according to any one of claims 4 to 11, wherein the following conditions are satisfied.
(4) 0.60<f1/f<6.50
f: focal length of the entire system when in focus at infinity f1: focal length of the first lens group G1 9. An imaging optical system according to claim 1, wherein the following conditions are satisfied.
(6) 2.00<K2<5.00
K2: focus sensitivity of the second lens group G2 in the infinity focused state K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f of the second lens group G2 in the above: focal length f12 of the entire system in the infinity focused state: combined focus f1 of the first lens group G1 and the second lens group G2 in the infinity focused state: Focal length of the first lens group G1 14. The imaging optical system according to any one of claims 1 to 13, wherein the following conditions are satisfied.
(7) 0.30<f2/f<0.95
f2: focal length of the second lens group G2 f: focal length of the entire system when in focus at infinity 15. The imaging optical system according to any one of claims 1 and 3 to 14, wherein the following conditions are satisfied.
(8) 0.30<|f3/f|<1.40
f3: focal length of the third lens group G3 f: focal length of the entire system when in focus at infinity 16. An imaging optical system according to any one of claims 1 to 3, 8, 9, and 12 to 15, which satisfies the following conditions.
(9) 0.50<((D1_2)*K2)/f<1.40
D1_2: Surface distance between the surface closest to the image side of the first lens group G1 and the surface closest to the object side of the second lens group G2 in the infinity focused state K2: Distance of the second lens group G2 in the infinity focused state Focus sensitivity K2=|Δdef/Δx|
=|(β3^2)*(1-β2^2)|
=|((f/f12)^2)*(1-(f12/f1)^2)|
Δdef: Small image plane movement amount in infinity focused state Δx: Small focus lens movement amount in infinity focused state β3: Lateral magnification of the third lens group G3 in infinity focused state β2: Infinity focused state Lateral magnification f of the second lens group G2 at : focal length f1 of the entire system in an infinity focused state: focal length f12 of the first lens group G1: the first lens group G1 and the Combined focal length of the second lens group G2 The first lens group G1 is fixed with respect to the image plane and the third lens group G3 is fixed with respect to the image plane when focusing from an object at infinity to a close object. 17. The imaging optical system according to any one of claims 1 to 8 and claims 10 to 16, characterized by: 18. The imaging optics according to any one of claims 1 to 17, wherein said aperture stop S is adjacent to said first lens group G1 on the image side and is fixed in the optical axis direction during focusing. system. 19. An imaging optical system according to any one of claims 1, 2, 4 to 6, and 8 to 18, wherein the following conditional expression is satisfied.
(10) 1.60<|EXP/Ymax|<3.50
EXP: Distance from the exit pupil position to the image plane when in focus at infinity
Ymax: Maximum image height 20. The imaging optics according to claim 1, wherein the first lens group G1 comprises a positive lens L1 and a negative lens L2 in order from the object side, and has a positive refractive power as a whole. system. 21. A lens system according to any one of claims 1 to 20, wherein said second lens group G2 consists of a negative lens L3, a positive lens L4, and a positive lens L5 in order from the object side, and has a positive refractive power as a whole. image optics. 22. A lens system according to any one of claims 1 to 21, wherein said third lens group G3 consists of a negative lens L6, a negative lens L7 and a positive lens L8 in order from the object side, and has a negative refractive power as a whole. image optics.

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