JP2011227124A - Ultra wide-angle lens system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra wide-angle lens system that employs a high-performance inner focusing system with compactness and low aberration fluctuation due to focusing despite the ultra wide-angle lens system with a photographing angle-of-view exceeding 120°.SOLUTION: An ultra wide-angle lens system includes, in order from an object side, a first lens group G1 with negative refractive power and a second lens group G2 with positive refractive power. The first lens group is composed of a first A lens group with negative refractive power and a first B lens group with negative refractive power. Further, the first A lens group is composed of a first lens L1 of a negative meniscus lens and a second lens L2 of a negative meniscus lens with an aspherical surface on at least one surface. The first B lens group is composed of a third lens L3 of a negative meniscus lens with an aspherical surface on at least one surface. In focusing, the first B lens group is moved to the object side.

Description

The present invention relates to a lens used in a digital camera, a silver salt camera, a video camera, and the like. Although it is a super-wide-angle lens system in which a shooting angle of view exceeds 120 °, it is compact and has high performance with little aberration fluctuation due to focusing. The present invention relates to an ultra-wide-angle lens system that employs an inner focus method.

Conventionally, an ultra-wide-angle lens system having an angle of view exceeding 120 ° is described in, for example, the following patent documents.

Patent Document 1 discloses a super wide-angle lens system with an angle of view exceeding 120 °.

Patent Document 2 discloses an ultra-wide-angle lens system that employs an inner focus method and has an angle of view exceeding 120 °.

JP 2001-124985 A

JP 2005-106878 A

The super wide-angle lens system described in Patent Document 1 has a problem that the back focus is too short to be adapted as a lens system for a single-lens reflex camera.

The super wide-angle lens system described in Patent Document 2 has a problem that the peripheral light amount becomes insufficient when applied to a digital camera.

In order to improve the shortage of peripheral light, it is generally necessary to increase the lens diameter.

However, in the super wide-angle lens system described in Patent Document 2, a large-aperture aspherical lens is not used in the first lens group in which the incident angle is large, and it is difficult to correct aberrations in peripheral performance. Since the decentering sensitivity of the four lens groups is large and it is difficult to increase the lens diameter of the fourth lens group, there remains a problem that a sufficient amount of peripheral light cannot be secured.

In addition, the super-wide-angle lens system described in Patent Document 2 has a problem that the decentering sensitivity of the fourth lens group and the like is large, and it is not easy to assemble the lens frame.

The super wide-angle lens system described in Patent Document 2 is a super-wide-angle zoom lens, and at the wide-angle end side, the performance degradation around the screen is reduced. As a result of emphasizing the correction of the lateral chromatic aberration, the problem of insufficient correction of the longitudinal chromatic aberration remained.

An object of the present invention is to provide an ultra-wide-angle lens system that solves the above-described problems, is compact, has little aberration fluctuation due to focusing, and has an angle of view exceeding 120 °.

In order to solve the above-described problem, an ultra-wide-angle lens system according to the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The lens group G1 includes a first A lens group G1A having a negative refractive power and a first B lens group G1B having a negative refractive power, and the first A lens group G1A includes, in order from the object side, first negative meniscus lenses. The first lens L1 is composed of a negative meniscus second lens L2 having at least one aspheric surface. The first B lens group G1B has a negative meniscus lens L3 having at least one aspheric surface on the most object side. In the focusing operation, the first B lens group G1B is moved to the object side,
The following conditions shall be satisfied.
(1) 1.0 <| f1 / fw | <2.0
(2) 1.0 <f1B / f1A <3.0
(3) 3.0 <f2 / fw <5.0
However,
fw: focal length of the entire lens system or focal length of the entire lens system at the wide angle end f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f2: focal length of the second lens group G2, or focal length of the second lens group G2 at the wide angle end

Furthermore, the super wide-angle lens system according to the present invention has a positive lens unit L2asp having at least one aspheric surface on the most image side in the second lens group G2, and satisfies the following conditions: Is desirable.
(4) 2.0 <f2asp / f2 <5.0
However,
f2asp: focal length of the positive lens unit L2asp having an aspherical surface on at least one surface in the second lens group G2 f2: focal length of the second lens group G2 or focal length of the second lens group G2 at the wide angle end

In the super wide-angle zoom lens according to the present invention, the second lens group G2 is composed of a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C, from the wide angle end side to the telephoto end side. During zooming, the distance between the first lens group G1 and the second A lens group G2A decreases, the distance between the second A lens group G2A and the second B lens group G2B decreases, and the second B lens group G2B. And the second C lens group G2C is increased, and it is preferable that the following condition is satisfied.
(5) 5.0 <f2A / fw <15.0
(6) 5.0 <| f2C / fw |
However,
fw: focal length of the entire lens system at the wide angle end f2A: focal length of the second A lens group G2A f2C: focal length of the second C lens group G2C

Furthermore, in the super wide-angle zoom lens according to the present invention, it is desirable that the second B lens group G2B satisfies the following conditions.
(7) 2.0 <f2B / fw <10.0
However,
fw: focal length of the entire lens system at the wide angle end f2B: focal length of the second B lens group G2B

Furthermore, in the super wide-angle zoom lens according to the present invention, the second C lens group G2C includes a cemented negative lens unit L2CJ including at least one negative lens and at least one positive lens, and satisfies the following conditions. It is desirable.
(8) -15.0 <f2CJ / fw <-2.0
However,
fw: focal length of the entire lens system at the wide-angle end f2CJ: focal length of the cemented negative lens unit L2CJ in the second C lens group G2C

Furthermore, in the super wide-angle zoom lens according to the present invention, it is desirable that the cemented negative lens unit L2CJ in the second C lens group G2C satisfies the following conditions.
(9) Nd2CN> 1.8
(10) νd2CP> 80
However,
Nd2CN: Refractive index of at least one negative lens in the cemented negative lens unit L2CJ νd2CP: Abbe number of at least one positive lens in the cemented negative lens unit L2CJ

According to the present invention, it is a lens system used for a digital camera, a silver salt camera, a video camera, etc., and is a super wide-angle lens system having a shooting angle of view exceeding 120 °, and is compact, and aberration fluctuations due to focusing. It is possible to provide a super-wide-angle lens system with few high-performance inner focus systems.

Cross-sectional view of the super wide-angle lens of Example 1 at infinity Longitudinal aberration diagram of the super-wide-angle lens of Example 1 at infinity Longitudinal aberration diagram of the super wide-angle lens of Example 1 at a photographing magnification of 1 / 40x Lateral aberration diagram of the super wide-angle lens of Example 1 at infinity Lateral aberration diagram of the super wide-angle lens of Example 1 at a photographing magnification of 1 / 40x Lens cross-sectional view at infinity of the super wide-angle lens of Example 2 Longitudinal aberration diagram of the super wide-angle lens of Example 2 at infinity Longitudinal aberration diagram of the super wide-angle lens of Example 2 at a photographing magnification of 1 / 40x Lateral aberration diagram of the super wide-angle lens of Example 2 at infinity Lateral aberration diagram of the super wide-angle lens system of Example 2 at an imaging magnification of 1 / 40x Lens cross-sectional view at infinity at the wide-angle end of the super wide-angle zoom lens of Example 3 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 3 at infinity at the wide-angle end Longitudinal aberration diagram of the super wide-angle zoom lens of Example 3 at a shooting magnification of 1/40 at the wide-angle end Longitudinal aberration diagram at infinity of the intermediate focal length of the super wide-angle zoom lens of Example 3 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 3 at an intermediate focal length at an imaging magnification of 1 / 40x Longitudinal aberration diagram at infinity of the telephoto end of the super wide-angle zoom lens of Example 3 Longitudinal aberration diagram at the telephoto end of the super wide-angle zoom lens of Example 3 at a photographing magnification of 1 / 40x Lateral aberration diagram of the super wide-angle zoom lens of Example 3 at infinity at the wide-angle end Lateral aberration diagram of the super wide-angle zoom lens of Example 3 at a shooting magnification of 1/40 at the wide-angle end Transverse aberration diagram of the super wide-angle zoom lens of Example 3 at infinity of the intermediate focal length Lateral aberration diagram of the super wide-angle zoom lens of Example 3 at an intermediate focal length at an imaging magnification of 1 / 40x Lateral aberration diagram of the super wide-angle zoom lens of Example 3 at infinity at the telephoto end Lateral aberration diagram of the super wide-angle zoom lens of Example 3 at a photographing magnification of 1/40 at the telephoto end Lens cross-sectional view at infinity at the wide-angle end of the super-wide-angle zoom lens of Example 4 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 4 at infinity at the wide-angle end Longitudinal aberration diagram of the super wide-angle zoom lens of Example 4 at a shooting magnification of 1/40 at the wide-angle end Longitudinal aberration diagram at infinity of the intermediate focal length of the super wide-angle zoom lens of Example 4 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 4 at an intermediate focal length at an imaging magnification of 1 / 40x Longitudinal aberration diagram of the super wide-angle zoom lens of Example 4 at infinity at the telephoto end Longitudinal aberration diagram at the telephoto end of the super wide-angle zoom lens of Example 4 at a magnification of 1 / 40x Lateral aberration diagram of the super wide-angle zoom lens of Example 4 at infinity at the wide-angle end Lateral aberration diagram of the super wide-angle zoom lens of Example 4 at a shooting magnification of 1/40 at the wide-angle end Lateral aberration diagram of the super wide-angle zoom lens of Example 4 at infinity of the intermediate focal length Lateral aberration diagram of the super-wide-angle zoom lens of Example 4 at an intermediate focal length at an imaging magnification of 1 / 40x Transverse aberration diagram at infinity at the telephoto end of the super wide-angle zoom lens of Example 4 Lateral aberration diagram of the super wide-angle zoom lens of Example 4 at a magnification of 1/40 at the telephoto end Lens cross-sectional view at infinity at the wide-angle end of the super wide-angle zoom lens of Example 5 Longitudinal aberration diagram at infinity of the wide angle end of the super wide angle zoom lens of Example 5 Longitudinal aberration diagram at the shooting magnification of 1/40 at the wide-angle end of the super-wide-angle zoom lens of Example 5 Longitudinal aberration diagram at infinity of the intermediate focal length of the super wide-angle zoom lens of Example 5 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 5 at an intermediate focal length at an imaging magnification of 1 / 40x Longitudinal aberration diagram of the super wide-angle zoom lens of Example 5 at infinity at the telephoto end Longitudinal aberration diagram at the photographing magnification of 1/40 at the telephoto end of the super wide-angle zoom lens of Example 5 Lateral aberration diagram of the super wide-angle zoom lens of Example 5 at infinity at the wide-angle end Lateral aberration diagram of the super wide-angle zoom lens of Example 5 at a wide-angle end at a photographing magnification of 1 / 40x Transverse aberration diagram at infinity of the intermediate focal length of the super wide-angle zoom lens of Example 5 Lateral aberration diagram of the super wide-angle zoom lens of Example 5 at an intermediate focal length at an imaging magnification of 40 times Lateral aberration diagram of the super wide-angle zoom lens of Example 5 at infinity at the telephoto end Lateral aberration diagram of the super wide-angle zoom lens of Example 5 at a photographing magnification of 1/40 at the telephoto end Lens cross-sectional view at infinity at the wide-angle end of the super wide-angle zoom lens of Example 6 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 6 at infinity at the wide-angle end Longitudinal aberration diagram of the super wide-angle zoom lens of Example 6 at a shooting magnification of 1/40 at the wide-angle end Longitudinal aberration diagram at infinity of the intermediate focal length of the super wide-angle zoom lens of Example 6 Longitudinal aberration diagram of the super wide-angle zoom lens of Example 6 at an intermediate focal length at an imaging magnification of 1 / 40x Longitudinal aberration diagram at infinity of the telephoto end of the super wide-angle zoom lens of Example 6 Longitudinal aberration diagram at the telephoto end of the super wide-angle zoom lens of Example 6 at a magnification of 1 / 40x Lateral aberration diagram of the super wide-angle zoom lens of Example 6 at infinity at the wide-angle end Lateral aberration diagram of the super wide-angle zoom lens of Example 6 at a shooting magnification of 1/40 at the wide-angle end Transverse aberration diagram at infinity of the intermediate focal length of the super wide-angle zoom lens of Example 6 Lateral aberration diagram of the super wide-angle zoom lens of Example 6 at an intermediate focal length at an imaging magnification of 1 / 40x Lateral aberration diagram of the super wide-angle zoom lens of Example 6 at infinity at the telephoto end Lateral aberration diagram of the super wide-angle zoom lens of Example 6 at a magnification of 1/40 at the telephoto end

The super wide-angle lens system of the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first lens group G1 has a negative refractive power. The first A lens group G1A and the first B lens group G1B having negative refractive power, and the first A lens group G1A are arranged in order from the object side to the first lens L1 of the negative meniscus lens. The first lens group G1B is composed of a negative meniscus second lens L2 having a spherical surface. The first B lens group G1B has a negative meniscus lens L3 having at least one aspheric surface on the most object side. The lens group G1B is moved to the object side.

In the embodiment according to the present invention, a negative meniscus lens having a convex surface facing the object side is employed in each of the first lens L1 and the second lens L2 constituting the first A lens group G1A.

An object of the present invention is to provide a super-wide-angle lens system having an angle of view exceeding 120 °, and it is important to appropriately guide a light beam having a large inclination of an incident angle at a peripheral angle of view.

Further, in the ultra-wide-angle lens system, the retrofocus type is preferable in order to ensure sufficient back focus, and it is necessary to increase the refractive power of the negative lens of the negative lens portion located in front.

Furthermore, it is necessary to set an appropriate inclination angle of the lens surface at the periphery of the lens in order to cope with the incident angle and the emission angle of the light beam having a large inclination at the peripheral field angle.

Therefore, in the present invention, in the two negative meniscus lenses constituting the first A lens group G1A, appropriate refractive power is distributed, and as a whole, sufficient negative refractive power is obtained, and generation of astigmatism is suppressed. Aimed at a configuration that can. In addition, the first A lens group G1A is composed of only two negative meniscus lenses, so that the entire super wide-angle lens system can be made compact.

Furthermore, the second lens L2 constituting the first A lens group G1A in the present invention employs an aspheric surface on at least one surface.

Here, the setting of the refractive power of the negative meniscus lens will be described.

In a negative meniscus lens, sufficient negative refractive power can be obtained by reducing the paraxial curvature of the convex surface located at the center of the lens surface closest to the object side.

In the present invention, when the paraxial curvature of the lens surface on the object side of the second lens L2 is reduced, the tilt angle of the lens surface with respect to incident light at the periphery of the lens surface is reduced, and the lens surface perpendicular to the peripheral luminous flux. The tilt angle cannot be obtained, which is disadvantageous in aberration correction. Therefore, while maintaining the paraxial curvature at the center of the lens surface closest to the object side, an aspheric surface is used for this lens surface, and a strong positive refracting power is given toward the periphery of the lens diameter. Accordingly, it is possible to obtain an appropriate inclination angle of the lens surface with respect to the peripheral luminous flux, and to obtain both negative refractive power and aberration correction effect.

In order to increase the negative refractive power of the negative meniscus lens, it is effective to increase the paraxial curvature of the concave surface located at the most central portion on the image plane side.

However, if the negative refractive power of the negative meniscus lens is increased by increasing the paraxial curvature at the center of the concave surface closest to the image plane, the tilt angle of the lens surface at the lens periphery becomes tight, so a negative meniscus lens The workability of will deteriorate. Therefore, by adopting an aspherical surface on the lens surface closest to the image plane of the negative meniscus lens, the tilt angle of the lens periphery can be controlled appropriately, and the lens can be processed while correcting the aberration appropriately for the peripheral luminous flux. Can be improved.

On the other hand, in order to weaken the refractive power of the negative meniscus lens, it is effective to increase the paraxial curvature of the convex surface located at the most central portion on the object side. However, when the paraxial curvature of the lens surface closest to the object is increased, the tilt angle of the lens surface with respect to the peripheral light flux at the lens peripheral portion is reduced, so that the workability of the lens is deteriorated.

Therefore, by adopting an aspherical surface for the lens surface closest to the object side, the inclination angle of the lens surface with respect to the light flux at the lens peripheral portion is made close to a right angle, so The tilt angle can be obtained, and the workability can be improved while appropriately correcting the aberration with respect to the peripheral light flux.

As described above, in a negative meniscus lens, by adopting an aspheric surface for any lens surface, the negative refractive power is appropriately controlled, and the tilt of the lens surface at the appropriate lens periphery with respect to the peripheral luminous flux The angle can be obtained, and appropriate aberration correction and lens processability can be taken into consideration.

Further, in the present invention, among the lenses included in the first B lens group G1B used for focusing, the third lens L3 arranged closest to the object side also has a negative meniscus lens, like the first lens L1 and the second lens L2. Is adopted.

The present invention is intended for an ultra-wide-angle lens system with an angle of view exceeding 120 degrees, and only the refractive power of the two negative meniscus lenses of the first A lens group G1A that guides the light beam to the peripheral light beam having a large inclination of the incident light beam. Is not sufficient, and the exit angle of the light beam from the first A lens group G1A still remains large, and therefore the inclination of the incident light beam needs to be further reduced in the first B lens group G1B.

Therefore, as with the first lens L1 and the second lens L2, a negative meniscus lens having a convex surface facing the object side is also adopted for the third lens L3.

In this way, it is possible to obtain an appropriate lens surface tilt angle at the periphery of the lens with respect to the peripheral light beam, and sufficiently correct the aberration of the peripheral light beam, and the light beam due to the difference in the shooting distance during focusing. Accordingly, it is possible to obtain a lens system having a small aberration variation with respect to the change in the incident angle.

Furthermore, in the third lens L3 as well as the second lens L2, by adopting an aspheric surface on at least one surface of the negative meniscus lens, an appropriate lens surface inclination angle with respect to the peripheral luminous flux is obtained. Aberration correction of the peripheral luminous flux can be sufficiently performed. In addition, an optical system with small aberration fluctuations can be obtained with respect to a change in the incident angle of a light beam due to a difference in shooting distance during focusing.

The object of the present invention is to obtain an ultra-wide-angle lens system with an angle of view exceeding 120 °, and appropriately balance the aberration balance at the center of the screen where the incident angle of the light greatly changes, the intermediate angle of view of the screen, and the periphery of the screen. It is important to take.

In the present invention, by appropriately controlling the shape of the two negative meniscus lenses adopting the aspherical surface included in the first A lens group G1A, the means for reducing aberration fluctuations due to focusing while balancing aberrations over the entire photographing screen Have taken.

Therefore, the present invention is characterized in that the following conditional expressions (1) and (2) are satisfied.
(1) 1.0 <| f1 / fw | <2.0
(2) 1.0 <f1B / f1A <3.0
However,
fw: focal length of the entire lens system or focal length of the entire lens system at the wide angle end f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B

Conditional expression (1) defines the ratio of the focal length of the first lens group G1 to the focal length of the entire lens system in the retrofocus type super wide-angle lens system of the present invention.

However, when the present invention is applied to an ultra-wide-angle zoom lens, the focal length of the entire lens system at the zoom wide-angle end is adopted as the focal length of the entire lens system.

If the lower limit of conditional expression (1) is exceeded, the negative refractive power of the first lens group G1 becomes strong, which is effective for making the entire lens system compact, but it becomes difficult to correct field curvature.

When the upper limit of conditional expression (1) is exceeded, the negative refractive power of the first lens group G1 becomes weak, and the entire lens system cannot be made compact.

In the focusing of the super wide-angle lens system of the present invention, it is necessary to dispose a large-diameter negative meniscus lens in the first A lens group G1A. In addition, the occurrence of curvature of field due to focusing becomes an issue. By adopting the inner focus for focusing, the effect of aberration correction by floating is added.

Conditional expression (2) defines the ratio between the focal length of the first A lens group G1A and the focal length of the first B lens group G1B in the super wide-angle lens system of the present invention.

When the lower limit of conditional expression (2) is exceeded, the refractive power of the first B lens group G1B increases, so that aberration fluctuations due to focusing increase. In addition, the refractive power of the first A lens group G1A becomes small, and there is a possibility that sufficient and sufficient refractive power for appropriately refracting incident light having an angle of view exceeding 120 ° may not be obtained.

If the upper limit of conditional expression (2) is exceeded, the refractive power of the first B lens group G1B becomes small, and the focus movement amount during close-up shooting of the first B lens group G1B becomes large.
Therefore, it is necessary to increase the lens interval between the first A lens group G1A and the first B lens group G1B, and the entire lens system cannot be made compact.

In addition, since the super wide-angle lens system of the present invention corresponds to a camera system such as a digital single-lens reflex camera that requires sufficient back focus, it is necessary to appropriately set the focal length of the second lens group G2.

Therefore, the present invention is characterized in that the following conditional expression (3) is satisfied.
(3) 3.0 <f2 / fw <5.0
However,
fw: focal length of the entire lens system or focal length of the entire lens system at the wide angle end f2: focal length of the second lens group G2 or focal length of the second lens group G2 at the wide angle end

Conditional expression (3) defines the ratio of the focal length of the second lens group G2 to the focal length of the entire lens system in a retrofocus type super wide-angle lens system.

However, when the present invention is applied to an ultra-wide-angle zoom lens, the focal length of the entire lens system is the focal length of the entire lens system at the zoom wide-angle end, and the focal length of the second lens group G2 is the zoom wide-angle. The focal length of the second lens group G2 at the end is adopted.

If the lower limit of conditional expression (3) is exceeded, the focal length of the second lens group is shortened, which is effective for making the entire lens system compact. However, since the curvature of each lens increases, there is a problem with super-wide-angle lens systems. It becomes difficult to correct aberrations such as astigmatism and coma.

When the upper limit of conditional expression (3) is exceeded, the focal length of the second lens group G2 becomes long, which is advantageous for aberration correction, but it is difficult to make the entire lens system compact.

Further, in the present invention, in order to perform sufficient aberration correction, an aspherical surface is adopted as at least one surface of the positive lens unit closest to the image plane in the second lens group G2, and the following conditional expression (4) is satisfied. It is desirable to do.
(4) 2.0 <f2asp / f2 <5.0
However,
f2asp: focal length of the positive lens unit L2asp having an aspherical surface on at least one surface in the second lens group G2 f2: focal length of the second lens group G2 or focal length of the second lens group G2 at the wide angle end

However, when the present invention is applied to an ultra-wide-angle zoom lens, the focal length of the second lens group G2 is the focal length of the second lens group G2 at the zoom wide-angle end.

In Patent Document 2, the lens unit closest to the image plane can effectively correct aberration by adopting an aspherical surface in an optical system having a strong negative refractive power.
However, since the second lens group G2 as a whole has a strong positive refractive power, if the lens unit closest to the image plane is a negative lens unit having an aspherical surface, the assembly accuracy of the lens barrel is increased due to the increased decentration sensitivity. Is difficult to maintain, and production problems arise.

Therefore, in the present invention, the lens unit closest to the image plane is a positive lens unit having an aspheric surface on at least one surface, and by appropriately setting the refractive power thereof, the lens unit is sensitive to eccentricity while obtaining a sufficient aberration correction effect. It was possible to obtain a lens system with a small degree.

Conditional expression (4) is the ratio of the focal length of the positive lens unit L2asp having the most aspherical surface in the second lens group G2 to the focal length of the second lens group G2 in the super wide-angle lens system of the present invention. It prescribes.

If the focal length of the positive lens unit is shortened beyond the lower limit of conditional expression (4) and the refractive power of the positive lens unit L2asp is increased, the refractive effect on the peripheral light beam becomes strong. The correction effect will be insufficient.

When the focal length of the positive lens unit is increased beyond the upper limit of the conditional expression (4), the refractive power of the peripheral light beam emitted from the optical system located in front of the positive lens unit L2asp becomes strong. The change in the inclination of the light beam at the incident angle and exit angle when passing through the positive lens unit L2asp increases, and the decentering sensitivity of the positive lens unit L2asp increases.

Next, an embodiment in which the super wide-angle lens system according to the present invention is applied to a super wide-angle zoom lens will be described.

The super wide-angle zoom lens according to the present invention specifically defines zooming while maintaining the basic characteristics of the super wide-angle lens system of the present invention. Therefore, the description of the conditional expressions (1) to (4) described above is omitted in the description of the embodiments of the super wide-angle zoom lens according to the present invention below.

The super wide-angle zoom lens according to the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first lens group G1 has a negative refractive power. The first A lens group G1A having a negative power and the first B lens group G1B having a negative refractive power. The first A lens group G1A is arranged in order from the object side on the first lens L1 of the negative meniscus lens, on at least one surface. The first lens group G1B includes a negative meniscus lens L3 having at least one aspheric surface on the most object side, and includes the second meniscus lens L3 having an aspheric surface. The 1B lens group G1B is moved to the object side, and the second lens group G2 includes a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C. During zooming, the distance between the first lens group G1 and the second A lens group G2A decreases, the distance between the second A lens group G2A and the second B lens group G2B decreases, and the second B lens. The super wide-angle zoom lens has a configuration in which the distance between the group G2B and the second C lens group G2C is increased, and the field angle exceeds 120 °.

In the super wide-angle zoom lens of the present invention, the focal length of the second A lens group G2A is appropriately set, and the strong divergent light beam from the first lens group G1 is converged, so that the exit angle from the second A lens group G2A is substantially reduced. By setting afocal, it is possible to cut the upper light flare with an appropriate light height from the intermediate range by using the second A lens group G2A without cutting the peripheral light on the wide-angle end side.

Furthermore, by appropriately setting the focal length of the second C lens group G2C, it is possible to appropriately control the eccentricity sensitivity of the second C lens group G2C while obtaining sufficient optical performance over the entire zoom range.

Therefore, it is desirable that the present invention satisfies the following conditional expressions (5) and (6).
(5) 5.0 <f2A / fw <15.0
(6) 5.0 <| f2C / fw |
However,
fw: focal length of the entire lens system at the wide angle end f2A: focal length of the second A lens group G2A f2C: focal length of the second C lens group G2C

Conditional expression (5) defines the ratio of the focal length of the second A lens group G2A to the focal length of the entire lens system at the wide angle end in the super wide-angle zoom lens of the present invention.

If the upper limit of conditional expression (5) is exceeded, the focal length of the second A lens group G2A becomes long, so that a sufficient convergence effect cannot be obtained with respect to the central light beam, and an appropriate flare cutting effect cannot be obtained.

If the lower limit of conditional expression (5) is exceeded and the focal length of the second lens group G2A becomes shorter, it becomes necessary to increase the negative refractive power of the first lens group G1, making it difficult to correct coma and astigmatism. Become.

Conditional expression (6) defines the ratio of the focal length of the second C lens group G2C to the focal length of the entire lens system at the wide angle end in the super wide-angle zoom lens of the present invention.

In the conditional expression (6), when the second C lens group G2C has a positive refractive power, if the lower limit is exceeded, the positive refractive power of the second C lens group G2C becomes strong.
As the curvature of each lens surface increases and the decentering sensitivity of the lens unit in the second C lens group G2C increases, the accuracy required during lens processing increases drastically.

In the conditional expression (6), when the second C lens group G2C has a negative refractive power, if the lower limit is exceeded, the negative refractive power of the second C lens group G2C becomes strong. Sensitivity increases and productivity in assembling the lens barrel becomes difficult.

In the present invention, it is desirable that the focal length of the second B lens group G2B satisfies the conditional expression (7).
(7) 2.0 <f2B / fw <10.0
However,
fw: focal length of the entire lens system at the wide angle end f2B: focal length of the second B lens group G2B

Conditional expression (7) defines the ratio of the focal length of the second lens group G2B to the focal length of the entire lens system at the wide-angle end in the super wide-angle zoom lens of the present invention.

When the upper limit of conditional expression (7) is exceeded, the refractive power of the second B lens group G2B becomes weak, the height of the peripheral rays incident on the second C lens group G2C increases, and the lens units in the second C lens group G2C increase. The sensitivity to eccentricity will increase.

When the lower limit of conditional expression (7) is exceeded, the positive refractive power of the second B lens group G2B becomes strong, and the decentering sensitivity of the second B lens group G2B increases.

Furthermore, in the super wide-angle zoom lens according to the present invention, the second C lens group G2C includes a cemented negative lens unit L2CJ including at least one negative lens and at least one positive lens, and conditional expression (8) is satisfied. It is desirable to be satisfied.

In the present invention, in order to correct aberrations such as chromatic aberration, it is an essential condition to dispose a negative lens in the second C lens group G2C.

However, if a negative lens is arranged in the second C lens group G2C where the exit angle of the peripheral luminous flux is large, the refractive power of the negative lens tends to be strong for aberration correction, and the decentering sensitivity of the negative lens increases. End up. In addition, the refractive power of the positive lens must be increased accordingly, and the eccentric sensitivity of the positive lens also increases at the same time.

Therefore, it is possible to reduce the decentration sensitivity while obtaining a sufficient aberration correction effect by cementing a negative lens having a strong refractive power and a positive lens and appropriately setting the focal length of the entire cemented negative lens unit. .

Therefore, it is desirable that the present invention satisfies the following conditional expression (8).
(8) -15.0 <f2CJ / fw <-2.0
However,
fw: focal length of the entire lens system at the wide-angle end f2CJ: focal length of the cemented negative lens unit L2CJ in the second C lens group G2C

Conditional expression (8) defines the ratio of the focal length of the entire cemented negative lens unit in the second C lens group G2C to the focal length of the entire lens system at the wide angle end in the super wide-angle zoom lens of the present invention. .

If the upper limit of conditional expression (8) is exceeded, the negative refractive power of the cemented negative lens unit L2CJ will increase, and the decentering sensitivity will increase.

If the lower limit of conditional expression (8) is exceeded, the negative refracting power of the cemented negative lens unit L2CJ becomes small, and the aberration correction effect becomes insufficient.

Furthermore, in the present invention, it is desirable that the cemented negative lens unit in the second C lens group G2C satisfies the conditional expression (9) and the conditional expression (10) at the same time.

Conditional expression (9) defines the refractive index of the negative lens constituting the cemented negative lens unit in the second C lens group G2C. Conditional expression (10) represents the cemented negative lens in the second C lens group G2C. It defines the Abbe number of the positive lens that constitutes the unit.
(9) Nd2CN> 1.8
(10) νd2CP> 80
However,
Nd2CN: Refractive index of at least one negative lens in the cemented negative lens unit L2CJ νd2CP: Abbe number of at least one positive lens in the cemented negative lens unit L2CJ

By making the refractive power of the negative lens constituting the cemented negative lens unit in the second C lens group G2C within the range of the conditional expression (9), the curvature of each lens surface is reduced while maintaining the refractive power of the negative lens. can do.

Further, when the Abbe number of the positive lens constituting the cemented negative lens unit in the second C lens group G2C is set within the range of the conditional expression (10), it is possible to correct the lateral chromatic aberration that is a problem in the wide-angle lens. At the same time, while maintaining the refractive power of the cemented negative lens unit, the curvature of the cemented surface can be reduced, and the refractive power of each of the positive lens and the negative lens can be reduced.

Numerical Examples 1 to 6 relating to the super wide-angle lens system of the present invention will be described below.

Numerical Example 1 to Numerical Example 2 correspond to Claims 1 to 2 in the scope of claims of the present application, and Numerical Example 3 to Numerical Example 6 correspond to claims 1 to in the scope of claims of the present application. This corresponds to item 6. That is, Numerical Example 1 to Numerical Example 2 show numerical examples of the super wide-angle lens of the super wide-angle lens system according to the present invention, and Numerical Example 3 to Numerical Example 6 represent the super-wide angle according to the present invention. Numerical examples of a super wide-angle zoom lens of a lens system are shown.

In each numerical example, f in [general specifications] indicates a focal length, Fno indicates an F number, and 2ω indicates an angle of view. Also, the number in [Lens Specification] is the lens surface number from the object side, R is the radius of curvature of the lens surface, D is the lens thickness and spacing, nd is the refractive index of d-line, and νd is the d-line. Indicates the Abbe number. The diaphragm indicates the position of the diaphragm surface. The symbol * indicates an aspherical surface, and the description of the refractive index n = 1.0000 of air is omitted. Further, fb represents the back focus, the dn surface represents the lens interval between the lens surfaces, and the d0 surface represents the distance from the subject to the first lens surface. [Variable interval] indicates the variable interval of the lens surface for each focal length f at the time of shooting at infinity and shooting equivalent to 1/40 times.

なお、「Ｅ−n」は「×１０−ⁿ」を示し、例えば、「１．２３４Ｅ−４ 」は「１．２３４×１０−^４」を示す。 (Aspherical data) represents an aspherical coefficient and a conic coefficient when the aspherical shape of the Nth lens surface is expressed by the following equation.

Incidentally, "E-n" denotes "× 10- ^n", for example, "1.234E-4" means "1.234 × 10- ^4".

In the drawing, d-line, g-line, and C-line are aberrations with respect to respective wavelengths, ΔS indicates a sagittal image plane, and ΔM indicates a meridional image plane.

Example 1

[Lens specifications]
R D nd νd
[0] d0
[1] 33.6140 1.8000 2.00099 29.14
[2] 23.3110 5.9510
[3] * 53.3560 2.5000 1.77250 49.62
[4] 19.8000 d4
[5] * 28.9640 1.5160 1.77250 49.62
[6] 14.9770 6.2330
[7] 1222.1100 0.9000 1.77250 49.62
[8] 40.1870 2.5940
[9] 3721.5600 2.0690 2.00099 29.14
[10] -79.8070 d10
[11] Aperture 7.3400
[12] 39.5970 0.8000 1.83481 42.72
[13] 8.5660 3.7920 1.84666 23.78
[14] -58.3000 1.2000
[15] 81.8260 3.6800 1.43700 95.00
[16] -11.2950 0.8000 2.00099 29.14
[17] 89.4260 0.3440
[18] 27.9990 5.2450 1.43700 95.00
[19] -15.2120 0.1500
[20] 115.5580 0.8000 2.00099 29.14
[21] 15.8330 8.8490 1.43700 95.00
[22] -16.8500 0.1500
[23] * -86.9780 0.1000 1.51840 52.09
[24] -95.7970 3.4270 1.48749 70.44
[25] -25.0090 Bf


[Overall specifications]
INF
f 8.30
Fno 4.63
2ω 121.50


[Variable interval]
INF 1:40
d0 INF 311.99
d4 9.7500 9.1116
d10 19.7100 20.3484
Bf 38.30 38.30


[Aspheric coefficient]
3 surfaces 5 surfaces 23 surfaces
k 0.7446 2.1725 0.0000
A 4.7858E-05 -6.0640E-05 -6.2501E-06
B -1.4601E-07 7.5911E-07 6.9395E-08
C 3.0761E-10 -4.2947E-09 1.6866E-10
D -4.2796E-13 1.3586E-11 1.0289E-12
E 2.5165E-16 -1.7386E-14 0.0000E + 00


[Conditional expression values]
Example 1
Conditional expression (1) | f1 / fw | 1.54 (f1 / fw = -1.54)
Conditional expression (2) f1B / f1A 1.33
Conditional expression (3) f2 / fw 3.50
Conditional expression (4) f2asp / f2 2.44

Example 2
[Lens specifications]
R D nd νd
[0] d0
[1] 34.3750 1.8000 1.91082 35.25
[2] 23.4720 9.2000
[3] * 72.6990 2.5000 1.76930 49.28
[4] 23.0780 d4
[5] * 47.7330 1.7570 1.76930 49.28
[6] * 21.8960 7.5000
[7] -262.3990 0.9000 1.84666 23.78
[8] 52.4890 3.1140
[9] 500.0000 3.0520 1.62004 36.30
[10] -49.8320 d10
[11] Aperture 2.9440
[12] 67.5990 0.8000 1.77250 49.62
[13] 7.9450 3.1050 1.75519 27.53
[14] -122.5310 7.9250
[15] -72.0800 4.6430 1.43700 95.00
[16] -10.3760 0.8000 2.00099 29.14
[17] -19.8560 0.1500
[18] 50.7980 5.5010 1.43700 95.00
[19] -17.7910 0.1500
[20] -42.0480 0.8000 2.00099 29.14
[21] 55.8340 7.6420 1.43700 95.00
[22] -16.0110 0.3120
[23] * -26.2430 2.1130 1.49710 81.56
[24] -18.2650 Bf


[Overall specifications]
INF
f 8.30
Fno 4.65
2ω 121.49


[Variable interval]
INF 1:40
d0 INF 308.99
d4 9.7500 8.8309
d10 21.2430 22.1621
Bf 38.30 38.30


[Aspheric coefficient]
3 surfaces 5 surfaces 6 surfaces 23 surfaces
k -6.3913 6.6751 0.1908 0.0000
A 5.5786E-05 1.0083E-05 9.1117E-05 -4.3805E-05
B -1.9136E-07 4.2135E-07 -2.8995E-07 -9.9854E-08
C 3.9382E-10 -3.3289E-09 1.7766E-10 2.6900E-10
D -4.6753E-13 1.1263E-11 -3.9045E-13 -4.5155E-12
E 2.3274E-16 -1.5424E-14 1.3186E-15 0.0000E + 00


[Conditional expression values]
Example 2
Conditional expression (1) | f1 / fw | 1.78 (f1 / fw = -1.78)
Conditional expression (2) f1B / f1A 1.62
Conditional expression (3) f2 / fw 3.65
Conditional expression (4) f2asp / f2 3.67

Example 3

[Lens specifications]
R D nd νd
[0] d0
[1] 34.3750 1.8000 1.91082 35.25
[2] 23.4720 9.2000
[3] * 79.2550 2.5000 1.77250 49.62
[4] 20.8930 d4
[5] * 31.9510 1.6000 1.77250 49.62
[6] 17.1890 7.4930
[7] -56.4400 0.9000 2.00069 25.46
[8] 91.4700 5.5940
[9] 86.7650 3.1340 2.00099 29.14
[10] -95.1710 d10
[11] 36.6290 0.8000 1.77250 49.62
[12] 9.2140 3.1340 1.69895 30.05
[13] -108.4040 1.4100
[14] Aperture d14
[15] -373.7020 2.8430 1.43700 95.00
[16] -11.0060 0.8000 1.77250 49.62
[17] -44.8740 0.5730
[18] 111.6480 3.1830 1.43700 95.00
[19] -15.1510 d19
[20] 46.5500 1.6620 1.49700 81.61
[21] -107983.0770 0.8500 2.00099 29.14
[22] 13.7690 3.2280 1.43700 95.00
[23] 87.4310 5.1940
[24] 251.8150 4.3250 1.43700 95.00
[25] -22.8800 0.1500
[26] * -36.4280 0.1500 1.51840 52.09
[27] -34.1960 3.6210 1.48749 70.44
[28] -19.0050 Bf


[Overall specifications]

Wide angle end Medium telephoto Telephoto end
f 8.30 11.99 15.40
Fno 4.62 5.08 5.54
2ω 121.55 99.49 84.51


(Variable interval for zooming at infinity)

f 8.30 11.99 15.40
d0 INF INF INF
d4 9.7500 9.7500 9.7500
d10 29.7250 10.8512 1.8500
d14 7.3660 4.0598 1.5281
d19 0.8500 5.0709 8.1147
fb 38.35 42.90 47.80


(Variable interval for zooming when shooting equivalent to 1 / 40x)

f 8.30 11.99 15.40
d0 309.8172 458.2347 591.8072
d4 8.6504 8.9958 9.1619
d10 30.8246 11.6054 2.4381
d14 7.3660 4.0598 1.5281
d19 0.8500 5.0709 8.1147
fb 38.35 42.90 47.80


[Aspheric coefficient]
3 surfaces 5 surfaces 26 surfaces
k 5.8936 0.3004 0.0000
A 3.7333E-05 -2.6245E-05 -1.0868E-05
B -1.2605E-07 4.0392E-07 2.8571E-08
C 3.2038E-10 -2.2937E-09 1.4666E-10
D -4.8867E-13 8.1094E-12 2.5303E-13
E 3.0166E-16 -1.0578E-14 0.0000E + 00


[Conditional expression values]
Example 3
Conditional expression (1) | f1 / fw | 1.80 (f1 / fw = -1.80)
Conditional expression (2) f1B / f1A 2.04
Conditional expression (3) f2 / fw 4.47
Conditional expression (4) f2asp / f2 2.05
Conditional expression (5) f2A / fw 6.21
Conditional expression (6) | f2C / fw | 11.26 (f2c / fw = 11.26)
Conditional expression (7) f2B / fw 6.03
Conditional expression (8) f2CJ / fw -3.46
Conditional expression (9) Nd2CN 2.00
Conditional expression (10) νd2CP 81.61

Example 4
[Lens specifications]
R D nd νd
[0] d0
[1] 34.3750 2.0000 1.91082 35.25
[2] 23.3150 9.2170
[3] * 77.6090 3.5000 1.77250 49.62
[4] * 19.1010 d4
[5] * 26.0000 1.7980 1.77250 49.62
[6] 14.7640 5.9220
[7] -381.6040 0.9000 2.00099 29.14
[8] 30.2180 0.4890
[9] 24.8920 3.9020 1.91082 35.25
[10] 243.7050 d10
[11] Aperture 1.5000
[12] 42.6160 0.8000 1.77250 49.62
[13] 9.2450 2.7100 1.72824 28.32
[14] -143.9350 d14
[15] -45.5130 4.4770 1.43700 95.00
[16] -9.2270 0.8000 1.77250 49.62
[17] -19.2810 0.1570
[18] 71.8320 4.6280 1.43700 95.00
[19] -16.2590 d19
[20] -59.9590 2.3340 1.49700 81.61
[21] -24.4780 0.8500 1.91082 35.25
[22] 20.2420 7.5030 1.43700 95.00
[23] -22.9000 1.1340
[24] 1000.0000 5.9290 1.43700 95.00
[25] -22.8720 0.2010
[26] * -30.2480 0.1000 1.51840 52.09
[27] -28.8280 2.5180 1.48749 70.44
[28] -22.4090 Bf


[Overall specifications]

Wide angle end Medium telephoto Telephoto end
f 8.30 12.00 15.40
Fno 4.60 4.98 5.48
2ω 121.51 100.24 84.50


(Variable interval for zooming at infinity)

f 8.30 12.00 15.40
d0 INF INF INF
d4 9.7500 9.7500 9.7500
d10 21.7440 9.3400 4.1590
d14 8.9380 4.8490 1.4570
d19 0.9000 5.0490 8.8610
fb 38.30 42.74 46.40


(Variable interval for zooming when shooting equivalent to 1 / 40x)

f 8.30 12.00 15.40
d0 307.0004 454.8709 590.9750
d4 9.1160 9.3137 9.4109
d10 22.3780 9.7763 4.4981
d14 8.9380 4.8490 1.4570
d19 0.9000 5.0490 8.8610
fb 38.30 42.74 46.40


[Aspheric coefficient]
3 sides 4 sides 5 sides 26 sides
k 6.1544 -1.1163 1.7080 0.0000
A 3.1091E-05 1.3029E-05 -3.4617E-05 -1.0691E-05
B -1.0600E-07 5.7507E-08 3.5229E-07 2.0126E-08
C 2.3118E-10 -4.0726E-10 -2.6930E-09 -2.8886E-11
D -2.3614E-13 1.6176E-12 1.2629E-11 4.4481E-13
E 8.7678E-17 0.0000E + 00 -2.5895E-14 0.0000E + 00


[Conditional expression values]
Example 4
Conditional expression (1) | f1 / fw | 1.46 (f1 / fw = -1.46)
Conditional expression (2) f1B / f1A 1.90
Conditional expression (3) f2 / fw 4.05
Conditional expression (4) f2asp / f2 4.72
Conditional expression (5) f2A / fw 6.59
Conditional expression (6) | f2C / fw | 10.57 (f2c / fw = 10.57)
Conditional expression (7) f2B / fw 4.07
Conditional expression (8) f2CJ / fw -4.83
Conditional expression (9) Nd2CN 1.91
Conditional expression (10) νd2CP 81.61

Example 5
[Lens specifications]
R D nd νd
[0] d0
[1] 34.1880 1.8000 1.91082 35.25
[2] 23.3380 8.0770
[3] * 51.6340 2.5000 1.77250 49.62
[4] * 17.5210 d4
[5] * 24.8310 1.6000 1.77250 49.62
[6] 16.4500 7.9430
[7] -45.5060 0.9000 2.00069 25.46
[8] 548.0210 7.2220
[9] -118.3220 2.1390 2.00099 29.14
[10] -48.3670 d10
[11] Aperture 1.5000
[12] 55.0360 0.8000 1.77250 49.62
[13] 8.2950 3.4720 1.75519 27.53
[14] -316.2530 d14
[15] 21.0760 3.6110 1.43700 95.00
[16] -11.0580 0.8000 1.77250 49.62
[17] -33.1180 1.7400
[18] 68.0960 2.7780 1.43700 95.00
[19] -16.9520 d19
[20] -30.7740 0.8000 2.00099 29.14
[21] 15.8860 5.7280 1.43700 95.00
[22] -12.1500 0.7300
[23] * -15.3830 0.1000 1.51840 52.09
[24] -15.6800 2.1730 1.48749 70.44
[25] -12.7400 Bf


[Overall specifications]
Wide angle end Medium telephoto Telephoto end
f 8.30 11.99 15.40
Fno 4.64 5.09 5.54
2ω 122.14 99.71 84.56


(Variable interval for zooming at infinity)

f 8.30 11.99 15.40
d0 INF INF INF
d4 9.7500 9.7500 9.7500
d10 25.2680 9.3920 1.8500
d14 4.8890 2.6820 1.2000
d19 0.9000 1.9540 2.9600
fb 38.29 43.72 48.21


(Variable interval for zooming when shooting equivalent to 1 / 40x)

f 8.30 11.99 15.40
d0 309.5055 456.0853 594.5946
d4 8.9500 9.1980 9.3230
d10 26.0680 9.9440 2.2770
d14 4.8890 2.6820 1.2000
d19 0.9000 1.9540 2.9600
fb 38.29 43.72 48.21


[Aspheric coefficient]
3 sides 4 sides 5 sides 23 sides
k -0.2837 -0.1021 1.3664 0.0000
A 2.2520E-05 -3.0309E-05 -5.2435E-05 -4.5987E-05
B -7.0753E-08 6.0042E-08 5.6070E-07 1.0904E-07
C 2.9454E-10 1.6355E-10 -3.6372E-09 -3.5203E-09
D -6.3545E-13 -3.9342E-13 1.3659E-11 6.0649E-11
E 4.8733E-16 -1.8463E-15 -2.3488E-14 0.0000E + 00


[Conditional expression values]
Example 5
Conditional expression (1) | f1 / fw | 1.61 (f1 / fw = -1.61)
Conditional expression (2) f1B / f1A 1.90
Conditional expression (3) f2 / fw 3.81
Conditional expression (4) f2asp / f2 3.77
Conditional expression (5) f2A / fw 8.44
Conditional expression (6) | f2C / fw | 12.05 (f2c / fw = -12.05)
Conditional expression (7) f2B / fw 2.80
Conditional expression (8) f2CJ / fw -5.42
Conditional expression (9) Nd2CN 2.00
Conditional expression (10) νd2CP 95.08

Example 6
[Lens specifications]
R D nd νd
[0] d0
[1] 34.6620 1.8000 1.91082 35.25
[2] 23.3570 9.2000
[3] * 76.5860 2.5000 1.77250 49.62
[4] 20.0460 d4
[5] * 30.5660 1.6000 1.77250 49.62
[6] 17.7330 7.8400
[7] -46.2110 0.9000 2.00069 25.46
[8] 94.4310 0.6770
[9] 70.1400 3.8740 2.00099 29.14
[10] -70.3510 d10
[11] Aperture 1.5000
[12] 49.9880 0.8000 1.77250 49.62
[13] 8.6860 4.7220 1.72825 28.32
[14] -178.3090 d14
[15] 82.8350 3.9790 1.43700 95.00
[16] -9.8500 0.8000 1.77250 49.62
[17] -25.8020 1.4250
[18] 66.8400 4.1340 1.43700 95.00
[19] -15.3930 d19
[20] -33.3250 0.8000 2.00099 29.14
[21] 29.3000 6.4580 1.43700 95.00
[22] -14.9060 0.6790
[23] * -19.8090 0.1000 1.51840 52.09
[24] -17.9500 2.3970 1.48749 70.44
[25] -14.7180 Bf


[Overall specifications]
Wide angle end Medium telephoto Telephoto end
f 8.30 12.00 15.40
Fno 4.63 5.00 5.44
2ω 122.03 100.04 84.57


(Variable interval for zooming at infinity)

f 8.30 12.00 15.40
d0 INF INF INF
d4 9.7500 9.7500 9.7500
d10 27.5190 11.9640 4.9600
d14 6.9270 3.6570 1.2000
d19 0.9000 3.2450 5.3470
fb 38.30 42.17 45.41


(Variable interval for zooming when shooting equivalent to 1 / 40x)

f 8.30 12.00 15.40
d0 310.4125 453.0260 592.1315
d4 8.8226 9.1040 9.2515
d10 28.4464 12.6100 5.4585
d14 6.9270 3.6570 1.2000
d19 0.9000 3.2450 5.3470
fb 38.30 42.17 45.41


[Aspheric coefficient]
3 surfaces 5 surfaces 23 surfaces
k -13.1740 2.2330 0.0000
A 4.2809E-05 -3.5996E-05 -5.0159E-05
B -1.3221E-07 4.3319E-07 -8.9341E-08
C 3.0885E-10 -2.7645E-09 -6.6527E-10
D -4.2443E-13 1.0003E-11 -3.3980E-12
E 2.4579E-16 -1.5507E-14 0.0000E + 00


[Conditional expression values]
Example 6
Conditional expression (1) | f1 / fw | 1.69 (f1 / fw = -1.69)
Conditional expression (2) f1B / f1A 2.23
Conditional expression (3) f2 / fw 3.81
Conditional expression (4) f2asp / f2 3.15
Conditional expression (5) f2A / fw 8.40
Conditional expression (6) | f2C / fw | 1204.78 (f2c / fw = -1204.78)
Conditional expression (7) f2B / fw 3.37
Conditional expression (8) f2CJ / fw -9.04
Conditional expression (9) Nd2CN 2.00
Conditional expression (10) νd2CP 95.08

G1 First lens group G2 Second lens group

G1A 1A lens group G1B 1B lens group G2A 2A lens group G2B 2B lens group G2C 2C lens group

L1 First lens L2 Second lens L3 Third lens

L2asp A positive lens unit L2CJ having an aspheric surface on at least one surface in the second lens group G2 A cemented negative lens unit in the second C lens group G2C

SP Aperture IP Image plane

d d line g g line C C line ΔS sagittal image plane ΔM meridional image plane

Claims (8)

In order from the object side, the first lens unit G1 has a negative refractive power and the second lens unit G2 has a positive refractive power.
The first lens group G1 includes a first A lens group G1A having a negative refractive power and a first B lens group G1B having a negative refractive power.
Further, the first A lens group G1A is composed of, in order from the object side, a first lens L1 of a negative meniscus lens and a second lens L2 of a negative meniscus lens having an aspheric surface on at least one surface.
The first B lens group G1B has a negative meniscus lens L3 having at least one aspheric surface on the most object side,
At the time of focusing, the first B lens group G1B is moved to the object side,
An ultra-wide-angle lens system that satisfies the following conditions.
(1) 1.0 <| f1 / fw | <2.0
(2) 1.0 <f1B / f1A <3.0
(3) 3.0 <f2 / fw <5.0
However,
fw: focal length of the entire lens system or focal length of the entire lens system at the wide angle end f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f2: focal length of the second lens group G2, or focal length of the second lens group G2 at the wide angle end
In the second lens group G2, a positive lens unit L2asp having an aspheric surface on at least one surface is provided closest to the image surface side,
The super-wide-angle lens system according to claim 1, wherein the following condition is satisfied.
(4) 2.0 <f2asp / f2 <5.0
However,
f2asp: focal length of the positive lens unit L2asp having an aspherical surface on at least one surface in the second lens group G2 f2: focal length of the second lens group G2 or focal length of the second lens group G2 at the wide angle end
In order from the object side, the first lens unit G1 has a negative refractive power and the second lens unit G2 has a positive refractive power.
The first lens group G1 includes a first A lens group G1A having a negative refractive power and a first B lens group G1B having a negative refractive power.
Further, the first A lens group G1A is composed of, in order from the object side, a first lens L1 of a negative meniscus lens and a second lens L2 of a negative meniscus lens having an aspheric surface on at least one surface.
The first B lens group G1B has a negative meniscus lens L3 having at least one aspheric surface on the most object side,
At the time of focusing, the first B lens group G1B is moved to the object side,
The second lens group G2 includes a second A lens group G2A, a second B lens group G2B, and a second C lens group G2C.
When zooming from the wide-angle end to the telephoto end,
The distance between the first lens group G1 and the second A lens group G2A decreases, the distance between the second A lens group G2A and the second B lens group G2B decreases, and the second B lens group G2B and the second C The distance from the lens group G2C increases,
An ultra-wide-angle zoom lens that satisfies the following conditions.
(1) 1.0 <| f1 / fw | <2.0
(2) 1.0 <f1B / f1A <3.0
(3) 3.0 <f2 / fw <5.0
However,
fw: focal length of the entire lens system at the wide angle end f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f2: second lens group at the wide angle end Focal length of G2
In the second lens group G2, a positive lens unit L2asp having an aspheric surface on at least one surface is provided closest to the image surface side,
The super wide-angle zoom lens according to claim 3, wherein the following condition is satisfied.
(4) 2.0 <f2asp / f2 <5.0
However,
f2asp: focal length of the positive lens unit L2asp having an aspheric surface on at least one surface in the second lens group G2 f2: focal length of the second lens group G2 at the wide angle end
Regarding the second A lens group G2A and the second C lens group G2C,
The super-wide-angle zoom lens according to any one of claims 3 to 4, wherein the following condition is satisfied.
(5) 5.0 <f2A / fw <15.0
(6) 5.0 <| f2C / fw |
However,
fw: focal length of the entire lens system at the wide angle end f2A: focal length of the second A lens group G2A f2C: focal length of the second C lens group G2C
The super wide-angle zoom lens according to any one of claims 3 to 5, wherein the following condition is satisfied for the second B lens group G2B.
(7) 2.0 <f2B / fw <10.0
However,
fw: focal length of the entire lens system at the wide angle end f2B: focal length of the second B lens group G2B
The second C lens group G2C includes a cemented negative lens unit L2CJ including at least one negative lens and at least one positive lens.
The super-wide-angle zoom lens according to any one of claims 3 to 6, wherein the following condition is satisfied.
(8) -15.0 <f2CJ / fw <-2.0
However,
fw: focal length of the entire lens system at the wide-angle end f2CJ: focal length of the cemented negative lens unit L2CJ in the second C lens group G2C
The cemented negative lens unit L2CJ in the second C lens group G2C is
The super-wide-angle zoom lens according to claim 3, wherein the following condition is satisfied.
(9) Nd2CN> 1.8
(10) νd2CP> 80
However,
Nd2CN: Refractive index of at least one negative lens in the cemented negative lens unit L2CJ νd2CP: Abbe number of at least one positive lens in the cemented negative lens unit L2CJ

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